From b214f4d2e3b701c1088ee6c172376905afa64cf9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonas=20H=C3=BCbotter?= <jonas.huebotter@gmail.com>
Date: Wed, 19 Aug 2020 14:36:51 +0200
Subject: [PATCH] [#131] Type constraints

---
 .yalc/tony-lang/.eslintrc.js                  |   30 +-
 .yalc/tony-lang/.prettierignore               |    2 +
 .yalc/tony-lang/package.json                  |    8 +-
 .yalc/tony-lang/src/ast/Abstraction.ts        |   16 +
 .yalc/tony-lang/src/ast/AbstractionBranch.ts  |   23 +
 .yalc/tony-lang/src/ast/Access.ts             |   25 +
 .yalc/tony-lang/src/ast/Application.ts        |   23 +
 .yalc/tony-lang/src/ast/Argument.ts           |   16 +
 .yalc/tony-lang/src/ast/Assignment.ts         |   26 +
 .yalc/tony-lang/src/ast/Block.ts              |   16 +
 .yalc/tony-lang/src/ast/Boolean.ts            |   19 +
 .yalc/tony-lang/src/ast/Case.ts               |   30 +
 .yalc/tony-lang/src/ast/Declaration.ts        |    4 +
 .../tony-lang/src/ast/DestructuringPattern.ts |   14 +
 .yalc/tony-lang/src/ast/ElseIf.ts             |   23 +
 .yalc/tony-lang/src/ast/Export.ts             |   16 +
 .yalc/tony-lang/src/ast/Expression.ts         |   40 +
 .yalc/tony-lang/src/ast/ExpressionPair.ts     |   25 +
 .yalc/tony-lang/src/ast/Generator.ts          |   39 +
 .yalc/tony-lang/src/ast/Identifier.ts         |   28 +
 .yalc/tony-lang/src/ast/IdentifierPattern.ts  |   28 +
 .yalc/tony-lang/src/ast/If.ts                 |   41 +
 .yalc/tony-lang/src/ast/Import.ts             |    3 +
 .yalc/tony-lang/src/ast/InfixApplication.ts   |   29 +
 .yalc/tony-lang/src/ast/Interpolation.ts      |   16 +
 .yalc/tony-lang/src/ast/List.ts               |   19 +
 .yalc/tony-lang/src/ast/ListComprehension.ts  |   23 +
 .yalc/tony-lang/src/ast/ListPattern.ts        |   16 +
 .yalc/tony-lang/src/ast/Literal.ts            |    8 +
 .yalc/tony-lang/src/ast/LiteralPattern.ts     |   14 +
 .yalc/tony-lang/src/ast/Map.ts                |   20 +
 .yalc/tony-lang/src/ast/MapPattern.ts         |   23 +
 .yalc/tony-lang/src/ast/Module.ts             |   22 +
 .yalc/tony-lang/src/ast/Number.ts             |   19 +
 .yalc/tony-lang/src/ast/Parameters.ts         |   19 +
 .yalc/tony-lang/src/ast/ParametricType.ts     |   15 +
 .yalc/tony-lang/src/ast/Pattern.ts            |    5 +
 .yalc/tony-lang/src/ast/PatternPair.ts        |   26 +
 .yalc/tony-lang/src/ast/Pipeline.ts           |   22 +
 .yalc/tony-lang/src/ast/PrefixApplication.ts  |   23 +
 .yalc/tony-lang/src/ast/Program.ts            |   16 +
 .yalc/tony-lang/src/ast/Regex.ts              |   19 +
 .yalc/tony-lang/src/ast/Rest.ts               |   20 +
 .yalc/tony-lang/src/ast/Return.ts             |   16 +
 .../src/ast/ShorthandAccessIdentifier.ts      |   21 +
 .../src/ast/ShorthandPairIdentifier.ts        |   21 +
 .../src/ast/ShorthandPairIdentifierPattern.ts |    3 +
 .yalc/tony-lang/src/ast/Spread.ts             |   20 +
 .yalc/tony-lang/src/ast/String.ts             |   22 +
 .yalc/tony-lang/src/ast/StringPattern.ts      |   15 +
 .yalc/tony-lang/src/ast/SyntaxNode.ts         |    1 +
 .yalc/tony-lang/src/ast/Tuple.ts              |   19 +
 .yalc/tony-lang/src/ast/TuplePattern.ts       |   16 +
 .yalc/tony-lang/src/ast/When.ts               |   23 +
 .yalc/tony-lang/src/ast/index.ts              |   51 +
 .../src/code_generation/GenerateCode.ts       |  646 ++++------
 .../services/CollectDefaultValues.ts          |   51 +-
 .../code_generation/services/GenerateBlock.ts |    4 +-
 .../services/GenerateImport.ts                |   18 +-
 .../services/GenerateProgram.ts               |   14 +-
 .../services/ParseStringContent.ts            |    3 +-
 .yalc/tony-lang/src/compile.ts                |    2 +-
 .yalc/tony-lang/src/constants.ts              |    4 -
 .yalc/tony-lang/src/errors/CompileError.ts    |   17 +-
 .../src/errors/IndeterminateTypeError.ts      |   16 +
 .../tony-lang/src/errors/InternalTypeError.ts |   28 +
 .../errors/InvalidExternalTypeImportError.ts  |   16 +
 .../src/errors/InvalidModuleAccessError.ts    |   22 +
 .../src/errors/InvalidPropertyAccessError.ts  |   28 -
 .../errors/InvalidUseOfTypeAsValueError.ts    |   16 +
 .../MissingExternalImportTypeHintError.ts     |   16 +
 .yalc/tony-lang/src/errors/TypeError.ts       |   45 +-
 .yalc/tony-lang/src/errors/index.ts           |    7 +-
 .yalc/tony-lang/src/index.ts                  |    7 +-
 .../src/symbol_table/BuildFileModuleScope.ts  |  175 ++-
 .../src/symbol_table/WalkFileModuleScope.ts   |   12 +-
 .yalc/tony-lang/src/symbol_table/index.ts     |    7 +-
 .../symbol_table/models/BasicTypeBinding.ts   |   21 +-
 .../src/symbol_table/models/Binding.ts        |    5 +
 .../symbol_table/models/BindingTemplate.ts    |   13 +
 .../symbol_table/models/FileModuleScope.ts    |   36 +
 .../symbol_table/models/IdentifierBinding.ts  |   61 +-
 .../models/IdentifierBindingTemplate.ts       |   89 ++
 .../symbol_table/models/IdentifierImport.ts   |   45 +
 .../src/symbol_table/models/Import.ts         |    8 +
 .../src/symbol_table/models/ImportBinding.ts  |    7 -
 .../models/ImportIdentifierBinding.ts         |   41 -
 .../symbol_table/models/ImportTypeBinding.ts  |   44 -
 .../src/symbol_table/models/ModuleBinding.ts  |   76 ++
 .../src/symbol_table/models/ModuleImport.ts   |   44 +
 .../src/symbol_table/models/NestedScope.ts    |   96 +-
 .../src/symbol_table/models/TypeBinding.ts    |   47 -
 .../src/symbol_table/models/index.ts          |   10 +-
 .../services/BuildImportBindings.ts           |  101 --
 .../src/symbol_table/services/BuildImports.ts |   90 ++
 .../services/BuildPatternBindings.ts          |   16 +-
 .../services/UnifyPatternBindings.ts          |    6 +-
 .../src/symbol_table/services/index.ts        |    2 +-
 .../src/type_inference/InferTypes.ts          | 1147 +++++++++++------
 .../models/AccumulatedAnswer.ts               |   23 +
 .../models/AccumulatedDisjunction.ts          |    6 +
 .../src/type_inference/models/Answer.ts       |   29 +
 .../src/type_inference/models/Disjunction.ts  |   19 +
 .../models/GeneralizedDisjunction.ts          |   16 +
 .../src/type_inference/models/index.ts        |    5 +
 .../services/AccumulateTypeDisjunction.ts     |   35 +
 .../services/DistributeTypeDisjunction.ts     |   52 +
 .../services/GetModuleTypeRepresentation.ts   |   19 +
 .../services/InferAbstractionBranchType.ts    |   50 +
 .../services/InferAccessType.ts               |  296 +++--
 .../services/InferApplicationType.ts          |  305 +++--
 .../services/InferAssignmentType.ts           |   41 +
 .../type_inference/services/InferBlockType.ts |   40 +
 .../services/InferBranchType.ts               |   40 +-
 .../services/InferExpressionPairType.ts       |   43 +
 .../services/InferGeneratorType.ts            |  152 +++
 .../services/InferIdentifierPatternType.ts    |  205 +++
 .../services/InferImportBindingTypes.ts       |  163 +++
 .../type_inference/services/InferListType.ts  |   94 +-
 .../type_inference/services/InferMapType.ts   |   64 +-
 .../services/InferPatternBindingTypes.ts      |  415 +++---
 .../services/InferPatternPairType.ts          |   61 +
 .../services/InferStringType.ts               |   53 +
 .../type_inference/services/InferTupleType.ts |   87 +-
 .../MergeAccumulatedTypeDisjunction.ts        |   48 +
 .../services/MergeTypeDisjunction.ts          |   43 +
 .../src/type_inference/services/index.ts      |   14 +
 .yalc/tony-lang/src/types/index.ts            |   14 +-
 .../tony-lang/src/types/models/CurriedType.ts |   69 -
 .../src/types/models/IdentifierProperty.ts    |   31 -
 .../tony-lang/src/types/models/ModuleType.ts  |   44 +
 .../src/types/models/ParametricType.ts        |   97 +-
 .yalc/tony-lang/src/types/models/Property.ts  |    8 -
 .../src/types/models/Representation.ts        |   34 -
 .yalc/tony-lang/src/types/models/Type.ts      |   25 +-
 .../src/types/models/TypeConstraint.ts        |   49 +
 .../src/types/models/TypeConstraints.ts       |   30 -
 .../src/types/models/TypeEqualityGraph.ts     |  148 +++
 .../src/types/models/TypeEquivalenceClass.ts  |   72 ++
 .../src/types/models/TypeProperty.ts          |   33 -
 .../src/types/models/TypeVariable.ts          |   37 +-
 .yalc/tony-lang/src/types/models/index.ts     |    8 +-
 .../src/types/services/BuildRepresentation.ts |   23 -
 .../tony-lang/src/types/services/BuildType.ts |   23 +-
 .yalc/tony-lang/src/types/services/index.ts   |    1 -
 .yalc/tony-lang/test/abstraction/quicksort.tn |    2 +-
 .yalc/tony-lang/test/application/index.tn     |    1 -
 .../test/assignment/duplicate_binding.tn      |    2 +
 .../test/assignment/duplicate_binding.txt     |    1 +
 .../tony-lang/test/assignment/overloading.tn  |    5 +
 .../tony-lang/test/assignment/overloading.txt |    2 +
 .../test/assignment/pattern_matching.tn       |    3 -
 .yalc/tony-lang/test/stdlib.tn                |    2 +-
 .yalc/tony-lang/tony-lang.d.ts                |   51 +-
 .yalc/tony-lang/yalc.sig                      |    2 +-
 src/CLI.ts                                    |    8 +-
 src/ErrorHandler.ts                           |   18 +-
 ...s => InvalidModuleAccessErrorFormatter.ts} |   11 +-
 src/formatting/TypeErrorFormatter.ts          |   29 +-
 src/formatting/index.ts                       |    2 +-
 test.js                                       |    1 +
 test.tn                                       |   30 +
 yalc.lock                                     |    2 +-
 yarn.lock                                     |    6 +-
 164 files changed, 5539 insertions(+), 2059 deletions(-)
 create mode 100644 .yalc/tony-lang/.prettierignore
 create mode 100644 .yalc/tony-lang/src/ast/Abstraction.ts
 create mode 100644 .yalc/tony-lang/src/ast/AbstractionBranch.ts
 create mode 100644 .yalc/tony-lang/src/ast/Access.ts
 create mode 100644 .yalc/tony-lang/src/ast/Application.ts
 create mode 100644 .yalc/tony-lang/src/ast/Argument.ts
 create mode 100644 .yalc/tony-lang/src/ast/Assignment.ts
 create mode 100644 .yalc/tony-lang/src/ast/Block.ts
 create mode 100644 .yalc/tony-lang/src/ast/Boolean.ts
 create mode 100644 .yalc/tony-lang/src/ast/Case.ts
 create mode 100644 .yalc/tony-lang/src/ast/Declaration.ts
 create mode 100644 .yalc/tony-lang/src/ast/DestructuringPattern.ts
 create mode 100644 .yalc/tony-lang/src/ast/ElseIf.ts
 create mode 100644 .yalc/tony-lang/src/ast/Export.ts
 create mode 100644 .yalc/tony-lang/src/ast/Expression.ts
 create mode 100644 .yalc/tony-lang/src/ast/ExpressionPair.ts
 create mode 100644 .yalc/tony-lang/src/ast/Generator.ts
 create mode 100644 .yalc/tony-lang/src/ast/Identifier.ts
 create mode 100644 .yalc/tony-lang/src/ast/IdentifierPattern.ts
 create mode 100644 .yalc/tony-lang/src/ast/If.ts
 create mode 100644 .yalc/tony-lang/src/ast/Import.ts
 create mode 100644 .yalc/tony-lang/src/ast/InfixApplication.ts
 create mode 100644 .yalc/tony-lang/src/ast/Interpolation.ts
 create mode 100644 .yalc/tony-lang/src/ast/List.ts
 create mode 100644 .yalc/tony-lang/src/ast/ListComprehension.ts
 create mode 100644 .yalc/tony-lang/src/ast/ListPattern.ts
 create mode 100644 .yalc/tony-lang/src/ast/Literal.ts
 create mode 100644 .yalc/tony-lang/src/ast/LiteralPattern.ts
 create mode 100644 .yalc/tony-lang/src/ast/Map.ts
 create mode 100644 .yalc/tony-lang/src/ast/MapPattern.ts
 create mode 100644 .yalc/tony-lang/src/ast/Module.ts
 create mode 100644 .yalc/tony-lang/src/ast/Number.ts
 create mode 100644 .yalc/tony-lang/src/ast/Parameters.ts
 create mode 100644 .yalc/tony-lang/src/ast/ParametricType.ts
 create mode 100644 .yalc/tony-lang/src/ast/Pattern.ts
 create mode 100644 .yalc/tony-lang/src/ast/PatternPair.ts
 create mode 100644 .yalc/tony-lang/src/ast/Pipeline.ts
 create mode 100644 .yalc/tony-lang/src/ast/PrefixApplication.ts
 create mode 100644 .yalc/tony-lang/src/ast/Program.ts
 create mode 100644 .yalc/tony-lang/src/ast/Regex.ts
 create mode 100644 .yalc/tony-lang/src/ast/Rest.ts
 create mode 100644 .yalc/tony-lang/src/ast/Return.ts
 create mode 100644 .yalc/tony-lang/src/ast/ShorthandAccessIdentifier.ts
 create mode 100644 .yalc/tony-lang/src/ast/ShorthandPairIdentifier.ts
 create mode 100644 .yalc/tony-lang/src/ast/ShorthandPairIdentifierPattern.ts
 create mode 100644 .yalc/tony-lang/src/ast/Spread.ts
 create mode 100644 .yalc/tony-lang/src/ast/String.ts
 create mode 100644 .yalc/tony-lang/src/ast/StringPattern.ts
 create mode 100644 .yalc/tony-lang/src/ast/SyntaxNode.ts
 create mode 100644 .yalc/tony-lang/src/ast/Tuple.ts
 create mode 100644 .yalc/tony-lang/src/ast/TuplePattern.ts
 create mode 100644 .yalc/tony-lang/src/ast/When.ts
 create mode 100644 .yalc/tony-lang/src/ast/index.ts
 create mode 100644 .yalc/tony-lang/src/errors/IndeterminateTypeError.ts
 create mode 100644 .yalc/tony-lang/src/errors/InternalTypeError.ts
 create mode 100644 .yalc/tony-lang/src/errors/InvalidExternalTypeImportError.ts
 create mode 100644 .yalc/tony-lang/src/errors/InvalidModuleAccessError.ts
 delete mode 100644 .yalc/tony-lang/src/errors/InvalidPropertyAccessError.ts
 create mode 100644 .yalc/tony-lang/src/errors/InvalidUseOfTypeAsValueError.ts
 create mode 100644 .yalc/tony-lang/src/errors/MissingExternalImportTypeHintError.ts
 create mode 100644 .yalc/tony-lang/src/symbol_table/models/BindingTemplate.ts
 create mode 100644 .yalc/tony-lang/src/symbol_table/models/IdentifierBindingTemplate.ts
 create mode 100644 .yalc/tony-lang/src/symbol_table/models/IdentifierImport.ts
 create mode 100644 .yalc/tony-lang/src/symbol_table/models/Import.ts
 delete mode 100644 .yalc/tony-lang/src/symbol_table/models/ImportBinding.ts
 delete mode 100644 .yalc/tony-lang/src/symbol_table/models/ImportIdentifierBinding.ts
 delete mode 100644 .yalc/tony-lang/src/symbol_table/models/ImportTypeBinding.ts
 create mode 100644 .yalc/tony-lang/src/symbol_table/models/ModuleBinding.ts
 create mode 100644 .yalc/tony-lang/src/symbol_table/models/ModuleImport.ts
 delete mode 100644 .yalc/tony-lang/src/symbol_table/models/TypeBinding.ts
 delete mode 100644 .yalc/tony-lang/src/symbol_table/services/BuildImportBindings.ts
 create mode 100644 .yalc/tony-lang/src/symbol_table/services/BuildImports.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/models/AccumulatedAnswer.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/models/AccumulatedDisjunction.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/models/Answer.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/models/Disjunction.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/models/GeneralizedDisjunction.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/models/index.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/services/AccumulateTypeDisjunction.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/services/DistributeTypeDisjunction.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/services/GetModuleTypeRepresentation.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/services/InferAbstractionBranchType.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/services/InferAssignmentType.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/services/InferBlockType.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/services/InferExpressionPairType.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/services/InferGeneratorType.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/services/InferIdentifierPatternType.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/services/InferImportBindingTypes.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/services/InferPatternPairType.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/services/InferStringType.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/services/MergeAccumulatedTypeDisjunction.ts
 create mode 100644 .yalc/tony-lang/src/type_inference/services/MergeTypeDisjunction.ts
 delete mode 100644 .yalc/tony-lang/src/types/models/CurriedType.ts
 delete mode 100644 .yalc/tony-lang/src/types/models/IdentifierProperty.ts
 create mode 100644 .yalc/tony-lang/src/types/models/ModuleType.ts
 delete mode 100644 .yalc/tony-lang/src/types/models/Property.ts
 delete mode 100644 .yalc/tony-lang/src/types/models/Representation.ts
 create mode 100644 .yalc/tony-lang/src/types/models/TypeConstraint.ts
 delete mode 100644 .yalc/tony-lang/src/types/models/TypeConstraints.ts
 create mode 100644 .yalc/tony-lang/src/types/models/TypeEqualityGraph.ts
 create mode 100644 .yalc/tony-lang/src/types/models/TypeEquivalenceClass.ts
 delete mode 100644 .yalc/tony-lang/src/types/models/TypeProperty.ts
 delete mode 100644 .yalc/tony-lang/src/types/services/BuildRepresentation.ts
 create mode 100644 .yalc/tony-lang/test/assignment/duplicate_binding.tn
 create mode 100644 .yalc/tony-lang/test/assignment/duplicate_binding.txt
 create mode 100644 .yalc/tony-lang/test/assignment/overloading.tn
 create mode 100644 .yalc/tony-lang/test/assignment/overloading.txt
 rename src/formatting/{InvalidPropertyAccessErrorFormatter.ts => InvalidModuleAccessErrorFormatter.ts} (55%)
 create mode 100644 test.js
 create mode 100644 test.tn

diff --git a/.yalc/tony-lang/.eslintrc.js b/.yalc/tony-lang/.eslintrc.js
index 2f04efd..7cef5a5 100644
--- a/.yalc/tony-lang/.eslintrc.js
+++ b/.yalc/tony-lang/.eslintrc.js
@@ -20,25 +20,31 @@ module.exports = {
   },
   plugins: ['@typescript-eslint'],
   rules: {
-    'max-lines-per-function': ['error', {
-      max: 20,
-      skipBlankLines: true,
-      skipComments: true,
-    }],
+    'max-lines-per-function': [
+      'error',
+      {
+        max: 25,
+        skipBlankLines: true,
+        skipComments: true,
+      },
+    ],
     'max-params': ['error', 5],
     'sort-imports': 'error',
     '@typescript-eslint/explicit-function-return-type': 'error',
     '@typescript-eslint/no-use-before-define': 'off',
     '@typescript-eslint/no-explicit-any': 'error',
     '@typescript-eslint/no-unused-vars': 'error',
-    '@typescript-eslint/member-delimiter-style': ['error', {
-      multiline: {
-        delimiter: 'none',
+    '@typescript-eslint/member-delimiter-style': [
+      'error',
+      {
+        multiline: {
+          delimiter: 'none',
+        },
+        singleline: {
+          delimiter: 'semi',
+        },
       },
-      singleline: {
-        delimiter: 'semi',
-      }
-    }],
+    ],
   },
   overrides: [
     {
diff --git a/.yalc/tony-lang/.prettierignore b/.yalc/tony-lang/.prettierignore
new file mode 100644
index 0000000..de4d1f0
--- /dev/null
+++ b/.yalc/tony-lang/.prettierignore
@@ -0,0 +1,2 @@
+dist
+node_modules
diff --git a/.yalc/tony-lang/package.json b/.yalc/tony-lang/package.json
index 8ba96e2..2b2da75 100644
--- a/.yalc/tony-lang/package.json
+++ b/.yalc/tony-lang/package.json
@@ -1,14 +1,14 @@
 {
   "name": "tony-lang",
-  "version": "0.1.4-afbd7cb8",
+  "version": "0.1.4-dae48e8c",
   "description": "The Tony programming language",
   "main": "dist/src/index.js",
   "types": "tony-lang.d.ts",
   "scripts": {
     "build": "babel . --ignore dist,node_modules --out-dir dist --extensions .ts",
     "start": "nodemon --watch src --watch test --exec 'yarn build' -e ts",
-    "lint": "prettier --check src test && eslint src test --ext .ts",
-    "prettier": "prettier --write src test",
+    "lint": "prettier --check '**/*.{ts,js}' && eslint src test --ext .ts",
+    "prettier": "prettier --write '**/*.{ts,js}'",
     "test": "ava dist/test/index.test.js"
   },
   "engines": {
@@ -28,7 +28,7 @@
   },
   "homepage": "https://github.com/tony-lang/tony#readme",
   "dependencies": {
-    "core-js": "^3.6.5",
+    "core-js": "^3.6.4",
     "deep-equal": "^2.0.1",
     "inquirer": "^7.1.0",
     "mkdirp": "^1.0.3",
diff --git a/.yalc/tony-lang/src/ast/Abstraction.ts b/.yalc/tony-lang/src/ast/Abstraction.ts
new file mode 100644
index 0000000..cceeaef
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Abstraction.ts
@@ -0,0 +1,16 @@
+import { AbstractionBranch } from './AbstractionBranch'
+import { SyntaxNode } from './SyntaxNode'
+
+export class Abstraction extends SyntaxNode {
+  private _branches: AbstractionBranch[]
+
+  constructor(branches: AbstractionBranch[]) {
+    super()
+
+    this._branches = branches
+  }
+
+  get branches(): AbstractionBranch[] {
+    return this._branches
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/AbstractionBranch.ts b/.yalc/tony-lang/src/ast/AbstractionBranch.ts
new file mode 100644
index 0000000..6cc3a06
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/AbstractionBranch.ts
@@ -0,0 +1,23 @@
+import { Block } from './Block'
+import { Parameters } from './Parameters'
+import { SyntaxNode } from './SyntaxNode'
+
+export class AbstractionBranch extends SyntaxNode {
+  private _body: Block
+  private _parameters: Parameters
+
+  constructor(parameters: Parameters, body: Block) {
+    super()
+
+    this._parameters = parameters
+    this._body = body
+  }
+
+  get body(): Block {
+    return this._body
+  }
+
+  get parameters(): Parameters {
+    return this._parameters
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Access.ts b/.yalc/tony-lang/src/ast/Access.ts
new file mode 100644
index 0000000..93570b3
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Access.ts
@@ -0,0 +1,25 @@
+import { Expression } from './Expression'
+import { ShorthandAccessIdentifier } from './ShorthandAccessIdentifier'
+import { SyntaxNode } from './SyntaxNode'
+
+type Accessor = ShorthandAccessIdentifier | Expression
+
+export class Access extends SyntaxNode {
+  private _value: Expression
+  private _accessor: Accessor
+
+  constructor(value: Expression, accessor: Accessor) {
+    super()
+
+    this._value = value
+    this._accessor = accessor
+  }
+
+  get value(): Expression {
+    return this._value
+  }
+
+  get accessor(): Accessor {
+    return this._accessor
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Application.ts b/.yalc/tony-lang/src/ast/Application.ts
new file mode 100644
index 0000000..1125a73
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Application.ts
@@ -0,0 +1,23 @@
+import { Argument } from './Argument'
+import { Expression } from './Expression'
+import { SyntaxNode } from './SyntaxNode'
+
+export class Application extends SyntaxNode {
+  private _arguments: Argument[]
+  private _value: Expression
+
+  constructor(value: Expression, args: Argument[]) {
+    super()
+
+    this._arguments = args
+    this._value = value
+  }
+
+  get arguments(): Argument[] {
+    return this._arguments
+  }
+
+  get value(): Expression {
+    return this._value
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Argument.ts b/.yalc/tony-lang/src/ast/Argument.ts
new file mode 100644
index 0000000..fdca5c9
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Argument.ts
@@ -0,0 +1,16 @@
+import { Expression } from './Expression'
+import { SyntaxNode } from './SyntaxNode'
+
+export class Argument extends SyntaxNode {
+  private _value: Expression | undefined
+
+  constructor(value?: Expression) {
+    super()
+
+    this._value = value
+  }
+
+  get value(): Expression | undefined {
+    return this._value
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Assignment.ts b/.yalc/tony-lang/src/ast/Assignment.ts
new file mode 100644
index 0000000..c5cf9a0
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Assignment.ts
@@ -0,0 +1,26 @@
+import { DestructuringPattern } from './DestructuringPattern'
+import { Expression } from './Expression'
+import { IdentifierPattern } from './IdentifierPattern'
+import { SyntaxNode } from './SyntaxNode'
+
+export type AssignablePattern = IdentifierPattern | DestructuringPattern
+
+export class Assignment extends SyntaxNode {
+  private _pattern: AssignablePattern
+  private _value: Expression
+
+  constructor(pattern: AssignablePattern, value: Expression) {
+    super()
+
+    this._pattern = pattern
+    this._value = value
+  }
+
+  get pattern(): AssignablePattern {
+    return this._pattern
+  }
+
+  get value(): Expression {
+    return this._value
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Block.ts b/.yalc/tony-lang/src/ast/Block.ts
new file mode 100644
index 0000000..e09074b
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Block.ts
@@ -0,0 +1,16 @@
+import { Expression } from './Expression'
+import { SyntaxNode } from './SyntaxNode'
+
+export class Block extends SyntaxNode {
+  private _expressions: Expression[]
+
+  constructor(expressions: Expression[]) {
+    super()
+
+    this._expressions = expressions
+  }
+
+  get expressions(): Expression[] {
+    return this._expressions
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Boolean.ts b/.yalc/tony-lang/src/ast/Boolean.ts
new file mode 100644
index 0000000..6e5652a
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Boolean.ts
@@ -0,0 +1,19 @@
+import { SyntaxNode } from './SyntaxNode'
+
+export class Boolean extends SyntaxNode {
+  private _text: string
+
+  constructor(text: string) {
+    super()
+
+    this._text = text
+  }
+
+  get text(): string {
+    return this._text
+  }
+
+  get value(): boolean {
+    return this.text === 'true'
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Case.ts b/.yalc/tony-lang/src/ast/Case.ts
new file mode 100644
index 0000000..b5bf87c
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Case.ts
@@ -0,0 +1,30 @@
+import { Block } from './Block'
+import { Expression } from './Expression'
+import { SyntaxNode } from './SyntaxNode'
+import { When } from './When'
+
+export class Case extends SyntaxNode {
+  private _branches: When[]
+  private _else: Block | undefined
+  private _value: Expression
+
+  constructor(value: Expression, branches: When[], els?: Block) {
+    super()
+
+    this._branches = branches
+    this._else = els
+    this._value = value
+  }
+
+  get branches(): When[] {
+    return this._branches
+  }
+
+  get else(): Block | undefined {
+    return this._else
+  }
+
+  get value(): Expression {
+    return this._value
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Declaration.ts b/.yalc/tony-lang/src/ast/Declaration.ts
new file mode 100644
index 0000000..e2ab1fb
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Declaration.ts
@@ -0,0 +1,4 @@
+import { Assignment } from './Assignment'
+import { Module } from './Module'
+
+export type Declaration = Assignment | Module
diff --git a/.yalc/tony-lang/src/ast/DestructuringPattern.ts b/.yalc/tony-lang/src/ast/DestructuringPattern.ts
new file mode 100644
index 0000000..284f6dd
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/DestructuringPattern.ts
@@ -0,0 +1,14 @@
+import { ListPattern } from './ListPattern'
+import { MapPattern } from './MapPattern'
+import { PatternPair } from './PatternPair'
+import { Rest } from './Rest'
+import { ShorthandPairIdentifierPattern } from './ShorthandPairIdentifierPattern'
+import { TuplePattern } from './TuplePattern'
+
+export type DestructuringPattern =
+  | ListPattern
+  | MapPattern
+  | PatternPair
+  | Rest
+  | ShorthandPairIdentifierPattern
+  | TuplePattern
diff --git a/.yalc/tony-lang/src/ast/ElseIf.ts b/.yalc/tony-lang/src/ast/ElseIf.ts
new file mode 100644
index 0000000..023dd2a
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/ElseIf.ts
@@ -0,0 +1,23 @@
+import { Block } from './Block'
+import { Expression } from './Expression'
+import { SyntaxNode } from './SyntaxNode'
+
+export class ElseIf extends SyntaxNode {
+  private _body: Block
+  private _condition: Expression
+
+  constructor(condition: Expression, body: Block) {
+    super()
+
+    this._body = body
+    this._condition = condition
+  }
+
+  get body(): Block {
+    return this._body
+  }
+
+  get condition(): Expression {
+    return this._condition
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Export.ts b/.yalc/tony-lang/src/ast/Export.ts
new file mode 100644
index 0000000..bcefc2f
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Export.ts
@@ -0,0 +1,16 @@
+import { Declaration } from './Declaration'
+import { SyntaxNode } from './SyntaxNode'
+
+export class Export extends SyntaxNode {
+  private _declaration: Declaration
+
+  constructor(declaration: Declaration) {
+    super()
+
+    this._declaration = declaration
+  }
+
+  get declaration(): Declaration {
+    return this._declaration
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Expression.ts b/.yalc/tony-lang/src/ast/Expression.ts
new file mode 100644
index 0000000..a2d259a
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Expression.ts
@@ -0,0 +1,40 @@
+import { Abstraction } from './Abstraction'
+import { Access } from './Access'
+import { Application } from './Application'
+import { Assignment } from './Assignment'
+import { Case } from './Case'
+import { Export } from './Export'
+import { Identifier } from './Identifier'
+import { If } from './If'
+import { Import } from './Import'
+import { InfixApplication } from './InfixApplication'
+import { List } from './List'
+import { ListComprehension } from './ListComprehension'
+import { Literal } from './Literal'
+import { Map } from './Map'
+import { Module } from './Module'
+import { Pipeline } from './Pipeline'
+import { PrefixApplication } from './PrefixApplication'
+import { Return } from './Return'
+import { Tuple } from './Tuple'
+
+export type Expression =
+  | Abstraction
+  | Access
+  | Application
+  | Assignment
+  | Case
+  | Export
+  | Identifier
+  | If
+  | Import
+  | InfixApplication
+  | List
+  | ListComprehension
+  | Literal
+  | Map
+  | Module
+  | Pipeline
+  | PrefixApplication
+  | Return
+  | Tuple
diff --git a/.yalc/tony-lang/src/ast/ExpressionPair.ts b/.yalc/tony-lang/src/ast/ExpressionPair.ts
new file mode 100644
index 0000000..94f03bb
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/ExpressionPair.ts
@@ -0,0 +1,25 @@
+import { Expression } from './Expression'
+import { ShorthandAccessIdentifier } from './ShorthandAccessIdentifier'
+import { SyntaxNode } from './SyntaxNode'
+
+type Key = ShorthandAccessIdentifier | Expression
+
+export class ExpressionPair extends SyntaxNode {
+  private _key: Key
+  private _value: Expression
+
+  constructor(key: Key, value: Expression) {
+    super()
+
+    this._key = key
+    this._value = value
+  }
+
+  get key(): Key {
+    return this._key
+  }
+
+  get value(): Expression {
+    return this._value
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Generator.ts b/.yalc/tony-lang/src/ast/Generator.ts
new file mode 100644
index 0000000..a7c1230
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Generator.ts
@@ -0,0 +1,39 @@
+import { Expression } from './Expression'
+import { SyntaxNode } from './SyntaxNode'
+
+export class Generator extends SyntaxNode {
+  private _condition: Expression | undefined
+  private _name: string
+  private _transformedName: string
+  private _value: Expression
+
+  constructor(
+    name: string,
+    transformedName: string,
+    value: Expression,
+    condition?: Expression,
+  ) {
+    super()
+
+    this._condition = condition
+    this._name = name
+    this._transformedName = transformedName
+    this._value = value
+  }
+
+  get condition(): Expression | undefined {
+    return this._condition
+  }
+
+  get name(): string {
+    return this._name
+  }
+
+  get transformedName(): string {
+    return this._transformedName
+  }
+
+  get value(): Expression {
+    return this._value
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Identifier.ts b/.yalc/tony-lang/src/ast/Identifier.ts
new file mode 100644
index 0000000..dc733f1
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Identifier.ts
@@ -0,0 +1,28 @@
+import { SyntaxNode } from './SyntaxNode'
+import { Type } from '../types'
+
+export class Identifier extends SyntaxNode {
+  private _name: string
+  private _transformedName: string
+  private _type: Type
+
+  constructor(type: Type, name: string, transformedName: string) {
+    super()
+
+    this._name = name
+    this._transformedName = transformedName
+    this._type = type
+  }
+
+  get name(): string {
+    return this._name
+  }
+
+  get transformedName(): string {
+    return this._transformedName
+  }
+
+  get type(): Type {
+    return this._type
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/IdentifierPattern.ts b/.yalc/tony-lang/src/ast/IdentifierPattern.ts
new file mode 100644
index 0000000..0857905
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/IdentifierPattern.ts
@@ -0,0 +1,28 @@
+import { Expression } from './Expression'
+import { SyntaxNode } from './SyntaxNode'
+
+export class IdentifierPattern extends SyntaxNode {
+  private _default: Expression | undefined
+  private _name: string
+  private _transformedName: string
+
+  constructor(name: string, transformedName: string, def?: Expression) {
+    super()
+
+    this._default = def
+    this._name = name
+    this._transformedName = transformedName
+  }
+
+  get default(): Expression | undefined {
+    return this._default
+  }
+
+  get name(): string {
+    return this._name
+  }
+
+  get transformedName(): string {
+    return this._transformedName
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/If.ts b/.yalc/tony-lang/src/ast/If.ts
new file mode 100644
index 0000000..76ff196
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/If.ts
@@ -0,0 +1,41 @@
+import { Block } from './Block'
+import { ElseIf } from './ElseIf'
+import { Expression } from './Expression'
+import { SyntaxNode } from './SyntaxNode'
+
+export class If extends SyntaxNode {
+  private _body: Block
+  private _condition: Expression
+  private _else: Block | undefined
+  private _elseIfs: ElseIf[]
+
+  constructor(
+    condition: Expression,
+    body: Block,
+    elseIfs: ElseIf[] = [],
+    els?: Block,
+  ) {
+    super()
+
+    this._body = body
+    this._condition = condition
+    this._else = els
+    this._elseIfs = elseIfs
+  }
+
+  get body(): Block {
+    return this._body
+  }
+
+  get condition(): Expression {
+    return this._condition
+  }
+
+  get else(): Block | undefined {
+    return this._else
+  }
+
+  get elseIfs(): ElseIf[] {
+    return this._elseIfs
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Import.ts b/.yalc/tony-lang/src/ast/Import.ts
new file mode 100644
index 0000000..19cea30
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Import.ts
@@ -0,0 +1,3 @@
+import { SyntaxNode } from './SyntaxNode'
+
+export class Import extends SyntaxNode {}
diff --git a/.yalc/tony-lang/src/ast/InfixApplication.ts b/.yalc/tony-lang/src/ast/InfixApplication.ts
new file mode 100644
index 0000000..345633b
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/InfixApplication.ts
@@ -0,0 +1,29 @@
+import { Expression } from './Expression'
+import { Identifier } from './Identifier'
+import { SyntaxNode } from './SyntaxNode'
+
+export class InfixApplication extends SyntaxNode {
+  private _left: Expression
+  private _right: Expression
+  private _value: Identifier
+
+  constructor(left: Expression, value: Identifier, right: Expression) {
+    super()
+
+    this._left = left
+    this._right = right
+    this._value = value
+  }
+
+  get left(): Expression {
+    return this._left
+  }
+
+  get right(): Expression {
+    return this._right
+  }
+
+  get value(): Identifier {
+    return this._value
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Interpolation.ts b/.yalc/tony-lang/src/ast/Interpolation.ts
new file mode 100644
index 0000000..fa6d1c5
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Interpolation.ts
@@ -0,0 +1,16 @@
+import { Expression } from './Expression'
+import { SyntaxNode } from './SyntaxNode'
+
+export class Interpolation extends SyntaxNode {
+  private _value: Expression
+
+  constructor(value: Expression) {
+    super()
+
+    this._value = value
+  }
+
+  get value(): Expression {
+    return this._value
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/List.ts b/.yalc/tony-lang/src/ast/List.ts
new file mode 100644
index 0000000..d73ef24
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/List.ts
@@ -0,0 +1,19 @@
+import { Expression } from './Expression'
+import { SpreadList } from './Spread'
+import { SyntaxNode } from './SyntaxNode'
+
+type Element = Expression | SpreadList
+
+export class List extends SyntaxNode {
+  private _elements: Element[]
+
+  constructor(elements: Element[]) {
+    super()
+
+    this._elements = elements
+  }
+
+  get elements(): Element[] {
+    return this._elements
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/ListComprehension.ts b/.yalc/tony-lang/src/ast/ListComprehension.ts
new file mode 100644
index 0000000..7196dbb
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/ListComprehension.ts
@@ -0,0 +1,23 @@
+import { Block } from './Block'
+import { Generator } from './Generator'
+import { SyntaxNode } from './SyntaxNode'
+
+export class ListComprehension extends SyntaxNode {
+  private _body: Block
+  private _generators: Generator[]
+
+  constructor(body: Block, generators: Generator[]) {
+    super()
+
+    this._body = body
+    this._generators = generators
+  }
+
+  get body(): Block {
+    return this._body
+  }
+
+  get generators(): Generator[] {
+    return this._generators
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/ListPattern.ts b/.yalc/tony-lang/src/ast/ListPattern.ts
new file mode 100644
index 0000000..2551394
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/ListPattern.ts
@@ -0,0 +1,16 @@
+import { Pattern } from './Pattern'
+import { SyntaxNode } from './SyntaxNode'
+
+export class ListPattern extends SyntaxNode {
+  private _elements: Pattern[]
+
+  constructor(elements: Pattern[]) {
+    super()
+
+    this._elements = elements
+  }
+
+  get elements(): Pattern[] {
+    return this._elements
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Literal.ts b/.yalc/tony-lang/src/ast/Literal.ts
new file mode 100644
index 0000000..3c2b71d
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Literal.ts
@@ -0,0 +1,8 @@
+import { Boolean } from './Boolean'
+import { Number } from './Number'
+import { ParametricType } from './ParametricType'
+import { Regex } from './Regex'
+import { String } from './String'
+
+// eslint-disable-next-line @typescript-eslint/ban-types
+export type Literal = Boolean | Number | ParametricType | Regex | String
diff --git a/.yalc/tony-lang/src/ast/LiteralPattern.ts b/.yalc/tony-lang/src/ast/LiteralPattern.ts
new file mode 100644
index 0000000..e201294
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/LiteralPattern.ts
@@ -0,0 +1,14 @@
+import { Boolean } from './Boolean'
+import { Number } from './Number'
+import { ParametricType } from './ParametricType'
+import { Regex } from './Regex'
+import { StringPattern } from './StringPattern'
+
+export type LiteralPattern =
+  // eslint-disable-next-line @typescript-eslint/ban-types
+  | Boolean
+  // eslint-disable-next-line @typescript-eslint/ban-types
+  | Number
+  | ParametricType
+  | Regex
+  | StringPattern
diff --git a/.yalc/tony-lang/src/ast/Map.ts b/.yalc/tony-lang/src/ast/Map.ts
new file mode 100644
index 0000000..2c260be
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Map.ts
@@ -0,0 +1,20 @@
+import { ExpressionPair } from './ExpressionPair'
+import { ShorthandPairIdentifier } from './ShorthandPairIdentifier'
+import { SpreadMap } from './Spread'
+import { SyntaxNode } from './SyntaxNode'
+
+export type MapElement = ExpressionPair | ShorthandPairIdentifier | SpreadMap
+
+export class Map extends SyntaxNode {
+  private _elements: MapElement[]
+
+  constructor(elements: MapElement[]) {
+    super()
+
+    this._elements = elements
+  }
+
+  get elements(): MapElement[] {
+    return this._elements
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/MapPattern.ts b/.yalc/tony-lang/src/ast/MapPattern.ts
new file mode 100644
index 0000000..afe2089
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/MapPattern.ts
@@ -0,0 +1,23 @@
+import { PatternPair } from './PatternPair'
+import { RestMap } from './Rest'
+import { ShorthandPairIdentifierPattern } from './ShorthandPairIdentifierPattern'
+import { SyntaxNode } from './SyntaxNode'
+
+export type MapPatternElement =
+  | PatternPair
+  | ShorthandPairIdentifierPattern
+  | RestMap
+
+export class MapPattern extends SyntaxNode {
+  private _elements: MapPatternElement[]
+
+  constructor(elements: MapPatternElement[]) {
+    super()
+
+    this._elements = elements
+  }
+
+  get elements(): MapPatternElement[] {
+    return this._elements
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Module.ts b/.yalc/tony-lang/src/ast/Module.ts
new file mode 100644
index 0000000..bac6e7b
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Module.ts
@@ -0,0 +1,22 @@
+import { Block } from './Block'
+import { SyntaxNode } from './SyntaxNode'
+
+export class Module extends SyntaxNode {
+  private _body: Block
+  private _name: string
+
+  constructor(name: string, body: Block) {
+    super()
+
+    this._body = body
+    this._name = name
+  }
+
+  get body(): Block {
+    return this._body
+  }
+
+  get name(): string {
+    return this._name
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Number.ts b/.yalc/tony-lang/src/ast/Number.ts
new file mode 100644
index 0000000..0d21faf
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Number.ts
@@ -0,0 +1,19 @@
+import { SyntaxNode } from './SyntaxNode'
+
+export class Number extends SyntaxNode {
+  private _text: string
+
+  constructor(text: string) {
+    super()
+
+    this._text = text
+  }
+
+  get text(): string {
+    return this._text
+  }
+
+  get value(): number {
+    return parseInt(this.text)
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Parameters.ts b/.yalc/tony-lang/src/ast/Parameters.ts
new file mode 100644
index 0000000..4f05d83
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Parameters.ts
@@ -0,0 +1,19 @@
+import { Pattern } from './Pattern'
+import { RestTuple } from './Rest'
+import { SyntaxNode } from './SyntaxNode'
+
+type Parameter = Pattern | RestTuple
+
+export class Parameters extends SyntaxNode {
+  private _parameters: Parameter[]
+
+  constructor(parameters: Parameter[] = []) {
+    super()
+
+    this._parameters = parameters
+  }
+
+  get parameters(): Parameter[] {
+    return this._parameters
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/ParametricType.ts b/.yalc/tony-lang/src/ast/ParametricType.ts
new file mode 100644
index 0000000..0d6874a
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/ParametricType.ts
@@ -0,0 +1,15 @@
+import { SyntaxNode } from './SyntaxNode'
+
+export class ParametricType extends SyntaxNode {
+  private _name: string
+
+  constructor(name: string) {
+    super()
+
+    this._name = name
+  }
+
+  get name(): string {
+    return this._name
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Pattern.ts b/.yalc/tony-lang/src/ast/Pattern.ts
new file mode 100644
index 0000000..e593c9f
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Pattern.ts
@@ -0,0 +1,5 @@
+import { DestructuringPattern } from './DestructuringPattern'
+import { IdentifierPattern } from './IdentifierPattern'
+import { LiteralPattern } from './LiteralPattern'
+
+export type Pattern = DestructuringPattern | IdentifierPattern | LiteralPattern
diff --git a/.yalc/tony-lang/src/ast/PatternPair.ts b/.yalc/tony-lang/src/ast/PatternPair.ts
new file mode 100644
index 0000000..3a92b93
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/PatternPair.ts
@@ -0,0 +1,26 @@
+import { Expression } from './Expression'
+import { Pattern } from './Pattern'
+import { ShorthandAccessIdentifier } from './ShorthandAccessIdentifier'
+import { SyntaxNode } from './SyntaxNode'
+
+type Key = ShorthandAccessIdentifier | Expression
+
+export class PatternPair extends SyntaxNode {
+  private _key: Key
+  private _value: Pattern
+
+  constructor(key: Key, value: Pattern) {
+    super()
+
+    this._key = key
+    this._value = value
+  }
+
+  get key(): Key {
+    return this._key
+  }
+
+  get value(): Pattern {
+    return this._value
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Pipeline.ts b/.yalc/tony-lang/src/ast/Pipeline.ts
new file mode 100644
index 0000000..55bbcfb
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Pipeline.ts
@@ -0,0 +1,22 @@
+import { Expression } from './Expression'
+import { SyntaxNode } from './SyntaxNode'
+
+export class Pipeline extends SyntaxNode {
+  private _argument: Expression
+  private _value: Expression
+
+  constructor(value: Expression, argument: Expression) {
+    super()
+
+    this._argument = argument
+    this._value = value
+  }
+
+  get argument(): Expression {
+    return this._argument
+  }
+
+  get value(): Expression {
+    return this._value
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/PrefixApplication.ts b/.yalc/tony-lang/src/ast/PrefixApplication.ts
new file mode 100644
index 0000000..84f132a
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/PrefixApplication.ts
@@ -0,0 +1,23 @@
+import { Expression } from './Expression'
+import { Identifier } from './Identifier'
+import { SyntaxNode } from './SyntaxNode'
+
+export class PrefixApplication extends SyntaxNode {
+  private _argument: Expression
+  private _value: Identifier
+
+  constructor(value: Identifier, argument: Expression) {
+    super()
+
+    this._argument = argument
+    this._value = value
+  }
+
+  get argument(): Expression {
+    return this._argument
+  }
+
+  get value(): Identifier {
+    return this._value
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Program.ts b/.yalc/tony-lang/src/ast/Program.ts
new file mode 100644
index 0000000..582db9e
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Program.ts
@@ -0,0 +1,16 @@
+import { Expression } from './Expression'
+import { SyntaxNode } from './SyntaxNode'
+
+export class Program extends SyntaxNode {
+  private _expressions: Expression[]
+
+  constructor(expressions: Expression[]) {
+    super()
+
+    this._expressions = expressions
+  }
+
+  get expressions(): Expression[] {
+    return this._expressions
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Regex.ts b/.yalc/tony-lang/src/ast/Regex.ts
new file mode 100644
index 0000000..f3da867
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Regex.ts
@@ -0,0 +1,19 @@
+import { SyntaxNode } from './SyntaxNode'
+
+export class Regex extends SyntaxNode {
+  private _text: string
+
+  constructor(text: string) {
+    super()
+
+    this._text = text
+  }
+
+  get text(): string {
+    return this._text
+  }
+
+  get value(): RegExp {
+    return new RegExp(this.text)
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/Rest.ts b/.yalc/tony-lang/src/ast/Rest.ts
new file mode 100644
index 0000000..f8ff4a6
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Rest.ts
@@ -0,0 +1,20 @@
+import { IdentifierPattern } from './IdentifierPattern'
+import { SyntaxNode } from './SyntaxNode'
+
+export abstract class Rest extends SyntaxNode {
+  private _name: IdentifierPattern
+
+  constructor(name: IdentifierPattern) {
+    super()
+
+    this._name = name
+  }
+
+  get name(): IdentifierPattern {
+    return this._name
+  }
+}
+
+export class RestList extends Rest {}
+export class RestMap extends Rest {}
+export class RestTuple extends Rest {}
diff --git a/.yalc/tony-lang/src/ast/Return.ts b/.yalc/tony-lang/src/ast/Return.ts
new file mode 100644
index 0000000..3b7ea45
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Return.ts
@@ -0,0 +1,16 @@
+import { Expression } from './Expression'
+import { SyntaxNode } from './SyntaxNode'
+
+export class Return extends SyntaxNode {
+  private _value: Expression | undefined
+
+  constructor(value?: Expression) {
+    super()
+
+    this._value = value
+  }
+
+  get value(): Expression | undefined {
+    return this._value
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/ShorthandAccessIdentifier.ts b/.yalc/tony-lang/src/ast/ShorthandAccessIdentifier.ts
new file mode 100644
index 0000000..42257f4
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/ShorthandAccessIdentifier.ts
@@ -0,0 +1,21 @@
+import { SyntaxNode } from './SyntaxNode'
+
+export class ShorthandAccessIdentifier extends SyntaxNode {
+  private _name: string
+  private _transformedName: string | undefined
+
+  constructor(name: string, transformedName?: string) {
+    super()
+
+    this._name = name
+    this._transformedName = transformedName
+  }
+
+  get name(): string {
+    return this._name
+  }
+
+  get transformedName(): string | undefined {
+    return this._transformedName
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/ShorthandPairIdentifier.ts b/.yalc/tony-lang/src/ast/ShorthandPairIdentifier.ts
new file mode 100644
index 0000000..57177ca
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/ShorthandPairIdentifier.ts
@@ -0,0 +1,21 @@
+import { SyntaxNode } from './SyntaxNode'
+
+export class ShorthandPairIdentifier extends SyntaxNode {
+  private _name: string
+  private _transformedName: string
+
+  constructor(name: string, transformedName: string) {
+    super()
+
+    this._name = name
+    this._transformedName = transformedName
+  }
+
+  get name(): string {
+    return this._name
+  }
+
+  get transformedName(): string {
+    return this._transformedName
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/ShorthandPairIdentifierPattern.ts b/.yalc/tony-lang/src/ast/ShorthandPairIdentifierPattern.ts
new file mode 100644
index 0000000..78548b8
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/ShorthandPairIdentifierPattern.ts
@@ -0,0 +1,3 @@
+import { IdentifierPattern } from './IdentifierPattern'
+
+export class ShorthandPairIdentifierPattern extends IdentifierPattern {}
diff --git a/.yalc/tony-lang/src/ast/Spread.ts b/.yalc/tony-lang/src/ast/Spread.ts
new file mode 100644
index 0000000..1de8cea
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Spread.ts
@@ -0,0 +1,20 @@
+import { Expression } from './Expression'
+import { SyntaxNode } from './SyntaxNode'
+
+export abstract class Spread extends SyntaxNode {
+  private _value: Expression
+
+  constructor(value: Expression) {
+    super()
+
+    this._value = value
+  }
+
+  get value(): Expression {
+    return this._value
+  }
+}
+
+export class SpreadList extends Spread {}
+export class SpreadMap extends Spread {}
+export class SpreadTuple extends Spread {}
diff --git a/.yalc/tony-lang/src/ast/String.ts b/.yalc/tony-lang/src/ast/String.ts
new file mode 100644
index 0000000..d13fa66
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/String.ts
@@ -0,0 +1,22 @@
+import { Interpolation } from './Interpolation'
+import { SyntaxNode } from './SyntaxNode'
+
+export class String extends SyntaxNode {
+  private _content: string
+  private _interpolations: Interpolation[]
+
+  constructor(content: string, interpolations: Interpolation[]) {
+    super()
+
+    this._content = content
+    this._interpolations = interpolations
+  }
+
+  get content(): string {
+    return this._content
+  }
+
+  get interpolations(): Interpolation[] {
+    return this._interpolations
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/StringPattern.ts b/.yalc/tony-lang/src/ast/StringPattern.ts
new file mode 100644
index 0000000..f96a6bc
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/StringPattern.ts
@@ -0,0 +1,15 @@
+import { SyntaxNode } from './SyntaxNode'
+
+export class StringPattern extends SyntaxNode {
+  private _content: string
+
+  constructor(content: string) {
+    super()
+
+    this._content = content
+  }
+
+  get content(): string {
+    return this._content
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/SyntaxNode.ts b/.yalc/tony-lang/src/ast/SyntaxNode.ts
new file mode 100644
index 0000000..f01b127
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/SyntaxNode.ts
@@ -0,0 +1 @@
+export abstract class SyntaxNode {}
diff --git a/.yalc/tony-lang/src/ast/Tuple.ts b/.yalc/tony-lang/src/ast/Tuple.ts
new file mode 100644
index 0000000..a8e6949
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/Tuple.ts
@@ -0,0 +1,19 @@
+import { Expression } from './Expression'
+import { SpreadTuple } from './Spread'
+import { SyntaxNode } from './SyntaxNode'
+
+type Element = Expression | SpreadTuple
+
+export class Tuple extends SyntaxNode {
+  private _elements: Element[]
+
+  constructor(elements: Element[]) {
+    super()
+
+    this._elements = elements
+  }
+
+  get elements(): Element[] {
+    return this._elements
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/TuplePattern.ts b/.yalc/tony-lang/src/ast/TuplePattern.ts
new file mode 100644
index 0000000..f8ee3ca
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/TuplePattern.ts
@@ -0,0 +1,16 @@
+import { Pattern } from './Pattern'
+import { SyntaxNode } from './SyntaxNode'
+
+export class TuplePattern extends SyntaxNode {
+  private _elements: Pattern[]
+
+  constructor(elements: Pattern[]) {
+    super()
+
+    this._elements = elements
+  }
+
+  get elements(): Pattern[] {
+    return this._elements
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/When.ts b/.yalc/tony-lang/src/ast/When.ts
new file mode 100644
index 0000000..ff4f61a
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/When.ts
@@ -0,0 +1,23 @@
+import { Block } from './Block'
+import { Pattern } from './Pattern'
+import { SyntaxNode } from './SyntaxNode'
+
+export class When extends SyntaxNode {
+  private _body: Block
+  private _patterns: Pattern[]
+
+  constructor(patterns: Pattern[], body: Block) {
+    super()
+
+    this._body = body
+    this._patterns = patterns
+  }
+
+  get body(): Block {
+    return this._body
+  }
+
+  get patterns(): Pattern[] {
+    return this._patterns
+  }
+}
diff --git a/.yalc/tony-lang/src/ast/index.ts b/.yalc/tony-lang/src/ast/index.ts
new file mode 100644
index 0000000..cce1319
--- /dev/null
+++ b/.yalc/tony-lang/src/ast/index.ts
@@ -0,0 +1,51 @@
+export { Abstraction } from './Abstraction'
+export { AbstractionBranch } from './AbstractionBranch'
+export { Access } from './Access'
+export { Application } from './Application'
+export { Argument } from './Argument'
+export { Assignment, AssignablePattern } from './Assignment'
+export { Block } from './Block'
+export { Boolean } from './Boolean'
+export { Case } from './Case'
+export { Declaration } from './Declaration'
+export { DestructuringPattern } from './DestructuringPattern'
+export { ElseIf } from './ElseIf'
+export { Export } from './Export'
+export { Expression } from './Expression'
+export { ExpressionPair } from './ExpressionPair'
+export { Generator } from './Generator'
+export { Identifier } from './Identifier'
+export { IdentifierPattern } from './IdentifierPattern'
+export { If } from './If'
+export { Import } from './Import'
+export { InfixApplication } from './InfixApplication'
+export { Interpolation } from './Interpolation'
+export { List } from './List'
+export { ListComprehension } from './ListComprehension'
+export { ListPattern } from './ListPattern'
+export { Literal } from './Literal'
+export { LiteralPattern } from './LiteralPattern'
+export { Map, MapElement } from './Map'
+export { MapPattern, MapPatternElement } from './MapPattern'
+export { Module } from './Module'
+export { Number } from './Number'
+export { Parameters } from './Parameters'
+export { ParametricType } from './ParametricType'
+export { Pattern } from './Pattern'
+export { PatternPair } from './PatternPair'
+export { Pipeline } from './Pipeline'
+export { PrefixApplication } from './PrefixApplication'
+export { Program } from './Program'
+export { Regex } from './Regex'
+export { Rest, RestList, RestMap, RestTuple } from './Rest'
+export { Return } from './Return'
+export { ShorthandAccessIdentifier } from './ShorthandAccessIdentifier'
+export { ShorthandPairIdentifier } from './ShorthandPairIdentifier'
+export { ShorthandPairIdentifierPattern } from './ShorthandPairIdentifierPattern'
+export { Spread, SpreadList, SpreadMap, SpreadTuple } from './Spread'
+export { String } from './String'
+export { StringPattern } from './StringPattern'
+export { SyntaxNode } from './SyntaxNode'
+export { Tuple } from './Tuple'
+export { TuplePattern } from './TuplePattern'
+export { When } from './When'
diff --git a/.yalc/tony-lang/src/code_generation/GenerateCode.ts b/.yalc/tony-lang/src/code_generation/GenerateCode.ts
index 9a6216a..bd12616 100644
--- a/.yalc/tony-lang/src/code_generation/GenerateCode.ts
+++ b/.yalc/tony-lang/src/code_generation/GenerateCode.ts
@@ -1,3 +1,4 @@
+import * as AST from '../ast'
 import {
   CollectDefaultValues,
   GenerateBlock,
@@ -11,31 +12,26 @@ import {
   TRANSFORM_PLACEHOLDER_ARGUMENT,
   TRANSFORM_REST_PATTERN,
 } from '../constants'
-import Parser from 'tree-sitter'
-import { isNotUndefined } from '../utilities'
 
 export const INTERNAL_TEMP_TOKEN = Object.freeze('#TONY_INTERNAL_TEMP')
 
 export class GenerateCode {
   private _fileScope: FileModuleScope
-  private _listComprehensionGeneratorCountStack: number[] = []
-
   private _walkFileModuleScope: WalkFileModuleScope
 
   constructor(fileScope: FileModuleScope) {
     this._fileScope = fileScope
-
     this._walkFileModuleScope = new WalkFileModuleScope(fileScope)
   }
 
   perform = (): string => {
     assert(
-      this._fileScope.tree !== undefined,
-      'Syntax tree of file scope should be present.',
+      this._fileScope.annotatedTree !== undefined,
+      'Annotated syntax tree of file scope should be present.',
     )
 
     try {
-      return this.handleProgram(this._fileScope.tree.rootNode)
+      return this.handleProgram(this._fileScope.annotatedTree)
     } catch (error) {
       if (error instanceof CompileError)
         error.filePath = this._fileScope.filePath
@@ -44,128 +40,110 @@ export class GenerateCode {
   }
 
   // eslint-disable-next-line max-lines-per-function
-  traverse = (node: Parser.SyntaxNode): string | undefined => {
-    switch (node.type) {
-      case 'abstraction':
-        return this.handleAbstraction(node)
-      case 'abstraction_branch':
-        return this.handleAbstractionBranch(node)
-      case 'access':
-        return this.handleAccess(node)
-      case 'application':
-        return this.handleApplication(node)
-      case 'argument':
-        return this.handleArgument(node)
-      case 'arguments':
-        return this.handleArguments(node)
-      case 'assignment':
-        return this.handleAssignment(node)
-      case 'block':
-        return this.handleBlock(node)
-      case 'boolean':
-        return node.text
-      case 'case':
-        return this.handleCase(node)
-      case 'comment':
-        return
-      case 'else_if_clause':
-        return this.handleElseIfClause(node)
-      case 'else_if_clauses':
-        return this.handleElseIfClauses(node)
-      case 'export':
-        return this.handleExport(node)
-      case 'expression_pair':
-        return this.handleExpressionPair(node)
-      case 'generator':
-        return this.handleGenerator(node)
-      case 'generators':
-        return this.handleGenerators(node)
-      case 'identifier':
-        return this.handleIdentifier(node)
-      case 'identifier_pattern':
-        return this.handleIdentifierPattern(node)
-      case 'identifier_pattern_name':
-        return this.handleIdentifierPatternName(node)
-      case 'if':
-        return this.handleIf(node)
-      case 'import':
-        return
-      case 'infix_application':
-        return this.handleInfixApplication(node)
-      case 'interpolation':
-        return this.handleInterpolation(node)
-      case 'list':
-        return this.handleList(node)
-      case 'list_comprehension':
-        return this.handleListComprehension(node)
-      case 'list_pattern':
-        return this.handleListPattern(node)
-      case 'map':
-        return this.handleMap(node)
-      case 'map_pattern':
-        return this.handleMapPattern(node)
-      case 'module':
-        return this.handleModule(node)
-      case 'number':
-        return node.text
-      case 'parameters':
-        return this.handleParameters(node)
-      case 'pattern_list':
-        return this.handlePatternList(node)
-      case 'pattern_pair':
-        return this.handlePatternPair(node)
-      case 'pipeline':
-        return this.handlePipeline(node)
-      case 'prefix_application':
-        return this.handlePrefixApplication(node)
-      case 'program':
-        return this.handleProgram(node)
-      case 'regex':
-        return node.text
-      case 'rest_list':
-        return this.handleRestList(node)
-      case 'rest_map':
-        return this.handleRestMap(node)
-      case 'rest_tuple':
-        return this.handleRestTuple(node)
-      case 'return':
-        return this.handleReturn(node)
-      case 'shorthand_access_identifier':
-        return this.handleShorthandAccessIdentifier(node)
-      case 'shorthand_pair_identifier':
-        return this.handleShorthandPairIdentifier(node)
-      case 'shorthand_pair_identifier_pattern':
-        return this.handleShorthandPairIdentifierPattern(node)
-      case 'spread_list':
-      case 'spread_map':
-      case 'spread_tuple':
-        return this.handleSpread(node)
-      case 'string':
-        return this.handleString(node)
-      case 'string_pattern':
-        return this.handleStringPattern(node)
-      case 'tuple':
-        return this.handleTuple(node)
-      case 'tuple_pattern':
-        return this.handleTuplePattern(node)
-      case 'type':
-        return this.handleType(node)
-      case 'when_clause':
-        return this.handleWhenClause(node)
-      case 'when_clauses':
-        return this.handleWhenClauses(node)
-      default:
-        throw new InternalError(
-          'GenerateCode: Could not find generator for AST node ' +
-            `'${node.type}'.`,
-        )
-    }
+  traverse = (node: AST.SyntaxNode): string => {
+    if (node.constructor === AST.Abstraction)
+      return this.handleAbstraction(node as AST.Abstraction)
+    else if (node.constructor === AST.AbstractionBranch)
+      return this.handleAbstractionBranch(node as AST.AbstractionBranch)
+    else if (node.constructor === AST.Access)
+      return this.handleAccess(node as AST.Access)
+    else if (node.constructor === AST.Application)
+      return this.handleApplication(node as AST.Application)
+    else if (node.constructor === AST.Argument)
+      return this.handleArgument(node as AST.Argument)
+    else if (node.constructor === AST.Assignment)
+      return this.handleAssignment(node as AST.Assignment)
+    else if (node.constructor === AST.Block)
+      return this.handleBlock(node as AST.Block)
+    else if (node.constructor === AST.Boolean) return (node as AST.Boolean).text
+    else if (node.constructor === AST.Case)
+      return this.handleCase(node as AST.Case)
+    else if (node.constructor === AST.ElseIf)
+      return this.handleElseIf(node as AST.ElseIf)
+    else if (node.constructor === AST.Export)
+      return this.handleExport(node as AST.Export)
+    else if (node.constructor === AST.ExpressionPair)
+      return this.handleExpressionPair(node as AST.ExpressionPair)
+    else if (node.constructor === AST.Generator)
+      return this.handleGenerator(node as AST.Generator)
+    else if (node.constructor === AST.Identifier)
+      return this.handleIdentifier(node as AST.Identifier)
+    else if (node.constructor === AST.IdentifierPattern)
+      return this.handleIdentifierPattern(node as AST.IdentifierPattern)
+    else if (node.constructor === AST.If) return this.handleIf(node as AST.If)
+    else if (node.constructor === AST.Import) return ''
+    else if (node.constructor === AST.InfixApplication)
+      return this.handleInfixApplication(node as AST.InfixApplication)
+    else if (node.constructor === AST.Interpolation)
+      return this.handleInterpolation(node as AST.Interpolation)
+    else if (node.constructor === AST.List)
+      return this.handleList(node as AST.List)
+    else if (node.constructor === AST.ListComprehension)
+      return this.handleListComprehension(node as AST.ListComprehension)
+    else if (node.constructor === AST.ListPattern)
+      return this.handleListPattern(node as AST.ListPattern)
+    else if (node.constructor === AST.Map)
+      return this.handleMap(node as AST.Map)
+    else if (node.constructor === AST.MapPattern)
+      return this.handleMapPattern(node as AST.MapPattern)
+    else if (node.constructor === AST.Module)
+      return this.handleModule(node as AST.Module)
+    else if (node.constructor === AST.Number) return (node as AST.Number).text
+    else if (node.constructor === AST.Parameters)
+      return this.handleParameters(node as AST.Parameters)
+    else if (node.constructor === AST.ParametricType)
+      return (node as AST.ParametricType).name
+    else if (node.constructor === AST.PatternPair)
+      return this.handlePatternPair(node as AST.PatternPair)
+    else if (node.constructor === AST.Pipeline)
+      return this.handlePipeline(node as AST.Pipeline)
+    else if (node.constructor === AST.PrefixApplication)
+      return this.handlePrefixApplication(node as AST.PrefixApplication)
+    else if (node.constructor === AST.Regex) return (node as AST.Regex).text
+    else if (
+      node.constructor === AST.RestList ||
+      node.constructor === AST.RestTuple
+    )
+      return this.handleRestListOrRestTuple(
+        node as AST.RestList | AST.RestTuple,
+      )
+    else if (node.constructor === AST.RestMap)
+      return this.handleRestMap(node as AST.RestMap)
+    else if (node.constructor === AST.Return)
+      return this.handleReturn(node as AST.Return)
+    else if (node.constructor === AST.ShorthandAccessIdentifier)
+      return this.handleShorthandAccessIdentifier(
+        node as AST.ShorthandAccessIdentifier,
+      )
+    else if (node.constructor === AST.ShorthandPairIdentifier)
+      return this.handleShorthandPairIdentifier(
+        node as AST.ShorthandPairIdentifier,
+      )
+    else if (node.constructor === AST.ShorthandPairIdentifierPattern)
+      return this.handleShorthandPairIdentifierPattern(
+        node as AST.ShorthandPairIdentifierPattern,
+      )
+    else if (node.constructor === AST.Spread)
+      return this.handleSpread(node as AST.Spread)
+    else if (node.constructor === AST.String)
+      return this.handleString(node as AST.String)
+    else if (node.constructor === AST.StringPattern)
+      return this.handleStringPattern(node as AST.StringPattern)
+    else if (node.constructor === AST.Tuple)
+      return this.handleTuple(node as AST.Tuple)
+    else if (node.constructor === AST.TuplePattern)
+      return this.handleTuplePattern(node as AST.TuplePattern)
+    else if (node.constructor === AST.When)
+      return this.handleWhen(node as AST.When)
+
+    throw new InternalError(
+      'Could not find generator for AST node ' + `'${node.constructor.name}'.`,
+    )
   }
 
-  private handleAbstraction = (node: Parser.SyntaxNode): string => {
-    const branches = node.namedChildren
-      .map((element) => this.traverse(element))
-      .filter(isNotUndefined)
+  private handleAbstraction = (node: AST.Abstraction): string => {
+    const branches = node.branches
+      .map((branch) => this.traverse(branch))
       .join(',')
 
     return (
@@ -174,14 +152,14 @@ export class GenerateCode {
     )
   }
 
-  private handleAbstractionBranch = (node: Parser.SyntaxNode): string => {
+  private handleAbstractionBranch = (node: AST.AbstractionBranch): string => {
     this._walkFileModuleScope.peekBlock()
-    const parameters = this.traverse(node.namedChild(0)!)!
+    const parameters = this.traverse(node.parameters)
     this._walkFileModuleScope.leaveBlock()
 
-    const body = this.traverse(node.namedChild(1)!)
+    const body = this.traverse(node.body)
     const [pattern, identifiers] = ResolvePattern.perform(parameters)
-    const defaults = new CollectDefaultValues(this).perform(node.namedChild(0)!)
+    const defaults = new CollectDefaultValues(this).perform(node.parameters)
 
     return (
       `[${pattern},${defaults},(match)=>{` +
@@ -189,55 +167,42 @@ export class GenerateCode {
     )
   }
 
-  private handleAccess = (node: Parser.SyntaxNode): string => {
-    const left = this.traverse(node.namedChild(0)!)
-    const right = this.traverse(node.namedChild(1)!)
+  private handleAccess = (node: AST.Access): string =>
+    `${this.traverse(node.value)}[${this.traverse(node.accessor)}]`
 
-    return `${left}[${right}]`
-  }
-
-  private handleApplication = (node: Parser.SyntaxNode): string => {
-    const abstraction = this.traverse(node.namedChild(0)!)
-    const args = this.traverse(node.namedChild(1)!)
-
-    return `${abstraction}(${args})`
-  }
-
-  private handleArgument = (node: Parser.SyntaxNode): string => {
-    if (node.namedChildCount == 0) return `"${TRANSFORM_PLACEHOLDER_ARGUMENT}"`
-
-    const expression = this.traverse(node.namedChild(0)!)!
-    return expression
-  }
-
-  private handleArguments = (node: Parser.SyntaxNode): string => {
-    const args = node.namedChildren
+  private handleApplication = (node: AST.Application): string =>
+    `${this.traverse(node.value)}(${node.arguments
       .map((argument) => this.traverse(argument))
-      .filter(isNotUndefined)
-      .join(',')
+      .join(',')})`
+
+  private handleArgument = (node: AST.Argument): string => {
+    if (node.value === undefined) return `"${TRANSFORM_PLACEHOLDER_ARGUMENT}"`
 
-    return args
+    return this.traverse(node.value)
   }
 
-  private handleAssignment = (node: Parser.SyntaxNode): string => {
-    const left = this.traverse(node.namedChild(0)!)!
-    const right = this.traverse(node.namedChild(1)!)
-    const [pattern, identifiers] = ResolvePattern.perform(left)
-    const defaults = new CollectDefaultValues(this).perform(node.namedChild(0)!)
+  private handleAssignment = (node: AST.Assignment): string => {
+    const [pattern, identifiers] = ResolvePattern.perform(
+      this.traverse(node.pattern),
+    )
+    const defaults = new CollectDefaultValues(this).perform(node.pattern)
 
     return (
-      `(()=>{const value=${right};[${identifiers.join(',')}]=new stdlib.` +
+      `(()=>{const value=${this.traverse(node.value)};[${identifiers.join(
+        ',',
+      )}]=new stdlib.` +
       `PatternMatch({defaults:${defaults},overmatching:true}).perform(` +
       `${pattern},value);return value})()`
     )
   }
 
-  private handleBlock = (node: Parser.SyntaxNode): string => {
+  private handleBlock = (node: AST.Block): string => {
     this._walkFileModuleScope.enterBlock()
-    const expressions = node.namedChildren
-      .map((expression) => this.traverse(expression))
-      .filter(isNotUndefined)
-    const endsWithReturn = node.lastNamedChild!.type === 'return'
+    const expressions = node.expressions.map((expression) =>
+      this.traverse(expression),
+    )
+    const endsWithReturn =
+      node.expressions[node.expressions.length - 1] instanceof AST.Return
     const block = new GenerateBlock(this._walkFileModuleScope.scope).perform(
       expressions,
       endsWithReturn,
@@ -247,235 +212,146 @@ export class GenerateCode {
     return block
   }
 
-  private handleCase = (node: Parser.SyntaxNode): string => {
-    const value = this.traverse(node.namedChild(0)!)
-    const branches = this.traverse(node.namedChild(1)!)
-    if (node.namedChildCount == 2)
+  private handleCase = (node: AST.Case): string => {
+    const value = this.traverse(node.value)
+    const branches = node.branches
+      .map((branch) => this.traverse(branch))
+      .join(',')
+    if (node.else === undefined)
       return `stdlib.ResolveAbstractionBranch.perform(${value},[${branches}])`
 
-    const defaultValue = this.traverse(node.namedChild(2)!)
+    const defaultValue = this.traverse(node.else)
     return (
       `stdlib.ResolveAbstractionBranch.perform(${value},[${branches}],` +
       `()=>${defaultValue},false)`
     )
   }
 
-  private handleElseIfClause = (node: Parser.SyntaxNode): string => {
-    const condition = this.traverse(node.namedChild(0)!)
-    const consequence = this.traverse(node.namedChild(1)!)
-
-    return `else if(${condition}){return ${consequence}}`
-  }
-
-  private handleElseIfClauses = (node: Parser.SyntaxNode): string => {
-    const clauses = node.namedChildren
-      .map((clause) => this.traverse(clause))
-      .filter(isNotUndefined)
-      .join('')
-
-    return clauses
-  }
-
-  private handleExport = (node: Parser.SyntaxNode): string => {
-    const declaration = this.traverse(node.namedChild(0)!)!
-
-    return declaration
-  }
-
-  private handleExpressionPair = (node: Parser.SyntaxNode): string => {
-    const left = this.traverse(node.namedChild(0)!)
-    const right = this.traverse(node.namedChild(1)!)
+  private handleElseIf = (node: AST.ElseIf): string =>
+    `else if(${this.traverse(node.condition)}){return ${this.traverse(
+      node.body,
+    )}}`
 
-    return `[${left}]:${right}`
-  }
-
-  private handleGenerator = (node: Parser.SyntaxNode): string => {
-    const name = node.namedChild(0)!.text
-    const binding = this._walkFileModuleScope.scope.resolveBinding(name)
-    assert(binding !== undefined, 'Binding should not be undefined.')
-    const value = this.traverse(node.namedChild(1)!)
-    if (node.namedChildCount == 2)
-      return `${value}.map((${binding.transformedName})=>`
+  private handleExport = (node: AST.Export): string =>
+    this.traverse(node.declaration)
 
-    const condition = this.traverse(node.namedChild(2)!)
-    return `${value}.map((${binding.transformedName})=>!${condition} ? "${INTERNAL_TEMP_TOKEN}" : `
-  }
+  private handleExpressionPair = (node: AST.ExpressionPair): string =>
+    `[${this.traverse(node.key)}]:${this.traverse(node.value)}`
 
-  private handleGenerators = (node: Parser.SyntaxNode): string => {
-    const generators = node.namedChildren
-      .map((generator) => this.traverse(generator))
-      .filter(isNotUndefined)
-      .join('')
+  private handleGenerator = (node: AST.Generator): string => {
+    const value = this.traverse(node.value)
+    if (node.condition === undefined)
+      return `${value}.map((${node.transformedName})=>`
 
-    this._listComprehensionGeneratorCountStack.push(node.namedChildCount)
-    return generators
+    return `${value}.map((${node.transformedName})=>!${this.traverse(
+      node.condition,
+    )} ? "${INTERNAL_TEMP_TOKEN}" : `
   }
 
-  private handleIdentifier = (node: Parser.SyntaxNode): string => {
-    const name = node.text
-    const binding = this._walkFileModuleScope.scope.resolveBinding(name)
+  private handleIdentifier = (node: AST.Identifier): string =>
+    node.transformedName
 
-    assert(binding !== undefined, 'Binding should not be undefined.')
+  private handleIdentifierPattern = (node: AST.IdentifierPattern): string =>
+    `"${INTERNAL_TEMP_TOKEN}${node.transformedName}"`
 
-    return binding.transformedName
-  }
+  private handleIf = (node: AST.If): string => {
+    let result = '(()=>{'
 
-  private handleIdentifierPattern = (node: Parser.SyntaxNode): string =>
-    this.traverse(node.namedChild(0)!)!
+    const condition = this.traverse(node.condition)
+    const body = this.traverse(node.body)
+    result += `if(${condition}){return ${body}}`
 
-  private handleIdentifierPatternName = (node: Parser.SyntaxNode): string => {
-    const name = node.text
-    const binding = this._walkFileModuleScope.scope.resolveBinding(name)
+    if (node.elseIfs.length > 0)
+      result += node.elseIfs.map((elseIf) => this.traverse(elseIf)).join('')
 
-    assert(binding !== undefined, 'Binding should not be undefined.')
-
-    return `"${INTERNAL_TEMP_TOKEN}${binding.transformedName}"`
-  }
-
-  // eslint-disable-next-line max-lines-per-function
-  private handleIf = (node: Parser.SyntaxNode): string => {
-    const condition = this.traverse(node.namedChild(0)!)
-    const consequence = this.traverse(node.namedChild(1)!)
-    if (node.namedChildCount == 2)
-      return `(()=>{if(${condition}){return ${consequence}}})()`
-
-    if (node.namedChild(node.namedChildCount - 1)!.type === 'else_if_clauses') {
-      const clauses = this.traverse(node.namedChild(2)!)
-
-      return `(()=>{if(${condition}){return ${consequence}}${clauses}})()`
-    } else if (node.namedChildCount == 3) {
-      const alternative = this.traverse(node.namedChild(2)!)
-
-      return (
-        `(()=>{if(${condition}){return ${consequence}}` +
-        `else{return ${alternative}}})()`
-      )
-    } else {
-      const clauses = this.traverse(node.namedChild(2)!)
-      const alternative = this.traverse(node.namedChild(3)!)
+    if (node.else) result += `else{return ${this.traverse(node.else)}}`
 
-      return (
-        `(()=>{if(${condition}){return ${consequence}}${clauses}` +
-        `else{return ${alternative}}})()`
-      )
-    }
+    result += '})()'
+    return result
   }
 
-  private handleInfixApplication = (node: Parser.SyntaxNode): string => {
-    const abstraction = this.traverse(node.namedChild(1)!)
-    const left = this.traverse(node.namedChild(0)!)
-    const right = this.traverse(node.namedChild(2)!)
-
-    return `${abstraction}(${left},${right})`
-  }
+  private handleInfixApplication = (node: AST.InfixApplication): string =>
+    `${this.traverse(node.value)}(${this.traverse(node.left)},${this.traverse(
+      node.right,
+    )})`
 
-  private handleInterpolation = (node: Parser.SyntaxNode): string =>
-    this.traverse(node.namedChild(0)!)!
+  private handleInterpolation = (node: AST.Interpolation): string =>
+    this.traverse(node.value)
 
-  private handleList = (node: Parser.SyntaxNode): string => {
-    const elements = node.namedChildren
+  private handleList = (node: AST.List): string => {
+    const elements = node.elements
       .map((element) => this.traverse(element))
-      .filter(isNotUndefined)
       .join(',')
 
     return `[${elements}]`
   }
 
-  private handleListComprehension = (node: Parser.SyntaxNode): string => {
+  private handleListComprehension = (node: AST.ListComprehension): string => {
     this._walkFileModuleScope.peekBlock()
-    const generators = this.traverse(node.namedChild(1)!)
+    const generators = node.generators
+      .map((generator) => this.traverse(generator))
+      .join('')
     this._walkFileModuleScope.leaveBlock()
 
-    const body = this.traverse(node.namedChild(0)!)
-    const generatorCount = this._listComprehensionGeneratorCountStack.pop()
-    assert(
-      generatorCount !== undefined,
-      'generatorCount should have been pushed when analyzing generators.',
-    )
+    const body = this.traverse(node.body)
 
     return (
-      `${generators}${body}${')'.repeat(generatorCount)}.flat(` +
-      `${generatorCount - 1}).filter(e=>e!=="${INTERNAL_TEMP_TOKEN}")`
+      `${generators}${body}${')'.repeat(node.generators.length)}.flat(` +
+      `${node.generators.length - 1}).filter(e=>e!=="${INTERNAL_TEMP_TOKEN}")`
     )
   }
 
-  private handleListPattern = (node: Parser.SyntaxNode): string => {
-    const elements = node.namedChildren
+  private handleListPattern = (node: AST.ListPattern): string => {
+    const elements = node.elements
       .map((element) => this.traverse(element))
-      .filter(isNotUndefined)
       .join(',')
 
     return `[${elements}]`
   }
 
-  private handleMap = (node: Parser.SyntaxNode): string => {
-    const elements = node.namedChildren
+  private handleMap = (node: AST.Map): string => {
+    const elements = node.elements
       .map((element) => this.traverse(element))
-      .filter(isNotUndefined)
       .join(',')
 
     return `{${elements}}`
   }
 
-  private handleMapPattern = (node: Parser.SyntaxNode): string => {
-    const elements = node.namedChildren
+  private handleMapPattern = (node: AST.MapPattern): string => {
+    const elements = node.elements
       .map((element) => this.traverse(element))
-      .filter(isNotUndefined)
       .join(',')
 
     return `{${elements}}`
   }
 
-  private handleModule = (node: Parser.SyntaxNode): string => {
-    const name = this.traverse(node.namedChild(0)!)
-    const body = this.traverse(node.namedChild(1)!)
+  private handleModule = (node: AST.Module): string => {
+    const name = this.traverse(node.name)
 
-    return `(()=>{${name}=${body};return ${name}})()`
+    return `(()=>{${name}=${this.traverse(node.body)};return ${name}})()`
   }
 
-  private handleParameters = (node: Parser.SyntaxNode): string => {
-    const parameters = node.namedChildren
+  private handleParameters = (node: AST.Parameters): string => {
+    const parameters = node.parameters
       .map((parameter) => this.traverse(parameter))
-      .filter(isNotUndefined)
       .join(',')
 
     return `[${parameters}]`
   }
 
-  private handlePatternList = (node: Parser.SyntaxNode): string => {
-    const patterns = node.namedChildren
-      .map((pattern) => this.traverse(pattern))
-      .filter(isNotUndefined)
-      .join(';')
-
-    return patterns
-  }
+  private handlePatternPair = (node: AST.PatternPair): string =>
+    `"[${this.traverse(node.key)}]":${this.traverse(node.value)}`
 
-  private handlePatternPair = (node: Parser.SyntaxNode): string => {
-    const left = this.traverse(node.namedChild(0)!)
-    const right = this.traverse(node.namedChild(1)!)
+  private handlePipeline = (node: AST.Pipeline): string =>
+    `${this.traverse(node.value)}(${this.traverse(node.argument)})`
 
-    return `"[${left}]":${right}`
-  }
+  private handlePrefixApplication = (node: AST.PrefixApplication): string =>
+    `${this.traverse(node.value)}(${this.traverse(node.argument)})`
 
-  private handlePipeline = (node: Parser.SyntaxNode): string => {
-    const left = this.traverse(node.namedChild(0)!)
-    const right = this.traverse(node.namedChild(1)!)
-
-    return `${right}(${left})`
-  }
-
-  private handlePrefixApplication = (node: Parser.SyntaxNode): string => {
-    const abstraction = this.traverse(node.namedChild(0)!)
-    const argument = this.traverse(node.namedChild(1)!)
-
-    return `${abstraction}(${argument})`
-  }
-
-  private handleProgram = (node: Parser.SyntaxNode): string => {
-    const expressions = node.namedChildren
-      .map((expression) => this.traverse(expression))
-      .filter(isNotUndefined)
+  private handleProgram = (node: AST.Program): string => {
+    const expressions = node.expressions.map((expression) =>
+      this.traverse(expression),
+    )
 
     assert(
       this._walkFileModuleScope.scope instanceof FileModuleScope,
@@ -487,114 +363,85 @@ export class GenerateCode {
     )
   }
 
-  private handleRestList = (node: Parser.SyntaxNode): string => {
-    const name = this.traverse(node.namedChild(0)!)!.slice(1, -1)
+  private handleRestListOrRestTuple = (
+    node: AST.RestList | AST.RestTuple,
+  ): string => {
+    const name = this.traverse(node.name).slice(1, -1)
 
     return `"${INTERNAL_TEMP_TOKEN}${name}"`
   }
 
-  private handleRestMap = (node: Parser.SyntaxNode): string => {
-    const name = this.traverse(node.namedChild(0)!)!.slice(1, -1)
+  private handleRestMap = (node: AST.RestMap): string => {
+    const name = this.traverse(node.name).slice(1, -1)
 
     return `"['${TRANSFORM_REST_PATTERN}']":"${name}"`
   }
 
-  private handleRestTuple = (node: Parser.SyntaxNode): string => {
-    const name = this.traverse(node.namedChild(0)!)!.slice(1, -1)
+  private handleReturn = (node: AST.Return): string => {
+    if (node.value === undefined) return 'return'
 
-    return `"${INTERNAL_TEMP_TOKEN}${name}"`
-  }
-
-  private handleReturn = (node: Parser.SyntaxNode): string => {
-    if (node.namedChildCount == 0) return 'return'
-
-    const value = this.traverse(node.namedChild(0)!)
-    return `return ${value}`
+    return `return ${this.traverse(node.value)}`
   }
 
   private handleShorthandAccessIdentifier = (
-    node: Parser.SyntaxNode,
-  ): string => {
-    const name = node.text
-
-    return `'${name}'`
-  }
-
-  private handleShorthandPairIdentifier = (node: Parser.SyntaxNode): string => {
-    const name = node.text
-    const binding = this._walkFileModuleScope.scope.resolveBinding(name)
+    node: AST.ShorthandAccessIdentifier,
+  ): string => `'${node.transformedName || node.name}'`
 
-    assert(binding !== undefined, 'Binding should not be undefined.')
-
-    return `${name}:${binding.transformedName}`
-  }
+  private handleShorthandPairIdentifier = (
+    node: AST.ShorthandPairIdentifier,
+  ): string => `${node.name}:${node.transformedName}`
 
   private handleShorthandPairIdentifierPattern = (
-    node: Parser.SyntaxNode,
-  ): string => {
-    const name = node.namedChild(0)!.text
-    const identifierPattern = this.traverse(node.namedChild(0)!)!
-
-    return `"${name}":${identifierPattern}`
-  }
-
-  private handleSpread = (node: Parser.SyntaxNode): string => {
-    const expression = this.traverse(node.namedChild(0)!)
+    node: AST.ShorthandPairIdentifierPattern,
+  ): string => `"${node.name}":"${INTERNAL_TEMP_TOKEN}${node.transformedName}"`
 
-    return `...${expression}`
-  }
+  private handleSpread = (node: AST.Spread): string =>
+    `...${this.traverse(node.value)}`
 
-  private handleString = (node: Parser.SyntaxNode): string => {
-    const interpolations = node.namedChildren
-      .filter((child) => child.type === 'interpolation')
-      .map((child) => this.handleInterpolation(child))
-    const content = ParseStringContent.perform(node.text)
+  private handleString = (node: AST.String): string => {
+    const interpolations = node.interpolations.map((child) =>
+      this.traverse(child),
+    )
+    const content = ParseStringContent.perform(node.content)
       .replace(/(?<!\\){/g, '${')
       .replace(/(?<=\${).+?(?=})/g, () => interpolations.shift()!)
 
     return `\`${content}\``
   }
 
-  private handleStringPattern = (node: Parser.SyntaxNode): string => {
-    const content = ParseStringContent.perform(node.text, '"')
+  private handleStringPattern = (node: AST.StringPattern): string => {
+    const content = ParseStringContent.perform(node.content, '"')
 
     return `"${content}"`
   }
 
-  private handleTuple = (node: Parser.SyntaxNode): string => {
-    const elements = node.namedChildren
+  private handleTuple = (node: AST.Tuple): string => {
+    const elements = node.elements
       .map((element) => this.traverse(element))
-      .filter(isNotUndefined)
       .join(',')
 
     return `[${elements}]`
   }
 
-  private handleTuplePattern = (node: Parser.SyntaxNode): string => {
-    const elements = node.namedChildren
+  private handleTuplePattern = (node: AST.TuplePattern): string => {
+    const elements = node.elements
       .map((element) => this.traverse(element))
-      .filter(isNotUndefined)
       .join(',')
 
     return `[${elements}]`
   }
 
-  private handleType = (node: Parser.SyntaxNode): string => node.text
-
-  // eslint-disable-next-line max-lines-per-function
-  private handleWhenClause = (node: Parser.SyntaxNode): string => {
+  private handleWhen = (node: AST.When): string => {
     this._walkFileModuleScope.peekBlock()
-    const patterns = this.traverse(node.namedChild(0)!)!
-      .split(';')
-      .map((pattern) => ResolvePattern.perform(pattern))
+    const patterns = node.patterns.map((pattern) =>
+      ResolvePattern.perform(this.traverse(pattern)),
+    )
     this._walkFileModuleScope.leaveBlock()
 
-    const body = this.traverse(node.namedChild(1)!)
-    const defaults = node
-      .namedChild(0)!
-      .namedChildren.map((pattern) =>
-        new CollectDefaultValues(this).perform(pattern),
-      )
+    const body = this.traverse(node.body)
+    const defaults = node.patterns.map((pattern) =>
+      new CollectDefaultValues(this).perform(pattern),
+    )
 
     return patterns
       .map(([pattern, identifiers], i) => {
@@ -605,13 +452,4 @@ export class GenerateCode {
       })
       .join(',')
   }
-
-  private handleWhenClauses = (node: Parser.SyntaxNode): string => {
-    const clauses = node.namedChildren
-      .map((clause) => this.traverse(clause))
-      .filter(isNotUndefined)
-      .join(',')
-
-    return clauses
-  }
 }
diff --git a/.yalc/tony-lang/src/code_generation/services/CollectDefaultValues.ts b/.yalc/tony-lang/src/code_generation/services/CollectDefaultValues.ts
index e866c1b..1557ab2 100644
--- a/.yalc/tony-lang/src/code_generation/services/CollectDefaultValues.ts
+++ b/.yalc/tony-lang/src/code_generation/services/CollectDefaultValues.ts
@@ -1,6 +1,6 @@
+import * as AST from '../../ast'
 import { GenerateCode } from '../GenerateCode'
-import { NODE_TYPES_WITH_DEFAULT_VALUES } from '../../constants'
-import Parser from 'tree-sitter'
+import { InternalError } from '../../errors'
 
 export class CollectDefaultValues {
   private codeGenerator: GenerateCode
@@ -9,18 +9,43 @@ export class CollectDefaultValues {
     this.codeGenerator = codeGenerator
   }
 
-  perform = (node: Parser.SyntaxNode): string => `[${this.rec(node).join(',')}]`
+  perform = (node: AST.Pattern | AST.Parameters): string =>
+    `[${this.traverse(node).join(',')}]`
 
-  private rec = (node: Parser.SyntaxNode): (string | undefined)[] => {
-    // prettier-ignore
-    if (NODE_TYPES_WITH_DEFAULT_VALUES.includes(node.type))
-      // eslint-disable-next-line @typescript-eslint/ban-ts-ignore
-      // @ts-ignore
-      if (node.defaultNode) return [this.codeGenerator.traverse(node.defaultNode)]
+  // eslint-disable-next-line max-lines-per-function
+  private traverse = (
+    node: AST.Pattern | AST.Parameters,
+  ): (string | undefined)[] => {
+    if (
+      node instanceof AST.IdentifierPattern ||
+      node instanceof AST.ShorthandPairIdentifierPattern
+    )
+      if (node.default) return [this.codeGenerator.traverse(node.default)]
       else return [undefined]
-    else
-      return node.namedChildren
-        .map(this.rec)
-        .reduce((acc, value) => acc.concat(value), [])
+    else if (node instanceof AST.ListPattern)
+      return this.handleWrapper(node.elements)
+    else if (node instanceof AST.MapPattern)
+      return this.handleWrapper(node.elements)
+    else if (node instanceof AST.Parameters)
+      return this.handleWrapper(node.parameters)
+    else if (node instanceof AST.TuplePattern)
+      return this.handleWrapper(node.elements)
+    else if (
+      node instanceof AST.Boolean ||
+      node instanceof AST.Number ||
+      node instanceof AST.Regex ||
+      node instanceof AST.StringPattern ||
+      node instanceof AST.ParametricType
+    )
+      return []
+
+    throw new InternalError(
+      'Could not find generator for AST node ' + `'${node.constructor.name}'.`,
+    )
   }
+
+  private handleWrapper = (
+    nodes: (AST.Pattern | AST.Parameters)[],
+  ): (string | undefined)[] =>
+    nodes.map(this.traverse).reduce((acc, value) => acc.concat(value), [])
 }
diff --git a/.yalc/tony-lang/src/code_generation/services/GenerateBlock.ts b/.yalc/tony-lang/src/code_generation/services/GenerateBlock.ts
index 1449029..d87c46b 100644
--- a/.yalc/tony-lang/src/code_generation/services/GenerateBlock.ts
+++ b/.yalc/tony-lang/src/code_generation/services/GenerateBlock.ts
@@ -30,7 +30,9 @@ export class GenerateBlock {
   }
 
   private generateDeclarations = (bindings: Binding[]): string => {
-    const declarations = bindings.map((binding) => binding.transformedName)
+    const declarations = [
+      ...new Set(bindings.map((binding) => binding.transformedName)),
+    ]
 
     return declarations.length > 0 ? `let ${declarations.join(',')}` : ''
   }
diff --git a/.yalc/tony-lang/src/code_generation/services/GenerateImport.ts b/.yalc/tony-lang/src/code_generation/services/GenerateImport.ts
index b59cc7b..8ace335 100644
--- a/.yalc/tony-lang/src/code_generation/services/GenerateImport.ts
+++ b/.yalc/tony-lang/src/code_generation/services/GenerateImport.ts
@@ -4,13 +4,13 @@ import {
   JAVASCRIPT_FILE_EXTENSION_REGEX,
   TARGET_FILE_EXTENSION,
 } from '../../constants'
-import { ImportBinding } from '../../symbol_table/models'
+import { Binding } from '../../symbol_table'
 import { InternalError } from '../../errors'
 
 const EXTERNAL_IMPORT_SUFFIX = Object.freeze('_EXT')
 
 export class GenerateImport {
-  perform = (sourcePath: string, bindings: ImportBinding[]): string => {
+  perform = (sourcePath: string, bindings: Binding[]): string => {
     if (FILE_EXTENSION_REGEX.test(sourcePath))
       return this.handleImport(sourcePath, bindings)
     else if (JAVASCRIPT_FILE_EXTENSION_REGEX.test(sourcePath))
@@ -23,19 +23,16 @@ export class GenerateImport {
 
   private handleImport = (
     sourcePath: string,
-    bindings: ImportBinding[],
+    bindings: Binding[],
     suffix?: string,
-    transformOriginalName = true,
   ): string => {
     const compiledSourcePath = GenerateImport.getCompiledSourcePath(sourcePath)
     const aliases = bindings
       .map((binding) => {
-        const originalName = transformOriginalName
-          ? binding.transformedOriginalName
-          : binding.originalName
-        const name = binding.transformedName
+        const name = binding.transformedImportName
+        const alias = binding.transformedName
 
-        return `${originalName} as ${name}${suffix ? suffix : ''}`
+        return `${name} as ${alias}${suffix ? suffix : ''}`
       })
       .join(',')
 
@@ -45,13 +42,12 @@ export class GenerateImport {
   // eslint-disable-next-line max-lines-per-function
   private handleJavaScript = (
     sourcePath: string,
-    bindings: ImportBinding[],
+    bindings: Binding[],
   ): string => {
     const importStatement = this.handleImport(
       sourcePath,
       bindings,
       EXTERNAL_IMPORT_SUFFIX,
-      false,
     )
     const currying = bindings
       .map((binding) => {
diff --git a/.yalc/tony-lang/src/code_generation/services/GenerateProgram.ts b/.yalc/tony-lang/src/code_generation/services/GenerateProgram.ts
index 49dd066..631a1af 100644
--- a/.yalc/tony-lang/src/code_generation/services/GenerateProgram.ts
+++ b/.yalc/tony-lang/src/code_generation/services/GenerateProgram.ts
@@ -1,5 +1,5 @@
-import { FileModuleScope, ImportBinding } from '../../symbol_table'
 import { DEFAULT_IMPORTS } from '../../constants'
+import { FileModuleScope } from '../../symbol_table'
 import { GenerateImport } from './GenerateImport'
 
 export class GenerateProgram {
@@ -17,9 +17,13 @@ export class GenerateProgram {
     )};${this.generateExports()}`
 
   private generateDeclarations = (): string => {
-    const declarations = this._scope.bindings
-      .filter((binding) => !binding.isImplicit)
-      .map((binding) => binding.transformedName)
+    const declarations = [
+      ...new Set(
+        this._scope.bindings
+          .filter((binding) => !binding.isImplicit)
+          .map((binding) => binding.transformedName),
+      ),
+    ]
 
     return declarations.length > 0 ? `let ${declarations.join(',')}` : ''
   }
@@ -27,7 +31,7 @@ export class GenerateProgram {
   private generateImports = (): string => {
     const importBindings = this._scope.bindings.filter(
       (binding) => binding.isImported,
-    ) as ImportBinding[]
+    )
 
     return this._scope.dependencies
       .map((sourcePath) => {
diff --git a/.yalc/tony-lang/src/code_generation/services/ParseStringContent.ts b/.yalc/tony-lang/src/code_generation/services/ParseStringContent.ts
index 57e5568..774bce9 100644
--- a/.yalc/tony-lang/src/code_generation/services/ParseStringContent.ts
+++ b/.yalc/tony-lang/src/code_generation/services/ParseStringContent.ts
@@ -1,11 +1,10 @@
 export class ParseStringContent {
   static perform = (text: string, qt = '`'): string => {
-    // removes on escape when there are an even number of escapes before a qt
+    // removes one escape when there are an even number of escapes before a qt
     // inside a string
     const regex = new RegExp(`(?<!\\\\)(\\\\\\\\)+(?!\\\\)(?=${qt})`, 'g')
 
     return text
-      .slice(1, -1)
       .replace(new RegExp(qt, 'g'), `\\${qt}`)
       .replace(regex, (s) => s.substring(1))
   }
diff --git a/.yalc/tony-lang/src/compile.ts b/.yalc/tony-lang/src/compile.ts
index f2efaba..53b0c0f 100644
--- a/.yalc/tony-lang/src/compile.ts
+++ b/.yalc/tony-lang/src/compile.ts
@@ -41,7 +41,7 @@ const inferTypes = (fileScopes: FileModuleScope[], verbose: boolean): void =>
     if (verbose)
       console.log(`Running type inference on ${fileScope.filePath}...`)
 
-    new InferTypes(fileScope).perform()
+    fileScope.annotatedTree = new InferTypes(fileScope).perform()
   })
 
 const generateCode = async (
diff --git a/.yalc/tony-lang/src/constants.ts b/.yalc/tony-lang/src/constants.ts
index 4e13a1d..f0cee39 100644
--- a/.yalc/tony-lang/src/constants.ts
+++ b/.yalc/tony-lang/src/constants.ts
@@ -15,10 +15,6 @@ export const IMPORT_FILE_EXTENSIONS = Object.freeze([
 export const OPERATOR_REGEX = Object.freeze(
   /(==|[!@$%^&*|<>~*\\\-+/.])[!@$%^&*|<>~*\\\-+/.=]*/,
 )
-export const NODE_TYPES_WITH_DEFAULT_VALUES = Object.freeze([
-  'identifier_pattern',
-  'shorthand_pair_identifier_pattern',
-])
 
 // standard library
 const STDLIB_PATH = Object.freeze(path.join(__dirname, 'stdlib'))
diff --git a/.yalc/tony-lang/src/errors/CompileError.ts b/.yalc/tony-lang/src/errors/CompileError.ts
index a352d69..0c227ce 100644
--- a/.yalc/tony-lang/src/errors/CompileError.ts
+++ b/.yalc/tony-lang/src/errors/CompileError.ts
@@ -30,10 +30,25 @@ export abstract class CompileError extends Error {
     this._filePath = value
   }
 
-  addContext = (node: Parser.SyntaxNode): void => {
+  private addContext = (node: Parser.SyntaxNode): void => {
     this._context = {
       start: node.startPosition,
       end: node.endPosition,
     }
   }
+
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  static addContext = <T extends Array<any>, U>(
+    fn: (node: Parser.SyntaxNode, ...args: T) => U,
+    node: Parser.SyntaxNode,
+    ...args: T
+  ): U => {
+    try {
+      return fn(node, ...args)
+    } catch (error) {
+      if (error instanceof CompileError && error.context === undefined)
+        error.addContext(node)
+      throw error
+    }
+  }
 }
diff --git a/.yalc/tony-lang/src/errors/IndeterminateTypeError.ts b/.yalc/tony-lang/src/errors/IndeterminateTypeError.ts
new file mode 100644
index 0000000..3ac3647
--- /dev/null
+++ b/.yalc/tony-lang/src/errors/IndeterminateTypeError.ts
@@ -0,0 +1,16 @@
+import { CompileError } from './CompileError'
+
+export class IndeterminateTypeError extends CompileError {
+  private _types: string[]
+
+  constructor(types: string[]) {
+    super(undefined)
+    this.name = this.constructor.name
+
+    this._types = types
+  }
+
+  get types(): string[] {
+    return this._types
+  }
+}
diff --git a/.yalc/tony-lang/src/errors/InternalTypeError.ts b/.yalc/tony-lang/src/errors/InternalTypeError.ts
new file mode 100644
index 0000000..c63cd88
--- /dev/null
+++ b/.yalc/tony-lang/src/errors/InternalTypeError.ts
@@ -0,0 +1,28 @@
+import { InternalError } from './InternalError'
+import { Type } from '../types'
+
+export type TypeMismatch = [string, string | undefined]
+
+export class InternalTypeError extends InternalError {
+  private _trace: TypeMismatch[]
+
+  constructor(expected: Type, actual: Type | undefined, message: string) {
+    super(message)
+    this.name = this.constructor.name
+
+    this._trace = [
+      [expected.toString(), actual ? actual.toString() : undefined],
+    ]
+  }
+
+  get trace(): TypeMismatch[] {
+    return this._trace
+  }
+
+  addTypeMismatch = (expected: Type, actual?: Type): void => {
+    this._trace = [
+      ...this.trace,
+      [expected.toString(), actual ? actual.toString() : undefined],
+    ]
+  }
+}
diff --git a/.yalc/tony-lang/src/errors/InvalidExternalTypeImportError.ts b/.yalc/tony-lang/src/errors/InvalidExternalTypeImportError.ts
new file mode 100644
index 0000000..ae4bb3d
--- /dev/null
+++ b/.yalc/tony-lang/src/errors/InvalidExternalTypeImportError.ts
@@ -0,0 +1,16 @@
+import { CompileError } from './CompileError'
+
+export class InvalidExternalTypeImportError extends CompileError {
+  private _type: string
+
+  constructor(type: string) {
+    super(undefined)
+    this.name = this.constructor.name
+
+    this._type = type
+  }
+
+  get type(): string {
+    return this._type
+  }
+}
diff --git a/.yalc/tony-lang/src/errors/InvalidModuleAccessError.ts b/.yalc/tony-lang/src/errors/InvalidModuleAccessError.ts
new file mode 100644
index 0000000..f22f17b
--- /dev/null
+++ b/.yalc/tony-lang/src/errors/InvalidModuleAccessError.ts
@@ -0,0 +1,22 @@
+import { CompileError } from './CompileError'
+
+export class InvalidModuleAccessError extends CompileError {
+  private _binding: string | undefined
+  private _type: string
+
+  constructor(type: string, binding?: string) {
+    super(undefined)
+    this.name = this.constructor.name
+
+    this._binding = binding
+    this._type = type
+  }
+
+  get binding(): string | undefined {
+    return this._binding
+  }
+
+  get type(): string {
+    return this._type
+  }
+}
diff --git a/.yalc/tony-lang/src/errors/InvalidPropertyAccessError.ts b/.yalc/tony-lang/src/errors/InvalidPropertyAccessError.ts
deleted file mode 100644
index a8998de..0000000
--- a/.yalc/tony-lang/src/errors/InvalidPropertyAccessError.ts
+++ /dev/null
@@ -1,28 +0,0 @@
-import { CompileError } from './CompileError'
-
-export class InvalidPropertyAccessError extends CompileError {
-  private _property: string
-  private _representation: string
-  private _type: string
-
-  constructor(property: string, type: string, representation: string) {
-    super(undefined)
-    this.name = this.constructor.name
-
-    this._property = property
-    this._type = type
-    this._representation = representation
-  }
-
-  get property(): string {
-    return this._property
-  }
-
-  get representation(): string {
-    return this._representation
-  }
-
-  get type(): string {
-    return this._type
-  }
-}
diff --git a/.yalc/tony-lang/src/errors/InvalidUseOfTypeAsValueError.ts b/.yalc/tony-lang/src/errors/InvalidUseOfTypeAsValueError.ts
new file mode 100644
index 0000000..5b43e36
--- /dev/null
+++ b/.yalc/tony-lang/src/errors/InvalidUseOfTypeAsValueError.ts
@@ -0,0 +1,16 @@
+import { CompileError } from './CompileError'
+
+export class InvalidUseOfTypeAsValueError extends CompileError {
+  private _type: string
+
+  constructor(type: string) {
+    super(undefined)
+    this.name = this.constructor.name
+
+    this._type = type
+  }
+
+  get type(): string {
+    return this._type
+  }
+}
diff --git a/.yalc/tony-lang/src/errors/MissingExternalImportTypeHintError.ts b/.yalc/tony-lang/src/errors/MissingExternalImportTypeHintError.ts
new file mode 100644
index 0000000..71df275
--- /dev/null
+++ b/.yalc/tony-lang/src/errors/MissingExternalImportTypeHintError.ts
@@ -0,0 +1,16 @@
+import { CompileError } from './CompileError'
+
+export class MissingExternalImportTypeHintError extends CompileError {
+  private _binding: string
+
+  constructor(binding: string) {
+    super(undefined)
+    this.name = this.constructor.name
+
+    this._binding = binding
+  }
+
+  get binding(): string {
+    return this._binding
+  }
+}
diff --git a/.yalc/tony-lang/src/errors/TypeError.ts b/.yalc/tony-lang/src/errors/TypeError.ts
index 1801f3b..1549bdc 100644
--- a/.yalc/tony-lang/src/errors/TypeError.ts
+++ b/.yalc/tony-lang/src/errors/TypeError.ts
@@ -1,28 +1,41 @@
 import { CompileError } from './CompileError'
-import { Type } from '../types'
-
-export type TypeMismatch = [string, string | undefined]
+import { InternalTypeError } from './InternalTypeError'
 
 export class TypeError extends CompileError {
-  private _typeTrace: TypeMismatch[]
+  private _trace: InternalTypeError[]
 
-  constructor(expected: Type, actual: Type | undefined, message: string) {
-    super(message)
+  constructor() {
+    super(undefined)
     this.name = this.constructor.name
 
-    this._typeTrace = [
-      [expected.toString(), actual ? actual.toString() : undefined],
-    ]
+    this._trace = TypeError.trace
+  }
+
+  get trace(): InternalTypeError[] {
+    return this._trace
+  }
+
+  static _trace: InternalTypeError[] = []
+
+  static get trace(): InternalTypeError[] {
+    return TypeError._trace
   }
 
-  get typeTrace(): TypeMismatch[] {
-    return this._typeTrace
+  static addError(error: InternalTypeError): void {
+    TypeError._trace = [...TypeError.trace, error]
   }
 
-  addTypeMismatch = (expected: Type, actual?: Type): void => {
-    this._typeTrace = [
-      ...this.typeTrace,
-      [expected.toString(), actual ? actual.toString() : undefined],
-    ]
+  static safe = <T>(fn: () => T): T | undefined => {
+    try {
+      return fn()
+    } catch (error) {
+      if (error instanceof InternalTypeError) {
+        TypeError.addError(error)
+
+        return
+      }
+
+      throw error
+    }
   }
 }
diff --git a/.yalc/tony-lang/src/errors/index.ts b/.yalc/tony-lang/src/errors/index.ts
index 062a54f..11906cf 100644
--- a/.yalc/tony-lang/src/errors/index.ts
+++ b/.yalc/tony-lang/src/errors/index.ts
@@ -3,9 +3,14 @@ export { CyclicDependenciesError } from './CyclicDependenciesError'
 export { DuplicateBindingError } from './DuplicateBindingError'
 export { ExportOutsideModuleScopeError } from './ExportOutsideModuleScopeError'
 export { ImportOutsideFileModuleScopeError } from './ImportOutsideFileModuleScopeError'
+export { IndeterminateTypeError } from './IndeterminateTypeError'
 export { assert, InternalError } from './InternalError'
-export { InvalidPropertyAccessError } from './InvalidPropertyAccessError'
+export { InternalTypeError } from './InternalTypeError'
+export { InvalidExternalTypeImportError } from './InvalidExternalTypeImportError'
+export { InvalidModuleAccessError } from './InvalidModuleAccessError'
+export { InvalidUseOfTypeAsValueError } from './InvalidUseOfTypeAsValueError'
 export { MissingBindingError } from './MissingBindingError'
+export { MissingExternalImportTypeHintError } from './MissingExternalImportTypeHintError'
 export { SyntaxError } from './SyntaxError'
 export { TypeError } from './TypeError'
 export { UnknownImportError } from './UnknownImportError'
diff --git a/.yalc/tony-lang/src/index.ts b/.yalc/tony-lang/src/index.ts
index fa65eaa..c4c0d9c 100644
--- a/.yalc/tony-lang/src/index.ts
+++ b/.yalc/tony-lang/src/index.ts
@@ -9,9 +9,14 @@ export {
   DuplicateBindingError,
   ExportOutsideModuleScopeError,
   ImportOutsideFileModuleScopeError,
+  IndeterminateTypeError,
   InternalError,
-  InvalidPropertyAccessError,
+  InternalTypeError,
+  InvalidExternalTypeImportError,
+  InvalidModuleAccessError,
+  InvalidUseOfTypeAsValueError,
   MissingBindingError,
+  MissingExternalImportTypeHintError,
   SyntaxError,
   TypeError,
   UnknownImportError,
diff --git a/.yalc/tony-lang/src/symbol_table/BuildFileModuleScope.ts b/.yalc/tony-lang/src/symbol_table/BuildFileModuleScope.ts
index 14c2214..8574850 100644
--- a/.yalc/tony-lang/src/symbol_table/BuildFileModuleScope.ts
+++ b/.yalc/tony-lang/src/symbol_table/BuildFileModuleScope.ts
@@ -1,33 +1,24 @@
 import {
-  Binding,
-  FileModuleScope,
-  GlobalScope,
-  IdentifierBinding,
-  ModuleScope,
-  NestedScope,
-  TypeBinding,
-} from './models'
-import {
-  BuildImportBindings,
+  BuildImports,
   BuildPatternBindings,
   UnifyPatternBindings,
 } from './services'
-import {
-  BuildRepresentation,
-  BuildType,
-  LIST_TYPE,
-  ParametricType,
-  RepresentationKind,
-  TypeVariable,
-} from '../types'
+import { BuildType, ModuleType } from '../types'
 import {
   CompileError,
-  DuplicateBindingError,
   ExportOutsideModuleScopeError,
   ImportOutsideFileModuleScopeError,
   MissingBindingError,
   assert,
 } from '../errors'
+import {
+  FileModuleScope,
+  GlobalScope,
+  IdentifierBindingTemplate,
+  ModuleBinding,
+  ModuleScope,
+  NestedScope,
+} from './models'
 import { IMPORT_FILE_EXTENSIONS } from '../constants'
 import Parser from 'tree-sitter'
 import { UnknownImportError } from '../errors/UnknownImportError'
@@ -58,7 +49,7 @@ export class BuildFileModuleScope {
       verbose: this._verbose,
     })
     try {
-      this.traverse(this._fileScope.tree.rootNode)
+      CompileError.addContext(this.traverse, this._fileScope.tree.rootNode)
     } catch (error) {
       if (error instanceof CompileError) error.filePath = this._filePath
       throw error
@@ -69,47 +60,43 @@ export class BuildFileModuleScope {
 
   // eslint-disable-next-line max-lines-per-function
   private traverse = (node: Parser.SyntaxNode): void => {
-    try {
-      switch (node.type) {
-        case 'abstraction_branch':
-          return this.handleAbstractionBranch(node)
-        case 'assignment':
-          return this.handleAssignment(node)
-        case 'block':
-          return this.handleBlock(node)
-        case 'export':
-          return this.handleExport(node)
-        case 'generator':
-          return this.handleGenerator(node)
-        case 'identifier':
-          return this.handleIdentifier(node)
-        case 'import':
-          return this.handleImport(node)
-        case 'list_comprehension':
-          return this.handleListComprehension(node)
-        case 'module':
-          return this.handleModule(node)
-        case 'parameters':
-          return this.handleParameters(node)
-        case 'pattern_list':
-          return this.handlePatternList(node)
-        case 'when_clause':
-          return this.handleWhenClause(node)
-        default:
-          node.namedChildren.forEach((child) => this.traverse(child))
-      }
-    } catch (error) {
-      if (error instanceof CompileError && error.context === undefined)
-        error.addContext(node)
-      throw error
+    switch (node.type) {
+      case 'abstraction_branch':
+        return this.handleAbstractionBranch(node)
+      case 'assignment':
+        return this.handleAssignment(node)
+      case 'block':
+        return this.handleBlock(node)
+      case 'export':
+        return this.handleExport(node)
+      case 'generator':
+        return this.handleGenerator(node)
+      case 'identifier':
+        return this.handleIdentifier(node)
+      case 'import':
+        return this.handleImport(node)
+      case 'list_comprehension':
+        return this.handleListComprehension(node)
+      case 'module':
+        return this.handleModule(node)
+      case 'parameters':
+        return this.handleParameters(node)
+      case 'pattern_list':
+        return this.handlePatternList(node)
+      case 'when_clause':
+        return this.handleWhenClause(node)
+      default:
+        node.namedChildren.forEach((child) =>
+          CompileError.addContext(this.traverse, child),
+        )
     }
   }
 
   private handleAbstractionBranch = (node: Parser.SyntaxNode): void => {
     this.enterBlock()
 
-    this.traverse(node.namedChild(0)!)
-    this.traverse(node.namedChild(1)!)
+    CompileError.addContext(this.traverse, node.namedChild(0)!)
+    CompileError.addContext(this.traverse, node.namedChild(1)!)
 
     this._scope.reduce()
     this.leaveBlock()
@@ -118,18 +105,22 @@ export class BuildFileModuleScope {
   private handleAssignment = (node: Parser.SyntaxNode): void => {
     const isExported = this.disableExports()
 
-    this.traverse(node.namedChild(0)!)
+    CompileError.addContext(this.traverse, node.namedChild(0)!)
     new BuildPatternBindings({ isExported, isImplicit: false })
       .perform(node.namedChild(0)!)
-      .forEach((binding) => this.addBinding(binding))
+      .forEach((bindingTemplate) =>
+        this._scope.addBindingTemplate(bindingTemplate),
+      )
 
-    this.traverse(node.namedChild(1)!)
+    CompileError.addContext(this.traverse, node.namedChild(1)!)
   }
 
   private handleBlock = (node: Parser.SyntaxNode): void => {
     this.enterBlock()
 
-    node.namedChildren.forEach((child) => this.traverse(child))
+    node.namedChildren.forEach((child) =>
+      CompileError.addContext(this.traverse, child),
+    )
 
     this.leaveBlock()
   }
@@ -139,28 +130,26 @@ export class BuildFileModuleScope {
       throw new ExportOutsideModuleScopeError()
 
     this.enableExports()
-    this.traverse(node.namedChild(0)!)
+    CompileError.addContext(this.traverse, node.namedChild(0)!)
   }
 
   private handleGenerator = (node: Parser.SyntaxNode): void => {
-    this.traverse(node.namedChild(1)!)
+    CompileError.addContext(this.traverse, node.namedChild(1)!)
 
     const name = node.namedChild(0)!.text
-    const binding = new IdentifierBinding(
-      name,
-      new ParametricType(LIST_TYPE, [new TypeVariable()]),
-      { isImplicit: true },
-    )
-    this.addBinding(binding)
+    const bindingTemplate = new IdentifierBindingTemplate(node, name, {
+      isImplicit: true,
+    })
+    this._scope.addBindingTemplate(bindingTemplate)
 
-    if (node.namedChildCount == 3) this.traverse(node.namedChild(2)!)
+    if (node.namedChildCount == 3)
+      CompileError.addContext(this.traverse, node.namedChild(2)!)
   }
 
   private handleIdentifier = (node: Parser.SyntaxNode): void => {
     const name = node.text
 
-    if (this._scope.resolveBinding(name) === undefined)
-      throw new MissingBindingError(name)
+    if (!this._scope.isBound(name)) throw new MissingBindingError(name)
   }
 
   private handleImport = (node: Parser.SyntaxNode): void => {
@@ -173,16 +162,16 @@ export class BuildFileModuleScope {
       throw new UnknownImportError(sourcePath)
     this._fileScope.addDependency(sourcePath)
 
-    new BuildImportBindings(sourcePath)
+    new BuildImports(sourcePath)
       .perform(node)
-      .forEach((binding) => this.addBinding(binding))
+      .forEach((imp) => this._fileScope.addImport(imp))
   }
 
   private handleListComprehension = (node: Parser.SyntaxNode): void => {
     this.enterBlock()
 
-    this.traverse(node.namedChild(1)!)
-    this.traverse(node.namedChild(0)!)
+    CompileError.addContext(this.traverse, node.namedChild(1)!)
+    CompileError.addContext(this.traverse, node.namedChild(0)!)
 
     this._scope.reduce()
     this.leaveBlock()
@@ -192,26 +181,21 @@ export class BuildFileModuleScope {
     this.enableDeclaration()
     const isExported = this.disableExports()
 
-    this.traverse(node.namedChild(1)!)
+    CompileError.addContext(this.traverse, node.namedChild(1)!)
 
-    const moduleScope = this._scope.lastNestedScope
-    const exportedBindings = moduleScope.bindings.filter(
-      (binding) => binding.isExported,
-    )
-    const representation = new BuildRepresentation().perform(
-      RepresentationKind.Instance,
-      exportedBindings,
-    )
-
-    const type = new BuildType().handleType(node.namedChild(0)!)
-    const binding = new TypeBinding(type, representation, { isExported })
-    this.addBinding(binding)
+    const moduleScope = this._scope.lastNestedScope!
+    const name = new BuildType().perform(node.namedChild(0)!)
+    const type = new ModuleType(moduleScope)
+    const binding = new ModuleBinding(node, name, type, { isExported })
+    this._scope.addBinding(binding)
   }
 
   private handleParameters = (node: Parser.SyntaxNode): void => {
     new BuildPatternBindings({ isExported: false, isImplicit: true })
       .perform(node)
-      .forEach((binding) => this.addBinding(binding))
+      .forEach((bindingTemplate) =>
+        this._scope.addBindingTemplate(bindingTemplate),
+      )
   }
 
   private handlePatternList = (node: Parser.SyntaxNode): void => {
@@ -224,14 +208,16 @@ export class BuildFileModuleScope {
 
     new UnifyPatternBindings()
       .perform(bindings)
-      .forEach((binding) => this.addBinding(binding))
+      .forEach((bindingTemplate) =>
+        this._scope.addBindingTemplate(bindingTemplate),
+      )
   }
 
   private handleWhenClause = (node: Parser.SyntaxNode): void => {
     this.enterBlock()
 
-    this.traverse(node.namedChild(0)!)
-    this.traverse(node.namedChild(1)!)
+    CompileError.addContext(this.traverse, node.namedChild(0)!)
+    CompileError.addContext(this.traverse, node.namedChild(1)!)
 
     this._scope.reduce()
     this.leaveBlock()
@@ -273,11 +259,4 @@ export class BuildFileModuleScope {
     this._exportBindings = false
     return value
   }
-
-  private addBinding = (binding: Binding): void => {
-    const matchingBinding = this._scope.resolveBinding(binding.name, 0)
-    if (matchingBinding) throw new DuplicateBindingError(matchingBinding.name)
-
-    this._scope.addBinding(binding)
-  }
 }
diff --git a/.yalc/tony-lang/src/symbol_table/WalkFileModuleScope.ts b/.yalc/tony-lang/src/symbol_table/WalkFileModuleScope.ts
index 2d6e885..8d9775e 100644
--- a/.yalc/tony-lang/src/symbol_table/WalkFileModuleScope.ts
+++ b/.yalc/tony-lang/src/symbol_table/WalkFileModuleScope.ts
@@ -4,7 +4,7 @@ import { assert } from '../errors'
 export class WalkFileModuleScope {
   private _scope: NestedScope
 
-  // tracks the progression through nested scopes within symbol table
+  // track the progression through nested scopes within symbol table
   private _currentNestedScopeIndex = -1
   private _nestedScopesIndexStack: number[] = []
 
@@ -18,14 +18,20 @@ export class WalkFileModuleScope {
 
   enterBlock = (): void => {
     this._nestedScopesIndexStack.push(this._currentNestedScopeIndex + 1)
-    this._scope = this.scope.nestedScope(this._currentNestedScopeIndex + 1)
+    const scope = this.scope.nestedScope(this._currentNestedScopeIndex + 1)
     this._currentNestedScopeIndex = -1
+
+    assert(scope !== undefined, 'Entering a scope that does not exist.')
+    this._scope = scope
   }
 
   peekBlock = (): void => {
     this._nestedScopesIndexStack.push(this._currentNestedScopeIndex)
-    this._scope = this.scope.nestedScope(this._currentNestedScopeIndex + 1)
+    const scope = this.scope.nestedScope(this._currentNestedScopeIndex + 1)
     this._currentNestedScopeIndex = -1
+
+    assert(scope !== undefined, 'Entering a scope that does not exist.')
+    this._scope = scope
   }
 
   leaveBlock = (): void => {
diff --git a/.yalc/tony-lang/src/symbol_table/index.ts b/.yalc/tony-lang/src/symbol_table/index.ts
index d830cd8..706ad0a 100644
--- a/.yalc/tony-lang/src/symbol_table/index.ts
+++ b/.yalc/tony-lang/src/symbol_table/index.ts
@@ -1,11 +1,14 @@
 export {
   Binding,
+  BindingTemplate,
   FileModuleScope,
   IdentifierBinding,
-  ImportBinding,
+  IdentifierBindingTemplate,
+  IdentifierImport,
   ModuleScope,
   NestedScope,
-  TypeBinding,
+  ModuleBinding,
+  ModuleImport,
 } from './models'
 export { BuildSymbolTable } from './BuildSymbolTable'
 export { WalkFileModuleScope } from './WalkFileModuleScope'
diff --git a/.yalc/tony-lang/src/symbol_table/models/BasicTypeBinding.ts b/.yalc/tony-lang/src/symbol_table/models/BasicTypeBinding.ts
index 4f1fa29..7336f19 100644
--- a/.yalc/tony-lang/src/symbol_table/models/BasicTypeBinding.ts
+++ b/.yalc/tony-lang/src/symbol_table/models/BasicTypeBinding.ts
@@ -1,11 +1,16 @@
 import { Binding } from './Binding'
 import { ParametricType } from '../../types'
+import Parser from 'tree-sitter'
 
 export class BasicTypeBinding implements Binding {
-  private _type: ParametricType
+  private _name: ParametricType
 
-  constructor(type: ParametricType) {
-    this._type = type
+  constructor(name: ParametricType) {
+    this._name = name
+  }
+
+  get filePath(): string | undefined {
+    return undefined
   }
 
   get isExported(): boolean {
@@ -21,10 +26,18 @@ export class BasicTypeBinding implements Binding {
   }
 
   get name(): string {
-    return this._type.name
+    return this._name.name
+  }
+
+  get node(): Parser.SyntaxNode | undefined {
+    return undefined
   }
 
   get transformedName(): string {
     return this.name
   }
+
+  get transformedImportName(): string | undefined {
+    return undefined
+  }
 }
diff --git a/.yalc/tony-lang/src/symbol_table/models/Binding.ts b/.yalc/tony-lang/src/symbol_table/models/Binding.ts
index b490c6f..892ba38 100644
--- a/.yalc/tony-lang/src/symbol_table/models/Binding.ts
+++ b/.yalc/tony-lang/src/symbol_table/models/Binding.ts
@@ -1,7 +1,12 @@
+import Parser from 'tree-sitter'
+
 export interface Binding {
+  filePath: string | undefined
   isExported: boolean
   isImplicit: boolean
   isImported: boolean
   name: string
+  node: Parser.SyntaxNode | undefined
+  transformedImportName: string | undefined
   transformedName: string
 }
diff --git a/.yalc/tony-lang/src/symbol_table/models/BindingTemplate.ts b/.yalc/tony-lang/src/symbol_table/models/BindingTemplate.ts
new file mode 100644
index 0000000..0503922
--- /dev/null
+++ b/.yalc/tony-lang/src/symbol_table/models/BindingTemplate.ts
@@ -0,0 +1,13 @@
+import { Type, TypeConstraint } from '../../types'
+import { Binding } from './Binding'
+import Parser from 'tree-sitter'
+
+export interface BindingTemplate {
+  isExported: boolean
+  isImplicit: boolean
+  name: string
+  node: Parser.SyntaxNode | undefined
+  transformedName: string
+
+  buildBinding: (typeConstraint: TypeConstraint<Type>) => Binding | undefined
+}
diff --git a/.yalc/tony-lang/src/symbol_table/models/FileModuleScope.ts b/.yalc/tony-lang/src/symbol_table/models/FileModuleScope.ts
index 8221d50..518e124 100644
--- a/.yalc/tony-lang/src/symbol_table/models/FileModuleScope.ts
+++ b/.yalc/tony-lang/src/symbol_table/models/FileModuleScope.ts
@@ -1,11 +1,17 @@
+import * as AST from '../../ast'
+import { GlobalScope } from './GlobalScope'
+import { Import } from './Import'
 import { ModuleScope } from './ModuleScope'
 import Parser from 'tree-sitter'
 import { Scope } from './Scope'
+import { assert } from '../../errors'
 
 export class FileModuleScope extends ModuleScope {
   private _dependencies: string[] = []
   private _filePath: string
+  private _imports: Import[] = []
   private _tree: Parser.Tree | undefined
+  private _annotatedTree: AST.Program | undefined
 
   constructor(parentScope: Scope, filePath: string) {
     super(parentScope)
@@ -21,6 +27,20 @@ export class FileModuleScope extends ModuleScope {
     return this._filePath
   }
 
+  get imports(): Import[] {
+    return this._imports
+  }
+
+  get parentScope(): GlobalScope {
+    const parentScope = super.parentScope
+    assert(
+      parentScope instanceof GlobalScope,
+      'Parent scope of file-level module scope should be the global scope.',
+    )
+
+    return parentScope
+  }
+
   get tree(): Parser.Tree | undefined {
     return this._tree
   }
@@ -29,7 +49,23 @@ export class FileModuleScope extends ModuleScope {
     this._tree = value
   }
 
+  get annotatedTree(): AST.Program | undefined {
+    return this._annotatedTree
+  }
+
+  set annotatedTree(value: AST.Program | undefined) {
+    this._annotatedTree = value
+  }
+
   addDependency = (filePath: string): void => {
     this._dependencies = [...this.dependencies, filePath]
   }
+
+  isBound = (name: string, depth?: number): boolean =>
+    this.resolveBindings(name, depth).length > 0 ||
+    this.imports.filter((imp) => imp.alias === name).length > 0
+
+  addImport = (imp: Import): void => {
+    this._imports = [imp, ...this.imports]
+  }
 }
diff --git a/.yalc/tony-lang/src/symbol_table/models/IdentifierBinding.ts b/.yalc/tony-lang/src/symbol_table/models/IdentifierBinding.ts
index d818c4b..6529c93 100644
--- a/.yalc/tony-lang/src/symbol_table/models/IdentifierBinding.ts
+++ b/.yalc/tony-lang/src/symbol_table/models/IdentifierBinding.ts
@@ -1,34 +1,53 @@
+import { Type, TypeConstraint } from '../../types'
 import { Binding } from './Binding'
-import { Type } from '../../types'
-
-const INTERNAL_IDENTIFIER_PREFIX = Object.freeze('tony_internal_')
+import Parser from 'tree-sitter'
 
 export class IdentifierBinding implements Binding {
-  private static count = 0
-
-  private _id: number
+  private _filePath: string | undefined
   private _isExported: boolean
   private _isImplicit: boolean
+  private _isImported: boolean
   private _name: string
-  protected _type: Type
+  private _node: Parser.SyntaxNode
+  private _transformedName: string
+  private _transformedImportName: string | undefined
+  protected _typeConstraint: TypeConstraint<Type>
 
+  // eslint-disable-next-line max-lines-per-function
   constructor(
+    node: Parser.SyntaxNode,
     name: string,
-    type: Type,
+    transformedName: string,
+    typeConstraint: TypeConstraint<Type>,
     {
       isExported = false,
       isImplicit = false,
-    }: { isExported?: boolean; isImplicit?: boolean } = {
+      importInformation,
+    }: {
+      isExported?: boolean
+      isImplicit?: boolean
+      importInformation?: {
+        filePath: string
+        transformedImportName: string
+      }
+    } = {
       isExported: false,
       isImplicit: false,
     },
   ) {
+    this._filePath = importInformation?.filePath
     this._isExported = isExported
     this._isImplicit = isImplicit
+    this._isImported = importInformation !== undefined
     this._name = name
-    this._type = type
+    this._node = node
+    this._transformedName = transformedName
+    this._transformedImportName = importInformation?.transformedImportName
+    this._typeConstraint = typeConstraint
+  }
 
-    this._id = IdentifierBinding.count += 1
+  get filePath(): string | undefined {
+    return this._filePath
   }
 
   get isExported(): boolean {
@@ -40,22 +59,30 @@ export class IdentifierBinding implements Binding {
   }
 
   get isImported(): boolean {
-    return false
+    return this._isImported
   }
 
   get name(): string {
     return this._name
   }
 
-  get type(): Type {
-    return this._type
+  get node(): Parser.SyntaxNode {
+    return this._node
   }
 
-  set type(value: Type) {
-    this._type = value
+  get typeConstraint(): TypeConstraint<Type> {
+    return this._typeConstraint
+  }
+
+  set typeConstraint(value: TypeConstraint<Type>) {
+    this._typeConstraint = value
   }
 
   get transformedName(): string {
-    return `${INTERNAL_IDENTIFIER_PREFIX}${this._id}`
+    return this._transformedName
+  }
+
+  get transformedImportName(): string | undefined {
+    return this._transformedImportName
   }
 }
diff --git a/.yalc/tony-lang/src/symbol_table/models/IdentifierBindingTemplate.ts b/.yalc/tony-lang/src/symbol_table/models/IdentifierBindingTemplate.ts
new file mode 100644
index 0000000..73e872f
--- /dev/null
+++ b/.yalc/tony-lang/src/symbol_table/models/IdentifierBindingTemplate.ts
@@ -0,0 +1,89 @@
+import { Type, TypeConstraint, TypeVariable } from '../../types'
+import { BindingTemplate } from './BindingTemplate'
+import { IdentifierBinding } from './IdentifierBinding'
+import Parser from 'tree-sitter'
+
+const INTERNAL_IDENTIFIER_PREFIX = Object.freeze('tony_internal_')
+
+export class IdentifierBindingTemplate implements BindingTemplate {
+  private static count = 0
+
+  private _isExported: boolean
+  private _isImplicit: boolean
+  private _name: string
+  private _node: Parser.SyntaxNode
+  private _transformedName: string
+  protected _type: TypeVariable
+
+  // eslint-disable-next-line max-lines-per-function
+  constructor(
+    node: Parser.SyntaxNode,
+    name: string,
+    {
+      isExported = false,
+      isImplicit = false,
+    }: {
+      isExported?: boolean
+      isImplicit?: boolean
+    } = {
+      isExported: false,
+      isImplicit: false,
+    },
+  ) {
+    this._isExported = isExported
+    this._isImplicit = isImplicit
+    this._name = name
+    this._node = node
+    this._type = new TypeVariable()
+
+    this._transformedName = IdentifierBindingTemplate.getTransformedName()
+  }
+
+  get isExported(): boolean {
+    return this._isExported
+  }
+
+  get isImplicit(): boolean {
+    return this._isImplicit
+  }
+
+  get name(): string {
+    return this._name
+  }
+
+  get node(): Parser.SyntaxNode {
+    return this._node
+  }
+
+  get type(): TypeVariable {
+    return this._type
+  }
+
+  get typeConstraint(): TypeConstraint<TypeVariable> {
+    return new TypeConstraint(this._type)
+  }
+
+  get transformedName(): string {
+    return this._transformedName
+  }
+
+  buildBinding = (
+    typeConstraint: TypeConstraint<Type>,
+  ): IdentifierBinding | undefined => {
+    const unifiedTypeConstraint = new TypeConstraint(this.type).unify(
+      typeConstraint,
+    )
+    if (unifiedTypeConstraint === undefined) return
+
+    return new IdentifierBinding(
+      this.node,
+      this.name,
+      this.transformedName,
+      unifiedTypeConstraint,
+      { isExported: this.isExported, isImplicit: this.isImplicit },
+    )
+  }
+
+  static getTransformedName = (): string =>
+    `${INTERNAL_IDENTIFIER_PREFIX}${(IdentifierBindingTemplate.count += 1)}`
+}
diff --git a/.yalc/tony-lang/src/symbol_table/models/IdentifierImport.ts b/.yalc/tony-lang/src/symbol_table/models/IdentifierImport.ts
new file mode 100644
index 0000000..b364f1c
--- /dev/null
+++ b/.yalc/tony-lang/src/symbol_table/models/IdentifierImport.ts
@@ -0,0 +1,45 @@
+import { Import } from './Import'
+import { ParametricType } from '../../types'
+import Parser from 'tree-sitter'
+
+export class IdentifierImport implements Import {
+  private _alias: string | undefined
+  private _filePath: string
+  private _name: string
+  private _node: Parser.SyntaxNode
+  private _type: ParametricType
+
+  constructor(
+    node: Parser.SyntaxNode,
+    filePath: string,
+    type: ParametricType,
+    name: string,
+    alias?: string,
+  ) {
+    this._alias = alias
+    this._filePath = filePath
+    this._name = name
+    this._node = node
+    this._type = type
+  }
+
+  get alias(): string {
+    return this._alias || this.name
+  }
+
+  get filePath(): string {
+    return this._filePath
+  }
+
+  get name(): string {
+    return this._name
+  }
+
+  get node(): Parser.SyntaxNode {
+    return this._node
+  }
+
+  get type(): ParametricType {
+    return this._type
+  }
+}
diff --git a/.yalc/tony-lang/src/symbol_table/models/Import.ts b/.yalc/tony-lang/src/symbol_table/models/Import.ts
new file mode 100644
index 0000000..afaea42
--- /dev/null
+++ b/.yalc/tony-lang/src/symbol_table/models/Import.ts
@@ -0,0 +1,8 @@
+import Parser from 'tree-sitter'
+
+export interface Import {
+  alias: string
+  filePath: string
+  name: string
+  node: Parser.SyntaxNode
+}
diff --git a/.yalc/tony-lang/src/symbol_table/models/ImportBinding.ts b/.yalc/tony-lang/src/symbol_table/models/ImportBinding.ts
deleted file mode 100644
index 8cd4eef..0000000
--- a/.yalc/tony-lang/src/symbol_table/models/ImportBinding.ts
+++ /dev/null
@@ -1,7 +0,0 @@
-import { Binding } from './Binding'
-
-export interface ImportBinding extends Binding {
-  filePath: string
-  originalName: string
-  transformedOriginalName: string
-}
diff --git a/.yalc/tony-lang/src/symbol_table/models/ImportIdentifierBinding.ts b/.yalc/tony-lang/src/symbol_table/models/ImportIdentifierBinding.ts
deleted file mode 100644
index e1b372c..0000000
--- a/.yalc/tony-lang/src/symbol_table/models/ImportIdentifierBinding.ts
+++ /dev/null
@@ -1,41 +0,0 @@
-import { IdentifierBinding } from './IdentifierBinding'
-import { ImportBinding } from './ImportBinding'
-import { Type } from '../../types'
-
-export class ImportIdentifierBinding extends IdentifierBinding
-  implements ImportBinding {
-  private _filePath: string
-  private _originalName: string
-
-  constructor(
-    filePath: string,
-    name: string,
-    originalName: string,
-    type: Type,
-  ) {
-    super(name, type, { isImplicit: true })
-
-    this._filePath = filePath
-    this._originalName = originalName
-  }
-
-  get filePath(): string {
-    return this._filePath
-  }
-
-  get isImported(): boolean {
-    return true
-  }
-
-  get originalName(): string {
-    return this._originalName
-  }
-
-  set originalName(value: string) {
-    this._originalName = value
-  }
-
-  get transformedOriginalName(): string {
-    return this.originalName
-  }
-}
diff --git a/.yalc/tony-lang/src/symbol_table/models/ImportTypeBinding.ts b/.yalc/tony-lang/src/symbol_table/models/ImportTypeBinding.ts
deleted file mode 100644
index a86ceae..0000000
--- a/.yalc/tony-lang/src/symbol_table/models/ImportTypeBinding.ts
+++ /dev/null
@@ -1,44 +0,0 @@
-import { Representation, RepresentationKind } from '../../types/models'
-import { ImportBinding } from './ImportBinding'
-import { ParametricType } from '../../types'
-import { TypeBinding } from './TypeBinding'
-
-export class ImportTypeBinding extends TypeBinding implements ImportBinding {
-  private _filePath: string
-  private _originalType: ParametricType
-
-  constructor(
-    filePath: string,
-    type: ParametricType,
-    originalType: ParametricType,
-  ) {
-    super(type, new Representation(RepresentationKind.Unknown, []))
-
-    this._filePath = filePath
-    this._originalType = originalType
-  }
-
-  get filePath(): string {
-    return this._filePath
-  }
-
-  get isImplicit(): boolean {
-    return true
-  }
-
-  get isImported(): boolean {
-    return true
-  }
-
-  get originalName(): string {
-    return this._originalType.name
-  }
-
-  set originalType(value: ParametricType) {
-    this._originalType = value
-  }
-
-  get transformedOriginalName(): string {
-    return this.originalName
-  }
-}
diff --git a/.yalc/tony-lang/src/symbol_table/models/ModuleBinding.ts b/.yalc/tony-lang/src/symbol_table/models/ModuleBinding.ts
new file mode 100644
index 0000000..3747585
--- /dev/null
+++ b/.yalc/tony-lang/src/symbol_table/models/ModuleBinding.ts
@@ -0,0 +1,76 @@
+import { ModuleType, ParametricType } from '../../types'
+import { Binding } from './Binding'
+import Parser from 'tree-sitter'
+
+export class ModuleBinding implements Binding {
+  private _filePath: string | undefined
+  private _isExported: boolean
+  private _isImported: boolean
+  private _name: ParametricType
+  private _node: Parser.SyntaxNode
+  private _transformedImportName: string | undefined
+  private _type: ModuleType
+
+  // eslint-disable-next-line max-lines-per-function
+  constructor(
+    node: Parser.SyntaxNode,
+    name: ParametricType,
+    type: ModuleType,
+    {
+      isExported = false,
+      importInformation,
+    }: {
+      isExported?: boolean
+      importInformation?: {
+        filePath: string
+        transformedImportName: string
+      }
+    } = {
+      isExported: false,
+    },
+  ) {
+    this._filePath = importInformation?.filePath
+    this._isExported = isExported
+    this._isImported = importInformation !== undefined
+    this._name = name
+    this._node = node
+    this._transformedImportName = importInformation?.transformedImportName
+    this._type = type
+  }
+
+  get filePath(): string | undefined {
+    return this._filePath
+  }
+
+  get isExported(): boolean {
+    return this._isExported
+  }
+
+  get isImplicit(): boolean {
+    return this.isImported
+  }
+
+  get isImported(): boolean {
+    return this._isImported
+  }
+
+  get name(): string {
+    return this._name.name
+  }
+
+  get node(): Parser.SyntaxNode {
+    return this._node
+  }
+
+  get transformedName(): string {
+    return this.name
+  }
+
+  get transformedImportName(): string | undefined {
+    return this._transformedImportName
+  }
+
+  get type(): ModuleType {
+    return this._type
+  }
+}
diff --git a/.yalc/tony-lang/src/symbol_table/models/ModuleImport.ts b/.yalc/tony-lang/src/symbol_table/models/ModuleImport.ts
new file mode 100644
index 0000000..e33b97c
--- /dev/null
+++ b/.yalc/tony-lang/src/symbol_table/models/ModuleImport.ts
@@ -0,0 +1,44 @@
+import { Import } from './Import'
+import { ParametricType } from '../../types'
+import Parser from 'tree-sitter'
+
+export class ModuleImport implements Import {
+  private _alias: ParametricType | undefined
+  private _filePath: string
+  private _name: ParametricType
+  private _node: Parser.SyntaxNode
+
+  constructor(
+    node: Parser.SyntaxNode,
+    filePath: string,
+    name: ParametricType,
+    alias?: ParametricType,
+  ) {
+    this._alias = alias
+    this._filePath = filePath
+    this._name = name
+    this._node = node
+  }
+
+  get alias(): string {
+    if (this._alias) return this._alias.name
+    else return this.name
+  }
+
+  get aliasType(): ParametricType {
+    if (this._alias) return this._alias
+    else return this._name
+  }
+
+  get filePath(): string {
+    return this._filePath
+  }
+
+  get name(): string {
+    return this._name.name
+  }
+
+  get node(): Parser.SyntaxNode {
+    return this._node
+  }
+}
diff --git a/.yalc/tony-lang/src/symbol_table/models/NestedScope.ts b/.yalc/tony-lang/src/symbol_table/models/NestedScope.ts
index 64b78a8..94ee1bc 100644
--- a/.yalc/tony-lang/src/symbol_table/models/NestedScope.ts
+++ b/.yalc/tony-lang/src/symbol_table/models/NestedScope.ts
@@ -1,11 +1,16 @@
 import { BASIC_TYPES, ParametricType } from '../../types'
+import { DuplicateBindingError, assert } from '../../errors'
 import { BasicTypeBinding } from './BasicTypeBinding'
 import { Binding } from './Binding'
+import { BindingTemplate } from './BindingTemplate'
+import { IdentifierBinding } from './IdentifierBinding'
 import { Scope } from './Scope'
-import { assert } from '../../errors'
+
+const OVERLOADED_BINDINGS = Object.freeze([IdentifierBinding])
 
 export class NestedScope extends Scope {
   private _bindings: Binding[] = []
+  private _bindingTemplates: BindingTemplate[] = []
   private _parentScope: Scope
 
   constructor(parentScope: Scope) {
@@ -18,6 +23,10 @@ export class NestedScope extends Scope {
     return this._bindings
   }
 
+  get bindingTemplates(): BindingTemplate[] {
+    return this._bindingTemplates
+  }
+
   get parentScope(): Scope {
     return this._parentScope
   }
@@ -29,7 +38,10 @@ export class NestedScope extends Scope {
     return scope
   }
 
-  resolveBinding = (name: string, depth?: number): Binding | undefined => {
+  resolveBinding = (
+    name: string,
+    depth?: number,
+  ): Binding | BindingTemplate | undefined => {
     // TODO: remove this when basic types are implemented in Tony
     const matchingBasicType = BASIC_TYPES.find((type) => type === name)
     if (matchingBasicType)
@@ -38,16 +50,88 @@ export class NestedScope extends Scope {
     const binding = this.bindings.find((binding) => binding.name === name)
     if (binding) return binding
 
+    const bindingTemplate = this.bindingTemplates.find(
+      (bindingTemplate) => bindingTemplate.name === name,
+    )
+    if (bindingTemplate) return bindingTemplate
+
     if (this.parentScope instanceof NestedScope)
       if (depth === undefined) return this.parentScope.resolveBinding(name)
       else if (depth > 0)
         return this.parentScope.resolveBinding(name, depth - 1)
   }
 
+  resolveBindings = (
+    name: string,
+    depth?: number,
+  ): (Binding | BindingTemplate)[] => {
+    const bindings = [
+      ...this.bindings.filter((binding) => binding.name === name),
+      ...this.bindingTemplates.filter(
+        (bindingTemplate) => bindingTemplate.name === name,
+      ),
+    ]
+
+    if (this.parentScope instanceof NestedScope)
+      if (depth === undefined)
+        return this.filterTemplateBindings([
+          ...bindings,
+          ...this.parentScope.resolveBindings(name),
+        ])
+      else if (depth > 0)
+        return this.filterTemplateBindings([
+          ...bindings,
+          ...this.parentScope.resolveBindings(name, depth - 1),
+        ])
+
+    return this.filterTemplateBindings(bindings)
+  }
+
+  // removes templates for which there are already actual bindings, depends on bindings being in front of templates
+  private filterTemplateBindings = (
+    bindings: (Binding | BindingTemplate)[],
+  ): (Binding | BindingTemplate)[] =>
+    bindings.reduce((newBindings: (Binding | BindingTemplate)[], binding) => {
+      if (
+        newBindings.find((otherBinding) => binding.node === otherBinding.node)
+      )
+        return newBindings
+      else return [...newBindings, binding]
+    }, [])
+
+  isBound = (name: string, depth?: number): boolean => {
+    if (this.resolveBinding(name, 0)) return true
+
+    if (this.parentScope instanceof NestedScope)
+      if (depth === undefined) return this.parentScope.isBound(name)
+      else if (depth > 0) return this.parentScope.isBound(name, depth - 1)
+
+    return false
+  }
+
   addBinding = (binding: Binding): void => {
+    if (!OVERLOADED_BINDINGS.find((type) => binding instanceof type)) {
+      const matchingBinding = this.resolveBinding(binding.name, 0)
+      if (matchingBinding) throw new DuplicateBindingError(binding.name)
+    }
+
     this._bindings = [binding, ...this.bindings]
   }
 
+  removeBinding = (binding: Binding): void => {
+    const index = this.bindings.indexOf(binding)
+    if (index < 0) return
+
+    this._bindings = [
+      ...this.bindings.slice(0, index),
+      ...this.bindings.slice(index + 1),
+    ]
+  }
+
+  addBindingTemplate = (bindingTemplate: BindingTemplate): void => {
+    this._bindingTemplates = [bindingTemplate, ...this.bindingTemplates]
+  }
+
   // takes the last nested scope and merges it with the current scope
   reduce = (): void => {
     assert(
@@ -60,14 +144,18 @@ export class NestedScope extends Scope {
     scope._scopes.map((nestedScope) => (nestedScope._parentScope = this))
 
     this._bindings = [...this.bindings, ...scope.bindings]
+    this._bindingTemplates = [
+      ...this.bindingTemplates,
+      ...scope.bindingTemplates,
+    ]
     this._scopes = scope._scopes
   }
 
-  nestedScope(index: number): NestedScope {
+  nestedScope(index: number): NestedScope | undefined {
     return this._scopes[index]
   }
 
-  get lastNestedScope(): NestedScope {
+  get lastNestedScope(): NestedScope | undefined {
     return this._scopes[this._scopes.length - 1]
   }
 }
diff --git a/.yalc/tony-lang/src/symbol_table/models/TypeBinding.ts b/.yalc/tony-lang/src/symbol_table/models/TypeBinding.ts
deleted file mode 100644
index ade794c..0000000
--- a/.yalc/tony-lang/src/symbol_table/models/TypeBinding.ts
+++ /dev/null
@@ -1,47 +0,0 @@
-import { Binding } from './Binding'
-import { ParametricType } from '../../types/models/ParametricType'
-import { Representation } from '../../types/models/Representation'
-
-export class TypeBinding implements Binding {
-  private _isExported: boolean
-  private _representation: Representation
-  private _type: ParametricType
-
-  constructor(
-    type: ParametricType,
-    representation: Representation,
-    { isExported = false }: { isExported?: boolean } = { isExported: false },
-  ) {
-    this._isExported = isExported
-    this._type = type
-    this._representation = representation
-  }
-
-  get isExported(): boolean {
-    return this._isExported
-  }
-
-  get isImplicit(): boolean {
-    return false
-  }
-
-  get isImported(): boolean {
-    return false
-  }
-
-  get name(): string {
-    return this.type.name
-  }
-
-  get representation(): Representation {
-    return this._representation
-  }
-
-  get type(): ParametricType {
-    return this._type
-  }
-
-  get transformedName(): string {
-    return this.name
-  }
-}
diff --git a/.yalc/tony-lang/src/symbol_table/models/index.ts b/.yalc/tony-lang/src/symbol_table/models/index.ts
index c1ad11c..a1aa6da 100644
--- a/.yalc/tony-lang/src/symbol_table/models/index.ts
+++ b/.yalc/tony-lang/src/symbol_table/models/index.ts
@@ -1,10 +1,12 @@
 export { Binding } from './Binding'
+export { BindingTemplate } from './BindingTemplate'
 export { FileModuleScope } from './FileModuleScope'
 export { GlobalScope } from './GlobalScope'
 export { IdentifierBinding } from './IdentifierBinding'
-export { ImportBinding } from './ImportBinding'
-export { ImportIdentifierBinding } from './ImportIdentifierBinding'
-export { ImportTypeBinding } from './ImportTypeBinding'
+export { IdentifierBindingTemplate } from './IdentifierBindingTemplate'
+export { IdentifierImport } from './IdentifierImport'
+export { Import } from './Import'
+export { ModuleBinding } from './ModuleBinding'
+export { ModuleImport } from './ModuleImport'
 export { ModuleScope } from './ModuleScope'
 export { NestedScope } from './NestedScope'
-export { TypeBinding } from './TypeBinding'
diff --git a/.yalc/tony-lang/src/symbol_table/services/BuildImportBindings.ts b/.yalc/tony-lang/src/symbol_table/services/BuildImportBindings.ts
deleted file mode 100644
index a87d32a..0000000
--- a/.yalc/tony-lang/src/symbol_table/services/BuildImportBindings.ts
+++ /dev/null
@@ -1,101 +0,0 @@
-import { BuildType, TypeVariable } from '../../types'
-import { DuplicateBindingError, InternalError } from '../../errors'
-import {
-  ImportBinding,
-  ImportIdentifierBinding,
-  ImportTypeBinding,
-} from '../models'
-import Parser from 'tree-sitter'
-import { isNotUndefined } from '../../utilities'
-
-export class BuildImportBindings {
-  private _filePath: string
-
-  constructor(filePath: string) {
-    this._filePath = filePath
-  }
-
-  perform = (node: Parser.SyntaxNode): ImportBinding[] => {
-    const importClauseNode = node.namedChild(0)!
-    const bindings = importClauseNode.namedChildren.reduce(
-      (bindings: ImportBinding[], child) =>
-        [...bindings, this.handleImportClauseEntry(child)].filter(
-          isNotUndefined,
-        ),
-      [],
-    )
-
-    this.checkDuplicateIdentifiers(bindings)
-
-    return bindings
-  }
-
-  private handleImportClauseEntry = (
-    node: Parser.SyntaxNode,
-  ): ImportBinding | undefined => {
-    switch (node.type) {
-      case 'identifier_pattern':
-        return this.handleIdentifierPattern(node)
-      case 'import_clause_identifier_pair':
-        return this.handleImportClauseIdentifierPair(node)
-      case 'import_clause_type_pair':
-        return this.handleImportClauseTypePair(node)
-      case 'type':
-        return this.handleType(node)
-      default:
-        throw new InternalError(
-          `ResolveImportBindings: Could not find generator for AST node '${node.type}'.`,
-        )
-    }
-  }
-
-  // prettier-ignore
-  private handleIdentifierPattern = (
-    node: Parser.SyntaxNode,
-  ): ImportIdentifierBinding => {
-    const name = node.namedChild(0)!.text
-    // eslint-disable-next-line @typescript-eslint/ban-ts-ignore
-    // @ts-ignore
-    const type = node.typeNode ? new BuildType().handleTypeConstructor(node.typeNode) : new TypeVariable
-
-    return new ImportIdentifierBinding(this._filePath, name, name, type)
-  }
-
-  private handleImportClauseIdentifierPair = (
-    node: Parser.SyntaxNode,
-  ): ImportIdentifierBinding => {
-    const originalName = node.namedChild(0)!.text
-    const binding = this.handleIdentifierPattern(node.namedChild(1)!)
-
-    binding.originalName = originalName
-
-    return binding
-  }
-
-  private handleImportClauseTypePair = (
-    node: Parser.SyntaxNode,
-  ): ImportTypeBinding => {
-    const originalType = this.handleType(node.namedChild(0)!)
-    const binding = this.handleType(node.namedChild(1)!)
-
-    binding.originalType = originalType.type
-
-    return binding
-  }
-
-  private handleType = (node: Parser.SyntaxNode): ImportTypeBinding => {
-    const type = new BuildType().handleType(node)
-
-    return new ImportTypeBinding(this._filePath, type, type)
-  }
-
-  private checkDuplicateIdentifiers = (bindings: ImportBinding[]): void => {
-    const identifiers = bindings.map((binding) => binding.name)
-    const duplicateIdentifier = identifiers.find((identifier, i) =>
-      identifiers.slice(i, i).includes(identifier),
-    )
-    if (!duplicateIdentifier) return
-
-    throw new DuplicateBindingError(duplicateIdentifier)
-  }
-}
diff --git a/.yalc/tony-lang/src/symbol_table/services/BuildImports.ts b/.yalc/tony-lang/src/symbol_table/services/BuildImports.ts
new file mode 100644
index 0000000..6000a6b
--- /dev/null
+++ b/.yalc/tony-lang/src/symbol_table/services/BuildImports.ts
@@ -0,0 +1,90 @@
+import { IdentifierImport, Import, ModuleImport } from '../models'
+import {
+  InternalError,
+  MissingExternalImportTypeHintError,
+  assert,
+} from '../../errors'
+import { BuildType } from '../../types'
+import Parser from 'tree-sitter'
+
+export class BuildImports {
+  private _filePath: string
+
+  constructor(filePath: string) {
+    this._filePath = filePath
+  }
+
+  perform = (node: Parser.SyntaxNode): Import[] => {
+    assert(node.type === 'import', 'Should be import node.')
+
+    const importClauseNode = node.namedChild(0)!
+    return importClauseNode.namedChildren.reduce(
+      (bindings: Import[], child) => [
+        ...bindings,
+        this.handleImportClauseEntry(child),
+      ],
+      [],
+    )
+  }
+
+  private handleImportClauseEntry = (node: Parser.SyntaxNode): Import => {
+    switch (node.type) {
+      case 'identifier_pattern':
+        return this.handleIdentifierPattern(node)
+      case 'import_clause_identifier_pair':
+        return this.handleImportClauseIdentifierPair(node)
+      case 'import_clause_type_pair':
+        return this.handleImportClauseTypePair(node)
+      case 'type':
+        return this.handleType(node)
+      default:
+        throw new InternalError(
+          `Could not find generator for AST node '${node.type}'.`,
+        )
+    }
+  }
+
+  private handleIdentifierPattern = (
+    node: Parser.SyntaxNode,
+  ): IdentifierImport => {
+    const name = node.namedChild(0)!.text
+    // eslint-disable-next-line @typescript-eslint/ban-ts-ignore
+    // @ts-ignore
+    const typeNode: Parser.SyntaxNode | undefined = node.typeNode
+    if (typeNode === undefined)
+      throw new MissingExternalImportTypeHintError(name)
+
+    const type = new BuildType().perform(typeNode)
+    return new IdentifierImport(node, this._filePath, type, name)
+  }
+
+  private handleImportClauseIdentifierPair = (
+    node: Parser.SyntaxNode,
+  ): IdentifierImport => {
+    const name = node.namedChild(0)!.text
+    const alias = this.handleIdentifierPattern(node.namedChild(1)!)
+
+    return new IdentifierImport(
+      node,
+      this._filePath,
+      alias.type,
+      name,
+      alias.name,
+    )
+  }
+
+  private handleImportClauseTypePair = (
+    node: Parser.SyntaxNode,
+  ): ModuleImport => {
+    const name = new BuildType().perform(node.namedChild(0)!)
+    const alias = new BuildType().perform(node.namedChild(1)!)
+
+    return new ModuleImport(node, this._filePath, name, alias)
+  }
+
+  private handleType = (node: Parser.SyntaxNode): ModuleImport => {
+    const name = new BuildType().perform(node)
+
+    return new ModuleImport(node, this._filePath, name)
+  }
+}
diff --git a/.yalc/tony-lang/src/symbol_table/services/BuildPatternBindings.ts b/.yalc/tony-lang/src/symbol_table/services/BuildPatternBindings.ts
index 0141e2c..be48221 100644
--- a/.yalc/tony-lang/src/symbol_table/services/BuildPatternBindings.ts
+++ b/.yalc/tony-lang/src/symbol_table/services/BuildPatternBindings.ts
@@ -1,5 +1,4 @@
-import { BuildType, TypeVariable } from '../../types'
-import { IdentifierBinding } from '../models'
+import { IdentifierBindingTemplate } from '../models'
 import Parser from 'tree-sitter'
 
 export class BuildPatternBindings {
@@ -17,7 +16,7 @@ export class BuildPatternBindings {
     this._isImplicit = isImplicit
   }
 
-  perform = (node: Parser.SyntaxNode): IdentifierBinding[] => {
+  perform = (node: Parser.SyntaxNode): IdentifierBindingTemplate[] => {
     if (
       node.type === 'identifier_pattern' ||
       node.type === 'shorthand_pair_identifier_pattern'
@@ -25,22 +24,19 @@ export class BuildPatternBindings {
       return this.handleIdentifierPattern(node)
 
     return node.namedChildren.reduce(
-      (names: IdentifierBinding[], child) => names.concat(this.perform(child)),
+      (names: IdentifierBindingTemplate[], child) =>
+        names.concat(this.perform(child)),
       [],
     )
   }
 
-  // prettier-ignore
   private handleIdentifierPattern = (
     node: Parser.SyntaxNode,
-  ): IdentifierBinding[] => {
+  ): IdentifierBindingTemplate[] => {
     const name = node.namedChild(0)!.text
-    // eslint-disable-next-line @typescript-eslint/ban-ts-ignore
-    // @ts-ignore
-    const type = node.typeNode ? new BuildType().handleTypeConstructor(node.typeNode) : new TypeVariable()
 
     return [
-      new IdentifierBinding(name, type, {
+      new IdentifierBindingTemplate(node, name, {
         isExported: this._isExported,
         isImplicit: this._isImplicit,
       }),
diff --git a/.yalc/tony-lang/src/symbol_table/services/UnifyPatternBindings.ts b/.yalc/tony-lang/src/symbol_table/services/UnifyPatternBindings.ts
index fe1ff65..1fdf099 100644
--- a/.yalc/tony-lang/src/symbol_table/services/UnifyPatternBindings.ts
+++ b/.yalc/tony-lang/src/symbol_table/services/UnifyPatternBindings.ts
@@ -1,8 +1,8 @@
-import { Binding } from '../models'
+import { BindingTemplate } from '../models'
 import { MissingBindingError } from '../../errors'
 
 export class UnifyPatternBindings {
-  perform = (bindings: Binding[][]): Binding[] => {
+  perform = (bindings: BindingTemplate[][]): BindingTemplate[] => {
     return bindings.reduce((acc, bindings) => {
       this.checkBindingMissing(acc, bindings)
 
@@ -10,7 +10,7 @@ export class UnifyPatternBindings {
     })
   }
 
-  checkBindingMissing = (a: Binding[], b: Binding[]): void => {
+  checkBindingMissing = (a: BindingTemplate[], b: BindingTemplate[]): void => {
     const missingBinding =
       a.find((binding) => !b.includes(binding)) ||
       b.find((binding) => !a.includes(binding))
diff --git a/.yalc/tony-lang/src/symbol_table/services/index.ts b/.yalc/tony-lang/src/symbol_table/services/index.ts
index 0fc3181..7f79fce 100644
--- a/.yalc/tony-lang/src/symbol_table/services/index.ts
+++ b/.yalc/tony-lang/src/symbol_table/services/index.ts
@@ -1,3 +1,3 @@
-export { BuildImportBindings } from './BuildImportBindings'
+export { BuildImports } from './BuildImports'
 export { BuildPatternBindings } from './BuildPatternBindings'
 export { UnifyPatternBindings } from './UnifyPatternBindings'
diff --git a/.yalc/tony-lang/src/type_inference/InferTypes.ts b/.yalc/tony-lang/src/type_inference/InferTypes.ts
index 90f63bc..7051d37 100644
--- a/.yalc/tony-lang/src/type_inference/InferTypes.ts
+++ b/.yalc/tony-lang/src/type_inference/InferTypes.ts
@@ -1,8 +1,36 @@
+import * as AST from '../ast'
+import {
+  AccumulateTypeDisjunction,
+  DistributeTypeDisjunction,
+  GetModuleTypeRepresentation,
+  InferAbstractionBranchType,
+  InferAccessType,
+  InferApplicationType,
+  InferAssignmentType,
+  InferBlockType,
+  InferBranchType,
+  InferExpressionPairType,
+  InferGeneratorType,
+  InferImportBindingTypes,
+  InferListType,
+  InferMapType,
+  InferPatternBindingTypes,
+  InferStringType,
+  InferTupleType,
+  MergeAccumulatedTypeDisjunction,
+  MergeTypeDisjunction,
+} from './services'
+import {
+  AccumulatedAnswer,
+  AccumulatedDisjunction,
+  Answer,
+  Disjunction,
+  GeneralizedDisjunction,
+} from './models'
 import {
   BOOLEAN_TYPE,
   BuildType,
-  CurriedType,
-  INTERNAL_PARTIAL_APPLICATION_TYPE_NAME,
+  FUNCTION_TYPE,
   LIST_TYPE,
   MAP_TYPE,
   NUMBER_TYPE,
@@ -10,57 +38,46 @@ import {
   REGULAR_EXPRESSION_TYPE,
   STRING_TYPE,
   TUPLE_TYPE,
-  Type,
-  TypeConstraints,
-  TypeVariable,
+  TypeConstraint,
+  TypeEqualityGraph,
   VOID_TYPE,
 } from '../types'
 import {
   CompileError,
+  IndeterminateTypeError,
   InternalError,
-  MissingBindingError,
+  TypeError,
   assert,
 } from '../errors'
 import {
   FileModuleScope,
   IdentifierBinding,
-  TypeBinding,
+  IdentifierBindingTemplate,
   WalkFileModuleScope,
 } from '../symbol_table'
-import {
-  InferAccessType,
-  InferApplicationType,
-  InferBranchType,
-  InferListType,
-  InferMapType,
-  InferPatternBindingTypes,
-  InferTupleType,
-} from './services'
 import Parser from 'tree-sitter'
 import { isNotUndefined } from '../utilities'
 
 export class InferTypes {
   private _fileScope: FileModuleScope
-  private _typeConstraints: TypeConstraints
   private _walkFileModuleScope: WalkFileModuleScope
 
-  // used to communicate type of provided value to when branches
-  private caseValueType: Type | undefined
-
   constructor(fileScope: FileModuleScope) {
     this._fileScope = fileScope
-    this._typeConstraints = new TypeConstraints()
     this._walkFileModuleScope = new WalkFileModuleScope(fileScope)
   }
 
-  perform = (): void => {
+  perform = (): AST.Program => {
     assert(
       this._fileScope.tree !== undefined,
       'Syntax tree of file scope should be present.',
     )
 
     try {
-      this.handleProgram(this._fileScope.tree.rootNode)
+      return CompileError.addContext(
+        this.chooseAnswer,
+        this._fileScope.tree.rootNode,
+      )
     } catch (error) {
       if (error instanceof CompileError)
         error.filePath = this._fileScope.filePath
@@ -68,471 +85,883 @@ export class InferTypes {
     }
   }
 
+  chooseAnswer = (node: Parser.SyntaxNode): AST.Program => {
+    const answers = CompileError.addContext(this.handleProgram, node)
+    console.log(
+      this._walkFileModuleScope.scope
+        .resolveBinding('quicksort')
+        .typeConstraint.toString(),
+    )
+
+    return answers.answers.reduce((acc, answer) => {
+      const unifiedTypeConstraint = acc.typeConstraint.unify(
+        answer.typeConstraint,
+      )
+      if (unifiedTypeConstraint === undefined)
+        throw new IndeterminateTypeError(
+          answers.answers.map((answer) => answer.typeConstraint.toString()),
+        )
+
+      return new Answer(acc.node, unifiedTypeConstraint)
+    }).node
+  }
+
   // eslint-disable-next-line max-lines-per-function
-  traverse = (node: Parser.SyntaxNode): Type | undefined => {
-    try {
-      switch (node.type) {
-        case 'abstraction':
-          return this.handleAbstraction(node)
-        case 'abstraction_branch':
-          return this.handleAbstractionBranch(node)
-        case 'access':
-          return this.handleAccess(node)
-        case 'application':
-          return this.handleApplication(node)
-        case 'argument':
-          return this.handleArgument(node)
-        case 'arguments':
-          return this.handleArguments(node)
-        case 'assignment':
-          return this.handleAssignment(node)
-        case 'block':
-          return this.handleBlock(node)
-        case 'boolean':
-          return new ParametricType(BOOLEAN_TYPE)
-        case 'case':
-          return this.handleCase(node)
-        case 'comment':
-          return
-        case 'escape_sequence':
-          return new ParametricType(STRING_TYPE)
-        case 'else_if_clause':
-          return this.handleElseIfClause(node)
-        case 'else_if_clauses':
-          return this.handleElseIfClauses(node)
-        case 'export':
-          return this.handleExport(node)
-        case 'expression_pair':
-          return this.handleExpressionPair(node)
-        case 'generator':
-          return this.handleGenerator(node)
-        case 'generators':
-          return this.handleGenerators(node)
-        case 'identifier':
-          return this.handleIdentifier(node)
-        case 'if':
-          return this.handleIf(node)
-        case 'import':
-          return new ParametricType(VOID_TYPE)
-        case 'infix_application':
-          return this.handleInfixApplication(node)
-        case 'interpolation':
-          return this.handleInterpolation(node)
-        case 'list':
-          return this.handleList(node)
-        case 'list_comprehension':
-          return this.handleListComprehension(node)
-        case 'map':
-          return this.handleMap(node)
-        case 'module':
-          return this.handleModule(node)
-        case 'number':
-          return new ParametricType(NUMBER_TYPE)
-        case 'parameters':
-          return this.handleParameters(node)
-        case 'pattern_list':
-          return this.handlePatternList(node)
-        case 'pipeline':
-          return this.handlePipeline(node)
-        case 'prefix_application':
-          return this.handlePrefixApplication(node)
-        case 'regex':
-          return new ParametricType(REGULAR_EXPRESSION_TYPE)
-        case 'return':
-          return this.handleReturn(node)
-        case 'shorthand_access_identifier':
-          return new ParametricType(STRING_TYPE)
-        case 'shorthand_pair_identifier':
-          return this.handleShorthandPairIdentifier(node)
-        case 'spread_list':
-          return this.handleSpreadList(node)
-        case 'spread_map':
-          return this.handleSpreadMap(node)
-        case 'spread_tuple':
-          return this.handleSpreadTuple(node)
-        case 'string':
-          return this.handleString(node)
-        case 'tuple':
-          return this.handleTuple(node)
-        case 'type':
-          return this.handleType(node)
-        case 'when_clause':
-          return this.handleWhenClause(node)
-        case 'when_clauses':
-          return this.handleWhenClauses(node)
-        default:
-          throw new InternalError(
-            `InferTypes: Could not find generator for AST node '${node.type}'.`,
-          )
-      }
-    } catch (error) {
-      if (error instanceof CompileError && error.context === undefined)
-        error.addContext(node)
-      throw error
+  traverse = (node: Parser.SyntaxNode): Disjunction<AST.SyntaxNode> => {
+    switch (node.type) {
+      case 'abstraction':
+        return this.handleAbstraction(node)
+      case 'abstraction_branch':
+        return this.handleAbstractionBranch(node)
+      case 'access':
+        return this.handleAccess(node)
+      case 'application':
+        return this.handleApplication(node)
+      case 'argument':
+        return this.handleArgument(node)
+      case 'assignment':
+        return this.handleAssignment(node)
+      case 'block':
+        return this.handleBlock(node)
+      case 'boolean':
+        return this.handleBoolean(node)
+      case 'case':
+        return this.handleCase(node)
+      case 'else_if':
+        return this.handleElseIf(node)
+      case 'export':
+        return this.handleExport(node)
+      case 'expression_pair':
+        return this.handleExpressionPair(node)
+      case 'generator':
+        return this.handleGenerator(node)
+      case 'identifier':
+        return this.handleIdentifier(node)
+      case 'if':
+        return this.handleIf(node)
+      case 'import':
+        return this.handleImport(node)
+      case 'infix_application':
+        return this.handleInfixApplication(node)
+      case 'list':
+        return this.handleList(node)
+      case 'list_comprehension':
+        return this.handleListComprehension(node)
+      case 'map':
+        return this.handleMap(node)
+      case 'module':
+        return this.handleModule(node)
+      case 'number':
+        return this.handleNumber(node)
+      case 'parameters':
+        return this.handleParameters(node)
+      case 'pipeline':
+        return this.handlePipeline(node)
+      case 'prefix_application':
+        return this.handlePrefixApplication(node)
+      case 'regex':
+        return this.handleRegex(node)
+      case 'return':
+        return this.handleReturn(node)
+      case 'shorthand_access_identifier':
+        return this.handleShorthandAccessIdentifier(node)
+      case 'shorthand_pair_identifier':
+        return this.handleShorthandPairIdentifier(node)
+      case 'spread_list':
+        return this.handleSpreadList(node)
+      case 'spread_map':
+        return this.handleSpreadMap(node)
+      case 'spread_tuple':
+        return this.handleSpreadTuple(node)
+      case 'string':
+        return this.handleString(node)
+      case 'tuple':
+        return this.handleTuple(node)
+      case 'type':
+        return this.handleType(node)
+      default:
+        throw new InternalError(
+          `Could not find generator for AST node '${node.type}'.`,
+        )
     }
   }
 
-  private handleAbstraction = (node: Parser.SyntaxNode): Type => {
-    const abstractionBranchTypes = node.namedChildren
-      .map((child) => this.traverse(child))
-      .filter(isNotUndefined)
-
-    return new InferBranchType(this._typeConstraints).perform(
-      abstractionBranchTypes,
+  private handleAbstraction = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.Abstraction> => {
+    const abstractionBranches = node.namedChildren.map((child) =>
+      CompileError.addContext(this.handleAbstractionBranch, child),
     )
+
+    return new InferBranchType<AST.AbstractionBranch, AST.Abstraction>(
+      (branches) => new AST.Abstraction(branches),
+    ).perform(abstractionBranches)
   }
 
-  private handleAbstractionBranch = (node: Parser.SyntaxNode): CurriedType => {
+  private handleAbstractionBranch = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.AbstractionBranch> => {
     this._walkFileModuleScope.peekBlock()
-    const parameterTypes = this.handleParameters(node.namedChild(0)!)
+    const parameters = CompileError.addContext(
+      this.handleParameters,
+      node.namedChild(0)!,
+    )
     this._walkFileModuleScope.leaveBlock()
 
-    const bodyType = this.handleBlock(node.namedChild(1)!)
+    const body = CompileError.addContext(this.handleBlock, node.namedChild(1)!)
 
-    return parameterTypes.concat(bodyType)
+    return new InferAbstractionBranchType().perform(parameters, body)
   }
 
-  private handleAccess = (node: Parser.SyntaxNode): Type => {
-    const valueType = this.traverse(node.namedChild(0)!)!
-    const accessorType = this.traverse(node.namedChild(1)!)!
+  private handleAccess = (node: Parser.SyntaxNode): Disjunction<AST.Access> => {
+    const value = CompileError.addContext(this.traverse, node.namedChild(0)!)!
+    const accessor = CompileError.addContext(
+      this.traverse,
+      node.namedChild(1)!,
+    )!
 
     return new InferAccessType(
-      node,
-      this._walkFileModuleScope.scope,
-      this._typeConstraints,
-    ).perform(valueType, accessorType)
+      new GetModuleTypeRepresentation(this._walkFileModuleScope.scope),
+    ).perform(value, accessor)
   }
 
-  private handleApplication = (node: Parser.SyntaxNode): Type => {
-    const valueType = this.traverse(node.namedChild(0)!)!
-    const argumentTypes = this.handleArguments(node.namedChild(1)!)
-
-    return new InferApplicationType(this._typeConstraints).perform(
-      valueType,
-      argumentTypes,
+  private handleApplication = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.Application> => {
+    const value = CompileError.addContext(this.traverse, node.namedChild(0)!)!
+    const args = CompileError.addContext(
+      this.handleArguments,
+      node.namedChild(1)!,
     )
+
+    return new InferApplicationType<
+      AST.Expression,
+      AST.Argument,
+      AST.Application
+    >(
+      (valueNode, argumentNodes, typeConstraint) =>
+        new Answer(
+          new AST.Application(valueNode, argumentNodes),
+          typeConstraint,
+        ),
+    ).perform(value, args)
   }
 
-  private handleArgument = (node: Parser.SyntaxNode): Type => {
+  private handleArgument = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.Argument> => {
     if (node.namedChildCount == 0)
-      return new TypeVariable(INTERNAL_PARTIAL_APPLICATION_TYPE_NAME)
-
-    return this.traverse(node.namedChild(0)!)!
+      return new Disjunction([
+        new Answer(
+          new AST.Argument(),
+          new TypeConstraint(new ParametricType(VOID_TYPE)),
+        ),
+      ])
+
+    const value = CompileError.addContext(this.traverse, node.namedChild(0)!)!
+    return new Disjunction(
+      value.answers.map(
+        (answer) =>
+          new Answer(new AST.Argument(answer.node), answer.typeConstraint),
+      ),
+    )
   }
 
-  private handleArguments = (node: Parser.SyntaxNode): CurriedType => {
-    if (node.namedChildCount == 0)
-      return new CurriedType([new ParametricType(VOID_TYPE)])
+  private handleArguments = (
+    node: Parser.SyntaxNode,
+  ): AccumulatedDisjunction<AST.Argument> => {
+    if (node.namedChildCount == 0) return [new AccumulatedAnswer()]
 
-    const argumentTypes = node.namedChildren
-      .map((child) => this.traverse(child))
-      .filter(isNotUndefined)
-    return new CurriedType(argumentTypes)
+    const args = node.namedChildren.map((child) =>
+      CompileError.addContext(this.handleArgument, child),
+    )
+    return new DistributeTypeDisjunction<AST.Argument>().perform(args)
   }
 
-  private handleAssignment = (node: Parser.SyntaxNode): Type => {
+  private handleAssignment = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.Assignment> => {
     const patternNode = node.namedChild(0)!
-    const valueType = this.traverse(node.namedChild(1)!)!
+    const value = CompileError.addContext(this.traverse, node.namedChild(1)!)!
 
-    return new InferPatternBindingTypes(
-      this,
-      this._walkFileModuleScope.scope,
-      this._typeConstraints,
-    ).perform(patternNode, valueType)
+    return new InferAssignmentType(
+      new InferPatternBindingTypes(this, this._walkFileModuleScope.scope),
+    ).perform(patternNode, value)
   }
 
-  private handleBlock = (node: Parser.SyntaxNode): Type => {
+  private handleBlock = (node: Parser.SyntaxNode): Disjunction<AST.Block> => {
     this._walkFileModuleScope.enterBlock()
-    const expressionTypes = node.namedChildren
-      .map((child) => this.traverse(child))
-      .filter(isNotUndefined)
+    const expressions = node.namedChildren.map((child) =>
+      CompileError.addContext(this.traverse, child),
+    )
     this._walkFileModuleScope.leaveBlock()
 
-    return expressionTypes[expressionTypes.length - 1]
+    return new InferBlockType<AST.Block>(
+      (expressions) => new AST.Block(expressions.nodes),
+    ).perform(expressions)
   }
 
-  private handleCase = (node: Parser.SyntaxNode): Type => {
-    this.caseValueType = this.traverse(node.namedChild(0)!)
-    const branchTypes = node.namedChildren
-      .slice(1)
-      .map((child) => this.traverse(child))
-      .filter(isNotUndefined)
+  private handleBoolean = (node: Parser.SyntaxNode): Disjunction<AST.Boolean> =>
+    new Disjunction([
+      new Answer(
+        new AST.Boolean(node.text),
+        new TypeConstraint(new ParametricType(BOOLEAN_TYPE)),
+      ),
+    ])
 
-    return new InferBranchType(this._typeConstraints).perform(branchTypes)
+  // eslint-disable-next-line max-lines-per-function
+  private handleCase = (node: Parser.SyntaxNode): Disjunction<AST.Case> => {
+    const value = CompileError.addContext(this.traverse, node.namedChild(0)!)
+    let branches: GeneralizedDisjunction<AST.SyntaxNode>[] = []
+    if (node.namedChildCount == 3)
+      branches = [
+        ...branches,
+        CompileError.addContext(this.handleBlock, node.namedChild(2)!),
+      ]
+
+    return new Disjunction(
+      value.answers
+        .map((valueAnswer) => {
+          branches = [
+            ...branches,
+            CompileError.addContext(
+              this.handleWhenClauses,
+              node.namedChild(1)!,
+              valueAnswer,
+            ),
+          ]
+
+          return new InferBranchType((branches) => {
+            const whens = branches.filter(
+              (node) => node instanceof AST.When,
+            ) as AST.When[]
+            const [els] = branches.filter(
+              (node) => node instanceof AST.Block,
+            ) as AST.Block[]
+
+            return new AST.Case(valueAnswer.node, whens, els)
+          }).perform(branches).answers
+        })
+        .flat(1),
+    )
   }
 
-  private handleElseIfClause = (node: Parser.SyntaxNode): Type => {
-    const conditionType = this.traverse(node.namedChild(0)!)!
-    const type = this.traverse(node.namedChild(1)!)!
-
-    new ParametricType(BOOLEAN_TYPE).unify(conditionType, this._typeConstraints)
+  // eslint-disable-next-line max-lines-per-function
+  private handleElseIf = (node: Parser.SyntaxNode): Disjunction<AST.ElseIf> => {
+    const condition = CompileError.addContext(
+      this.traverse,
+      node.namedChild(0)!,
+    )
+    const body = CompileError.addContext(this.handleBlock, node.namedChild(1)!)
+
+    return new MergeTypeDisjunction<AST.SyntaxNode, AST.Block, AST.ElseIf>(
+      (condition, body) => {
+        const unifiedConditionTypeConstraint = new TypeConstraint(
+          new ParametricType(BOOLEAN_TYPE),
+        ).unify(condition.typeConstraint)
+        if (unifiedConditionTypeConstraint === undefined) return
+
+        return new Answer(
+          new AST.ElseIf(condition.node, body.node),
+          new TypeConstraint(
+            body.typeConstraint.type,
+            TypeEqualityGraph.build(
+              unifiedConditionTypeConstraint.typeEqualityGraph,
+              body.typeConstraint.typeEqualityGraph,
+            ),
+          ),
+        )
+      },
+    ).perform(condition, body)
+  }
+
+  private handleElseIfClauses = (
+    node: Parser.SyntaxNode,
+  ): AccumulatedDisjunction<AST.ElseIf> => {
+    const branches = node.namedChildren.map((child) =>
+      CompileError.addContext(this.handleElseIf, child),
+    )
 
-    return type
+    return new DistributeTypeDisjunction<AST.ElseIf>().perform(branches)
   }
 
-  private handleElseIfClauses = (node: Parser.SyntaxNode): Type => {
-    const branchTypes = node.namedChildren
-      .map((child) => this.traverse(child))
-      .filter(isNotUndefined)
-
-    return new InferBranchType(this._typeConstraints).perform(branchTypes)
-  }
+  private handleExport = (node: Parser.SyntaxNode): Disjunction<AST.Export> => {
+    const declaration = CompileError.addContext(
+      this.traverse,
+      node.namedChild(0)!,
+    )!
 
-  private handleExport = (node: Parser.SyntaxNode): Type => {
-    return this.traverse(node.namedChild(0)!)!
+    return new Disjunction(
+      declaration.answers.map(
+        (answer) =>
+          new Answer(
+            new AST.Export(answer.node as AST.Declaration),
+            answer.typeConstraint,
+          ),
+      ),
+    )
   }
 
-  private handleExpressionPair = (node: Parser.SyntaxNode): ParametricType => {
-    const keyType = this.traverse(node.namedChild(0)!)!
-    const valueType = this.traverse(node.namedChild(1)!)!
+  private handleExpressionPair = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.ExpressionPair> => {
+    const key = CompileError.addContext(this.traverse, node.namedChild(0)!)!
+    const value = CompileError.addContext(this.traverse, node.namedChild(1)!)!
 
-    return new ParametricType(MAP_TYPE, [keyType, valueType])
+    return new InferExpressionPairType().perform(key, value)
   }
 
-  // eslint-disable-next-line max-lines-per-function
-  private handleGenerator = (node: Parser.SyntaxNode): undefined => {
-    const name = node.namedChild(0)!.text
-    const valueType = this.traverse(node.namedChild(1)!)!
-    const binding = this._walkFileModuleScope.scope.resolveBinding(name, 0)
+  private handleGenerator = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.Generator> => {
+    const value = CompileError.addContext(this.traverse, node.namedChild(1)!)
+    const condition =
+      node.namedChildCount == 3
+        ? CompileError.addContext(this.traverse, node.namedChild(2)!)
+        : undefined
+    const bindingTemplate = this._walkFileModuleScope.scope.bindingTemplates.find(
+      (bindingTemplate) => bindingTemplate.node === node,
+    )
 
     assert(
-      binding instanceof IdentifierBinding,
+      bindingTemplate instanceof IdentifierBindingTemplate,
       'Generator binding should be found in current scope.',
     )
 
-    const type = new ParametricType(LIST_TYPE, [new TypeVariable()]).unify(
-      valueType,
-      this._typeConstraints,
-    ).parameters[0]
-    binding.type = type
-
-    if (node.namedChildCount == 3) {
-      const conditionType = this.traverse(node.namedChild(2)!)!
-
-      new ParametricType(BOOLEAN_TYPE).unify(
-        conditionType,
-        this._typeConstraints,
-      )
-    }
-
-    return
+    return new InferGeneratorType(this._walkFileModuleScope.scope).perform(
+      bindingTemplate,
+      value,
+      condition,
+    )
   }
 
-  private handleGenerators = (node: Parser.SyntaxNode): undefined => {
-    node.namedChildren.forEach((child) => this.traverse(child))
+  private handleGenerators = (
+    node: Parser.SyntaxNode,
+  ): AccumulatedDisjunction<AST.Generator> => {
+    const generators = node.namedChildren.map((child) =>
+      CompileError.addContext(this.handleGenerator, child),
+    )
 
-    return
+    return new DistributeTypeDisjunction<AST.Generator>().perform(generators)
   }
 
-  private handleIdentifier = (node: Parser.SyntaxNode): Type => {
+  private handleIdentifier = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.Identifier> => {
     const name = node.text
-    const binding = this._walkFileModuleScope.scope.resolveBinding(name)
-
-    assert(
-      binding instanceof IdentifierBinding,
-      'Identifier binding should be found in scope.',
+    const bindings = this._walkFileModuleScope.scope.resolveBindings(name)
+
+    return new Disjunction(
+      bindings.map((binding) => {
+        assert(
+          binding instanceof IdentifierBinding ||
+            binding instanceof IdentifierBindingTemplate,
+          'Binding should be an identifier binding.',
+        )
+
+        return new Answer(
+          new AST.Identifier(
+            binding.typeConstraint.type,
+            binding.name,
+            binding.transformedName,
+          ),
+          binding.typeConstraint,
+        )
+      }),
     )
+  }
 
-    return binding.type
+  // eslint-disable-next-line max-lines-per-function
+  private handleIf = (node: Parser.SyntaxNode): Disjunction<AST.If> => {
+    const condition = CompileError.addContext(
+      this.traverse,
+      node.namedChild(0)!,
+    )
+    let branches: GeneralizedDisjunction<AST.SyntaxNode>[] = [
+      CompileError.addContext(this.handleBlock, node.namedChild(1)!),
+    ]
+    if (node.namedChildCount >= 3)
+      if (node.namedChild(2)!.type === 'block')
+        branches = [
+          ...branches,
+          CompileError.addContext(this.handleBlock, node.namedChild(2)!),
+        ]
+      else
+        branches = [
+          ...branches,
+          CompileError.addContext(
+            this.handleElseIfClauses,
+            node.namedChild(2)!,
+          ),
+        ]
+    if (node.namedChildCount >= 4)
+      branches = [
+        ...branches,
+        CompileError.addContext(this.handleBlock, node.namedChild(3)!),
+      ]
+
+    return new Disjunction(
+      condition.answers
+        .map((conditionAnswer) => {
+          return new InferBranchType((branches) => {
+            const [body, els] = branches.filter(
+              (node) => node instanceof AST.Block,
+            ) as (AST.Block | undefined)[]
+            const elseIfs = branches.filter(
+              (node) => node instanceof AST.ElseIf,
+            ) as AST.ElseIf[]
+
+            assert(body !== undefined, 'Body node should be given.')
+
+            return new AST.If(conditionAnswer.node, body, elseIfs, els)
+          }).perform(branches).answers
+        })
+        .flat(1),
+    )
   }
 
-  private handleIf = (node: Parser.SyntaxNode): Type => {
-    const [conditionType, ...branchTypes] = node.namedChildren
-      .map((child) => this.traverse(child))
-      .filter(isNotUndefined)
+  private handleImport = (node: Parser.SyntaxNode): Disjunction<AST.Import> => {
+    const typeEqualityGraph = new TypeEqualityGraph()
 
-    new ParametricType(BOOLEAN_TYPE).unify(conditionType, this._typeConstraints)
+    new InferImportBindingTypes(
+      this._fileScope,
+      this._fileScope.parentScope.scopes,
+      typeEqualityGraph,
+    ).perform(node)
 
-    return new InferBranchType(this._typeConstraints).perform(branchTypes)
+    return new Disjunction([
+      new Answer(
+        new AST.Import(),
+        new TypeConstraint(new ParametricType(VOID_TYPE), typeEqualityGraph),
+      ),
+    ])
   }
 
-  private handleInfixApplication = (node: Parser.SyntaxNode): Type => {
-    const leftType = this.traverse(node.namedChild(0)!)!
-    const valueType = this.traverse(node.namedChild(1)!)!
-    const rightType = this.traverse(node.namedChild(2)!)!
-    const argumentTypes = new CurriedType([leftType, rightType])
-
-    return new InferApplicationType(this._typeConstraints).perform(
-      valueType,
-      argumentTypes,
+  // eslint-disable-next-line max-lines-per-function
+  private handleInfixApplication = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.InfixApplication> => {
+    const left = CompileError.addContext(this.traverse, node.namedChild(0)!)!
+    const value = CompileError.addContext(
+      this.handleIdentifier,
+      node.namedChild(1)!,
+    )!
+    const right = CompileError.addContext(this.traverse, node.namedChild(2)!)!
+    const args = new AccumulateTypeDisjunction<AST.Expression>(
+      (left, right) => new AccumulatedAnswer([left, right]),
+    ).perform(left, right)
+
+    return new InferApplicationType<
+      AST.Identifier,
+      AST.Expression,
+      AST.InfixApplication
+    >(
+      (valueNode, argumentNodes, typeConstraint) =>
+        new Answer(
+          new AST.InfixApplication(
+            argumentNodes[0],
+            valueNode,
+            argumentNodes[1],
+          ),
+          typeConstraint,
+        ),
+    ).perform(value, args)
+  }
+
+  private handleList = (node: Parser.SyntaxNode): Disjunction<AST.List> => {
+    const elements = node.namedChildren.map((child) =>
+      CompileError.addContext(this.traverse, child),
     )
-  }
-
-  private handleInterpolation = (node: Parser.SyntaxNode): Type => {
-    const type = this.traverse(node.namedChild(0)!)!
-
-    return new ParametricType(STRING_TYPE).unify(type, this._typeConstraints)
-  }
 
-  private handleList = (node: Parser.SyntaxNode): ParametricType => {
-    return new InferListType(this, this._typeConstraints).perform(
-      node.namedChildren,
+    return new InferListType((elements) => new AST.List(elements)).perform(
+      elements,
     )
   }
 
+  // eslint-disable-next-line max-lines-per-function
   private handleListComprehension = (
     node: Parser.SyntaxNode,
-  ): ParametricType => {
+  ): Disjunction<AST.ListComprehension> => {
     this._walkFileModuleScope.peekBlock()
-    this.handleGenerators(node.namedChild(1)!)
+    const generators = CompileError.addContext(
+      this.handleGenerators,
+      node.namedChild(1)!,
+    )
     this._walkFileModuleScope.leaveBlock()
 
-    const bodyType = this.traverse(node.namedChild(0)!)!
+    const body = this.handleBlock(node.namedChild(0)!)!
+
+    return new MergeAccumulatedTypeDisjunction<
+      AST.Generator,
+      AST.Block,
+      AST.ListComprehension
+    >(
+      (generators, body) =>
+        new Answer(
+          new AST.ListComprehension(body.node, generators.nodes),
+          new TypeConstraint(
+            new ParametricType(LIST_TYPE, [body.typeConstraint.type]),
+            TypeEqualityGraph.build(
+              body.typeConstraint.typeEqualityGraph,
+              ...generators.typeConstraints.map(
+                (typeConstraint) => typeConstraint.typeEqualityGraph,
+              ),
+            ),
+          ),
+        ),
+    ).perform(generators, body)
+  }
+
+  private handleMap = (node: Parser.SyntaxNode): Disjunction<AST.Map> => {
+    const elements = node.namedChildren.map((child) =>
+      CompileError.addContext(this.traverse, child),
+    )
 
-    return new ParametricType(LIST_TYPE, [bodyType])
+    return new InferMapType(
+      (elements) => new AST.Map(elements as AST.MapElement[]),
+    ).perform(elements)
   }
 
-  private handleMap = (node: Parser.SyntaxNode): ParametricType => {
-    const mapTypes = node.namedChildren
-      .map((child) => this.traverse(child))
-      .filter(isNotUndefined)
-
-    return new InferMapType(this._typeConstraints).perform(mapTypes)
+  private handleModule = (node: Parser.SyntaxNode): Disjunction<AST.Module> => {
+    const type = new BuildType().perform(node.namedChild(0)!)
+    const representation = new GetModuleTypeRepresentation(
+      this._walkFileModuleScope.scope,
+    ).perform(type)
+    const body = CompileError.addContext(this.handleBlock, node.namedChild(1)!)
+
+    return new Disjunction(
+      body.answers.map(
+        (answer) =>
+          new Answer(
+            new AST.Module(type.name, answer.node),
+            new TypeConstraint(
+              representation,
+              answer.typeConstraint.typeEqualityGraph,
+            ),
+          ),
+      ),
+    )
   }
 
-  private handleModule = (node: Parser.SyntaxNode): ParametricType => {
-    const type = new BuildType().handleType(node.namedChild(0)!)
-
-    this.traverse(node.namedChild(1)!)
-
-    return type
-  }
+  private handleNumber = (node: Parser.SyntaxNode): Disjunction<AST.Number> =>
+    new Disjunction([
+      new Answer(
+        new AST.Number(node.text),
+        new TypeConstraint(new ParametricType(NUMBER_TYPE)),
+      ),
+    ])
 
-  private handleParameters = (node: Parser.SyntaxNode): CurriedType => {
+  // eslint-disable-next-line max-lines-per-function
+  private handleParameters = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.Parameters> => {
     if (node.namedChildCount == 0)
-      return new CurriedType([new ParametricType(VOID_TYPE)])
-
-    const parameterTypes = new InferPatternBindingTypes(
+      return new Disjunction([
+        new Answer(
+          new AST.Parameters(),
+          new TypeConstraint(
+            new ParametricType(FUNCTION_TYPE, [new ParametricType(VOID_TYPE)]),
+          ),
+        ),
+      ])
+
+    const parameters = new InferPatternBindingTypes(
       this,
       this._walkFileModuleScope.scope,
-      this._typeConstraints,
-    ).perform(node)
-    assert(parameterTypes instanceof ParametricType, 'Should be tuple type.')
+    )
+      .perform(node)
+      ?.answers.map((answer) => {
+        assert(
+          answer.node instanceof AST.TuplePattern,
+          'Should be a tuple pattern.',
+        )
+
+        return new Answer(
+          new AST.Parameters(answer.node.elements),
+          answer.typeConstraint,
+        )
+      })
+    if (parameters === undefined) throw new TypeError()
 
-    return new CurriedType(parameterTypes.parameters)
+    return new Disjunction(parameters)
   }
 
-  private handlePatternList = (node: Parser.SyntaxNode): undefined => {
-    node.namedChildren.forEach((patternNode) => {
-      new InferPatternBindingTypes(
-        this,
-        this._walkFileModuleScope.scope,
-        this._typeConstraints,
-      ).perform(patternNode, this.caseValueType!)
-    })
+  private handlePatternList = (
+    node: Parser.SyntaxNode,
+    value: Answer<AST.Expression>,
+  ): AccumulatedDisjunction<AST.Pattern> => {
+    const patterns = node.namedChildren
+      .map((patternNode) =>
+        new InferPatternBindingTypes(
+          this,
+          this._walkFileModuleScope.scope,
+        ).perform(patternNode, value.typeConstraint),
+      )
+      .filter(isNotUndefined)
 
-    return
+    return new DistributeTypeDisjunction<AST.Pattern>().perform(patterns)
   }
 
-  private handlePipeline = (node: Parser.SyntaxNode): Type => {
-    const argumentType = this.traverse(node.namedChild(0)!)!
-    const valueType = this.traverse(node.namedChild(1)!)!
-    const argumentTypes = new CurriedType([argumentType])
-
-    return new InferApplicationType(this._typeConstraints).perform(
-      valueType,
-      argumentTypes,
+  // eslint-disable-next-line max-lines-per-function
+  private handlePipeline = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.Pipeline> => {
+    const argument = CompileError.addContext(
+      this.traverse,
+      node.namedChild(0)!,
+    )!
+    const value = CompileError.addContext(this.traverse, node.namedChild(1)!)!
+    const args = argument.answers.map(
+      (answer) => new AccumulatedAnswer([answer]),
     )
-  }
 
-  private handlePrefixApplication = (node: Parser.SyntaxNode): Type => {
-    const valueType = this.traverse(node.namedChild(0)!)!
-    const argumentType = this.traverse(node.namedChild(1)!)!
-    const argumentTypes = new CurriedType([argumentType])
+    return new InferApplicationType<
+      AST.Expression,
+      AST.Expression,
+      AST.Pipeline
+    >(
+      (valueNode, argumentNodes, typeConstraint) =>
+        new Answer(
+          new AST.Pipeline(valueNode, argumentNodes[0]),
+          typeConstraint,
+        ),
+    ).perform(value, args)
+  }
 
-    return new InferApplicationType(this._typeConstraints).perform(
-      valueType,
-      argumentTypes,
+  // eslint-disable-next-line max-lines-per-function
+  private handlePrefixApplication = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.PrefixApplication> => {
+    const value = CompileError.addContext(
+      this.handleIdentifier,
+      node.namedChild(0)!,
+    )!
+    const argument = CompileError.addContext(
+      this.traverse,
+      node.namedChild(1)!,
+    )!
+    const args = argument.answers.map(
+      (answer) => new AccumulatedAnswer([answer]),
     )
+
+    return new InferApplicationType<
+      AST.Identifier,
+      AST.Expression,
+      AST.PrefixApplication
+    >(
+      (valueNode, argumentNodes, typeConstraint) =>
+        new Answer(
+          new AST.PrefixApplication(valueNode, argumentNodes[0]),
+          typeConstraint,
+        ),
+    ).perform(value, args)
   }
 
-  private handleProgram = (node: Parser.SyntaxNode): void => {
-    node.namedChildren.forEach((child) => this.traverse(child))
+  private handleProgram = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.Program> => {
+    const expressions = node.namedChildren.map((child) =>
+      CompileError.addContext(this.traverse, child),
+    )
+
+    return new InferBlockType<AST.Program>(
+      (expressions) => new AST.Program(expressions.nodes),
+    ).perform(expressions)
   }
 
-  private handleReturn = (node: Parser.SyntaxNode): Type =>
-    this.traverse(node.namedChild(0)!)!
+  private handleRegex = (node: Parser.SyntaxNode): Disjunction<AST.Regex> =>
+    new Disjunction([
+      new Answer(
+        new AST.Regex(node.text),
+        new TypeConstraint(new ParametricType(REGULAR_EXPRESSION_TYPE)),
+      ),
+    ])
 
-  private handleShorthandPairIdentifier = (
-    node: Parser.SyntaxNode,
-  ): ParametricType => {
-    const name = node.text
-    const binding = this._walkFileModuleScope.scope.resolveBinding(name)
+  private handleReturn = (node: Parser.SyntaxNode): Disjunction<AST.Return> => {
+    const value = CompileError.addContext(this.traverse, node.namedChild(0)!)!
 
-    assert(
-      binding instanceof IdentifierBinding,
-      'Identifier binding should be found in scope.',
+    return new Disjunction(
+      value.answers.map(
+        (answer) =>
+          new Answer(new AST.Return(answer.node), answer.typeConstraint),
+      ),
     )
+  }
 
-    const keyType = new ParametricType(STRING_TYPE)
-    const valueType = binding.type
+  private handleShorthandAccessIdentifier = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.ShorthandAccessIdentifier> => {
+    const name = node.text
+    const shorthandAccessIdentifier = new AST.ShorthandAccessIdentifier(name)
 
-    return new ParametricType(MAP_TYPE, [keyType, valueType])
+    return new Disjunction([
+      new Answer(
+        shorthandAccessIdentifier,
+        new TypeConstraint(new ParametricType(STRING_TYPE)),
+      ),
+    ])
   }
 
-  private handleSpreadList = (node: Parser.SyntaxNode): Type => {
-    const valueType = this.traverse(node.namedChild(0)!)!
+  // eslint-disable-next-line max-lines-per-function
+  private handleShorthandPairIdentifier = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.ShorthandPairIdentifier> => {
+    const name = node.text
+    const bindings = this._walkFileModuleScope.scope.resolveBindings(name)
+    const keyType = new ParametricType(STRING_TYPE)
 
-    return new ParametricType(LIST_TYPE).unify(
-      valueType,
-      this._typeConstraints,
-      true,
+    return new Disjunction(
+      bindings.map((binding) => {
+        assert(
+          binding instanceof IdentifierBinding ||
+            binding instanceof IdentifierBindingTemplate,
+          'Binding should be an identifier binding.',
+        )
+
+        return new Answer(
+          new AST.ShorthandPairIdentifier(
+            binding.name,
+            binding.transformedName,
+          ),
+          new TypeConstraint(
+            new ParametricType(MAP_TYPE, [
+              keyType,
+              binding.typeConstraint.type,
+            ]),
+            binding.typeConstraint.typeEqualityGraph,
+          ),
+        )
+      }),
     )
   }
 
-  private handleSpreadMap = (node: Parser.SyntaxNode): Type => {
-    const valueType = this.traverse(node.namedChild(0)!)!
-
-    return new ParametricType(MAP_TYPE, []).unify(
-      valueType,
-      this._typeConstraints,
-      true,
+  private handleSpreadList = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.SpreadList> => {
+    const value = CompileError.addContext(this.traverse, node.namedChild(0)!)!
+
+    return new Disjunction(
+      value.answers.map((answer) => {
+        const typeConstraint = new TypeConstraint(
+          new ParametricType(LIST_TYPE, []),
+        ).unify(answer.typeConstraint, true)
+        if (typeConstraint === undefined) return
+
+        return new Answer(new AST.SpreadList(answer.node), typeConstraint)
+      }),
     )
   }
 
-  private handleSpreadTuple = (node: Parser.SyntaxNode): Type => {
-    const valueType = this.traverse(node.namedChild(0)!)!
+  private handleSpreadMap = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.SpreadMap> => {
+    const value = CompileError.addContext(this.traverse, node.namedChild(0)!)!
+
+    return new Disjunction(
+      value.answers.map((answer) => {
+        const typeConstraint = new TypeConstraint(
+          new ParametricType(MAP_TYPE, []),
+        ).unify(answer.typeConstraint, true)
+        if (typeConstraint === undefined) return
+
+        return new Answer(new AST.SpreadMap(answer.node), typeConstraint)
+      }),
+    )
+  }
 
-    return new ParametricType(TUPLE_TYPE, []).unify(
-      valueType,
-      this._typeConstraints,
-      true,
+  private handleSpreadTuple = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.SpreadTuple> => {
+    const value = CompileError.addContext(this.traverse, node.namedChild(0)!)!
+
+    return new Disjunction(
+      value.answers.map((answer) => {
+        const typeConstraint = new TypeConstraint(
+          new ParametricType(TUPLE_TYPE, []),
+        ).unify(answer.typeConstraint, true)
+        if (typeConstraint === undefined) return
+
+        return new Answer(new AST.SpreadTuple(answer.node), typeConstraint)
+      }),
     )
   }
 
-  private handleString = (node: Parser.SyntaxNode): ParametricType => {
-    node.namedChildren.forEach((child) => this.traverse(child))
+  private handleString = (node: Parser.SyntaxNode): Disjunction<AST.String> => {
+    const content = node.text.slice(1, -1)
+    const interpolationValues = node.namedChildren.map((child) =>
+      CompileError.addContext(this.traverse, child.namedChild(0)!),
+    )
 
-    return new ParametricType(STRING_TYPE)
+    return new InferStringType().perform(content, interpolationValues)
   }
 
-  private handleTuple = (node: Parser.SyntaxNode): ParametricType => {
-    return new InferTupleType(this, this._typeConstraints).perform(
-      node.namedChildren,
+  private handleTuple = (node: Parser.SyntaxNode): Disjunction<AST.Tuple> => {
+    const elements = node.namedChildren.map((child) =>
+      CompileError.addContext(this.traverse, child),
+    )
+
+    return new InferTupleType((elements) => new AST.Tuple(elements)).perform(
+      elements,
     )
   }
 
-  private handleType = (node: Parser.SyntaxNode): Type => {
-    const name = node.text
-    const binding = this._walkFileModuleScope.scope.resolveBinding(name)
+  private handleType = (
+    node: Parser.SyntaxNode,
+  ): Disjunction<AST.ParametricType> => {
+    const type = new BuildType().perform(node)
 
-    if (binding instanceof TypeBinding) return binding.type
-    else throw new MissingBindingError(name)
+    return new Disjunction([
+      new Answer(
+        new AST.ParametricType(type.name),
+        new TypeConstraint(
+          new GetModuleTypeRepresentation(
+            this._walkFileModuleScope.scope,
+          ).perform(type),
+        ),
+      ),
+    ])
   }
 
-  private handleWhenClause = (node: Parser.SyntaxNode): Type => {
+  // eslint-disable-next-line max-lines-per-function
+  private handleWhen = (
+    node: Parser.SyntaxNode,
+    value: Answer<AST.Expression>,
+  ): Disjunction<AST.When> => {
     this._walkFileModuleScope.peekBlock()
-    this.handlePatternList(node.namedChild(0)!)
+    const patterns = this.handlePatternList(node.namedChild(0)!, value)
     this._walkFileModuleScope.leaveBlock()
 
-    return this.traverse(node.namedChild(1)!)!
-  }
-
-  private handleWhenClauses = (node: Parser.SyntaxNode): Type => {
-    const branchTypes = node.namedChildren
-      .map((child) => this.traverse(child))
-      .filter(isNotUndefined)
+    const body = this.handleBlock(node.namedChild(1)!)!
+
+    return new MergeAccumulatedTypeDisjunction<
+      AST.Pattern,
+      AST.Block,
+      AST.When
+    >(
+      (patterns, body) =>
+        new Answer(
+          new AST.When(patterns.nodes, body.node),
+          new TypeConstraint(
+            body.typeConstraint.type,
+            TypeEqualityGraph.build(
+              ...patterns.typeConstraints.map(
+                (typeConstraint) => typeConstraint.typeEqualityGraph,
+              ),
+              body.typeConstraint.typeEqualityGraph,
+            ),
+          ),
+        ),
+    ).perform(patterns, body)
+  }
+
+  private handleWhenClauses = (
+    node: Parser.SyntaxNode,
+    value: Answer<AST.Expression>,
+  ): AccumulatedDisjunction<AST.When> => {
+    const branches = node.namedChildren.map((child) =>
+      CompileError.addContext(this.handleWhen, child, value),
+    )
 
-    return new InferBranchType(this._typeConstraints).perform(branchTypes)
+    return new DistributeTypeDisjunction<AST.When>().perform(branches)
   }
 }
diff --git a/.yalc/tony-lang/src/type_inference/models/AccumulatedAnswer.ts b/.yalc/tony-lang/src/type_inference/models/AccumulatedAnswer.ts
new file mode 100644
index 0000000..803380b
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/models/AccumulatedAnswer.ts
@@ -0,0 +1,23 @@
+import * as AST from '../../ast'
+import { Type, TypeConstraint } from '../../types'
+import { Answer } from './Answer'
+
+export class AccumulatedAnswer<T extends AST.SyntaxNode> {
+  private _answers: Answer<T>[]
+
+  constructor(answers: Answer<T>[] = []) {
+    this._answers = answers
+  }
+
+  get answers(): Answer<T>[] {
+    return this._answers
+  }
+
+  get nodes(): T[] {
+    return this._answers.map((answer) => answer.node)
+  }
+
+  get typeConstraints(): TypeConstraint<Type>[] {
+    return this._answers.map((answer) => answer.typeConstraint)
+  }
+}
diff --git a/.yalc/tony-lang/src/type_inference/models/AccumulatedDisjunction.ts b/.yalc/tony-lang/src/type_inference/models/AccumulatedDisjunction.ts
new file mode 100644
index 0000000..5588225
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/models/AccumulatedDisjunction.ts
@@ -0,0 +1,6 @@
+import * as AST from '../../ast'
+import { AccumulatedAnswer } from './AccumulatedAnswer'
+
+export type AccumulatedDisjunction<
+  T extends AST.SyntaxNode
+> = AccumulatedAnswer<T>[]
diff --git a/.yalc/tony-lang/src/type_inference/models/Answer.ts b/.yalc/tony-lang/src/type_inference/models/Answer.ts
new file mode 100644
index 0000000..984ed8f
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/models/Answer.ts
@@ -0,0 +1,29 @@
+import * as AST from '../../ast'
+import { Type, TypeConstraint } from '../../types'
+
+export class Answer<T extends AST.SyntaxNode> {
+  private _node: T
+  private _typeConstraint: TypeConstraint<Type>
+
+  constructor(node: T, typeConstraint: TypeConstraint<Type>) {
+    this._node = node
+    this._typeConstraint = typeConstraint
+  }
+
+  get node(): T {
+    return this._node
+  }
+
+  get typeConstraint(): TypeConstraint<Type> {
+    return this._typeConstraint
+  }
+
+  static build = <T>(
+    node: T,
+    typeConstraint?: TypeConstraint<Type>,
+  ): Answer<T> | undefined => {
+    if (typeConstraint === undefined) return
+
+    return new Answer(node, typeConstraint)
+  }
+}
diff --git a/.yalc/tony-lang/src/type_inference/models/Disjunction.ts b/.yalc/tony-lang/src/type_inference/models/Disjunction.ts
new file mode 100644
index 0000000..9a10723
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/models/Disjunction.ts
@@ -0,0 +1,19 @@
+import * as AST from '../../ast'
+import { Answer } from './Answer'
+import { TypeError } from '../../errors'
+import { isNotUndefined } from '../../utilities'
+
+export class Disjunction<T extends AST.SyntaxNode> {
+  private _answers: Answer<T>[]
+
+  constructor(answers: (Answer<T> | undefined)[]) {
+    const filteredAnswers = answers.filter(isNotUndefined)
+    if (filteredAnswers.length == 0) throw new TypeError()
+
+    this._answers = filteredAnswers
+  }
+
+  get answers(): Answer<T>[] {
+    return this._answers
+  }
+}
diff --git a/.yalc/tony-lang/src/type_inference/models/GeneralizedDisjunction.ts b/.yalc/tony-lang/src/type_inference/models/GeneralizedDisjunction.ts
new file mode 100644
index 0000000..fb18abe
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/models/GeneralizedDisjunction.ts
@@ -0,0 +1,16 @@
+import * as AST from '../../ast'
+import { AccumulatedAnswer } from './AccumulatedAnswer'
+import { AccumulatedDisjunction } from './AccumulatedDisjunction'
+import { Answer } from './Answer'
+import { Disjunction } from './Disjunction'
+
+export type GeneralizedDisjunction<T extends AST.SyntaxNode> =
+  | Disjunction<T>
+  | AccumulatedDisjunction<T>
+
+export const getAnswers = <T>(
+  disjunction: GeneralizedDisjunction<T>,
+): (Answer<T> | AccumulatedAnswer<T>)[] => {
+  if (disjunction instanceof Disjunction) return disjunction.answers
+  else return disjunction
+}
diff --git a/.yalc/tony-lang/src/type_inference/models/index.ts b/.yalc/tony-lang/src/type_inference/models/index.ts
new file mode 100644
index 0000000..ceb18cf
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/models/index.ts
@@ -0,0 +1,5 @@
+export { AccumulatedAnswer } from './AccumulatedAnswer'
+export { AccumulatedDisjunction } from './AccumulatedDisjunction'
+export { Answer } from './Answer'
+export { Disjunction } from './Disjunction'
+export { GeneralizedDisjunction, getAnswers } from './GeneralizedDisjunction'
diff --git a/.yalc/tony-lang/src/type_inference/services/AccumulateTypeDisjunction.ts b/.yalc/tony-lang/src/type_inference/services/AccumulateTypeDisjunction.ts
new file mode 100644
index 0000000..3a634a4
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/services/AccumulateTypeDisjunction.ts
@@ -0,0 +1,35 @@
+import * as AST from '../../ast'
+import {
+  AccumulatedAnswer,
+  AccumulatedDisjunction,
+  Answer,
+  Disjunction,
+} from '../models'
+
+type Factory<T> = (fst: Answer<T>, snd: Answer<T>) => AccumulatedAnswer<T>
+
+export class AccumulateTypeDisjunction<T extends AST.SyntaxNode> {
+  private _factory: Factory<T>
+
+  constructor(factory: Factory<T>) {
+    this._factory = factory
+  }
+
+  perform = (
+    fstDisj: Disjunction<T>,
+    sndDisj: Disjunction<T>,
+  ): AccumulatedDisjunction<T> =>
+    fstDisj.answers.reduce(
+      (answers: AccumulatedDisjunction<T>, fst) => [
+        ...answers,
+        ...sndDisj.answers.reduce(
+          (answers: AccumulatedDisjunction<T>, snd) => [
+            ...answers,
+            this._factory(fst, snd),
+          ],
+          [],
+        ),
+      ],
+      [],
+    )
+}
diff --git a/.yalc/tony-lang/src/type_inference/services/DistributeTypeDisjunction.ts b/.yalc/tony-lang/src/type_inference/services/DistributeTypeDisjunction.ts
new file mode 100644
index 0000000..b6382c3
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/services/DistributeTypeDisjunction.ts
@@ -0,0 +1,52 @@
+import * as AST from '../../ast'
+import {
+  AccumulatedAnswer,
+  AccumulatedDisjunction,
+  Answer,
+  GeneralizedDisjunction,
+  getAnswers,
+} from '../models'
+
+export class DistributeTypeDisjunction<T extends AST.SyntaxNode> {
+  perform = ([disjunction, ...otherDisjunctions]: GeneralizedDisjunction<
+    T
+  >[]): AccumulatedDisjunction<T> => {
+    if (disjunction === undefined) return []
+
+    const distributedAnswers = this.perform(otherDisjunctions)
+    if (distributedAnswers.length == 0)
+      return getAnswers(disjunction).map((answer) =>
+        this.buildAccumulatedAnswer(answer),
+      )
+
+    return getAnswers(disjunction).reduce(
+      (answers: AccumulatedAnswer<T>[], answer) => [
+        ...answers,
+        ...distributedAnswers.map((accumulatedAnswer) =>
+          this.mergeAccumulatedAnswers(accumulatedAnswer, answer),
+        ),
+      ],
+      [],
+    )
+  }
+
+  private buildAccumulatedAnswer = (
+    answer: Answer<T> | AccumulatedAnswer<T>,
+  ): AccumulatedAnswer<T> => {
+    if (answer instanceof Answer) return new AccumulatedAnswer([answer])
+    else return answer
+  }
+
+  private mergeAccumulatedAnswers = (
+    accumulatedAnswer: AccumulatedAnswer<T>,
+    answer: Answer<T> | AccumulatedAnswer<T>,
+  ): AccumulatedAnswer<T> => {
+    if (answer instanceof Answer)
+      return new AccumulatedAnswer([answer, ...accumulatedAnswer.answers])
+    else
+      return new AccumulatedAnswer([
+        ...answer.answers,
+        ...accumulatedAnswer.answers,
+      ])
+  }
+}
diff --git a/.yalc/tony-lang/src/type_inference/services/GetModuleTypeRepresentation.ts b/.yalc/tony-lang/src/type_inference/services/GetModuleTypeRepresentation.ts
new file mode 100644
index 0000000..2eeb954
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/services/GetModuleTypeRepresentation.ts
@@ -0,0 +1,19 @@
+import { InvalidUseOfTypeAsValueError, MissingBindingError } from '../../errors'
+import { ModuleBinding, NestedScope } from '../../symbol_table'
+import { ModuleType, ParametricType } from '../../types'
+
+export class GetModuleTypeRepresentation {
+  private _scope: NestedScope
+
+  constructor(scope: NestedScope) {
+    this._scope = scope
+  }
+
+  perform = (type: ParametricType): ModuleType => {
+    const binding = this._scope.resolveBinding(type.name)
+
+    if (binding === undefined) throw new MissingBindingError(type.name)
+    else if (binding instanceof ModuleBinding) return binding.type
+    else throw new InvalidUseOfTypeAsValueError(binding.name)
+  }
+}
diff --git a/.yalc/tony-lang/src/type_inference/services/InferAbstractionBranchType.ts b/.yalc/tony-lang/src/type_inference/services/InferAbstractionBranchType.ts
new file mode 100644
index 0000000..1dfd44e
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/services/InferAbstractionBranchType.ts
@@ -0,0 +1,50 @@
+import * as AST from '../../ast'
+import { Answer, Disjunction } from '../models'
+import {
+  FUNCTION_TYPE,
+  ParametricType,
+  TypeConstraint,
+  TypeEqualityGraph,
+} from '../../types'
+import { MergeTypeDisjunction } from './MergeTypeDisjunction'
+import { assert } from '../../errors'
+
+export class InferAbstractionBranchType<T> {
+  perform = (
+    parameters: Disjunction<AST.Parameters>,
+    body: Disjunction<AST.Block>,
+  ): Disjunction<AST.AbstractionBranch> =>
+    new MergeTypeDisjunction<AST.Parameters, AST.Block, AST.AbstractionBranch>(
+      (parametersAnswer, bodyAnswer) => {
+        const typeEqualityGraph = TypeEqualityGraph.build(
+          parametersAnswer.typeConstraint.typeEqualityGraph,
+          bodyAnswer.typeConstraint.typeEqualityGraph,
+        )
+        if (typeEqualityGraph === undefined) return
+
+        return this.buildAnswer(parametersAnswer, bodyAnswer, typeEqualityGraph)
+      },
+    ).perform(parameters, body)
+
+  private buildAnswer = (
+    parametersAnswer: Answer<AST.Parameters>,
+    bodyAnswer: Answer<AST.Block>,
+    typeEqualityGraph: TypeEqualityGraph,
+  ): Answer<AST.AbstractionBranch> => {
+    assert(
+      parametersAnswer.typeConstraint.type instanceof ParametricType,
+      'Parameter types should be a parametric function type.',
+    )
+
+    return new Answer(
+      new AST.AbstractionBranch(parametersAnswer.node, bodyAnswer.node),
+      new TypeConstraint(
+        new ParametricType(FUNCTION_TYPE, [
+          ...parametersAnswer.typeConstraint.type.parameters,
+          bodyAnswer.typeConstraint.type,
+        ]),
+        typeEqualityGraph,
+      ),
+    )
+  }
+}
diff --git a/.yalc/tony-lang/src/type_inference/services/InferAccessType.ts b/.yalc/tony-lang/src/type_inference/services/InferAccessType.ts
index 7fd99a2..d233259 100644
--- a/.yalc/tony-lang/src/type_inference/services/InferAccessType.ts
+++ b/.yalc/tony-lang/src/type_inference/services/InferAccessType.ts
@@ -1,9 +1,12 @@
+import * as AST from '../../ast'
+import { Answer, Disjunction } from '../models'
 import {
-  InternalError,
-  InvalidPropertyAccessError,
-  TypeError,
-  assert,
-} from '../../errors'
+  Binding,
+  BindingTemplate,
+  IdentifierBinding,
+  IdentifierBindingTemplate,
+} from '../../symbol_table'
+import { InternalError, InvalidModuleAccessError, assert } from '../../errors'
 import {
   LIST_TYPE,
   MAP_TYPE,
@@ -12,110 +15,235 @@ import {
   STRING_TYPE,
   TUPLE_TYPE,
   Type,
-  TypeConstraints,
+  TypeConstraint,
+  TypeEqualityGraph,
+  TypeVariable,
 } from '../../types'
-import { NestedScope, TypeBinding } from '../../symbol_table'
-import Parser from 'tree-sitter'
+import { GetModuleTypeRepresentation } from './GetModuleTypeRepresentation'
+import { MergeTypeDisjunction } from './MergeTypeDisjunction'
 
 export class InferAccessType {
-  private _node: Parser.SyntaxNode
-  private _scope: NestedScope
-  private _typeConstraints: TypeConstraints
-
-  constructor(
-    node: Parser.SyntaxNode,
-    scope: NestedScope,
-    typeConstraints: TypeConstraints,
-  ) {
-    this._node = node
-    this._scope = scope
-    this._typeConstraints = typeConstraints
+  private _getModuleTypeRepresentation: GetModuleTypeRepresentation
+
+  constructor(getModuleTypeRepresentation: GetModuleTypeRepresentation) {
+    this._getModuleTypeRepresentation = getModuleTypeRepresentation
   }
 
-  perform = (valueType: Type, accessorType: Type): Type => {
-    if (valueType instanceof ParametricType) {
-      if (valueType.name === LIST_TYPE)
-        return this.accessList(valueType, accessorType)
-      else if (valueType.name === TUPLE_TYPE)
-        return this.accessTuple(valueType, accessorType)
-      else if (valueType.name === MAP_TYPE)
-        return this.accessMap(valueType, accessorType)
-      else return this.accessRepresentation(valueType, accessorType)
-    }
-
-    throw new TypeError(
-      valueType,
-      undefined,
-      'The access operator may only be used on objects or values of a list, ' +
-        'tuple or map type.',
+  perform = (
+    value: Disjunction<AST.Expression>,
+    accessor: Disjunction<AST.Expression>,
+  ): Disjunction<AST.Access> =>
+    new MergeTypeDisjunction<AST.Expression, AST.Expression, AST.Access>(
+      this.buildAnswers,
+    ).perform(value, accessor)
+
+  private buildAnswers = (
+    value: Answer<AST.Expression>,
+    accessor: Answer<AST.Expression>,
+  ): Disjunction<AST.Access> | undefined => {
+    const typeEqualityGraph = TypeEqualityGraph.build(
+      value.typeConstraint.typeEqualityGraph,
+      accessor.typeConstraint.typeEqualityGraph,
     )
+    if (typeEqualityGraph === undefined) return
+
+    return this.inferType(value, accessor, typeEqualityGraph)
+  }
+
+  // eslint-disable-next-line max-lines-per-function
+  private inferType = (
+    value: Answer<AST.Expression>,
+    accessor: Answer<AST.Expression>,
+    typeEqualityGraph: TypeEqualityGraph,
+  ): Disjunction<AST.Access> | undefined => {
+    const valueType = value.typeConstraint.type
+    const accessorType = accessor.typeConstraint.type
+
+    return new Disjunction([
+      this.buildAnswer(
+        value,
+        accessor,
+        this.inferListAccessType(valueType, accessorType, typeEqualityGraph),
+        typeEqualityGraph,
+      ),
+      this.buildAnswer(
+        value,
+        accessor,
+        this.inferMapAccessType(valueType, accessorType, typeEqualityGraph),
+        typeEqualityGraph,
+      ),
+      this.buildAnswer(
+        value,
+        accessor,
+        this.inferTupleAccessType(
+          valueType,
+          accessorType,
+          accessor.node,
+          typeEqualityGraph,
+        ),
+        typeEqualityGraph,
+      ),
+      ...this.inferModuleAccessType(
+        valueType,
+        value.node,
+        accessorType,
+        accessor.node,
+        typeEqualityGraph,
+      ),
+    ])
   }
 
-  private accessList = (
-    valueType: ParametricType,
+  private buildAnswer = (
+    value: Answer<AST.Expression>,
+    accessor: Answer<AST.Expression>,
+    type: Type | undefined,
+    typeEqualityGraph: TypeEqualityGraph,
+  ): Answer<AST.Access> | undefined =>
+    Answer.build(
+      new AST.Access(value.node, accessor.node),
+      TypeConstraint.build(type, typeEqualityGraph),
+    )
+
+  private inferListAccessType = (
+    valueType: Type,
     accessorType: Type,
-  ): Type => {
-    new ParametricType(NUMBER_TYPE).unify(accessorType, this._typeConstraints)
+    typeEqualityGraph: TypeEqualityGraph,
+  ): Type | undefined => {
+    const unifiedValueType = new ParametricType(LIST_TYPE, [
+      new TypeVariable(),
+    ]).unify(valueType, typeEqualityGraph)
+    if (unifiedValueType === undefined) return
+    const unifiedAccessorType = new ParametricType(NUMBER_TYPE).unify(
+      accessorType,
+      typeEqualityGraph,
+    )
+    if (unifiedAccessorType === undefined) return
 
-    return valueType.parameters[0]
+    assert(
+      unifiedValueType instanceof ParametricType,
+      'Should be parametric type.',
+    )
+    return unifiedValueType.parameters[0]
   }
 
-  private accessMap = (valueType: ParametricType, accessorType: Type): Type => {
-    valueType.parameters[0].unify(accessorType, this._typeConstraints)
+  private inferMapAccessType = (
+    valueType: Type,
+    accessorType: Type,
+    typeEqualityGraph: TypeEqualityGraph,
+  ): Type | undefined => {
+    const unifiedValueType = new ParametricType(MAP_TYPE, [
+      new TypeVariable(),
+      new TypeVariable(),
+    ]).unify(valueType, typeEqualityGraph)
+    if (unifiedValueType === undefined) return
+
+    assert(
+      unifiedValueType instanceof ParametricType,
+      'Should be parametric type.',
+    )
+    const unifiedAccessorType = unifiedValueType.parameters[0].unify(
+      accessorType,
+      typeEqualityGraph,
+    )
+    if (unifiedAccessorType === undefined) return
 
-    return valueType.parameters[1]
+    return unifiedValueType.parameters[1]
   }
 
-  private accessTuple = (
-    valueType: ParametricType,
+  private inferTupleAccessType = (
+    valueType: Type,
     accessorType: Type,
-  ): Type => {
-    new ParametricType(NUMBER_TYPE).unify(accessorType, this._typeConstraints)
+    accessorNode: AST.Expression,
+    typeEqualityGraph: TypeEqualityGraph,
+  ): Type | undefined => {
+    if (!(valueType instanceof ParametricType) || valueType.name !== TUPLE_TYPE)
+      return
+    const unifiedAccessorType = new ParametricType(NUMBER_TYPE).unify(
+      accessorType,
+      typeEqualityGraph,
+    )
+    if (unifiedAccessorType === undefined) return
 
     // TODO: implement dynamic access with union types
-    if (this._node.namedChild(1)!.type === 'number') {
-      const numberNode = this._node.namedChild(1)!
-      const index = parseInt(numberNode.text)
-
-      return valueType.parameters[index]
-    } else
+    if (accessorNode instanceof AST.Number)
+      return valueType.parameters[accessorNode.value]
+    else
       throw new InternalError(
         'Dynamic tuple access has not been implemented yet.',
       )
   }
 
-  private accessRepresentation = (
-    valueType: ParametricType,
+  // eslint-disable-next-line max-lines-per-function
+  private inferModuleAccessType = (
+    valueType: Type,
+    valueNode: AST.Expression,
     accessorType: Type,
-  ): Type => {
-    new ParametricType(STRING_TYPE).unify(accessorType, this._typeConstraints)
-
-    // TODO: implement dynamic access with union types
-    if (this._node.namedChild(1)!.type === 'shorthand_access_identifier') {
-      const propertyName = this._node.namedChild(1)!.text
-
-      const binding = this._scope.resolveBinding(valueType.name)
-      assert(binding instanceof TypeBinding, 'Should be a type binding.')
-
-      return this.accessRepresentationProperty(binding, propertyName)
-    } else
-      throw new InternalError(
-        'Dynamic object access has not been implemented yet.',
-      )
+    accessorNode: AST.Expression,
+    typeEqualityGraph: TypeEqualityGraph,
+  ): Answer<AST.Access>[] => {
+    if (!(valueType instanceof ParametricType)) return []
+    const unifiedAccessorType = new ParametricType(STRING_TYPE).unify(
+      accessorType,
+      typeEqualityGraph,
+    )
+    if (unifiedAccessorType === undefined) return []
+
+    const moduleType = this._getModuleTypeRepresentation.perform(valueType)
+
+    if (accessorNode instanceof AST.ShorthandAccessIdentifier) {
+      const bindings = moduleType.resolveProperty(accessorNode.name)
+
+      if (bindings.length > 0)
+        return this.inferModuleBindingType(
+          valueNode,
+          bindings,
+          typeEqualityGraph,
+        )
+      else
+        throw new InvalidModuleAccessError(
+          accessorNode.name,
+          moduleType.toString(),
+        )
+    } else throw new InvalidModuleAccessError(moduleType.toString())
   }
 
-  private accessRepresentationProperty = (
-    binding: TypeBinding,
-    propertyName: string,
-  ): Type => {
-    const property = binding.representation.findProperty(propertyName)
-
-    if (property) return property.type
-    else
-      throw new InvalidPropertyAccessError(
-        propertyName,
-        binding.type.toString(),
-        binding.representation.toString(),
+  private inferModuleBindingType = (
+    valueNode: AST.Expression,
+    bindings: (Binding | BindingTemplate)[],
+    typeEqualityGraph: TypeEqualityGraph,
+  ): Answer<AST.Access>[] =>
+    bindings.reduce((answers: Answer<AST.Access>[], binding) => {
+      assert(
+        binding instanceof IdentifierBinding ||
+          binding instanceof IdentifierBindingTemplate,
+        'Binding should be an identifier binding.',
       )
-  }
+
+      return [
+        ...answers,
+        this.buildModuleAccessAnswer(valueNode, binding, typeEqualityGraph),
+      ]
+    }, [])
+
+  private buildModuleAccessAnswer = (
+    valueNode: AST.Expression,
+    binding: IdentifierBinding | IdentifierBindingTemplate,
+    typeEqualityGraph: TypeEqualityGraph,
+  ): Answer<AST.Access> =>
+    new Answer(
+      new AST.Access(
+        valueNode,
+        new AST.ShorthandAccessIdentifier(
+          binding.name,
+          binding.transformedName,
+        ),
+      ),
+      new TypeConstraint(
+        binding.typeConstraint.type,
+        TypeEqualityGraph.build(
+          typeEqualityGraph,
+          binding.typeConstraint.typeEqualityGraph,
+        ),
+      ),
+    )
 }
diff --git a/.yalc/tony-lang/src/type_inference/services/InferApplicationType.ts b/.yalc/tony-lang/src/type_inference/services/InferApplicationType.ts
index 1eb5971..25af60d 100644
--- a/.yalc/tony-lang/src/type_inference/services/InferApplicationType.ts
+++ b/.yalc/tony-lang/src/type_inference/services/InferApplicationType.ts
@@ -1,120 +1,259 @@
+import * as AST from '../../ast'
 import {
-  CurriedType,
-  INTERNAL_PARTIAL_APPLICATION_TYPE_NAME,
+  AccumulatedAnswer,
+  AccumulatedDisjunction,
+  Answer,
+  Disjunction,
+} from '../models'
+import {
+  FUNCTION_TYPE,
   ParametricType,
   Type,
-  TypeConstraints,
+  TypeConstraint,
+  TypeEqualityGraph,
   TypeVariable,
   VOID_TYPE,
 } from '../../types'
-import { TypeError } from '../../errors'
+import { InternalTypeError, TypeError } from '../../errors'
 
-export class InferApplicationType {
-  private _typeConstraints: TypeConstraints
+type Factory<T, U, V> = (
+  valueNode: T,
+  argumentNodes: U[],
+  typeConstraint: TypeConstraint<Type>,
+) => Answer<V>
 
-  constructor(typeConstraints: TypeConstraints) {
-    this._typeConstraints = typeConstraints
-  }
+export class InferApplicationType<
+  T extends AST.SyntaxNode,
+  U extends AST.SyntaxNode,
+  V extends AST.SyntaxNode
+> {
+  private _factory: Factory<T, U, V>
 
-  perform = (valueType: Type, argumentTypes: CurriedType): Type => {
-    if (valueType instanceof TypeVariable) {
-      valueType.unify(
-        argumentTypes.concat(new TypeVariable()),
-        this._typeConstraints,
-      )
+  constructor(factory: Factory<T, U, V>) {
+    this._factory = factory
+  }
 
-      return new TypeVariable()
-    }
+  perform = (
+    value: Disjunction<T>,
+    args: AccumulatedDisjunction<U>,
+  ): Disjunction<V> =>
+    new Disjunction(
+      value.answers.reduce(
+        (answers: (Answer<V> | undefined)[], valueAnswer) => [
+          ...answers,
+          ...args.map((argumentsAnswer) =>
+            this.buildAnswers(valueAnswer, argumentsAnswer),
+          ),
+        ],
+        [],
+      ),
+    )
 
-    this.checkAppliedToNonCurriedType(valueType, argumentTypes)
-    this.handleVoidParameterType(valueType)
-    this.checkAppliedTooManyArguments(valueType, argumentTypes)
+  private buildAnswers = (
+    valueAnswer: Answer<T>,
+    argumentsAnswer: AccumulatedAnswer<U>,
+  ): Answer<V> | undefined => {
+    const typeConstraint = this.inferType(valueAnswer, argumentsAnswer)
+    if (typeConstraint === undefined) return
 
-    return this.inferType(valueType, argumentTypes)
+    return this._factory(
+      valueAnswer.node,
+      argumentsAnswer.nodes,
+      typeConstraint,
+    )
   }
 
+  // eslint-disable-next-line max-lines-per-function
   private inferType = (
-    valueType: CurriedType,
-    argumentTypes: CurriedType,
-  ): Type => {
-    const typeConstraints = new TypeConstraints()
-    const inferParameterType = this.inferParameterTypeFactory(
-      typeConstraints,
-      valueType,
-      argumentTypes,
-    )
-    const parameterTypes = valueType.parameters.reduce(inferParameterType, [])
-
-    if (parameterTypes.length == 1)
-      return parameterTypes[0]._reduce(typeConstraints)
-    else return new CurriedType(parameterTypes)._reduce(typeConstraints)
-  }
+    value: Answer<T>,
+    args: AccumulatedAnswer<U>,
+  ): TypeConstraint<Type> | undefined => {
+    let valueTypeConstraint = value.typeConstraint
+    const argumentsTypeEqualityGraph = TypeEqualityGraph.build(
+      ...args.typeConstraints.map(
+        (typeConstraint) => typeConstraint.typeEqualityGraph,
+      ),
+    )
+    if (argumentsTypeEqualityGraph === undefined) return
 
-  private inferParameterTypeFactory = (
-    typeConstraints: TypeConstraints,
-    valueType: CurriedType,
-    argumentTypes: CurriedType,
-  ) => (parameterTypes: Type[], parameterType: Type, i: number): Type[] => {
-    const argumentType = argumentTypes.parameters[i]
-    if (argumentType === undefined || this.isPlaceholderArgument(argumentType))
-      return parameterTypes.concat([parameterType])
+    const argumentsTypeConstraint = new TypeConstraint(
+      new ParametricType(
+        FUNCTION_TYPE,
+        args.typeConstraints.map((typeConstraint) => typeConstraint.type),
+      ),
+      argumentsTypeEqualityGraph,
+    )
+    console.log(
+      valueTypeConstraint.toString(),
+      argumentsTypeConstraint.toString(),
+    )
 
-    try {
-      parameterType.unify(argumentType, typeConstraints)
-    } catch (error) {
-      if (error instanceof TypeError)
-        this.handleArgumentTypeMismatch(error, valueType, argumentTypes)
-      throw error
-    }
+    if (valueTypeConstraint.type instanceof TypeVariable)
+      return this.inferValueType(value, argumentsTypeConstraint)
 
-    return parameterTypes
-  }
+    if (
+      !this.checkAppliedToNonCurriedType(
+        valueTypeConstraint.type,
+        argumentsTypeConstraint.type,
+      )
+    )
+      return
+    valueTypeConstraint = this.handleVoidParameterType(
+      valueTypeConstraint as TypeConstraint<ParametricType>,
+    )
+    if (
+      !this.checkAppliedTooManyArguments(
+        valueTypeConstraint.type as ParametricType,
+        argumentsTypeConstraint.type,
+      )
+    )
+      return
 
-  private handleArgumentTypeMismatch = (
-    error: TypeError,
-    valueType: CurriedType,
-    argumentTypes: CurriedType,
-  ): void =>
-    error.addTypeMismatch(
-      new CurriedType(valueType.parameters.slice(0, -1)),
-      argumentTypes,
+    return this.matchArgumentsAndParameters(
+      valueTypeConstraint as TypeConstraint<ParametricType>,
+      argumentsTypeConstraint,
     )
+  }
 
-  private handleVoidParameterType = (valueType: CurriedType): void => {
-    if (!(valueType instanceof ParametricType && valueType.name === VOID_TYPE))
-      return
+  private inferValueType = (
+    value: Answer<T>,
+    argumentsType: TypeConstraint<ParametricType>,
+  ): TypeConstraint<Type> | undefined => {
+    const returnType = new TypeVariable()
+    const functionType = new TypeConstraint(
+      argumentsType.type.concat(returnType),
+      argumentsType.typeEqualityGraph,
+    )
+    const applicationTypeConstraint = value.typeConstraint.unify(functionType)
+    if (applicationTypeConstraint === undefined) return
 
-    valueType.parameters.pop()
+    return new TypeConstraint(
+      returnType,
+      applicationTypeConstraint.typeEqualityGraph,
+    )
   }
 
   private checkAppliedToNonCurriedType(
     valueType: Type,
-    argumentTypes: CurriedType,
-  ): asserts valueType is CurriedType {
-    if (valueType instanceof CurriedType) return
+    argumentsType: ParametricType,
+  ): valueType is ParametricType {
+    if (valueType instanceof ParametricType && valueType.name === FUNCTION_TYPE)
+      return true
 
-    throw new TypeError(
-      valueType,
-      argumentTypes,
-      'Cannot apply to a non-curried type.',
+    TypeError.addError(
+      new InternalTypeError(
+        valueType,
+        argumentsType,
+        'Cannot apply to a non-curried type.',
+      ),
+    )
+    return false
+  }
+
+  private handleVoidParameterType = (
+    valueTypeConstraint: TypeConstraint<ParametricType>,
+  ): TypeConstraint<ParametricType> => {
+    const firstParameter = valueTypeConstraint.type.parameters[0]
+    if (
+      !(
+        firstParameter instanceof ParametricType &&
+        firstParameter.name === VOID_TYPE
+      )
+    )
+      return valueTypeConstraint
+
+    return new TypeConstraint(
+      new ParametricType(
+        FUNCTION_TYPE,
+        valueTypeConstraint.type.parameters.slice(1),
+      ),
+      valueTypeConstraint.typeEqualityGraph,
     )
   }
 
   private checkAppliedTooManyArguments = (
-    valueType: CurriedType,
-    argumentTypes: CurriedType,
-  ): void => {
-    if (valueType.parameters.length > argumentTypes.parameters.length) return
+    valueType: ParametricType,
+    argumentsType: ParametricType,
+  ): boolean => {
+    if (valueType.parameters.length > argumentsType.parameters.length)
+      return true
 
-    throw new TypeError(
-      new CurriedType(valueType.parameters.slice(0, -1)),
-      argumentTypes,
-      `Applied ${argumentTypes.parameters.length} arguments to a curried ` +
-        `type accepting at most ${valueType.parameters.length - 1} arguments.`,
+    TypeError.addError(
+      new InternalTypeError(
+        new ParametricType(FUNCTION_TYPE, valueType.parameters.slice(0, -1)),
+        argumentsType,
+        `Applied ${argumentsType.parameters.length} arguments to a curried ` +
+          `type accepting at most ${
+            valueType.parameters.length - 1
+          } arguments.`,
+      ),
     )
+    return false
   }
 
+  // eslint-disable-next-line max-lines-per-function
+  private matchArgumentsAndParameters = (
+    valueTypeConstraint: TypeConstraint<ParametricType>,
+    argumentsTypeConstraint: TypeConstraint<ParametricType>,
+  ): TypeConstraint<Type> | undefined => {
+    const typeEqualityGraph = TypeEqualityGraph.build(
+      valueTypeConstraint.typeEqualityGraph,
+      argumentsTypeConstraint.typeEqualityGraph,
+    )
+    const returnTypeEqualityGraph = TypeEqualityGraph.build(
+      valueTypeConstraint.typeEqualityGraph,
+      argumentsTypeConstraint.typeEqualityGraph,
+    )
+    if (
+      typeEqualityGraph === undefined ||
+      returnTypeEqualityGraph === undefined
+    )
+      return
+
+    const parameterTypes = valueTypeConstraint.type.parameters.reduce(
+      this.inferParameterType(typeEqualityGraph, argumentsTypeConstraint.type),
+      [],
+    )
+    if (parameterTypes === undefined) return
+
+    return this.buildReturnTypeConstraint(
+      parameterTypes,
+      returnTypeEqualityGraph,
+    )
+  }
+
+  private inferParameterType = (
+    typeEqualityGraph: TypeEqualityGraph,
+    argumentTypes: ParametricType,
+  ) => (
+    parameterTypes: Type[] | undefined,
+    parameterType: Type,
+    i: number,
+  ): Type[] | undefined => {
+    if (parameterTypes === undefined) return
+
+    const argumentType = argumentTypes.parameters[i]
+    if (argumentType === undefined || this.isPlaceholderArgument(argumentType))
+      return [...parameterTypes, parameterType]
+    if (parameterType.unify(argumentType, typeEqualityGraph) === undefined)
+      return
+
+    return parameterTypes
+  }
+
+  private buildReturnTypeConstraint = (
+    parameterTypes: Type[],
+    typeEqualityGraph: TypeEqualityGraph,
+  ): TypeConstraint<Type> =>
+    new TypeConstraint(
+      parameterTypes.length == 1
+        ? parameterTypes[0].reduce(typeEqualityGraph)
+        : new ParametricType(FUNCTION_TYPE, parameterTypes).reduce(
+            typeEqualityGraph,
+          ),
+      typeEqualityGraph,
+    )
+
   private isPlaceholderArgument = (argumentType: Type): boolean =>
-    argumentType instanceof TypeVariable &&
-    argumentType.name === INTERNAL_PARTIAL_APPLICATION_TYPE_NAME
+    argumentType instanceof ParametricType && argumentType.name === VOID_TYPE
 }
diff --git a/.yalc/tony-lang/src/type_inference/services/InferAssignmentType.ts b/.yalc/tony-lang/src/type_inference/services/InferAssignmentType.ts
new file mode 100644
index 0000000..4006971
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/services/InferAssignmentType.ts
@@ -0,0 +1,41 @@
+import * as AST from '../../ast'
+import { Answer, Disjunction } from '../models'
+import { InferPatternBindingTypes } from './InferPatternBindingTypes'
+import Parser from 'tree-sitter'
+
+export class InferAssignmentType {
+  private _inferPatternBindingTypes: InferPatternBindingTypes
+
+  constructor(inferPatternBindingTypes: InferPatternBindingTypes) {
+    this._inferPatternBindingTypes = inferPatternBindingTypes
+  }
+
+  perform = (
+    patternNode: Parser.SyntaxNode,
+    value: Disjunction<AST.Expression>,
+  ): Disjunction<AST.Assignment> =>
+    new Disjunction(
+      value.answers.reduce((answers: Answer<AST.Assignment>[], valueAnswer) => {
+        const patternAnswers = this._inferPatternBindingTypes
+          .perform(patternNode, valueAnswer.typeConstraint)
+          ?.answers.map((patternAnswer) =>
+            this.buildAnswer(patternAnswer, valueAnswer),
+          )
+
+        if (patternAnswers !== undefined) return [...answers, ...patternAnswers]
+        else return answers
+      }, []),
+    )
+
+  private buildAnswer = (
+    patternAnswer: Answer<AST.Pattern>,
+    valueAnswer: Answer<AST.Expression>,
+  ): Answer<AST.Assignment> =>
+    new Answer(
+      new AST.Assignment(
+        patternAnswer.node as AST.AssignablePattern,
+        valueAnswer.node,
+      ),
+      patternAnswer.typeConstraint,
+    )
+}
diff --git a/.yalc/tony-lang/src/type_inference/services/InferBlockType.ts b/.yalc/tony-lang/src/type_inference/services/InferBlockType.ts
new file mode 100644
index 0000000..fe905f4
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/services/InferBlockType.ts
@@ -0,0 +1,40 @@
+import * as AST from '../../ast'
+import { AccumulatedAnswer, Answer, Disjunction } from '../models'
+import { TypeConstraint, TypeEqualityGraph } from '../../types'
+import { DistributeTypeDisjunction } from './DistributeTypeDisjunction'
+
+type Factory<T> = (expressions: AccumulatedAnswer<AST.Expression>) => T
+
+export class InferBlockType<T extends AST.SyntaxNode> {
+  private _factory: Factory<T>
+
+  constructor(factory: Factory<T>) {
+    this._factory = factory
+  }
+
+  perform = (expressions: Disjunction<AST.Expression>[]): Disjunction<T> =>
+    new Disjunction(
+      new DistributeTypeDisjunction<AST.Expression>()
+        .perform(expressions)
+        .map(this.buildBlock),
+    )
+
+  private buildBlock = (
+    expressions: AccumulatedAnswer<AST.Expression>,
+  ): Answer<T> | undefined => {
+    const typeEqualityGraph = TypeEqualityGraph.build(
+      ...expressions.typeConstraints.map(
+        (typeConstraint) => typeConstraint.typeEqualityGraph,
+      ),
+    )
+    if (typeEqualityGraph === undefined) return
+
+    return new Answer(
+      this._factory(expressions),
+      new TypeConstraint(
+        expressions.answers[expressions.answers.length - 1].typeConstraint.type,
+        typeEqualityGraph,
+      ),
+    )
+  }
+}
diff --git a/.yalc/tony-lang/src/type_inference/services/InferBranchType.ts b/.yalc/tony-lang/src/type_inference/services/InferBranchType.ts
index ae7e7e1..b005ae6 100644
--- a/.yalc/tony-lang/src/type_inference/services/InferBranchType.ts
+++ b/.yalc/tony-lang/src/type_inference/services/InferBranchType.ts
@@ -1,16 +1,34 @@
-import { Type, TypeConstraints } from '../../types'
+import * as AST from '../../ast'
+import { Answer, Disjunction, GeneralizedDisjunction } from '../models'
+import { Type, TypeConstraint, TypeVariable } from '../../types'
+import { DistributeTypeDisjunction } from './DistributeTypeDisjunction'
 
-export class InferBranchType {
-  private _typeConstraints: TypeConstraints
+type Factory<T, U> = (branches: T[]) => U
 
-  constructor(typeConstraints: TypeConstraints) {
-    this._typeConstraints = typeConstraints
+export class InferBranchType<
+  T extends AST.SyntaxNode,
+  U extends AST.SyntaxNode
+> {
+  private _factory: Factory<T, U>
+
+  constructor(factory: Factory<T, U>) {
+    this._factory = factory
   }
 
-  perform = (branchTypes: Type[]): Type =>
-    branchTypes
-      .reduce((type, branchType) =>
-        type.unify(branchType, this._typeConstraints),
-      )
-      ._reduce(this._typeConstraints)
+  perform = (branches: GeneralizedDisjunction<T>[]): Disjunction<U> =>
+    new Disjunction(
+      new DistributeTypeDisjunction<T>().perform(branches).map((branches) => {
+        const typeConstraint = branches.typeConstraints.reduce(
+          (acc: TypeConstraint<Type> | undefined, typeConstraint) => {
+            if (acc === undefined) return
+
+            return acc.unify(typeConstraint)
+          },
+          new TypeConstraint(new TypeVariable()),
+        )
+        if (typeConstraint === undefined) return
+
+        return new Answer(this._factory(branches.nodes), typeConstraint)
+      }),
+    )
 }
diff --git a/.yalc/tony-lang/src/type_inference/services/InferExpressionPairType.ts b/.yalc/tony-lang/src/type_inference/services/InferExpressionPairType.ts
new file mode 100644
index 0000000..47590be
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/services/InferExpressionPairType.ts
@@ -0,0 +1,43 @@
+import * as AST from '../../ast'
+import { Answer, Disjunction } from '../models'
+import {
+  MAP_TYPE,
+  ParametricType,
+  TypeConstraint,
+  TypeEqualityGraph,
+} from '../../types'
+import { MergeTypeDisjunction } from './MergeTypeDisjunction'
+
+export class InferExpressionPairType {
+  perform = (
+    key: Disjunction<AST.Expression>,
+    value: Disjunction<AST.Expression>,
+  ): Disjunction<AST.ExpressionPair> =>
+    new MergeTypeDisjunction<
+      AST.Expression,
+      AST.Expression,
+      AST.ExpressionPair
+    >(this.buildAnswer).perform(key, value)
+
+  private buildAnswer = (
+    key: Answer<AST.Expression>,
+    value: Answer<AST.Expression>,
+  ): Answer<AST.ExpressionPair> | undefined => {
+    const typeEqualityGraph = TypeEqualityGraph.build(
+      key.typeConstraint.typeEqualityGraph,
+      value.typeConstraint.typeEqualityGraph,
+    )
+    if (typeEqualityGraph === undefined) return
+
+    return new Answer(
+      new AST.ExpressionPair(key.node, value.node),
+      new TypeConstraint(
+        new ParametricType(MAP_TYPE, [
+          key.typeConstraint.type,
+          value.typeConstraint.type,
+        ]),
+        typeEqualityGraph,
+      ),
+    )
+  }
+}
diff --git a/.yalc/tony-lang/src/type_inference/services/InferGeneratorType.ts b/.yalc/tony-lang/src/type_inference/services/InferGeneratorType.ts
new file mode 100644
index 0000000..1f91f54
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/services/InferGeneratorType.ts
@@ -0,0 +1,152 @@
+import * as AST from '../../ast'
+import { Answer, Disjunction } from '../models'
+import {
+  BOOLEAN_TYPE,
+  LIST_TYPE,
+  ParametricType,
+  Type,
+  TypeConstraint,
+  TypeEqualityGraph,
+  VOID_TYPE,
+} from '../../types'
+import { IdentifierBindingTemplate, NestedScope } from '../../symbol_table'
+
+export class InferGeneratorType<T> {
+  private _scope: NestedScope
+
+  constructor(scope: NestedScope) {
+    this._scope = scope
+  }
+
+  perform = (
+    bindingTemplate: IdentifierBindingTemplate,
+    value: Disjunction<AST.SyntaxNode>,
+    condition?: Disjunction<AST.SyntaxNode>,
+  ): Disjunction<AST.Generator> =>
+    new Disjunction(
+      value.answers.reduce(
+        this.handleValueAnswer(bindingTemplate, condition),
+        [],
+      ),
+    )
+
+  // eslint-disable-next-line max-lines-per-function
+  private handleValueAnswer = (
+    bindingTemplate: IdentifierBindingTemplate,
+    condition: Disjunction<AST.SyntaxNode> | undefined,
+    // eslint-disable-next-line max-lines-per-function
+  ) => (
+    answers: (Answer<AST.Generator> | undefined)[],
+    valueAnswer: Answer<AST.SyntaxNode>,
+  ): (Answer<AST.Generator> | undefined)[] => {
+    const valueTypeConstraint = this.unifyValueTypeConstraint(
+      bindingTemplate,
+      valueAnswer,
+    )
+    if (valueTypeConstraint === undefined) return answers
+
+    if (condition) {
+      return [
+        ...answers,
+        ...this.buildAnswersWithCondition(
+          bindingTemplate,
+          valueTypeConstraint,
+          valueAnswer,
+          condition,
+        ),
+      ]
+    } else
+      return [
+        ...answers,
+        this.buildAnswer(bindingTemplate, valueTypeConstraint, valueAnswer),
+      ]
+  }
+
+  private unifyValueTypeConstraint = (
+    bindingTemplate: IdentifierBindingTemplate,
+    value: Answer<AST.SyntaxNode>,
+  ): TypeConstraint<Type> | undefined => {
+    const unifiedTypeConstraint = new TypeConstraint(
+      new ParametricType(LIST_TYPE, [bindingTemplate.type]),
+    ).unify(value.typeConstraint) as TypeConstraint<ParametricType>
+    if (unifiedTypeConstraint === undefined) return unifiedTypeConstraint
+
+    const binding = bindingTemplate.buildBinding(
+      new TypeConstraint(
+        unifiedTypeConstraint.type.parameters[0],
+        unifiedTypeConstraint.typeEqualityGraph,
+      ),
+    )
+    if (binding === undefined) return
+
+    this._scope.addBinding(binding)
+    return unifiedTypeConstraint
+  }
+
+  private buildAnswer = (
+    bindingTemplate: IdentifierBindingTemplate,
+    typeConstraint: TypeConstraint<Type>,
+    value: Answer<AST.SyntaxNode>,
+  ): Answer<AST.Generator> =>
+    new Answer(
+      new AST.Generator(
+        bindingTemplate.name,
+        bindingTemplate.transformedName,
+        value.node,
+      ),
+      new TypeConstraint(
+        new ParametricType(VOID_TYPE),
+        typeConstraint.typeEqualityGraph,
+      ),
+    )
+
+  private buildAnswersWithCondition = (
+    bindingTemplate: IdentifierBindingTemplate,
+    valueTypeConstraint: TypeConstraint<Type>,
+    valueAnswer: Answer<AST.SyntaxNode>,
+    condition: Disjunction<AST.SyntaxNode>,
+  ): (Answer<AST.Generator> | undefined)[] =>
+    condition.answers.map(
+      this.handleConditionAnswer(
+        bindingTemplate,
+        valueTypeConstraint,
+        valueAnswer,
+      ),
+    )
+
+  // eslint-disable-next-line max-lines-per-function
+  private handleConditionAnswer = (
+    bindingTemplate: IdentifierBindingTemplate,
+    valueTypeConstraint: TypeConstraint<Type>,
+    value: Answer<AST.SyntaxNode>,
+    // eslint-disable-next-line max-lines-per-function
+  ) => (
+    condition: Answer<AST.SyntaxNode>,
+  ): Answer<AST.Generator> | undefined => {
+    const conditionTypeConstraint = this.unifyConditionTypeConstraint(condition)
+    if (conditionTypeConstraint === undefined) return
+
+    return new Answer(
+      new AST.Generator(
+        bindingTemplate.name,
+        bindingTemplate.transformedName,
+        value.node,
+        condition.node,
+      ),
+      new TypeConstraint(
+        new ParametricType(VOID_TYPE),
+        TypeEqualityGraph.build(
+          valueTypeConstraint.typeEqualityGraph,
+          conditionTypeConstraint.typeEqualityGraph,
+        ),
+      ),
+    )
+  }
+
+  private unifyConditionTypeConstraint = (
+    condition: Answer<AST.SyntaxNode>,
+  ): TypeConstraint<Type> | undefined =>
+    new TypeConstraint(new ParametricType(BOOLEAN_TYPE)).unify(
+      condition.typeConstraint,
+    )
+}
diff --git a/.yalc/tony-lang/src/type_inference/services/InferIdentifierPatternType.ts b/.yalc/tony-lang/src/type_inference/services/InferIdentifierPatternType.ts
new file mode 100644
index 0000000..49a9911
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/services/InferIdentifierPatternType.ts
@@ -0,0 +1,205 @@
+import * as AST from '../../ast'
+import { Answer, Disjunction } from '../models'
+import { DuplicateBindingError, assert } from '../../errors'
+import {
+  IdentifierBinding,
+  IdentifierBindingTemplate,
+  NestedScope,
+} from '../../symbol_table'
+import { Type, TypeConstraint, TypeVariable } from '../../types'
+import { InferTypes } from '../InferTypes'
+import Parser from 'tree-sitter'
+
+type Factory<T> = (
+  name: string,
+  transformedName: string,
+  def?: AST.Expression,
+) => T
+type TypeFactory = (type: Type) => Type
+type TypeConstraintFactory = (
+  type: TypeConstraint<Type>,
+) => TypeConstraint<Type>
+
+export class InferIdentifierPatternType<T extends AST.IdentifierPattern> {
+  private _factory: Factory<T>
+  private _inferTypes: InferTypes
+  private _scope: NestedScope
+  private _typeFactory: TypeFactory
+  private _typeConstraintFactory: TypeConstraintFactory
+
+  constructor(
+    inferTypes: InferTypes,
+    scope: NestedScope,
+    factory: Factory<T>,
+    typeFactory = (type: Type): Type => type,
+    typeConstraintFactory = (
+      type: TypeConstraint<Type>,
+    ): TypeConstraint<Type> => type,
+  ) {
+    this._factory = factory
+    this._inferTypes = inferTypes
+    this._scope = scope
+    this._typeFactory = typeFactory
+    this._typeConstraintFactory = typeConstraintFactory
+  }
+
+  // eslint-disable-next-line max-lines-per-function
+  perform = (
+    patternNode: Parser.SyntaxNode,
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<T> => {
+    const bindingTemplate = this.findBindingTemplate(patternNode)
+    // prettier-ignore
+    // eslint-disable-next-line @typescript-eslint/ban-ts-ignore
+    // @ts-ignore
+    const type = patternNode.typeNode ? new BuildType().perform(patternNode.typeNode) : new TypeVariable()
+
+    const unifiedTypeConstraint = new TypeConstraint(
+      this._typeFactory(type).unsafeUnify(
+        typeConstraint.type,
+        typeConstraint.typeEqualityGraph,
+      ),
+      typeConstraint.typeEqualityGraph,
+    )
+
+    // eslint-disable-next-line @typescript-eslint/ban-ts-ignore
+    // @ts-ignore
+    const defaultNode: Parser.SyntaxNode | undefined = patternNode.defaultNode
+    if (defaultNode)
+      return this.handleDefaultNode(
+        bindingTemplate,
+        unifiedTypeConstraint,
+        this._inferTypes.traverse(defaultNode),
+      )
+
+    if (
+      !this.buildIdentifierBinding(
+        bindingTemplate,
+        this._typeConstraintFactory(unifiedTypeConstraint),
+      )
+    )
+      return new Disjunction([])
+
+    return new Disjunction([
+      new Answer(
+        this._factory(bindingTemplate.name, bindingTemplate.transformedName),
+        unifiedTypeConstraint,
+      ),
+    ])
+  }
+
+  private findBindingTemplate = (
+    patternNode: Parser.SyntaxNode,
+  ): IdentifierBindingTemplate => {
+    const bindingTemplate = this._scope.bindingTemplates.find(
+      (bindingTemplate) => bindingTemplate.node === patternNode,
+    )
+
+    assert(
+      bindingTemplate instanceof IdentifierBindingTemplate,
+      'Pattern identifier binding should be found in current scope.',
+    )
+
+    return bindingTemplate
+  }
+
+  // eslint-disable-next-line max-lines-per-function
+  private handleDefaultNode = (
+    bindingTemplate: IdentifierBindingTemplate,
+    typeConstraint: TypeConstraint<Type>,
+    def: Disjunction<AST.Expression>,
+  ): Disjunction<T> =>
+    new Disjunction(
+      def.answers.map((answer) => {
+        const unifiedTypeConstraint = typeConstraint.unify(
+          new TypeConstraint(
+            this._typeFactory(answer.typeConstraint.type),
+            answer.typeConstraint.typeEqualityGraph,
+          ),
+        )
+        if (unifiedTypeConstraint === undefined) return
+
+        if (
+          !this.buildIdentifierBinding(
+            bindingTemplate,
+            this._typeConstraintFactory(unifiedTypeConstraint),
+          )
+        )
+          return
+
+        return new Answer(
+          this._factory(
+            bindingTemplate.name,
+            bindingTemplate.transformedName,
+            answer.node,
+          ),
+          unifiedTypeConstraint,
+        )
+      }),
+    )
+
+  private buildIdentifierBinding = (
+    bindingTemplate: IdentifierBindingTemplate,
+    typeConstraint: TypeConstraint<Type>,
+  ): boolean => {
+    this.checkDuplicateBinding(bindingTemplate, typeConstraint)
+
+    const binding = this.findBindingForTemplate(bindingTemplate)
+    if (binding) {
+      const unifiedTypeConstraint = binding.typeConstraint.unify(typeConstraint)
+      if (unifiedTypeConstraint === undefined) return false
+
+      this._scope.removeBinding(binding)
+      return this.addBinding(bindingTemplate, unifiedTypeConstraint)
+    }
+
+    return this.addBinding(bindingTemplate, typeConstraint)
+  }
+
+  private checkDuplicateBinding = (
+    bindingTemplate: IdentifierBindingTemplate,
+    typeConstraint: TypeConstraint<Type>,
+  ): void => {
+    const duplicateBinding = this._scope
+      .resolveBindings(bindingTemplate.name)
+      .find(
+        (binding) =>
+          binding instanceof IdentifierBinding &&
+          binding.node !== bindingTemplate.node &&
+          typeConstraint.unify(binding.typeConstraint),
+      )
+    if (duplicateBinding === undefined) return
+
+    throw new DuplicateBindingError(bindingTemplate.name)
+  }
+
+  private findBindingForTemplate = (
+    bindingTemplate: IdentifierBindingTemplate,
+  ): IdentifierBinding | undefined => {
+    const binding = this._scope
+      .resolveBindings(bindingTemplate.name)
+      .find(
+        (binding) =>
+          binding.node === bindingTemplate.node &&
+          binding instanceof IdentifierBinding,
+      )
+    if (binding === undefined) return
+
+    assert(
+      binding instanceof IdentifierBinding,
+      'Should be identifier binding.',
+    )
+    return binding
+  }
+
+  private addBinding = (
+    bindingTemplate: IdentifierBindingTemplate,
+    typeConstraint: TypeConstraint<Type>,
+  ): boolean => {
+    const binding = bindingTemplate.buildBinding(typeConstraint)
+    if (binding === undefined) return false
+
+    this._scope.addBinding(binding)
+    return true
+  }
+}
diff --git a/.yalc/tony-lang/src/type_inference/services/InferImportBindingTypes.ts b/.yalc/tony-lang/src/type_inference/services/InferImportBindingTypes.ts
new file mode 100644
index 0000000..26b0feb
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/services/InferImportBindingTypes.ts
@@ -0,0 +1,163 @@
+import { BuildType, TypeConstraint, TypeEqualityGraph } from '../../types'
+import {
+  FileModuleScope,
+  IdentifierBinding,
+  IdentifierBindingTemplate,
+} from '../../symbol_table'
+import {
+  IdentifierImport,
+  ModuleBinding,
+  ModuleImport,
+} from '../../symbol_table'
+import {
+  InvalidExternalTypeImportError,
+  MissingBindingError,
+  assert,
+} from '../../errors'
+import Parser from 'tree-sitter'
+import { isNotUndefined } from '../../utilities'
+
+export class InferImportBindingTypes {
+  private _typeEqualityGraph: TypeEqualityGraph
+  private _fileScopes: FileModuleScope[]
+  private _scope: FileModuleScope
+
+  constructor(
+    scope: FileModuleScope,
+    fileScopes: FileModuleScope[],
+    typeEqualityGraph: TypeEqualityGraph,
+  ) {
+    this._typeEqualityGraph = typeEqualityGraph
+    this._fileScopes = fileScopes
+    this._scope = scope
+  }
+
+  perform = (node: Parser.SyntaxNode): void => {
+    assert(node.type === 'import', 'Should be import node.')
+
+    this.traverse(node)
+  }
+
+  private traverse = (node: Parser.SyntaxNode): void => {
+    switch (node.type) {
+      case 'identifier_pattern':
+        return this.handleIdentifier(node)
+      case 'import_clause_identifier_pair':
+        return this.handleIdentifier(node)
+      case 'import_clause_type_pair':
+        return this.handleType(node)
+      case 'type':
+        return this.handleType(node)
+      default:
+        return node.namedChildren.forEach(this.traverse)
+    }
+  }
+
+  private handleIdentifier = (node: Parser.SyntaxNode): void => {
+    const imp = this._scope.imports.find((imp) => imp.node === node)
+    assert(imp instanceof IdentifierImport, 'Should be an identifier import.')
+
+    const fileScope = this._fileScopes.find(
+      (fileScope) => fileScope.filePath === imp.filePath,
+    )
+
+    if (fileScope) this.handleInternalIdentifierImport(node, imp, fileScope)
+    else this.handleExternalIdentifierImport(node, imp)
+  }
+
+  // eslint-disable-next-line max-lines-per-function
+  private handleInternalIdentifierImport = (
+    node: Parser.SyntaxNode,
+    imp: IdentifierImport,
+    fileScope: FileModuleScope,
+  ): void => {
+    const bindings = fileScope
+      .resolveBindings(imp.name)
+      .map((binding) => {
+        assert(
+          binding instanceof IdentifierBinding,
+          'Should be an identifier binding.',
+        )
+
+        const typeConstraint = new TypeConstraint(
+          imp.type,
+          this._typeEqualityGraph,
+        ).unify(binding.typeConstraint)
+        if (typeConstraint === undefined) return
+
+        return new IdentifierBinding(
+          node,
+          imp.alias,
+          IdentifierBindingTemplate.getTransformedName(),
+          typeConstraint,
+          {
+            isImplicit: true,
+            importInformation: {
+              filePath: imp.filePath,
+              transformedImportName: binding.transformedName,
+            },
+          },
+        )
+      })
+      .filter(isNotUndefined)
+
+    if (bindings.length > 0)
+      bindings.forEach((binding) => this._scope.addBinding(binding))
+    else throw new MissingBindingError(name)
+  }
+
+  private handleExternalIdentifierImport = (
+    node: Parser.SyntaxNode,
+    imp: IdentifierImport,
+  ): void => {
+    this._scope.addBinding(
+      new IdentifierBinding(
+        node,
+        imp.alias,
+        IdentifierBindingTemplate.getTransformedName(),
+        new TypeConstraint(imp.type),
+        {
+          isImplicit: true,
+          importInformation: {
+            filePath: imp.filePath,
+            transformedImportName: imp.name,
+          },
+        },
+      ),
+    )
+  }
+
+  private handleType = (node: Parser.SyntaxNode): void => {
+    const name = new BuildType().perform(node).name
+    const imp = this._scope.imports.find((imp) => imp.node === node)
+    assert(imp instanceof ModuleImport, 'Should be a module import.')
+
+    const fileScope = this._fileScopes.find(
+      (fileScope) => fileScope.filePath === imp.filePath,
+    )
+
+    if (fileScope) this.handleInternalTypeImport(node, imp, fileScope)
+    else throw new InvalidExternalTypeImportError(name)
+  }
+
+  private handleInternalTypeImport = (
+    node: Parser.SyntaxNode,
+    imp: ModuleImport,
+    fileScope: FileModuleScope,
+  ): void => {
+    const bindings = fileScope.resolveBindings(imp.name).map((binding) => {
+      assert(binding instanceof ModuleBinding, 'Should be a module binding.')
+
+      return new ModuleBinding(node, imp.aliasType, binding.type, {
+        importInformation: {
+          filePath: imp.filePath,
+          transformedImportName: binding.transformedName,
+        },
+      })
+    })
+
+    if (bindings.length > 0)
+      bindings.forEach((binding) => this._scope.addBinding(binding))
+    else throw new MissingBindingError(name)
+  }
+}
diff --git a/.yalc/tony-lang/src/type_inference/services/InferListType.ts b/.yalc/tony-lang/src/type_inference/services/InferListType.ts
index 3d9cede..861101e 100644
--- a/.yalc/tony-lang/src/type_inference/services/InferListType.ts
+++ b/.yalc/tony-lang/src/type_inference/services/InferListType.ts
@@ -1,39 +1,87 @@
+import * as AST from '../../ast'
+import { AccumulatedAnswer, Answer, Disjunction } from '../models'
 import {
   LIST_TYPE,
   ParametricType,
   Type,
-  TypeConstraints,
+  TypeConstraint,
+  TypeEqualityGraph,
   TypeVariable,
 } from '../../types'
-import { InferTypes } from '../InferTypes'
-import Parser from 'tree-sitter'
+import { DistributeTypeDisjunction } from './DistributeTypeDisjunction'
 
-export class InferListType {
-  private _inferTypes: InferTypes
-  private _typeConstraints: TypeConstraints
+type Factory<T> = (elements: AST.SyntaxNode[]) => T
 
-  constructor(inferTypes: InferTypes, typeConstraints: TypeConstraints) {
-    this._inferTypes = inferTypes
-    this._typeConstraints = typeConstraints
+export class InferListType<T extends AST.SyntaxNode> {
+  private _factory: Factory<T>
+
+  constructor(factory: Factory<T>) {
+    this._factory = factory
+  }
+
+  perform = (elements: Disjunction<AST.SyntaxNode>[]): Disjunction<T> => {
+    const answers = this.inferAnswers(elements)
+    if (answers.length == 0)
+      return new Disjunction([
+        new Answer(
+          this._factory([]),
+          new TypeConstraint(
+            new ParametricType(LIST_TYPE, [new TypeVariable()]),
+          ),
+        ),
+      ])
+
+    return new Disjunction(answers)
   }
 
-  perform = (valueNodes: Parser.SyntaxNode[]): ParametricType => {
-    const valueType = valueNodes.reduce((valueType: Type, valueNode) => {
-      const otherValueType = this._inferTypes.traverse(valueNode)!
+  private inferAnswers = (
+    elements: Disjunction<AST.SyntaxNode>[],
+  ): (Answer<T> | undefined)[] =>
+    new DistributeTypeDisjunction().perform(elements).map((elements) => {
+      const typeEqualityGraph = TypeEqualityGraph.build(
+        ...elements.typeConstraints.map(
+          (typeConstraint) => typeConstraint.typeEqualityGraph,
+        ),
+      )
+      if (typeEqualityGraph === undefined) return
+      const type = this.inferType(elements, typeEqualityGraph)
+      if (type === undefined) return
+
+      return new Answer(
+        this._factory(elements.nodes),
+        new TypeConstraint(type, typeEqualityGraph),
+      )
+    })
+
+  private inferType = (
+    elements: AccumulatedAnswer<AST.SyntaxNode>,
+    typeEqualityGraph: TypeEqualityGraph,
+  ): Type | undefined =>
+    elements.answers.reduce((type: Type | undefined, answer) => {
+      if (type === undefined) return
 
-      if (valueNode.type === 'spread_list') {
-        const restType = new ParametricType(LIST_TYPE).unify(
-          otherValueType,
-          this._typeConstraints,
-          true,
-        )
+      if (
+        answer.node instanceof AST.RestList ||
+        answer.node instanceof AST.SpreadList
+      )
+        this.handleSpread(type, answer, typeEqualityGraph)
 
-        return valueType.unify(restType.parameters[0], this._typeConstraints)
-      }
+      return type.unify(
+        new ParametricType(LIST_TYPE, [answer.typeConstraint.type]),
+        typeEqualityGraph,
+      )
+    }, new ParametricType(LIST_TYPE, [new TypeVariable()]))
 
-      return valueType.unify(otherValueType, this._typeConstraints)
-    }, new TypeVariable())
+  private handleSpread = (
+    type: Type,
+    answer: Answer<AST.SyntaxNode>,
+    typeEqualityGraph: TypeEqualityGraph,
+  ): Type | undefined => {
+    const spreadType = new ParametricType(LIST_TYPE, [
+      new TypeVariable(),
+    ]).unify(answer.typeConstraint.type, typeEqualityGraph)
+    if (spreadType === undefined) return
 
-    return new ParametricType(LIST_TYPE, [valueType])
+    return type.unify(spreadType, typeEqualityGraph)
   }
 }
diff --git a/.yalc/tony-lang/src/type_inference/services/InferMapType.ts b/.yalc/tony-lang/src/type_inference/services/InferMapType.ts
index 934857c..e2066fa 100644
--- a/.yalc/tony-lang/src/type_inference/services/InferMapType.ts
+++ b/.yalc/tony-lang/src/type_inference/services/InferMapType.ts
@@ -1,20 +1,68 @@
+import * as AST from '../../ast'
+import { AccumulatedAnswer, Answer, Disjunction } from '../models'
 import {
   MAP_TYPE,
   ParametricType,
   Type,
-  TypeConstraints,
+  TypeConstraint,
+  TypeEqualityGraph,
   TypeVariable,
 } from '../../types'
+import { DistributeTypeDisjunction } from './DistributeTypeDisjunction'
 
-export class InferMapType {
-  private _typeConstraints: TypeConstraints
+type Factory<T> = (elements: AST.SyntaxNode[]) => T
 
-  constructor(typeConstraints: TypeConstraints) {
-    this._typeConstraints = typeConstraints
+export class InferMapType<T extends AST.SyntaxNode> {
+  private _factory: Factory<T>
+
+  constructor(factory: Factory<T>) {
+    this._factory = factory
+  }
+
+  perform = (elements: Disjunction<AST.SyntaxNode>[]): Disjunction<T> => {
+    const answers = this.inferAnswers(elements)
+    if (answers.length == 0)
+      return new Disjunction([
+        new Answer(
+          this._factory([]),
+          new TypeConstraint(
+            new ParametricType(MAP_TYPE, [
+              new TypeVariable(),
+              new TypeVariable(),
+            ]),
+          ),
+        ),
+      ])
+
+    return new Disjunction(answers)
   }
 
-  perform = (mapTypes: Type[]): ParametricType =>
-    mapTypes.reduce((mapType: ParametricType, otherMapType) => {
-      return mapType.unify(otherMapType, this._typeConstraints)
+  private inferAnswers = (
+    elements: Disjunction<AST.SyntaxNode>[],
+  ): (Answer<T> | undefined)[] =>
+    new DistributeTypeDisjunction().perform(elements).map((elements) => {
+      const typeEqualityGraph = TypeEqualityGraph.build(
+        ...elements.typeConstraints.map(
+          (typeConstraint) => typeConstraint.typeEqualityGraph,
+        ),
+      )
+      if (typeEqualityGraph === undefined) return
+      const type = this.inferType(elements, typeEqualityGraph)
+      if (type === undefined) return
+
+      return new Answer(
+        this._factory(elements.nodes),
+        new TypeConstraint(type, typeEqualityGraph),
+      )
+    })
+
+  private inferType = (
+    elements: AccumulatedAnswer<AST.SyntaxNode>,
+    typeEqualityGraph: TypeEqualityGraph,
+  ): Type | undefined =>
+    elements.answers.reduce((type: Type | undefined, answer) => {
+      if (type === undefined) return
+
+      return type.unify(answer.typeConstraint.type, typeEqualityGraph)
     }, new ParametricType(MAP_TYPE, [new TypeVariable(), new TypeVariable()]))
 }
diff --git a/.yalc/tony-lang/src/type_inference/services/InferPatternBindingTypes.ts b/.yalc/tony-lang/src/type_inference/services/InferPatternBindingTypes.ts
index e667c6c..3393987 100644
--- a/.yalc/tony-lang/src/type_inference/services/InferPatternBindingTypes.ts
+++ b/.yalc/tony-lang/src/type_inference/services/InferPatternBindingTypes.ts
@@ -1,3 +1,5 @@
+import * as AST from '../../ast'
+import { Answer, Disjunction } from '../models'
 import {
   BOOLEAN_TYPE,
   BuildType,
@@ -9,274 +11,311 @@ import {
   STRING_TYPE,
   TUPLE_TYPE,
   Type,
-  TypeConstraints,
+  TypeConstraint,
   TypeVariable,
 } from '../../types'
-import { CompileError, InternalError, assert } from '../../errors'
-import { IdentifierBinding, NestedScope } from '../../symbol_table'
+import { CompileError, InternalError, TypeError } from '../../errors'
+import { InferIdentifierPatternType } from './InferIdentifierPatternType'
+import { InferListType } from './InferListType'
 import { InferMapType } from './InferMapType'
+import { InferPatternPairType } from './InferPatternPairType'
+import { InferTupleType } from './InferTupleType'
 import { InferTypes } from '../InferTypes'
+import { NestedScope } from '../../symbol_table'
 import Parser from 'tree-sitter'
 
 export class InferPatternBindingTypes {
   private _inferTypes: InferTypes
   private _scope: NestedScope
-  private _typeConstraints: TypeConstraints
 
-  constructor(
-    inferTypes: InferTypes,
-    scope: NestedScope,
-    typeConstraints: TypeConstraints,
-  ) {
+  constructor(inferTypes: InferTypes, scope: NestedScope) {
     this._inferTypes = inferTypes
     this._scope = scope
-    this._typeConstraints = typeConstraints
   }
 
   perform = (
     patternNode: Parser.SyntaxNode,
-    type: Type = new TypeVariable(),
-  ): Type => {
-    const patternType = this.traverse(patternNode, type)
-
-    assert(patternType !== undefined, 'Should not be undefined.')
-
-    return patternType
-  }
+    typeConstraint: TypeConstraint<Type> = new TypeConstraint(
+      new TypeVariable(),
+    ),
+  ): Disjunction<AST.Pattern> | undefined =>
+    TypeError.safe(() =>
+      CompileError.addContext(this.traverse, patternNode, typeConstraint),
+    )
 
   // eslint-disable-next-line max-lines-per-function
   private traverse = (
     patternNode: Parser.SyntaxNode,
-    type: Type,
-  ): Type | undefined => {
-    try {
-      switch (patternNode.type) {
-        case 'boolean':
-          return this.handleBoolean(patternNode, type)
-        case 'comment':
-          return
-        case 'identifier_pattern':
-          return this.handleIdentifierPattern(patternNode, type)
-        case 'list_pattern':
-          return this.handleListPattern(patternNode, type)
-        case 'map_pattern':
-          return this.handleMapPattern(patternNode, type)
-        case 'number':
-          return this.handleNumber(patternNode, type)
-        case 'pattern_pair':
-          return this.handlePatternPair(patternNode, type)
-        case 'regex':
-          return this.handleRegex(patternNode, type)
-        case 'rest_list':
-          return this.handleRestList(patternNode, type)
-        case 'rest_map':
-          return this.handleRestMap(patternNode, type)
-        case 'rest_tuple':
-          return this.handleRestTuple(patternNode, type)
-        case 'shorthand_pair_identifier_pattern':
-          return this.handleShorthandPairIdentifierPattern(patternNode, type)
-        case 'string_pattern':
-          return this.handleStringPattern(patternNode, type)
-        case 'parameters':
-        case 'tuple_pattern':
-          return this.handleTuplePattern(patternNode, type)
-        case 'type':
-          return this.handleType(patternNode, type)
-        default:
-          throw new InternalError(
-            'InferPatternBindingTypes: Could not find matcher for AST pattern ' +
-              `node '${patternNode.type}'.`,
-          )
-      }
-    } catch (error) {
-      if (error instanceof CompileError && error.context === undefined)
-        error.addContext(patternNode)
-      throw error
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.Pattern> => {
+    switch (patternNode.type) {
+      case 'boolean':
+        return this.handleBoolean(patternNode, typeConstraint)
+      case 'identifier_pattern':
+        return this.handleIdentifierPattern(patternNode, typeConstraint)
+      case 'list_pattern':
+        return this.handleListPattern(patternNode, typeConstraint)
+      case 'map_pattern':
+        return this.handleMapPattern(patternNode, typeConstraint)
+      case 'number':
+        return this.handleNumber(patternNode, typeConstraint)
+      case 'pattern_pair':
+        return this.handlePatternPair(patternNode, typeConstraint)
+      case 'regex':
+        return this.handleRegex(patternNode, typeConstraint)
+      case 'rest_list':
+        return this.handleRestList(patternNode, typeConstraint)
+      case 'rest_map':
+        return this.handleRestMap(patternNode, typeConstraint)
+      case 'rest_tuple':
+        return this.handleRestTuple(patternNode, typeConstraint)
+      case 'shorthand_pair_identifier_pattern':
+        return this.handleShorthandPairIdentifierPattern(
+          patternNode,
+          typeConstraint,
+        )
+      case 'string_pattern':
+        return this.handleStringPattern(patternNode, typeConstraint)
+      case 'parameters':
+      case 'tuple_pattern':
+        return this.handleTuplePattern(patternNode, typeConstraint)
+      case 'type':
+        return this.handleType(patternNode, typeConstraint)
+      default:
+        throw new InternalError(
+          'Could not find matcher for AST pattern ' +
+            `node '${patternNode.type}'.`,
+        )
     }
   }
 
   private handleBoolean = (
     patternNode: Parser.SyntaxNode,
-    type: Type,
-  ): ParametricType =>
-    new ParametricType(BOOLEAN_TYPE).unify(type, this._typeConstraints)
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.Boolean> => {
+    const unifiedTypeConstraint = new TypeConstraint(
+      new ParametricType(BOOLEAN_TYPE),
+    ).unify(typeConstraint)
+    if (unifiedTypeConstraint === undefined) return new Disjunction([])
+
+    return new Disjunction([
+      new Answer(new AST.Boolean(patternNode.text), unifiedTypeConstraint),
+    ])
+  }
 
-  // prettier-ignore
   private handleIdentifierPattern = (
     patternNode: Parser.SyntaxNode,
-    type: Type,
-  ): Type => {
-    const name = patternNode.namedChild(0)!.text
-    // eslint-disable-next-line @typescript-eslint/ban-ts-ignore
-    // @ts-ignore
-    const typeHint = patternNode.typeNode ? new BuildType().perform(patternNode.typeNode) : new TypeVariable()
-    // eslint-disable-next-line @typescript-eslint/ban-ts-ignore
-    // @ts-ignore
-    const defaultType = patternNode.defaultNode ? this._inferTypes.traverse(patternNode.defaultNode)! : new TypeVariable()
-    const binding = this._scope.resolveBinding(name, 0)
-
-    assert(
-      binding instanceof IdentifierBinding,
-      'Pattern identifier binding should be found in current scope.',
-    )
-
-    type = typeHint.unify(type, this._typeConstraints)
-    type = defaultType.unify(type, this._typeConstraints)
-    binding.type = binding.type.unify(type, this._typeConstraints)
-
-    return binding.type
-  }
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.IdentifierPattern> =>
+    new InferIdentifierPatternType(
+      this._inferTypes,
+      this._scope,
+      (name, transformedName, def) =>
+        new AST.IdentifierPattern(name, transformedName, def),
+    ).perform(patternNode, typeConstraint)
 
   private handleListPattern = (
     patternNode: Parser.SyntaxNode,
-    type: Type,
-  ): ParametricType => {
-    const unifiedType = new ParametricType(LIST_TYPE, [
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.ListPattern> => {
+    const listType = new ParametricType(LIST_TYPE, [
       new TypeVariable(),
-    ]).unify(type, this._typeConstraints)
-    const valueTypes = patternNode.namedChildren.map((child) =>
-      this.perform(child, unifiedType.parameters[0]),
+    ]).unsafeUnify(typeConstraint.type, typeConstraint.typeEqualityGraph)
+    const elements = patternNode.namedChildren.map((elementNode) =>
+      CompileError.addContext(
+        this.traverse,
+        elementNode,
+        new TypeConstraint(
+          listType.parameters[0],
+          typeConstraint.typeEqualityGraph,
+        ),
+      ),
     )
 
-    return valueTypes.reduce((valueType: ParametricType, otherValueType) => {
-      return valueType.unify(
-        new ParametricType(LIST_TYPE, [otherValueType]),
-        this._typeConstraints,
-      )
-    }, new ParametricType(LIST_TYPE, [new TypeVariable()]))
+    return new InferListType(
+      (elements) => new AST.ListPattern(elements as AST.Pattern[]),
+    ).perform(elements)
   }
 
   private handleMapPattern = (
     patternNode: Parser.SyntaxNode,
-    type: Type,
-  ): ParametricType => {
-    const mapTypes = patternNode.namedChildren.map((child) =>
-      this.perform(child, type),
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.MapPattern> => {
+    const elements = patternNode.namedChildren.map((elementNode) =>
+      CompileError.addContext(this.traverse, elementNode, typeConstraint),
     )
 
-    return new InferMapType(this._typeConstraints).perform(mapTypes)
+    return new InferMapType(
+      (elements) => new AST.MapPattern(elements as AST.MapPatternElement[]),
+    ).perform(elements)
   }
 
   private handleNumber = (
     patternNode: Parser.SyntaxNode,
-    type: Type,
-  ): ParametricType =>
-    new ParametricType(NUMBER_TYPE).unify(type, this._typeConstraints)
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.Number> => {
+    const unifiedTypeConstraint = new TypeConstraint(
+      new ParametricType(NUMBER_TYPE),
+    ).unify(typeConstraint)
+    if (unifiedTypeConstraint === undefined) return new Disjunction([])
+
+    return new Disjunction([
+      new Answer(new AST.Number(patternNode.text), unifiedTypeConstraint),
+    ])
+  }
 
   private handlePatternPair = (
     patternNode: Parser.SyntaxNode,
-    type: Type,
-  ): Type => {
-    const keyType = this._inferTypes.traverse(patternNode.namedChild(0)!)!
-    const unifiedType = new ParametricType(MAP_TYPE, [
-      keyType,
-      new TypeVariable(),
-    ]).unify(type, this._typeConstraints)
-    const valueType = this.perform(
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.PatternPair> => {
+    const key = this._inferTypes.traverse(patternNode.namedChild(0)!)
+    const value = CompileError.addContext(
+      this.traverse,
       patternNode.namedChild(1)!,
-      unifiedType.parameters[1],
+      new TypeConstraint(new TypeVariable(), typeConstraint.typeEqualityGraph),
     )
 
-    return new ParametricType(MAP_TYPE, [keyType, valueType])
+    return new InferPatternPairType().perform(key, value, typeConstraint)
   }
 
   private handleRegex = (
     patternNode: Parser.SyntaxNode,
-    type: Type,
-  ): ParametricType =>
-    new ParametricType(REGULAR_EXPRESSION_TYPE).unify(
-      type,
-      this._typeConstraints,
-    )
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.Regex> => {
+    const unifiedTypeConstraint = new TypeConstraint(
+      new ParametricType(REGULAR_EXPRESSION_TYPE),
+    ).unify(typeConstraint)
+    if (unifiedTypeConstraint === undefined) return new Disjunction([])
+
+    return new Disjunction([
+      new Answer(new AST.Regex(patternNode.text), unifiedTypeConstraint),
+    ])
+  }
 
   private handleRestList = (
     patternNode: Parser.SyntaxNode,
-    type: Type,
-  ): Type => {
-    const valueType = this.perform(
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.RestList> => {
+    const value = CompileError.addContext(
+      this.handleIdentifierPattern,
       patternNode.namedChild(0)!,
-      new ParametricType(LIST_TYPE, [type]),
+      new TypeConstraint(
+        new ParametricType(LIST_TYPE, [typeConstraint.type]),
+        typeConstraint.typeEqualityGraph,
+      ),
     )
 
-    assert(valueType instanceof ParametricType, 'Should be parametric type.')
-
-    return valueType.parameters[0]
+    return new Disjunction(
+      value.answers.map(
+        (answer) =>
+          new Answer(new AST.RestList(answer.node), answer.typeConstraint),
+      ),
+    )
   }
 
-  private handleRestMap = (patternNode: Parser.SyntaxNode, type: Type): Type =>
-    this.perform(patternNode.namedChild(0)!, type)
-
-  private handleRestTuple = (
+  private handleRestMap = (
     patternNode: Parser.SyntaxNode,
-    type: Type,
-  ): ParametricType => {
-    const valueType = this.perform(patternNode.namedChild(0)!, type)
-
-    assert(valueType instanceof ParametricType, 'Should be parametric type.')
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.RestMap> => {
+    const value = CompileError.addContext(
+      this.handleIdentifierPattern,
+      patternNode.namedChild(0)!,
+      typeConstraint,
+    )
 
-    return valueType
+    return new Disjunction(
+      value.answers.map(
+        (answer) =>
+          new Answer(new AST.RestMap(answer.node), answer.typeConstraint),
+      ),
+    )
   }
 
-  // prettier-ignore
-  private handleShorthandPairIdentifierPattern = (
+  private handleRestTuple = (
     patternNode: Parser.SyntaxNode,
-    type: Type,
-  ): ParametricType => {
-    // eslint-disable-next-line @typescript-eslint/ban-ts-ignore
-    // @ts-ignore
-    const typeHint = patternNode.typeNode ? new BuildType().perform(patternNode.typeNode) : new TypeVariable()
-    // eslint-disable-next-line @typescript-eslint/ban-ts-ignore
-    // @ts-ignore
-    const defaultType = patternNode.defaultNode ? this._inferTypes.traverse(patternNode.defaultNode)! : new TypeVariable()
-    const valueType = typeHint.unify(defaultType, this._typeConstraints)
-    const keyType = new ParametricType(STRING_TYPE)
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.RestTuple> => {
+    const value = CompileError.addContext(
+      this.handleIdentifierPattern,
+      patternNode.namedChild(0)!,
+      typeConstraint,
+    )
 
-    return new ParametricType(MAP_TYPE, [keyType, valueType]).unify(
-      type,
-      this._typeConstraints,
+    return new Disjunction(
+      value.answers.map(
+        (answer) =>
+          new Answer(new AST.RestTuple(answer.node), answer.typeConstraint),
+      ),
     )
   }
 
+  private handleShorthandPairIdentifierPattern = (
+    patternNode: Parser.SyntaxNode,
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.ShorthandPairIdentifierPattern> =>
+    new InferIdentifierPatternType(
+      this._inferTypes,
+      this._scope,
+      (name, transformedName, def) =>
+        new AST.ShorthandPairIdentifierPattern(name, transformedName, def),
+      (type) =>
+        new ParametricType(MAP_TYPE, [new ParametricType(STRING_TYPE), type]),
+      (typeConstraint) =>
+        new TypeConstraint(
+          (typeConstraint.type as ParametricType).parameters[1],
+          typeConstraint.typeEqualityGraph,
+        ),
+    ).perform(patternNode, typeConstraint)
+
   private handleStringPattern = (
     patternNode: Parser.SyntaxNode,
-    type: Type,
-  ): ParametricType =>
-    new ParametricType(STRING_TYPE).unify(type, this._typeConstraints)
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.StringPattern> => {
+    const content = patternNode.text.slice(1, -1)
+    const unifiedTypeConstraint = new TypeConstraint(
+      new ParametricType(STRING_TYPE),
+    ).unify(typeConstraint)
+    if (unifiedTypeConstraint === undefined) return new Disjunction([])
+
+    return new Disjunction([
+      new Answer(new AST.StringPattern(content), unifiedTypeConstraint),
+    ])
+  }
 
   private handleTuplePattern = (
     patternNode: Parser.SyntaxNode,
-    type: Type,
-  ): ParametricType => {
-    const tupleType = new ParametricType(TUPLE_TYPE, []).unify(
-      type,
-      this._typeConstraints,
-      true,
-    )
-    const parameters = patternNode.namedChildren.reduce(
-      this.handleTuplePatternValues(tupleType),
-      [],
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.TuplePattern> => {
+    const tupleType = new ParametricType(
+      TUPLE_TYPE,
+      [...Array(patternNode.namedChildCount)].map(() => new TypeVariable()),
+    ).unsafeUnify(typeConstraint.type, typeConstraint.typeEqualityGraph)
+    const elements = patternNode.namedChildren.map((elementNode, i) =>
+      CompileError.addContext(
+        this.traverse,
+        elementNode,
+        new TypeConstraint(
+          tupleType.parameters[i],
+          typeConstraint.typeEqualityGraph,
+        ),
+      ),
     )
 
-    return new ParametricType(TUPLE_TYPE, parameters)
+    return new InferTupleType(
+      (elements) => new AST.TuplePattern(elements as AST.Pattern[]),
+    ).perform(elements)
   }
 
-  private handleTuplePatternValues = (type: ParametricType) => (
-    parameters: Type[],
+  private handleType = (
     patternNode: Parser.SyntaxNode,
-    i: number,
-  ): Type[] => {
-    if (patternNode.type === 'rest_tuple')
-      return [
-        ...parameters,
-        ...this.handleRestTuple(
-          patternNode,
-          new ParametricType(TUPLE_TYPE, type.parameters.slice(i)),
-        ).parameters,
-      ]
-
-    return [...parameters, this.perform(patternNode, type.parameters[i])]
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.ParametricType> => {
+    const type = new BuildType().perform(patternNode)
+    const unifiedTypeConstraint = new TypeConstraint(type).unify(typeConstraint)
+    if (unifiedTypeConstraint === undefined) return new Disjunction([])
+
+    return new Disjunction([
+      new Answer(new AST.ParametricType(type.name), unifiedTypeConstraint),
+    ])
   }
-
-  private handleType = (patternNode: Parser.SyntaxNode, type: Type): Type =>
-    new BuildType().handleType(patternNode).unify(type, this._typeConstraints)
 }
diff --git a/.yalc/tony-lang/src/type_inference/services/InferPatternPairType.ts b/.yalc/tony-lang/src/type_inference/services/InferPatternPairType.ts
new file mode 100644
index 0000000..d106ea0
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/services/InferPatternPairType.ts
@@ -0,0 +1,61 @@
+import * as AST from '../../ast'
+import { Answer, Disjunction } from '../models'
+import {
+  MAP_TYPE,
+  ParametricType,
+  Type,
+  TypeConstraint,
+  TypeEqualityGraph,
+} from '../../types'
+
+export class InferPatternPairType {
+  perform = (
+    key: Disjunction<AST.SyntaxNode>,
+    value: Disjunction<AST.Pattern>,
+    typeConstraint: TypeConstraint<Type>,
+  ): Disjunction<AST.PatternPair> =>
+    new Disjunction(
+      key.answers
+        .map((keyAnswer) =>
+          value.answers.map((valueAnswer) =>
+            this.buildAnswer(keyAnswer, valueAnswer, typeConstraint),
+          ),
+        )
+        .flat(1),
+    )
+
+  private buildAnswer = (
+    key: Answer<AST.SyntaxNode>,
+    value: Answer<AST.Pattern>,
+    typeConstraint: TypeConstraint<Type>,
+  ): Answer<AST.PatternPair> | undefined => {
+    const unifiedTypeConstraint = this.unifyTypeConstraints(
+      key.typeConstraint,
+      value.typeConstraint,
+      typeConstraint,
+    )
+    if (unifiedTypeConstraint === undefined) return
+
+    return new Answer(
+      new AST.PatternPair(key.node, value.node),
+      unifiedTypeConstraint,
+    )
+  }
+
+  private unifyTypeConstraints = (
+    key: TypeConstraint<Type>,
+    value: TypeConstraint<Type>,
+    typeConstraint: TypeConstraint<Type>,
+  ): TypeConstraint<Type> | undefined => {
+    const typeEqualityGraph = TypeEqualityGraph.build(
+      key.typeEqualityGraph,
+      value.typeEqualityGraph,
+    )
+    if (typeEqualityGraph === undefined) return
+
+    return new TypeConstraint(
+      new ParametricType(MAP_TYPE, [key.type, value.type]),
+      typeEqualityGraph,
+    ).unify(typeConstraint)
+  }
+}
diff --git a/.yalc/tony-lang/src/type_inference/services/InferStringType.ts b/.yalc/tony-lang/src/type_inference/services/InferStringType.ts
new file mode 100644
index 0000000..063fc74
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/services/InferStringType.ts
@@ -0,0 +1,53 @@
+import * as AST from '../../ast'
+import { Answer, Disjunction } from '../models'
+import { ParametricType, STRING_TYPE, TypeConstraint } from '../../types'
+
+export class InferStringType {
+  perform = (
+    content: string,
+    interpolationValues: Disjunction<AST.Expression>[],
+  ): Disjunction<AST.String> => {
+    const interpolations = this.handleInterpolations(interpolationValues)
+    const string = new AST.String(
+      content,
+      interpolations.map((answer) => answer.node),
+    )
+    const typeConstraint = interpolations.reduce(
+      (typeConstraint: TypeConstraint<ParametricType>, answer) =>
+        typeConstraint.unify(answer.typeConstraint) as TypeConstraint<
+          ParametricType
+        >,
+      new TypeConstraint(new ParametricType(STRING_TYPE)),
+    )
+
+    return new Disjunction([new Answer(string, typeConstraint)])
+  }
+
+  private handleInterpolations = (
+    values: Disjunction<AST.Expression>[],
+  ): Answer<AST.Interpolation>[] =>
+    values.reduce(
+      (interpolations: Answer<AST.Interpolation>[], value) => [
+        ...interpolations,
+        this.handleInterpolation(value).answers[0],
+      ],
+      [],
+    )
+
+  private handleInterpolation = (
+    value: Disjunction<AST.Expression>,
+  ): Disjunction<AST.Interpolation> =>
+    new Disjunction(
+      value.answers.reduce((answers: Answer<AST.Interpolation>[], answer) => {
+        const typeConstraint = new TypeConstraint(
+          new ParametricType(STRING_TYPE),
+        ).unify(answer.typeConstraint)
+        if (typeConstraint === undefined) return answers
+
+        return [
+          ...answers,
+          new Answer(new AST.Interpolation(answer.node), typeConstraint),
+        ]
+      }, []),
+    )
+}
diff --git a/.yalc/tony-lang/src/type_inference/services/InferTupleType.ts b/.yalc/tony-lang/src/type_inference/services/InferTupleType.ts
index c4cffc8..32c3abc 100644
--- a/.yalc/tony-lang/src/type_inference/services/InferTupleType.ts
+++ b/.yalc/tony-lang/src/type_inference/services/InferTupleType.ts
@@ -1,33 +1,76 @@
-import { ParametricType, TUPLE_TYPE, Type, TypeConstraints } from '../../types'
-import { InferTypes } from '../InferTypes'
-import Parser from 'tree-sitter'
+import * as AST from '../../ast'
+import { AccumulatedAnswer, Answer, Disjunction } from '../models'
+import {
+  ParametricType,
+  TUPLE_TYPE,
+  Type,
+  TypeConstraint,
+  TypeEqualityGraph,
+} from '../../types'
+import { DistributeTypeDisjunction } from './DistributeTypeDisjunction'
 
-export class InferTupleType {
-  private _inferTypes: InferTypes
-  private _typeConstraints: TypeConstraints
+type Factory<T> = (elements: AST.SyntaxNode[]) => T
 
-  constructor(inferTypes: InferTypes, typeConstraints: TypeConstraints) {
-    this._inferTypes = inferTypes
-    this._typeConstraints = typeConstraints
+export class InferTupleType<T extends AST.SyntaxNode> {
+  private _factory: Factory<T>
+
+  constructor(factory: Factory<T>) {
+    this._factory = factory
   }
 
-  perform = (valueNodes: Parser.SyntaxNode[]): ParametricType => {
-    const valueTypes = valueNodes.reduce((valueTypes: Type[], valueNode) => {
-      const valueType = this._inferTypes.traverse(valueNode)!
+  perform = (elements: Disjunction<AST.SyntaxNode>[]): Disjunction<T> =>
+    new Disjunction(
+      new DistributeTypeDisjunction().perform(elements).map((elements) => {
+        const typeEqualityGraph = TypeEqualityGraph.build(
+          ...elements.typeConstraints.map(
+            (typeConstraint) => typeConstraint.typeEqualityGraph,
+          ),
+        )
+        if (typeEqualityGraph === undefined) return
+        const type = this.inferType(elements, typeEqualityGraph)
+        if (type === undefined) return
+
+        return new Answer(
+          this._factory(elements.nodes),
+          new TypeConstraint(type, typeEqualityGraph),
+        )
+      }),
+    )
 
-      if (valueNode.type === 'spread_tuple') {
-        const restType = new ParametricType(TUPLE_TYPE).unify(
-          valueType,
-          this._typeConstraints,
-          true,
+  private inferType = (
+    elements: AccumulatedAnswer<AST.SyntaxNode>,
+    typeEqualityGraph: TypeEqualityGraph,
+  ): ParametricType | undefined => {
+    const parameterTypes = elements.answers.reduce(
+      (parameters: Type[] | undefined, answer) => {
+        if (parameters === undefined) return
+        if (
+          answer.node instanceof AST.RestTuple ||
+          answer.node instanceof AST.SpreadTuple
         )
+          return this.handleSpread(parameters, answer, typeEqualityGraph)
+
+        return [...parameters, answer.typeConstraint.type]
+      },
+      [],
+    )
+    if (parameterTypes === undefined) return
 
-        return [...valueTypes, ...restType.parameters]
-      }
+    return new ParametricType(TUPLE_TYPE, parameterTypes)
+  }
 
-      return [...valueTypes, valueType]
-    }, [])
+  private handleSpread = (
+    parameters: Type[],
+    answer: Answer<AST.SyntaxNode>,
+    typeEqualityGraph: TypeEqualityGraph,
+  ): Type[] | undefined => {
+    const spreadType = new ParametricType(TUPLE_TYPE, []).unify(
+      answer.typeConstraint.type,
+      typeEqualityGraph,
+      true,
+    )
+    if (!(spreadType instanceof ParametricType)) return
 
-    return new ParametricType(TUPLE_TYPE, valueTypes)
+    return [...parameters, ...spreadType.parameters]
   }
 }
diff --git a/.yalc/tony-lang/src/type_inference/services/MergeAccumulatedTypeDisjunction.ts b/.yalc/tony-lang/src/type_inference/services/MergeAccumulatedTypeDisjunction.ts
new file mode 100644
index 0000000..b201165
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/services/MergeAccumulatedTypeDisjunction.ts
@@ -0,0 +1,48 @@
+import * as AST from '../../ast'
+import {
+  AccumulatedAnswer,
+  AccumulatedDisjunction,
+  Answer,
+  Disjunction,
+} from '../models'
+
+type Factory<T, U, V> = (
+  fst: AccumulatedAnswer<T>,
+  snd: Answer<U>,
+) => Disjunction<V> | Answer<V> | undefined
+
+export class MergeAccumulatedTypeDisjunction<
+  T extends AST.SyntaxNode,
+  U extends AST.SyntaxNode,
+  V extends AST.SyntaxNode
+> {
+  private _factory: Factory<T, U, V>
+
+  constructor(factory: Factory<T, U, V>) {
+    this._factory = factory
+  }
+
+  perform = (
+    fstDisj: AccumulatedDisjunction<T>,
+    sndDisj: Disjunction<U>,
+  ): Disjunction<V> =>
+    new Disjunction(
+      fstDisj.reduce(
+        (answers: (Answer<V> | undefined)[], fst) => [
+          ...answers,
+          ...sndDisj.answers.reduce(this.merge(fst), []),
+        ],
+        [],
+      ),
+    )
+
+  private merge = (fst: AccumulatedAnswer<T>) => (
+    answers: (Answer<V> | undefined)[],
+    snd: Answer<U>,
+  ): (Answer<V> | undefined)[] => {
+    const merged = this._factory(fst, snd)
+
+    if (merged instanceof Disjunction) return [...answers, ...merged.answers]
+    else return [...answers, merged]
+  }
+}
diff --git a/.yalc/tony-lang/src/type_inference/services/MergeTypeDisjunction.ts b/.yalc/tony-lang/src/type_inference/services/MergeTypeDisjunction.ts
new file mode 100644
index 0000000..d269923
--- /dev/null
+++ b/.yalc/tony-lang/src/type_inference/services/MergeTypeDisjunction.ts
@@ -0,0 +1,43 @@
+import * as AST from '../../ast'
+import { Answer, Disjunction } from '../models'
+
+type Factory<T, U, V> = (
+  fst: Answer<T>,
+  snd: Answer<U>,
+) => Disjunction<V> | Answer<V> | undefined
+
+export class MergeTypeDisjunction<
+  T extends AST.SyntaxNode,
+  U extends AST.SyntaxNode,
+  V extends AST.SyntaxNode
+> {
+  private _factory: Factory<T, U, V>
+
+  constructor(factory: Factory<T, U, V>) {
+    this._factory = factory
+  }
+
+  perform = (
+    fstDisj: Disjunction<T>,
+    sndDisj: Disjunction<U>,
+  ): Disjunction<V> =>
+    new Disjunction(
+      fstDisj.answers.reduce(
+        (answers: (Answer<V> | undefined)[], fst) => [
+          ...answers,
+          ...sndDisj.answers.reduce(this.merge(fst), []),
+        ],
+        [],
+      ),
+    )
+
+  private merge = (fst: Answer<T>) => (
+    answers: (Answer<V> | undefined)[],
+    snd: Answer<U>,
+  ): (Answer<V> | undefined)[] => {
+    const merged = this._factory(fst, snd)
+
+    if (merged instanceof Disjunction) return [...answers, ...merged.answers]
+    else return [...answers, merged]
+  }
+}
diff --git a/.yalc/tony-lang/src/type_inference/services/index.ts b/.yalc/tony-lang/src/type_inference/services/index.ts
index f4ef2be..9cc0c84 100644
--- a/.yalc/tony-lang/src/type_inference/services/index.ts
+++ b/.yalc/tony-lang/src/type_inference/services/index.ts
@@ -1,7 +1,21 @@
+export { AccumulateTypeDisjunction } from './AccumulateTypeDisjunction'
+export { DistributeTypeDisjunction } from './DistributeTypeDisjunction'
+export { GetModuleTypeRepresentation } from './GetModuleTypeRepresentation'
+export { InferAbstractionBranchType } from './InferAbstractionBranchType'
 export { InferAccessType } from './InferAccessType'
 export { InferApplicationType } from './InferApplicationType'
+export { InferAssignmentType } from './InferAssignmentType'
+export { InferBlockType } from './InferBlockType'
 export { InferBranchType } from './InferBranchType'
+export { InferExpressionPairType } from './InferExpressionPairType'
+export { InferGeneratorType } from './InferGeneratorType'
+export { InferIdentifierPatternType } from './InferIdentifierPatternType'
+export { InferImportBindingTypes } from './InferImportBindingTypes'
 export { InferListType } from './InferListType'
 export { InferMapType } from './InferMapType'
 export { InferPatternBindingTypes } from './InferPatternBindingTypes'
+export { InferPatternPairType } from './InferPatternPairType'
+export { InferStringType } from './InferStringType'
 export { InferTupleType } from './InferTupleType'
+export { MergeAccumulatedTypeDisjunction } from './MergeAccumulatedTypeDisjunction'
+export { MergeTypeDisjunction } from './MergeTypeDisjunction'
diff --git a/.yalc/tony-lang/src/types/index.ts b/.yalc/tony-lang/src/types/index.ts
index 7273d5f..54c9b97 100644
--- a/.yalc/tony-lang/src/types/index.ts
+++ b/.yalc/tony-lang/src/types/index.ts
@@ -1,17 +1,14 @@
 export {
-  CurriedType,
-  IdentifierProperty,
+  ModuleType,
   ParametricType,
-  RepresentationKind,
   Type,
-  TypeConstraints,
-  TypeProperty,
+  TypeConstraint,
+  TypeEqualityGraph,
   TypeVariable,
 } from './models'
-export { BuildRepresentation, BuildType } from './services'
-
-export const INTERNAL_PARTIAL_APPLICATION_TYPE_NAME = Object.freeze('?')
+export { BuildType } from './services'
 
+export const FUNCTION_TYPE = Object.freeze('->')
 export const VOID_TYPE = Object.freeze('Void')
 export const BOOLEAN_TYPE = Object.freeze('Boolean')
 export const NUMBER_TYPE = Object.freeze('Number')
@@ -22,6 +19,7 @@ export const MAP_TYPE = Object.freeze('Map')
 export const TUPLE_TYPE = Object.freeze('Tuple')
 
 export const BASIC_TYPES = Object.freeze([
+  FUNCTION_TYPE,
   VOID_TYPE,
   BOOLEAN_TYPE,
   NUMBER_TYPE,
diff --git a/.yalc/tony-lang/src/types/models/CurriedType.ts b/.yalc/tony-lang/src/types/models/CurriedType.ts
deleted file mode 100644
index 9d6bc09..0000000
--- a/.yalc/tony-lang/src/types/models/CurriedType.ts
+++ /dev/null
@@ -1,69 +0,0 @@
-import { TypeError, assert } from '../../errors'
-import { Type } from './Type'
-import { TypeConstraints } from './TypeConstraints'
-import { TypeVariable } from './TypeVariable'
-
-export class CurriedType extends Type {
-  private _parameters: Type[]
-
-  constructor(parameters: Type[]) {
-    super()
-
-    this._parameters = parameters
-  }
-
-  get parameters(): Type[] {
-    return this._parameters
-  }
-
-  concat = (type: Type): CurriedType =>
-    new CurriedType(this.parameters.concat(type))
-
-  unify = (actual: Type, constraints: TypeConstraints): CurriedType =>
-    this._unify(actual, constraints)._reduce(constraints)
-
-  _unify = (actual: Type, constraints: TypeConstraints): CurriedType => {
-    if (actual instanceof TypeVariable) {
-      constraints.add(actual, this)
-      return this
-    } else if (
-      actual instanceof CurriedType &&
-      this.parameters.length == actual.parameters.length
-    ) {
-      return new CurriedType(this.unifyParameters(actual, constraints))
-    }
-
-    throw new TypeError(this, actual, 'Non-variable types do not match')
-  }
-
-  private unifyParameters = (
-    actual: CurriedType,
-    constraints: TypeConstraints,
-  ): Type[] =>
-    this.parameters.map((parameter, i) => {
-      try {
-        return parameter._unify(actual.parameters[i], constraints)
-      } catch (error) {
-        assert(error instanceof TypeError, 'Should be TypeError.')
-
-        error.addTypeMismatch(this, actual)
-        throw error
-      }
-    })
-
-  _reduce = (constraints: TypeConstraints): CurriedType => {
-    const parameters = this.parameters.map((parameter) =>
-      parameter._reduce(constraints),
-    )
-
-    return new CurriedType(parameters)
-  }
-
-  toString = (): string => {
-    const parameters = this.parameters
-      .map((parameter) => parameter.toString())
-      .join(' -> ')
-
-    return `(${parameters})`
-  }
-}
diff --git a/.yalc/tony-lang/src/types/models/IdentifierProperty.ts b/.yalc/tony-lang/src/types/models/IdentifierProperty.ts
deleted file mode 100644
index 8474b0e..0000000
--- a/.yalc/tony-lang/src/types/models/IdentifierProperty.ts
+++ /dev/null
@@ -1,31 +0,0 @@
-import { Property } from './Property'
-import { Type } from './Type'
-
-export class IdentifierProperty implements Property {
-  private _name: string
-  protected _type: Type
-
-  constructor(name: string, type: Type) {
-    this._name = name
-    this._type = type
-  }
-
-  get name(): string {
-    return this._name
-  }
-
-  get type(): Type {
-    return this._type
-  }
-
-  set type(value: Type) {
-    this._type = value
-  }
-
-  toString = (): string => {
-    if (this.type === undefined) return this.name
-
-    const type = this.type.toString()
-    return `${this.name}: ${type}`
-  }
-}
diff --git a/.yalc/tony-lang/src/types/models/ModuleType.ts b/.yalc/tony-lang/src/types/models/ModuleType.ts
new file mode 100644
index 0000000..ed0edef
--- /dev/null
+++ b/.yalc/tony-lang/src/types/models/ModuleType.ts
@@ -0,0 +1,44 @@
+import { Binding, BindingTemplate, ModuleScope } from '../../symbol_table'
+import { InternalError } from '../../errors'
+import { Type } from './Type'
+
+export class ModuleType extends Type {
+  private _scope: ModuleScope
+
+  constructor(scope: ModuleScope) {
+    super()
+
+    this._scope = scope
+  }
+
+  get scope(): ModuleScope {
+    return this._scope
+  }
+
+  get properties(): Binding[] {
+    return this.scope.bindings.filter((binding) => binding.isExported)
+  }
+
+  resolveProperty = (name: string): (Binding | BindingTemplate)[] =>
+    this.scope.resolveBindings(name, 0).filter((binding) => binding.isExported)
+
+  unsafeUnify = (): Type => {
+    throw new InternalError('Module types may not be unified.')
+  }
+
+  reduce = (): Type => {
+    throw new InternalError('Module types may not be reduced.')
+  }
+
+  equals = (type: Type): boolean => this === type
+
+  toString = (): string => {
+    if (this.properties.length == 0) return '{}'
+
+    const properties = this.properties
+      .map((binding) => binding.toString())
+      .join(', ')
+
+    return `{ ${properties} }`
+  }
+}
diff --git a/.yalc/tony-lang/src/types/models/ParametricType.ts b/.yalc/tony-lang/src/types/models/ParametricType.ts
index 5215f08..eb11d1f 100644
--- a/.yalc/tony-lang/src/types/models/ParametricType.ts
+++ b/.yalc/tony-lang/src/types/models/ParametricType.ts
@@ -1,7 +1,6 @@
-import { TypeError, assert } from '../../errors'
-import { CurriedType } from './CurriedType'
+import { InternalTypeError } from '../../errors'
 import { Type } from './Type'
-import { TypeConstraints } from './TypeConstraints'
+import { TypeEqualityGraph } from './TypeEqualityGraph'
 import { TypeVariable } from './TypeVariable'
 
 export class ParametricType extends Type {
@@ -23,73 +22,67 @@ export class ParametricType extends Type {
     return this._parameters
   }
 
-  concat = (type: Type): CurriedType => {
-    if (type instanceof CurriedType) return type.concat(this)
+  concat = (type: Type): ParametricType =>
+    new ParametricType(this.name, [...this.parameters, type])
 
-    return new CurriedType([this, type])
-  }
-
-  unify = (
-    actual: Type,
-    constraints: TypeConstraints,
-    useActualParameters = false,
-  ): ParametricType =>
-    this._unify(actual, constraints, useActualParameters)._reduce(constraints)
-
-  _unify = (
+  // eslint-disable-next-line max-lines-per-function
+  unsafeUnify = (
     actual: Type,
-    constraints: TypeConstraints,
-    useActualParameters = false,
+    typeEqualityGraph?: TypeEqualityGraph,
+    ignoreExpectedParameters = false,
   ): ParametricType => {
     if (actual instanceof TypeVariable) {
-      constraints.add(actual, this)
+      if (typeEqualityGraph) typeEqualityGraph.add(actual, this)
+
       return this
     } else if (
       actual instanceof ParametricType &&
       this.name === actual.name &&
-      (useActualParameters ||
+      (ignoreExpectedParameters ||
         this.parameters.length == actual.parameters.length)
-    )
-      return this.buildUnifiedType(actual, constraints, useActualParameters)
-
-    throw new TypeError(this, actual, 'Non-variable types do not match')
-  }
-
-  private buildUnifiedType = (
-    actual: ParametricType,
-    constraints: TypeConstraints,
-    useActualParameters = false,
-  ): ParametricType =>
-    new ParametricType(
-      this.name,
-      useActualParameters
+    ) {
+      const parameters = ignoreExpectedParameters
         ? actual.parameters
-        : this.unifyParameters(actual, constraints),
+        : this.parameters.map((parameter, i) => {
+            try {
+              return parameter.unsafeUnify(
+                actual.parameters[i],
+                typeEqualityGraph,
+              )
+            } catch (error) {
+              if (error instanceof InternalTypeError)
+                error.addTypeMismatch(this, actual)
+              throw error
+            }
+          })
+
+      return new ParametricType(this.name, parameters)
+    }
+
+    throw new InternalTypeError(
+      this,
+      actual,
+      'Non-variable types do not match.',
     )
+  }
 
-  private unifyParameters = (
-    actual: ParametricType,
-    constraints: TypeConstraints,
-  ): Type[] =>
-    this.parameters.map((parameter, i) => {
-      try {
-        return parameter._unify(actual.parameters[i], constraints)
-      } catch (error) {
-        assert(error instanceof TypeError, 'Should be TypeError.')
-
-        error.addTypeMismatch(this, actual)
-        throw error
-      }
-    })
-
-  _reduce = (constraints: TypeConstraints): ParametricType => {
+  reduce = (typeEqualityGraph: TypeEqualityGraph): Type => {
     const parameters = this.parameters.map((parameter) =>
-      parameter._reduce(constraints),
+      parameter.reduce(typeEqualityGraph),
     )
 
     return new ParametricType(this.name, parameters)
   }
 
+  equals = (type: Type): boolean => {
+    if (!(type instanceof ParametricType)) return false
+    if (this.parameters.length != type.parameters.length) return false
+
+    return this.name === type.name && this.parameters.every((parameter, i) =>
+      parameter.equals(type.parameters[i]),
+    )
+  }
+
   toString = (): string => {
     const parameters = this.parameters.map((parameter) => parameter.toString())
     const combinedParameters =
diff --git a/.yalc/tony-lang/src/types/models/Property.ts b/.yalc/tony-lang/src/types/models/Property.ts
deleted file mode 100644
index 502bc6d..0000000
--- a/.yalc/tony-lang/src/types/models/Property.ts
+++ /dev/null
@@ -1,8 +0,0 @@
-import { Type } from './Type'
-
-export interface Property {
-  name: string
-  type: Type
-
-  toString(): string
-}
diff --git a/.yalc/tony-lang/src/types/models/Representation.ts b/.yalc/tony-lang/src/types/models/Representation.ts
deleted file mode 100644
index bc1c96b..0000000
--- a/.yalc/tony-lang/src/types/models/Representation.ts
+++ /dev/null
@@ -1,34 +0,0 @@
-import { Property } from './Property'
-
-export enum RepresentationKind {
-  Instance,
-  Interface,
-  Unknown,
-}
-
-export class Representation {
-  private _kind: RepresentationKind
-  private _properties: Property[]
-
-  constructor(kind: RepresentationKind, properties: Property[]) {
-    this._kind = kind
-    this._properties = properties
-  }
-
-  get properties(): Property[] {
-    return this._properties
-  }
-
-  findProperty = (name: string): Property | undefined =>
-    this.properties.find((property) => property.name === name)
-
-  toString = (): string => {
-    if (this.properties.length == 0) return '{}'
-
-    const properties = this.properties
-      .map((property) => property.toString())
-      .join(', ')
-
-    return `{ ${properties} }`
-  }
-}
diff --git a/.yalc/tony-lang/src/types/models/Type.ts b/.yalc/tony-lang/src/types/models/Type.ts
index 542f110..35db0c1 100644
--- a/.yalc/tony-lang/src/types/models/Type.ts
+++ b/.yalc/tony-lang/src/types/models/Type.ts
@@ -1,12 +1,25 @@
-import { CurriedType } from './CurriedType'
-import { TypeConstraints } from './TypeConstraints'
+import { TypeEqualityGraph } from './TypeEqualityGraph'
+import { TypeError } from '../../errors'
 
 export abstract class Type {
-  abstract concat: (type: Type) => CurriedType
+  abstract unsafeUnify: (
+    actual: Type,
+    typeEqualityGraph?: TypeEqualityGraph,
+    ignoreExpectedParameters?: boolean,
+  ) => Type
 
-  abstract unify: (actual: Type, constraints: TypeConstraints) => Type
-  abstract _unify: (actual: Type, constraints: TypeConstraints) => Type
-  abstract _reduce: (constraints: TypeConstraints) => Type
+  unify = (
+    actual: Type,
+    typeEqualityGraph?: TypeEqualityGraph,
+    ignoreExpectedParameters?: boolean,
+  ): Type | undefined =>
+    TypeError.safe(() =>
+      this.unsafeUnify(actual, typeEqualityGraph, ignoreExpectedParameters),
+    )
+
+  abstract reduce: (typeEqualityGraph: TypeEqualityGraph) => Type
+
+  abstract equals: (type: Type) => boolean
 
   abstract toString: () => string
 }
diff --git a/.yalc/tony-lang/src/types/models/TypeConstraint.ts b/.yalc/tony-lang/src/types/models/TypeConstraint.ts
new file mode 100644
index 0000000..c99ee4e
--- /dev/null
+++ b/.yalc/tony-lang/src/types/models/TypeConstraint.ts
@@ -0,0 +1,49 @@
+import { Type } from './Type'
+import { TypeEqualityGraph } from './TypeEqualityGraph'
+
+export class TypeConstraint<T extends Type> {
+  private _type: T
+  private _typeEqualityGraph: TypeEqualityGraph
+
+  constructor(type: T, typeEqualityGraph = new TypeEqualityGraph()) {
+    this._type = type
+    this._typeEqualityGraph = typeEqualityGraph
+  }
+
+  get type(): T {
+    return this._type
+  }
+
+  get typeEqualityGraph(): TypeEqualityGraph {
+    return this._typeEqualityGraph
+  }
+
+  unify = (
+    actual: TypeConstraint<Type>,
+    ignoreExpectedParameters = false,
+  ): TypeConstraint<Type> | undefined => {
+    const typeEqualityGraph = TypeEqualityGraph.build(
+      this.typeEqualityGraph,
+      actual.typeEqualityGraph,
+    )
+    if (typeEqualityGraph === undefined) return
+
+    const type = this.type
+      .unify(actual.type, typeEqualityGraph, ignoreExpectedParameters)
+      ?.reduce(typeEqualityGraph)
+
+    if (type) return new TypeConstraint(type, typeEqualityGraph)
+  }
+
+  toString = (): string =>
+    `${this.type.toString()}${this.typeEqualityGraph.toString()}`
+
+  static build = <T extends Type>(
+    type?: T,
+    typeEqualityGraph = new TypeEqualityGraph(),
+  ): TypeConstraint<T> | undefined => {
+    if (type === undefined) return
+
+    return new TypeConstraint(type, typeEqualityGraph)
+  }
+}
diff --git a/.yalc/tony-lang/src/types/models/TypeConstraints.ts b/.yalc/tony-lang/src/types/models/TypeConstraints.ts
deleted file mode 100644
index 5d65a30..0000000
--- a/.yalc/tony-lang/src/types/models/TypeConstraints.ts
+++ /dev/null
@@ -1,30 +0,0 @@
-import { Type } from './Type'
-import { TypeVariable } from './TypeVariable'
-
-export class TypeConstraints {
-  private _map = new Map<string, Type>()
-
-  has = (variable: TypeVariable): boolean => this._map.has(variable.name)
-
-  resolve = (variable: TypeVariable): Type | undefined => {
-    const type = this._map.get(variable.name)
-
-    if (type instanceof TypeVariable && this.has(type))
-      return this.resolve(type)
-
-    return type
-  }
-
-  add = (variable: TypeVariable, type: Type): void => {
-    if (this.has(variable)) {
-      this.resolve(variable)!.unify(type, this)
-      return
-    }
-    if (type instanceof TypeVariable && this.has(type)) {
-      this.resolve(type)!.unify(variable, this)
-      return
-    }
-
-    this._map.set(variable.name, type)
-  }
-}
diff --git a/.yalc/tony-lang/src/types/models/TypeEqualityGraph.ts b/.yalc/tony-lang/src/types/models/TypeEqualityGraph.ts
new file mode 100644
index 0000000..0fdbae4
--- /dev/null
+++ b/.yalc/tony-lang/src/types/models/TypeEqualityGraph.ts
@@ -0,0 +1,148 @@
+import { ParametricType } from './ParametricType'
+import { Type } from './Type'
+import { TypeEquivalenceClass } from './TypeEquivalenceClass'
+import { TypeError } from '../../errors'
+import { TypeVariable } from './TypeVariable'
+
+export class TypeEqualityGraph {
+  private _equivalenceClasses: TypeEquivalenceClass[]
+
+  constructor(equivalenceClasses: TypeEquivalenceClass[] = []) {
+    this._equivalenceClasses = equivalenceClasses
+  }
+
+  add = (typeVariable: TypeVariable, type: Type): void =>
+    this.addEquivalenceClass(new TypeEquivalenceClass(this, [typeVariable, type]))
+
+  private addEquivalenceClass = (equivalence: TypeEquivalenceClass): void => {
+    const [
+      unifiedEquivalenceClass,
+      equivalenceClasses,
+    ] = this._equivalenceClasses.reduce(
+      (
+        [unifiedEquivalenceClass, equivalenceClasses]: [
+          TypeEquivalenceClass,
+          TypeEquivalenceClass[],
+        ],
+        equivalenceClass,
+      ) => {
+        if (
+          unifiedEquivalenceClass.types.some((type) =>
+            equivalenceClass.includes(type),
+          )
+        )
+          return [
+            TypeEquivalenceClass.unify(this, [
+              unifiedEquivalenceClass,
+              equivalenceClass,
+            ]),
+            equivalenceClasses,
+          ]
+
+        return [
+          unifiedEquivalenceClass,
+          [...equivalenceClasses, equivalenceClass],
+        ]
+      },
+      [equivalence, []],
+    )
+
+    this._equivalenceClasses = [...equivalenceClasses, unifiedEquivalenceClass]
+  }
+
+  reduce = (type: Type): Type =>
+    this.equivalenceClass(type)?.representative(this) || type
+
+  private equivalenceClass = (type: Type): TypeEquivalenceClass | undefined =>
+    this._equivalenceClasses.find((equivalenceClass) =>
+      equivalenceClass.includes(type),
+    )
+
+  toString = (): string => {
+    if (this._equivalenceClasses.length == 0) return ''
+
+    const equivalenceClasses = this._equivalenceClasses
+      .map((equivalenceClass) => equivalenceClass.toString())
+      .join(', ')
+    return `{${equivalenceClasses}}`
+  }
+
+  // private connectedComponent = (start: Type): Set<TypeEquality> =>
+  //   new Set(this.buildConnectedComponent([start]))
+
+  // private buildConnectedComponent = (
+  //   frontier: Type[],
+  //   explored: TypeEquality[] = [],
+  // ): TypeEquality[] => {
+  //   if (frontier.length == 0) return explored
+
+  //   const [type, ...remainingFrontier] = frontier
+  //   return Array.from(this._internal).reduce((newExplored, typeEquality) => {
+  //     if (!explored.includes(typeEquality) && typeEquality.has(type))
+  //       return this.buildConnectedComponent(remainingFrontier, [
+  //         ...newExplored,
+  //         typeEquality,
+  //       ])
+  //     return newExplored
+  //   }, explored)
+  // }
+
+  static build = (
+    ...typeEqualityGraphs: TypeEqualityGraph[]
+  ): TypeEqualityGraph | undefined =>
+    TypeError.safe(() =>
+      typeEqualityGraphs.reduce(
+        (unifiedTypeEqualityGraph, typeEqualityGraph) => {
+          typeEqualityGraph._equivalenceClasses.forEach((equivalenceClass) =>
+            unifiedTypeEqualityGraph.addEquivalenceClass(equivalenceClass),
+          )
+          return unifiedTypeEqualityGraph
+        },
+      ),
+    )
+
+  // private static reduce = (
+  //   frontier: TypeEquality[],
+  //   explored: Set<TypeEquality> = new Set(),
+  // ): Set<TypeEquality> => {
+  //   if (frontier.length == 0) return explored
+
+  //   const [typeEquality, ...remainingFrontier] = frontier
+  //   const newFrontier = Array.from(explored).reduce(
+  //     (newFrontier, otherTypeEquality) => {
+  //       if (typeEquality.types.some((type) => otherTypeEquality.has(type)))
+  //         return [
+  //           ...newFrontier,
+  //           ...TypeEqualityGraph.unify(otherTypeEquality, typeEquality),
+  //         ]
+
+  //       return newFrontier
+  //     },
+  //     remainingFrontier,
+  //   )
+
+  //   if (newFrontier.length == remainingFrontier.length)
+  //     return TypeEqualityGraph.reduce(
+  //       remainingFrontier,
+  //       new Set([...explored, typeEquality]),
+  //     )
+  //   else return TypeEqualityGraph.reduce(newFrontier, explored)
+  // }
+
+  // private static unify = (
+  //   expected: TypeEquality,
+  //   actual: TypeEquality,
+  // ): Set<TypeEquality> => {
+  //   const typeEqualityGraph = new TypeEqualityGraph()
+
+  //   expected.types.every((expectedType) =>
+  //     actual.types.every(
+  //       (actualType) =>
+  //         actualType instanceof ParametricType &&
+  //         expectedType.unsafeUnify(actualType, typeEqualityGraph),
+  //     ),
+  //   )
+
+  //   return typeEqualityGraph._internal
+  // }
+}
diff --git a/.yalc/tony-lang/src/types/models/TypeEquivalenceClass.ts b/.yalc/tony-lang/src/types/models/TypeEquivalenceClass.ts
new file mode 100644
index 0000000..960b445
--- /dev/null
+++ b/.yalc/tony-lang/src/types/models/TypeEquivalenceClass.ts
@@ -0,0 +1,72 @@
+import { Type } from './Type'
+import { TypeEqualityGraph } from './TypeEqualityGraph'
+import { TypeVariable } from './TypeVariable'
+
+export class TypeEquivalenceClass {
+  private _types: Type[]
+
+  constructor(
+    typeEqualityGraph: TypeEqualityGraph,
+    types: Type[]
+  ) {
+    this._types = TypeEquivalenceClass.reduce(typeEqualityGraph, types)
+  }
+
+  get size(): number {
+    return this._types.length
+  }
+
+  get types(): Type[] {
+    return this._types
+  }
+
+  includes = (type: Type): boolean => this._types.some(otherType => type.equals(otherType))
+
+  representative = (
+    typeEqualityGraph: TypeEqualityGraph
+  ): Type | undefined =>
+    TypeEquivalenceClass.buildRepresentative(typeEqualityGraph, this._types)
+
+  toString = (): string =>
+    `[${this._types.map((type) => type.toString()).join(', ')}]`
+
+  static unify = (
+    typeEqualityGraph: TypeEqualityGraph,
+    equivalenceClasses: TypeEquivalenceClass[],
+  ): TypeEquivalenceClass =>
+    new TypeEquivalenceClass(
+      typeEqualityGraph,
+      equivalenceClasses.reduce(
+        (types: Type[], equivalenceClass) => [
+          ...types,
+          ...equivalenceClass._types,
+        ],
+        [],
+      ),
+    )
+
+  private static reduce = (
+    typeEqualityGraph: TypeEqualityGraph,
+    types: Type[],
+  ): Type[] =>
+    types.reduce((types: Type[], type) => {
+      if (types.some(otherType => type.equals(otherType))) return types
+
+      TypeEquivalenceClass.buildRepresentative(typeEqualityGraph, types)
+      return [...types, type]
+    }, [])
+
+  private static buildRepresentative = (
+    typeEqualityGraph: TypeEqualityGraph,
+    types: Type[],
+  ): Type | undefined => {
+    const immediateTypes = types.filter(type => !(type instanceof TypeVariable))
+    if (immediateTypes.length == 0) return
+
+    console.log(typeEqualityGraph.toString(), immediateTypes.map(t => t.toString()))
+    return immediateTypes.reduce((representative: Type, type) =>
+      representative.unsafeUnify(type, typeEqualityGraph),
+      // representative.unsafeUnify(type),
+    ).reduce(typeEqualityGraph)
+  }
+}
diff --git a/.yalc/tony-lang/src/types/models/TypeProperty.ts b/.yalc/tony-lang/src/types/models/TypeProperty.ts
deleted file mode 100644
index 78a92cf..0000000
--- a/.yalc/tony-lang/src/types/models/TypeProperty.ts
+++ /dev/null
@@ -1,33 +0,0 @@
-import { ParametricType } from './ParametricType'
-import { Property } from './Property'
-import { Representation } from './Representation'
-
-export class TypeProperty implements Property {
-  private _representation: Representation | undefined
-  private _type: ParametricType
-
-  constructor(type: ParametricType, representation?: Representation) {
-    this._type = type
-    this._representation = representation
-  }
-
-  get name(): string {
-    return this.type.name
-  }
-
-  get representation(): Representation | undefined {
-    return this._representation
-  }
-
-  get type(): ParametricType {
-    return this._type
-  }
-
-  toString = (): string => {
-    const type = this.type.toString()
-    if (this.representation === undefined) return type
-
-    const representation = this.representation.toString()
-    return `${type}: ${representation}`
-  }
-}
diff --git a/.yalc/tony-lang/src/types/models/TypeVariable.ts b/.yalc/tony-lang/src/types/models/TypeVariable.ts
index 17364e5..a580540 100644
--- a/.yalc/tony-lang/src/types/models/TypeVariable.ts
+++ b/.yalc/tony-lang/src/types/models/TypeVariable.ts
@@ -1,6 +1,5 @@
-import { CurriedType } from './CurriedType'
 import { Type } from './Type'
-import { TypeConstraints } from './TypeConstraints'
+import { TypeEqualityGraph } from './TypeEqualityGraph'
 
 export class TypeVariable extends Type {
   private static unnamedVariableCount = 0
@@ -17,37 +16,29 @@ export class TypeVariable extends Type {
     return this._name
   }
 
-  concat = (type: Type): CurriedType => {
-    if (type instanceof CurriedType) return type.concat(this)
-
-    return new CurriedType([this, type])
-  }
-
-  unify = (actual: Type, constraints: TypeConstraints): Type =>
-    this._unify(actual, constraints)._reduce(constraints)
-
-  _unify = (actual: Type, constraints: TypeConstraints): Type => {
+  unsafeUnify = (actual: Type, typeEqualityGraph?: TypeEqualityGraph): Type => {
     if (!(actual instanceof TypeVariable)) {
-      constraints.add(this, actual)
+      if (typeEqualityGraph) typeEqualityGraph.add(this, actual)
+
       return actual
     }
 
-    if (this.name !== actual.name) constraints.add(actual, this)
+    if (this.name !== actual.name && typeEqualityGraph)
+      typeEqualityGraph.add(actual, this)
     return this
   }
 
-  _reduce = (constraints: TypeConstraints): Type => {
-    if (constraints.has(this)) return constraints.resolve(this)!
+  reduce = (typeEqualityGraph: TypeEqualityGraph): Type =>
+    typeEqualityGraph.reduce(this)
 
-    return this
+  equals = (type: Type): boolean => {
+    if (!(type instanceof TypeVariable)) return false
+
+    return this.name === type.name
   }
 
   toString = (): string => this.name
 
-  private static getUnusedVariableName = (): string => {
-    const name = `t${TypeVariable.unnamedVariableCount}`
-    TypeVariable.unnamedVariableCount += 1
-
-    return name
-  }
+  private static getUnusedVariableName = (): string =>
+    `t${(TypeVariable.unnamedVariableCount += 1)}`
 }
diff --git a/.yalc/tony-lang/src/types/models/index.ts b/.yalc/tony-lang/src/types/models/index.ts
index 7bd0b07..400e913 100644
--- a/.yalc/tony-lang/src/types/models/index.ts
+++ b/.yalc/tony-lang/src/types/models/index.ts
@@ -1,8 +1,6 @@
-export { CurriedType } from './CurriedType'
-export { IdentifierProperty } from './IdentifierProperty'
+export { ModuleType } from './ModuleType'
 export { ParametricType } from './ParametricType'
-export { Representation, RepresentationKind } from './Representation'
 export { Type } from './Type'
-export { TypeConstraints } from './TypeConstraints'
-export { TypeProperty } from './TypeProperty'
+export { TypeConstraint } from './TypeConstraint'
+export { TypeEqualityGraph } from './TypeEqualityGraph'
 export { TypeVariable } from './TypeVariable'
diff --git a/.yalc/tony-lang/src/types/services/BuildRepresentation.ts b/.yalc/tony-lang/src/types/services/BuildRepresentation.ts
deleted file mode 100644
index ab12e59..0000000
--- a/.yalc/tony-lang/src/types/services/BuildRepresentation.ts
+++ /dev/null
@@ -1,23 +0,0 @@
-import { Binding, IdentifierBinding, TypeBinding } from '../../symbol_table'
-import {
-  IdentifierProperty,
-  Representation,
-  RepresentationKind,
-  TypeProperty,
-} from '../models'
-import { isNotUndefined } from '../../utilities'
-
-export class BuildRepresentation {
-  perform = (kind: RepresentationKind, bindings: Binding[]): Representation => {
-    const properties = bindings
-      .map((binding) => {
-        if (binding instanceof IdentifierBinding)
-          return new IdentifierProperty(binding.name, binding.type)
-        else if (binding instanceof TypeBinding)
-          return new TypeProperty(binding.type, binding.representation)
-      })
-      .filter(isNotUndefined)
-
-    return new Representation(kind, properties)
-  }
-}
diff --git a/.yalc/tony-lang/src/types/services/BuildType.ts b/.yalc/tony-lang/src/types/services/BuildType.ts
index 9ca7475..2010be3 100644
--- a/.yalc/tony-lang/src/types/services/BuildType.ts
+++ b/.yalc/tony-lang/src/types/services/BuildType.ts
@@ -1,10 +1,10 @@
-import { CurriedType, ParametricType, Type } from '../models'
-import { InternalError, assert } from '../../errors'
-import { LIST_TYPE, MAP_TYPE, TUPLE_TYPE } from '..'
+import { FUNCTION_TYPE, LIST_TYPE, MAP_TYPE, TUPLE_TYPE } from '..'
+import { InternalError } from '../../errors'
+import { ParametricType } from '../models'
 import Parser from 'tree-sitter'
 
 export class BuildType {
-  perform = (node: Parser.SyntaxNode): Type => {
+  perform = (node: Parser.SyntaxNode): ParametricType => {
     switch (node.type) {
       case 'list_type':
         return this.handleListType(node)
@@ -18,7 +18,7 @@ export class BuildType {
         return this.handleType(node)
       default:
         throw new InternalError(
-          `ParseType: Could not find generator for AST node '${node.type}'.`,
+          `Could not find generator for AST node '${node.type}'.`,
         )
     }
   }
@@ -42,12 +42,7 @@ export class BuildType {
     return new ParametricType(TUPLE_TYPE, valueTypes)
   }
 
-  handleTypeConstructor = (node: Parser.SyntaxNode): Type => {
-    assert(
-      node.type === 'type_constructor',
-      'Should be `type_constructor` node.',
-    )
-
+  private handleTypeConstructor = (node: Parser.SyntaxNode): ParametricType => {
     if (node.namedChildCount == 1) {
       const type = this.perform(node.namedChild(0)!)
 
@@ -55,12 +50,10 @@ export class BuildType {
     }
 
     const types = node.namedChildren.map((childNode) => this.perform(childNode))
-    return new CurriedType(types)
+    return new ParametricType(FUNCTION_TYPE, types)
   }
 
-  handleType = (node: Parser.SyntaxNode): ParametricType => {
-    assert(node.type === 'type', 'Should be `type` node.')
-
+  private handleType = (node: Parser.SyntaxNode): ParametricType => {
     const name = node.text
 
     return new ParametricType(name)
diff --git a/.yalc/tony-lang/src/types/services/index.ts b/.yalc/tony-lang/src/types/services/index.ts
index ac967b6..02638e9 100644
--- a/.yalc/tony-lang/src/types/services/index.ts
+++ b/.yalc/tony-lang/src/types/services/index.ts
@@ -1,2 +1 @@
-export { BuildRepresentation } from './BuildRepresentation'
 export { BuildType } from './BuildType'
diff --git a/.yalc/tony-lang/test/abstraction/quicksort.tn b/.yalc/tony-lang/test/abstraction/quicksort.tn
index a5ce368..629b17d 100644
--- a/.yalc/tony-lang/test/abstraction/quicksort.tn
+++ b/.yalc/tony-lang/test/abstraction/quicksort.tn
@@ -3,7 +3,7 @@ quicksort :=
   ([pivot, ...rest]) =>
     l := quicksort([n | n in rest if n <= pivot])
     r := quicksort([n | n in rest if n > pivot])
-    l ++ [pivot] ++ r
+    l + [pivot] + r
 
 list := quicksort([5, 7, 2, 0, 4, 3])
 print(list[0].to_str)
diff --git a/.yalc/tony-lang/test/application/index.tn b/.yalc/tony-lang/test/application/index.tn
index c88528d..64af1aa 100644
--- a/.yalc/tony-lang/test/application/index.tn
+++ b/.yalc/tony-lang/test/application/index.tn
@@ -1,3 +1,2 @@
 print(((a, b) => [a, b])(1, 2)[0].to_str)
-# print(((a, b = 1) => [a, b])(1)[1].to_str)
 print('hello world')
diff --git a/.yalc/tony-lang/test/assignment/duplicate_binding.tn b/.yalc/tony-lang/test/assignment/duplicate_binding.tn
new file mode 100644
index 0000000..841ae63
--- /dev/null
+++ b/.yalc/tony-lang/test/assignment/duplicate_binding.tn
@@ -0,0 +1,2 @@
+x := 1
+x := 2
diff --git a/.yalc/tony-lang/test/assignment/duplicate_binding.txt b/.yalc/tony-lang/test/assignment/duplicate_binding.txt
new file mode 100644
index 0000000..f4c2755
--- /dev/null
+++ b/.yalc/tony-lang/test/assignment/duplicate_binding.txt
@@ -0,0 +1 @@
+DuplicateBindingError
diff --git a/.yalc/tony-lang/test/assignment/overloading.tn b/.yalc/tony-lang/test/assignment/overloading.tn
new file mode 100644
index 0000000..0b6afb7
--- /dev/null
+++ b/.yalc/tony-lang/test/assignment/overloading.tn
@@ -0,0 +1,5 @@
+x := 1
+x := 'string'
+
+print(x)
+print(x.to_str)
diff --git a/.yalc/tony-lang/test/assignment/overloading.txt b/.yalc/tony-lang/test/assignment/overloading.txt
new file mode 100644
index 0000000..c5119f1
--- /dev/null
+++ b/.yalc/tony-lang/test/assignment/overloading.txt
@@ -0,0 +1,2 @@
+string
+1
diff --git a/.yalc/tony-lang/test/assignment/pattern_matching.tn b/.yalc/tony-lang/test/assignment/pattern_matching.tn
index b228326..c644d9f 100644
--- a/.yalc/tony-lang/test/assignment/pattern_matching.tn
+++ b/.yalc/tony-lang/test/assignment/pattern_matching.tn
@@ -12,9 +12,6 @@ print(z.to_str)
 
 [(1, h), i] := [(1, 'hello'), (2, 'Tony')]
 print(h)
-# Dynamic tuple access
-# print(i[0].to_str)
-# print(i[1])
 
 [j, 1, k = 200] := [0, 1]
 print(j.to_str)
diff --git a/.yalc/tony-lang/test/stdlib.tn b/.yalc/tony-lang/test/stdlib.tn
index 5aa79fa..89712b1 100644
--- a/.yalc/tony-lang/test/stdlib.tn
+++ b/.yalc/tony-lang/test/stdlib.tn
@@ -5,7 +5,7 @@ import {
   add: + :: Number -> Number -> Number,
   sub: - :: Number -> Number -> Number,
   mod: % :: Number -> Number -> Number,
-  concat: ++ :: [Number] -> [Number] -> [Number],
+  concat: + :: [Number] -> [Number] -> [Number],
   leq: <= :: Number -> Number -> Boolean,
   lt: < :: Number -> Number -> Boolean,
   geq: >= :: Number -> Number -> Boolean,
diff --git a/.yalc/tony-lang/tony-lang.d.ts b/.yalc/tony-lang/tony-lang.d.ts
index a7c6583..1c8ca76 100644
--- a/.yalc/tony-lang/tony-lang.d.ts
+++ b/.yalc/tony-lang/tony-lang.d.ts
@@ -3,24 +3,30 @@ import Parser from 'tree-sitter'
 declare module 'tony-lang' {
   export function compile(
     file: string,
-    { outFile, emit, webpack, webpackMode, verbose }: {
-      outFile?: string;
-      emit?: boolean;
-      webpack?: boolean;
-      webpackMode?: string;
-      verbose?: boolean;
-    }
+    {
+      outFile,
+      emit,
+      webpack,
+      webpackMode,
+      verbose,
+    }: {
+      outFile?: string
+      emit?: boolean
+      webpack?: boolean
+      webpackMode?: string
+      verbose?: boolean
+    },
   ): Promise<string | undefined>
 
   export function exec(
     file: string,
     args: string[],
-    { verbose }: { verbose?: boolean }
+    { verbose }: { verbose?: boolean },
   ): Promise<void>
 
   export function parse(
     file: string,
-    { verbose }: { verbose?: boolean }
+    { verbose }: { verbose?: boolean },
   ): Promise<Parser.Tree>
 
   export const VERSION: string
@@ -44,11 +50,26 @@ declare module 'tony-lang' {
 
   export class ImportOutsideFileModuleScopeError extends CompileError {}
 
+  export class IndeterminateTypeError extends CompileError {
+    get types(): string[]
+  }
+
   export class InternalError extends Error {}
 
-  export class InvalidPropertyAccessError extends CompileError {
-    get property(): string
-    get representation(): string
+  export class InternalTypeError extends InternalError {
+    get trace(): [string, string][]
+  }
+
+  export class InvalidExternalTypeImportError extends CompileError {
+    get type(): string
+  }
+
+  export class InvalidModuleAccessError extends CompileError {
+    get binding(): string | undefined
+    get type(): string
+  }
+
+  export class InvalidUseOfTypeAsValueError extends CompileError {
     get type(): string
   }
 
@@ -56,13 +77,17 @@ declare module 'tony-lang' {
     get binding(): string
   }
 
+  export class MissingExternalImportTypeHintError extends CompileError {
+    get binding(): string
+  }
+
   export class SyntaxError extends Error {
     get filePath(): string
     get tree(): Parser.Tree
   }
 
   export class TypeError extends CompileError {
-    get typeTrace(): [string, string][]
+    get trace(): InternalTypeError[]
   }
 
   export class UnknownImportError extends CompileError {
diff --git a/.yalc/tony-lang/yalc.sig b/.yalc/tony-lang/yalc.sig
index 5848715..11fdd1f 100644
--- a/.yalc/tony-lang/yalc.sig
+++ b/.yalc/tony-lang/yalc.sig
@@ -1 +1 @@
-afbd7cb804326aa5fded581a46697147
\ No newline at end of file
+dae48e8c032e9be3346d19eba294b036
\ No newline at end of file
diff --git a/src/CLI.ts b/src/CLI.ts
index 3b07f3a..a8f6310 100644
--- a/src/CLI.ts
+++ b/src/CLI.ts
@@ -40,7 +40,7 @@ export default class CLI {
 
         return Tony.exec(entryPath, args, { verbose: this.options.debug })
       })
-      .catch((error) => new ErrorHandler().perform(error))
+      .catch((error) => new ErrorHandler(this.options.debug).perform(error))
   }
 
   compile = async (
@@ -70,18 +70,18 @@ export default class CLI {
         if (emit)
           console.log(`Your compiled file can be found here: ${entryPath}`)
       })
-      .catch((error) => new ErrorHandler().perform(error))
+      .catch((error) => new ErrorHandler(this.options.debug).perform(error))
   }
 
   exec = async (file: string, args: string[]): Promise<void> => {
     await Tony.exec(path.join(process.cwd(), file), args, {
       verbose: this.options.debug,
-    }).catch((error) => new ErrorHandler().perform(error))
+    }).catch((error) => new ErrorHandler(this.options.debug).perform(error))
   }
 
   parse = async (file: string): Promise<void> => {
     await Tony.parse(file, { verbose: this.options.debug })
       .then((tree) => console.log(new TreeFormatter().perform(tree.rootNode)))
-      .catch((error) => new ErrorHandler().perform(error))
+      .catch((error) => new ErrorHandler(this.options.debug).perform(error))
   }
 }
diff --git a/src/ErrorHandler.ts b/src/ErrorHandler.ts
index 4a6848e..1e9ffa5 100644
--- a/src/ErrorHandler.ts
+++ b/src/ErrorHandler.ts
@@ -5,7 +5,7 @@ import {
   ExportOutsideModuleScopeErrorFormatter,
   ImportOutsideFileModuleScopeErrorFormatter,
   InternalErrorFormatter,
-  InvalidPropertyAccessErrorFormatter,
+  InvalidModuleAccessErrorFormatter,
   MissingBindingErrorFormatter,
   SyntaxErrorFormatter,
   TypeErrorFormatter,
@@ -14,6 +14,12 @@ import {
 import chalk from 'chalk'
 
 export class ErrorHandler {
+  private _verbose: boolean
+
+  constructor(verbose: boolean) {
+    this._verbose = verbose
+  }
+
   perform = async (error: Error): Promise<void> => {
     console.error(
       `${chalk.gray(error.stack)}\n\n${chalk.bold.underline.redBright(
@@ -33,14 +39,16 @@ export class ErrorHandler {
       await new ExportOutsideModuleScopeErrorFormatter().perform(error)
     else if (error instanceof Tony.ImportOutsideFileModuleScopeError)
       await new ImportOutsideFileModuleScopeErrorFormatter().perform(error)
-    else if (error instanceof Tony.InvalidPropertyAccessError)
-      await new InvalidPropertyAccessErrorFormatter().perform(error)
+    else if (error instanceof Tony.InvalidModuleAccessError)
+      await new InvalidModuleAccessErrorFormatter().perform(error)
     else if (error instanceof Tony.MissingBindingError)
-      return new MissingBindingErrorFormatter().perform(error)
+      await new MissingBindingErrorFormatter().perform(error)
     else if (error instanceof Tony.TypeError)
-      return new TypeErrorFormatter().perform(error)
+      await new TypeErrorFormatter().perform(error)
     else if (error instanceof Tony.UnknownImportError)
       await new UnknownImportErrorFormatter().perform(error)
     else console.error(error.message)
+
+    if (this._verbose) console.error(error)
   }
 }
diff --git a/src/formatting/InvalidPropertyAccessErrorFormatter.ts b/src/formatting/InvalidModuleAccessErrorFormatter.ts
similarity index 55%
rename from src/formatting/InvalidPropertyAccessErrorFormatter.ts
rename to src/formatting/InvalidModuleAccessErrorFormatter.ts
index 8de4a2b..42c0725 100644
--- a/src/formatting/InvalidPropertyAccessErrorFormatter.ts
+++ b/src/formatting/InvalidModuleAccessErrorFormatter.ts
@@ -1,15 +1,14 @@
-import { InvalidPropertyAccessError } from 'tony-lang'
+import { InvalidModuleAccessError } from 'tony-lang'
 import { SourceFormatter } from './SourceFormatter'
 import chalk from 'chalk'
 
-export class InvalidPropertyAccessErrorFormatter {
-  perform = async (error: InvalidPropertyAccessError): Promise<void> => {
+export class InvalidModuleAccessErrorFormatter {
+  perform = async (error: InvalidModuleAccessError): Promise<void> => {
     console.error(
       `The name ${chalk.bold.whiteBright(
-        error.property,
+        error.binding,
       )} is not a property of ` +
-        `the type ${chalk.whiteBright(error.type)} with the representation ` +
-        `${chalk.whiteBright(error.representation)}.`,
+        `the module ${chalk.whiteBright(error.type)}.`,
     )
 
     if (error.filePath && error.context) {
diff --git a/src/formatting/TypeErrorFormatter.ts b/src/formatting/TypeErrorFormatter.ts
index 32cbb5c..6daaa51 100644
--- a/src/formatting/TypeErrorFormatter.ts
+++ b/src/formatting/TypeErrorFormatter.ts
@@ -5,21 +5,24 @@ import chalk from 'chalk'
 export class TypeErrorFormatter {
   perform = async (error: TypeError): Promise<void> => {
     console.error(
-      'Types could not be unified.\n\n' +
-        `${chalk.bold.whiteBright(error.message)}\n\nUnification trace:`,
+      'Type unification resulted in an empty type disjunction.\n\nUnification trace:',
     )
 
-    error.typeTrace.forEach(([expected, actual]) => {
-      if (actual)
-        console.error(
-          `${chalk.gray('- expected')} ${chalk.whiteBright(
-            expected,
-          )}\n       ` + `${chalk.gray('got')} ${chalk.whiteBright(actual)}`,
-        )
-      else
-        console.error(
-          `${chalk.gray('-')}          ${chalk.whiteBright(expected)}`,
-        )
+    error.trace.forEach((internalTypeError) => {
+      console.error(chalk.bold.whiteBright(internalTypeError.message))
+
+      internalTypeError.trace.forEach(([expected, actual]) => {
+        if (actual)
+          console.error(
+            `${chalk.gray('- expected')} ${chalk.whiteBright(
+              expected,
+            )}\n       ` + `${chalk.gray('got')} ${chalk.whiteBright(actual)}`,
+          )
+        else
+          console.error(
+            `${chalk.gray('-')}          ${chalk.whiteBright(expected)}`,
+          )
+      })
     })
 
     if (error.filePath && error.context) {
diff --git a/src/formatting/index.ts b/src/formatting/index.ts
index 5cb558d..e5febdc 100644
--- a/src/formatting/index.ts
+++ b/src/formatting/index.ts
@@ -3,7 +3,7 @@ export { DuplicateBindingErrorFormatter } from './DuplicateBindingErrorFormatter
 export { ExportOutsideModuleScopeErrorFormatter } from './ExportOutsideModuleScopeErrorFormatter'
 export { ImportOutsideFileModuleScopeErrorFormatter } from './ImportOutsideFileModuleScopeErrorFormatter'
 export { InternalErrorFormatter } from './InternalErrorFormatter'
-export { InvalidPropertyAccessErrorFormatter } from './InvalidPropertyAccessErrorFormatter'
+export { InvalidModuleAccessErrorFormatter } from './InvalidModuleAccessErrorFormatter'
 export { MissingBindingErrorFormatter } from './MissingBindingErrorFormatter'
 export { SyntaxErrorFormatter } from './SyntaxErrorFormatter'
 export { TreeFormatter } from './TreeFormatter'
diff --git a/test.js b/test.js
new file mode 100644
index 0000000..70775e5
--- /dev/null
+++ b/test.js
@@ -0,0 +1 @@
+!function(t){var e={};function r(n){if(e[n])return e[n].exports;var o=e[n]={i:n,l:!1,exports:{}};return t[n].call(o.exports,o,o.exports,r),o.l=!0,o.exports}r.m=t,r.c=e,r.d=function(t,e,n){r.o(t,e)||Object.defineProperty(t,e,{enumerable:!0,get:n})},r.r=function(t){"undefined"!=typeof Symbol&&Symbol.toStringTag&&Object.defineProperty(t,Symbol.toStringTag,{value:"Module"}),Object.defineProperty(t,"__esModule",{value:!0})},r.t=function(t,e){if(1&e&&(t=r(t)),8&e)return t;if(4&e&&"object"==typeof t&&t&&t.__esModule)return t;var n=Object.create(null);if(r.r(n),Object.defineProperty(n,"default",{enumerable:!0,value:t}),2&e&&"string"!=typeof t)for(var o in t)r.d(n,o,function(e){return t[e]}.bind(null,o));return n},r.n=function(t){var e=t&&t.__esModule?function(){return t.default}:function(){return t};return r.d(e,"a",e),e},r.o=function(t,e){return Object.prototype.hasOwnProperty.call(t,e)},r.p="",r(r.s=26)}([function(t,e,r){"use 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\ No newline at end of file
diff --git a/test.tn b/test.tn
new file mode 100644
index 0000000..f92112e
--- /dev/null
+++ b/test.tn
@@ -0,0 +1,30 @@
+import {
+  print :: String -> Void,
+  to_str :: Number -> String,
+  neg: ! :: Number -> Number,
+  add: + :: Number -> Number -> Number,
+  sub: - :: Number -> Number -> Number,
+  mod: % :: Number -> Number -> Number,
+  concat: + :: [Number] -> [Number] -> [Number],
+  leq: <= :: Number -> Number -> Boolean,
+  lt: < :: Number -> Number -> Boolean,
+  geq: >= :: Number -> Number -> Boolean,
+  gt: > :: Number -> Number -> Boolean,
+  eq: == :: Number -> Number -> Boolean
+} from '../tony/dist/test/stdlib.js'
+
+
+quicksort :=
+  ([]) => []
+  ([pivot, ...rest]) =>
+    l := quicksort([n | n in rest if n <= pivot])
+    r := quicksort([n | n in rest if n > pivot])
+    l + [pivot] + r
+
+list := quicksort([5, 7, 2, 0, 4, 3])
+print(list[0].to_str)
+print(list[1].to_str)
+print(list[2].to_str)
+print(list[3].to_str)
+print(list[4].to_str)
+print(list[5].to_str)
diff --git a/yalc.lock b/yalc.lock
index dbbcf98..6f0a724 100644
--- a/yalc.lock
+++ b/yalc.lock
@@ -2,7 +2,7 @@
   "version": "v1",
   "packages": {
     "tony-lang": {
-      "signature": "afbd7cb804326aa5fded581a46697147",
+      "signature": "dae48e8c032e9be3346d19eba294b036",
       "file": true
     }
   }
diff --git a/yarn.lock b/yarn.lock
index de8577d..8c14089 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1785,7 +1785,7 @@ core-js-compat@^3.6.2:
     browserslist "^4.8.3"
     semver "7.0.0"
 
-core-js@^3.6.5:
+core-js@^3.6.4:
   version "3.6.5"
   resolved "https://registry.yarnpkg.com/core-js/-/core-js-3.6.5.tgz#7395dc273af37fb2e50e9bd3d9fe841285231d1a"
   integrity sha512-vZVEEwZoIsI+vPEuoF9Iqf5H7/M3eeQqWlQnYa8FSKKePuYTf5MWnxb5SDAzCa60b3JBRS5g9b+Dq7b1y/RCrA==
@@ -5064,9 +5064,9 @@ to-regex@^3.0.1, to-regex@^3.0.2:
     safe-regex "^1.1.0"
 
 "tony-lang@file:.yalc/tony-lang":
-  version "0.1.4-afbd7cb8"
+  version "0.1.4-698841e7"
   dependencies:
-    core-js "^3.6.5"
+    core-js "^3.6.4"
     deep-equal "^2.0.1"
     inquirer "^7.1.0"
     mkdirp "^1.0.3"