Project 7 - Second Milestone (Const Statement)

.vscode/settings.json

@@ -0,0 +1,5 @@
+{
+    "githubPullRequests.ignoredPullRequestBranches": [
+        "main"
+    ]
+}

Cargo.toml

@@ -8,3 +8,8 @@ nom = "7"
 
 [dev-dependencies]
 nom = "7"
+proptest = "1.10.0"
+
+[[test]]
+name = "property"
+path = "tests/property/mod.rs"

setupctags.sh

@@ -0,0 +1,44 @@
+#!/bin/bash
+## Setup ctags for nom, rust-std crates and project
+set -e  # Exit on error
+
+## check existence of stdlib
+if [ ! -d rust ]; then
+    echo "Cloning Rust source..."
+    git clone --depth 1 https://github.com/rust-lang/rust.git
+fi
+
+## create stdlib tags
+if [ -d rust ]; then
+    echo "Generating stdlib tags..."
+    (cd rust && ctags -R --languages=Rust -f ~/rust-stdlib.tags library/)
+    echo "✅ Created ~/rust-stdlib.tags"
+fi
+
+## create project tags
+echo "Generating project tags..."
+ctags -R --languages=Rust --exclude=target -f tags .
+echo "✅ Created ./tags"
+
+## find and tag nom (if exists)
+NOM_PATH=$(find ~/.cargo/registry/src -type d -name "nom-*" 2>/dev/null | head -1)
+if [ -n "$NOM_PATH" ]; then
+    echo "Generating nom tags..."
+    ctags -R --languages=Rust -f nom.tags "$NOM_PATH/src"
+    echo "✅ Created nom.tags"
+else
+    echo "⚠️  nom not found in cargo cache (build your project first?)"
+fi
+
+## find and tag proptest (if exists)
+PROPTEST_PATH=$(find ~/.cargo/registry/src/index.crates.io-* -type d -name "proptest-*" 2>/dev/null | head -1)
+if [ -n "$PROPTEST_PATH" ]; then
+    echo "Generating proptest tags..."
+    ctags -R --languages=Rust -f proptest.tags "$PROPTEST_PATH/src"
+    echo "✅ Created proptest.tags"
+else
+    echo "⚠️  proptest not found in cargo cache (build your project first?)"
+fi
+
+echo ""
+echo "🎉 Done! Add to Vim: :set tags=./tags,~/rust-stdlib.tags"

src/interpreter/exec_stmt.rs

@@ -52,6 +52,13 @@ pub fn exec_stmt(stmt: &CheckedStmt, env: &mut Environment<Value>) -> ExecResult
             Ok(None)
         }
 
+        // --- Constant declaration ---
+        Statement::ConstDecl { name, init, .. } => {
+            let val = eval_expr(init, env)?;
+            env.declare(name.clone(), val);
+            Ok(None)
+        }
+
         // --- Assignment ---
         Statement::Assign { target, value } => {
             let val = eval_expr(value, env)?;

src/interpreter/mod.rs

@@ -60,11 +60,21 @@ use crate::stdlib::NativeRegistry;
 
 use eval_expr::eval_call;
 use value::{FnValue, RuntimeError, Value};
+use crate::ir::ast::Statement;
+use crate::interpreter::eval_expr::eval_expr;
 
 /// Interpret a type-checked MiniC program, starting execution at `main`.
 pub fn interpret(program: &CheckedProgram) -> Result<(), RuntimeError> {
     let mut env = Environment::<Value>::new();
 
+    for constant in &program.constants {
+        if let Statement::ConstDecl { name, init, .. } = &constant.stmt {
+            // Evaluate the initializer expression to a value
+            let value = eval_expr(init, &mut env)?; 
+            env.declare(name.clone(), value);
+        }
+    }
+
     // Register native stdlib functions as Value::Fn(FnValue::Native) bindings.
     let registry = NativeRegistry::default();
     for (name, entry) in registry.iter() {

src/ir/ast.rs

@@ -128,6 +128,12 @@ pub enum Statement<Ty> {
         ty: Type,
         init: Box<ExprD<Ty>>,
     },
+    /// Constant declaration with initialization: `const int x = expr`.
+    ConstDecl {
+        name: String,
+        ty: Type,
+        init: Box<ExprD<Ty>>,
+    },
     Assign {
         target: Box<ExprD<Ty>>,
         value: Box<ExprD<Ty>>,
@@ -169,6 +175,7 @@ pub struct FunDecl<Ty> {
 #[derive(Debug, Clone, PartialEq)]
 pub struct Program<Ty> {
     pub functions: Vec<FunDecl<Ty>>,
+    pub constants: Vec<StatementD<Ty>>,
 }
 
 // Type synonyms for checked and unchecked phases.

src/parser/mod.rs

@@ -66,4 +66,4 @@ pub use functions::fun_decl;
 pub use identifiers::identifier;
 pub use literals::{literal, Literal};
 pub use program::program;
-pub use statements::{assignment, statement};
+pub use statements::{assignment, const_statement, statement};

src/parser/program.rs

@@ -15,6 +15,11 @@
 //! function declaration causes the parse to stop. The type checker then
 //! verifies that a `main` function exists.
 //!
+//! Local `const T name = expr ;` is recognised inside function bodies via
+//! [`crate::parser::statements::const_statement`] (wired from [`crate::parser::statements::statement`]).
+//! Extending this module with `alt((const_statement, fun_decl))` plus a rich enough
+//! [`crate::ir::ast::Program`] is the usual next step for top-level constants.
+//!
 //! # Design Decisions
 //!
 //! ## `many0` as the top-level combinator
@@ -26,12 +31,103 @@
 //! `main` is a semantic constraint checked in the next pipeline stage, not
 //! a syntactic one enforced here.
 
-use crate::ir::ast::{Program, UncheckedProgram};
+// use crate::ir::ast::{Program, UncheckedProgram};
+// use crate::parser::functions::fun_decl;
+// use nom::{combinator::map, multi::many0, IResult};
+//
+// /// Parse a complete MiniC program: zero or more function declarations.
+// /// Execution starts at the `main` function (validated by the type checker).
+// pub fn program(input: &str) -> IResult<&str, UncheckedProgram> {
+//     map(many0(fun_decl), |functions| Program { 
+//         functions, 
+//         constants: vec![] 
+//     })(input)
+// }
+// use crate::ir::ast::{Program, UncheckedProgram, FunDecl, StatementD};
+// use crate::parser::functions::fun_decl;
+// // Import the constant statement parser mentioned in your docs
+// use crate::parser::statements::const_statement;
+//
+// use nom::{
+//     branch::alt,
+//     combinator::map,
+//     multi::many0,
+//     IResult,
+// };
+//
+// /// An internal enum used to differentiate top-level elements during parsing.
+// enum GlobalItem {
+//     Function(FunDecl<()>),
+//     Constant(StatementD<()>),
+// }
+//
+// /// Parse a complete MiniC program: zero or more global constant declarations 
+// /// and function declarations in any order.
+// pub fn program(input: &str) -> IResult<&str, UncheckedProgram> {
+//     // 1. Repeatedly parse either a function declaration OR a global constant
+//     map(
+//         many0(alt((
+//             map(fun_decl, GlobalItem::Function),
+//             map(const_statement, GlobalItem::Constant),
+//         ))),
+//         |items| {
+//             let mut functions = Vec::new();
+//             let mut constants = Vec::new();
+//
+//             // 2. Separate them into their respective vectors for the Program AST
+//             for item in items {
+//                 match item {
+//                     GlobalItem::Function(f) => functions.push(f),
+//                     GlobalItem::Constant(c) => constants.push(c),
+//                 }
+//             }
+//
+//             Program { functions, constants }
+//         },
+//     )(input)
+// }
+use crate::ir::ast::{Program, UncheckedProgram, FunDecl, StatementD};
 use crate::parser::functions::fun_decl;
-use nom::{combinator::map, multi::many0, IResult};
+use crate::parser::statements::const_statement;
+
+use nom::{
+    branch::alt,
+    combinator::map,
+    multi::many0,
+    character::complete::multispace0,
+    sequence::delimited,
+    IResult,
+};
+
+enum GlobalItem {
+    Function(FunDecl<()>),
+    Constant(StatementD<()>),
+}
 
-/// Parse a complete MiniC program: zero or more function declarations.
-/// Execution starts at the `main` function (validated by the type checker).
 pub fn program(input: &str) -> IResult<&str, UncheckedProgram> {
-    map(many0(fun_decl), |functions| Program { functions })(input)
+    // Wrap the top level elements so that trailing or leading whitespace/newlines 
+    // do not prematurely break `many0`
+    map(
+        many0(delimited(
+            multispace0,
+            alt((
+                map(fun_decl, GlobalItem::Function),
+                map(const_statement, GlobalItem::Constant),
+            )),
+            multispace0,
+        )),
+        |items| {
+            let mut functions = Vec::new();
+            let mut constants = Vec::new();
+
+            for item in items {
+                match item {
+                    GlobalItem::Function(f) => functions.push(f),
+                    GlobalItem::Constant(c) => constants.push(c),
+                }
+            }
+
+            Program { functions, constants }
+        },
+    )(input)
 }

src/parser/statements.rs

@@ -5,8 +5,10 @@
 //! Exposes two public functions:
 //!
 //! * [`statement`] — the top-level entry point; tries each statement form in
-//!   order: `return`, `if`, `while`, call-statement, block, declaration,
-//!   assignment.
+//!   order: `return`, `if`, `while`, call-statement, block, `const` declaration,
+//!   declaration, assignment.
+//! * [`const_statement`] — `const T name = expr ;`, producing
+//!   [`Statement::ConstDecl`].
 //! * [`assignment`] — parses `lvalue = expression ;`; exported separately
 //!   because the test suite uses it directly.
 //!
@@ -47,7 +49,7 @@ use crate::parser::identifiers::identifier;
 use nom::{
     branch::alt,
     bytes::complete::tag,
-    character::complete::{char, multispace0},
+    character::complete::{char, multispace0, multispace1},
     combinator::{map, opt},
     multi::many0,
     sequence::{delimited, preceded, tuple},
@@ -58,7 +60,7 @@ fn wrap(s: Statement<()>) -> UncheckedStmt {
     StatementD { stmt: s, ty: () }
 }
 
-/// Parse any statement: block | if | while | return | decl | call | assignment.
+/// Parse any statement: block | if | while | return | const | decl | call | assignment.
 pub fn statement(input: &str) -> IResult<&str, UncheckedStmt> {
     preceded(
         multispace0,
@@ -67,6 +69,7 @@ pub fn statement(input: &str) -> IResult<&str, UncheckedStmt> {
             if_statement,
             while_statement,
             return_statement,
+            const_statement,
             decl_statement,
             call_statement,
             assignment,
@@ -82,6 +85,30 @@ fn return_statement(input: &str) -> IResult<&str, UncheckedStmt> {
     Ok((rest, wrap(Statement::Return(expr.map(Box::new)))))
 }
 
+/// Parse `const T name = expr ;`.
+///
+/// Produces [`Statement::ConstDecl`] so later phases can preserve immutability
+/// information.
+pub fn const_statement(input: &str) -> IResult<&str, UncheckedStmt> {
+    map(
+        tuple((
+            preceded(multispace0, tag("const")),
+            preceded(multispace1, type_name),
+            preceded(multispace1, identifier),
+            preceded(multispace0, tag("=")),
+            preceded(multispace0, expression),
+            preceded(multispace0, char(';')),
+        )),
+        |(_, ty, name, _, init, _)| {
+            wrap(Statement::ConstDecl {
+                name: name.to_string(),
+                ty,
+                init: Box::new(init),
+            })
+        },
+    )(input)
+}
+
 /// Parse a variable declaration: `Type ident = expr ;`. Must come before assignment.
 fn decl_statement(input: &str) -> IResult<&str, UncheckedStmt> {
     map(
@@ -207,3 +234,56 @@ pub fn assignment(input: &str) -> IResult<&str, UncheckedStmt> {
         },
     )(input)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::statement;
+    use crate::ir::ast::{Expr, Literal, Statement, Type};
+    use nom::combinator::all_consuming;
+
+    #[test]
+    fn parses_const_declaration_as_const_decl() {
+        let (_, stmt) = all_consuming(statement)("const int MAX_SIZE = 100;").expect("should parse");
+
+        match stmt.stmt {
+            Statement::ConstDecl { name, ty, init } => {
+                assert_eq!(name, "MAX_SIZE");
+                assert_eq!(ty, Type::Int);
+                assert_eq!(init.exp, Expr::Literal(Literal::Int(100)));
+            }
+            other => panic!("expected ConstDecl, got {:?}", other),
+        }
+    }
+
+    #[test]
+    fn parses_const_expression_initializer() {
+        let (_, stmt) = all_consuming(statement)("const int DOUBLE = 2 * 21;").expect("should parse");
+
+        match stmt.stmt {
+            Statement::ConstDecl { name, ty, .. } => {
+                assert_eq!(name, "DOUBLE");
+                assert_eq!(ty, Type::Int);
+            }
+            other => panic!("expected ConstDecl, got {:?}", other),
+        }
+    }
+
+    #[test]
+    fn keeps_mutable_declaration_as_decl() {
+        let (_, stmt) = all_consuming(statement)("int x = 5;").expect("should parse");
+
+        match stmt.stmt {
+            Statement::Decl { .. } => {}
+            Statement::ConstDecl { .. } => panic!("plain Decl must not produce ConstDecl"),
+            other => panic!("unexpected statement: {:?}", other),
+        }
+    }
+
+    #[test]
+    fn rejects_const_without_initializer() {
+        assert!(
+            all_consuming(statement)("const int X;").is_err(),
+            "const without initializer should fail to parse"
+        );
+    }
+}