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Merged
frendsick merged 3 commits into from
Jun 12, 2026
Merged

feat: add block scoping for if/elif/else and match arms #254

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34365bd
feat: add block scoping for if/elif/else and match arms
frendsick May 29, 2026
6209a75
fix: tighten block binding scopes
frendsick Jun 1, 2026
efeb20b
refactor: model scoped variable types
frendsick Jun 1, 2026
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469 changes: 238 additions & 231 deletions compiler/bytecode.casa
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14 changes: 2 additions & 12 deletions compiler/lexer.casa
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Original file line number Diff line number Diff line change
Expand Up @@ -102,12 +102,7 @@ impl Lexer {
loc "Expected two hex digits after \\x" ErrorKind::Syntax self.add_error
"" Option::Some return
fi
if high_opt Option::Some(high) is then
high hex_digit_value = high_value
else
empty_location "Expected high hex digit" ErrorKind::Syntax raise_error
1 exit
fi
high_opt.unwrap hex_digit_value = high_value
if 0 high_value < then
3 self Lexer::cursor Cursor::pos 3 - self.loc = loc
loc "Invalid hex digit in \\x escape" ErrorKind::Syntax self.add_error
Expand All @@ -119,12 +114,7 @@ impl Lexer {
loc "Expected two hex digits after \\x" ErrorKind::Syntax self.add_error
"" Option::Some return
fi
if low_opt Option::Some(low) is then
low hex_digit_value = low_value
else
empty_location "Expected low hex digit" ErrorKind::Syntax raise_error
1 exit
fi
low_opt.unwrap hex_digit_value = low_value
if 0 low_value < then
4 self Lexer::cursor Cursor::pos 4 - self.loc = loc
loc "Invalid hex digit in \\x escape" ErrorKind::Syntax self.add_error
Expand Down
24 changes: 21 additions & 3 deletions compiler/pattern.casa
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Original file line number Diff line number Diff line change
Expand Up @@ -144,6 +144,7 @@ fn unify_arm_stacks tc:TypeChecker match_ctx:MatchContext op:Op {
# by a struct destructure arm.

fn assign_struct_binding_type
tc:TypeChecker
matched_struct:CasaStruct
field_name:str
bound_var:str
Expand All @@ -152,7 +153,7 @@ fn assign_struct_binding_type
{
for member in matched_struct CasaStruct::members.iter do
if field_name member Member::name == then
store function_opt member Member::typ bound_var set_binding_type
store function_opt member Member::typ bound_var tc set_binding_type
fi
done
}
Expand All @@ -171,7 +172,7 @@ fn register_struct_pattern_bindings
struct_pattern StructPattern::bindings.keys = binding_keys
for field_name in binding_keys.iter do
if field_name struct_pattern StructPattern::bindings.get Option::Some(bound_var) is then
tc.store function_opt bound_var field_name matched_struct assign_struct_binding_type
tc.store function_opt bound_var field_name matched_struct tc assign_struct_binding_type
else
empty_location "Expected option value while unwrapping field_name struct_pattern StructPattern::bindings.get" ErrorKind::Syntax raise_error
1 exit
Expand Down Expand Up @@ -233,7 +234,7 @@ fn apply_enum_bindings
if binding_type.format type_bindings.get Option::Some(resolved) is then
resolved = binding_type
fi
tc.store function_opt binding_type binding_var set_binding_type
tc.store function_opt binding_type binding_var tc set_binding_type
1 += bind_index
done
}
Expand Down Expand Up @@ -275,6 +276,10 @@ fn typecheck_match_op tc:TypeChecker function_opt:Option[Function] op:Op {
op pattern_covered_key = covered_key
match_subject_type parse_type_str.match_base = arm_base

# A prior arm has already opened (and left open) its scope frame iff the
# match has seen a condition. Capture this before the block below sets it.
match_ctx MatchContext::condition_present = arm_has_predecessor

if op pattern_value_of PatternValue::EnumVariant(variant) is then
if op pattern_is_wildcard ! then
arm_base variant op tc diagnose_bare_enum_pattern
Expand All @@ -291,11 +296,24 @@ fn typecheck_match_op tc:TypeChecker function_opt:Option[Function] op:Op {
tc.stack match_ctx MatchContext::after.restore
fi

# Each arm body gets its own scope frame: pattern bindings and any
# block-local assignments live here, invisible to other arms and after
# `end`. Close the previous arm's frame before opening this one.
if arm_has_predecessor then tc.pop_block_scope fi
tc.push_block_scope

# Record pattern bindings in the arm scope; implicit bindings cannot
# shadow an accessible outer variable (same rule as is-bindings).
for binding_var in op pattern_bindings.iter do
true op binding_var tc.record_var_scope
done

match_subject_type op function_opt tc register_pattern_bindings

if op pattern_is_guarded then
op pattern_guard_ops = guard_ops
tc.store TypeChecker::new = guard_checker
guard_checker tc.copy_scope_state_to
function_opt guard_ops guard_checker.run_type_check_ops
guard_checker.stack.types = guard_stack
false = guard_ok
Expand Down
90 changes: 41 additions & 49 deletions compiler/syntax.casa
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Original file line number Diff line number Diff line change
Expand Up @@ -227,6 +227,7 @@ fn parse_type_ast cursor:TokenCursor -> Type {
fi
peek_opt.unwrap = peek

"" = base
if "fn" peek Token::value == then
cursor.pop drop
"fn" = base
Expand All @@ -252,11 +253,7 @@ fn parse_type_ast cursor:TokenCursor -> Type {
while cursor.is_finished ! do
cursor.peek = inner_opt
if inner_opt.is_none then break fi
if inner_opt Option::Some(inner) is then
inner Token::value = ival
else
break
fi
inner_opt.unwrap Token::value = ival
if "]" ival == then
cursor.pop drop
break
Expand Down Expand Up @@ -738,11 +735,7 @@ fn parse_bound_type_args cursor:TokenCursor trait_token:Token -> List[str] {
trait_token Token::location "Unclosed trait bound type argument list" ErrorKind::Syntax raise_error
bound_args return
fi
if arg_tok_opt Option::Some(arg_tok) is then
arg_tok Token::value = arg_val
else
bound_args return
fi
arg_tok_opt.unwrap Token::value = arg_val
if "[" arg_val == then
1 += pba_depth
arg_val pba_current.append
Expand Down Expand Up @@ -1960,6 +1953,7 @@ fn parse_impl_block parser:Parser cursor:TokenCursor {

# Get base type name (without type params)
impl_type "[" str::find = bracket
"" = base_type
if 0 bracket > then
impl_type 0 bracket str::substring = base_type
else
Expand Down Expand Up @@ -2083,11 +2077,7 @@ fn parse_pattern_terminator parser:Parser cursor:TokenCursor function_name:str -
while cursor.is_finished ! do
cursor.peek = next_opt
if next_opt.is_none then break fi
if next_opt Option::Some(next) is then
next Token::value = next_value
else
break
fi
next_opt.unwrap Token::value = next_value
if "=>" next_value == 0 match_depth == && then break fi
cursor.pop = guard_token_opt
if guard_token_opt.is_none then break fi
Expand Down Expand Up @@ -3160,23 +3150,24 @@ fn parse_and_resolve tokens:List[Token] search_paths:List[str] -> ParseResolveRe

fn gather_captures store:SymbolStore lambda_function:Function function:Function {
for op in lambda_function Function::ops.iter do
if op.value OpValue::Identifier(name) is ! then continue fi
false = captured

# Check enclosing function variables
for variable in function Function::variables.iter do
if name variable Variable::name == then
variable lambda_function Function::captures.push
true = captured
break
fi
done
if op.value OpValue::Identifier(name) is then
false = captured

# Check enclosing function variables
for variable in function Function::variables.iter do
if name variable Variable::name == then
variable lambda_function Function::captures.push
true = captured
break
fi
done

if captured ! then
# Check global variables
name store.variables.get = global_var_opt
if global_var_opt Option::Some(global_var) is then
global_var lambda_function Function::captures.push
if captured ! then
# Check global variables
name store.variables.get = global_var_opt
if global_var_opt Option::Some(global_var) is then
global_var lambda_function Function::captures.push
fi
fi
fi
done
Expand Down Expand Up @@ -3422,24 +3413,25 @@ fn register_struct_pattern_binding store:SymbolStore function:Function binding_n
}

fn resolve_match_op store:SymbolStore function:Function op:Op errors:List[CasaError] {
if op.value OpValue::MatchArm(arm) is ! then return fi
arm.pattern_value match
PatternValue::Struct(struct_pattern) => {
struct_pattern.bindings.keys = pattern_keys
for pattern_key in pattern_keys.iter do
pattern_key struct_pattern.bindings.get.unwrap = binding_name
binding_name function store register_struct_pattern_binding
done
}
PatternValue::EnumVariant(variant) => {
errors function op variant store resolve_enum_variant
}
PatternValue::Literal => { }
end
arm.guard_ops = guard_ops
if guard_ops.length 0 != then
function guard_ops store resolve_identifiers = resolved_guard
resolved_guard arm MatchArm::set_guard_ops
if op.value OpValue::MatchArm(arm) is then
arm.pattern_value match
PatternValue::Struct(struct_pattern) => {
struct_pattern.bindings.keys = pattern_keys
for pattern_key in pattern_keys.iter do
pattern_key struct_pattern.bindings.get.unwrap = binding_name
binding_name function store register_struct_pattern_binding
done
}
PatternValue::EnumVariant(variant) => {
errors function op variant store resolve_enum_variant
}
PatternValue::Literal => { }
end
arm.guard_ops = guard_ops
if guard_ops.length 0 != then
function guard_ops store resolve_identifiers = resolved_guard
resolved_guard arm MatchArm::set_guard_ops
fi
fi
}
# Try resolving `&name` and `&K::method` function references. Returns true
Expand Down
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