function literals (non-capturing)

compiler/ast/ast.odin

@@ -104,6 +104,7 @@ Expr_Kind :: enum u8 {
 	Call,
 	Try,
 	Catch,
+	Function_Literal,
 }
 
 Expr :: struct {
@@ -209,6 +210,7 @@ Function :: struct {
 	file:       File_Id,
 	c_abi:      bool,
 	imported:   bool,
+	generated:  bool,
 	has_body:   bool,
 	variadic:   bool,
 	params:     []Param,

compiler/checker/checker.odin

@@ -518,9 +518,20 @@ find_import_symbol :: proc(index: []Import_Index_Entry, scope: ast.File_Id, name
 }
 
 build_symbol_indexes :: proc(checker: ^Checker) {
-	checker.function_index = make([]Function_Index_Entry, len(checker.ast_module.functions), checker.allocator)
+	function_count := 0
+	for function in checker.ast_module.functions {
+		if !function.generated {
+			function_count += 1
+		}
+	}
+	checker.function_index = make([]Function_Index_Entry, function_count, checker.allocator)
+	function_index := 0
 	for function, id in checker.ast_module.functions {
-		checker.function_index[id] = Function_Index_Entry{scope=function.pkg, name=function.name, id=ast.function_id(id)}
+		if function.generated {
+			continue
+		}
+		checker.function_index[function_index] = Function_Index_Entry{scope=function.pkg, name=function.name, id=ast.function_id(id)}
+		function_index += 1
 	}
 	slice.sort_by(checker.function_index, function_index_less)
 
@@ -1038,6 +1049,12 @@ mark_expr_imports_used :: proc(checker: ^Checker, expr_id: ast.Expr_Id, file: as
 				append(&stack, expr.right)
 			}
 			mark_block_imports_used(checker, expr.body, file)
+		case .Function_Literal:
+			function_id := ast.Function_Id(u32(expr.integer))
+			if function_id != ast.INVALID_FUNCTION && int(function_id) < len(checker.ast_module.functions) {
+				function := checker.ast_module.functions[function_id]
+				mark_block_imports_used(checker, function.body, function.file)
+			}
 		case .Add, .Sub, .Mul, .Div, .Index, .Orelse, .Eq, .Ne, .Lt, .Le, .Gt, .Ge, .And, .Or, .Range:
 			append(&stack, expr.left, expr.right)
 		case .Invalid, .Integer, .Float, .String, .Bool, .None, .Undefined, .Type, .Name:
@@ -1865,6 +1882,11 @@ infer_expr :: proc(
 			     .Comptime, .Bool, .Not, .Eq, .Ne, .Lt, .Le, .Gt, .Ge, .And, .Or, .Range:
 				last = infer_compound_expr(checker, expr, locals, pkg, file, demanded, local_types)
 				_ = pop(&stack)
+			case .Function_Literal:
+				template := ast.Function_Id(u32(expr.integer))
+				pointer_type, _, ok := function_pointer_type_for_template(checker, template, demanded)
+				last = pointer_type if ok else types.INVALID
+				_ = pop(&stack)
 			case .Name:
 				last = types.INVALID
 				if !symbol.is_valid(expr.qualifier) {
@@ -2421,7 +2443,7 @@ infer_statements :: proc(
 			if statement.expr != ast.INVALID_EXPR {
 				returned := infer_expr(checker, statement.expr, locals^[:], pkg, file, demanded, local_types)
 				if is_runtime_type(checker, result_hint) {
-					_ = record_demand(checker, statement.expr, result_hint, locals^[:], local_types, pkg, file)
+					_ = record_demand_shallow(checker, statement.expr, result_hint, locals^[:], local_types, pkg, file)
 					expr := checker.ast_module.exprs[statement.expr]
 					if expr.kind == .Name && !symbol.is_valid(expr.qualifier) {
 						if local_index, ok := find_infer_local_index(locals^[:], expr.name); ok {
@@ -2433,7 +2455,7 @@ infer_statements :: proc(
 							returned = result_hint
 						} else {
 							// `return G` for a global const: demand the result type onto it.
-							record_demand(checker, statement.expr, result_hint, locals^[:], local_types, pkg, file)
+							record_demand_shallow(checker, statement.expr, result_hint, locals^[:], local_types, pkg, file)
 						}
 					}
 				}
@@ -2861,6 +2883,49 @@ expr_accepts_numeric_demand :: proc(
 	return false
 }
 
+DEMAND_RECURSION_LIMIT :: 4096
+
+record_demand_too_deep :: proc(checker: ^Checker, expr_id: ast.Expr_Id) -> bool {
+	stack: [dynamic]ast.Expr_Id
+	stack.allocator = checker.allocator
+	defer delete(stack)
+	append(&stack, expr_id)
+	seen := 0
+	for len(stack) > 0 {
+		current := pop(&stack)
+		if current == ast.INVALID_EXPR || int(current) >= len(checker.ast_module.exprs) {
+			continue
+		}
+		seen += 1
+		if seen > DEMAND_RECURSION_LIMIT {
+			return true
+		}
+		expr := checker.ast_module.exprs[current]
+		#partial switch expr.kind {
+		case .Negate:
+			append(&stack, expr.left)
+		case .Add, .Sub, .Mul, .Div:
+			append(&stack, expr.left, expr.right)
+		}
+	}
+	return false
+}
+
+record_demand_shallow :: proc(
+	checker: ^Checker,
+	expr_id: ast.Expr_Id,
+	demand: types.Type,
+	locals: []Infer_Local,
+	local_types: []types.Type,
+	pkg: ast.Package_Id,
+	file: ast.File_Id,
+) -> bool {
+	if record_demand_too_deep(checker, expr_id) {
+		return false
+	}
+	return record_demand(checker, expr_id, demand, locals, local_types, pkg, file)
+}
+
 // record_demand pushes a concrete type demand onto open numeric slots reachable
 // through bare names and numeric arithmetic. Calls remain a boundary (milestone 14.5).
 record_demand :: proc(
@@ -4569,6 +4634,10 @@ build_expr :: proc(
 					checker, expr, locals, global_reads, calls, frame.expected, pkg, file,
 				)
 				_ = pop(&stack)
+			case .Function_Literal:
+				template := ast.Function_Id(u32(expr.integer))
+				last = build_function_value(checker, template, expr.span, frame.expected)
+				_ = pop(&stack)
 			case .Type:
 				id := source.add(checker.diagnostics, expr.span, "type is not a runtime value")
 				last = invalid_hir_expr(checker, expr.span, id)
@@ -5234,6 +5303,9 @@ make_link_name :: proc(checker: ^Checker, id: Spec_Id) -> string {
 	if function.pkg == 0 && function.name == checker.main_symbol {
 		return fmt.aprintf("main", allocator = checker.allocator)
 	}
+	if function.generated {
+		return fmt.aprintf("bro__p%d__anon%d", function.pkg, spec.template, allocator = checker.allocator)
+	}
 	if !function.has_body && function.c_abi {
 		if len(function.link_name) > 0 {
 			return strings.clone(function.link_name, checker.allocator)
@@ -8423,8 +8495,11 @@ check :: proc(
 	}
 
 	for function, index in ast_module.functions {
+		if function.generated {
+			continue
+		}
 		for previous in ast_module.functions[:index] {
-			if previous.pkg == function.pkg && previous.name == function.name {
+			if !previous.generated && previous.pkg == function.pkg && previous.name == function.name {
 				source.addf(diagnostics, function.span, "duplicate function '%s'", symbol_text(&checker, function.name))
 			}
 		}

compiler/parser/parser.odin

@@ -736,6 +736,8 @@ parse_primary :: proc(parser: ^Parser, nesting: int) -> ast.Expr_Id {
 			right=ast.INVALID_EXPR,
 			diagnostic=source.INVALID_DIAGNOSTIC,
 		})
+	case .Keyword_Func:
+		return parse_function_literal(parser)
 	case .Left_Bracket:
 		return parse_array_literal(parser, nesting)
 	case .Dot:
@@ -2111,6 +2113,56 @@ parse_function :: proc(parser: ^Parser, name: token.Token, c_abi: bool) {
 	})
 }
 
+parse_function_literal :: proc(parser: ^Parser) -> ast.Expr_Id {
+	start := advance(parser)
+	if _, ok := allow(parser, .Left_Paren); !ok {
+		source.add(parser.diagnostics, current(parser).span, "expected '(' after 'func'")
+	}
+	params, variadic := parse_params(parser)
+	if _, ok := allow(parser, .Right_Paren); !ok {
+		source.add(parser.diagnostics, current(parser).span, "expected ')' after parameters")
+	}
+	skip_newlines(parser)
+	result := parse_type(parser)
+	error_type := types.INVALID
+	if _, ok := allow(parser, .Bang); ok {
+		error_type = parse_error_type(parser)
+	}
+	if current(parser).kind == .Newline {
+		skip_newlines(parser)
+	}
+	if current(parser).kind != .Left_Brace {
+		delete(params, parser.module.allocator)
+		return invalid_expr(parser, start.span, "expected function literal body")
+	}
+	body := parse_block(parser)
+	end := previous(parser)
+	function_id := ast.function_id(len(parser.module.functions))
+	append(&parser.module.functions, ast.Function{
+		span=span_from(start.span, end.span),
+		name=symbol.INVALID,
+		pkg=parser.pkg,
+		file=parser.file,
+		c_abi=false,
+		generated=true,
+		has_body=true,
+		variadic=variadic,
+		params=params,
+		result=result,
+		error=error_type,
+		body=body,
+		diagnostic=source.INVALID_DIAGNOSTIC,
+	})
+	return add_expr(parser, ast.Expr{
+		kind=.Function_Literal,
+		span=span_from(start.span, end.span),
+		integer=u64(function_id),
+		left=ast.INVALID_EXPR,
+		right=ast.INVALID_EXPR,
+		diagnostic=source.INVALID_DIAGNOSTIC,
+	})
+}
+
 parse_record_field_type :: proc(parser: ^Parser, allow_anonymous_struct_payload: bool) -> types.Type {
 	if allow_anonymous_struct_payload && current(parser).kind == .Keyword_Struct {
 		return parse_inline_struct_payload_type(parser)

compiler_tests.odin

@@ -2913,19 +2913,21 @@ milestone_24_rejects_invalid_forms :: proc(t: ^testing.T) {
 }
 
 @(test)
-field_function_pointer_calls_lower_as_indirect_calls :: proc(t: ^testing.T) {
+function_literals_lower_as_function_pointer_values :: proc(t: ^testing.T) {
 	text := `Callbacks :: struct {
 	call @func(value i32) i32
 	value i32
 }
-plus_one func(value i32) i32 {
-	return value + 1
-}
 run func(callbacks Callbacks) i32 {
 	return callbacks.call(callbacks.value)
 }
 main func() i32 {
-	callbacks Callbacks = Callbacks { call = plus_one, value = 41 }
+	callbacks Callbacks = Callbacks {
+		call = func(value i32) i32 {
+			return value + 1
+		},
+		value = 41,
+	}
 	return run(callbacks) - 42
 }
 `
@@ -2943,6 +2945,14 @@ main func() i32 {
 	ir_module := lower.lower(&hir_module)
 	defer ir.destroy_module(&ir_module)
 
+	generated_functions := 0
+	literal_exprs := 0
+	for function in ast_module.functions {
+		generated_functions += 1 if function.generated else 0
+	}
+	for expr in ast_module.exprs {
+		literal_exprs += 1 if expr.kind == .Function_Literal else 0
+	}
 	indirect_calls := 0
 	for expr in hir_module.exprs {
 		if expr.kind == .Call && expr.left != hir.INVALID_EXPR {
@@ -2950,10 +2960,41 @@ main func() i32 {
 		}
 	}
 	testing.expect_value(t, len(diagnostics.items), 0)
+	testing.expect_value(t, generated_functions, 1)
+	testing.expect_value(t, literal_exprs, 1)
 	testing.expect(t, len(ir_module.functions) > 0)
 	testing.expect(t, indirect_calls > 0)
 }
 
+@(test)
+function_literals_do_not_capture_locals :: proc(t: ^testing.T) {
+	text := `main func() i32 {
+	offset i32 = 1
+	callback @func(value i32) i32 = func(value i32) i32 {
+		return value + offset
+	}
+	return callback(1)
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	ast_module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&ast_module)
+	hir_module := checker.check(&ast_module, &diagnostics, &symbols)
+	defer hir.destroy_module(&hir_module)
+
+	found := false
+	for diagnostic in diagnostics.items {
+		found = found || strings.contains(diagnostic.message, "unresolved global 'offset'")
+	}
+	testing.expect(t, found)
+}
+
 @(test)
 field_function_pointer_calls_reject_non_callable_fields :: proc(t: ^testing.T) {
 	text := `Box :: struct {

std/mem/mem.bro

@@ -8,16 +8,12 @@ Allocator :: struct {
 
 heap Allocator :: Allocator {
 	context = none,
-	alloc = heap_alloc,
-	free = heap_free,
-}
-
-heap_alloc func(context ?*mut anyopaque, size usize, alignment usize) ?*mut u8 {
+	alloc = func(context ?*mut anyopaque, size usize, alignment usize) ?*mut u8 {
 		return ptr_cast(u8, c.malloc(size))
-}
-
-heap_free func(context ?*mut anyopaque, memory ?*mut u8, size usize, alignment usize) void {
+	},
+	free = func(context ?*mut anyopaque, memory ?*mut u8, size usize, alignment usize) void {
 		c.free(memory)
+	},
 }
 
 alloc func(allocator Allocator, size usize, alignment usize) ?*mut u8 {