Lambdas were not type checked thoroughly #1185.

releasenotes.md

@@ -24,6 +24,7 @@
 - Fixed issue in safe mode when converting enums.
 - Better checking of operator methods.
 - Bug when assigning an optional from an optional.
+- Lambdas were not type checked thoroughly #1185. 
 
 ### Stdlib changes
 - "init_new/init_temp" removed. 

src/compiler/sema_expr.c

@@ -7691,8 +7691,7 @@ static inline bool sema_expr_analyse_lambda(SemaContext *context, Type *target_t
 	}
 	if (to_sig && vec_size(to_sig->params) != vec_size(sig->params))
 	{
-		SEMA_ERROR(expr, "The lambda doesn't match the required type %s.", type_quoted_error_string(target_type));
-		return false;
+		RETURN_SEMA_ERROR(expr, "The lambda doesn't match the required type %s.", type_quoted_error_string(target_type));
 	}
 	FOREACH_BEGIN_IDX(i, Decl *param, sig->params)
 		if (param->var.type_info) continue;
@@ -7730,6 +7729,12 @@ static inline bool sema_expr_analyse_lambda(SemaContext *context, Type *target_t
 	decl->extname = decl->name = scratch_buffer_copy();
 	decl->type = type_new_func(decl, sig);
 	if (!sema_analyse_function_signature(context, decl, sig->abi, sig)) return false;
+	if (target_type && flat->pointer->function.prototype->raw_type != decl->type->function.prototype->raw_type)
+	{
+		RETURN_SEMA_ERROR(expr, "The lambda has type %s, which doesn't match the required type %s.",
+		                  type_quoted_error_string(decl->type),
+						  type_quoted_error_string(target_type));
+	}
 	decl->func_decl.lambda_ct_parameters = ct_lambda_parameters;
 	decl->func_decl.is_lambda = true;
 	decl->alignment = type_alloca_alignment(decl->type);

test/test_suite/lambda/lambda_checks.c3

@@ -0,0 +1,14 @@
+module test;
+def Func = fn void (bool);
+
+fn bool foo (String) => true;
+fn void bar(Func func) => func(false);
+
+fn void main()
+{
+	Func funcX = &foo; // #error: Implicitly casting
+	bar(&foo); // #error: Implicitly casting
+
+	Func func = fn bool (String) { return true; }; // #error: which doesn't match
+	bar(fn bool (String) { return true; }); // #error: which doesn't match
+}