From ee0e30934ac2d2e52e2b3286e37a5737141c311c Mon Sep 17 00:00:00 2001
From: Sofia <sofia@teascade.net>
Date: Mon, 13 Apr 2026 21:32:34 +0300
Subject: [PATCH] Allow typechecker to perform implicit casts

---
 src/typechecker.cpp | 13 +++++++++----
 src/types.cpp       |  2 +-
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/typechecker.cpp b/src/typechecker.cpp
index c941e69..1c697d2 100644
--- a/src/typechecker.cpp
+++ b/src/typechecker.cpp
@@ -10,10 +10,15 @@ namespace {
         Castable,
     };
 
-    Result<TypecheckRes, std::string> check_type(std::shared_ptr<types::Type> checked, std::shared_ptr<types::Type> target) {
+    Result<TypecheckRes, std::string> check_type(typecheck::State& state, std::shared_ptr<types::Type> checked, std::shared_ptr<types::Type> target) {
+        auto potential_cast = types::find_cast(state.casts, checked, target);
+
         if (types::types_equal(checked, target)) {
             return TypecheckRes::Ok;
         }
+        else if (potential_cast.has_value() && potential_cast->allow_implicit) {
+            return TypecheckRes::Castable;
+        }
 
         return std::string{ "Types " + checked->formatted() + " and " + target->formatted() + " incompatible" };
     }
@@ -156,7 +161,7 @@ namespace AST {
                     auto expected_param_ty = fn_ty->m_param_tys[i];
                     auto param_ty = this->m_args[i]->typecheck(state, scope, expected_param_ty);
 
-                    auto check_res = check_type(param_ty, expected_param_ty);
+                    auto check_res = check_type(state, param_ty, expected_param_ty);
                     this->m_args[i] = handle_res(std::move(this->m_args[i]), check_res, state);
                 }
                 else {
@@ -190,7 +195,7 @@ namespace AST {
     void ReturnStatement::typecheck(typecheck::State& state, typecheck::Scope& scope) {
         auto res_ty = this->m_expr->typecheck(state, scope, scope.return_ty);
         if (scope.return_ty) {
-            auto check_res = check_type(res_ty, *scope.return_ty);
+            auto check_res = check_type(state, res_ty, *scope.return_ty);
             this->m_expr = handle_res(std::move(this->m_expr), check_res, state);
         }
     }
@@ -211,7 +216,7 @@ namespace AST {
             new types::FundamentalType{ types::FundamentalTypeKind::Bool } };
         auto expr_ty = this->m_condition->typecheck(state, scope, bool_ty);
 
-        auto check_res = check_type(expr_ty, bool_ty);
+        auto check_res = check_type(state, expr_ty, bool_ty);
         this->m_condition = handle_res(std::move(this->m_condition), check_res, state);
 
         this->m_then->typecheck(state, scope);
diff --git a/src/types.cpp b/src/types.cpp
index e715457..dde30a8 100644
--- a/src/types.cpp
+++ b/src/types.cpp
@@ -76,7 +76,7 @@ namespace types {
     }
 
     bool Type::is_signed() {
-        false;
+        return false;
     }
 
     std::pair<llvm::Value*, std::shared_ptr<Type>> FundamentalType::load(codegen::Builder&, llvm::Value* ptr) {