From 31cc68c8d77406dbce5c628c42e8082452ec775d Mon Sep 17 00:00:00 2001
From: Akuli <akuviljanen17@gmail.com>
Date: Tue, 19 Dec 2023 13:22:57 +0200
Subject: [PATCH] Unnecessary cast warning (#467)

---
 src/typecheck.c                                   | 6 +++++-
 tests/should_succeed/unnecessary_cast_warning.jou | 6 ++++++
 2 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 tests/should_succeed/unnecessary_cast_warning.jou

diff --git a/src/typecheck.c b/src/typecheck.c
index a7d034e3..473a4f05 100644
--- a/src/typecheck.c
+++ b/src/typecheck.c
@@ -571,8 +571,12 @@ static void do_explicit_cast(ExpressionTypes *types, const Type *to, Location lo
 {
     assert(!types->implicit_cast_type);
     const Type *from = types->type;
+
+    if (from == to)
+        show_warning(location, "unnecessary cast from %s to %s", from->name, to->name);
+
     if (
-        from != to  // TODO: should probably be error if it's the same type.
+        from != to
         && !(from->kind == TYPE_ARRAY && to->kind == TYPE_POINTER && from->data.array.membertype == to->data.valuetype)
         && !(is_pointer_type(from) && is_pointer_type(to))
         && !(is_number_type(from) && is_number_type(to))
diff --git a/tests/should_succeed/unnecessary_cast_warning.jou b/tests/should_succeed/unnecessary_cast_warning.jou
new file mode 100644
index 00000000..7dc9e829
--- /dev/null
+++ b/tests/should_succeed/unnecessary_cast_warning.jou
@@ -0,0 +1,6 @@
+import "stdlib/io.jou"
+
+def main() -> int:
+    x = 1 as int  # Warning: unnecessary cast from int to int
+    printf("%d\n", x)  # Output: 1
+    return 0