Add test for unexpected type in assign

crates/concrete_driver/tests/checks.rs

@@ -18,6 +18,21 @@ fn module_not_found() {
     );
 }
 
+#[test]
+fn assign_unexpected_type() {
+    let (source, name) = (
+        include_str!("invalid_programs/assign_unexpected_type.con"),
+        "assign_unexpected_type",
+    );
+    let error = check_invalid_program(source, name);
+
+    assert!(
+        matches!(&error, LoweringError::UnexpectedType { .. }),
+        "{:#?}",
+        error
+    );
+}
+
 #[test]
 fn import_not_found() {
     let (source, name) = (include_str!("invalid_programs/import2.con"), "import2");

crates/concrete_driver/tests/invalid_programs/assign_unexpected_type.con

@@ -0,0 +1,8 @@
+mod Simple {
+    fn main() -> i32 {
+        let var: i32 = 5;
+        var = foo();
+    }
+
+    fn foo() {}
+}