checker: remove default message from check_subtype (#13546)

hauntsaninja · web-flow · commit 92118a9ad8a9 · 2022-08-28T14:31:22.000-07:00
There isn't really a good reason to have a default here, feels like it
mainly just increases the chance of a bug. Also remove the `del code`
from the last PR.
diff --git a/mypy/checker.py b/mypy/checker.py
@@ -5602,7 +5602,7 @@ def check_subtype(
         subtype: Type,
         supertype: Type,
         context: Context,
-        msg: ErrorMessage = message_registry.INCOMPATIBLE_TYPES,
+        msg: ErrorMessage,
         subtype_label: str | None = None,
         supertype_label: str | None = None,
         *,
@@ -5615,7 +5615,7 @@ def check_subtype(
         subtype: Type,
         supertype: Type,
         context: Context,
-        msg: str | ErrorMessage = message_registry.INCOMPATIBLE_TYPES,
+        msg: str | ErrorMessage,
         subtype_label: str | None = None,
         supertype_label: str | None = None,
         *,
@@ -5628,7 +5628,6 @@ def check_subtype(
 
         if isinstance(msg, str):
             msg = ErrorMessage(msg, code=code)
-            del code
 
         orig_subtype = subtype
         subtype = get_proper_type(subtype)
@@ -5720,7 +5719,9 @@ def check_possible_missing_await(
             aw_type = self.get_precise_awaitable_type(subtype, local_errors)
             if aw_type is None:
                 return
-            if not self.check_subtype(aw_type, supertype, context):
+            if not self.check_subtype(
+                aw_type, supertype, context, msg=message_registry.INCOMPATIBLE_TYPES
+            ):
                 return
         self.msg.possible_missing_await(context)
 
