fix: avoid unnecessary union members when proposed type is current ty…

…pe (without crashing pattern matching)

mypy/checker.py

@@ -7581,7 +7581,10 @@ def _get_instance_path_from_current_to_proposed(
                     break
 
             # Transfer the current type's type variable argument or type variable tuple arguments:
-            if (pos2 is not None) and isinstance(proposed_args[pos2], (AnyType, UnpackType)):
+            if (
+                (pos2 is not None) and
+                isinstance(get_proper_type(proposed_args[pos2]), (AnyType, UnpackType))
+            ):
                 if current.type.has_type_var_tuple_type:
                     assert (prefix := current.type.type_var_tuple_prefix) is not None
                     assert (suffix := current.type.type_var_tuple_suffix) is not None