fix: remove redundant get_proper_type() call in checker.py

The make_simplified_union return type is already specific enough
for isinstance check, no need to unwrap further.

Bahtya

Author: Bahtya

mypy/checker.py

@@ -8042,11 +8042,7 @@ def get_type_range_of_type(self, typ: Type) -> TypeRange | None:
             # type precision (e.g. from a widened _ClassInfo alias). Return None
             # to avoid narrowing to a useless type.
             item = make_simplified_union([t.item for t in valid_ranges])
-            proper_item = get_proper_type(item)
-            if (
-                isinstance(proper_item, Instance)
-                and proper_item.type.fullname == "builtins.object"
-            ):
+            if isinstance(item, Instance) and item.type.fullname == "builtins.object":
                 return None
             return TypeRange(item, is_upper_bound=True)
         if isinstance(typ, FunctionLike) and typ.is_type_obj():