Fix own typing

Author: sterliakov

mypy/checker.py

@@ -7692,10 +7692,12 @@ def get_isinstance_type(self, expr: Expression) -> list[TypeRange] | None:
         for typ in all_types:
             if isinstance(typ, FunctionLike) and typ.is_type_obj():
                 # If a type is generic, `isinstance` can only narrow its variables to Any.
-                erased_type = fill_typevars_with_any(typ.type_object())
+                any_parameterized = fill_typevars_with_any(typ.type_object())
                 # Tuples may have unattended type variables among their items
-                if isinstance(erased_type, TupleType):
-                    erased_type = erase_typevars(erased_type)
+                if isinstance(any_parameterized, TupleType):
+                    erased_type = erase_typevars(any_parameterized)
+                else:
+                    erased_type = any_parameterized
                 types.append(TypeRange(erased_type, is_upper_bound=False))
             elif isinstance(typ, TypeType):
                 # Type[A] means "any type that is a subtype of A" rather than "precisely type A"