gh-89828: Do not relay the __class__ attribute in GenericAlias (#93754)

list[int].__class__ returned type, and isinstance(list[int], type)
returned True. It caused numerous problems in code that checks
isinstance(x, type).

1 files changed, 2 insertions, 2 deletions

diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py
index 18ab690..69cab8c 100644
--- a/Lib/dataclasses.py
+++ b/Lib/dataclasses.py
@@ -230,7 +230,7 @@ class InitVar:
         self.type = type
 
     def __repr__(self):
-        if isinstance(self.type, type) and not isinstance(self.type, GenericAlias):
+        if isinstance(self.type, type):
             type_name = self.type.__name__
         else:
             # typing objects, e.g. List[int]
@@ -1248,7 +1248,7 @@ def _is_dataclass_instance(obj):
 def is_dataclass(obj):
     """Returns True if obj is a dataclass or an instance of a
     dataclass."""
-    cls = obj if isinstance(obj, type) and not isinstance(obj, GenericAlias) else type(obj)
+    cls = obj if isinstance(obj, type) else type(obj)
     return hasattr(cls, _FIELDS)