gh-93910: Fix enum performance regression

Lib/enum.py

@@ -309,16 +309,17 @@ def __set_name__(self, enum_class, member_name):
         if descriptor and not need_override:
             # previous enum.property found, no further action needed
             pass
-        else:
+        elif descriptor and need_override:
             redirect = property()
             redirect.__set_name__(enum_class, member_name)
-            if descriptor and need_override:
-                # previous enum.property found, but some other inherited attribute
-                # is in the way; copy fget, fset, fdel to this one
-                redirect.fget = descriptor.fget
-                redirect.fset = descriptor.fset
-                redirect.fdel = descriptor.fdel
+            # previous enum.property found, but some other inherited attribute
+            # is in the way; copy fget, fset, fdel to this one
+            redirect.fget = descriptor.fget
+            redirect.fset = descriptor.fset
+            redirect.fdel = descriptor.fdel
             setattr(enum_class, member_name, redirect)
+        else:
+            setattr(enum_class, member_name, enum_member)
         # now add to _member_map_ (even aliases)
         enum_class._member_map_[member_name] = enum_member
         try:
@@ -647,7 +648,7 @@ def __new__(metacls, cls, bases, classdict, *, boundary=None, _simple=False, **k
                         'member order does not match _order_:\n  %r\n  %r'
                         % (enum_class._member_names_, _order_)
                         )
-        #
+
         return enum_class
 
     def __bool__(cls):

Lib/test/test_enum.py

@@ -2646,6 +2646,7 @@ class Private(Enum):
         self.assertEqual(Private._Private__corporal, 'Radar')
         self.assertEqual(Private._Private__major_, 'Hoolihan')
 
+    @unittest.skip("Accessing all values retained for performance reasons, see GH-93910")
     def test_exception_for_member_from_member_access(self):
         with self.assertRaisesRegex(AttributeError, "<enum .Di.> member has no attribute .NO."):
             class Di(Enum):

Misc/NEWS.d/next/Library/2022-07-06-14-45-12.gh-issue-93910.iZcp67.rst

@@ -0,0 +1,3 @@
+The ability to access the other values of an enum on an enum (e.g.
+``Color.RED.BLUE``) has been restored in order to fix a performance
+regression.