code review

Author: hongweipeng

Lib/test/test_typing.py

@@ -2368,8 +2368,9 @@ def foo(a: c1_gth, b: c2_gth):
         self.assertEqual(c1, c2)
         self.assertEqual(c1, c1_gth)
         self.assertEqual(c1_gth, c2_gth)
-        self.assertEqual(Union[c1], Union[c1_gth])
-        self.assertEqual(Union[c1, c1_gth, c2, c2_gth], Union[c1])
+        self.assertEqual(List[c1], List[c1_gth])
+        self.assertNotEqual(List[c1], List[C])
+        self.assertNotEqual(List[c1_gth], List[C])
 
     def test_forward_equality_hash(self):
         c1 = typing.ForwardRef('int')

Lib/typing.py

@@ -230,12 +230,7 @@ def _remove_dups_flatten(parameters):
         else:
             params.append(p)
     # Weed out strict duplicates, preserving the first of each occurrence.
-    new_params = []
-    for p in params:
-        if p not in new_params:
-            new_params.append(p)
-    params = new_params
-    return tuple(params)
+    return tuple(dict.fromkeys(params))
 
 
 _cleanups = []