copy: use _copy_atomic_types instead; add tests

Author: vstinner

Lib/copy.py

@@ -101,11 +101,11 @@ def copy(x):
 
 
 _copy_atomic_types = frozenset({types.NoneType, int, float, bool, complex, str, tuple,
-          bytes, frozenset, type, range, slice, property,
+          bytes, frozenset, frozendict, type, range, slice, property,
           types.BuiltinFunctionType, types.EllipsisType,
           types.NotImplementedType, types.FunctionType, types.CodeType,
           weakref.ref, super})
-_copy_builtin_containers = frozenset({list, dict, frozendict, set, bytearray})
+_copy_builtin_containers = frozenset({list, dict, set, bytearray})
 
 def deepcopy(x, memo=None):
     """Deep copy operation on arbitrary Python objects.

Lib/test/test_copy.py

@@ -161,6 +161,12 @@ def test_copy_frozenset(self):
         x = frozenset()
         self.assertIs(copy.copy(x), x)
 
+    def test_copy_frozendict(self):
+        x = frozendict(x=1, y=2)
+        self.assertIs(copy.copy(x), x)
+        x = frozendict()
+        self.assertIs(copy.copy(x), x)
+
     def test_copy_bytearray(self):
         x = bytearray(b'abc')
         y = copy.copy(x)