bpo-42345: Fix hash implementation of typing.Literal (GH-23383)

Fix hash implementation of `typing.Literal`. Update docs regarding `typing.Litaral` caching. Base implementation was done in PR GH-23294. (cherry picked from commit 1b54077) Co-authored-by: Yurii Karabas <1998uriyyo@gmail.com>

Author: miss-islington

Doc/library/typing.rst

@@ -1687,9 +1687,9 @@ Introspection helpers
  For a typing object of the form ``X[Y, Z, ...]`` these functions return
  ``X`` and ``(Y, Z, ...)``. If ``X`` is a generic alias for a builtin or
  :mod:`collections` class, it gets normalized to the original class.
- If ``X`` is a :class:`Union` contained in another generic type,
- the order of ``(Y, Z, ...)`` may be different from the order of
- the original arguments ``[Y, Z, ...]`` due to type caching.
+ If ``X`` is a :class:`Union` or :class:`Literal` contained in another
+ generic type, the order of ``(Y, Z, ...)`` may be different from the order
+ of the original arguments ``[Y, Z, ...]`` due to type caching.
  For unsupported objects return ``None`` and ``()`` correspondingly.
  Examples::
 

Lib/test/test_typing.py

@@ -573,6 +573,11 @@ def test_equal(self):
  self.assertEqual(Literal[1, 2], Literal[2, 1])
  self.assertEqual(Literal[1, 2, 3], Literal[1, 2, 3, 3])
 
+ def test_hash(self):
+ self.assertEqual(hash(Literal[1]), hash(Literal[1]))
+ self.assertEqual(hash(Literal[1, 2]), hash(Literal[2, 1]))
+ self.assertEqual(hash(Literal[1, 2, 3]), hash(Literal[1, 2, 3, 3]))
+
  def test_args(self):
  self.assertEqual(Literal[1, 2, 3].__args__, (1, 2, 3))
  self.assertEqual(Literal[1, 2, 3, 3].__args__, (1, 2, 3))

Lib/typing.py

@@ -932,7 +932,7 @@ def __eq__(self, other):
  return set(_value_and_type_iter(self.__args__)) == set(_value_and_type_iter(other.__args__))
 
  def __hash__(self):
- return hash(tuple(_value_and_type_iter(self.__args__)))
+ return hash(frozenset(_value_and_type_iter(self.__args__)))
 
 
 class Generic: