bpo-44731: Simplify the union type implementation (GH-27318) (GH-27334)

Remove direct support of typing types in the C code because they are already supported by defining methods __or__ and __ror__ in the Python code.

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

2 files changed, 19 insertions, 13 deletions

diff --git a/Lib/test/test_types.py b/Lib/test/test_types.py
index d149e6b..3f491ee 100644
--- a/Lib/test/test_types.py
+++ b/Lib/test/test_types.py
@@ -776,31 +776,32 @@ class UnionTests(unittest.TestCase):
         self.assertEqual((list[T] | list[S])[int, int], list[int])
 
     def test_union_parameter_substitution(self):
-        def eq(actual, expected):
+        def eq(actual, expected, typed=True):
             self.assertEqual(actual, expected)
-            self.assertIs(type(actual), type(expected))
+            if typed:
+                self.assertIs(type(actual), type(expected))
 
         T = typing.TypeVar('T')
         S = typing.TypeVar('S')
         NT = typing.NewType('NT', str)
         x = int | T | bytes
 
-        eq(x[str], int | str | bytes)
-        eq(x[list[int]], int | list[int] | bytes)
+        eq(x[str], int | str | bytes, typed=False)
+        eq(x[list[int]], int | list[int] | bytes, typed=False)
         eq(x[typing.List], int | typing.List | bytes)
         eq(x[typing.List[int]], int | typing.List[int] | bytes)
         eq(x[typing.Hashable], int | typing.Hashable | bytes)
         eq(x[collections.abc.Hashable],
-           int | collections.abc.Hashable | bytes)
+           int | collections.abc.Hashable | bytes, typed=False)
         eq(x[typing.Callable[[int], str]],
            int | typing.Callable[[int], str] | bytes)
         eq(x[collections.abc.Callable[[int], str]],
-           int | collections.abc.Callable[[int], str] | bytes)
+           int | collections.abc.Callable[[int], str] | bytes, typed=False)
         eq(x[typing.Tuple[int, str]], int | typing.Tuple[int, str] | bytes)
         eq(x[typing.Literal['none']], int | typing.Literal['none'] | bytes)
-        eq(x[str | list], int | str | list | bytes)
+        eq(x[str | list], int | str | list | bytes, typed=False)
         eq(x[typing.Union[str, list]], typing.Union[int, str, list, bytes])
-        eq(x[str | int], int | str | bytes)
+        eq(x[str | int], int | str | bytes, typed=False)
         eq(x[typing.Union[str, int]], typing.Union[int, str, bytes])
         eq(x[NT], int | NT | bytes)
         eq(x[S], int | S | bytes)
@@ -829,9 +830,9 @@ class UnionTests(unittest.TestCase):
         with self.assertRaisesRegex(ValueError, r"args must be not empty"):
             types.Union._from_args(())
 
-        alias = types.Union._from_args((int, str, T))
+        alias = types.Union._from_args((int, list[T], None))
 
-        self.assertEqual(alias.__args__, (int, str, T))
+        self.assertEqual(alias.__args__, (int, list[T], type(None)))
         self.assertEqual(alias.__parameters__, (T,))
 
         result = types.Union._from_args((int,))
@@ -894,7 +895,6 @@ class UnionTests(unittest.TestCase):
         assert repr(int | None) == "int | None"
         assert repr(int | type(None)) == "int | None"
         assert repr(int | typing.GenericAlias(list, int)) == "int | list[int]"
-        assert repr(int | typing.TypeVar('T')) == "int | ~T"
 
     def test_or_type_operator_with_genericalias(self):
         a = list[int]
@@ -939,9 +939,9 @@ class UnionTests(unittest.TestCase):
         TypeVar = BadMeta('TypeVar', (), {})
         _SpecialForm = BadMeta('_SpecialForm', (), {})
         # Crashes in Issue44483
-        with self.assertRaises(ZeroDivisionError):
+        with self.assertRaises((TypeError, ZeroDivisionError)):
             str | TypeVar()
-        with self.assertRaises(ZeroDivisionError):
+        with self.assertRaises((TypeError, ZeroDivisionError)):
             str | _SpecialForm()
 
     @cpython_only
diff --git a/Lib/typing.py b/Lib/typing.py
index e2fb7d1..0570b4e 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -375,6 +375,12 @@ class _SpecialForm(_Final, _root=True):
     def __call__(self, *args, **kwds):
         raise TypeError(f"Cannot instantiate {self!r}")
 
+    def __or__(self, other):
+        return Union[self, other]
+
+    def __ror__(self, other):
+        return Union[other, self]
+
     def __instancecheck__(self, obj):
         raise TypeError(f"{self} cannot be used with isinstance()")