bpo-40396: Support GenericAlias in the typing functions. (GH-19718)

Lib/test/test_typing.py

@@ -22,7 +22,7 @@ from typing import NewType
 from typing import NamedTuple, TypedDict
 from typing import IO, TextIO, BinaryIO
 from typing import Pattern, Match
-from typing import Annotated
+from typing import Annotated, ForwardRef
 import abc
 import typing
 import weakref
@@ -1756,11 +1756,17 @@ class GenericTests(BaseTestCase):
 
     def test_generic_forward_ref(self):
         def foobar(x: List[List['CC']]): ...
+        def foobar2(x: list[list[ForwardRef('CC')]]): ...
         class CC: ...
         self.assertEqual(
             get_type_hints(foobar, globals(), locals()),
             {'x': List[List[CC]]}
         )
+        self.assertEqual(
+            get_type_hints(foobar2, globals(), locals()),
+            {'x': list[list[CC]]}
+        )
+
         T = TypeVar('T')
         AT = Tuple[T, ...]
         def barfoo(x: AT): ...
@@ -2446,6 +2452,12 @@ class ForwardRefTests(BaseTestCase):
         self.assertEqual(get_type_hints(foo, globals(), locals()),
                          {'a': Tuple[T]})
 
+        def foo(a: tuple[ForwardRef('T')]):
+            pass
+
+        self.assertEqual(get_type_hints(foo, globals(), locals()),
+                         {'a': tuple[T]})
+
     def test_forward_recursion_actually(self):
         def namespace1():
             a = typing.ForwardRef('A')
@@ -2909,6 +2921,18 @@ class GetTypeHintTests(BaseTestCase):
             get_type_hints(foobar, globals(), locals(), include_extras=True),
             {'x': List[Annotated[int, (1, 10)]]}
         )
+
+        def foobar(x: list[ForwardRef('X')]): ...
+        X = Annotated[int, (1, 10)]
+        self.assertEqual(
+            get_type_hints(foobar, globals(), locals()),
+            {'x': list[int]}
+        )
+        self.assertEqual(
+            get_type_hints(foobar, globals(), locals(), include_extras=True),
+            {'x': list[Annotated[int, (1, 10)]]}
+        )
+
         BA = Tuple[Annotated[T, (1, 0)], ...]
         def barfoo(x: BA): ...
         self.assertEqual(get_type_hints(barfoo, globals(), locals())['x'], Tuple[T, ...])
@@ -2916,12 +2940,22 @@ class GetTypeHintTests(BaseTestCase):
             get_type_hints(barfoo, globals(), locals(), include_extras=True)['x'],
             BA
         )
+
+        BA = tuple[Annotated[T, (1, 0)], ...]
+        def barfoo(x: BA): ...
+        self.assertEqual(get_type_hints(barfoo, globals(), locals())['x'], tuple[T, ...])
+        self.assertIs(
+            get_type_hints(barfoo, globals(), locals(), include_extras=True)['x'],
+            BA
+        )
+
         def barfoo2(x: typing.Callable[..., Annotated[List[T], "const"]],
                     y: typing.Union[int, Annotated[T, "mutable"]]): ...
         self.assertEqual(
             get_type_hints(barfoo2, globals(), locals()),
             {'x': typing.Callable[..., List[T]], 'y': typing.Union[int, T]}
         )
+
         BA2 = typing.Callable[..., List[T]]
         def barfoo3(x: BA2): ...
         self.assertIs(
@@ -2972,6 +3006,9 @@ class GetUtilitiesTestCase(TestCase):
         self.assertIs(get_origin(Generic[T]), Generic)
         self.assertIs(get_origin(List[Tuple[T, T]][int]), list)
         self.assertIs(get_origin(Annotated[T, 'thing']), Annotated)
+        self.assertIs(get_origin(List), list)
+        self.assertIs(get_origin(list[int]), list)
+        self.assertIs(get_origin(list), None)
 
     def test_get_args(self):
         T = TypeVar('T')
@@ -2993,6 +3030,9 @@ class GetUtilitiesTestCase(TestCase):
         self.assertEqual(get_args(Tuple[int, ...]), (int, ...))
         self.assertEqual(get_args(Tuple[()]), ((),))
         self.assertEqual(get_args(Annotated[T, 'one', 2, ['three']]), (T, 'one', 2, ['three']))
+        self.assertEqual(get_args(List), (typing.T,))
+        self.assertEqual(get_args(list[int]), (int,))
+        self.assertEqual(get_args(list), ())
 
 
 class CollectionsAbcTests(BaseTestCase):

Lib/typing.py

@@ -191,7 +191,7 @@ def _subs_tvars(tp, tvars, subs):
     """Substitute type variables 'tvars' with substitutions 'subs'.
     These two must have the same length.
     """
-    if not isinstance(tp, _GenericAlias):
+    if not isinstance(tp, (_GenericAlias, GenericAlias)):
         return tp
     new_args = list(tp.__args__)
     for a, arg in enumerate(tp.__args__):
@@ -203,7 +203,10 @@ def _subs_tvars(tp, tvars, subs):
             new_args[a] = _subs_tvars(arg, tvars, subs)
     if tp.__origin__ is Union:
         return Union[tuple(new_args)]
-    return tp.copy_with(tuple(new_args))
+    if isinstance(tp, GenericAlias):
+        return GenericAlias(tp.__origin__, tuple(new_args))
+    else:
+        return tp.copy_with(tuple(new_args))
 
 
 def _check_generic(cls, parameters):
@@ -278,6 +281,11 @@ def _eval_type(t, globalns, localns):
         res = t.copy_with(ev_args)
         res._special = t._special
         return res
+    if isinstance(t, GenericAlias):
+        ev_args = tuple(_eval_type(a, globalns, localns) for a in t.__args__)
+        if ev_args == t.__args__:
+            return t
+        return GenericAlias(t.__origin__, ev_args)
     return t
 
 
@@ -1368,6 +1376,11 @@ def _strip_annotations(t):
         res = t.copy_with(stripped_args)
         res._special = t._special
         return res
+    if isinstance(t, GenericAlias):
+        stripped_args = tuple(_strip_annotations(a) for a in t.__args__)
+        if stripped_args == t.__args__:
+            return t
+        return GenericAlias(t.__origin__, stripped_args)
     return t
 
 
@@ -1387,7 +1400,7 @@ def get_origin(tp):
     """
     if isinstance(tp, _AnnotatedAlias):
         return Annotated
-    if isinstance(tp, _GenericAlias):
+    if isinstance(tp, (_GenericAlias, GenericAlias)):
         return tp.__origin__
     if tp is Generic:
         return Generic
@@ -1407,9 +1420,9 @@ def get_args(tp):
     """
     if isinstance(tp, _AnnotatedAlias):
         return (tp.__origin__,) + tp.__metadata__
-    if isinstance(tp, _GenericAlias):
+    if isinstance(tp, (_GenericAlias, GenericAlias)):
         res = tp.__args__
-        if get_origin(tp) is collections.abc.Callable and res[0] is not Ellipsis:
+        if tp.__origin__ is collections.abc.Callable and res[0] is not Ellipsis:
             res = (list(res[:-1]), res[-1])
         return res
     return ()

Misc/NEWS.d/next/Library/2020-04-26-19-07-40.bpo-40396.Fn-is1.rst

@@ -0,0 +1,3 @@
+Functions :func:`typing.get_origin`, :func:`typing.get_args` and
+:func:`typing.get_type_hints` support now generic aliases like
+``list[int]``.