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bpo-46539: Pass status of special typeforms to forward references (GH-30926)
Previously this didn't matter because there weren't any valid code paths that could trigger a type check with a special form, but after the bug fix for `Annotated` wrapping special forms it's now possible to annotate something like `Annotated['ClassVar[int]', (3, 4)]`. This change would also be needed for proposed future changes, such as allowing `ClassVar` and `Final` to nest each other in dataclasses.
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@ -2870,6 +2870,20 @@ def foo(a: 'Callable[..., T]'):
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self.assertEqual(get_type_hints(foo, globals(), locals()),
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{'a': Callable[..., T]})
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def test_special_forms_forward(self):
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class C:
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a: Annotated['ClassVar[int]', (3, 5)] = 4
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b: Annotated['Final[int]', "const"] = 4
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class CF:
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b: List['Final[int]'] = 4
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self.assertEqual(get_type_hints(C, globals())['a'], ClassVar[int])
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self.assertEqual(get_type_hints(C, globals())['b'], Final[int])
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with self.assertRaises(TypeError):
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get_type_hints(CF, globals()),
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def test_syntax_error(self):
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with self.assertRaises(SyntaxError):
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@ -142,12 +142,12 @@ def _idfunc(_, x):
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# legitimate imports of those modules.
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def _type_convert(arg, module=None):
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def _type_convert(arg, module=None, *, allow_special_forms=False):
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"""For converting None to type(None), and strings to ForwardRef."""
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if arg is None:
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return type(None)
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if isinstance(arg, str):
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return ForwardRef(arg, module=module)
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return ForwardRef(arg, module=module, is_class=allow_special_forms)
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return arg
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@ -169,7 +169,7 @@ def _type_check(arg, msg, is_argument=True, module=None, *, allow_special_forms=
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if is_argument:
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invalid_generic_forms += (Final,)
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arg = _type_convert(arg, module=module)
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arg = _type_convert(arg, module=module, allow_special_forms=allow_special_forms)
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if (isinstance(arg, _GenericAlias) and
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arg.__origin__ in invalid_generic_forms):
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raise TypeError(f"{arg} is not valid as type argument")
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@ -0,0 +1 @@
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In :func:`typing.get_type_hints`, support evaluating stringified ``ClassVar`` and ``Final`` annotations inside ``Annotated``. Patch by Gregory Beauregard.
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