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bpo-46539: Pass status of special typeforms to forward references (GH-30926)

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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.
(cherry picked from commit ced50051bb)

Co-authored-by: Gregory Beauregard <greg@greg.red>
This commit is contained in:
Miss Islington (bot) 2022-01-27 08:47:35 -08:00 • committed by GitHub
parent 8e98ccc4c3
commit 37577033ba
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3 changed files with 18 additions and 3 deletions
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6
Lib/typing.py
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@ -125,12 +125,12 @@
# legitimate imports of those modules.
def _type_convert(arg, module=None):
def _type_convert(arg, module=None, *, allow_special_forms=False):
"""For converting None to type(None), and strings to ForwardRef."""
if arg is None:
return type(None)
if isinstance(arg, str):
return ForwardRef(arg, module=module)
return ForwardRef(arg, module=module, is_class=allow_special_forms)
return arg
@ -152,7 +152,7 @@ def _type_check(arg, msg, is_argument=True, module=None, *, allow_special_forms=
if is_argument:
invalid_generic_forms += (Final,)
arg = _type_convert(arg, module=module)
arg = _type_convert(arg, module=module, allow_special_forms=allow_special_forms)
if (isinstance(arg, _GenericAlias) and
arg.__origin__ in invalid_generic_forms):
raise TypeError(f"{arg} is not valid as type argument")