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.
(cherry picked from commit ced50051bb752a7c1e616f4b0c001f37f0354f32)
Co-authored-by: Gregory Beauregard <greg@greg.red>
diff --git a/Lib/typing.py b/Lib/typing.py
index aca3f7a..0ea389d 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -134,12 +134,12 @@
# 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
@@ -161,7 +161,7 @@ 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")