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bpo-46491: Allow Annotated on outside of Final/ClassVar (GH-30864)

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We treat Annotated type arg as class-level annotation. This exempts it from checks against Final and ClassVar in order to allow using them in any nesting order.

Automerge-Triggered-By: GH:gvanrossum
(cherry picked from commit e1abffca45)

Co-authored-by: Gregory Beauregard <greg@greg.red>
This commit is contained in:
Miss Islington (bot) 2022-01-25 06:39:12 -08:00 • committed by GitHub
parent 3178efbf06
commit b0b8388a1c
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3 changed files with 13 additions and 4 deletions
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8
Lib/typing.py
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@ -134,7 +134,7 @@ def _type_convert(arg, module=None):
return arg
def _type_check(arg, msg, is_argument=True, module=None, *, is_class=False):
def _type_check(arg, msg, is_argument=True, module=None, *, allow_special_forms=False):
"""Check that the argument is a type, and return it (internal helper).
As a special case, accept None and return type(None) instead. Also wrap strings
@ -147,7 +147,7 @@ def _type_check(arg, msg, is_argument=True, module=None, *, is_class=False):
We append the repr() of the actual value (truncated to 100 chars).
"""
invalid_generic_forms = (Generic, Protocol)
if not is_class:
if not allow_special_forms:
invalid_generic_forms += (ClassVar,)
if is_argument:
invalid_generic_forms += (Final,)
@ -554,7 +554,7 @@ class ForwardRef(_Final, _root=True):
eval(self.__forward_code__, globalns, localns),
"Forward references must evaluate to types.",
is_argument=self.__forward_is_argument__,
is_class=self.__forward_is_class__,
allow_special_forms=self.__forward_is_class__,
)
self.__forward_value__ = _eval_type(
type_, globalns, localns, recursive_guard | {self.__forward_arg__}
@ -1336,7 +1336,7 @@ class Annotated:
"with at least two arguments (a type and an "
"annotation).")
msg = "Annotated[t, ...]: t must be a type."
origin = _type_check(params[0], msg)
origin = _type_check(params[0], msg, allow_special_forms=True)
metadata = tuple(params[1:])
return _AnnotatedAlias(origin, metadata)