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[3.13] gh-118772: Allow TypeVars without a default to follow those with a default when constructing aliases (GH-118774) (#118776)

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(cherry picked from commit aac6b019fe)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
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Miss Islington (bot) 2024-05-08 21:31:41 +02:00 • committed by GitHub
parent 02d49af219
commit c6680cdc5a
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3 changed files with 34 additions and 10 deletions
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25
Lib/typing.py
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@ -257,7 +257,7 @@ def _type_repr(obj):
return repr(obj)
def _collect_parameters(args):
def _collect_parameters(args, *, enforce_default_ordering: bool = True):
"""Collect all type variables and parameter specifications in args
in order of first appearance (lexicographic order).
@ -286,15 +286,16 @@ def _collect_parameters(args):
parameters.append(collected)
elif hasattr(t, '__typing_subst__'):
if t not in parameters:
if type_var_tuple_encountered and t.has_default():
raise TypeError('Type parameter with a default'
' follows TypeVarTuple')
if enforce_default_ordering:
if type_var_tuple_encountered and t.has_default():
raise TypeError('Type parameter with a default'
' follows TypeVarTuple')
if t.has_default():
default_encountered = True
elif default_encountered:
raise TypeError(f'Type parameter {t!r} without a default'
' follows type parameter with a default')
if t.has_default():
default_encountered = True
elif default_encountered:
raise TypeError(f'Type parameter {t!r} without a default'
' follows type parameter with a default')
parameters.append(t)
else:
@ -1416,7 +1417,11 @@ class _GenericAlias(_BaseGenericAlias, _root=True):
args = (args,)
self.__args__ = tuple(... if a is _TypingEllipsis else
a for a in args)
self.__parameters__ = _collect_parameters(args)
enforce_default_ordering = origin in (Generic, Protocol)
self.__parameters__ = _collect_parameters(
args,
enforce_default_ordering=enforce_default_ordering,
)
if not name:
self.__module__ = origin.__module__