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gh-112903: Handle non-types in _BaseGenericAlias.__mro_entries__() (#115191)

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Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
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Carl Meyer 2024-02-09 12:19:09 -07:00 • committed by GitHub
parent 5a173efa69
commit a225520af9
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3 changed files with 92 additions and 1 deletions
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22
Lib/typing.py
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@ -1135,9 +1135,29 @@ class _BaseGenericAlias(_Final, _root=True):
res = []
if self.__origin__ not in bases:
res.append(self.__origin__)
# Check if any base that occurs after us in `bases` is either itself a
# subclass of Generic, or something which will add a subclass of Generic
# to `__bases__` via its `__mro_entries__`. If not, add Generic
# ourselves. The goal is to ensure that Generic (or a subclass) will
# appear exactly once in the final bases tuple. If we let it appear
# multiple times, we risk "can't form a consistent MRO" errors.
i = bases.index(self)
for b in bases[i+1:]:
if isinstance(b, _BaseGenericAlias) or issubclass(b, Generic):
if isinstance(b, _BaseGenericAlias):
break
if not isinstance(b, type):
meth = getattr(b, "__mro_entries__", None)
new_bases = meth(bases) if meth else None
if (
isinstance(new_bases, tuple) and
any(
isinstance(b2, type) and issubclass(b2, Generic)
for b2 in new_bases
)
):
break
elif issubclass(b, Generic):
break
else:
res.append(Generic)