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Bug report
Bug description:
In typing._eval_type, generic aliases are reconstructed this way:
Lines 488 to 489 in e53d105
As GenericAlias is subclassable, we can loose the actual subclass in some cases:
from typing import get_type_hints
from collections.abc import Callable
C = Callable[[str, 'int'], int]
C.__class__
#> <class 'collections.abc._CallableGenericAlias'>
C.__class__.__bases__
#> (<class 'types.GenericAlias'>,)
class A:
c: C
hints = get_type_hints(A)
hints['c'].__class__
#> <class 'types.GenericAlias'>I couldn't find a way to get actual bugs from it, but the repr is different:
hints['c']
#> collections.abc.Callable[str, int, int]
C
#> collections.abc.Callable[[str, 'int'], int]The issue is also relevant for typing._strip_annotations().
Proposed fix
diff --git a/Lib/typing.py b/Lib/typing.py
index 4b3c63b25ae..25e0576839f 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -486,7 +486,9 @@ def _eval_type(t, globalns, localns, type_params=_sentinel, *, recursive_guard=f
if ev_args == t.__args__:
return t
if isinstance(t, GenericAlias):
- return GenericAlias(t.__origin__, ev_args)
+ if _should_unflatten_callable_args(t, ev_args):
+ return t.__class__(t.__origin__, (ev_args[:-1], ev_args[-1]))
+ return t.__class__(t.__origin__, ev_args)
if isinstance(t, Union):
return functools.reduce(operator.or_, ev_args)
else:CPython versions tested on:
3.13
Operating systems tested on:
Linux
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Python modules in the Lib dirPython modules in the Lib dirAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error