bpo-43224: Implement substitution of unpacked TypeVarTuple in C by serhiy-storchaka · Pull Request #31828 · python/cpython
There need to be more tests for cases where we substitute an unpacked tuple into the TypeVarTuple. I found a crash on your branch:
% ./python.exe
Python 3.11.0a6+ (heads/serhiy-storchaka-typevartuple-subst-c:a35af462a3, Mar 11 2022, 19:02:45) [Clang 13.0.0 (clang-1300.0.29.3)] on darwin
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>>> from typing import Unpack, TypeVarTuple
>>> Ts = TypeVarTuple("Ts")
>>> t = tuple[Ts]
>>> t[int, Unpack[tuple[int, str]], str]
Assertion failed: (iparam != varparam), function _Py_subs_parameters, file genericaliasobject.c, line 382.
zsh: abort ./python.exe