New submission from Serhiy Storchaka <storchaka+cpyt...@gmail.com>:
There are two empty typing.Tuple. They have the same repr but are not equal. >>> from typing import * >>> t1 = Tuple[()] >>> t2 = t1.copy_with(()) >>> t1 typing.Tuple[()] >>> t2 typing.Tuple[()] >>> t1 == t2 False >>> t1.__args__ ((),) >>> t2.__args__ () The only differences is that one has empty __args__, while other has __args__ containing an empty tuple. There is a code purposed to make __args__ containing an empty tuple in this case. What is the purpose? It is not pure theoretical question. This affects unpacked TypeVarTuple substitution. With natural implementation Tuple[Unpack[Ts]][()] is not equal to Tuple[()] and I still have not figured which and where code should be added to handle this special case. It would be easier if such special case did not exist. Built-in tuple does not have a special case: >>> tuple[()].__args__ () ---------- components: Library (Lib) messages: 414892 nosy: gvanrossum, kj, serhiy.storchaka priority: normal severity: normal status: open title: Empty typing.Tuple _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue46981> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
