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Incorrect argument substitution on Unpack[tuple[...]] #118168

@JelleZijlstra

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@JelleZijlstra

Bug report

Bug description:

In the code below, all of the prints should be equivalent:

from typing import Generic, Tuple, TypeVarTuple, Unpack Ts = TypeVarTuple("Ts") class Old(Generic[*Ts]): ... class New[*Ts]: ... PartOld = Old[int, *Ts] print(PartOld[str]) print(PartOld[*tuple[str]]) print(PartOld[*Tuple[str]]) print(PartOld[Unpack[tuple[str]]]) # Old[int, typing.Unpack[tuple[str]]] print(PartOld[Unpack[Tuple[str]]]) PartNew = New[int, *Ts] print(PartNew[str]) print(PartNew[*tuple[str]]) print(PartNew[*Tuple[str]]) print(PartNew[Unpack[tuple[str]]]) # New[int, typing.Unpack[tuple[str]]] print(PartNew[Unpack[Tuple[str]]])

However, the Unpack[tuple[]] variants print something different. This is because the implementation of Unpack doesn't deal correctly with builtin aliases. I'll send a PR.

CPython versions tested on:

3.12, CPython main branch

Operating systems tested on:

macOS

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3.12only security fixes3.13bugs and security fixestopic-typingtype-bugAn unexpected behavior, bug, or error

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