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Remove list.__add__ overloads. #14282

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Remove list.__add__ overloads. #14282

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4 changes: 0 additions & 4 deletions stdlib/builtins.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -1115,10 +1115,6 @@ class list(MutableSequence[_T]):
@overload
def __setitem__(self, key: slice, value: Iterable[_T], /) -> None: ...
def __delitem__(self, key: SupportsIndex | slice, /) -> None: ...
# Overloading looks unnecessary, but is needed to work around complex mypy problems
@overload
def __add__(self, value: list[_T], /) -> list[_T]: ...
@overload
def __add__(self, value: list[_S], /) -> list[_S | _T]: ...
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maybe something like this could work?

Suggested change
def __add__(self, value: list[_S], /) -> list[_S | _T]: ...
def __add__(self: list[_S], value: list[_S], /) -> list[_S]: ...

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@randolf-scholz randolf-scholz Jun 26, 2025 •
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With this, wouldn't we get list[str] + list[int] = list[object] when checking with mypy, rather then list[str | int]?

I'd prefer python/mypy#19304 be fixed; then I think we would see most mypy-primer issues here go away. If you have seen this before and know and easier way to reproduce, please comment it.

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With this, wouldn't we get list[str] + list[int] = list[object] when checking with mypy, rather then list[str | int]?

With this, wouldn't we get list[str] + list[int] = list[object] when checking with mypy, rather then list[str | int]?

I'd prefer python/mypy#19304 be fixed; then I think we would see most mypy-primer issues here go away. If you have seen this before and know and easier way to reproduce, please comment it.

That's what I indeed expect here, given mypy's join vs union behavior. But if that's how they decide to behave, then that's up to them, afaik. At least it won't be rejected this way (is the hope)

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Well, my goal with this PR was to reduce type-checker divergence, not to cement it.

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fair enough

def __iadd__(self, value: Iterable[_T], /) -> Self: ... # type: ignore[misc]
def __mul__(self, value: SupportsIndex, /) -> list[_T]: ...
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