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iter("") --> Iterator[Never] #13902

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iter("") --> Iterator[Never] #13902

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9657872
`iter("")` --> `Iterator[Never]`
Avasam Apr 29, 2025
18d806f
Add tests
Avasam Apr 29, 2025
ad29a09
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Apr 29, 2025
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6 changes: 5 additions & 1 deletion stdlib/@tests/test_cases/builtins/check_iteration.py
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
from __future__ import annotations

from typing import Iterator
from typing_extensions import assert_type
from typing_extensions import Never, assert_type


class OldStyleIter:
Expand All @@ -14,3 +14,7 @@ def __getitem__(self, index: int) -> str:

assert_type(iter(OldStyleIter()), Iterator[str])
assert_type(next(iter(OldStyleIter())), str)

assert_type(iter(()), Iterator[Never])
assert_type(iter(list[Never]()), Iterator[Never])
assert_type(iter(""), Iterator[Never])
3 changes: 3 additions & 0 deletions stdlib/builtins.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,7 @@ from typing_extensions import ( # noqa: Y023
Concatenate,
Literal,
LiteralString,
Never,
ParamSpec,
Self,
TypeAlias,
Expand Down Expand Up @@ -1470,6 +1471,8 @@ def input(prompt: object = "", /) -> str: ...
class _GetItemIterable(Protocol[_T_co]):
def __getitem__(self, i: int, /) -> _T_co: ...

@overload
def iter(object: Literal[""], /) -> Iterator[Never]: ...
@overload
def iter(object: SupportsIter[_SupportsNextT_co], /) -> _SupportsNextT_co: ...
@overload
Expand Down