Support for `@type_check_only`?

[jungerm2]

Is typing.type_check_only planned to be added soon? It's supported in mypy as of 1.18 and was introduced way back in this PEP. Thoughts?

[AlexWaygood]

The decorator itself is deliberately only available at type-check time, not at runtime. Could you clarify what support you'd like typing_extensions to provide here?

[jungerm2]

Well, in a pyi file under python 3.14 I can simply from typing import type_check_only and add it to stubs that will not have a runtime implementation, but I'd like to also support older python versions, eg do from typing_extensions import type_check_only in say python 3.9. But this trips up stubtest/mypy:

error: not checking stubs due to mypy build errors:
mystubs.pyi:30: error: Module "typing_extensions" does not explicitly export attribute "type_check_only"  [attr-defined]

[jungerm2]

Mypy seems to think typing extensions has this, does it not?

https://github.com/python/mypy/blob/131f9d92da58294bb2f273425e8778bd7d5b861f/mypy/types.py#L153-L155

[Daraan]

Does is make any difference to you from which module you import it? Sticking to from typing import type_check_only for 3.7+ should always work.

At runtime type_check_only exits in neither module. For type checking - following the idea that both modules should be equivalent - both modules should have it, but this is something on the type-ckeckers end.
I am surprised that there is different handling between versions. Possibly this is better asked at mypy? Does the problem appear with other type checkers as well?