Upgrade `typing.type_check_only` to be applicable to variables(and maybe import statements)

from typing import _KT, _promote

Success: no issues found in 1 source file

Sure it has an underscore, but seems super sus that there is no mechanism to specify that a variable in a stub is just a type time helper and has no bearing on reality whatsoever.

You can specify explicitly that an import is accessible by importing it with an alias, although this in itself looks extremely hacky/workaroundy.

Also if it were possible to mark something in a stub as 'type time' only, then you could remove all the underscores and make a bunch of types look a lot nicer.

Very much related to https://github.com/python/mypy/issues/11503, where a module import in a stub can be completely fictitious, and there is currently no way to specify it one way or the other.

首先检查针对变量和导入语句所要求的 typing.type_check_only 行为，然后阅读关于存根中虚构模块导入的相关 issue #11503。只有在所需的、仅在类型检查时生效的语义以及导入行为都得到明确说明并达成一致后，才算完成。