Spec: Version and platform checking underspecified

Currently, the "Version and platform checking" section of the typing spec is very barebones. It basically says:

Type checkers are expected to understand simple version and platform checks. [...] Don’t expect a checker to understand obfuscations like "".join(reversed(sys.platform)) == "xunil".

Of course, there's a world of difference between these two forms.

The type stubs document goes into a bit more of detail, and reflects the currently implemented functionality quite well, as far as I know. It would be a good starting point.

Maybe it would also make sense to support platform checks using startswith(), as that is officially recommended in the Python docs, and is required to properly support some Unix variants, like FreeBSD, that include the version number in the platform string. See also python/typeshed#11876.

まず、typing 仕様の「Version and platform checking」セクションと、現在の動作を反映しているリンク先の型スタブ文書を比較します。報告でリンクされている Python ドキュメントと typeshed issue を確認し、サポートするチェックを定義したうえで、startswith() を仕様に含めるべきか判断します。仕様が意図するバージョンおよびプラットフォームチェックの動作を正確に記述していれば完了です。