[Pitch] Inferring @Sendable for methods and key path literals

[hborla (Holly Borla)]

@KeithBauerANZ

Also note there's currently a major safety hole with KeyPaths and global actors: KeyPath discards global actor · Issue #66830 · apple/swift · GitHub . I'm guessing this pitch as written wouldn't fix that, but perhaps it should be extended to do so?

Thank you for pointing this out! I agree. I think a key-path literal that contains an isolated property in its path can only be formed in that isolation domain, and it should not be Sendable. This also means that it is an error to form a key path that contains two path components with different global actors applied.