Interesting. I’ve never felt a need for this, and as the other reply here said it was really unpopular in other languages.
I would have guessed you would have said something about how it’s annoying to type callable arguments, and how Protocol
exists but doesn’t seem that widely known.
My work uses python and it hasn’t been bad for new code that has tests and types. Old code we inherited from contractors and “yolo startup” types is less good, but we’ve generally be improving that as we touch it.