I think it would be helpful to make it clearer what's experimental and what's not. Is the `in` keyword experimental? How about `scope`? There's just a minor note in the docs (https://dlang.org/spec/attribute.html#scope) saying "The -preview=dip1000 switch must also be enabled.". That's really not making it clear if that's an experimental feature, it sounds to me that using the preview flag just does additional checks, but that implies `scope` is NOT experimental?! Which is it?