[Pitch] Introduce existential `any`

[xwu (Xiaodi Wu)]

@DevAndArtist

I'm against the meaning of (any P).Type as proposed. This goes against:

@Joe_Groff

Another thing that making existential types explicit would hopefully enable is clearer syntax for existential metatypes, since instead of the .Type / .Protocol weirdness we could say that any (P.Type) is the type of all types conforming to P , and (any P).Type is the type of the existential itself.

I’m of the understanding that the pitched meaning for (any P).Type is exactly what @Joe_Groff describes in the text you quote (“the type of the existential itself”). Indeed I cannot contemplate that spelling meaning anything else.

So long as that is agreed, everything else about changing metatype syntax can be a separate proposal—I would be strongly opposed to tackling any of that in one go as it’s an extensive topic of its own, as you well know.