[Pitch] Light-weight same-type constraint syntax

[regexident (Vincent Esche)]

A big +1 on anything that @Karl and @DevAndArtist already wrote int this discussion, but most importantly (emphasis mine):

@Karl

[…] the difference between generic parameters and associated types is a fundamental thing. As nice as this syntax is, it makes me uncomfortable to mix the concepts this way.

@DevAndArtist

I'm strongly against misusing the generic parameterization on protocols declaration just for associated types. This simply kills off any potential future for generic protocols (an expert feature) and to me this feels like an "shut up already" move (please don't take that offensively).

@DevAndArtist

The order of associated types never mattered, so why would we want to make that a thing, especially in combination with some sugar code?!

@DevAndArtist

So far, from my personal point of view, the proposed sugar in the current state of the pitch would not improve anything except unlocking the ability to write the constraint, but the use-site will be extremely limited as not only does it seem to increase the cognitive load on me but it also will prevent future extension of general language features.

That said, in my opinion, the ability to write a few less characters and not introducing any new spelling has too many tradeoffs in the long term, which is simply not worth it.