RE: Long term RFC: Associated traits / Trait generics / ConstraintKinds

language design
1

The topic Long term RFC: Associated traits / Trait generics / ConstraintKinds was posted in 2018 and now closed, and there is a corresponding issue about it too, just wanna re-bring-it-up again.

But to boil it down, its a proposal to treat traits as first-class types of kind Type -> Constraint so that you can stick them into where you would usually stick types, e.g.

trait Foo {
  trait Bar;
  fn baz<T: Self::Bar>(t: T);
}
fn foo_bar_baz<trait M, T: M, F: Foo<Bar=M>>(t: T) { F::baz(t) }

Outside of this trait-alias RFC I haven't seen the idea of "ConstraintKinds for Rust" being mentioned in any "official" Rust sources, so just wanted bring it up again.

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