src/test/ui/generic-associated-types/issue-91762.rs

   1 // check-fail
   2
   3 // FIXME(generic_associated_types): We almost certaintly want this to pass, but
   4 // it's particularly difficult currently, because we need a way of specifying
   5 // that `<Self::Base as Functor>::With<T> = Self` without using that when we have
   6 // a `U`. See `https://github.com/rust-lang/rust/pull/92728` for a (hacky)
   7 // solution. This might be better to just wait for Chalk.
   8
   9 #![feature(generic_associated_types)]
  10
  11 pub trait Functor {
  12     type With<T>;
  13
  14     fn fmap<T, U>(this: Self::With<T>) -> Self::With<U>;
  15 }
  16
  17 pub trait FunctorExt<T>: Sized {
  18     type Base: Functor<With<T> = Self>;
  19
  20     fn fmap<U>(self) {
  21         let arg: <Self::Base as Functor>::With<T>;
  22         let ret: <Self::Base as Functor>::With<U>;
  23
  24         arg = self;
  25         ret = <Self::Base as Functor>::fmap(arg);
  26         //~^ type annotations needed
  27     }
  28 }
  29
  30 fn main() {}