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// check-fail
// known-bug
// We almost certaintly want this to pass, but
// it's particularly difficult currently, because we need a way of specifying
// that `<Self::Base as Functor>::With<T> = Self` without using that when we have
// a `U`. See `https://github.com/rust-lang/rust/pull/92728` for a (hacky)
// solution. This might be better to just wait for Chalk.
pub trait Functor {
type With<T>;
fn fmap<T, U>(this: Self::With<T>) -> Self::With<U>;
}
pub trait FunctorExt<T>: Sized {
type Base: Functor<With<T> = Self>;
fn fmap<U>(self) {
let arg: <Self::Base as Functor>::With<T>;
let ret: <Self::Base as Functor>::With<U>;
arg = self;
ret = <Self::Base as Functor>::fmap(arg);
//~^ type annotations needed
}
}
fn main() {}
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