rust/tests/ui/self/dispatch-from-dyn-zst-transmute.rs

#![feature(arbitrary_self_types)]
#![feature(unsize)]
#![feature(dispatch_from_dyn)]

use std::marker::PhantomData;
use std::marker::Unsize;
use std::ops::DispatchFromDyn;
use std::ops::Deref;

struct IsSendToken<T: ?Sized>(PhantomData<fn(T) -> T>);

struct Foo<'a, U: ?Sized> {
    token: IsSendToken<U>,
    ptr: &'a U,
}

impl<'a, T, U> DispatchFromDyn<Foo<'a, U>> for Foo<'a, T>
//~^ ERROR implementing the `DispatchFromDyn` trait requires multiple coercions
where
    T: Unsize<U> + ?Sized,
    U: ?Sized {}

trait Bar {
    fn f(self: Foo<'_, Self>);
}

impl<U: ?Sized> Deref for Foo<'_, U> {
    type Target = U;
    fn deref(&self) -> &U {
        self.ptr
    }
}

fn main() {}