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// run-pass
#![allow(unused)]
fn main() {
}
fn foo() {
let b = mk::<
Forward<(Box<dyn Future<Error = u32>>,)>,
>();
b.map_err(|_| ()).join();
}
fn mk<T>() -> T {
loop {}
}
impl<I: Future<Error = E>, E> Future for (I,) {
type Error = E;
}
struct Forward<T: Future> {
_a: T,
}
impl<T: Future> Future for Forward<T>
where
T::Error: From<u32>,
{
type Error = T::Error;
}
trait Future {
type Error;
fn map_err<F, E>(self, _: F) -> (Self, F)
where
F: FnOnce(Self::Error) -> E,
Self: Sized,
{
loop {}
}
fn join(self) -> (MaybeDone<Self>, ())
where
Self: Sized,
{
loop {}
}
}
impl<S: ?Sized + Future> Future for Box<S> {
type Error = S::Error;
}
enum MaybeDone<A: Future> {
_Done(A::Error),
}
impl<U, A: Future, F> Future for (A, F)
where
F: FnOnce(A::Error) -> U,
{
type Error = U;
}
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