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// edition:2021
// check-pass
#![feature(type_alias_impl_trait)]
#![feature(closure_lifetime_binder)]
use std::future::Future;
trait AsyncFn<I, R>: FnMut(I) -> Self::Fut {
type Fut: Future<Output = R>;
}
impl<F, I, R, Fut> AsyncFn<I, R> for F
where
Fut: Future<Output = R>,
F: FnMut(I) -> Fut,
{
type Fut = Fut;
}
async fn call<C, R, F>(mut ctx: C, mut f: F) -> Result<R, ()>
where
F: for<'a> AsyncFn<&'a mut C, Result<R, ()>>,
{
loop {
match f(&mut ctx).await {
Ok(val) => return Ok(val),
Err(_) => continue,
}
}
}
trait Cap<'a> {}
impl<T> Cap<'_> for T {}
fn works(ctx: &mut usize) {
let mut inner = 0;
type Ret<'a, 'b: 'a> = impl Future<Output = Result<usize, ()>> + 'a + Cap<'b>;
let callback = for<'a, 'b> |c: &'a mut &'b mut usize| -> Ret<'a, 'b> {
inner += 1;
async move {
let _c = c;
Ok(1usize)
}
};
call(ctx, callback);
}
fn doesnt_work_but_should(ctx: &mut usize) {
let mut inner = 0;
type Ret<'a, 'b: 'a> = impl Future<Output = Result<usize, ()>> + 'a + Cap<'b>;
call(ctx, for<'a, 'b> |c: &'a mut &'b mut usize| -> Ret<'a, 'b> {
inner += 1;
async move {
let _c = c;
Ok(1usize)
}
});
}
fn main() {}
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