tests/ui/higher-rank-trait-bounds/issue-95034.rs

   1 // check-pass
   2 // compile-flags: --edition=2021 --crate-type=lib
   3
   4 use std::{
   5     future::Future,
   6     marker::PhantomData,
   7     pin::Pin,
   8     task::{Context, Poll},
   9 };
  10
  11 mod object {
  12     use super::*;
  13
  14     pub trait Object<'a> {
  15         type Error;
  16         type Future: Future<Output = Self>;
  17         fn create() -> Self::Future;
  18     }
  19
  20     impl<'a> Object<'a> for u8 {
  21         type Error = ();
  22         type Future = Pin<Box<dyn Future<Output = Self>>>;
  23         fn create() -> Self::Future {
  24             unimplemented!()
  25         }
  26     }
  27
  28     impl<'a, E, A: Object<'a, Error = E>> Object<'a> for (A,) {
  29         type Error = ();
  30         type Future = CustomFut<'a, E, A>;
  31         fn create() -> Self::Future {
  32             unimplemented!()
  33         }
  34     }
  35
  36     pub struct CustomFut<'f, E, A: Object<'f, Error = E>> {
  37         ph: PhantomData<(A::Future,)>,
  38     }
  39
  40     impl<'f, E, A: Object<'f, Error = E>> Future for CustomFut<'f, E, A> {
  41         type Output = (A,);
  42         fn poll(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Self::Output> {
  43             unimplemented!()
  44         }
  45     }
  46 }
  47
  48 mod async_fn {
  49     use super::*;
  50
  51     pub trait AsyncFn {
  52         type Future: Future<Output = ()>;
  53         fn call(&self) -> Self::Future;
  54     }
  55
  56     impl<F, Fut> AsyncFn for F
  57     where
  58         F: Fn() -> Fut,
  59         Fut: Future<Output = ()>,
  60     {
  61         type Future = Fut;
  62         fn call(&self) -> Self::Future {
  63             (self)()
  64         }
  65     }
  66 }
  67
  68 pub async fn test() {
  69     use self::{async_fn::AsyncFn, object::Object};
  70
  71     async fn create<T: Object<'static>>() {
  72         T::create().await;
  73     }
  74
  75     async fn call_async_fn(inner: impl AsyncFn) {
  76         inner.call().await;
  77     }
  78
  79     call_async_fn(create::<(u8,)>).await;
  80 }