56 lines
1.2 KiB
Rust
56 lines
1.2 KiB
Rust
// edition: 2021
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// known-bug: #108309
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#![feature(min_specialization)]
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#![feature(noop_waker)]
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struct MyStruct;
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trait MyTrait<T> {
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async fn foo(_: T) -> &'static str;
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}
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impl<T> MyTrait<T> for MyStruct {
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default async fn foo(_: T) -> &'static str {
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"default"
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}
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}
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impl MyTrait<i32> for MyStruct {
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async fn foo(_: i32) -> &'static str {
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"specialized"
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}
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}
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async fn async_main() {
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assert_eq!(MyStruct::foo(42).await, "specialized");
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assert_eq!(indirection(42).await, "specialized");
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}
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async fn indirection<T>(x: T) -> &'static str {
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//explicit type coercion is currently necessary
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// because of https://github.com/rust-lang/rust/issues/67918
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<MyStruct as MyTrait<T>>::foo(x).await
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}
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// ------------------------------------------------------------------------- //
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// Implementation Details Below...
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use std::pin::{pin, Pin};
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use std::task::*;
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fn main() {
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let mut fut = pin!(async_main());
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// Poll loop, just to test the future...
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let waker = Waker::noop();
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let ctx = &mut Context::from_waker(&waker);
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loop {
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match fut.as_mut().poll(ctx) {
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Poll::Pending => {}
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Poll::Ready(()) => break,
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}
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}
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}
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