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Rollup merge of #107445 - Swatinem:rm-genfuture, r=cuviper

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Remove `GenFuture` from core

The handling of async constructs in the compiler does not rely on `GenFuture` anymore since `1.67`, so this code can now be removed from `core`.
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Yuki Okushi 2023-01-31 11:46:23 +09:00 committed by GitHub
commit 39d2639f81
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1 changed files with 0 additions and 45 deletions
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library/core/src/future/mod.rs
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@ -56,51 +56,6 @@ unsafe impl Send for ResumeTy {}
#[unstable(feature = "gen_future", issue = "50547")]
unsafe impl Sync for ResumeTy {}
/// Wrap a generator in a future.
///
/// This function returns a `GenFuture` underneath, but hides it in `impl Trait` to give
/// better error messages (`impl Future` rather than `GenFuture<[closure.....]>`).
// This is `const` to avoid extra errors after we recover from `const async fn`
#[doc(hidden)]
#[unstable(feature = "gen_future", issue = "50547")]
#[rustc_const_unstable(feature = "gen_future", issue = "50547")]
#[inline]
pub const fn from_generator<T>(gen: T) -> impl Future<Output = T::Return>
where
T: crate::ops::Generator<ResumeTy, Yield = ()>,
{
use crate::{
ops::{Generator, GeneratorState},
pin::Pin,
task::Poll,
};
#[rustc_diagnostic_item = "gen_future"]
struct GenFuture<T: Generator<ResumeTy, Yield = ()>>(T);
// We rely on the fact that async/await futures are immovable in order to create
// self-referential borrows in the underlying generator.
impl<T: Generator<ResumeTy, Yield = ()>> !Unpin for GenFuture<T> {}
impl<T: Generator<ResumeTy, Yield = ()>> Future for GenFuture<T> {
type Output = T::Return;
#[track_caller]
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
// SAFETY: Safe because we're !Unpin + !Drop, and this is just a field projection.
let gen = unsafe { Pin::map_unchecked_mut(self, |s| &mut s.0) };
// Resume the generator, turning the `&mut Context` into a `NonNull` raw pointer. The
// `.await` lowering will safely cast that back to a `&mut Context`.
match gen.resume(ResumeTy(NonNull::from(cx).cast::<Context<'static>>())) {
GeneratorState::Yielded(()) => Poll::Pending,
GeneratorState::Complete(x) => Poll::Ready(x),
}
}
}
GenFuture(gen)
}
#[lang = "get_context"]
#[doc(hidden)]
#[unstable(feature = "gen_future", issue = "50547")]