Rollup merge of #68524 - jonas-schievink:generator-resume-arguments, r=Zoxc

Generator Resume Arguments

cc https://github.com/rust-lang/rust/issues/43122 and https://github.com/rust-lang/rust/issues/56974

Blockers:
* [x] Fix miscompilation when resume argument is live across a yield point (https://github.com/rust-lang/rust/pull/68524#issuecomment-578459069)
* [x] Fix 10% compile time regression in `await-call-tree` benchmarks (https://github.com/rust-lang/rust/pull/68524#issuecomment-578487162)
  * [x] Fix remaining 1-3% regression (https://github.com/rust-lang/rust/pull/68524#issuecomment-579566255) - resolved (https://github.com/rust-lang/rust/pull/68524#issuecomment-581144901)
* [x] Make dropck rules account for resume arguments (https://github.com/rust-lang/rust/pull/68524#issuecomment-578541137)

Follow-up work:
* Change async/await desugaring to make use of this feature
* Rewrite [`box_region.rs`](https://github.com/rust-lang/rust/blob/3d8778d767f0dde6fe2bc9459f21ead8e124d8cb/src/librustc_data_structures/box_region.rs) to use resume arguments (this shows up in profiles too)

1 files changed, 24 insertions, 0 deletions

diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs
index 7e5efbe3078..d65aee09232 100644
--- a/src/liballoc/boxed.rs
+++ b/src/liballoc/boxed.rs
@@ -1104,6 +1104,7 @@ impl<T: ?Sized> AsMut<T> for Box<T> {
 #[stable(feature = "pin", since = "1.33.0")]
 impl<T: ?Sized> Unpin for Box<T> {}
 
+#[cfg(bootstrap)]
 #[unstable(feature = "generator_trait", issue = "43122")]
 impl<G: ?Sized + Generator + Unpin> Generator for Box<G> {
     type Yield = G::Yield;
@@ -1114,6 +1115,7 @@ impl<G: ?Sized + Generator + Unpin> Generator for Box<G> {
     }
 }
 
+#[cfg(bootstrap)]
 #[unstable(feature = "generator_trait", issue = "43122")]
 impl<G: ?Sized + Generator> Generator for Pin<Box<G>> {
     type Yield = G::Yield;
@@ -1124,6 +1126,28 @@ impl<G: ?Sized + Generator> Generator for Pin<Box<G>> {
     }
 }
 
+#[cfg(not(bootstrap))]
+#[unstable(feature = "generator_trait", issue = "43122")]
+impl<G: ?Sized + Generator<R> + Unpin, R> Generator<R> for Box<G> {
+    type Yield = G::Yield;
+    type Return = G::Return;
+
+    fn resume(mut self: Pin<&mut Self>, arg: R) -> GeneratorState<Self::Yield, Self::Return> {
+        G::resume(Pin::new(&mut *self), arg)
+    }
+}
+
+#[cfg(not(bootstrap))]
+#[unstable(feature = "generator_trait", issue = "43122")]
+impl<G: ?Sized + Generator<R>, R> Generator<R> for Pin<Box<G>> {
+    type Yield = G::Yield;
+    type Return = G::Return;
+
+    fn resume(mut self: Pin<&mut Self>, arg: R) -> GeneratorState<Self::Yield, Self::Return> {
+        G::resume((*self).as_mut(), arg)
+    }
+}
+
 #[stable(feature = "futures_api", since = "1.36.0")]
 impl<F: ?Sized + Future + Unpin> Future for Box<F> {
     type Output = F::Output;