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, 31 insertions, 4 deletions

diff --git a/src/libcore/ops/generator.rs b/src/libcore/ops/generator.rs
index 5401fff860e..4e43561996c 100644
--- a/src/libcore/ops/generator.rs
+++ b/src/libcore/ops/generator.rs
@@ -50,11 +50,11 @@ pub enum GeneratorState<Y, R> {
 ///         return "foo"
 ///     };
 ///
-///     match Pin::new(&mut generator).resume() {
+///     match Pin::new(&mut generator).resume(()) {
 ///         GeneratorState::Yielded(1) => {}
 ///         _ => panic!("unexpected return from resume"),
 ///     }
-///     match Pin::new(&mut generator).resume() {
+///     match Pin::new(&mut generator).resume(()) {
 ///         GeneratorState::Complete("foo") => {}
 ///         _ => panic!("unexpected return from resume"),
 ///     }
@@ -67,7 +67,7 @@ pub enum GeneratorState<Y, R> {
 #[lang = "generator"]
 #[unstable(feature = "generator_trait", issue = "43122")]
 #[fundamental]
-pub trait Generator {
+pub trait Generator<#[cfg(not(bootstrap))] R = ()> {
     /// The type of value this generator yields.
     ///
     /// This associated type corresponds to the `yield` expression and the
@@ -110,9 +110,13 @@ pub trait Generator {
     /// been returned previously. While generator literals in the language are
     /// guaranteed to panic on resuming after `Complete`, this is not guaranteed
     /// for all implementations of the `Generator` trait.
-    fn resume(self: Pin<&mut Self>) -> GeneratorState<Self::Yield, Self::Return>;
+    fn resume(
+        self: Pin<&mut Self>,
+        #[cfg(not(bootstrap))] arg: R,
+    ) -> GeneratorState<Self::Yield, Self::Return>;
 }
 
+#[cfg(bootstrap)]
 #[unstable(feature = "generator_trait", issue = "43122")]
 impl<G: ?Sized + Generator> Generator for Pin<&mut G> {
     type Yield = G::Yield;
@@ -123,6 +127,7 @@ impl<G: ?Sized + Generator> Generator for Pin<&mut G> {
     }
 }
 
+#[cfg(bootstrap)]
 #[unstable(feature = "generator_trait", issue = "43122")]
 impl<G: ?Sized + Generator + Unpin> Generator for &mut G {
     type Yield = G::Yield;
@@ -132,3 +137,25 @@ impl<G: ?Sized + Generator + Unpin> Generator for &mut G {
         G::resume(Pin::new(&mut *self))
     }
 }
+
+#[cfg(not(bootstrap))]
+#[unstable(feature = "generator_trait", issue = "43122")]
+impl<G: ?Sized + Generator<R>, R> Generator<R> for Pin<&mut 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)
+    }
+}
+
+#[cfg(not(bootstrap))]
+#[unstable(feature = "generator_trait", issue = "43122")]
+impl<G: ?Sized + Generator<R> + Unpin, R> Generator<R> for &mut 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)
+    }
+}