Add a resume type parameter to `Generator`

46 files changed, 185 insertions, 122 deletions

diff --git a/src/doc/unstable-book/src/language-features/generators.md b/src/doc/unstable-book/src/language-features/generators.md
index 97cf58e57e6..8bc62418b39 100644
--- a/src/doc/unstable-book/src/language-features/generators.md
+++ b/src/doc/unstable-book/src/language-features/generators.md
@@ -37,11 +37,11 @@ fn main() {
         return "foo"
     };
 
-    match Pin::new(&mut generator).resume() {
+    match Pin::new(&mut generator).resume(()) {
         GeneratorState::Yielded(1) => {}
         _ => panic!("unexpected value from resume"),
     }
-    match Pin::new(&mut generator).resume() {
+    match Pin::new(&mut generator).resume(()) {
         GeneratorState::Complete("foo") => {}
         _ => panic!("unexpected value from resume"),
     }
@@ -71,9 +71,9 @@ fn main() {
     };
 
     println!("1");
-    Pin::new(&mut generator).resume();
+    Pin::new(&mut generator).resume(());
     println!("3");
-    Pin::new(&mut generator).resume();
+    Pin::new(&mut generator).resume(());
     println!("5");
 }
 ```
@@ -92,10 +92,10 @@ The `Generator` trait in `std::ops` currently looks like:
 # use std::ops::GeneratorState;
 # use std::pin::Pin;
 
-pub trait Generator {
+pub trait Generator<R = ()> {
     type Yield;
     type Return;
-    fn resume(self: Pin<&mut Self>) -> GeneratorState<Self::Yield, Self::Return>;
+    fn resume(self: Pin<&mut Self>, resume: R) -> GeneratorState<Self::Yield, Self::Return>;
 }
 ```
 
@@ -152,10 +152,6 @@ closure-like semantics. Namely:
 * Whenever a generator is dropped it will drop all captured environment
   variables.
 
-Note that unlike closures, generators at this time cannot take any arguments.
-That is, generators must always look like `|| { ... }`. This restriction may be
-lifted at a future date, the design is ongoing!
-
 ### Generators as state machines
 
 In the compiler, generators are currently compiled as state machines. Each
@@ -179,8 +175,8 @@ fn main() {
         return ret
     };
 
-    Pin::new(&mut generator).resume();
-    Pin::new(&mut generator).resume();
+    Pin::new(&mut generator).resume(());
+    Pin::new(&mut generator).resume(());
 }
 ```
 
@@ -205,7 +201,7 @@ fn main() {
             type Yield = i32;
             type Return = &'static str;
 
-            fn resume(mut self: Pin<&mut Self>) -> GeneratorState<i32, &'static str> {
+            fn resume(mut self: Pin<&mut Self>, resume: ()) -> GeneratorState<i32, &'static str> {
                 use std::mem;
                 match mem::replace(&mut *self, __Generator::Done) {
                     __Generator::Start(s) => {
@@ -228,8 +224,8 @@ fn main() {
         __Generator::Start(ret)
     };
 
-    Pin::new(&mut generator).resume();
-    Pin::new(&mut generator).resume();
+    Pin::new(&mut generator).resume(());
+    Pin::new(&mut generator).resume(());
 }
 ```
 
diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs
index 8735c2c8f36..04be86862ae 100644
--- a/src/liballoc/boxed.rs
+++ b/src/liballoc/boxed.rs
@@ -1103,6 +1103,7 @@ 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;
@@ -1113,6 +1114,7 @@ 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;
@@ -1123,6 +1125,28 @@ 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;
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)
+    }
+}
diff --git a/src/librustc/traits/util.rs b/src/librustc/traits/util.rs
index ae1a5e3efa2..947d66e38b4 100644
--- a/src/librustc/traits/util.rs
+++ b/src/librustc/traits/util.rs
@@ -643,8 +643,10 @@ pub fn generator_trait_ref_and_outputs(
     self_ty: Ty<'tcx>,
     sig: ty::PolyGenSig<'tcx>,
 ) -> ty::Binder<(ty::TraitRef<'tcx>, Ty<'tcx>, Ty<'tcx>)> {
-    let trait_ref =
-        ty::TraitRef { def_id: fn_trait_def_id, substs: tcx.mk_substs_trait(self_ty, &[]) };
+    let trait_ref = ty::TraitRef {
+        def_id: fn_trait_def_id,
+        substs: tcx.mk_substs_trait(self_ty, &[tcx.mk_unit().into()]),
+    };
     ty::Binder::bind((trait_ref, sig.skip_binder().yield_ty, sig.skip_binder().return_ty))
 }
 
diff --git a/src/librustc/ty/layout.rs b/src/librustc/ty/layout.rs
index bda42db40b0..966b60c6cfb 100644
--- a/src/librustc/ty/layout.rs
+++ b/src/librustc/ty/layout.rs
@@ -2350,8 +2350,8 @@ impl<'tcx> ty::Instance<'tcx> {
                     ]);
                     let ret_ty = tcx.mk_adt(state_adt_ref, state_substs);
 
-                    tcx.mk_fn_sig(iter::once(env_ty),
-                        ret_ty,
+                    tcx.mk_fn_sig([env_ty, tcx.mk_unit()].iter(),
+                        &ret_ty,
                         false,
                         hir::Unsafety::Normal,
                         rustc_target::spec::abi::Abi::Rust
diff --git a/src/librustc_error_codes/error_codes/E0626.md b/src/librustc_error_codes/error_codes/E0626.md
index db50bd7ac4f..cc6e03d1ca7 100644
--- a/src/librustc_error_codes/error_codes/E0626.md
+++ b/src/librustc_error_codes/error_codes/E0626.md
@@ -12,7 +12,7 @@ let mut b = || {
     yield (); // ...is still in scope here, when the yield occurs.
     println!("{}", a);
 };
-Pin::new(&mut b).resume();
+Pin::new(&mut b).resume(());
 ```
 
 At present, it is not permitted to have a yield that occurs while a
@@ -31,7 +31,7 @@ let mut b = || {
     yield ();
     println!("{}", a);
 };
-Pin::new(&mut b).resume();
+Pin::new(&mut b).resume(());
 ```
 
 This is a very simple case, of course. In more complex cases, we may
@@ -50,7 +50,7 @@ let mut b = || {
     yield x; // ...when this yield occurs.
   }
 };
-Pin::new(&mut b).resume();
+Pin::new(&mut b).resume(());
 ```
 
 Such cases can sometimes be resolved by iterating "by value" (or using
@@ -66,7 +66,7 @@ let mut b = || {
     yield x; // <-- Now yield is OK.
   }
 };
-Pin::new(&mut b).resume();
+Pin::new(&mut b).resume(());
 ```
 
 If taking ownership is not an option, using indices can work too:
@@ -83,7 +83,7 @@ let mut b = || {
     yield x; // <-- Now yield is OK.
   }
 };
-Pin::new(&mut b).resume();
+Pin::new(&mut b).resume(());
 
 // (*) -- Unfortunately, these temporaries are currently required.
 // See <https://github.com/rust-lang/rust/issues/43122>.
diff --git a/src/librustc_mir/dataflow/impls/storage_liveness.rs b/src/librustc_mir/dataflow/impls/storage_liveness.rs
index 6a48d1e9803..040c13e8210 100644
--- a/src/librustc_mir/dataflow/impls/storage_liveness.rs
+++ b/src/librustc_mir/dataflow/impls/storage_liveness.rs
@@ -31,10 +31,12 @@ impl<'a, 'tcx> BitDenotation<'tcx> for MaybeStorageLive<'a, 'tcx> {
         self.body.local_decls.len()
     }
 
-    fn start_block_effect(&self, _on_entry: &mut BitSet<Local>) {
-        // Nothing is live on function entry (generators only have a self
-        // argument, and we don't care about that)
-        assert_eq!(1, self.body.arg_count);
+    fn start_block_effect(&self, on_entry: &mut BitSet<Local>) {
+        // The resume argument is live on function entry (we don't care about
+        // the `self` argument)
+        for arg in self.body.args_iter().skip(1) {
+            on_entry.insert(arg);
+        }
     }
 
     fn statement_effect(&self, trans: &mut GenKillSet<Local>, loc: Location) {
@@ -100,10 +102,12 @@ impl<'mir, 'tcx> BitDenotation<'tcx> for RequiresStorage<'mir, 'tcx> {
         self.body.local_decls.len()
     }
 
-    fn start_block_effect(&self, _sets: &mut BitSet<Local>) {
-        // Nothing is live on function entry (generators only have a self
-        // argument, and we don't care about that)
-        assert_eq!(1, self.body.arg_count);
+    fn start_block_effect(&self, on_entry: &mut BitSet<Local>) {
+        // The resume argument is live on function entry (we don't care about
+        // the `self` argument)
+        for arg in self.body.args_iter().skip(1) {
+            on_entry.insert(arg);
+        }
     }
 
     fn before_statement_effect(&self, sets: &mut GenKillSet<Self::Idx>, loc: Location) {
diff --git a/src/librustc_mir/transform/generator.rs b/src/librustc_mir/transform/generator.rs
index 1c86d6f3f65..a8defd03f71 100644
--- a/src/librustc_mir/transform/generator.rs
+++ b/src/librustc_mir/transform/generator.rs
@@ -885,6 +885,7 @@ fn create_generator_drop_shim<'tcx>(
     drop_clean: BasicBlock,
 ) -> BodyAndCache<'tcx> {
     let mut body = body.clone();
+    body.arg_count = 1; // make sure the resume argument is not included here
 
     let source_info = source_info(&body);
 
@@ -1164,7 +1165,7 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
 
         // Update our MIR struct to reflect the changed we've made
         body.yield_ty = None;
-        body.arg_count = 1;
+        body.arg_count = 2; // self, resume arg
         body.spread_arg = None;
         body.generator_layout = Some(layout);
 
diff --git a/src/librustc_mir_build/build/mod.rs b/src/librustc_mir_build/build/mod.rs
index 1f536b63a39..ab539e6179e 100644
--- a/src/librustc_mir_build/build/mod.rs
+++ b/src/librustc_mir_build/build/mod.rs
@@ -75,13 +75,16 @@ fn mir_build(tcx: TyCtxt<'_>, def_id: DefId) -> BodyAndCache<'_> {
                     // HACK(eddyb) Avoid having RustCall on closures,
                     // as it adds unnecessary (and wrong) auto-tupling.
                     abi = Abi::Rust;
-                    Some(ArgInfo(liberated_closure_env_ty(tcx, id, body_id), None, None, None))
+                    vec![ArgInfo(liberated_closure_env_ty(tcx, id, body_id), None, None, None)]
                 }
                 ty::Generator(..) => {
                     let gen_ty = tcx.body_tables(body_id).node_type(id);
-                    Some(ArgInfo(gen_ty, None, None, None))
+                    vec![
+                        ArgInfo(gen_ty, None, None, None),
+                        ArgInfo(tcx.mk_unit(), None, None, None),
+                    ]
                 }
-                _ => None,
+                _ => vec![],
             };
 
             let safety = match fn_sig.unsafety {
diff --git a/src/libstd/future.rs b/src/libstd/future.rs
index 9c7422c2b20..f74c84e6dfd 100644
--- a/src/libstd/future.rs
+++ b/src/libstd/future.rs
@@ -40,7 +40,10 @@ impl<T: Generator<Yield = ()>> Future for GenFuture<T> {
         // Safe because we're !Unpin + !Drop mapping to a ?Unpin value
         let gen = unsafe { Pin::map_unchecked_mut(self, |s| &mut s.0) };
         let _guard = unsafe { set_task_context(cx) };
-        match gen.resume() {
+        match gen.resume(
+            #[cfg(not(bootstrap))]
+            (),
+        ) {
             GeneratorState::Yielded(()) => Poll::Pending,
             GeneratorState::Complete(x) => Poll::Ready(x),
         }
diff --git a/src/test/debuginfo/generator-locals.rs b/src/test/debuginfo/generator-locals.rs
index 59dbfecc39f..fd46c1a8b4d 100644
--- a/src/test/debuginfo/generator-locals.rs
+++ b/src/test/debuginfo/generator-locals.rs
@@ -78,9 +78,9 @@ fn main() {
         _zzz(); // #break
         a = c;
     };
-    Pin::new(&mut b).resume();
-    Pin::new(&mut b).resume();
-    Pin::new(&mut b).resume();
+    Pin::new(&mut b).resume(());
+    Pin::new(&mut b).resume(());
+    Pin::new(&mut b).resume(());
     _zzz(); // #break
 }
 
diff --git a/src/test/debuginfo/generator-objects.rs b/src/test/debuginfo/generator-objects.rs
index bfa7a05cad0..f19a3c71dd8 100644
--- a/src/test/debuginfo/generator-objects.rs
+++ b/src/test/debuginfo/generator-objects.rs
@@ -57,11 +57,11 @@ fn main() {
         println!("{} {} {}", a, c, d);
     };
     _zzz(); // #break
-    Pin::new(&mut b).resume();
+    Pin::new(&mut b).resume(());
     _zzz(); // #break
-    Pin::new(&mut b).resume();
+    Pin::new(&mut b).resume(());
     _zzz(); // #break
-    Pin::new(&mut b).resume();
+    Pin::new(&mut b).resume(());
     _zzz(); // #break
 }
 
diff --git a/src/test/debuginfo/issue-57822.rs b/src/test/debuginfo/issue-57822.rs
index f18e41db0e6..4de88e9dae6 100644
--- a/src/test/debuginfo/issue-57822.rs
+++ b/src/test/debuginfo/issue-57822.rs
@@ -45,7 +45,7 @@ fn main() {
         yield;
     };
     let mut b = move || {
-        Pin::new(&mut a).resume();
+        Pin::new(&mut a).resume(());
         yield;
     };
 
diff --git a/src/test/run-fail/generator-resume-after-panic.rs b/src/test/run-fail/generator-resume-after-panic.rs
index 910b4903bf6..1a7c2e80629 100644
--- a/src/test/run-fail/generator-resume-after-panic.rs
+++ b/src/test/run-fail/generator-resume-after-panic.rs
@@ -16,7 +16,7 @@ fn main() {
         yield;
     };
     panic::catch_unwind(panic::AssertUnwindSafe(|| {
-        let x = Pin::new(&mut g).resume();
+        let x = Pin::new(&mut g).resume(());
     }));
-    Pin::new(&mut g).resume();
+    Pin::new(&mut g).resume(());
 }
diff --git a/src/test/ui/async-await/issues/issue-65419/issue-65419-generator-resume-after-completion.rs b/src/test/ui/async-await/issues/issue-65419/issue-65419-generator-resume-after-completion.rs
index 23e3483e01c..9fc5667d684 100644
--- a/src/test/ui/async-await/issues/issue-65419/issue-65419-generator-resume-after-completion.rs
+++ b/src/test/ui/async-await/issues/issue-65419/issue-65419-generator-resume-after-completion.rs
@@ -19,7 +19,7 @@ fn main() {
     let mut g = || {
         yield;
     };
-    Pin::new(&mut g).resume(); // Yields once.
-    Pin::new(&mut g).resume(); // Completes here.
-    Pin::new(&mut g).resume(); // Panics here.
+    Pin::new(&mut g).resume(()); // Yields once.
+    Pin::new(&mut g).resume(()); // Completes here.
+    Pin::new(&mut g).resume(()); // Panics here.
 }
diff --git a/src/test/ui/drop/dynamic-drop.rs b/src/test/ui/drop/dynamic-drop.rs
index b4406204a5d..659e520d4cd 100644
--- a/src/test/ui/drop/dynamic-drop.rs
+++ b/src/test/ui/drop/dynamic-drop.rs
@@ -184,7 +184,7 @@ fn generator(a: &Allocator, run_count: usize) {
          );
     };
     for _ in 0..run_count {
-        Pin::new(&mut gen).resume();
+        Pin::new(&mut gen).resume(());
     }
 }
 
diff --git a/src/test/ui/generator/auxiliary/xcrate-reachable.rs b/src/test/ui/generator/auxiliary/xcrate-reachable.rs
index 33337f8038f..2dd5ea67523 100644
--- a/src/test/ui/generator/auxiliary/xcrate-reachable.rs
+++ b/src/test/ui/generator/auxiliary/xcrate-reachable.rs
@@ -6,7 +6,7 @@ fn msg() -> u32 {
     0
 }
 
-pub fn foo() -> impl Generator<Yield=(), Return=u32> {
+pub fn foo() -> impl Generator<(), Yield=(), Return=u32> {
     || {
         yield;
         return msg();
diff --git a/src/test/ui/generator/auxiliary/xcrate.rs b/src/test/ui/generator/auxiliary/xcrate.rs
index 613c495832f..d07abd0918c 100644
--- a/src/test/ui/generator/auxiliary/xcrate.rs
+++ b/src/test/ui/generator/auxiliary/xcrate.rs
@@ -3,7 +3,7 @@
 use std::marker::Unpin;
 use std::ops::Generator;
 
-pub fn foo() -> impl Generator<Yield = (), Return = ()> {
+pub fn foo() -> impl Generator<(), Yield = (), Return = ()> {
     || {
         if false {
             yield;
@@ -11,7 +11,7 @@ pub fn foo() -> impl Generator<Yield = (), Return = ()> {
     }
 }
 
-pub fn bar<T: 'static>(t: T) -> Box<Generator<Yield = T, Return = ()> + Unpin> {
+pub fn bar<T: 'static>(t: T) -> Box<Generator<(), Yield = T, Return = ()> + Unpin> {
     Box::new(|| {
         yield t;
     })
diff --git a/src/test/ui/generator/borrowing.rs b/src/test/ui/generator/borrowing.rs
index 6234b738048..d36592583cd 100644
--- a/src/test/ui/generator/borrowing.rs
+++ b/src/test/ui/generator/borrowing.rs
@@ -6,7 +6,7 @@ use std::pin::Pin;
 fn main() {
     let _b = {
         let a = 3;
-        Pin::new(&mut || yield &a).resume()
+        Pin::new(&mut || yield &a).resume(())
         //~^ ERROR: `a` does not live long enough
     };
 
diff --git a/src/test/ui/generator/borrowing.stderr b/src/test/ui/generator/borrowing.stderr
index 3d58873f826..83987e19839 100644
--- a/src/test/ui/generator/borrowing.stderr
+++ b/src/test/ui/generator/borrowing.stderr
@@ -1,7 +1,7 @@
 error[E0597]: `a` does not live long enough
   --> $DIR/borrowing.rs:9:33
    |
-LL |         Pin::new(&mut || yield &a).resume()
+LL |         Pin::new(&mut || yield &a).resume(())
    |                       ----------^
    |                       |         |
    |                       |         borrowed value does not live long enough
diff --git a/src/test/ui/generator/conditional-drop.rs b/src/test/ui/generator/conditional-drop.rs
index 907f7a3c06d..990d94e6efc 100644
--- a/src/test/ui/generator/conditional-drop.rs
+++ b/src/test/ui/generator/conditional-drop.rs
@@ -35,9 +35,9 @@ fn t1() {
     };
 
     let n = A.load(Ordering::SeqCst);
-    Pin::new(&mut a).resume();
+    Pin::new(&mut a).resume(());
     assert_eq!(A.load(Ordering::SeqCst), n + 1);
-    Pin::new(&mut a).resume();
+    Pin::new(&mut a).resume(());
     assert_eq!(A.load(Ordering::SeqCst), n + 1);
 }
 
@@ -51,8 +51,8 @@ fn t2() {
     };
 
     let n = A.load(Ordering::SeqCst);
-    Pin::new(&mut a).resume();
+    Pin::new(&mut a).resume(());
     assert_eq!(A.load(Ordering::SeqCst), n);
-    Pin::new(&mut a).resume();
+    Pin::new(&mut a).resume(());
     assert_eq!(A.load(Ordering::SeqCst), n + 1);
 }
diff --git a/src/test/ui/generator/control-flow.rs b/src/test/ui/generator/control-flow.rs
index df70e013bd3..9d4c217b76e 100644
--- a/src/test/ui/generator/control-flow.rs
+++ b/src/test/ui/generator/control-flow.rs
@@ -7,10 +7,10 @@ use std::ops::{GeneratorState, Generator};
 use std::pin::Pin;
 
 fn finish<T>(mut amt: usize, mut t: T) -> T::Return
-    where T: Generator<Yield = ()> + Unpin,
+    where T: Generator<(), Yield = ()> + Unpin,
 {
     loop {
-        match Pin::new(&mut t).resume() {
+        match Pin::new(&mut t).resume(()) {
             GeneratorState::Yielded(()) => amt = amt.checked_sub(1).unwrap(),
             GeneratorState::Complete(ret) => {
                 assert_eq!(amt, 0);
diff --git a/src/test/ui/generator/drop-and-replace.rs b/src/test/ui/generator/drop-and-replace.rs
index bb33502815b..a9a50a122a1 100644
--- a/src/test/ui/generator/drop-and-replace.rs
+++ b/src/test/ui/generator/drop-and-replace.rs
@@ -37,7 +37,7 @@ fn main() {
     };
 
     loop {
-        match Pin::new(&mut a).resume() {
+        match Pin::new(&mut a).resume(()) {
             GeneratorState::Complete(()) => break,
             _ => (),
         }
diff --git a/src/test/ui/generator/drop-env.rs b/src/test/ui/generator/drop-env.rs
index ac4e0665628..7ba71188104 100644
--- a/src/test/ui/generator/drop-env.rs
+++ b/src/test/ui/generator/drop-env.rs
@@ -30,7 +30,7 @@ fn t1() {
     };
 
     let n = A.load(Ordering::SeqCst);
-    drop(Pin::new(&mut foo).resume());
+    drop(Pin::new(&mut foo).resume(()));
     assert_eq!(A.load(Ordering::SeqCst), n);
     drop(foo);
     assert_eq!(A.load(Ordering::SeqCst), n + 1);
@@ -43,7 +43,7 @@ fn t2() {
     };
 
     let n = A.load(Ordering::SeqCst);
-    drop(Pin::new(&mut foo).resume());
+    drop(Pin::new(&mut foo).resume(()));
     assert_eq!(A.load(Ordering::SeqCst), n + 1);
     drop(foo);
     assert_eq!(A.load(Ordering::SeqCst), n + 1);
diff --git a/src/test/ui/generator/dropck.rs b/src/test/ui/generator/dropck.rs
index 65c61fbaac4..da00b230d9f 100644
--- a/src/test/ui/generator/dropck.rs
+++ b/src/test/ui/generator/dropck.rs
@@ -15,6 +15,6 @@ fn main() {
         let _d = ref_.take(); //~ ERROR `ref_` does not live long enough
         yield;
     };
-    Pin::new(&mut gen).resume();
+    Pin::new(&mut gen).resume(());
     // drops the RefCell and then the Ref, leading to use-after-free
 }
diff --git a/src/test/ui/generator/generator-region-requirements.rs b/src/test/ui/generator/generator-region-requirements.rs
index 41cb339f459..5f0a6bb09b7 100644
--- a/src/test/ui/generator/generator-region-requirements.rs
+++ b/src/test/ui/generator/generator-region-requirements.rs
@@ -8,7 +8,7 @@ fn dangle(x: &mut i32) -> &'static mut i32 {
         x
     };
     loop {
-        match Pin::new(&mut g).resume() {
+        match Pin::new(&mut g).resume(()) {
             GeneratorState::Complete(c) => return c,
             //~^ ERROR explicit lifetime required
             GeneratorState::Yielded(_) => (),
diff --git a/src/test/ui/generator/issue-44197.rs b/src/test/ui/generator/issue-44197.rs
index 6efaff50c1e..389b9d13969 100644
--- a/src/test/ui/generator/issue-44197.rs
+++ b/src/test/ui/generator/issue-44197.rs
@@ -2,14 +2,14 @@
 
 #![feature(generators, generator_trait)]
 
-use std::ops::{ Generator, GeneratorState };
+use std::ops::{Generator, GeneratorState};
 use std::pin::Pin;
 
 fn foo(_: &str) -> String {
     String::new()
 }
 
-fn bar(baz: String) -> impl Generator<Yield = String, Return = ()> {
+fn bar(baz: String) -> impl Generator<(), Yield = String, Return = ()> {
     move || {
         yield foo(&baz);
     }
@@ -19,7 +19,7 @@ fn foo2(_: &str) -> Result<String, ()> {
     Err(())
 }
 
-fn bar2(baz: String) -> impl Generator<Yield = String, Return = ()> {
+fn bar2(baz: String) -> impl Generator<(), Yield = String, Return = ()> {
     move || {
         if let Ok(quux) = foo2(&baz) {
             yield quux;
@@ -28,6 +28,9 @@ fn bar2(baz: String) -> impl Generator<Yield = String, Return = ()> {
 }
 
 fn main() {
-    assert_eq!(Pin::new(&mut bar(String::new())).resume(), GeneratorState::Yielded(String::new()));
-    assert_eq!(Pin::new(&mut bar2(String::new())).resume(), GeneratorState::Complete(()));
+    assert_eq!(
+        Pin::new(&mut bar(String::new())).resume(()),
+        GeneratorState::Yielded(String::new())
+    );
+    assert_eq!(Pin::new(&mut bar2(String::new())).resume(()), GeneratorState::Complete(()));
 }
diff --git a/src/test/ui/generator/issue-61442-stmt-expr-with-drop.rs b/src/test/ui/generator/issue-61442-stmt-expr-with-drop.rs
index e3d19029348..187c374021d 100644
--- a/src/test/ui/generator/issue-61442-stmt-expr-with-drop.rs
+++ b/src/test/ui/generator/issue-61442-stmt-expr-with-drop.rs
@@ -18,12 +18,12 @@ fn drop_and_yield() {
         String::new();
         yield;
     };
-    Box::pin(x).as_mut().resume();
+    Box::pin(x).as_mut().resume(());
     let y = static || {
         String::new();
         yield;
     };
-    Box::pin(y).as_mut().resume();
+    Box::pin(y).as_mut().resume(());
 }
 
 fn main() {
diff --git a/src/test/ui/generator/iterator-count.rs b/src/test/ui/generator/iterator-count.rs
index ac7e122dd58..90eefe02f66 100644
--- a/src/test/ui/generator/iterator-count.rs
+++ b/src/test/ui/generator/iterator-count.rs
@@ -10,18 +10,18 @@ struct W<T>(T);
 
 // This impl isn't safe in general, but the generator used in this test is movable
 // so it won't cause problems.
-impl<T: Generator<Return = ()> + Unpin> Iterator for W<T> {
+impl<T: Generator<(), Return = ()> + Unpin> Iterator for W<T> {
     type Item = T::Yield;
 
     fn next(&mut self) -> Option<Self::Item> {
-        match Pin::new(&mut self.0).resume() {
+        match Pin::new(&mut self.0).resume(()) {
             GeneratorState::Complete(..) => None,
             GeneratorState::Yielded(v) => Some(v),
         }
     }
 }
 
-fn test() -> impl Generator<Return=(), Yield=u8> + Unpin {
+fn test() -> impl Generator<(), Return=(), Yield=u8> + Unpin {
     || {
         for i in 1..6 {
             yield i
diff --git a/src/test/ui/generator/live-upvar-across-yield.rs b/src/test/ui/generator/live-upvar-across-yield.rs
index a1064165b2f..6a2e42a5573 100644
--- a/src/test/ui/generator/live-upvar-across-yield.rs
+++ b/src/test/ui/generator/live-upvar-across-yield.rs
@@ -10,5 +10,5 @@ fn main() {
     let mut a = || {
         b(yield);
     };
-    Pin::new(&mut a).resume();
+    Pin::new(&mut a).resume(());
 }
diff --git a/src/test/ui/generator/nested_generators.rs b/src/test/ui/generator/nested_generators.rs
index b56cce1dc44..45519150eec 100644
--- a/src/test/ui/generator/nested_generators.rs
+++ b/src/test/ui/generator/nested_generators.rs
@@ -11,7 +11,7 @@ fn main() {
             yield 2;
         };
 
-        match Pin::new(&mut sub_generator).resume() {
+        match Pin::new(&mut sub_generator).resume(()) {
             GeneratorState::Yielded(x) => {
                 yield x;
             }
diff --git a/src/test/ui/generator/panic-drops.rs b/src/test/ui/generator/panic-drops.rs
index f88687858fd..c9a201725ae 100644
--- a/src/test/ui/generator/panic-drops.rs
+++ b/src/test/ui/generator/panic-drops.rs
@@ -35,7 +35,7 @@ fn main() {
 
     assert_eq!(A.load(Ordering::SeqCst), 0);
     let res = panic::catch_unwind(panic::AssertUnwindSafe(|| {
-        Pin::new(&mut foo).resume()
+        Pin::new(&mut foo).resume(())
     }));
     assert!(res.is_err());
     assert_eq!(A.load(Ordering::SeqCst), 1);
@@ -50,7 +50,7 @@ fn main() {
 
     assert_eq!(A.load(Ordering::SeqCst), 1);
     let res = panic::catch_unwind(panic::AssertUnwindSafe(|| {
-        Pin::new(&mut foo).resume()
+        Pin::new(&mut foo).resume(())
     }));
     assert!(res.is_err());
     assert_eq!(A.load(Ordering::SeqCst), 1);
diff --git a/src/test/ui/generator/panic-safe.rs b/src/test/ui/generator/panic-safe.rs
index 5f6778674dc..500a3c9c295 100644
--- a/src/test/ui/generator/panic-safe.rs
+++ b/src/test/ui/generator/panic-safe.rs
@@ -17,13 +17,13 @@ fn main() {
     };
 
     let res = panic::catch_unwind(panic::AssertUnwindSafe(|| {
-        Pin::new(&mut foo).resume()
+        Pin::new(&mut foo).resume(())
     }));
     assert!(res.is_err());
 
     for _ in 0..10 {
         let res = panic::catch_unwind(panic::AssertUnwindSafe(|| {
-            Pin::new(&mut foo).resume()
+            Pin::new(&mut foo).resume(())
         }));
         assert!(res.is_err());
     }
diff --git a/src/test/ui/generator/resume-after-return.rs b/src/test/ui/generator/resume-after-return.rs
index 71a68ff684a..efed08bd470 100644
--- a/src/test/ui/generator/resume-after-return.rs
+++ b/src/test/ui/generator/resume-after-return.rs
@@ -16,12 +16,12 @@ fn main() {
         yield;
     };
 
-    match Pin::new(&mut foo).resume() {
+    match Pin::new(&mut foo).resume(()) {
         GeneratorState::Complete(()) => {}
         s => panic!("bad state: {:?}", s),
     }
 
-    match panic::catch_unwind(move || Pin::new(&mut foo).resume()) {
+    match panic::catch_unwind(move || Pin::new(&mut foo).resume(())) {
         Ok(_) => panic!("generator successfully resumed"),
         Err(_) => {}
     }
diff --git a/src/test/ui/generator/sized-yield.rs b/src/test/ui/generator/sized-yield.rs
index f64849b3149..c6dd738d6ac 100644
--- a/src/test/ui/generator/sized-yield.rs
+++ b/src/test/ui/generator/sized-yield.rs
@@ -9,6 +9,6 @@ fn main() {
    //~^ ERROR the size for values of type
        yield s[..];
    };
-   Pin::new(&mut gen).resume();
+   Pin::new(&mut gen).resume(());
    //~^ ERROR the size for values of type
 }
diff --git a/src/test/ui/generator/sized-yield.stderr b/src/test/ui/generator/sized-yield.stderr
index c2caac7ebe2..79aeec2ec02 100644
--- a/src/test/ui/generator/sized-yield.stderr
+++ b/src/test/ui/generator/sized-yield.stderr
@@ -15,7 +15,7 @@ LL | |    };
 error[E0277]: the size for values of type `str` cannot be known at compilation time
   --> $DIR/sized-yield.rs:12:23
    |
-LL |    Pin::new(&mut gen).resume();
+LL |    Pin::new(&mut gen).resume(());
    |                       ^^^^^^ doesn't have a size known at compile-time
    |
    = help: the trait `std::marker::Sized` is not implemented for `str`
diff --git a/src/test/ui/generator/smoke.rs b/src/test/ui/generator/smoke.rs
index 533f2399084..9289710b34b 100644
--- a/src/test/ui/generator/smoke.rs
+++ b/src/test/ui/generator/smoke.rs
@@ -17,7 +17,7 @@ fn simple() {
         }
     };
 
-    match Pin::new(&mut foo).resume() {
+    match Pin::new(&mut foo).resume(()) {
         GeneratorState::Complete(()) => {}
         s => panic!("bad state: {:?}", s),
     }
@@ -33,7 +33,7 @@ fn return_capture() {
         a
     };
 
-    match Pin::new(&mut foo).resume() {
+    match Pin::new(&mut foo).resume(()) {
         GeneratorState::Complete(ref s) if *s == "foo" => {}
         s => panic!("bad state: {:?}", s),
     }
@@ -45,11 +45,11 @@ fn simple_yield() {
         yield;
     };
 
-    match Pin::new(&mut foo).resume() {
+    match Pin::new(&mut foo).resume(()) {
         GeneratorState::Yielded(()) => {}
         s => panic!("bad state: {:?}", s),
     }
-    match Pin::new(&mut foo).resume() {
+    match Pin::new(&mut foo).resume(()) {
         GeneratorState::Complete(()) => {}
         s => panic!("bad state: {:?}", s),
     }
@@ -62,11 +62,11 @@ fn yield_capture() {
         yield b;
     };
 
-    match Pin::new(&mut foo).resume() {
+    match Pin::new(&mut foo).resume(()) {
         GeneratorState::Yielded(ref s) if *s == "foo" => {}
         s => panic!("bad state: {:?}", s),
     }
-    match Pin::new(&mut foo).resume() {
+    match Pin::new(&mut foo).resume(()) {
         GeneratorState::Complete(()) => {}
         s => panic!("bad state: {:?}", s),
     }
@@ -79,11 +79,11 @@ fn simple_yield_value() {
         return String::from("foo")
     };
 
-    match Pin::new(&mut foo).resume() {
+    match Pin::new(&mut foo).resume(()) {
         GeneratorState::Yielded(ref s) if *s == "bar" => {}
         s => panic!("bad state: {:?}", s),
     }
-    match Pin::new(&mut foo).resume() {
+    match Pin::new(&mut foo).resume(()) {
         GeneratorState::Complete(ref s) if *s == "foo" => {}
         s => panic!("bad state: {:?}", s),
     }
@@ -97,11 +97,11 @@ fn return_after_yield() {
         return a
     };
 
-    match Pin::new(&mut foo).resume() {
+    match Pin::new(&mut foo).resume(()) {
         GeneratorState::Yielded(()) => {}
         s => panic!("bad state: {:?}", s),
     }
-    match Pin::new(&mut foo).resume() {
+    match Pin::new(&mut foo).resume(()) {
         GeneratorState::Complete(ref s) if *s == "foo" => {}
         s => panic!("bad state: {:?}", s),
     }
@@ -149,11 +149,11 @@ fn send_and_sync() {
 fn send_over_threads() {
     let mut foo = || { yield };
     thread::spawn(move || {
-        match Pin::new(&mut foo).resume() {
+        match Pin::new(&mut foo).resume(()) {
             GeneratorState::Yielded(()) => {}
             s => panic!("bad state: {:?}", s),
         }
-        match Pin::new(&mut foo).resume() {
+        match Pin::new(&mut foo).resume(()) {
             GeneratorState::Complete(()) => {}
             s => panic!("bad state: {:?}", s),
         }
@@ -162,11 +162,11 @@ fn send_over_threads() {
     let a = String::from("a");
     let mut foo = || { yield a };
     thread::spawn(move || {
-        match Pin::new(&mut foo).resume() {
+        match Pin::new(&mut foo).resume(()) {
             GeneratorState::Yielded(ref s) if *s == "a" => {}
             s => panic!("bad state: {:?}", s),
         }
-        match Pin::new(&mut foo).resume() {
+        match Pin::new(&mut foo).resume(()) {
             GeneratorState::Complete(()) => {}
             s => panic!("bad state: {:?}", s),
         }
diff --git a/src/test/ui/generator/static-generators.rs b/src/test/ui/generator/static-generators.rs
index 965d3c61c22..3980766c428 100644
--- a/src/test/ui/generator/static-generators.rs
+++ b/src/test/ui/generator/static-generators.rs
@@ -15,6 +15,6 @@ fn main() {
     // Safety: We shadow the original generator variable so have no safe API to
     // move it after this point.
     let mut generator = unsafe { Pin::new_unchecked(&mut generator) };
-    assert_eq!(generator.as_mut().resume(), GeneratorState::Yielded(()));
-    assert_eq!(generator.as_mut().resume(), GeneratorState::Complete(()));
+    assert_eq!(generator.as_mut().resume(()), GeneratorState::Yielded(()));
+    assert_eq!(generator.as_mut().resume(()), GeneratorState::Complete(()));
 }
diff --git a/src/test/ui/generator/xcrate-reachable.rs b/src/test/ui/generator/xcrate-reachable.rs
index 9483ad7395e..1b1cff3387d 100644
--- a/src/test/ui/generator/xcrate-reachable.rs
+++ b/src/test/ui/generator/xcrate-reachable.rs
@@ -10,5 +10,5 @@ use std::ops::Generator;
 use std::pin::Pin;
 
 fn main() {
-    Pin::new(&mut foo::foo()).resume();
+    Pin::new(&mut foo::foo()).resume(());
 }
diff --git a/src/test/ui/generator/xcrate.rs b/src/test/ui/generator/xcrate.rs
index febf5c3583f..40986bbeb65 100644
--- a/src/test/ui/generator/xcrate.rs
+++ b/src/test/ui/generator/xcrate.rs
@@ -12,18 +12,18 @@ use std::pin::Pin;
 fn main() {
     let mut foo = xcrate::foo();
 
-    match Pin::new(&mut foo).resume() {
+    match Pin::new(&mut foo).resume(()) {
         GeneratorState::Complete(()) => {}
         s => panic!("bad state: {:?}", s),
     }
 
     let mut foo = xcrate::bar(3);
 
-    match Pin::new(&mut foo).resume() {
+    match Pin::new(&mut foo).resume(()) {
         GeneratorState::Yielded(3) => {}
         s => panic!("bad state: {:?}", s),
     }
-    match Pin::new(&mut foo).resume() {
+    match Pin::new(&mut foo).resume(()) {
         GeneratorState::Complete(()) => {}
         s => panic!("bad state: {:?}", s),
     }
diff --git a/src/test/ui/generator/yield-while-iterating.rs b/src/test/ui/generator/yield-while-iterating.rs
index e42781d1279..985e5d8bdc8 100644
--- a/src/test/ui/generator/yield-while-iterating.rs
+++ b/src/test/ui/generator/yield-while-iterating.rs
@@ -43,7 +43,7 @@ fn yield_during_iter_borrowed_slice_3() {
             yield p;
         }
     };
-    Pin::new(&mut b).resume();
+    Pin::new(&mut b).resume(());
 }
 
 fn yield_during_iter_borrowed_slice_4() {
@@ -56,7 +56,7 @@ fn yield_during_iter_borrowed_slice_4() {
         }
     };
     println!("{}", x[0]); //~ ERROR
-    Pin::new(&mut b).resume();
+    Pin::new(&mut b).resume(());
 }
 
 fn yield_during_range_iter() {
@@ -69,7 +69,7 @@ fn yield_during_range_iter() {
             yield x;
         }
     };
-    Pin::new(&mut b).resume();
+    Pin::new(&mut b).resume(());
 }
 
 fn main() { }
diff --git a/src/test/ui/generator/yield-while-iterating.stderr b/src/test/ui/generator/yield-while-iterating.stderr
index 6a96b25b19f..b6563475235 100644
--- a/src/test/ui/generator/yield-while-iterating.stderr
+++ b/src/test/ui/generator/yield-while-iterating.stderr
@@ -16,7 +16,7 @@ LL |         for p in &mut x {
 ...
 LL |     println!("{}", x[0]);
    |                    ^ immutable borrow occurs here
-LL |     Pin::new(&mut b).resume();
+LL |     Pin::new(&mut b).resume(());
    |              ------ mutable borrow later used here
 
 error: aborting due to 2 previous errors
diff --git a/src/test/ui/generator/yield-while-local-borrowed.rs b/src/test/ui/generator/yield-while-local-borrowed.rs
index b643bbf3376..061a64dbc36 100644
--- a/src/test/ui/generator/yield-while-local-borrowed.rs
+++ b/src/test/ui/generator/yield-while-local-borrowed.rs
@@ -15,7 +15,7 @@ fn borrow_local_inline() {
         yield();
         println!("{}", a);
     };
-    Pin::new(&mut b).resume();
+    Pin::new(&mut b).resume(());
 }
 
 fn borrow_local_inline_done() {
@@ -26,7 +26,7 @@ fn borrow_local_inline_done() {
         }
         yield();
     };
-    Pin::new(&mut b).resume();
+    Pin::new(&mut b).resume(());
 }
 
 fn borrow_local() {
@@ -43,7 +43,7 @@ fn borrow_local() {
             println!("{}", b);
         }
     };
-    Pin::new(&mut b).resume();
+    Pin::new(&mut b).resume(());
 }
 
 fn main() { }
diff --git a/src/test/ui/generator/yield-while-ref-reborrowed.rs b/src/test/ui/generator/yield-while-ref-reborrowed.rs
index f54a4f468f6..a03ef945dd2 100644
--- a/src/test/ui/generator/yield-while-ref-reborrowed.rs
+++ b/src/test/ui/generator/yield-while-ref-reborrowed.rs
@@ -12,7 +12,7 @@ fn reborrow_shared_ref(x: &i32) {
         yield();
         println!("{}", a);
     };
-    Pin::new(&mut b).resume();
+    Pin::new(&mut b).resume(());
 }
 
 fn reborrow_mutable_ref(x: &mut i32) {
@@ -23,7 +23,7 @@ fn reborrow_mutable_ref(x: &mut i32) {
         yield();
         println!("{}", a);
     };
-    Pin::new(&mut b).resume();
+    Pin::new(&mut b).resume(());
 }
 
 fn reborrow_mutable_ref_2(x: &mut i32) {
@@ -34,7 +34,7 @@ fn reborrow_mutable_ref_2(x: &mut i32) {
         println!("{}", a);
     };
     println!("{}", x); //~ ERROR
-    Pin::new(&mut b).resume();
+    Pin::new(&mut b).resume(());
 }
 
 fn main() { }
diff --git a/src/test/ui/generator/yield-while-ref-reborrowed.stderr b/src/test/ui/generator/yield-while-ref-reborrowed.stderr
index 4c37cd35173..fd885660d09 100644
--- a/src/test/ui/generator/yield-while-ref-reborrowed.stderr
+++ b/src/test/ui/generator/yield-while-ref-reborrowed.stderr
@@ -8,7 +8,7 @@ LL |         let a = &mut *x;
 ...
 LL |     println!("{}", x);
    |                    ^ second borrow occurs here
-LL |     Pin::new(&mut b).resume();
+LL |     Pin::new(&mut b).resume(());
    |              ------ first borrow later used here
 
 error: aborting due to previous error
diff --git a/src/test/ui/nll/issue-55850.rs b/src/test/ui/nll/issue-55850.rs
index a8f7299f899..e6279bd028e 100644
--- a/src/test/ui/nll/issue-55850.rs
+++ b/src/test/ui/nll/issue-55850.rs
@@ -15,7 +15,7 @@ where
     type Item = G::Yield;
 
     fn next(&mut self) -> Option<Self::Item> {
-        match Pin::new(&mut self.0).resume() {
+        match Pin::new(&mut self.0).resume(()) {
             Yielded(y) => Some(y),
             _ => None
         }