Add a couple helpers, make return types less confusing

Author: compiler-errors

compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs

@@ -305,15 +305,14 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_callable<'tcx>(
                     return Err(NoSolution);
                 }
 
-                sig.to_coroutine_given_kind_and_upvars(
+                coroutine_closure_to_certain_coroutine(
                     tcx,
-                    args.parent_args(),
-                    tcx.coroutine_for_closure(def_id),
                     goal_kind,
                     // No captures by ref, so this doesn't matter.
                     tcx.lifetimes.re_static,
-                    args.tupled_upvars_ty(),
-                    args.coroutine_captures_by_ref_ty(),
+                    def_id,
+                    args,
+                    sig,
                 )
             } else {
                 // Closure kind is not yet determined, so we return ambiguity unless
@@ -322,33 +321,13 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_callable<'tcx>(
                     return Ok(None);
                 }
 
-                let async_fn_kind_trait_def_id =
-                    tcx.require_lang_item(LangItem::AsyncFnKindHelper, None);
-                let upvars_projection_def_id = tcx
-                    .associated_items(async_fn_kind_trait_def_id)
-                    .filter_by_name_unhygienic(sym::Upvars)
-                    .next()
-                    .unwrap()
-                    .def_id;
-                let tupled_upvars_ty = Ty::new_projection(
-                    tcx,
-                    upvars_projection_def_id,
-                    [
-                        ty::GenericArg::from(kind_ty),
-                        Ty::from_closure_kind(tcx, goal_kind).into(),
-                        // No captures by ref, so this doesn't matter.
-                        tcx.lifetimes.re_static.into(),
-                        sig.tupled_inputs_ty.into(),
-                        args.tupled_upvars_ty().into(),
-                        args.coroutine_captures_by_ref_ty().into(),
-                    ],
-                );
-                sig.to_coroutine(
+                coroutine_closure_to_ambiguous_coroutine(
                     tcx,
-                    args.parent_args(),
-                    Ty::from_closure_kind(tcx, goal_kind),
-                    tcx.coroutine_for_closure(def_id),
-                    tupled_upvars_ty,
+                    goal_kind, // No captures by ref, so this doesn't matter.
+                    tcx.lifetimes.re_static,
+                    def_id,
+                    args,
+                    sig,
                 )
             };
 
@@ -385,6 +364,19 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_callable<'tcx>(
     }
 }
 
+/// Relevant types for an async callable, including its inputs, output,
+/// and the return type you get from awaiting the output.
+#[derive(Copy, Clone, Debug, TypeVisitable, TypeFoldable)]
+pub(in crate::solve) struct AsyncCallableRelevantTypes<'tcx> {
+    pub tupled_inputs_ty: Ty<'tcx>,
+    /// Type returned by calling the closure
+    /// i.e. `f()`.
+    pub output_coroutine_ty: Ty<'tcx>,
+    /// Type returned by `await`ing the output
+    /// i.e. `f().await`.
+    pub coroutine_return_ty: Ty<'tcx>,
+}
+
 // Returns a binder of the tupled inputs types, output type, and coroutine type
 // from a builtin coroutine-closure type. If we don't yet know the closure kind of
 // the coroutine-closure, emit an additional trait predicate for `AsyncFnKindHelper`
@@ -395,8 +387,10 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_async_callable<'tc
     self_ty: Ty<'tcx>,
     goal_kind: ty::ClosureKind,
     env_region: ty::Region<'tcx>,
-) -> Result<(ty::Binder<'tcx, (Ty<'tcx>, Ty<'tcx>, Ty<'tcx>)>, Vec<ty::Predicate<'tcx>>), NoSolution>
-{
+) -> Result<
+    (ty::Binder<'tcx, AsyncCallableRelevantTypes<'tcx>>, Vec<ty::Predicate<'tcx>>),
+    NoSolution,
+> {
     match *self_ty.kind() {
         ty::CoroutineClosure(def_id, args) => {
             let args = args.as_coroutine_closure();
@@ -407,24 +401,11 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_async_callable<'tc
                 if !closure_kind.extends(goal_kind) {
                     return Err(NoSolution);
                 }
-                sig.to_coroutine_given_kind_and_upvars(
-                    tcx,
-                    args.parent_args(),
-                    tcx.coroutine_for_closure(def_id),
-                    goal_kind,
-                    env_region,
-                    args.tupled_upvars_ty(),
-                    args.coroutine_captures_by_ref_ty(),
+
+                coroutine_closure_to_certain_coroutine(
+                    tcx, goal_kind, env_region, def_id, args, sig,
                 )
             } else {
-                let async_fn_kind_trait_def_id =
-                    tcx.require_lang_item(LangItem::AsyncFnKindHelper, None);
-                let upvars_projection_def_id = tcx
-                    .associated_items(async_fn_kind_trait_def_id)
-                    .filter_by_name_unhygienic(sym::Upvars)
-                    .next()
-                    .unwrap()
-                    .def_id;
                 // When we don't know the closure kind (and therefore also the closure's upvars,
                 // which are computed at the same time), we must delay the computation of the
                 // generator's upvars. We do this using the `AsyncFnKindHelper`, which as a trait
@@ -435,38 +416,23 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_async_callable<'tc
                 nested.push(
                     ty::TraitRef::new(
                         tcx,
-                        async_fn_kind_trait_def_id,
+                        tcx.require_lang_item(LangItem::AsyncFnKindHelper, None),
                         [kind_ty, Ty::from_closure_kind(tcx, goal_kind)],
                     )
                     .to_predicate(tcx),
                 );
-                let tupled_upvars_ty = Ty::new_projection(
-                    tcx,
-                    upvars_projection_def_id,
-                    [
-                        ty::GenericArg::from(kind_ty),
-                        Ty::from_closure_kind(tcx, goal_kind).into(),
-                        env_region.into(),
-                        sig.tupled_inputs_ty.into(),
-                        args.tupled_upvars_ty().into(),
-                        args.coroutine_captures_by_ref_ty().into(),
-                    ],
-                );
-                sig.to_coroutine(
-                    tcx,
-                    args.parent_args(),
-                    Ty::from_closure_kind(tcx, goal_kind),
-                    tcx.coroutine_for_closure(def_id),
-                    tupled_upvars_ty,
+
+                coroutine_closure_to_ambiguous_coroutine(
+                    tcx, goal_kind, env_region, def_id, args, sig,
                 )
             };
 
             Ok((
-                args.coroutine_closure_sig().rebind((
-                    sig.tupled_inputs_ty,
-                    sig.return_ty,
-                    coroutine_ty,
-                )),
+                args.coroutine_closure_sig().rebind(AsyncCallableRelevantTypes {
+                    tupled_inputs_ty: sig.tupled_inputs_ty,
+                    output_coroutine_ty: coroutine_ty,
+                    coroutine_return_ty: sig.return_ty,
+                }),
                 nested,
             ))
         }
@@ -490,7 +456,11 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_async_callable<'tc
                 .def_id;
             let future_output_ty = Ty::new_projection(tcx, future_output_def_id, [sig.output()]);
             Ok((
-                bound_sig.rebind((Ty::new_tup(tcx, sig.inputs()), sig.output(), future_output_ty)),
+                bound_sig.rebind(AsyncCallableRelevantTypes {
+                    tupled_inputs_ty: Ty::new_tup(tcx, sig.inputs()),
+                    output_coroutine_ty: sig.output(),
+                    coroutine_return_ty: future_output_ty,
+                }),
                 nested,
             ))
         }
@@ -541,7 +511,14 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_async_callable<'tc
                 .unwrap()
                 .def_id;
             let future_output_ty = Ty::new_projection(tcx, future_output_def_id, [sig.output()]);
-            Ok((bound_sig.rebind((sig.inputs()[0], sig.output(), future_output_ty)), nested))
+            Ok((
+                bound_sig.rebind(AsyncCallableRelevantTypes {
+                    tupled_inputs_ty: sig.inputs()[0],
+                    output_coroutine_ty: sig.output(),
+                    coroutine_return_ty: future_output_ty,
+                }),
+                nested,
+            ))
         }
 
         ty::Bool
@@ -574,6 +551,68 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_async_callable<'tc
     }
 }
 
+/// Given a coroutine-closure, project to its returned coroutine when we are *certain*
+/// that the closure's kind is compatible with the goal.
+fn coroutine_closure_to_certain_coroutine<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    goal_kind: ty::ClosureKind,
+    goal_region: ty::Region<'tcx>,
+    def_id: DefId,
+    args: ty::CoroutineClosureArgs<'tcx>,
+    sig: ty::CoroutineClosureSignature<'tcx>,
+) -> Ty<'tcx> {
+    sig.to_coroutine_given_kind_and_upvars(
+        tcx,
+        args.parent_args(),
+        tcx.coroutine_for_closure(def_id),
+        goal_kind,
+        goal_region,
+        args.tupled_upvars_ty(),
+        args.coroutine_captures_by_ref_ty(),
+    )
+}
+
+/// Given a coroutine-closure, project to its returned coroutine when we are *not certain*
+/// that the closure's kind is compatible with the goal, and therefore also don't know
+/// yet what the closure's upvars are.
+///
+/// Note that we do not also push a `AsyncFnKindHelper` goal here.
+fn coroutine_closure_to_ambiguous_coroutine<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    goal_kind: ty::ClosureKind,
+    goal_region: ty::Region<'tcx>,
+    def_id: DefId,
+    args: ty::CoroutineClosureArgs<'tcx>,
+    sig: ty::CoroutineClosureSignature<'tcx>,
+) -> Ty<'tcx> {
+    let async_fn_kind_trait_def_id = tcx.require_lang_item(LangItem::AsyncFnKindHelper, None);
+    let upvars_projection_def_id = tcx
+        .associated_items(async_fn_kind_trait_def_id)
+        .filter_by_name_unhygienic(sym::Upvars)
+        .next()
+        .unwrap()
+        .def_id;
+    let tupled_upvars_ty = Ty::new_projection(
+        tcx,
+        upvars_projection_def_id,
+        [
+            ty::GenericArg::from(args.kind_ty()),
+            Ty::from_closure_kind(tcx, goal_kind).into(),
+            goal_region.into(),
+            sig.tupled_inputs_ty.into(),
+            args.tupled_upvars_ty().into(),
+            args.coroutine_captures_by_ref_ty().into(),
+        ],
+    );
+    sig.to_coroutine(
+        tcx,
+        args.parent_args(),
+        Ty::from_closure_kind(tcx, goal_kind),
+        tcx.coroutine_for_closure(def_id),
+        tupled_upvars_ty,
+    )
+}
+
 /// Assemble a list of predicates that would be present on a theoretical
 /// user impl for an object type. These predicates must be checked any time
 /// we assemble a built-in object candidate for an object type, since they

compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs

@@ -1,5 +1,6 @@
 use crate::traits::{check_args_compatible, specialization_graph};
 
+use super::assembly::structural_traits::AsyncCallableRelevantTypes;
 use super::assembly::{self, structural_traits, Candidate};
 use super::{EvalCtxt, GoalSource};
 use rustc_hir::def::DefKind;
@@ -392,46 +393,56 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
                 goal_kind,
                 env_region,
             )?;
-        let output_is_sized_pred =
-            tupled_inputs_and_output_and_coroutine.map_bound(|(_, output, _)| {
-                ty::TraitRef::from_lang_item(tcx, LangItem::Sized, DUMMY_SP, [output])
-            });
+        let output_is_sized_pred = tupled_inputs_and_output_and_coroutine.map_bound(
+            |AsyncCallableRelevantTypes { output_coroutine_ty: output_ty, .. }| {
+                ty::TraitRef::from_lang_item(tcx, LangItem::Sized, DUMMY_SP, [output_ty])
+            },
+        );
 
         let pred = tupled_inputs_and_output_and_coroutine
-            .map_bound(|(inputs, output, coroutine)| {
-                let (projection_ty, term) = match tcx.item_name(goal.predicate.def_id()) {
-                    sym::CallOnceFuture => (
-                        ty::AliasTy::new(
-                            tcx,
-                            goal.predicate.def_id(),
-                            [goal.predicate.self_ty(), inputs],
+            .map_bound(
+                |AsyncCallableRelevantTypes {
+                     tupled_inputs_ty,
+                     output_coroutine_ty,
+                     coroutine_return_ty,
+                 }| {
+                    let (projection_ty, term) = match tcx.item_name(goal.predicate.def_id()) {
+                        sym::CallOnceFuture => (
+                            ty::AliasTy::new(
+                                tcx,
+                                goal.predicate.def_id(),
+                                [goal.predicate.self_ty(), tupled_inputs_ty],
+                            ),
+                            output_coroutine_ty.into(),
                         ),
-                        coroutine.into(),
-                    ),
-                    sym::CallMutFuture | sym::CallFuture => (
-                        ty::AliasTy::new(
-                            tcx,
-                            goal.predicate.def_id(),
-                            [
-                                ty::GenericArg::from(goal.predicate.self_ty()),
-                                inputs.into(),
-                                env_region.into(),
-                            ],
+                        sym::CallMutFuture | sym::CallFuture => (
+                            ty::AliasTy::new(
+                                tcx,
+                                goal.predicate.def_id(),
+                                [
+                                    ty::GenericArg::from(goal.predicate.self_ty()),
+                                    tupled_inputs_ty.into(),
+                                    env_region.into(),
+                                ],
+                            ),
+                            output_coroutine_ty.into(),
                         ),
-                        coroutine.into(),
-                    ),
-                    sym::Output => (
-                        ty::AliasTy::new(
-                            tcx,
-                            goal.predicate.def_id(),
-                            [ty::GenericArg::from(goal.predicate.self_ty()), inputs.into()],
+                        sym::Output => (
+                            ty::AliasTy::new(
+                                tcx,
+                                goal.predicate.def_id(),
+                                [
+                                    ty::GenericArg::from(goal.predicate.self_ty()),
+                                    tupled_inputs_ty.into(),
+                                ],
+                            ),
+                            coroutine_return_ty.into(),
                         ),
-                        output.into(),
-                    ),
-                    name => bug!("no such associated type: {name}"),
-                };
-                ty::ProjectionPredicate { projection_ty, term }
-            })
+                        name => bug!("no such associated type: {name}"),
+                    };
+                    ty::ProjectionPredicate { projection_ty, term }
+                },
+            )
             .to_predicate(tcx);
 
         // A built-in `AsyncFn` impl only holds if the output is sized.

compiler/rustc_trait_selection/src/solve/trait_goals.rs

@@ -2,6 +2,7 @@
 
 use crate::traits::supertrait_def_ids;
 
+use super::assembly::structural_traits::AsyncCallableRelevantTypes;
 use super::assembly::{self, structural_traits, Candidate};
 use super::{EvalCtxt, GoalSource, SolverMode};
 use rustc_data_structures::fx::FxIndexSet;
@@ -327,14 +328,19 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
                 // This region doesn't matter because we're throwing away the coroutine type
                 tcx.lifetimes.re_static,
             )?;
-        let output_is_sized_pred =
-            tupled_inputs_and_output_and_coroutine.map_bound(|(_, output, _)| {
-                ty::TraitRef::from_lang_item(tcx, LangItem::Sized, DUMMY_SP, [output])
-            });
+        let output_is_sized_pred = tupled_inputs_and_output_and_coroutine.map_bound(
+            |AsyncCallableRelevantTypes { output_coroutine_ty, .. }| {
+                ty::TraitRef::from_lang_item(tcx, LangItem::Sized, DUMMY_SP, [output_coroutine_ty])
+            },
+        );
 
         let pred = tupled_inputs_and_output_and_coroutine
-            .map_bound(|(inputs, _, _)| {
-                ty::TraitRef::new(tcx, goal.predicate.def_id(), [goal.predicate.self_ty(), inputs])
+            .map_bound(|AsyncCallableRelevantTypes { tupled_inputs_ty, .. }| {
+                ty::TraitRef::new(
+                    tcx,
+                    goal.predicate.def_id(),
+                    [goal.predicate.self_ty(), tupled_inputs_ty],
+                )
             })
             .to_predicate(tcx);
         // A built-in `AsyncFn` impl only holds if the output is sized.