Use map_bound(_ref) instead of Binder::bind when possible

5 files changed, 60 insertions, 40 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/auto_trait.rs b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
index e40067202e1..96a0c339e18 100644
--- a/compiler/rustc_trait_selection/src/traits/auto_trait.rs
+++ b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
@@ -642,7 +642,8 @@ impl AutoTraitFinder<'tcx> {
             // We check this by calling is_of_param on the relevant types
             // from the various possible predicates
 
-            match predicate.skip_binders() {
+            let bound_predicate = predicate.bound_atom(select.infcx().tcx);
+            match bound_predicate.skip_binder() {
                 ty::PredicateAtom::Trait(p, _) => {
                     if self.is_param_no_infer(p.trait_ref.substs)
                         && !only_projections
@@ -650,10 +651,10 @@ impl AutoTraitFinder<'tcx> {
                     {
                         self.add_user_pred(computed_preds, predicate);
                     }
-                    predicates.push_back(ty::Binder::bind(p));
+                    predicates.push_back(bound_predicate.map_bound_ref(|_| p));
                 }
                 ty::PredicateAtom::Projection(p) => {
-                    let p = ty::Binder::bind(p);
+                    let p = bound_predicate.map_bound_ref(|_| p);
                     debug!(
                         "evaluate_nested_obligations: examining projection predicate {:?}",
                         predicate
@@ -783,13 +784,13 @@ impl AutoTraitFinder<'tcx> {
                     }
                 }
                 ty::PredicateAtom::RegionOutlives(binder) => {
-                    let binder = ty::Binder::bind(binder);
+                    let binder = bound_predicate.map_bound_ref(|_| binder);
                     if select.infcx().region_outlives_predicate(&dummy_cause, binder).is_err() {
                         return false;
                     }
                 }
                 ty::PredicateAtom::TypeOutlives(binder) => {
-                    let binder = ty::Binder::bind(binder);
+                    let binder = bound_predicate.map_bound_ref(|_| binder);
                     match (
                         binder.no_bound_vars(),
                         binder.map_bound_ref(|pred| pred.0).no_bound_vars(),
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
index 05e3ed34351..3c4394e7d03 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
@@ -255,9 +255,10 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     return;
                 }
 
-                match obligation.predicate.skip_binders() {
+                let bound_predicate = obligation.predicate.bound_atom(self.tcx);
+                match bound_predicate.skip_binder() {
                     ty::PredicateAtom::Trait(trait_predicate, _) => {
-                        let trait_predicate = ty::Binder::bind(trait_predicate);
+                        let trait_predicate = bound_predicate.map_bound_ref(|_| trait_predicate);
                         let trait_predicate = self.resolve_vars_if_possible(&trait_predicate);
 
                         if self.tcx.sess.has_errors() && trait_predicate.references_error() {
@@ -531,7 +532,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     }
 
                     ty::PredicateAtom::RegionOutlives(predicate) => {
-                        let predicate = ty::Binder::bind(predicate);
+                        let predicate = bound_predicate.map_bound_ref(|_| predicate);
                         let predicate = self.resolve_vars_if_possible(&predicate);
                         let err = self
                             .region_outlives_predicate(&obligation.cause, predicate)
@@ -1078,9 +1079,10 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
         }
 
         // FIXME: It should be possible to deal with `ForAll` in a cleaner way.
-        let (cond, error) = match (cond.skip_binders(), error.skip_binders()) {
+        let bound_error = error.bound_atom(self.tcx);
+        let (cond, error) = match (cond.skip_binders(), bound_error.skip_binder()) {
             (ty::PredicateAtom::Trait(..), ty::PredicateAtom::Trait(error, _)) => {
-                (cond, ty::Binder::bind(error))
+                (cond, bound_error.map_bound_ref(|_| error))
             }
             _ => {
                 // FIXME: make this work in other cases too.
@@ -1089,9 +1091,10 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
         };
 
         for obligation in super::elaborate_predicates(self.tcx, std::iter::once(cond)) {
-            if let ty::PredicateAtom::Trait(implication, _) = obligation.predicate.skip_binders() {
+            let bound_predicate = obligation.predicate.bound_atom(self.tcx);
+            if let ty::PredicateAtom::Trait(implication, _) = bound_predicate.skip_binder() {
                 let error = error.to_poly_trait_ref();
-                let implication = ty::Binder::bind(implication.trait_ref);
+                let implication = bound_predicate.map_bound_ref(|_| implication.trait_ref);
                 // FIXME: I'm just not taking associated types at all here.
                 // Eventually I'll need to implement param-env-aware
                 // `Γ₁ ⊦ φ₁ => Γ₂ ⊦ φ₂` logic.
@@ -1169,12 +1172,13 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
             //
             // this can fail if the problem was higher-ranked, in which
             // cause I have no idea for a good error message.
-            if let ty::PredicateAtom::Projection(data) = predicate.skip_binders() {
+            let bound_predicate = predicate.bound_atom(self.tcx);
+            if let ty::PredicateAtom::Projection(data) = bound_predicate.skip_binder() {
                 let mut selcx = SelectionContext::new(self);
                 let (data, _) = self.replace_bound_vars_with_fresh_vars(
                     obligation.cause.span,
                     infer::LateBoundRegionConversionTime::HigherRankedType,
-                    &ty::Binder::bind(data),
+                    &bound_predicate.map_bound_ref(|_| data),
                 );
                 let mut obligations = vec![];
                 let normalized_ty = super::normalize_projection_type(
@@ -1455,10 +1459,11 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
             return;
         }
 
-        let mut err = match predicate.skip_binders() {
+        let bound_predicate = predicate.bound_atom(self.tcx);
+        let mut err = match bound_predicate.skip_binder() {
             ty::PredicateAtom::Trait(data, _) => {
-                let trait_ref = ty::Binder::bind(data.trait_ref);
-                let self_ty = trait_ref.skip_binder().self_ty();
+                let self_ty = data.trait_ref.self_ty();
+                let trait_ref = bound_predicate.map_bound_ref(|_| data.trait_ref);
                 debug!("self_ty {:?} {:?} trait_ref {:?}", self_ty, self_ty.kind(), trait_ref);
 
                 if predicate.references_error() {
@@ -1582,7 +1587,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
                 self.emit_inference_failure_err(body_id, span, a.into(), ErrorCode::E0282)
             }
             ty::PredicateAtom::Projection(data) => {
-                let trait_ref = ty::Binder::bind(data).to_poly_trait_ref(self.tcx);
+                let trait_ref = bound_predicate.map_bound_ref(|_| data).to_poly_trait_ref(self.tcx);
                 let self_ty = trait_ref.skip_binder().self_ty();
                 let ty = data.ty;
                 if predicate.references_error() {
diff --git a/compiler/rustc_trait_selection/src/traits/fulfill.rs b/compiler/rustc_trait_selection/src/traits/fulfill.rs
index 97dd180b27b..01217457eb4 100644
--- a/compiler/rustc_trait_selection/src/traits/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/traits/fulfill.rs
@@ -353,7 +353,7 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
                 // This means we need to pass it the bound version of our
                 // predicate.
                 ty::PredicateAtom::Trait(trait_ref, _constness) => {
-                    let trait_obligation = obligation.with(Binder::bind(trait_ref));
+                    let trait_obligation = obligation.with(binder.map_bound_ref(|_| trait_ref));
 
                     self.process_trait_obligation(
                         obligation,
@@ -362,7 +362,7 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
                     )
                 }
                 ty::PredicateAtom::Projection(data) => {
-                    let project_obligation = obligation.with(Binder::bind(data));
+                    let project_obligation = obligation.with(binder.map_bound_ref(|_| data));
 
                     self.process_projection_obligation(
                         project_obligation,
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 8dbf7ec51c6..295ba6041fb 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -623,7 +623,8 @@ fn prune_cache_value_obligations<'a, 'tcx>(
         .obligations
         .iter()
         .filter(|obligation| {
-            match obligation.predicate.skip_binders() {
+            let bound_predicate = obligation.predicate.bound_atom(infcx.tcx);
+            match bound_predicate.skip_binder() {
                 // We found a `T: Foo<X = U>` predicate, let's check
                 // if `U` references any unresolved type
                 // variables. In principle, we only care if this
@@ -633,9 +634,9 @@ fn prune_cache_value_obligations<'a, 'tcx>(
                 // indirect obligations (e.g., we project to `?0`,
                 // but we have `T: Foo<X = ?1>` and `?1: Bar<X =
                 // ?0>`).
-                ty::PredicateAtom::Projection(data) => {
-                    infcx.unresolved_type_vars(&ty::Binder::bind(data.ty)).is_some()
-                }
+                ty::PredicateAtom::Projection(data) => infcx
+                    .unresolved_type_vars(&bound_predicate.map_bound_ref(|_| data.ty))
+                    .is_some(),
 
                 // We are only interested in `T: Foo<X = U>` predicates, whre
                 // `U` references one of `unresolved_type_vars`. =)
@@ -907,8 +908,9 @@ fn assemble_candidates_from_predicates<'cx, 'tcx>(
     let infcx = selcx.infcx();
     for predicate in env_predicates {
         debug!(?predicate);
+        let bound_predicate = predicate.bound_atom(infcx.tcx);
         if let ty::PredicateAtom::Projection(data) = predicate.skip_binders() {
-            let data = ty::Binder::bind(data);
+            let data = bound_predicate.map_bound_ref(|_| data);
             let same_def_id = data.projection_def_id() == obligation.predicate.item_def_id;
 
             let is_match = same_def_id
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 4d347380c6c..29c9c29d208 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -449,16 +449,17 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         }
 
         let result = ensure_sufficient_stack(|| {
-            match obligation.predicate.skip_binders() {
+            let bound_predicate = obligation.predicate.bound_atom(self.infcx().tcx);
+            match bound_predicate.skip_binder() {
                 ty::PredicateAtom::Trait(t, _) => {
-                    let t = ty::Binder::bind(t);
+                    let t = bound_predicate.map_bound_ref(|_| t);
                     debug_assert!(!t.has_escaping_bound_vars());
                     let obligation = obligation.with(t);
                     self.evaluate_trait_predicate_recursively(previous_stack, obligation)
                 }
 
                 ty::PredicateAtom::Subtype(p) => {
-                    let p = ty::Binder::bind(p);
+                    let p = bound_predicate.map_bound_ref(|_| p);
                     // Does this code ever run?
                     match self.infcx.subtype_predicate(&obligation.cause, obligation.param_env, p) {
                         Some(Ok(InferOk { mut obligations, .. })) => {
@@ -502,7 +503,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 }
 
                 ty::PredicateAtom::Projection(data) => {
-                    let data = ty::Binder::bind(data);
+                    let data = bound_predicate.map_bound_ref(|_| data);
                     let project_obligation = obligation.with(data);
                     match project::poly_project_and_unify_type(self, &project_obligation) {
                         Ok(Ok(Some(mut subobligations))) => {
@@ -1174,8 +1175,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             .iter()
             .enumerate()
             .filter_map(|(idx, bound)| {
-                if let ty::PredicateAtom::Trait(pred, _) = bound.skip_binders() {
-                    let bound = ty::Binder::bind(pred.trait_ref);
+                let bound_predicate = bound.bound_atom(self.infcx.tcx);
+                if let ty::PredicateAtom::Trait(pred, _) = bound_predicate.skip_binder() {
+                    let bound = bound_predicate.map_bound_ref(|_| pred.trait_ref);
                     if self.infcx.probe(|_| {
                         match self.match_projection(
                             obligation,
@@ -1529,16 +1531,18 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
             ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => None,
 
-            ty::Tuple(tys) => {
-                Where(ty::Binder::bind(tys.last().into_iter().map(|k| k.expect_ty()).collect()))
-            }
+            ty::Tuple(tys) => Where(
+                obligation
+                    .predicate
+                    .map_bound_ref(|_| tys.last().into_iter().map(|k| k.expect_ty()).collect()),
+            ),
 
             ty::Adt(def, substs) => {
                 let sized_crit = def.sized_constraint(self.tcx());
                 // (*) binder moved here
-                Where(ty::Binder::bind(
-                    sized_crit.iter().map(|ty| ty.subst(self.tcx(), substs)).collect(),
-                ))
+                Where(obligation.predicate.map_bound_ref(|_| {
+                    sized_crit.iter().map(|ty| ty.subst(self.tcx(), substs)).collect()
+                }))
             }
 
             ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => None,
@@ -1590,12 +1594,16 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
             ty::Array(element_ty, _) => {
                 // (*) binder moved here
-                Where(ty::Binder::bind(vec![element_ty]))
+                Where(obligation.predicate.map_bound_ref(|_| vec![*element_ty]))
             }
 
             ty::Tuple(tys) => {
                 // (*) binder moved here
-                Where(ty::Binder::bind(tys.iter().map(|k| k.expect_ty()).collect()))
+                Where(
+                    obligation
+                        .predicate
+                        .map_bound_ref(|_| tys.iter().map(|k| k.expect_ty()).collect()),
+                )
             }
 
             ty::Closure(_, substs) => {
@@ -1605,7 +1613,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     // Not yet resolved.
                     Ambiguous
                 } else {
-                    Where(ty::Binder::bind(substs.as_closure().upvar_tys().collect()))
+                    Where(
+                        obligation
+                            .predicate
+                            .map_bound_ref(|_| substs.as_closure().upvar_tys().collect()),
+                    )
                 }
             }