From eba10270c6b7927672da6e73f58ec80afff4a2d6 Mon Sep 17 00:00:00 2001
From: Jack Huey <jack.huey@umassmed.edu>
Date: Fri, 16 Oct 2020 14:04:11 -0400
Subject: [PATCH] map_bound_ref -> rebind

---
 compiler/rustc_infer/src/infer/combine.rs     |  6 ++--
 .../rustc_infer/src/infer/nll_relate/mod.rs   |  2 +-
 compiler/rustc_infer/src/traits/util.rs       |  2 +-
 compiler/rustc_middle/src/ty/_match.rs        |  3 +-
 compiler/rustc_middle/src/ty/print/pretty.rs  |  2 +-
 .../rustc_middle/src/ty/structural_impls.rs   |  2 +-
 compiler/rustc_middle/src/ty/sty.rs           | 22 +++++++-----
 .../src/traits/auto_trait.rs                  |  8 ++---
 .../src/traits/error_reporting/mod.rs         | 14 ++++----
 .../src/traits/fulfill.rs                     |  4 +--
 .../src/traits/project.rs                     |  8 ++---
 .../src/traits/select/mod.rs                  | 35 ++++++++-----------
 compiler/rustc_typeck/src/astconv/mod.rs      |  4 +--
 compiler/rustc_typeck/src/check/closure.rs    |  2 +-
 compiler/rustc_typeck/src/check/coercion.rs   |  2 +-
 compiler/rustc_typeck/src/check/dropck.rs     | 12 +++----
 .../rustc_typeck/src/check/method/probe.rs    |  2 +-
 .../rustc_typeck/src/check/method/suggest.rs  |  2 +-
 compiler/rustc_typeck/src/check/mod.rs        |  2 +-
 src/librustdoc/clean/auto_trait.rs            | 14 ++++----
 src/librustdoc/clean/mod.rs                   |  7 ++--
 21 files changed, 77 insertions(+), 78 deletions(-)

diff --git a/compiler/rustc_infer/src/infer/combine.rs b/compiler/rustc_infer/src/infer/combine.rs
index afa6a2a8166a..6a1715ef8189 100644
--- a/compiler/rustc_infer/src/infer/combine.rs
+++ b/compiler/rustc_infer/src/infer/combine.rs
@@ -551,8 +551,7 @@ impl TypeRelation<'tcx> for Generalizer<'_, 'tcx> {
     where
         T: Relate<'tcx>,
     {
-        let result = self.relate(a.skip_binder(), b.skip_binder())?;
-        Ok(a.map_bound(|_| result))
+        Ok(ty::Binder::bind(self.relate(a.skip_binder(), b.skip_binder())?))
     }
 
     fn relate_item_substs(
@@ -834,8 +833,7 @@ impl TypeRelation<'tcx> for ConstInferUnifier<'_, 'tcx> {
     where
         T: Relate<'tcx>,
     {
-        let result = self.relate(a.skip_binder(), b.skip_binder())?;
-        Ok(a.map_bound(|_| result))
+        Ok(ty::Binder::bind(self.relate(a.skip_binder(), b.skip_binder())?))
     }
 
     fn tys(&mut self, t: Ty<'tcx>, _t: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
diff --git a/compiler/rustc_infer/src/infer/nll_relate/mod.rs b/compiler/rustc_infer/src/infer/nll_relate/mod.rs
index b1ec7a7902db..abdd6edea902 100644
--- a/compiler/rustc_infer/src/infer/nll_relate/mod.rs
+++ b/compiler/rustc_infer/src/infer/nll_relate/mod.rs
@@ -1004,6 +1004,6 @@ where
         self.first_free_index.shift_in(1);
         let result = self.relate(a.skip_binder(), a.skip_binder())?;
         self.first_free_index.shift_out(1);
-        Ok(a.map_bound(|_| result))
+        Ok(ty::Binder::bind(result))
     }
 }
diff --git a/compiler/rustc_infer/src/traits/util.rs b/compiler/rustc_infer/src/traits/util.rs
index 043d24c9767d..2116c2365263 100644
--- a/compiler/rustc_infer/src/traits/util.rs
+++ b/compiler/rustc_infer/src/traits/util.rs
@@ -134,7 +134,7 @@ impl Elaborator<'tcx> {
 
                 let obligations = predicates.predicates.iter().map(|&(pred, _)| {
                     predicate_obligation(
-                        pred.subst_supertrait(tcx, &bound_predicate.map_bound(|_| data.trait_ref)),
+                        pred.subst_supertrait(tcx, &bound_predicate.rebind(data.trait_ref)),
                         obligation.param_env,
                         obligation.cause.clone(),
                     )
diff --git a/compiler/rustc_middle/src/ty/_match.rs b/compiler/rustc_middle/src/ty/_match.rs
index 5f5593eb0d81..27bccc0bcafa 100644
--- a/compiler/rustc_middle/src/ty/_match.rs
+++ b/compiler/rustc_middle/src/ty/_match.rs
@@ -118,7 +118,6 @@ impl TypeRelation<'tcx> for Match<'tcx> {
     where
         T: Relate<'tcx>,
     {
-        let result = self.relate(a.skip_binder(), b.skip_binder())?;
-        Ok(a.map_bound(|_| result))
+        Ok(ty::Binder::bind(self.relate(a.skip_binder(), b.skip_binder())?))
     }
 }
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index eaddfefb8e5f..acdf1f642ab9 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -620,7 +620,7 @@ pub trait PrettyPrinter<'tcx>:
                         // FIXME(lcnr): Find out why exactly this is the case :)
                         let bound_predicate = predicate.bound_atom_with_opt_escaping(self.tcx());
                         if let ty::PredicateAtom::Trait(pred, _) = bound_predicate.skip_binder() {
-                            let trait_ref = bound_predicate.map_bound(|_| pred.trait_ref);
+                            let trait_ref = bound_predicate.rebind(pred.trait_ref);
                             // Don't print +Sized, but rather +?Sized if absent.
                             if Some(trait_ref.def_id()) == self.tcx().lang_items().sized_trait() {
                                 is_sized = true;
diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index 5f326d700ee0..15803dbd8429 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -549,7 +549,7 @@ impl<'a, 'tcx> Lift<'tcx> for ty::PredicateAtom<'a> {
 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::Binder<T> {
     type Lifted = ty::Binder<T::Lifted>;
     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
-        tcx.lift(self.as_ref().skip_binder()).map(|v| self.map_bound_ref(|_| v))
+        tcx.lift(self.as_ref().skip_binder()).map(|v| self.rebind(v))
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 932cadee1003..fd2c7dd5b5ab 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -702,16 +702,14 @@ impl<'tcx> Binder<ExistentialPredicate<'tcx>> {
     pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Predicate<'tcx> {
         use crate::ty::ToPredicate;
         match self.skip_binder() {
-            ExistentialPredicate::Trait(tr) => self
-                .map_bound_ref(|_| tr)
-                .with_self_ty(tcx, self_ty)
-                .without_const()
-                .to_predicate(tcx),
+            ExistentialPredicate::Trait(tr) => {
+                self.rebind(tr).with_self_ty(tcx, self_ty).without_const().to_predicate(tcx)
+            }
             ExistentialPredicate::Projection(p) => {
-                self.map_bound_ref(|_| p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
+                self.rebind(p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
             }
             ExistentialPredicate::AutoTrait(did) => {
-                let trait_ref = self.map_bound_ref(|_| ty::TraitRef {
+                let trait_ref = self.rebind(ty::TraitRef {
                     def_id: did,
                     substs: tcx.mk_substs_trait(self_ty, &[]),
                 });
@@ -779,7 +777,7 @@ impl<'tcx> List<ExistentialPredicate<'tcx>> {
 
 impl<'tcx> Binder<&'tcx List<ExistentialPredicate<'tcx>>> {
     pub fn principal(&self) -> Option<ty::Binder<ExistentialTraitRef<'tcx>>> {
-        self.map_bound_ref(|b| b.principal()).transpose()
+        self.map_bound(|b| b.principal()).transpose()
     }
 
     pub fn principal_def_id(&self) -> Option<DefId> {
@@ -1004,6 +1002,14 @@ impl<T> Binder<T> {
         Binder(f(self.0))
     }
 
+    /// Wraps a `value` in a binder, using the same bound variables as the
+    /// current `Binder`. This should not be used if the new value *changes*
+    /// the bound variables. Note: the (old or new) value itself does not
+    /// necessarily need to *name* all the bound variables.
+    pub fn rebind<U>(&self, value: U) -> Binder<U> {
+        Binder(value)
+    }
+
     /// Unwraps and returns the value within, but only if it contains
     /// no bound vars at all. (In other words, if this binder --
     /// and indeed any enclosing binder -- doesn't bind anything at
diff --git a/compiler/rustc_trait_selection/src/traits/auto_trait.rs b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
index 96a0c339e185..867ecea04e42 100644
--- a/compiler/rustc_trait_selection/src/traits/auto_trait.rs
+++ b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
@@ -651,10 +651,10 @@ impl AutoTraitFinder<'tcx> {
                     {
                         self.add_user_pred(computed_preds, predicate);
                     }
-                    predicates.push_back(bound_predicate.map_bound_ref(|_| p));
+                    predicates.push_back(bound_predicate.rebind(p));
                 }
                 ty::PredicateAtom::Projection(p) => {
-                    let p = bound_predicate.map_bound_ref(|_| p);
+                    let p = bound_predicate.rebind(p);
                     debug!(
                         "evaluate_nested_obligations: examining projection predicate {:?}",
                         predicate
@@ -784,13 +784,13 @@ impl AutoTraitFinder<'tcx> {
                     }
                 }
                 ty::PredicateAtom::RegionOutlives(binder) => {
-                    let binder = bound_predicate.map_bound_ref(|_| binder);
+                    let binder = bound_predicate.rebind(binder);
                     if select.infcx().region_outlives_predicate(&dummy_cause, binder).is_err() {
                         return false;
                     }
                 }
                 ty::PredicateAtom::TypeOutlives(binder) => {
-                    let binder = bound_predicate.map_bound_ref(|_| binder);
+                    let binder = bound_predicate.rebind(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 3c4394e7d034..2b95da4c5b96 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
@@ -258,7 +258,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 let bound_predicate = obligation.predicate.bound_atom(self.tcx);
                 match bound_predicate.skip_binder() {
                     ty::PredicateAtom::Trait(trait_predicate, _) => {
-                        let trait_predicate = bound_predicate.map_bound_ref(|_| trait_predicate);
+                        let trait_predicate = bound_predicate.rebind(trait_predicate);
                         let trait_predicate = self.resolve_vars_if_possible(&trait_predicate);
 
                         if self.tcx.sess.has_errors() && trait_predicate.references_error() {
@@ -532,7 +532,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     }
 
                     ty::PredicateAtom::RegionOutlives(predicate) => {
-                        let predicate = bound_predicate.map_bound_ref(|_| predicate);
+                        let predicate = bound_predicate.rebind(predicate);
                         let predicate = self.resolve_vars_if_possible(&predicate);
                         let err = self
                             .region_outlives_predicate(&obligation.cause, predicate)
@@ -1082,7 +1082,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
         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, bound_error.map_bound_ref(|_| error))
+                (cond, bound_error.rebind(error))
             }
             _ => {
                 // FIXME: make this work in other cases too.
@@ -1094,7 +1094,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
             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 = bound_predicate.map_bound_ref(|_| implication.trait_ref);
+                let implication = bound_predicate.rebind(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.
@@ -1178,7 +1178,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
                 let (data, _) = self.replace_bound_vars_with_fresh_vars(
                     obligation.cause.span,
                     infer::LateBoundRegionConversionTime::HigherRankedType,
-                    &bound_predicate.map_bound_ref(|_| data),
+                    &bound_predicate.rebind(data),
                 );
                 let mut obligations = vec![];
                 let normalized_ty = super::normalize_projection_type(
@@ -1463,7 +1463,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
         let mut err = match bound_predicate.skip_binder() {
             ty::PredicateAtom::Trait(data, _) => {
                 let self_ty = data.trait_ref.self_ty();
-                let trait_ref = bound_predicate.map_bound_ref(|_| data.trait_ref);
+                let trait_ref = bound_predicate.rebind(data.trait_ref);
                 debug!("self_ty {:?} {:?} trait_ref {:?}", self_ty, self_ty.kind(), trait_ref);
 
                 if predicate.references_error() {
@@ -1587,7 +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 = bound_predicate.map_bound_ref(|_| data).to_poly_trait_ref(self.tcx);
+                let trait_ref = bound_predicate.rebind(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 01217457eb4b..495a250be7c1 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.map_bound_ref(|_| trait_ref));
+                    let trait_obligation = obligation.with(binder.rebind(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.map_bound_ref(|_| data));
+                    let project_obligation = obligation.with(binder.rebind(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 295ba6041fb9..63e1fe4a38a9 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -634,9 +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(&bound_predicate.map_bound_ref(|_| data.ty))
-                    .is_some(),
+                ty::PredicateAtom::Projection(data) => {
+                    infcx.unresolved_type_vars(&bound_predicate.rebind(data.ty)).is_some()
+                }
 
                 // We are only interested in `T: Foo<X = U>` predicates, whre
                 // `U` references one of `unresolved_type_vars`. =)
@@ -910,7 +910,7 @@ fn assemble_candidates_from_predicates<'cx, 'tcx>(
         debug!(?predicate);
         let bound_predicate = predicate.bound_atom(infcx.tcx);
         if let ty::PredicateAtom::Projection(data) = predicate.skip_binders() {
-            let data = bound_predicate.map_bound_ref(|_| data);
+            let data = bound_predicate.rebind(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 29c9c29d2089..d0f1af253eb3 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -449,17 +449,18 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         }
 
         let result = ensure_sufficient_stack(|| {
-            let bound_predicate = obligation.predicate.bound_atom(self.infcx().tcx);
+            let bound_predicate =
+                obligation.predicate.bound_atom_with_opt_escaping(self.infcx().tcx);
             match bound_predicate.skip_binder() {
                 ty::PredicateAtom::Trait(t, _) => {
-                    let t = bound_predicate.map_bound_ref(|_| t);
+                    let t = bound_predicate.rebind(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 = bound_predicate.map_bound_ref(|_| p);
+                    let p = bound_predicate.rebind(p);
                     // Does this code ever run?
                     match self.infcx.subtype_predicate(&obligation.cause, obligation.param_env, p) {
                         Some(Ok(InferOk { mut obligations, .. })) => {
@@ -503,7 +504,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 }
 
                 ty::PredicateAtom::Projection(data) => {
-                    let data = bound_predicate.map_bound_ref(|_| data);
+                    let data = bound_predicate.rebind(data);
                     let project_obligation = obligation.with(data);
                     match project::poly_project_and_unify_type(self, &project_obligation) {
                         Ok(Ok(Some(mut subobligations))) => {
@@ -1177,7 +1178,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             .filter_map(|(idx, bound)| {
                 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);
+                    let bound = bound_predicate.rebind(pred.trait_ref);
                     if self.infcx.probe(|_| {
                         match self.match_projection(
                             obligation,
@@ -1534,15 +1535,17 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             ty::Tuple(tys) => Where(
                 obligation
                     .predicate
-                    .map_bound_ref(|_| tys.last().into_iter().map(|k| k.expect_ty()).collect()),
+                    .rebind(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(obligation.predicate.map_bound_ref(|_| {
-                    sized_crit.iter().map(|ty| ty.subst(self.tcx(), substs)).collect()
-                }))
+                Where(
+                    obligation.predicate.rebind({
+                        sized_crit.iter().map(|ty| ty.subst(self.tcx(), substs)).collect()
+                    }),
+                )
             }
 
             ty::Projection(_) | ty::Param(_) | ty::Opaque(..) => None,
@@ -1594,16 +1597,12 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
             ty::Array(element_ty, _) => {
                 // (*) binder moved here
-                Where(obligation.predicate.map_bound_ref(|_| vec![*element_ty]))
+                Where(obligation.predicate.rebind(vec![*element_ty]))
             }
 
             ty::Tuple(tys) => {
                 // (*) binder moved here
-                Where(
-                    obligation
-                        .predicate
-                        .map_bound_ref(|_| tys.iter().map(|k| k.expect_ty()).collect()),
-                )
+                Where(obligation.predicate.rebind(tys.iter().map(|k| k.expect_ty()).collect()))
             }
 
             ty::Closure(_, substs) => {
@@ -1613,11 +1612,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     // Not yet resolved.
                     Ambiguous
                 } else {
-                    Where(
-                        obligation
-                            .predicate
-                            .map_bound_ref(|_| substs.as_closure().upvar_tys().collect()),
-                    )
+                    Where(obligation.predicate.rebind(substs.as_closure().upvar_tys().collect()))
                 }
             }
 
diff --git a/compiler/rustc_typeck/src/astconv/mod.rs b/compiler/rustc_typeck/src/astconv/mod.rs
index cea7eaec9a71..7674259b8fe4 100644
--- a/compiler/rustc_typeck/src/astconv/mod.rs
+++ b/compiler/rustc_typeck/src/astconv/mod.rs
@@ -1098,7 +1098,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 let bound_predicate = obligation.predicate.bound_atom(tcx);
                 match bound_predicate.skip_binder() {
                     ty::PredicateAtom::Trait(pred, _) => {
-                        let pred = bound_predicate.map_bound_ref(|_| pred);
+                        let pred = bound_predicate.rebind(pred);
                         associated_types.entry(span).or_default().extend(
                             tcx.associated_items(pred.def_id())
                                 .in_definition_order()
@@ -1107,7 +1107,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         );
                     }
                     ty::PredicateAtom::Projection(pred) => {
-                        let pred = bound_predicate.map_bound_ref(|_| pred);
+                        let pred = bound_predicate.rebind(pred);
                         // A `Self` within the original bound will be substituted with a
                         // `trait_object_dummy_self`, so check for that.
                         let references_self =
diff --git a/compiler/rustc_typeck/src/check/closure.rs b/compiler/rustc_typeck/src/check/closure.rs
index 500cc92921b9..5b42a9c4c0bc 100644
--- a/compiler/rustc_typeck/src/check/closure.rs
+++ b/compiler/rustc_typeck/src/check/closure.rs
@@ -200,7 +200,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // the complete signature.
                     self.deduce_sig_from_projection(
                         Some(obligation.cause.span),
-                        bound_predicate.map_bound_ref(|_| proj_predicate),
+                        bound_predicate.rebind(proj_predicate),
                     )
                 } else {
                     None
diff --git a/compiler/rustc_typeck/src/check/coercion.rs b/compiler/rustc_typeck/src/check/coercion.rs
index 0eb5593e8bd7..53ad10020629 100644
--- a/compiler/rustc_typeck/src/check/coercion.rs
+++ b/compiler/rustc_typeck/src/check/coercion.rs
@@ -595,7 +595,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
                             has_unsized_tuple_coercion = true;
                         }
                     }
-                    bound_predicate.map_bound_ref(|_| trait_pred)
+                    bound_predicate.rebind(trait_pred)
                 }
                 _ => {
                     coercion.obligations.push(obligation);
diff --git a/compiler/rustc_typeck/src/check/dropck.rs b/compiler/rustc_typeck/src/check/dropck.rs
index c777b87d4886..9fcb3a8cdfda 100644
--- a/compiler/rustc_typeck/src/check/dropck.rs
+++ b/compiler/rustc_typeck/src/check/dropck.rs
@@ -229,12 +229,12 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
             let bound_predicate = predicate.bound_atom(tcx);
             let bound_p = p.bound_atom(tcx);
             match (predicate.skip_binders(), p.skip_binders()) {
-                (ty::PredicateAtom::Trait(a, _), ty::PredicateAtom::Trait(b, _)) => relator
-                    .relate(bound_predicate.map_bound_ref(|_| a), bound_p.map_bound_ref(|_| b))
-                    .is_ok(),
-                (ty::PredicateAtom::Projection(a), ty::PredicateAtom::Projection(b)) => relator
-                    .relate(bound_predicate.map_bound_ref(|_| a), bound_p.map_bound_ref(|_| b))
-                    .is_ok(),
+                (ty::PredicateAtom::Trait(a, _), ty::PredicateAtom::Trait(b, _)) => {
+                    relator.relate(bound_predicate.rebind(a), bound_p.rebind(b)).is_ok()
+                }
+                (ty::PredicateAtom::Projection(a), ty::PredicateAtom::Projection(b)) => {
+                    relator.relate(bound_predicate.rebind(a), bound_p.rebind(b)).is_ok()
+                }
                 _ => predicate == p,
             }
         };
diff --git a/compiler/rustc_typeck/src/check/method/probe.rs b/compiler/rustc_typeck/src/check/method/probe.rs
index e6e7e229f888..a70705bd85a0 100644
--- a/compiler/rustc_typeck/src/check/method/probe.rs
+++ b/compiler/rustc_typeck/src/check/method/probe.rs
@@ -803,7 +803,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 ty::PredicateAtom::Trait(trait_predicate, _) => {
                     match trait_predicate.trait_ref.self_ty().kind() {
                         ty::Param(ref p) if *p == param_ty => {
-                            Some(bound_predicate.map_bound_ref(|_| trait_predicate.trait_ref))
+                            Some(bound_predicate.rebind(trait_predicate.trait_ref))
                         }
                         _ => None,
                     }
diff --git a/compiler/rustc_typeck/src/check/method/suggest.rs b/compiler/rustc_typeck/src/check/method/suggest.rs
index d1d6d002d4c9..bd0ac75c8ed9 100644
--- a/compiler/rustc_typeck/src/check/method/suggest.rs
+++ b/compiler/rustc_typeck/src/check/method/suggest.rs
@@ -640,7 +640,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         let bound_predicate = pred.bound_atom(tcx);
                         match bound_predicate.skip_binder() {
                             ty::PredicateAtom::Projection(pred) => {
-                                let pred = bound_predicate.map_bound_ref(|_| pred);
+                                let pred = bound_predicate.rebind(pred);
                                 // `<Foo as Iterator>::Item = String`.
                                 let trait_ref =
                                     pred.skip_binder().projection_ty.trait_ref(self.tcx);
diff --git a/compiler/rustc_typeck/src/check/mod.rs b/compiler/rustc_typeck/src/check/mod.rs
index 124ba91f74c9..94f961218ba4 100644
--- a/compiler/rustc_typeck/src/check/mod.rs
+++ b/compiler/rustc_typeck/src/check/mod.rs
@@ -862,7 +862,7 @@ fn bounds_from_generic_predicates<'tcx>(
                 }
             }
             ty::PredicateAtom::Projection(projection_pred) => {
-                projections.push(bound_predicate.map_bound_ref(|_| projection_pred));
+                projections.push(bound_predicate.rebind(projection_pred));
             }
             _ => {}
         }
diff --git a/src/librustdoc/clean/auto_trait.rs b/src/librustdoc/clean/auto_trait.rs
index f6a4dfd85a5e..20d6bda1f115 100644
--- a/src/librustdoc/clean/auto_trait.rs
+++ b/src/librustdoc/clean/auto_trait.rs
@@ -317,14 +317,12 @@ impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> {
     ) -> FxHashSet<GenericParamDef> {
         let bound_predicate = pred.bound_atom(tcx);
         let regions = match bound_predicate.skip_binder() {
-            ty::PredicateAtom::Trait(poly_trait_pred, _) => tcx
-                .collect_referenced_late_bound_regions(
-                    &bound_predicate.map_bound_ref(|_| poly_trait_pred),
-                ),
-            ty::PredicateAtom::Projection(poly_proj_pred) => tcx
-                .collect_referenced_late_bound_regions(
-                    &bound_predicate.map_bound_ref(|_| poly_proj_pred),
-                ),
+            ty::PredicateAtom::Trait(poly_trait_pred, _) => {
+                tcx.collect_referenced_late_bound_regions(&bound_predicate.rebind(poly_trait_pred))
+            }
+            ty::PredicateAtom::Projection(poly_proj_pred) => {
+                tcx.collect_referenced_late_bound_regions(&bound_predicate.rebind(poly_proj_pred))
+            }
             _ => return FxHashSet::default(),
         };
 
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 776b131a0761..f74dd875ca30 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1689,7 +1689,10 @@ impl<'tcx> Clean<Type> for Ty<'tcx> {
                     .filter_map(|bound| {
                         // Note: The substs of opaque types can contain unbound variables,
                         // meaning that we have to use `ignore_quantifiers_with_unbound_vars` here.
-                        let trait_ref = match bound.bound_atom(cx.tcx).skip_binder() {
+                        let trait_ref = match bound
+                            .bound_atom_with_opt_escaping(cx.tcx)
+                            .skip_binder()
+                        {
                             ty::PredicateAtom::Trait(tr, _constness) => {
                                 ty::Binder::bind(tr.trait_ref)
                             }
@@ -1713,7 +1716,7 @@ impl<'tcx> Clean<Type> for Ty<'tcx> {
                             .iter()
                             .filter_map(|bound| {
                                 if let ty::PredicateAtom::Projection(proj) =
-                                    bound.bound_atom(cx.tcx).skip_binder()
+                                    bound.bound_atom_with_opt_escaping(cx.tcx).skip_binder()
                                 {
                                     if proj.projection_ty.trait_ref(cx.tcx)
                                         == trait_ref.skip_binder()