Rollup merge of #89001 - jackh726:binder-cleanup, r=nikomatsakis

Be explicit about using Binder::dummy

This is somewhat of a late followup to the binder refactor PR. It removes `ToPredicate` and `ToPolyTraitImpls` that hide the use of `Binder::dummy`. While this does make code a bit more verbose, it allows us be more careful about where we create binders.

Another alternative here might be to add a new trait `ToBinder` or something with a `dummy()` fn. Which could still allow grepping but allows doing something like `trait_ref.dummy()` (but I also wonder if longer-term, it would be better to be even more explicit with a `bind_with_vars(ty::List::empty())` *but* that's not clear yet.

r? ``@nikomatsakis``

compiler/rustc_borrowck/src/type_check/canonical.rs

@@ -89,10 +89,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         category: ConstraintCategory,
     ) {
         self.prove_predicates(
-            Some(ty::PredicateKind::Trait(ty::TraitPredicate {
+            Some(ty::Binder::dummy(ty::PredicateKind::Trait(ty::TraitPredicate {
                 trait_ref,
                 constness: ty::BoundConstness::NotConst,
-            })),
+            }))),
             locations,
             category,
         );

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1080,7 +1080,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     }
 
                     self.prove_predicate(
-                        ty::PredicateKind::WellFormed(inferred_ty.into()).to_predicate(self.tcx()),
+                        ty::Binder::dummy(ty::PredicateKind::WellFormed(inferred_ty.into()))
+                            .to_predicate(self.tcx()),
                         Locations::All(span),
                         ConstraintCategory::TypeAnnotation,
                     );
@@ -1316,7 +1317,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     obligations.obligations.push(traits::Obligation::new(
                         ObligationCause::dummy(),
                         param_env,
-                        ty::PredicateKind::WellFormed(revealed_ty.into()).to_predicate(infcx.tcx),
+                        ty::Binder::dummy(ty::PredicateKind::WellFormed(revealed_ty.into()))
+                            .to_predicate(infcx.tcx),
                     ));
                     obligations.add(
                         infcx
@@ -1599,7 +1601,9 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 self.check_call_dest(body, term, &sig, destination, term_location);
 
                 self.prove_predicates(
-                    sig.inputs_and_output.iter().map(|ty| ty::PredicateKind::WellFormed(ty.into())),
+                    sig.inputs_and_output
+                        .iter()
+                        .map(|ty| ty::Binder::dummy(ty::PredicateKind::WellFormed(ty.into()))),
                     term_location.to_locations(),
                     ConstraintCategory::Boring,
                 );

compiler/rustc_infer/src/infer/canonical/query_response.rs

@@ -669,8 +669,10 @@ impl<'tcx> TypeRelatingDelegate<'tcx> for QueryTypeRelatingDelegate<'_, 'tcx> {
         self.obligations.push(Obligation {
             cause: self.cause.clone(),
             param_env: self.param_env,
-            predicate: ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(sup, sub))
+            predicate: ty::Binder::dummy(ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(
-                .to_predicate(self.infcx.tcx),
+                sup, sub,
+            )))
+            .to_predicate(self.infcx.tcx),
             recursion_depth: 0,
         });
     }

compiler/rustc_infer/src/infer/combine.rs

@@ -360,7 +360,8 @@ impl<'infcx, 'tcx> CombineFields<'infcx, 'tcx> {
             self.obligations.push(Obligation::new(
                 self.trace.cause.clone(),
                 self.param_env,
-                ty::PredicateKind::WellFormed(b_ty.into()).to_predicate(self.infcx.tcx),
+                ty::Binder::dummy(ty::PredicateKind::WellFormed(b_ty.into()))
+                    .to_predicate(self.infcx.tcx),
             ));
         }
 
@@ -463,7 +464,7 @@ impl<'infcx, 'tcx> CombineFields<'infcx, 'tcx> {
         self.obligations.push(Obligation::new(
             self.trace.cause.clone(),
             self.param_env,
-            predicate.to_predicate(self.tcx()),
+            ty::Binder::dummy(predicate).to_predicate(self.tcx()),
         ));
     }
 }

compiler/rustc_infer/src/infer/sub.rs

@@ -97,11 +97,11 @@ impl TypeRelation<'tcx> for Sub<'combine, 'infcx, 'tcx> {
                 self.fields.obligations.push(Obligation::new(
                     self.fields.trace.cause.clone(),
                     self.fields.param_env,
-                    ty::PredicateKind::Subtype(ty::SubtypePredicate {
+                    ty::Binder::dummy(ty::PredicateKind::Subtype(ty::SubtypePredicate {
                         a_is_expected: self.a_is_expected,
                         a,
                         b,
-                    })
+                    }))
                     .to_predicate(self.tcx()),
                 ));
 

compiler/rustc_infer/src/traits/engine.rs

@@ -35,7 +35,7 @@ pub trait TraitEngine<'tcx>: 'tcx {
                 cause,
                 recursion_depth: 0,
                 param_env,
-                predicate: trait_ref.without_const().to_predicate(infcx.tcx),
+                predicate: ty::Binder::dummy(trait_ref).without_const().to_predicate(infcx.tcx),
             },
         );
     }

compiler/rustc_infer/src/traits/util.rs

@@ -231,6 +231,7 @@ impl Elaborator<'tcx> {
                                 None
                             }
                         })
+                        .map(ty::Binder::dummy)
                         .map(|predicate_kind| predicate_kind.to_predicate(tcx))
                         .filter(|&predicate| visited.insert(predicate))
                         .map(|predicate| {

compiler/rustc_middle/src/ty/mod.rs

@@ -769,12 +769,6 @@ pub trait ToPolyTraitRef<'tcx> {
     fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx>;
 }
 
-impl<'tcx> ToPolyTraitRef<'tcx> for TraitRef<'tcx> {
-    fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx> {
-        ty::Binder::dummy(*self)
-    }
-}
-
 impl<'tcx> ToPolyTraitRef<'tcx> for PolyTraitPredicate<'tcx> {
     fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx> {
         self.map_bound_ref(|trait_pred| trait_pred.trait_ref)
@@ -792,23 +786,6 @@ impl ToPredicate<'tcx> for Binder<'tcx, PredicateKind<'tcx>> {
     }
 }
 
-impl ToPredicate<'tcx> for PredicateKind<'tcx> {
-    #[inline(always)]
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        tcx.mk_predicate(Binder::dummy(self))
-    }
-}
-
-impl<'tcx> ToPredicate<'tcx> for ConstnessAnd<TraitRef<'tcx>> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        PredicateKind::Trait(ty::TraitPredicate {
-            trait_ref: self.value,
-            constness: self.constness,
-        })
-        .to_predicate(tcx)
-    }
-}
-
 impl<'tcx> ToPredicate<'tcx> for ConstnessAnd<PolyTraitRef<'tcx>> {
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         self.value

compiler/rustc_middle/src/ty/sty.rs

@@ -844,8 +844,11 @@ impl<'tcx> TraitRef<'tcx> {
 
     /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
     /// are the parameters defined on trait.
-    pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> TraitRef<'tcx> {
+    pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> Binder<'tcx, TraitRef<'tcx>> {
-        TraitRef { def_id, substs: InternalSubsts::identity_for_item(tcx, def_id) }
+        ty::Binder::dummy(TraitRef {
+            def_id,
+            substs: InternalSubsts::identity_for_item(tcx, def_id),
+        })
     }
 
     #[inline]

compiler/rustc_trait_selection/src/autoderef.rs

@@ -135,7 +135,7 @@ impl<'a, 'tcx> Autoderef<'a, 'tcx> {
         let obligation = traits::Obligation::new(
             cause.clone(),
             self.param_env,
-            trait_ref.without_const().to_predicate(tcx),
+            ty::Binder::dummy(trait_ref).without_const().to_predicate(tcx),
         );
         if !self.infcx.predicate_may_hold(&obligation) {
             debug!("overloaded_deref_ty: cannot match obligation");

compiler/rustc_trait_selection/src/infer.rs

@@ -120,7 +120,7 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'cx, 'tcx> {
             cause: traits::ObligationCause::dummy(),
             param_env,
             recursion_depth: 0,
-            predicate: trait_ref.without_const().to_predicate(self.tcx),
+            predicate: ty::Binder::dummy(trait_ref).without_const().to_predicate(self.tcx),
         };
         self.evaluate_obligation(&obligation).unwrap_or(traits::EvaluationResult::EvaluatedToErr)
     }

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -726,7 +726,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
             let new_obligation = Obligation::new(
                 ObligationCause::dummy(),
                 param_env,
-                new_trait_ref.without_const().to_predicate(self.tcx),
+                ty::Binder::dummy(new_trait_ref).without_const().to_predicate(self.tcx),
             );
 
             if self.predicate_must_hold_modulo_regions(&new_obligation) {

compiler/rustc_trait_selection/src/traits/fulfill.rs

@@ -418,7 +418,8 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
                 | ty::PredicateKind::Coerce(_)
                 | ty::PredicateKind::ConstEvaluatable(..)
                 | ty::PredicateKind::ConstEquate(..) => {
-                    let pred = infcx.replace_bound_vars_with_placeholders(binder);
+                    let pred =
+                        ty::Binder::dummy(infcx.replace_bound_vars_with_placeholders(binder));
                     ProcessResult::Changed(mk_pending(vec![
                         obligation.with(pred.to_predicate(self.selcx.tcx())),
                     ]))

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -140,7 +140,8 @@ pub fn type_known_to_meet_bound_modulo_regions<'a, 'tcx>(
         infcx.tcx.def_path_str(def_id)
     );
 
-    let trait_ref = ty::TraitRef { def_id, substs: infcx.tcx.mk_substs_trait(ty, &[]) };
+    let trait_ref =
+        ty::Binder::dummy(ty::TraitRef { def_id, substs: infcx.tcx.mk_substs_trait(ty, &[]) });
     let obligation = Obligation {
         param_env,
         cause: ObligationCause::misc(span, hir::CRATE_HIR_ID),

compiler/rustc_trait_selection/src/traits/object_safety.rs

@@ -250,7 +250,7 @@ fn predicates_reference_self(
     trait_def_id: DefId,
     supertraits_only: bool,
 ) -> SmallVec<[Span; 1]> {
-    let trait_ref = ty::Binder::dummy(ty::TraitRef::identity(tcx, trait_def_id));
+    let trait_ref = ty::TraitRef::identity(tcx, trait_def_id);
     let predicates = if supertraits_only {
         tcx.super_predicates_of(trait_def_id)
     } else {
@@ -554,11 +554,11 @@ fn object_ty_for_trait<'tcx>(
 
     let trait_ref = ty::TraitRef::identity(tcx, trait_def_id);
 
-    let trait_predicate = ty::Binder::dummy(ty::ExistentialPredicate::Trait(
+    let trait_predicate = trait_ref.map_bound(|trait_ref| {
-        ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref),
+        ty::ExistentialPredicate::Trait(ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref))
-    ));
+    });
 
-    let mut associated_types = traits::supertraits(tcx, ty::Binder::dummy(trait_ref))
+    let mut associated_types = traits::supertraits(tcx, trait_ref)
         .flat_map(|super_trait_ref| {
             tcx.associated_items(super_trait_ref.def_id())
                 .in_definition_order()
@@ -671,10 +671,10 @@ fn receiver_is_dispatchable<'tcx>(
         let param_env = tcx.param_env(method.def_id);
 
         // Self: Unsize<U>
-        let unsize_predicate = ty::TraitRef {
+        let unsize_predicate = ty::Binder::dummy(ty::TraitRef {
             def_id: unsize_did,
             substs: tcx.mk_substs_trait(tcx.types.self_param, &[unsized_self_ty.into()]),
-        }
+        })
         .without_const()
         .to_predicate(tcx);
 
@@ -689,7 +689,9 @@ fn receiver_is_dispatchable<'tcx>(
                     }
                 });
 
-            ty::TraitRef { def_id: unsize_did, substs }.without_const().to_predicate(tcx)
+            ty::Binder::dummy(ty::TraitRef { def_id: unsize_did, substs })
+                .without_const()
+                .to_predicate(tcx)
         };
 
         let caller_bounds: Vec<Predicate<'tcx>> = param_env
@@ -703,10 +705,10 @@ fn receiver_is_dispatchable<'tcx>(
 
     // Receiver: DispatchFromDyn<Receiver[Self => U]>
     let obligation = {
-        let predicate = ty::TraitRef {
+        let predicate = ty::Binder::dummy(ty::TraitRef {
             def_id: dispatch_from_dyn_did,
             substs: tcx.mk_substs_trait(receiver_ty, &[unsized_receiver_ty.into()]),
-        }
+        })
         .without_const()
         .to_predicate(tcx);
 
@@ -789,8 +791,7 @@ fn contains_illegal_self_type_reference<'tcx, T: TypeFoldable<'tcx>>(
 
                     // Compute supertraits of current trait lazily.
                     if self.supertraits.is_none() {
-                        let trait_ref =
+                        let trait_ref = ty::TraitRef::identity(self.tcx, self.trait_def_id);
-                            ty::Binder::dummy(ty::TraitRef::identity(self.tcx, self.trait_def_id));
                         self.supertraits = Some(
                             traits::supertraits(self.tcx, trait_ref).map(|t| t.def_id()).collect(),
                         );

compiler/rustc_trait_selection/src/traits/project.rs

@@ -27,7 +27,7 @@ use rustc_hir::lang_items::LangItem;
 use rustc_infer::infer::resolve::OpportunisticRegionResolver;
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder};
 use rustc_middle::ty::subst::Subst;
-use rustc_middle::ty::{self, ToPolyTraitRef, ToPredicate, Ty, TyCtxt, WithConstness};
+use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt, WithConstness};
 use rustc_span::symbol::sym;
 
 use std::collections::BTreeMap;
@@ -1028,7 +1028,7 @@ fn normalize_to_error<'a, 'tcx>(
     cause: ObligationCause<'tcx>,
     depth: usize,
 ) -> NormalizedTy<'tcx> {
-    let trait_ref = projection_ty.trait_ref(selcx.tcx()).to_poly_trait_ref();
+    let trait_ref = ty::Binder::dummy(projection_ty.trait_ref(selcx.tcx()));
     let trait_obligation = Obligation {
         cause,
         recursion_depth: depth,
@@ -1290,7 +1290,7 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
 
     // If we are resolving `<T as TraitRef<...>>::Item == Type`,
     // start out by selecting the predicate `T as TraitRef<...>`:
-    let poly_trait_ref = obligation.predicate.trait_ref(selcx.tcx()).to_poly_trait_ref();
+    let poly_trait_ref = ty::Binder::dummy(obligation.predicate.trait_ref(selcx.tcx()));
     let trait_obligation = obligation.with(poly_trait_ref.to_poly_trait_predicate());
     let _ = selcx.infcx().commit_if_ok(|_| {
         let impl_source = match selcx.select(&trait_obligation) {

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -141,6 +141,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             let placeholder_trait_predicate =
                 self.infcx().replace_bound_vars_with_placeholders(trait_predicate);
             let placeholder_self_ty = placeholder_trait_predicate.self_ty();
+            let placeholder_trait_predicate = ty::Binder::dummy(placeholder_trait_predicate);
             let (def_id, substs) = match *placeholder_self_ty.kind() {
                 ty::Projection(proj) => (proj.item_def_id, proj.substs),
                 ty::Opaque(def_id, substs) => (def_id, substs),
@@ -164,7 +165,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             obligations.extend(self.infcx.commit_if_ok(|_| {
                 self.infcx
                     .at(&obligation.cause, obligation.param_env)
-                    .sup(placeholder_trait_predicate.trait_ref.to_poly_trait_ref(), candidate.value)
+                    .sup(placeholder_trait_predicate.to_poly_trait_ref(), candidate.value)
                     .map(|InferOk { obligations, .. }| obligations)
                     .map_err(|_| Unimplemented)
             })?);
@@ -646,7 +647,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             obligations.push(Obligation::new(
                 obligation.cause.clone(),
                 obligation.param_env,
-                ty::PredicateKind::ClosureKind(closure_def_id, substs, kind)
+                ty::Binder::dummy(ty::PredicateKind::ClosureKind(closure_def_id, substs, kind))
                     .to_predicate(self.tcx()),
             ));
         }
@@ -898,10 +899,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 );
 
                 // We can only make objects from sized types.
-                let tr = ty::TraitRef::new(
+                let tr = ty::Binder::dummy(ty::TraitRef::new(
                     tcx.require_lang_item(LangItem::Sized, None),
                     tcx.mk_substs_trait(source, &[]),
-                );
+                ));
                 nested.push(predicate_to_obligation(tr.without_const().to_predicate(tcx)));
 
                 // If the type is `Foo + 'a`, ensure that the type

compiler/rustc_trait_selection/src/traits/util.rs

@@ -248,7 +248,7 @@ pub fn predicate_for_trait_ref<'tcx>(
         cause,
         param_env,
         recursion_depth,
-        predicate: trait_ref.without_const().to_predicate(tcx),
+        predicate: ty::Binder::dummy(trait_ref).without_const().to_predicate(tcx),
     }
 }
 

compiler/rustc_trait_selection/src/traits/wf.rs

@@ -349,7 +349,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                         new_cause,
                         depth,
                         param_env,
-                        ty::PredicateKind::WellFormed(arg).to_predicate(tcx),
+                        ty::Binder::dummy(ty::PredicateKind::WellFormed(arg)).to_predicate(tcx),
                     )
                 }),
         );
@@ -399,7 +399,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                         cause.clone(),
                         depth,
                         param_env,
-                        ty::PredicateKind::WellFormed(arg).to_predicate(tcx),
+                        ty::Binder::dummy(ty::PredicateKind::WellFormed(arg)).to_predicate(tcx),
                     )
                 }),
         );
@@ -416,7 +416,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                 cause,
                 self.recursion_depth,
                 self.param_env,
-                trait_ref.without_const().to_predicate(self.infcx.tcx),
+                ty::Binder::dummy(trait_ref).without_const().to_predicate(self.infcx.tcx),
             ));
         }
     }
@@ -443,9 +443,9 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                             let obligations = self.nominal_obligations(uv.def.did, substs);
                             self.out.extend(obligations);
 
-                            let predicate = ty::PredicateKind::ConstEvaluatable(
+                            let predicate = ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(
                                 ty::Unevaluated::new(uv.def, substs),
-                            )
+                            ))
                             .to_predicate(self.tcx());
                             let cause = self.cause(traits::MiscObligation);
                             self.out.push(traits::Obligation::with_depth(
@@ -469,8 +469,10 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                                     cause,
                                     self.recursion_depth,
                                     self.param_env,
-                                    ty::PredicateKind::WellFormed(resolved_constant.into())
+                                    ty::Binder::dummy(ty::PredicateKind::WellFormed(
-                                        .to_predicate(self.tcx()),
+                                        resolved_constant.into(),
+                                    ))
+                                    .to_predicate(self.tcx()),
                                 ));
                             }
                         }
@@ -556,8 +558,10 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                             cause,
                             depth,
                             param_env,
-                            ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(rty, r))
+                            ty::Binder::dummy(ty::PredicateKind::TypeOutlives(
-                                .to_predicate(self.tcx()),
+                                ty::OutlivesPredicate(rty, r),
+                            ))
+                            .to_predicate(self.tcx()),
                         ));
                     }
                 }
@@ -646,7 +650,8 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                                 cause.clone(),
                                 depth,
                                 param_env,
-                                ty::PredicateKind::ObjectSafe(did).to_predicate(tcx),
+                                ty::Binder::dummy(ty::PredicateKind::ObjectSafe(did))
+                                    .to_predicate(tcx),
                             )
                         }));
                     }
@@ -673,7 +678,8 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                             cause,
                             self.recursion_depth,
                             param_env,
-                            ty::PredicateKind::WellFormed(ty.into()).to_predicate(self.tcx()),
+                            ty::Binder::dummy(ty::PredicateKind::WellFormed(ty.into()))
+                                .to_predicate(self.tcx()),
                         ));
                     } else {
                         // Yes, resolved, proceed with the result.

compiler/rustc_traits/src/type_op.rs

@@ -156,7 +156,8 @@ impl AscribeUserTypeCx<'me, 'tcx> {
             self.relate(self_ty, Variance::Invariant, impl_self_ty)?;
 
             self.prove_predicate(
-                ty::PredicateKind::WellFormed(impl_self_ty.into()).to_predicate(self.tcx()),
+                ty::Binder::dummy(ty::PredicateKind::WellFormed(impl_self_ty.into()))
+                    .to_predicate(self.tcx()),
                 span,
             );
         }
@@ -173,7 +174,7 @@ impl AscribeUserTypeCx<'me, 'tcx> {
         // type were ill-formed but did not appear in `ty`,
         // which...could happen with normalization...
         self.prove_predicate(
-            ty::PredicateKind::WellFormed(ty.into()).to_predicate(self.tcx()),
+            ty::Binder::dummy(ty::PredicateKind::WellFormed(ty.into())).to_predicate(self.tcx()),
             span,
         );
         Ok(())

compiler/rustc_typeck/src/check/_match.rs

@@ -524,13 +524,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 for o in obligations {
                     match o.predicate.kind().skip_binder() {
                         ty::PredicateKind::Trait(t) => {
-                            let pred = ty::PredicateKind::Trait(ty::TraitPredicate {
+                            let pred =
-                                trait_ref: ty::TraitRef {
+                                ty::Binder::dummy(ty::PredicateKind::Trait(ty::TraitPredicate {
-                                    def_id: t.def_id(),
+                                    trait_ref: ty::TraitRef {
-                                    substs: self.infcx.tcx.mk_substs_trait(outer_ty, &[]),
+                                        def_id: t.def_id(),
-                                },
+                                        substs: self.infcx.tcx.mk_substs_trait(outer_ty, &[]),
-                                constness: t.constness,
+                                    },
-                            });
+                                    constness: t.constness,
+                                }));
                             let obl = Obligation::new(
                                 o.cause.clone(),
                                 self.param_env,

compiler/rustc_typeck/src/check/coercion.rs

@@ -256,10 +256,10 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
                     obligations.push(Obligation::new(
                         self.cause.clone(),
                         self.param_env,
-                        ty::PredicateKind::Coerce(ty::CoercePredicate {
+                        ty::Binder::dummy(ty::PredicateKind::Coerce(ty::CoercePredicate {
                             a: source_ty,
                             b: target_ty,
-                        })
+                        }))
                         .to_predicate(self.tcx()),
                     ));
                 }

compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs

@@ -585,7 +585,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         self.register_predicate(traits::Obligation::new(
             cause,
             self.param_env,
-            ty::PredicateKind::WellFormed(arg).to_predicate(self.tcx),
+            ty::Binder::dummy(ty::PredicateKind::WellFormed(arg)).to_predicate(self.tcx),
         ));
     }
 

compiler/rustc_typeck/src/check/method/mod.rs

@@ -21,7 +21,7 @@ use rustc_infer::infer::{self, InferOk};
 use rustc_middle::ty::subst::Subst;
 use rustc_middle::ty::subst::{InternalSubsts, SubstsRef};
 use rustc_middle::ty::GenericParamDefKind;
-use rustc_middle::ty::{self, ToPolyTraitRef, ToPredicate, Ty, TypeFoldable, WithConstness};
+use rustc_middle::ty::{self, ToPredicate, Ty, TypeFoldable, WithConstness};
 use rustc_span::symbol::Ident;
 use rustc_span::Span;
 use rustc_trait_selection::traits;
@@ -331,7 +331,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let trait_ref = ty::TraitRef::new(trait_def_id, substs);
 
         // Construct an obligation
-        let poly_trait_ref = trait_ref.to_poly_trait_ref();
+        let poly_trait_ref = ty::Binder::dummy(trait_ref);
         let obligation = traits::Obligation::misc(
             span,
             self.body_id,
@@ -413,7 +413,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         obligations.push(traits::Obligation::new(
             cause,
             self.param_env,
-            ty::PredicateKind::WellFormed(method_ty.into()).to_predicate(tcx),
+            ty::Binder::dummy(ty::PredicateKind::WellFormed(method_ty.into())).to_predicate(tcx),
         ));
 
         let callee = MethodCallee { def_id, substs: trait_ref.substs, sig: fn_sig };

compiler/rustc_typeck/src/check/method/probe.rs

@@ -21,9 +21,7 @@ use rustc_infer::infer::{self, InferOk, TyCtxtInferExt};
 use rustc_middle::middle::stability;
 use rustc_middle::ty::subst::{InternalSubsts, Subst, SubstsRef};
 use rustc_middle::ty::GenericParamDefKind;
-use rustc_middle::ty::{
+use rustc_middle::ty::{self, ParamEnvAnd, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness};
-    self, ParamEnvAnd, ToPolyTraitRef, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness,
-};
 use rustc_session::lint;
 use rustc_span::def_id::LocalDefId;
 use rustc_span::lev_distance::{find_best_match_for_name, lev_distance};
@@ -967,7 +965,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
 
         if self.tcx.is_trait_alias(trait_def_id) {
             // For trait aliases, assume all super-traits are relevant.
-            let bounds = iter::once(trait_ref.to_poly_trait_ref());
+            let bounds = iter::once(ty::Binder::dummy(trait_ref));
             self.elaborate_bounds(bounds, |this, new_trait_ref, item| {
                 let new_trait_ref = this.erase_late_bound_regions(new_trait_ref);
 
@@ -1372,7 +1370,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         trait_ref: ty::TraitRef<'tcx>,
     ) -> traits::SelectionResult<'tcx, traits::Selection<'tcx>> {
         let cause = traits::ObligationCause::misc(self.span, self.body_id);
-        let predicate = trait_ref.to_poly_trait_ref().to_poly_trait_predicate();
+        let predicate = ty::Binder::dummy(trait_ref).to_poly_trait_predicate();
         let obligation = traits::Obligation::new(cause, self.param_env, predicate);
         traits::SelectionContext::new(self).select(&obligation)
     }
@@ -1470,7 +1468,8 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                             }
                         }
                     }
-                    let predicate = trait_ref.without_const().to_predicate(self.tcx);
+                    let predicate =
+                        ty::Binder::dummy(trait_ref).without_const().to_predicate(self.tcx);
                     let obligation = traits::Obligation::new(cause, self.param_env, predicate);
                     if !self.predicate_may_hold(&obligation) {
                         result = ProbeResult::NoMatch;

compiler/rustc_typeck/src/check/method/suggest.rs

@@ -12,9 +12,7 @@ use rustc_hir::{ExprKind, Node, QPath};
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_middle::ty::fast_reject::simplify_type;
 use rustc_middle::ty::print::with_crate_prefix;
-use rustc_middle::ty::{
+use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness};
-    self, ToPolyTraitRef, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness,
-};
 use rustc_span::lev_distance;
 use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::{source_map, FileName, Span};
@@ -53,7 +51,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 .into()],
                         );
                         let trait_ref = ty::TraitRef::new(fn_once, fn_once_substs);
-                        let poly_trait_ref = trait_ref.to_poly_trait_ref();
+                        let poly_trait_ref = ty::Binder::dummy(trait_ref);
                         let obligation = Obligation::misc(
                             span,
                             self.body_id,

compiler/rustc_typeck/src/check/wfcheck.rs

@@ -540,10 +540,10 @@ fn check_type_defn<'tcx, F>(
                 fcx.register_predicate(traits::Obligation::new(
                     cause,
                     fcx.param_env,
-                    ty::PredicateKind::ConstEvaluatable(ty::Unevaluated::new(
+                    ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(ty::Unevaluated::new(
                         ty::WithOptConstParam::unknown(discr_def_id.to_def_id()),
                         discr_substs,
-                    ))
+                    )))
                     .to_predicate(tcx),
                 ));
             }
@@ -1151,10 +1151,10 @@ fn receiver_is_implemented(
     cause: ObligationCause<'tcx>,
     receiver_ty: Ty<'tcx>,
 ) -> bool {
-    let trait_ref = ty::TraitRef {
+    let trait_ref = ty::Binder::dummy(ty::TraitRef {
         def_id: receiver_trait_def_id,
         substs: fcx.tcx.mk_substs_trait(receiver_ty, &[]),
-    };
+    });
 
     let obligation = traits::Obligation::new(
         cause,

compiler/rustc_typeck/src/collect.rs

@@ -40,7 +40,7 @@ use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::subst::InternalSubsts;
 use rustc_middle::ty::util::Discr;
 use rustc_middle::ty::util::IntTypeExt;
-use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, ToPolyTraitRef, Ty, TyCtxt};
+use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, Ty, TyCtxt};
 use rustc_middle::ty::{ReprOptions, ToPredicate, WithConstness};
 use rustc_session::lint;
 use rustc_session::parse::feature_err;
@@ -2042,7 +2042,9 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
             match item.kind {
                 ItemKind::Impl(ref impl_) => {
                     if impl_.defaultness.is_default() {
-                        is_default_impl_trait = tcx.impl_trait_ref(def_id);
+                        is_default_impl_trait = tcx
+                            .impl_trait_ref(def_id)
+                            .map(|trait_ref| ty::Binder::dummy(trait_ref));
                     }
                     &impl_.generics
                 }
@@ -2122,10 +2124,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
     // (see below). Recall that a default impl is not itself an impl, but rather a
     // set of defaults that can be incorporated into another impl.
     if let Some(trait_ref) = is_default_impl_trait {
-        predicates.insert((
+        predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
-            trait_ref.to_poly_trait_ref().without_const().to_predicate(tcx),
-            tcx.def_span(def_id),
-        ));
     }
 
     // Collect the region predicates that were declared inline as
@@ -2238,8 +2237,10 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
                         }
                         _ => bug!(),
                     };
-                    let pred = ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(r1, r2))
+                    let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
-                        .to_predicate(icx.tcx);
+                        ty::OutlivesPredicate(r1, r2),
+                    ))
+                    .to_predicate(icx.tcx);
 
                     (pred, span)
                 }))
@@ -2304,7 +2305,8 @@ fn const_evaluatable_predicates_of<'tcx>(
                 assert_eq!(uv.promoted, None);
                 let span = self.tcx.hir().span(c.hir_id);
                 self.preds.insert((
-                    ty::PredicateKind::ConstEvaluatable(uv.shrink()).to_predicate(self.tcx),
+                    ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
+                        .to_predicate(self.tcx),
                     span,
                 ));
             }

compiler/rustc_typeck/src/hir_wf_check.rs

@@ -83,7 +83,8 @@ fn diagnostic_hir_wf_check<'tcx>(
                     traits::Obligation::new(
                         cause,
                         self.param_env,
-                        ty::PredicateKind::WellFormed(tcx_ty.into()).to_predicate(self.tcx),
+                        ty::Binder::dummy(ty::PredicateKind::WellFormed(tcx_ty.into()))
+                            .to_predicate(self.tcx),
                     ),
                 );
 

compiler/rustc_typeck/src/outlives/mod.rs

@@ -104,13 +104,15 @@ fn inferred_outlives_crate(tcx: TyCtxt<'_>, (): ()) -> CratePredicatesMap<'_> {
                 |(ty::OutlivesPredicate(kind1, region2), &span)| {
                     match kind1.unpack() {
                         GenericArgKind::Type(ty1) => Some((
-                            ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(ty1, region2))
+                            ty::Binder::dummy(ty::PredicateKind::TypeOutlives(
-                                .to_predicate(tcx),
+                                ty::OutlivesPredicate(ty1, region2),
+                            ))
+                            .to_predicate(tcx),
                             span,
                         )),
                         GenericArgKind::Lifetime(region1) => Some((
-                            ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(
+                            ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
-                                region1, region2,
+                                ty::OutlivesPredicate(region1, region2),
                             ))
                             .to_predicate(tcx),
                             span,

src/librustdoc/clean/blanket_impl.rs

@@ -64,7 +64,11 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                             .instantiate(self.cx.tcx, impl_substs)
                             .predicates
                             .into_iter()
-                            .chain(Some(trait_ref.without_const().to_predicate(infcx.tcx)));
+                            .chain(Some(
+                                ty::Binder::dummy(trait_ref)
+                                    .without_const()
+                                    .to_predicate(infcx.tcx),
+                            ));
                         for predicate in predicates {
                             debug!("testing predicate {:?}", predicate);
                             let obligation = traits::Obligation::new(

src/librustdoc/clean/mod.rs

@@ -132,7 +132,7 @@ impl Clean<GenericBound> for hir::GenericBound<'_> {
             hir::GenericBound::LangItemTrait(lang_item, span, _, generic_args) => {
                 let def_id = cx.tcx.require_lang_item(lang_item, Some(span));
 
-                let trait_ref = ty::TraitRef::identity(cx.tcx, def_id);
+                let trait_ref = ty::TraitRef::identity(cx.tcx, def_id).skip_binder();
 
                 let generic_args = generic_args.clean(cx);
                 let bindings = match generic_args {

src/tools/clippy/clippy_lints/src/escape.rs

@@ -92,7 +92,7 @@ impl<'tcx> LateLintPass<'tcx> for BoxedLocal {
                         // be sure we have `self` parameter in this function
                         if let AssocItemKind::Fn { has_self: true } = trait_item.kind {
                             trait_self_ty =
-                                Some(TraitRef::identity(cx.tcx, trait_item.id.def_id.to_def_id()).self_ty());
+                                Some(TraitRef::identity(cx.tcx, trait_item.id.def_id.to_def_id()).self_ty().skip_binder());
                         }
                     }
                 }

src/tools/clippy/clippy_lints/src/methods/mod.rs

@@ -2061,7 +2061,7 @@ impl<'tcx> LateLintPass<'tcx> for Methods {
             then {
                 let first_arg_span = first_arg_ty.span;
                 let first_arg_ty = hir_ty_to_ty(cx.tcx, first_arg_ty);
-                let self_ty = TraitRef::identity(cx.tcx, item.def_id.to_def_id()).self_ty();
+                let self_ty = TraitRef::identity(cx.tcx, item.def_id.to_def_id()).self_ty().skip_binder();
                 wrong_self_convention::check(
                     cx,
                     &item.ident.name.as_str(),
@@ -2078,7 +2078,7 @@ impl<'tcx> LateLintPass<'tcx> for Methods {
             if item.ident.name == sym::new;
             if let TraitItemKind::Fn(_, _) = item.kind;
             let ret_ty = return_ty(cx, item.hir_id());
-            let self_ty = TraitRef::identity(cx.tcx, item.def_id.to_def_id()).self_ty();
+            let self_ty = TraitRef::identity(cx.tcx, item.def_id.to_def_id()).self_ty().skip_binder();
             if !contains_ty(cx.tcx, ret_ty, self_ty);
 
             then {