move Constness into TraitPredicate

compiler/rustc_hir/src/hir.rs

@@ -2751,6 +2751,15 @@ pub enum Constness {
     NotConst,
 }
 
+impl fmt::Display for Constness {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(match *self {
+            Self::Const => "const",
+            Self::NotConst => "non-const",
+        })
+    }
+}
+
 #[derive(Copy, Clone, Encodable, Debug, HashStable_Generic)]
 pub struct FnHeader {
     pub unsafety: Unsafety,

compiler/rustc_infer/src/traits/util.rs

@@ -124,7 +124,7 @@ impl Elaborator<'tcx> {
 
         let bound_predicate = obligation.predicate.kind();
         match bound_predicate.skip_binder() {
-            ty::PredicateKind::Trait(data, _) => {
+            ty::PredicateKind::Trait(data) => {
                 // Get predicates declared on the trait.
                 let predicates = tcx.super_predicates_of(data.def_id());
 

compiler/rustc_lint/src/traits.rs

@@ -87,7 +87,7 @@ impl<'tcx> LateLintPass<'tcx> for DropTraitConstraints {
         let predicates = cx.tcx.explicit_predicates_of(item.def_id);
         for &(predicate, span) in predicates.predicates {
             let trait_predicate = match predicate.kind().skip_binder() {
-                Trait(trait_predicate, _constness) => trait_predicate,
+                Trait(trait_predicate) => trait_predicate,
                 _ => continue,
             };
             let def_id = trait_predicate.trait_ref.def_id;

compiler/rustc_lint/src/unused.rs

@@ -211,7 +211,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
                     let mut has_emitted = false;
                     for &(predicate, _) in cx.tcx.explicit_item_bounds(def) {
                         // We only look at the `DefId`, so it is safe to skip the binder here.
-                        if let ty::PredicateKind::Trait(ref poly_trait_predicate, _) =
+                        if let ty::PredicateKind::Trait(ref poly_trait_predicate) =
                             predicate.kind().skip_binder()
                         {
                             let def_id = poly_trait_predicate.trait_ref.def_id;

compiler/rustc_middle/src/ty/context.rs

@@ -2169,7 +2169,7 @@ impl<'tcx> TyCtxt<'tcx> {
             let generic_predicates = self.super_predicates_of(trait_did);
 
             for (predicate, _) in generic_predicates.predicates {
-                if let ty::PredicateKind::Trait(data, _) = predicate.kind().skip_binder() {
+                if let ty::PredicateKind::Trait(data) = predicate.kind().skip_binder() {
                     if set.insert(data.def_id()) {
                         stack.push(data.def_id());
                     }

compiler/rustc_middle/src/ty/error.rs

@@ -33,6 +33,7 @@ impl<T> ExpectedFound<T> {
 #[derive(Clone, Debug, TypeFoldable)]
 pub enum TypeError<'tcx> {
     Mismatch,
+    ConstnessMismatch(ExpectedFound<hir::Constness>),
     UnsafetyMismatch(ExpectedFound<hir::Unsafety>),
     AbiMismatch(ExpectedFound<abi::Abi>),
     Mutability,
@@ -106,6 +107,9 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
             CyclicTy(_) => write!(f, "cyclic type of infinite size"),
             CyclicConst(_) => write!(f, "encountered a self-referencing constant"),
             Mismatch => write!(f, "types differ"),
+            ConstnessMismatch(values) => {
+                write!(f, "expected {} fn, found {} fn", values.expected, values.found)
+            }
             UnsafetyMismatch(values) => {
                 write!(f, "expected {} fn, found {} fn", values.expected, values.found)
             }
@@ -213,9 +217,11 @@ impl<'tcx> TypeError<'tcx> {
     pub fn must_include_note(&self) -> bool {
         use self::TypeError::*;
         match self {
-            CyclicTy(_) | CyclicConst(_) | UnsafetyMismatch(_) | Mismatch | AbiMismatch(_)
+            CyclicTy(_) | CyclicConst(_) | UnsafetyMismatch(_) | ConstnessMismatch(_)
-            | FixedArraySize(_) | ArgumentSorts(..) | Sorts(_) | IntMismatch(_)
+            | Mismatch | AbiMismatch(_) | FixedArraySize(_) | ArgumentSorts(..) | Sorts(_)
-            | FloatMismatch(_) | VariadicMismatch(_) | TargetFeatureCast(_) => false,
+            | IntMismatch(_) | FloatMismatch(_) | VariadicMismatch(_) | TargetFeatureCast(_) => {
+                false
+            }
 
             Mutability
             | ArgumentMutability(_)

compiler/rustc_middle/src/ty/flags.rs

@@ -216,7 +216,7 @@ impl FlagComputation {
 
     fn add_predicate_atom(&mut self, atom: ty::PredicateKind<'_>) {
         match atom {
-            ty::PredicateKind::Trait(trait_pred, _constness) => {
+            ty::PredicateKind::Trait(trait_pred) => {
                 self.add_substs(trait_pred.trait_ref.substs);
             }
             ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => {

compiler/rustc_middle/src/ty/mod.rs

@@ -456,7 +456,7 @@ pub enum PredicateKind<'tcx> {
     /// A trait predicate will have `Constness::Const` if it originates
     /// from a bound on a `const fn` without the `?const` opt-out (e.g.,
     /// `const fn foobar<Foo: Bar>() {}`).
-    Trait(TraitPredicate<'tcx>, Constness),
+    Trait(TraitPredicate<'tcx>),
 
     /// `where 'a: 'b`
     RegionOutlives(RegionOutlivesPredicate<'tcx>),
@@ -612,6 +612,11 @@ impl<'tcx> Predicate<'tcx> {
 #[derive(HashStable, TypeFoldable)]
 pub struct TraitPredicate<'tcx> {
     pub trait_ref: TraitRef<'tcx>,
+
+    /// A trait predicate will have `Constness::Const` if it originates
+    /// from a bound on a `const fn` without the `?const` opt-out (e.g.,
+    /// `const fn foobar<Foo: Bar>() {}`).
+    pub constness: hir::Constness,
 }
 
 pub type PolyTraitPredicate<'tcx> = ty::Binder<'tcx, TraitPredicate<'tcx>>;
@@ -745,7 +750,10 @@ impl ToPredicate<'tcx> for PredicateKind<'tcx> {
 
 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 }, self.constness)
+        PredicateKind::Trait(ty::TraitPredicate {
+            trait_ref: self.value,
+            constness: self.constness,
+        })
         .to_predicate(tcx)
     }
 }
@@ -754,15 +762,15 @@ impl<'tcx> ToPredicate<'tcx> for ConstnessAnd<PolyTraitRef<'tcx>> {
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         self.value
             .map_bound(|trait_ref| {
-                PredicateKind::Trait(ty::TraitPredicate { trait_ref }, self.constness)
+                PredicateKind::Trait(ty::TraitPredicate { trait_ref, constness: self.constness })
             })
             .to_predicate(tcx)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for ConstnessAnd<PolyTraitPredicate<'tcx>> {
+impl<'tcx> ToPredicate<'tcx> for PolyTraitPredicate<'tcx> {
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        self.value.map_bound(|value| PredicateKind::Trait(value, self.constness)).to_predicate(tcx)
+        self.map_bound(PredicateKind::Trait).to_predicate(tcx)
     }
 }
 
@@ -788,8 +796,8 @@ impl<'tcx> Predicate<'tcx> {
     pub fn to_opt_poly_trait_ref(self) -> Option<ConstnessAnd<PolyTraitRef<'tcx>>> {
         let predicate = self.kind();
         match predicate.skip_binder() {
-            PredicateKind::Trait(t, constness) => {
+            PredicateKind::Trait(t) => {
-                Some(ConstnessAnd { constness, value: predicate.rebind(t.trait_ref) })
+                Some(ConstnessAnd { constness: t.constness, value: predicate.rebind(t.trait_ref) })
             }
             PredicateKind::Projection(..)
             | PredicateKind::Subtype(..)

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -630,7 +630,7 @@ pub trait PrettyPrinter<'tcx>:
                     for (predicate, _) in bounds {
                         let predicate = predicate.subst(self.tcx(), substs);
                         let bound_predicate = predicate.kind();
-                        if let ty::PredicateKind::Trait(pred, _) = bound_predicate.skip_binder() {
+                        if let ty::PredicateKind::Trait(pred) = bound_predicate.skip_binder() {
                             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() {
@@ -2264,10 +2264,7 @@ define_print_and_forward_display! {
 
     ty::PredicateKind<'tcx> {
         match *self {
-            ty::PredicateKind::Trait(ref data, constness) => {
+            ty::PredicateKind::Trait(ref data) => {
-                if let hir::Constness::Const = constness {
-                    p!("const ");
-                }
                 p!(print(data))
             }
             ty::PredicateKind::Subtype(predicate) => p!(print(predicate)),

compiler/rustc_middle/src/ty/relate.rs

@@ -200,6 +200,20 @@ impl<'tcx> Relate<'tcx> for ty::FnSig<'tcx> {
     }
 }
 
+impl<'tcx> Relate<'tcx> for ast::Constness {
+    fn relate<R: TypeRelation<'tcx>>(
+        relation: &mut R,
+        a: ast::Constness,
+        b: ast::Constness,
+    ) -> RelateResult<'tcx, ast::Constness> {
+        if a != b {
+            Err(TypeError::ConstnessMismatch(expected_found(relation, a, b)))
+        } else {
+            Ok(a)
+        }
+    }
+}
+
 impl<'tcx> Relate<'tcx> for ast::Unsafety {
     fn relate<R: TypeRelation<'tcx>>(
         relation: &mut R,
@@ -767,7 +781,10 @@ impl<'tcx> Relate<'tcx> for ty::TraitPredicate<'tcx> {
         a: ty::TraitPredicate<'tcx>,
         b: ty::TraitPredicate<'tcx>,
     ) -> RelateResult<'tcx, ty::TraitPredicate<'tcx>> {
-        Ok(ty::TraitPredicate { trait_ref: relation.relate(a.trait_ref, b.trait_ref)? })
+        Ok(ty::TraitPredicate {
+            trait_ref: relation.relate(a.trait_ref, b.trait_ref)?,
+            constness: relation.relate(a.constness, b.constness)?,
+        })
     }
 }
 

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -155,6 +155,9 @@ impl fmt::Debug for ty::ParamConst {
 
 impl fmt::Debug for ty::TraitPredicate<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if let hir::Constness::Const = self.constness {
+            write!(f, "const ")?;
+        }
         write!(f, "TraitPredicate({:?})", self.trait_ref)
     }
 }
@@ -174,12 +177,7 @@ impl fmt::Debug for ty::Predicate<'tcx> {
 impl fmt::Debug for ty::PredicateKind<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
-            ty::PredicateKind::Trait(ref a, constness) => {
+            ty::PredicateKind::Trait(ref a) => a.fmt(f),
-                if let hir::Constness::Const = constness {
-                    write!(f, "const ")?;
-                }
-                a.fmt(f)
-            }
             ty::PredicateKind::Subtype(ref pair) => pair.fmt(f),
             ty::PredicateKind::RegionOutlives(ref pair) => pair.fmt(f),
             ty::PredicateKind::TypeOutlives(ref pair) => pair.fmt(f),
@@ -366,7 +364,8 @@ impl<'a, 'tcx> Lift<'tcx> for ty::ExistentialPredicate<'a> {
 impl<'a, 'tcx> Lift<'tcx> for ty::TraitPredicate<'a> {
     type Lifted = ty::TraitPredicate<'tcx>;
     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<ty::TraitPredicate<'tcx>> {
-        tcx.lift(self.trait_ref).map(|trait_ref| ty::TraitPredicate { trait_ref })
+        tcx.lift(self.trait_ref)
+            .map(|trait_ref| ty::TraitPredicate { trait_ref, constness: self.constness })
     }
 }
 
@@ -419,9 +418,7 @@ impl<'a, 'tcx> Lift<'tcx> for ty::PredicateKind<'a> {
     type Lifted = ty::PredicateKind<'tcx>;
     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
         match self {
-            ty::PredicateKind::Trait(data, constness) => {
+            ty::PredicateKind::Trait(data) => tcx.lift(data).map(ty::PredicateKind::Trait),
-                tcx.lift(data).map(|data| ty::PredicateKind::Trait(data, constness))
-            }
             ty::PredicateKind::Subtype(data) => tcx.lift(data).map(ty::PredicateKind::Subtype),
             ty::PredicateKind::RegionOutlives(data) => {
                 tcx.lift(data).map(ty::PredicateKind::RegionOutlives)
@@ -584,6 +581,7 @@ impl<'a, 'tcx> Lift<'tcx> for ty::error::TypeError<'a> {
 
         Some(match self {
             Mismatch => Mismatch,
+            ConstnessMismatch(x) => ConstnessMismatch(x),
             UnsafetyMismatch(x) => UnsafetyMismatch(x),
             AbiMismatch(x) => AbiMismatch(x),
             Mutability => Mutability,

compiler/rustc_middle/src/ty/sty.rs

@@ -876,7 +876,10 @@ impl<'tcx> PolyTraitRef<'tcx> {
     }
 
     pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
-        self.map_bound(|trait_ref| ty::TraitPredicate { trait_ref })
+        self.map_bound(|trait_ref| ty::TraitPredicate {
+            trait_ref,
+            constness: hir::Constness::NotConst,
+        })
     }
 }
 

compiler/rustc_mir/src/borrow_check/type_check/mod.rs

@@ -2688,10 +2688,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         category: ConstraintCategory,
     ) {
         self.prove_predicates(
-            Some(ty::PredicateKind::Trait(
+            Some(ty::PredicateKind::Trait(ty::TraitPredicate {
-                ty::TraitPredicate { trait_ref },
+                trait_ref,
-                hir::Constness::NotConst,
+                constness: hir::Constness::NotConst,
-            )),
+            })),
             locations,
             category,
         );

compiler/rustc_mir/src/transform/check_consts/check.rs

@@ -423,7 +423,7 @@ impl Checker<'mir, 'tcx> {
                     ty::PredicateKind::Subtype(_) => {
                         bug!("subtype predicate on function: {:#?}", predicate)
                     }
-                    ty::PredicateKind::Trait(pred, _constness) => {
+                    ty::PredicateKind::Trait(pred) => {
                         if Some(pred.def_id()) == tcx.lang_items().sized_trait() {
                             continue;
                         }
@@ -817,7 +817,10 @@ impl Visitor<'tcx> for Checker<'mir, 'tcx> {
                     let obligation = Obligation::new(
                         ObligationCause::dummy(),
                         param_env,
-                        Binder::dummy(TraitPredicate { trait_ref }),
+                        Binder::dummy(TraitPredicate {
+                            trait_ref,
+                            constness: hir::Constness::Const,
+                        }),
                     );
 
                     let implsrc = tcx.infer_ctxt().enter(|infcx| {

compiler/rustc_mir/src/transform/function_item_references.rs

@@ -132,7 +132,7 @@ impl<'a, 'tcx> FunctionItemRefChecker<'a, 'tcx> {
 
     /// If the given predicate is the trait `fmt::Pointer`, returns the bound parameter type.
     fn is_pointer_trait(&self, bound: &PredicateKind<'tcx>) -> Option<Ty<'tcx>> {
-        if let ty::PredicateKind::Trait(predicate, _) = bound {
+        if let ty::PredicateKind::Trait(predicate) = bound {
             if self.tcx.is_diagnostic_item(sym::pointer_trait, predicate.def_id()) {
                 Some(predicate.trait_ref.self_ty())
             } else {

compiler/rustc_privacy/src/lib.rs

@@ -122,7 +122,7 @@ where
 
     fn visit_predicate(&mut self, predicate: ty::Predicate<'tcx>) -> ControlFlow<V::BreakTy> {
         match predicate.kind().skip_binder() {
-            ty::PredicateKind::Trait(ty::TraitPredicate { trait_ref }, _) => {
+            ty::PredicateKind::Trait(ty::TraitPredicate { trait_ref, constness: _ }) => {
                 self.visit_trait(trait_ref)
             }
             ty::PredicateKind::Projection(ty::ProjectionPredicate { projection_ty, ty }) => {

compiler/rustc_resolve/src/late/lifetimes.rs

@@ -2657,7 +2657,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
             let obligations = predicates.predicates.iter().filter_map(|&(pred, _)| {
                 let bound_predicate = pred.kind();
                 match bound_predicate.skip_binder() {
-                    ty::PredicateKind::Trait(data, _) => {
+                    ty::PredicateKind::Trait(data) => {
                         // The order here needs to match what we would get from `subst_supertrait`
                         let pred_bound_vars = bound_predicate.bound_vars();
                         let mut all_bound_vars = bound_vars.clone();

compiler/rustc_trait_selection/src/traits/auto_trait.rs

@@ -285,6 +285,7 @@ impl AutoTraitFinder<'tcx> {
                 def_id: trait_did,
                 substs: infcx.tcx.mk_substs_trait(ty, &[]),
             },
+            constness: hir::Constness::NotConst,
         }));
 
         let computed_preds = param_env.caller_bounds().iter();
@@ -344,10 +345,7 @@ impl AutoTraitFinder<'tcx> {
                 Err(SelectionError::Unimplemented) => {
                     if self.is_param_no_infer(pred.skip_binder().trait_ref.substs) {
                         already_visited.remove(&pred);
-                        self.add_user_pred(
+                        self.add_user_pred(&mut user_computed_preds, pred.to_predicate(self.tcx));
-                            &mut user_computed_preds,
-                            pred.without_const().to_predicate(self.tcx),
-                        );
                         predicates.push_back(pred);
                     } else {
                         debug!(
@@ -414,10 +412,8 @@ impl AutoTraitFinder<'tcx> {
     ) {
         let mut should_add_new = true;
         user_computed_preds.retain(|&old_pred| {
-            if let (
+            if let (ty::PredicateKind::Trait(new_trait), ty::PredicateKind::Trait(old_trait)) =
-                ty::PredicateKind::Trait(new_trait, _),
+                (new_pred.kind().skip_binder(), old_pred.kind().skip_binder())
-                ty::PredicateKind::Trait(old_trait, _),
-            ) = (new_pred.kind().skip_binder(), old_pred.kind().skip_binder())
             {
                 if new_trait.def_id() == old_trait.def_id() {
                     let new_substs = new_trait.trait_ref.substs;
@@ -638,7 +634,7 @@ impl AutoTraitFinder<'tcx> {
 
             let bound_predicate = predicate.kind();
             match bound_predicate.skip_binder() {
-                ty::PredicateKind::Trait(p, _) => {
+                ty::PredicateKind::Trait(p) => {
                     // Add this to `predicates` so that we end up calling `select`
                     // with it. If this predicate ends up being unimplemented,
                     // then `evaluate_predicates` will handle adding it the `ParamEnv`

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

@@ -277,7 +277,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
                 let bound_predicate = obligation.predicate.kind();
                 match bound_predicate.skip_binder() {
-                    ty::PredicateKind::Trait(trait_predicate, _) => {
+                    ty::PredicateKind::Trait(trait_predicate) => {
                         let trait_predicate = bound_predicate.rebind(trait_predicate);
                         let trait_predicate = self.resolve_vars_if_possible(trait_predicate);
 
@@ -518,8 +518,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                                 );
                                 trait_pred
                             });
-                            let unit_obligation =
+                            let unit_obligation = obligation.with(predicate.to_predicate(tcx));
-                                obligation.with(predicate.without_const().to_predicate(tcx));
                             if self.predicate_may_hold(&unit_obligation) {
                                 err.note("this trait is implemented for `()`.");
                                 err.note(
@@ -1148,7 +1147,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
         // FIXME: It should be possible to deal with `ForAll` in a cleaner way.
         let bound_error = error.kind();
         let (cond, error) = match (cond.kind().skip_binder(), bound_error.skip_binder()) {
-            (ty::PredicateKind::Trait(..), ty::PredicateKind::Trait(error, _)) => {
+            (ty::PredicateKind::Trait(..), ty::PredicateKind::Trait(error)) => {
                 (cond, bound_error.rebind(error))
             }
             _ => {
@@ -1159,7 +1158,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
 
         for obligation in super::elaborate_predicates(self.tcx, std::iter::once(cond)) {
             let bound_predicate = obligation.predicate.kind();
-            if let ty::PredicateKind::Trait(implication, _) = bound_predicate.skip_binder() {
+            if let ty::PredicateKind::Trait(implication) = bound_predicate.skip_binder() {
                 let error = error.to_poly_trait_ref();
                 let implication = bound_predicate.rebind(implication.trait_ref);
                 // FIXME: I'm just not taking associated types at all here.
@@ -1536,7 +1535,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
 
         let bound_predicate = predicate.kind();
         let mut err = match bound_predicate.skip_binder() {
-            ty::PredicateKind::Trait(data, _) => {
+            ty::PredicateKind::Trait(data) => {
                 let trait_ref = bound_predicate.rebind(data.trait_ref);
                 debug!("trait_ref {:?}", trait_ref);
 
@@ -1803,7 +1802,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
             match (obligation.predicate.kind().skip_binder(), obligation.cause.code.peel_derives())
             {
                 (
-                    ty::PredicateKind::Trait(pred, _),
+                    ty::PredicateKind::Trait(pred),
                     &ObligationCauseCode::BindingObligation(item_def_id, span),
                 ) => (pred, item_def_id, span),
                 _ => return,

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

@@ -1386,7 +1386,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         // bound was introduced. At least one generator should be present for this diagnostic to be
         // modified.
         let (mut trait_ref, mut target_ty) = match obligation.predicate.kind().skip_binder() {
-            ty::PredicateKind::Trait(p, _) => (Some(p.trait_ref), Some(p.self_ty())),
+            ty::PredicateKind::Trait(p) => (Some(p.trait_ref), Some(p.self_ty())),
             _ => (None, None),
         };
         let mut generator = None;

compiler/rustc_trait_selection/src/traits/fulfill.rs

@@ -352,7 +352,7 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
                 // Evaluation will discard candidates using the leak check.
                 // This means we need to pass it the bound version of our
                 // predicate.
-                ty::PredicateKind::Trait(trait_ref, _constness) => {
+                ty::PredicateKind::Trait(trait_ref) => {
                     let trait_obligation = obligation.with(binder.rebind(trait_ref));
 
                     self.process_trait_obligation(
@@ -388,7 +388,7 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
                 }
             },
             Some(pred) => match pred {
-                ty::PredicateKind::Trait(data, _) => {
+                ty::PredicateKind::Trait(data) => {
                     let trait_obligation = obligation.with(Binder::dummy(data));
 
                     self.process_trait_obligation(

compiler/rustc_trait_selection/src/traits/object_safety.rs

@@ -280,7 +280,7 @@ fn predicate_references_self(
     let self_ty = tcx.types.self_param;
     let has_self_ty = |arg: &GenericArg<'_>| arg.walk().any(|arg| arg == self_ty.into());
     match predicate.kind().skip_binder() {
-        ty::PredicateKind::Trait(ref data, _) => {
+        ty::PredicateKind::Trait(ref data) => {
             // In the case of a trait predicate, we can skip the "self" type.
             if data.trait_ref.substs[1..].iter().any(has_self_ty) { Some(sp) } else { None }
         }
@@ -331,7 +331,7 @@ fn generics_require_sized_self(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
     let predicates = predicates.instantiate_identity(tcx).predicates;
     elaborate_predicates(tcx, predicates.into_iter()).any(|obligation| {
         match obligation.predicate.kind().skip_binder() {
-            ty::PredicateKind::Trait(ref trait_pred, _) => {
+            ty::PredicateKind::Trait(ref trait_pred) => {
                 trait_pred.def_id() == sized_def_id && trait_pred.self_ty().is_param(0)
             }
             ty::PredicateKind::Projection(..)

compiler/rustc_trait_selection/src/traits/query/type_op/prove_predicate.rs

@@ -15,7 +15,7 @@ impl<'tcx> super::QueryTypeOp<'tcx> for ProvePredicate<'tcx> {
         // `&T`, accounts for about 60% percentage of the predicates
         // we have to prove. No need to canonicalize and all that for
         // such cases.
-        if let ty::PredicateKind::Trait(trait_ref, _) = key.value.predicate.kind().skip_binder() {
+        if let ty::PredicateKind::Trait(trait_ref) = key.value.predicate.kind().skip_binder() {
             if let Some(sized_def_id) = tcx.lang_items().sized_trait() {
                 if trait_ref.def_id() == sized_def_id {
                     if trait_ref.self_ty().is_trivially_sized(tcx) {

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

@@ -42,7 +42,7 @@ use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::relate::TypeRelation;
 use rustc_middle::ty::subst::{GenericArgKind, Subst, SubstsRef};
 use rustc_middle::ty::{self, PolyProjectionPredicate, ToPolyTraitRef, ToPredicate};
-use rustc_middle::ty::{Ty, TyCtxt, TypeFoldable, WithConstness};
+use rustc_middle::ty::{Ty, TyCtxt, TypeFoldable};
 use rustc_span::symbol::sym;
 
 use std::cell::{Cell, RefCell};
@@ -454,7 +454,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         let result = ensure_sufficient_stack(|| {
             let bound_predicate = obligation.predicate.kind();
             match bound_predicate.skip_binder() {
-                ty::PredicateKind::Trait(t, _) => {
+                ty::PredicateKind::Trait(t) => {
                     let t = bound_predicate.rebind(t);
                     debug_assert!(!t.has_escaping_bound_vars());
                     let obligation = obligation.with(t);
@@ -762,8 +762,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             // if the regions match exactly.
             let cycle = stack.iter().skip(1).take_while(|s| s.depth >= cycle_depth);
             let tcx = self.tcx();
-            let cycle =
+            let cycle = cycle.map(|stack| stack.obligation.predicate.to_predicate(tcx));
-                cycle.map(|stack| stack.obligation.predicate.without_const().to_predicate(tcx));
             if self.coinductive_match(cycle) {
                 debug!("evaluate_stack --> recursive, coinductive");
                 Some(EvaluatedToOk)
@@ -873,7 +872,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
     fn coinductive_predicate(&self, predicate: ty::Predicate<'tcx>) -> bool {
         let result = match predicate.kind().skip_binder() {
-            ty::PredicateKind::Trait(ref data, _) => self.tcx().trait_is_auto(data.def_id()),
+            ty::PredicateKind::Trait(ref data) => self.tcx().trait_is_auto(data.def_id()),
             _ => false,
         };
         debug!(?predicate, ?result, "coinductive_predicate");
@@ -1213,7 +1212,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             .enumerate()
             .filter_map(|(idx, bound)| {
                 let bound_predicate = bound.kind();
-                if let ty::PredicateKind::Trait(pred, _) = bound_predicate.skip_binder() {
+                if let ty::PredicateKind::Trait(pred) = bound_predicate.skip_binder() {
                     let bound = bound_predicate.rebind(pred.trait_ref);
                     if self.infcx.probe(|_| {
                         match self.match_normalize_trait_ref(

compiler/rustc_trait_selection/src/traits/wf.rs

@@ -108,7 +108,7 @@ pub fn predicate_obligations<'a, 'tcx>(
 
     // It's ok to skip the binder here because wf code is prepared for it
     match predicate.kind().skip_binder() {
-        ty::PredicateKind::Trait(t, _) => {
+        ty::PredicateKind::Trait(t) => {
             wf.compute_trait_ref(&t.trait_ref, Elaborate::None);
         }
         ty::PredicateKind::RegionOutlives(..) => {}
@@ -226,7 +226,7 @@ fn extend_cause_with_original_assoc_item_obligation<'tcx>(
                 }
             }
         }
-        ty::PredicateKind::Trait(pred, _) => {
+        ty::PredicateKind::Trait(pred) => {
             // An associated item obligation born out of the `trait` failed to be met. An example
             // can be seen in `ui/associated-types/point-at-type-on-obligation-failure-2.rs`.
             debug!("extended_cause_with_original_assoc_item_obligation trait proj {:?}", pred);

compiler/rustc_traits/src/chalk/lowering.rs

@@ -87,7 +87,7 @@ impl<'tcx> LowerInto<'tcx, chalk_ir::InEnvironment<chalk_ir::Goal<RustInterner<'
                 ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
                     chalk_ir::DomainGoal::FromEnv(chalk_ir::FromEnv::Ty(ty.lower_into(interner)))
                 }
-                ty::PredicateKind::Trait(predicate, _) => chalk_ir::DomainGoal::FromEnv(
+                ty::PredicateKind::Trait(predicate) => chalk_ir::DomainGoal::FromEnv(
                     chalk_ir::FromEnv::Trait(predicate.trait_ref.lower_into(interner)),
                 ),
                 ty::PredicateKind::RegionOutlives(predicate) => chalk_ir::DomainGoal::Holds(
@@ -137,7 +137,7 @@ impl<'tcx> LowerInto<'tcx, chalk_ir::GoalData<RustInterner<'tcx>>> for ty::Predi
             collect_bound_vars(interner, interner.tcx, self.kind());
 
         let value = match predicate {
-            ty::PredicateKind::Trait(predicate, _) => {
+            ty::PredicateKind::Trait(predicate) => {
                 chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::Holds(
                     chalk_ir::WhereClause::Implemented(predicate.trait_ref.lower_into(interner)),
                 ))
@@ -569,7 +569,7 @@ impl<'tcx> LowerInto<'tcx, Option<chalk_ir::QuantifiedWhereClause<RustInterner<'
         let (predicate, binders, _named_regions) =
             collect_bound_vars(interner, interner.tcx, self.kind());
         let value = match predicate {
-            ty::PredicateKind::Trait(predicate, _) => {
+            ty::PredicateKind::Trait(predicate) => {
                 Some(chalk_ir::WhereClause::Implemented(predicate.trait_ref.lower_into(interner)))
             }
             ty::PredicateKind::RegionOutlives(predicate) => {
@@ -702,7 +702,7 @@ impl<'tcx> LowerInto<'tcx, Option<chalk_solve::rust_ir::QuantifiedInlineBound<Ru
         let (predicate, binders, _named_regions) =
             collect_bound_vars(interner, interner.tcx, self.kind());
         match predicate {
-            ty::PredicateKind::Trait(predicate, _) => Some(chalk_ir::Binders::new(
+            ty::PredicateKind::Trait(predicate) => Some(chalk_ir::Binders::new(
                 binders,
                 chalk_solve::rust_ir::InlineBound::TraitBound(
                     predicate.trait_ref.lower_into(interner),

compiler/rustc_typeck/src/astconv/mod.rs

@@ -1340,7 +1340,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
 
                 let bound_predicate = obligation.predicate.kind();
                 match bound_predicate.skip_binder() {
-                    ty::PredicateKind::Trait(pred, _) => {
+                    ty::PredicateKind::Trait(pred) => {
                         let pred = bound_predicate.rebind(pred);
                         associated_types.entry(span).or_default().extend(
                             tcx.associated_items(pred.def_id())

compiler/rustc_typeck/src/check/_match.rs

@@ -606,16 +606,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let mut suggest_box = !obligations.is_empty();
                 for o in obligations {
                     match o.predicate.kind().skip_binder() {
-                        ty::PredicateKind::Trait(t, constness) => {
+                        ty::PredicateKind::Trait(t) => {
-                            let pred = ty::PredicateKind::Trait(
+                            let pred = ty::PredicateKind::Trait(ty::TraitPredicate {
-                                ty::TraitPredicate {
                                 trait_ref: ty::TraitRef {
                                     def_id: t.def_id(),
                                     substs: self.infcx.tcx.mk_substs_trait(outer_ty, &[]),
                                 },
-                                },
+                                constness: t.constness,
-                                constness,
+                            });
-                            );
                             let obl = Obligation::new(
                                 o.cause.clone(),
                                 self.param_env,

compiler/rustc_typeck/src/check/coercion.rs

@@ -587,9 +587,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
             debug!("coerce_unsized resolve step: {:?}", obligation);
             let bound_predicate = obligation.predicate.kind();
             let trait_pred = match bound_predicate.skip_binder() {
-                ty::PredicateKind::Trait(trait_pred, _)
+                ty::PredicateKind::Trait(trait_pred) if traits.contains(&trait_pred.def_id()) => {
-                    if traits.contains(&trait_pred.def_id()) =>
-                {
                     if unsize_did == trait_pred.def_id() {
                         let self_ty = trait_pred.self_ty();
                         let unsize_ty = trait_pred.trait_ref.substs[1].expect_ty();

compiler/rustc_typeck/src/check/dropck.rs

@@ -229,7 +229,7 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
             let predicate = predicate.kind();
             let p = p.kind();
             match (predicate.skip_binder(), p.skip_binder()) {
-                (ty::PredicateKind::Trait(a, _), ty::PredicateKind::Trait(b, _)) => {
+                (ty::PredicateKind::Trait(a), ty::PredicateKind::Trait(b)) => {
                     relator.relate(predicate.rebind(a), p.rebind(b)).is_ok()
                 }
                 (ty::PredicateKind::Projection(a), ty::PredicateKind::Projection(b)) => {

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

@@ -796,7 +796,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         bound_predicate.rebind(data).required_poly_trait_ref(self.tcx),
                         obligation,
                     )),
-                    ty::PredicateKind::Trait(data, _) => {
+                    ty::PredicateKind::Trait(data) => {
                         Some((bound_predicate.rebind(data).to_poly_trait_ref(), obligation))
                     }
                     ty::PredicateKind::Subtype(..) => None,

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

@@ -923,7 +923,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 continue;
             }
 
-            if let ty::PredicateKind::Trait(predicate, _) =
+            if let ty::PredicateKind::Trait(predicate) =
                 error.obligation.predicate.kind().skip_binder()
             {
                 // Collect the argument position for all arguments that could have caused this
@@ -974,7 +974,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             if let hir::ExprKind::Path(qpath) = &path.kind {
                 if let hir::QPath::Resolved(_, path) = &qpath {
                     for error in errors {
-                        if let ty::PredicateKind::Trait(predicate, _) =
+                        if let ty::PredicateKind::Trait(predicate) =
                             error.obligation.predicate.kind().skip_binder()
                         {
                             // If any of the type arguments in this path segment caused the

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

@@ -194,7 +194,7 @@ impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
             predicates: tcx.arena.alloc_from_iter(
                 self.param_env.caller_bounds().iter().filter_map(|predicate| {
                     match predicate.kind().skip_binder() {
-                        ty::PredicateKind::Trait(data, _) if data.self_ty().is_param(index) => {
+                        ty::PredicateKind::Trait(data) if data.self_ty().is_param(index) => {
                             // HACK(eddyb) should get the original `Span`.
                             let span = tcx.def_span(def_id);
                             Some((predicate, span))

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

@@ -507,7 +507,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         traits::elaborate_predicates(self.tcx, predicates.predicates.iter().copied())
             // We don't care about regions here.
             .filter_map(|obligation| match obligation.predicate.kind().skip_binder() {
-                ty::PredicateKind::Trait(trait_pred, _) if trait_pred.def_id() == sized_def_id => {
+                ty::PredicateKind::Trait(trait_pred) if trait_pred.def_id() == sized_def_id => {
                     let span = iter::zip(&predicates.predicates, &predicates.spans)
                         .find_map(
                             |(p, span)| {

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

@@ -832,7 +832,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         let bounds = self.param_env.caller_bounds().iter().filter_map(|predicate| {
             let bound_predicate = predicate.kind();
             match bound_predicate.skip_binder() {
-                ty::PredicateKind::Trait(trait_predicate, _) => {
+                ty::PredicateKind::Trait(trait_predicate) => {
                     match *trait_predicate.trait_ref.self_ty().kind() {
                         ty::Param(p) if p == param_ty => {
                             Some(bound_predicate.rebind(trait_predicate.trait_ref))

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

@@ -683,7 +683,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     let mut collect_type_param_suggestions =
                         |self_ty: Ty<'tcx>, parent_pred: &ty::Predicate<'tcx>, obligation: &str| {
                             // We don't care about regions here, so it's fine to skip the binder here.
-                            if let (ty::Param(_), ty::PredicateKind::Trait(p, _)) =
+                            if let (ty::Param(_), ty::PredicateKind::Trait(p)) =
                                 (self_ty.kind(), parent_pred.kind().skip_binder())
                             {
                                 if let ty::Adt(def, _) = p.trait_ref.self_ty().kind() {
@@ -763,7 +763,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 bound_span_label(projection_ty.self_ty(), &obligation, &quiet);
                                 Some((obligation, projection_ty.self_ty()))
                             }
-                            ty::PredicateKind::Trait(poly_trait_ref, _) => {
+                            ty::PredicateKind::Trait(poly_trait_ref) => {
                                 let p = poly_trait_ref.trait_ref;
                                 let self_ty = p.self_ty();
                                 let path = p.print_only_trait_path();
@@ -1200,7 +1200,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     match p.kind().skip_binder() {
                         // Hide traits if they are present in predicates as they can be fixed without
                         // having to implement them.
-                        ty::PredicateKind::Trait(t, _) => t.def_id() == info.def_id,
+                        ty::PredicateKind::Trait(t) => t.def_id() == info.def_id,
                         ty::PredicateKind::Projection(p) => {
                             p.projection_ty.item_def_id == info.def_id
                         }

compiler/rustc_typeck/src/check/mod.rs

@@ -689,7 +689,7 @@ fn bounds_from_generic_predicates<'tcx>(
         debug!("predicate {:?}", predicate);
         let bound_predicate = predicate.kind();
         match bound_predicate.skip_binder() {
-            ty::PredicateKind::Trait(trait_predicate, _) => {
+            ty::PredicateKind::Trait(trait_predicate) => {
                 let entry = types.entry(trait_predicate.self_ty()).or_default();
                 let def_id = trait_predicate.def_id();
                 if Some(def_id) != tcx.lang_items().sized_trait() {

compiler/rustc_typeck/src/collect.rs

@@ -640,7 +640,7 @@ fn type_param_predicates(
         )
         .into_iter()
         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
-            ty::PredicateKind::Trait(data, _) => data.self_ty().is_param(index),
+            ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
             _ => false,
         }),
     );
@@ -1198,7 +1198,7 @@ fn super_predicates_that_define_assoc_type(
             // which will, in turn, reach indirect supertraits.
             for &(pred, span) in superbounds {
                 debug!("superbound: {:?}", pred);
-                if let ty::PredicateKind::Trait(bound, _) = pred.kind().skip_binder() {
+                if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
                     tcx.at(span).super_predicates_of(bound.def_id());
                 }
             }
@@ -2439,7 +2439,7 @@ fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicat
             .iter()
             .copied()
             .filter(|(pred, _)| match pred.kind().skip_binder() {
-                ty::PredicateKind::Trait(tr, _) => !is_assoc_item_ty(tr.self_ty()),
+                ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
                 ty::PredicateKind::Projection(proj) => {
                     !is_assoc_item_ty(proj.projection_ty.self_ty())
                 }

compiler/rustc_typeck/src/collect/item_bounds.rs

@@ -38,7 +38,7 @@ fn associated_type_bounds<'tcx>(
 
     let bounds_from_parent = trait_predicates.predicates.iter().copied().filter(|(pred, _)| {
         match pred.kind().skip_binder() {
-            ty::PredicateKind::Trait(tr, _) => tr.self_ty() == item_ty,
+            ty::PredicateKind::Trait(tr) => tr.self_ty() == item_ty,
             ty::PredicateKind::Projection(proj) => proj.projection_ty.self_ty() == item_ty,
             ty::PredicateKind::TypeOutlives(outlives) => outlives.0 == item_ty,
             _ => false,

compiler/rustc_typeck/src/impl_wf_check/min_specialization.rs

@@ -366,7 +366,10 @@ fn check_specialization_on<'tcx>(tcx: TyCtxt<'tcx>, predicate: ty::Predicate<'tc
         _ if predicate.is_global() => (),
         // We allow specializing on explicitly marked traits with no associated
         // items.
-        ty::PredicateKind::Trait(pred, hir::Constness::NotConst) => {
+        ty::PredicateKind::Trait(ty::TraitPredicate {
+            trait_ref,
+            constness: hir::Constness::NotConst,
+        }) => {
             if !matches!(
                 trait_predicate_kind(tcx, predicate),
                 Some(TraitSpecializationKind::Marker)
@@ -376,7 +379,7 @@ fn check_specialization_on<'tcx>(tcx: TyCtxt<'tcx>, predicate: ty::Predicate<'tc
                         span,
                         &format!(
                             "cannot specialize on trait `{}`",
-                            tcx.def_path_str(pred.def_id()),
+                            tcx.def_path_str(trait_ref.def_id),
                         ),
                     )
                     .emit()
@@ -394,10 +397,11 @@ fn trait_predicate_kind<'tcx>(
     predicate: ty::Predicate<'tcx>,
 ) -> Option<TraitSpecializationKind> {
     match predicate.kind().skip_binder() {
-        ty::PredicateKind::Trait(pred, hir::Constness::NotConst) => {
+        ty::PredicateKind::Trait(ty::TraitPredicate {
-            Some(tcx.trait_def(pred.def_id()).specialization_kind)
+            trait_ref,
-        }
+            constness: hir::Constness::NotConst,
-        ty::PredicateKind::Trait(_, hir::Constness::Const)
+        }) => Some(tcx.trait_def(trait_ref.def_id).specialization_kind),
+        ty::PredicateKind::Trait(_)
         | ty::PredicateKind::RegionOutlives(_)
         | ty::PredicateKind::TypeOutlives(_)
         | ty::PredicateKind::Projection(_)

src/librustdoc/clean/auto_trait.rs

@@ -316,7 +316,7 @@ impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> {
         let bound_predicate = pred.kind();
         let tcx = self.cx.tcx;
         let regions = match bound_predicate.skip_binder() {
-            ty::PredicateKind::Trait(poly_trait_pred, _) => {
+            ty::PredicateKind::Trait(poly_trait_pred) => {
                 tcx.collect_referenced_late_bound_regions(&bound_predicate.rebind(poly_trait_pred))
             }
             ty::PredicateKind::Projection(poly_proj_pred) => {
@@ -463,7 +463,7 @@ impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> {
             .filter(|p| {
                 !orig_bounds.contains(p)
                     || match p.kind().skip_binder() {
-                        ty::PredicateKind::Trait(pred, _) => pred.def_id() == sized_trait,
+                        ty::PredicateKind::Trait(pred) => pred.def_id() == sized_trait,
                         _ => false,
                     }
             })

src/librustdoc/clean/mod.rs

@@ -325,7 +325,7 @@ impl<'a> Clean<Option<WherePredicate>> for ty::Predicate<'a> {
     fn clean(&self, cx: &mut DocContext<'_>) -> Option<WherePredicate> {
         let bound_predicate = self.kind();
         match bound_predicate.skip_binder() {
-            ty::PredicateKind::Trait(pred, _) => Some(bound_predicate.rebind(pred).clean(cx)),
+            ty::PredicateKind::Trait(pred) => Some(bound_predicate.rebind(pred).clean(cx)),
             ty::PredicateKind::RegionOutlives(pred) => pred.clean(cx),
             ty::PredicateKind::TypeOutlives(pred) => pred.clean(cx),
             ty::PredicateKind::Projection(pred) => Some(pred.clean(cx)),
@@ -637,7 +637,7 @@ impl<'a, 'tcx> Clean<Generics> for (&'a ty::Generics, ty::GenericPredicates<'tcx
                 let param_idx = (|| {
                     let bound_p = p.kind();
                     match bound_p.skip_binder() {
-                        ty::PredicateKind::Trait(pred, _constness) => {
+                        ty::PredicateKind::Trait(pred) => {
                             if let ty::Param(param) = pred.self_ty().kind() {
                                 return Some(param.index);
                             }
@@ -1555,9 +1555,7 @@ impl<'tcx> Clean<Type> for Ty<'tcx> {
                     .filter_map(|bound| {
                         let bound_predicate = bound.kind();
                         let trait_ref = match bound_predicate.skip_binder() {
-                            ty::PredicateKind::Trait(tr, _constness) => {
+                            ty::PredicateKind::Trait(tr) => bound_predicate.rebind(tr.trait_ref),
-                                bound_predicate.rebind(tr.trait_ref)
-                            }
                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(_ty, reg)) => {
                                 if let Some(r) = reg.clean(cx) {
                                     regions.push(GenericBound::Outlives(r));

src/librustdoc/clean/simplify.rs

@@ -139,7 +139,7 @@ fn trait_is_same_or_supertrait(cx: &DocContext<'_>, child: DefId, trait_: DefId)
         .predicates
         .iter()
         .filter_map(|(pred, _)| {
-            if let ty::PredicateKind::Trait(pred, _) = pred.kind().skip_binder() {
+            if let ty::PredicateKind::Trait(pred) = pred.kind().skip_binder() {
                 if pred.trait_ref.self_ty() == self_ty { Some(pred.def_id()) } else { None }
             } else {
                 None

src/test/ui/rfc-2632-const-trait-impl/assoc-type.rs

@@ -1,5 +1,5 @@
 // ignore-test
-
+//
 // FIXME: This test should fail since, within a const impl of `Foo`, the bound on `Foo::Bar` should
 // require a const impl of `Add` for the associated type.
 

src/tools/clippy/clippy_lints/src/future_not_send.rs

@@ -93,7 +93,7 @@ impl<'tcx> LateLintPass<'tcx> for FutureNotSend {
                             cx.tcx.infer_ctxt().enter(|infcx| {
                                 for FulfillmentError { obligation, .. } in send_errors {
                                     infcx.maybe_note_obligation_cause_for_async_await(db, &obligation);
-                                    if let Trait(trait_pred, _) = obligation.predicate.kind().skip_binder() {
+                                    if let Trait(trait_pred) = obligation.predicate.kind().skip_binder() {
                                         db.note(&format!(
                                             "`{}` doesn't implement `{}`",
                                             trait_pred.self_ty(),

src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs

@@ -121,7 +121,7 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
             .filter_map(|obligation| {
                 // Note that we do not want to deal with qualified predicates here.
                 match obligation.predicate.kind().no_bound_vars() {
-                    Some(ty::PredicateKind::Trait(pred, _)) if pred.def_id() != sized_trait => Some(pred),
+                    Some(ty::PredicateKind::Trait(pred)) if pred.def_id() != sized_trait => Some(pred),
                     _ => None,
                 }
             })

src/tools/clippy/clippy_lints/src/unit_return_expecting_ord.rs

@@ -45,7 +45,7 @@ fn get_trait_predicates_for_trait_id<'tcx>(
     let mut preds = Vec::new();
     for (pred, _) in generics.predicates {
         if_chain! {
-            if let PredicateKind::Trait(poly_trait_pred, _) = pred.kind().skip_binder();
+            if let PredicateKind::Trait(poly_trait_pred) = pred.kind().skip_binder();
             let trait_pred = cx.tcx.erase_late_bound_regions(pred.kind().rebind(poly_trait_pred));
             if let Some(trait_def_id) = trait_id;
             if trait_def_id == trait_pred.trait_ref.def_id;

src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs

@@ -36,7 +36,7 @@ pub fn is_min_const_fn(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, msrv: Option<&Ru
                 ty::PredicateKind::ObjectSafe(_) => panic!("object safe predicate on function: {:#?}", predicate),
                 ty::PredicateKind::ClosureKind(..) => panic!("closure kind predicate on function: {:#?}", predicate),
                 ty::PredicateKind::Subtype(_) => panic!("subtype predicate on function: {:#?}", predicate),
-                ty::PredicateKind::Trait(pred, _) => {
+                ty::PredicateKind::Trait(pred) => {
                     if Some(pred.def_id()) == tcx.lang_items().sized_trait() {
                         continue;
                     }

src/tools/clippy/clippy_utils/src/ty.rs

@@ -157,7 +157,7 @@ pub fn is_must_use_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
         ty::Tuple(substs) => substs.types().any(|ty| is_must_use_ty(cx, ty)),
         ty::Opaque(ref def_id, _) => {
             for (predicate, _) in cx.tcx.explicit_item_bounds(*def_id) {
-                if let ty::PredicateKind::Trait(trait_predicate, _) = predicate.kind().skip_binder() {
+                if let ty::PredicateKind::Trait(trait_predicate) = predicate.kind().skip_binder() {
                     if must_use_attr(cx.tcx.get_attrs(trait_predicate.trait_ref.def_id)).is_some() {
                         return true;
                     }