get rid of to_poly_trait_predicate

compiler/rustc_hir_typeck/src/coercion.rs

@@ -792,8 +792,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
             self.param_env,
             ty::Binder::dummy(
                 self.tcx.at(self.cause.span).mk_trait_ref(hir::LangItem::PointerSized, [a]),
-            )
+            ),
-            .to_poly_trait_predicate(),
         ));
 
         Ok(InferOk {

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -1096,8 +1096,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 ty::Binder::dummy(self.tcx.mk_trait_ref(
                     into_def_id,
                     [expr_ty, expected_ty]
-                ))
+                )),
-                .to_poly_trait_predicate(),
             ))
         {
             let sugg = if expr.precedence().order() >= PREC_POSTFIX {

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -1430,7 +1430,7 @@ 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 = ty::Binder::dummy(trait_ref).to_poly_trait_predicate();
+        let predicate = ty::Binder::dummy(trait_ref);
         let obligation = traits::Obligation::new(self.tcx, cause, self.param_env, predicate);
         traits::SelectionContext::new(self).select(&obligation)
     }

compiler/rustc_middle/src/ty/mod.rs

@@ -1153,6 +1153,25 @@ impl<'tcx> ToPredicate<'tcx, Predicate<'tcx>> for Binder<'tcx, PredicateKind<'tc
     }
 }
 
+impl<'tcx> ToPredicate<'tcx, Predicate<'tcx>> for Binder<'tcx, TraitRef<'tcx>> {
+    #[inline(always)]
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        let pred: PolyTraitPredicate<'tcx> = self.to_predicate(tcx);
+        pred.to_predicate(tcx)
+    }
+}
+
+impl<'tcx> ToPredicate<'tcx, PolyTraitPredicate<'tcx>> for Binder<'tcx, TraitRef<'tcx>> {
+    #[inline(always)]
+    fn to_predicate(self, _: TyCtxt<'tcx>) -> PolyTraitPredicate<'tcx> {
+        self.map_bound(|trait_ref| TraitPredicate {
+            trait_ref,
+            constness: ty::BoundConstness::NotConst,
+            polarity: ty::ImplPolarity::Positive,
+        })
+    }
+}
+
 impl<'tcx> ToPredicate<'tcx, Predicate<'tcx>> for PolyTraitPredicate<'tcx> {
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         self.map_bound(PredicateKind::Trait).to_predicate(tcx)

compiler/rustc_middle/src/ty/sty.rs

@@ -853,23 +853,6 @@ impl<'tcx> PolyTraitRef<'tcx> {
     pub fn def_id(&self) -> DefId {
         self.skip_binder().def_id
     }
-
-    pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
-        self.map_bound(|trait_ref| ty::TraitPredicate {
-            trait_ref,
-            constness: ty::BoundConstness::NotConst,
-            polarity: ty::ImplPolarity::Positive,
-        })
-    }
-
-    /// Same as [`PolyTraitRef::to_poly_trait_predicate`] but sets a negative polarity instead.
-    pub fn to_poly_trait_predicate_negative_polarity(&self) -> ty::PolyTraitPredicate<'tcx> {
-        self.map_bound(|trait_ref| ty::TraitPredicate {
-            trait_ref,
-            constness: ty::BoundConstness::NotConst,
-            polarity: ty::ImplPolarity::Negative,
-        })
-    }
 }
 
 impl rustc_errors::IntoDiagnosticArg for PolyTraitRef<'_> {

compiler/rustc_trait_selection/src/traits/auto_trait.rs

@@ -10,7 +10,7 @@ use crate::traits::project::ProjectAndUnifyResult;
 use rustc_middle::mir::interpret::ErrorHandled;
 use rustc_middle::ty::fold::{TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::visit::TypeVisitable;
-use rustc_middle::ty::{PolyTraitRef, Region, RegionVid};
+use rustc_middle::ty::{ImplPolarity, Region, RegionVid};
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
 
@@ -88,19 +88,22 @@ impl<'tcx> AutoTraitFinder<'tcx> {
 
         let trait_ref = tcx.mk_trait_ref(trait_did, [ty]);
 
-        let trait_pred = ty::Binder::dummy(trait_ref);
-
         let infcx = tcx.infer_ctxt().build();
         let mut selcx = SelectionContext::new(&infcx);
-        for f in [
+        for polarity in [true, false] {
-            PolyTraitRef::to_poly_trait_predicate,
-            PolyTraitRef::to_poly_trait_predicate_negative_polarity,
-        ] {
             let result = selcx.select(&Obligation::new(
                 tcx,
                 ObligationCause::dummy(),
                 orig_env,
-                f(&trait_pred),
+                ty::Binder::dummy(ty::TraitPredicate {
+                    trait_ref,
+                    constness: ty::BoundConstness::NotConst,
+                    polarity: if polarity {
+                        ImplPolarity::Positive
+                    } else {
+                        ImplPolarity::Negative
+                    },
+                }),
             ));
             if let Ok(Some(ImplSource::UserDefined(_))) = result {
                 debug!(

compiler/rustc_trait_selection/src/traits/codegen.rs

@@ -39,8 +39,7 @@ pub fn codegen_select_candidate<'tcx>(
     let mut selcx = SelectionContext::new(&infcx);
 
     let obligation_cause = ObligationCause::dummy();
-    let obligation =
+    let obligation = Obligation::new(tcx, obligation_cause, param_env, trait_ref);
-        Obligation::new(tcx, obligation_cause, param_env, trait_ref.to_poly_trait_predicate());
 
     let selection = match selcx.select(&obligation) {
         Ok(Some(selection)) => selection,

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

@@ -2111,7 +2111,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     )
                 };
 
-                let obligation = obligation.with(self.tcx, trait_ref.to_poly_trait_predicate());
+                let obligation = obligation.with(self.tcx, trait_ref);
                 let mut selcx = SelectionContext::new(&self);
                 match selcx.select_from_obligation(&obligation) {
                     Ok(None) => {

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -477,7 +477,7 @@ fn subst_and_check_impossible_predicates<'tcx>(
     // associated items.
     if let Some(trait_def_id) = tcx.trait_of_item(key.0) {
         let trait_ref = ty::TraitRef::from_method(tcx, trait_def_id, key.1);
-        predicates.push(ty::Binder::dummy(trait_ref).to_poly_trait_predicate().to_predicate(tcx));
+        predicates.push(ty::Binder::dummy(trait_ref).to_predicate(tcx));
     }
 
     predicates.retain(|predicate| !predicate.needs_subst());

compiler/rustc_trait_selection/src/traits/project.rs

@@ -1328,8 +1328,7 @@ fn assemble_candidate_for_impl_trait_in_trait<'cx, 'tcx>(
             obligation.predicate.substs.truncate_to(tcx, tcx.generics_of(trait_def_id));
         // FIXME(named-returns): Binders
         let trait_predicate =
-            ty::Binder::dummy(ty::TraitRef { def_id: trait_def_id, substs: trait_substs })
+            ty::Binder::dummy(ty::TraitRef { def_id: trait_def_id, substs: trait_substs });
-                .to_poly_trait_predicate();
 
         let _ = selcx.infcx().commit_if_ok(|_| {
             match selcx.select(&obligation.with(tcx, trait_predicate)) {
@@ -1527,7 +1526,7 @@ 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 = ty::Binder::dummy(obligation.predicate.trait_ref(selcx.tcx()));
-    let trait_obligation = obligation.with(selcx.tcx(), poly_trait_ref.to_poly_trait_predicate());
+    let trait_obligation = obligation.with(selcx.tcx(), poly_trait_ref);
     let _ = selcx.infcx().commit_if_ok(|_| {
         let impl_source = match selcx.select(&trait_obligation) {
             Ok(Some(impl_source)) => impl_source,

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

@@ -640,12 +640,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         );
         let tr =
             ty::Binder::dummy(self.tcx().at(cause.span).mk_trait_ref(LangItem::Sized, [output_ty]));
-        nested.push(Obligation::new(
+        nested.push(Obligation::new(self.infcx.tcx, cause, obligation.param_env, tr));
-            self.infcx.tcx,
-            cause,
-            obligation.param_env,
-            tr.to_poly_trait_predicate(),
-        ));
 
         Ok(ImplSourceFnPointerData { fn_ty: self_ty, nested })
     }

src/librustdoc/clean/blanket_impl.rs

@@ -67,12 +67,7 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                     .instantiate(cx.tcx, impl_substs)
                     .predicates
                     .into_iter()
-                    .chain(Some(
+                    .chain(Some(ty::Binder::dummy(impl_trait_ref).to_predicate(infcx.tcx)));
-                        ty::Binder::dummy(impl_trait_ref)
-                            .to_poly_trait_predicate()
-                            .map_bound(ty::PredicateKind::Trait)
-                            .to_predicate(infcx.tcx),
-                    ));
                 for predicate in predicates {
                     debug!("testing predicate {:?}", predicate);
                     let obligation = traits::Obligation::new(