Rename ToPredicate for Upcast

44 files changed, 214 insertions, 220 deletions

diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index ccc45e2829a..15050c87b39 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -24,8 +24,8 @@ use rustc_middle::mir::{
 };
 use rustc_middle::ty::print::PrintTraitRefExt as _;
 use rustc_middle::ty::{
-    self, suggest_constraining_type_params, PredicateKind, ToPredicate, Ty, TyCtxt,
-    TypeSuperVisitable, TypeVisitor,
+    self, suggest_constraining_type_params, PredicateKind, Ty, TyCtxt, TypeSuperVisitable,
+    TypeVisitor, Upcast,
 };
 use rustc_middle::util::CallKind;
 use rustc_mir_dataflow::move_paths::{InitKind, MoveOutIndex, MovePathIndex};
@@ -1915,7 +1915,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             self.infcx.err_ctxt().suggest_derive(
                 &obligation,
                 err,
-                trait_ref.to_predicate(self.infcx.tcx),
+                trait_ref.upcast(self.infcx.tcx),
             );
         }
     }
diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
index c9a09c19ce6..35017b9e6b5 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -9,7 +9,7 @@ use rustc_hir::{self as hir, BindingMode, ByRef, Node};
 use rustc_infer::traits;
 use rustc_middle::bug;
 use rustc_middle::mir::{Mutability, Place, PlaceRef, ProjectionElem};
-use rustc_middle::ty::{self, InstanceDef, ToPredicate, Ty, TyCtxt};
+use rustc_middle::ty::{self, InstanceDef, Ty, TyCtxt, Upcast};
 use rustc_middle::{
     hir::place::PlaceBase,
     mir::{self, BindingForm, Local, LocalDecl, LocalInfo, LocalKind, Location},
@@ -1255,7 +1255,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                                 self.infcx.err_ctxt().suggest_derive(
                                     &obligation,
                                     err,
-                                    trait_ref.to_predicate(self.infcx.tcx),
+                                    trait_ref.upcast(self.infcx.tcx),
                                 );
                             }
                             Some(errors) => {
diff --git a/compiler/rustc_borrowck/src/type_check/canonical.rs b/compiler/rustc_borrowck/src/type_check/canonical.rs
index 49d3f7381d9..2b89fa9b770 100644
--- a/compiler/rustc_borrowck/src/type_check/canonical.rs
+++ b/compiler/rustc_borrowck/src/type_check/canonical.rs
@@ -4,7 +4,7 @@ use rustc_errors::ErrorGuaranteed;
 use rustc_infer::infer::canonical::Canonical;
 use rustc_middle::bug;
 use rustc_middle::mir::ConstraintCategory;
-use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt, TypeFoldable};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, Upcast};
 use rustc_span::def_id::DefId;
 use rustc_span::Span;
 use rustc_trait_selection::traits::query::type_op::{self, TypeOpOutput};
@@ -115,7 +115,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
     pub(super) fn prove_predicates(
         &mut self,
-        predicates: impl IntoIterator<Item: ToPredicate<'tcx> + std::fmt::Debug>,
+        predicates: impl IntoIterator<Item: Upcast<'tcx> + std::fmt::Debug>,
         locations: Locations,
         category: ConstraintCategory<'tcx>,
     ) {
@@ -127,12 +127,12 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
     #[instrument(skip(self), level = "debug")]
     pub(super) fn prove_predicate(
         &mut self,
-        predicate: impl ToPredicate<'tcx> + std::fmt::Debug,
+        predicate: impl Upcast<'tcx> + std::fmt::Debug,
         locations: Locations,
         category: ConstraintCategory<'tcx>,
     ) {
         let param_env = self.param_env;
-        let predicate = predicate.to_predicate(self.tcx());
+        let predicate = predicate.upcast(self.tcx());
         let _: Result<_, ErrorGuaranteed> = self.fully_perform_op(
             locations,
             category,
diff --git a/compiler/rustc_borrowck/src/type_check/relate_tys.rs b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
index 493c41e59e3..2b01b8dbbf4 100644
--- a/compiler/rustc_borrowck/src/type_check/relate_tys.rs
+++ b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
@@ -546,7 +546,7 @@ impl<'bccx, 'tcx> ObligationEmittingRelation<'tcx> for NllTypeRelating<'_, 'bccx
         self.type_checker.param_env
     }
 
-    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {
+    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::Upcast<'tcx>>) {
         self.register_obligations(
             obligations
                 .into_iter()
diff --git a/compiler/rustc_hir_analysis/src/bounds.rs b/compiler/rustc_hir_analysis/src/bounds.rs
index 5562b81871f..38ecd7dd082 100644
--- a/compiler/rustc_hir_analysis/src/bounds.rs
+++ b/compiler/rustc_hir_analysis/src/bounds.rs
@@ -2,7 +2,7 @@
 //! [`rustc_middle::ty`] form.
 
 use rustc_hir::LangItem;
-use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt, Upcast};
 use rustc_span::Span;
 
 /// Collects together a list of type bounds. These lists of bounds occur in many places
@@ -34,7 +34,7 @@ impl<'tcx> Bounds<'tcx> {
         span: Span,
     ) {
         self.clauses
-            .push((region.map_bound(|p| ty::ClauseKind::TypeOutlives(p)).to_predicate(tcx), span));
+            .push((region.map_bound(|p| ty::ClauseKind::TypeOutlives(p)).upcast(tcx), span));
     }
 
     pub fn push_trait_bound(
@@ -49,7 +49,7 @@ impl<'tcx> Bounds<'tcx> {
                 .map_bound(|trait_ref| {
                     ty::ClauseKind::Trait(ty::TraitPredicate { trait_ref, polarity })
                 })
-                .to_predicate(tcx),
+                .upcast(tcx),
             span,
         );
         // FIXME(-Znext-solver): We can likely remove this hack once the new trait solver lands.
@@ -67,7 +67,7 @@ impl<'tcx> Bounds<'tcx> {
         span: Span,
     ) {
         self.clauses.push((
-            projection.map_bound(|proj| ty::ClauseKind::Projection(proj)).to_predicate(tcx),
+            projection.map_bound(|proj| ty::ClauseKind::Projection(proj)).upcast(tcx),
             span,
         ));
     }
@@ -76,7 +76,7 @@ impl<'tcx> Bounds<'tcx> {
         let sized_def_id = tcx.require_lang_item(LangItem::Sized, Some(span));
         let trait_ref = ty::TraitRef::new(tcx, sized_def_id, [ty]);
         // Preferable to put this obligation first, since we report better errors for sized ambiguity.
-        self.clauses.insert(0, (trait_ref.to_predicate(tcx), span));
+        self.clauses.insert(0, (trait_ref.upcast(tcx), span));
     }
 
     pub fn clauses(&self) -> impl Iterator<Item = (ty::Clause<'tcx>, Span)> + '_ {
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 39940c8f0f3..19645049d0c 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -14,7 +14,7 @@ use rustc_infer::traits::{util, FulfillmentError};
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::util::ExplicitSelf;
-use rustc_middle::ty::ToPredicate;
+use rustc_middle::ty::Upcast;
 use rustc_middle::ty::{
     self, GenericArgs, Ty, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
 };
@@ -2211,7 +2211,7 @@ fn param_env_with_gat_bounds<'tcx>(
                     },
                     bound_vars,
                 )
-                .to_predicate(tcx),
+                .upcast(tcx),
             ),
         };
     }
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index b918a8c32d8..059e4141e15 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -20,8 +20,8 @@ use rustc_middle::query::Providers;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::trait_def::TraitSpecializationKind;
 use rustc_middle::ty::{
-    self, AdtKind, GenericParamDefKind, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable,
-    TypeVisitable, TypeVisitableExt, TypeVisitor,
+    self, AdtKind, GenericParamDefKind, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable,
+    TypeVisitable, TypeVisitableExt, TypeVisitor, Upcast,
 };
 use rustc_middle::ty::{GenericArgKind, GenericArgs};
 use rustc_middle::{bug, span_bug};
@@ -685,7 +685,7 @@ fn gather_gat_bounds<'tcx, T: TypeFoldable<TyCtxt<'tcx>>>(
                 // `Self: 'me`.)
                 bounds.insert(
                     ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(ty_param, region_param))
-                        .to_predicate(tcx),
+                        .upcast(tcx),
                 );
             }
         }
@@ -730,7 +730,7 @@ fn gather_gat_bounds<'tcx, T: TypeFoldable<TyCtxt<'tcx>>>(
                         region_a_param,
                         region_b_param,
                     ))
-                    .to_predicate(tcx),
+                    .upcast(tcx),
                 );
             }
         }
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index 0b9f7fd41fb..a1f44f82279 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -29,7 +29,7 @@ use rustc_infer::traits::ObligationCause;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::util::{Discr, IntTypeExt};
-use rustc_middle::ty::{self, AdtKind, Const, IsSuggestable, ToPredicate, Ty, TyCtxt};
+use rustc_middle::ty::{self, AdtKind, Const, IsSuggestable, Ty, TyCtxt, Upcast};
 use rustc_middle::{bug, span_bug};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
@@ -1665,7 +1665,7 @@ fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicate
             def_id, inferred_outlives,
         );
         let inferred_outlives_iter =
-            inferred_outlives.iter().map(|(clause, span)| ((*clause).to_predicate(tcx), *span));
+            inferred_outlives.iter().map(|(clause, span)| ((*clause).upcast(tcx), *span));
         if result.predicates.is_empty() {
             result.predicates = tcx.arena.alloc_from_iter(inferred_outlives_iter);
         } else {
diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
index d348d6f789f..eeca67cb56e 100644
--- a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
@@ -9,7 +9,7 @@ use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_middle::ty::{self, Ty, TyCtxt};
-use rustc_middle::ty::{GenericPredicates, ImplTraitInTraitData, ToPredicate};
+use rustc_middle::ty::{GenericPredicates, ImplTraitInTraitData, Upcast};
 use rustc_middle::{bug, span_bug};
 use rustc_span::symbol::Ident;
 use rustc_span::{Span, DUMMY_SP};
@@ -42,7 +42,7 @@ pub(super) fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredic
 
         result.predicates =
             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
-                ty::TraitRef::identity(tcx, def_id).to_predicate(tcx),
+                ty::TraitRef::identity(tcx, def_id).upcast(tcx),
                 span,
             ))));
     }
@@ -165,7 +165,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
     // (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((trait_ref.to_predicate(tcx), tcx.def_span(def_id)));
+        predicates.insert((trait_ref.upcast(tcx), tcx.def_span(def_id)));
     }
 
     // Collect the predicates that were written inline by the user on each
@@ -197,7 +197,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
                     .expect("const parameters cannot be generic");
                 let ct = icx.lowerer().lower_const_param(param.hir_id, ct_ty);
                 predicates.insert((
-                    ty::ClauseKind::ConstArgHasType(ct, ct_ty).to_predicate(tcx),
+                    ty::ClauseKind::ConstArgHasType(ct, ct_ty).upcast(tcx),
                     param.span,
                 ));
             }
@@ -228,7 +228,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
                             ty::ClauseKind::WellFormed(ty.into()),
                             bound_vars,
                         );
-                        predicates.insert((predicate.to_predicate(tcx), span));
+                        predicates.insert((predicate.upcast(tcx), span));
                     }
                 }
 
@@ -258,7 +258,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
                         }
                     };
                     let pred = ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(r1, r2))
-                        .to_predicate(tcx);
+                        .upcast(tcx);
                     (pred, span)
                 }))
             }
@@ -328,12 +328,12 @@ fn compute_bidirectional_outlives_predicates<'tcx>(
             let span = tcx.def_span(param.def_id);
             predicates.push((
                 ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(orig_lifetime, dup_lifetime))
-                    .to_predicate(tcx),
+                    .upcast(tcx),
                 span,
             ));
             predicates.push((
                 ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(dup_lifetime, orig_lifetime))
-                    .to_predicate(tcx),
+                    .upcast(tcx),
                 span,
             ));
         }
@@ -355,7 +355,7 @@ fn const_evaluatable_predicates_of(
             if let ty::ConstKind::Unevaluated(_) = ct.kind() {
                 let span = self.tcx.def_span(c.def_id);
                 self.preds
-                    .insert((ty::ClauseKind::ConstEvaluatable(ct).to_predicate(self.tcx), span));
+                    .insert((ty::ClauseKind::ConstEvaluatable(ct).upcast(self.tcx), span));
             }
         }
 
@@ -694,7 +694,7 @@ pub(super) fn type_param_predicates(
         && param_id == item_hir_id
     {
         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id.to_def_id());
-        extend = Some((identity_trait_ref.to_predicate(tcx), item.span));
+        extend = Some((identity_trait_ref.upcast(tcx), item.span));
     }
 
     let icx = ItemCtxt::new(tcx, item_def_id);
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/object_safety.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/object_safety.rs
index 30b99a095f3..4f7a39d0250 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/object_safety.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/object_safety.rs
@@ -9,7 +9,7 @@ use rustc_lint_defs::builtin::UNUSED_ASSOCIATED_TYPE_BOUNDS;
 use rustc_middle::span_bug;
 use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::{self, ExistentialPredicateStableCmpExt as _, Ty, TyCtxt, TypeFoldable};
-use rustc_middle::ty::{DynKind, ToPredicate};
+use rustc_middle::ty::{DynKind, Upcast};
 use rustc_span::{ErrorGuaranteed, Span};
 use rustc_trait_selection::traits::error_reporting::report_object_safety_error;
 use rustc_trait_selection::traits::{self, hir_ty_lowering_object_safety_violations};
@@ -119,7 +119,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             .filter(|(trait_ref, _)| !tcx.trait_is_auto(trait_ref.def_id()));
 
         for (base_trait_ref, span) in regular_traits_refs_spans {
-            let base_pred: ty::Predicate<'tcx> = base_trait_ref.to_predicate(tcx);
+            let base_pred: ty::Predicate<'tcx> = base_trait_ref.upcast(tcx);
             for pred in traits::elaborate(tcx, [base_pred]).filter_only_self() {
                 debug!("observing object predicate `{pred:?}`");
 
diff --git a/compiler/rustc_hir_analysis/src/outlives/mod.rs b/compiler/rustc_hir_analysis/src/outlives/mod.rs
index a87112dcc12..97fd7731b1e 100644
--- a/compiler/rustc_hir_analysis/src/outlives/mod.rs
+++ b/compiler/rustc_hir_analysis/src/outlives/mod.rs
@@ -2,7 +2,7 @@ use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::GenericArgKind;
-use rustc_middle::ty::{self, CratePredicatesMap, ToPredicate, TyCtxt};
+use rustc_middle::ty::{self, CratePredicatesMap, TyCtxt, Upcast};
 use rustc_span::Span;
 
 mod explicit;
@@ -75,14 +75,14 @@ fn inferred_outlives_crate(tcx: TyCtxt<'_>, (): ()) -> CratePredicatesMap<'_> {
                         match kind1.unpack() {
                             GenericArgKind::Type(ty1) => Some((
                                 ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(ty1, *region2))
-                                    .to_predicate(tcx),
+                                    .upcast(tcx),
                                 span,
                             )),
                             GenericArgKind::Lifetime(region1) => Some((
                                 ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(
                                     region1, *region2,
                                 ))
-                                .to_predicate(tcx),
+                                .upcast(tcx),
                                 span,
                             )),
                             GenericArgKind::Const(_) => {
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
index fe0dd4e393f..56e13cd679d 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
@@ -28,8 +28,8 @@ use rustc_middle::middle::stability::EvalResult;
 use rustc_middle::span_bug;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{
-    self, suggest_constraining_type_params, Article, Binder, IsSuggestable, ToPredicate, Ty,
-    TypeVisitableExt,
+    self, suggest_constraining_type_params, Article, Binder, IsSuggestable, Ty, TypeVisitableExt,
+    Upcast,
 };
 use rustc_session::errors::ExprParenthesesNeeded;
 use rustc_span::source_map::Spanned;
@@ -1716,7 +1716,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         }
                     }
                 }
-                self.suggest_derive(diag, &[(trait_ref.to_predicate(self.tcx), None, None)]);
+                self.suggest_derive(diag, &[(trait_ref.upcast(self.tcx), None, None)]);
             }
         }
     }
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 6cfdacf6a24..7ec0bdbef99 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -21,7 +21,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::ty::fast_reject::{simplify_type, TreatParams};
 use rustc_middle::ty::AssocItem;
 use rustc_middle::ty::GenericParamDefKind;
-use rustc_middle::ty::ToPredicate;
+use rustc_middle::ty::Upcast;
 use rustc_middle::ty::{self, ParamEnvAnd, Ty, TyCtxt, TypeVisitableExt};
 use rustc_middle::ty::{GenericArgs, GenericArgsRef};
 use rustc_middle::{bug, span_bug};
@@ -1496,7 +1496,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                         }
                     }
 
-                    trait_predicate = Some(ty::Binder::dummy(trait_ref).to_predicate(self.tcx));
+                    trait_predicate = Some(ty::Binder::dummy(trait_ref).upcast(self.tcx));
                 }
                 ObjectCandidate(poly_trait_ref) | WhereClauseCandidate(poly_trait_ref) => {
                     let trait_ref = self.instantiate_binder_with_fresh_vars(
diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index d0687dfc6fd..f4618fb8243 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -73,7 +73,7 @@ use rustc_middle::bug;
 use rustc_middle::dep_graph::DepContext;
 use rustc_middle::ty::print::{with_forced_trimmed_paths, PrintError, PrintTraitRefExt as _};
 use rustc_middle::ty::relate::{self, RelateResult, TypeRelation};
-use rustc_middle::ty::ToPredicate;
+use rustc_middle::ty::Upcast;
 use rustc_middle::ty::{
     self, error::TypeError, IsSuggestable, List, Region, Ty, TyCtxt, TypeFoldable,
     TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
@@ -516,7 +516,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
 
                     RegionResolutionError::CannotNormalize(clause, origin) => {
                         let clause: ty::Clause<'tcx> =
-                            clause.map_bound(ty::ClauseKind::TypeOutlives).to_predicate(self.tcx);
+                            clause.map_bound(ty::ClauseKind::TypeOutlives).upcast(self.tcx);
                         self.tcx
                             .dcx()
                             .struct_span_err(origin.span(), format!("cannot normalize `{clause}`"))
diff --git a/compiler/rustc_infer/src/infer/relate/combine.rs b/compiler/rustc_infer/src/infer/relate/combine.rs
index c1baadfa8df..18727335006 100644
--- a/compiler/rustc_infer/src/infer/relate/combine.rs
+++ b/compiler/rustc_infer/src/infer/relate/combine.rs
@@ -29,7 +29,7 @@ use rustc_middle::infer::canonical::OriginalQueryValues;
 use rustc_middle::infer::unify_key::EffectVarValue;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::relate::{RelateResult, TypeRelation};
-use rustc_middle::ty::{self, InferConst, ToPredicate, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{self, InferConst, Ty, TyCtxt, TypeVisitableExt, Upcast};
 use rustc_middle::ty::{IntType, UintType};
 use rustc_span::Span;
 
@@ -337,7 +337,7 @@ impl<'infcx, 'tcx> CombineFields<'infcx, 'tcx> {
         self.obligations.extend(obligations);
     }
 
-    pub fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ToPredicate<'tcx>>) {
+    pub fn register_predicates(&mut self, obligations: impl IntoIterator<Item: Upcast<'tcx>>) {
         self.obligations.extend(obligations.into_iter().map(|to_pred| {
             Obligation::new(self.infcx.tcx, self.trace.cause.clone(), self.param_env, to_pred)
         }))
@@ -360,7 +360,7 @@ pub trait ObligationEmittingRelation<'tcx>: TypeRelation<'tcx> {
     /// Register predicates that must hold in order for this relation to hold. Uses
     /// a default obligation cause, [`ObligationEmittingRelation::register_obligations`] should
     /// be used if control over the obligation causes is required.
-    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ToPredicate<'tcx>>);
+    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: Upcast<'tcx>>);
 
     /// Register `AliasRelate` obligation(s) that both types must be related to each other.
     fn register_type_relate_obligation(&mut self, a: Ty<'tcx>, b: Ty<'tcx>);
diff --git a/compiler/rustc_infer/src/infer/relate/glb.rs b/compiler/rustc_infer/src/infer/relate/glb.rs
index b86d1b2671d..1a8f02fc5ca 100644
--- a/compiler/rustc_infer/src/infer/relate/glb.rs
+++ b/compiler/rustc_infer/src/infer/relate/glb.rs
@@ -140,7 +140,7 @@ impl<'tcx> ObligationEmittingRelation<'tcx> for Glb<'_, '_, 'tcx> {
         self.fields.param_env
     }
 
-    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {
+    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::Upcast<'tcx>>) {
         self.fields.register_predicates(obligations);
     }
 
diff --git a/compiler/rustc_infer/src/infer/relate/lub.rs b/compiler/rustc_infer/src/infer/relate/lub.rs
index 20f5f65c984..18f92ca5236 100644
--- a/compiler/rustc_infer/src/infer/relate/lub.rs
+++ b/compiler/rustc_infer/src/infer/relate/lub.rs
@@ -140,7 +140,7 @@ impl<'tcx> ObligationEmittingRelation<'tcx> for Lub<'_, '_, 'tcx> {
         self.fields.param_env
     }
 
-    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {
+    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::Upcast<'tcx>>) {
         self.fields.register_predicates(obligations);
     }
 
diff --git a/compiler/rustc_infer/src/infer/relate/type_relating.rs b/compiler/rustc_infer/src/infer/relate/type_relating.rs
index 86a24eef7f5..2dd37022319 100644
--- a/compiler/rustc_infer/src/infer/relate/type_relating.rs
+++ b/compiler/rustc_infer/src/infer/relate/type_relating.rs
@@ -312,7 +312,7 @@ impl<'tcx> ObligationEmittingRelation<'tcx> for TypeRelating<'_, '_, 'tcx> {
         self.structurally_relate_aliases
     }
 
-    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {
+    fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::Upcast<'tcx>>) {
         self.fields.register_predicates(obligations);
     }
 
diff --git a/compiler/rustc_infer/src/traits/engine.rs b/compiler/rustc_infer/src/traits/engine.rs
index cb067c7a660..cf523f056a3 100644
--- a/compiler/rustc_infer/src/traits/engine.rs
+++ b/compiler/rustc_infer/src/traits/engine.rs
@@ -2,7 +2,7 @@ use crate::infer::InferCtxt;
 use crate::traits::Obligation;
 use rustc_hir::def_id::DefId;
 use rustc_macros::extension;
-use rustc_middle::ty::{self, ToPredicate, Ty};
+use rustc_middle::ty::{self, Ty, Upcast};
 
 use super::FulfillmentError;
 use super::{ObligationCause, PredicateObligation};
@@ -26,7 +26,7 @@ pub trait TraitEngine<'tcx>: 'tcx {
                 cause,
                 recursion_depth: 0,
                 param_env,
-                predicate: ty::Binder::dummy(trait_ref).to_predicate(infcx.tcx),
+                predicate: ty::Binder::dummy(trait_ref).upcast(infcx.tcx),
             },
         );
     }
diff --git a/compiler/rustc_infer/src/traits/mod.rs b/compiler/rustc_infer/src/traits/mod.rs
index f77a92bf9bc..f8999689241 100644
--- a/compiler/rustc_infer/src/traits/mod.rs
+++ b/compiler/rustc_infer/src/traits/mod.rs
@@ -16,7 +16,7 @@ use rustc_hir as hir;
 use rustc_middle::traits::query::NoSolution;
 use rustc_middle::traits::solve::Certainty;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
-use rustc_middle::ty::{self, Const, ToPredicate, Ty, TyCtxt};
+use rustc_middle::ty::{self, Const, Ty, TyCtxt, Upcast};
 use rustc_span::Span;
 
 pub use self::ImplSource::*;
@@ -155,7 +155,7 @@ impl<'tcx, O> Obligation<'tcx, O> {
         tcx: TyCtxt<'tcx>,
         cause: ObligationCause<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-        predicate: impl ToPredicate<'tcx, O>,
+        predicate: impl Upcast<'tcx, O>,
     ) -> Obligation<'tcx, O> {
         Self::with_depth(tcx, cause, 0, param_env, predicate)
     }
@@ -173,9 +173,9 @@ impl<'tcx, O> Obligation<'tcx, O> {
         cause: ObligationCause<'tcx>,
         recursion_depth: usize,
         param_env: ty::ParamEnv<'tcx>,
-        predicate: impl ToPredicate<'tcx, O>,
+        predicate: impl Upcast<'tcx, O>,
     ) -> Obligation<'tcx, O> {
-        let predicate = predicate.to_predicate(tcx);
+        let predicate = predicate.upcast(tcx);
         Obligation { cause, param_env, recursion_depth, predicate }
     }
 
@@ -184,16 +184,12 @@ impl<'tcx, O> Obligation<'tcx, O> {
         span: Span,
         body_id: LocalDefId,
         param_env: ty::ParamEnv<'tcx>,
-        trait_ref: impl ToPredicate<'tcx, O>,
+        trait_ref: impl Upcast<'tcx, O>,
     ) -> Obligation<'tcx, O> {
         Obligation::new(tcx, ObligationCause::misc(span, body_id), param_env, trait_ref)
     }
 
-    pub fn with<P>(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        value: impl ToPredicate<'tcx, P>,
-    ) -> Obligation<'tcx, P> {
+    pub fn with<P>(&self, tcx: TyCtxt<'tcx>, value: impl Upcast<'tcx, P>) -> Obligation<'tcx, P> {
         Obligation::with_depth(tcx, self.cause.clone(), self.recursion_depth, self.param_env, value)
     }
 }
diff --git a/compiler/rustc_infer/src/traits/util.rs b/compiler/rustc_infer/src/traits/util.rs
index d8d84b777e0..6de32dd0774 100644
--- a/compiler/rustc_infer/src/traits/util.rs
+++ b/compiler/rustc_infer/src/traits/util.rs
@@ -3,7 +3,7 @@ use smallvec::smallvec;
 use crate::infer::outlives::components::{push_outlives_components, Component};
 use crate::traits::{self, Obligation, ObligationCauseCode, PredicateObligation};
 use rustc_data_structures::fx::FxHashSet;
-use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt, Upcast};
 use rustc_span::symbol::Ident;
 use rustc_span::Span;
 
@@ -358,7 +358,7 @@ impl<'tcx, O: Elaboratable<'tcx>> Elaborator<'tcx, O> {
                             }
                         })
                         .map(|clause| {
-                            elaboratable.child(bound_clause.rebind(clause).to_predicate(tcx))
+                            elaboratable.child(bound_clause.rebind(clause).upcast(tcx))
                         }),
                 );
             }
@@ -409,14 +409,14 @@ pub fn supertraits<'tcx>(
     tcx: TyCtxt<'tcx>,
     trait_ref: ty::PolyTraitRef<'tcx>,
 ) -> FilterToTraits<Elaborator<'tcx, ty::Predicate<'tcx>>> {
-    elaborate(tcx, [trait_ref.to_predicate(tcx)]).filter_only_self().filter_to_traits()
+    elaborate(tcx, [trait_ref.upcast(tcx)]).filter_only_self().filter_to_traits()
 }
 
 pub fn transitive_bounds<'tcx>(
     tcx: TyCtxt<'tcx>,
     trait_refs: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
 ) -> FilterToTraits<Elaborator<'tcx, ty::Predicate<'tcx>>> {
-    elaborate(tcx, trait_refs.map(|trait_ref| trait_ref.to_predicate(tcx)))
+    elaborate(tcx, trait_refs.map(|trait_ref| trait_ref.upcast(tcx)))
         .filter_only_self()
         .filter_to_traits()
 }
@@ -431,7 +431,7 @@ pub fn transitive_bounds_that_define_assoc_item<'tcx>(
     trait_refs: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
     assoc_name: Ident,
 ) -> FilterToTraits<Elaborator<'tcx, ty::Predicate<'tcx>>> {
-    elaborate(tcx, trait_refs.map(|trait_ref| trait_ref.to_predicate(tcx)))
+    elaborate(tcx, trait_refs.map(|trait_ref| trait_ref.upcast(tcx)))
         .filter_only_self_that_defines(assoc_name)
         .filter_to_traits()
 }
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index b9be92b89af..9c36e22aa29 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -57,8 +57,8 @@ use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty::layout::LayoutOf;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::GenericArgKind;
-use rustc_middle::ty::ToPredicate;
 use rustc_middle::ty::TypeVisitableExt;
+use rustc_middle::ty::Upcast;
 use rustc_middle::ty::{self, Ty, TyCtxt, VariantDef};
 use rustc_session::lint::{BuiltinLintDiag, FutureIncompatibilityReason};
 use rustc_session::{declare_lint, declare_lint_pass, impl_lint_pass};
@@ -734,7 +734,7 @@ fn type_implements_negative_copy_modulo_regions<'tcx>(
         cause: traits::ObligationCause::dummy(),
         param_env,
         recursion_depth: 0,
-        predicate: ty::Binder::dummy(pred).to_predicate(tcx),
+        predicate: ty::Binder::dummy(pred).upcast(tcx),
     };
 
     tcx.infer_ctxt().build().predicate_must_hold_modulo_regions(&obligation)
diff --git a/compiler/rustc_middle/src/traits/solve.rs b/compiler/rustc_middle/src/traits/solve.rs
index 3ad6b68d129..fe9a4c0f677 100644
--- a/compiler/rustc_middle/src/traits/solve.rs
+++ b/compiler/rustc_middle/src/traits/solve.rs
@@ -7,8 +7,8 @@ use crate::infer::canonical::{CanonicalVarValues, QueryRegionConstraints};
 use crate::traits::query::NoSolution;
 use crate::traits::Canonical;
 use crate::ty::{
-    self, FallibleTypeFolder, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeVisitable,
-    TypeVisitor,
+    self, FallibleTypeFolder, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeVisitable, TypeVisitor,
+    Upcast,
 };
 
 use super::BuiltinImplSource;
@@ -33,14 +33,14 @@ impl<'tcx, P> Goal<'tcx, P> {
     pub fn new(
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-        predicate: impl ToPredicate<'tcx, P>,
+        predicate: impl Upcast<'tcx, P>,
     ) -> Goal<'tcx, P> {
-        Goal { param_env, predicate: predicate.to_predicate(tcx) }
+        Goal { param_env, predicate: predicate.upcast(tcx) }
     }
 
     /// Updates the goal to one with a different `predicate` but the same `param_env`.
-    pub fn with<Q>(self, tcx: TyCtxt<'tcx>, predicate: impl ToPredicate<'tcx, Q>) -> Goal<'tcx, Q> {
-        Goal { param_env: self.param_env, predicate: predicate.to_predicate(tcx) }
+    pub fn with<Q>(self, tcx: TyCtxt<'tcx>, predicate: impl Upcast<'tcx, Q>) -> Goal<'tcx, Q> {
+        Goal { param_env: self.param_env, predicate: predicate.upcast(tcx) }
     }
 }
 
diff --git a/compiler/rustc_middle/src/traits/util.rs b/compiler/rustc_middle/src/traits/util.rs
index 3419827a742..707e076921b 100644
--- a/compiler/rustc_middle/src/traits/util.rs
+++ b/compiler/rustc_middle/src/traits/util.rs
@@ -1,6 +1,6 @@
 use rustc_data_structures::fx::FxHashSet;
 
-use crate::ty::{Clause, PolyTraitRef, ToPolyTraitRef, ToPredicate, TyCtxt};
+use crate::ty::{Clause, PolyTraitRef, ToPolyTraitRef, TyCtxt, Upcast};
 
 /// Given a [`PolyTraitRef`], get the [`Clause`]s implied by the trait's definition.
 ///
@@ -11,7 +11,7 @@ pub fn super_predicates_for_pretty_printing<'tcx>(
     tcx: TyCtxt<'tcx>,
     trait_ref: PolyTraitRef<'tcx>,
 ) -> impl Iterator<Item = Clause<'tcx>> {
-    let clause = trait_ref.to_predicate(tcx);
+    let clause = trait_ref.upcast(tcx);
     Elaborator { tcx, visited: FxHashSet::from_iter([clause]), stack: vec![clause] }
 }
 
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 93ccc0a7de4..7d2c3ee2df8 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -102,7 +102,7 @@ pub use self::predicate::{
     PolyExistentialTraitRef, PolyProjectionPredicate, PolyRegionOutlivesPredicate,
     PolySubtypePredicate, PolyTraitPredicate, PolyTraitRef, PolyTypeOutlivesPredicate, Predicate,
     PredicateKind, ProjectionPredicate, RegionOutlivesPredicate, SubtypePredicate, ToPolyTraitRef,
-    ToPredicate, TraitPredicate, TraitRef, TypeOutlivesPredicate,
+    TraitPredicate, TraitRef, TypeOutlivesPredicate, Upcast,
 };
 pub use self::region::{
     BoundRegion, BoundRegionKind, BoundRegionKind::*, EarlyParamRegion, LateParamRegion, Region,
diff --git a/compiler/rustc_middle/src/ty/predicate.rs b/compiler/rustc_middle/src/ty/predicate.rs
index 16ca098853e..41b016830d0 100644
--- a/compiler/rustc_middle/src/ty/predicate.rs
+++ b/compiler/rustc_middle/src/ty/predicate.rs
@@ -234,10 +234,10 @@ impl<'tcx> PolyExistentialPredicate<'tcx> {
     pub fn with_self_ty(&self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> ty::Clause<'tcx> {
         match self.skip_binder() {
             ExistentialPredicate::Trait(tr) => {
-                self.rebind(tr).with_self_ty(tcx, self_ty).to_predicate(tcx)
+                self.rebind(tr).with_self_ty(tcx, self_ty).upcast(tcx)
             }
             ExistentialPredicate::Projection(p) => {
-                self.rebind(p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
+                self.rebind(p.with_self_ty(tcx, self_ty)).upcast(tcx)
             }
             ExistentialPredicate::AutoTrait(did) => {
                 let generics = tcx.generics_of(did);
@@ -249,7 +249,7 @@ impl<'tcx> PolyExistentialPredicate<'tcx> {
                     let err_args = ty::GenericArgs::extend_with_error(tcx, did, &[self_ty.into()]);
                     ty::TraitRef::new(tcx, did, err_args)
                 };
-                self.rebind(trait_ref).to_predicate(tcx)
+                self.rebind(trait_ref).upcast(tcx)
             }
         }
     }
@@ -544,106 +544,106 @@ impl<'tcx> ToPolyTraitRef<'tcx> for PolyTraitPredicate<'tcx> {
     }
 }
 
-pub trait ToPredicate<'tcx, P = Predicate<'tcx>> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> P;
+pub trait Upcast<'tcx, P = Predicate<'tcx>> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> P;
 }
 
-impl<'tcx, T> ToPredicate<'tcx, T> for T {
-    fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> T {
+impl<'tcx, T> Upcast<'tcx, T> for T {
+    fn upcast(self, _tcx: TyCtxt<'tcx>) -> T {
         self
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for PredicateKind<'tcx> {
+impl<'tcx> Upcast<'tcx> for PredicateKind<'tcx> {
     #[inline(always)]
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        ty::Binder::dummy(self).to_predicate(tcx)
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        ty::Binder::dummy(self).upcast(tcx)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, PredicateKind<'tcx>> {
+impl<'tcx> Upcast<'tcx> for Binder<'tcx, PredicateKind<'tcx>> {
     #[inline(always)]
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         tcx.mk_predicate(self)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for ClauseKind<'tcx> {
+impl<'tcx> Upcast<'tcx> for ClauseKind<'tcx> {
     #[inline(always)]
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         tcx.mk_predicate(ty::Binder::dummy(ty::PredicateKind::Clause(self)))
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, ClauseKind<'tcx>> {
+impl<'tcx> Upcast<'tcx> for Binder<'tcx, ClauseKind<'tcx>> {
     #[inline(always)]
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         tcx.mk_predicate(self.map_bound(ty::PredicateKind::Clause))
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for Clause<'tcx> {
+impl<'tcx> Upcast<'tcx> for Clause<'tcx> {
     #[inline(always)]
-    fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+    fn upcast(self, _tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         self.as_predicate()
     }
 }
 
-impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for ClauseKind<'tcx> {
+impl<'tcx> Upcast<'tcx, Clause<'tcx>> for ClauseKind<'tcx> {
     #[inline(always)]
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
         tcx.mk_predicate(Binder::dummy(ty::PredicateKind::Clause(self))).expect_clause()
     }
 }
 
-impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for Binder<'tcx, ClauseKind<'tcx>> {
+impl<'tcx> Upcast<'tcx, Clause<'tcx>> for Binder<'tcx, ClauseKind<'tcx>> {
     #[inline(always)]
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
         tcx.mk_predicate(self.map_bound(|clause| ty::PredicateKind::Clause(clause))).expect_clause()
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for TraitRef<'tcx> {
+impl<'tcx> Upcast<'tcx> for TraitRef<'tcx> {
     #[inline(always)]
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        ty::Binder::dummy(self).to_predicate(tcx)
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        ty::Binder::dummy(self).upcast(tcx)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx, TraitPredicate<'tcx>> for TraitRef<'tcx> {
+impl<'tcx> Upcast<'tcx, TraitPredicate<'tcx>> for TraitRef<'tcx> {
     #[inline(always)]
-    fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> TraitPredicate<'tcx> {
+    fn upcast(self, _tcx: TyCtxt<'tcx>) -> TraitPredicate<'tcx> {
         TraitPredicate { trait_ref: self, polarity: PredicatePolarity::Positive }
     }
 }
 
-impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for TraitRef<'tcx> {
+impl<'tcx> Upcast<'tcx, Clause<'tcx>> for TraitRef<'tcx> {
     #[inline(always)]
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
-        let p: Predicate<'tcx> = self.to_predicate(tcx);
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        let p: Predicate<'tcx> = self.upcast(tcx);
         p.expect_clause()
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, TraitRef<'tcx>> {
+impl<'tcx> Upcast<'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)
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        let pred: PolyTraitPredicate<'tcx> = self.upcast(tcx);
+        pred.upcast(tcx)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for Binder<'tcx, TraitRef<'tcx>> {
+impl<'tcx> Upcast<'tcx, Clause<'tcx>> for Binder<'tcx, TraitRef<'tcx>> {
     #[inline(always)]
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
-        let pred: PolyTraitPredicate<'tcx> = self.to_predicate(tcx);
-        pred.to_predicate(tcx)
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        let pred: PolyTraitPredicate<'tcx> = self.upcast(tcx);
+        pred.upcast(tcx)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx, PolyTraitPredicate<'tcx>> for Binder<'tcx, TraitRef<'tcx>> {
+impl<'tcx> Upcast<'tcx, PolyTraitPredicate<'tcx>> for Binder<'tcx, TraitRef<'tcx>> {
     #[inline(always)]
-    fn to_predicate(self, _: TyCtxt<'tcx>) -> PolyTraitPredicate<'tcx> {
+    fn upcast(self, _: TyCtxt<'tcx>) -> PolyTraitPredicate<'tcx> {
         self.map_bound(|trait_ref| TraitPredicate {
             trait_ref,
             polarity: ty::PredicatePolarity::Positive,
@@ -651,73 +651,73 @@ impl<'tcx> ToPredicate<'tcx, PolyTraitPredicate<'tcx>> for Binder<'tcx, TraitRef
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for TraitPredicate<'tcx> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        PredicateKind::Clause(ClauseKind::Trait(self)).to_predicate(tcx)
+impl<'tcx> Upcast<'tcx> for TraitPredicate<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        PredicateKind::Clause(ClauseKind::Trait(self)).upcast(tcx)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for PolyTraitPredicate<'tcx> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        self.map_bound(|p| PredicateKind::Clause(ClauseKind::Trait(p))).to_predicate(tcx)
+impl<'tcx> Upcast<'tcx> for PolyTraitPredicate<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        self.map_bound(|p| PredicateKind::Clause(ClauseKind::Trait(p))).upcast(tcx)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for TraitPredicate<'tcx> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
-        let p: Predicate<'tcx> = self.to_predicate(tcx);
+impl<'tcx> Upcast<'tcx, Clause<'tcx>> for TraitPredicate<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        let p: Predicate<'tcx> = self.upcast(tcx);
         p.expect_clause()
     }
 }
 
-impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for PolyTraitPredicate<'tcx> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
-        let p: Predicate<'tcx> = self.to_predicate(tcx);
+impl<'tcx> Upcast<'tcx, Clause<'tcx>> for PolyTraitPredicate<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        let p: Predicate<'tcx> = self.upcast(tcx);
         p.expect_clause()
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for PolyRegionOutlivesPredicate<'tcx> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        self.map_bound(|p| PredicateKind::Clause(ClauseKind::RegionOutlives(p))).to_predicate(tcx)
+impl<'tcx> Upcast<'tcx> for PolyRegionOutlivesPredicate<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        self.map_bound(|p| PredicateKind::Clause(ClauseKind::RegionOutlives(p))).upcast(tcx)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        ty::Binder::dummy(PredicateKind::Clause(ClauseKind::TypeOutlives(self))).to_predicate(tcx)
+impl<'tcx> Upcast<'tcx> for OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        ty::Binder::dummy(PredicateKind::Clause(ClauseKind::TypeOutlives(self))).upcast(tcx)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for ProjectionPredicate<'tcx> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        ty::Binder::dummy(PredicateKind::Clause(ClauseKind::Projection(self))).to_predicate(tcx)
+impl<'tcx> Upcast<'tcx> for ProjectionPredicate<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        ty::Binder::dummy(PredicateKind::Clause(ClauseKind::Projection(self))).upcast(tcx)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for PolyProjectionPredicate<'tcx> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        self.map_bound(|p| PredicateKind::Clause(ClauseKind::Projection(p))).to_predicate(tcx)
+impl<'tcx> Upcast<'tcx> for PolyProjectionPredicate<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        self.map_bound(|p| PredicateKind::Clause(ClauseKind::Projection(p))).upcast(tcx)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for ProjectionPredicate<'tcx> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
-        let p: Predicate<'tcx> = self.to_predicate(tcx);
+impl<'tcx> Upcast<'tcx, Clause<'tcx>> for ProjectionPredicate<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        let p: Predicate<'tcx> = self.upcast(tcx);
         p.expect_clause()
     }
 }
 
-impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for PolyProjectionPredicate<'tcx> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
-        let p: Predicate<'tcx> = self.to_predicate(tcx);
+impl<'tcx> Upcast<'tcx, Clause<'tcx>> for PolyProjectionPredicate<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        let p: Predicate<'tcx> = self.upcast(tcx);
         p.expect_clause()
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for NormalizesTo<'tcx> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
-        PredicateKind::NormalizesTo(self).to_predicate(tcx)
+impl<'tcx> Upcast<'tcx> for NormalizesTo<'tcx> {
+    fn upcast(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        PredicateKind::NormalizesTo(self).upcast(tcx)
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index 7f3d6a713d9..8c14f1e080a 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -4,8 +4,8 @@ use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use crate::query::{IntoQueryParam, Providers};
 use crate::ty::layout::{FloatExt, IntegerExt};
 use crate::ty::{
-    self, FallibleTypeFolder, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
-    TypeVisitableExt,
+    self, FallibleTypeFolder, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
+    TypeVisitableExt, Upcast,
 };
 use crate::ty::{GenericArgKind, GenericArgsRef};
 use rustc_apfloat::Float as _;
@@ -1094,7 +1094,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for OpaqueTypeExpander<'tcx> {
                     // anything that requires `ParamEnv::with_reveal_all_normalized`.
                     term: projection_pred.term,
                 })
-                .to_predicate(self.tcx)
+                .upcast(self.tcx)
         } else {
             p.super_fold_with(self)
         }
diff --git a/compiler/rustc_trait_selection/src/infer.rs b/compiler/rustc_trait_selection/src/infer.rs
index 3dc55509dad..6797be5cdd0 100644
--- a/compiler/rustc_trait_selection/src/infer.rs
+++ b/compiler/rustc_trait_selection/src/infer.rs
@@ -10,7 +10,7 @@ use rustc_middle::infer::canonical::{Canonical, CanonicalQueryResponse, QueryRes
 use rustc_middle::traits::query::NoSolution;
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeVisitableExt};
-use rustc_middle::ty::{GenericArg, ToPredicate};
+use rustc_middle::ty::{GenericArg, Upcast};
 use rustc_span::DUMMY_SP;
 
 use std::fmt::Debug;
@@ -63,7 +63,7 @@ impl<'tcx> InferCtxt<'tcx> {
             cause: traits::ObligationCause::dummy(),
             param_env,
             recursion_depth: 0,
-            predicate: ty::Binder::dummy(trait_ref).to_predicate(self.tcx),
+            predicate: ty::Binder::dummy(trait_ref).upcast(self.tcx),
         };
         self.evaluate_obligation(&obligation).unwrap_or(traits::EvaluationResult::EvaluatedToErr)
     }
diff --git a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
index 97bea28f06a..e09ddc7fb5e 100644
--- a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
@@ -13,7 +13,7 @@ use rustc_middle::traits::BuiltinImplSource;
 use rustc_middle::ty::fast_reject::{SimplifiedType, TreatParams};
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::ty::{fast_reject, TypeFoldable};
-use rustc_middle::ty::{ToPredicate, TypeVisitableExt};
+use rustc_middle::ty::{TypeVisitableExt, Upcast};
 use rustc_span::{ErrorGuaranteed, DUMMY_SP};
 use std::fmt::Debug;
 
@@ -744,7 +744,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
                     ecx,
                     CandidateSource::BuiltinImpl(BuiltinImplSource::Object { vtable_base }),
                     goal,
-                    assumption.to_predicate(tcx),
+                    assumption.upcast(tcx),
                 ));
             });
         }
diff --git a/compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs b/compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs
index 9e844d78702..cf826596392 100644
--- a/compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs
+++ b/compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs
@@ -7,9 +7,7 @@ use rustc_infer::traits::query::NoSolution;
 use rustc_macros::{TypeFoldable, TypeVisitable};
 use rustc_middle::bug;
 use rustc_middle::traits::solve::Goal;
-use rustc_middle::ty::{
-    self, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
-};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable, Upcast};
 use rustc_span::sym;
 
 use crate::solve::EvalCtxt;
@@ -429,7 +427,7 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_async_callable<'tc
                         tcx.require_lang_item(LangItem::AsyncFnKindHelper, None),
                         [kind_ty, Ty::from_closure_kind(tcx, goal_kind)],
                     )
-                    .to_predicate(tcx),
+                    .upcast(tcx),
                 );
 
                 coroutine_closure_to_ambiguous_coroutine(
@@ -456,7 +454,7 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_async_callable<'tc
             let nested = vec![
                 bound_sig
                     .rebind(ty::TraitRef::new(tcx, future_trait_def_id, [sig.output()]))
-                    .to_predicate(tcx),
+                    .upcast(tcx),
             ];
             let future_output_def_id = tcx
                 .associated_items(future_trait_def_id)
@@ -484,7 +482,7 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_async_callable<'tc
             let mut nested = vec![
                 bound_sig
                     .rebind(ty::TraitRef::new(tcx, future_trait_def_id, [sig.output()]))
-                    .to_predicate(tcx),
+                    .upcast(tcx),
             ];
 
             // Additionally, we need to check that the closure kind
@@ -510,7 +508,7 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_async_callable<'tc
                         async_fn_kind_trait_def_id,
                         [kind_ty, Ty::from_closure_kind(tcx, goal_kind)],
                     )
-                    .to_predicate(tcx),
+                    .upcast(tcx),
                 );
             }
 
diff --git a/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs b/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
index 6ec0ad9d29a..7ab27374e7a 100644
--- a/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
@@ -16,7 +16,7 @@ use rustc_middle::traits::BuiltinImplSource;
 use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
 use rustc_middle::ty::NormalizesTo;
 use rustc_middle::ty::{self, Ty, TyCtxt};
-use rustc_middle::ty::{ToPredicate, TypeVisitableExt};
+use rustc_middle::ty::{TypeVisitableExt, Upcast};
 use rustc_middle::{bug, span_bug};
 use rustc_span::{sym, ErrorGuaranteed, DUMMY_SP};
 
@@ -370,7 +370,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
                 ),
                 term: output.into(),
             })
-            .to_predicate(tcx);
+            .upcast(tcx);
 
         // A built-in `Fn` impl only holds if the output is sized.
         // (FIXME: technically we only need to check this if the type is a fn ptr...)
@@ -452,7 +452,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
                     ty::ProjectionPredicate { projection_term, term }
                 },
             )
-            .to_predicate(tcx);
+            .upcast(tcx);
 
         // A built-in `AsyncFn` impl only holds if the output is sized.
         // (FIXME: technically we only need to check this if the type is a fn ptr...)
@@ -629,7 +629,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
                 projection_term: ty::AliasTerm::new(ecx.tcx(), goal.predicate.def_id(), [self_ty]),
                 term,
             }
-            .to_predicate(tcx),
+            .upcast(tcx),
             // Technically, we need to check that the future type is Sized,
             // but that's already proven by the coroutine being WF.
             [],
@@ -661,7 +661,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
                 projection_term: ty::AliasTerm::new(ecx.tcx(), goal.predicate.def_id(), [self_ty]),
                 term,
             }
-            .to_predicate(tcx),
+            .upcast(tcx),
             // Technically, we need to check that the iterator type is Sized,
             // but that's already proven by the generator being WF.
             [],
@@ -749,7 +749,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
                 ),
                 term,
             }
-            .to_predicate(tcx),
+            .upcast(tcx),
             // Technically, we need to check that the coroutine type is Sized,
             // but that's already proven by the coroutine being WF.
             [],
diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals.rs b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
index 1cafa970b68..b46edb32f72 100644
--- a/compiler/rustc_trait_selection/src/solve/trait_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
@@ -15,7 +15,7 @@ use rustc_middle::traits::solve::inspect::ProbeKind;
 use rustc_middle::traits::solve::{CandidateSource, Certainty, Goal, QueryResult};
 use rustc_middle::traits::{BuiltinImplSource, Reveal};
 use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
-use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt, Upcast};
 use rustc_middle::ty::{TraitPredicate, TypeVisitableExt};
 use rustc_span::ErrorGuaranteed;
 
@@ -315,7 +315,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
             .map_bound(|(inputs, _)| {
                 ty::TraitRef::new(tcx, goal.predicate.def_id(), [goal.predicate.self_ty(), inputs])
             })
-            .to_predicate(tcx);
+            .upcast(tcx);
         // A built-in `Fn` impl only holds if the output is sized.
         // (FIXME: technically we only need to check this if the type is a fn ptr...)
         Self::probe_and_consider_implied_clause(
@@ -363,7 +363,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
                     [goal.predicate.self_ty(), tupled_inputs_ty],
                 )
             })
-            .to_predicate(tcx);
+            .upcast(tcx);
         // A built-in `AsyncFn` impl only holds if the output is sized.
         // (FIXME: technically we only need to check this if the type is a fn ptr...)
         Self::probe_and_consider_implied_clause(
@@ -560,7 +560,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
             CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),
             goal,
             ty::TraitRef::new(tcx, goal.predicate.def_id(), [self_ty, coroutine.resume_ty()])
-                .to_predicate(tcx),
+                .upcast(tcx),
             // Technically, we need to check that the coroutine types are Sized,
             // but that's already proven by the coroutine being WF.
             [],
diff --git a/compiler/rustc_trait_selection/src/traits/auto_trait.rs b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
index 60562acfe93..1ea207cc375 100644
--- a/compiler/rustc_trait_selection/src/traits/auto_trait.rs
+++ b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
@@ -303,7 +303,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
                 Err(SelectionError::Unimplemented) => {
                     if self.is_param_no_infer(pred.skip_binder().trait_ref.args) {
                         already_visited.remove(&pred);
-                        self.add_user_pred(&mut user_computed_preds, pred.to_predicate(self.tcx));
+                        self.add_user_pred(&mut user_computed_preds, pred.upcast(self.tcx));
                         predicates.push_back(pred);
                     } else {
                         debug!(
diff --git a/compiler/rustc_trait_selection/src/traits/engine.rs b/compiler/rustc_trait_selection/src/traits/engine.rs
index 551c8e7702e..ad56b8f329b 100644
--- a/compiler/rustc_trait_selection/src/traits/engine.rs
+++ b/compiler/rustc_trait_selection/src/traits/engine.rs
@@ -25,8 +25,8 @@ use rustc_macros::extension;
 use rustc_middle::arena::ArenaAllocatable;
 use rustc_middle::traits::query::NoSolution;
 use rustc_middle::ty::error::TypeError;
-use rustc_middle::ty::ToPredicate;
 use rustc_middle::ty::TypeFoldable;
+use rustc_middle::ty::Upcast;
 use rustc_middle::ty::Variance;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 
@@ -96,7 +96,7 @@ impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
             cause,
             recursion_depth: 0,
             param_env,
-            predicate: ty::Binder::dummy(trait_ref).to_predicate(tcx),
+            predicate: ty::Binder::dummy(trait_ref).upcast(tcx),
         });
     }
 
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index 86610855441..921275100d2 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -31,8 +31,8 @@ use rustc_middle::traits::IsConstable;
 use rustc_middle::ty::error::TypeError::{self, Sorts};
 use rustc_middle::ty::{
     self, suggest_arbitrary_trait_bound, suggest_constraining_type_param, AdtKind, GenericArgs,
-    InferTy, IsSuggestable, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
-    TypeVisitableExt, TypeckResults,
+    InferTy, IsSuggestable, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
+    TypeVisitableExt, TypeckResults, Upcast,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_span::def_id::LocalDefId;
@@ -192,7 +192,7 @@ pub fn suggest_restriction<'tcx, G: EmissionGuarantee>(
             },
             // `fn foo(t: impl Trait)`
             //                       ^ suggest `where <T as Trait>::A: Bound`
-            predicate_constraint(hir_generics, trait_pred.to_predicate(tcx)),
+            predicate_constraint(hir_generics, trait_pred.upcast(tcx)),
         ];
         sugg.extend(ty_spans.into_iter().map(|s| (s, type_param_name.to_string())));
 
@@ -215,7 +215,7 @@ pub fn suggest_restriction<'tcx, G: EmissionGuarantee>(
                 .find(|p| !matches!(p.kind, hir::GenericParamKind::Type { synthetic: true, .. })),
             super_traits,
         ) {
-            (_, None) => predicate_constraint(hir_generics, trait_pred.to_predicate(tcx)),
+            (_, None) => predicate_constraint(hir_generics, trait_pred.upcast(tcx)),
             (None, Some((ident, []))) => (
                 ident.span.shrink_to_hi(),
                 format!(": {}", trait_pred.print_modifiers_and_trait_path()),
@@ -2703,12 +2703,12 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         obligated_types: &mut Vec<Ty<'tcx>>,
         seen_requirements: &mut FxHashSet<DefId>,
     ) where
-        T: ToPredicate<'tcx>,
+        T: Upcast<'tcx>,
     {
         let mut long_ty_file = None;
 
         let tcx = self.tcx;
-        let predicate = predicate.to_predicate(tcx);
+        let predicate = predicate.upcast(tcx);
         match *cause_code {
             ObligationCauseCode::ExprAssignable
             | ObligationCauseCode::MatchExpressionArm { .. }
@@ -3378,7 +3378,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                             break;
                         }
                         data = derived;
-                        parent_predicate = child_trait_ref.to_predicate(tcx);
+                        parent_predicate = child_trait_ref.upcast(tcx);
                         parent_trait_pred = child_trait_ref;
                     }
                 }
@@ -3392,7 +3392,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     }
                     count += 1;
                     data = &child.derived;
-                    parent_predicate = child_trait_pred.to_predicate(tcx);
+                    parent_predicate = child_trait_pred.upcast(tcx);
                     parent_trait_pred = child_trait_pred;
                 }
                 if count > 0 {
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
index f9824acdae0..e3e3e30ff92 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
@@ -42,8 +42,8 @@ use rustc_middle::ty::print::{
     PrintTraitRefExt as _,
 };
 use rustc_middle::ty::{
-    self, SubtypePredicate, ToPolyTraitRef, ToPredicate, TraitRef, Ty, TyCtxt, TypeFoldable,
-    TypeVisitable, TypeVisitableExt,
+    self, SubtypePredicate, ToPolyTraitRef, TraitRef, Ty, TyCtxt, TypeFoldable, TypeVisitable,
+    TypeVisitableExt, Upcast,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_session::config::DumpSolverProofTree;
@@ -302,9 +302,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         suggest_increasing_limit: bool,
     ) -> !
     where
-        T: ToPredicate<'tcx> + Clone,
+        T: Upcast<'tcx> + Clone,
     {
-        let predicate = obligation.predicate.clone().to_predicate(self.tcx);
+        let predicate = obligation.predicate.clone().upcast(self.tcx);
         let predicate = self.resolve_vars_if_possible(predicate);
         self.report_overflow_error(
             OverflowCause::TraitSolver(predicate),
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index 61f47bc1f23..7dd944ba850 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -34,7 +34,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::span_bug;
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::visit::{TypeVisitable, TypeVisitableExt};
-use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt, TypeFolder, TypeSuperVisitable};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeFolder, TypeSuperVisitable, Upcast};
 use rustc_middle::ty::{GenericArgs, GenericArgsRef};
 use rustc_span::def_id::DefId;
 use rustc_span::Span;
@@ -142,7 +142,7 @@ pub fn type_known_to_meet_bound_modulo_regions<'tcx>(
 fn pred_known_to_hold_modulo_regions<'tcx>(
     infcx: &InferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
-    pred: impl ToPredicate<'tcx>,
+    pred: impl Upcast<'tcx>,
 ) -> bool {
     let obligation = Obligation::new(infcx.tcx, ObligationCause::dummy(), param_env, pred);
 
@@ -457,7 +457,7 @@ fn instantiate_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_predicate(tcx));
+        predicates.push(ty::Binder::dummy(trait_ref).upcast(tcx));
     }
 
     predicates.retain(|predicate| !predicate.has_param());
diff --git a/compiler/rustc_trait_selection/src/traits/object_safety.rs b/compiler/rustc_trait_selection/src/traits/object_safety.rs
index 41080b3d9d3..9402fb417a6 100644
--- a/compiler/rustc_trait_selection/src/traits/object_safety.rs
+++ b/compiler/rustc_trait_selection/src/traits/object_safety.rs
@@ -22,7 +22,7 @@ use rustc_middle::ty::{
     TypeVisitable, TypeVisitor,
 };
 use rustc_middle::ty::{GenericArg, GenericArgs};
-use rustc_middle::ty::{ToPredicate, TypeVisitableExt};
+use rustc_middle::ty::{TypeVisitableExt, Upcast};
 use rustc_session::lint::builtin::WHERE_CLAUSES_OBJECT_SAFETY;
 use rustc_span::symbol::Symbol;
 use rustc_span::Span;
@@ -649,7 +649,7 @@ fn object_ty_for_trait<'tcx>(
     ));
     debug!(?trait_predicate);
 
-    let pred: ty::Predicate<'tcx> = trait_ref.to_predicate(tcx);
+    let pred: ty::Predicate<'tcx> = trait_ref.upcast(tcx);
     let mut elaborated_predicates: Vec<_> = elaborate(tcx, [pred])
         .filter_map(|pred| {
             debug!(?pred);
@@ -753,7 +753,7 @@ fn receiver_is_dispatchable<'tcx>(
         // Self: Unsize<U>
         let unsize_predicate =
             ty::TraitRef::new(tcx, unsize_did, [tcx.types.self_param, unsized_self_ty])
-                .to_predicate(tcx);
+                .upcast(tcx);
 
         // U: Trait<Arg1, ..., ArgN>
         let trait_predicate = {
@@ -762,7 +762,7 @@ fn receiver_is_dispatchable<'tcx>(
                 if param.index == 0 { unsized_self_ty.into() } else { tcx.mk_param_from_def(param) }
             });
 
-            ty::TraitRef::new(tcx, trait_def_id, args).to_predicate(tcx)
+            ty::TraitRef::new(tcx, trait_def_id, args).upcast(tcx)
         };
 
         let caller_bounds =
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 2e7d2790dc3..c5590cbf4ef 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -35,7 +35,7 @@ use rustc_infer::infer::DefineOpaqueTypes;
 use rustc_middle::traits::select::OverflowError;
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::visit::{MaxUniverse, TypeVisitable, TypeVisitableExt};
-use rustc_middle::ty::{self, Term, ToPredicate, Ty, TyCtxt};
+use rustc_middle::ty::{self, Term, Ty, TyCtxt, Upcast};
 use rustc_span::symbol::sym;
 
 pub use rustc_middle::traits::Reveal;
@@ -538,7 +538,7 @@ fn normalize_to_error<'a, 'tcx>(
         cause,
         recursion_depth: depth,
         param_env,
-        predicate: trait_ref.to_predicate(selcx.tcx()),
+        predicate: trait_ref.upcast(selcx.tcx()),
     };
     Normalized { value: new_value, obligations: vec![trait_obligation] }
 }
@@ -877,7 +877,7 @@ fn assemble_candidates_from_object_ty<'cx, 'tcx>(
     let env_predicates = data
         .projection_bounds()
         .filter(|bound| bound.item_def_id() == obligation.predicate.def_id)
-        .map(|p| p.with_self_ty(tcx, object_ty).to_predicate(tcx));
+        .map(|p| p.with_self_ty(tcx, object_ty).upcast(tcx));
 
     assemble_candidates_from_predicates(
         selcx,
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 24c6951a014..27bdc1da7df 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -14,8 +14,8 @@ use rustc_infer::infer::{DefineOpaqueTypes, InferOk};
 use rustc_infer::traits::ObligationCauseCode;
 use rustc_middle::traits::{BuiltinImplSource, SignatureMismatchData};
 use rustc_middle::ty::{
-    self, GenericArgs, GenericArgsRef, GenericParamDefKind, ToPolyTraitRef, ToPredicate,
-    TraitPredicate, Ty, TyCtxt,
+    self, GenericArgs, GenericArgsRef, GenericParamDefKind, ToPolyTraitRef, TraitPredicate, Ty,
+    TyCtxt, Upcast,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_span::def_id::DefId;
@@ -676,7 +676,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     let assoc_ty_args = tcx.mk_args(&args);
                     let bound =
                         bound.map_bound(|b| b.kind().skip_binder()).instantiate(tcx, assoc_ty_args);
-                    ty::Binder::bind_with_vars(bound, bound_vars).to_predicate(tcx)
+                    ty::Binder::bind_with_vars(bound, bound_vars).upcast(tcx)
                 };
                 let normalized_bound = normalize_with_depth_to(
                     self,
@@ -1253,13 +1253,13 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     tcx.require_lang_item(LangItem::Sized, Some(obligation.cause.span)),
                     [source],
                 );
-                nested.push(predicate_to_obligation(tr.to_predicate(tcx)));
+                nested.push(predicate_to_obligation(tr.upcast(tcx)));
 
                 // If the type is `Foo + 'a`, ensure that the type
                 // being cast to `Foo + 'a` outlives `'a`:
                 let outlives = ty::OutlivesPredicate(source, r);
                 nested.push(predicate_to_obligation(
-                    ty::Binder::dummy(ty::ClauseKind::TypeOutlives(outlives)).to_predicate(tcx),
+                    ty::Binder::dummy(ty::ClauseKind::TypeOutlives(outlives)).upcast(tcx),
                 ));
 
                 ImplSource::Builtin(BuiltinImplSource::Misc, nested)
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 5b25c62689f..501d6f6fd8f 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -45,7 +45,7 @@ use rustc_middle::ty::abstract_const::NotConstEvaluatable;
 use rustc_middle::ty::print::PrintTraitRefExt as _;
 use rustc_middle::ty::relate::TypeRelation;
 use rustc_middle::ty::GenericArgsRef;
-use rustc_middle::ty::{self, PolyProjectionPredicate, ToPredicate};
+use rustc_middle::ty::{self, PolyProjectionPredicate, Upcast};
 use rustc_middle::ty::{Ty, TyCtxt, TypeFoldable, TypeVisitableExt};
 use rustc_span::symbol::sym;
 use rustc_span::Symbol;
@@ -740,7 +740,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                             let cycle = stack.iter().take_while(|s| s.depth > stack_arg.1);
                             let tcx = self.tcx();
                             let cycle =
-                                cycle.map(|stack| stack.obligation.predicate.to_predicate(tcx));
+                                cycle.map(|stack| stack.obligation.predicate.upcast(tcx));
                             if self.coinductive_match(cycle) {
                                 stack.update_reached_depth(stack_arg.1);
                                 return Ok(EvaluatedToOk);
@@ -1174,7 +1174,7 @@ 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 = cycle.map(|stack| stack.obligation.predicate.to_predicate(tcx));
+            let cycle = cycle.map(|stack| stack.obligation.predicate.upcast(tcx));
             if self.coinductive_match(cycle) {
                 debug!("evaluate_stack --> recursive, coinductive");
                 Some(EvaluatedToOk)
@@ -1379,7 +1379,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         error_obligation: &Obligation<'tcx, T>,
     ) -> Result<(), OverflowError>
     where
-        T: ToPredicate<'tcx> + Clone,
+        T: Upcast<'tcx> + Clone,
     {
         if !self.infcx.tcx.recursion_limit().value_within_limit(depth) {
             match self.query_mode {
@@ -1408,7 +1408,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         error_obligation: &Obligation<'tcx, V>,
     ) -> Result<(), OverflowError>
     where
-        V: ToPredicate<'tcx> + Clone,
+        V: Upcast<'tcx> + Clone,
     {
         self.check_recursion_depth(obligation.recursion_depth, error_obligation)
     }
diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs
index 83edddb9a96..445fa1761b9 100644
--- a/compiler/rustc_trait_selection/src/traits/util.rs
+++ b/compiler/rustc_trait_selection/src/traits/util.rs
@@ -8,7 +8,7 @@ use rustc_hir::def_id::DefId;
 use rustc_infer::infer::{InferCtxt, InferOk};
 use rustc_middle::bug;
 use rustc_middle::ty::GenericArgsRef;
-use rustc_middle::ty::{self, ImplSubject, ToPredicate, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{self, ImplSubject, Ty, TyCtxt, TypeVisitableExt, Upcast};
 use rustc_middle::ty::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_span::Span;
 use smallvec::{smallvec, SmallVec};
@@ -105,7 +105,7 @@ impl<'tcx> TraitAliasExpander<'tcx> {
     fn expand(&mut self, item: &TraitAliasExpansionInfo<'tcx>) -> bool {
         let tcx = self.tcx;
         let trait_ref = item.trait_ref();
-        let pred = trait_ref.to_predicate(tcx);
+        let pred = trait_ref.upcast(tcx);
 
         debug!("expand_trait_aliases: trait_ref={:?}", trait_ref);
 
@@ -122,7 +122,7 @@ impl<'tcx> TraitAliasExpander<'tcx> {
             .iter()
             .rev()
             .skip(1)
-            .any(|&(tr, _)| anonymize_predicate(tcx, tr.to_predicate(tcx)) == anon_pred)
+            .any(|&(tr, _)| anonymize_predicate(tcx, tr.upcast(tcx)) == anon_pred)
         {
             return false;
         }
diff --git a/compiler/rustc_trait_selection/src/traits/vtable.rs b/compiler/rustc_trait_selection/src/traits/vtable.rs
index 8fd9889b4ea..c93ec43944a 100644
--- a/compiler/rustc_trait_selection/src/traits/vtable.rs
+++ b/compiler/rustc_trait_selection/src/traits/vtable.rs
@@ -9,7 +9,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::traits::BuiltinImplSource;
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::GenericArgs;
-use rustc_middle::ty::{self, GenericParamDefKind, ToPredicate, Ty, TyCtxt, VtblEntry};
+use rustc_middle::ty::{self, GenericParamDefKind, Ty, TyCtxt, Upcast, VtblEntry};
 use rustc_span::{sym, Span};
 use smallvec::{smallvec, SmallVec};
 
@@ -87,7 +87,7 @@ fn prepare_vtable_segments_inner<'tcx, T>(
 
     let mut emit_vptr_on_new_entry = false;
     let mut visited = PredicateSet::new(tcx);
-    let predicate = trait_ref.to_predicate(tcx);
+    let predicate = trait_ref.upcast(tcx);
     let mut stack: SmallVec<[(ty::PolyTraitRef<'tcx>, _, _); 5]> =
         smallvec![(trait_ref, emit_vptr_on_new_entry, maybe_iter(None))];
     visited.insert(predicate);
@@ -130,7 +130,7 @@ fn prepare_vtable_segments_inner<'tcx, T>(
 
             // Find an unvisited supertrait
             match direct_super_traits_iter
-                .find(|&super_trait| visited.insert(super_trait.to_predicate(tcx)))
+                .find(|&super_trait| visited.insert(super_trait.upcast(tcx)))
             {
                 // Push it to the stack for the next iteration of 'diving_in to pick up
                 Some(unvisited_super_trait) => {
@@ -165,7 +165,7 @@ fn prepare_vtable_segments_inner<'tcx, T>(
             }
 
             if let Some(next_inner_most_trait_ref) =
-                siblings.find(|&sibling| visited.insert(sibling.to_predicate(tcx)))
+                siblings.find(|&sibling| visited.insert(sibling.upcast(tcx)))
             {
                 // We're throwing away potential constness of super traits here.
                 // FIXME: handle ~const super traits
diff --git a/compiler/rustc_ty_utils/src/ty.rs b/compiler/rustc_ty_utils/src/ty.rs
index 492cc1d55cb..3094956fa5f 100644
--- a/compiler/rustc_ty_utils/src/ty.rs
+++ b/compiler/rustc_ty_utils/src/ty.rs
@@ -6,7 +6,7 @@ use rustc_index::bit_set::BitSet;
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, EarlyBinder, Ty, TyCtxt, TypeVisitableExt, TypeVisitor};
-use rustc_middle::ty::{ToPredicate, TypeSuperVisitable, TypeVisitable};
+use rustc_middle::ty::{TypeSuperVisitable, TypeVisitable, Upcast};
 use rustc_span::def_id::{DefId, LocalDefId, CRATE_DEF_ID};
 use rustc_span::DUMMY_SP;
 use rustc_trait_selection::traits;
@@ -220,7 +220,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInTraitFinder<'_, 'tcx> {
                     },
                     self.bound_vars,
                 )
-                .to_predicate(self.tcx),
+                .upcast(self.tcx),
             );
 
             // We walk the *un-shifted* alias ty, because we're tracking the de bruijn