a small wf and clause cleanup

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -16,6 +16,7 @@ use rustc_infer::traits::util;
 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::{
     self, GenericArgs, Ty, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
 };
@@ -2279,16 +2280,16 @@ pub(super) fn check_type_bounds<'tcx>(
                 //
                 // impl<T> X for T where T: X { type Y = <T as X>::Y; }
             }
-            _ => predicates.push(ty::Clause::from_projection_clause(
+            _ => predicates.push(
-                tcx,
                 ty::Binder::bind_with_vars(
                     ty::ProjectionPredicate {
                         projection_ty: tcx.mk_alias_ty(trait_ty.def_id, rebased_args),
                         term: normalize_impl_ty.into(),
                     },
                     bound_vars,
-                ),
+                )
-            )),
+                .to_predicate(tcx),
+            ),
         };
         ty::ParamEnv::new(tcx.mk_clauses(&predicates), Reveal::UserFacing)
     };

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1105,11 +1105,11 @@ fn check_associated_type_bounds(wfcx: &WfCheckingCtxt<'_, '_>, item: ty::AssocIt
     let wf_obligations =
         bounds.instantiate_identity_iter_copied().flat_map(|(bound, bound_span)| {
             let normalized_bound = wfcx.normalize(span, None, bound);
-            traits::wf::predicate_obligations(
+            traits::wf::clause_obligations(
                 wfcx.infcx,
                 wfcx.param_env,
                 wfcx.body_def_id,
-                normalized_bound.as_predicate(),
+                normalized_bound,
                 bound_span,
             )
         });
@@ -1209,7 +1209,7 @@ fn check_impl<'tcx>(
                     wfcx.infcx,
                     wfcx.param_env,
                     wfcx.body_def_id,
-                    &trait_pred,
+                    trait_pred,
                     ast_trait_ref.path.span,
                     item,
                 );
@@ -1418,13 +1418,7 @@ fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, span: Span, def_id
     debug!(?predicates.predicates);
     assert_eq!(predicates.predicates.len(), predicates.spans.len());
     let wf_obligations = predicates.into_iter().flat_map(|(p, sp)| {
-        traits::wf::predicate_obligations(
+        traits::wf::clause_obligations(infcx, wfcx.param_env, wfcx.body_def_id, p, sp)
-            infcx,
-            wfcx.param_env,
-            wfcx.body_def_id,
-            p.as_predicate(),
-            sp,
-        )
     });
     let obligations: Vec<_> = wf_obligations.chain(default_obligations).collect();
     wfcx.register_obligations(obligations);

compiler/rustc_middle/src/ty/mod.rs

@@ -578,11 +578,6 @@ impl rustc_errors::IntoDiagnosticArg for Clause<'_> {
 pub struct Clause<'tcx>(Interned<'tcx, WithCachedTypeInfo<ty::Binder<'tcx, PredicateKind<'tcx>>>>);
 
 impl<'tcx> Clause<'tcx> {
-    pub fn from_projection_clause(tcx: TyCtxt<'tcx>, pred: PolyProjectionPredicate<'tcx>) -> Self {
-        let pred: Predicate<'tcx> = pred.to_predicate(tcx);
-        pred.expect_clause()
-    }
-
     pub fn as_predicate(self) -> Predicate<'tcx> {
         Predicate(self.0)
     }
@@ -1296,12 +1291,25 @@ 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> 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> ToPredicate<'tcx, Clause<'tcx>> for TraitPredicate<'tcx> {
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
+        let p: Predicate<'tcx> = self.to_predicate(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);
@@ -1340,9 +1348,10 @@ impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for ProjectionPredicate<'tcx> {
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for TraitPredicate<'tcx> {
+impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for PolyProjectionPredicate<'tcx> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
-        PredicateKind::Clause(ClauseKind::Trait(self)).to_predicate(tcx)
+        let p: Predicate<'tcx> = self.to_predicate(tcx);
+        p.expect_clause()
     }
 }
 

compiler/rustc_middle/src/ty/sty.rs

@@ -725,7 +725,7 @@ impl<'tcx> PolyExistentialPredicate<'tcx> {
                 self.rebind(tr).with_self_ty(tcx, self_ty).to_predicate(tcx)
             }
             ExistentialPredicate::Projection(p) => {
-                ty::Clause::from_projection_clause(tcx, self.rebind(p.with_self_ty(tcx, self_ty)))
+                self.rebind(p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
             }
             ExistentialPredicate::AutoTrait(did) => {
                 let generics = tcx.generics_of(did);

compiler/rustc_trait_selection/src/solve/project_goals.rs

@@ -346,14 +346,13 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
             ty::TraitRef::from_lang_item(tcx, LangItem::Sized, DUMMY_SP, [output])
         });
 
-        let pred = ty::Clause::from_projection_clause(
+        let pred = tupled_inputs_and_output
-            tcx,
+            .map_bound(|(inputs, output)| ty::ProjectionPredicate {
-            tupled_inputs_and_output.map_bound(|(inputs, output)| ty::ProjectionPredicate {
                 projection_ty: tcx
                     .mk_alias_ty(goal.predicate.def_id(), [goal.predicate.self_ty(), inputs]),
                 term: output.into(),
-            }),
+            })
-        );
+            .to_predicate(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...)

compiler/rustc_trait_selection/src/traits/project.rs

@@ -1644,7 +1644,7 @@ 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| ty::Clause::from_projection_clause(tcx, p.with_self_ty(tcx, object_ty)));
+        .map(|p| p.with_self_ty(tcx, object_ty).to_predicate(tcx));
 
     assemble_candidates_from_predicates(
         selcx,

compiler/rustc_trait_selection/src/traits/wf.rs

@@ -105,13 +105,13 @@ pub fn unnormalized_obligations<'tcx>(
 
 /// Returns the obligations that make this trait reference
 /// well-formed. For example, if there is a trait `Set` defined like
-/// `trait Set<K:Eq>`, then the trait reference `Foo: Set<Bar>` is WF
+/// `trait Set<K: Eq>`, then the trait bound `Foo: Set<Bar>` is WF
 /// if `Bar: Eq`.
 pub fn trait_obligations<'tcx>(
     infcx: &InferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     body_id: LocalDefId,
-    trait_pred: &ty::TraitPredicate<'tcx>,
+    trait_pred: ty::TraitPredicate<'tcx>,
     span: Span,
     item: &'tcx hir::Item<'tcx>,
 ) -> Vec<traits::PredicateObligation<'tcx>> {
@@ -129,12 +129,17 @@ pub fn trait_obligations<'tcx>(
     wf.normalize(infcx)
 }
 
+/// Returns the requirements for `clause` to be well-formed.
+///
+/// For example, if there is a trait `Set` defined like
+/// `trait Set<K: Eq>`, then the trait bound `Foo: Set<Bar>` is WF
+/// if `Bar: Eq`.
 #[instrument(skip(infcx), ret)]
-pub fn predicate_obligations<'tcx>(
+pub fn clause_obligations<'tcx>(
     infcx: &InferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     body_id: LocalDefId,
-    predicate: ty::Predicate<'tcx>,
+    clause: ty::Clause<'tcx>,
     span: Span,
 ) -> Vec<traits::PredicateObligation<'tcx>> {
     let mut wf = WfPredicates {
@@ -148,45 +153,32 @@ pub fn predicate_obligations<'tcx>(
     };
 
     // It's ok to skip the binder here because wf code is prepared for it
-    match predicate.kind().skip_binder() {
+    match clause.kind().skip_binder() {
-        ty::PredicateKind::Clause(ty::ClauseKind::Trait(t)) => {
+        ty::ClauseKind::Trait(t) => {
-            wf.compute_trait_pred(&t, Elaborate::None);
+            wf.compute_trait_pred(t, Elaborate::None);
         }
-        ty::PredicateKind::Clause(ty::ClauseKind::RegionOutlives(..)) => {}
+        ty::ClauseKind::RegionOutlives(..) => {}
-        ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(
+        ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(ty, _reg)) => {
-            ty,
-            _reg,
-        ))) => {
             wf.compute(ty.into());
         }
-        ty::PredicateKind::Clause(ty::ClauseKind::Projection(t)) => {
+        ty::ClauseKind::Projection(t) => {
             wf.compute_projection(t.projection_ty);
             wf.compute(match t.term.unpack() {
                 ty::TermKind::Ty(ty) => ty.into(),
                 ty::TermKind::Const(c) => c.into(),
             })
         }
-        ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ty)) => {
+        ty::ClauseKind::ConstArgHasType(ct, ty) => {
             wf.compute(ct.into());
             wf.compute(ty.into());
         }
-        ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(arg)) => {
+        ty::ClauseKind::WellFormed(arg) => {
             wf.compute(arg);
         }
 
-        ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(ct)) => {
+        ty::ClauseKind::ConstEvaluatable(ct) => {
             wf.compute(ct.into());
         }
-
-        ty::PredicateKind::ObjectSafe(_)
-        | ty::PredicateKind::ClosureKind(..)
-        | ty::PredicateKind::Subtype(..)
-        | ty::PredicateKind::Coerce(..)
-        | ty::PredicateKind::ConstEquate(..)
-        | ty::PredicateKind::Ambiguous
-        | ty::PredicateKind::AliasRelate(..) => {
-            bug!("We should only wf check where clauses, unexpected predicate: {predicate:?}")
-        }
     }
 
     wf.normalize(infcx)
@@ -233,7 +225,7 @@ enum Elaborate {
 
 fn extend_cause_with_original_assoc_item_obligation<'tcx>(
     tcx: TyCtxt<'tcx>,
-    trait_ref: &ty::TraitRef<'tcx>,
+    trait_ref: ty::TraitRef<'tcx>,
     item: Option<&hir::Item<'tcx>>,
     cause: &mut traits::ObligationCause<'tcx>,
     pred: ty::Predicate<'tcx>,
@@ -336,9 +328,9 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
     }
 
     /// Pushes the obligations required for `trait_ref` to be WF into `self.out`.
-    fn compute_trait_pred(&mut self, trait_pred: &ty::TraitPredicate<'tcx>, elaborate: Elaborate) {
+    fn compute_trait_pred(&mut self, trait_pred: ty::TraitPredicate<'tcx>, elaborate: Elaborate) {
         let tcx = self.tcx();
-        let trait_ref = &trait_pred.trait_ref;
+        let trait_ref = trait_pred.trait_ref;
 
         // Negative trait predicates don't require supertraits to hold, just
         // that their args are WF.
@@ -411,7 +403,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
 
     // Compute the obligations that are required for `trait_ref` to be WF,
     // given that it is a *negative* trait predicate.
-    fn compute_negative_trait_pred(&mut self, trait_ref: &ty::TraitRef<'tcx>) {
+    fn compute_negative_trait_pred(&mut self, trait_ref: ty::TraitRef<'tcx>) {
         for arg in trait_ref.args {
             self.compute(arg);
         }

compiler/rustc_ty_utils/src/ty.rs

@@ -3,9 +3,8 @@ use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_index::bit_set::BitSet;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::{
+use rustc_middle::ty::{self, EarlyBinder, Ty, TyCtxt, TypeVisitor};
-    self, EarlyBinder, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor,
+use rustc_middle::ty::{ToPredicate, TypeSuperVisitable, TypeVisitable};
-};
 use rustc_span::def_id::{DefId, LocalDefId, CRATE_DEF_ID};
 use rustc_span::DUMMY_SP;
 use rustc_trait_selection::traits;
@@ -214,10 +213,10 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInTraitFinder<'_, 'tcx> {
             // strategy, then just reinterpret the associated type like an opaque :^)
             let default_ty = self.tcx.type_of(shifted_alias_ty.def_id).instantiate(self.tcx, shifted_alias_ty.args);
 
-            self.predicates.push(ty::Clause::from_projection_clause(self.tcx, ty::Binder::bind_with_vars(
+            self.predicates.push(ty::Binder::bind_with_vars(
                 ty::ProjectionPredicate { projection_ty: shifted_alias_ty, term: default_ty.into() },
                 self.bound_vars,
-            )));
+            ).to_predicate(self.tcx));
 
             // We walk the *un-shifted* alias ty, because we're tracking the de bruijn
             // binder depth, and if we were to walk `shifted_alias_ty` instead, we'd