Generalize the ToPredicate trait

Its name is now not accurate anymore, but we'll adjust that later

Author: oli-obk

compiler/rustc_borrowck/src/type_check/canonical.rs

@@ -122,7 +122,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
     pub(super) fn prove_predicates(
         &mut self,
-        predicates: impl IntoIterator<Item = impl ToPredicate<'tcx>>,
+        predicates: impl IntoIterator<Item = impl ToPredicate<'tcx, ty::Predicate<'tcx>>>,
         locations: Locations,
         category: ConstraintCategory<'tcx>,
     ) {

compiler/rustc_middle/src/ty/mod.rs

@@ -1125,42 +1125,42 @@ impl<'tcx> ToPolyTraitRef<'tcx> for PolyTraitPredicate<'tcx> {
     }
 }
 
-pub trait ToPredicate<'tcx> {
-    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx>;
+pub trait ToPredicate<'tcx, Predicate> {
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate;
 }
 
-impl<'tcx> ToPredicate<'tcx> for Predicate<'tcx> {
+impl<'tcx> ToPredicate<'tcx, Predicate<'tcx>> for Predicate<'tcx> {
     fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         self
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, PredicateKind<'tcx>> {
+impl<'tcx> ToPredicate<'tcx, Predicate<'tcx>> for Binder<'tcx, PredicateKind<'tcx>> {
     #[inline(always)]
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         tcx.mk_predicate(self)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for PolyTraitPredicate<'tcx> {
+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)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for PolyRegionOutlivesPredicate<'tcx> {
+impl<'tcx> ToPredicate<'tcx, Predicate<'tcx>> for PolyRegionOutlivesPredicate<'tcx> {
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         self.map_bound(PredicateKind::RegionOutlives).to_predicate(tcx)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for PolyTypeOutlivesPredicate<'tcx> {
+impl<'tcx> ToPredicate<'tcx, Predicate<'tcx>> for PolyTypeOutlivesPredicate<'tcx> {
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         self.map_bound(PredicateKind::TypeOutlives).to_predicate(tcx)
     }
 }
 
-impl<'tcx> ToPredicate<'tcx> for PolyProjectionPredicate<'tcx> {
+impl<'tcx> ToPredicate<'tcx, Predicate<'tcx>> for PolyProjectionPredicate<'tcx> {
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         self.map_bound(PredicateKind::Projection).to_predicate(tcx)
     }