move visit_predicate into TypeVisitor

compiler/rustc_middle/src/ty/fold.rs

@@ -30,8 +30,6 @@
 //!
 //! These methods return true to indicate that the visitor has found what it is
 //! looking for, and does not need to visit anything else.
-
-use crate::ty::structural_impls::PredicateVisitor;
 use crate::ty::{self, flags::FlagComputation, Binder, Ty, TyCtxt, TypeFlags};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
@@ -211,6 +209,10 @@ pub trait TypeVisitor<'tcx>: Sized {
     fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> bool {
         c.super_visit_with(self)
     }
+
+    fn visit_predicate(&mut self, p: ty::Predicate<'tcx>) -> bool {
+        p.super_visit_with(self)
+    }
 }
 
 ///////////////////////////////////////////////////////////////////////////
@@ -868,9 +870,7 @@ impl<'tcx> TypeVisitor<'tcx> for HasEscapingVarsVisitor {
             _ => ct.super_visit_with(self),
         }
     }
-}
 
-impl<'tcx> PredicateVisitor<'tcx> for HasEscapingVarsVisitor {
     fn visit_predicate(&mut self, predicate: ty::Predicate<'tcx>) -> bool {
         predicate.inner.outer_exclusive_binder > self.outer_index
     }
@@ -903,9 +903,7 @@ impl<'tcx> TypeVisitor<'tcx> for HasTypeFlagsVisitor {
         debug!("HasTypeFlagsVisitor: c={:?} c.flags={:?} self.flags={:?}", c, flags, self.flags);
         flags.intersects(self.flags)
     }
-}
 
-impl<'tcx> PredicateVisitor<'tcx> for HasTypeFlagsVisitor {
     fn visit_predicate(&mut self, predicate: ty::Predicate<'tcx>) -> bool {
         debug!(
             "HasTypeFlagsVisitor: predicate={:?} predicate.flags={:?} self.flags={:?}",
@@ -914,6 +912,7 @@ impl<'tcx> PredicateVisitor<'tcx> for HasTypeFlagsVisitor {
         predicate.inner.flags.intersects(self.flags)
     }
 }
+
 /// Collects all the late-bound regions at the innermost binding level
 /// into a hash set.
 struct LateBoundRegionsCollector {

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -1040,16 +1040,6 @@ impl<'tcx> TypeFoldable<'tcx> for ty::Predicate<'tcx> {
     }
 }
 
-pub(super) trait PredicateVisitor<'tcx>: TypeVisitor<'tcx> {
-    fn visit_predicate(&mut self, predicate: ty::Predicate<'tcx>) -> bool;
-}
-
-impl<T: TypeVisitor<'tcx>> PredicateVisitor<'tcx> for T {
-    default fn visit_predicate(&mut self, predicate: ty::Predicate<'tcx>) -> bool {
-        predicate.super_visit_with(self)
-    }
-}
-
 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Predicate<'tcx>> {
     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
         fold_list(*self, folder, |tcx, v| tcx.intern_predicates(v))