Rollup merge of #110345 - nnethercote:rm-Super-impls-for-Region, r=compiler-errors

Remove `TypeSuper{Foldable,Visitable}` impls for `Region`.

These traits exist so that folders/visitors can recurse into types of interest: binders, types, regions, predicates, and consts. But `Region` is non-recursive and cannot contain other types of interest, so its methods in these traits are trivial.

This commit inlines and removes those trivial methods.

r? `@compiler-errors`

compiler/rustc_middle/src/ty/fold.rs

@@ -37,7 +37,8 @@ where
     }
 
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
-        let r = r.super_fold_with(self);
+        // This one is a little different, because `super_fold_with` is not
+        // implemented on non-recursive `Region`.
         (self.lt_op)(r)
     }
 

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -2518,7 +2518,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
                     self.used_region_names.insert(name);
                 }
 
-                r.super_visit_with(self)
+                ControlFlow::Continue(())
             }
 
             // We collect types in order to prevent really large types from compiling for

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -583,24 +583,6 @@ impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for ty::Region<'tcx> {
     }
 }
 
-impl<'tcx> TypeSuperFoldable<TyCtxt<'tcx>> for ty::Region<'tcx> {
-    fn try_super_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
-        self,
-        _folder: &mut F,
-    ) -> Result<Self, F::Error> {
-        Ok(self)
-    }
-}
-
-impl<'tcx> TypeSuperVisitable<TyCtxt<'tcx>> for ty::Region<'tcx> {
-    fn super_visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(
-        &self,
-        _visitor: &mut V,
-    ) -> ControlFlow<V::BreakTy> {
-        ControlFlow::Continue(())
-    }
-}
-
 impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ty::Predicate<'tcx> {
     fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,

compiler/rustc_middle/src/ty/visit.rs

@@ -364,7 +364,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ValidateBoundVars<'tcx> {
             _ => (),
         };
 
-        r.super_visit_with(self)
+        ControlFlow::Continue(())
     }
 }