do not implement type traversal for EarlyBinder

Author: lcnr

compiler/rustc_middle/src/ty/layout.rs

@@ -2770,7 +2770,10 @@ impl<'tcx> ty::Instance<'tcx> {
                 // track of a polymorphization `ParamEnv` to allow normalizing later.
                 let mut sig = match *ty.kind() {
                     ty::FnDef(def_id, substs) => tcx
-                        .normalize_erasing_regions(tcx.param_env(def_id), tcx.bound_fn_sig(def_id))
+                        .bound_fn_sig(def_id)
+                        .map_bound(|fn_sig| {
+                            tcx.normalize_erasing_regions(tcx.param_env(def_id), fn_sig)
+                        })
                         .subst(tcx, substs),
                     _ => unreachable!(),
                 };

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -557,18 +557,6 @@ impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Box<[T]> {
     }
 }
 
-impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::EarlyBinder<T> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
-        self.try_map_bound(|ty| ty.try_fold_with(folder))
-    }
-}
-
-impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for ty::EarlyBinder<T> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        self.as_ref().0.visit_with(visitor)
-    }
-}
-
 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::Binder<'tcx, T> {
     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
         folder.try_fold_binder(self)

compiler/rustc_middle/src/ty/sty.rs

@@ -919,6 +919,10 @@ impl<'tcx> PolyExistentialTraitRef<'tcx> {
 #[derive(Encodable, Decodable, HashStable)]
 pub struct EarlyBinder<T>(pub T);
 
+/// For early binders, you should first call `subst` before using any visitors.
+impl<'tcx, T> !TypeFoldable<'tcx> for ty::EarlyBinder<T> {}
+impl<'tcx, T> !TypeVisitable<'tcx> for ty::EarlyBinder<T> {}
+
 impl<T> EarlyBinder<T> {
     pub fn as_ref(&self) -> EarlyBinder<&T> {
         EarlyBinder(&self.0)