add negative impl

Author: lcnr

compiler/rustc_borrowck/src/lib.rs

@@ -9,6 +9,7 @@
 #![feature(file_buffered)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
+#![feature(negative_impls)]
 #![feature(never_type)]
 #![feature(rustc_attrs)]
 #![feature(rustdoc_internals)]
@@ -36,7 +37,9 @@ use rustc_infer::infer::{
 };
 use rustc_middle::mir::*;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::{self, ParamEnv, RegionVid, Ty, TyCtxt, TypingMode, fold_regions};
+use rustc_middle::ty::{
+    self, ParamEnv, RegionVid, Ty, TyCtxt, TypeFoldable, TypeVisitable, TypingMode, fold_regions,
+};
 use rustc_middle::{bug, span_bug};
 use rustc_mir_dataflow::impls::{
     EverInitializedPlaces, MaybeInitializedPlaces, MaybeUninitializedPlaces,
@@ -236,13 +239,14 @@ pub enum ClosureOutlivesSubject<'tcx> {
 /// This abstraction is necessary because the type may include `ReVar` regions,
 /// which is what we use internally within NLL code, and they can't be used in
 /// a query response.
-///
-/// DO NOT implement `TypeVisitable` or `TypeFoldable` traits, because this
-/// type is not recognized as a binder for late-bound region.
 #[derive(Copy, Clone, Debug)]
 pub struct ClosureOutlivesSubjectTy<'tcx> {
     inner: Ty<'tcx>,
 }
+// DO NOT implement `TypeVisitable` or `TypeFoldable` traits, because this
+// type is not recognized as a binder for late-bound region.
+impl<'tcx, I> !TypeVisitable<I> for ClosureOutlivesSubjectTy<'tcx> {}
+impl<'tcx, I> !TypeFoldable<I> for ClosureOutlivesSubjectTy<'tcx> {}
 
 impl<'tcx> ClosureOutlivesSubjectTy<'tcx> {
     /// All regions of `ty` must be of kind `ReVar` and must represent