Rollup merge of #127808 - oli-obk:tainting_visitors2, r=lcnr,nnethercote

Make ErrorGuaranteed discoverable outside types, consts, and lifetimes

types like `PatKind` could contain `ErrorGuaranteed`, but not return them via `tainted_by_errors` or `error_reported` (see https://github.com/rust-lang/rust/pull/127687#discussion_r1679027883). Now this happens, but it's a bit fragile as you can see with the `TypeSuperVisitable for Ty` impl.

We will catch any problems around Ty, Region or Const at runtime with an assert, and everything using derives will not have such issues, as it will just invoke the `TypeVisitable for ErrorGuaranteed` impl

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -257,7 +257,6 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
     crate::ty::adjustment::PointerCoercion,
     ::rustc_span::Span,
     ::rustc_span::symbol::Ident,
-    ::rustc_errors::ErrorGuaranteed,
     ty::BoundVar,
     ty::ValTree<'tcx>,
 }
@@ -443,13 +442,14 @@ fn super_visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> V::
                 pat.visit_with(visitor)
             }
 
+            ty::Error(guar) => guar.visit_with(visitor),
+
             ty::Bool
             | ty::Char
             | ty::Str
             | ty::Int(_)
             | ty::Uint(_)
             | ty::Float(_)
-            | ty::Error(_)
             | ty::Infer(_)
             | ty::Bound(..)
             | ty::Placeholder(..)
@@ -602,6 +602,21 @@ fn super_visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> V::
     }
 }
 
+impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for rustc_span::ErrorGuaranteed {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> V::Result {
+        visitor.visit_error(*self)
+    }
+}
+
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for rustc_span::ErrorGuaranteed {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        _folder: &mut F,
+    ) -> Result<Self, F::Error> {
+        Ok(self)
+    }
+}
+
 impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for InferConst {
     fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,
@@ -617,12 +632,6 @@ fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, _visitor: &mut V) -> V::Resul
     }
 }
 
-impl<'tcx> TypeSuperVisitable<TyCtxt<'tcx>> for ty::UnevaluatedConst<'tcx> {
-    fn super_visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> V::Result {
-        self.args.visit_with(visitor)
-    }
-}
-
 impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for TyAndLayout<'tcx, Ty<'tcx>> {
     fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> V::Result {
         visitor.visit_ty(self.ty)

compiler/rustc_type_ir/src/visit.rs

@@ -101,9 +101,13 @@ fn visit_ty(&mut self, t: I::Ty) -> Self::Result {
 
     // The default region visitor is a no-op because `Region` is non-recursive
     // and has no `super_visit_with` method to call.
-    fn visit_region(&mut self, _r: I::Region) -> Self::Result {
+    fn visit_region(&mut self, r: I::Region) -> Self::Result {
+        if let ty::ReError(guar) = r.kind() {
+            self.visit_error(guar)
+        } else {
             Self::Result::output()
         }
+    }
 
     fn visit_const(&mut self, c: I::Const) -> Self::Result {
         c.super_visit_with(self)
@@ -116,6 +120,10 @@ fn visit_predicate(&mut self, p: I::Predicate) -> Self::Result {
     fn visit_clauses(&mut self, p: I::Clauses) -> Self::Result {
         p.super_visit_with(self)
     }
+
+    fn visit_error(&mut self, _guar: I::ErrorGuaranteed) -> Self::Result {
+        Self::Result::output()
+    }
 }
 
 ///////////////////////////////////////////////////////////////////////////
@@ -439,6 +447,15 @@ fn visit_clauses(&mut self, clauses: I::Clauses) -> Self::Result {
             ControlFlow::Continue(())
         }
     }
+
+    #[inline]
+    fn visit_error(&mut self, _guar: <I as Interner>::ErrorGuaranteed) -> Self::Result {
+        if self.flags.intersects(TypeFlags::HAS_ERROR) {
+            ControlFlow::Break(FoundFlags)
+        } else {
+            ControlFlow::Continue(())
+        }
+    }
 }
 
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
@@ -547,27 +564,7 @@ fn visit_clauses(&mut self, clauses: I::Clauses) -> Self::Result {
 impl<I: Interner> TypeVisitor<I> for HasErrorVisitor {
     type Result = ControlFlow<I::ErrorGuaranteed>;
 
-    fn visit_ty(&mut self, t: <I as Interner>::Ty) -> Self::Result {
-        if let ty::Error(guar) = t.kind() {
+    fn visit_error(&mut self, guar: <I as Interner>::ErrorGuaranteed) -> Self::Result {
         ControlFlow::Break(guar)
-        } else {
-            t.super_visit_with(self)
-        }
-    }
-
-    fn visit_const(&mut self, c: <I as Interner>::Const) -> Self::Result {
-        if let ty::ConstKind::Error(guar) = c.kind() {
-            ControlFlow::Break(guar)
-        } else {
-            c.super_visit_with(self)
-        }
-    }
-
-    fn visit_region(&mut self, r: <I as Interner>::Region) -> Self::Result {
-        if let ty::ReError(guar) = r.kind() {
-            ControlFlow::Break(guar)
-        } else {
-            ControlFlow::Continue(())
-        }
     }
 }