Implement TypeVisitable and TypeFoldable for Spanned

The traits are already implemented for Span, so it makes sense to also
have them for Spanned (upcoming commits will make use of this).

Author: Enselic

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -9,6 +9,7 @@ use crate::ty::print::{with_no_trimmed_paths, FmtPrinter, Printer};
 use crate::ty::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
 use crate::ty::{self, AliasTy, InferConst, Lift, Term, TermKind, Ty, TyCtxt};
 use rustc_hir::def::Namespace;
+use rustc_span::source_map::Spanned;
 use rustc_target::abi::TyAndLayout;
 use rustc_type_ir::{ConstKind, DebugWithInfcx, InferCtxtLike, WithInfcx};
 
@@ -819,3 +820,27 @@ impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for TyAndLayout<'tcx, Ty<'tcx>> {
         visitor.visit_ty(self.ty)
     }
 }
+
+impl<'tcx, T: TypeVisitable<TyCtxt<'tcx>> + Debug + Clone> TypeVisitable<TyCtxt<'tcx>>
+    for Spanned<T>
+{
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+        self.node.visit_with(visitor)?;
+        self.span.visit_with(visitor)?;
+        ControlFlow::Continue(())
+    }
+}
+
+impl<'tcx, T: TypeFoldable<TyCtxt<'tcx>> + Debug + Clone> TypeFoldable<TyCtxt<'tcx>>
+    for Spanned<T>
+{
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
+        Ok(Spanned {
+            node: self.node.try_fold_with(folder)?,
+            span: self.span.try_fold_with(folder)?,
+        })
+    }
+}