Implement generalized object and type parameter bounds (Fixes #16462)

src/libsyntax/ast_util.rs

@@ -349,12 +349,20 @@ pub trait IdVisitingOperation {
 /// A visitor that applies its operation to all of the node IDs
 /// in a visitable thing.
 
+#[cfg(stage0)]
 pub struct IdVisitor<'a, O> {
     pub operation: &'a O,
     pub pass_through_items: bool,
     pub visited_outermost: bool,
 }
 
+#[cfg(not(stage0))]
+pub struct IdVisitor<'a, O:'a> {
+    pub operation: &'a O,
+    pub pass_through_items: bool,
+    pub visited_outermost: bool,
+}
+
 impl<'a, O: IdVisitingOperation> IdVisitor<'a, O> {
     fn visit_generics_helper(&self, generics: &Generics) {
         for type_parameter in generics.ty_params.iter() {