Generate the `NodeId` for `existential type` in the AST

5 files changed, 10 insertions, 6 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 53465c071f3..ca07ac7988d 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -1547,7 +1547,11 @@ pub enum TyKind {
     TraitObject(GenericBounds, TraitObjectSyntax),
     /// An `impl Bound1 + Bound2 + Bound3` type
     /// where `Bound` is a trait or a lifetime.
-    ImplTrait(GenericBounds),
+    ///
+    /// The `NodeId` exists to prevent lowering from having to
+    /// generate `NodeId`s on the fly, which would complicate
+    /// the generation of `existential type` items significantly
+    ImplTrait(NodeId, GenericBounds),
     /// No-op; kept solely so that we can pretty-print faithfully
     Paren(P<Ty>),
     /// Unused for now
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index 712d00fde32..1035be3a159 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -396,8 +396,8 @@ pub fn noop_fold_ty<T: Folder>(t: P<Ty>, fld: &mut T) -> P<Ty> {
             TyKind::TraitObject(bounds, syntax) => {
                 TyKind::TraitObject(bounds.move_map(|b| fld.fold_param_bound(b)), syntax)
             }
-            TyKind::ImplTrait(bounds) => {
-                TyKind::ImplTrait(bounds.move_map(|b| fld.fold_param_bound(b)))
+            TyKind::ImplTrait(id, bounds) => {
+                TyKind::ImplTrait(fld.new_id(id), bounds.move_map(|b| fld.fold_param_bound(b)))
             }
             TyKind::Mac(mac) => {
                 TyKind::Mac(fld.fold_mac(mac))
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 21bd6c08324..8690918c805 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -1537,7 +1537,7 @@ impl<'a> Parser<'a> {
             // Always parse bounds greedily for better error recovery.
             let bounds = self.parse_generic_bounds()?;
             impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
-            TyKind::ImplTrait(bounds)
+            TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
         } else if self.check_keyword(keywords::Dyn) &&
                   self.look_ahead(1, |t| t.can_begin_bound() &&
                                          !can_continue_type_after_non_fn_ident(t)) {
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 3359225e159..74edf538842 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -1078,7 +1078,7 @@ impl<'a> State<'a> {
                 let prefix = if syntax == ast::TraitObjectSyntax::Dyn { "dyn" } else { "" };
                 self.print_type_bounds(prefix, &bounds[..])?;
             }
-            ast::TyKind::ImplTrait(ref bounds) => {
+            ast::TyKind::ImplTrait(_, ref bounds) => {
                 self.print_type_bounds("impl", &bounds[..])?;
             }
             ast::TyKind::Array(ref ty, ref length) => {
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index 41e3ad9d4f4..bb35bcee438 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -338,7 +338,7 @@ pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) {
             visitor.visit_anon_const(length)
         }
         TyKind::TraitObject(ref bounds, ..) |
-        TyKind::ImplTrait(ref bounds) => {
+        TyKind::ImplTrait(_, ref bounds) => {
             walk_list!(visitor, visit_param_bound, bounds);
         }
         TyKind::Typeof(ref expression) => {