pre-expansion gate trait_alias.

3 files changed, 5 insertions, 9 deletions

diff --git a/src/libsyntax/feature_gate/check.rs b/src/libsyntax/feature_gate/check.rs
index 172511f0f09..97172691a11 100644
--- a/src/libsyntax/feature_gate/check.rs
+++ b/src/libsyntax/feature_gate/check.rs
@@ -423,15 +423,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                                    "auto traits are experimental and possibly buggy");
             }
 
-            ast::ItemKind::TraitAlias(..) => {
-                gate_feature_post!(
-                    &self,
-                    trait_alias,
-                    i.span,
-                    "trait aliases are experimental"
-                );
-            }
-
             ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
                 let msg = "`macro` is experimental";
                 gate_feature_post!(&self, decl_macro, i.span, msg);
@@ -867,6 +858,7 @@ pub fn check_crate(krate: &ast::Crate,
     gate_all!(yields, generators, "yield syntax is experimental");
     gate_all!(or_patterns, "or-patterns syntax is experimental");
     gate_all!(const_extern_fn, "`const extern fn` definitions are unstable");
+    gate_all!(trait_alias, "trait aliases are experimental");
 
     visit::walk_crate(&mut visitor, krate);
 }
diff --git a/src/libsyntax/parse/parser/item.rs b/src/libsyntax/parse/parser/item.rs
index 01dc0c21d4d..c5498236da1 100644
--- a/src/libsyntax/parse/parser/item.rs
+++ b/src/libsyntax/parse/parser/item.rs
@@ -828,6 +828,8 @@ impl<'a> Parser<'a> {
                     .emit();
             }
 
+            self.sess.gated_spans.trait_alias.borrow_mut().push(whole_span);
+
             Ok((ident, ItemKind::TraitAlias(tps, bounds), None))
         } else {
             // It's a normal trait.
diff --git a/src/libsyntax/sess.rs b/src/libsyntax/sess.rs
index e49d3954f8e..b48b2b494c8 100644
--- a/src/libsyntax/sess.rs
+++ b/src/libsyntax/sess.rs
@@ -30,6 +30,8 @@ crate struct GatedSpans {
     crate or_patterns: Lock<Vec<Span>>,
     /// Spans collected for gating `const_extern_fn`, e.g. `const extern fn foo`.
     crate const_extern_fn: Lock<Vec<Span>>,
+    /// Spans collected for gating `trait_alias`, e.g. `trait Foo = Ord + Eq;`.
+    pub trait_alias: Lock<Vec<Span>>,
 }
 
 /// Info about a parsing session.