From 36909c7575e2ddfe2925423aceb62d82ae8208b2 Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@mimiga.net>
Date: Thu, 28 Mar 2013 18:55:35 -0700
Subject: [PATCH] libsyntax: Don't allow `impl (Trait) for Type` (with the
 parentheses).

---
 src/libsyntax/parse/parser.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 51a7f7fbd1c0a..c52162b7f14ed 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -3107,11 +3107,15 @@ pub impl Parser {
         // XXX: clownshoes
         let ident = special_idents::clownshoes_extensions;
 
+        // Special case: if the next identifier that follows is '(', don't
+        // allow this to be parsed as a trait.
+        let could_be_trait = *self.token != token::LPAREN;
+
         // Parse the trait.
         let mut ty = self.parse_ty(false);
 
         // Parse traits, if necessary.
-        let opt_trait = if self.eat_keyword(&~"for") {
+        let opt_trait = if could_be_trait && self.eat_keyword(&~"for") {
             // New-style trait. Reinterpret the type as a trait.
             let opt_trait_ref = match ty.node {
                 ty_path(path, node_id) => {