From 607f60712c7c9d3b96a162d2605a89ff2554fc7e Mon Sep 17 00:00:00 2001
From: Flavio Percoco <flaper87@gmail.com>
Date: Tue, 23 Dec 2014 10:57:44 +0100
Subject: Keep track of the whole error chain

---
 src/libsyntax/ext/deriving/bounds.rs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

(limited to 'src/libsyntax/ext')

diff --git a/src/libsyntax/ext/deriving/bounds.rs b/src/libsyntax/ext/deriving/bounds.rs
index c27a27fce6a..cf29bb048d6 100644
--- a/src/libsyntax/ext/deriving/bounds.rs
+++ b/src/libsyntax/ext/deriving/bounds.rs
@@ -26,8 +26,11 @@ pub fn expand_deriving_bound<F>(cx: &mut ExtCtxt,
         MetaWord(ref tname) => {
             match tname.get() {
                 "Copy" => "Copy",
-                "Send" => "Send",
-                "Sync" => "Sync",
+                "Send" | "Sync" => {
+                    return cx.span_err(span,
+                                       format!("{} is an unsafe trait and it \
+                                               should be implemented explicitly", *tname)[])
+                }
                 ref tname => {
                     cx.span_bug(span,
                                 format!("expected built-in trait name but \
-- 
cgit 1.4.1-3-g733a5