From ae9c09d3602fff3c98dbb4488147059f1024ff69 Mon Sep 17 00:00:00 2001
From: hank-der-hafenarbeiter <kevinkielholz@web.de>
Date: Tue, 9 Aug 2016 01:39:23 +0200
Subject: [PATCH 1/2] Updated error for E0045 (no bonus)

---
 src/librustc_typeck/lib.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/librustc_typeck/lib.rs b/src/librustc_typeck/lib.rs
index 65e00705121..37de3b1f609 100644
--- a/src/librustc_typeck/lib.rs
+++ b/src/librustc_typeck/lib.rs
@@ -181,8 +181,10 @@ fn require_c_abi_if_variadic(tcx: TyCtxt,
                              abi: Abi,
                              span: Span) {
     if decl.variadic && abi != Abi::C {
-        span_err!(tcx.sess, span, E0045,
+        let mut err = struct_span_err!(tcx.sess, span, E0045,
                   "variadic function must have C calling convention");
+        err.span_label(span, &("variadics require C calling conventions").to_string())
+            .emit();
     }
 }
 

From 2adc07f462fbd9bc2dc4a3b756d1e580fa337558 Mon Sep 17 00:00:00 2001
From: hank-der-hafenarbeiter <kevinkielholz@web.de>
Date: Tue, 9 Aug 2016 14:40:07 +0200
Subject: [PATCH 2/2] added unit test

---
 src/test/compile-fail/E0045.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/test/compile-fail/E0045.rs b/src/test/compile-fail/E0045.rs
index 2a731596b4b..a3fea8e0db2 100644
--- a/src/test/compile-fail/E0045.rs
+++ b/src/test/compile-fail/E0045.rs
@@ -8,7 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-extern "Rust" { fn foo(x: u8, ...); } //~ ERROR E0045
+extern "Rust" { fn foo(x: u8, ...); }   //~ ERROR E0045
+                                        //~| NOTE variadics require C calling conventions
 
 fn main() {
 }