Update E0303 to new error format

Author: jfirebaugh

src/librustc_const_eval/check_match.rs

@@ -1238,8 +1238,10 @@ impl<'a, 'b, 'tcx, 'v> Visitor<'v> for AtBindingPatternVisitor<'a, 'b, 'tcx> {
         match pat.node {
             PatKind::Binding(.., ref subpat) => {
                 if !self.bindings_allowed {
-                    span_err!(self.cx.tcx.sess, pat.span, E0303,
-                              "pattern bindings are not allowed after an `@`");
+                    struct_span_err!(self.cx.tcx.sess, pat.span, E0303,
+                                     "pattern bindings are not allowed after an `@`")
+                        .span_label(pat.span,  &format!("not allowed after `@`"))
+                        .emit();
                 }
 
                 if subpat.is_some() {

src/test/compile-fail/E0007.rs

@@ -15,6 +15,7 @@ fn main() {
         //~^ ERROR E0007
         //~| NOTE binds an already bound by-move value by moving it
         //~| ERROR E0303
+        //~| NOTE not allowed after `@`
         None => {},
     }
 }

src/test/compile-fail/E0303.rs

@@ -10,8 +10,12 @@
 
 fn main() {
     match Some("hi".to_string()) {
-        ref op_string_ref @ Some(s) => {}, //~ ERROR E0303
-                                           //~^ ERROR E0009
+        ref op_string_ref @ Some(s) => {},
+        //~^ ERROR pattern bindings are not allowed after an `@` [E0303]
+        //~| NOTE not allowed after `@`
+        //~| ERROR E0009
+        //~| NOTE by-move pattern here
+        //~| NOTE both by-ref and by-move used
         None => {},
     }
 }