Updated E0081 to new format

Author: Christian Poveda

src/librustc_typeck/check/mod.rs

@@ -1251,8 +1251,9 @@ pub fn check_enum_variants<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
                 let mut err = struct_span_err!(ccx.tcx.sess, v.span, E0081,
                     "discriminant value `{}` already exists", disr_vals[i]);
                 let variant_i_node_id = ccx.tcx.map.as_local_node_id(variants[i].did).unwrap();
-                span_note!(&mut err, ccx.tcx.map.span(variant_i_node_id),
-                    "conflicting discriminant here");
+                err.span_label(ccx.tcx.map.span(variant_i_node_id),
+                               &format!("first use of `{}`", disr_vals[i]));
+                err.span_label(v.span , &format!("enum already has `{}`", disr_vals[i]));
                 err.emit();
             }
             disr_vals.push(current_disr_val);

src/test/compile-fail/issue-15524.rs

@@ -12,13 +12,16 @@ const N: isize = 1;
 
 enum Foo {
     A = 1,
-    B = 1, //~ ERROR discriminant value `1isize` already exists
-    //~^^ NOTE conflicting
+    B = 1, //~ ERROR discriminant value
+    //~^ NOTE enum already
+    //~^^^ NOTE first use
     C = 0,
-    D, //~ ERROR discriminant value `1isize` already exists
-    //~^^^^^ NOTE conflicting
-    E = N, //~ ERROR discriminant value `1isize` already exists
-    //~^^^^^^^ NOTE conflicting
+    D, //~ ERROR discriminant value
+    //~^ NOTE enum already
+    //~^^^^^^^ NOTE first use
+    E = N, //~ ERROR discriminant value
+    //~^ NOTE enum already
+    //~^^^^^^^^^^ NOTE first use
 }
 
 fn main() {}