e0062.rs

                    let mut err = struct_span_err!(self.tcx.sess,
                                                field.name.span,
                                                E0062,
                                                "field `{}` specified more than once",
                                                field.name.node);

                    err.span_label(field.name.span, &format!("used more than once"));

                    if let Some(prev_span) = seen_fields.get(&field.name.node) {
                        err.span_label(*prev_span, &format!("first use of `{}`", field.name.node));
                    }

                    err.emit();

modified rustc (new style)

error[E0062]: field `x` specified more than once
  --> src\test\compile-fail\E0062.rs:18:9
   |
17 |         x: 0,
   |         ---- first use of `x`
18 |         x: 0, //~ ERROR E0062
   |         ^ used more than once

modified rustc (old style)

src\test\compile-fail\E0062.rs:18:9: 18:10 error: field `x` specified more than once [E0062]
src\test\compile-fail\E0062.rs:18         x: 0,
                                          ^~~~

vanilla rustc (old style)

src\test\compile-fail\E0062.rs:18:9: 18:10 error: field `x` specified more than once [E0062]
src\test\compile-fail\E0062.rs:18         x: 0, //~ ERROR E0062
                                          ^