message: follow-up to review
diff: @@ -221,10 +221,7 @@ pub fn eval_main<'tcx>(tcx: TyCtxt<'tcx>, main_id: DefId, config: MiriConfig) {
  };
  let msg = format!("Miri evaluation error: {}", msg);
  - let mut err = {
  - let new_tcx = ecx.tcx.tcx.at(span);
  - new_tcx.sess.struct_span_err(new_tcx.span, msg.as_str())
  - };
  + let mut err = ecx.tcx.sess.struct_span_err(span, msg.as_str());
  let frames = ecx.generate_stacktrace(None);
  err.span_label(span, msg);
  // We iterate with indices because we need to look at the next frame (the caller).
  