message: print local fields as `_2.1` instead of `_2 (field 1)`
diff: @@ -1367,13 +1367,13 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
  if let Lvalue::Local { frame, local, field } = lvalue {
  let mut allocs = Vec::new();
  let mut msg = format!("{:?}", local);
  + if let Some(field) = field {
  + write!(msg, ".{}", field).unwrap();
  + }
  let last_frame = self.stack.len() - 1;
  if frame != last_frame {
  write!(msg, " ({} frames up)", last_frame - frame).unwrap();
  }
  - if let Some(field) = field {
  - write!(msg, " (field {:?})", field).unwrap();
  - }
  write!(msg, ":").unwrap();
  match self.stack[frame].get_local(local, field.map(|(i, _)| i)) {
  