error: `refs_tuple` should be set only once
 --> tests/ui/errors/attr.tuples.unique.refs-tuple.rs:7:15
  |
7 |     #[tuples::refs_tuple(mut)]
  |               ^^^^^^^^^^

error: the first definition was here
 --> tests/ui/errors/attr.tuples.unique.refs-tuple.rs:6:15
  |
6 |     #[tuples::refs_tuple]
  |               ^^^^^^^^^^