error: duplicate borrowed lifetime `'a`
 --> tests/ui/borrow/duplicate_lifetime.rs:5:22
  |
3 | #[derive(Deserialize)]
  |          ----------- in this derive macro expansion
4 | struct Test<'a> {
5 |     #[serde(borrow = "'a + 'a")]
  |                      ^^^^^^^^^
  |
  = note: this error originates in the derive macro `Deserialize` (in Nightly builds, run with -Z macro-backtrace for more info)