Invalid lifetime syntax in "conflicting implementation" error message

[dtolnay]

I noticed error output like the following in the ui tests of #54687.

error[E0119]: conflicting implementations of trait `std::marker::Copy` for type `&NotSync`:
  --> $DIR/coherence-impls-copy.rs:41:1
   |
   | impl Copy for &'static NotSync {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: conflicting implementation in crate `core`:
           - impl<'_, T> std::marker::Copy for &T
             where T: ?Sized;

The impl<'_, T> is not valid syntax. The error message should use impl<T>.

[scottmcm]

In case it helps, this doesn't seem to happen inside a single module:

trait Trait {}
impl Trait for &() {}
impl Trait for &'static () {}

error[E0119]: conflicting implementations of trait `Trait` for type `&()`:
 --> src/lib.rs:3:1
  |
2 | impl Trait for &() {}
  | ------------------ first implementation here
3 | impl Trait for &'static () {}
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `&()`

Also, cc the impl_header_lifetime_elision tracking issue: #15872

[scottmcm]

Look like this affects rustdoc too:

impl<'_, T> Borrow<T> for &'_ T 

https://doc.rust-lang.org/nightly/std/borrow/trait.Borrow.html#impl-Borrow%3CT%3E