error: implementation of `Trait` is not general enough
  --> $DIR/issue-57362-1.rs:20:7
   |
LL |     a.f(); //~ ERROR not general enough
   |       ^
   |
   = note: `Trait` would have to be implemented for the type `fn(&'0 u8)`, for some specific lifetime `'0`
   = note: but `Trait` is actually implemented for the type `for<'r> fn(&'r u8)`

error: aborting due to previous error