error[E0207]: the lifetime parameter `'a` is not constrained by the impl trait, self type, or predicates
  --> $DIR/issue-74761.rs:7:6
   |
LL | impl<'a, 'b> A for () {
   |      ^^ unconstrained lifetime parameter

error[E0207]: the lifetime parameter `'b` is not constrained by the impl trait, self type, or predicates
  --> $DIR/issue-74761.rs:7:10
   |
LL | impl<'a, 'b> A for () {
   |          ^^ unconstrained lifetime parameter

error[E0792]: expected generic lifetime parameter, found `'_`
  --> $DIR/issue-74761.rs:12:28
   |
LL | impl<'a, 'b> A for () {
   |      -- this generic parameter must be used with a generic lifetime parameter
...
LL |     fn f(&self) -> Self::B {}
   |                            ^^

error: aborting due to 3 previous errors

Some errors have detailed explanations: E0207, E0792.
For more information about an error, try `rustc --explain E0207`.