error[E0623]: lifetime mismatch
  --> $DIR/ex3-both-anon-regions-self-is-anon.rs:7:19
   |
LL |     fn foo<'a>(&self, x: &Foo) -> &Foo {
   |                          ----     ----
   |                          |
   |                          this parameter and the return type are declared with different lifetimes...
LL |         if true { x } else { self }
   |                   ^ ...but data from `x` is returned here
   |
   = note: each elided lifetime in input position becomes a distinct lifetime
help: consider introducing a named lifetime parameter and update trait if needed
   |
LL |     fn foo<'a>(&'a self, x: &'a Foo) -> &Foo {
   |                 ++           ++

error: aborting due to previous error

For more information about this error, try `rustc --explain E0623`.