error[E0106]: missing lifetime specifiers --> $DIR/issue-84592.rs:12:57 | LL | fn two_lifetimes_needed(a: &(), b: &()) -> TwoLifetimes<'_, '_> { | --- --- ^^ ^^ expected named lifetime parameter | | | expected named lifetime parameter | = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `a` or `b` help: consider introducing a named lifetime parameter | LL | fn two_lifetimes_needed<'a>(a: &'a (), b: &'a ()) -> TwoLifetimes<'a, 'a> { | ++++ ++ ++ ~~ ~~ error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0106`.