error[E0700]: hidden type for `impl Trait<'a, 'b>` captures lifetime that does not appear in bounds --> $DIR/ordinary-bounds-unsuited.rs:31:33 | LL | fn upper_bounds<'a, 'b>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'a, 'b> | -- ------------------ opaque type defined here | | | hidden type `Ordinary<'b>` captures the lifetime `'b` as defined here ... LL | if condition() { a } else { b } | ^ | help: to declare that `impl Trait<'a, 'b>` captures `'b`, you can add an explicit `'b` lifetime bound | LL | fn upper_bounds<'a, 'b>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'a, 'b> + 'b | ++++ error: aborting due to previous error For more information about this error, try `rustc --explain E0700`.