error[E0700]: hidden type for `impl Swap + 'a` captures lifetime that does not appear in bounds --> $DIR/hidden-lifetimes.rs:29:5 | LL | fn hide_ref<'a, 'b, T: 'static>(x: &'a mut &'b T) -> impl Swap + 'a { | -- -------------- opaque type defined here | | | hidden type `&'a mut &'b T` captures the lifetime `'b` as defined here LL | x | ^ | help: to declare that `impl Swap + 'a` captures `'b`, you can add an explicit `'b` lifetime bound | LL | fn hide_ref<'a, 'b, T: 'static>(x: &'a mut &'b T) -> impl Swap + 'a + 'b { | ++++ error[E0700]: hidden type for `impl Swap + 'a` captures lifetime that does not appear in bounds --> $DIR/hidden-lifetimes.rs:46:5 | LL | fn hide_rc_refcell<'a, 'b: 'a, T: 'static>(x: Rc>) -> impl Swap + 'a { | -- -------------- opaque type defined here | | | hidden type `Rc>` captures the lifetime `'b` as defined here LL | x | ^ | help: to declare that `impl Swap + 'a` captures `'b`, you can add an explicit `'b` lifetime bound | LL | fn hide_rc_refcell<'a, 'b: 'a, T: 'static>(x: Rc>) -> impl Swap + 'a + 'b { | ++++ error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0700`.