error[E0277]: the trait bound `for<'a> (): Trait2<'a>` is not satisfied --> $DIR/issue-35570.rs:8:40 | LL | fn _ice(param: Box Trait1<<() as Trait2<'a>>::Ty>>) { | ^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'a> Trait2<'a>` is not implemented for `()` | help: this trait has no implementations, consider adding one --> $DIR/issue-35570.rs:4:1 | LL | trait Trait2<'a> { | ^^^^^^^^^^^^^^^^ error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0277`.