1 error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
2 --> $DIR/issue-87340.rs:8:6
4 LL | impl<T> X for () {
5 | ^ unconstrained type parameter
7 error: aborting due to previous error
9 For more information about this error, try `rustc --explain E0207`.