--- /dev/null
+error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
+ --> $DIR/impl-with-unconstrained-param.rs:14:6
+ |
+LL | impl<T> X for () {
+ | ^ unconstrained type parameter
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0207`.