1 error[E0392]: parameter `T` is never used
2 --> $DIR/issue-17904-2.rs:4:12
4 LL | struct Foo<T> where T: Copy;
7 = help: consider removing `T`, referring to it in a field, or using a marker such as `PhantomData`
9 error: aborting due to previous error
11 For more information about this error, try `rustc --explain E0392`.