error[E0392]: lifetime parameter `'a` is never used --> $DIR/dedup.rs:6:12 | LL | struct Foo<'a>; | ^^ unused lifetime parameter | = help: consider removing `'a`, referring to it in a field, or using a marker such as `PhantomData` error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0392`.