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`.