error: `impl` item signature doesn't match `trait` item signature
  --> $DIR/param-without-lifetime-constraint.rs:14:5
   |
LL |     fn get_relation(&self) -> To;
   |     ----------------------------- expected `fn(&'1 Article) -> &'2 ProofReader`
...
LL |     fn get_relation(&self) -> &ProofReader {
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ found `fn(&'1 Article) -> &'1 ProofReader`
   |
   = note: expected signature `fn(&'1 Article) -> &'2 ProofReader`
              found signature `fn(&'1 Article) -> &'1 ProofReader`
help: the lifetime requirements from the `impl` do not correspond to the requirements in the `trait`
  --> $DIR/param-without-lifetime-constraint.rs:10:31
   |
LL |     fn get_relation(&self) -> To;
   |                               ^^ consider borrowing this type parameter in the trait

error: aborting due to 1 previous error