error[E0195]: lifetime parameters or bounds on method `scan` do not match the trait declaration
  --> $DIR/issue-87803.rs:20:12
   |
LL |     fn scan<'a>(&mut self, i : Self::Input<'a>) -> Self::Token<'a>;
   |            ---- lifetimes in impl do not match this method in trait
...
LL |     fn scan<'a>(&mut self, s : &'a str) -> &'a str {
   |            ^^^^ lifetimes do not match method in trait

error: aborting due to previous error

For more information about this error, try `rustc --explain E0195`.