error[E0207]: the lifetime parameter `'a` is not constrained by the impl trait, self type, or predicates --> $DIR/issue-22886.rs:23:6 | LL | impl<'a> Iterator for Newtype { //~ ERROR E0207 | ^^ unconstrained lifetime parameter error: aborting due to previous error If you want more information on this error, try using "rustc --explain E0207"