error[E0276]: impl has stricter requirements than trait
  --> $DIR/traits-misc-mismatch-2.rs:23:5
   |
19 |       fn zip<B, U: Iterator<U>>(self, other: U) -> ZipIterator<Self, U>;
   |       ------------------------------------------------------------------ definition of `zip` from trait
...
23 |       fn zip<B, U: Iterator<B>>(self, other: U) -> ZipIterator<T, U> {
   |  _____^ starting here...
24 | |     //~^ ERROR E0276
25 | |         ZipIterator{a: self, b: other}
26 | |     }
   | |_____^ ...ending here: impl has extra requirement `U: Iterator<B>`

error: aborting due to previous error