error[E0405]: cannot find trait `OuterTrait` in this scope
  --> $DIR/issue-21221-3.rs:15:6
   |
LL | impl OuterTrait for Foo {}
   |      ^^^^^^^^^^ not found in this scope
   |
help: consider importing this trait
   |
LL + use issue_21221_3::outer::OuterTrait;
   |

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0405`.