error[E0277]: the trait bound `impl Send: Duh` is not satisfied
  --> $DIR/nested-return-type2-tait3.rs:25:13
   |
LL | fn foo() -> Traitable {
   |             ^^^^^^^^^ the trait `Duh` is not implemented for `impl Send`
   |
   = help: the trait `Duh` is implemented for `i32`
note: required because of the requirements on the impl of `Trait` for `[closure@$DIR/nested-return-type2-tait3.rs:27:5: 27:10]`
  --> $DIR/nested-return-type2-tait3.rs:14:31
   |
LL | impl<R: Duh, F: FnMut() -> R> Trait for F {
   |                               ^^^^^     ^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.