error[E0277]: the trait bound `u32: Bound` is not satisfied
  --> $DIR/closure-wf.rs:9:33
   |
LL |     constrain_inner(1u32, |&(), _| ());
   |                                 ^ the trait `Bound` is not implemented for `u32`
   |
help: this trait has no implementations, consider adding one
  --> $DIR/closure-wf.rs:1:1
   |
LL | trait Bound {}
   | ^^^^^^^^^^^
note: required by a bound in `NeedsBound`
  --> $DIR/closure-wf.rs:2:22
   |
LL | struct NeedsBound<T: Bound>(T);
   |                      ^^^^^ required by this bound in `NeedsBound`

error: aborting due to 1 previous error

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