error[E0277]: the trait bound `B: Bar` is not satisfied
  --> $DIR/wf-check-fn-def.rs:11:5
   |
LL |     mop // NOTE: no function pointer, but function zst item
   |     ^^^ the trait `Bar` is not implemented for `B`
   |
note: required by a bound in `mop`
  --> $DIR/wf-check-fn-def.rs:10:15
   |
LL |     fn mop<B: Bar>(bar: B) { bar.bar() }
   |               ^^^ required by this bound in `mop`
help: consider restricting type parameter `B`
   |
LL | type FooFn<B: Bar> = impl FnOnce(B);
   |             +++++

error: aborting due to previous error

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