error[E0277]: the trait bound `B: Bar` is not satisfied
  --> $DIR/issue-90400-1.rs:22:9
   |
LL |         move || bar.bar()
   |         ^^^^^^^^^^^^^^^^^ the trait `Bar` is not implemented for `B`
   |
note: required by a bound in `<MyFoo as Foo>::foo`
  --> $DIR/issue-90400-1.rs:21:15
   |
LL |     fn foo<B: Bar>(&self, bar: B) -> Self::FooFn<B> {
   |               ^^^ required by this bound in `<MyFoo as Foo>::foo`
help: consider restricting type parameter `B`
   |
LL |     type FooFn<B: Bar> = impl FnOnce();
   |                 +++++

error: aborting due to previous error

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