error[E0277]: the trait bound `B: Bar` is not satisfied
  --> $DIR/issue-90400-2.rs:25:9
   |
LL |         MyBaz(bar)
   |         ^^^^^^^^^^ the trait `Bar` is not implemented for `B`
   |
note: required for `MyBaz<B>` to implement `Baz`
  --> $DIR/issue-90400-2.rs:30:14
   |
LL | impl<B: Bar> Baz for MyBaz<B> {
   |         ---  ^^^     ^^^^^^^^
   |         |
   |         unsatisfied trait bound introduced here
note: required by a bound in an opaque type
  --> $DIR/issue-90400-2.rs:22:26
   |
LL |     type FooFn<B> = impl Baz;
   |                          ^^^
note: this definition site has more where clauses than the opaque type
  --> $DIR/issue-90400-2.rs:24:5
   |
LL |     fn foo<B: Bar>(&self, bar: B) -> Self::FooFn<B> {
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: consider restricting type parameter `B` with trait `Bar`
   |
LL |     type FooFn<B: Bar> = impl Baz;
   |                 +++++

error: aborting due to 1 previous error

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