error[E0191]: the value of the associated type `Bar` in `Trait` must be specified
  --> $DIR/E0191.rs:5:16
   |
LL |     type Bar;
   |     -------- `Bar` defined here
...
LL | type Foo = dyn Trait;
   |                ^^^^^ help: specify the associated type: `Trait<Bar = Type>`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0191`.