Trait objects need to have all associated types specified. Erroneous code
example:

```compile_fail,E0191
trait Trait {
    type Bar;
}

type Foo = Trait; // error: the value of the associated type `Bar` (from
                  //        the trait `Trait`) must be specified
```

Please verify you specified all associated types of the trait and that you
used the right trait. Example:

```
trait Trait {
    type Bar;
}

type Foo = Trait<Bar=i32>; // ok!
```