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# Error code E0191

An associated type wasn’t specified for a trait object.

Erroneous code example:

    #![allow(unused)]
    fn main() {
    trait Trait {
        type Bar;
    }

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

Trait objects need to have all associated types specified. Please verify that all associated types of the trait were specified and the correct trait was used. Example:

    #![allow(unused)]
    fn main() {
    trait Trait {
        type Bar;
    }

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