Why must the associated type be specified in a collection of references to types implementing a trait?

Question

Here is an offending example:

// Some traits
trait Behaviour {
    type Sub: SubBehaviour;
}
trait SubBehaviour {}

// Some implementations of these traits
s         


        

Answer 1

You need to specify the associated type of the trait (i.e. Behavior).

When adding the associated type at all places, it compiles:

struct Example<'a, S: SubBehaviour + 'a> {
    behaviours: Vec<&'a Behaviour>,
}

impl<'a, S: SubBehaviour> Example<'a, S> {
    fn add_behaviour>(&mut self, b: &'a T) {
        self.behaviours.push(b);
    }
}

See this in action on the Playground