Your register method shouldn't be creating the instances.

In your case, your register needn't be more than:

public function register()
{
    $this->app->bind('UserRepositoryInterface', 'UserEloquentRepository');
}

You can change the class to something like ServiceProvider and register multiple bindings. For example:

public function register()
{
    $this->app->bind('UserRepositoryInterface', 'UserEloquentRepository');
    $this->app->bind('VehicleRepositoryInterface', 'VehicleEloquentRepository');
}

Ya I know, I accidentally copied that from a service provider where I was using the register method to register additional service providers.

I understand how to bind interfaces, but when you bind these you can only auto inject into Controllers (and some other special cases within Laravel). Did you take a look at the paste? I am trying to figure out how to auto inject additional dependencies without passing them into the constructor (either concrete or via bind)

Any help would be appreciated - I've put the past code here:

<?php

interface BaseRepositoryInterface {}

abstract class BaseEloquentRepository implements BaseRepositoryInterface {

    protected $model;

    protected $repoDep;

    public function __construct(Model $model, RepoDep $repoDep)
    {
        $this->model = $model;
    }

}

interface UserRepositoryInterface extends BaseRepositoryInterface {}


class UserEloquentRepository extends BaseEloquentRepository implements UserRepositoryInterface
{
    // I feel like there is a way to bind the RepoDep above so that 
    // I don't have to pass it to the constructor / service provider below

    public function __construct(User $user)
    {
        parent::__construct($user);
    }

}


// I'm auto injecting the model using service providers
// when resolving the Repos but again I don't want to pass in the 
// repoDep above into the service provider

class UserServiceProvider extends ServiceProvider {

    public function register()
    {
        $this->app->bind('UserRepositoryInterface',function (){
                return new UserEloquentRepository(new User());
            }
        );

        // want to avoid this
         return new UserEloquentRepository(new User(), $this->app->make('RepoDep'));
    }
}


// The only way I have found is to resolve any deps directly in the constructor
// of these base classes - but it just doesn't feel right

public function __construct(Model $model) 
{
     $this->model = $model;

     $this->app = App::getFacadeRoot();

     $this->dispatcher = $this->app->make('Illuminate\Contracts\Events\Dispatcher');
}