Laravel 5 - Interface is not instantiable

Thank you everyone, but problem was in my AppRepositoryProvider. As it's binding exception, then obviously the problem was with binding :)

Correct file is:

<?php namespace App\Providers;

use Illuminate\Support\ServiceProvider;

class AppRepositoryProvider extends ServiceProvider {

    public function boot() {}

    public function register() {
        $models = array(
            'CustomModel',
            'CustomModel2',
            'CustomModel3'
        );

        foreach ($models as $model) {
            $this->app->bind("App\Contracts\\{$model}Interface", "App\Repositories\\{$model}Repository");
        }
    }
}

Note, that I'm using "App\Contracts\\{$model}Interface" (not escaping "{" symbol) and it generate correct string App\Contracts\CustomModelInterface instead of App\Contracts\{$model}Interface (with unexpected escaping).

Every time I create a new repository/contract pair I make sure I do the following:

1. check the classes used in the service provider (copy/paste the namespaces)
2. register a new binding in config/app.php
3. php artisan optimize

Many hours of useless debugging led me to this short checklist.