Migration:method references not found

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;


class CreatePhoneNumbersTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('phone_numbers', function (Blueprint $table) {
            $table->increments('id');
            $table->unsignedInteger('contact_id');
            $table->foreign('user_id')->references('id')->on('users');
            $table->string('number');
            $table->timestamps();
        });

I what to connect the table, but phpstorm is showing me that references metod not found in Illuminate\Support\Flunet. i have no idea why i don't have this method, and i don't know what means unsignedInteger?

via Chebli Mohamed