public class TestContraVariant {
    main(x, y) {
    	var y2 = m(x, y);
    	var y3 = y2.snd();
		var z;
		y3 = z;
		return new Pair(x,z);
    }

    m(x, y) {
    	var x2 = main(x, y);
    	var x3 = x2.fst();
	    var z;
		x3 = z;
        return new Pair(z, y);
    }
}