Enum.HasFlag in .NET 2 / Unity 5

UtilsEnum.cs

public static class UtilsEnum
{
    public static bool HasFlag(this Enum mask, Enum flags) // Same behavior than Enum.HasFlag is .NET 4
    {
#if DEBUG
        if (mask.GetType() != flags.GetType())
            throw new System.ArgumentException(
                string.Format("The argument type, '{0}', is not the same as the enum type '{1}'.",
                flags.GetType(), mask.GetType()));
#endif
        return ((int)(IConvertible)mask & (int)(IConvertible)flags) == (int)(IConvertible)flags;
    }
}


// UNIT TESTS
internal class TestUtilsEnum
{
    enum Flags
    {
        Null = 0,
        Motor = 1 << 1,
        Wheels = 1 << 2,
        Trunk = 1 << 3,

        Bike = Wheels,
        Motocross = Wheels | Motor,
        Car = Motor | Wheels | Trunk,
    }

    enum Flags2
    {
        Null = 0,
        Motor = 1 << 1,
    }

    [Test]
    public void EnumHasFlag()
    {
        Assert.IsTrue(Flags.Null.HasFlag(Flags.Null));
        Assert.IsFalse(Flags.Null.HasFlag(Flags.Motor));
        Assert.IsTrue(Flags.Car.HasFlag(Flags.Null));
        Assert.IsTrue(Flags.Car.HasFlag(Flags.Motor));
        Assert.IsTrue(Flags.Car.HasFlag(Flags.Trunk));
        Assert.IsTrue(Flags.Car.HasFlag(Flags.Motor | Flags.Wheels));
        Assert.IsTrue(Flags.Bike.HasFlag(Flags.Wheels));
        Assert.IsFalse(Flags.Bike.HasFlag(Flags.Motor));
        Assert.IsFalse(Flags.Bike.HasFlag(Flags.Wheels | Flags.Motor));
        Assert.IsFalse(Flags.Bike.HasFlag(Flags.Motor | Flags.Trunk));
        Assert.IsFalse(Flags.Wheels.HasFlag(Flags.Car));
#if DEBUG
        Assert.Throws<ArgumentException>(() => Flags.Car.HasFlag(Flags2.Motor));
#endif
    }
}