[System.Flags]
        internal enum Foo
        {
            Bar = 0x00,
            Foof = 0x01,
            Xyzzy = 0x02,
            Baz = 0x04
        }

        private class Fubar
        {
            internal Foo foo;
            internal HasLocation location;
        }

        private static long CountBit(Fubar[] fubars, long len)
        {
            long count = 0;
            for (long i = 0; i < len; ++i)
                if ((fubars[i].foo & Foo.Xyzzy) > 0)
                    ++count;
            return count;
        }

        private static long CountIs(Fubar[] fubars, long len)
        {
            long count = 0;
            for (long i = 0; i < len; ++i)
                if (fubars[i].location is Rectangle rect)
                    ++count;
            return count;
        }

        [Test]
        public void TestIsVsBitFlag()
        {
            var len = Base.Cent * Base.Cent * 1000 * 10;
            var fubars = new Fubar[len];
            for (int i = 0; i < len; ++i)
            {
                if ((i % 2) == 0)
                    fubars[i] = new Fubar { foo = Foo.Foof | Foo.Baz, location = Location.Zero };
                else
                    fubars[i] = new Fubar { foo = Foo.Xyzzy, location = Rectangle.CreateRectangle(0, 0, 0, 0) };

            }

            GC.Collect();

            long bitAxx = 0L;
            {
                var watch = System.Diagnostics.Stopwatch.StartNew();
                long count = CountBit(fubars, len: len);
                bitAxx = watch.ElapsedMilliseconds;
            }

            long isAxx = 0L;
            {
                var watch = System.Diagnostics.Stopwatch.StartNew();
                long count = CountIs(fubars, len: len);
                isAxx = watch.ElapsedMilliseconds;
            }

            Assert.That(isAxx, Is.LessThan(bitAxx), "Got isAxx: {0} ms vs bitAxx: {1} ms.", isAxx, bitAxx);
        }