void Main()
{
	var d = new Dog();
	var c1 = (Cat)d; // yes
	var c2 = d as Cat; // Cannot convert type 'Dog' to 'Cat' via a reference conversion, boxing conversion, unboxing conversion, wrapping conversion, or null type conversion

}

// Define other methods and classes here

class Cat
{
}

class Dog
{
	public implicit operator Cat(Dog d)
	{
		return new Cat();
	}
}