In the following example, ++x calls opUnary while x++ is performed on x directly:

struct X
{
	int x;
	alias x this;
	
	typeof(this) opUnary (string operator) ()
	{
		writeln ("operator called");
		return this;
	}
}
unittest
{	
	X x;
	++x; //operator called
	auto y = x++; //BUG! (alias this used. returns int)
}