Is there a cleaner way of doing this?

[Shachar Shemesh via Digitalmars-d]

It is often desired to have a struct with an extra parameter. The common 
way to do this is like so:

struct S(T) {
	T param;

	void initialize(T param) {
		this.param = param;
		// Other stuff
	}
}

The problem is what happens when the param is optional. The common way 
to do this is to set T to void. This results in the following code:

struct S(T) {
	enum HasParam = !is(T == void);
	static if( HasParam ) {
		T param;
	}

	static if( HasParam ) {
		void initialize(T param) {
			this.param = param;
			// Other stuff
		}
	} else {
		void initialize() {
			// Same other stuff as above!
		}
	}
}

This is both tedious and error prone. Is there a cleaner way of doing this?

Just as an unrealistic fantasy, if the following code was legal, the 
problem would be resolved on its own:
void func(void p) {
	void param;

	param = p;

	return param;
}


Of course, that code has its own set of problems, and I'm not really 
suggesting that change.

Shachar