Function default parameters

[Tim M]

I want to use the return value of another member function as the default  
for a parameter. I could just overload it but I would prefer to do it like:

module test;

class Thing
{
	char[] getString(uint len = this.strLen())
	{
		char[] a = new char[len];
		return a;
	}
	uint strLen()
	{
		return 6;
	}
}

int main()
{
	Thing t = new Thing;
	char[] abc = t.getString;
	return 0;
}

test.d(6): Error: 'this' is only defined in non-static member functions,  
not Thing