"Value class instance" pattern?

[Dicebot]

On Sunday, 14 July 2013 at 15:17:43 UTC, bearophile wrote:
> test.d(4): Error: slice x[] is not mutable

This is almost 100% a bug. I have played a bit with this snippet 
and seems like void initialization breaks usual rule that you can 
cook const/immutable field in constructor (which is kind of 
guaranteed by TDPL). Simple test case:

class A
{
	immutable int x; // works
	// immutable int x = void; // works not

	this()
	{
		x = 42;
	}
}