Is this a bug when creating proxies in classes?

[Martin Nowak via Digitalmars-d-learn]

On Monday, 25 August 2014 at 18:10:33 UTC, Gary Willoughby wrote:
> 	class Foo
> 	{
> 		private int foo;
>
> 		mixin Proxy!(foo);
>
> 		this(int x)
> 		{
> 			this.foo = x;
> 		}
> 	}

Apparently Proxy doesn't work correctly inside classes.
Is wrapping something inside a class particularly useful?
Please comment on https://issues.dlang.org/show_bug.cgi?id=13623.