Question about garbage collection specification

[deadalnix via Digitalmars-d]

On Saturday, 13 June 2015 at 11:32:20 UTC, rsw0x wrote:
> http://dlang.org/garbage.html
>
> Do not take advantage of alignment of pointers to store bit 
> flags in the low order bits:
> p = cast(void*)(cast(int)p | 1);  // error: undefined behavior
>
> if this restriction is actually imposed - why does 
> std.bitmanip.tagged{ClassRef,Pointer} even exist?

That seems like an arbitrary limitation. This will create an 
interior pointer, which the GC needs to recognize anyway.

The doc need to be updated.