WTF abstract is?

[Zhouxuan]

On Friday, 4 October 2013 at 06:22:57 UTC, Ali Çehreli wrote:
> On 10/03/2013 11:10 PM, deadalnix wrote:
>
> > On Friday, 4 October 2013 at 05:07:53 UTC, Zhouxuan wrote:
> >> ////////////////////////////////////////////////////////////
> >> //case 1
> >>
> >> class A
> >> {
> >>     abstract void foo();
> >> }
> >>
> >> class B : A
> >> {
> >>     static if( __traits(isAbstractClass, typeof(this) ))
> >
> > this is invalid here. Not sure what you try to achieve via
> this static if.
>
> Well, obviously that is the reason for the bug. :) I think 
> Zhouxuan thinks that it is an 'abstract' bug but actually it is 
> some sort of __traits caching issue.
>
> It would indeed be weird for isAbstractClass to delay its value 
> until the whole class definition is seen.
>
> Instead, what seems to happen is that isAbstractClass caches 
> the first value that it determines and perhaps at least for 
> consistency uses that value. Moving isAbstractClass after the 
> definition of B.foo removes the issue in this case:

Indeed I found the issue from use of isAbstractClass, but after 
some
tests I'm confused by these abstract use cases.