Appender and CTFE

[Kevin Bealer]

== Quote from Andrei Alexandrescu (SeeWebsiteForEmail at erdani.org)'s article
> I see nothing wrong with the occasional forking conditioned by __ctfe.
> Even today, code may fork an optimized but nonportable implementation of
> some algorithm. The main requirement is that such forks are rare enough
> to not cause undue maintenance burden.
>
> Andrei

Regarding maintenance burden, it should be easy to test the correctness of
such code:

in a unit test:

  enum a = f(...);
  assert(a == f(...));

Kevin