__if_exists __if_not_exists alternative

[Dmitry Sychov]

Hello,

Doing meta programming without "__if_exists"
is tricky.
The result solutions are heavy and take many
lines of source code (trait classes).

Will gcc include such a feature or alternative
in the near future?

Also, anyone interested in writing a patch?

I can sponsor the result at certain degree with possible 
cooperation with others, who is interested.

Thanks, Dmitry