Sounds like this previous internals thread: Cfg, keyword for "if multiple/more than one" , in which a stable solution to the "error at compile-time if not exactly one of these features is enabled" problem is provided.
Sounds like this previous internals thread: Cfg, keyword for "if multiple/more than one" , in which a stable solution to the "error at compile-time if not exactly one of these features is enabled" problem is provided.