MyLevel

mixin generateStyle!(MyLevel
            , MyLevel.Debug,   "Debug: %1$s",   "[%2$s] Debug: %1$s"
            , MyLevel.Error,   "Fatal: %1$s",   "[%2$s] Fatal: %1$s"
            );

import std.datetime;

string myTimeFormatting(DistType t, SysTime time)
{
    final switch(t)
    {
        case(DistType.Console): return time.toSimpleString();
        case(DistType.File): return time.toISOExtString();
    }
}

mixin generateStyle!(MyLevel, myTimeFormatting
            , MyLevel.Debug,   "Debug: %1$s",   "[%2$s] Debug: %1$s"
            , MyLevel.Error,   "Fatal: %1$s",   "[%2$s] Fatal: %1$s"
            );