I'm doing a fair amount of repeatedly checking if a function
compiles with __traits(compiles...), executing the function if
so, erroring out if not, like this:

   static if (__traits(compiles, generateFunc1())) {
     return generateFunc1();
   } static if (__traits(compiles, generateFunc2())) {
     return generateFunc2();
   } else static assert(false);

But it seems inefficient to have to evaluate those functions
twice, so I'd like to optimise this so if __traits(compiles...)
succeeds, the result is cached and then used when the function is
actually called. I wondered if using std.functional.memoize would
help?