// return Int.MAX_VALUE if not applicable
// Lower score is better
static int methodApplicabilityScore(Method m, O[] args) {
   Class<?>[] types = m.getParameterTypes();
   if (types.length != args.length) ret Int.MAX_VALUE;
   int score = 0;
   for (int i = 0; i < types.length; i++) {
     O a = args[i];
     Class c = types[i];
     if (a == null) ++score;
     else if (c == a.getClass()) {} // perfect match
     else if (isInstanceX(c, a)) ++score;
     else ret Int.MAX_VALUE;
  }
  ret score;
}