// returns IF0 (already evaluated) or null when method not found

// varargs assignment fixer for a single string array argument
static IF0 call_optional(O o, S method, S[] arg) {
  ret call_optional(o, method, new O[] {arg});
}

static IF0 call_optional(O o, S method, O... args) {
  if (!canCallWithVarargs(o, method, args)) null;
  ret if0_const(call(o, method, args));
}