// calling a method with a fixed name and
// argument type on a (possibly) changing object
// as fast as possible

static Symbol symbol_bla = toSymbol("bla");

sclass CallSiteCache_oneArg {
  Class targetClass;
  Class argType; // set to null if target method is not overloaded
  MethodHandle mh;
}

static WeakReference<CallSiteCache_oneArg> callSite1_cache;

if (o != null) {
  var cache == getWeakRef(callSite1_cache);
  Class c = o.getClass();
  Class argType = _getClass(arg);
  if (cache != null && cache! == c
    && (cache.argType == null || cache.argType == argType)) {}
  else {
    cache = findCachedMethod(x, symbol_bla, arg);
    callSite1_cache = weakRef(cache);
  }
  invoke(cache.mh, arg);
}