static L<Pair> _registerDangerousWeakMap_preList;

static <A> A _registerDangerousWeakMap(A map) {
  ret _registerDangerousWeakMap(map, null);
}

static <A> A _registerDangerousWeakMap(A map, O init) {
  ifndef LeanMode
  callF(init, map);
  
  if (init instanceof S) {
    fS f = cast init;
    init = voidfunc(Map map) { callMC(f, map) };
  }
    
  if (javax() == null) {
    // We're in class init
    if (_registerDangerousWeakMap_preList == null) _registerDangerousWeakMap_preList = synchroList();
    _registerDangerousWeakMap_preList.add(pair(map, init));
    ret map;
  }
  
  call(javax(), '_registerDangerousWeakMap, map, init);
  endifndef
  ret map;
}

static void _onLoad_registerDangerousWeakMap() {
  ifndef LeanMode
  assertNotNull(javax());
  if (_registerDangerousWeakMap_preList == null) ret;
  for (Pair p : _registerDangerousWeakMap_preList)
    _registerDangerousWeakMap(p.a, p.b);
  _registerDangerousWeakMap_preList = null;
  endifndef
}

Began life as a copy of #1010619