@Override
  public @Nullable PsiParameter getParameter(int index) {
    if (index < 0) {
      throw new IllegalArgumentException("index is negative: " + index);
    }
    int count = 0;
    for (StubElement<?> child : getStub().getChildrenStubs()) {
      if (child.getStubType() == JavaStubElementTypes.PARAMETER) {
        if (count == index) return (PsiParameter)child.getPsi();
        count++;
      }
    }
    return null;
  }
@Override
  public @Nullable PsiParameter getParameter(int index)