This problem only occurs when `asEP_DISALLOW_VALUE_ASSIGN_FOR_REF_TYPE` is enabled.

engine->SetEngineProperty(asEP_DISALLOW_VALUE_ASSIGN_FOR_REF_TYPE, 1);

First of all, set as above.

void main()
{
  dictionary d2 = {{'a', dictionary = {{'aa', 1}, {'ab', 2}}}, 
                   {'b', dictionary = {{'ba', 1}, {'bb', 2}}}};
  
  auto d2a = cast<dictionary>(d2['a']);
  print("d2a.getSize:" + d2a.getSize() + "\n");
}

Next, when you execute the above, the result is as follows.

>asrun.exe script2.as
d2a.getSize:0

Thanks!, However it seems that another problem has occurred.

  dictionary d1;
  d1.set('a', dictionary = {{'aa', 1}, {'ab', 2}});

Executing the above code will result in the following.

Assertion failed: tempVariables.GetLength() == 0, file ...\sdk\angelscript\source\as_compiler.cpp, line 1165