@Override
  public DfaInstructionState[] accept(@NotNull DataFlowInterpreter interpreter, @NotNull DfaMemoryState stateBefore) {
    final DfaValue a = stateBefore.pop();
    final DfaValue b = stateBefore.pop();
    stateBefore.push(a);
    stateBefore.push(b);
    return nextStates(interpreter, stateBefore);
  }
@Override
  public DfaInstructionState[] accept(@NotNull DataFlowInterpreter interpreter, @NotNull DfaMemoryState stateBefore)