code: protected void registerNewVar(ASTNode vas){
  		if (pbCtx.hasDefined(vas.token.text) != null)
  		{
  			GrammarToken token = pbCtx.hasDefined(vas.token.text);
  			BeetlException ex = new BeetlException(BeetlException.VAR_ALREADY_DEFINED, "已经在第" + token.line + "行定义");
  			ex.pushToken(vas.token);
  			throw ex;
  		}
  		pbCtx.addVar(vas.token.text);
  		pbCtx.setVarPosition(vas.token.text, vas);	
  	}
docs: 纪录一个新变量