带有 @init block 的 ANTLR4 词法分析器规则

Question

我在我的 ANTLR v3 语法文件中定义了这个词法分析器规则 - 它用双引号对文本进行数学运算。
我需要将其转换为 ANTLR v4。 ANTLR 编译器抛出错误“语法错误:匹配词法规则时不匹配的输入‘@’期望 COLON”(在 @init 行中)。词法分析器规则可以包含 @init 块吗？这应该怎么改写？

DOUBLE_QUOTED_CHARACTERS
@init 
{
   int doubleQuoteMark = input.mark(); 
   int semiColonPos = -1;
}
: ('"' WS* '"') => '"' WS* '"' { $channel = HIDDEN; }
{
    RecognitionException re = new RecognitionException("Illegal empty quotes\"\"!", input);
    reportError(re);
}
| '"' (options {greedy=false;}: ~('"'))+ 
  ('"'|';' { semiColonPos = input.index(); } ('\u0020'|'\t')* ('\n'|'\r'))
{ 
    if (semiColonPos >= 0)
    {
        input.rewind(doubleQuoteMark);

        RecognitionException re = new RecognitionException("Missing closing double quote!", input);
        reportError(re);
        input.consume();            
    }
    else
    {
        setText(getText().substring(1, getText().length()-1));
    }
}
; 

样本数据:

""-> 抛出错误“非法的空引号!”;

"asd -> 抛出错误"缺少结束双引号!"

“text” -> 返回文本(有效输入，“...”的内容)

Answer 1

我认为这是做到这一点的正确方法。

DOUBLE_QUOTED_CHARACTERS
:
{
   int doubleQuoteMark = input.mark();
   int semiColonPos = -1;
}
(
    ('"' WS* '"') => '"' WS* '"' { $channel = HIDDEN; }
    {
        RecognitionException re = new RecognitionException("Illegal empty quotes\"\"!", input);
        reportError(re);
    }
    | '"' (options {greedy=false;}: ~('"'))+
      ('"'|';' { semiColonPos = input.index(); } ('\u0020'|'\t')* ('\n'|'\r'))
    {
        if (semiColonPos >= 0)
        {
            input.rewind(doubleQuoteMark);

            RecognitionException re = new RecognitionException("Missing closing double quote!", input);
            reportError(re);
            input.consume();
        }
        else
        {
            setText(getText().substring(1, getText().length()-1));
        }
    }
)
;

上面还有一些其他错误，例如 WS .. => ... 但我不会在此答案中更正它们。只是为了让事情简单。我从 here 得到提示

只是为了防止该链接在一段时间后移动或变得无效，按原样引用文本:

从 4.2 开始，词法分析器 Action 可以出现在任何地方，而不仅仅是最外层选项的末尾。词法分析器根据操作在规则中的位置在适当的输入位置执行操作。要为具有多个选项的角色执行单个操作，您可以将 alt 括在括号中，然后将操作放在后面:

END : ('endif'|'end') {System.out.println("found an end");} ;

The action conforms to the syntax of the target language. ANTLR copies the action’s contents into the generated code verbatim; there is no translation of expressions like $x.y as there is in parser actions.

Only actions within the outermost token rule are executed. In other words, if STRING calls ESC_CHAR and ESC_CHAR has an action, that action is not executed when the lexer starts matching in STRING.