如何在这里实现JavaScript / ECMAScript“no LineTerminator” JavaCC中的规则？ [英] How to implement JavaScript/ECMAScript "no LineTerminator here" rule in JavaCC?

问题描述

我继续处理我的 ECMAScript 5.1 的JavaCC语法。它实际上相当顺利，我想我现在已经涵盖了大部分表达式。​​

I continue working on my JavaCC grammar for ECMAScript 5.1. It actually goes quite well, I think I've covered most of the expressions now.

我现在有两个问题，它们都与自动分号插入有关（ §7.9.1）。这是其中之一。

I have now two questions, both of them are related to the automatic semicolon insertion (§7.9.1). This is one of them.

规范定义了以下产品：

PostfixExpression :
    LeftHandSideExpression
    LeftHandSideExpression [no LineTerminator here] ++
    LeftHandSideExpression [no LineTerminator here] --

如何在这里实施可靠的禁止LineTerminator检查？

记录我的 LINE_TERMINATOR 目前是这样的：

For the record my LINE_TERMINATOR is at the moment something like:

SPECIAL_TOKEN :
{
    <LINE_TERMINATOR: <LF> | <CR> | <LS> | <PS> >
|   < #LF: "\n" > /* Line Feed */
|   < #CR: "\r" > /* Carriage Return */
|   < #LS: "\u2028" > /* Line separator */
|   < #PS: "\u2029" > /* Paragraph separator */
}

我读过词汇状态，但我不确定这是不是是一个正确的方向。我已经检查了一些我找到的其他JavaScript语法，但没有找到任何类似的规则。 （当我试图从这些语法中取代某些东西时，我实际上觉得自己是总货物祸害。）

I have read about lexical states, but I am not sure if this is a right direction. I've checked a few other JavaScript grammars I have found, but did not find any similar rules there. (I actually feel myself a total cargo culter when I try to overtake something from these grammars.)

我很感激指针，提示或只是正确搜索方向的关键字。

I'd be grateful for a pointer, a hint or just a keyword for the right search direction.

推荐答案

我认为对于限制性制作你可以这样做

I think for the "restricted productions" you can do this

void PostfixExpression() : 
{} {
     LeftHandSideExpression() 
     (
         LOOKAHEAD( "++", {getToken(0).beginLine == getToken(1).beginLine})
         "++"
     |
         LOOKAHEAD( "--", {getToken(0).beginLine == getToken(1).beginLine})
         "--"
     |
         {}
     )
}

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