NullLiteral 如何以树形式表示？
根据 ECMAScript 规范 中的 < strong>7.8.1 a NullLiteral 定义如下：
NullLiteral ::
null
我试图理解的是，当 NullLiteral 包含在其中时，它如何以树形式表示以下产生式可在 7.6.1 和 7.8 节中找到。
ReservedWord ::
Keyword
FutureReservedWord
NullLiteral
BooleanLiteral
Literal ::
NullLiteral
BooleanLiteral
NumericLiteral
StringLiteral
我对它的外观的最佳猜测是：
InputElementDiv
|
Token
|
IdentifierName
|
ReservedWord
|
Literal
|
NullLiteral
|
null
但这对我来说似乎并不正确。
注意
根据我的研究，似乎很少有编译器真正从语言语法生成 CST。我当然可以理解为什么，但这对我来说是一个学习练习，所以我想在转向更专业的解析方法（例如使用解析器生成器）之前先解决这个问题。
According to the ECMAScript specification in section 7.8.1 a NullLiteral is defined as follows:
NullLiteral ::
null
What I am trying to understand is how this is represented in tree form when a NullLiteral is included in the following productions found in sections 7.6.1 and 7.8.
ReservedWord ::
Keyword
FutureReservedWord
NullLiteral
BooleanLiteral
Literal ::
NullLiteral
BooleanLiteral
NumericLiteral
StringLiteral
My best guess as to how it would look is this:
InputElementDiv
|
Token
|
IdentifierName
|
ReservedWord
|
Literal
|
NullLiteral
|
null
This just does not seem right to me though.
Note
From my research it seems that very few compilers actually generate CSTs from the language grammar. I can of course understand why but this is a learning exercise for me so I want to get this right before I move to more professional means of parsing such as using a parser generator.
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语法未涵盖所示的树，因为它不提供从
IdentifierName到ReservedWord的派生，并且不提供派生ReservedWordcode> 到Literal之一。事实上，
ReservedWord产生式仅用于限制IdentifierName的有效值，这应该在词法级别上看到。它不会进入 CST，在 CST 中您只能看到IdentifierName。Literal 的上下文是 PrimaryExpression，因此真实 CST 的片段可能如下所示：
The tree as shown is not covered by the grammar, because that does not provide a derivation from
IdentifierNametoReservedWord, and it does not provide for derivingReservedWordtoLiteraleither.The
ReservedWordproduction in fact is used only to restrict valid values ofIdentifierName, and this should be seen on the lexical level. It does not make it into a CST, where you would see just theIdentifierName.The context of Literal is PrimaryExpression, so a fragment of a real CST could look like this: