斯卡拉(Scala):如何在字面上避免反引号? [英] Scala: How to escape a backtick in a literal?

问题描述

Scala中的文字允许定义此 answer 描述的标识符.有没有办法在字面量内转义反引号`?做类似的事情:

Literals in Scala allow to define identifier as this answer describes. Is there a way though to escape a backtick ` within a literal? To do something like:

 val `hello `world` = "hello world"

更新:
一种用例是使用 refined 库针对与包含以下内容的正则表达式匹配的某些精炼类型反引号，例如:

Update:
One of the use case for this is to use the refined library for some refined types that matches a regex containing a backtick, for instance:

  import eu.timepit.refined._
  import eu.timepit.refined.api.Refined

  type MatchesRegexWithBacktick = String Refined MatchesRegex[W.`(a|`)`.T]

推荐答案

使用Scala编译器不能按原样完成，但是也许可以通过更改编译器插件来实现标识符的解析方式(也许如果反勾号的功能被某种晦涩的unicode字符替换了).

It can't be done with the Scala compiler as-is, but maybe it would be possible with a compiler plugin that changed the way identifiers were parsed (perhaps if the back-tick's function was somehow replaced with some obscure unicode character).

在 Scala SLS 1.1 ，其中包含标识符的词汇语法:

In the Scala SLS 1.1, there is the lexical syntax for identifiers:

op       ::=  opchar {opchar}
varid    ::=  lower idrest
boundvarid ::=  varid
             | ‘`’ varid ‘`’
plainid  ::=  upper idrest
           |  varid
           |  op
id       ::=  plainid
           |  ‘`’ { charNoBackQuoteOrNewline | UnicodeEscape | charEscapeSeq } ‘`’
idrest   ::=  {letter | digit} [‘_’ op]

问题是，唯一允许除字母，数字或_之外的任何字符的规则是要求标识符用反引号引起来的规则:

The problem is, the only rule that allows any character other than letters, digits, or _ is the one that requires the identifier be quoted with back-ticks:

‘`’ { charNoBackQuoteOrNewline | UnicodeEscape | charEscapeSeq } ‘`’

但是，它明确不允许使用charNoBackQuoteOrNewline来回引号，并且如果您认为可以使用UnicodeEscape来解决它，那么也将不起作用:

However, it explicitly doesn't allow back-ticks with charNoBackQuoteOrNewline, and in case you think you can work around it with UnicodeEscape, that doesn't work either:

scala> val `hello \u0060world` = "hello world"
<console>:1: error: unclosed quoted identifier
val `hello \u0060world` = "hello world"
                      ^

这篇关于斯卡拉(Scala):如何在字面上避免反引号?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！