using ~> and <~ enables backtracking disabled by ~!

[scabug]

// using ~> and <~ enables backtracking disabled by ~!
// it seems that scala.util.parsing.combinator.Parsers.OnceParser must implement own ~> <~ instead of inheriting them.

// testcase:

import scala.util.parsing.input.CharSequenceReader
import scala.util.parsing.combinator.RegexParsers


object SspParser extends RegexParsers {
  val ok: Parser[Any] =
    ( "<%" ~! rep(' ') ~  "\\w+".r  ~ rep(' ') ~ "%>"
    | "<%" ~! error("should not fail here, because of ~!") )

  val buggy: Parser[Any] =
    ( "<%" ~! rep(' ') ~> "\\w+".r <~ rep(' ') ~ "%>"
    | "<%" ~! error("should not fail here, because of ~!") )

  def main(args:Array[String]) {
    println( phrase(ok)   (new CharSequenceReader("<% hi %>")))  // [1.9] parsed: ((((<%~List( ))~hi)~List( ))~%>)
    println( phrase(ok)   (new CharSequenceReader("<%    %>")))  // [1.7] error: string matching regex `\w+' expected but `%' found
    println( phrase(buggy)(new CharSequenceReader("<% hi %>")))  // [1.9] parsed: hi
    println( phrase(buggy)(new CharSequenceReader("<%    %>")))  // java.lang.RuntimeException: should not fail here, because of ~!
  }
}

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Imported From: https://issues.scala-lang.org/browse/SI-6464?orig=1
Reporter: Denis Petrov (denis)
Affected Versions: 2.10.0-M6

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Denis Petrov (denis) said:
pull request scala/scala#1445

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Denis Petrov (denis) said:
hi, are you the reviewer for library pull requests, aren't you?

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@SethTisue said:
The parser combinators library is now community-maintained. Issues with it are now tracked at scala/scala-parser-combinators#61 instead of here in the Scala JIRA.

Interested community members: if you consider this issue significant, feel free to open a new issue for it on GitHub, with links in both directions.