Scalastyle doesn't support 2.13's singleton types

[MateuszKubuszok]

In Scala 2.13 singleton types are supported. They are useful e.g. in combination with Refined Types:

@newtype final case class Email(emailString: String Refined MatchesRegex[Email.Pattern])
object Email {
  type Pattern = "(.+)@(.+)"
  ...
}

however even in 1.5 Scalastyle doesn't handle such input:

[error] /path/to/my/file.scala: Expected identifier, but got Token(STRING_LITERAL,"(.+)@(.+)",1054,"(.+)@(.+)")

Would it be possible to add such support?

[mwz]

Hey, this parsing error originates from scala-ide/scalariform, which I'm afraid hasn't been maintained for a long time (since mid 2019). While it's definitely possible to implement this (and probably quite easy too), we'd need to contribute and release those changes from a separate fork.

It's probably not worth investing much effort into this given that scalariform is essentially a dead project along with scalastyle, but if you're keen to make the changes necessary to make this work I'd be happy to review and update/release a new version of scalastyle.