Trailing commas lead to very confusing scalastyle errors

[steinybot]

Trailing commas lead to very confusing errors. Trailing commas were added in SIP-27 (Scala 2.12.2). I don't actually use them intentionally but it can take a very long time to find it since scalac passes but scalastyle fails without any line information and usually on an unrelated token.

For example:

[error] MySpec.scala: illegal start of simple expression: Token(RPAREN,),295,))

import org.scalatest.FlatSpec
import org.scalatest.prop.GeneratorDrivenPropertyChecks

class MySpec extends FlatSpec with GeneratorDrivenPropertyChecks {

  case class Foo(a: String, b: Int)

  Foo(
    "hello",
    123,
  )
}

[jtjeferreira]

Relevant ticket is scalastyle/scalastyle#276

[BardurArantsson]

This comment may be of interest scalastyle/scalastyle#327 (comment)