Exception while typechecking and compiling pattern matching with @

[vuspenskiy]

object Fail {
  case class So[+T]()

  def main(args: Array[String]): Unit = {
    So[Int]() match {
      case p@So[_] => Console.println("Yep")
      case _       => Console.println("Nope")
    }
  }
}

Compiler says,

exception occurred while typechecking /path/to/Src.scala
exception occurred while compiling /path/to/Src.scala

Works well if underscore in pattern matching is replaced with a specific type.

[liufengyun]

@vuspenskiy Thanks for reporting, we'll investigate the crash and why there's no error message about syntax.

Regarding the syntax, we need to either use p : So[_] or p @ So(_) in the code example.

Following code has the same stack trace:

object Fail {
  def f(m: Option[Int]): Unit = {
     m match {
      case x @ Some[_] =>
      case _       =>
    }
  }
}

[jvican]

I think I will take care of this, am I stepping on someone's toes?

[jvican]

I propose to follow scalac's behaviour here:

 found   : Some[_]
 required: Some[Int]
                  case p@Some[_] => println(

[liufengyun]

Thanks @jvican for help, please go ahead 👍

[jvican]

Sorry @liufengyun, I won't be able to do this any time soon. I unassign me just in case someone wants to give it a try.

[liufengyun]

No worry @jvican , I'll take care of it.