Scala Could not find implicit value supplied by mixin

Question

Using Scala version 2.11.12.

I can't seem to make the implicit config supplied by the mixin Foundation trait visible to the Path class' constructor.

case class Config() {
  val content = "hello"
}

trait Foundation {
  implicit val config: Config = Config()
}

trait PathBase {
  def somePath: String = "/user/xxx"
}

class Path(implicit val config: Config) extends PathBase {
  def someOtherPath: String = "/user/yyy"
}

trait NavigatorBase {
  protected implicit val hdfs: PathBase
}

trait Navigator extends NavigatorBase with Foundation {
//  private implicit val config1: Config = config
  protected implicit val hdfs = new Path
}

The above code raises the following error:

:39: error: could not find implicit value for parameter config: Config protected implicit val hdfs = new Path

However, if I define a new implicit val using the config supplied by Foundation before calling Path's constructor (see the commented line in the code), the code works. If I write trait Navigator extends Foundation without mixing in NavigatorBase, the code also works.

Is there a way to make the implicit config visible to Path's constructor without having to define a new implicit variable or remove the extension of NavigatorBase?

It compiles for me: scastie.scala-lang.org/BalmungSan/yRtIa6cMS2GktJzTi1q0Bg - Are you sure the error is real? maybe is just IntellIJ. Have you checked using your build tool? - If it is real, then are you sure you have all you need to reproduce it in that example? Maybe specify the Scala version. — Luis Miguel Mejía Suárez
Amended the question to include Scala version, thanks for the reminder! I encountered the error when using sbt and reproduced it in the spark-shell. — largecats
I tried the 2.11.12 scala version in Scastie and was able to reproduce the error. Seems to be a version issue. Thanks a lot for sharing this! — largecats

largecats largecats · Accepted Answer · 2021-02-16T17:14:32

Solution: As pointed out by @Luis Miguel Mejía Suárez in the comment, use the latest version of Scala.

Scala 2.11.12 raises the error: https://scastie.scala-lang.org/yZU850eUQvKSt6LJ0GIeVA

Scala 2.13.4 works fine: https://scastie.scala-lang.org/8FYzJdimSOanOLow25rN3g

Scala Could not find implicit value supplied by mixin

1 Answers