Inline implicit methods with lambdas cause AssertionError across files

[guyde2011]

If you use in implicit inline method for instance generation, and you return an anonymous instance, which has a lambda in one of its methods implementation, then an assertion error is thrown.

Example:

Exec.scala

object exec{
  trait Runner[T]{
    def run(t: T): Unit
  }
  object Runner{
    def run[T: Runner](t: T): Unit = implicitly[Runner[T]].run(t) 
    implicit inline def runImplicitly[T]: Runner[T] = new {
      def run(t: T) = List(()).map(x => x).head // <<<
    }
  }  
}

Main.scala

object Main{
  def main(args: Array[String]): Unit = {
    import exec._
    Runner.run(Some(5))
  }
}

And it crashes with:

[error] Total time: 1 s, completed 15:17:31 25/01/2019
java.lang.AssertionError: assertion failed: private method $anonfun in object Main in C:\vscode\dotty\crash\main\src\main\scala\Main.scala accessed from method run in C:\vscode\dotty\crash\main\src\main\scala\Exec.scala while compiling C:\vscode\dotty\crash\main\src\main\scala\Exec.scala, C:\vscode\dotty\crash\main\src\main\scala\Main.scala

If we were to change

  object Runner{
    def run[T: Runner](t: T): Unit = implicitly[Runner[T]].run(t) 
    implicit inline def runImplicitly[T]: Runner[T] = new {
      def run(t: T) = List(()).map(x => x).head // <<<
    }
  }  

to

  object Runner{
    val mapping = (x: Unit) => x
    def run[T: Runner](t: T): Unit = implicitly[Runner[T]].run(t) 
    implicit inline def runImplicitly[T]: Runner[T] = new {
      def run(t: T) = List(()).map(mapping).head // <<<
    }
  }  

It works.

It works as well if we move the two sources to the same file.