i16018-orig.scala

// The original akka-minimized reproduction from #16018 (verbatim, modulo
// `_` → `?` syntax migration). Posted by @He-Pin on 2022-09-17:
//
//   https://github.com/scala/scala3/issues/16018#issuecomment-1250066489
//
// Pre-fix this rejected with
//
//   Found:    (other : ?1.CAP)
//   Required: Main.Source[T, M] & ?1.CAP
//   where:    ?1 is an unknown value of type
//             scala.runtime.TypeBox[Nothing, Main.Graph[Main.SourceShape[T], ? <: M]]
//
// The directional minimizations of this same shape live in
// tests/pos/i16018b.scala (the matrix); this file pins the exact
// reproduction so that the original ticket cannot regress in either
// direction.

import scala.collection.immutable

object Main:

  class Source[+Out, +Mat] extends Graph[SourceShape[Out], Mat]

  class Shape
  class SourceShape[+T] extends Shape
  class Graph[+S <: Shape, +M]

  def combine[T, U, M](sources: java.util.List[? <: Graph[SourceShape[T], ? <: M]])
      : Source[U, java.util.List[M]] =
    val seq: immutable.Seq[Graph[SourceShape[T], M]] =
      if sources != null then
        immutableSeq(sources).collect {
          case source: Source[T, M] @unchecked => source
          case other                           => other
        }
      else immutable.Seq()
    ???

  def immutableSeq[T](iterable: java.lang.Iterable[T]): immutable.Seq[T] = ???