Type Lambda Crashes Compiler

[AugustNagro]

Compiler version

3.0.2

Minimized code

Full runnable example below, but this is the key part:

  private inline def summonElementTypeClasses[A](m: Mirror.Of[A]): IArray[Object] =
    // this doesn't work
    summonAll[Tuple.Map[m.MirroredElemTypes, [A] =>> Lazy[MyTypeClass[A]]]].toIArray
    // but this does
    // summonAll[Tuple.Map[Tuple.Map[m.MirroredElemTypes, MyTypeClass], Lazy]].toIArray

Full reproducer:

https://scastie.scala-lang.org/OI631SqsStStKTxVkwJbjg

import scala.compiletime.*
import scala.deriving.Mirror

class Lazy[A](obj: => A) {
  lazy val value: A = obj
}
object Lazy {
  given [A](using obj: => A ): Lazy[A] = new Lazy(obj) 
}

trait MyTypeClass[A] {
  def makeString(a: A): String
}
object MyTypeClass {
  
  given IntTypeClass: MyTypeClass[Int] with
    def makeString(a: Int): String = a.toString
  
  inline given derived[A](using m: Mirror.Of[A]): MyTypeClass[A] =
    inline m match
      case p: Mirror.ProductOf[A] => productConverter(p)
  
  
  private inline def summonElementTypeClasses[A](m: Mirror.Of[A]): IArray[Object] =
    // this doesn't work
    summonAll[Tuple.Map[m.MirroredElemTypes, [A] =>> Lazy[MyTypeClass[A]]]].toIArray
    // but this does
    // summonAll[Tuple.Map[Tuple.Map[m.MirroredElemTypes, MyTypeClass], Lazy]].toIArray
  
  private inline def productConverter[A](m: Mirror.ProductOf[A]): MyTypeClass[A] = {
    val elementTypeClasses = summonElementTypeClasses(m)
    new MyTypeClass[A] {
      def makeString(a: A): String = {
        val product = a.asInstanceOf[Product]
        elementTypeClasses
          .view
          .zipWithIndex
          .map((obj, i) => {
            val tc = obj.asInstanceOf[Lazy[MyTypeClass[Any]]].value
            tc.makeString(product.productElement(i))
          })
          .mkString("[", ", ", "]")
      }
    }
  }
}

case class Example(a: Int, b: Int) derives MyTypeClass

object Main {
  def main(args: Array[String]): Unit = {
    println("hello world")
    println(summon[MyTypeClass[Example]].makeString(Example(1,2)))
  }
}

Output (click arrow to expand)

scala.MatchError: ClassInfo(ThisType(TypeRef(NoPrefix,module class <empty>)), class Example, List(TypeRef(ThisType(TypeRef(NoPrefix,module class lang)),class Object), TypeRef(TermRef(TermRef(NoPrefix,object _root_),object scala),trait Product), TypeRef(ThisType(TypeRef(NoPrefix,module class io)),trait Serializable))) (of class dotty.tools.dotc.core.Types$CachedClassInfo)
	at dotty.tools.dotc.core.Types$TypeLambdaCompanion.toPInfo(Types.scala:3735)
	at dotty.tools.dotc.core.Types$TypeLambdaCompanion.toPInfo(Types.scala:3733)
	at dotty.tools.dotc.core.Types$LambdaTypeCompanion.fromParams$$anonfun$4$$anonfun$1(Types.scala:3721)
	at scala.collection.immutable.List.map(List.scala:246)
	at dotty.tools.dotc.core.Types$LambdaTypeCompanion.fromParams$$anonfun$2(Types.scala:3721)
	at dotty.tools.dotc.core.Types$HKTypeLambda.<init>(Types.scala:3850)
	at dotty.tools.dotc.core.Types$HKTypeLambda$.apply(Types.scala:3956)
	at dotty.tools.dotc.core.Types$HKTypeLambda$.apply(Types.scala:3951)
	at dotty.tools.dotc.core.Types$HKTypeLambda$.apply(Types.scala:3948)
	at dotty.tools.dotc.core.Types$LambdaTypeCompanion.fromParams(Types.scala:3722)
	at dotty.tools.dotc.core.Types$HKTypeLambda$.fromParams(Types.scala:3968)
	at dotty.tools.dotc.typer.TypeAssigner.assignType(TypeAssigner.scala:467)
	at dotty.tools.dotc.typer.TypeAssigner.assignType$(TypeAssigner.scala:19)
	at dotty.tools.dotc.typer.Typer.assignType(Typer.scala:106)
	at dotty.tools.dotc.typer.Typer.typeIndexedLambdaTypeTree(Typer.scala:1921)
	at dotty.tools.dotc.typer.Typer.typedLambdaTypeTree(Typer.scala:1926)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2720)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2756)
	at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:118)
	at dotty.tools.dotc.typer.Inliner$InlineTyper.typedUnadapted(Inliner.scala:1622)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2821)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2825)
	at dotty.tools.dotc.typer.Typer.typedArg$1(Typer.scala:1882)
	at dotty.tools.dotc.typer.Typer.$anonfun$25(Typer.scala:1886)
	at dotty.tools.dotc.core.Decorators$ListDecorator$.zipWithConserve$extension(Decorators.scala:153)
	at dotty.tools.dotc.core.Decorators$ListDecorator$.zipWithConserve$extension(Decorators.scala:154)

I would expect that the type lambda works here.

This isn't a critical bug since it's easy to replace with two Tuple.Map, but I figured it's good to record an issue.

[soronpo]

Same error on 3.1.0-RC1