Crash for generation of higher-kinded mirror

[odersky]

Minimized code

This is a version of the test tests/run/poly-kinded-derives.scala where all type parameters are made explicit. The critical change is in the the line marked // <<<<

import scala.deriving._

object Test extends App {
  {
    trait Show[T]
    object Show {
      given Show[Int] {}
      given [T](using st: Show[T]) as Show[Tuple1[T]]
      given t2[T, U](using st: Show[T], su: Show[U]) as Show[(T, U)]
      given t3 [T, U, V](using st: Show[T], su: Show[U], sv: Show[V]) as Show[(T, U, V)]

      def derived[T](using m: Mirror.Of[T], r: Show[m.MirroredElemTypes]): Show[T] = new Show[T] {}
    }

    case class Mono(i: Int) derives Show
    case class Poly[A](a: A) derives Show
    //case class Poly11[F[_]](fi: F[Int]) derives Show
    case class Poly2[A, B](a: A, b: B) derives Show
    case class Poly3[A, B, C](a: A, b: B, c: C) derives Show
  }

  {
    trait Functor[F[_]]
    object Functor {
      given [C] as Functor[[T] =>> C] {}
      given Functor[[T] =>> Tuple1[T]] {}
      given t2 [T] as Functor[[U] =>> (T, U)] {}
      given t3 [T, U] as Functor[[V] =>> (T, U, V)] {}

      def derived[F[_]](using m: Mirror { type MirroredType[X] = F[X] ; type MirroredElemTypes[_] }, r: Functor[m.MirroredElemTypes]): Functor[F] = new Functor[F] {}
    }

    case class Mono(i: Int) derives Functor
    case class Poly[A](a: A) derives Functor
    //case class Poly11[F[_]](fi: F[Int]) derives Functor
    case class Poly2[A, B](a: A, b: B) derives Functor
    case class Poly3[A, B, C](a: A, b: B, c: C) derives Functor
  }

  {
    trait FunctorK[F[_[_]]]
    object FunctorK {
      given [C] as FunctorK[[F[_]] =>> C] {}
      given [T] as FunctorK[[F[_]] =>> Tuple1[F[T]]]

      def derived[F[_[_]]](using m: Mirror { type MirroredType[X[_]] = F[X] ; type MirroredElemTypes[_[_]] }, r: FunctorK[m.MirroredElemTypes]): FunctorK[F] = new FunctorK[F] {} // <<<<
    }

    case class Mono(i: Int) derives FunctorK
    //case class Poly[A](a: A) derives FunctorK
    case class Poly11[F[_]](fi: F[Int]) derives FunctorK
    //case class Poly2[A, B](a: A, b: B) derives FunctorK
    //case class Poly3[A, B, C](a: A, b: B, c: C) derives FunctorK
  }

  {
    trait Bifunctor[F[_, _]]
    object Bifunctor {
      given [C] as Bifunctor[[T, U] =>> C] {}
      given Bifunctor[[T, U] =>> Tuple1[U]] {}
      given t2 as Bifunctor[[T, U] =>> (T, U)] {}
      given t3 [T] as Bifunctor[[U, V] =>> (T, U, V)] {}

      def derived[F[_, _]](using m: Mirror { type MirroredType[X, Y] = F[X, Y] ; type MirroredElemTypes[_, _] }, r: Bifunctor[m.MirroredElemTypes]): Bifunctor[F] = ???
    }

    case class Mono(i: Int) derives Bifunctor
    case class Poly[A](a: A) derives Bifunctor
    //case class Poly11[F[_]](fi: F[Int]) derives Bifunctor
    case class Poly2[A, B](a: A, b: B) derives Bifunctor
    case class Poly3[A, B, C](a: A, b: B, c: C) derives Bifunctor
  }
}

Output

We get a crash in productMirror:

exception occurred while typechecking ../run/poly-kinded-derives.scala
exception occurred while compiling ../run/poly-kinded-derives.scala
java.lang.AssertionError: assertion failed: invalid prefix HKTypeLambda(List(X), List(TypeBounds(TypeRef(ThisType(TypeRef(NoPrefix,module class scala)),class Nothing),TypeRef(ThisType(TypeRef(NoPrefix,module class scala)),class Any))), AppliedType(TypeVar(TypeParamRef(F)),List(TypeParamRef(X)))) while compiling ../run/poly-kinded-derives.scala
Exception in thread "main" java.lang.AssertionError: assertion failed: invalid prefix HKTypeLambda(List(X), List(TypeBounds(TypeRef(ThisType(TypeRef(NoPrefix,module class scala)),class Nothing),TypeRef(ThisType(TypeRef(NoPrefix,module class scala)),class Any))), AppliedType(TypeVar(TypeParamRef(F)),List(TypeParamRef(X))))
	at dotty.DottyPredef$.assertFail(DottyPredef.scala:17)
	at dotty.tools.dotc.core.Types$NamedType.<init>(Types.scala:1870)
	at dotty.tools.dotc.core.Types$TypeRef.<init>(Types.scala:2426)
	at dotty.tools.dotc.core.Types$CachedTypeRef.<init>(Types.scala:2482)
	at dotty.tools.dotc.core.Uniques$NamedTypeUniques.newType$1(Uniques.scala:64)
	at dotty.tools.dotc.core.Uniques$NamedTypeUniques.enterIfNew(Uniques.scala:68)
	at dotty.tools.dotc.core.Types$TypeRef$.apply(Types.scala:2538)
	at dotty.tools.dotc.core.Types$NamedType$.apply(Types.scala:2514)
	at dotty.tools.dotc.core.Types$NamedType.withPrefix(Types.scala:2361)
	at dotty.tools.dotc.core.Types$NamedType.derivedSelect(Types.scala:2294)
	at dotty.tools.dotc.core.Types$TypeMap.derivedSelect(Types.scala:4873)
	at dotty.tools.dotc.core.Types$ApproximatingTypeMap.derivedSelect(Types.scala:5165)
	at dotty.tools.dotc.core.TypeOps$AsSeenFromMap.op$1(TypeOps.scala:102)
	at dotty.tools.dotc.core.TypeOps$AsSeenFromMap.apply(TypeOps.scala:110)
	at dotty.tools.dotc.core.TypeOps$.asSeenFrom(TypeOps.scala:55)
	at dotty.tools.dotc.core.Types$Type.asSeenFrom(Types.scala:901)
	at dotty.tools.dotc.core.Types$Type.memberInfo(Types.scala:893)
	at dotty.tools.dotc.typer.Synthesizer.$anonfun$3(Synthesizer.scala:282)
	at scala.collection.immutable.List.map(List.scala:223)
	at dotty.tools.dotc.typer.Synthesizer.productMirror(Synthesizer.scala:282)

Expectation

Should compile.