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regression: assertion error in TypeRef#transform #8170

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scabug opened this issue Jan 22, 2014 · 3 comments
Closed

regression: assertion error in TypeRef#transform #8170

scabug opened this issue Jan 22, 2014 · 3 comments
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@retronym
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2.11.0-RC1

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@scabug
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scabug commented Jan 22, 2014 

object ScalaZeee {
  trait HFold[M[_], U] {
    type Apply[E, A <: U] <: U
  }
  trait GenericCons[M[_], H, +T <: GenericList[M]] extends GenericList[M] {
    val tail: T
    override type Folded[N[X] >: M[X], U, F <: HFold[N, U]] = F#Apply[H, tail.Folded[N, U, F]]
  }
  val KNil: GenericList[Nothing] = ???
  sealed trait GenericList[+M[_]] {
     type Folded[N[X] >: M[X], U, F <: HFold[N, U]] <: U
  }
}

object TypelevelUsage {
  import ScalaZeee._
  type T = GenericCons[Some, String, KNil.type]
  val klist1: T = ???
  type T2 = klist1.Folded[Option, Int, HFold[Option, Int]]
  val count2: T2 = ???
  
  count2.ensuring(x => x) // trigger an implicit search
}

error: java.lang.AssertionError: assertion failed: (List(type N, type U, type F),List(type N, type U, type F))
	at scala.reflect.internal.Types$ArgsTypeRef.transform(Types.scala:1995)
	at scala.reflect.internal.Types$TypeRef.baseTypeSeqImpl(Types.scala:2309)
	at scala.reflect.internal.Types$class.defineBaseTypeSeqOfTypeRef(Types.scala:2452)

Regressed in #8046
@scabug
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scabug commented Jan 22, 2014

Imported From: https://issues.scala-lang.org/browse/SI-8170?orig=1
Reporter: @retronym
Affected Versions: 2.11.0-M8
See #8046

@scabug
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scabug commented Jan 22, 2014

@retronym said (edited on Jan 22, 2014 1:52:46 PM UTC):
After a little whittling:

object O {
  trait X
  trait B extends A {
    override type T[F <: X] = F
  }
  trait A {
    type T[F <: X]
  }
}

object Test {
  import O._
  val a: B = ???
  val b: a.T[X] = ???
  b.ensuring(x => true) // trigger an implicit search
}

@scabug
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scabug commented Jan 22, 2014

@retronym said:
scala/scala#3400

@scabug scabug closed this as completed Feb 5, 2014
@scabug scabug added this to the 2.11.0-RC1 milestone Apr 7, 2017
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