Recursive match type failing to expand completely

[nicolasstucki]

type F[N <: Int] = N match {
  case 1 => Int => Int
  case 2 => F[1]
}

val s: F[2] = ???
s.apply(4)

fails Ycheck:posttyper with

checking tests/run-with-compiler/i6281.scala after phase posttyper
exception while typing Test.s.$asInstanceOf$[Test.F[Int(1)]].apply(4) of class class dotty.tools.dotc.ast.Trees$Apply # 1259
exception while typing @scala.annotation.internal.SourceFile("tests/run-with-compiler/i6281.scala") 
  final module
 class Test() extends Object(), _root_.scala.Serializable { this: Test.type => 
  private def writeReplace(): AnyRef = 
    new scala.runtime.ModuleSerializationProxy(classOf[Test.type])
  type F[N >: Nothing <: Int] = 
    N match 
      {
        case 1.type => Function1[Int, Int]
        case 2.type => Test.F[1.type]
      }
  val s: Test.F[2.type] = ???
  Test.s.$asInstanceOf$[Test.F[Int(1)]].apply(4)
} of class class dotty.tools.dotc.ast.Trees$TypeDef # 1269
exception while typing package <empty> {
  import scala.quoted._
  final lazy module val Test: Test = new Test()
  @scala.annotation.internal.SourceFile("tests/run-with-compiler/i6281.scala") 
    final module
   class Test() extends Object(), _root_.scala.Serializable { this: Test.type =>
     
    private def writeReplace(): AnyRef = 
      new scala.runtime.ModuleSerializationProxy(classOf[Test.type])
    type F[N >: Nothing <: Int] = 
      N match 
        {
          case 1.type => Function1[Int, Int]
          case 2.type => Test.F[1.type]
        }
    val s: Test.F[2.type] = ???
    Test.s.$asInstanceOf$[Test.F[Int(1)]].apply(4)
  }
} of class class dotty.tools.dotc.ast.Trees$PackageDef # 1270
*** error while checking tests/run-with-compiler/i6281.scala after phase posttyper ***
java.lang.AssertionError: assertion failed: Found:    Int(4)
Required: T1
tree = 4 while compiling tests/run-with-compiler/i6281.scala
exception occurred while compiling tests/run-with-compiler/i6281.scala
Exception in thread "main" java.lang.AssertionError: assertion failed: Found:    Int(4)
Required: T1
tree = 4
        at scala.Predef$.assert(Predef.scala:223)
        at dotty.tools.dotc.transform.TreeChecker$Checker.adapt(TreeChecker.scala:461)
        at dotty.tools.dotc.typer.ProtoTypes$FunProto.typedArg(ProtoTypes.scala:329)
        at dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:784)
        at dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:782)
        at dotty.tools.dotc.typer.Applications$Application.addTyped$1(Applications.scala:550)
        at dotty.tools.dotc.typer.Applications$Application.matchArgs(Applications.scala:593)
        at dotty.tools.dotc.typer.Applications$Application.init(Applications.scala:371)
        at dotty.tools.dotc.typer.Applications$TypedApply.<init>(Applications.scala:685)
        at dotty.tools.dotc.typer.Applications$ApplyToUntyped.<init>(Applications.scala:783)
        at dotty.tools.dotc.typer.Applications.simpleApply$1(Applications.scala:856)
        at dotty.tools.dotc.typer.Applications.$anonfun$typedApply$9(Applications.scala:885)
        at dotty.tools.dotc.typer.Typer.tryEither(Typer.scala:2262)
        at dotty.tools.dotc.typer.Applications.$anonfun$typedApply$1(Applications.scala:886)
        at dotty.tools.dotc.util.Stats$.track(Stats.scala:37)
        at dotty.tools.dotc.typer.Applications.realApply$1(Applications.scala:825)
        at dotty.tools.dotc.typer.Applications.typedApply(Applications.scala:931)
        at dotty.tools.dotc.typer.Applications.typedApply$(Applications.scala:823)
        at dotty.tools.dotc.typer.Typer.typedApply(Typer.scala:87)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2078)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2132)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:124)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:267)
        at dotty.tools.dotc.typer.Typer.$anonfun$typed$2(Typer.scala:2166)
        at dotty.tools.dotc.reporting.TraceSyntax.apply(trace.scala:56)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2159)

[nicolasstucki]

This might be the cause of #6281