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// non-deterministic type errors, non-termination.
// seems to be due to inconsistent hashing/equality in SubTypePair
import scala.language.{existentials, implicitConversions}
import scala.annotation.unchecked.uncheckedVariance
trait Column[T]
// Turning this into a trait reduces (eliminates?) the likelihood of type errors (but not of non-termination)
abstract class Shape[Level <: ShapeLevel, -Mixed_, Unpacked_, Packed_]
trait ShapeLevel
trait NestedShapeLevel extends ShapeLevel
trait FlatShapeLevel extends NestedShapeLevel
trait ColumnsShapeLevel extends FlatShapeLevel
trait ProvenShape[U]
object ProvenShape {
implicit def proveShapeOf[T, U](v: T)(implicit sh: Shape[_ <: FlatShapeLevel, T, U, _]): ProvenShape[U] = ???
}
sealed abstract class HList {
type Self <: HList
type :: [E] = HCons[E, Self]
final def :: [E](elem: E): :: [E] = ???
}
final class HCons[+H, +T <: HList](val head: H, val tail: T) extends HList {
type Self = HCons[H @uncheckedVariance, T @uncheckedVariance]
}
final object HNil extends HList {
type Self = HNil.type
}
// Success is more likely when not using these aliases
object syntax {
type :: [+H, +T <: HList] = HCons[H, T]
type HNil = HNil.type
}
class HListBench {
import syntax._
implicit def columnShape[T, Level <: ShapeLevel]: Shape[Level, Column[T], T, Column[T]] = ???
implicit def provenShape[T, P](implicit shape: Shape[_ <: FlatShapeLevel, T, _, P]): Shape[FlatShapeLevel, ProvenShape[T], T, P] = ???
final class HListShape[Level <: ShapeLevel, M <: HList, U <: HList, P <: HList](val shapes: Seq[Shape[_ <: ShapeLevel, _, _, _]]) extends Shape[Level, M, U, P]
implicit def hnilShape[Level <: ShapeLevel] = new HListShape[Level, HNil.type, HNil.type, HNil.type](Nil)
implicit def hconsShape[Level <: ShapeLevel, M1, M2 <: HList, U1, U2 <: HList, P1, P2 <: HList]
(implicit s1: Shape[_ <: Level, M1, U1, P1], s2: HListShape[_ <: Level, M2, U2, P2]) =
new HListShape[Level, M1 :: M2, U1 :: U2, P1 :: P2](s1 +: s2.shapes)
trait A[T] {
def * : ProvenShape[T]
}
trait B extends A[
Int :: Int :: Int :: Int :: Int ::
Int :: Int :: Int :: Int :: Int ::
Int :: Int :: Int :: Int :: Int ::
Int :: Int :: Int :: Int :: Int ::
Int :: Int :: Int :: Int :: Int ::
Int :: Int :: HNil ] {
def c: Column[Int]
def * = c :: c :: c :: c :: c ::
c :: c :: c :: c :: c ::
c :: c :: c :: c :: c ::
c :: c :: c :: c :: c ::
c :: c :: c :: c :: c ::
c :: c :: HNil
}
}
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