Fix ExprHKDGeneric sum impl

Author: Katrix

dotty/derivation/src/main/scala/perspective/derivation/exprHkdGeneric.scala

@@ -212,7 +212,7 @@ object ExprHKDProductGeneric:
     private lazy val nameMap = namesArr.zipWithIndex.toMap
 
     override def nameToIndex(name: Names): IdxWrapper[_ <: ElemTop] =
-      IdxWrapper(Finite.unsafeApply(nameMap(name)))
+      HKDGeneric.IdxWrapper(Finite.unsafeApply(nameMap(name)))
 
     override type TupleRep = ElemTypes
 
@@ -494,7 +494,6 @@ object ExprHKDProductGeneric:
 
 trait ExprHKDSumGeneric[A] extends GenHKDSumGeneric[A] with ExprHKDGeneric[A]:
   type Cat[B] = Expr[Option[B]]
-  type ElemTop <: A
 
   /**
     * Returns the index of a value. Because of soundness, this method can not be
@@ -555,7 +554,6 @@ object ExprHKDSumGeneric:
     }
   }
 
-  /*
   transparent inline given derived[A](using q: Quotes, aType: Type[A]): ExprHKDSumGeneric[A] =
     Expr.summon[Mirror.SumOf[A]] match
       case Some('{
@@ -621,9 +619,11 @@ object ExprHKDSumGeneric:
     type Index[_]  = Finite[typeLength.Length]
     type TypeName  = Label
     type TupleRep  = ElemTypes
+    type ElemTop   = A & Helpers.TupleUnion[TupleRep, Nothing]
   } = new ExprHKDSumGeneric[A]:
     override type Gen[F[_]] = ProductK[F, ElemTypes]
     override type Index[_]  = Finite[typeLength.Length]
+    override type ElemTop = A & Helpers.TupleUnion[TupleRep, Nothing]
 
     override def genType: Type[Gen] = Type.of[Gen]
 
@@ -643,7 +643,7 @@ object ExprHKDSumGeneric:
     private lazy val nameMap = namesArr.zipWithIndex.toMap
 
     override def nameToIndex(name: Names): IdxWrapper[_ <: ElemTop] =
-      IdxWrapper(Finite.unsafeApply(nameMap(name)))
+      HKDGeneric.IdxWrapper(Finite.unsafeApply(nameMap(name)))
 
     override type TupleRep = ElemTypes
 
@@ -686,21 +686,15 @@ object ExprHKDSumGeneric:
       '{ $ret._2 }
 
 
-    /*
     override def indexOf[X <: ElemTop: Type](x: Expr[X]): Expr[Index[X]] =
       '{ Finite.unsafeApply($m.ordinal($x)) }
 
     override def indexOfA(a: Expr[A]): Expr[IdxWrapper[_ <: ElemTop]] =
-      given Type[IdxWrapper] = Type.of[IdxWrapper]
-      given Type[ElemTop] = Type.of[ElemTop]
-      '{ new IdxWrapper(${ indexOf(a.asInstanceOf[Expr[ElemTop]]) }) }
+      '{ new HKDGeneric.IdxWrapper[Index, ElemTop](Finite.unsafeApply($m.ordinal($a))) }
 
     override def indexOfACasting(a: Expr[A]): IndexOfACasting[Index, ElemTop] =
-      given Type[IdxWrapper] = Type.of[IdxWrapper]
-      given Type[ElemTop] = Type.of[ElemTop]
-      val idx = indexOfA(a)
-      new IndexOfACasting.IndexOfACastingImpl[Index, ElemTop, ElemTop]('{ $idx.idx }, a.asInstanceOf[Expr[ElemTop]])
-     */
+      val idx = '{ Finite.unsafeApply[typeLength.Length]($m.ordinal($a)) }
+      new IndexOfACasting.IndexOfACastingImpl[Index, ElemTop, ElemTop](idx, a.asInstanceOf[Expr[ElemTop]])
 
     extension [B[_]: Type](gen: Gen[B])
       override def traverseKExprId[D[_]: Type](f: B :~>: Compose2[Expr, D]): Expr[Gen[D]] =
@@ -749,5 +743,4 @@ object ExprHKDSumGeneric:
       ProductK.productKInstance[ElemTypes]
 
     override val representable: BoundedRepresentableKC.Aux[Gen, Index] = instance
-    override val traverse: TraverseKC[Gen]                             = instance
-*/
+    override val traverse: TraverseKC[Gen]                             = instance

dotty/derivation/src/main/scala/perspective/derivation/hkdGeneric.scala

@@ -23,13 +23,13 @@ trait GenHKDGeneric[A]:
   type ElemTop
 
   /** A wrapper for [[Index]] where we want wildcards of it. */
-  case class IdxWrapper[X](idx: Index[X])
+  type IdxWrapper[X] = HKDGeneric.IdxWrapper[Index, X]
   given [X]: Conversion[IdxWrapper[X], Index[X]] = _.idx
-  given [X]: Conversion[Index[X], IdxWrapper[X]] = IdxWrapper(_)
+  given [X]: Conversion[Index[X], IdxWrapper[X]] = HKDGeneric.IdxWrapper(_)
 
   /** Upcast an index to its bound. */
   inline def upcastIndex[X](idx: Index[X]): IdxWrapper[_ <: ElemTop] =
-    IdxWrapper(idx).asInstanceOf[IdxWrapper[_ <: ElemTop]]
+    HKDGeneric.IdxWrapper(idx).asInstanceOf[IdxWrapper[_ <: ElemTop]]
 
   /** The name of the [[A]] type. */
   type TypeName <: String
@@ -117,6 +117,8 @@ object HKDGeneric:
     type Gen[B[_]] = Gen0[B]
   }
 
+  case class IdxWrapper[Index[_], X](idx: Index[X])
+
   transparent inline given derived[A](using m: Mirror.Of[A], typeLength: TypeLength[A])(
       using Finite.NotZero[typeLength.Length] =:= true
   ): HKDGeneric[A] = inline m match
@@ -270,7 +272,7 @@ object HKDProductGeneric:
 
       private lazy val nameMap = namesArr.zipWithIndex.toMap
 
-      override def nameToIndex(name: Names): IdxWrapper[_ <: ElemTop] = IdxWrapper(Finite.unsafeApply(nameMap(name)))
+      override def nameToIndex(name: Names): IdxWrapper[_ <: ElemTop] = HKDGeneric.IdxWrapper(Finite.unsafeApply(nameMap(name)))
 
       override type TupleRep = ElemTypes
       override def genToTuple[F[_]](gen: Gen[F]): Helpers.TupleMap[TupleRep, F]   = gen.tuple
@@ -316,11 +318,9 @@ trait GenHKDSumGeneric[A] extends GenHKDGeneric[A]:
   * @tparam A
   *   The type being abstracted over.
   */
-trait HKDSumGeneric[A] extends HKDGeneric[A]:
+trait HKDSumGeneric[A] extends HKDGeneric[A] with GenHKDSumGeneric[A]:
   type Cat[B] = Option[B]
 
-  override type ElemTop <: A
-
   /**
     * Returns the index of a value. Because of soundness, this method can not be
     * used if X = A. In that case, use [[indexOfA]] instead.
@@ -358,7 +358,7 @@ trait HKDSumGeneric[A] extends HKDGeneric[A]:
     ) { a =>
       val index = indexOf((a: A).asInstanceOf[ElemTop])
       // This cast is safe as we know A = Z
-      representable.tabulateK([Z] => (i: Index[Z]) => if i == index.idx then Some((a: A).asInstanceOf[Z]) else None)
+      representable.tabulateK([Z] => (i: Index[Z]) => if i == index then Some((a: A).asInstanceOf[Z]) else None)
     }
 
   /**
@@ -426,10 +426,12 @@ object HKDSumGeneric:
     type Gen[F[_]] = ProductK[F, TupleRep]
     type Index[_]  = Finite[typeLength.Length]
     type TypeName  = Label
+    type ElemTop   = A & Helpers.TupleUnion[TupleRep, Nothing]
   } =
     new HKDSumGeneric[A]:
       type Gen[F[_]] = ProductK[F, TupleRep]
       type Index[_]  = Finite[typeLength.Length]
+      type ElemTop = A & Helpers.TupleUnion[TupleRep, Nothing]
 
       override type TypeName = Label
       override def typeName: TypeName = label
@@ -441,7 +443,7 @@ object HKDSumGeneric:
 
       private lazy val nameMap = namesArr.zipWithIndex.toMap
 
-      override def nameToIndex(name: Names): IdxWrapper[_ <: ElemTop] = IdxWrapper(Finite.unsafeApply(nameMap(name)))
+      override def nameToIndex(name: Names): IdxWrapper[_ <: ElemTop] = HKDGeneric.IdxWrapper(Finite.unsafeApply(nameMap(name)))
 
       override def indexOf[X <: ElemTop](x: X): Index[X] = Finite(typeLength.length, m.ordinal(x))