Use a This parameter instead of this.type in Tuple.toList

Author: mbovel

library/src/scala/Tuple.scala

@@ -13,9 +13,9 @@ sealed trait Tuple extends Product {
     runtime.Tuples.toArray(this)
 
   /** Create a copy of this tuple as a List */
-  inline def toList: List[Union[this.type]] =
+  inline def toList[This >: this.type <: Tuple]: List[Union[This]] =
     this.productIterator.toList
-      .asInstanceOf[List[Union[this.type]]]
+      .asInstanceOf[List[Union[This]]]
 
   /** Create a copy of this tuple as an IArray */
   inline def toIArray: IArray[Object] =

tests/pos/16654.scala

@@ -0,0 +1,7 @@
+def toCsvFlat[A <: Product](a: A)(using m: scala.deriving.Mirror.ProductOf[A]) = {
+  def flatTuple(any: Any): Tuple = any match
+    case p: Product => p.productIterator.map(flatTuple).foldLeft(EmptyTuple: Tuple)(_ ++ _)
+    case a          => Tuple1(a)
+
+  val tuple = flatTuple(Tuple.fromProductTyped(a)).toList
+}