Remove FunctionalRandom asInstanceOf casts

src/main/scala/net/eagle0/common/FunctionalRandom.scala

@@ -1,6 +1,6 @@
 package net.eagle0.common
 
-import scala.annotation.{nowarn, tailrec}
+import scala.annotation.tailrec
 import scala.collection.SeqFactory
 
 case class RandomState[+T](
@@ -160,10 +160,9 @@ abstract class FunctionalRandom {
   )(
       f: (T, FunctionalRandom) => RandomState[S[U]]
   )(using xFactory: FACT): RandomState[S[U]] = {
-    @nowarn def foldGen(rsU: RandomState[S[U]], t: T): RandomState[S[U]] =
-      rsU.continue {
-        case (us: S[U], fr: FunctionalRandom) =>
-          f(t, fr).map(x => (us ++ x).asInstanceOf[S[U]])
+    def foldGen(rsU: RandomState[S[U]], t: T): RandomState[S[U]] =
+      rsU.continue { (us, fr) =>
+        f(t, fr).map(x => xFactory.from(us ++ x))
       }
     FunctionalRandom.nextFoldLeft(
       seq,
@@ -179,17 +178,16 @@ abstract class FunctionalRandom {
     nextFlatMapImpl[T, U, Vector, SeqFactory[Vector]](vec)(f)(using Vector)
 
   private def nextMapImpl[T, U, S[X] <: Seq[X], FACT <: SeqFactory[S]](
-      seq: Vector[T]
+      seq: S[T]
   )(
       f: (T, FunctionalRandom) => RandomState[U]
   )(using xFactory: FACT): RandomState[S[U]] = {
-    @nowarn def foldGen(
+    def foldGen(
         rsU: RandomState[S[U]],
         t: T
     ): RandomState[S[U]] =
-      rsU.continue {
-        case (us: S[U], fr: FunctionalRandom) =>
-          f(t, fr).map(x => (us :+ x).asInstanceOf[S[U]])
+      rsU.continue { (us, fr) =>
+        f(t, fr).map(x => xFactory.from(us :+ x))
       }
 
     FunctionalRandom.nextFoldLeft(seq, RandomState(xFactory.empty[U], this))(