Unable to accumulate a Seq[Seq[SomeType]] in foldLeft

Question

I need to iterate a list of base trait items and based on certain condition group all instances of a specific type. But i am facing a syntax error on one of the branches of the match clause inside the foldLeft.

trait Base {
  def foo: Int
}
case class TypeA(foo: Int) extends Base
case class TypeB(foo: Int) extends Base

object Main {
  def main(args: Array[String]): Unit = {
    val items: Seq[Base] = Seq(TypeA(1), TypeB(2), TypeB(3), TypeA(2), TypeA(3))

    val typeAs: Seq[Seq[TypeA]] = items.foldLeft(Seq.empty[Seq[TypeA]]) { case (acc, item) =>
      val someCondition = true
      item match {
        case el:TypeA =>
          if (acc.nonEmpty) {
            if (someCondition)
              acc :+ Seq(Seq(el)) // type mismatch error here
            else
              acc.init :+ (acc.last :+ el)
          } else
            Seq(Seq(el))

        case _:TypeB =>
          acc
      }
    }
  }
}

The error on compilation is

error: type mismatch;

found : Seq[Seq[Equals]]

required: Seq[Seq[TypeA]]

acc :+ Seq(Seq(el))

Using Scala 2.13.3 via the maven compiler plugin.

Answer 1

Ahh, made a careless mistake Should be trying to append a Seq[TypeA] to the accumulator

acc :+ Seq(el)