Cannot construct a collection of type TraversableOnce[A] with elements of type A based on a collection of type TraversableOnce[A]

[kwalcock]

I inherited some Scala 2.11/12 code which is having difficulty compiling in Scala 2.13 despite the compatibility library. Simplified, it looks like this:

import scala.collection.generic.CanBuildFrom
import scala.language.higherKinds

object Example {
  def f1[A](xs: TraversableOnce[A]): A = {
    f2(xs, 1).toIterator.next
  }

  def f2[A, CC[X] <: TraversableOnce[X]](xs: CC[A], k: Int)(implicit cbf: CanBuildFrom[CC[A], A, CC[A]]): CC[A] = {
    xs
  }
}

The error message must have to do with this:

package scala.collection.generic
@scala.annotation.implicitNotFound("Cannot construct a collection of type ${To} with elements of type ${Elem} based on a collection of type ${From}.")
trait CanBuildFrom[-From, -Elem, +To] extends scala.AnyRef {
  def apply(from : From) : scala.collection.mutable.Builder[Elem, To]
  def apply() : scala.collection.mutable.Builder[Elem, To]
}

Any ideas?

I've added the plugin, the library dependencies, and

// Add for Scala 2.13 compatibility.
ThisBuild / scalafixDependencies += "org.scala-lang.modules" %% "scala-collection-migrations" % "2.6.0"
addCompilerPlugin(scalafixSemanticdb)
scalacOptions ++= List("-Yrangepos", "-P:semanticdb:synthetics:on")