Scala break/continue zero-cost loop abstraction

loops.scala

//> using scala "3.3.0"

import scala.util.boundary, boundary.break

object Loops:

  type ExitToken = Unit { type Exit }
  type ContinueToken = Unit { type Continue }

  type Exit = boundary.Label[ExitToken]
  type Continue = boundary.Label[ContinueToken]

  object loop:
    inline def apply(inline op: (Exit, Continue) ?=> Unit): Unit =
      boundary[ExitToken]:
        while true do
          boundary[ContinueToken]:
            op
    inline def exit()(using Exit) = break(().asInstanceOf[ExitToken])
    inline def continue()(using Continue) = break(().asInstanceOf[ContinueToken])

oddsUpToLimit.scala

import Loops.*

@main def oddsUpToLimit(limit: Int) =
  var i = 0
  loop:
    i += 1
    if i == limit then loop.exit()
    if i % 2 == 0 then loop.continue()
    println(i)