Scala 3 custom newtypes

examples.scala

type Timestamp = Timestamp.Type
object Timestamp extends Newtype[Instant]

type Quantity = Quantity.Type
object Quantity extends Newtype[Int]

type Source = String
object Source extends Newtype[String]

type SocketId = SocketId.Type
object SocketId extends IdNewtype

IsUUID.scala

import java.util.UUID

import monocle.Iso

trait IsUUID[A]:
  def iso: Iso[UUID, A]

object IsUUID:
  def apply[A](using ev: IsUUID[A]): IsUUID[A] = ev

  given IsUUID[UUID] with
    def iso: Iso[UUID, UUID] =
      Iso[UUID, UUID](identity)(identity)

Newtype.scala

import java.util.UUID

import cats.{ Eq, Order, Show }
import io.circe.{ Decoder, Encoder }
import monocle.Iso

abstract class Newtype[A](using
    eqv: Eq[A],
    ord: Order[A],
    shw: Show[A],
    enc: Encoder[A],
    dec: Decoder[A]
):
  opaque type Type = A

  inline def apply(a: A): Type = a

  protected inline final def derive[F[_]](using ev: F[A]): F[Type] = ev

  extension (t: Type) inline def value: A = t

  given Eq[Type]       = eqv
  given Order[Type]    = ord
  given Show[Type]     = shw
  given Encoder[Type]  = enc
  given Decoder[Type]  = dec
  given Ordering[Type] = ord.toOrdering

abstract class IdNewtype extends Newtype[UUID]:
  given IsUUID[Type] = derive[IsUUID]

abstract class NumNewtype[A](using
    eqv: Eq[A],
    ord: Order[A],
    shw: Show[A],
    enc: Encoder[A],
    dec: Decoder[A],
    num: Numeric[A]
) extends Newtype[A]:

  extension (x: Type)
    inline def -[T](using inv: T =:= Type)(y: T): Type = apply(num.minus(x.value, inv.apply(y).value))
    inline def +[T](using inv: T =:= Type)(y: T): Type = apply(num.plus(x.value, inv.apply(y).value))