Desugaring Doobie for comprehension

doobietest.scala

  case class Foo(id: Int, name: String)

  case class Bar(id: Int, name: String)
  
  case class FooWithBar(foo: Foo, bars: List[Bar])

  // The for-comprehension way
  def get1(id: Int): ConnectionIO[Option[FooWithBar]] = for {
    fooOpt <- sql"""SELECT id, name  FROM foo WHERE id=$id""".query[Foo].option
    fooOpt2 <- fooOpt match {
      case Some(foo) =>
        (for {
          bars <- sql"""SELECT id,name FROM bar WHERE foo_id=${foo.id}""".query[Bar].to[List]
        } yield bars).map { bars =>
          Some(FooWithBar(foo, bars))
        }
      case None => None.pure[ConnectionIO]
    }
  } yield fooOpt2

  // de-sugaring into a flatmap
  def get2(id: Int): ConnectionIO[Option[FooWithBar]] = sql"""SELECT id, name  FROM foo WHERE id=$id""".query[Foo].option.flatMap {
      case Some(foo) =>
        sql"""SELECT id,name FROM bar WHERE foo_id=$foo.id""".query[Bar].to[List].map(bars => bars).map(bars =>
          Some(FooWithBar(foo, bars)))
      // Complains about None.type <: Option[FooWithBar], but class Free is invariant in type A.
      case None => None.pure[ConnectionIO]
    }

  // letting IntelliJ de-sugar the for-comprehension
  def get3(id: Int): ConnectionIO[Option[FooWithBar]] = sql"""SELECT id, name  FROM foo WHERE id=$id""".query[Foo].option.flatMap(fooOpt => (fooOpt match {
    case Some(foo) =>
      sql"""SELECT id,name FROM bar WHERE foo_id=$foo.id""".query[Bar].to[List].map(bars => bars).map(bars =>
        Some(FooWithBar(foo, bars)))
    case None => None.pure[ConnectionIO]
  }).map(fooOpt2 => fooOpt2))


// Artificial example using Option[Option[Int] instead of ConnectionIO[Option[FooWithBar]]
// f1 & f2 are equivalent
def f1(x: Option[Option[Int]]): Option[Option[Int]] = x.flatMap {
  z =>
    (z match {
      case Some(y) => Some(Some(y + 1))
      case None => Some(None)
    }).map(a => a)
}

def f2(x: Option[Option[Int]]): Option[Option[Int]] = x.flatMap {
      case Some(y) => Some(Some(y + 1))
      case None => Some(None)
}