Cannot get field Annotations

[clementrey]

Hello
I am trying to create field annotation but I was not to make it work so far. I try to use the small snippet of code in the documentation

import shapeless.Annotations
import shapeless._
import labelled._

object TestAnnotations {

  case class First(s: String)
  case class CC(i: Int, @First("a") s: String)

  sealed trait Base

  @First("b") case class BaseI(i: Int) extends Base

  case class BaseS(s: String) extends Base

  val ccFirsts = Annotations[First, CC]
  val baseFirsts = Annotations[First, Base]

}

When I try to get the Out type ccFirsts.Out I got the type "Nothing" whereas I am expecting something like _ <: HList

Compiled with scala 2.12.8, shapeless 2.3.3 and sbt 1.2.6

Do you what is wrong with my implementation of the example ?

Thnk you very much for your time
Clement

[Dmytro Mitin]

@clementrey How do you check that

When I try to get the Out type ccFirsts.Out I got the type "Nothing"

?

For me

implicitly[ccFirsts.Out =:= (None.type :: Some[First] :: HNil)]
implicitly[Annotations.Aux[First, CC, None.type :: Some[First] :: HNil]]
the[ccFirsts.Out =:= (None.type :: Some[First] :: HNil)]
the[Annotations.Aux[First, CC, None.type :: Some[First] :: HNil]]

[Dmytro Mitin]

Also in REPL I have:

scala> import shapeless.Annotations 
import shapeless.Annotations

scala> import shapeless._ 
import shapeless._

scala> import labelled._ 
import labelled._

scala> case class First(s: String) 
defined class First

scala> case class CC(i: Int, @First("a") s: String) 
defined class CC

scala> sealed trait Base 
defined trait Base

scala> @First("b") case class BaseI(i: Int) extends Base 
defined class BaseI

scala> case class BaseS(s: String) extends Base 
defined class BaseS

scala> val ccFirsts = Annotations[First, CC] 
ccFirsts: shapeless.Annotations[First,CC]{type Out = None.type :: Some[First] :: shapeless.HNil} = shapeless.Annotations$$anon$1@6764bc8b

If you mean that IntelliJ IDEA generates (Alt+Enter) type Annotations.Aux[First, CC, Nothing] for ccFirsts then you not always should rely on types generated by IDE automatically.

You can check that the line
val ccFirsts: Annotations.Aux[First, CC, Nothing] = Annotations[First, CC]
doesn't compile

Error: type mismatch;
found   : shapeless.Annotations[First,CC]{type Out = None.type :: Some[First] :: shapeless.HNil}
required: shapeless.Annotations.Aux[First,CC,Nothing]
(which expands to)  shapeless.Annotations[First,CC]{type Out = Nothing}
val ccFirsts: Aux[First, CC, Nothing] = Annotations[First, CC]

[clementrey]

Thank a lot,

I gave to intellij too much credits.

Sorry for the silly questions

Regards