Help to understands "Fruitless specialization" warning

Hello, I just move to version 2.13.2 and use the package “slick_2.13-3.3.2.jar”.
I have the following simplified code:

package database
import slick.collection.heterogeneous._
object Bug {
val AValue = 314 :: “3.14f” :: HNil
}

When I compile it, I obtain:

warning: Fruitless specialization of Unit in parameter position. Consider using @specialized(Specializable.Arg) instead.

Could you help me to understand this warning? Is it normal to have no file not line specified for this warning?

Thanks

Looks like https://github.com/scala/bug/issues/11965 . (Let’s discuss there.)

Is it normal to have no file not line specified for this warning?

No. You shouldn’t be getting the warning at all, but also, every warning should include a location.

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