Potential Issue Deriving Tags on Scala 3

[adamgfraser]

This works:

import zio._

trait DgraphClient

object Example extends scala.App:

  type DgClient = Has[DgClient.Service]

  object DgClient:
    trait Service:
      val dgraphClient: UIO[DgraphClient]

    val getDgClient: URIO[DgClient, DgraphClient] =
      ZIO.accessM[DgClient](_.get.dgraphClient)

  println("It compiles!")

However, if I remove the return type of getDgClient like so:

import zio._

trait DgraphClient

object Example extends scala.App:

  type DgClient = Has[DgClient.Service]

  object DgClient:
    trait Service:
      val dgraphClient: UIO[DgraphClient]

    val getDgClient =
      ZIO.accessM[DgClient](_.get.dgraphClient)

  println("It compiles!")

Then I get the following error message:

could not find implicit value for izumi.reflect.Tag[Example.DgClient.Service]. Did you forget to put on a Tag, TagK or TagKK context bound on one of the parameters in Example.DgClient.Service? e.g. def x[T: Tag, F[_]: TagK] = ....
I found:

    izumi.reflect.Tag.tagFromTagMacro[Example.DgClient.Service]

But method tagFromTagMacro in object Tag does not match type izumi.reflect.Tag[Example.DgClient.Service].

Seems like that should work given that I am explicitly supplying the type parameter to accessM.

[neko-kai]

@adamgfraser
Upstream issue - scala/scala3#8764
Fix enroute: scala/scala3#9984

[adamgfraser]

@neko-kai Nice!