Add `HasNoScope` type class (#9597) #9604

987Nabil · 2025-02-16T14:13:14Z

fixes #9597
/claim #9597

core/shared/src/main/scala-2/zio/HasNoScopeCompanionVersionSpecific.scala

core/shared/src/main/scala/zio/HasNoScope.scala

core/shared/src/main/scala-3/zio/HasNoScopeCompanionVersionSpecific.scala

managed-tests/shared/src/test/scala/zio/managed/HasNoScopeSpec.scala

hearnadam

I think this is possible without a macro, but I couldn't get the Scope & case to work:

import zio.Scope
import zio.ZEnvironment

abstract class Foo


sealed abstract class HasNoScope[R]
object HasNoScope extends HighPriorityImplicits {
  override protected val instance = new HasNoScope[Any] {}

  def f[R: HasNoScope] = ???


  f[Any] // compiles - correct
  f[Foo & Any] // compiles - correct
  //f[Scope] // doesn't compile - correct
  f[Foo & Scope] // compiles - incorrect

sealed abstract class LowPriorityImplicits {
  protected val instance: HasNoScope[Any]

  @annotation.implicitAmbiguous("Cannot provde that ZEnvironment[${R}] does not contain zio.Scope")
  implicit def supScope1[R >: Scope]: HasNoScope[R] =
    instance.asInstanceOf[HasNoScope[R]]
  implicit def supScope2[R >: Scope]: HasNoScope[R] =
    instance.asInstanceOf[HasNoScope[R]]
}

sealed abstract class MediumPriorityImplicits extends LowPriorityImplicits {
  implicit def hasNoScope[R]: HasNoScope[R] =
    instance.asInstanceOf[HasNoScope[R]]
}
abstract class HighPriorityImplicits extends MediumPriorityImplicits {
  implicit val hasNoScopeAny: HasNoScope[Any] = instance
}

hearnadam · 2025-02-17T18:53:34Z

core/shared/src/main/scala-3/zio/HasNoScopeCompanionVersionSpecific.scala

+        s"Can not prove that $rName does not contain a zio.Scope. Please add a context bound ${rName}: HasNoScope."
+      )
+    } else {
+      '{ HasNoScope.noScope.asInstanceOf[HasNoScope[R]] }


I think this can cause some cyclic issues in edge cases. My suggestion would be to use protected def instance and the object can override with a val

I don't get the override val part

hearnadam · 2025-02-17T18:53:58Z

core/shared/src/main/scala-3/zio/HasNoScopeCompanionVersionSpecific.scala

+
+import scala.quoted._
+
+private[zio] trait HasNoScopeCompanionVersionSpecific {


Suggested change

private[zio] trait HasNoScopeCompanionVersionSpecific {

private[zio] abstract class HasNoScopeCompanionVersionSpecific {

traits are compiled to interfaces which can introduce interface dispatch. In this case, it's probably equivalent. However, it's a good precedence to set going forward. It's not binary compat to go from class -> trait, but it's easy to go the other way (if necessary).

hearnadam · 2025-02-17T18:54:14Z

core/shared/src/main/scala-2/zio/HasNoScopeCompanionVersionSpecific.scala

+import scala.language.experimental.macros
+import scala.reflect.macros.blackbox
+
+private[zio] trait HasNoScopeCompanionVersionSpecific {


Suggested change

private[zio] trait HasNoScopeCompanionVersionSpecific {

private[zio] abstract class HasNoScopeCompanionVersionSpecific {

managed-tests/shared/src/test/scala/zio/managed/HasNoScopeSpec.scala

hearnadam · 2025-02-17T18:55:16Z

core/shared/src/main/scala/zio/HasNoScope.scala

+sealed trait HasNoScope[R]
+
+object HasNoScope extends HasNoScopeCompanionVersionSpecific {
+  val noScope: HasNoScope[Any] = new HasNoScope[Any] {}


private/protected

I am quite sure, that won't work. Because the access will be inlined and the place of inlining won't have the correct access rights

If you make it package-private it'll work. package-private methods don't exist on the JVM so they're compiled to public methods.

PS: It will also work if you make it private; but in that case the Scala compiler will create a public proxy method which we probably want to avoid

987Nabil · 2025-02-17T19:39:36Z

I think this is possible without a macro, but I couldn't get the Scope & case to work:

import zio.Scope
import zio.ZEnvironment

abstract class Foo


sealed abstract class HasNoScope[R]
object HasNoScope extends HighPriorityImplicits {
  override protected val instance = new HasNoScope[Any] {}

  def f[R: HasNoScope] = ???


  f[Any] // compiles - correct
  f[Foo & Any] // compiles - correct
  //f[Scope] // doesn't compile - correct
  f[Foo & Scope] // compiles - incorrect

sealed abstract class LowPriorityImplicits {
  protected val instance: HasNoScope[Any]

  @annotation.implicitAmbiguous("Cannot provde that ZEnvironment[${R}] does not contain zio.Scope")
  implicit def supScope1[R >: Scope]: HasNoScope[R] =
    instance.asInstanceOf[HasNoScope[R]]
  implicit def supScope2[R >: Scope]: HasNoScope[R] =
    instance.asInstanceOf[HasNoScope[R]]
}

sealed abstract class MediumPriorityImplicits extends LowPriorityImplicits {
  implicit def hasNoScope[R]: HasNoScope[R] =
    instance.asInstanceOf[HasNoScope[R]]
}
abstract class HighPriorityImplicits extends MediumPriorityImplicits {
  implicit val hasNoScopeAny: HasNoScope[Any] = instance
}

The macro works and is on the simple side of macros. I think it is okay.
Also I think you still miss one point. That is a generic method calling the use side of the :HasNoScope context bound.
This is in the test, but not here. The macro forces you to propagate an implicit HasNoScope[R] from a place where R is a non generic type.

kyri-petrou · 2025-02-18T06:04:56Z

managed-tests/shared/src/test/scala/zio/managed/HasNoScopeSpec.scala

@@ -0,0 +1,56 @@
+package zio.managed


I feel like this is the wrong place with this suite. Any reason it's not under the core-tests folder?

I just took a look where the other tests that use macros where. I can move it

Yes let's please move it. I'm not even sure why the other macro tests are under there but we should probably move those too (not in this PR ofc)

hearnadam

Code LGTM, as discussed over Discord I think Scala 3's typecheck should be a transparent inline to correctly show the macro errors. That would allow unification of suites.

kyri-petrou · 2025-02-19T05:02:25Z

core/shared/src/main/scala/zio/HasNoScope.scala

+sealed trait HasNoScope[R]
+
+object HasNoScope extends HasNoScopeCompanionVersionSpecific {
+  override val instance: HasNoScope[Any] = new HasNoScope[Any] {}


Can we change this to package-private?

This will be called by the inlined code of the macro. If it is not public, the compiler will fail

package-private methods / vals are public when compiled. Have you tried changing it to package-private and it didn't work?

core/shared/src/main/scala-3/zio/HasNoScopeCompanionVersionSpecific.scala

algora-pbc bot mentioned this pull request Feb 16, 2025

Create type class HasNoScope[R] for checking that R does not contain Scope #9597

Closed

algora-pbc bot added the 🙋 Bounty claim label Feb 16, 2025

paulpdaniels reviewed Feb 17, 2025

View reviewed changes

987Nabil force-pushed the has-no-scope branch from 82ee7e7 to 22b867b Compare February 17, 2025 06:07

hearnadam reviewed Feb 17, 2025

View reviewed changes

kyri-petrou reviewed Feb 18, 2025

View reviewed changes

987Nabil added 2 commits February 18, 2025 17:19

Add HasNoScope type class (zio#9597)

d86246f

Add HasNoScope type class (zio#9597)

278295f

987Nabil force-pushed the has-no-scope branch from 22b867b to 278295f Compare February 18, 2025 16:19

hearnadam approved these changes Feb 18, 2025

View reviewed changes

kyri-petrou reviewed Feb 19, 2025

View reviewed changes

regiskuckaertz reviewed Feb 19, 2025

View reviewed changes

core/shared/src/main/scala-3/zio/HasNoScopeCompanionVersionSpecific.scala Show resolved Hide resolved

kyri-petrou approved these changes Feb 19, 2025

View reviewed changes

kyri-petrou merged commit f080050 into zio:series/2.x Feb 19, 2025
18 checks passed

amumurst mentioned this pull request Mar 12, 2025

Unused local from HasNoScope macro #9690

Open


		import scala.quoted._

		private[zio] trait HasNoScopeCompanionVersionSpecific {

	private[zio] trait HasNoScopeCompanionVersionSpecific {
	private[zio] abstract class HasNoScopeCompanionVersionSpecific {

Uh oh!

Add HasNoScope type class (#9597) #9604

Add HasNoScope type class (#9597) #9604

Uh oh!

Conversation

987Nabil commented Feb 16, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

hearnadam left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

kyri-petrou Feb 18, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

987Nabil commented Feb 17, 2025

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

kyri-petrou Feb 18, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

hearnadam left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

Add `HasNoScope` type class (#9597) #9604

Add `HasNoScope` type class (#9597) #9604

987Nabil commented Feb 16, 2025 •

edited

Loading

kyri-petrou Feb 18, 2025 •

edited

Loading

kyri-petrou Feb 18, 2025 •

edited

Loading