In a compiler plugin in the `SyntheticResolverExte...

# compiler

[raulraja]

In a compiler plugin in the SyntheticResolverExtension I’m overriding generateSyntheticClasses(PackageFragmentDescriptor, ...) and addSyntheticSupertypes. I’m attempting to add a super type to a class that I generate myself in that pass.

For example:

package x
interface Foo<A>
class Bar

I want to expand to:

package x
interface Foo<A>
class GeneratedClass
class Bar : Foo<GeneratedClass>

The issue I’m having is that addSyntheticSupertypes happens before GeneratedClass has a valid ClasDescriptor so when I add the supertype I get:

Bar : Foo<[ERROR : Unsubstituted type for <ERROR CLASS>]>

e: java.lang.IllegalStateException: Backend Internal error: Exception during code generation
Cause: Error type encountered: [ERROR : Unsubstituted type for <ERROR CLASS>] (ErrorType).

How can I generate a valid descriptor in that phase for GeneratedClass or how can I add a supertype to a class given the class the type refers to may not have been generated yet?
Is this the wrong phase to do this kind of work?

[dsavvinov]

How do you generate GeneratedClass?

[raulraja]

In the generateSyntheticClasses overload that takes first the PackageFragmentDescriptor with something like:

fun PackageFragmentDescriptor.kindMarker(ctx: LazyClassContext, target: ClassDescriptor): ClassDescriptor =
  ClassDescriptorImpl(
    containingDeclaration,
    target.markerName.shortName(),
    Modality.FINAL,
    ClassKind.CLASS,
    emptyList<KotlinType>(),
    SourceElement.NO_SOURCE,
    false,
    ctx.storageManager
  )

[raulraja]

Not sure if there is anything extra I have to do, I add that descriptor to the result: MutableSet<ClassDescriptor> which is passed to me in generateSyntheticClasses

[dsavvinov]

Hm, that’s seems reasonable for me.

And how do you find the generated descriptor in the addSyntheticSupertypes? Is it possible to see the actual code?

[raulraja]

I’m using :

someOtherClassDescriptor.module.resolveClassByFqName(GeneratedClassName, NoLookupLocation.FROM_BACKEND)

[raulraja]

@dsavvinov if that doesn’t look suspicious I can setup a small plugin on a public repo that better illustrates the issue. Also thanks for you help 🙂

[dsavvinov]

Yeah, I don’t know that the exactly correct way to do it, but it doesn’t look overly suspicious for me, and I’d probably do the same at first.

The only thing I’d re-check is that, quite obviously, you should add synthetic descriptor to the packageFragmentDescriptor of the module which you later query in addSyntheticSupertypes (but most probably you’ve checked that already)

[raulraja]

That does not seem to be possible based on what I’m seeing because addSynthetiClasses which is where one can access the packageFragmentDescriptor is invoked after addSyntheticSupertypes. I could create a valid ClassDescriptor inside addSyntheticSupertypes if I get access to a StorageManager. For what I can see the storage manager which is a requirement in ClassDescriptorImpl is not available because is private in the KotlinBuiltIns and other objects that reference it. Can I access the StorageManager as global service and request it wherever needed?

[raulraja]

I was able to create a descriptor with:

ClassDescriptorImpl(
  descriptor.parents.first(),
  Name("GeneratedClass"),
  Modality.FINAL,
  ClassKind.CLASS,
  emptyList<KotlinType>(),
  SourceElement.NO_SOURCE,
  false,
  LockBasedStorageManager.NO_LOCKS
) {
  override fun getUnsubstitutedMemberScope(): MemberScope = MemberScope.Empty
  override fun getConstructors(): Collection<ClassConstructorDescriptor> = emptyList()
}

I had to override those two methods so it would not blow up. The issue I see now is that GeneratedClass is in the metadata properly in the bytecode but no actual class is generated since Class.forName("sample.GeneratedClass") blows up.
I suppose I’m missing the IR generation step.
Is there an example somewhere that shows how to generate a marker simple class with no methods in the IR backend?

[raulraja]

Any ideas as to what I’m missing? I’m currently overriding generateSyntheticClasses(PackageFramentProvider, ....), addSyntheticSupertypes and doing all the IR generation for the class with transformDeclarationsFlat. Do I also need to add the class to the package declaration somehow?

[kralli]

Do you specify the descriptor of the GeneratedClass in the PackageFragmentProvider of the sample package via the PackageFragmentProviderExtension? Thats what I am doing and it worked out quite well for me. Though I'm not sure whether it's available in IR.

[raulraja]

@kralli yes and just changed from a ClassDescriptorImpl to SyntheticClassOrObjectDescriptor just in case but its constructor requieres a KtPureClassorObject which I'm not sure how to get in that phase

[raulraja]

Actually I take it back it's in the synthetic resolver extension I was doing that but will try that extension thanks !