ArC fails to construct bean with self-referencing generic constraint

[Felk]

ArC appears to be unable to generate beans if they have a generic parameter and a constraint referencing the generic parameter, as is common for e.g. T extends Comparable<T>. The issue can be reproduced as follows:

public class CdiProducers {
    @Produces
    public <T extends Comparable<T>> List<T> getSpecificList() {
        return new ArrayList<>();
    }
}

which results in the following error at build time:

[ERROR] Failed to execute goal io.quarkus:quarkus-maven-plugin:1.13.3.Final:build (default) on project my-project: Failed to build quarkus application: io.quarkus.builder.BuildException: Build failure: Build failed due to errors
[ERROR]         [error]: Build step io.quarkus.arc.deployment.ArcProcessor#generateResources threw an exception: java.lang.IllegalStateException: Unable to construct the type handle for PRODUCER METHOD bean [types=[java.util.List<T extends java.util.List>, java.util.Collection<T extends java.util.List>, java.lang.Object, java.lang.Iterable<T extends java.util.List>], qualifiers=[@Default, @Any], target=java.util.List<T extends java.util.List> getSpecificList(), declaringBean=me.demo.CdiProducers]: Unsupported bean type: UNRESOLVED_TYPE_VARIABLE, T
[ERROR]         at io.quarkus.arc.processor.BeanGenerator.initConstructor(BeanGenerator.java:671)
[ERROR]         at io.quarkus.arc.processor.BeanGenerator.createConstructor(BeanGenerator.java:566)
[ERROR]         at io.quarkus.arc.processor.BeanGenerator.generateProducerMethodBean(BeanGenerator.java:398)
[ERROR]         at io.quarkus.arc.processor.BeanGenerator.generate(BeanGenerator.java:115)
[ERROR]         at io.quarkus.arc.processor.BeanProcessor.generateResources(BeanProcessor.java:181)
[ERROR]         at io.quarkus.arc.deployment.ArcProcessor.generateResources(ArcProcessor.java:458)
[ERROR]         at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[ERROR]         at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[ERROR]         at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[ERROR]         at java.base/java.lang.reflect.Method.invoke(Method.java:566)
[ERROR]         at io.quarkus.deployment.ExtensionLoader$2.execute(ExtensionLoader.java:920)
[ERROR]         at io.quarkus.builder.BuildContext.run(BuildContext.java:277)
[ERROR]         at org.jboss.threads.EnhancedQueueExecutor$Task.run(EnhancedQueueExecutor.java:2415)
[ERROR]         at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1452)
[ERROR]         at java.base/java.lang.Thread.run(Thread.java:829)
[ERROR]         at org.jboss.threads.JBossThread.run(JBossThread.java:501)

with a prettyfied error message:

Build step io.quarkus.arc.deployment.ArcProcessor#generateResources threw an exception:
java.lang.IllegalStateException: Unable to construct the type handle for PRODUCER METHOD bean [
    types=[
        java.util.List<T extends java.util.List>,
        java.util.Collection<T extends java.util.List>,
        java.lang.Object,
        java.lang.Iterable<T extends java.util.List>
    ],
    qualifiers=[@Default, @Any],
    target=java.util.List<T extends java.util.List> getSpecificList(),
    declaringBean=me.demo.CdiProducers
]: Unsupported bean type: UNRESOLVED_TYPE_VARIABLE, T

A few more examples:

• does not work: <T extends List<T>>
• does work: <T extends Serializable>
• does work: <T>

I have attached a sample project to reproduce the problem: arc-selfreferencing-generic-constraint.zip

[quarkus-bot]

/cc @manovotn, @mkouba

[mkouba]

Hi @Felk, thanks for reporting this problem. It's a known issue - see also smallrye/jandex#88 and we can't do much until this jandex issue is resolved.

[Felk]

Thanks for letting me know, I'll watch that issue

[mkouba]

@Ladicek would you care to take a look at the ArC part? You fixed the Jandex issue, hence a perfect candidate 😉 .

[Ladicek]

Sure thing!

[Ladicek]

So the reproducer actually builds and runs just fine (I believe due to #27631), but I can't inject the produced bean anywhere, nor can I look it up programmatically -- and I don't even have an idea how to express such injection or programmatic lookup. I'm trying this:

@Dependent
static class Producer {
    @Produces
    @Dependent
    public <T extends Comparable<T>> List<T> produce() {
        return new ArrayList<>();
    }
}

// inject
@Dependent
static class Target<T extends Comparable<T>> {
    @Inject
    List<T> list;

    public List<T> getList() {
        return list;
    }
}

// lookup
public <T extends Comparable<T>> void test() {
    ArcContainer arc = Arc.container();
    InstanceHandle<List<T>> handle = arc.instance(new TypeLiteral<List<T>>() {});
}

But I'm not exactly sure if that's supposed to work or not. Any opinions? :-)

[Felk]

In my original usecase I think I injected a concrete type, e.g.

@Inject
List<String> stringList;

[Ladicek]

Yeah, I originally thought about that, but I'm not sure that's supposed to work as well. If I'm reading Assignability of raw and parameterized types, it probably should. It currently doesn't, because our AssignabilityCheck.findAssignables relies on presence of the types in Jandex -- I'll try to figure something out there, but getAllKnownSubclasses or getAllKnownImplementors can't really work well with on-demand indexing.

My attempts in the previous comment are most likely wrong, because those Ts are different type variables, even if they have the same name.