quarkusio/quarkus · error · IllegalArgumentException

Illegal type in hierarchy: ${type}

Error message

Illegal type in hierarchy: ${type}

What it means

IllegalArgumentException from JandexUtil.mapGenerics default branch: the type being mapped has a Jandex kind not handled by the switch (not array, class, parameterized, or type variable) — e.g. a wildcard or unresolved type appearing where a concrete mapped type is required. The offending type is interpolated into the message.

Source

Thrown at independent-projects/resteasy-reactive/common/processor/src/main/java/org/jboss/resteasy/reactive/common/processor/JandexUtil.java:306

                return ArrayType.create(mapGenerics(arrayType.constituent(), mapping), arrayType.dimensions());
            case CLASS:
                return type;
            case PARAMETERIZED_TYPE:
                ParameterizedType parameterizedType = type.asParameterizedType();
                Type owner = null;
                if (parameterizedType.owner() != null) {
                    owner = mapGenerics(parameterizedType.owner(), mapping);
                }
                return ParameterizedType.create(parameterizedType.name(),
                        mapGenerics(parameterizedType.arguments(), mapping).toArray(new Type[0]), owner);
            case TYPE_VARIABLE:
                Type ret = mapping.get(type.asTypeVariable().identifier());
                if (ret == null) {
                    throw new IllegalArgumentException("Missing type argument mapping for " + type);
                }
                return ret;
            default:
                throw new IllegalArgumentException("Illegal type in hierarchy: " + type);
        }
    }

    private static ClassInfo fetchFromIndex(DotName dotName, IndexView index) {
        final ClassInfo classInfo = index.getClassByName(dotName);
        if (classInfo == null) {
            throw new IllegalArgumentException("Class " + dotName + " was not found in the index");
        }
        return classInfo;
    }

    /**
     * Returns the enclosing class of the given annotation instance. For field, method or record component annotations,
     * this will return the enclosing class. For parameters, this will return the enclosing class of the enclosing
     * method. For classes, it will return the class itself. For type annotations, it will return the class enclosing
     * the annotated type usage.
     *
     * @param annotationInstance the annotation whose enclosing class to look up

View on GitHub (pinned to e1c734241f)

Solutions

1. Replace the wildcard/unusual generic construct with a concrete type in the resource signature
2. Report as a RESTEasy Reactive issue if the type usage looks valid

When it happens

Trigger: Thrown at independent-projects/resteasy-reactive/common/processor/src/main/java/org/jboss/resteasy/reactive/common/processor/JandexUtil.java:306 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/f46575a9dd6a0e60. Report an issue: GitHub.