oracle/graal · error · IllegalArgumentException

Unsupported annotation member type: {}

Error message

Unsupported annotation member type: {}

What it means

Error "Unsupported annotation member type: {}" thrown in oracle/graal.

Source

Thrown at espresso-compiler-stub/src/com.oracle.truffle.espresso.vmaccess/src/com/oracle/truffle/espresso/vmaccess/EspressoExternalHostProxies.java:972

        if ("Ljava/lang/String;".equals(expectedType.getName())) {
            return value.asString();
        }
        if ("Ljava/lang/Class;".equals(expectedType.getName())) {
            return EspressoExternalConstantReflectionProvider.classAsType(value, access);
        }
        if (!(expectedType instanceof ResolvedJavaType resolvedExpectedType)) {
            throw new IllegalArgumentException("Expected resolved annotation member type, got " + expectedType);
        }
        if (resolvedExpectedType.isArray()) {
            return guestAnnotationArrayMemberValueAsHost(value, resolvedExpectedType);
        }
        if (resolvedExpectedType.isEnum()) {
            return new EnumElement(resolvedExpectedType, value.invokeMember("name").asString());
        }
        if (access.java_lang_annotation_Annotation.isAssignableFrom(resolvedExpectedType)) {
            return guestAnnotationAsAnnotationValue(value);
        }
        throw new IllegalArgumentException("Unsupported annotation member type: " + expectedType);
    }

    /**
     * Recursively converts a typed guest annotation array to an immutable list of JVMCI element
     * representations.
     */
    private Object guestAnnotationArrayMemberValueAsHost(Value value, ResolvedJavaType arrayType) {
        ResolvedJavaType componentType = arrayType.getComponentType();
        int length = Math.toIntExact(value.getArraySize());
        List<Object> elements = new ArrayList<>(length);
        for (int i = 0; i < length; i++) {
            elements.add(guestAnnotationMemberValueAsHost(value.getArrayElement(i), componentType));
        }
        return List.copyOf(elements);
    }

}

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Fix the condition reported by the error: Unsupported annotation member type: {}
2. Check the throwing call site and ensure its documented preconditions (argument values, types, environment, or configuration) are satisfied before the call.

Example fix

Validate inputs and environment so that the failing condition does not occur: Unsupported annotation member type: {}

When it happens

Trigger: Thrown at espresso-compiler-stub/src/com.oracle.truffle.espresso.vmaccess/src/com/oracle/truffle/espresso/vmaccess/EspressoExternalHostProxies.java:972 when the library encounters an invalid state.

Common situations: Occurs when a caller violates the contract guarded by this check: Unsupported annotation member type: {}

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/08a4bec28e32180b. Report an issue: GitHub.