oracle/graal · error · ElementException

Node class constructor must be public or protected

Error message

Node class constructor must be public or protected

What it means

Every declared constructor of a @NodeInfo node class must be public or protected (private ones are simply skipped as internal helpers, e.g. for vannatable constructors). Package-private constructors would prevent the generated node metas and instantiation machinery from creating the node reliably across packages. GraphNodeVerifier throws this ElementException on the offending constructor during annotation processing.

Source

Thrown at compiler/src/jdk.graal.compiler.processor/src/jdk/graal/compiler/nodeinfo/processor/GraphNodeVerifier.java:215

        return processor.env().getTypeUtils().isSameType(type1, type2);
    }

    private TypeElement getSuperType(TypeElement element) {
        if (element.getSuperclass() != null) {
            return processor.asTypeElement(element.getSuperclass());
        }
        return null;
    }

    void verify(TypeElement node) {
        scanFields(node);

        boolean foundValidConstructor = false;
        for (ExecutableElement constructor : ElementFilter.constructorsIn(node.getEnclosedElements())) {
            if (constructor.getModifiers().contains(PRIVATE)) {
                continue;
            } else if (!constructor.getModifiers().contains(PUBLIC) && !constructor.getModifiers().contains(PROTECTED)) {
                throw new ElementException(constructor, "Node class constructor must be public or protected");
            }

            foundValidConstructor = true;
        }

        if (!foundValidConstructor) {
            throw new ElementException(node, "Node class must have at least one protected constructor");
        }
    }
}

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Add protected or public to the constructor declaration.
2. If the constructor is internal-only, make it private so the verifier skips it — but then ensure at least one non-private constructor remains (else error 'Node class must have at least one protected constructor' follows).
3. Rebuild to confirm.

Example fix

// before
MyNode(ValueNode x) {
    super(...);
}

// after
protected MyNode(ValueNode x) {
    super(...);
}

When it happens

Trigger: A constructor whose modifiers contain neither PRIVATE, PUBLIC nor PROTECTED — i.e. package-private — is found by ElementFilter.constructorsIn(node.getEnclosedElements()) (GraphNodeVerifier.java:211-216). Example: 'MyNode(ValueNode x) { ... }' with no visibility modifier.

Common situations: Adding a helper constructor without an access modifier (Java defaults to package-private); refactoring visibility during test wiring; nodes in packages different from where they are instantiated.

Related errors

• Node class must have at least one protected constructor
• Input list field must not be final
• Input list field must not be public
• Input field type must be an interface or assignable to Node
• Input field must not be final

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/d9be299c4fc938a5. Report an issue: GitHub.