oracle/graal · error · ElementException

Successor list field must not be final

Error message

Successor list field must not be final

What it means

A control-flow successor field typed NodeSuccessorList and annotated @Successor must not be final. Successor lists are rewritten whenever the control-flow graph is transformed (e.g. block reordering, node deletion), so the field must remain reassignable. The NodeInfo processor enforces this invariant at annotation-processing time.

Source

Thrown at compiler/src/jdk.graal.compiler.processor/src/jdk/graal/compiler/nodeinfo/processor/GraphNodeVerifier.java:147

                        }
                        if (modifiers.contains(PUBLIC)) {
                            throw new ElementException(field, "Input list field must not be public");
                        }
                    } else {
                        if (!isAssignableWithErasure(field, Node) && field.getKind() == ElementKind.INTERFACE) {
                            throw new ElementException(field, "Input field type must be an interface or assignable to Node");
                        }
                        if (modifiers.contains(FINAL)) {
                            throw new ElementException(field, "Input field must not be final");
                        }
                        if (modifiers.contains(PUBLIC)) {
                            throw new ElementException(field, "Input field must not be public");
                        }
                    }
                } else if (isSuccessor) {
                    if (isAssignableWithErasure(field, NodeSuccessorList)) {
                        if (modifiers.contains(FINAL)) {
                            throw new ElementException(field, "Successor list field must not be final");
                        }
                        if (modifiers.contains(PUBLIC)) {
                            throw new ElementException(field, "Successor list field must not be public");
                        }
                    } else {
                        if (!isAssignableWithErasure(field, Node)) {
                            throw new ElementException(field, "Successor field must be a Node type");
                        }
                        if (modifiers.contains(FINAL)) {
                            throw new ElementException(field, "Successor field must not be final");
                        }
                        if (modifiers.contains(PUBLIC)) {
                            throw new ElementException(field, "Successor field must not be public");
                        }
                    }

                } else {
                    if (isAssignableWithErasure(field, Node) && !field.getSimpleName().contentEquals("Null")) {

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Remove final from the NodeSuccessorList field.
2. Initialize the list in the constructor (new NodeSuccessorList<>(this, ...)).
3. Keep visibility protected or package-private.
4. Rebuild to confirm.

Example fix

// before
@Successor
protected final NodeSuccessorList<FixedNode> nexts;

// after
@Successor
protected NodeSuccessorList<FixedNode> nexts;

When it happens

Trigger: modifiers.contains(FINAL) on a @Successor field whose erased type is assignable to NodeSuccessorList (GraphNodeVerifier.java:146-148). Example: '@Successor protected final NodeSuccessor<FixedNode> successors;'.

Common situations: New control-flow nodes (FixedWithNext successors, branching nodes) written with immutable-field style; applying 'effectively final' refactors; porting node code between Graal versions.

Related errors

• Successor list field must not be public
• Successor field must be a Node type
• Successor field must not be final
• Successor field must not be public
• NodeSuccessorList field must be annotated with @${Successor.

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/78dfe0ecd15410f4. Report an issue: GitHub.