oracle/graal · error · IllegalArgumentException

The provided argument is a method variant name: %s

Error message

The provided argument is a method variant name: %s

What it means

Method's constructor rejects any methodName containing the method variant key separator '%%' (StableMethodNameFormatter.METHOD_VARIANT_KEY_SEPARATOR). Method objects must hold plain method names; names carrying a variant key are only valid input to splitMethodVariantName/removeMethodVariantKey. It is an IllegalArgumentException, i.e. a programmer/contract error, not bad input data.

Source

Thrown at compiler/src/org.graalvm.profdiff/src/org/graalvm/profdiff/core/Method.java:78

    /**
     * The list of Graal compilations of this method.
     */
    private final List<CompilationUnit> compilationUnits;

    /**
     * The sum of execution periods of the individual compilation units.
     */
    private long totalPeriod;

    /**
     * Constructs a method.
     *
     * @param methodName the name of the method
     * @param experiment the experiment to which the method belongs
     */
    public Method(String methodName, Experiment experiment) {
        if (methodName.contains(StableMethodNameFormatter.METHOD_VARIANT_KEY_SEPARATOR)) {
            throw new IllegalArgumentException("The provided argument is a method variant name: " + methodName);
        }
        compilationUnits = new ArrayList<>();
        this.methodName = methodName;
        this.experiment = experiment;
        totalPeriod = 0;
    }

    /**
     * Gets the experiment to which this compilation unit belongs.
     */
    public Experiment getExperiment() {
        return experiment;
    }

    /**
     * Gets the full signature of the root method of this compilation unit including parameter types
     * as reported in the optimization log.
     *

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Normalize the name before construction: Method.removeMethodVariantKey(name) or Method.splitMethodVariantName(name).
2. If you intended to key by variant, keep the variant name as a map key and construct Method with only the base name.
3. Add a unit test asserting Method is never constructed from names containing '%%'.

Example fix

// before
Method m = new Method(rawName, experiment); // rawName = "java.util.List%%v0.add(int)"
// after
Method m = new Method(Method.removeMethodVariantKey(rawName), experiment);

if (name.contains(StableMethodNameFormatter.METHOD_VARIANT_KEY_SEPARATOR)) {
    name = Method.removeMethodVariantKey(name);
}
Method m = new Method(name, experiment);

static boolean isPlainMethodName(String name) {
    return name != null && !name.contains("%%");
}

try {
    new Method(name, experiment);
} catch (IllegalArgumentException e) {
    if (e.getMessage().contains("method variant name")) { name = Method.removeMethodVariantKey(name); }
}

When it happens

Trigger: Calling 'new Method(name, experiment)' where name came straight from an optimization log position that still contains a variant key like 'java.lang.String%%variant0(int)'. The fix is to strip the key first with Method.removeMethodVariantKey or Method.splitMethodVariantName.

Common situations: New parsing code that feeds raw optimization-log method names into Method; logs produced by GraalVM versions that emit variant keys (duplicate inlined shapes of the same method) hitting older/naive call sites.

Related errors

• Malformed method variant name: %s
• classForNode method shall return node class representation r
• Cannot compare {JavaLangRuntimeVersion.__name__} to {type(ot
• Out of scratch registers: %s
• Should be recognized as signature:

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/a40ec4cc51095879. Report an issue: GitHub.