oracle/graal · error · IllegalArgumentException

Expected a non-void primitive kind, got {}

Error message

Expected a non-void primitive kind, got {}

What it means

Thrown by HostVMAccess.createPrimitiveArray when the requested JavaKind is null, not primitive, or Void. Array creation needs a concrete primitive class (kind.toJavaClass()), so reference kinds and void are rejected up front.

Source

Thrown at compiler/src/jdk.graal.compiler.hostvmaccess/src/jdk/graal/compiler/hostvmaccess/HostVMAccess.java:294

        Class<?> componentClass = snippetReflection.originalClass(componentType);
        if (componentClass == null) {
            throw new IllegalArgumentException("Could not obtain the original class for " + componentType);
        }
        Object array = Array.newInstance(componentClass, elements.length);
        for (int i = 0; i < elements.length; i++) {
            doWriteArrayElement(array, componentType, i, elements[i]);
        }
        return snippetReflection.forObject(array);
    }

    /**
     * Host mode materializes the primitive array with reflection and then wraps it as a
     * {@link JavaConstant} through {@link SnippetReflectionProvider#forObject(Object)}.
     */
    @Override
    public JavaConstant createPrimitiveArray(JavaKind kind, int length) {
        if (kind == null || !kind.isPrimitive() || kind == JavaKind.Void) {
            throw new IllegalArgumentException("Expected a non-void primitive kind, got " + kind);
        }
        Object array = Array.newInstance(kind.toJavaClass(), length);
        return providers.getSnippetReflection().forObject(array);
    }

    @Override
    public JavaConstant clonePrimitiveArray(JavaConstant primitiveArray) {
        ResolvedJavaType arrayType = getProviders().getMetaAccess().lookupJavaType(primitiveArray);
        if (arrayType == null || !arrayType.isArray() || !arrayType.getComponentType().isPrimitive()) {
            throw new IllegalArgumentException("Expected a primitive array constant, got " + primitiveArray);
        }
        Object source = providers.getSnippetReflection().asObject(Object.class, primitiveArray);
        if (source == null) {
            throw new IllegalArgumentException("Could not unwrap a primitive array constant: " + primitiveArray);
        }
        /*
         * Keep cloning explicit by primitive array kind. This avoids reflective clone access and
         * preserves exact array runtime type through each typed clone() call.

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Pass one of the eight primitive kinds (Boolean, Byte, Short, Char, Int, Long, Float, Double)
2. Branch on kind.isPrimitive() && kind != JavaKind.Void before calling
3. Map 'no value' to skipping the call rather than passing Void

Example fix

// before
hostVM.createPrimitiveArray(kindFromSignature, n);  // Object kind -> throws

// after
if (kindFromSignature != null && kindFromSignature.isPrimitive() && kindFromSignature != JavaKind.Void) {
    hostVM.createPrimitiveArray(kindFromSignature, n);
}

if (kind == null || !kind.isPrimitive() || kind == JavaKind.Void) {
    throw new IllegalArgumentException("need a primitive kind, got " + kind);

static boolean isNonVoidPrimitive(JavaKind k) { return k != null && k.isPrimitive() && k != JavaKind.Void; }

catch (IllegalArgumentException e) { pick the correct kind from the value/signature and retry }

When it happens

Trigger: Calling createPrimitiveArray(kind, length) with kind == null, an object kind like JavaKind.Object/Illegal, or JavaKind.Void; length is not validated here (negative length surfaces later as NegativeArraySizeException from Array.newInstance).

Common situations: Forwarding a kind obtained from a value or signature without checking isPrimitive(); using JavaKind.Void as a placeholder for 'no value' in generic constant-building code; defaulting a kind variable to null on an unhandled branch.

Related errors

• Expected an array constant for src, got {}
• Expected an array constant for dest, got {}
• Could not obtain the original class for {}
• Expected a primitive array constant, got {}
• Could not unwrap a primitive array constant: {}

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/f645c4e8fed110cc. Report an issue: GitHub.