oracle/graal · error · IllegalArgumentException

Element should be a , got

Error message

Element  should be a , got 

What it means

Error "Element should be a , got " thrown in oracle/graal.

Source

Thrown at espresso-compiler-stub/src/com.oracle.truffle.espresso.vmaccess/src/com/oracle/truffle/espresso/vmaccess/EspressoExternalVMAccess.java:640

            }
            throw e;
        }
    }

    @Override
    public void writeArrayElement(JavaConstant array, int index, JavaConstant element) {
        if (!(array instanceof EspressoExternalObjectConstant espressoArray)) {
            throw new IllegalArgumentException("Expected an EspressoExternalObjectConstant, got " + safeGetClass(array));
        }
        EspressoResolvedObjectType arrayType = espressoArray.getType();
        if (!arrayType.isArray()) {
            throw new IllegalArgumentException("Expected an array type, got " + arrayType);
        }
        ResolvedJavaType componentType = arrayType.getComponentType();
        Object unwrappedValue;
        if (componentType.isPrimitive()) {
            if (componentType.getJavaKind() != element.getJavaKind()) {
                throw new IllegalArgumentException("Element " + element + " should be a " + componentType.getJavaKind() + ", got " + element.getJavaKind());
            }
            unwrappedValue = element.asBoxedPrimitive();
        } else if (element.isNull()) {
            unwrappedValue = null;
        } else {
            if (!(element instanceof EspressoExternalObjectConstant objectElement)) {
                throw new IllegalArgumentException("Element " + element + " should be an espresso object constant, got " + safeGetClass(element));
            }
            unwrappedValue = objectElement.getValue();
        }
        try {
            espressoArray.getValue().setArrayElement(index, unwrappedValue);
        } catch (ClassCastException e) {
            /*
             * This exception suggests that the element is not assignable to the component type of
             * the array, but let's double-check to make sure we do not re-interpret an unrelated
             * exception.
             */

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Fix the condition reported by the error: Element should be a , got
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: Element  should be a , got

When it happens

Trigger: Thrown at espresso-compiler-stub/src/com.oracle.truffle.espresso.vmaccess/src/com/oracle/truffle/espresso/vmaccess/EspressoExternalVMAccess.java:640 when the library encounters an invalid state.

Common situations: Occurs when a caller violates the contract guarded by this check: Element should be a , got

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/cf5eeb5f4b3ec243. Report an issue: GitHub.