oracle/graal · error · IllegalArgumentException

Element of type is not assignable to

Error message

Element  of type  is not assignable to 

What it means

Error "Element of type is not assignable to " thrown in oracle/graal.

Source

Thrown at espresso-compiler-stub/src/com.oracle.truffle.espresso.vmaccess/src/com/oracle/truffle/espresso/vmaccess/EspressoExternalVMAccess.java:660

            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.
             */
            if (element instanceof EspressoExternalObjectConstant objectConstant && !componentType.isAssignableFrom(objectConstant.getType())) {
                throw new IllegalArgumentException("Element " + element + " of type " + objectConstant.getType() + " is not assignable to " + componentType, e);
            }
            // Unrelated exception, just rethrow it.
            throw e;
        }
    }

    @Override
    public ResolvedJavaMethod asResolvedJavaMethod(Constant constant) {
        if (constant instanceof EspressoExternalObjectConstant espressoConstant) {
            // j.l.r.Executable?
            Value value = espressoConstant.getValue();
            String name = value.getMetaObject().getMetaQualifiedName();
            if ("java.lang.reflect.Method".equals(name) || "java.lang.reflect.Constructor".equals(name)) {
                return EspressoExternalConstantReflectionProvider.methodAsJavaResolvedMethod(value, this);
            }
        }
        return null;
    }

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Fix the condition reported by the error: Element of type is not assignable to
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  of type  is not assignable to

When it happens

Trigger: Thrown at espresso-compiler-stub/src/com.oracle.truffle.espresso.vmaccess/src/com/oracle/truffle/espresso/vmaccess/EspressoExternalVMAccess.java:660 when the library encounters an invalid state.

Common situations: Occurs when a caller violates the contract guarded by this check: Element of type is not assignable to

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/cbe0af2da930688d. Report an issue: GitHub.