There are numerous places in JVMCI where raw arrays are returned (e.g. ResolvedJavaType.getInstanceFields) where the expected is expected to treat them as immutable. Unfortunately, this cannot be enforced. Instead, immutable List objects should be returned.

This will be a significantly breaking JVMCI API change and so should only be done once the Graal code base has migrated to only supporting one JDK version.