public Set<String> getImmutableCopyOfRoutines() {
    Set<String> routines = new LinkedHashSet<>(style().immutableCopyOfRoutinesNames());
    for (ValueType v : nested) {
      routines.addAll(v.style().immutableCopyOfRoutinesNames());
    }
    return routines;
  }
Means object hashcode is cached at some point. Either lazily (on first access)
or eagerly (during construction).
@see #isUseLazyhash()
@see #isUsePrehashed()
value-processor/src/org/immutables/value/processor/meta/ValueType.java