@Override
  protected TypeHierarchyCollector collectTypeHierarchy(final TypeMirror typeMirror) {
    this.hierarchiCollector = createTypeHierarchyCollector(report(), element);
    this.hierarchiCollector.collectFrom(typeMirror);
    return hierarchiCollector;
  }
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