public ThrowForInvalidImmutableState getThrowForInvalidImmutableState() {
    if (throwForInvalidImmutableState == null) {
      throwForInvalidImmutableState = ThrowForInvalidImmutableState.from(
          constitution.protoclass().processing(),
          style());
    }
    return throwForInvalidImmutableState;
  }
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