public boolean isUseCompactBuilder() {
    return !kind().isFactory()
        && !isUseStrictBuilder()
        && !isGenerateBuildOrThrow()
        && !isGenerateBuilderToString()
        && !getThrowForInvalidImmutableState().isCustom;
  }
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