(note: offshoot of #5045)

Method:

    public PotentialCreator findPreferredCreator(MapperConfig<?> config,
            AnnotatedClass valueClass,
            List<PotentialCreator> declaredConstructors,
            List<PotentialCreator> declaredFactories) {

does not pass so-called "default constructor -- zero-parameter Constructor -- in declaredConstructors. Although it'd be possible to change things to add it there, compatibility concerns suggests it's better to pass one more parameter, like:

Optional<PotentialCreator> zeroParamsConstructor

esp. since change can only be made in 3.0, so difference from 2.x more clearly indicates difference in passed information.