Using a collection builder with ImmutableSortedSet

[jonfreedman]

I want to have a class similar to the below but ImmutableSortedSet.Builder throws an exception from it's factory method. Is this possible?

public abstract static class Builder {
    private static Builder builder() {
        return new AutoValue_Object.Builder();
    }

    abstract ImmutableSortedSet.Builder<ComparableObject> pointsBuilder();

    public abstract Builder setPoints(final ImmutableList<ComparableObject> points);

    public Builder addPoint(final ComparableObject point) {
        pointsBuilder().add(point);
        return this;
    }
    
    public abstract Object build();
}

[jonfreedman]

I had a quick look into what's going on, I would say that ImmutableSortedSetDeserializer in jackson-datatype-guava sets president for using ImmutableSortedSet.naturalOrder() instead of ImmutableSortedSet.builder()

[eamonnmcmanus]

It's a fair point. ImmutableSortedSet.builder() throws UnsupportedOperationException because its signature would ideally be the same as ImmutableSortedSet.naturalOrder(), i.e. static <E extends Comparable<?>> Builder<E> builder(). But that's not possible because it conflicts with the signature in the ancestor class ImmutableSet, which is static <E> Builder<E> builder(). I think throwing an exception is kind of obnoxious but that's how it is (and has been since 2009).

We could recognize naturalOrder() for ImmutableSortedSet and ImmutableSortedMap. If the element type is not actually Comparable then this would provoke a surprising error in the generated code, unless AutoValue makes the Comparable check itself.

[jonfreedman]

I think the alternative would involve being able to define the factory method somehow with an annotation?