Probably one of the few places where inheritance would really make sense: Have one subclass for trees (documents and elements) and one for leafs (the rest). This would replace all the node type conditionals with polymorphism and also make smaller instances on static targets (even if fields are null, they still take 8 bytes each).

Sure, inheritance or enum could make sense. Would have to benchmark to see the impact. This small change has a good performance impact without any API changes though.

Surely this should use a switch instead.

@Simn for what specifically? It's two overlapping conditions...

Does this have an effect on the null safety invariants of this class?

Does this have an effect on the null safety invariants of this class?

Sorry, what?

The children field is typed as Array<Xml>, not Null<Array<Xml>> which it maybe should be now since it can be null. (it's also curious that this didn't trigger an error in CI)

I was wondering if making it null instead of [] can break some methods that assume a non-null array, however, looking into it, it appears there are appropriate ensureElementType checks already which should make sure an exception is thrown instead of a null-access error.

Haxe std is only trying to be null-safe as external interface right now, not by implementation. Marking type as nullable should be correct change (since this is also public field)