[flatline]

Yes, value types, thank you.

Agreed on the defaults, although you then have the problem of reconciling with the native JS type system. I'm unclear on what this PR does to address that for TS - in strict null check mode, can an e.g. Node be null by default? If so, does the native "Node" object then become "Node|null"? At some level this has to be addressed.

[spion]

There is no native type system.

Native objects can never be null. If its an object, it already isnt null. Functions，property accessors etc. can return Node or null or undefined, which can be modelled accordingly on a per-function basis