Developing a plan for D2.0: Getting everything on the table

[bearophile]

Lutger:
>Can't nullable / non-nullable be done in library?<

Yes, of course, people in the Scheme language have shown that you can do almost everything in library code. But to do that you need (beside fixing D library code, because the default now becomes non-null object references) a "pluggable type system", that is you must be able to plug-in a new piece of type system.

You can do that with a meta (programmable) type-system like Haskell one, or with some kind of true plug-in (think about the "neutral" function/argument type annotations of Python3, that are a simple example of machinery that can be used to plug-in a library defined type system).
I don't see both such things to be added to D2 anytime soon because they are complex, quite more complex than nonnullable object references.

So I'm looking for just the ""small"" change in the type system plus the short leading "?" syntax.

If D developers aren't interested in such thing, then a DEP can be written and then marked as officially refused, to avoid wasting future time discussing about this idea (this is another quite important purpose of Python PEPs, to mark ideas as refused and avoid discussing something hopeless over and over again).

Bye,
bearophile