How does D handle null pointers?

[bearophile]

Adam Ruppe:

> The way I solved it was to sprinkle
> assert( var !is null );
> before I start using or storing the thing, and in the contracts to the
> functions.

Yes, contracts reduce this problem a lot. Recently here I have shown a paper about this topic.

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Jonathan M Davis:

>There are quite a few people who want Walter to put in null checks in at least debug mode, but he's against it and no one has been able to convince him.<

I think that Walter is right here, adding tons of null checks in debug mode helps a bit (stack traces are good), but it's just a rough patch on the problem, but it's not a good solution of it.

In my opinion a better solution to this problem is to:
1) Introduce nonnullable pointers/references, to denote them I have proposed a leading @.
2) Require explicit tests every time a nullable pointers/references is about to be deferenced (and then after this test in the else branch the reference type "becomes" a nonnullable one. This is an application of the idea of "TypeState", used by the Mozilla Rust language. The type doesn't actually change, it's just its state that changes...).

Bye,
bearophile