Disallow null references in safe code?

[Adam D. Ruppe]

On Tuesday, 4 February 2014 at 14:34:49 UTC, Idan Arye wrote:
> Probably because `Nullable!` suggests that's it's a library 
> solution - and it isn't.

It should be. The way I'd do it is

Object o; // not null
@nullable Object o; // like we have today

BUT, user code would never use that. Instead, we'd have:

struct Nullable(T) if(__traits(compiles, (@nullable T) {}) {
    @nullable T;
}

// and a corresponding one so stuff like Nullable!int works


This gives us:

* Implementation help - no binary cost for Nullable!Object since 
it just uses null directly instead of a bool isNull field (the 
optimizer also knows this)

* Consistency with all other types. Nullable!int works, 
Nullable!Object can be passed to a template, inspected, etc. 
without new traits for isNullable and everything.

* Library functionality so we can also make other types that do 
the same kind of thing


Then, if we did the Type? syntax, it would just be rewritten into 
Nullable!Type. Nullable's definition would probably be in the 
auto-imported object.d so it always works.