NotNull pointers

[bearophile]

Walter:

>   I've implemented the ability to disable default initialization. This makes it 
> practical to implement a library based "NotNull" type without a special syntax 
> for it. The rationale for this is (rather than making it builtin)

If it works well enough, a syntax is allowed to come later, as it's happening with tuple unpacking now (dmd pull 341).

I have tried the feature, but what's the way to use it?


import core.stdc.stdio;

struct NotNull(P) if (__traits(compiles, {P p = null;})) {
     private P p;

     this() @disable;

     this(P q) {
         assert(q);
         p = q;
     }

     NotNull opAssign(P q) {
         assert(q);
         p = q;
         return this;
     }

     @property P get() {
         return p;
     }

     alias get this; // force rvalue access
}

struct Foo { int x; }

alias NotNull!(Foo*) NFooP;

void bar(NFooP foop) { // Error: variable test2.bar.foop initializer required for type NotNull!(Foo*)
    printf("d\n", foop.x);
}

void main() {
    NFooP p = new Foo;
    bar(p);
}


Bye,
bearophile