Introducing Nullable Reference Types in C#. Is there hope for D, too?

[Walter Bright]

On 11/16/2017 5:47 PM, Michael V. Franklin wrote:
> the lack of any warning or error for this trivial case surprised me.

Consider the following code:

   void test() {
     int* p;
     *p = 3;
   }

Compiling it with -O gives:

   Error: null dereference in function _D5test54testFNaZv

The -O is necessary because the optimizer uses data flow analysis, which makes 
the error easy to pick up.

Note that if the code were written:

   void test(int i) {
     int* p;
     if (i) p = &i;
     *p = 3;
   }

no error is diagnosed. Data flow analysis determines all paths, and some of 
those paths may (legitimately) never happen, and so giving an error would be 
spurious.