Understanding DIP 1000 semantics -- Where's the bug?

[Olivier FAURE]

On Tuesday, 24 September 2019 at 13:35:04 UTC, ag0aep6g wrote:
>
> When using a pointer instead of `ref`, the code is rejected as 
> expected even with the more complex body:
>
> ----
> @safe:
>
> int* foo(int* x)
> {
>     int* a = x;
>     return x;
> }
>
> void main() {
>     int* p;
>     {
>         int x;
>         p = foo(&x); /* error here */
>     }
> }
> ----

That's a bad comparison. Refs aren't equivalent to unqualified 
pointers, they're equivalent to a scope pointers. By the way, 
with the following code:

     @safe:

     int* foo(scope int* x)
     {
         int* a = x;
         return a;              // Compile error: scope variable 
*a* may not be returned
     }

     void main() {
         int* p;
         {
             int x;
             p = foo(&x);
         }
         *p = 1;			// Memory corruption
     }

the compiler correctly identifies that the problem isn't 
"foo(&x)", but "return a", and gives an appropriate error message.

So the problem isn't a lack of flow analysis or wrong ref 
semantics, it's that ref isn't implemented the same way as scope.

(Anyone feel like submitting a bug report? I don't have an 
account)