DIP 1021--Argument Ownership and Function Calls--Community Review Round 1

[Walter Bright]

On 7/18/2019 7:59 PM, David Bennett wrote:
> For me it's unclear if the examples as given would become compile time errors 
> because it states "The checks would only be enforced for @safe code." and the 
> examples are not @safe.

Any container is going to wrap a call to free() in @trusted.


> Also, does it also check simple non-heap references, for example would this 
> become compile time error?
> 
> ---
> @safe void f(scope ref int a, scope ref int b)
> {
>       a=1;
>       assert(b==1);
> }
> @safe void main()
> {
>      int i = 0;
>      f(i, i);
>      assert(i==1);
> }
> ---

Yes, because you are passing two mutable references to the same memory.


> If it's going to be an error, a simple example like this in the Breaking Changes 
> and Deprecations section could help clear up whats changing from a practical sense.

Since the DIP disallows passing two mutable pointers to the same memory object, 
any code that does will break.