Modern C++ Won't Save Us

[Walter Bright]

On 4/27/2021 5:17 PM, Paul Backus wrote:
> On Tuesday, 27 April 2021 at 23:38:14 UTC, Walter Bright wrote:
>>
>> As always, when confused about this, rewrite the code in terms of simple ref's 
>> and pointers.
> 
> I think a large part of the confusion here stems from the fact that `scope ref 
> T` behaves very differently from `scope T*`, even though `ref T` and `T*` are 
> the same "under the hood."
> 
>     @safe:
>     static int* betty(scope ref S s) { return s.ptr; } // Error
>     static int* veronica(scope S* s) { return s.ptr; } // Ok
> 
> Unfortunately, there is no documentation of this distinction in the language 
> spec (or anywhere else, as far as I know), so the only way anyone can learn 
> about it is through trial and error.

`scope` is for pointers, `ref` is for references. That's the distinction.

`ref` never applies to pointers, `scope` never applies to references.

(A class reference is treated as a pointer.)