[Issue 19097] Extend Return Scope Semantics

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19097

--- Comment #12 from Mike Franklin <slavo5150 at yahoo.com> ---
I'm wondering if it might be possible to do something like this:

```  
void betty(ref scope int* r, return(r) scope int* p) 
{ 
    r = p;
}
```

`return(r)` explicitly ties p's lifetime to r's.  

So, the `return` attribute would take an argument specifying which "output"
parameter to tie the input lifetime to, and the semantics no longer rely on
convention or the order of arguments.

--