First Draft: ref For Variable Declarations

[Steven Schveighoffer]

On Monday, 15 April 2024 at 17:20:59 UTC, Dennis wrote:
> On Monday, 15 April 2024 at 16:24:51 UTC, Steven Schveighoffer 
> wrote:
>> This seems like an unnecessary restriction.
>
> It's necessary to prevent the creation of dangling stack 
> pointers, since a `ref` can be bound to a stack variable.

Yes, so you don't allow returning the ref in that case? It is 
trivial to know what a `ref` is bound to at compile time.

> When you fix foo's return type to be `ref int`, you get:
>
>> Error: returning `bar(x)` escapes a reference to parameter `x`

Yes, I forgot to update the message after I fixed the return type 
in my test, but it compiled for me. I forgot to add `@safe` as 
well, I always forget that when testing dip1000.

But also, returning `x` is disallowed in this case.

You also have to add `return` to the parameter, and then it 
compiles.

For reference, the edited code which compiles is:

```d
@safe ref int foo(return ref int x)
{
     // ref int y = x;
     // return y;
     // same as:
     ref int bar(ref int x2) {
         return x2;
     }
     return bar(x);
}
```

-Steve