Syntax ideas for `ref` returning delegate and FP parameters

[user1234]

On Saturday, 10 April 2021 at 14:27:31 UTC, Q. Schroll wrote:
> Currently in D, one cannot directly express that a function 
> parameter's type is a delegate or function pointer that returns 
> by `ref`. If you write
> ```D
> void f(ref int delegate() dg) { .. }
> ```
> then `dg` will be bound by reference which is probably not what 
> the user likely intended. It is equivalent to:
> ```D
> alias DG = int delegate();
> void f(ref DG dg) { .. }
> ```

Slightly off topic but very curiously `auto ref` seems to have 
for effect to set the function pointer type return as `ref` 
rather than the parameter itself

```d
void f(DG/* = int function()*/)(auto ref DG dg) {
     dg()++;
}

ref int a() {
     static int b;
     return b;
}

void main() {
     f(&a);
     assert(a == 1); // passes
}
```

a bug certainly.