DIP1000: Walter's proposal to resolve ambiguity of ref-return-scope parameters

[Nick Treleaven]

On Saturday, 27 November 2021 at 03:41:05 UTC, Paul Backus wrote:
> For example, here's a really common error that beginning D 
> programmers make:
>
> ```d
> struct S
> {
>     private int[] a;
>     const int[] getArray() const { return a; }
> }
> ```
...
> With an explicit `this` parameter, there is no room for 
> ambiguity:
>
> ```d
>     const int[] getArray(const ref this) { return a; }
> ```
>
> The outer `const` can only apply to the return value, and the 
> inner `const` can only apply to the `this` reference.

Explicit `this` parameter is OK but more verbose. It also could 
be confusing for learners if declaring the `this` parameter is 
not required for methods with no `this` attributes. And if it is 
required, would that break existing code? I suppose there could 
be a rule that all methods of a type must follow the same 
convention.

Another solution is to require attributes that apply to `this` to 
go after the parameters, not before. That would be less verbose, 
but may break code and so would need a long deprecation cycle. 
(This was first suggested some years ago).