first draft Reducing the legal permutations of ref-return-scope

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On Tuesday, 13 May 2025 at 18:57:21 UTC, Walter Bright wrote:
> The implicit `this` declaration is another source of confusion. 
> I've been toying with the idea of allowing it to be part of the 
> parameter list.

That is a great idea; I've wanted it in D for a long time. We 
could even extend it so a hypothetical "explicit this" syntax 
applies to free functions as well, and enables UFCS, although 
that's probably too much of a breaking change.