Why can't I give a function's return type the scope storage class?

[Meta]

On Saturday, 16 March 2019 at 17:59:41 UTC, Walter Bright wrote:
> On 3/15/2019 10:29 PM, Meta wrote:
>> Am I wrong in thinking that this is something one would want 
>> to do? It seems like it would be useful for the callee to 
>> enforce that its return value is assigned to a scope variable.
>
> Scope on function return values comes from the scope of any 
> arguments passed to the function marked as 'return scope'. 
> Scope on a function return with no such arguments is currently 
> meaningless in D.
>
> To add such a feature, there woul'd need to be compelling use 
> cases.

So to be clear, you *can* add scope to the return type of a 
function, and it will propagate the shortest lifetime among any 
parameters marked with `return` or `return scope` to the return 
value? I don't think this is mentioned anywhere in the docs, 
which is what confused me. I thought that scope on the return 
type was either a no-op, or that it applied to the function 
(despite being on the left-hand side). I *think* I can get the 
effect that I want, given that's how it works. I'll play around a 
bit and report back.

Also, I'd like to echo the request that you document this stuff. 
What's already there is fairly useful, but obviously it's not 
complete.