What is that "enum function" supposed to be ?

[Paul Backus]

On Thursday, 22 July 2021 at 13:32:48 UTC, Elmar wrote:
> On Monday, 19 July 2021 at 21:16:57 UTC, Elmar wrote:
>>  ...
>
> Btw does anybody know why "`enum` functions" only work with 
> `inout` but not `const` or `immutable` ?

By accident, I assume. Nobody really writes "`enum` functions" so 
these code paths in the compiler are not well-tested.