[Issue 21109] Wrong result when using sort() on enum arrays

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21109

--- Comment #6 from Andrej Mitrovic <andrej.mitrovich at gmail.com> ---
(In reply to Boris Carvajal from comment #5)
> There is no 'opCmp' defined for the struct so the runtime just use a memcmp
> for the comparison.
> The code itself calls '__cmp' from core/internal/array/comparison.d (because
> the element are an array '[S(2, [0, 0])]') and there the 3 'static if'
> conditions fail but if you define 'opCmp' the second path is taken.
> 
> So the following works:
> 
> struct S
> {
>     int[] arr;
>     int opCmp(ref const S s) const { return arr < s.arr; }
> }
> 
> There is a comment on clone.d file that says:
> 
> "Essentially, a struct which does not define opCmp is not comparable."
> 
> This concise phrase should be on the spec.

Hmm.

In the past the compiler would also do memcmp when a struct didn't define
`opEquals`, but we changed it so it does member-by-member `==` comparison.

I wonder if we can do something similar for opCmp, or if that wouldn't make
sense..

--