dub test errors during linking for struct with uninstantiated templated opEquals

[Per Nordlöw]

On Sunday, 21 June 2020 at 17:05:11 UTC, kinke wrote:
> On Sunday, 21 June 2020 at 16:58:43 UTC, kinke wrote:
>> Your sample works with `-main -unittest` on run.dlang.io
>
> After quickly looking at your list of compiler flags in 
> dub.sdl, the problem manifests when adding `-preview=in`. 
> Please file an issue.

Thanks a lot! I'll do so.