https://issues.dlang.org/show_bug.cgi?id=13599
--- Comment #3 from Walter Bright <bugzilla at digitalmars.com> ---
Workaround, in case it is blocking anyone:
(In reply to Walter Bright from comment #2)
> E R()
> {
> foreach ( U ; P )
> return U;
> assert(0);
return E(); // add this line
> }
> }
--