JuliaLang/julia — comment on commit a6dc8c5470d4a9e3bef42f5a116a4241d0db6fa0
File: j/set.j line 45
By StefanKarpinski:

Well, we could do it by promotion, but that gives weird results too. The alternatives that seemed sensible to me were keeping the same type if they match or just going straight to `Any` if they don't.