vcat(Ones(∞),1) is not handled

[putianyi889]

Currently this will cause memory overflow.

[dlfivefifty]

I don’t think that should work

[putianyi889]

That should throw an error.

[jishnub]

In #128, I had implemented

julia> vcat(1:∞,1)
1:∞

but perhaps this should be removed?