Languages are definitely not consistent in what they do if you try to coerce null to various types, nor are they consistent (often even internally) about whethe

Languages are definitely not consistent in what they do if you try to coerce null to various types, nor are they consistent (often even internally) about whether they perform coercions implicitly. The Ruby example seemed to deal mostly with the latter. I think implicit coercion is bad, but that's a separate issue from null.