I read the referenced note

[http://caml.inria.fr/caml-list/0967.html]

and while I agree with most of what's said there, I think that putting
the "option" attribute onto a field would reduce its value.

Specifically, it is a highly common (albeit problematic) idiom in C,
C++, Java, and other languages, to program with a pointer to X, which
is perhaps null, and is only checked late, at the point when it is
destructured somehow.

That sort of idiom would not be possible to capture -- when we fetch
the value of an "option" field, we are implicitly asking for the field
to be checked for non-null-ness.

In other words, I think that "nullability" is a useful property of
types in general, and not merely of types of fields.

--chet--