To bring a different angle, the best front-end for arithmetic operations
that may overflow is:
typeof(lhs + rhs) add(L, R)(const L lhs, const R rhs, ref bool overflow)
if (isIntegral!L && isIntegral!R);
The overflow bit is set if and only if the mathematical result is not
the same as the concrete result. Interestingly, things like add(5u, -1)
should succeed without overflow (returning 4u) even though the negative
value is conceptually converted to a large positive number and the
operation overflows. (I've implemented this behavior in the DbI checkedint.)
One point that escaped me initially is that sometimes there's no need
for any checks, e.g. adding any two types smaller than int doesn't need
to be checked.
I'm not sure whether this function belongs in core.checkedint, but
that's the right front end design for the primitives in there.
Andrei
