id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
13120	optional o<size_t>.  x<(size_t)0 is different to x<0	harris.pc@…	Fernando Cacciola	"This is a very subtle but key bug.
Comparing slightly different types changes the way the comparison is done.

{{{
#include <boost/optional.hpp>
#include <cassert>

int main()
{
   boost::optional<size_t> x;
   assert((x < (size_t)0) == (x < 0));
   return 0;
}
}}}

result:
{{{
$ g++ -g -I boost_1_64_0/ -o test_optional-d test_optional.cpp
$ ./test_optional-d
$ test_optional.cpp:7: int main(): Assertion `(x < (size_t)0) == (x < 0)' failed.
}}}

I am scared to think what this might affect in my code...

---

I would actually prefer to turn off the implicit cast in operator<(),
and only allow : optional<T> < optional<T>

I'd rather it throw a compile error and instead force me to do something like
if (x && *x < 0)

Because I do not always thing 'none' should be 'less than' anything.  It should not be comparable.
"	Bugs	new	To Be Determined	optional	Boost 1.64.0	Showstopper