[On a side note, if From must be different to To, why is this is not stated in the docs? There's even a case whith From=To in is_convertible_test.cpp:
BOOST_CHECK_INTEGRAL_CONSTANT( (::tt::is_convertible<Base,Base>::value), true);
end of side note.]
Um, because I overstated the case :-) They can be the same, it just doesn't tell you anything useful: either the result is true (T is copy-constructible) or the code doesn't compile.
So, if we exclude the case where From=To, is is_convertible supposed to work for the call pattern
is_convertible<const X,Y>
where X is non-copyable and Y!=X? From Alexei tests seems like this could be failing too, and does not fall under the forbidden From=To case. I don't have any compiler handy right now, will try to check out by myself in a few days.
No that should work just fine, indeed that was the test case attached to my last message. John.