Kevlin Henney <kevlin@curbralan.com> writes:
I have yet to see a convincing reason to make it explicit. Autoboxing has been a part of boost::any's design from day 1, which existed before Boost -- and, indeed, the "autoboxing" terminology. Supporting such conversions was intentional. There is no more reason to make the converting constructor of boost::any explicit than there is to make the converting constructor of std::string explicit, or the conversion from int to long explicit, or the conversion from T * to void *, or indeed any other widening conversion.
The conversion to boost::any isn't a widening conversion in the usual sense, though, is it? Normally, a widening conversion preserves not only the information but the *interface* of the original data -- you wouldn't consider an implicit conversion from int to string a widening conversion, would you? Similar to boost::any, you *can* go through a set of gyrations to extract the integer -- I bet that if boost::any could preserve the interface of the boxed type, Vladimir's bug wouldn't have come up. -- Dave Abrahams Boost Consulting www.boost-consulting.com