I imagine the warning is following the rules for explicit constructors/operators in C++: an if condition is considered an "explicit" call to an `operator bool`.

I imagine the warning is following the rules for explicit constructors/operators in C++: an if condition is considered an "explicit" call to an `operator bool`. http://en.cppreference.com/w/cpp/language/explicit http://en.cppreference.com/w/cpp/language/explicit