It sucks versus Foo() { if(...) throw whatever; }. It needs more code (check for constructed() every time, and if you forget to checking it you've introduced a

It sucks versus Foo() { if(...) throw whatever; }. It needs more code (check for constructed() every time, and if you forget to checking it you've introduced a bug), and is less performant (since you will have one additional branch in the "if(constructed())" mandatory check.