Implicit cast to bool of basic_istream/ifstream/ofstream doesn't work in Visual Studio 2013

Question

The code below compiles in VS 2012 but not in VS 2013

std::ofstream stm;
if(stm != NULL)
{
}

In VS 2013 you get this compilation error:

Answer 1

The operator is defined in section 27.5.5 Class template basic_ios.

27.5.5.1 Overview

explicit operator bool() const;

And then

27.5.5.4 basic_ios flags functions

explicit operator bool() const;

Returns: !fail().