Using "this->" to differentiate variable names inside constructors

Question

I recall I used to be able to do this and have it work as intended:

class foobar
{
public:
    foobar(int x, int y)
    {
        x = x; //the variables x, y belonging to the class got correctly initialized
        y = y;
    }

private:
    int x, y;
};

The above worked in circa 200x on Microsoft Visual C++ 6.0 and some later versions, I believe.
But now I have to do this on Microsoft Studio 2013 and I have to use this->, as such:

class foobar
{
public:
    foobar(int x, int y)
    {
        this->x = x; //the other way no longer initializes class vars
        this->y = y;
    }

private:
    int x, y;
};

Was there a language spec change or Microsoft compiler change?

Answer 1

Perhaps you are thinking instead of initializer list syntax, which would be unambiguous and should work correctly on any (non-buggy) C++ compiler:

foobar(int x, int y) : x(x), y(y) { }

In this case, the x and y before the parens are unambiguously data members, because that's the only thing that can go there (besides constructors for parent types). Inside the parens, the x and y refer to the constructor arguments that shadow the data members.

I can't think of any circumstance under which x = x; would do anything other than no-op self-assignment (buggy user-defined assignment operator overloads aside). If this worked in a prior VC++ version then it would have been a VC++ compiler bug. More likely, you used to use initializer list syntax (which does work) and forgot that's what you did.