Even after closing bug #49003, there remain problems regarding the handling of N3282 (resolution of DR 1207). Specifically, the problems have to do with a definition of a member function outside of the class.

Consider these test cases:

int& ref(int& x) { return x; }
const int& ref(const int& x) { return x; }

class A {
	int x;
	int f() const;
	auto test1() const -> decltype(this);
	auto test2() const -> decltype(ref(x));
	auto test3() const -> decltype(f());
};

auto A::test1() const -> decltype(this) {
	return this;
}

auto A::test2() const -> decltype(ref(x)) {
	return ref(x);
}

auto A::test3() const -> decltype(f()) {
	return f();
}

This gives the following compiler errors in the C++0x mode of gcc 4.7.1:

- test1(): invalid use of 'this' at top level
- test2(): prototype for 'int& A::test2() const' does not match any in class 'A' (candidate is: const int& A::test2() const); additionally, 'int A::x' is private
- test3(): cannot call member function 'int A::f() const' without object; additionally, 'int A::f() const' is private

In summary, in the trailing return type of a const member function definition outside of a class declaration, it seems:
1. I cannot explicitly reference 'this'
2. I can reference data members, but not private ones, and they are not const
3. I cannot invoke member functions

I believe all three function definitions should compile. Similarly, inline definitions of the same member functions have no such problems:

class B {
	int x;
	int f() const;
	auto test1() const -> decltype(this) { return this; }
	auto test2() const -> decltype(ref(x)) { return ref(x); }
	auto test3() const -> decltype(f()) { return f(); }
};

It seems that issue #2 is a regression compared to gcc 4.6, which seemed to allow some access to data members. Consider test4():

template<typename X>
class C {
	const X& x;
	auto test4() const -> decltype(x);
};

template<typename X>
auto C<X>::test4() const -> decltype(x) {
	return x;
}

This test compiles without problems under gcc 4.6.3. Whereas gcc 4.7.1 gives:

prototype for 'decltype (((C<X>*)0)->C<X>::x) C<X>::test4() const' does not match any in class 'C<X>' (candidate is: decltype (((const C<X>*)this)->C<X>::x) C<X>::test4() const)