This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 115e. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
2024-11-11
[Moved to DR at the May, 2015 meeting.]
The note in 13.8.3.2 [temp.dep.type] paragraph 7 reads,
[Note: the result of name lookup differs only when the member of the current instantiation was found in a non-dependent base class of the current instantiation and a member with the same name is also introduced by the substitution for a dependent base class of the current instantiation. —end note]
However, this is not correct. Consider the following example:
struct Y { int X; };
template<typename T>
struct A : Y {
enum B : int;
void f() { A::X; } // finds Y::X here!
};
template<typename T>
enum A<T>::B : int {
X // introduces member A::X into A<T>!
};
void g() { A<int> a; a.f(); }
A::X is a member of the current instantiation, so paragraph 7 requires it to be looked up again when instantiating and to give a diagnostic if the lookup differs from the lookup in the definition context. The note incorrectly indicates that this can only happen if the conflicting name was introduced by a dependent base class.
Proposed resolution (August, 2011) [SUPERSEDED]:
Change 13.8.3.2 [temp.dep.type] paragraph 7 as follows:
...If the result of this lookup differs from the result of name lookup in the template definition context, name lookup is ambiguous.
[Note: the result of name lookup differs only when the member of the current instantiation was found in a non-dependent base class of the current instantiation and a member with the same name is also introduced by the substitution for a dependent base class of the current instantiation. —end note][Example:struct A { int m; }; struct B { int m; }; template<typename T> struct C : A, T { int f() { return this->m; } // finds A::m in the template definition context }; int g(C<B> cb) { return cb.f(); // error: finds both A::m and B::m in the template instantiation context }—end example]
Notes from the December, 2011 teleconference:
Changes to the exposition were suggested and the issue returned to "drafting" status.
Proposed resolution (November, 2014):
Change 13.8.3.2 [temp.dep.type] paragraph 7 as follows:
...If the result of this lookup differs from the result of name lookup in the template definition context, name lookup is ambiguous.
[Note: the result of name lookup differs only when the member of the current instantiation was found in a non-dependent base class of the current instantiation and a member with the same name is also introduced by the substitution for a dependent base class of the current instantiation. —end note][Example:struct A { int m; }; struct B { int m; }; template<typename T> struct C : A, T { int f() { return this->m; } // finds A::m in the template definition context }; template int C<B>::f(); // error: finds both A::m and B::m—end example]