I have run into a strange situation where my derived class is able to access a private member of its base class where templates are involved.
Consider this example:
class A
{
template<typename T>
struct a { using type = a; };
};
class B : A
{
template<typename T>
using type = typename a<T>::type;
};
int main(){ }
COMPILATION RESULTS:
mingw64/mingw-w64-x86_64-clang 3.9.1-3 (from MSYS2)
$ clang++ -Wall test.cpp -o test.exe -std=c++14
mingw64/mingw-w64-x86_64-gcc 6.3.0-2 (from MSYS2)
$ g++ -Wall test.cpp -o test.exe -std=c++14
Both compilers accept without error! Additionally, if you simply move B::type into something like B::b::type clang suddenly recognizes it shouldn't be accessing a private member, while g++ compiles without a problem:
class A
{
template<typename T>
struct a { using type = a; };
};
class B : A
{
template<typename T>
struct b { using type = typename a<T>::type; };
};
int main(){ }
COMPILATION RESULTS
mingw64/mingw-w64-x86_64-clang 3.9.1-3 (from MSYS2)
$ clang++ -Wall test.cpp -o test.exe -std=c++14
test.cpp:10:39: error: 'a' is a private member of 'A'
struct b { using type = typename a<T>::type; };
^
test.cpp:4:13: note: implicitly declared private here
struct a { using type = a; };
^
1 error generated.
mingw64/mingw-w64-x86_64-gcc 6.3.0-2 (from MSYS2)
$ g++ -Wall test.cpp -o test.exe -std=c++14
My question is, what is causing this behavior where a derived class sometimes has access to its base class' members, and sometimes does not, and is this expected behavior?
