[Bug c++/84586] New: Incorrect acess checking with inheritance

[dllmain at yandex dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84586

            Bug ID: 84586
           Summary: Incorrect acess checking with inheritance
           Product: gcc
           Version: 6.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dllmain at yandex dot ru
  Target Milestone: ---

Created attachment 43516
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43516&action=edit
preprocessed source(in version which cause error)

Consider the code:

#include <tuple>
#ifdef USING_SIMPLE_BASE
        #define BASE base<T>
#else
        #ifdef USING_DIFFERENT_NAME
                #define NAME type_
        #else
                #define NAME type
        #endif
        #define BASE tuple_element_t<0,std::tuple<base<T>>>
#endif

//Simple trait for replacement of nested name
template<std::size_t I, typename T> struct tuple_element
        :private std::tuple_element<I,T>::type
{
        using NAME = typename std::tuple_element<I,T>::type;
};
template<std::size_t I, typename T>
using tuple_element_t = typename tuple_element<I,T>::NAME;

template<typename> struct base { protected: using type = int; };
template<typename T> struct derived :private BASE { using BASE::type; };
int main() { return derived<int>::type(0); }


It fails to compile until 'USING_SIMPLE_BASE' or 'USING_DIFFERENT_NAME' macros
would be defined:

$ g++ -xc++ -std=c++14 -pedantic-errors -DUSING_SIMPLE_BASE -o/dev/null
test.cxx
$ #build success
$ g++ -xc++ -std=c++14 -pedantic-errors -DUSING_DIFFERENT_NAME -o/dev/null
test.cxx
$ #build success
$ g++ -xc++ -std=c++14 -pedantic-errors -o/dev/null test.cxx
test.cxx: In function 'int main()':
test.cxx:27:35: error: 'using type = int' is protected within this context
 int main() { return derived<int>::type(0); }
                                   ^~~~
test.cxx:23:61: note: declared protected here
 template<typename> struct base { protected: using type = int; };
                                                             ^

In all cases 'derived' inherits 'base', so 'base::type' is available in context
of 'derived' class. Using declaration in public section of 'derived' do
'derived<>::type' available in global context. However, g++ not accepts all
variants of code.

$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/6/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 6.3.0-18+deb9u1'
--with-bugurl=file:///usr/share/doc/gcc-6/README.Bugs
--enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-6 --program-prefix=x86_64-linux-gnu- --enable-shared
--enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/
--enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie
--with-system-zlib --disable-browser-plugin --enable-java-awt=gtk
--enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-6-amd64/jre
--enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-6-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-6-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--with-target-system-zlib --enable-objc-gc=auto --enable-multiarch
--with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32
--enable-multilib --with-tune=generic --enable-checking=release
--build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 6.3.0 20170516 (Debian 6.3.0-18+deb9u1)

Also error is reproductable on g++ version 7.2.0(Ubuntu 7.2.0-1ubuntu1~16.04).
Clang 3.8 behaves similary