[Bug c++/59294] New: template friend declaration 'hidden' by member of same name

[stefan.schwarzer at ipm dot fraunhofer.de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59294

            Bug ID: 59294
           Summary: template friend declaration 'hidden' by member of same
                    name
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: stefan.schwarzer at ipm dot fraunhofer.de

/* Dear experts,

   I would like to use the same identifier for a member function and 
   a friend function of similar signature. Either declaring the friend 
   or the member works fine, but if both (#ifdef PROBLEM true) are present, 
   g++ starts yelling at me:
*/

template <class T> class Q;

template <class T> 
const Q<T> conjugate(const Q<T> &);

template<class T>
struct Q {

#define PROBLEM
#ifdef PROBLEM
        const Q conjugate() { return *this; }
#endif 

        friend const Q<T> conjugate<T>(const Q<T> &); // PROBLEM
        // friend const Q conjugate<T>(const Q &); // -- equivalent
        // friend const Q conjugate<>(const Q &);  // -- equivalent
};

template <class T> 
const Q<T> conjugate(const Q<T> &) { return Q<T>(); }

int main () {
        Q<int> q;
#ifdef PROBLEM 
        q.conjugate();
#endif
        conjugate(q);
        return 0;
}

/*
$ g++ t.cc
t.cc:17:20: error: ‘conjugate’ is neither function nor member function; cannot
be declared friend
  friend const Q<T> conjugate<T>(const Q<T> &);
                    ^
t.cc:17:20: error: expected ‘;’ at end of member declaration
t.cc:17:29: error: expected unqualified-id before ‘<’ token
  friend const Q<T> conjugate<T>(const Q<T> &);

  Nothing I tried really helps:
  - the existence or not of the forward declaration does not help
  - my three feeble attempts of syntax variation (in comments) behave
equivalently
  - using a qualified-id ::conjugate in the friend declaration only changes the 
    error message

  Am I missing something basic or is this a compiler bug?

(debian testing)
$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.8/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.8.2-1'
--with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.8 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin
--with-system-zlib --disable-browser-plugin --enable-java-awt=gtk
--enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/jre
--enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --with-arch-32=i586 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --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 4.8.2 (Debian 4.8.2-1)  

*/