[Bug c++/19288] New: No more possible to have a template function that uses a nested class of a template class

[jean-pierre dot chevallet at imag dot fr]

#include <iostream>

using namespace std;

template <typename T> class C1 {
public:
  T V;
  C1(T v) : V(v) {};
  
  class nested {
  public:
    T W;
    nested(T w) : W(w) {};
  };
  
};

// This works well

template <typename T>
T f1 ( C1<T>& c) { return c.V; }

// the problem is HERE

template <typename T>
T f2 ( typename C1<T>::nested& c) { return c.W; }

// This is correct with gcc 3.3.2 20031022
// This is incorrect with gcc 3.4.2 20041017
// This is incorrect with gcc 3.4.3 20041226
// This is incorrect with gcc4 4.0.0 20041228
// Error :
// nestedFriendTemplateFunction.cc:44: error: no matching function for call to
`f2(C1<float>::nested&)'
// Need EXPLICITE instantiation ==> GCC BUG !!!
// float f2 (C1<float>::nested& c) { return c.W; }


int main() {
  C1<int> c(123);
  cout<<f1(c)<<endl;
  
  C1<float>::nested n(3.5);
  cout<<n.W<<endl;
  cout<<f2(n)<<endl;  // CANNOT FIND THE CORRECT CODE FOR THIS
}


So, starting from version 3.4.2 it is no more possible to use a template
function that refers to a nested class of a template class.

g++ versions :
Reading specs from /usr/lib/gcc/i386-redhat-linux/3.4.3/specs
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix
--disable-checking --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-java-awt=gtk --host=i386-redhat-linux
Thread model: posix
gcc version 3.4.3 20041226 (Red Hat 3.4.3-11)

Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix
--enable-checking=release --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --with-gxx-include-dir=/usr/include/c++/3.4.3
--enable-languages=c,c++,java,f95 --enable-java-awt=gtk --host=i386-redhat-linux
Thread model: posix
gcc version 4.0.0 20041228 (Red Hat 4.0.0-0.17)

-- 
           Summary: No more possible to have a template function that uses a
                    nested class of a template class
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jean-pierre dot chevallet at imag dot fr
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i386-redhat-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19288