[Bug c++/59151] New: gcc name lookup for friend template finds class outside of

[gafunchal at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59151

            Bug ID: 59151
           Summary: gcc name lookup for friend template finds class
                    outside of
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gafunchal at gmail dot com

template<typename T>
class Class1;

namespace B {
  template<typename U>
  class Class2 {
    template<typename V>
    friend class Class1;
  private:
    int something_private;
  };
}

template<typename T>
class Class1
{
  void error() {
    B::Class2 b;
    b.something_private = 42;
  }
};

I orignally thought this to be a clang bug, it seems to actually be a problem
in gcc incorrectly accepting this code.

Richard Smith mentions in http://llvm.org/bugs/show_bug.cgi?id=17950:

--8<--

7.3.1.2/3:

"If the name in a friend declaration is neither qualified nor a template-id and
the declaration is a function or an elaborated-type-specifier, the lookup to
determine whether the entity has been previously declared shall not consider
any scopes outside the innermost enclosing namespace."

Therefore a (not-yet-declared) 'template<typename V> class B::Class1;' is
befriended, not the global Class1.

-->8--

So gcc should require replacing the friend declaration by:

    template<typename V>
    friend class ::Class1;