[Bug c++/63263] New: friend declaration of template specialization of function gets confused when specialization was forward declared

["carlo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63263

            Bug ID: 63263
           Summary: friend declaration of template specialization of
                    function gets confused when specialization was forward
                    declared
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: carlo at gcc dot gnu.org

The following code snippet should compile, but it doesn't.

template<typename T>
void f(T&, float&)
{
  T(1);
}

struct B;

template<>
void f(B&, float&)
{
}

struct B {
  friend void f<B>(B&, float&);
};

void g()
{
  B b;
  float n;
  f(b, n);
}

The result is:

troep.cc: In instantiation of ‘void f(T&, float&) [with T = B]’:
troep.cc:22:9:   required from here
troep.cc:4:3: error: no matching function for call to ‘B::B(int)’
troep.cc:4:3: note: candidates are:
troep.cc:14:8: note: B::B()
troep.cc:14:8: note:   candidate expects 0 arguments, 1 provided
troep.cc:14:8: note: B::B(const B&)
troep.cc:14:8: note:   no known conversion for argument 1 from ‘int’ to ‘const
B&’
troep.cc:4: confused by earlier errors, bailing out
Preprocessed source stored into /tmp/ccjzbrcd.out file, please attach this to
your bugreport.

If I either comment out the friend declaration, or move the
specialization to after the struct B declaration (so that the
friend declaration caused the specialization), then it compiles
and works.

clang compiles this fine.
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From: "carlo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/63263] friend declaration of function template specialization gets confused when specialization was forward declared.
Date: Sun, 14 Sep 2014 21:22:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idc263

--- Comment #1 from Carlo Wood <carlo at gcc dot gnu.org> ---
Guess the float isn't needed:

template<typename T> void f(T&) { T(1); }
struct B;
template<> void f(B&) { }
struct B { friend void f<B>(B&); };
void g() { B b; f(b); }