[Bug c++/56821] New: Unable to overload with references to 'this'.

["3dw4rd at verizon dot net" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56821

             Bug #: 56821
           Summary: Unable to overload with references to 'this'.
    Classification: Unclassified
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: 3dw4rd@verizon.net


Created attachment 29783
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29783
This is a reference for 'this' toy.

Here is a busybox I wrote to play with the new feature in gcc-4.8.1 and trunk:
--------------------------------------------------------
class Foo
{
public:
  Foo(int i) : _M_i(i) { }
  int bar() & { return _M_i /= 2; }
  int bar() const & { return _M_i; }
  int bar() && { return 2 * _M_i; }

private:
  int _M_i = 42;
};

int
main()
{
  Foo ph(333);
  ph.bar();

  const Foo ff(123);
  ff.bar();

  Foo(333).bar();
}
--------------------------------------------------------

It looks to me reading the standard 8.3.5 that the three bar() methods should
be overloadable. I get a linker error though:

--------------------------------------------------------
[ed@localhost ref_this]$ ../bin/bin/g++ -std=c++11 -o ref_this ref_this.cpp
/tmp/ccwPhzqr.s: Assembler messages:
/tmp/ccwPhzqr.s:73: Error: symbol `_ZN3Foo3barEv' is already defined
--------------------------------------------------------

If I comment out 'int bar() const &' I am unable to resolve 'ff.bar()':

--------------------------------------------------------
[ed@localhost ref_this]$ ../bin/bin/g++ -std=c++11 -o ref_this ref_this.cpp
ref_this.cpp: In function âint main()â:
ref_this.cpp:26:10: error: no matching function for call to âFoo::bar() constâ
   ff.bar();
          ^
ref_this.cpp:26:10: note: candidates are:
ref_this.cpp:11:7: note: int Foo::bar() &
   int bar() & { return _M_i /= 2; }
       ^
ref_this.cpp:11:7: note:   no known conversion for implicit âthisâ parameter
from âconst Fooâ to âFoo&â
ref_this.cpp:13:7: note: int Foo::bar() &&
   int bar() && { return 2 * _M_i; }
       ^
ref_this.cpp:13:7: note:   no known conversion for implicit âthisâ parameter
from âconst Fooâ to âFoo&&â
--------------------------------------------------------

I think this is gcc bug.