[Bug c++/50280] New: Incorrect type deduced for T& when passed a const bitfield

[jyasskin at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50280

             Bug #: 50280
           Summary: Incorrect type deduced for T& when passed a const
                    bitfield
    Classification: Unclassified
           Product: gcc
           Version: 4.6.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: jyass...@gcc.gnu.org


$ cat test.cc
struct S { int bf : 3; };

template<class _T1>
void make_pair(_T1& __x) {}

void foo() {
  const S s = S();
  make_pair(s.bf);
}
$ g++-4.6 -c test.cc
test.cc: In function 'void foo()':
test.cc:8:17: error: cannot bind bitfield 's.S::bf' to 'int&'
$ clang++ -c test.cc
$ 


It looks like gcc is deducing the parameter type from the base type of the
bitfield rather than its type modified by qualifiers on the containing object.

This seems related to PR43663, but isn't the same issue because using "const
_T1&" in make_pair makes this compile.

This showed up when compiling a make_pair(val, bitfield) call in C++0x mode
that worked in C++98 mode, but the underlying issue is present in C++98 too.