[Bug c++/51786] New: [c++0x] Invalid declaration with decltype accepted

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51786

             Bug #: 51786
           Summary: [c++0x] Invalid declaration with decltype accepted
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: reichelt@gcc.gnu.org


The error message "declaration does not declare anything" is not
triggered in certain cases when using decltype:

===================================
struct A {};
void foo() { decltype(A()); }
===================================

It *is* triggered if I write decltype(int) instead.

Another testcase is the following:

===================================
template<int> struct A
{
  A() { decltype(this); }
};

A<0> a;
===================================

It *is* triggered if I make A a non-template class.

This bug is similar to PR21120 where the same problems occured with "typeof".