[LLVMbugs] [Bug 9540] New: Terrible recovery for broken default template argument

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=9540

           Summary: Terrible recovery for broken default template argument
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: jyasskin at google.com
                CC: llvmbugs at cs.uiuc.edu, dgregor at apple.com


The following code has a single mistake, but clang produces 6 errors and 5
instantiation notes:

$ cat ~/tmp/test.cc
#include <algorithm>
#include <iterator>
#include <vector>

struct my_iterator : std::iterator<std::output_iterator_tag, void
#ifdef CORRECT
                                   , void, void, void
#endif
                                   > {
  my_iterator& operator++();
  my_iterator& operator*();
  template<typename T>
  void operator=(T) {}
};

void foo() {
  std::vector<int> v;
  std::copy(v.begin(), v.end(), my_iterator());
}

$ clang++ -c ~/tmp/test.cc
In file included from /home/jyasskin/tmp/test.cc:1:
In file included from /usr/include/c++/4.4/algorithm:60:
In file included from /usr/include/c++/4.4/bits/stl_algobase.h:67:
/usr/include/c++/4.4/bits/stl_iterator_base_types.h:102:63: error: cannot form
a reference
      to 'void'
           typename _Pointer = _Tp*, typename _Reference = _Tp&>
                                                              ^
/home/jyasskin/tmp/test.cc:5:27: note: in instantiation of default argument for
      'iterator<std::output_iterator_tag, void, long, void *>' required here
struct my_iterator : std::iterator<std::output_iterator_tag, void
                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /home/jyasskin/tmp/test.cc:1:
In file included from /usr/include/c++/4.4/algorithm:60:
In file included from /usr/include/c++/4.4/bits/stl_algobase.h:67:
/usr/include/c++/4.4/bits/stl_iterator_base_types.h:126:35: error: no type
named
      'iterator_category' in 'my_iterator'
      typedef typename _Iterator::iterator_category iterator_category;
              ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
In file included from /home/jyasskin/tmp/test.cc:1:
In file included from /usr/include/c++/4.4/algorithm:60:
/usr/include/c++/4.4/bits/stl_algobase.h:389:24: note: in instantiation of
template class
      'std::iterator_traits<my_iterator>' requested here
      typedef typename iterator_traits<_OI>::value_type _ValueTypeO;
                       ^
/usr/include/c++/4.4/bits/stl_algobase.h:433:18: note: in instantiation of
function
      template specialization 'std::__copy_move_a<false, int *, my_iterator>'
requested
      here
      return _OI(std::__copy_move_a<_IsMove>
                 ^
/usr/include/c++/4.4/bits/stl_algobase.h:466:15: note: in instantiation of
function
      template specialization 'std::__copy_move_a2<false,
__gnu_cxx::__normal_iterator<int
      *, std::vector<int, std::allocator<int> > >, my_iterator>' requested here
      return (std::__copy_move_a2<__is_move_iterator<_II>::__value>
              ^
/home/jyasskin/tmp/test.cc:18:3: note: in instantiation of function template
      specialization 'std::copy<__gnu_cxx::__normal_iterator<int *,
std::vector<int,
      std::allocator<int> > >, my_iterator>' requested here
  std::copy(v.begin(), v.end(), my_iterator());
  ^
In file included from /home/jyasskin/tmp/test.cc:1:
In file included from /usr/include/c++/4.4/algorithm:60:
In file included from /usr/include/c++/4.4/bits/stl_algobase.h:67:
/usr/include/c++/4.4/bits/stl_iterator_base_types.h:127:35: error: no type
named
      'value_type' in 'my_iterator'
      typedef typename _Iterator::value_type        value_type;
              ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~
/usr/include/c++/4.4/bits/stl_iterator_base_types.h:128:35: error: no type
named
      'difference_type' in 'my_iterator'
      typedef typename _Iterator::difference_type   difference_type;
              ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
/usr/include/c++/4.4/bits/stl_iterator_base_types.h:129:35: error: no type
named 'pointer'
      in 'my_iterator'
      typedef typename _Iterator::pointer           pointer;
              ~~~~~~~~~~~~~~~~~~~~^~~~~~~
/usr/include/c++/4.4/bits/stl_iterator_base_types.h:130:35: error: no type
named
      'reference' in 'my_iterator'
      typedef typename _Iterator::reference         reference;
              ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~
6 errors generated.


====================

It looks like it's throwing out the entire base class instead of instantiating
it with an error type for the _Reference parameter. This looks related to
PR5923, but is about using broken types instead of broken values.

-- 
Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.