Fix PR39619 - iterator_traits isn't SFINAE-friendly enough. Thanks to Eric for the report

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@346738 91177308-0d34-0410-b5e6-96231b3b80d8

include/iterator

@@ -437,6 +437,23 @@ struct _LIBCPP_TEMPLATE_VIS forward_iterator_tag       : public input_iterator_t
 struct _LIBCPP_TEMPLATE_VIS bidirectional_iterator_tag : public forward_iterator_tag {};
 struct _LIBCPP_TEMPLATE_VIS random_access_iterator_tag : public bidirectional_iterator_tag {};
 
+template <class _Tp>
+struct __has_iterator_typedefs
+{
+private:
+    struct __two {char __lx; char __lxx;};
+    template <class _Up> static __two __test(...);
+    template <class _Up> static char __test(typename std::__void_t<typename _Up::iterator_category>::type* = 0,
+    										typename std::__void_t<typename _Up::difference_type>::type* = 0,
+    										typename std::__void_t<typename _Up::value_type>::type* = 0,
+    										typename std::__void_t<typename _Up::reference>::type* = 0,
+    										typename std::__void_t<typename _Up::pointer>::type* = 0
+    										);
+public:
+    static const bool value = sizeof(__test<_Tp>(0,0,0,0,0)) == 1;
+};
+
+
 template <class _Tp>
 struct __has_iterator_category
 {
@@ -479,7 +496,7 @@ struct __iterator_traits<_Iter, true>
 
 template <class _Iter>
 struct _LIBCPP_TEMPLATE_VIS iterator_traits
-    : __iterator_traits<_Iter, __has_iterator_category<_Iter>::value> {};
+    : __iterator_traits<_Iter, __has_iterator_typedefs<_Iter>::value> {};
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS iterator_traits<_Tp*>

test/std/iterators/iterator.primitives/iterator.traits/empty.fail.cpp

@@ -0,0 +1,122 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <iterator>
+
+// struct iterator_traits
+// {
+// };
+
+#include <iterator>
+#include "test_macros.h"
+
+struct A {};
+struct NotAnIteratorEmpty {};
+
+struct NotAnIteratorNoDifference
+{
+//     typedef int                       difference_type;
+    typedef A                         value_type;
+    typedef A*                        pointer;
+    typedef A&                        reference;
+    typedef std::forward_iterator_tag iterator_category;
+};
+
+struct NotAnIteratorNoValue
+{
+    typedef int                       difference_type;
+//     typedef A                         value_type;
+    typedef A*                        pointer;
+    typedef A&                        reference;
+    typedef std::forward_iterator_tag iterator_category;
+};
+
+struct NotAnIteratorNoPointer
+{
+    typedef int                       difference_type;
+    typedef A                         value_type;
+//     typedef A*                        pointer;
+    typedef A&                        reference;
+    typedef std::forward_iterator_tag iterator_category;
+};
+
+struct NotAnIteratorNoReference
+{
+    typedef int                       difference_type;
+    typedef A                         value_type;
+    typedef A*                        pointer;
+//    typedef A&                        reference;
+    typedef std::forward_iterator_tag iterator_category;
+};
+
+struct NotAnIteratorNoCategory
+{
+    typedef int                       difference_type;
+    typedef A                         value_type;
+    typedef A*                        pointer;
+    typedef A&                        reference;
+//     typedef std::forward_iterator_tag iterator_category;
+};
+
+int main()
+{
+    {
+    typedef std::iterator_traits<NotAnIteratorEmpty> T;
+    typedef T::difference_type   DT; // expected-error-re {{no type named 'difference_type' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::value_type        VT; // expected-error-re {{no type named 'value_type' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::pointer           PT; // expected-error-re {{no type named 'pointer' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::reference         RT; // expected-error-re {{no type named 'reference' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::iterator_category CT; // expected-error-re {{no type named 'iterator_category' in 'std::__1::iterator_traits<{{.+}}>}}
+    }
+
+    {
+    typedef std::iterator_traits<NotAnIteratorNoDifference> T;
+    typedef T::difference_type   DT; // expected-error-re {{no type named 'difference_type' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::value_type        VT; // expected-error-re {{no type named 'value_type' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::pointer           PT; // expected-error-re {{no type named 'pointer' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::reference         RT; // expected-error-re {{no type named 'reference' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::iterator_category CT; // expected-error-re {{no type named 'iterator_category' in 'std::__1::iterator_traits<{{.+}}>}}
+    }
+
+    {
+    typedef std::iterator_traits<NotAnIteratorNoValue> T;
+    typedef T::difference_type   DT; // expected-error-re {{no type named 'difference_type' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::value_type        VT; // expected-error-re {{no type named 'value_type' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::pointer           PT; // expected-error-re {{no type named 'pointer' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::reference         RT; // expected-error-re {{no type named 'reference' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::iterator_category CT; // expected-error-re {{no type named 'iterator_category' in 'std::__1::iterator_traits<{{.+}}>}}
+    }
+
+    {
+    typedef std::iterator_traits<NotAnIteratorNoPointer> T;
+    typedef T::difference_type   DT; // expected-error-re {{no type named 'difference_type' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::value_type        VT; // expected-error-re {{no type named 'value_type' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::pointer           PT; // expected-error-re {{no type named 'pointer' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::reference         RT; // expected-error-re {{no type named 'reference' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::iterator_category CT; // expected-error-re {{no type named 'iterator_category' in 'std::__1::iterator_traits<{{.+}}>}}
+    }
+
+    {
+    typedef std::iterator_traits<NotAnIteratorNoReference> T;
+    typedef T::difference_type   DT; // expected-error-re {{no type named 'difference_type' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::value_type        VT; // expected-error-re {{no type named 'value_type' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::pointer           PT; // expected-error-re {{no type named 'pointer' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::reference         RT; // expected-error-re {{no type named 'reference' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::iterator_category CT; // expected-error-re {{no type named 'iterator_category' in 'std::__1::iterator_traits<{{.+}}>}}
+    }
+
+    {
+    typedef std::iterator_traits<NotAnIteratorNoCategory> T;
+    typedef T::difference_type   DT; // expected-error-re {{no type named 'difference_type' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::value_type        VT; // expected-error-re {{no type named 'value_type' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::pointer           PT; // expected-error-re {{no type named 'pointer' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::reference         RT; // expected-error-re {{no type named 'reference' in 'std::__1::iterator_traits<{{.+}}>}}
+    typedef T::iterator_category CT; // expected-error-re {{no type named 'iterator_category' in 'std::__1::iterator_traits<{{.+}}>}}
+    }
+}

test/std/iterators/iterator.primitives/iterator.traits/iterator.pass.cpp

@@ -39,5 +39,6 @@ int main()
     static_assert((std::is_same<It::difference_type, int>::value), "");
     static_assert((std::is_same<It::value_type, A>::value), "");
     static_assert((std::is_same<It::pointer, A*>::value), "");
+    static_assert((std::is_same<It::reference, A&>::value), "");
     static_assert((std::is_same<It::iterator_category, std::forward_iterator_tag>::value), "");
 }