From d7d3929226df1c8f8174ac63d11b6fad47997840 Mon Sep 17 00:00:00 2001
From: q66 <daniel@octaforge.org>
Date: Wed, 10 Jan 2018 00:02:22 +0100
Subject: [PATCH] refactor expression SFINAE tests not to use pointers

---
 ostd/format.hh | 13 ++++++++-----
 ostd/range.hh  | 30 ++++++++++++++++--------------
 2 files changed, 24 insertions(+), 19 deletions(-)

diff --git a/ostd/format.hh b/ostd/format.hh
index 77b7db8..2de816f 100644
--- a/ostd/format.hh
+++ b/ostd/format.hh
@@ -217,7 +217,8 @@ namespace detail {
      * pair, array, possibly other types added later or overridden...
      */
     template<typename T>
-    inline std::true_type tuple_like_test(typename std::tuple_size<T>::type *);
+    inline auto tuple_like_test(int) ->
+        typename std::is_integral<decltype(std::tuple_size<T>::value)>::type;
 
     template<typename>
     inline std::false_type tuple_like_test(...);
@@ -228,10 +229,12 @@ namespace detail {
 
     /* test if format traits are available for the type */
     template<typename T, typename R>
-    inline std::true_type test_tofmt(decltype(format_traits<T>::to_format(
-        std::declval<T const &>(), std::declval<R &>(),
-        std::declval<format_spec const &>()
-    )) *);
+    inline auto test_tofmt(int) -> typename std::is_void<
+        decltype(format_traits<T>::to_format(
+            std::declval<T const &>(), std::declval<R &>(),
+            std::declval<format_spec const &>()
+        ))
+    >::type;
 
     template<typename, typename>
     inline std::false_type test_tofmt(...);
diff --git a/ostd/range.hh b/ostd/range.hh
index dedffde..e9a4ea4 100644
--- a/ostd/range.hh
+++ b/ostd/range.hh
@@ -592,9 +592,9 @@ static inline constexpr bool const is_contiguous_range =
 
 namespace detail {
     template<typename R, typename T>
-    inline std::true_type test_outrange(typename std::is_same<
-        decltype(std::declval<R &>().put(std::declval<T>())), void
-    >::type *);
+    inline auto test_outrange(int) -> typename std::is_void<
+        decltype(std::declval<R &>().put(std::declval<T>()))
+    >::tyoe;
 
     template<typename, typename>
     inline std::false_type test_outrange(...);
@@ -1208,9 +1208,9 @@ inline auto zip(R1 &&r1, R &&...rr) {
 
 namespace detail {
     template<typename C>
-    inline std::true_type test_direct_iter(
-        decltype(std::declval<C &>().iter()) *
-    );
+    inline auto test_direct_iter(int) -> std::integral_constant<
+        bool, is_input_range<decltype(std::declval<C &>().iter())>
+    >;
 
     template<typename>
     inline std::false_type test_direct_iter(...);
@@ -1219,18 +1219,20 @@ namespace detail {
     static inline constexpr bool const direct_iter_test =
         decltype(test_direct_iter<C>(0))::value;
 
+
     template<typename C>
-    inline std::true_type test_std_iter(
-        decltype(std::begin(std::declval<C &>())) *,
-        decltype(std::end(std::declval<C &>())) *
-    );
+    inline auto test_std_iter(int) -> std::integral_constant<
+        bool,
+        !std::is_void_v<decltype(std::begin(std::declval<C &>()))> &&
+        !std::is_void_v<decltype(std::end(std::declval<C &>()))>
+    >;
 
     template<typename>
     inline std::false_type test_std_iter(...);
 
     template<typename C>
     static inline constexpr bool const std_iter_test =
-        decltype(test_std_iter<C>(0, 0))::value;
+        decltype(test_std_iter<C>(0))::value;
 
     /* direct iter and std iter; the case for std iter is
      * specialized after iterator_range is actually defined
@@ -1303,9 +1305,9 @@ inline auto citer(T const &r) -> decltype(ranged_traits<T const>::iter(r)) {
 
 namespace detail {
     template<typename T>
-    inline std::true_type test_iterable(
-        decltype(ostd::iter(std::declval<T>())) *
-    );
+    inline auto test_iterable(int) -> std::integral_constant<
+        bool, is_input_range<decltype(ostd::iter(std::declval<T>()))>
+    >;
     template<typename>
     inline std::false_type test_iterable(...);