From 965b1119cb1d8533cdc48101378c661871a5d290 Mon Sep 17 00:00:00 2001
From: Zach Laine <whatwasthataddress@gmail.com>
Date: Sun, 26 Mar 2023 14:14:00 -0500
Subject: [PATCH] Disable iterator_interface::operator-> when pointer is void
 or reference is not a language reference.

---
 .../stl_interfaces/iterator_interface.hpp     | 40 ++++++++++++-------
 test/compile_sfinae_path_mutable_iterator.cpp |  4 +-
 test/input.cpp                                |  8 ++--
 3 files changed, 31 insertions(+), 21 deletions(-)

diff --git a/include/boost/stl_interfaces/iterator_interface.hpp b/include/boost/stl_interfaces/iterator_interface.hpp
index 304de2b..037b801 100644
--- a/include/boost/stl_interfaces/iterator_interface.hpp
+++ b/include/boost/stl_interfaces/iterator_interface.hpp
@@ -70,19 +70,25 @@ namespace boost { namespace stl_interfaces {
     };
 
     namespace detail {
-        template<typename Pointer, typename T>
+        template<typename Pointer, typename Reference, typename T>
         auto make_pointer(
             T && value,
-            std::enable_if_t<std::is_pointer<Pointer>::value, int> = 0)
-            -> decltype(std::addressof(value))
+            std::enable_if_t<
+                std::is_pointer<Pointer>::value &&
+                    std::is_reference<Reference>::value,
+                int> = 0) -> decltype(std::addressof(value))
         {
             return std::addressof(value);
         }
 
-        template<typename Pointer, typename T>
+        template<typename Pointer, typename Reference, typename T>
         auto make_pointer(
             T && value,
-            std::enable_if_t<!std::is_pointer<Pointer>::value, int> = 0)
+            std::enable_if_t<
+                !std::is_pointer<Pointer>::value &&
+                    !std::is_same<Pointer, void>::value &&
+                    std::is_reference<Reference>::value,
+                int> = 0)
         {
             return Pointer(std::forward<T>(value));
         }
@@ -368,20 +374,22 @@ namespace boost { namespace stl_interfaces { BOOST_STL_INTERFACES_NAMESPACE_V1 {
         }
 
         template<typename D = Derived>
-        constexpr auto operator-> () noexcept(
-            noexcept(detail::make_pointer<pointer>(*std::declval<D &>())))
+        constexpr auto operator->() noexcept(noexcept(
+            detail::make_pointer<pointer, reference>(*std::declval<D &>())))
             -> decltype(
-                detail::make_pointer<pointer>(*std::declval<D &>()))
+                detail::make_pointer<pointer, reference>(*std::declval<D &>()))
         {
-            return detail::make_pointer<pointer>(*derived());
+            return detail::make_pointer<pointer, reference>(*derived());
         }
         template<typename D = Derived>
-        constexpr auto operator-> () const noexcept(
-            noexcept(detail::make_pointer<pointer>(*std::declval<D const &>())))
+        constexpr auto operator->() const noexcept(noexcept(
+            detail::make_pointer<pointer, reference>(
+                *std::declval<D const &>())))
             -> decltype(
-                detail::make_pointer<pointer>(*std::declval<D const &>()))
+                detail::make_pointer<pointer, reference>(
+                    *std::declval<D const &>()))
         {
-            return detail::make_pointer<pointer>(*derived());
+            return detail::make_pointer<pointer, reference>(*derived());
         }
 
         template<typename D = Derived>
@@ -757,11 +765,13 @@ namespace boost { namespace stl_interfaces { BOOST_STL_INTERFACES_NAMESPACE_V2 {
         }
 
       constexpr auto operator->()
-        requires requires (D d) { *d; } {
+        requires (!std::same_as<pointer, void> && std::is_reference_v<reference> &&
+                  requires (D d) { *d; }) {
           return detail::make_pointer<pointer>(*derived());
         }
       constexpr auto operator->() const
-        requires requires (D const d) { *d; } {
+        requires (!std::same_as<pointer, void> && std::is_reference_v<reference> &&
+                  requires (D const d) { *d; }) {
           return detail::make_pointer<pointer>(*derived());
         }
 
diff --git a/test/compile_sfinae_path_mutable_iterator.cpp b/test/compile_sfinae_path_mutable_iterator.cpp
index bdec0d7..c499370 100644
--- a/test/compile_sfinae_path_mutable_iterator.cpp
+++ b/test/compile_sfinae_path_mutable_iterator.cpp
@@ -68,7 +68,7 @@ private:
 void compile_sfinae_path_mutable_iterator()
 {
     auto it = iterator<node>{};
-    if (it->first == 42) {
-        it->second = 13;
+    if ((*it).first == 42) {
+        (*it).second = 13;
     }
 }
diff --git a/test/input.cpp b/test/input.cpp
index 8000bc3..27c90b0 100644
--- a/test/input.cpp
+++ b/test/input.cpp
@@ -315,7 +315,7 @@ int main()
         pair_input first(pairs.data());
         pair_input last(pairs.data() + pairs.size());
         for (auto out = firsts_copy.begin(); first != last; ++first) {
-            *out++ = first->first;
+            *out++ = (*first).first;
         }
         BOOST_TEST(firsts_copy == ints);
     }
@@ -325,7 +325,7 @@ int main()
         proxy_input_iter<std::pair<int, int>> first(pairs.data());
         proxy_input_iter<std::pair<int, int>> last(pairs.data() + pairs.size());
         for (auto out = firsts_copy.begin(); first != last; ++first) {
-            *out++ = first->first;
+            *out++ = (*first).first;
         }
         BOOST_TEST(firsts_copy == ints);
     }
@@ -354,7 +354,7 @@ int main()
         const_pair_input first(pairs.data());
         const_pair_input last(pairs.data() + pairs.size());
         for (auto out = firsts_copy.begin(); first != last; ++first) {
-            *out++ = first->first;
+            *out++ = (*first).first;
         }
         BOOST_TEST(firsts_copy == ints);
     }
@@ -365,7 +365,7 @@ int main()
         proxy_input_iter<std::pair<int, int> const> last(
             pairs.data() + pairs.size());
         for (auto out = firsts_copy.begin(); first != last; ++first) {
-            *out++ = first->first;
+            *out++ = (*first).first;
         }
         BOOST_TEST(firsts_copy == ints);
     }