From 6fab3bbfa4e970b53dd79ccef8ff35085a1fcd36 Mon Sep 17 00:00:00 2001
From: Andrey Semashev <andrey.semashev@gmail.com>
Date: Tue, 28 Jan 2025 00:29:35 +0300
Subject: [PATCH] Removed dependency on MPL from is_lvalue_iterator.hpp.

Also removed workarounds for older compilers and simplified implementation.
---
 include/boost/iterator/is_lvalue_iterator.hpp | 142 +++++++-----------
 1 file changed, 54 insertions(+), 88 deletions(-)

diff --git a/include/boost/iterator/is_lvalue_iterator.hpp b/include/boost/iterator/is_lvalue_iterator.hpp
index 260e21b..179de06 100644
--- a/include/boost/iterator/is_lvalue_iterator.hpp
+++ b/include/boost/iterator/is_lvalue_iterator.hpp
@@ -2,107 +2,73 @@
 // subject to the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 #ifndef IS_LVALUE_ITERATOR_DWA2003112_HPP
-# define IS_LVALUE_ITERATOR_DWA2003112_HPP
-
-#include <boost/detail/workaround.hpp>
+#define IS_LVALUE_ITERATOR_DWA2003112_HPP
 
 #include <boost/iterator/detail/type_traits/conjunction.hpp>
-#include <boost/mpl/aux_/lambda_support.hpp>
 
 #include <iterator>
 #include <type_traits>
 
 namespace boost {
-
 namespace iterators {
+namespace detail {
 
-namespace detail
+// Guts of is_lvalue_iterator.  It is the iterator type and
+// Value is the iterator's value_type.
+template< typename It, typename Value >
+struct is_lvalue_iterator_impl :
+    public detail::conjunction<
+        std::is_convertible< decltype(*std::declval< It& >()), typename std::add_lvalue_reference< Value >::type >,
+        std::is_lvalue_reference< decltype(*std::declval< It& >()) >
+    >::type
 {
-  // Guts of is_lvalue_iterator.  Value is the iterator's value_type
-  // and the result is computed in the nested rebind template.
-  template <class Value>
-  struct is_lvalue_iterator_impl
-  {
-      template <class It>
-      using DerefT = decltype(*std::declval<It&>());
-
-      template <class It>
-      struct rebind : detail::conjunction<
-                        std::is_convertible<DerefT<It>, typename std::add_lvalue_reference<Value>::type>
-                      , std::is_lvalue_reference<DerefT<It>>
-                      >::type
-      {
-      };
-  };
-
-  //
-  // void specializations to handle std input and output iterators
-  //
-  template <>
-  struct is_lvalue_iterator_impl<void>
-  {
-      template <class It>
-      struct rebind : std::false_type
-      {};
-  };
-
-#ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
-  template <>
-  struct is_lvalue_iterator_impl<const void>
-  {
-      template <class It>
-      struct rebind : std::false_type
-      {};
-  };
-
-  template <>
-  struct is_lvalue_iterator_impl<volatile void>
-  {
-      template <class It>
-      struct rebind : std::false_type
-      {};
-  };
-
-  template <>
-  struct is_lvalue_iterator_impl<const volatile void>
-  {
-      template <class It>
-      struct rebind : std::false_type
-      {};
-  };
-#endif
-
-  //
-  // This level of dispatching is required for Borland.  We might save
-  // an instantiation by removing it for others.
-  //
-  template <class It>
-  struct is_readable_lvalue_iterator_impl
-    : is_lvalue_iterator_impl<
-          BOOST_DEDUCED_TYPENAME std::iterator_traits<It>::value_type const
-      >::template rebind<It>
-  {};
-
-  template <class It>
-  struct is_non_const_lvalue_iterator_impl
-    : is_lvalue_iterator_impl<
-          BOOST_DEDUCED_TYPENAME std::iterator_traits<It>::value_type
-      >::template rebind<It>
-  {};
-} // namespace detail
-
-template< typename T > struct is_lvalue_iterator
-: public std::integral_constant<bool,::boost::iterators::detail::is_readable_lvalue_iterator_impl<T>::value>
-{
-public:
-    BOOST_MPL_AUX_LAMBDA_SUPPORT(1,is_lvalue_iterator,(T))
 };
 
-template< typename T > struct is_non_const_lvalue_iterator
-: public std::integral_constant<bool,::boost::iterators::detail::is_non_const_lvalue_iterator_impl<T>::value>
+//
+// void specializations to handle std input and output iterators
+//
+template< typename It >
+struct is_lvalue_iterator_impl< It, void > :
+    public std::false_type
+{
+};
+
+template< typename It >
+struct is_lvalue_iterator_impl< It, const void > :
+    public std::false_type
+{
+};
+
+template< typename It >
+struct is_lvalue_iterator_impl< It, volatile void > :
+    public std::false_type
+{
+};
+
+template< typename It >
+struct is_lvalue_iterator_impl< It, const volatile void > :
+    public std::false_type
+{
+};
+
+} // namespace detail
+
+template< typename T >
+struct is_lvalue_iterator :
+    public iterators::detail::is_lvalue_iterator_impl<
+        T,
+        typename std::iterator_traits< T >::value_type const
+    >::type
+{
+};
+
+template< typename T >
+struct is_non_const_lvalue_iterator :
+    public iterators::detail::is_lvalue_iterator_impl<
+        T,
+        typename std::iterator_traits< T >::value_type
+    >::type
 {
-public:
-    BOOST_MPL_AUX_LAMBDA_SUPPORT(1,is_non_const_lvalue_iterator,(T))
 };
 
 } // namespace iterators