LWG3872 basic_const_iterator should have custom iter_move

Author: burblebee

source/iterators.tex

@@ -4216,10 +4216,16 @@
   template<class I>
     concept @\exposconcept{not-a-const-iterator}@ = @\seebelow@;                   // \expos
 
+  template<@\libconcept{indirectly_readable}@ I>
+    using @\exposidnc{iter-const-rvalue-reference-t}@ =                       // \expos
+      common_reference_t<const iter_value_t<I>&&, iter_rvalue_reference_t<I>>;
+
   template<@\libconcept{input_iterator}@ Iterator>
   class @\libglobal{basic_const_iterator}@ {
     Iterator @\exposidnc{current_}@ = Iterator();                             // \expos
     using @\exposidnc{reference}@ = iter_const_reference_t<Iterator>;         // \expos
+    using @\exposidnc{rvalue-reference}@ =                                    // \expos
+      @\exposid{iter-const-rvalue-reference-t}@<Iterator>;
 
   public:
     using iterator_concept = @\seebelow@;
@@ -4315,6 +4321,11 @@
     template<@\exposconcept{not-a-const-iterator}@ S>
       requires @\libconcept{sized_sentinel_for}@<S, Iterator>
       friend constexpr difference_type operator-(const S& x, const basic_const_iterator& y);
+    friend constexpr @\exposid{rvalue-reference}@ iter_move(const basic_const_iterator& i)
+      noexcept(noexcept(static_cast<@\exposid{rvalue-reference}@>(ranges::iter_move(i.@\exposid{current_}@))))
+      {
+        return static_cast<@\exposid{rvalue-reference}@>(ranges::iter_move(i.@\exposid{current_}@));
+      }
   };
 }
 \end{codeblock}