LWG3569 join_view fails to support ranges of ranges with non-default_initializable iterators

Author: burblebee

source/ranges.tex

@@ -6497,7 +6497,7 @@
       is_reference_v<range_reference_t<@\exposidnc{Base}@>>;
 
     @\exposidnc{OuterIter}@ @\exposid{outer_}@ = @\exposidnc{OuterIter}@();                             // \expos
-    @\exposidnc{InnerIter}@ @\exposid{inner_}@ = @\exposidnc{InnerIter}@();                             // \expos
+    optional<@\exposidnc{InnerIter}@> @\exposid{inner_}@;                                 // \expos
     @\exposidnc{Parent}@* @\exposid{parent_}@  = nullptr;                                 // \expos
 
     constexpr void @\exposidnc{satisfy}@();                                   // \expos
@@ -6508,15 +6508,14 @@
     using value_type        = range_value_t<range_reference_t<@\exposid{Base}@>>;
     using difference_type   = @\seebelow@;
 
-    @\exposid{iterator}@() requires @\libconcept{default_initializable}@<@\exposid{OuterIter}@> &&
-                         @\itcorr[-2]\libconcept{default_initializable}@<@\exposid{InnerIter}@> = default;
+    @\exposid{iterator}@() requires @\libconcept{default_initializable}@<@\exposid{OuterIter}@> = default;
     constexpr @\exposid{iterator}@(@\exposid{Parent}@& parent, @\exposid{OuterIter}@ outer);
     constexpr @\exposid{iterator}@(@\exposid{iterator}@<!Const> i)
       requires Const &&
                @\libconcept{convertible_to}@<iterator_t<V>, @\exposid{OuterIter}@> &&
                @\libconcept{convertible_to}@<iterator_t<@\exposid{InnerRng}@>, @\exposid{InnerIter}@>;
 
-    constexpr decltype(auto) operator*() const { return *@\exposid{inner_}@; }
+    constexpr decltype(auto) operator*() const { return **@\exposid{inner_}@; }
 
     constexpr @\exposid{InnerIter}@ operator->() const
       requires @\exposconcept{has-arrow}@<@\exposid{InnerIter}@> && @\libconcept{copyable}@<@\exposid{InnerIter}@>;
@@ -6542,12 +6541,12 @@
                @\libconcept{equality_comparable}@<iterator_t<range_reference_t<@\exposid{Base}@>>>;
 
     friend constexpr decltype(auto) iter_move(const @\exposid{iterator}@& i)
-    noexcept(noexcept(ranges::iter_move(i.@\exposid{inner_}@))) {
-      return ranges::iter_move(i.@\exposid{inner_}@);
+    noexcept(noexcept(ranges::iter_move(*i.@\exposid{inner_}@))) {
+      return ranges::iter_move(*i.@\exposid{inner_}@);
     }
 
     friend constexpr void iter_swap(const @\exposid{iterator}@& x, const @\exposid{iterator}@& y)
-      noexcept(noexcept(ranges::iter_swap(x.@\exposid{inner_}@, y.@\exposid{inner_}@)))
+      noexcept(noexcept(ranges::iter_swap(*x.@\exposid{inner_}@, *y.@\exposid{inner_}@)))
       requires @\libconcept{indirectly_swappable}@<@\exposid{InnerIter}@>;
   };
 }
@@ -6624,11 +6623,11 @@
 for (; @\exposid{outer_}@ != ranges::end(@\exposid{parent_}@->@\exposid{base_}@); ++@\exposid{outer_}@) {
   auto&& inner = update_inner(@\exposid{outer_}@);
   @\exposid{inner_}@ = ranges::begin(inner);
-  if (@\exposid{inner_}@ != ranges::end(inner))
+  if (*@\exposid{inner_}@ != ranges::end(inner))
     return;
 }
 if constexpr (@\exposid{ref-is-glvalue}@)
-  @\exposid{inner_}@ = @\exposid{InnerIter}@();
+  @\exposid{inner_}@.reset();
 \end{codeblock}
 \end{itemdescr}
 
@@ -6669,7 +6668,7 @@
 \begin{itemdescr}
 \pnum
 \effects
-Equivalent to \tcode{return \exposid{inner_};}
+Equivalent to: \tcode{return *\exposid{inner_};}
 \end{itemdescr}
 
 \indexlibrarymember{operator++}{join_view::\exposid{iterator}}%
@@ -6690,7 +6689,7 @@
 Equivalent to:
 \begin{codeblock}
 auto&& inner_rng = @\placeholder{inner-range}@;
-if (++@\exposid{inner_}@ == ranges::end(inner_rng)) {
+if (++*@\exposid{inner_}@ == ranges::end(inner_rng)) {
   ++@\exposid{outer_}@;
   @\exposid{satisfy}@();
 }
@@ -6742,9 +6741,9 @@
 \begin{codeblock}
 if (@\exposid{outer_}@ == ranges::end(@\exposid{parent_}@->@\exposid{base_}@))
   @\exposid{inner_}@ = ranges::end(*--@\exposid{outer_}@);
-while (@\exposid{inner_}@ == ranges::begin(*@\exposid{outer_}@))
-  @\exposid{inner_}@ = ranges::end(*--@\exposid{outer_}@);
---@\exposid{inner_}@;
+while (*@\exposid{inner_}@ == ranges::begin(*@\exposid{outer_}@))
+  *@\exposid{inner_}@ = ranges::end(*--@\exposid{outer_}@);
+--*@\exposid{inner_}@;
 return *this;
 \end{codeblock}
 \end{itemdescr}
@@ -6785,14 +6784,14 @@
 \indexlibrarymember{iter_swap}{join_view::\exposid{iterator}}%
 \begin{itemdecl}
 friend constexpr void iter_swap(const @\exposid{iterator}@& x, const @\exposid{iterator}@& y)
-  noexcept(noexcept(ranges::iter_swap(x.@\exposid{inner_}@, y.@\exposid{inner_}@)))
+  noexcept(noexcept(ranges::iter_swap(*x.@\exposid{inner_}@, *y.@\exposid{inner_}@)))
   requires @\libconcept{indirectly_swappable}@<@\exposid{InnerIter}@>;
 \end{itemdecl}
 
 \begin{itemdescr}
 \pnum
 \effects
-Equivalent to: \tcode{return ranges::iter_swap(x.\exposid{inner_}, y.\exposid{inner_});}
+Equivalent to: \tcode{return ranges::iter_swap(*x.\exposid{inner_}, *y.\exposid{inner_});}
 \end{itemdescr}
 
 \rSec3[range.join.sentinel]{Class template \tcode{join_view::\exposid{sentinel}}}