LWG3769 basic_const_iterator::operator== causes infinite constraint recursion

Author: burblebee

source/iterators.tex

@@ -4256,34 +4256,35 @@
       requires @\libconcept{random_access_iterator}@<Iterator>;
 
     template<@\libconcept{sentinel_for}@<Iterator> S>
-      friend constexpr bool operator==(const basic_const_iterator& x, const S& s);
+      constexpr bool operator==(const S& s) const;
 
-    friend constexpr bool operator<(const basic_const_iterator& x, const basic_const_iterator& y)
+    constexpr bool operator<(const basic_const_iterator& y) const
       requires @\libconcept{random_access_iterator}@<Iterator>;
-    friend constexpr bool operator>(const basic_const_iterator& x, const basic_const_iterator& y)
+    constexpr bool operator>(const basic_const_iterator& y) const
       requires @\libconcept{random_access_iterator}@<Iterator>;
-    friend constexpr bool operator<=(const basic_const_iterator& x,
-                                     const basic_const_iterator& y)
+    constexpr bool operator<=(const basic_const_iterator& y) const
       requires @\libconcept{random_access_iterator}@<Iterator>;
-    friend constexpr bool operator>=(const basic_const_iterator& x,
-                                     const basic_const_iterator& y)
+    constexpr bool operator>=(const basic_const_iterator& y) const
       requires @\libconcept{random_access_iterator}@<Iterator>;
-    friend constexpr auto operator<=>(const basic_const_iterator& x,
-                                      const basic_const_iterator& y)
+    constexpr auto operator<=>(const basic_const_iterator& y) const
       requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{three_way_comparable}@<Iterator>;
 
     template<@\exposconcept{different-from}@<basic_const_iterator> I>
-      friend constexpr bool operator<(const basic_const_iterator& x, const I& y)
+      constexpr bool operator<(const I& y) const
         requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
     template<@\exposconcept{different-from}@<basic_const_iterator> I>
-      friend constexpr bool operator>(const basic_const_iterator& x, const I& y)
+      constexpr bool operator>(const I& y) const
         requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
     template<@\exposconcept{different-from}@<basic_const_iterator> I>
-      friend constexpr bool operator<=(const basic_const_iterator& x, const I& y)
+      constexpr bool operator<=(const I& y) const
         requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
     template<@\exposconcept{different-from}@<basic_const_iterator> I>
-      friend constexpr bool operator>=(const basic_const_iterator& x, const I& y)
+      constexpr bool operator>=(const I& y) const
         requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
+    template<@\exposconcept{different-from}@<basic_const_iterator> I>
+      constexpr auto operator<=>(const I& y) const
+        requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I> &&
+                 @\libconcept{three_way_comparable_with}@<Iterator, I>;
     template<@\exposconcept{not-a-const-iterator}@ I>
       friend constexpr bool operator<(const I& x, const basic_const_iterator& y)
         requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
@@ -4296,10 +4297,6 @@
     template<@\exposconcept{not-a-const-iterator}@ I>
       friend constexpr bool operator>=(const I& x, const basic_const_iterator& y)
         requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
-    template<@\exposconcept{different-from}@<basic_const_iterator> I>
-      friend constexpr auto operator<=>(const basic_const_iterator& x, const I& y)
-        requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I> &&
-                 @\libconcept{three_way_comparable_with}@<Iterator, I>;
 
     friend constexpr basic_const_iterator operator+(const basic_const_iterator& i,
                                                     difference_type n)
@@ -4311,9 +4308,9 @@
                                                     difference_type n)
       requires @\libconcept{random_access_iterator}@<Iterator>;
     template<@\libconcept{sized_sentinel_for}@<Iterator> S>
-      friend constexpr difference_type operator-(const basic_const_iterator& x, const S& y);
-    template<@\libconcept{sized_sentinel_for}@<Iterator> S>
-      requires @\exposconcept{different-from}@<S, basic_const_iterator>
+      constexpr difference_type operator-(const S& y) const;
+    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);
   };
 }
@@ -4549,13 +4546,13 @@
 \indexlibrarymember{operator==}{basic_const_iterator}%
 \begin{itemdecl}
 template<@\libconcept{sentinel_for}@<Iterator> S>
-  friend constexpr bool operator==(const basic_const_iterator& x, const S& s);
+  constexpr bool operator==(const S& s) const;
 \end{itemdecl}
 
 \begin{itemdescr}
 \pnum
 \effects
-Equivalent to: \tcode{return x.\exposid{current_} == s;}
+Equivalent to: \tcode{return \exposid{current_} == s;}
 \end{itemdescr}
 
 \indexlibrarymember{operator<}{basic_const_iterator}%
@@ -4564,15 +4561,15 @@
 \indexlibrarymember{operator>=}{basic_const_iterator}%
 \indexlibrarymember{operator<=>}{basic_const_iterator}%
 \begin{itemdecl}
-friend constexpr bool operator<(const basic_const_iterator& x, const basic_const_iterator& y)
+constexpr bool operator<(const basic_const_iterator& y) const
   requires @\libconcept{random_access_iterator}@<Iterator>;
-friend constexpr bool operator>(const basic_const_iterator& x, const basic_const_iterator& y)
+constexpr bool operator>(const basic_const_iterator& y) const
   requires @\libconcept{random_access_iterator}@<Iterator>;
-friend constexpr bool operator<=(const basic_const_iterator& x, const basic_const_iterator& y)
+constexpr bool operator<=(const basic_const_iterator& y) const
   requires @\libconcept{random_access_iterator}@<Iterator>;
-friend constexpr bool operator>=(const basic_const_iterator& x, const basic_const_iterator& y)
+constexpr bool operator>=(const basic_const_iterator& y) const
   requires @\libconcept{random_access_iterator}@<Iterator>;
-friend constexpr auto operator<=>(const basic_const_iterator& x, const basic_const_iterator& y)
+constexpr auto operator<=>(const basic_const_iterator& y) const
   requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{three_way_comparable}@<Iterator>;
 \end{itemdecl}
 
@@ -4583,7 +4580,7 @@
 \pnum
 \effects
 Equivalent to:
-\tcode{return x.\exposid{current_} \placeholder{op} \exposid{y.current_};}
+\tcode{return \exposid{current_} \placeholder{op} \exposid{y.current_};}
 \end{itemdescr}
 
 \indexlibrarymember{operator<}{basic_const_iterator}%
@@ -4593,19 +4590,19 @@
 \indexlibrarymember{operator<=>}{basic_const_iterator}%
 \begin{itemdecl}
 template<@\exposconcept{different-from}@<basic_const_iterator> I>
-  friend constexpr bool operator<(const basic_const_iterator& x, const I& y)
+  constexpr bool operator<(const I& y) const
     requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
 template<@\exposconcept{different-from}@<basic_const_iterator> I>
-  friend constexpr bool operator>(const basic_const_iterator& x, const I& y)
+  constexpr bool operator>(const I& y) const
     requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
 template<@\exposconcept{different-from}@<basic_const_iterator> I>
-  friend constexpr bool operator<=(const basic_const_iterator& x, const I& y)
+  constexpr bool operator<=(const I& y) const
     requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
 template<@\exposconcept{different-from}@<basic_const_iterator> I>
-  friend constexpr bool operator>=(const basic_const_iterator& x, const I& y)
+  constexpr bool operator>=(const I& y) const
     requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I>;
 template<@\exposconcept{different-from}@<basic_const_iterator> I>
-  friend constexpr auto operator<=>(const basic_const_iterator& x, const I& y)
+  constexpr auto operator<=>(const I& y) const
     requires @\libconcept{random_access_iterator}@<Iterator> && @\libconcept{totally_ordered_with}@<Iterator, I> &&
              @\libconcept{three_way_comparable_with}@<Iterator, I>;
 \end{itemdecl}
@@ -4615,8 +4612,8 @@
 Let \tcode{\placeholder{op}} be the operator.
 
 \pnum
-\returns
-Equivalent to: \tcode{return x.\exposid{current_} \placeholder{op} y;}
+\effects
+Equivalent to: \tcode{return \exposid{current_} \placeholder{op} y;}
 \end{itemdescr}
 
 \indexlibrarymember{operator<}{basic_const_iterator}%
@@ -4675,19 +4672,19 @@
 \indexlibrarymember{operator-}{basic_const_iterator}%
 \begin{itemdecl}
 template<@\libconcept{sized_sentinel_for}@<Iterator> S>
-  friend constexpr difference_type operator-(const basic_const_iterator& x, const S& y);
+  constexpr difference_type operator-(const S& y) const;
 \end{itemdecl}
 
 \begin{itemdescr}
 \pnum
 \effects
-Equivalent to: \tcode{return x.\exposid{current_} - y;}
+Equivalent to: \tcode{return \exposid{current_} - y;}
 \end{itemdescr}
 
 \indexlibrarymember{operator-}{basic_const_iterator}%
 \begin{itemdecl}
-template<@\libconcept{sized_sentinel_for}@<Iterator> S>
-  requires @\exposconcept{different-from}@<S, basic_const_iterator>
+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);
 \end{itemdecl}