Merge 2019-11 LWG Motion 21

P1959R0 Remove std::weak_equality and std::strong_equality

Author: zygoloid

source/basic.tex

@@ -4974,7 +4974,7 @@
 \end{note}
 The type of a pointer that can designate a function
 is called a \defn{function pointer type}.
-A pointer to objects of type \tcode{T} is referred to as a ``pointer to
+A pointer to an object of type \tcode{T} is referred to as a ``pointer to
 \tcode{T}''.
 \begin{example}
 A pointer to an object of type \tcode{int} is

source/classes.tex

@@ -6816,18 +6816,6 @@
          partial_ordering::unordered
 \end{codeblock}
 
-\item
-Otherwise, if \tcode{R} is \tcode{strong_equality}, then
-\begin{codeblock}
-a == b ? strong_equality::equal : strong_equality::nonequal
-\end{codeblock}
-
-\item
-Otherwise, if \tcode{R} is \tcode{weak_equality}, then
-\begin{codeblock}
-a == b ? weak_equality::equivalent : weak_equality::nonequivalent
-\end{codeblock}
-
 \item
 Otherwise, the synthesized three-way comparison is not defined.
 \end{itemize}
@@ -6889,18 +6877,6 @@
 is not a comparison category type\iref{cmp.categories},
 \tcode{U} is \tcode{void}.
 
-\item
-Otherwise, if
-at least one $\tcode{T}_i$ is \tcode{std::weak_equality}, or
-at least one $\tcode{T}_i$ is \tcode{std::strong_equality} and
-at least one $\tcode{T}_j$ is \tcode{std::partial_ordering} or
-                              \tcode{std::weak_ordering},
-\tcode{U} is \tcode{std::weak_equality}\iref{cmp.weakeq}.
-
-\item
-Otherwise, if at least one $\tcode{T}_i$ is \tcode{std::strong_equality},
-\tcode{U} is \tcode{std::strong_equality}\iref{cmp.strongeq}.
-
 \item
 Otherwise, if at least one $\tcode{T}_i$ is \tcode{std::partial_ordering},
 \tcode{U} is \tcode{std::partial_ordering}\iref{cmp.partialord}.
@@ -6944,8 +6920,10 @@
 \pnum
 \begin{example}
 \begin{codeblock}
+struct HasNoLessThan { };
+
 struct C {
-  friend std::strong_equality operator<=>(const C&, const C&);
+  friend HasNoLessThan operator<=>(const C&, const C&);
   bool operator<(const C&) const = default;             // OK, function is deleted
 };
 \end{codeblock}

source/expressions.tex

@@ -5955,20 +5955,6 @@
 array-to-pointer conversions\iref{conv.array} are not applied.
 \end{note}
 
-\pnum
-If the composite pointer type is
-a function pointer type,
-a pointer-to-member type, or
-\tcode{std::nullptr_t},
-the result is of type \tcode{std::strong_equality};
-the result is
-\tcode{std::strong_equality::equal}
-if the (possibly converted) operands compare equal\iref{expr.eq}
-and
-\tcode{std::strong_equality::nonequal}
-if they compare unequal,
-otherwise the result of the operator is unspecified.
-
 \pnum
 If the composite pointer type is an object pointer type,
 \tcode{p <=> q} is of type \tcode{std::strong_ordering}.
@@ -5987,12 +5973,10 @@
 Otherwise, the program is ill-formed.
 
 \pnum
-The five comparison category types\iref{cmp.categories}
+The three comparison category types\iref{cmp.categories}
 (the types
 \tcode{std::strong_ordering},
-\tcode{std::strong_equality},
-\tcode{std::weak_ordering},
-\tcode{std::weak_equality}, and
+\tcode{std::weak_ordering}, and
 \tcode{std::partial_ordering})
 are not predefined;
 if the header \libheaderref{compare}

source/iterators.tex

@@ -295,7 +295,7 @@
     constexpr bool operator>=(
       const reverse_iterator<Iterator1>& x,
       const reverse_iterator<Iterator2>& y);
-  template<class Iterator1, three_way_comparable_with<Iterator1, weak_equality> Iterator2>
+  template<class Iterator1, three_way_comparable_with<Iterator1> Iterator2>
     constexpr compare_three_way_result_t<Iterator1, Iterator2>
       operator<=>(const reverse_iterator<Iterator1>& x,
                   const reverse_iterator<Iterator2>& y);
@@ -350,7 +350,7 @@
   template<class Iterator1, class Iterator2>
     constexpr bool operator>=(
       const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);
-  template<class Iterator1, three_way_comparable_with<Iterator1, weak_equality> Iterator2>
+  template<class Iterator1, three_way_comparable_with<Iterator1> Iterator2>
     constexpr compare_three_way_result_t<Iterator1, Iterator2>
       operator<=>(const move_iterator<Iterator1>& x,
                   const move_iterator<Iterator2>& y);
@@ -3526,7 +3526,7 @@
 
 \indexlibrarymember{operator<=>}{reverse_iterator}%
 \begin{itemdecl}
-template<class Iterator1, three_way_comparable_with<Iterator1, weak_equality> Iterator2>
+template<class Iterator1, three_way_comparable_with<Iterator1> Iterator2>
   constexpr compare_three_way_result_t<Iterator1, Iterator2>
     operator<=>(const reverse_iterator<Iterator1>& x,
                 const reverse_iterator<Iterator2>& y);
@@ -4470,7 +4470,7 @@
 
 \indexlibrarymember{operator<=>}{move_iterator}%
 \begin{itemdecl}
-template<class Iterator1, three_way_comparable_with<Iterator1, weak_equality> Iterator2>
+template<class Iterator1, three_way_comparable_with<Iterator1> Iterator2>
   constexpr compare_three_way_result_t<Iterator1, Iterator2>
     operator<=>(const move_iterator<Iterator1>& x,
                 const move_iterator<Iterator2>& y);

source/overloading.tex

@@ -4114,9 +4114,8 @@
 is a pointer-to-member type or \tcode{std::nullptr_t},
 there exist candidate operator functions of the form
 \begin{codeblock}
-bool                 operator==(@\placeholder{T}@, @\placeholder{T}@);
-bool                 operator!=(@\placeholder{T}@, @\placeholder{T}@);
-std::strong_equality operator<=>(@\placeholder{T}@, @\placeholder{T}@);
+bool operator==(@\placeholder{T}@, @\placeholder{T}@);
+bool operator!=(@\placeholder{T}@, @\placeholder{T}@);
 \end{codeblock}
 
 \pnum