Rebase on current draft

Author: steve-downey

include/beman/optional26/optional.hpp

@@ -362,9 +362,9 @@ class optional {
     constexpr T&       value() &;
     constexpr const T& value() const&;
     constexpr T&&      value() &&;
-    template <class U>
+    template <class U = std::remove_cv_t<T>>
     constexpr T value_or(U&& u) const&;
-    template <class U>
+    template <class U = std::remove_cv_t<T>>
     constexpr T value_or(U&& u) &&;
 
     // \ref{optional.monadic}, monadic operations

papers/P2988/base-optional.tex

@@ -86,7 +86,7 @@
     constexpr void swap(optional<T>&, optional<T>&) noexcept(@\seebelow@);
 
   template<class T>
-    constexpr optional<@\seebelow@> make_optional(T&&);
+    constexpr optional<decay_t<T>> make_optional(T&&);
   template<class T, class... Args>
     constexpr optional<T> make_optional(Args&&... args);
   template<class T, class U, class... Args>
@@ -122,7 +122,7 @@
       constexpr explicit optional(in_place_t, Args&&...);
     template<class U, class... Args>
       constexpr explicit optional(in_place_t, initializer_list<U>, Args&&...);
-    template<class U = T>
+    template<class U = remove_cv_t<T>>
       constexpr explicit(@\seebelow@) optional(U&&);
     template<class U>
       constexpr explicit(@\seebelow@) optional(const optional<U>&);
@@ -136,7 +136,7 @@
     constexpr optional& operator=(nullopt_t) noexcept;
     constexpr optional& operator=(const optional&);
     constexpr optional& operator=(optional&&) noexcept(@\seebelow@);
-    template<class U = T> constexpr optional& operator=(U&&);
+    template<class U = remove_cv_t<T>> constexpr optional& operator=(U&&);
     template<class U> constexpr optional& operator=(const optional<U>&);
     template<class U> constexpr optional& operator=(optional<U>&&);
     template<class... Args> constexpr T& emplace(Args&&...);
@@ -164,8 +164,8 @@
     constexpr T& value() &;                                             // freestanding-deleted
     constexpr T&& value() &&;                                           // freestanding-deleted
     constexpr const T&& value() const &&;                               // freestanding-deleted
-    template<class U> constexpr T value_or(U&&) const &;
-    template<class U> constexpr T value_or(U&&) &&;
+    template<class U = remove_cv_t<T>> constexpr T value_or(U&&) const &;
+    template<class U = remove_cv_t<T>> constexpr T value_or(U&&) &&;
 
     // \ref{optional.monadic}, monadic operations
     template<class F> constexpr auto and_then(F&& f) &;
@@ -183,7 +183,7 @@
     constexpr void reset() noexcept;
 
   private:
-    T *val;         // \expos
+    T* val;         // \expos
   };
 
   template<class T>
@@ -195,8 +195,7 @@
 Any instance of \tcode{optional<T>} at any given time either contains a value or does not contain a value.
 When an instance of \tcode{optional<T>} \defnx{contains a value}{contains a value!\idxcode{optional}},
 it means that an object of type \tcode{T}, referred to as the optional object's \defnx{contained value}{contained value!\idxcode{optional}},
-is allocated within the storage of the optional object.
-Implementations are not permitted to use additional storage, such as dynamic memory, to allocate its contained value.
+is nested within\iref{intro.object} the optional object.
 When an object of type \tcode{optional<T>} is contextually converted to \tcode{bool},
 the conversion returns \tcode{true} if the object contains a value;
 otherwise the conversion returns \tcode{false}.
@@ -357,7 +356,7 @@
 
 \indexlibraryctor{optional}%
 \begin{itemdecl}
-template<class U = T> constexpr explicit(@\seebelow@) optional(U&& v);
+template<class U = remove_cv_t<T>> constexpr explicit(@\seebelow@) optional(U&& v);
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -609,16 +608,18 @@
 
 \indexlibrarymember{operator=}{optional}%
 \begin{itemdecl}
-template<class U = T> constexpr optional<T>& operator=(U&& v);
+template<class U = remove_cv_t<T>> constexpr optional& operator=(U&& v);
 \end{itemdecl}
 
 \begin{itemdescr}
 \pnum
 \constraints
-\tcode{is_same_v<remove_cvref_t<U>, optional>} is \tcode{false},
-\tcode{conjunction_v<is_scalar<T>, is_same<T, decay_t<U>>>} is \tcode{false},
-\tcode{is_constructible_v<T, U>} is \tcode{true}, and
-\tcode{is_assignable_v<T\&, U>} is \tcode{true}.
+\begin{itemize}
+\item \tcode{is_same_v<remove_cvref_t<U>, optional>} is \tcode{false},
+\item \tcode{conjunction_v<is_scalar<T>, is_same<T, decay_t<U>>>} is \tcode{false},
+\item \tcode{is_constructible_v<T, U>} is \tcode{true}, and
+\item \tcode{is_assignable_v<T\&, U>} is \tcode{true}.
+\end{itemize}
 
 \pnum
 \effects
@@ -1044,7 +1045,7 @@
 
 \indexlibrarymember{value_or}{optional}%
 \begin{itemdecl}
-template<class U> constexpr T value_or(U&& v) const &;
+template<class U = remove_cv_t<T>> constexpr T value_or(U&& v) const &;
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -1062,7 +1063,7 @@
 
 \indexlibrarymember{value_or}{optional}%
 \begin{itemdecl}
-template<class U> constexpr T value_or(U&& v) &&;
+template<class U = remove_cv_t<T>> constexpr T value_or(U&& v) &&;
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -1510,6 +1511,7 @@
 \begin{itemdescr}
 \pnum
 \constraints
+\tcode{U} is not a specialization of \tcode{optional}.
 The expression \tcode{*x == v} is well-formed and
 its result is convertible to \tcode{bool}.
 \begin{note}
@@ -1529,6 +1531,7 @@
 \begin{itemdescr}
 \pnum
 \constraints
+\tcode{T} is not a specialization of \tcode{optional}.
 The expression \tcode{v == *x} is well-formed and
 its result is convertible to \tcode{bool}.
 
@@ -1545,6 +1548,7 @@
 \begin{itemdescr}
 \pnum
 \constraints
+\tcode{U} is not a specialization of \tcode{optional}.
 The expression \tcode{*x != v} is well-formed and
 its result is convertible to \tcode{bool}.
 
@@ -1561,6 +1565,7 @@
 \begin{itemdescr}
 \pnum
 \constraints
+\tcode{T} is not a specialization of \tcode{optional}.
 The expression \tcode{v != *x} is well-formed and
 its result is convertible to \tcode{bool}.
 
@@ -1577,6 +1582,7 @@
 \begin{itemdescr}
 \pnum
 \constraints
+\tcode{U} is not a specialization of \tcode{optional}.
 The expression \tcode{*x < v} is well-formed and
 its result is convertible to \tcode{bool}.
 
@@ -1593,6 +1599,7 @@
 \begin{itemdescr}
 \pnum
 \constraints
+\tcode{T} is not a specialization of \tcode{optional}.
 The expression \tcode{v < *x} is well-formed and
 its result is convertible to \tcode{bool}.
 
@@ -1609,6 +1616,7 @@
 \begin{itemdescr}
 \pnum
 \constraints
+\tcode{U} is not a specialization of \tcode{optional}.
 The expression \tcode{*x > v} is well-formed and
 its result is convertible to \tcode{bool}.
 
@@ -1625,6 +1633,7 @@
 \begin{itemdescr}
 \pnum
 \constraints
+\tcode{T} is not a specialization of \tcode{optional}.
 The expression \tcode{v > *x} is well-formed and
 its result is convertible to \tcode{bool}.
 
@@ -1641,6 +1650,7 @@
 \begin{itemdescr}
 \pnum
 \constraints
+\tcode{U} is not a specialization of \tcode{optional}.
 The expression \tcode{*x <= v} is well-formed and
 its result is convertible to \tcode{bool}.
 
@@ -1657,6 +1667,7 @@
 \begin{itemdescr}
 \pnum
 \constraints
+\tcode{T} is not a specialization of \tcode{optional}.
 The expression \tcode{v <= *x} is well-formed and
 its result is convertible to \tcode{bool}.
 
@@ -1673,6 +1684,7 @@
 \begin{itemdescr}
 \pnum
 \constraints
+\tcode{U} is not a specialization of \tcode{optional}.
 The expression \tcode{*x >= v} is well-formed and
 its result is convertible to \tcode{bool}.
 
@@ -1689,6 +1701,7 @@
 \begin{itemdescr}
 \pnum
 \constraints
+\tcode{T} is not a specialization of \tcode{optional}.
 The expression \tcode{v >= *x} is well-formed and
 its result is convertible to \tcode{bool}.
 

papers/P2988/new-optional.tex

@@ -92,7 +92,7 @@
     constexpr void swap(optional<T>&, optional<T>&) noexcept(@\seebelow@);
 
   template<class T>
-    constexpr optional<@\seebelow@> make_optional(T&&);
+    constexpr optional<decay_t<T>> make_optional(T&&);
   template<class T, class... Args>
     constexpr optional<T> make_optional(Args&&... args);
   template<class T, class U, class... Args>
@@ -129,7 +129,7 @@
       constexpr explicit optional(in_place_t, Args&&...);
     template<class U, class... Args>
       constexpr explicit optional(in_place_t, initializer_list<U>, Args&&...);
-    template<class U = T>
+    template<class U = remove_cv_t<T>>
       constexpr explicit(@\seebelow@) optional(U&&);
     template<class U>
       constexpr explicit(@\seebelow@) optional(const optional<U>&);
@@ -151,7 +151,7 @@
     constexpr optional& operator=(nullopt_t) noexcept;
     constexpr optional& operator=(const optional&);
     constexpr optional& operator=(optional&&) noexcept(@\seebelow@);
-    template<class U = T> constexpr optional& operator=(U&&);
+    template<class U = remove_cv_t<T>> constexpr optional& operator=(U&&);
     template<class U> constexpr optional& operator=(const optional<U>&);
 \end{codeblock}
 \color{addclr}
@@ -186,8 +186,8 @@
     constexpr T& value() &;                                             // freestanding-deleted
     constexpr T&& value() &&;                                           // freestanding-deleted
     constexpr const T&& value() const &&;                               // freestanding-deleted
-    template<class U> constexpr T value_or(U&&) const &;
-    template<class U> constexpr T value_or(U&&) &&;
+    template<class U = remove_cv_t<T>> constexpr T value_or(U&&) const &;
+    template<class U = remove_cv_t<T>> constexpr T value_or(U&&) &&;
 
     // \ref{optional.monadic}, monadic operations
     template<class F> constexpr auto and_then(F&& f) &;
@@ -205,7 +205,7 @@
     constexpr void reset() noexcept;
 
   private:
-    T *val;         // \expos
+    T* val;         // \expos
   };
 
   template<class T>
@@ -217,8 +217,7 @@
 Any instance of \tcode{optional<T>} at any given time either contains a value or does not contain a value.
 When an instance of \tcode{optional<T>} \defnx{contains a value}{contains a value!\idxcode{optional}},
 it means that an object of type \tcode{T}, referred to as the optional object's \defnx{contained value}{contained value!\idxcode{optional}},
-is allocated within the storage of the optional object.
-Implementations are not permitted to use additional storage, such as dynamic memory, to allocate its contained value.
+is nested within\iref{intro.object} the optional object.
 When an object of type \tcode{optional<T>} is contextually converted to \tcode{bool},
 the conversion returns \tcode{true} if the object contains a value;
 otherwise the conversion returns \tcode{false}.
@@ -389,7 +388,7 @@
 
 \indexlibraryctor{optional}%
 \begin{itemdecl}
-template<class U = T> constexpr explicit(@\seebelow@) optional(U&& v);
+template<class U = remove_cv_t<T>> constexpr explicit(@\seebelow@) optional(U&& v);
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -661,16 +660,18 @@
 
 \indexlibrarymember{operator=}{optional}%
 \begin{itemdecl}
-template<class U = T> constexpr optional<T>& operator=(U&& v);
+template<class U = remove_cv_t<T>> constexpr optional<T>& operator=(U&& v);
 \end{itemdecl}
 
 \begin{itemdescr}
 \pnum
 \constraints
-\tcode{is_same_v<remove_cvref_t<U>, optional>} is \tcode{false},
-\tcode{conjunction_v<is_scalar<T>, is_same<T, decay_t<U>>>} is \tcode{false},
-\tcode{is_constructible_v<T, U>} is \tcode{true}, and
-\tcode{is_assignable_v<T\&, U>} is \tcode{true}.
+\begin{itemize}
+\item \tcode{is_same_v<remove_cvref_t<U>, optional>} is \tcode{false},
+\item \tcode{conjunction_v<is_scalar<T>, is_same<T, decay_t<U>>>} is \tcode{false},
+\item \tcode{is_constructible_v<T, U>} is \tcode{true}, and
+\item \tcode{is_assignable_v<T\&, U>} is \tcode{true}.
+\end{itemize}
 
 \pnum
 \effects