P0602R4 variant and optional should propagate copy/move triviality

Author: Dawn Perchik

source/utilities.tex

@@ -2224,8 +2224,8 @@
 
     // \ref{optional.assign}, assignment
     optional& operator=(nullopt_t) noexcept;
-    optional& operator=(const optional&);
-    optional& operator=(optional&&) noexcept(@\seebelow@);
+    constexpr optional& operator=(const optional&);
+    constexpr optional& operator=(optional&&) noexcept(@\seebelow@);
     template<class U = T> optional& operator=(U&&);
     template<class U> optional& operator=(const optional<U>&);
     template<class U> optional& operator=(optional<U>&&);
@@ -2325,7 +2325,7 @@
 This constructor shall be defined as deleted unless
 \tcode{is_copy_constructible_v<T>} is \tcode{true}.
 If \tcode{is_trivially_copy_constructible_v<T>} is \tcode{true},
-this constructor shall be a \tcode{constexpr} constructor.
+this constructor is trivial..
 \end{itemdescr}
 
 \indexlibrary{\idxcode{optional}!constructor}%
@@ -2355,7 +2355,7 @@
 This constructor shall not participate in overload resolution
 unless \tcode{is_move_constructible_v<T>} is \tcode{true}.
 If \tcode{is_trivially_move_constructible_v<T>} is \tcode{true},
-this constructor shall be a \tcode{constexpr} constructor.
+this constructor is trivial.
 \end{itemdescr}
 
 \indexlibrary{\idxcode{optional}!constructor}%
@@ -2565,7 +2565,7 @@
 
 \indexlibrarymember{operator=}{optional}%
 \begin{itemdecl}
-optional<T>& operator=(const optional& rhs);
+constexpr optional<T>& operator=(const optional& rhs);
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -2603,11 +2603,15 @@
 This operator shall be defined as deleted unless
 \tcode{is_copy_constructible_v<T>} is \tcode{true} and
 \tcode{is_copy_assignable_v<T>} is \tcode{true}.
+If \tcode{is_trivially_copy_constructible_v<T> \&\&}
+\tcode{is_trivially_copy_assignable_v<T> \&\&}
+\tcode{is_trivially_destructible_v<T>} is \tcode{true},
+this assignment operator is trivial.
 \end{itemdescr}
 
 \indexlibrarymember{operator=}{optional}%
 \begin{itemdecl}
-optional<T>& operator=(optional&& rhs) noexcept(@\seebelow@);
+constexpr optional<T>& operator=(optional&& rhs) noexcept(@\seebelow@);
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -2653,6 +2657,10 @@
 This operator shall not participate in overload resolution unless
 \tcode{is_move_constructible_v<T>} is \tcode{true} and
 \tcode{is_move_assignable_v<T>} is \tcode{true}.
+If \tcode{is_trivially_move_constructible_v<T> \&\&}
+\tcode{is_trivially_move_assignable_v<T> \&\&}
+\tcode{is_trivially_destructible_v<T>} is \tcode{true},
+this assignment operator is trivial.
 \end{itemdescr}
 
 \indexlibrarymember{operator=}{optional}%
@@ -3803,8 +3811,8 @@
   public:
     // \ref{variant.ctor}, constructors
     constexpr variant() noexcept(@\seebelow@);
-    variant(const variant&);
-    variant(variant&&) noexcept(@\seebelow@);
+    constexpr variant(const variant&);
+    constexpr variant(variant&&) noexcept(@\seebelow@);
 
     template<class T>
       constexpr variant(T&&) noexcept(@\seebelow@);
@@ -3823,8 +3831,8 @@
     ~variant();
 
     // \ref{variant.assign}, assignment
-    variant& operator=(const variant&);
-    variant& operator=(variant&&) noexcept(@\seebelow@);
+    constexpr variant& operator=(const variant&);
+    constexpr variant& operator=(variant&&) noexcept(@\seebelow@);
 
     template<class T> variant& operator=(T&&) noexcept(@\seebelow@);
 
@@ -3908,7 +3916,7 @@
 
 \indexlibrary{\idxcode{variant}!constructor}%
 \begin{itemdecl}
-variant(const variant& w);
+constexpr variant(const variant& w);
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -3927,11 +3935,13 @@
 \remarks
 This constructor shall be defined as deleted unless
 \tcode{is_copy_constructible_v<$\tcode{T}_i$>} is \tcode{true} for all $i$.
+If \tcode{is_trivially_copy_constructible_v<$\tcode{T}_i$>}
+is \tcode{true} for all $i$, this constructor is trivial.
 \end{itemdescr}
 
 \indexlibrary{\idxcode{variant}!constructor}%
 \begin{itemdecl}
-variant(variant&& w) noexcept(@\seebelow@);
+constexpr variant(variant&& w) noexcept(@\seebelow@);
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -3952,6 +3962,8 @@
 \tcode{is_nothrow_move_constructible_v<$\tcode{T}_i$>} for all $i$.
 This function shall not participate in overload resolution unless
 \tcode{is_move_constructible_v<$\tcode{T}_i$>} is \tcode{true} for all $i$.
+If \tcode{is_trivially_move_constructible_v<$\tcode{T}_i$>}
+is \tcode{true} for all $i$, this constructor is trivial.
 \end{itemdescr}
 
 \indexlibrary{\idxcode{variant}!constructor}%
@@ -4165,7 +4177,7 @@
 
 \indexlibrarymember{operator=}{variant}%
 \begin{itemdecl}
-variant& operator=(const variant& rhs);
+constexpr variant& operator=(const variant& rhs);
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -4204,11 +4216,15 @@
 \tcode{is_copy_constructible_v<$\tcode{T}_i$> \&\&}
 \tcode{is_copy_assignable_v<$\tcode{T}_i$>}
 is \tcode{true} for all $i$.
+If \tcode{is_trivially_copy_constructible_v<$\tcode{T}_i$> \&\&}
+\tcode{is_trivially_copy_assignable_v<$\tcode{T}_i$> \&\&}
+\tcode{is_trivially_destructible_v<$\tcode{T}_i$>}
+is true for all $i$, this assignment operator is trivial.
 \end{itemdescr}
 
 \indexlibrarymember{operator=}{variant}%
 \begin{itemdecl}
-variant& operator=(variant&& rhs) noexcept(@\seebelow@);
+constexpr variant& operator=(variant&& rhs) noexcept(@\seebelow@);
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -4236,8 +4252,13 @@
 \pnum
 \remarks
 This function shall not participate in overload resolution unless
-\tcode{is_move_constructible_v<$\tcode{T}_i$> \&\& is_move_assignable_v<$\tcode{T}_i$>} is
+\tcode{is_move_constructible_v<$\tcode{T}_i$> \&\&}
+\tcode{is_move_assignable_v<$\tcode{T}_i$>} is
 \tcode{true} for all $i$.
+If \tcode{is_trivially_move_constructible_v<$\tcode{T}_i$> \&\&}
+\tcode{is_trivially_move_assignable_v<$\tcode{T}_i$> \&\&}
+\tcode{is_trivially_destructible_v<$\tcode{T}_i$>}
+is true for all $i$, this assignment operator is trivial.
 The expression inside \tcode{noexcept} is equivalent to:
 \tcode{is_nothrow_move_constructible_v<$\tcode{T}_i$> \&\& is_nothrow_move_assignable_v<$\tcode{T}_i$>} for all $i$.
 \begin{itemize}