P2401R0 Add a conditional noexcept specification to std::exchange

Author: jensmaurer

source/utilities.tex

@@ -52,7 +52,7 @@
 
   // \ref{utility.exchange}, exchange
   template<class T, class U = T>
-    constexpr T exchange(T& obj, U&& new_val);
+    constexpr T exchange(T& obj, U&& new_val) noexcept(@\seebelow@);
 
   // \ref{forward}, forward/move
   template<class T>
@@ -263,7 +263,7 @@
 \indexlibraryglobal{exchange}%
 \begin{itemdecl}
 template<class T, class U = T>
-  constexpr T exchange(T& obj, U&& new_val);
+  constexpr T exchange(T& obj, U&& new_val) noexcept(@\seebelow@);
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -275,6 +275,13 @@
 obj = std::forward<U>(new_val);
 return old_val;
 \end{codeblock}
+
+\pnum
+\remarks
+The exception specification is equivalent to:
+\begin{codeblock}
+is_nothrow_move_constructible_v<T> && is_nothrow_assignable_v<T&, U>
+\end{codeblock}
 \end{itemdescr}