CWG2658 Trivial copying of unions in core constant expressions

Author: burblebee

source/expressions.tex

@@ -7616,6 +7616,15 @@
 to storage allocated with \tcode{std::allocator<T>} or
 to an object whose lifetime began within the evaluation of $E$.
 
+\pnum
+For the purposes of determining whether $E$ is a core constant expression,
+the evaluation of a call to
+a trivial copy/move constructor or copy/move assignment operator of a union
+is considered to copy/move the active member of the union, if any.
+\begin{note}
+The copy/move of the active member is trivial.
+\end{note}
+
 \pnum
 During the evaluation of an expression $E$ as a core constant expression,
 all \grammarterm{id-expression}s and uses of \tcode{*\keyword{this}}