Merge 2022-11 CWG Motion 2

P2709R0 Core Language Working Group "ready" issues for the November, 2022 meeting; issue 2635

Author: tkoeppe

source/declarations.tex

@@ -172,11 +172,19 @@
 \pnum
 A \grammarterm{simple-declaration} with an \grammarterm{identifier-list} is called
 a \defn{structured binding declaration}\iref{dcl.struct.bind}.
-If the \grammarterm{decl-specifier-seq} contains
-any \grammarterm{decl-specifier} other than
-\keyword{static}, \keyword{thread_local}, \keyword{auto}\iref{dcl.spec.auto}, or
-\grammarterm{cv-qualifier}{s},
-the program is ill-formed.
+Each \grammarterm{decl-specifier} in the \grammarterm{decl-specifier-seq}
+shall be
+\tcode{static},
+\tcode{thread_local},
+\tcode{auto}\iref{dcl.spec.auto}, or
+a \grammarterm{cv-qualifier}.
+\begin{example}
+\begin{codeblock}
+template<class T> concept C = true;
+C auto [x, y] = std::pair{1, 2};    // error: constrained \grammarterm{placeholder-type-specifier}
+                                    // not permitted for structured bindings
+\end{codeblock}
+\end{example}
 The \grammarterm{initializer} shall be
 of the form ``\tcode{=} \grammarterm{assignment-expression}'',
 of the form ``\tcode{\{} \grammarterm{assignment-expression} \tcode{\}}'',