Merge 2021-02 CWG Motion 3

Author: tkoeppe

source/expressions.tex

@@ -1636,8 +1636,8 @@
 
 \begin{bnf}
 \nontermdef{lambda-expression}\br
-    lambda-introducer \opt{lambda-declarator} compound-statement\br
-    lambda-introducer \terminal{<} template-parameter-list \terminal{>} \opt{requires-clause} \opt{lambda-declarator} compound-statement
+    lambda-introducer lambda-declarator compound-statement\br
+    lambda-introducer \terminal{<} template-parameter-list \terminal{>} \opt{requires-clause} lambda-declarator compound-statement
 \end{bnf}
 
 \begin{bnf}
@@ -1647,8 +1647,13 @@
 
 \begin{bnf}
 \nontermdef{lambda-declarator}\br
-    \terminal{(} parameter-declaration-clause \terminal{)} \opt{decl-specifier-seq}\br
-    \bnfindent\opt{noexcept-specifier} \opt{attribute-specifier-seq} \opt{trailing-return-type} \opt{requires-clause}
+    lambda-specifiers\br
+    \terminal{(} parameter-declaration-clause \terminal{)} lambda-specifiers \opt{requires-clause}
+\end{bnf}
+
+\begin{bnf}
+\nontermdef{lambda-specifiers}\br
+    \opt{decl-specifier-seq} \opt{noexcept-specifier} \opt{attribute-specifier-seq} \opt{trailing-return-type}
 \end{bnf}
 
 \pnum
@@ -1681,7 +1686,7 @@
 \end{note}
 
 \pnum
-If a \grammarterm{lambda-expression} does not include a
+If a \grammarterm{lambda-expression} includes an empty
 \grammarterm{lambda-declarator}, it is as if the \grammarterm{lambda-declarator} were
 \tcode{()}.
 The lambda return type is \tcode{auto}, which is replaced by the