Merge 2017-07 CWG Motion 9

Author: zygoloid

source/declarations.tex

@@ -1546,7 +1546,7 @@
 from an initializer. The \tcode{auto}
 \grammarterm{type-specifier} is also used to
 introduce a function type having a \grammarterm{trailing-return-type} or to
-signify that a lambda is a generic lambda (\ref{expr.prim.lambda.closure}).
+signify that a lambda is a generic lambda (\ref{expr.prim.lambda}).
 The \tcode{auto} \grammarterm{type-specifier} is also used to introduce a
 structured binding declaration (\ref{dcl.struct.bind}).
 
@@ -1563,17 +1563,6 @@
 deduced from non-discarded \tcode{return} statements, if any, in the body
 of the function~(\ref{stmt.if}).
 
-\pnum
-If the \tcode{auto} \grammarterm{type-specifier} appears as one of the
-\grammarterm{decl-specifier}{s} in the \grammarterm{decl-specifier-seq} of a
-\grammarterm{parameter-declaration} of a \grammarterm{lambda-expression}, the
-\indextext{generic lambda!definition of}%
-lambda is a \term{generic lambda}~(\ref{expr.prim.lambda.closure}). \begin{example}
-\begin{codeblock}
-auto glambda = [](int i, auto a) { return i; };     // OK: a generic lambda
-\end{codeblock}
-\end{example}
-
 \pnum
 The type of a variable declared using \tcode{auto} or \tcode{decltype(auto)} is
 deduced from its initializer.

source/expressions.tex

@@ -596,7 +596,8 @@
 
 \begin{bnf}
 \nontermdef{lambda-expression}\br
-    lambda-introducer lambda-declarator\opt compound-statement
+    lambda-introducer lambda-declarator\opt{} compound-statement\br
+    lambda-introducer \tcode{<} template-parameter-list \tcode{>} lambda-declarator\opt{} compound-statement
 \end{bnf}
 
 \begin{bnf}
@@ -659,6 +660,19 @@
 \end{codeblock}
 \end{example}
 
+\pnum
+A lambda is a \defn{generic lambda}
+if the \tcode{auto} \grammarterm{type-specifier} appears as one of the
+\grammarterm{decl-specifier}{s} in the \grammarterm{decl-specifier-seq} of a
+\grammarterm{parameter-declaration} of the \grammarterm{lambda-expression},
+or if the lambda has a \grammarterm{template-parameter-list}.
+\begin{example}
+\begin{codeblock}
+int i = [](int i, auto a) { return i; }(3, 4);         // OK: a generic lambda
+int j = []<class T>(T t, int i) { return i; }(3, 4);   // OK: a generic lambda
+\end{codeblock}
+\end{example}
+
 \rSec3[expr.prim.lambda.closure]{Closure types}%
 
 \pnum
@@ -700,7 +714,9 @@
 respectively.
 For a generic lambda, the closure type has a public inline function call
 operator member template~(\ref{temp.mem}) whose
-\grammarterm{template-parameter-list} consists of one invented type
+\grammarterm{template-parameter-list} consists of
+the specified \grammarterm{template-parameter-list}, if any,
+to which is appended one invented type
 \grammarterm{template-parameter} for each occurrence of \tcode{auto} in the
 lambda's \grammarterm{parameter-declaration-clause}, in order of appearance.
 The invented type \grammarterm{template-parameter} is a parameter pack if
@@ -808,7 +824,7 @@
 For a generic lambda with no \grammarterm{lambda-capture}, the closure type has a
 conversion function template to
 pointer to function. The conversion function template has the same invented
-\grammarterm{template-parameter-list}, and the pointer to function has the same
+template parameter list, and the pointer to function has the same
 parameter types, as the function call operator template.  The return type of
 the pointer to function shall behave as if it were a
 \grammarterm{decltype-specifier} denoting the return type of the corresponding