CWG2233 Function parameter packs following default arguments

Author: jensmaurer

source/declarators.tex

@@ -1644,7 +1644,10 @@
 \grammarterm{parameter-declaration}{} this
 \grammarterm{initializer-clause}{}
 is used as a default argument.
-Default arguments will be used in calls where trailing arguments are missing.
+\begin{note}
+Default arguments will be used in calls
+where trailing arguments are missing\iref{expr.call}.
+\end{note}
 
 \pnum
 \indextext{argument!example of default}%
@@ -1709,7 +1712,8 @@
 In
 a given function declaration, each parameter subsequent to a
 parameter with a default argument shall have a default argument
-supplied in this or a previous declaration
+supplied in this or a previous declaration,
+unless the parameter was expanded from a parameter pack,
 or shall be a function parameter pack.
 A default argument
 shall not be redefined by a later declaration (not even to the
@@ -1735,6 +1739,10 @@
 void n() {
   f(6);                         // OK, calls \tcode{f(6, 7)}
 }
+template<class ... T> struct C {
+  void f(int n = 0, T...);
+};
+C<int> c;                       // OK, instantiates declaration \tcode{void C::f(int n = 0, int)}
 \end{codeblock}
 \end{example}
 For a given inline function defined in different translation units,

source/expressions.tex

@@ -2237,12 +2237,21 @@
 \indextext{function argument|see{argument}}%
 \indextext{function parameter|see{parameter}}%
 \indextext{initialization!parameter}%
-When a function is called, each parameter\iref{dcl.fct} shall be
+When a function is called, each parameter\iref{dcl.fct} is
 initialized~(\ref{dcl.init}, \ref{class.copy}, \ref{class.ctor}) with
 its corresponding argument.
+If there is no corresponding argument,
+the default argument for the parameter is used;
+the program is ill-formed if one is not present.
+\begin{example}
+\begin{codeblock}
+  template<typename ...T> int f(int n = 0, T ...t);
+  int x = f<int>();             // error: no argument for second function parameter
+\end{codeblock}
+\end{example}
 If the function is a non-static member
 function, the \tcode{this} parameter of the function\iref{class.this}
-shall be initialized with a pointer to the object of the call, converted
+is initialized with a pointer to the object of the call, converted
 as if by an explicit type conversion\iref{expr.cast}.
 \begin{note}
 There is no access or ambiguity checking on this conversion; the access