[Moved to DR at the November, 2014 meeting.]

Proposed resolution (February, 2014):

1. Change 13.10.3.2 [temp.deduct.call] paragraph 1 as follows:

Template argument deduction is done by comparing each function template parameter type (call it P) with the type of the corresponding argument of the call (call it A) as described below. If removing references and cv-qualifiers from P gives std::initializer_list<P'> for some P' and the argument is an initializer list (9.5.5 [dcl.init.list]), then deduction is performed instead for each element of the initializer list, taking P' as a function template parameter type and the initializer element as its argument. Otherwise, an initializer list argument causes the parameter to be considered a non-deduced context (13.10.3.6 [temp.deduct.type]). [Example:

  template<class T> void f(std::initializer_list<T>);
  f({1,2,3});              // T deduced to int
  f({1,"asdf"});           // error: T deduced to both int and const char*

  template<class T> void g(T);
  g({1,2,3});              // error: no argument deduced for T

—end example] For a function parameter pack...

2. Change the penultimate bullet of 13.10.3.6 [temp.deduct.type] paragraph 5 as follows:

The non-deduced contexts are:

• ...

• A function parameter for which the associated argument is an initializer list (9.5.5 [dcl.init.list]) but the parameter does not have std::initializer_list or reference to possibly cv-qualified std::initializer_list type . [Example:...

• A function parameter pack that does not occur at the end of the parameter-declaration-list.

Additional note (March, 2013):

The element type should also be deducible.

Currently, 13.10.3.2 [temp.deduct.call] paragraph 1 says,

Template argument deduction is done by comparing each function template parameter type (call it P) with the type of the corresponding argument of the call (call it A) as described below. If removing references and cv-qualifiers from P gives std::initializer_list<P'> for some P' and the argument is an initializer list (9.5.5 [dcl.init.list]), then deduction is performed instead for each element of the initializer list, taking P' as a function template parameter type and the initializer element as its argument. Otherwise, an initializer list argument causes the parameter to be considered a non-deduced context (13.10.3.6 [temp.deduct.type]).

It would seem reasonable, however, to allow an array bound to be deduced from the number of elements in the initializer list, e.g.,

  template<int N> void g(int const (&)[N]);
  void f() {
    g( { 1, 2, 3, 4 } );
  }