[Bug c++/49205] New: Default constructor with pack expansion parameter not detected

[schaub.johannes at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49205

           Summary: Default constructor with pack expansion parameter not
                    detected
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: schaub.johan...@googlemail.com


This is rejected as "ambiguous" by GCC:

struct A { 
  template<typename ...T> A(T...); 
  A(initializer_list<short>); 
  A(initializer_list<long>); 
}; 

A a{};

But in fact, 8.5.4p3:

"If the initializer list has no elements and T is a class type with a default
constructor, the object is value-initialized."

And 12.1p5:

"A default constructor for a class X is a constructor of class X that can be
called without an argument."

So, there is no ambiguity. The default ctor is called, and "T" is deduced to
"<>"(empty pack).