[Bug c++/53311] New: [C++0x] argument packs are not handled correctly in decltype

[chesstr at hotmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53311

             Bug #: 53311
           Summary: [C++0x] argument packs are not handled correctly in
                    decltype
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: chesstr@hotmail.com


Created attachment 27368
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27368
test case with both errors

Hi, it seems there are two major argument pack expansion problems in decltype :

1. mismatched argument pack lengths while expanding std::forward<Ts>(args)...

from sample code :
=====================================
> template<class func,class...arg3Ts>
> auto testbug1(func fun,arg2Ts...arg2s,arg3Ts...arg3s) ->
> decltype(fun(std::forward<arg2Ts>(arg2s)...,std::forward<arg3Ts>(arg3s)...))
> {
>	return fun(std::forward<arg2Ts>(arg2s)...,std::forward<arg3Ts>(arg3s)...);
> }
=====================================

2. 0 length argument packs in decltype result in ICE
( Bug 53307 : http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53307 )