[Bug c++/68177] New: Lambda capture doesn't work correctly when lambda is used in a pack expansion

[rs2740 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68177

            Bug ID: 68177
           Summary: Lambda capture doesn't work correctly when lambda is
                    used in a pack expansion
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rs2740 at gmail dot com
  Target Milestone: ---

Repro:

void swallow(...) {}
template<int... Is>
void foo() {
  int t = 0;
  swallow(
   ([&t]{return 0;}(), Is)...
  );
}


int main()
{
  foo<1, 2>();
  return 0;
}

gcc HEAD 6.0.0 20151031 (experimental) reports:

prog.cc: In instantiation of 'void foo() [with int ...Is = 1, 2]':
prog.cc:13:13:   required from here
prog.cc:6:5: error: member 'foo() [with int ...Is = 1, 2]::<lambda()>::<t
capture>' is uninitialized reference
    ([&t]{return 0;}(), Is)...
     ^

It appears that only the capture in the first element in the pack expansion
gets initialized correctly.

Clang accepts this code, as does MSVC.