[Bug c++/68437] New: [concepts] fold expression, pack expansion, and deduced constraint requirement

[lucdanton at free dot fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68437

            Bug ID: 68437
           Summary: [concepts] fold expression, pack expansion, and
                    deduced constraint requirement
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lucdanton at free dot fr
  Target Milestone: ---

Created attachment 36775
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36775&action=edit
Minimal testcase

This is using g++-trunk (GCC) 6.0.0 20151103 (experimental). Attached testcase
is as minimal as I could manage. If I change the fold expression in the
requirement to a 'manual', compile-time fold (not included in the testcase for
brevity) then the program compiles as expected--this is the workaround that I'm
using in the meantime.