[Bug c++/65553] New: ICE on valid variadic template

[webrown.cpp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65553

            Bug ID: 65553
           Summary: ICE on valid variadic template
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: webrown.cpp at gmail dot com

Created attachment 35134
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35134&action=edit
program producing ICE

When compiling enclosed program via
  g++-mp-5 (MacPorts gcc5 5-20150308_0) 5.0.0 20150308 (experimental)
via command line
  g++-mp-5 -std=c++14 junk.cpp
the following messages obtain:

junk.cpp:10:38: internal compiler error: tree check: accessed elt 2 of tree_vec
with 1 elts in check_instantiated_args, at cp/pt.c:15822
 template< typename... Args, bool B = F2<Args...> >
                                      ^
junk.cpp:10:38: internal compiler error: Abort trap: 6
g++-mp-5: internal compiler error: Abort trap: 6 (program cc1plus)

Thanks to Andrew Sutton for reducing the test case.