[Bug c++/69009] New: ICE in instantiate_decl, at cp/pt.c:21511

[webrown.cpp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69009

            Bug ID: 69009
           Summary: ICE in instantiate_decl, at cp/pt.c:21511
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: webrown.cpp at gmail dot com
  Target Milestone: ---

Created attachment 37101
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37101&action=edit
Preprocessed source

Using g++-mp-6 (MacPorts gcc6 6-20151220_0) 6.0.0 20151220 (experimental)

compiling via
  g++-mp-6 -x c++ -std=c++1z -O3  (plus lots of -W flags)

Preprocessed source attached.

The problem manifested after revising my implementation of tuple_size and
tuple_size_v as outlined below:

template< class T >
constexpr auto
  tuple_size_v = 0;

...
// several tuple_size_v specializations later:

template< class T >
using
  tuple_size = integral_constant<size_t, tuple_size_v<T>>;