[Bug c++/66743] New: ICE on formerly working code

[webrown.cpp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66743

            Bug ID: 66743
           Summary: ICE on formerly working code
           Product: gcc
           Version: c++-concepts
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: webrown.cpp at gmail dot com
  Target Milestone: ---

This appears to be a recently introduced regression.  Although I'm using the
concepts branch, no concepts features are used to reproduce the problem.


Reduced test case:

template< class T >
struct
  type_is { using type = T; };

template< class T >
  using underlying_type = type_is<__underlying_type(T)>;

int
  main( )
{
  return 0;
}


Compiler version:
concepts-g++ (GCC) 6.0.0 20150702 (experimental)


Command line (numerous -W options elided):
concepts-g++ -Og -std=c++1z ... <filename>


Diagnostic:

internal compiler error: tree check: expected record_type or union_type or
qual_union_type, have underlying_type in for_each_template_parm_r, at
cp/pt.c:8726