[Bug c++/70635] New: ICE on (and rejects) valid code on x86_64-linux-gnu: Segmentation fault (program cc1plus)

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70635

            Bug ID: 70635
           Summary: ICE on (and rejects) valid code on x86_64-linux-gnu:
                    Segmentation fault (program cc1plus)
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu
  Target Milestone: ---

The following code causes an ICE when compiled with the current GCC trunk (and
4.9.x and later) on x86_64-linux-gnu in both 32-bit and 64-bit modes.  

The code does not cause an ICE for 4.8.x (and earlier), but is rejected. It
looks valid and is accepted by clang.


$ g++-trunk -v
Using built-in specs.
COLLECT_GCC=g++-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-source-trunk/configure --enable-languages=c,c++,lto
--prefix=/usr/local/gcc-trunk --disable-bootstrap
Thread model: posix
gcc version 6.0.0 20160411 (experimental) [trunk revision 234874] (GCC) 
$ 
$ g++-trunk -c small.cpp
small.cpp:11:37: error: declaration of ‘typedef typename A<typename
A<T>::B::type>::type A<T>::B::type’ -fpermissive]
   typedef typename A < type >::type type;
                                     ^~~~
small.cpp:5:28: error: changes meaning of ‘type’ from ‘typedef typename
A<T>::B::type A<T>::type’ [-fpermissive]
   typedef typename B::type type;
                            ^~~~
g++-trunk: internal compiler error: Segmentation fault (program cc1plus)
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.
$ 
$ g++-4.8 -c small.cpp
small.cpp:11:37: error: declaration of ‘typedef typename A<typename
A<T>::B::type>::type A<T>::B::type’ [-fpermissive]
   typedef typename A < type >::type type;
                                     ^
small.cpp:5:28: error: changes meaning of ‘type’ from ‘typedef typename
A<T>::B::type A<T>::type’ [-fpermissive]
   typedef typename B::type type;
                            ^
$ 
$ clang++-trunk -c small.cpp -Weverything
$ 


------------------------------------------------


template < typename T > 
struct A
{
  struct B;
  typedef typename B::type type;
};

template < typename T > 
struct A < T >::B
{
  typedef typename A < type >::type type;
  type Foo ();
};

template < typename T > 
typename A < T >::B::type
A < T >::B::Foo ()
{
  return 0;
}