[Bug c++/84423] [6/7/8 Regression] [concepts] ICE with invalid using declaration

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84423

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |nathan at gcc dot gnu.org
            Summary|[concepts] ICE with invalid |[6/7/8 Regression]
                   |using declaration           |[concepts] ICE with invalid
                   |                            |using declaration

--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
Bisection points to r229629 as the cause of the ICE (gcc 6.0.0):

r229629 | jason | 2015-10-31 12:20:05 -0400 (Sat, 31 Oct 2015) | 15 lines

        Implement multiple 'auto' feature from Concepts TS.

Prior to that the code was rejected with:

pr84423.C:1:30: error: invalid use of ‘auto’
 template<typename> using A = auto;
                              ^
pr84423.C:5:3: error: ‘A’ was not declared in this scope
 B<A> b;
   ^
pr84423.C:5:4: error: template argument 1 is invalid
 B<A> b;
    ^