[Bug c++/71825] New: incorrectly rejects valid C++ code with a template class inside a namespace

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71825

            Bug ID: 71825
           Summary: incorrectly rejects valid C++ code with a template
                    class inside a namespace
           Product: gcc
           Version: 7.0
            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 code is accepted by both Clang and MSVC. The issue seems to do with the
wrong name lookup for A in the constructor definition. 

$ 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/7.0.0/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 7.0.0 20160709 (experimental) [trunk revision 238191] (GCC) 
$ 
$ clang++-3.8 -c small.cpp
$ 
$ g++-trunk -c small.cpp
small.cpp:8:6: error: expected unqualified-id before ‘)’ token
   A () {}
      ^
$ 


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


namespace N 
{
  template < class > struct A; 
}

template < class A > struct N::A 
{
  A () {} 
};