[Bug c++/77523] New: rejects valid C++14 code with initialized lambda capture

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77523

            Bug ID: 77523
           Summary: rejects valid C++14 code with initialized lambda
                    capture
           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 (it is derived from PR 77522's
test). 


$ 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 20160907 (experimental) [trunk revision 240025] (GCC) 
$ 
$ clang++ -c -std=c++14 small.cpp
$ 
$ g++-trunk -c -std=c++14 small.cpp
small.cpp: In function ‘void f(T)’:
small.cpp:3:18: error: cannot capture ‘f<>’ by reference
   auto g = [&a = f <>] () {};
                  ^~~~
small.cpp: In instantiation of ‘void f(T) [with T = int]’:
small.cpp:8:7:   required from here
small.cpp:3:12: error: cannot bind non-const lvalue reference of type ‘void
(*&)(int)’ to an rvalue of type ‘void (*)(int)’
   auto g = [&a = f <>] () {};
            ^
$ 


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


template < class T = int > void f (T)
{
  auto g = [&a = f <>] () {};
}

int main ()
{
  f (0);
  return 0; 
}