Description of problem:
Compiling a C++ program that includes <optional> yields a compile error with clang++.


Version-Release number of selected component (if applicable):
clang-4.0.0-3.fc26.x86_64

How reproducible:
always

Steps to Reproduce:
1. $ cat > test_optional.cc 
#include <optional>
int main()
{
  return 0;
}
2. clang++ -std=c++1z test_optional.cc
3.

Actual results:
In file included from test_optional.cc:1:
/usr/bin/../lib/gcc/x86_64-redhat-linux/7/../../../../include/c++/7/optional:1032:27: error: use of class template 'optional' requires template arguments
  template <typename _Tp> optional(_Tp) -> optional<_Tp>;
                          ^
/usr/bin/../lib/gcc/x86_64-redhat-linux/7/../../../../include/c++/7/optional:451:11: note: template is declared here
    class optional
          ^
/usr/bin/../lib/gcc/x86_64-redhat-linux/7/../../../../include/c++/7/optional:1032:40: error: expected ';' at end of declaration
  template <typename _Tp> optional(_Tp) -> optional<_Tp>;
                                       ^
/usr/bin/../lib/gcc/x86_64-redhat-linux/7/../../../../include/c++/7/optional:1032:41: error: cannot use arrow operator on a type
  template <typename _Tp> optional(_Tp) -> optional<_Tp>;
                                        ^
3 errors generated.

Expected results:
No compile errors, successful compilation.

Additional info:
It works with g++ as expected:

$ g++ -std=c++1z test_optional.cc

Apparently, the libstdc++ which is also used by Fedora's clang++ implements std::optional in a way that is not (yet) supported by clang.

See also: https://bugs.archlinux.org/index.php?do=details&task_id=54276