static assertion fail

satacker@ubuntu:~/wg21_p2300_std_execution/build$ clang++-12 -std=c++2b ../examples/schedulers/inline_scheduler.cpp -I../include/  -fcoroutines-ts -lpthread -stdlib=libc++
../examples/schedulers/inline_scheduler.cpp:10:17: error: static_assert expression is not an integral constant expression
  static_assert(k==std::execution::forward_progress_guarantee::weakly_parallel);
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../examples/schedulers/inline_scheduler.cpp:10:17: note: read of non-const variable 'k' is not allowed in a constant expression
../examples/schedulers/inline_scheduler.cpp:8:8: note: declared here
  auto k = std::execution::get_forward_progress_guarantee(std::ref(s));
       ^
1 error generated.