./absl/functional/function_ref.h:124:16: warning: definition of implicit copy constructor for 'FunctionRef<void (int, int, int)>' is deprecated because it has a user-declared copy assignment operator [-Wdeprecated-copy]
  FunctionRef& operator=(const FunctionRef& rhs) = delete;
               ^
absl/functional/function_ref_benchmark.cc:89:12: note: in implicit copy constructor for 'absl::FunctionRef<void (int, int, int)>' first required here
  Function f = c;