% cat test.cpp                   
#include <compare>

int main()
{
  double foo = -0.0;
  double bar = 0.0;
  return std::is_eq(foo <=> bar);
}
% clang++ -std=c++20 test.cpp        
test.cpp:7:15: error: no member named 'is_eq' in namespace 'std'
  return std::is_eq(foo <=> bar);
         ~~~~~^
1 error generated.
% clang -v                           
Apple clang version 14.0.0 (clang-1400.0.29.202)
Target: x86_64-apple-darwin21.6.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin