anchor.diff:        (lib.withFeatureAs scpSupport "libssh2" (lib.getDev libssh2))
         (lib.enableFeature ldapSupport "ldap")
         (lib.enableFeature ldapSupport "ldaps")
  -      (lib.withFeatureAs idnSupport "libidn" (lib.getDev libidn))
  +      (lib.withFeatureAs idnSupport "libidn2" (lib.getDev libidn2))
         (lib.withFeature brotliSupport "brotli")
       ]
       ++ lib.optional wolfsslSupport "--with-wolfssl=${lib.getDev wolfssl}"
  
positive.code:   # applications that use Curl.
    propagatedBuildInputs = with lib;
      optional http2Support nghttp2 ++
      optional idnSupport libidn ++
      optional ldapSupport openldap ++
      optional zlibSupport zlib ++
      optional gssSupport libkrb5 ++
  
negative.code: # files.
  
  assert http2Support -> nghttp2 != null;
  assert idnSupport -> libidn2 != null;
  assert ldapSupport -> openldap != null;
  assert zlibSupport -> zlib != null;
  assert opensslSupport -> openssl != null;
  