* fine for the synthetic TypeVariable to be unequal to any native TypeVariable anyway.
   */
  static final class NativeTypeVariableEquals<X> {
    static final boolean NATIVE_TYPE_VARIABLE_ONLY =
        !NativeTypeVariableEquals.class.getTypeParameters()[0].equals(
            newArtificialTypeVariable(NativeTypeVariableEquals.class, "X"));
  }

  private Types() {}

  private static class TypeVariableEqualsTester {
    private final EqualsTester tester = new EqualsTester();

    TypeVariableEqualsTester addEqualityGroup(Type jvmType, Type... types) {
      if (Types.NativeTypeVariableEquals.NATIVE_TYPE_VARIABLE_ONLY) {
        tester.addEqualityGroup(jvmType);
        tester.addEqualityGroup((Object[]) types);
      } else {
        tester.addEqualityGroup(Lists.asList(jvmType, types).toArray());

  private static class TypeVariableEqualsTester {
    private final EqualsTester tester = new EqualsTester();

    TypeVariableEqualsTester addEqualityGroup(Type jvmType, Type... types) {
      if (Types.NativeTypeVariableEquals.NATIVE_TYPE_VARIABLE_ONLY) {
        tester.addEqualityGroup(jvmType);
        tester.addEqualityGroup((Object[]) types);
      } else {
        tester.addEqualityGroup(Lists.asList(jvmType, types).toArray());