final <T> T isSubtype(T sub) {
    Type returnType = method.getGenericReturnType();
    Type paramType = getOnlyParameterType();
    TestSubtype spec = method.getAnnotation(TestSubtype.class);
    assertWithMessage("%s is subtype of %s", paramType, returnType)
        .that(TypeToken.of(paramType).isSubtypeOf(returnType))
        .isTrue();
    assertWithMessage("%s is supertype of %s", returnType, paramType)

  final <T> T isSubtype(T sub) {
    Type returnType = method.getGenericReturnType();
    Type paramType = getOnlyParameterType();
    TestSubtype spec = method.getAnnotation(TestSubtype.class);
    assertWithMessage("%s is subtype of %s", paramType, returnType)
        .that(TypeToken.of(paramType).isSubtypeOf(returnType))
        .isTrue();
    assertWithMessage("%s is supertype of %s", returnType, paramType)

    ): Any? {
      val callArgs = args ?: arrayOf<Any?>()
      val methodName = method.name
      val returnType = method.returnType
      if (methodName == "supports" && Boolean::class.javaPrimitiveType == returnType) {
        return true // ALPN is supported.
      } else if (methodName == "unsupported" && Void.TYPE == returnType) {
        this.unsupported = true // Peer doesn't support ALPN.
        return null

    protected final String methodName;

    /** Array of method parameter types */
    protected final Class<?>[] parameterTypes;

    /** The return type of the method */
    protected final Class<?> returnType;

    /** Information about parameterized argument types */
    protected final ParameterizedClassDesc[] parameterizedClassDescs;

    /** Information about the parameterized return type */

    public static Class<?> getElementTypeOfCollectionFromReturnType(final Method method) {
        assertArgumentNotNull("method", method);

        final Type returnType = method.getGenericReturnType();
        return GenericsUtil.getRawClass(GenericsUtil.getElementTypeOfCollection(returnType));
    }

    /**
     * Returns the key type of the parameterized map declared as the method's argument type.
     *
     * @param method

    @SuppressWarnings("unchecked") // interfaceType is T
    T result = (T) dummy;
    return result;
  }

  /** Returns the dummy return value for {@code returnType}. */
  abstract <R> @Nullable R dummyReturnValue(TypeToken<R> returnType);

  private final class DummyHandler extends AbstractInvocationHandler implements Serializable {
    private final TypeToken<?> interfaceType;

    TypeToken<?> keyType =
        TypeToken.of(returnType).resolveType(WithFalseRecursiveType.class.getTypeParameters()[0]);
    assertThat(keyType.getType().toString()).isEqualTo("java.util.List<java.util.List<V>>");
  }

  public void testFalseRecursiveType_intermediaryTypeMappingDoesNotConfuseMe() {
    Type returnType =

    TypeToken<?> keyType =
        TypeToken.of(returnType).resolveType(WithFalseRecursiveType.class.getTypeParameters()[0]);
    assertThat(keyType.getType().toString()).isEqualTo("java.util.List<java.util.List<V>>");
  }

  public void testFalseRecursiveType_intermediaryTypeMappingDoesNotConfuseMe() {
    Type returnType =

                    String entity = baseName.substring(baseName.indexOf('_') + 1);
                    try {
                        Type returnType = m.getParameterTypes()[0]
                                .getMethod("get" + entity)
                                .getGenericReturnType();
                        if (returnType instanceof ParameterizedType parameterizedType) {

      } catch (NoSuchMethodException e) {
        throw new AssertionError("Annotation is missing required method", e);
      }
      Class<?> returnType = method.getReturnType();
      assertTrue(
          rootLocaleFormat("%s.%s() must return an array.", annotationClass, propertyName),
          returnType.isArray());
      assertWithMessage(
              rootLocaleFormat(
                  "%s.%s() must return an array of %s.",