private static boolean isJavaLangClass(TypeMirror type) {
    return type.getKind().equals(TypeKind.DECLARED)
        && MoreTypes.asTypeElement(type).getQualifiedName().contentEquals("java.lang.Class");
  }
Throws an exception if this annotation contains a value for a Class element that is not
actually a type. The assumption is that the value is the string {@code "<error>"} which javac
presents when a Class value is an undefined type.
value/src/main/java/com/google/auto/value/processor/AnnotationOutput.java