checkArgument(!cls.isPrimitive(), "Primitive type '%s' used as %s", cls, usedAs);
      }
    }
  }

  /** Returns the {@code Class} object of arrays with {@code componentType}. */
  static Class<?> getArrayClass(Class<?> componentType) {
    // TODO(user): This is not the most efficient way to handle generic
    // arrays, but is there another way to extract the array class in a

      @Override
      void visitClass(Class<?> t) {
        builder.add(t);
      }

      @Override
      void visitGenericArrayType(GenericArrayType t) {
        builder.add(Types.getArrayClass(of(t.getGenericComponentType()).getRawType()));
      }
    }.visit(runtimeType);
    // Cast from ImmutableSet<Class<?>> to ImmutableSet<Class<? super T>>
    @SuppressWarnings({"unchecked", "rawtypes"})