Method from

java/dagger/internal/codegen/OptionalType.java:146–149

Returns a OptionalType for type. @throws IllegalArgumentException if type is not an Optional type

(TypeMirror type)

   * @throws IllegalArgumentException if {@code type} is not an {@code Optional} type
   */
  static OptionalType from(TypeMirror type) {
    checkArgument(isOptional(type), "%s must be an Optional", type);
    return new AutoValue_OptionalType(MoreTypes.equivalence().wrap(MoreTypes.asDeclared(type)));
  }

  /**
   * Returns a {@link OptionalType} for {@code key}'s {@link Key#type() type}.