code: /*
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  
  package io.reactivex.rxjava3.internal.fuseable;
  
  import io.reactivex.rxjava3.annotations.NonNull;
  import io.reactivex.rxjava3.core.Maybe;
  
  /**
   * Interface indicating an operator implementation can be macro-fused back to Maybe in case
   * the operator goes from Maybe to some other reactive type and then the sequence calls
   * for toMaybe again:
   * <pre>
   * {@code
   * Single<Integer> single = Maybe.just(1).isEmpty();
   * Maybe<Integer> maybe = single.toMaybe();
   * }
   * </pre>
   *
   * The {@code Single.toMaybe()} will check for this interface and call the {@link #fuseToMaybe()}
   * to return a Maybe which could be the Maybe-specific implementation of isEmpty().
   * <p>
   * This causes a slight overhead in assembly time (1 instanceof check, 1 operator allocation and 1 dropped
   * operator) but does not incur the conversion overhead at runtime.
   *
   * @param <T> the value type
   */
  public interface FuseToMaybe<@NonNull T> {
  
      /**
       * Returns a (direct) Maybe for the operator.
       * <p>The implementation should handle the necessary RxJavaPlugins wrapping.
       * @return the Maybe instance
       */
      @NonNull
      Maybe<T> fuseToMaybe();
  }
  