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.operators.single;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.internal.disposables.EmptyDisposable;
  
  import java.util.Objects;
  
  public final class SingleLift<T, R> extends Single<R> {
  
      final SingleSource<T> source;
  
      final SingleOperator<? extends R, ? super T> onLift;
  
      public SingleLift(SingleSource<T> source, SingleOperator<? extends R, ? super T> onLift) {
          this.source = source;
          this.onLift = onLift;
      }
  
      @Override
      protected void subscribeActual(SingleObserver<? super R> observer) {
          SingleObserver<? super T> sr;
  
          try {
              sr = Objects.requireNonNull(onLift.apply(observer), "The onLift returned a null SingleObserver");
          } catch (Throwable ex) {
              Exceptions.throwIfFatal(ex);
              EmptyDisposable.error(ex, observer);
              return;
          }
  
          source.subscribe(sr);
      }
  
  }
  