SingleAsync<TSource>
using System.Runtime.CompilerServices;
namespace System.Reactive.Linq.ObservableImpl
{
    [System.Runtime.CompilerServices.NullableContext(1)]
    [System.Runtime.CompilerServices.Nullable(0)]
    internal static class SingleAsync<[System.Runtime.CompilerServices.Nullable(2)] TSource>
    {
        [System.Runtime.CompilerServices.Nullable(new byte[] {
            0,
            1,
            1,
            0
        })]
        internal sealed class Sequence : Producer<TSource, Sequence._>
        {
            [System.Runtime.CompilerServices.Nullable(new byte[] {
                0,
                1
            })]
            internal sealed class _ : IdentitySink<TSource>
            {
                [System.Runtime.CompilerServices.Nullable(2)]
                private TSource _value;
                private bool _seenValue;
                public _(IObserver<TSource> observer)
                    : base(observer)
                {
                }
                public override void OnNext(TSource value)
                {
                    if (_seenValue)
                        try {
                            throw new InvalidOperationException(Strings_Linq.MORE_THAN_ONE_ELEMENT);
                        } catch (Exception error) {
                            ForwardOnError(error);
                        }
                    else {
                        _value = value;
                        _seenValue = true;
                    }
                }
                public override void OnCompleted()
                {
                    if (!_seenValue)
                        try {
                            throw new InvalidOperationException(Strings_Linq.NO_ELEMENTS);
                        } catch (Exception error) {
                            ForwardOnError(error);
                        }
                    else {
                        ForwardOnNext(_value);
                        ForwardOnCompleted();
                    }
                }
            }
            private readonly IObservable<TSource> _source;
            public Sequence(IObservable<TSource> source)
            {
                _source = source;
            }
            [return: System.Runtime.CompilerServices.Nullable(new byte[] {
                1,
                0
            })]
            protected override _ CreateSink(IObserver<TSource> observer)
            {
                return new _(observer);
            }
            protected override void Run([System.Runtime.CompilerServices.Nullable(new byte[] {
                1,
                0
            })] _ sink)
            {
                sink.Run(_source);
            }
        }
        [System.Runtime.CompilerServices.Nullable(new byte[] {
            0,
            1,
            1,
            0
        })]
        internal sealed class Predicate : Producer<TSource, Predicate._>
        {
            [System.Runtime.CompilerServices.Nullable(new byte[] {
                0,
                1
            })]
            internal sealed class _ : IdentitySink<TSource>
            {
                private readonly Func<TSource, bool> _predicate;
                [System.Runtime.CompilerServices.Nullable(2)]
                private TSource _value;
                private bool _seenValue;
                public _(Func<TSource, bool> predicate, IObserver<TSource> observer)
                    : base(observer)
                {
                    _predicate = predicate;
                }
                public override void OnNext(TSource value)
                {
                    bool flag = false;
                    try {
                        flag = _predicate(value);
                    } catch (Exception error) {
                        ForwardOnError(error);
                        return;
                    }
                    if (flag) {
                        if (_seenValue)
                            try {
                                throw new InvalidOperationException(Strings_Linq.MORE_THAN_ONE_MATCHING_ELEMENT);
                            } catch (Exception error2) {
                                ForwardOnError(error2);
                            }
                        else {
                            _value = value;
                            _seenValue = true;
                        }
                    }
                }
                public override void OnCompleted()
                {
                    if (!_seenValue)
                        try {
                            throw new InvalidOperationException(Strings_Linq.NO_MATCHING_ELEMENTS);
                        } catch (Exception error) {
                            ForwardOnError(error);
                        }
                    else {
                        ForwardOnNext(_value);
                        ForwardOnCompleted();
                    }
                }
            }
            private readonly IObservable<TSource> _source;
            private readonly Func<TSource, bool> _predicate;
            public Predicate(IObservable<TSource> source, Func<TSource, bool> predicate)
            {
                _source = source;
                _predicate = predicate;
            }
            [return: System.Runtime.CompilerServices.Nullable(new byte[] {
                1,
                0
            })]
            protected override _ CreateSink(IObserver<TSource> observer)
            {
                return new _(_predicate, observer);
            }
            protected override void Run([System.Runtime.CompilerServices.Nullable(new byte[] {
                1,
                0
            })] _ sink)
            {
                sink.Run(_source);
            }
        }
    }
}