reactive/Ix.NET/Source/System.Linq.Async/System/Linq/Operators/Min.Primitive.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

namespace System.Linq
{
    public static partial class AsyncEnumerable
    {
        private static async Task<int> MinCore(IAsyncEnumerable<int> source, CancellationToken cancellationToken)
        {
            int value;

            IAsyncEnumerator<int> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = e.Current;

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    int x = e.Current;

                    if (x < value)
                    {
                        value = x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<int?> MinCore(IAsyncEnumerable<int?> source, CancellationToken cancellationToken)
        {
            int? value = null;

            IAsyncEnumerator<int?> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                // Start off knowing that we've a non-null value (or exit here, knowing we don't)
                // so we don't have to keep testing for nullity.
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = e.Current;
                }
                while (!value.HasValue);

                // Keep hold of the wrapped value, and do comparisons on that, rather than
                // using the lifted operation each time.
                int valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    int? cur = e.Current;
                    int x = cur.GetValueOrDefault();

                    // Do not replace & with &&. The branch prediction cost outweighs the extra operation
                    // unless nulls either never happen or always happen.
                    if (cur.HasValue & x < valueVal)
                    {
                        valueVal = x;
                        value = cur;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<long> MinCore(IAsyncEnumerable<long> source, CancellationToken cancellationToken)
        {
            long value;

            IAsyncEnumerator<long> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = e.Current;

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    long x = e.Current;

                    if (x < value)
                    {
                        value = x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<long?> MinCore(IAsyncEnumerable<long?> source, CancellationToken cancellationToken)
        {
            long? value = null;

            IAsyncEnumerator<long?> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = e.Current;
                }
                while (!value.HasValue);

                long valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    long? cur = e.Current;
                    long x = cur.GetValueOrDefault();

                    // Do not replace & with &&. The branch prediction cost outweighs the extra operation
                    // unless nulls either never happen or always happen.
                    if (cur.HasValue & x < valueVal)
                    {
                        valueVal = x;
                        value = cur;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<float> MinCore(IAsyncEnumerable<float> source, CancellationToken cancellationToken)
        {
            float value;

            IAsyncEnumerator<float> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = e.Current;

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    float x = e.Current;

                    if (x < value)
                    {
                        value = x;
                    }
                    else if (float.IsNaN(x))
                    {
                        // Normally NaN < anything is false, as is anything < NaN
                        // However, this leads to some irksome outcomes in Min and Max.
                        // If we use those semantics then Min(NaN, 5.0) is NaN, but
                        // Min(5.0, NaN) is 5.0!  To fix this, we impose a total
                        // ordering where NaN is smaller than every value, including
                        // negative infinity.
                        // Not testing for NaN therefore isn't an option, but since we
                        // can't find a smaller value, we can short-circuit.
                        return x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<float?> MinCore(IAsyncEnumerable<float?> source, CancellationToken cancellationToken)
        {
            float? value = null;

            IAsyncEnumerator<float?> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = e.Current;
                }
                while (!value.HasValue);

                float valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    float? cur = e.Current;

                    if (cur.HasValue)
                    {
                        float x = cur.GetValueOrDefault();

                        if (x < valueVal)
                        {
                            valueVal = x;
                            value = cur;
                        }
                        else if (float.IsNaN(x))
                        {
                            return cur;
                        }
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<double> MinCore(IAsyncEnumerable<double> source, CancellationToken cancellationToken)
        {
            double value;

            IAsyncEnumerator<double> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = e.Current;

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    double x = e.Current;

                    if (x < value)
                    {
                        value = x;
                    }
                    else if (double.IsNaN(x))
                    {
                        return x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<double?> MinCore(IAsyncEnumerable<double?> source, CancellationToken cancellationToken)
        {
            double? value = null;

            IAsyncEnumerator<double?> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = e.Current;
                }
                while (!value.HasValue);

                double valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    double? cur = e.Current;

                    if (cur.HasValue)
                    {
                        double x = cur.GetValueOrDefault();

                        if (x < valueVal)
                        {
                            valueVal = x;
                            value = cur;
                        }
                        else if (double.IsNaN(x))
                        {
                            return cur;
                        }
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<decimal> MinCore(IAsyncEnumerable<decimal> source, CancellationToken cancellationToken)
        {
            decimal value;

            IAsyncEnumerator<decimal> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = e.Current;

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    decimal x = e.Current;

                    if (x < value)
                    {
                        value = x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<decimal?> MinCore(IAsyncEnumerable<decimal?> source, CancellationToken cancellationToken)
        {
            decimal? value = null;

            IAsyncEnumerator<decimal?> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = e.Current;
                }
                while (!value.HasValue);

                decimal valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    decimal? cur = e.Current;
                    decimal x = cur.GetValueOrDefault();

                    if (cur.HasValue && x < valueVal)
                    {
                        valueVal = x;
                        value = cur;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<int> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, int> selector, CancellationToken cancellationToken)
        {
            int value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = selector(e.Current);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    int x = selector(e.Current);

                    if (x < value)
                    {
                        value = x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<int?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, int?> selector, CancellationToken cancellationToken)
        {
            int? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                // Start off knowing that we've a non-null value (or exit here, knowing we don't)
                // so we don't have to keep testing for nullity.
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = selector(e.Current);
                }
                while (!value.HasValue);

                // Keep hold of the wrapped value, and do comparisons on that, rather than
                // using the lifted operation each time.
                int valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    int? cur = selector(e.Current);
                    int x = cur.GetValueOrDefault();

                    // Do not replace & with &&. The branch prediction cost outweighs the extra operation
                    // unless nulls either never happen or always happen.
                    if (cur.HasValue & x < valueVal)
                    {
                        valueVal = x;
                        value = cur;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<long> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, long> selector, CancellationToken cancellationToken)
        {
            long value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = selector(e.Current);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    long x = selector(e.Current);

                    if (x < value)
                    {
                        value = x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<long?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, long?> selector, CancellationToken cancellationToken)
        {
            long? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = selector(e.Current);
                }
                while (!value.HasValue);

                long valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    long? cur = selector(e.Current);
                    long x = cur.GetValueOrDefault();

                    // Do not replace & with &&. The branch prediction cost outweighs the extra operation
                    // unless nulls either never happen or always happen.
                    if (cur.HasValue & x < valueVal)
                    {
                        valueVal = x;
                        value = cur;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<float> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, float> selector, CancellationToken cancellationToken)
        {
            float value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = selector(e.Current);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    float x = selector(e.Current);

                    if (x < value)
                    {
                        value = x;
                    }
                    else if (float.IsNaN(x))
                    {
                        // Normally NaN < anything is false, as is anything < NaN
                        // However, this leads to some irksome outcomes in Min and Max.
                        // If we use those semantics then Min(NaN, 5.0) is NaN, but
                        // Min(5.0, NaN) is 5.0!  To fix this, we impose a total
                        // ordering where NaN is smaller than every value, including
                        // negative infinity.
                        // Not testing for NaN therefore isn't an option, but since we
                        // can't find a smaller value, we can short-circuit.
                        return x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<float?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, float?> selector, CancellationToken cancellationToken)
        {
            float? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = selector(e.Current);
                }
                while (!value.HasValue);

                float valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    float? cur = selector(e.Current);

                    if (cur.HasValue)
                    {
                        float x = cur.GetValueOrDefault();

                        if (x < valueVal)
                        {
                            valueVal = x;
                            value = cur;
                        }
                        else if (float.IsNaN(x))
                        {
                            return cur;
                        }
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<double> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, double> selector, CancellationToken cancellationToken)
        {
            double value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = selector(e.Current);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    double x = selector(e.Current);

                    if (x < value)
                    {
                        value = x;
                    }
                    else if (double.IsNaN(x))
                    {
                        return x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<double?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, double?> selector, CancellationToken cancellationToken)
        {
            double? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = selector(e.Current);
                }
                while (!value.HasValue);

                double valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    double? cur = selector(e.Current);

                    if (cur.HasValue)
                    {
                        double x = cur.GetValueOrDefault();

                        if (x < valueVal)
                        {
                            valueVal = x;
                            value = cur;
                        }
                        else if (double.IsNaN(x))
                        {
                            return cur;
                        }
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<decimal> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, decimal> selector, CancellationToken cancellationToken)
        {
            decimal value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = selector(e.Current);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    decimal x = selector(e.Current);

                    if (x < value)
                    {
                        value = x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<decimal?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, decimal?> selector, CancellationToken cancellationToken)
        {
            decimal? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = selector(e.Current);
                }
                while (!value.HasValue);

                decimal valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    decimal? cur = selector(e.Current);
                    decimal x = cur.GetValueOrDefault();

                    if (cur.HasValue && x < valueVal)
                    {
                        valueVal = x;
                        value = cur;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<int> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, ValueTask<int>> selector, CancellationToken cancellationToken)
        {
            int value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = await selector(e.Current).ConfigureAwait(false);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    int x = await selector(e.Current).ConfigureAwait(false);

                    if (x < value)
                    {
                        value = x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<int?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, ValueTask<int?>> selector, CancellationToken cancellationToken)
        {
            int? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                // Start off knowing that we've a non-null value (or exit here, knowing we don't)
                // so we don't have to keep testing for nullity.
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = await selector(e.Current).ConfigureAwait(false);
                }
                while (!value.HasValue);

                // Keep hold of the wrapped value, and do comparisons on that, rather than
                // using the lifted operation each time.
                int valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    int? cur = await selector(e.Current).ConfigureAwait(false);
                    int x = cur.GetValueOrDefault();

                    // Do not replace & with &&. The branch prediction cost outweighs the extra operation
                    // unless nulls either never happen or always happen.
                    if (cur.HasValue & x < valueVal)
                    {
                        valueVal = x;
                        value = cur;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<long> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, ValueTask<long>> selector, CancellationToken cancellationToken)
        {
            long value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = await selector(e.Current).ConfigureAwait(false);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    long x = await selector(e.Current).ConfigureAwait(false);

                    if (x < value)
                    {
                        value = x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<long?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, ValueTask<long?>> selector, CancellationToken cancellationToken)
        {
            long? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = await selector(e.Current).ConfigureAwait(false);
                }
                while (!value.HasValue);

                long valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    long? cur = await selector(e.Current).ConfigureAwait(false);
                    long x = cur.GetValueOrDefault();

                    // Do not replace & with &&. The branch prediction cost outweighs the extra operation
                    // unless nulls either never happen or always happen.
                    if (cur.HasValue & x < valueVal)
                    {
                        valueVal = x;
                        value = cur;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<float> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, ValueTask<float>> selector, CancellationToken cancellationToken)
        {
            float value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = await selector(e.Current).ConfigureAwait(false);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    float x = await selector(e.Current).ConfigureAwait(false);

                    if (x < value)
                    {
                        value = x;
                    }
                    else if (float.IsNaN(x))
                    {
                        // Normally NaN < anything is false, as is anything < NaN
                        // However, this leads to some irksome outcomes in Min and Max.
                        // If we use those semantics then Min(NaN, 5.0) is NaN, but
                        // Min(5.0, NaN) is 5.0!  To fix this, we impose a total
                        // ordering where NaN is smaller than every value, including
                        // negative infinity.
                        // Not testing for NaN therefore isn't an option, but since we
                        // can't find a smaller value, we can short-circuit.
                        return x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<float?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, ValueTask<float?>> selector, CancellationToken cancellationToken)
        {
            float? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = await selector(e.Current).ConfigureAwait(false);
                }
                while (!value.HasValue);

                float valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    float? cur = await selector(e.Current).ConfigureAwait(false);

                    if (cur.HasValue)
                    {
                        float x = cur.GetValueOrDefault();

                        if (x < valueVal)
                        {
                            valueVal = x;
                            value = cur;
                        }
                        else if (float.IsNaN(x))
                        {
                            return cur;
                        }
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<double> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, ValueTask<double>> selector, CancellationToken cancellationToken)
        {
            double value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = await selector(e.Current).ConfigureAwait(false);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    double x = await selector(e.Current).ConfigureAwait(false);

                    if (x < value)
                    {
                        value = x;
                    }
                    else if (double.IsNaN(x))
                    {
                        return x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<double?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, ValueTask<double?>> selector, CancellationToken cancellationToken)
        {
            double? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = await selector(e.Current).ConfigureAwait(false);
                }
                while (!value.HasValue);

                double valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    double? cur = await selector(e.Current).ConfigureAwait(false);

                    if (cur.HasValue)
                    {
                        double x = cur.GetValueOrDefault();

                        if (x < valueVal)
                        {
                            valueVal = x;
                            value = cur;
                        }
                        else if (double.IsNaN(x))
                        {
                            return cur;
                        }
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<decimal> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, ValueTask<decimal>> selector, CancellationToken cancellationToken)
        {
            decimal value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = await selector(e.Current).ConfigureAwait(false);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    decimal x = await selector(e.Current).ConfigureAwait(false);

                    if (x < value)
                    {
                        value = x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<decimal?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, ValueTask<decimal?>> selector, CancellationToken cancellationToken)
        {
            decimal? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = await selector(e.Current).ConfigureAwait(false);
                }
                while (!value.HasValue);

                decimal valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    decimal? cur = await selector(e.Current).ConfigureAwait(false);
                    decimal x = cur.GetValueOrDefault();

                    if (cur.HasValue && x < valueVal)
                    {
                        valueVal = x;
                        value = cur;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

#if !NO_DEEP_CANCELLATION
        private static async Task<int> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, ValueTask<int>> selector, CancellationToken cancellationToken)
        {
            int value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = await selector(e.Current, cancellationToken).ConfigureAwait(false);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    int x = await selector(e.Current, cancellationToken).ConfigureAwait(false);

                    if (x < value)
                    {
                        value = x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<int?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, ValueTask<int?>> selector, CancellationToken cancellationToken)
        {
            int? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                // Start off knowing that we've a non-null value (or exit here, knowing we don't)
                // so we don't have to keep testing for nullity.
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = await selector(e.Current, cancellationToken).ConfigureAwait(false);
                }
                while (!value.HasValue);

                // Keep hold of the wrapped value, and do comparisons on that, rather than
                // using the lifted operation each time.
                int valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    int? cur = await selector(e.Current, cancellationToken).ConfigureAwait(false);
                    int x = cur.GetValueOrDefault();

                    // Do not replace & with &&. The branch prediction cost outweighs the extra operation
                    // unless nulls either never happen or always happen.
                    if (cur.HasValue & x < valueVal)
                    {
                        valueVal = x;
                        value = cur;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<long> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, ValueTask<long>> selector, CancellationToken cancellationToken)
        {
            long value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = await selector(e.Current, cancellationToken).ConfigureAwait(false);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    long x = await selector(e.Current, cancellationToken).ConfigureAwait(false);

                    if (x < value)
                    {
                        value = x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<long?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, ValueTask<long?>> selector, CancellationToken cancellationToken)
        {
            long? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = await selector(e.Current, cancellationToken).ConfigureAwait(false);
                }
                while (!value.HasValue);

                long valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    long? cur = await selector(e.Current, cancellationToken).ConfigureAwait(false);
                    long x = cur.GetValueOrDefault();

                    // Do not replace & with &&. The branch prediction cost outweighs the extra operation
                    // unless nulls either never happen or always happen.
                    if (cur.HasValue & x < valueVal)
                    {
                        valueVal = x;
                        value = cur;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<float> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, ValueTask<float>> selector, CancellationToken cancellationToken)
        {
            float value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = await selector(e.Current, cancellationToken).ConfigureAwait(false);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    float x = await selector(e.Current, cancellationToken).ConfigureAwait(false);

                    if (x < value)
                    {
                        value = x;
                    }
                    else if (float.IsNaN(x))
                    {
                        // Normally NaN < anything is false, as is anything < NaN
                        // However, this leads to some irksome outcomes in Min and Max.
                        // If we use those semantics then Min(NaN, 5.0) is NaN, but
                        // Min(5.0, NaN) is 5.0!  To fix this, we impose a total
                        // ordering where NaN is smaller than every value, including
                        // negative infinity.
                        // Not testing for NaN therefore isn't an option, but since we
                        // can't find a smaller value, we can short-circuit.
                        return x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<float?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, ValueTask<float?>> selector, CancellationToken cancellationToken)
        {
            float? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = await selector(e.Current, cancellationToken).ConfigureAwait(false);
                }
                while (!value.HasValue);

                float valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    float? cur = await selector(e.Current, cancellationToken).ConfigureAwait(false);

                    if (cur.HasValue)
                    {
                        float x = cur.GetValueOrDefault();

                        if (x < valueVal)
                        {
                            valueVal = x;
                            value = cur;
                        }
                        else if (float.IsNaN(x))
                        {
                            return cur;
                        }
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<double> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, ValueTask<double>> selector, CancellationToken cancellationToken)
        {
            double value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = await selector(e.Current, cancellationToken).ConfigureAwait(false);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    double x = await selector(e.Current, cancellationToken).ConfigureAwait(false);

                    if (x < value)
                    {
                        value = x;
                    }
                    else if (double.IsNaN(x))
                    {
                        return x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<double?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, ValueTask<double?>> selector, CancellationToken cancellationToken)
        {
            double? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = await selector(e.Current, cancellationToken).ConfigureAwait(false);
                }
                while (!value.HasValue);

                double valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    double? cur = await selector(e.Current, cancellationToken).ConfigureAwait(false);

                    if (cur.HasValue)
                    {
                        double x = cur.GetValueOrDefault();

                        if (x < valueVal)
                        {
                            valueVal = x;
                            value = cur;
                        }
                        else if (double.IsNaN(x))
                        {
                            return cur;
                        }
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<decimal> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, ValueTask<decimal>> selector, CancellationToken cancellationToken)
        {
            decimal value;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                if (!await e.MoveNextAsync().ConfigureAwait(false))
                {
                    throw Error.NoElements();
                }

                value = await selector(e.Current, cancellationToken).ConfigureAwait(false);

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    decimal x = await selector(e.Current, cancellationToken).ConfigureAwait(false);

                    if (x < value)
                    {
                        value = x;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }

        private static async Task<decimal?> MinCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, ValueTask<decimal?>> selector, CancellationToken cancellationToken)
        {
            decimal? value = null;

            IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);

            try
            {
                do
                {
                    if (!await e.MoveNextAsync().ConfigureAwait(false))
                    {
                        return value;
                    }

                    value = await selector(e.Current, cancellationToken).ConfigureAwait(false);
                }
                while (!value.HasValue);

                decimal valueVal = value.GetValueOrDefault();

                while (await e.MoveNextAsync().ConfigureAwait(false))
                {
                    decimal? cur = await selector(e.Current, cancellationToken).ConfigureAwait(false);
                    decimal x = cur.GetValueOrDefault();

                    if (cur.HasValue && x < valueVal)
                    {
                        valueVal = x;
                        value = cur;
                    }
                }
            }
            finally
            {
                await e.DisposeAsync().ConfigureAwait(false);
            }

            return value;
        }
#endif
    }
}