Clean up Contains.

Ix.NET/Source/System.Linq.Async/System/Linq/Operators/Contains.cs

@@ -10,54 +10,45 @@ namespace System.Linq
 {
     public static partial class AsyncEnumerable
     {
-        public static Task<bool> Contains<TSource>(this IAsyncEnumerable<TSource> source, TSource value, IEqualityComparer<TSource> comparer)
+        public static Task<bool> Contains<TSource>(this IAsyncEnumerable<TSource> source, TSource value)
         {
             if (source == null)
-            {
                 throw new ArgumentNullException(nameof(source));
-            }
 
+            return ContainsCore(source, value, EqualityComparer<TSource>.Default, CancellationToken.None);
+        }
+
+        public static Task<bool> Contains<TSource>(this IAsyncEnumerable<TSource> source, TSource value, IEqualityComparer<TSource> comparer)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
             if (comparer == null)
-            {
                 throw new ArgumentNullException(nameof(comparer));
-            }
 
-            return Contains(source, value, comparer, CancellationToken.None);
+            return ContainsCore(source, value, comparer, CancellationToken.None);
         }
 
-        public static Task<bool> Contains<TSource>(this IAsyncEnumerable<TSource> source, TSource value)
+        public static Task<bool> Contains<TSource>(this IAsyncEnumerable<TSource> source, TSource value, CancellationToken cancellationToken)
         {
             if (source == null)
-            {
                 throw new ArgumentNullException(nameof(source));
-            }
 
-            return Contains(source, value, CancellationToken.None);
+            return ContainsCore(source, value, EqualityComparer<TSource>.Default, cancellationToken);
         }
 
         public static Task<bool> Contains<TSource>(this IAsyncEnumerable<TSource> source, TSource value, IEqualityComparer<TSource> comparer, CancellationToken cancellationToken)
         {
             if (source == null)
-            {
                 throw new ArgumentNullException(nameof(source));
-            }
-
             if (comparer == null)
-            {
                 throw new ArgumentNullException(nameof(comparer));
-            }
 
-            return source.Any(x => comparer.Equals(x, value), cancellationToken);
+            return ContainsCore(source, value, comparer, cancellationToken);
         }
 
-        public static Task<bool> Contains<TSource>(this IAsyncEnumerable<TSource> source, TSource value, CancellationToken cancellationToken)
+        private static Task<bool> ContainsCore<TSource>(IAsyncEnumerable<TSource> source, TSource value, IEqualityComparer<TSource> comparer, CancellationToken cancellationToken)
         {
-            if (source == null)
-            {
-                throw new ArgumentNullException(nameof(source));
-            }
-
-            return source.Contains(value, EqualityComparer<TSource>.Default, cancellationToken);
+            return source.Any(x => comparer.Equals(x, value), cancellationToken);
         }
     }
 }