Reordering overloads of ToLookup.

Ix.NET/Source/System.Interactive.Async/ToLookup.cs

@@ -12,30 +12,24 @@ namespace System.Linq
 {
     public static partial class AsyncEnumerable
     {
-        public static Task<ILookup<TKey, TElement>> ToLookup<TSource, TKey, TElement>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer)
+        public static Task<ILookup<TKey, TSource>> ToLookup<TSource, TKey>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
             if (keySelector == null)
                 throw new ArgumentNullException(nameof(keySelector));
-            if (elementSelector == null)
-                throw new ArgumentNullException(nameof(elementSelector));
-            if (comparer == null)
-                throw new ArgumentNullException(nameof(comparer));
 
-            return ToLookup(source, keySelector, elementSelector, comparer, CancellationToken.None);
+            return ToLookup(source, keySelector, CancellationToken.None);
         }
 
-        public static Task<ILookup<TKey, TElement>> ToLookup<TSource, TKey, TElement>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector)
+        public static Task<ILookup<TKey, TSource>> ToLookup<TSource, TKey>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, CancellationToken cancellationToken)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
             if (keySelector == null)
                 throw new ArgumentNullException(nameof(keySelector));
-            if (elementSelector == null)
-                throw new ArgumentNullException(nameof(elementSelector));
 
-            return ToLookup(source, keySelector, elementSelector, CancellationToken.None);
+            return source.ToLookup(keySelector, x => x, EqualityComparer<TKey>.Default, cancellationToken);
         }
 
         public static Task<ILookup<TKey, TSource>> ToLookup<TSource, TKey>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
@@ -50,17 +44,19 @@ namespace System.Linq
             return ToLookup(source, keySelector, comparer, CancellationToken.None);
         }
 
-        public static Task<ILookup<TKey, TSource>> ToLookup<TSource, TKey>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector)
+        public static Task<ILookup<TKey, TSource>> ToLookup<TSource, TKey>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer, CancellationToken cancellationToken)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
             if (keySelector == null)
                 throw new ArgumentNullException(nameof(keySelector));
+            if (comparer == null)
+                throw new ArgumentNullException(nameof(comparer));
 
-            return ToLookup(source, keySelector, CancellationToken.None);
+            return source.ToLookup(keySelector, x => x, comparer, cancellationToken);
         }
 
-        public static async Task<ILookup<TKey, TElement>> ToLookup<TSource, TKey, TElement>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer, CancellationToken cancellationToken)
+        public static Task<ILookup<TKey, TElement>> ToLookup<TSource, TKey, TElement>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
@@ -68,12 +64,8 @@ namespace System.Linq
                 throw new ArgumentNullException(nameof(keySelector));
             if (elementSelector == null)
                 throw new ArgumentNullException(nameof(elementSelector));
-            if (comparer == null)
-                throw new ArgumentNullException(nameof(comparer));
-
-            var lookup = await Internal.Lookup<TKey, TElement>.CreateAsync(source, keySelector, elementSelector, comparer).ConfigureAwait(false);
 
-            return lookup;
+            return ToLookup(source, keySelector, elementSelector, CancellationToken.None);
         }
 
         public static Task<ILookup<TKey, TElement>> ToLookup<TSource, TKey, TElement>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, CancellationToken cancellationToken)
@@ -88,26 +80,34 @@ namespace System.Linq
             return source.ToLookup(keySelector, elementSelector, EqualityComparer<TKey>.Default, cancellationToken);
         }
 
-        public static Task<ILookup<TKey, TSource>> ToLookup<TSource, TKey>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer, CancellationToken cancellationToken)
+        public static Task<ILookup<TKey, TElement>> ToLookup<TSource, TKey, TElement>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
             if (keySelector == null)
                 throw new ArgumentNullException(nameof(keySelector));
+            if (elementSelector == null)
+                throw new ArgumentNullException(nameof(elementSelector));
             if (comparer == null)
                 throw new ArgumentNullException(nameof(comparer));
 
-            return source.ToLookup(keySelector, x => x, comparer, cancellationToken);
+            return ToLookup(source, keySelector, elementSelector, comparer, CancellationToken.None);
         }
 
-        public static Task<ILookup<TKey, TSource>> ToLookup<TSource, TKey>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, CancellationToken cancellationToken)
+        public static async Task<ILookup<TKey, TElement>> ToLookup<TSource, TKey, TElement>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer, CancellationToken cancellationToken)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
             if (keySelector == null)
                 throw new ArgumentNullException(nameof(keySelector));
+            if (elementSelector == null)
+                throw new ArgumentNullException(nameof(elementSelector));
+            if (comparer == null)
+                throw new ArgumentNullException(nameof(comparer));
 
-            return source.ToLookup(keySelector, x => x, EqualityComparer<TKey>.Default, cancellationToken);
+            var lookup = await Internal.Lookup<TKey, TElement>.CreateAsync(source, keySelector, elementSelector, comparer).ConfigureAwait(false);
+
+            return lookup;
         }
     }
 }