Reordering Scan overloads.

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

@@ -10,24 +10,24 @@ namespace System.Linq
 {
     public static partial class AsyncEnumerable
     {
-        public static IAsyncEnumerable<TAccumulate> Scan<TSource, TAccumulate>(this IAsyncEnumerable<TSource> source, TAccumulate seed, Func<TAccumulate, TSource, TAccumulate> accumulator)
+        public static IAsyncEnumerable<TSource> Scan<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, TSource, TSource> accumulator)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
             if (accumulator == null)
                 throw new ArgumentNullException(nameof(accumulator));
 
-            return new ScanAsyncEnumerable<TSource, TAccumulate>(source, seed, accumulator);
+            return new ScanAsyncEnumerable<TSource>(source, accumulator);
         }
 
-        public static IAsyncEnumerable<TSource> Scan<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, TSource, TSource> accumulator)
+        public static IAsyncEnumerable<TAccumulate> Scan<TSource, TAccumulate>(this IAsyncEnumerable<TSource> source, TAccumulate seed, Func<TAccumulate, TSource, TAccumulate> accumulator)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
             if (accumulator == null)
                 throw new ArgumentNullException(nameof(accumulator));
 
-            return new ScanAsyncEnumerable<TSource>(source, accumulator);
+            return new ScanAsyncEnumerable<TSource, TAccumulate>(source, seed, accumulator);
         }
 
         private sealed class ScanAsyncEnumerable<TSource, TAccumulate> : AsyncIterator<TAccumulate>