Reordering First overloads.

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

@@ -18,17 +18,15 @@ namespace System.Linq
             return First(source, CancellationToken.None);
         }
 
-        public static Task<TSource> First<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate)
+        public static Task<TSource> First<TSource>(this IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
-            if (predicate == null)
-                throw new ArgumentNullException(nameof(predicate));
 
-            return First(source, predicate, CancellationToken.None);
+            return First_(source, cancellationToken);
         }
 
-        public static Task<TSource> First<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate)
+        public static Task<TSource> First<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
@@ -38,22 +36,24 @@ namespace System.Linq
             return First(source, predicate, CancellationToken.None);
         }
 
-        public static Task<TSource> First<TSource>(this IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
+        public static Task<TSource> First<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
+            if (predicate == null)
+                throw new ArgumentNullException(nameof(predicate));
 
-            return First_(source, cancellationToken);
+            return source.Where(predicate).First(cancellationToken);
         }
 
-        public static Task<TSource> First<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
+        public static Task<TSource> First<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return source.Where(predicate).First(cancellationToken);
+            return First(source, predicate, CancellationToken.None);
         }
 
         public static Task<TSource> First<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate, CancellationToken cancellationToken)
@@ -74,17 +74,15 @@ namespace System.Linq
             return FirstOrDefault(source, CancellationToken.None);
         }
 
-        public static Task<TSource> FirstOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate)
+        public static Task<TSource> FirstOrDefault<TSource>(this IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
-            if (predicate == null)
-                throw new ArgumentNullException(nameof(predicate));
 
-            return FirstOrDefault(source, predicate, CancellationToken.None);
+            return FirstOrDefault_(source, cancellationToken);
         }
 
-        public static Task<TSource> FirstOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate)
+        public static Task<TSource> FirstOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
@@ -94,22 +92,24 @@ namespace System.Linq
             return FirstOrDefault(source, predicate, CancellationToken.None);
         }
 
-        public static Task<TSource> FirstOrDefault<TSource>(this IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
+        public static Task<TSource> FirstOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
+            if (predicate == null)
+                throw new ArgumentNullException(nameof(predicate));
 
-            return FirstOrDefault_(source, cancellationToken);
+            return source.Where(predicate).FirstOrDefault(cancellationToken);
         }
 
-        public static Task<TSource> FirstOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
+        public static Task<TSource> FirstOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return source.Where(predicate).FirstOrDefault(cancellationToken);
+            return FirstOrDefault(source, predicate, CancellationToken.None);
         }
 
         public static Task<TSource> FirstOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate, CancellationToken cancellationToken)