Fix type warning in Result.release.

R=floitsch@google.com

Review-Url: https://codereview.chromium.org//2707883002 .
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2f62234..6073ae4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 1.13.2
+
+* Fix a type-warning.
+
 ## 1.13.1
 
 * Use `FutureOr` for various APIs that had previously used `dynamic`.
diff --git a/lib/src/result.dart b/lib/src/result.dart
index 51db558..7c45846 100644
--- a/lib/src/result.dart
+++ b/lib/src/result.dart
@@ -90,7 +90,7 @@
   /// If [future] completes with an error, the returned future completes with
   /// the same error.
   static Future<T> release<T>(Future<Result<T>> future) =>
-      future.then<Future<T>>((result) => result.asFuture);
+      future.then<T>((result) => result.asFuture);
 
   /// Capture the results of a stream into a stream of [Result] values.
   ///
diff --git a/pubspec.yaml b/pubspec.yaml
index c666434..adb2c82 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: async
-version: 1.13.1
+version: 1.13.2
 author: Dart Team <misc@dartlang.org>
 description: Utility functions and classes related to the 'dart:async' library.
 homepage: https://www.github.com/dart-lang/async