Fix void foo(..) => ... to use { } instead.

tests/lib/convert/close_test.dart

+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import "package:expect/expect.dart";
+import "dart:convert";
+
+class MySink implements Sink<List<int>> {
+  List<int> accumulated = <int>[];
+  bool isClosed = false;
+
+  add(List<int> list) {
+    accumulated.addAll(list);
+    return list.length;
+  }
+
+  close() {
+    isClosed = true;
+    // Returning a value here triggered a bug, where the caller was trying to
+    // pass the value through its 'void' return type.
+    // Example: void close() => _sink.close();
+    return "done";
+  }
+}
+
+main() {
+  var mySink = new MySink();
+  var byteSink = new ByteConversionSink.from(mySink);
+  byteSink.add([1, 2, 3]);
+  byteSink.close();
+  Expect.listEquals([1, 2, 3], mySink.accumulated);
+  Expect.isTrue(mySink.isClosed);
+}