THRIFT-3981 Enable analyzer strong mode in Dart library
Client: Dart
Patch: Mark Erickson <merickson@apache.org>

This closes #1135
diff --git a/test/dart/test_client/bin/main.dart b/test/dart/test_client/bin/main.dart
index 78a4f79..996844b 100644
--- a/test/dart/test_client/bin/main.dart
+++ b/test/dart/test_client/bin/main.dart
@@ -251,7 +251,7 @@
   }));
 
   tests.add(new TTest(TEST_CONTAINERS, 'testSet', () async {
-    var input = new Set.from([-2, -1, 0, 1, 2]);
+    var input = new Set<int>.from([-2, -1, 0, 1, 2]);
     var result = await client.testSet(input);
     var equality = const SetEquality();
     if (!equality.equals(result, input)) throw new TTestError(result, input);