Enable downward inference on default params

test/checker/inferred_type_test.dart

Index: test/checker/inferred_type_test.dart
diff --git a/test/checker/inferred_type_test.dart b/test/checker/inferred_type_test.dart
index bf2d70922844cb71e17539d55aea5533550f1dec..3efac2a8bebebb98f1d1f575a341ffa0e58f0d4d 100644
--- a/test/checker/inferred_type_test.dart
+++ b/test/checker/inferred_type_test.dart
@@ -1342,6 +1342,10 @@ void main() {
 
   test('downwards inference on list literals', () {
     String mk(String info) => '''
+      void foo([List<String> list1 = /*$info*/const [],
+                List<String> list2 = /*severe:StaticTypeError*/const [42]]) {
+      }
+
       void main() {
         {
           List<int> l0 = /*$info*/[];
@@ -1423,6 +1427,9 @@ void main() {
 
   test('downwards inference on map literals', () {
     String mk(String info) => '''
+      void foo([Map<int, String> m1 = /*$info*/const {1: "hello"},
+                Map<int, String> m1 = /*severe:StaticTypeError*/const {"hello": "world"}]) {
+      }
       void main() {
         {
           Map<int, String> l0 = /*$info*/{};