Fixes #178

test/codegen/expect/constructors.txt

Index: test/codegen/expect/constructors.txt
diff --git a/test/codegen/expect/constructors.txt b/test/codegen/expect/constructors.txt
index 7b36d6c11b00e76318af27fe8584ff272439f4b7..99d01f16eae3460aaa1020ab9a76052eed112a3b 100644
--- a/test/codegen/expect/constructors.txt
+++ b/test/codegen/expect/constructors.txt
@@ -1 +1,10 @@
 // Messages from compiling constructors.dart
+warning: line 90, column 14 of test/codegen/constructors.dart: [DownCastComposite] y (dynamic) will need runtime check to cast to type T
+  Q(y) : x = y;
+             ^
+info: line 96, column 12 of test/codegen/constructors.dart: [DynamicCast] q.x (dynamic) will need runtime check to cast to type String
+    return q.x;
+           ^^^
+info: line 101, column 12 of test/codegen/constructors.dart: [DynamicCast] q.x (dynamic) will need runtime check to cast to type String
+    return q.x;
+           ^^^