Log the runtime type of messages

test/dart_codegen/expect/types.txt

Index: test/dart_codegen/expect/types.txt
diff --git a/test/dart_codegen/expect/types.txt b/test/dart_codegen/expect/types.txt
index a65c14a3284d0cb67ab72d7e8a322f35d4b7ded5..11c859096e1ff436ff47f3b2107f6be5f5072c3e 100644
--- a/test/dart_codegen/expect/types.txt
+++ b/test/dart_codegen/expect/types.txt
@@ -1,19 +1,19 @@
 // Messages from compiling types.dart
-info: line 10, column 6 of test/dart_codegen/types/c.dart: f4(3) (dynamic) will need runtime check to cast to type A
+info: line 10, column 6 of test/dart_codegen/types/c.dart: [DownCast] f4(3) (dynamic) will need runtime check to cast to type A
   f3(f4(3));
      ^^^^^
-warning: line 11, column 6 of test/dart_codegen/types/c.dart: f4 ((dynamic) → dynamic) will need to be wrapped with a closure of type (A) → A
+warning: line 11, column 6 of test/dart_codegen/types/c.dart: [ClosureWrap] f4 ((dynamic) → dynamic) will need to be wrapped with a closure of type (A) → A
   f1(f4);
      ^^
-warning: line 12, column 6 of test/dart_codegen/types/c.dart: f3 ((A) → A) will need to be wrapped with a closure of type (dynamic) → dynamic
+warning: line 12, column 6 of test/dart_codegen/types/c.dart: [ClosureWrap] f3 ((A) → A) will need to be wrapped with a closure of type (dynamic) → dynamic
   f2(f3);
      ^^
-info: line 10, column 14 of test/dart_codegen/types/d.dart: f4("""hello""") (dynamic) will need runtime check to cast to type A
+info: line 10, column 14 of test/dart_codegen/types/d.dart: [DownCast] f4("""hello""") (dynamic) will need runtime check to cast to type A
   var x = f3(f4("""hello"""));
              ^^^^^^^^^^^^^^^
-warning: line 11, column 14 of test/dart_codegen/types/d.dart: f4 ((dynamic) → dynamic) will need to be wrapped with a closure of type (A) → A
+warning: line 11, column 14 of test/dart_codegen/types/d.dart: [ClosureWrap] f4 ((dynamic) → dynamic) will need to be wrapped with a closure of type (A) → A
   var y = f1(f4);
              ^^
-warning: line 12, column 14 of test/dart_codegen/types/d.dart: f3 ((A) → A) will need to be wrapped with a closure of type (dynamic) → dynamic
+warning: line 12, column 14 of test/dart_codegen/types/d.dart: [ClosureWrap] f3 ((A) → A) will need to be wrapped with a closure of type (dynamic) → dynamic
   var z = f2(f3);
              ^^