Fix type warnings and a few other warnings, and probably even an error.

lib/compiler/implementation/ssa/tracer.dart

Index: lib/compiler/implementation/ssa/tracer.dart
diff --git a/lib/compiler/implementation/ssa/tracer.dart b/lib/compiler/implementation/ssa/tracer.dart
index 4e453141e73aa97cad12628710b1d17e9c1ffedd..c4c58ebafd0dded8deb9a6b8b248a1019678f3b3 100644
--- a/lib/compiler/implementation/ssa/tracer.dart
+++ b/lib/compiler/implementation/ssa/tracer.dart
@@ -419,7 +419,7 @@ class HInstructionStringifier implements HVisitor<String> {
   }
 
   String visitIs(HIs node) {
-    String type = node.typeExpression.toString();
+    String type = node.typeName.toString();
     return "TypeTest: ${temporaryId(node.expression)} is $type";
   }
 }