Don't allow statement-nodes in expression contexts.

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 8f543d4784576876550d0342287751c3ce97f2b3..de9fa3f0f47d96f837fa8edc3e19fca73322a8e6 100644
--- a/lib/compiler/implementation/ssa/tracer.dart
+++ b/lib/compiler/implementation/ssa/tracer.dart
@@ -243,12 +243,14 @@ class HInstructionStringifier implements HVisitor<String> {
   String visitExit(HExit node) => "exit";
 
   String visitFieldGet(HFieldGet node) {
-    return 'get ${temporaryId(node.receiver)}';
+    String fieldName = node.element.name.slowToString();
+    return 'get ${temporaryId(node.receiver)}.$fieldName';
   }
 
   String visitFieldSet(HFieldSet node) {
     String valueId = temporaryId(node.value);
-    return 'set ${temporaryId(node.receiver)} to $valueId';
+    String fieldName = node.element.name.slowToString();
+    return 'set ${temporaryId(node.receiver)}.$fieldName to $valueId';
   }
 
   String visitLocalGet(HLocalGet node) => visitFieldGet(node);
@@ -478,7 +480,7 @@ class HInstructionStringifier implements HVisitor<String> {
         envBuffer.add(" ${temporaryId(inputs[i])}");
       }
     }
-    String on = node.isOn ? "on" : "off";
+    String on = node.isEnabled ? "enabled" : "disabled";
     String id = temporaryId(node.guarded);
     return "TypeGuard($on): $id is $type env: $envBuffer";
   }