Map deleted enum values to a sentinel value.

runtime/vm/class_finalizer.cc

Index: runtime/vm/class_finalizer.cc
diff --git a/runtime/vm/class_finalizer.cc b/runtime/vm/class_finalizer.cc
index 98d74ff073efddae795a4921b18cbceedb87f616..d5f3d5688f56e0e38af6d1c195a53448e1e20ba1 100644
--- a/runtime/vm/class_finalizer.cc
+++ b/runtime/vm/class_finalizer.cc
@@ -2478,16 +2478,34 @@ void ClassFinalizer::AllocateEnumValues(const Class& enum_cls) {
   ASSERT(Instance::Handle(zone, values_field.StaticValue()).IsArray());
   Array& values_list =
       Array::Handle(zone, Array::RawCast(values_field.StaticValue()));
+  const String& enum_name = String::Handle(enum_cls.ScrubbedName());
+  const String& name_prefix =
+      String::Handle(String::Concat(enum_name, Symbols::Dot()));
+
+  const String& deleted_enum_senintel_name = String::Handle(
+      zone,
+      Symbols::FromConcat(thread, Symbols::_DeletedEnumPrefix(), enum_name));
+  Instance& deleted_enum_sentinel_value =
+      Instance::Handle(zone, Instance::New(enum_cls, Heap::kOld));
+  deleted_enum_sentinel_value.SetField(index_field,
+                                       Smi::Handle(zone, Smi::New(-1)));
+  deleted_enum_sentinel_value.SetField(name_field, deleted_enum_senintel_name);
+  const char* error_msg = NULL;
+  deleted_enum_sentinel_value =
+      deleted_enum_sentinel_value.CheckAndCanonicalize(thread, &error_msg);
+  ASSERT(!deleted_enum_sentinel_value.IsNull());
+  ASSERT(deleted_enum_sentinel_value.IsCanonical());
+  const Field& deleted_enum_field = Field::Handle(
+      zone, enum_cls.LookupStaticField(Symbols::_DeletedEnumSentinel()));
+  ASSERT(!deleted_enum_field.IsNull());
+  deleted_enum_field.SetStaticValue(deleted_enum_sentinel_value, true);
+  deleted_enum_field.RecordStore(deleted_enum_sentinel_value);
 
   const Array& fields = Array::Handle(zone, enum_cls.fields());
   Field& field = Field::Handle(zone);
   Instance& ordinal_value = Instance::Handle(zone);
   Instance& enum_value = Instance::Handle(zone);
 
-  const String& enum_name = String::Handle(enum_cls.ScrubbedName());
-  const String& name_prefix =
-      String::Handle(String::Concat(enum_name, Symbols::Dot()));
-
   String& enum_ident = String::Handle();

[siva, 2016/11/14 22:18:23]

A samll nit, the same handles created here field, enum_value, enum_ident etc.
could be used for the code above instead of creating a new set of handles
deleted_enum_field, deleted_enum_sentinel_value, deleted_enum_sentinel_name.

[Cutch, 2016/11/15 22:13:55]

Done.

   for (intptr_t i = 0; i < fields.Length(); i++) {
     field = Field::RawCast(fields.At(i));
@@ -2509,7 +2527,6 @@ void ClassFinalizer::AllocateEnumValues(const Class& enum_cls) {
     enum_value = Instance::New(enum_cls, Heap::kOld);
     enum_value.SetField(index_field, ordinal_value);
     enum_value.SetField(name_field, enum_ident);
-    const char* error_msg = "";
     enum_value = enum_value.CheckAndCanonicalize(thread, &error_msg);
     ASSERT(!enum_value.IsNull());
     ASSERT(enum_value.IsCanonical());
@@ -2520,7 +2537,6 @@ void ClassFinalizer::AllocateEnumValues(const Class& enum_cls) {
     values_list.SetAt(ord, enum_value);
   }
   values_list.MakeImmutable();
-  const char* error_msg = NULL;
   values_list ^= values_list.CheckAndCanonicalize(thread, &error_msg);
   ASSERT(!values_list.IsNull());
 }