Track representations of fields

src/json-parser.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 386 matching lines @@
           Handle<Map> target = JSObject::FindTransitionToField(map, key);
           // If a transition was found, follow it and continue.
           if (!target.is_null()) {
             map = target;
           } else {
             // If no transition was found, commit the intermediate state to the
             // object and stop transitioning.
             JSObject::TransitionToMap(json_object, map);
             int length = properties.length();
             for (int i = 0; i < length; i++) {
-              json_object->FastPropertyAtPut(i, *properties[i]);
+              Handle<Object> value = properties[i];
+              Representation representation =
+                  map->instance_descriptors()->GetDetails(i).representation();
+              if (representation.IsDouble() && value->IsSmi()) {
+                // TODO(verwaest): Allocate heap number.
+              }
+              json_object->FastPropertyAtPut(i, *value);
             }
             transitioning = false;
           }
         }
         if (c0_ != ':') return ReportUnexpectedCharacter();
 
         AdvanceSkipWhitespace();
         value = ParseJsonValue();
         if (value.is_null()) return ReportUnexpectedCharacter();
 
         properties.Add(value, zone());
-        if (transitioning) continue;
+        if (transitioning) {
+          int field = properties.length() - 1;
+          Representation expected_representation =
+              map->instance_descriptors()->GetDetails(field).representation();
+          if (!value->FitsRepresentation(expected_representation)) {
+            map = Map::GeneralizeRepresentation(
+                map, field, value->OptimalRepresentation());
+          }
+          continue;
+        }
       } else {
         key = ParseJsonInternalizedString();
         if (key.is_null() || c0_ != ':') return ReportUnexpectedCharacter();
 
         AdvanceSkipWhitespace();
         value = ParseJsonValue();
         if (value.is_null()) return ReportUnexpectedCharacter();
       }
 
       JSObject::SetLocalPropertyIgnoreAttributes(
           json_object, key, value, NONE);
     } while (MatchSkipWhiteSpace(','));
     if (c0_ != '}') {
       return ReportUnexpectedCharacter();
     }
 
     // If we transitioned until the very end, transition the map now.
     if (transitioning) {
       JSObject::TransitionToMap(json_object, map);
       int length = properties.length();
       for (int i = 0; i < length; i++) {
-        json_object->FastPropertyAtPut(i, *properties[i]);
+        Handle<Object> value = properties[i];
+        Representation representation =
+            map->instance_descriptors()->GetDetails(i).representation();
+        if (representation.IsDouble() && value->IsSmi()) {
+          // TODO(verwaest): Allocate heap number.
+        }
+        json_object->FastPropertyAtPut(i, *value);
       }
     }
   }
   AdvanceSkipWhitespace();
   return scope.CloseAndEscape(json_object);
 }
 
 // Parse a JSON array. Position must be right at '['.
 template <bool seq_ascii>
 Handle<Object> JsonParser<seq_ascii>::ParseJsonArray() {
@@ skipping 330 matching lines @@
 
   ASSERT_EQ('"', c0_);
   // Advance past the last '"'.
   AdvanceSkipWhitespace();
   return result;
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_JSON_PARSER_H_