anchor.diff:          }
           String variableName =
               argumentCount < 1 ? null : argumentValues[0].toStringValue();
  -        if (identical(definingClass, typeProvider.boolType)) {
  +        if (definingClass == typeProvider.boolType) {
             DartObject valueFromEnvironment;
             valueFromEnvironment =
                 _declaredVariables.getBool(typeProvider, variableName);
  
positive.code:               valueFromEnvironment,
                new DartObjectImpl(typeProvider.nullType, NullState.NULL_STATE),
                namedArgumentValues);
          } else if (identical(definingClass, typeProvider.stringType)) {
            DartObject valueFromEnvironment;
            valueFromEnvironment =
                _declaredVariables.getString(typeProvider, variableName);
  
negative.code:               namedArgumentValues);
          }
        } else if (constructor.name == "" &&
            definingClass == typeProvider.symbolType &&
            argumentCount == 1) {
          if (!checkSymbolArguments(
              arguments, argumentValues, namedArgumentValues)) {
  