code: private JSType getPropertyTypeIfDeclared(@Nullable ObjectType objectType, String propertyName) {
      if (objectType != null
          && objectType.hasProperty(propertyName)
          && !objectType.isPropertyTypeInferred(propertyName)) {
        return objectType.getPropertyType(propertyName);
      }
      return getNativeType(UNKNOWN_TYPE);
    }
docs: Returns the type of the property with the given name if declared. Otherwise returns unknown.