code: @Nullable
    static StaticSourceFile getDefiningSource(
        Node node, @Nullable ObjectType referenceType, String propertyName) {
      if (referenceType != null) {
        Node propDefNode = referenceType.getPropertyDefSite(propertyName);
        if (propDefNode != null) {
          return propDefNode.getStaticSourceFile();
        }
      }
      return node.getStaticSourceFile();
    }
docs: Returns the source file in which the given property is defined, or null if it is not known.