code: public final Node useSourceInfoIfMissingFrom(Node other) {
      if (getStaticSourceFile() == null) {
        setStaticSourceFileFrom(other);
        sourcePosition = other.sourcePosition;
        length = other.length;
      }
  
      // TODO(lharker): should this be inside the above if condition?
      // If the node already has a source file, it seems strange to
      // go ahead and set the original name anyway.
      if (getProp(Prop.ORIGINALNAME) == null) {
        putProp(Prop.ORIGINALNAME, other.getProp(Prop.ORIGINALNAME));
      }
  
      return this;
    }
docs: Overwrite all the source information in this node with
  that of {@code other} iff the source info is missing.