gc(store, parentGCd) {
    if (!this.deleted) {
      throw error.unexpectedCase();
    }

    this.content.gc(store);

    if (parentGCd) {
      replaceStruct(store, this, new GC(this.id, this.length));
    } else {
      this.content = new ContentDeleted(this.length);
    }
  }
@param {StructStore} store
@param {boolean} parentGCd