rustdoc-search: address typescript nit

Co-authored-by: lolbinarycat <[email protected]

Author: notriddle

src/librustdoc/html/static/js/rustdoc.d.ts

@@ -435,6 +435,18 @@ declare namespace rustdoc {
      */
     type RawFunctionType = number | [number, Array<RawFunctionType>] | [number, Array<RawFunctionType>, Array<[RawFunctionType, RawFunctionType[]]>];
 
+    /**
+     * Utility typedef for deserializing compact JSON.
+     *
+     * R is the required part, O is the optional part, which goes afterward.
+     * For example, `ArrayWithOptionals<[A, B], [C, D]>` matches
+     * `[A, B] | [A, B, C] | [A, B, C, D]`.
+     */
+    type ArrayWithOptionals<R extends any[], O extends any[]> =
+        O extends [infer First, ...infer Rest] ?
+            R | ArrayWithOptionals<[...R, First], Rest> :
+            R;
+
     /**
      * The type signature entry in the decoded search index.
      * (The "Raw" objects are encoded differently to save space in the JSON).

src/librustdoc/html/static/js/search.js

@@ -1541,24 +1541,15 @@ class DocSearch {
          * deprecated,
          * isUnstable,
          * associated_item_disambiguator
-         * @type {[
+         * @type {rustdoc.ArrayWithOptionals<[
          *     number,
          *     rustdoc.ItemType,
          *     number,
          *     number,
          *     number,
          *     number,
          *     number,
-         *     string,
-         * ] | [
-         *     number,
-         *     rustdoc.ItemType,
-         *     number,
-         *     number,
-         *     number,
-         *     number,
-         *     number,
-         * ]}
+         * ], [string]>}
          */
         const raw = JSON.parse(encoded);
         return {
@@ -1587,26 +1578,8 @@ class DocSearch {
             return null;
         }
         /**
-         *  ty, module_path, exact_module_path, search_unbox, inverted_function_signature_index
-         * @type {[
-         *     rustdoc.ItemType,
-         *     string,
-         *     string|0,
-         *     0|1,
-         *     string,
-         * ] | [
-         *     rustdoc.ItemType,
-         *     string,
-         *     string|0,
-         *     0|1,
-         * ] | [
-         *     rustdoc.ItemType,
-         *     string,
-         *     string,
-         * ] | [
-         *     rustdoc.ItemType,
-         *     string,
-         * ]}
+         * ty, module_path, exact_module_path, search_unbox, inverted_function_signature_index
+         * @type {rustdoc.ArrayWithOptionals<[rustdoc.ItemType, string], [string|0, 0|1, string]>}
          */
         const raw = JSON.parse(encoded);
         return {