Add default value to WP_REST_Request generic template (#409)

Fixes #408

Author: Nikschavan

functionMap.php

@@ -288,7 +288,7 @@
     'WP_List_Table::set_pagination_args' => ['void', 'args' => 'array{total_items?: int, total_pages?: int, per_page?: int}'],
     'WP_Query' => [null, '@phpstan-property-read bool $query_vars_changed' => '', '@phpstan-property-read bool|string $query_vars_hash' => '', '@phpstan-method void init_query_flags()' => ''],
     'WP_Query::have_posts' => [null, '@phpstan-impure' => ''],
-    'WP_REST_Request' => [null, '@phpstan-template' => 'T of array', '@phpstan-implements' => 'ArrayAccess<key-of<T>, value-of<T>>'],
+    'WP_REST_Request' => [null, '@phpstan-template' => 'T of array = array<string, mixed>', '@phpstan-implements' => 'ArrayAccess<key-of<T>, value-of<T>>'],
     'WP_REST_Request::get_param' => ['T[TOffset]|null', '@phpstan-template' => 'TOffset of key-of<T>', 'key' => 'TOffset'],
     'WP_REST_Request::get_params' => ['T'],
     'WP_REST_Request::has_param' => [null, 'key' => 'key-of<T>'],

wordpress-stubs.php

@@ -72889,7 +72889,7 @@ public function merge_with(&$other)
      * @since 4.4.0
      *
      * @link https://www.php.net/manual/en/class.arrayaccess.php
-     * @phpstan-template T of array
+     * @phpstan-template T of array = array<string, mixed>
      * @phpstan-implements ArrayAccess<key-of<T>, value-of<T>>
      */
     #[\AllowDynamicProperties]