[9.x] Makes with generic

src/Illuminate/Support/helpers.php

@@ -368,9 +368,11 @@ function windows_os()
     /**
      * Return the given value, optionally passed through the given callback.
      *
-     * @param  mixed  $value
-     * @param  callable|null  $callback
-     * @return mixed
+     * @template TValue
+     *
+     * @param  TValue  $value
+     * @param  (callable(TValue): TValue)|null  $callback
+     * @return TValue
      */
     function with($value, callable $callback = null)
     {

types/Support/Helpers.php

@@ -0,0 +1,15 @@
+<?php
+
+use function PHPStan\Testing\assertType;
+
+assertType('User', with(new User()));
+assertType('bool', with(new User())->save());
+assertType('User', with(new User(), function (User $user) {
+    return $user;
+}));
+
+assertType('int|User', with(new User(), function ($user) {
+    assertType('int|User', $user);
+
+    return 10;
+}));