fix: provide mixed for lower laravel versions

src/Stubs/InteractsWithInput.stubphp

@@ -0,0 +1,21 @@
+<?php
+
+namespace Illuminate\Http\Concerns;
+
+use Illuminate\Http\UploadedFile;
+use Illuminate\Support\Arr;
+use Illuminate\Support\Str;
+use SplFileInfo;
+use stdClass;
+
+trait InteractsWithInput
+{
+    /**
+     * Retrieve an input item from the request.
+     *
+     * @param  string|null  $key
+     * @param  mixed  $default
+     * @return mixed
+     */
+    public function input($key = null, $default = null) { }
+}

tests/acceptance/RequestTypes.feature

@@ -0,0 +1,36 @@
+Feature: redirect
+  The global redirect helper will return the correct type depending on args
+
+  Background:
+    Given I have the following config
+      """
+      <?xml version="1.0"?>
+      <psalm totallyTyped="false">
+        <projectFiles>
+          <directory name="."/>
+          <ignoreFiles> <directory name="../../vendor"/> </ignoreFiles>
+        </projectFiles>
+        <plugins>
+          <pluginClass class="Psalm\LaravelPlugin\Plugin"/>
+        </plugins>
+      </psalm>
+      """
+    And I have the following code preamble
+    """
+    <?php declare(strict_types=1);
+
+     namespace Tests\Psalm\LaravelPlugin\Sandbox;
+
+     use \Illuminate\Http\Request;
+    """
+
+  Scenario: input returns various types
+    Given I have the following code
+    """
+    function test(Request $request): bool
+    {
+      return $request->input('foo', false);
+    }
+    """
+    When I run psalm
+    Then I see no errors