in closure test

rules-tests/DowngradePhp82/Rector/FunctionLike/DowngradeStandaloneNullTrueFalseReturnTypeRector/Fixture/in_closure.php.inc

@@ -0,0 +1,21 @@
+<?php
+
+namespace Rector\Tests\DowngradePhp82\Rector\Class_\DowngradeStandaloneNullTrueFalseReturnTypeRector\Fixture;
+
+$a = function(): null
+{
+    return null;
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\DowngradePhp82\Rector\Class_\DowngradeStandaloneNullTrueFalseReturnTypeRector\Fixture;
+
+$a = function(): mixed
+{
+    return null;
+}
+
+?>

rules/DowngradePhp82/Rector/FunctionLike/DowngradeStandaloneNullTrueFalseReturnTypeRector.php

@@ -84,6 +84,8 @@ public function refactor(Node $node): ?Node
         if (! $node instanceof ClassMethod) {
             $node->returnType = new Identifier('mixed');
 
+            // in closure and arrow function can't add `@return null` docblock as they are Expr
+            // that rely on Stmt
             $phpDocInfo = $this->phpDocInfoFactory->createFromNodeOrEmpty($node);
             $this->phpDocTypeChanger->changeReturnType($node, $phpDocInfo, new NullType());