Add more explicit nullable types for default null values

Author: alexandre-daubois

Tests/Fixtures/FooInterface.php

@@ -7,5 +7,5 @@ interface FooInterface
     /**
      * Hello.
      */
-    public function foo(?\stdClass $a, \stdClass $b = null);
+    public function foo(?\stdClass $a, ?\stdClass $b = null);
 }

Tests/Fixtures/Twig.php

@@ -18,7 +18,7 @@ class __TwigTemplate_VarDumperFixture_u75a09 extends AbstractTwigTemplate
 {
     private $path;
 
-    public function __construct(Twig\Environment $env = null, $path = null)
+    public function __construct(?Twig\Environment $env = null, $path = null)
     {
         if (null !== $env) {
             parent::__construct($env);

Tests/Fixtures/dumb-var.php

@@ -22,7 +22,7 @@ class DumbFoo
     '[]' => [],
     'res' => $g,
     'obj' => $foo,
-    'closure' => function ($a, \PDO &$b = null) {},
+    'closure' => function ($a, ?\PDO &$b = null) {},
     'line' => __LINE__ - 1,
     'nobj' => [(object) []],
 ];