Add new class for auto set vars to certain types or null

Convert\VarSetType for always return type expected (eg string will be string)
or Convert\VarSetTypeNull to return string or null on failure

The return value for failure if not matching type can be set for both, but
only for Convert\VarSetTypeNull the return value can be set to null.

www/vendor/composer/ClassLoader.php

@@ -42,6 +42,9 @@ namespace Composer\Autoload;
  */
 class ClassLoader
 {
+    /** @var \Closure(string):void */
+    private static $includeFile;
+
     /** @var ?string */
     private $vendorDir;
 
@@ -106,6 +109,7 @@ class ClassLoader
     public function __construct($vendorDir = null)
     {
         $this->vendorDir = $vendorDir;
+        self::initializeIncludeClosure();
     }
 
     /**
@@ -149,7 +153,7 @@ class ClassLoader
 
     /**
      * @return string[] Array of classname => path
-     * @psalm-var array<string, string>
+     * @psalm-return array<string, string>
      */
     public function getClassMap()
     {
@@ -425,7 +429,7 @@ class ClassLoader
     public function loadClass($class)
     {
         if ($file = $this->findFile($class)) {
-            includeFile($file);
+            (self::$includeFile)($file);
 
             return true;
         }
@@ -555,18 +559,23 @@ class ClassLoader
 
         return false;
     }
-}
 
-/**
- * Scope isolated include.
- *
- * Prevents access to $this/self from included files.
- *
- * @param  string $file
- * @return void
- * @private
- */
-function includeFile($file)
-{
-    include $file;
+    private static function initializeIncludeClosure(): void
+    {
+        if (self::$includeFile !== null) {
+            return;
+        }
+
+        /**
+         * Scope isolated include.
+         *
+         * Prevents access to $this/self from included files.
+         *
+         * @param  string $file
+         * @return void
+         */
+        self::$includeFile = static function($file) {
+            include $file;
+        };
+    }
 }