TypeString::isKeyword(): correctly handle FQN null/true/false

Includes tests.

Author: jrfnl

PHPCSUtils/Utils/TypeString.php

@@ -129,7 +129,7 @@ public static function isKeyword($type)
             return false;
         }
 
-        $typeLC = \strtolower(\trim($type));
+        $typeLC = \strtolower(\ltrim(\trim($type), '\\'));
         return isset(self::$keywordTypes[$typeLC]);
     }
 

Tests/Utils/TypeString/IsKeywordTest.php

@@ -117,6 +117,13 @@ public static function dataIsKeywordValid()
             ];
         }
 
+        $data['true: fully qualified']             = ['type' => '\true'];
+        $data['false: fully qualified']            = ['type' => '\false'];
+        $data['null: fully qualified']             = ['type' => '\null'];
+        $data['true: fully qualified, uppercase']  = ['type' => '\TRUE'];
+        $data['false: fully qualified, uppercase'] = ['type' => '\FALSE'];
+        $data['null: fully qualified, uppercase']  = ['type' => '\NULL'];
+
         return $data;
     }