Adds support for PHP 7.4 arrow functions in PEAR.Functions.ValidDefaultValue sniff

Related to #2523

Author: michalbundyra

src/Standards/PEAR/Sniffs/Functions/ValidDefaultValueSniff.php

@@ -26,6 +26,7 @@ public function register()
         return [
             T_FUNCTION,
             T_CLOSURE,
+            T_FN,
         ];
 
     }//end register()

src/Standards/PEAR/Tests/Functions/ValidDefaultValueUnitTest.inc

@@ -98,5 +98,7 @@ $closure = function ($arg1, $arg2='hello') {};
 // Invalid closure
 $closure = function(array $arg2=array(), array $arg1) {}
 
+$fn = fn($a = [], $b) => $a[] = $b;
+
 // Intentional syntax error. Must be last thing in the file.
 function

src/Standards/PEAR/Tests/Functions/ValidDefaultValueUnitTest.php

@@ -34,6 +34,7 @@ public function getErrorList()
             81 => 1,
             91 => 1,
             99 => 1,
+            101 => 1,
         ];
 
     }//end getErrorList()