Fixes detecting usage of $this variable

Recursion for anonymous classes as $this can be used in the constructor
parameter. Fixes failing tests.

src/Standards/Squiz/Sniffs/Scope/StaticThisUsageSniff.php

@@ -68,22 +68,45 @@ public function processTokenWithinScope(File $phpcsFile, $stackPtr, $currScope)
         $next = $stackPtr;
         $end  = $tokens[$stackPtr]['scope_closer'];
 
+        $this->checkThisUsage($phpcsFile, $next, $end);
+
+    }//end processTokenWithinScope()
+
+
+    /**
+     * Check for $this variable usage between $next and $end tokens.
+     *
+     * @param File $phpcsFile The current file being scanned.
+     * @param int  $next      The position of the next token to check.
+     * @param int  $end       The position of the last token to check.
+     *
+     * @return void
+     */
+    private function checkThisUsage(File $phpcsFile, $next, $end)
+    {
+        $tokens = $phpcsFile->getTokens();
+
         do {
             $next = $phpcsFile->findNext([T_VARIABLE, T_ANON_CLASS], ($next + 1), $end);
             if ($next === false) {
                 continue;
-            } else if ($tokens[$next]['code'] === T_ANON_CLASS) {
+            }
+
+            if ($tokens[$next]['code'] === T_ANON_CLASS) {
+                $this->checkThisUsage($phpcsFile, $next, $tokens[$next]['scope_opener']);
                 $next = $tokens[$next]['scope_closer'];
                 continue;
-            } else if ($tokens[$next]['content'] !== '$this') {
+            }
+
+            if ($tokens[$next]['content'] !== '$this') {
                 continue;
             }
 
             $error = 'Usage of "$this" in static methods will cause runtime errors';
             $phpcsFile->addError($error, $next, 'Found');
         } while ($next !== false);
 
-    }//end processTokenWithinScope()
+    }//end checkThisUsage()
 
 
     /**