Fix #4380, making get code and get message final

hphp/system/php/lang/Exception.php

@@ -66,7 +66,7 @@ function __construct($message = '', $code = 0, Exception $previous = null) {
    *
    * @return     mixed   Returns the Exception message as a string.
    */
-  function getMessage() {
+  final function getMessage() {
     return $this->message;
   }
 
@@ -108,7 +108,7 @@ final function setPreviousChain(Exception $previous) {
    *                     but possibly as other type in Exception descendants
    *                     (for example as string in PDOException).
    */
-  function getCode() {
+  final function getCode() {
     return $this->code;
   }
 

hphp/test/slow/exceptions/getcodefinal.php

@@ -0,0 +1,9 @@
+<?php
+class FooException extends Exception {
+  protected $code = 123;
+  public function getCode() {
+    return $this->code;
+  }
+}
+$e = new FooException();
+var_dump($e->getCode());

hphp/test/slow/exceptions/getcodefinal.php.expectf

@@ -0,0 +1,2 @@
+
+Fatal error: Cannot override final method Exception::getCode() in %s on line %s