Compile Error about magento2-ordercomments HOT 4 CLOSED

diff --git a/Block/Order/Comment.php b/Block/Order/Comment.php
index a5b5da3..120806b 100644
--- a/Block/Order/Comment.php
+++ b/Block/Order/Comment.php
@@ -27,22 +27,22 @@ class Comment extends \Magento\Framework\View\Element\Template
         parent::__construct($context, $data);
     }

-    public function getOrder() : Order
+    public function getOrder()
     {
         return $this->coreRegistry->registry('current_order');
     }

-    public function getOrderComment(): string
+    public function getOrderComment()
     {
         return trim($this->getOrder()->getData(OrderComment::COMMENT_FIELD_NAME));
     }

-    public function hasOrderComment() : bool
+    public function hasOrderComment()
     {
         return strlen($this->getOrderComment()) > 0;
     }

-    public function getOrderCommentHtml() : string
+    public function getOrderCommentHtml()
     {
         return nl2br($this->escapeHtml($this->getOrderComment()));
     }
diff --git a/Test/Unit/Model/OrderCommentManagementTest.php b/Test/Unit/Model/OrderCommentManagementTest.php
index 9f48f45..88e0ee6 100644
--- a/Test/Unit/Model/OrderCommentManagementTest.php
+++ b/Test/Unit/Model/OrderCommentManagementTest.php
@@ -140,7 +140,7 @@ class OrderCommentManagementTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals(strip_tags($comment), $this->quoteMock->getData(OrderComment::COMMENT_FIELD_NAME));
     }

-    private function setupQuoteRepositoryMockQueries(int $cartId, int $cartItemCount)
+    private function setupQuoteRepositoryMockQueries($cartId, $cartItemCount)
     {
         $this->quoteRepositoryMock->expects($this->once())
             ->method('getActive')->with($cartId)->will($this->returnValue($this->quoteMock));
@@ -150,7 +150,7 @@ class OrderCommentManagementTest extends \PHPUnit_Framework_TestCase
     /**
      * @return \PHPUnit_Framework_MockObject_MockObject|OrderCommentInterface
      */
-    private function mockOrderComment(string $comment = null): \PHPUnit_Framework_MockObject_MockObject
+    private function mockOrderComment($comment = null)
     {
         $orderCommentMock = $this->getMockBuilder(OrderComment::class)
             ->disableOriginalConstructor()