From 9f4b7fc82e45531e0057f807548a4d1c2b248186 Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Wed, 15 Jul 2020 23:30:32 +0900
Subject: Check warning flags only if available to run with old versions

---
 tool/lib/leakchecker.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tool/lib/leakchecker.rb b/tool/lib/leakchecker.rb
index 5311cddfe0..4b01d57792 100644
--- a/tool/lib/leakchecker.rb
+++ b/tool/lib/leakchecker.rb
@@ -265,7 +265,7 @@ class LeakChecker
     leaked
   end
 
-  WARNING_CATEGORIES = %i[deprecated experimental].freeze
+  WARNING_CATEGORIES = (Warning.respond_to?(:[]) ? %i[deprecated experimental] : []).freeze
 
   def find_warning_flags
     WARNING_CATEGORIES.to_h do |category|
-- 
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