From c6e5659fec42b1c2ac39292a1ba2ee5852c66846 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby-lang.org>
Date: Fri, 10 Mar 2017 10:39:43 +0900
Subject: Use string#upto() if available; fix #3489

Terminate loop if the value is longer than the last otherwise.
---
 mrblib/range.rb | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/mrblib/range.rb b/mrblib/range.rb
index 5e5fd9bdc..3322af5f1 100644
--- a/mrblib/range.rb
+++ b/mrblib/range.rb
@@ -26,6 +26,14 @@ class Range
       return self
     end
 
+    if val.kind_of?(String) && last.kind_of?(String) # fixnums are special
+      if val.respond_to? :upto
+        return val.upto(last, exclude_end?, &block)
+      else
+        str_each = true
+      end
+    end
+
     raise TypeError, "can't iterate" unless val.respond_to? :succ
 
     return self if (val <=> last) > 0
@@ -33,6 +41,9 @@ class Range
     while (val <=> last) < 0
       block.call(val)
       val = val.succ
+      if str_each
+        break if val.size > last.size
+      end
     end
 
     block.call(val) if !exclude_end? && (val <=> last) == 0
-- 
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