save a few method calls

1 files changed, 3 insertions, 2 deletions

diff --git a/activesupport/lib/active_support/multibyte/chars.rb b/activesupport/lib/active_support/multibyte/chars.rb
index 0820579bec..f9607f1aaf 100644
--- a/activesupport/lib/active_support/multibyte/chars.rb
+++ b/activesupport/lib/active_support/multibyte/chars.rb
@@ -270,13 +270,14 @@ module ActiveSupport #:nodoc:
           @wrapped_string[*args] = replace_by
         else
           result = Unicode.u_unpack(@wrapped_string)
-          if args[0].is_a?(Fixnum)
+          case args.first
+          when Fixnum
             raise IndexError, "index #{args[0]} out of string" if args[0] >= result.length
             min = args[0]
             max = args[1].nil? ? min : (min + args[1] - 1)
             range = Range.new(min, max)
             replace_by = [replace_by].pack('U') if replace_by.is_a?(Fixnum)
-          elsif args.first.is_a?(Range)
+          when Range
             raise RangeError, "#{args[0]} out of range" if args[0].min >= result.length
             range = args[0]
           else