don't map bang that

activesupport/lib/active_support/core_ext/hash/slice.rb

@@ -17,7 +17,7 @@ module Hash #:nodoc:
       module Slice
         # Returns a new hash with only the given keys.
         def slice(*keys)
-          keys = keys.map! { |key| convert_key(key) } if respond_to?(:convert_key, true)
+          keys = keys.map { |key| convert_key(key) } if respond_to?(:convert_key, true)
           hash = self.class.new
           keys.each { |k| hash[k] = self[k] if has_key?(k) }
           hash
@@ -27,7 +27,7 @@ def slice(*keys)
         # Returns a hash contained the removed key/value pairs
         #   {:a => 1, :b => 2, :c => 3, :d => 4}.slice!(:a, :b) # => {:c => 3, :d =>4}
         def slice!(*keys)
-          keys = keys.map! { |key| convert_key(key) } if respond_to?(:convert_key, true)
+          keys = keys.map { |key| convert_key(key) } if respond_to?(:convert_key, true)
           omit = slice(*(self.keys - keys))
           hash = slice(*keys)
           replace(hash)