HashWithIndifferentAccess#dup doc [ci skip]

The phrase "exact copy" in the existing docmentation is somewhat
misleading.

1 files changed, 8 insertions, 1 deletions

diff --git a/activesupport/lib/active_support/hash_with_indifferent_access.rb b/activesupport/lib/active_support/hash_with_indifferent_access.rb
index a4ebdea598..ed41b28d54 100644
--- a/activesupport/lib/active_support/hash_with_indifferent_access.rb
+++ b/activesupport/lib/active_support/hash_with_indifferent_access.rb
@@ -176,7 +176,14 @@ module ActiveSupport
       indices.collect { |key| self[convert_key(key)] }
     end
 
-    # Returns an exact copy of the hash.
+    # Returns a shallow copy of the hash.
+    #
+    #   hash = ActiveSupport::HashWithIndifferentAccess.new({ a: { b: 'b' } })
+    #   dup  = hash.dup
+    #   dup[:a][:c] = 'c'
+    #
+    #   hash[:a][:c] #=> "c"
+    #   dup[:a][:c]  #=> "c"
     def dup
       self.class.new(self).tap do |new_hash|
         new_hash.default = default