knu	2013-07-19 11:22:11 +0900 (Fri, 19 Jul 2013)

  New Revision: 42051

  http://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=rev&revision=42051

  Log:
    Define Set#to_set so that aSet.to_set returns self.
    
    * lib/set.rb (Set#to_set): Define Set#to_set so that aSet.to_set
      returns self. [Fixes GH-359]

  Modified files:
    trunk/ChangeLog
    trunk/NEWS
    trunk/lib/set.rb
    trunk/test/test_set.rb

Index: ChangeLog
===================================================================
--- ChangeLog	(revision 42050)
+++ ChangeLog	(revision 42051)
@@ -1,3 +1,8 @@ https://github.com/ruby/ruby/blob/trunk/ChangeLog#L1
+Fri Jul 19 11:16:54 2013  Akinori MUSHA  <knu@i...>
+
+	* lib/set.rb (Set#to_set): Define Set#to_set so that aSet.to_set
+	  returns self. [Fixes GH-359]
+
 Fri Jul 19 11:10:23 2013  Zachary Scott  <e@z...>
 
 	* lib/rake/*: [DOC] Capitalize "Ruby" in documentation
Index: lib/set.rb
===================================================================
--- lib/set.rb	(revision 42050)
+++ lib/set.rb	(revision 42051)
@@ -148,6 +148,16 @@ class Set https://github.com/ruby/ruby/blob/trunk/lib/set.rb#L148
     @hash.keys
   end
 
+  # Returns self if no arguments are given.  Otherwise, converts the
+  # set to another with klass.new(self, *args, &block).
+  #
+  # In subclasses, returns klass.new(self, *args, &block) unless
+  # overridden.
+  def to_set(klass = Set, *args, &block)
+    return self if instance_of?(Set) && klass == Set && block.nil? && args.empty?
+    klass.new(self, *args, &block)
+  end
+
   def flatten_merge(set, seen = Set.new) # :nodoc:
     set.each { |e|
       if e.is_a?(Set)
Index: NEWS
===================================================================
--- NEWS	(revision 42050)
+++ NEWS	(revision 42051)
@@ -137,6 +137,10 @@ with all sufficient information, see the https://github.com/ruby/ruby/blob/trunk/NEWS#L137
 
 === Stdlib compatibility issues (excluding feature bug fixes)
 
+* Set
+  * incompatible changes:
+    * Set#to_set now returns self instead of generating a copy.
+
 * URI
   * incompatible changes:
     * URI.decode_www_form follows current WHATWG URL Standard.
Index: test/test_set.rb
===================================================================
--- test/test_set.rb	(revision 42050)
+++ test/test_set.rb	(revision 42051)
@@ -625,6 +625,9 @@ class TC_Enumerable < Test::Unit::TestCa https://github.com/ruby/ruby/blob/trunk/test/test_set.rb#L625
     assert_instance_of(Set, set)
     assert_equal([-10,-8,-6,-4,-2], set.sort)
 
+    assert_same set, set.to_set
+    assert_not_same set, set.to_set { |o| o }
+
     set = ary.to_set(SortedSet)
     assert_instance_of(SortedSet, set)
     assert_equal([1,2,3,4,5], set.to_a)

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