Remove Class#descendants

NEWS.md

@@ -126,20 +126,6 @@ Note: We're only listing outstanding class updates.
 
 * Class
 
-    *   Class#descendants, which returns an array of classes
-        directly or indirectly inheriting from the receiver, not
-        including the receiver or singleton classes.
-        [[Feature #14394]]
-
-        ```ruby
-        class A; end
-        class B < A; end
-        class C < B; end
-        A.descendants    #=> [B, C]
-        B.descendants    #=> [C]
-        C.descendants    #=> []
-        ```
-
     *   Class#subclasses, which returns an array of classes
         directly inheriting from the receiver, not
         including singleton classes.
@@ -555,7 +541,6 @@ See [the repository](https://github.com/ruby/error_highlight) in detail.
 [Feature #12495]: https://bugs.ruby-lang.org/issues/12495
 [Feature #12913]: https://bugs.ruby-lang.org/issues/12913
 [Feature #14256]: https://bugs.ruby-lang.org/issues/14256
-[Feature #14394]: https://bugs.ruby-lang.org/issues/14394
 [Feature #14579]: https://bugs.ruby-lang.org/issues/14579
 [Feature #15198]: https://bugs.ruby-lang.org/issues/15198
 [Feature #15211]: https://bugs.ruby-lang.org/issues/15211

class.c

@@ -1427,31 +1427,6 @@ class_descendants(VALUE klass, bool immediate_only)
     return data.buffer;
 }
 
-/*
- *  call-seq:
- *     descendants -> array
- *
- *  Returns an array of classes where the receiver is one of
- *  the ancestors of the class, excluding the receiver and
- *  singleton classes. The order of the returned array is not
- *  defined.
- *
- *     class A; end
- *     class B < A; end
- *     class C < B; end
- *
- *     A.descendants        #=> [B, C]
- *     B.descendants        #=> [C]
- *     C.descendants        #=> []
- */
-
-VALUE
-rb_class_descendants(VALUE klass)
-{
-    return class_descendants(klass, false);
-}
-
-
 /*
  *  call-seq:
  *     subclasses -> array

object.c

@@ -4660,7 +4660,6 @@ InitVM_Object(void)
     rb_define_method(rb_cClass, "new", rb_class_new_instance_pass_kw, -1);
     rb_define_method(rb_cClass, "initialize", rb_class_initialize, -1);
     rb_define_method(rb_cClass, "superclass", rb_class_superclass, 0);
-    rb_define_method(rb_cClass, "descendants", rb_class_descendants, 0); /* in class.c */
     rb_define_method(rb_cClass, "subclasses", rb_class_subclasses, 0); /* in class.c */
     rb_define_alloc_func(rb_cClass, rb_class_s_alloc);
     rb_undef_method(rb_cClass, "extend_object");

test/ruby/test_class.rb

@@ -738,38 +738,6 @@ def test_assign_frozen_class_to_const
     assert_same(c, Module.new.const_set(:Foo, c))
   end
 
-  def test_descendants
-    c = Class.new
-    sc = Class.new(c)
-    ssc = Class.new(sc)
-    [c, sc, ssc].each do |k|
-      k.include Module.new
-      k.new.define_singleton_method(:force_singleton_class){}
-    end
-    assert_equal([sc, ssc], c.descendants)
-    assert_equal([ssc], sc.descendants)
-    assert_equal([], ssc.descendants)
-
-    object_descendants = Object.descendants
-    assert_include(object_descendants, c)
-    assert_include(object_descendants, sc)
-    assert_include(object_descendants, ssc)
-  end
-
-  def test_descendants_gc
-    c = Class.new
-    100000.times { Class.new(c) }
-    assert(c.descendants.size <= 100000)
-  end
-
-  def test_descendants_gc_stress
-    10000.times do
-      c = Class.new
-      100.times { Class.new(c) }
-      assert(c.descendants.size <= 100)
-    end
-  end
-
   def test_subclasses
     c = Class.new
     sc = Class.new(c)