Minor documentation fixes [ci skip]

From zverok (Victor Shepelev)

Fixes [Misc #16126]

enumerator.c

@@ -26,8 +26,8 @@
  * A class which allows both internal and external iteration.
  *
  * An Enumerator can be created by the following methods.
- * - Kernel#to_enum
- * - Kernel#enum_for
+ * - Object#to_enum
+ * - Object#enum_for
  * - Enumerator.new
  *
  * Most methods have two forms: a block form where the contents
@@ -417,7 +417,7 @@ enumerator_init(VALUE enum_obj, VALUE obj, VALUE meth, int argc, const VALUE *ar
  * In the second, deprecated, form, a generated Enumerator iterates over the
  * given object using the given method with the given arguments passed.
  *
- * Use of this form is discouraged.  Use Kernel#enum_for or Kernel#to_enum
+ * Use of this form is discouraged.  Use Object#enum_for or Object#to_enum
  * instead.
  *
  *   e = Enumerator.new(ObjectSpace, :each_object)
@@ -1862,7 +1862,7 @@ lazy_to_enum_i(VALUE obj, VALUE meth, int argc, const VALUE *argv, rb_enumerator
  *
  * For example, continuing from the example in Object#to_enum:
  *
- *   # See Kernel#to_enum for the definition of repeat
+ *   # See Object#to_enum for the definition of repeat
  *   r = 1..Float::INFINITY
  *   r.repeat(2).first(5) # => [1, 1, 2, 2, 3]
  *   r.repeat(2).class # => Enumerator

error.c

@@ -300,7 +300,7 @@ warning_write(int argc, VALUE *argv, VALUE buf)
 
 /*
  * call-seq:
- *    warn(msg, ...)   -> nil
+ *    warn(*msgs, uplevel: nil)   -> nil
  *
  * If warnings have been disabled (for example with the
  * <code>-W0</code> flag), does nothing.  Otherwise,
@@ -2446,6 +2446,7 @@ syserr_eqq(VALUE self, VALUE exc)
  *    * IndexError
  *      * KeyError
  *      * StopIteration
+ *        * ClosedQueueError
  *    * LocalJumpError
  *    * NameError
  *      * NoMethodError

object.c

@@ -572,23 +572,23 @@ rb_obj_size(VALUE self, VALUE args, VALUE obj)
  *     3.next.then {|x| x**x }.to_s             #=> "256"
  *     "my string".yield_self {|s| s.upcase }   #=> "MY STRING"
  *
- *  Good usage for +yield_self+ is value piping in method chains:
+ *  Good usage for +then+ is value piping in method chains:
  *
  *     require 'open-uri'
  *     require 'json'
  *
  *     construct_url(arguments).
- *       yield_self {|url| open(url).read }.
- *       yield_self {|response| JSON.parse(response) }
+ *       then {|url| open(url).read }.
+ *       then {|response| JSON.parse(response) }
  *
  *  When called without block, the method returns +Enumerator+,
  *  which can be used, for example, for conditional
  *  circuit-breaking:
  *
  *     # meets condition, no-op
- *     1.yield_self.detect(&:odd?)            # => 1
+ *     1.then.detect(&:odd?)            # => 1
  *     # does not meet condition, drop value
- *     2.yield_self.detect(&:odd?)            # => nil
+ *     2.then.detect(&:odd?)            # => nil
  *
  */