merge revision(s) r45375,r48260,r48320,r48746: [Backport #10526]

	* complax.c: [DOC] Document number conversion of `nil` by @skade [fix GH-570] [ci skip]

	* object.c, rational.c: ditto.
	* object.c: fix document of Kernel.Stirng by @suzukaze
	  [fix GH-743][ci skip]

	* object.c (Module#const_defined?): [DOC] Revise the documentation.
	  Patch by Xavier Noria.
	  [Fixes GH-754] https://github.com/ruby/ruby/pull/754

	* object.c: [DOC] Revise documentation by Marcus Stollsteimer at
	  [ruby-core:66368].  [Bug #10526]
	  * #inspect: be more specific about generated string, remove
	    obsolete example.
	  * #nil?: use code examples instead of different call-seq's.
	  * #tap: clarify what is yielded.
	  * Integer(): be more specific about to_int and to_i, remove
	    reference to Ruby 1.8.
	  * Array(): fix error.
	  * Class: fix variable name style and indentation in example.
	  * improve consistency, fix typos and formatting.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@49367 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

5 files changed, 130 insertions, 84 deletions

diff --git a/ChangeLog b/ChangeLog
index 71a2015981..131e7f16af 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,29 @@
+Thu Jan 22 00:49:52 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* object.c: [DOC] Revise documentation by Marcus Stollsteimer at
+	  [ruby-core:66368].  [Bug #10526]
+
+	  * #inspect: be more specific about generated string, remove
+	    obsolete example.
+	  * #nil?: use code examples instead of different call-seq's.
+	  * #tap: clarify what is yielded.
+	  * Integer(): be more specific about to_int and to_i, remove
+	    reference to Ruby 1.8.
+	  * Array(): fix error.
+	  * Class: fix variable name style and indentation in example.
+	  * improve consistency, fix typos and formatting.
+
+Thu Jan 22 00:49:52 2015  Benoit Daloze  <eregontp@gmail.com>
+
+	* object.c (Module#const_defined?): [DOC] Revise the documentation.
+	  Patch by Xavier Noria.
+	  [Fixes GH-754] https://github.com/ruby/ruby/pull/754
+
+Thu Jan 22 00:49:52 2015  SHIBATA Hiroshi  <shibata.hiroshi@gmail.com>
+
+	* object.c: fix document of Kernel.Stirng by @suzukaze
+	  [fix GH-743][ci skip]
+
 Thu Jan 22 00:25:15 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* load.c (rb_f_load): path name needs to be transcoded to OS path
diff --git a/complex.c b/complex.c
index e1d5ff9f2a..67b45dd6ae 100644
--- a/complex.c
+++ b/complex.c
@@ -433,6 +433,8 @@ f_complex_new2(VALUE klass, VALUE x, VALUE y)
  *
  *    Complex(1, 2)    #=> (1+2i)
  *    Complex('1+2i')  #=> (1+2i)
+ *    Complex(nil)     #=> TypeError
+ *    Complex(1, nil)  #=> TypeError
  *
  * Syntax of string form:
  *
diff --git a/object.c b/object.c
index 0d7e03a95f..d7b37e56b3 100644
--- a/object.c
+++ b/object.c
@@ -154,7 +154,7 @@ rb_obj_equal(VALUE obj1, VALUE obj2)
  * capacity of a Fixnum will be truncated before being used.
  *
  * The hash value for an object may not be identical across invocations or
- * implementations of ruby.  If you need a stable identifier across ruby
+ * implementations of Ruby.  If you need a stable identifier across Ruby
  * invocations and implementations you will need to generate one with a custom
  * method.
  */
@@ -233,7 +233,7 @@ rb_obj_class(VALUE obj)
  *     obj.singleton_class    -> class
  *
  *  Returns the singleton class of <i>obj</i>.  This method creates
- *  a new singleton class if <i>obj</i> does not have it.
+ *  a new singleton class if <i>obj</i> does not have one.
  *
  *  If <i>obj</i> is <code>nil</code>, <code>true</code>, or
  *  <code>false</code>, it returns NilClass, TrueClass, or FalseClass,
@@ -314,9 +314,9 @@ init_copy(VALUE dest, VALUE obj)
  *     obj.clone -> an_object
  *
  *  Produces a shallow copy of <i>obj</i>---the instance variables of
- *  <i>obj</i> are copied, but not the objects they reference. Copies
- *  the frozen and tainted state of <i>obj</i>. See also the discussion
- *  under <code>Object#dup</code>.
+ *  <i>obj</i> are copied, but not the objects they reference.
+ *  <code>clone</code> copies the frozen and tainted state of <i>obj</i>.
+ *  See also the discussion under <code>Object#dup</code>.
  *
  *     class Klass
  *        attr_accessor :str
@@ -364,8 +364,8 @@ rb_obj_clone(VALUE obj)
  *     obj.dup -> an_object
  *
  *  Produces a shallow copy of <i>obj</i>---the instance variables of
- *  <i>obj</i> are copied, but not the objects they reference. <code>dup</code>
- *  copies the tainted state of <i>obj</i>.
+ *  <i>obj</i> are copied, but not the objects they reference.
+ *  <code>dup</code> copies the tainted state of <i>obj</i>.
  *
  *  This method may have class-specific behavior.  If so, that
  *  behavior will be documented under the #+initialize_copy+ method of
@@ -379,7 +379,7 @@ rb_obj_clone(VALUE obj)
  *  typically uses the class of the descendant object to create the new
  *  instance.
  *
- *  When using #dup any modules that the object has been extended with will not
+ *  When using #dup, any modules that the object has been extended with will not
  *  be copied.
  *
  *	class Klass
@@ -445,7 +445,7 @@ rb_obj_init_dup_clone(VALUE obj, VALUE orig)
  *  Returns a string representing <i>obj</i>. The default
  *  <code>to_s</code> prints the object's class and an encoding of the
  *  object id. As a special case, the top-level object that is the
- *  initial execution context of Ruby programs returns ``main.''
+ *  initial execution context of Ruby programs returns ``main''.
  */
 
 VALUE
@@ -462,7 +462,7 @@ rb_any_to_s(VALUE obj)
 
 /*
  * If the default external encoding is ASCII compatible, the encoding of
- * inspected result must be compatible with it.
+ * the inspected result must be compatible with it.
  * If the default external encoding is ASCII incompatible,
  * the result must be ASCII only.
  */
@@ -531,9 +531,10 @@ inspect_obj(VALUE obj, VALUE str, int recur)
  *     obj.inspect   -> string
  *
  * Returns a string containing a human-readable representation of <i>obj</i>.
- * By default, show the class name and the list of the instance variables and
+ * The default <code>inspect</code> shows the object's class name,
+ * an encoding of the object id, and a list of the instance variables and
  * their values (by calling #inspect on each of them).
- * User defined classes should override this method to make better
+ * User defined classes should override this method to provide a better
  * representation of <i>obj</i>.  When overriding this method, it should
  * return a string whose encoding is compatible with the default external
  * encoding.
@@ -551,13 +552,6 @@ inspect_obj(VALUE obj, VALUE str, int recur)
  *       end
  *     end
  *     Bar.new.inspect                  #=> "#<Bar:0x0300c868 @bar=1>"
- *
- *     class Baz
- *       def to_s
- *         "baz"
- *       end
- *     end
- *     Baz.new.inspect                  #=> "#<Baz:0x0300c868>"
  */
 
 static VALUE
@@ -680,14 +674,14 @@ rb_class_search_ancestor(VALUE cl, VALUE c)
  *  call-seq:
  *     obj.tap{|x|...}    -> obj
  *
- *  Yields <code>x</code> to the block, and then returns <code>x</code>.
+ *  Yields self to the block, and then returns self.
  *  The primary purpose of this method is to "tap into" a method chain,
  *  in order to perform operations on intermediate results within the chain.
  *
  *	(1..10)                .tap {|x| puts "original: #{x.inspect}"}
  *	  .to_a                .tap {|x| puts "array: #{x.inspect}"}
  *	  .select {|x| x%2==0} .tap {|x| puts "evens: #{x.inspect}"}
- *	  .map { |x| x*x }     .tap {|x| puts "squares: #{x.inspect}"}
+ *	  .map {|x| x*x}       .tap {|x| puts "squares: #{x.inspect}"}
  *
  */
 
@@ -721,7 +715,7 @@ rb_obj_tap(VALUE obj)
  *    class Baz < Bar
  *    end
  *
- * produces:
+ * <em>produces:</em>
  *
  *    New subclass: Bar
  *    New subclass: Baz
@@ -743,7 +737,7 @@ rb_obj_tap(VALUE obj)
  *     def some_instance_method() end
  *   end
  *
- * produces:
+ * <em>produces:</em>
  *
  *   Adding :some_instance_method
  *
@@ -769,7 +763,7 @@ rb_obj_tap(VALUE obj)
  *     remove_method :some_instance_method
  *   end
  *
- * produces:
+ * <em>produces:</em>
  *
  *   Removing :some_instance_method
  *
@@ -957,13 +951,13 @@ rb_obj_tainted(VALUE obj)
  *
  *  Objects that are marked as tainted will be restricted from various built-in
  *  methods. This is to prevent insecure data, such as command-line arguments
- *  or strings read from Kernel#gets, from inadvertently compromising the users
+ *  or strings read from Kernel#gets, from inadvertently compromising the user's
  *  system.
  *
- *  To check whether an object is tainted, use #tainted?
+ *  To check whether an object is tainted, use #tainted?.
  *
  *  You should only untaint a tainted object if your code has inspected it and
- *  determined that it is safe. To do so use #untaint
+ *  determined that it is safe. To do so use #untaint.
  *
  *  In $SAFE level 3, all newly created objects are tainted and you can't untaint
  *  objects.
@@ -1249,7 +1243,7 @@ true_and(VALUE obj, VALUE obj2)
  *  call-seq:
  *     true | obj   -> true
  *
- *  Or---Returns <code>true</code>. As <i>anObject</i> is an argument to
+ *  Or---Returns <code>true</code>. As <i>obj</i> is an argument to
  *  a method call, it is always evaluated; there is no short-circuit
  *  evaluation in this case.
  *
@@ -1373,10 +1367,12 @@ rb_true(VALUE obj)
 
 /*
  * call-seq:
- *   nil.nil?               -> true
- *   <anything_else>.nil?   -> false
+ *   obj.nil?               -> true or false
  *
  * Only the object <i>nil</i> responds <code>true</code> to <code>nil?</code>.
+ *
+ *    Object.new.nil?   #=> false
+ *    nil.nil?          #=> true
  */
 
 
@@ -1453,7 +1449,7 @@ rb_obj_cmp(VALUE obj1, VALUE obj2)
  *  Instance methods appear as methods in a class when the module is
  *  included, module methods do not. Conversely, module methods may be
  *  called without creating an encapsulating object, while instance
- *  methods may not. (See <code>Module#module_function</code>)
+ *  methods may not. (See <code>Module#module_function</code>.)
  *
  *  In the descriptions that follow, the parameter <i>sym</i> refers
  *  to a symbol, which is either a quoted string or a
@@ -1476,7 +1472,7 @@ rb_obj_cmp(VALUE obj1, VALUE obj2)
  * call-seq:
  *   mod.to_s   -> string
  *
- * Return a string representing this module or class. For basic
+ * Returns a string representing this module or class. For basic
  * classes and modules, this is the name. For singletons, we
  * show information on the thing we're attached to as well.
  */
@@ -1536,7 +1532,7 @@ rb_mod_freeze(VALUE mod)
  *  call-seq:
  *     mod === obj    -> true or false
  *
- *  Case Equality---Returns <code>true</code> if <i>anObject</i> is an
+ *  Case Equality---Returns <code>true</code> if <i>obj</i> is an
  *  instance of <i>mod</i> or one of <i>mod</i>'s descendants. Of
  *  limited use for modules, but can be used in <code>case</code>
  *  statements to classify objects by class.
@@ -1556,7 +1552,7 @@ rb_mod_eqq(VALUE mod, VALUE arg)
  * is the same as <i>other</i>. Returns
  * <code>nil</code> if there's no relationship between the two.
  * (Think of the relationship in terms of the class definition:
- * "class A<B" implies "A<B").
+ * "class A<B" implies "A<B".)
  *
  */
 
@@ -1587,7 +1583,7 @@ rb_class_inherited_p(VALUE mod, VALUE arg)
  * Returns true if <i>mod</i> is a subclass of <i>other</i>. Returns
  * <code>nil</code> if there's no relationship between the two.
  * (Think of the relationship in terms of the class definition:
- * "class A<B" implies "A<B").
+ * "class A<B" implies "A<B".)
  *
  */
 
@@ -1607,7 +1603,7 @@ rb_mod_lt(VALUE mod, VALUE arg)
  * two modules are the same. Returns
  * <code>nil</code> if there's no relationship between the two.
  * (Think of the relationship in terms of the class definition:
- * "class A<B" implies "B>A").
+ * "class A<B" implies "B>A".)
  *
  */
 
@@ -1628,7 +1624,7 @@ rb_mod_ge(VALUE mod, VALUE arg)
  * Returns true if <i>mod</i> is an ancestor of <i>other</i>. Returns
  * <code>nil</code> if there's no relationship between the two.
  * (Think of the relationship in terms of the class definition:
- * "class A<B" implies "B>A").
+ * "class A<B" implies "B>A".)
  *
  */
 
@@ -1875,7 +1871,7 @@ rb_class_new_instance(int argc, VALUE *argv, VALUE klass)
  *     class Bar < Foo; end
  *     Bar.superclass           #=> Foo
  *
- *  returns nil when the given class hasn't a parent class:
+ *  Returns nil when the given class does not have a parent class:
  *
  *     BasicObject.superclass   #=> nil
  *
@@ -2050,9 +2046,9 @@ rb_mod_attr_accessor(int argc, VALUE *argv, VALUE klass)
  *     mod.const_get(sym, inherit=true)    -> obj
  *     mod.const_get(str, inherit=true)    -> obj
  *
- *  Checks for a constant with the given name in <i>mod</i>
+ *  Checks for a constant with the given name in <i>mod</i>.
  *  If +inherit+ is set, the lookup will also search
- *  the ancestors (and +Object+ if <i>mod</i> is a +Module+.)
+ *  the ancestors (and +Object+ if <i>mod</i> is a +Module+).
  *
  *  The value of the constant is returned if a definition is found,
  *  otherwise a +NameError+ is raised.
@@ -2078,7 +2074,7 @@ rb_mod_attr_accessor(int argc, VALUE *argv, VALUE klass)
  *     Object.const_get 'Foo::Baz::VAL'         # => 10
  *     Object.const_get 'Foo::Baz::VAL', false  # => NameError
  *
- *  If neither +sym+ nor +str+ is not a valid constant name a NameError will be
+ *  If the argument is not a valid constant name a +NameError+ will be
  *  raised with a warning "wrong constant name".
  *
  *	Object.const_get 'foobar' #=> NameError: wrong constant name foobar
@@ -2190,7 +2186,7 @@ rb_mod_const_get(int argc, VALUE *argv, VALUE mod)
  *     Math.const_set("HIGH_SCHOOL_PI", 22.0/7.0)   #=> 3.14285714285714
  *     Math::HIGH_SCHOOL_PI - Math::PI              #=> 0.00126448926734968
  *
- *  If neither +sym+ nor +str+ is not a valid constant name a NameError will be
+ *  If +sym+ or +str+ is not a valid constant name a +NameError+ will be
  *  raised with a warning "wrong constant name".
  *
  *	Object.const_set('foobar', 42) #=> NameError: wrong constant name foobar
@@ -2210,20 +2206,39 @@ rb_mod_const_set(VALUE mod, VALUE name, VALUE value)
  *     mod.const_defined?(sym, inherit=true)   -> true or false
  *     mod.const_defined?(str, inherit=true)   -> true or false
  *
- *  Checks for a constant with the given name in <i>mod</i>
- *  If +inherit+ is set, the lookup will also search
- *  the ancestors (and +Object+ if <i>mod</i> is a +Module+.)
+ *  Says whether _mod_ or its ancestors have a constant with the given name:
  *
- *  Returns whether or not a definition is found:
+ *    Float.const_defined?(:EPSILON)      #=> true, found in Float itself
+ *    Float.const_defined?("String")      #=> true, found in Object (ancestor)
+ *    BasicObject.const_defined?(:Hash)   #=> false
  *
- *     Math.const_defined? "PI"   #=> true
- *     IO.const_defined? :SYNC   #=> true
- *     IO.const_defined? :SYNC, false   #=> false
+ *  If _mod_ is a +Module+, additionally +Object+ and its ancestors are checked:
  *
- *  If neither +sym+ nor +str+ is not a valid constant name a NameError will be
- *  raised with a warning "wrong constant name".
+ *    Math.const_defined?(:String)   #=> true, found in Object
+ *
+ *  In each of the checked classes or modules, if the constant is not present
+ *  but there is an autoload for it, +true+ is returned directly without
+ *  autoloading:
+ *
+ *    module Admin
+ *      autoload :User, 'admin/user'
+ *    end
+ *    Admin.const_defined?(:User)   #=> true
+ *
+ *  If the constant is not found the callback +const_missing+ is *not* called
+ *  and the method returns +false+.
+ *
+ *  If +inherit+ is false, the lookup only checks the constants in the receiver:
  *
- *	Hash.const_defined? 'foobar' #=> NameError: wrong constant name foobar
+ *    IO.const_defined?(:SYNC)          #=> true, found in File::Constants (ancestor)
+ *    IO.const_defined?(:SYNC, false)   #=> false, not found in IO itself
+ *
+ *  In this case, the same logic for autoloading applies.
+ *
+ *  If the argument is not a valid constant name a +NameError+ is raised with the
+ *  message "wrong constant name _name_":
+ *
+ *    Hash.const_defined? 'foobar'   #=> NameError: wrong constant name foobar
  *
  */
 
@@ -2373,10 +2388,10 @@ rb_obj_ivar_get(VALUE obj, VALUE iv)
  *     obj.instance_variable_set(symbol, obj)    -> obj
  *     obj.instance_variable_set(string, obj)    -> obj
  *
- *  Sets the instance variable names by <i>symbol</i> to
- *  <i>object</i>, thereby frustrating the efforts of the class's
+ *  Sets the instance variable named by <i>symbol</i> to the given
+ *  object, thereby frustrating the efforts of the class's
  *  author to attempt to provide proper encapsulation. The variable
- *  did not have to exist prior to this call.
+ *  does not have to exist prior to this call.
  *  If the instance variable name is passed as a string, that string
  *  is converted to a symbol.
  *
@@ -2446,7 +2461,7 @@ rb_obj_ivar_defined(VALUE obj, VALUE iv)
  *
  *  Returns the value of the given class variable (or throws a
  *  <code>NameError</code> exception). The <code>@@</code> part of the
- *  variable name should be included for regular class variables
+ *  variable name should be included for regular class variables.
  *  String arguments are converted to symbols.
  *
  *     class Fred
@@ -2482,8 +2497,8 @@ rb_mod_cvar_get(VALUE obj, VALUE iv)
  *     obj.class_variable_set(symbol, obj)    -> obj
  *     obj.class_variable_set(string, obj)    -> obj
  *
- *  Sets the class variable names by <i>symbol</i> to
- *  <i>object</i>.
+ *  Sets the class variable named by <i>symbol</i> to the given
+ *  object.
  *  If the class variable name is passed as a string, that string
  *  is converted to a symbol.
  *
@@ -2740,24 +2755,26 @@ rb_Integer(VALUE val)
 
 /*
  *  call-seq:
- *     Integer(arg,base=0)    -> integer
+ *     Integer(arg, base=0)    -> integer
  *
  *  Converts <i>arg</i> to a <code>Fixnum</code> or <code>Bignum</code>.
  *  Numeric types are converted directly (with floating point numbers
- *  being truncated).    <i>base</i> (0, or between 2 and 36) is a base for
+ *  being truncated).  <i>base</i> (0, or between 2 and 36) is a base for
  *  integer string representation.  If <i>arg</i> is a <code>String</code>,
- *  when <i>base</i> is omitted or equals to zero, radix indicators
+ *  when <i>base</i> is omitted or equals zero, radix indicators
  *  (<code>0</code>, <code>0b</code>, and <code>0x</code>) are honored.
  *  In any case, strings should be strictly conformed to numeric
  *  representation. This behavior is different from that of
- *  <code>String#to_i</code>.  Non string values will be converted using
- *  <code>to_int</code>, and <code>to_i</code>.
+ *  <code>String#to_i</code>.  Non string values will be converted by first
+ *  trying <code>to_int</code>, then <code>to_i</code>. Passing <code>nil</code>
+ *  raises a TypeError.
  *
  *     Integer(123.999)    #=> 123
  *     Integer("0x1a")     #=> 26
  *     Integer(Time.new)   #=> 1204973019
  *     Integer("0930", 10) #=> 930
  *     Integer("111", 2)   #=> 7
+ *     Integer(nil)        #=> TypeError
  */
 
 static VALUE
@@ -2923,8 +2940,8 @@ rb_Float(VALUE val)
  *     Float(arg)    -> float
  *
  *  Returns <i>arg</i> converted to a float. Numeric types are converted
- *  directly, the rest are converted using <i>arg</i>.to_f. As of Ruby
- *  1.8, converting <code>nil</code> generates a <code>TypeError</code>.
+ *  directly, the rest are converted using <i>arg</i>.to_f.
+ *  Converting <code>nil</code> generates a <code>TypeError</code>.
  *
  *     Float(1)           #=> 1.0
  *     Float("123.456")   #=> 123.456
@@ -2996,8 +3013,9 @@ rb_String(VALUE val)
  *  call-seq:
  *     String(arg)   -> string
  *
- *  Converts <i>arg</i> to a <code>String</code> by calling its
- *  <code>to_s</code> method.
+ *  Returns <i>arg</i> as a <code>String</code>.
+ *
+ *  First tries to call its <code>to_str</code> method, then its <code>to_s</code> method.
  *
  *     String(self)        #=> "main"
  *     String(self.class)  #=> "Object"
@@ -3030,7 +3048,7 @@ rb_Array(VALUE val)
  *
  *  Returns +arg+ as an Array.
  *
- *  First tries to call Array#to_ary on +arg+, then Array#to_a.
+ *  First tries to call <code>to_ary</code> on +arg+, then <code>to_a</code>.
  *
  *     Array(1..5)   #=> [1, 2, 3, 4, 5]
  */
@@ -3085,7 +3103,7 @@ rb_f_hash(VALUE obj, VALUE arg)
  *  Typically, you create a new class by using:
  *
  *    class Name
- *     # some class describing the class behavior
+ *     # some code describing the class behavior
  *    end
  *
  *  When a new class is created, an object of type Class is initialized and
@@ -3097,19 +3115,17 @@ rb_f_hash(VALUE obj, VALUE arg)
  *  <code>Class</code>:
  *
  *     class Class
- *        alias oldNew  new
- *        def new(*args)
- *          print "Creating a new ", self.name, "\n"
- *          oldNew(*args)
- *        end
- *      end
- *
- *
- *      class Name
- *      end
+ *       alias old_new new
+ *       def new(*args)
+ *         print "Creating a new ", self.name, "\n"
+ *         old_new(*args)
+ *       end
+ *     end
  *
+ *     class Name
+ *     end
  *
- *      n = Name.new
+ *     n = Name.new
  *
  *  <em>produces:</em>
  *
@@ -3117,7 +3133,7 @@ rb_f_hash(VALUE obj, VALUE arg)
  *
  *  Classes, modules, and objects are interrelated. In the diagram
  *  that follows, the vertical arrows represent inheritance, and the
- *  parentheses meta-classes. All metaclasses are instances
+ *  parentheses metaclasses. All metaclasses are instances
  *  of the class `Class'.
  *                             +---------+             +-...
  *                             |         |             |
@@ -3178,7 +3194,7 @@ rb_f_hash(VALUE obj, VALUE arg)
  *
  *  BasicObject does not include Kernel (for methods like +puts+) and
  *  BasicObject is outside of the namespace of the standard library so common
- *  classes will not be found without a using a full class path.
+ *  classes will not be found without using a full class path.
  *
  *  A variety of strategies can be used to provide useful portions of the
  *  standard library to subclasses of BasicObject.  A subclass could
@@ -3216,7 +3232,7 @@ rb_f_hash(VALUE obj, VALUE arg)
  *
  *  Object is the default root of all Ruby objects.  Object inherits from
  *  BasicObject which allows creating alternate object hierarchies.  Methods
- *  on object are available to all classes unless explicitly overridden.
+ *  on Object are available to all classes unless explicitly overridden.
  *
  *  Object mixes in the Kernel module, making the built-in kernel functions
  *  globally accessible.  Although the instance methods of Object are defined
diff --git a/rational.c b/rational.c
index 7bc7206376..d8bee601e0 100644
--- a/rational.c
+++ b/rational.c
@@ -584,6 +584,8 @@ f_rational_new_no_reduce2(VALUE klass, VALUE x, VALUE y)
  *
  *    Rational(1, 2)   #=> (1/2)
  *    Rational('1/2')  #=> (1/2)
+ *    Rational(nil)    #=> TypeError
+ *    Rational(1, nil) #=> TypeError
  *
  * Syntax of string form:
  *
diff --git a/version.h b/version.h
index 535e5d9192..26416efee6 100644
--- a/version.h
+++ b/version.h
@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.1.5"
 #define RUBY_RELEASE_DATE "2015-01-22"
-#define RUBY_PATCHLEVEL 280
+#define RUBY_PATCHLEVEL 281
 
 #define RUBY_RELEASE_YEAR 2015
 #define RUBY_RELEASE_MONTH 1