From: "nobu (Nobuyoshi Nakada) via ruby-core" <ruby-core@...>
Date: 2023-01-03T13:05:16+00:00
Subject: [ruby-core:111595] [Ruby master Feature#19300] Move public objects from Kernel to Object

Issue #19300 has been updated by nobu (Nobuyoshi Nakada).

Status changed from Open to Third Party's Issue

This is an issue of RDoc.
RDoc replaces `rb_mKernel` with `rb_cObject` (= `Object`) internally, but it seems not working in some cases (maybe in `kernel.rb`?).

There is no visibility differences between `Kernel` and `Object`.

----------------------------------------
Feature #19300: Move public objects from Kernel to Object
https://bugs.ruby-lang.org/issues/19300#change-100964

* Author: zverok (Victor Shepelev)
* Status: Third Party's Issue
* Priority: Normal
----------------------------------------
In my understanding, `Kernel` is a container for methods that are perceived as "global", and are available inside every objects as its private methods, like `puts`
```ruby
class A
  def foo = puts "foo"
end

a = A.new
a.foo # prints "foo"
a.puts 'bar'
# private method `puts' called for #<A:0x00007f39a683db28> (NoMethodError)
```

There are, though, exactly three (if I am not missing something) methods that, **according to documentation**, break this intuition and belong to [Kernel](https://docs.ruby-lang.org/en/master/Kernel.html):
* `clone`
* `tap`
* `then`

All those methods are public method for a receiver, and they mostly make sense with an explicit receiver. The most confusing of them is `#clone`, which is close cousin of `#dup`, but it is [Kernel#clone](https://docs.ruby-lang.org/en/master/Kernel.html#method-i-clone) and [Object#dup](https://docs.ruby-lang.org/en/master/Object.html#method-i-dup).

This state of things is mostly harmless in practical code, but very inconvenient for teaching, reasoning about the meaning of modules and objects, and lookup for documentation.

**But**, in the description above, **according to documentation** is important statement. Because according to introspection, method definitions are spread differently:
```ruby
puts "Public"
Object.new
  .then { |o| o.methods.group_by { o.method(_1).owner } }
  .each { puts "#{_1}: #{_2.sort.join(', ')}" }

puts
puts "Private:"
Object.new
  .then { |o| o.private_methods.group_by { o.method(_1).owner } }
  .each { puts "#{_1}: #{_2.sort.join(', ')}" }
```
Output:
```
Public
Kernel: !~, <=>, ===, class, clone, define_singleton_method, display, dup, enum_for, eql?, extend, freeze, frozen?, hash, inspect, instance_of?, instance_variable_defined?, instance_variable_get, instance_variable_set, instance_variables, is_a?, itself, kind_of?, method, methods, nil?, object_id, private_methods, protected_methods, public_method, public_methods, public_send, remove_instance_variable, respond_to?, send, singleton_class, singleton_method, singleton_methods, tap, then, to_enum, to_s, yield_self
BasicObject: !, !=, ==, __id__, __send__, equal?, instance_eval, instance_exec

Private:
Kernel: Array, Complex, Float, Hash, Integer, Rational, String, __callee__, __dir__, __method__, `, abort, at_exit, autoload, autoload?, binding, block_given?, caller, caller_locations, catch, eval, exec, exit, exit!, fail, fork, format, gem, gem_original_require, gets, global_variables, initialize_clone, initialize_copy, initialize_dup, iterator?, lambda, load, local_variables, loop, open, p, pp, print, printf, proc, putc, puts, raise, rand, readline, readlines, require, require_relative, respond_to_missing?, select, set_trace_func, sleep, spawn, sprintf, srand, syscall, system, test, throw, trace_var, trap, untrace_var, warn
BasicObject: initialize, method_missing, singleton_method_added, singleton_method_removed, singleton_method_undefined
```
E.g., internally, `Object` doesn't have _any_ method defined, and is just a `BasicObject` with `Kernel` included.

So, there are three questions/proposals:
1. Does this disposition has some internal sense, or it is more of a historical thing?
2. Can it be changed so that public methods belonged to `Object` instead of `Kernel`?
3. If the answer to (2) is "no", can at least docs for `clone`, `tap` and `then` be adjusted to follow other public methods in pretending they are `Object`'s features?



-- 
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