Review Kernel methods: deprecate 12 redundant methods

- Deprecate 6 singleton_class synonyms: eigenclass (tribute to _why),
  extension, instance_class, qua_class, object_class, and update
  meta_class to delegate to singleton_class internally
- Keep meta_class/meta_def/meta_eval/meta_alias as concise alternatives
- Deprecate object_send (use public_send), instance_send (use __send__)
- Deprecate load_relative (use require_relative)
- Deprecate returning (use tap)
- Deprecate memo (use Module#memoize; global $MEMO is problematic)
- 40 unique methods kept

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: trans

HISTORY.md

@@ -110,6 +110,14 @@ Changes:
   * Deprecate `Module#can` (use `Module#extend`).
   * Deprecate `File.null` (use `File::NULL` constant, Ruby 1.9.3+).
   * Deprecate `File.read_binary` (use `File.binread`, Ruby 1.9.3+).
+  * Deprecate `Kernel#eigenclass` (use `singleton_class` or `meta_class`; kept in tribute to _why).
+  * Deprecate `Kernel#extension`, `#instance_class`, `#qua_class`, `#object_class`
+    (use `singleton_class` or `meta_class`).
+  * Deprecate `Kernel#object_send` (use `public_send`), `#instance_send` (use `__send__`).
+  * Deprecate `Kernel#load_relative` (use `require_relative`).
+  * Deprecate `Kernel#returning` (use `Kernel#tap`).
+  * Deprecate `Kernel#memo` (use `Module#memoize`; global `$MEMO` is problematic).
+  * Update `Kernel#meta_class` to delegate to `singleton_class` internally.
   * Fix dead requires for removed `kernel/singleton_class` in Proc and Kernel.
   * Remove misplaced `applique/file_helpers` from core (test infrastructure).
   * Drop unused `test_files` directive from gemspec. (PR#301)

lib/core/facets/kernel/eigenclass.rb

@@ -3,22 +3,22 @@ module Kernel
   # During this trying time when no one can get their
   # techie catchwords to stick to the refrigerator no
   # matter how hard they slap it with the enchanted
-  # magnetic spatula, it’s good to know that the
+  # magnetic spatula, it's good to know that the
   # contrived phrases really do fly, graceful and
   # unclasped and bearing north toward chilled shrimp.
-  # I know what my Hallowe’en pumpkin is going to say.
+  # I know what my Hallowe'en pumpkin is going to say.
   #
-  # NOTE: This method is not a common core extension and is not
-  # loaded automatically when using `require 'facets'`.
+  # @deprecated Use singleton_class or meta_class instead.
+  #   Kept in tribute to WhyTheLuckyStiff who coined the term.
   #
   # CREDIT: WhyTheLuckyStiff
   #
   # @uncommon
   #   require 'facets/kernel/eigenclass'
   #
   def eigenclass
-    (class << self; self; end)
+    warn "Kernel#eigenclass is deprecated. Use singleton_class or meta_class instead.", uplevel: 1
+    singleton_class
   end
 
 end
-

lib/core/facets/kernel/extension.rb

@@ -1,12 +1,9 @@
 module Kernel
 
-  # TODO: Must reduce the number of singleton method methods.
-
-  # Don't say it!
-  #
+  # @deprecated Use singleton_class or meta_class instead.
   def extension
-    class << self; self; end
+    warn "Kernel#extension is deprecated. Use singleton_class or meta_class instead.", uplevel: 1
+    singleton_class
   end
 
 end
-

lib/core/facets/kernel/instance_class.rb

@@ -1,26 +1,10 @@
 module Kernel
 
-  # Kernel extension prefixed by instance_ which provide
-  # internal (eg private) access to the object.
-  # Kernel extension using instance_ prefix which is beneficial
-  # to separation of metaprogramming from general programming.
-  # object_ methods, in contrast to the instance_ methods,
-  # do not access internal state.
-
-  # Easy access to an object qua class, otherwise known
-  # as the object's metaclass or singleton class. This
-  # implemnetation alwasy returns the class, even if a
-  # block is provided to eval against it...
-  #
-  #     It is what it is.
-  #     But I think I like this one best.
-  #
-  # CREDIT: Trans
-
+  # @deprecated Use singleton_class or meta_class instead.
   def instance_class(&block)
-    (class << self; self; end).module_eval(&block) if block
-    (class << self; self; end)
+    warn "Kernel#instance_class is deprecated. Use singleton_class or meta_class instead.", uplevel: 1
+    singleton_class.module_eval(&block) if block
+    singleton_class
   end
 
 end
-

lib/core/facets/kernel/instance_send.rb

@@ -1,7 +1,9 @@
 module Kernel
 
-  # Private send.
-  alias_method :instance_send, :__send__
+  # @deprecated Use __send__ instead.
+  def instance_send(name, *args, &blk)
+    warn "Kernel#instance_send is deprecated. Use __send__ instead.", uplevel: 1
+    __send__(name, *args, &blk)
+  end
 
 end
-

lib/core/facets/kernel/load_relative.rb

@@ -1,25 +1,13 @@
 module Kernel
 
-  unless private_method_defined?(:load_relative)  # Will Ruby ever support out-of-the-box?
-
-    # Load file from same dir as calling script.
-    #
-    #   load_relative 'myscript'
-    #
-    # CREDIT: Paul Brannan, Pragmatic Programmers
-    #
-    def load_relative(relative_feature, safe=nil)
-      c = caller.first
-      fail "Can't parse #{c}" unless c.rindex(/:\d+(:in `.*')?$/)
-      file = $` # File.dirname(c)
-      if /\A\((.*)\)/ =~ file # eval, etc.
-        raise LoadError, "require_relative is called in #{$1}"
-      end
-      absolute = File.expand_path(relative_feature, File.dirname(file))
-      load absolute, safe
-    end
-
+  # @deprecated Use require_relative for requires; for load, use
+  #   an absolute path via File.expand_path.
+  def load_relative(relative_feature, safe=nil)
+    warn "Kernel#load_relative is deprecated.", uplevel: 1
+    loc = caller_locations(1, 1).first
+    file = loc.absolute_path || loc.path
+    absolute = File.expand_path(relative_feature, File.dirname(file))
+    load absolute, safe
   end
 
 end
-

lib/core/facets/kernel/memo.rb

@@ -1,35 +1,14 @@
-require 'facets/binding/eval'
-require 'facets/kernel/__method__'
-
 module Kernel
 
-  # Global memo cache.
-  $MEMO ||= {}
-
-  # Memoize a method.
-  # 
-  #   class MemoExample
-  #     attr_accessor :a
-  #     def m
-  #       memo{ @a }
-  #     end
-  #   end
-  #
-  #   ex = MemoExample.new
-  #
-  #   ex.a = 10
-  #   ex.m  #=> 10
-  #
-  #   ex.a = 20
-  #   ex.m  #=> 10
-  #
-  # NOTE: This method is not a common core extension and is not
-  # loaded automatically when using <code>require 'facets'</code>.
+  # @deprecated Use Module#memoize instead, which provides proper
+  #   per-object memoization without a global variable.
   #
   # @uncommon
   #   require 'facets/kernel/memo'
   #
   def memo(*args, &block)
+    warn "Kernel#memo is deprecated. Use Module#memoize instead.", uplevel: 1
+    $MEMO ||= {}
     if args.empty?
       args = block.binding.eval('[self, __method__]')
     end
@@ -41,4 +20,3 @@ def memo(*args, &block)
   end
 
 end
-

lib/core/facets/kernel/meta_class.rb

@@ -1,17 +1,21 @@
 module Kernel
 
-  # Easy access to an object's "special" class, otherwise known as it's
-  # singleton class, eigenclass, adhoc class or object-qua-class.
-  # 
+  # Easy access to an object's singleton class, with optional block eval.
+  #
+  #   obj.meta_class  #=> #<Class:obj>
+  #   obj.meta_class { def foo; end }
+  #
+  # This is a concise alternative to Ruby's `singleton_class` that also
+  # accepts a block for class_eval.
+  #
   def meta_class(&block)
     if block_given?
-      (class << self; self; end).class_eval(&block)
+      singleton_class.class_eval(&block)
     else
-      (class << self; self; end)
+      singleton_class
     end
   end
 
-  # The non-underscored form of #meta_class if faily common.
   alias_method :metaclass, :meta_class
 
 end

lib/core/facets/kernel/object_class.rb

@@ -1,10 +1,9 @@
 module Kernel
 
-  # Defines object_classas an alias of class.
-  # This is an alternative to __class__, akin to
-  # #object_id.
-
-  alias_method :object_class, :class
+  # @deprecated Use __class__ instead.
+  def object_class
+    warn "Kernel#object_class is deprecated. Use __class__ instead.", uplevel: 1
+    self.class
+  end
 
 end
-

lib/core/facets/kernel/object_send.rb

@@ -1,30 +1,9 @@
 module Kernel
 
-  # Send only to public methods.
-  #
-  #   class SendExample
-  #     private
-  #     def foo; end
-  #   end
-  #
-  #   obj = SendExample.new
-  #
-  #   expect NoMethodError do
-  #     obj.object_send(:foo)
-  #   end
-  #
-  # DEPRECATED: Use #public_send instead.
-
-  alias object_send public_send rescue nil
-
-  #def object_send(name, *args, &blk)
-  #  #instance_eval "self.#{name}(*args)"
-  #  if respond_to?(name)
-  #    __send__(name, *args, &blk)
-  #  else
-  #    __send__(:method_missing, name, *args, &blk)
-  #  end
-  #end
+  # @deprecated Use public_send instead (built-in since Ruby 1.9.2).
+  def object_send(name, *args, &blk)
+    warn "Kernel#object_send is deprecated. Use public_send instead.", uplevel: 1
+    public_send(name, *args, &blk)
+  end
 
 end
-