fix Forwardable warnings in WrappedModule/Candidate

lib/pry.rb

@@ -2,12 +2,11 @@
 # MIT License
 #
 require 'pp'
-
+require 'pry/forwardable'
 require 'pry/input_lock'
 require 'pry/exceptions'
 require 'pry/helpers/base_helpers'
 require 'pry/hooks'
-require 'forwardable'
 
 class Pry
   # The default hooks - display messages when beginning and ending Pry sessions.

lib/pry/forwardable.rb

@@ -0,0 +1,23 @@
+class Pry
+  module Forwardable
+    require 'forwardable'
+    include ::Forwardable
+
+    #
+    # Since Ruby 2.4, Forwardable will print a warning when
+    # calling a method that is private on a delegate, and
+    # in the future it could be an error: https://bugs.ruby-lang.org/issues/12782#note-3
+    #
+    # That's why we revert to a custom implementation for delegating one
+    # private method to another.
+    #
+    def def_private_delegators(target, *private_delegates)
+      private_delegates.each do |private_delegate|
+        define_method(private_delegate) do |*a, &b|
+          instance_variable_get(target).__send__(private_delegate, *a, &b)
+        end
+      end
+      class_eval { private *private_delegates }
+    end
+  end
+end

lib/pry/pry_class.rb

@@ -5,7 +5,7 @@ class Pry
   LOCAL_RC_FILE = "./.pryrc"
 
   class << self
-    extend Forwardable
+    extend Pry::Forwardable
     attr_accessor :custom_completions
     attr_accessor :current_line
     attr_accessor :line_buffer

lib/pry/repl.rb

@@ -2,7 +2,7 @@ require 'forwardable'
 
 class Pry
   class REPL
-    extend Forwardable
+    extend Pry::Forwardable
     def_delegators :@pry, :input, :output
 
     # @return [Pry] The instance of {Pry} that the user is controlling.

lib/pry/test/helper.rb

@@ -102,7 +102,7 @@ def pry_eval(*eval_strs)
 end
 
 class PryTester
-  extend Forwardable
+  extend Pry::Forwardable
 
   attr_reader :pry, :out
 

lib/pry/wrapped_module/candidate.rb

@@ -1,5 +1,4 @@
 require 'pry/helpers/documentation_helpers'
-require 'forwardable'
 
 class Pry
   class WrappedModule
@@ -10,7 +9,7 @@ class Pry
     class Candidate
       include Pry::Helpers::DocumentationHelpers
       include Pry::CodeObject::Helpers
-      extend Forwardable
+      extend Pry::Forwardable
 
       # @return [String] The file where the module definition is located.
       attr_reader :file
@@ -22,15 +21,12 @@ class Pry
 
       # Methods to delegate to associated `Pry::WrappedModule
       # instance`.
-      private_delegates = [:lines_for_file, :method_candidates,
-                           :yard_docs?]
-
-      public_delegates = [:wrapped, :module?, :class?, :name, :nonblank_name,
+      private_delegates = [:lines_for_file, :method_candidates, :yard_docs?, :name]
+      public_delegates = [:wrapped, :module?, :class?, :nonblank_name,
                           :number_of_candidates]
 
-      def_delegators :@wrapper, *(private_delegates + public_delegates)
-      private(*private_delegates)
-      public(*public_delegates)
+      def_delegators :@wrapper, *public_delegates
+      def_private_delegators :@wrapper, *private_delegates
 
       # @raise [Pry::CommandError] If `rank` is out of bounds.
       # @param [Pry::WrappedModule] wrapper The associated