[ruby/delegate] Reapply "Merge pull request #46 from byroot/use-forward-send"

This reverts commit https://github.com/ruby/delegate/commit/fc2bd0498af0.

https://github.com/ruby/delegate/commit/7d5c1e0842

Co-authored-by: Jean Boussier <byroot@ruby-lang.org>

lib/delegate.rb

@@ -405,6 +405,17 @@ def DelegateClass(superclass, &block)
   protected_instance_methods -= ignores
   public_instance_methods = superclass.public_instance_methods
   public_instance_methods -= ignores
+
+  normal, special = public_instance_methods.partition { |m| m.match?(/\A[a-zA-Z]\w*[!\?]?\z/) }
+
+  source = normal.map do |method|
+    "def #{method}(...); __getobj__.#{method}(...); end"
+  end
+
+  protected_instance_methods.each do |method|
+    source << "def #{method}(...); __getobj__.__send__(#{method.inspect}, ...); end"
+  end
+
   klass.module_eval do
     def __getobj__ # :nodoc:
       unless defined?(@delegate_dc_obj)
@@ -413,18 +424,21 @@ def DelegateClass(superclass, &block)
       end
       @delegate_dc_obj
     end
+
     def __setobj__(obj)  # :nodoc:
       __raise__ ::ArgumentError, "cannot delegate to self" if self.equal?(obj)
       @delegate_dc_obj = obj
     end
-    protected_instance_methods.each do |method|
-      define_method(method, Delegator.delegating_block(method))
-      protected method
-    end
-    public_instance_methods.each do |method|
+
+    class_eval(source.join(";"), __FILE__, __LINE__)
+
+    special.each do |method|
       define_method(method, Delegator.delegating_block(method))
     end
+
+    protected(*protected_instance_methods)
   end
+
   klass.define_singleton_method :public_instance_methods do |all=true|
     super(all) | superclass.public_instance_methods
   end

test/test_delegate.rb

@@ -93,15 +93,21 @@ class TestDelegateClass < Test::Unit::TestCase
   end
 
   class Parent
-    def parent_public; end
+    def parent_public
+      :public
+    end
 
     protected
 
-    def parent_protected; end
+    def parent_protected
+      :protected
+    end
 
     private
 
-    def parent_private; end
+    def parent_private
+      :private
+    end
   end
 
   class Child < DelegateClass(Parent)
@@ -157,6 +163,13 @@ class TestDelegateClass < Test::Unit::TestCase
     assert_instance_of UnboundMethod, Child.public_instance_method(:to_s)
   end
 
+  def test_call_visibiltiy
+    obj = Child.new(Parent.new)
+    assert_equal :public, obj.parent_public
+    assert_equal :protected, obj.__send__(:parent_protected)
+    assert_raise(NoMethodError) { obj.__send__(:parent_private) }
+  end
+
   class IV < DelegateClass(Integer)
     attr_accessor :var