Merge pull request #16964 from Agis-/issue-16956

Make delegation work with the reserved words passed to `:to`

activesupport/CHANGELOG.md

+*   Delegation now works with ruby reserved words passed to `:to` option.
+
+    Fixes #16956.
+
+    *Agis Anastasopoulos*
+
 *   Added method `#eql?` to `ActiveSupport::Duration`, in addition to `#==`.
 
     Currently, the following returns `false`, contrary to expectation:

activesupport/lib/active_support/core_ext/module/delegation.rb

+require 'set'
+
 class Module
   # Error generated by +delegate+ when a method is called on +nil+ and +allow_nil+
   # option is not used.
   class DelegationError < NoMethodError; end
 
+  RUBY_RESERVED_WORDS = Set.new(
+    %w(alias and BEGIN begin break case class def defined? do else elsif END
+       end ensure false for if in module next nil not or redo rescue retry
+       return self super then true undef unless until when while yield)
+  ).freeze
+
   # Provides a +delegate+ class method to easily expose contained objects'
   # public methods as your own.
   #
@@ -163,7 +171,7 @@ def delegate(*methods)
     line = line.to_i
 
     to = to.to_s
-    to = 'self.class' if to == 'class'
+    to = "self.#{to}" if RUBY_RESERVED_WORDS.include?(to)
 
     methods.each do |method|
       # Attribute writer methods only accept one argument. Makes sure []=

activesupport/test/core_ext/module_test.rb

@@ -56,8 +56,14 @@ def self.table_name
   delegate :name, :to => :client, :prefix => nil
 end
 
+Event = Struct.new(:case) do
+  delegate :foo, :to => :case
+end
+
 Tester = Struct.new(:client) do
   delegate :name, :to => :client, :prefix => false
+
+  def foo; 1; end
 end
 
 Product = Struct.new(:name) do
@@ -495,4 +501,9 @@ def duck; 'duck' end
     assert_equal 'duck_with_orange', @instance.duck
     assert FooClassWithBarMethod.public_method_defined?(:duck)
   end
+
+  def test_delegate_with_case
+    event = Event.new(Tester.new)
+    assert_equal 1, event.foo
+  end
 end