Delegation works with reserved words passed to `:to`

Fixes #16956.

3 files changed, 26 insertions, 1 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 8f328335b2..4204057737 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,9 @@
+*   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:
diff --git a/activesupport/lib/active_support/core_ext/module/delegation.rb b/activesupport/lib/active_support/core_ext/module/delegation.rb
index e926392952..570585b89a 100644
--- a/activesupport/lib/active_support/core_ext/module/delegation.rb
+++ b/activesupport/lib/active_support/core_ext/module/delegation.rb
@@ -1,8 +1,16 @@
+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 @@ class Module
     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 []=
diff --git a/activesupport/test/core_ext/module_test.rb b/activesupport/test/core_ext/module_test.rb
index 380f5ad42b..3c49c4d14f 100644
--- a/activesupport/test/core_ext/module_test.rb
+++ b/activesupport/test/core_ext/module_test.rb
@@ -56,8 +56,14 @@ Developer = Struct.new(:client) do
   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 @@ class MethodAliasingTest < ActiveSupport::TestCase
     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