From ce9e14e578af9b39de8edd6e7a2a48e40201420c Mon Sep 17 00:00:00 2001
From: Marc-Andre Lafortune <github@marc-andre.ca>
Date: Mon, 10 Aug 2020 23:20:19 -0400
Subject: [PATCH] In Ruby 2.4, `Set#===` is harmonized with Ruby 2.5+ to call
 `include?`

---
 CHANGELOG.md               | 4 ++++
 lib/rubocop/ast.rb         | 1 +
 lib/rubocop/ast/ext/set.rb | 8 ++++++++
 3 files changed, 13 insertions(+)
 create mode 100644 lib/rubocop/ast/ext/set.rb

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ede2be76e..75675fb71 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,10 @@
 * [#89](https://github.com/rubocop-hq/rubocop-ast/pull/89): Support right hand assignment for Ruby 2.8 (3.0) parser. ([@koic][])
 * [#93](https://github.com/rubocop-hq/rubocop-ast/pull/93): Add `Node#{left|right}_sibling{s}` ([@marcandre][])
 
+### Changes
+
+* [#x](https://github.com/rubocop-hq/rubocop-ast/issue/x): In Ruby 2.4, `Set#===` is harmonized with Ruby 2.5+ to call `include?`. ([@marcandre][])
+
 ## 0.3.0 (2020-08-01)
 
 ### New features
diff --git a/lib/rubocop/ast.rb b/lib/rubocop/ast.rb
index 253e80a3f..153ada376 100644
--- a/lib/rubocop/ast.rb
+++ b/lib/rubocop/ast.rb
@@ -5,6 +5,7 @@
 require 'set'
 
 require_relative 'ast/ext/range'
+require_relative 'ast/ext/set'
 require_relative 'ast/node_pattern'
 require_relative 'ast/sexp'
 require_relative 'ast/node'
diff --git a/lib/rubocop/ast/ext/set.rb b/lib/rubocop/ast/ext/set.rb
new file mode 100644
index 000000000..89061b055
--- /dev/null
+++ b/lib/rubocop/ast/ext/set.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+# Harmonize `Set#===`
+unless Set[:foo] === :foo # typically RUBY_VERSION <= 2.4
+  class Set
+    alias === include?
+  end
+end