From 9de6fff05472032774baab3cb95bac1a2af041e9 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       | 12 ++++++++++++
 spec/rubocop/ast/ext/set_spec.rb |  9 +++++++++
 4 files changed, 26 insertions(+)
 create mode 100644 lib/rubocop/ast/ext/set.rb
 create mode 100644 spec/rubocop/ast/ext/set_spec.rb

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ede2be76e..cdfc2d989 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
+
+* [#94](https://github.com/rubocop-hq/rubocop-ast/pull/94): 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..fb41b9748
--- /dev/null
+++ b/lib/rubocop/ast/ext/set.rb
@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+test = :foo
+case test
+when Set[:foo]
+  # ok, RUBY_VERSION > 2.4
+else
+  # Harmonize `Set#===`
+  class Set
+    alias === include?
+  end
+end
diff --git a/spec/rubocop/ast/ext/set_spec.rb b/spec/rubocop/ast/ext/set_spec.rb
new file mode 100644
index 000000000..370f1da8c
--- /dev/null
+++ b/spec/rubocop/ast/ext/set_spec.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+# rubocop:disable RSpec/DescribeClass, Style/CaseEquality
+RSpec.describe 'Set#===' do
+  it 'tests for inclusion' do
+    expect(Set[1, 2, 3] === 2).to eq true
+  end
+end
+# rubocop:enable RSpec/DescribeClass, Style/CaseEquality