From 71f07786c8aca5d8dc292c1976ca7cf47760a7e4 Mon Sep 17 00:00:00 2001
From: Kevin Menard <kevin.menard@shopify.com>
Date: Tue, 17 Jan 2023 15:45:15 -0500
Subject: [PATCH] Implement `Array#intersect?`.

---
 CHANGELOG.md                            |  1 +
 spec/ruby/core/array/intersect_spec.rb  |  6 ++++--
 spec/tags/core/array/intersect_tags.txt |  2 --
 src/main/ruby/truffleruby/core/array.rb | 15 +++++++++++++++
 4 files changed, 20 insertions(+), 4 deletions(-)
 delete mode 100644 spec/tags/core/array/intersect_tags.txt

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d6cfb1b5f78b..e67c167cb880 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -61,6 +61,7 @@ Compatibility:
 * Fix execution order of `END` blocks and `at_exit` callbacks (#2818, @andrykonchin).
 * Fix `String#casecmp?` for empty strings of different encodings (#2826, @eregon).
 * Implement `Enumerable#compact` and `Enumerator::Lazy#compact` (#2733, @andrykonchin).
+* Implement `Array#intersect?` (#2831, @nirvdrum).
 
 Performance:
 
diff --git a/spec/ruby/core/array/intersect_spec.rb b/spec/ruby/core/array/intersect_spec.rb
index b8c5b1e69add..773e44c0734c 100644
--- a/spec/ruby/core/array/intersect_spec.rb
+++ b/spec/ruby/core/array/intersect_spec.rb
@@ -4,13 +4,15 @@
   ruby_version_is '3.1' do # https://bugs.ruby-lang.org/issues/15198
     describe 'when at least one element in two Arrays is the same' do
       it 'returns true' do
-        [1, 2].intersect?([2, 3]).should == true
+        [1, 2].intersect?([2, 3, 4]).should == true
+        [2, 3, 4].intersect?([1, 2]).should == true
       end
     end
 
     describe 'when there are no elements in common between two Arrays' do
       it 'returns false' do
-        [1, 2].intersect?([3, 4]).should == false
+        [0, 1, 2].intersect?([3, 4]).should == false
+        [3, 4].intersect?([0, 1, 2]).should == false
       end
     end
   end
diff --git a/spec/tags/core/array/intersect_tags.txt b/spec/tags/core/array/intersect_tags.txt
deleted file mode 100644
index cce8ad66e2fe..000000000000
--- a/spec/tags/core/array/intersect_tags.txt
+++ /dev/null
@@ -1,2 +0,0 @@
-fails:Array#intersect? when at least one element in two Arrays is the same returns true
-fails:Array#intersect? when there are no elements in common between two Arrays returns false
diff --git a/src/main/ruby/truffleruby/core/array.rb b/src/main/ruby/truffleruby/core/array.rb
index dad874dc3df8..2c07ca0ca375 100644
--- a/src/main/ruby/truffleruby/core/array.rb
+++ b/src/main/ruby/truffleruby/core/array.rb
@@ -614,6 +614,21 @@ def inspect
   end
   alias_method :to_s, :inspect
 
+  def intersect?(other)
+    return false if size == 0 || other.size == 0
+
+    shorter, longer = size > other.size ? [other, self] : [self, other]
+
+    shorter_set = {}
+    shorter.each { |e| shorter_set[e] = true }
+
+    longer.each do |e|
+      return true if shorter_set.include?(e)
+    end
+
+    false
+  end
+
   def intersection(*others)
     return self & others.first if others.size == 1