[GR-40333] Ruby 3.1 Array#intersect?

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:
 

spec/ruby/core/array/intersect_spec.rb

@@ -1,17 +1,66 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe 'Array#intersect?' do
   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
+        [3, 4].intersect?([]).should == false
+        [].intersect?([0, 1, 2]).should == false
       end
     end
+
+    it "tries to convert the passed argument to an Array using #to_ary" do
+      obj = mock('[1,2,3]')
+      obj.should_receive(:to_ary).and_return([1, 2, 3])
+
+      [1, 2].intersect?(obj).should == true
+    end
+
+    it "determines equivalence between elements in the sense of eql?" do
+      obj1 = mock('1')
+      obj2 = mock('2')
+      obj1.stub!(:hash).and_return(0)
+      obj2.stub!(:hash).and_return(0)
+      obj1.stub!(:eql?).and_return(true)
+      obj2.stub!(:eql?).and_return(true)
+
+      [obj1].intersect?([obj2]).should == true
+
+      obj1 = mock('3')
+      obj2 = mock('4')
+      obj1.stub!(:hash).and_return(0)
+      obj2.stub!(:hash).and_return(0)
+      obj1.stub!(:eql?).and_return(false)
+      obj2.stub!(:eql?).and_return(false)
+
+      [obj1].intersect?([obj2]).should == false
+    end
+
+    it "does not call to_ary on array subclasses" do
+      [5, 6].intersect?(ArraySpecs::ToAryArray[1, 2, 5, 6]).should == true
+    end
+
+    it "properly handles an identical item even when its #eql? isn't reflexive" do
+      x = mock('x')
+      x.stub!(:hash).and_return(42)
+      x.stub!(:eql?).and_return(false) # Stubbed for clarity and latitude in implementation; not actually sent by MRI.
+
+      [x].intersect?([x]).should == true
+    end
+
+    it "has semantic of !(a & b).empty?" do
+      [].intersect?([]).should == false
+      [nil].intersect?([nil]).should == true
+    end
   end
 end

spec/ruby/core/array/shared/intersection.rb

@@ -11,7 +11,8 @@
   end
 
   it "creates an array with elements in order they are first encountered" do
-    [ 1, 2, 3, 2, 5 ].send(@method, [ 5, 2, 3, 4 ]).should == [2, 3, 5]
+    [ 1, 2, 3, 2, 5, 6, 7, 8 ].send(@method, [ 5, 2, 3, 4 ]).should == [2, 3, 5] # array > other
+    [ 5, 2, 3, 4 ].send(@method, [ 1, 2, 3, 2, 5, 6, 7, 8 ]).should == [5, 2, 3] # array < other
   end
 
   it "does not modify the original Array" do

src/main/ruby/truffleruby/core/array.rb

@@ -614,6 +614,22 @@ def inspect
   end
   alias_method :to_s, :inspect
 
+  def intersect?(other)
+    other = Truffle::Type.coerce_to other, Array, :to_ary
+
+    shorter, longer = size > other.size ? [other, self] : [self, other]
+    return false if shorter.empty?
+
+    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
 

src/main/ruby/truffleruby/core/truffle/versioned_array.rb

@@ -420,6 +420,11 @@ def inspect(*args, &block)
     copy.inspect(*args, &block)
   end
 
+  def intersect?(*args, &block)
+    copy = TruffleRuby.synchronized(@lock) { Array.new self }
+    copy.intersect?(*args, &block)
+  end
+
   def intersection(*args, &block)
     copy = TruffleRuby.synchronized(@lock) { Array.new self }
     copy.intersection(*args, &block)