[Bug #18971] Add precheck to enumerator

1 files changed, 20 insertions, 0 deletions

diff --git a/test/ruby/test_lazy_enumerator.rb b/test/ruby/test_lazy_enumerator.rb
index 2116d0ee31..32bf097318 100644
--- a/test/ruby/test_lazy_enumerator.rb
+++ b/test/ruby/test_lazy_enumerator.rb
@@ -295,6 +295,26 @@ class TestLazyEnumerator < Test::Unit::TestCase
     assert_equal(nil, a.current)
   end
 
+  def test_take_0_bug_18971
+    def (bomb = Object.new.extend(Enumerable)).each
+      raise
+    end
+    [2..10, bomb].each do |e|
+      assert_equal([], e.lazy.take(0).map(&:itself).to_a)
+      assert_equal([], e.lazy.take(0).select(&:even?).to_a)
+      assert_equal([], e.lazy.take(0).select(&:odd?).to_a)
+      assert_equal([], e.lazy.take(0).reject(&:even?).to_a)
+      assert_equal([], e.lazy.take(0).reject(&:odd?).to_a)
+      assert_equal([], e.lazy.take(0).take(1).to_a)
+      assert_equal([], e.lazy.take(0).take(0).take(1).to_a)
+      assert_equal([], e.lazy.take(0).drop(0).to_a)
+      assert_equal([], e.lazy.take(0).find_all {|_| true}.to_a)
+      assert_equal([], e.lazy.take(0).zip((12..20)).to_a)
+      assert_equal([], e.lazy.take(0).uniq.to_a)
+      assert_equal([], e.lazy.take(0).sort.to_a)
+    end
+  end
+
   def test_take_bad_arg
     a = Step.new(1..10)
     assert_raise(ArgumentError) { a.lazy.take(-1) }