From fd8991f797c145615820b4c76e6b7ac5a71339ea Mon Sep 17 00:00:00 2001
From: Jeremy Evans <code@jeremyevans.net>
Date: Thu, 27 May 2021 13:29:24 -0700
Subject: [PATCH] Fix lazy enumerator with index size

Fixes [Bug #17889]
---
 enumerator.c                      | 7 ++++++-
 test/ruby/test_lazy_enumerator.rb | 4 ++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/enumerator.c b/enumerator.c
index 3ea4330802..fac83b4360 100644
--- a/enumerator.c
+++ b/enumerator.c
@@ -2700,8 +2700,13 @@ lazy_with_index_proc(VALUE proc_entry, struct MEMO* result, VALUE memos, long me
     return result;
 }
 
+static VALUE
+lazy_with_index_size(VALUE proc, VALUE receiver) {
+    return receiver;
+}
+
 static const lazyenum_funcs lazy_with_index_funcs = {
-    lazy_with_index_proc, 0,
+    lazy_with_index_proc, lazy_with_index_size,
 };
 
 /*
diff --git a/test/ruby/test_lazy_enumerator.rb b/test/ruby/test_lazy_enumerator.rb
index 3f5a05555b..2116d0ee31 100644
--- a/test/ruby/test_lazy_enumerator.rb
+++ b/test/ruby/test_lazy_enumerator.rb
@@ -682,4 +682,8 @@ EOS
     ary = (0..Float::INFINITY).lazy.with_index.take(2).to_a
     assert_equal([[0, 0], [1, 1]], ary)
   end
+
+  def test_with_index_size
+    assert_equal(3, Enumerator::Lazy.new([1, 2, 3], 3){|y, v| y << v}.with_index.size)
+  end
 end