From: "rwstauner (Randy Stauner) via ruby-core" <ruby-core@...>
Date: 2026-11-02T18:15:46+00:00
Subject: [ruby-core:127301] [Ruby Bug#22496] Lazy enumerator `.each_with_index` no longer executes block

Issue #22496 has been reported by rwstauner (Randy Stauner).

----------------------------------------
Bug #22496: Lazy enumerator `.each_with_index` no longer executes block
https://bugs.ruby-lang.org/issues/22496

* Author: rwstauner (Randy Stauner)
* Status: Open
* Backport: 3.3: DONTNEED, 3.4: DONTNEED, 4.0: DONTNEED
----------------------------------------
The fix for #21142 changed the behavior such that `lazy#each_with_index { ... }` is no longer running the block and just returning the enumerator.

4.0:
```
$ ruby -ve 'arr = []; p 3.times.lazy.each { |*a| arr << a }; p arr;'
ruby 4.0.7 (2026-09-15 revision 229531a6cf) +PRISM [x86_64-linux]
3
[[0], [1], [2]]

$ ruby -ve 'arr = []; p 3.times.lazy.each_with_index { |*a| arr << a }; p arr;'
ruby 4.0.7 (2026-09-15 revision 229531a6cf) +PRISM [x86_64-linux]
3
[[0, 0], [1, 1], [2, 2]]
```

4.1.0dev:
```
$ ruby -ve 'arr = []; p 3.times.lazy.each { |*a| arr << a }; p arr;'
ruby 4.1.0dev (2026-10-28T17:51:51Z master 5127bd0dbc) +PRISM [x86_64-linux]
3
[[0], [1], [2]]

$ ruby -ve 'arr = []; p 3.times.lazy.each_with_index { |*a| arr << a }; p arr;'
ruby 4.1.0dev (2026-10-28T17:51:51Z master 5127bd0dbc) +PRISM [x86_64-linux]
#<Enumerator::Lazy: #<Enumerator::Lazy: #<Enumerator: 3:times>>:each_with_index(0)>
[]
```

This seems inconsistent and likely unintentional.
We must be missing tests for this case.



-- 
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