ruby-core@ruby-lang.org archive (unofficial mirror)
 help / color / mirror / Atom feed
From: "mame (Yusuke Endoh) via ruby-core" <ruby-core@ml.ruby-lang.org>
To: ruby-core@ml.ruby-lang.org
Cc: "mame (Yusuke Endoh)" <noreply@ruby-lang.org>
Subject: [ruby-core:120369] [Ruby master Bug#20965] `it` vs `binding.local_variables`
Date: Mon, 23 Dec 2024 03:37:39 +0000 (UTC)	[thread overview]
Message-ID: <redmine.journal-111145.20241223033739.710@ruby-lang.org> (raw)
In-Reply-To: <redmine.issue-20965.20241218195830.710@ruby-lang.org>

Issue #20965 has been updated by mame (Yusuke Endoh).

Status changed from Closed to Open

Let's revert this change.

Below is our local discussion of this issue with @nobu and @ko1.

First, consider the following example.

```ruby
"foo".tap do
  it
  "bar".tap do
    p eval("it") # what should happen?
  end
end
```

There are three possible options.

1. Raises an exeption
2. Returns `"bar"`
3. Returns `"foo"`

1 is the only realistic choice. 2 would require keeping all arguments conservatively even when `it` does not appear lexically, which we want to avoid for a performance reason (including the possibility of future optimizations, as @ko1 said). 3 is clearly counterintuitive.

Then, consider the following example.

```ruby
"foo".tap do
  it
  "bar".tap do
    p binding.local_variables #=> []? [:it]?
    eval("it")
  end
end
```

If `local_variables` contains `:it`, `eval("it")` is expected to return some value. However, it is impossible for the reason above. Therefore, `local_variables` should return `[]`.

The difference between `_1` and `it` is that `_1` is prohibited to be referenced outside of a block, while `it` is not.

Note that if `it` is defined as an ordinary local variable by an assignment, `local_variables` should contain `:it`.

----------------------------------------
Bug #20965: `it` vs `binding.local_variables`
https://bugs.ruby-lang.org/issues/20965#change-111145

* Author: zverok (Victor Shepelev)
* Status: Open
* ruby -v: ruby 3.4.0dev (2024-12-15T13:36:38Z master 366fd9642f) +PRISM [x86_64-linux]
* Backport: 3.1: DONTNEED, 3.2: DONTNEED, 3.3: DONTNEED
----------------------------------------
`it` is not available in the list of `binding.local_varaibles`, **unlike** numbered parameters:

```ruby
p(proc { binding.local_variables }.call)  # []
p(proc { |x| binding.local_variables }.call)  # [:x]
p(proc { _1; binding.local_variables }.call)  # [:_1]
p(proc { vars = binding.local_variables; _1; vars }.call)  # [:_1, :vars]
p(proc { it; binding.local_variables }.call)  # []
```

I wonder if it is deliberate or accidental.



-- 
https://bugs.ruby-lang.org/
 ______________________________________________
 ruby-core mailing list -- ruby-core@ml.ruby-lang.org
 To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org
 ruby-core info -- https://ml.ruby-lang.org/mailman3/lists/ruby-core.ml.ruby-lang.org/

  parent reply	other threads:[~2024-12-23  3:38 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-12-18 19:58 [ruby-core:120303] " zverok (Victor Shepelev) via ruby-core
2024-12-19  0:41 ` [ruby-core:120308] " shan (Shannon Skipper) via ruby-core
2024-12-19  6:28 ` [ruby-core:120317] " nobu (Nobuyoshi Nakada) via ruby-core
2024-12-19  9:33 ` [ruby-core:120326] " tompng (tomoya ishida) via ruby-core
2024-12-23  3:37 ` mame (Yusuke Endoh) via ruby-core [this message]
2024-12-23  4:55 ` [ruby-core:120372] " k0kubun (Takashi Kokubun) via ruby-core
2024-12-23  6:19 ` [ruby-core:120374] " zverok (Victor Shepelev) via ruby-core
2024-12-23  8:52 ` [ruby-core:120375] " mame (Yusuke Endoh) via ruby-core
2025-01-09 12:03 ` [ruby-core:120574] " mame (Yusuke Endoh) via ruby-core
2025-01-20  9:47 ` [ruby-core:120744] " mame (Yusuke Endoh) via ruby-core

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=redmine.journal-111145.20241223033739.710@ruby-lang.org \
    --to=ruby-core@ml.ruby-lang.org \
    --cc=noreply@ruby-lang.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).