From: "vinistock (Vinicius Stock) via ruby-core" <ruby-core@...>
Date: 2025-07-28T18:41:56+00:00
Subject: [ruby-core:122876] [Ruby Bug#21139] Prism and parse.y parses `it = it` differently

Issue #21139 has been updated by vinistock (Vinicius Stock).


Thanks for the context, I understand your point about consistency. So this case

```ruby
42.tap { |x| x = x; p x }
```

Works because by the time we reach `x = x`, the block parameter already declared `x` as a local and so it doesn't end up setting it equal to `nil`. Would it make sense to automatically declare `it` as a local inside the block?

Or another question, do we agree that these two should return the same result?

```ruby
42.tap { it = it; p it }
42.tap { |x| x = x; p x }
```

----------------------------------------
Bug #21139: Prism and parse.y parses `it = it` differently
https://bugs.ruby-lang.org/issues/21139#change-114179

* Author: tompng (tomoya ishida)
* Status: Feedback
* Assignee: prism
* ruby -v: ruby 3.5.0dev (2025-02-14T16:49:52Z master ee181d1bb7) +PRISM [x86_64-linux]
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
~~~
# ruby --parser=parse.y -e "42.tap { it = it; p it }"
nil
# ruby --parser=prism -e "42.tap { it = it; p it }"
42
~~~


---Files--------------------------------
clipboard-202503081702-idzz2.png (22.6 KB)


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