From: "nagachika (Tomoyuki Chikanaga) via ruby-core" <ruby-core@...>
Date: 2025-06-14T02:04:21+00:00
Subject: [ruby-core:122527] [Ruby Bug#21048] [Prism] rescue in modifier form with condition behaves differently

Issue #21048 has been updated by nagachika (Tomoyuki Chikanaga).


Backporting c2908613368b2ae404d094a15df61d830fc46dc9 depends on many changesets about prism in ruby_3_3. Please make a backport pull request. 

----------------------------------------
Bug #21048: [Prism] rescue in modifier form with condition behaves differently
https://bugs.ruby-lang.org/issues/21048#change-113752

* Author: Earlopain (Earlopain _)
* Status: Closed
* Assignee: prism
* ruby -v: ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +PRISM [x86_64-linux]
* Backport: 3.1: DONTNEED, 3.2: DONTNEED, 3.3: REQUIRED, 3.4: DONE
----------------------------------------
With the following code there is a discrepancy in how prism and parse.y consider precedence:

```rb
$called = false
def foo
  $called = true
end

foo rescue nil if false

puts "Called: #{$called}"
```

Prism interprets it as `foo rescue (nil if false)`, calling the method. `parse.y` does `(foo rescue nil) if false` since at least Ruby 2.0

```sh
$ ruby -v
ruby 3.5.0dev (2025-01-19T12:44:20Z master f27ed98eff) +PRISM [x86_64-linux]

$ ruby code.rb
Called: true

$ ruby --parser=parse.y code.rb
Called: false
```



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