Bug #21048: [Prism] rescue in modifier form with condition behaves differently

• Status: Closed
• Assignee: prism
• Target version: -
• ruby -v: ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +PRISM [x86_64-linux]
• Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: DONE

[Earlopain (Earlopain _)]

With the following code there is a discrepancy in how prism and parse.y consider precedence:

$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

$ 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

[Earlopain (Earlopain _)]

• ruby -v changed from 3.4.1 to ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +PRISM [x86_64-linux]

[nobu (Nobuyoshi Nakada)]

Earlopain (Earlopain _) wrote:

Prism interprets it as (foo rescue nil) if false, not calling the method. parse.y does foo rescue (nil if false) since at least Ruby 2.0

Inverse?

$ 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

[Earlopain (Earlopain _)]

Yes, I switched it up in the text. Fixed

[Earlopain (Earlopain _)]

• Description updated (diff)

[tenderlovemaking (Aaron Patterson)]

• Assignee set to prism

[kddnewton (Kevin Newton)]

• Backport changed from 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN to 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: REQUIRED

[kddnewton (Kevin Newton)]

• Status changed from Open to Closed

Fixed by https://github.com/ruby/ruby/commit/c2908613368b2ae404d094a15df61d830fc46dc9

[hsbt (Hiroshi SHIBATA)]

• Has duplicate Bug #21132: Changed postposition `rescue` and `if` behavior since Ruby 3.4 added

[k0kubun (Takashi Kokubun)]

• Backport changed from 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: REQUIRED to 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: DONE

ruby_3_4 04298f2d158fa860293d2ed2779cba69bc47f404 merged revision(s) c2908613368b2ae404d094a15df61d830fc46dc9.