Bug #21029: Prism behavior for `defined? (;x)` differs

• Status: Open
• Assignee: prism
• Target version: -
• ruby -v: ruby 3.5.0dev (2025-01-11T03:21:57Z master 1b3037081e) +PRISM [x86_64-linux]
• Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN

[qnighy (Masaki Hara)]

Prism has a different behavior for (;expr) when used in defined? predicate:

% ./miniruby --parser=prism -e "p defined? (;x)"
nil
% ./miniruby --parser=parse.y -e "p defined? (;x)"
"expression"

Although not a significant difference, aligning either of them with the other would be better.

[kddnewton (Kevin Newton)]

• Assignee set to prism

[kddnewton (Kevin Newton)]

I think we should change parse.y to match this behavior. I will ask around.