Ruby Issue Tracking System

09/14/2026

07:13 PM Ruby Bug #22310: parse.y rejects a variable binding that precedes an unrelated alternative pattern

Filed the `**rest` one separately as #22314 (fix in https://github.com/ruby/ruby/pull/18831). yuki300 (y h)

06:49 PM Ruby Bug #22310: parse.y rejects a variable binding that precedes an unrelated alternative pattern

Thanks, that matches what I was seeing.
I got curious about *which* change actually started rejecting these, so I built the two commits around https://github.com/ruby/ruby/pull/15329 and ran the `ng.rb` from the description through `-... yuki300 (y h)

07:02 PM Ruby Bug #22314 (Open): parse.y does not check **rest bindings in patterns (duplicate / alternation)

`p_kwrest` is the only binding rule in patterns that does not go through
`error_duplicate_pattern_variable`. `p_variable`, `p_rest` and the `{a:}`
shorthand in `p_kw` all call it before `assignable`; for `**rest` the name is
handed st... yuki300 (y h)

09/13/2026

11:41 AM Ruby Bug #22310 (Open): parse.y rejects a variable binding that precedes an unrelated alternative pattern

`parse.y` rejects patterns in which a variable binding appears *before*
an alternative pattern, even when the alternative itself binds nothing.
Prism accepts the same code. Is this intended?
## Reproduction
```ruby
# ok.rb
case... yuki300 (y h)