[ruby-core:123631] [Ruby Bug#21660] No-parentheses endless method definition that has parameter destructuring is wrongly accepted in Prism

1 Nov 2025


      Issue #21660 has been reported by tompng (tomoya ishida).

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Bug #21660: No-parentheses endless method definition that has parameter destructuring is wrongly accepted in Prism
https://bugs.ruby-lang.org/issues/21660

* Author: tompng (tomoya ishida)
* Status: Open
* Assignee: prism
* ruby -v: ruby 3.5.0dev (2025-11-01T00:18:01Z master 17a7b4e031) +PRISM [x86_64-linux]
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
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This is syntax error in parse.y but not in Prism.
~~~ruby
def f a, (b) = 1
~~~
Related to #21623


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