From: "shugo (Shugo Maeda) via ruby-core" <ruby-core@...>
Date: 2026-07-04T14:58:11+00:00
Subject: [ruby-core:125928] [Ruby Bug#22177] Prism rejects a nested destructuring target in a for loop index, while parse.y accepts it

Issue #22177 has been updated by shugo (Shugo Maeda).

Assignee set to prism

I've created a pull request: https://github.com/ruby/prism/pull/4156

----------------------------------------
Bug #22177: Prism rejects a nested destructuring target in a for loop index, while parse.y accepts it
https://bugs.ruby-lang.org/issues/22177#change-117896

* Author: shugo (Shugo Maeda)
* Status: Open
* Assignee: prism
* ruby -v: ruby 4.0.5 (2026-05-20 revision 64336ffd0e) +PRISM [x86_64-linux]
* Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN
----------------------------------------
## Summary

When the index of a `for` loop is a multiple-assignment target whose first element is itself a parenthesized target (for example `(a, b), c`), Prism reports a syntax error, but parse.y accepts it.
The same target works in a normal multiple assignment in both parsers, so the difference is specific to the `for` loop index.

## Reproduction

```ruby
for (a, b), c in [[[1, 2], 3]] do
  p [a, b, c]
end
```

### parse.y (--parser=parse.y)

Accepted. Prints:

```
[1, 2, 3]
```

### Prism (default, --parser=prism)

Rejected:

```
> 1 | for (a, b), c in [[[1, 2], 3]] do
    |     ^~~~~ unexpected write target
```




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