From: "yui-knk (Kaneko Yuichiro) via ruby-core" <ruby-core@...>
Date: 2025-09-30T02:12:35+00:00
Subject: [ruby-core:123347] [Ruby Bug#21168] Prism doesn't require argument parentheses (in some cases) when a block is present but parse.y does

Issue #21168 has been updated by yui-knk (Kaneko Yuichiro).


@matz Just clarification, do we support `a[cmd 1, 2 do end]` and `a[cmd 1, 2 do end] = 3` too? IIRC, we discussed those cases in previous devmeeting and these codes are also accepted. However meeting notes has no description about them, so I want to confirm it.

----------------------------------------
Bug #21168: Prism doesn't require argument parentheses (in some cases) when a block is present but parse.y does
https://bugs.ruby-lang.org/issues/21168#change-114719

* Author: Earlopain (Earlopain _)
* Status: Open
* ruby -v: ruby 3.4.2 (2025-02-15 revision d2930f8e7a) +PRISM [x86_64-linux]
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
It's a bit more than that but explaining it in full would be a bit much. Instead, see this:

```rb
foo(
  bar baz do
  end
)
```

```sh
$ ruby -c --parser=prism test.rb
Syntax OK
$ ruby -c --parser=parse.y test.rb
ruby: test.rb:2: syntax error, unexpected 'do' for block, expecting ')' (SyntaxError)
  bar baz do
          ^~
```

OTOH, this is consistently rejected:
```rb
[
  foo bar do
  end,
]
# And also
foo || bar baz do
end
```



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