[ruby-core:123134] [Ruby Bug#21168] Prism doesn't require argument parentheses (in some cases) when a block is present but parse.y does

30 Aug 2025

      Issue #21168 has been updated by Earlopain (Earlopain _).

I found out that this was discussed in a developer meeting: https://github.com/ruby/dev-meeting-log/blob/c35441297cd397fa3626ca0aa38efd7...

matz said:
...
matz: I'll reply it. I like parse.y behavior. I don't want to allow the code any more
I revisited this and got more weird behaviour:

```rb
# Accepted by both
foo(
  bar baz {
  }
)
# Accepted by both
(
  bar baz do
  end
)
```

I don't think these are so different that they should suddenly be allowed. Should this be consistenly rejected in both parsers?

----------------------------------------
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-114463

* Author: Earlopain (Earlopain _)
* Status: Assigned
* Assignee: prism
* 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
```

-- 
https://bugs.ruby-lang.org/