Bug #18267: Argument forwarding requires parenthesis on method definitions

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 3.1.0dev (2021-10-21T22:47:38Z master 844588f915) [x86_64-darwin20]
• Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN

[tenderlovemaking (Aaron Patterson)]

I like to write my method definitions without parenthesis. For example:

def foo bar
  # ...
end

I tried to use ..., but it doesn't work. For example if I do:

def call a, ...
  a.nil?(...)
end

It will be a syntax error, and the program exits. Can we make this syntax work so that I can always omit parenthesis?

Thank you!

[matz (Yukihiro Matsumoto)]

I agree that this is a bug.

Matz.

[byroot (Jean Boussier)]

It was known when the feature was introduced https://bugs.ruby-lang.org/projects/ruby-master/repository/git/revisions/d1ae2bc27fd4183e6abb9e83691e192bfe1e5316/diff, @mame (Yusuke Endoh) added a NEWS entry specifically for it.

I presume it would clash with endless ranges?

[Eregon (Benoit Daloze)]

[joke] Maybe a reason to be a little bit more consistent about Ruby syntax and always use parens for method definitions? :D [/joke]

[Eregon (Benoit Daloze)]

On a more serious note, def= also has this restriction:

$ ruby -e 'def m(a) = 2'
OK
$ ruby -e 'def m a = 2'
-e:1: syntax error, unexpected end-of-input
$ ruby -e 'def m a = a'
-e:1: circular argument reference - a
-e:1: syntax error, unexpected end-of-input

Which I guess is trivially ambiguous because the = could be for an optional arg or for the method body.

Because (...) anyway needs parenthesis on call sites (ambiguous with endless ranges otherwise), I personally think it makes sense to also have parens as a parameter.

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset git|13a9597c7ca83fced5738e9345660ae6aef87eb7.

---

Argument forwarding definition without parentheses [Bug #18267]