From: "pabloh (Pablo Herrero) via ruby-core" <ruby-core@...>
Date: 2026-01-14T06:09:38+00:00
Subject: [ruby-core:124524] [Ruby Feature#21813] Add  [:forward, :...] symbol tuple to indicate forwarding arguments when calling `Method#parameters`

Issue #21813 has been updated by pabloh (Pablo Herrero).


@nobu Perhaps I came up with a contrived example, but I wanted to point out that there is a lack of symmetry when it comes to `....`. As of right now, there is no way to know from the `Method` class API alone whether a method is using argument forwarding. You���d have to use Method#source_location and then parse the source file somehow.

----------------------------------------
Feature #21813: Add  [:forward, :...] symbol tuple to indicate forwarding arguments when calling `Method#parameters`
https://bugs.ruby-lang.org/issues/21813#change-116085

* Author: pabloh (Pablo Herrero)
* Status: Open
----------------------------------------
When accessing `Method#parameters` for a method using forwarding parameters, an unexpected behavior arises:

```ruby
def foo(*, **, &)
  binding.eval "print(#{(method(__method__).parameters.dig(0,1))})" # Works fine
end

foo(1,2,3,4) # => 1234

def bar(...)
  binding.eval "print(#{(method(__method__).parameters.dig(0,1))})" # Fails!
end

bar(1,2,3,3) # SyntaxError
```

It's very strange that you can't access the parameters, on `eval`, using the symbols provided at `Method#parameters`.

Adding `[:forward, :...]` or `[:forwarding, :...]` for those cases feels simply natural.




-- 
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