[ruby-core:124784] [Ruby Feature#21813] Add [:forward, :...] symbol tuple to indicate forwarding arguments when calling `Method#parameters`

12 Feb 2026

      Issue #21813 has been updated by matz (Yukihiro Matsumoto).

Status changed from Open to Rejected

I failed to persuade me. I admit there's a lack of symmetry, but I don't think it's not worth the potential performance burden.

Matz.

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Feature #21813: Add  [:forward, :...] symbol tuple to indicate forwarding arguments when calling `Method#parameters`
https://bugs.ruby-lang.org/issues/21813#change-116395

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

```ruby
def foo(*, **, &)
  args = method(__method__).parameters.map(&:last).join(',')

  binding.eval "print(#{args})" # Works fine
end

foo(1,2,3,4, a: 23) # => 1234{a: 23}

def bar(...)
  args = method(__method__).parameters.map(&:last).join(',') 

  binding.eval "print(#{args})" # Fails!
end

bar(1,2,3,3, a: 23) # 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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