From: "sawa (Tsuyoshi Sawada) via ruby-core" <ruby-core@...>
Date: 2023-04-06T02:19:04+00:00
Subject: [ruby-core:113140] [Ruby master Feature#19370] Anonymous parameters for blocks?

Issue #19370 has been updated by sawa (Tsuyoshi Sawada).


zverok (Victor Shepelev) wrote in #note-2:
> Note that it might lead to very confusing behavior when the surrounding method does have anonymous arguments:
> 
> ```ruby
> def test(*)
>   # ...
> 
>   proc { |*| p(*) }.call(1)
> end
> ```

I think nesting anonymous arguments should be prohibited on as with numbered parameters:

```ruby
"foo".then{_1.then{_1.upcase}}
# >> SyntaxError ((irb):21: numbered parameter is already used in) outer block here
```

----------------------------------------
Feature #19370: Anonymous parameters for blocks?
https://bugs.ruby-lang.org/issues/19370#change-102676

* Author: zverok (Victor Shepelev)
* Status: Assigned
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
----------------------------------------
Just to clarify: are anonymous parameters delegation is planned to support in blocks? 

It would be a nice addition, if it is possible to implement:
```ruby
# data in form [request method, URL, params]:
[
  [:get, 'https://google.com', {q: 'Ruby'}, {'User-Argent': 'Google-Chrome'}],
  [:post, 'https://gist.github.com', 'body'],
  # ...
].each { |method, *| request(method.to_s.upcase, *) }
```
...and at the very least, consistent with what the method definition can have.

If they are NOT planned to be implemented, I believe that at least error messages should be made much clearer, because currently, this would happen while running the code above:
> no anonymous rest parameter (SyntaxError)

I understand the reason (the `request` clause doesn't "see" anonymous parameter of the **block**, and claims that current **method** doesn't have them), but it looks honestly confusing and inconsistent.



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