From: merch-redmine@...
Date: 2021-06-29T04:40:53+00:00
Subject: [ruby-core:104431] [Ruby master Bug#18011] `Method#parameters` is incorrect for forwarded arguments

Issue #18011 has been updated by jeremyevans0 (Jeremy Evans).


Forwarded arguments is implemented as `(*args, &block)` with `ruby2_keywords`, not as `(*args, **kwargs, &block)`. If you add `def wrapper4(*r, &b) = wrapped(*r, &b),` to `methods` and then `ruby2_keywords :wrapper4` after `methods`, you can see it gives the same output as `wrapper1` and `wrapper3`.

If we want to indicate which methods have `ruby2_keywords`, one way would be to include `ruby2_keywords` into `Method#parameters` output if it is enabled for the method.  Possibly this could be done by adding `[:ruby2_keywords]` as the last value in the returned array.

----------------------------------------
Bug #18011: `Method#parameters` is incorrect for forwarded arguments
https://bugs.ruby-lang.org/issues/18011#change-92685

* Author: josh.cheek (Josh Cheek)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.0.1p64 (2021-04-05 revision 0fb782ee38) [arm64-darwin20]
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN
----------------------------------------
When asking a method about its parameters, forwarded arguments say they are a rest and a block (`wrapper1` in the example below).
However, when we use that signature, it raises an ArgumentError (`wrapper2` in the example below).
When I add a keyrest to the signature, it works as expected (`wrapper3` in the example below).
So I think forwarded arguments should include a keyrest in the output of `Method#parameters`

```ruby
def wrapped(ord, kw:) = [ord, {kw: kw}]

methods = [
 def wrapper1(...)         = wrapped(...),
 def wrapper2(*r, &b)      = wrapped(*r, &b),
 def wrapper3(*r, **k, &b) = wrapped(*r, **k, &b),
]

methods.each do |name|
  puts File.read(__FILE__)[/#{name}\(.*?\)/]
  puts "  params: #{method(name).parameters.inspect}"
  puts "  result: #{(method(name).call 123, kw: 456 rescue $!).inspect}"
  puts
end
```

Output:

```
wrapper1(...)
  params: [[:rest, :*], [:block, :&]]
  result: [123, {:kw=>456}]

wrapper2(*r, &b)
  params: [[:rest, :r], [:block, :b]]
  result: #<ArgumentError: wrong number of arguments (given 2, expected 1; required keyword: kw)>

wrapper3(*r, **k, &b)
  params: [[:rest, :r], [:keyrest, :k], [:block, :b]]
  result: [123, {:kw=>456}]
```



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