[ruby-core:96637] [Ruby master Bug#16473] New deprecated warning disallows keyword arguments bypassing

Issue #16473 has been updated by Dan0042 (Daniel DeLorme).


In this particular case there would be a bug if `*args` had more than one element, so I think the cleaner fix would be 

```ruby
def non_kw(a = {}, b = {})
  puts "non kw #{a}"
  kw **b
end
```

I really think the `ruby2_keywords` workaround should be strictly reserved for cases where portability and generic delegation _require_ it.

----------------------------------------
Bug #16473: New deprecated warning disallows keyword arguments bypassing
https://bugs.ruby-lang.org/issues/16473#change-83606

* Author: puchuu (Andrew Aladjev)
* Status: Rejected
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 2.7.0
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
Hello. I see that ruby 2.7.0 prints unnecessary deprecated warning during arguments bypassing.

```ruby
def kw(a: 1)
  puts "kw #{a}"
end

def non_kw(a = {}, *args)
  puts "non kw #{a}"
  kw *args
end

non_kw({ :a => 2 }, :a => 2)
non_kw({ :a => 3 })
non_kw
```

The right output is:

```
non kw {:a=>2}
kw 2
non kw {:a=>3}
kw 1
non kw {}
kw 1
```

Ruby 2.7.0 provides deprecated warning:
```ruby
warning: Using the last argument as keyword parameters is deprecated; maybe ** should be added to the call
```

`*args` is bypassing arguments without any conversion. It looks like ruby converts last hash to keywords and than converts it back to hash. I think it is a bug.



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