ruby-core

Issue #16560 has been updated by jeremyevans0 (Jeremy Evans).


Dan0042 (Daniel DeLorme) wrote:
> Although imho that would be the expected behavior in 3.0, and in 2.7 it should be a warning with the same behavior as 2.6.

No, in 2.7 empty keyword splats are removed in most cases without warning, that is unrelated to proc autosplatting:

```ruby
def a(b, c=0)
  [b, c]
end
h = {}
a([1, 2], **h)
# => [[1, 2], {}] # 2.6
# => [[1, 2], 0]  # 2.7
```

The cases where they aren't removed in 2.7:

* Empty keyword splat is needed for mandatory positional argument (issues a warning)
* ruby2_keywords methods so that a final positional hash before keywords is not treated as keywords by target method

----------------------------------------
Bug #16560: Proc autosplats first argument if called with one argument and empty keyword splat
https://bugs.ruby-lang.org/issues/16560#change-84053

* Author: Dan0042 (Daniel DeLorme)
* Status: Closed
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: REQUIRED
----------------------------------------
While working on understanding the vm_args.c code via refactoring, I found the following:

```ruby
b = proc{ |a,b=0| [a,b] }
h = {k:42}
b.call([1,2,3],**h) #=> [[1, 2, 3], {:k=>42}]
h = {} 
b.call([1,2,3],**h) #=> [1, 2]           (in 2.7)
                    #=> [[1, 2, 3], {}]  (in 2.6)
```

Since the result is different from 2.6 I think this is a bug, especially since the result in 2.7 is so different based on being an empty or non-empty splat.

In my refactoring branch I'm solving this by moving the `args_check_block_arg0` check before the `ignore_keyword_hash_p` check, but that doesn't look so easy in master.



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