[ruby-core:96993] [Ruby master Bug#16560] Proc autosplats first argument if called with one argument and empty keyword splat
From:
merch-redmine@...
Date:
2020-01-24 20:20:23 UTC
List:
ruby-core #96993
Issue #16560 has been updated by jeremyevans0 (Jeremy Evans).
Backport changed from 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN to 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: REQUIRED
I have submitted a pull request to fix this: https://github.com/ruby/ruby/pull/2861
Note that behavior still changes slightly compared to 2.6:
```ruby
h = {}
b.call([1,2,3],**h) #=> [[1, 2, 3], 0] (with patch)
#=> [[1, 2, 3], {}] (in 2.6)
```
This is because the splat argument is still removed, so only a single argument is provided, and the second parameter uses the default argument. This is the expected behavior in 2.7+.
----------------------------------------
Bug #16560: Proc autosplats first argument if called with one argument and empty keyword splat
https://bugs.ruby-lang.org/issues/16560#change-84050
* Author: Dan0042 (Daniel DeLorme)
* Status: Open
* 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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