Issue #14909 has been updated by mame (Yusuke Endoh).

Status changed from Open to Feedback

In the plan of Ruby 3 (#14183), keyword arguments will be separated from other kinds of arguments.  If this plan is implemented successfully, you can use `my_func(Test.new)` and `my_func(**Test.new)` for each purpose.  If you call `my_func(Test.new)`, the argument will be passed as a part of the rest parameter `objects`.  If you call `my_func(**Test.new)`, the argument will be handled as a keyword parameter.

So, I'd like to propose keeping the current behavior as is, because changing the semantics will bring extra complexity.  Instead, just wait for Ruby 3.

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Bug #14909: Method call with object that has to_hash method crashes (method with splat and keyword arguments)
https://bugs.ruby-lang.org/issues/14909#change-72935

* Author: johannes_luedke (Johannes Ldke)
* Status: Feedback
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-darwin17]
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN
----------------------------------------
In a method with a splat method argument followed by a keyword argument, it leads to an `ArgumentError` when calling the method with an object that reacts to `to_hash`


~~~ruby
def my_func(*objects, error_code: 400)
  objects.inspect
end

class Test
  def to_hash
    # an example hash
    { to_hash_key: "to_hash" }
  end
end

my_func(Test.new)
~~~

Observed result: an exception is raised: `in my_func: unknown keyword: to_hash_key (ArgumentError)` 
Expected result: `[#<Test:0x007fc8c9825318>]` is returned by the `my_func` call

It should behave the same when calling with objects that have a `to_hash` method and objects that don't, shouldn't it?



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