Issue #12717 has been reported by Andy Holland.

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Bug #12717: Optional argument treated as kwarg
https://bugs.ruby-lang.org/issues/12717

* Author: Andy Holland
* Status: Open
* Priority: Normal
* Assignee: Yukihiro Matsumoto
* ruby -v: 2.3.1
* Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
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When you define a method with an optional argument and keyword arguments (whether explicitly or with options splat) the defaulted argument can not take a hash argument, instead it is interpreted as keyword arguments:

~~~ ruby
class Foo
  def self.options(value = nil, **options)
    puts value.inspect
    puts options.inspect
  end

  def self.kwarg(value = nil, kw: nil)
    puts value.inspect
    puts kw.inspect
  end

  def self.splat(*args, kw: nil)
    puts args.inspect
    puts kw.inspect
  end
end

Foo.options({})
# nil
# {}
Foo.kwarg({})
# nil
# nil
Foo.splat({})
# []
# nil

Foo.options({ key: :value })
# nil
# {:key=>:value}
Foo.kwarg({ key: :value })
# ArgumentError: unknown keyword: key
Foo.splat({ key: :value })
# ArgumentError: unknown keyword: key
~~~

I would expect the output to be:

~~~ ruby
Foo.options({})
# {}
# {}
Foo.kwarg({})
# {}
# nil
Foo.splat({})
# [{}]
# nil

Foo.options({ key: :value })
# {:key=>:value}
# {}
Foo.kwarg({ key: :value })
# {:key=>:value}
# nil
Foo.splat({ key: :value })
# [{:key=>:value}]
# nil
~~~




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