Ruby automatically expands Hash into keyword arguments without double splat -

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the below ruby code results in: unknown keyword: (argumenterror):

def test(x={}, y: true); end  test({a:1})

why? expect happen test(**{a:1}), don't understand why hash being automagically expanded without double splat.

since x optional, hash moves on kwarg argument. unspecified keywords raise error in case:

def foo(name:)   p name end  foo # raises "argumenterror: missing keyword: name" expected foo({name: 'joe', age: 10}) # raises "argumenterror: unknown keyword: age"

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