Data types seems to be messed up on hash parameters

define test ($b) {

  $a = { key => undef }

  notice("a: $a")

  notice("b: $b")

  $a.each |Array $values| {

    notice("a values: $values")

  }

  $b.each |Array $values| {

    notice("b values: $values")

  }

}

$a = { key => undef }

test { "test":

  b => $a,

}

puppet apply test.pp

Notice: Scope(Test[test]): a: {key => }

Notice: Scope(Test[test]): b: {key => }

Notice: Scope(Test[test]): a values: [key, ]

Error: Evaluation Error: Error while evaluating a Resource Statement, Evaluation Error: Error while evaluating a Method call, block parameter 'values' expects an Array value, got Tuple at /home/rvicinus/test.pp:8:5  at /home/rvicinus/test.pp:14 on node puppetmaster