Parser does not allow comma after last element in nested Variant Types

Puppet Version: 6.7.2
Puppet Server Version: 6.5.0
OS Name/Version: Ubuntu 18.04.3 LTS

The following code does not parse:

type A = Variant[Pattern[/a/]]

type B = Variant[

  A,

]

define x (

  Variant[

    A,

  ] $a,

) {

}

with the following error:

Error: Could not parse for environment production: Syntax error at ']' (file: ~/test.pp, line: 9, column: 3)

Desired Behavior:

The code should be parsed without error.

Actual Behavior:

The parsing the code with puppet parser validate ~/test.pp throws the above mentioned error.

The code does parse if the comma behind type A in the Variant block is removed. But this is a inconsistent behavior, because, as far as i know, all array like enumerations in puppet allow a comma after the last element. Also it works if the type is declared with the type keyword. And it works if the elements in the enumeration are not Variants themselves.