Duplicated nullable variables in RNGLR parsing

[woutersl]

Original report by Laurent Wouters (Bitbucket: 557058:675792b6-d731-4823-9f7d-c6dfcb2df2b5, ).

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In some cases, nullable varialbes get duplicated in the output AST with the RNGLR parsing method.

Test case:

grammar Test
{
    options
    {
        Axiom = "unit";
    }
    terminals
    { }
    rules
    {
        unit -> 'X' nullable ;
        nullable -> ;
    }
}

The expected AST is unit(X nullable).

The produced (incorrect) AST is unit(X nullable nullable).

[woutersl]

Original comment by Laurent Wouters (Bitbucket: 557058:675792b6-d731-4823-9f7d-c6dfcb2df2b5, ).

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Verified with the use case.

[woutersl]

Original comment by Laurent Wouters (Bitbucket: 557058:675792b6-d731-4823-9f7d-c6dfcb2df2b5, ).

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[fix] Fixed issue #21 with duplicated nullable variables in RNGLR parsers

[woutersl]

Original comment by Laurent Wouters (Bitbucket: 557058:675792b6-d731-4823-9f7d-c6dfcb2df2b5, ).

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[fix] Fixed issue #21 with duplicated nullable variables in RNGLR parsers