Runtime Exception when pretty printing grammar

[ssrmm]

I have this grammar:

namespace Test
{
  syntax module Test
  {
    using Nitra.Core;

    [StartRule]
    syntax Expression = (Foo; nl)+;

    syntax Foo = "foo";
  }
}

When I'm pretty-printing any accepted string that consists of more than one "foo" I get an System.ArgumentOutOfRangeException. Input that produces the error is e.g. "foofoo", "foo foo" or "foofoo foo". The only input that can be pretty printed is "foo".

If I change the rule syntax Expression = (Foo; nl)+; to syntax Expression = Foo+; or syntax Expression = (Foo nl)+;, then it works correctly. Other pretty-print markers like sm and inl produce the same result.

---

Some more infos for debugging purposes

The stack trace (might not be that useful because of the generated sources):

Unhandled Exception: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: id
   at Test.TestParseTree.Expression.__Parsed__Node.__ReadSequenceParseTreeStandardMode(Int32 id, Int32& pos) in C:\Users\<...>\AppData\Local\Temp\_N_GeneratedSource_Experiments.n:Line 392.
   at Nitra.Internal.ParseTreeFactory.CreateListWithSeparatorOnlyItems[TItemLoader,TItem,TSeparatorLoader](ParseResult parseResult, ISequenceParseTreeLoader`1itemLoader, Int32 itemSequenceId, ParseTreeCastHelper`2 itemConverter, ISequenceParseTreeLoader`1 separatorLoader, Int32 separatorSequenceId, Int32 rawTreePtr,Int32 offset, Int32& pos) in D:\<...>\Nitra\Nitra\Nitra.Runtime\ParseTree\ParseTreeFactory.n:Line 187.
   at Test.TestParseTree.Expression.__Parsed__Node.get_Foos() in C:\Users\<...>\AppData\Local\Temp\_N_GeneratedSource_Experiments.n:Line 260.
   at Test.TestParseTree.Expression.PrettyPrint(PrettyPrintWriter writer, Int32 callerBindingPower, SpanClass spanClass) in C:\Users\<...>\AppData\Local\Temp\_N_GeneratedSource_Experiments.n:Line 380.
   at Nitra.ParseTree.ToString(PrettyPrintOptions options) in D:\<...>\Nitra\Nitra\Nitra.Runtime\ParseTree\ParseTree.n:Line 45.
   at Nitra.ParseTree.ToString() in D:\<...>\Nitra\Nitra\Nitra.Runtime\ParseTree\ParseTree.n:Line 32.
   at System.String.Concat(Object arg0, Object arg1)
   at TesstApp.Program.Main(String[] args) in d:\<...>\Program.cs:Line 23.

The test program I used:

using System;
using Nitra;
using Nitra.ProjectSystem;

namespace TesstApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Console.Write("> ");
            var input = Console.ReadLine();

            while (input != string.Empty)
            {
                var session = new ParseSession(Test.Test.Expression, compilerMessages: new ConsoleCompilerMessages());

                var result = session.Parse(input);

                if (result.IsSuccess)
                {
                    Console.WriteLine("Parsing succeeded!");
                    Console.WriteLine("PrettyPrint: " + result.CreateParseTree());
                }
                else
                {
                    Console.Error.WriteLine("Parsing failed!");
                }

                Console.Write("> ");
                input = Console.ReadLine();
            }
        }
    }
}

[ssrmm]

As a workaround one can write syntax Expression = (Foo; !Any nl)+;. This does not produce the error, but (according to my understanding) should be equivalent to the original rule.