InvalidCastException when using .Then<T>() where T is not IConvertible

[nicro950]

Hi, after we updated to version 1.4.0 of parlot we started to get System.InvalidCastException : Object must implement IConvertible. exceptions in the code. It looks like it happens when using .Then<T>() where T is not IConvertible. Was this intentional, that Then now requires a IConvertible to discard the result?

Here is a snippet of test code which now fails after 1.4.0. The first case with the // A comment fails, but the other one is ok.

using Parlot.Fluent;
using static Parlot.Fluent.Parsers;

public class TestClass
{
    [Theory]
    [InlineData("""
        // A Comment
        var a = 'test'
        """)]
    [InlineData("""
        var a = 'test'
        """)]
    public void SimpleTest(string testString)
    {
        var commentParser = Terms.Text("//").And(AnyCharBefore(OneOf(Literals.Char('\n'), Literals.Char('\r'))));
        var varKeyword = Terms.Text("var");
        var identifier = Terms.Identifier();
        var equal = Terms.Char('=');
        var str = Terms.String();

        var expressionParser = varKeyword.And(identifier).And(equal).And(str).Then<BaseExp?>(a => new AssignExpression(a.Item2.ToString()!, a.Item4.ToString()!));

        var simpleParser = OneOf(commentParser.Then<BaseExp>(), expressionParser);

        var result = simpleParser.Parse(testString);
    }

    public abstract record BaseExp;

    public record AssignExpression(string Name, string Value) : BaseExp;
}

We were able to work around it by calling .Then(default(BaseExp)) instead, for ignoring the value