Description

I have a List of objects whose constructors take 'in' parameters of DateTime and TimeSpan.

public class TestClass
    {
        public TestClass(in DateTime dateTime, in TimeSpan timeSpan)
        {
            DateTime = dateTime;
            TimeSpan = timeSpan;
        }

        public DateTime DateTime { get; set; }

        public TimeSpan TimeSpan { get; set; }
    }

When serializing a list of these objects, I am seeing the exception in the title being thrown:

This is specifically being thrown at IEnumerableDefaultConverter.cs line 255:

state.Current.DeclaredJsonPropertyInfo = state.Current.JsonClassInfo.ElementClassInfo!.PropertyInfoForClassInfo;

Unfortunately I have absolutely no clue what the issue is here. I'm hoping you might be able to help.