Support C# 9.0 records

With the advent of .NET 5.0 and C# 9 we now have a new, immutable-on-demand, kind of class with additional special features called record. Would it be possible to add support for them (especially the type known as positional record) out-of-the-box?

Right now using them as if they were a normal class gives this exception:

public record SampleModel(string Name, int Age);

var sample = JsonSerializer.Generic.Utf8.Deserialize<SampleModel, ExcludeNullsCamelCaseResolver<byte>>(Encoding.UTF8.GetBytes(jsonString));

Positional records only have one public constructor:

var sample = new SampleModel("Name", 100);

[Tornhoof]

I published 3.1.0-rc1 to include the records stuff. It was a bit more complicated than expected, as records also support a mixed concept where not only those positional properties are used but additionally normal properties. SpanJson did not support that by now (as soon as you used the constructor attribute, it only used that and nothing else, other properties would be ignored). So I had to extend it for this functionality.

[Tornhoof]

Yeah, I plan to add support for it in the next few days. I just haven’t looked into records much yet.