Cannot generate proper metadata for record structs

[airbreather]

Operating System: Windows

DocFX Version Used: 2.59.3.0

Template used: whatever docfx-seed uses

Steps to Reproduce:

1. git clone https://github.com/docascode/docfx-seed
2. In docfx.json, change src/DotnetNew/*.csproj to DotnetNew/*.csproj
3. In src/DotnetNew, update the .csproj file's TargetFramework to net6.0 and add a record struct. Examples down below.
4. docfx docfx.json --serve
5. Navigate to http://localhost:8080/api/DotnetNew.html

Expected Behavior:

You should see the record struct in the list of types.

Actual Behavior:

Where it should have been, there's a link to DotnetNew..html.

Sample Files:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
  </PropertyGroup>

</Project>

using System;

namespace DotnetNew
{
    // generates just fine:
    public class Class1
    {
    }

    // generates OK, though it could be better
    public record Class2
    {
    }

    // generates just fine:
    public struct Struct1
    {
    }

    // generates just fine:
    public readonly struct Struct2
    {
    }

    // fails:
    public record struct Struct3
    {
    }

    // fails:
    public readonly record struct Struct4
    {
    }
}

[airbreather]

A workaround might be to build first and do this for the metadata:

"metadata": [
  {
    "src": [
      {
        "files": ["DotnetNew/**/bin/**/Release/**.dll" ],
        "src": "src"
      }
    ],
    "dest": "obj/api"
  }
],

While this also seems to have problems, it's also not the absolute worst...

[yufeih]

We now support record structs and other latest C# features in the latest version.