[Bug] Docfx throws InvalidOperationException: Unexpected member type but gives no further info

[doombubbles]

Describe the bug
Running docfx for my project is failing with InvalidOperationException: Unexpected member type but it does not give any information about which member is actually causing the error.

To Reproduce
Running docfx --verbose for the project at https://github.com/gurrenm3/BTD-Mod-Helper/tree/master/BloonsTD6%20Mod%20Helper using docfx.json

{
  "metadata": [
    {
      "src": [
        {
          "files": ["BloonsTD6 Mod Helper.csproj"]
        }
      ],
      "dest": "../NewDocumentation"
    }
  ]
}

Expected behavior
I would expect to be told in what source file / class the unexpected member type is in and what its name / type is. As of now there aren't any reasonable steps I can take to figure out what is causing this and how I could make docfx actually work for my project.

Context:

• OS: Windows
• Docfx version: 2.78.4+ba9dfcbb96a4ceed2ac6d3ba93e12e16550b3e2a
• Dotnet version: 10.0.100

Additional context
The full console output I get with --verbose is

Loading project C:/Users/jpgale/Documents/Coding/BTD6 Mods/BTD-Mod-Helper/BloonsTD6 Mod Helper/BloonsTD6 Mod Helper.csproj
Restore complete (0.2s)

Build succeeded in 0.4s
Processing BloonsTD6 Mod Helper
No PDB file found for C:\Program Files (x86)\Steam\steamapps\common\BloonsTD6\MelonLoader\Il2CppAssemblies\UnityEngine.AudioModule.dll, skip loading source link.
No PDB file found for C:\Program Files (x86)\Steam\steamapps\common\BloonsTD6\MelonLoader\net6\Newtonsoft.Json.dll, skip loading source link.
No PDB file found for C:\Program Files (x86)\Steam\steamapps\common\BloonsTD6\MelonLoader\Il2CppAssemblies\Assembly-CSharp.dll, skip loading source link.
No PDB file found for C:\Program Files (x86)\Steam\steamapps\common\BloonsTD6\MelonLoader\Il2CppAssemblies\Il2Cppmscorlib.dll, skip loading source link.
No PDB file found for C:\Program Files (x86)\Steam\steamapps\common\BloonsTD6\MelonLoader\Il2CppAssemblies\Il2CppNinjaKiwi.Common.dll, skip loading source link.
No PDB file found for C:\Program Files (x86)\Steam\steamapps\common\BloonsTD6\MelonLoader\Il2CppAssemblies\UnityEngine.UI.dll, skip loading source link.
No PDB file found for C:\Program Files (x86)\Steam\steamapps\common\BloonsTD6\MelonLoader\Il2CppAssemblies\UnityEngine.CoreModule.dll, skip loading source link.
No PDB file found for C:\Program Files (x86)\Steam\steamapps\common\BloonsTD6\MelonLoader\net6\Il2CppInterop.Runtime.dll, skip loading source link.
No PDB file found for C:\Program Files (x86)\Steam\steamapps\common\BloonsTD6\MelonLoader\net6\0Harmony.dll, skip loading source link.
No PDB file found for C:\Program Files (x86)\Steam\steamapps\common\BloonsTD6\MelonLoader\Il2CppAssemblies\UnityEngine.AssetBundleModule.dll, skip loading source link.
No PDB file found for C:\Program Files (x86)\Steam\steamapps\common\BloonsTD6\MelonLoader\Il2CppAssemblies\UnityEngine.AnimationModule.dll, skip loading source link.
No PDB file found for C:\Program Files (x86)\Steam\steamapps\common\BloonsTD6\MelonLoader\Il2CppAssemblies\Unity.TextMeshPro.dll, skip loading source link.
No PDB file found for C:\Users\jpgale\.nuget\packages\commandlineparser\2.9.1\lib\netstandard2.0\CommandLine.dll, skip loading source link.
No PDB file found for C:\Program Files (x86)\Steam\steamapps\common\BloonsTD6\MelonLoader\Il2CppAssemblies\UnityEngine.UIModule.dll, skip loading source link.
No PDB file found for C:\Program Files (x86)\Steam\steamapps\common\BloonsTD6\MelonLoader\Il2CppAssemblies\Il2CppNewtonsoft.Json.dll, skip loading source link.
No PDB file found for C:\Users\jpgale\.nuget\packages\naudio.core\2.2.1\lib\netstandard2.0\NAudio.Core.dll, skip loading source link.
No PDB file found for C:\Users\jpgale\.nuget\packages\naudio\2.2.1\lib\net6.0\NAudio.dll, skip loading source link.
No PDB file found for C:\Users\jpgale\.nuget\packages\naudio.vorbis.latest\1.5.1\lib\netstandard2.0\NAudio.Vorbis.dll, skip loading source link.
InvalidOperationException: Unexpected member type.
  at string AddReference(ISymbol symbol) in SymbolVisitorAdapter.cs:376                                                                                                                          
  at MetadataItem VisitNamedType(INamedTypeSymbol symbol) in SymbolVisitorAdapter.cs:200                                                                                                         
  at List<MetadataItem> VisitDescendants<T>(IEnumerable<T> children, Func<T, IEnumerable<T>> getChildren, Func<T, bool> filter) in SymbolVisitorAdapter.cs:512                                   
  at MetadataItem VisitNamespace(INamespaceSymbol symbol) in SymbolVisitorAdapter.cs:133                                                                                                         
  at List<MetadataItem> VisitDescendants<T>(IEnumerable<T> children, Func<T, IEnumerable<T>> getChildren, Func<T, bool> filter) in SymbolVisitorAdapter.cs:512                                   
  at MetadataItem VisitAssembly(IAssemblySymbol symbol) in SymbolVisitorAdapter.cs:117                                                                                                           
  at TResult Accept<TResult>(SymbolVisitor<TResult> visitor)                                                                                                                                     
  at TResult Accept<TResult>(SymbolVisitor<TResult> visitor)                                                                                                                                     
  at void CreateManagedReference((ValueTuple<IAssemblySymbol, Compilation> symbol) assemblies, ExtractMetadataConfig config, DotnetApiOptions options) in DotnetApiCatalog.ManagedReference.cs:25
  at async Task <Exec>g__Build|7_0(ExtractMetadataConfig config, DotnetApiOptions options) in DotnetApiCatalog.cs:112                                                                            
  at async Task Exec(MetadataJsonConfig config, DotnetApiOptions options, string configDirectory, string outputDirectory) in DotnetApiCatalog.cs:73                                              
  at void <Execute>b__0() in DefaultCommand.cs:45                                                                                                                                                
  at int Run(LogOptions options, Action run) in CommandHelper.cs:48                                                                                                                              
  at int Execute(CommandContext context, Options options, CancellationToken cancellationToken) in DefaultCommand.cs:31                                                                           
  at int Execute(CommandContext context, TSettings settings) in CancellableCommandBase.cs:24                                                                                                     
  at Task<int> Execute(CommandContext context, CommandSettings settings) in CommandOfT.cs:40                                                                                                     
  at async Task<int> Execute(CommandTree leaf, CommandTree tree, CommandContext context, ITypeResolver resolver, IConfiguration configuration) in CommandExecutor.cs:259

[filzrev]

It seems target repository using C# 14 Extension members.

Currently docfx don't support C# 14 features. and failed to generate metadata.
There are PR to update Roslyn version to 5.0.0. But it's not merged yet.