ComWrappers source generator fails to run: CSC : warning CS8785: Generator 'ComInterfaceGenerator' failed to generate source

[smourier]

Description

I'm compiling a class library project with Visual Studio 2022 .NET 9 and when I compile, it raises a CSC 8785 warning and the description of exception: Exception was of type 'ArgumentException' with message 'An item with the same key has already been added.'.

Reproduction Steps

Unfortunately, I can't provide a reproducing project this is a private project that defines around 500 COM interfaces like this:

[GeneratedComInterface, Guid("1f9fc1d0-c39b-4b26-817f-011967d3440e")]
public partial interface IPropertyDescriptionList
{
    ....
}

And the csproj is defined like this:

<PropertyGroup>
	<TargetFramework>net9.0</TargetFramework>
	<Nullable>enable</Nullable>
	<IsAotCompatible>true</IsAotCompatible>
	<AllowUnsafeBlocks>true</AllowUnsafeBlocks>
	<PublishAot>true</PublishAot>
	<GenerateAssemblyInfo>false</GenerateAssemblyInfo>
</PropertyGroup>

I've tried to reproduce on a small project but it never fail, it works and I have similar projects that compile fine. It seems the ComInterfaceGenerator doesn't like something specific, but I can't find what it is

Expected behavior

I believe the 'ComInterfaceGenerator' should not fail with unexpected/internal errors like ArgumentException only with a predefined set of diagnostics

Actual behavior

This is Visual Studio CSC outputs:

1>------ Rebuild All started: Project: ShellN, Configuration: Release Any CPU ------
Restored E:\smo\GitHub\ShellN\ShellN\ShellN.csproj (in 14 ms).
1>CSC : warning CS8785: Generator 'ComInterfaceGenerator' failed to generate source. It will not contribute to the output and compilation errors may occur as a result. Exception was of type 'ArgumentException' with message 'An item with the same key has already been added.'.
1>ShellN -> E:\smo\GitHub\ShellN\ShellN\bin\Release\net9.0\ShellN.dll
1>Done building project "ShellN.csproj".
========== Rebuild All: 1 succeeded, 0 failed, 0 skipped ==========
========== Rebuild completed at 19:08 and took 03,168 seconds ==========

Regression?

I don't know, I've not tested .NET 8

Known Workarounds

I don't have any

Configuration

Visual Studio 2022 17.12.4
.NET 9.0.1
Windows 11 24H2 x64 26100.2894

Other information

Is there a way to enable some logs or diagnostics so I could at least see where/how it's failing?

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