Description

Since v1.44 compilation fail when using mocking (MyType.Mock()).

CS9262 - Cannot use 'OverloadResolutionPriorityAttribute' on this member.

The issue happens in generated obj\Debug\net9.0\TUnit.Mocks.SourceGenerator\TUnit.Mocks.SourceGenerator.MockGenerator\ProjectName_MyType_MockMembers.g.cs file that unfortunately get automatically get cleaned up.

Expected Behavior

Generated mocked file should compile

Actual Behavior

Generated mocked file doesn't compile with error CS9262

Steps to Reproduce

public interface IDumb
{}

/// <summary>
/// Error CS9262 : Cannot use 'OverloadResolutionPriorityAttribute' on this member.
/// Starting from Tunit.Mocks 1.44.0 -> https://github.com/thomhurst/TUnit/commit/15f8062a70fd840ec62df159ebd1d6bc321e3635
/// </summary>
public class MyTests
{
  [Test]
  public async Task MOCK_TEST()
  {
    ///Arrange
    // raises the CS9262 error when building
    var dumbMock = IDumb.Mock(); 
    // Or : var dumbMock = Mock.Of<IDumb>();

    ///Act

    ///Assert

    await Assert.That(true).IsTrue();
  }
}

TUnit Version

from 1.44.0

.NET Version

.NET 9.0

Operating System

Windows

IDE / Test Runner

Visual Studio

Error Output / Stack Trace

CS9262 - Cannot use 'OverloadResolutionPriorityAttribute' on this member.
CS9262 - Cannot use 'OverloadResolutionPriorityAttribute' on this member.
CS9262 - Cannot use 'OverloadResolutionPriorityAttribute' on this member.

Additional Context

I am using Visual Studio 2022 Version 17.14.35 (June 2026)

My .csproj is

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

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net9.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
    <LangVersion>preview</LangVersion>
  </PropertyGroup>
  
  <ItemGroup>
    <PackageReference Include="TUnit" Version="1.58.0" />
    <PackageReference Include="TUnit.Mocks" Version="1.58.0" />
    <PackageReference Include="TUnit.Mocks.Assertions" Version="1.58.0" />
  </ItemGroup>
</Project>

IDE-Specific Issue?

• I've confirmed this issue occurs when running via dotnet test or dotnet run, not just in my IDE