Fix S3168 FN: Async implementation of non-async interfaces

[qhris]

Description

Async implementations of non-async interface methods are not properly reported as an issue.

Repro steps

Minimal reproduction code:

public interface ITestReproduction
{
    void TestMethod();
}

public class TestReproduction : ITestReproduction
{
    async void TestMethod() // FN: Not reported as an issue.
    {
        await Task.Delay(1000);
    }
}

Expected behavior

The above code should report an issue with the async void implementation of the interface.

Actual behavior

Nothing is reported.

Known workarounds

Nothing.

Related information

• C# 12
• .NET 8.0
• Rider 2024.3 with SonarLint 10.12.0.79769
• Operating System Linux