Fix S2325 FP: Partial method implementations

[E4est]

Description

S2325 is raised on partial implementations that only refer to their own parameters. The rule correctly recognizes that no instance-specific methods or properties are accessed, but making the partial implementation static doesn't even compile, because both partial declarations should be static.
The original declaring partial class is generated, so it's not an option to edit that.

Repro steps

// In our project this class is generated.
partial class Class
{
    public void WriteEverything()
    {
        Console.WriteLine("Something");

        WriteMore();
    }

    partial void WriteMore();
}

partial class Class
{
    partial void WriteMore() // Noncompliant - FP
    {
        Console.WriteLine("More");
    }
}

Expected behavior

S2325 is not triggered on methods that are part of an external contract.
(This works fine for interfaces.)

Actual behavior

S2325 is triggered.

Known workarounds

Add a private readonly field for any constant value that is used and access that.

// In our project this class is generated.
partial class Class
{
    public void WriteEverything()
    {
        Console.WriteLine("Something");

        WriteMore();
    }

    partial void WriteMore();
}

partial class Class
{
    private readonly string _workaround = "More";

    partial void WriteMore()
    {
        Console.WriteLine(_workaround);
    }
}

Related information

• C#/VB.NET Plugins version: SonarAnalyzer.CSharp 9.10.0.77988
• Visual Studio version: 2022 Professional v17.7.3
• MSBuild / dotnet version: 17.7.2+d6990bcfa / 7.0.400
• SonarScanner for .NET version (if used): -
• Operating System: Windows 10 22H2 19045.3448