Fix S2589 FP: Rule ignores case guards

[manpil]

Description

S2589 is raised on a switch expression on a tuple where the second parameter is discarded but for the first one there is a guard clause.

Repro steps

 private static string Example(string input, bool y)
    {
        return (input, y) switch
        {
            ("Foo", true) => "FooTrue",
            ("Foo", false) => "FooFalse",
            (var x, true) when x.StartsWith("ab") => "AbTrue",
            (var x, _) when x.StartsWith("CD") => "CD",
            _ => "empty",
        };
    }

Expected behavior

S2589 is not raised

Actual behavior

S2589 is raised on the line containing: (var x, _) when x.StartsWith("CD") => "CD",

Known workarounds

None/ Disable with pragma

Related information

• C#/VB.NET Plugins version: 9.32
• Visual Studio version: N/A -> Rider 2024.2.4
• MSBuild / dotnet version: .net8.0
• SonarScanner for .NET version (if used): N/A
• Operating System: Ubuntu 22.04 LTS

Kindof relates to: #8008

[sebastien-marichal]

Hello @manpil,

Thank you for reporting this issue.
I confirm this is a false positive.

I am adding this issue to our backlog to tackle it in the future.

Have a good day!