S2589 FP: Rule is erroneously raised on var-type pattern matches that use when clauses

[rjgotten]

Description

S2589 is erroneously raised on var-type pattern matches in e.g. switch expressions that implement the condition using a when clause.

Repro steps

[Flags]
public enum Flags
{
  None,
  Foo,
  Bar
}

// ...

public int Test(Flags flags)
{
  return flags switch
  {
    var value when value.HasFlag(Flags.Foo) => 1,
    var value when value.HasFlag(Flags.Bar) => 2,
    _ => 0
  };
}

Expected behavior

Rule S2589 is not raised.

Actual behavior

Rule S2589 is raised on both var value when pattern matches.

Known workarounds

Disable or suppress S2589.

Related information

• C#/VB.NET Plugins version: 9.8 (via SonarLint v7.3.0.77872)
• Visual Studio version: VS2022 v17.7.4
• MSBuild / dotnet version: .NET SDK 7.0.401
• SonarScanner for .NET version (if used): N/A
• Operating System: Windows 11

[gregory-paidis-sonarsource]

Hey @rjgotten ,

Thanks for the information.
I added a reproducer you can find here: #8014

I also added to our dedicated backlog, where it will be taken care of sometimes in the future.