Repro for FN 2589: Support redundant recursive pattern null check (#9234

)

analyzers/tests/SonarAnalyzer.Test/TestCases/SymbolicExecution/Roslyn/ConditionEvaluatesToConstant.CSharp8.cs

@@ -669,3 +669,17 @@ public void Method()
     private string SomeString() => "";
     private bool SomeBool() => true;
 }
+
+// https://github.com/SonarSource/sonar-dotnet/issues/9203
+class Repro_9203
+{
+    void RecursivePattern(string s)
+    {
+        s.GetHashCode();
+        if (s is { }) // FN: Recursive pattern null check is not supported
+        { }
+
+        if (s is { }) // Compliant: not just null-check, the property value is also checked
+        { }
+    }
+}