Fix S3267 FN: Support list pattern

analyzers/src/SonarAnalyzer.CSharp/Rules/LoopsAndLinq.cs

@@ -67,12 +67,17 @@ node switch
                 _ => null
             };
 
-        private static bool CanIfStatementBeMoved(IfStatementSyntax ifStatementSyntax) =>
-            ifStatementSyntax.Else == null
-            && ifStatementSyntax.Condition is InvocationExpressionSyntax invocationExpressionSyntax
-            && !invocationExpressionSyntax.DescendantNodes()
-                                          .OfType<ArgumentSyntax>()
-                                          .Any(argument => argument.RefOrOutKeyword.IsAnyKind(SyntaxKind.OutKeyword, SyntaxKind.RefKeyword));
+        private static bool CanIfStatementBeMoved(IfStatementSyntax ifStatementSyntax)
+        {
+            return ifStatementSyntax.Else == null && (ConditionIsPattern() || ConditionValidInvocation());
+
+            bool ConditionIsPattern() => IsPatternExpressionSyntaxWrapper.IsInstance(ifStatementSyntax.Condition);
+
+            bool ConditionValidInvocation() => ifStatementSyntax.Condition is InvocationExpressionSyntax invocationExpressionSyntax
+                                               && !invocationExpressionSyntax.DescendantNodes()
+                                               .OfType<ArgumentSyntax>()
+                                               .Any(argument => argument.RefOrOutKeyword.IsAnyKind(SyntaxKind.OutKeyword, SyntaxKind.RefKeyword));
+        }
 
         /// <remarks>
         /// There are multiple scenarios where the code can be simplified using LINQ.
@@ -135,7 +140,7 @@ private static void CheckIfCanBeSimplifiedUsingSelect(ForEachStatementSyntax for
                 !(memberAccess.Parent is AssignmentExpressionSyntax assignment && assignment.Left == memberAccess);
         }
 
-        private class UsageStats
+        private sealed class UsageStats
         {
             public int Count { get; set; }
 

analyzers/tests/SonarAnalyzer.UnitTest/TestCases/LoopsAndLinq.CSharp11.cs

@@ -7,13 +7,14 @@ class MyClass
     {
         void ListPattern(List<int[]> list)
         {
-            foreach (int[] array in list) // FN
+            foreach (int[] array in list) // Noncompliant
             {
-                if (array is [1, 2, 3]) // FN
+                if (array is [1, 2, 3]) // Secondary
                 {
-                    Console.WriteLine("Test");
+                    Console.WriteLine("Pattern match successful");
                 }
             }
         }
     }
 }
+

analyzers/tests/SonarAnalyzer.UnitTest/TestCases/LoopsAndLinq.cs

@@ -309,5 +309,16 @@ public class Point
 
             public int GetX() => X;
         }
+
+        void IsPattern(List<int> list)
+        {
+            foreach (var item in list) // Noncompliant
+            {
+                if (item is 42) // Secondary
+                {
+                    Console.WriteLine("The meaning of Life.");
+                }
+            }
+        }
     }
 }