Fix S3267 FN: Support list pattern

analyzers/its/expected/akka.net/Akka.DistributedData--netstandard2.0-S3267.json

@@ -23,6 +23,30 @@
 }
 }
 ]
+},
+{
+"id":  "S3267",
+"message":  "Loops should be simplified with "LINQ" expressions",
+"location":  [
+{
+"uri":  "sources\akka.net\src\contrib\cluster\Akka.DistributedData\Serialization\ReplicatorMessageSerializer.cs",
+"region":  {
+"startLine":  313,
+"startColumn":  31,
+"endLine":  313,
+"endColumn":  55
+}
+},
+{
+"uri":  "sources\akka.net\src\contrib\cluster\Akka.DistributedData\Serialization\ReplicatorMessageSerializer.cs",
+"region":  {
+"startLine":  315,
+"startColumn":  21,
+"endLine":  315,
+"endColumn":  48
+}
+}
+]
 }
 ]
 }

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

@@ -67,12 +67,21 @@ 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 && (ConditionValidIsPattern() || ConditionValidInvocation());
+
+            bool ConditionValidIsPattern() => (IsPatternExpressionSyntaxWrapper.IsInstance(ifStatementSyntax.Condition) || ifStatementSyntax.Condition.IsKind(SyntaxKind.IsExpression))
+                                              && !ifStatementSyntax.Condition.DescendantNodes()
+                                                                             .Any(d => d.IsAnyKind(SyntaxKindEx.VarPattern,
+                                                                                                   SyntaxKindEx.SingleVariableDesignation,
+                                                                                                   SyntaxKindEx.ParenthesizedVariableDesignation));
+
+            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 +144,7 @@ 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

@@ -3,17 +3,35 @@
 
 namespace Tests.Diagnostics
 {
-    class MyClass
+    class IsPatternTests
     {
         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");
                 }
             }
+
+            foreach (var array in list) // Compliant, do not raise on VarPattern in ListPattern
+            {
+                if (array is [1, var x, var z])
+                {
+                    Console.WriteLine("Pattern match successful");
+                }
+
+            }
+
+            foreach (var array in list) // Compliant, do not raise on declaration statements in ListPattern 
+            {
+                if (array is [1, ..] local)
+                {
+                    Console.WriteLine("Pattern match successful");
+                }
+
+            }
         }
     }
 }

analyzers/tests/SonarAnalyzer.UnitTest/TestCases/LoopsAndLinq.CSharp8.cs

@@ -29,5 +29,42 @@ public class Point
             public int X { get; set; }
             public int? Y { get; set; }
         }
+
+        void IsPatterns(List<string> strings, List<Tuple<string, int>> tuples)
+        {
+            const string target = "42";
+
+            foreach (var s in strings) // Noncompliant
+            {
+                if (s is target) // Secondary 
+                {
+                    Console.WriteLine("Pattern match successful");
+                }
+            }
+
+            foreach (var s in strings) // Compliant, do not raise on VarPattern in IsPattern
+            {
+                if (s is var s2)
+                {
+                    Console.WriteLine("Pattern match successful");
+                }
+            }
+
+            foreach (var s in strings) // Compliant, do not raise on SingleVariableDeclaration in IsPattern
+            {
+                if (s is { Length: 42 } str)
+                {
+                    Console.WriteLine("Pattern match successful");
+                }
+            }
+
+            foreach (var t in tuples) // Compliant, do not raise on ParenthesizedVariableDeclaration in IsPattern
+            {
+                if (t is var (t1, t2))
+                {
+                    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.");
+                }
+            }
+        }
     }
 }