Fix S1144 FN: Unused local functions (#9071)

Author: cristian-ambrosini-sonarsource

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

@@ -320,14 +320,19 @@ public CSharpRemovableSymbolWalker(Func<SyntaxTree, bool, SemanticModel> getSema
                 this.containingTypeAccessibility = containingTypeAccessibility;
             }
 
-            // This override is needed because VisitRecordDeclaration is not available due to the Roslyn version.
+            // This override is needed because VisitRecordDeclaration and LocalFunctionStatementSyntax are not available due to the Roslyn version.
             public override void Visit(SyntaxNode node)
             {
                 if (node.IsAnyKind(SyntaxKindEx.RecordClassDeclaration, SyntaxKindEx.RecordStructDeclaration))
                 {
                     VisitBaseTypeDeclaration(node);
                 }
 
+                if (node.IsKind(SyntaxKindEx.LocalFunctionStatement))
+                {
+                    ConditionalStore((IMethodSymbol)GetDeclaredSymbol(node), IsRemovableMethod);
+                }
+
                 base.Visit(node);
             }
 
@@ -488,7 +493,7 @@ static bool IsPartial(TypeDeclarationSyntax typeDeclaration) =>
 
             private static bool IsRemovableMethod(IMethodSymbol methodSymbol) =>
                 IsRemovableMember(methodSymbol)
-                && (methodSymbol.MethodKind == MethodKind.Ordinary || methodSymbol.MethodKind == MethodKind.Constructor)
+                && (methodSymbol.MethodKind is MethodKind.Ordinary or MethodKind.Constructor or MethodKindEx.LocalFunction)
                 && !methodSymbol.IsMainMethod()
                 && (!methodSymbol.IsEventHandler() || !IsDeclaredInPartialClass(methodSymbol)) // Event handlers could be added in XAML and no method reference will be generated in the .g.cs file.
                 && !methodSymbol.IsSerializationConstructor()

analyzers/src/SonarAnalyzer.Common/Helpers/SymbolHelper.cs

@@ -315,6 +315,7 @@ public static string GetClassification(this ISymbol symbol) =>
                     { MethodKind: MethodKind.Destructor } => "destructor",
                     { MethodKind: MethodKind.PropertyGet } => "getter",
                     { MethodKind: MethodKind.PropertySet } => "setter",
+                    { MethodKind: MethodKindEx.LocalFunction } => "local function",
                     _ => "method",
                 },
                 INamedTypeSymbol namedTypeSymbol => namedTypeSymbol switch

analyzers/tests/SonarAnalyzer.Test/Helpers/SymbolHelperTest.cs

@@ -398,7 +398,7 @@ public void GetClassification_Record(TypeKind typeKind, string expected)
         [DataRow(MethodKind.ExplicitInterfaceImplementation, "method")]
         [DataRow(MethodKind.FunctionPointerSignature, "method")]
         [DataRow(MethodKind.LambdaMethod, "method")]
-        [DataRow(MethodKind.LocalFunction, "method")]
+        [DataRow(MethodKind.LocalFunction, "local function")]
         [DataRow(MethodKind.Ordinary, "method")]
         [DataRow(MethodKind.PropertyGet, "getter")]
         [DataRow(MethodKind.PropertySet, "setter")]

analyzers/tests/SonarAnalyzer.Test/TestCases/UnusedPrivateMember.CSharp10.cs

@@ -70,7 +70,7 @@ static void Quix() { }
             [Obsolete]
             static void ForCoverage() { }
 
-            static void NoAttribute() { }
+            static void NoAttribute() { } // Noncompliant
         }
     }
 

analyzers/tests/SonarAnalyzer.Test/TestCases/UnusedPrivateMember.CSharp7.cs

@@ -198,15 +198,6 @@ private enum Y
     }
 }
 
-// https://github.com/SonarSource/sonar-dotnet/issues/6699
-public class Repro_6699
-{
-    public void MethodUsingLocalMethod()
-    {
-        void LocalMethod() { } // FN
-    }
-}
-
 // https://github.com/SonarSource/sonar-dotnet/issues/6724
 public class Repro_6724
 {

analyzers/tests/SonarAnalyzer.Test/TestCases/UnusedPrivateMember.CSharp9.cs

@@ -69,7 +69,7 @@ static void Quix() { }
             [Obsolete]
             static void ForCoverage() { }
 
-            static void NoAttribute() { }
+            static void NoAttribute() { } // Noncompliant
         }
     }
 
@@ -158,7 +158,7 @@ public bool MethodWithLocalFunction()
             {
                 return false;
 
-                bool PrintMembers(StringBuilder builder) => true;       // FN - local functions are not handled
+                bool PrintMembers(StringBuilder builder) => true;       // Noncompliant
             }
         }
 

analyzers/tests/SonarAnalyzer.Test/TestCases/UnusedPrivateMember.Fixed.Batch.cs

@@ -94,11 +94,13 @@ private interface MyInterface
         void Method();
     }
 
+    // https://github.com/SonarSource/sonar-dotnet/issues/6699
     public void MethodUsingLocalMethod()
     {
-        void LocalMethod() // FN: local function is never used
-        {
+        LocalMethod();
 
+        void LocalMethod()
+        {
         }
     }
 }

analyzers/tests/SonarAnalyzer.Test/TestCases/UnusedPrivateMember.Fixed.cs

@@ -78,11 +78,13 @@ private int MyProperty
     [My]
     private class Class1 { }
 
+    // https://github.com/SonarSource/sonar-dotnet/issues/6699
     public void MethodUsingLocalMethod()
     {
-        void LocalMethod() // FN: local function is never used
-        {
+        LocalMethod();
 
+        void LocalMethod()
+        {
         }
     }
 }

analyzers/tests/SonarAnalyzer.Test/TestCases/UnusedPrivateMember.cs

@@ -144,11 +144,17 @@ internal class Class4 : MyInterface // Noncompliant {{Remove the unused internal
         public void Method() { }
     }
 
+    // https://github.com/SonarSource/sonar-dotnet/issues/6699
     public void MethodUsingLocalMethod()
     {
-        void LocalMethod() // FN: local function is never used
+        LocalMethod();
+
+        void LocalMethod()
         {
+        }
 
+        void UnusedLocalMethod() // Noncompliant {{Remove the unused private local function 'UnusedLocalMethod'.}}
+        {
         }
     }
 }