Rule S1144: remove duplicate issues in top level statements

- the symbols were processed twice, once for the Program symbol and
the second time for the types defined in the top level statement file.

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

@@ -72,16 +72,11 @@ protected override void Initialize(SonarAnalysisContext context) =>
                         {
                             var namedType = (INamedTypeSymbol)cc.Symbol;
 
-                            if (namedType.TypeKind != TypeKind.Struct
-                                && namedType.TypeKind != TypeKind.Class
-                                && namedType.TypeKind != TypeKind.Delegate
-                                && namedType.TypeKind != TypeKind.Enum
-                                && namedType.TypeKind != TypeKind.Interface)
-                            {
-                                return;
-                            }
-
-                            if (namedType.ContainingType != null || namedType.DerivesFromAny(IgnoredTypes))
+                            if (namedType.ContainingType != null
+                                // We skip top level statements since they cannot have fields. Other declared types are analyzed separately.
+                                || IsTopLevelProgram(namedType)
+                                || !IsType(namedType)
+                                || namedType.DerivesFromAny(IgnoredTypes))
                             {
                                 return;
                             }
@@ -137,8 +132,24 @@ protected override void Initialize(SonarAnalysisContext context) =>
                         });
                 });
 
-        private static IEnumerable<Diagnostic> GetDiagnosticsForUnusedPrivateMembers(CSharpSymbolUsageCollector usageCollector, ISet<ISymbol> removableSymbols, string accessibility,
-            BidirectionalDictionary<ISymbol, SyntaxNode> fieldLikeSymbols)
+        private static bool IsTopLevelProgram(ISymbol symbol) =>
+            // If the symbol is named `Program` and the containing namespace is the global one, we will assume that we are analyzing a top level file.
+            // We cannot tell for sure, but in this case we prefer to have FNs instead of FPs, considering that there is a low chance to have
+            // a program class in the global namespace.
+            symbol.Name == "Program"
+            && symbol.ContainingNamespace.IsGlobalNamespace;
+
+        private static bool IsType(ITypeSymbol namedType) =>
+            namedType.TypeKind == TypeKind.Struct
+            || namedType.TypeKind == TypeKind.Class
+            || namedType.TypeKind == TypeKind.Delegate
+            || namedType.TypeKind == TypeKind.Enum
+            || namedType.TypeKind == TypeKind.Interface;
+
+        private static IEnumerable<Diagnostic> GetDiagnosticsForUnusedPrivateMembers(CSharpSymbolUsageCollector usageCollector,
+                                                                                     ISet<ISymbol> removableSymbols,
+                                                                                     string accessibility,
+                                                                                     BidirectionalDictionary<ISymbol, SyntaxNode> fieldLikeSymbols)
         {
             var unusedSymbols = GetUnusedSymbols(usageCollector, removableSymbols);
 
@@ -181,7 +192,9 @@ private static IEnumerable<Diagnostic> GetDiagnosticsForUnreadFields(IEnumerable
         private static string GetFieldAccessibilityForMessage(ISymbol symbol) =>
             symbol.DeclaredAccessibility == Accessibility.Private ? "private" : "private class";
 
-        private static IEnumerable<Diagnostic> GetDiagnosticsForMembers(ICollection<ISymbol> unusedSymbols, string accessibility, BidirectionalDictionary<ISymbol, SyntaxNode> fieldLikeSymbols)
+        private static IEnumerable<Diagnostic> GetDiagnosticsForMembers(ICollection<ISymbol> unusedSymbols,
+                                                                        string accessibility,
+                                                                        BidirectionalDictionary<ISymbol, SyntaxNode> fieldLikeSymbols)
         {
             var diagnostics = new List<Diagnostic>();
             var alreadyReportedFieldLikeSymbols = new HashSet<ISymbol>();

analyzers/tests/SonarAnalyzer.UnitTest/Rules/UnusedPrivateMemberTest.cs

@@ -203,7 +203,11 @@ public void UnusedPrivateMember_FromCSharp8() =>
         [TestMethod]
         public void UnusedPrivateMember_FromCSharp9() =>
             Verifier.VerifyAnalyzerFromCSharp9Library(
-                @"TestCases\UnusedPrivateMember.CSharp9.cs",
+                new[]
+                {
+                    @"TestCases\UnusedPrivateMember.CSharp9.cs",
+                    @"TestCases\UnusedPrivateMember.CSharp9.Second.cs"
+                },
                 new UnusedPrivateMember());
 
         [TestMethod]

analyzers/tests/SonarAnalyzer.UnitTest/TestCases/UnusedPrivateMember.CSharp9.Second.cs

@@ -0,0 +1,7 @@
+namespace Tests.Diagnostics
+{
+    public partial class PartialMethods
+    {
+        partial void UnusedMethod(); // Noncompliant
+    }
+}

analyzers/tests/SonarAnalyzer.UnitTest/TestCases/UnusedPrivateMember.CSharp9.TopLevelStatements.cs

@@ -13,19 +13,16 @@ public record Product(string Name, int CategoryId);
 public record Record
 {
     private int a; // Noncompliant {{Remove the unused private field 'a'.}}
-                   // Noncompliant@-1 - duplicate issue reported
 
     private int b;
     public int B() => b;
 
     private nint Value { get; init; }
     private nint UnusedValue { get; init; } // Noncompliant
-                                            // Noncompliant@-1 - duplicate issue reported
 
     public Record Create() => new() { Value = 1 };
 
     private interface IFoo // Noncompliant
-                           // Noncompliant@-1 - duplicate issue reported
     {
         public void Bar() { }
     }
@@ -45,7 +42,6 @@ public void UseNested2()
     }
 
     private record UnusedNested1(string Name, int CategoryId);   // Noncompliant
-                                                                 // Noncompliant@-1 - duplicate issue reported
     internal record UnusedNested2(string Name, int CategoryId);  // Noncompliant
     public record UnusedNested3(string Name, int CategoryId);
 
@@ -76,7 +72,6 @@ private TargetTypedNew(int arg)
     }
 
     private TargetTypedNew(string arg) // Noncompliant - FP
-                                       // Noncompliant@-1 - duplicate issue reported
     {
         var x = arg;
     }

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

@@ -100,4 +100,8 @@ public static void Foo()
             PositionalRecord @record = new PositionalRecord("");
         }
     }
+
+    public partial class PartialMethods
+    {
+    }
 }