Fix MA0182 false positive for delegates used in new expressions

src/Meziantou.Analyzer/Rules/AvoidUnusedInternalTypesAnalyzer.cs

@@ -43,6 +43,7 @@ public override void Initialize(AnalysisContext context)
             ctx.RegisterOperationAction(analyzerContext.AnalyzeVariableDeclarator, OperationKind.VariableDeclarator);
             ctx.RegisterOperationAction(analyzerContext.AnalyzeConversion, OperationKind.Conversion);
             ctx.RegisterOperationAction(analyzerContext.AnalyzeIsPattern, OperationKind.IsPattern);
+            ctx.RegisterOperationAction(analyzerContext.AnalyzeDelegateCreation, OperationKind.DelegateCreation);
             ctx.RegisterCompilationEndAction(analyzerContext.AnalyzeCompilationEnd);
         });
     }
@@ -270,6 +271,15 @@ public void AnalyzeIsPattern(OperationAnalysisContext context)
             }
         }
 
+        public void AnalyzeDelegateCreation(OperationAnalysisContext context)
+        {
+            var operation = (IDelegateCreationOperation)context.Operation;
+            if (operation.Type is not null)
+            {
+                AddUsedType(operation, operation.Type);
+            }
+        }
+
         public void AnalyzeCompilationEnd(CompilationAnalysisContext context)
         {
             foreach (var type in _potentialUnusedTypes)

tests/Meziantou.Analyzer.Test/Rules/AvoidUnusedInternalTypesAnalyzerTests.cs

@@ -1877,4 +1877,72 @@ await CreateProjectBuilder()
               .WithSourceCode(SourceCode)
               .ValidateAsync();
     }
+
+    [Fact]
+    public async Task InternalDelegateUsedInNewExpression_NoDiagnostic()
+    {
+        const string SourceCode = """
+            using System;
+
+            internal delegate void MyDelegate(string key, string comment, TimeSpan timeout, out string lockToken);
+
+            public class Consumer
+            {
+                public void Method()
+                {
+                    var callback = new MyDelegate((string key, string comment, TimeSpan timeout, out string lockToken) =>
+                    {
+                        lockToken = "42";
+                    });
+                }
+            }
+            """;
+        await CreateProjectBuilder()
+              .WithSourceCode(SourceCode)
+              .ValidateAsync();
+    }
+
+    [Fact]
+    public async Task PrivateDelegateUsedInNewExpression_NoDiagnostic()
+    {
+        const string SourceCode = """
+            using System;
+
+            public class OuterClass
+            {
+                private delegate void TryAcquireLockDelegate(string key, string comment, TimeSpan timeout, out string lockToken);
+
+                public void Method()
+                {
+                    var callback = new TryAcquireLockDelegate((string key, string comment, TimeSpan timeout, out string lockToken) =>
+                    {
+                        lockToken = "test";
+                    });
+                }
+            }
+            """;
+        await CreateProjectBuilder()
+              .WithSourceCode(SourceCode)
+              .ValidateAsync();
+    }
+
+    [Fact]
+    public async Task UnusedInternalDelegate_Diagnostic()
+    {
+        const string SourceCode = """
+            using System;
+
+            internal delegate void [|UnusedDelegate|](string message);
+
+            public class Consumer
+            {
+                public void Method()
+                {
+                }
+            }
+            """;
+        await CreateProjectBuilder()
+              .WithSourceCode(SourceCode)
+              .ValidateAsync();
+    }
 }