Handle null initializer for array creation operation

src/NetAnalyzers/Core/Microsoft.NetCore.Analyzers/Runtime/AvoidConstArrays.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the MIT license.  See License.txt in the project root for license information.
+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the MIT license.  See License.txt in the project root for license information.
 
 using System.Linq;
 using System.Collections.Generic;
@@ -103,7 +103,8 @@ public override void Initialize(AnalysisContext context)
                     }
 
                     // Must be literal array
-                    if (arrayCreationOperation.Initializer.ElementValues.Any(x => x is not ILiteralOperation))
+                    if (arrayCreationOperation.Initializer is { } initializer &&
+                        initializer.ElementValues.Any(x => x is not ILiteralOperation))
                     {
                         return;
                     }

src/NetAnalyzers/UnitTests/Microsoft.NetCore.Analyzers/Runtime/AvoidConstArraysTests.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the MIT license.  See License.txt in the project root for license information.
+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the MIT license.  See License.txt in the project root for license information.
 
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CSharp;
@@ -804,5 +804,30 @@ private void M(string eventName, string msg)
                 LanguageVersion = LanguageVersion.CSharp8
             }.RunAsync();
         }
+
+        [Fact, WorkItem(6686, "https://github.com/dotnet/roslyn-analyzers/issues/6686")]
+        public Task ArrayWithoutInitializer_Diagnostic()
+        {
+            var source = @"using System.Collections.Generic;
+
+public class MyClass
+{
+    public List<object> Cases => new() { {|CA1861:new object[0]|} };
+}";
+            var fixedSource = @"using System.Collections.Generic;
+
+public class MyClass
+{
+    public List<object> Cases => new() { item };
+
+    private static readonly object[] item = new object[0];
+}";
+            return new VerifyCS.Test
+            {
+                TestCode = source,
+                FixedCode = fixedSource,
+                LanguageVersion = LanguageVersion.CSharp10
+            }.RunAsync();
+        }
     }
 }