Avoid conflicting values of DkmEvaluationFlags (dotnet#55675)

src/ExpressionEvaluator/CSharp/Test/ResultProvider/ResultProviderTests.cs

@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Linq;
+using Microsoft.CodeAnalysis.ExpressionEvaluator;
+using Microsoft.VisualStudio.Debugger.Evaluation;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.CSharp.ExpressionEvaluator.UnitTests
+{
+    public class ResultProviderTests
+    {
+        [Fact]
+        public void DkmEvaluationFlagsConflict()
+        {
+            var values = Enum.GetValues(typeof(DkmEvaluationFlags)).Cast<DkmEvaluationFlags>().ToArray();
+            Assert.False(values.Contains(ResultProvider.NoResults));
+            Assert.False(values.Contains(ResultProvider.NotRoot));
+        }
+    }
+}

src/ExpressionEvaluator/Core/Source/ResultProvider/ResultProvider.cs

@@ -33,16 +33,24 @@ namespace Microsoft.CodeAnalysis.ExpressionEvaluator
     /// </remarks>
     public abstract class ResultProvider : IDkmClrResultProvider
     {
-        static ResultProvider()
-        {
-            FatalError.Handler = FailFast.OnFatalException;
-        }
+        // TODO: There is a potential that these values will conflict with debugger defined flags in future.
+        // It'd be better if we attached these flags to the DkmClrValue object via data items, however DkmClrValue is currently mutable
+        // and we can't clone it -- in some cases we might need to attach different flags in different code paths and it wouldn't be possible
+        // to do so due to mutability.
+        // See https://github.com/dotnet/roslyn/issues/55676.
+        internal const DkmEvaluationFlags NotRoot = (DkmEvaluationFlags)(1 << 30);
+        internal const DkmEvaluationFlags NoResults = (DkmEvaluationFlags)(1 << 31);
 
         // Fields should be removed and replaced with calls through DkmInspectionContext.
         // (see https://github.com/dotnet/roslyn/issues/6899).
         internal readonly IDkmClrFormatter2 Formatter2;
         internal readonly IDkmClrFullNameProvider FullNameProvider;
 
+        static ResultProvider()
+        {
+            FatalError.Handler = FailFast.OnFatalException;
+        }
+
         internal ResultProvider(IDkmClrFormatter2 formatter2, IDkmClrFullNameProvider fullNameProvider)
         {
             Formatter2 = formatter2;
@@ -101,9 +109,6 @@ DkmClrValue IDkmClrResultProvider.GetClrValue(DkmSuccessEvaluationResult evaluat
             }
         }
 
-        internal const DkmEvaluationFlags NotRoot = (DkmEvaluationFlags)0x20000;
-        internal const DkmEvaluationFlags NoResults = (DkmEvaluationFlags)0x40000;
-
         void IDkmClrResultProvider.GetChildren(DkmEvaluationResult evaluationResult, DkmWorkList workList, int initialRequestSize, DkmInspectionContext inspectionContext, DkmCompletionRoutine<DkmGetChildrenAsyncResult> completionRoutine)
         {
             var dataItem = evaluationResult.GetDataItem<EvalResultDataItem>();