Skip GetMemberValue for Nullable<T> error value

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

@@ -2152,5 +2152,36 @@ protected class C : B
             // Also need to check Access, StorageType, and TypeModifierFlags fields.
             // ...
         }
+
+        [WorkItem(1130978)]
+        [Fact]
+        public void NullableValue_Error()
+        {
+            var source =
+@"class C
+{
+    bool F() { return false; }
+    int? P
+    {
+        get
+        {
+            while (!F()) { }
+            return null;
+        }
+    }
+}";
+            DkmClrRuntimeInstance runtime = null;
+            GetMemberValueDelegate getMemberValue = (v, m) => (m == "P") ? CreateErrorValue(runtime.GetType(typeof(int?)), "Function evaluation timed out") : null;
+            runtime = new DkmClrRuntimeInstance(ReflectionUtilities.GetMscorlibAndSystemCore(GetAssembly(source)), getMemberValue: getMemberValue);
+            using (runtime.Load())
+            {
+                var type = runtime.GetType("C");
+                var value = CreateDkmClrValue(type.Instantiate(), type: type);
+                var memberValue = value.GetMemberValue("P", (int)System.Reflection.MemberTypes.Property, "C", DefaultInspectionContext);
+                var evalResult = FormatResult("o.P", memberValue);
+                Verify(evalResult,
+                    EvalFailedResult("o.P", "Function evaluation timed out", "int?", "o.P"));
+            }
+        }
     }
 }

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

@@ -143,6 +143,8 @@ internal string GetUnderlyingString(DkmClrValue value, DkmInspectionContext insp
 
         private string GetUnderlyingStringImpl(DkmClrValue value, DkmInspectionContext inspectionContext)
         {
+            Debug.Assert(!value.IsError());
+
             if (value.IsNull)
             {
                 return null;
@@ -167,22 +169,15 @@ private string GetUnderlyingStringImpl(DkmClrValue value, DkmInspectionContext i
             else if (!IsPredefinedType(lmrType))
             {
                 // Check for special cased non-primitives that have underlying strings
-                if (string.Equals(lmrType.FullName, "System.Data.SqlTypes.SqlString", StringComparison.Ordinal))
+                if (lmrType.IsType("System.Data.SqlTypes", "SqlString"))
                 {
                     var fieldValue = value.GetFieldValue(InternalWellKnownMemberNames.SqlStringValue, inspectionContext);
                     return fieldValue.HostObjectValue as string;
                 }
-
-                do
+                else if (lmrType.IsOrInheritsFrom("System.Xml.Linq", "XNode"))
                 {
-                    if (string.Equals(lmrType.FullName, "System.Xml.Linq.XNode", StringComparison.Ordinal))
-                    {
-                        return value.EvaluateToString(inspectionContext);
-                    }
-
-                    lmrType = lmrType.BaseType;
+                    return value.EvaluateToString(inspectionContext);
                 }
-                while (lmrType != null);
             }
 
             return null;

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

@@ -595,11 +595,26 @@ private static bool IsMscorlibType(this Type type, string @namespace, string nam
             return type.IsType(@namespace, name) /*&& type.Assembly.IsMscorlib()*/;
         }
 
-        private static bool IsType(this Type type, string @namespace, string name)
+        internal static bool IsOrInheritsFrom(this Type type, string @namespace, string name)
+        {
+            do
+            {
+                if (type.IsType(@namespace, name))
+                {
+                    return true;
+                }
+                type = type.BaseType;
+            }
+            while (type != null);
+            return false;
+        }
+
+        internal static bool IsType(this Type type, string @namespace, string name)
         {
             Debug.Assert((@namespace == null) || (@namespace.Length > 0)); // Type.Namespace is null not empty.
             Debug.Assert(!string.IsNullOrEmpty(name));
-            return (type.Namespace == @namespace) && (type.Name == name);
+            return string.Equals(type.Namespace, @namespace, StringComparison.Ordinal) &&
+                string.Equals(type.Name, name, StringComparison.Ordinal);
         }
     }
 }

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

@@ -297,8 +297,12 @@ private static string GetTypeName(DkmInspectionContext inspectionContext, DkmClr
             {
                 Debug.Assert(value.Type.GetProxyType() == null);
 
-                var nullableValue = value.GetNullableValue(inspectionContext);
-                if (nullableValue == null)
+                DkmClrValue nullableValue;
+                if (value.IsError())
+                {
+                    expansion = null;
+                }
+                else if ((nullableValue = value.GetNullableValue(inspectionContext)) == null)
                 {
                     Debug.Assert(declaredType.Equals(value.Type.GetLmrType()));
                     // No expansion of "null".

src/ExpressionEvaluator/Core/Test/ResultProvider/Debugger/Engine/DkmClrValue.cs

@@ -330,6 +330,11 @@ public DkmClrValue GetMemberValue(string MemberName, int MemberType, string Pare
                 throw new ArgumentNullException("inspectionContext");
             }
 
+            if (this.IsError())
+            {
+                throw new InvalidOperationException();
+            }
+
             var runtime = this.Type.RuntimeInstance;
 
             var memberValue = runtime.GetMemberValue(this, MemberName);