[cDac] Fix failing cDac test on OSX

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/TargetFieldExtensions.cs

@@ -212,8 +212,12 @@ private static void AssertPrimitiveType<T>(Target.FieldInfo field, string fieldN
     [Conditional("DEBUG")]
     private static void AssertPointerType(Target.FieldInfo field, string fieldName)
     {
+        // Managed field signatures report IntPtr/UIntPtr as native ints, which the contract descriptor maps to
+        // "nint"/"nuint" (as distinct from raw pointer element types which map to "pointer").
+        // Accept those in addition to "pointer" so pointer-valued fields on managed types can be
+        // read via ReadPointer, which reads the value unsigned at full pointer width.
         Debug.Assert(
-            field.TypeName is null or "" or "pointer",
+            field.TypeName is null or "" or "pointer" or "nint" or "nuint",
             $"Type mismatch reading field '{fieldName}': declared as '{field.TypeName}', expected pointer");
     }
 

src/native/managed/cdac/tests/UnitTests/ObjectiveCMarshalTests.cs

@@ -71,12 +71,14 @@ private static TestPlaceholderTarget CreateObjectiveCMarshalTargetWithCWT(
         };
 
         // Register ObjcTrackingInformation type with a single pointer-sized _memory field at offset 0.
+        // The managed _memory field is an IntPtr, so the contract descriptor reports its type as "nint";
+        // model that here so the pointer read path is validated against the real descriptor type.
         var trackingInfoType = new Target.TypeInfo
         {
             Size = (uint)helpers.PointerSize,
             Fields = new Dictionary<string, Target.FieldInfo>
             {
-                ["_memory"] = new Target.FieldInfo { Offset = 0 }
+                ["_memory"] = new Target.FieldInfo { Offset = 0, TypeName = "nint" }
             }
         };