Review updates

Author: ajcvickers

src/MongoDB.Driver/IAggregateFluent.cs

@@ -15,7 +15,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Linq.Expressions;
 using System.Threading;
 using System.Threading.Tasks;
 using MongoDB.Bson;

src/MongoDB.Driver/PipelineStageDefinitionBuilder.cs

@@ -1478,10 +1478,9 @@ public static PipelineStageDefinition<TInput, TOutput> Search<TInput, TOutput>(
                     }
                     else
                     {
-                        outputSerializer = args.SerializerRegistry.GetSerializer<TOutput>();
-                        renderedSearchDefinition.Add("returnScope", new BsonDocument { { "path", returnScope.Render(args).FieldName } });
-                        searchOptions = searchOptions.Clone();
-                        searchOptions.ReturnStoredSource = true;
+                        var renderedField = returnScope.Render(args);
+                        outputSerializer = (IBsonSerializer<TOutput>)renderedField.ValueSerializer.GetItemSerializer();
+                        renderedSearchDefinition.Add("returnScope", new BsonDocument { { "path", renderedField.FieldName } });
                     }
 
                     renderedSearchDefinition.Add("highlight", () => searchOptions.Highlight.Render(args), searchOptions.Highlight != null);

src/MongoDB.Driver/Search/SearchDefinitionBuilder.cs

@@ -320,7 +320,7 @@ public SearchDefinition<TDocument> GeoWithin<TCoordinates>(
         /// </summary>
         /// <typeparam name="TField">The type of the ancestor documents.</typeparam>
         /// <param name="path">The path from the root to the ancestor.</param>
-        /// <param name="operator">The operator to execute at the root.</param>
+        /// <param name="operator">The operator to execute in the ancestor context specified by <paramref name="path"/>.</param>
         /// <param name="score">The score modifier.</param>
         /// <returns>A search definition for the ancestor.</returns>
         public SearchDefinition<TDocument> HasAncestor<TField>(
@@ -336,7 +336,7 @@ public SearchDefinition<TDocument> HasAncestor<TField>(
         /// </summary>
         /// <typeparam name="TField">The type of the ancestor documents.</typeparam>
         /// <param name="path">The path from the root to the ancestor.</param>
-        /// <param name="operator">The operator to execute at the root.</param>
+        /// <param name="operator">The operator to execute in the ancestor context specified by <paramref name="path"/>.</param>
         /// <param name="score">The score modifier.</param>
         /// <returns>A search definition for the ancestor.</returns>
         public SearchDefinition<TDocument> HasAncestor<TField>(

src/MongoDB.Driver/Search/SearchTrackingOptions.cs

@@ -38,7 +38,7 @@ public string SearchTerms
         /// Creates a clone of the options.
         /// </summary>
         /// <returns>A clone of the options.</returns>
-        public SearchTrackingOptions Clone() => new() { SearchTerms = SearchTerms };
+        public SearchTrackingOptions Clone() => new() { _searchTerms = SearchTerms };
 
         internal BsonDocument Render() =>
             new()