using MongoDB.Bson;
using MongoDB.Driver;
using MongoDB.Driver.Linq;

var settings = new MongoClientSettings { LinqProvider = LinqProvider.V3 };
var client = new MongoClient(settings);
var db = client.GetDatabase("test");
var coll = db.GetCollection<C>("coll");

var query = coll.AsQueryable().GroupBy(k => k.Id, (k, g) => new { Value = g.Count(x => x.NullableBool.HasValue && x.NullableBool.Value)});
Console.WriteLine(query);

record C(ObjectId Id, bool? NullableBool);

System.NotSupportedException: Serializer for System.Nullable`1[System.Boolean] must implement IBsonDocumentSerializer to be used with LINQ.
   at MongoDB.Driver.Linq.Linq3Implementation.Misc.DocumentSerializerHelper.GetFieldInfo(IBsonSerializer serializer, String memberName) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Misc/DocumentSerializerHelper.cs:line 27
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.MemberExpressionToAggregationExpressionTranslator.Translate(TranslationContext context, MemberExpression expression) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/MemberExpressionToAggregationExpressionTranslator.cs:line 64
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.ExpressionToAggregationExpressionTranslator.Translate(TranslationContext context, Expression expression) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/ExpressionToAggregationExpressionTranslator.cs:line 67
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.BinaryExpressionToAggregationExpressionTranslator.Translate(TranslationContext context, BinaryExpression expression) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/BinaryExpressionToAggregationExpressionTranslator.cs:line 49
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.ExpressionToAggregationExpressionTranslator.Translate(TranslationContext context, Expression expression) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/ExpressionToAggregationExpressionTranslator.cs:line 54
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.ExpressionToAggregationExpressionTranslator.TranslateLambdaBody(TranslationContext context, LambdaExpression lambdaExpression, IBsonSerializer parameterSerializer, Boolean asRoot) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/ExpressionToAggregationExpressionTranslator.cs:line 115
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.MethodTranslators.CountMethodToAggregationExpressionTranslator.Translate(TranslationContext context, MethodCallExpression expression) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/MethodTranslators/CountMethodToAggregationExpressionTranslator.cs:line 69
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.MethodCallExpressionToAggregationExpressionTranslator.Translate(TranslationContext context, MethodCallExpression expression) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/MethodCallExpressionToAggregationExpressionTranslator.cs:line 82
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.ExpressionToAggregationExpressionTranslator.Translate(TranslationContext context, Expression expression) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/ExpressionToAggregationExpressionTranslator.cs:line 61
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.NewExpressionToAggregationExpressionTranslator.Translate(TranslationContext context, NewExpression expression) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/NewExpressionToAggregationExpressionTranslator.cs:line 51
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToAggregationExpressionTranslators.ExpressionToAggregationExpressionTranslator.Translate(TranslationContext context, Expression expression) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/ExpressionToAggregationExpressionTranslator.cs:line 71
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToPipelineTranslators.GroupByMethodToPipelineTranslator.TranslateResultSelector(TranslationContext context, AstPipeline pipeline, ReadOnlyCollection`1 arguments, IBsonSerializer keySerializer, IBsonSerializer elementSerializer) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToPipelineTranslators/GroupByMethodToPipelineTranslator.cs:line 149
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToPipelineTranslators.GroupByMethodToPipelineTranslator.Translate(TranslationContext context, MethodCallExpression expression) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToPipelineTranslators/GroupByMethodToPipelineTranslator.cs:line 89
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToPipelineTranslators.ExpressionToPipelineTranslator.Translate(TranslationContext context, Expression expression) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToPipelineTranslators/ExpressionToPipelineTranslator.cs:line 40
   at MongoDB.Driver.Linq.Linq3Implementation.Translators.ExpressionToExecutableQueryTranslators.ExpressionToExecutableQueryTranslator.Translate[TDocument,TOutput](MongoQueryProvider`1 provider, Expression expression) in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToExecutableQueryTranslators/ExpressionToExecutableQueryTranslator.cs:line 34
   at MongoDB.Driver.Linq.Linq3Implementation.MongoQuery`2.ToString() in /Users/james/Dropbox/code/mongodb/mongo-csharp-driver/src/MongoDB.Driver/Linq/Linq3Implementation/MongoQuery.cs:line 108