Cannot do Distinct().Count() on complex anonymous type projection

[alfeg]

Following test fails (in DistinctTests.cs)

[Test]
public void DistinctCountOnComplexAnonymousTypeProjection()
{
	var result = db.Orders
	               .Select(x => new { x.ShippingDate, x.OrderDate })
	               .Distinct()
	               .Count();
	Assert.That(result, Is.EqualTo(774));
}

To do a count over distinct we need to wrap into sub select

select
    distinct order0_.ShippedDate as col_0_0_,
             order0_.OrderDate as col_1_0_
from
    Orders order0_ ;

select count(*) as col_0_0
from ( select
           distinct order0_.ShippedDate as col_0_0_,
                    order0_.OrderDate as col_1_0_
       from
           Orders order0_ ) as q

But my knowledge of the Expressions is not that good to do a proper wrap in the TransformCountExpression

Error message:

System.NotSupportedException : New
   at NHibernate.Linq.Visitors.HqlGeneratorExpressionVisitor.VisitExpression(Expression expression) in B:\source\nhibernate-core\src\NHibernate\Linq\Visitors\HqlGeneratorExpressionVisitor.cs:line 150
   at NHibernate.Linq.Visitors.HqlGeneratorExpressionVisitor.VisitNhDistinct(NhDistinctExpression expression) in B:\source\nhibernate-core\src\NHibernate\Linq\Visitors\HqlGeneratorExpressionVisitor.cs:line 299
   at NHibernate.Linq.Visitors.HqlGeneratorExpressionVisitor.VisitExpression(Expression expression) in B:\source\nhibernate-core\src\NHibernate\Linq\Visitors\HqlGeneratorExpressionVisitor.cs:line 138
   at NHibernate.Linq.Visitors.HqlGeneratorExpressionVisitor.VisitNhCount(NhCountExpression expression) in B:\source\nhibernate-core\src\NHibernate\Linq\Visitors\HqlGeneratorExpressionVisitor.cs:line 271
   at NHibernate.Linq.Visitors.HqlGeneratorExpressionVisitor.VisitExpression(Expression expression) in B:\source\nhibernate-core\src\NHibernate\Linq\Visitors\HqlGeneratorExpressionVisitor.cs:line 136
   at NHibernate.Linq.Visitors.HqlGeneratorExpressionVisitor.Visit(Expression expression) in B:\source\nhibernate-core\src\NHibernate\Linq\Visitors\HqlGeneratorExpressionVisitor.cs:line 45
   at NHibernate.Linq.Visitors.SelectClauseVisitor.Visit(Expression expression) in B:\source\nhibernate-core\src\NHibernate\Linq\Visitors\SelectClauseVisitor.cs:line 88
   at NHibernate.Linq.Visitors.SelectClauseVisitor.VisitSelector(Expression expression, Boolean isSubQuery) in B:\source\nhibernate-core\src\NHibernate\Linq\Visitors\SelectClauseVisitor.cs:line 60
   at NHibernate.Linq.Visitors.QueryModelVisitor.GetSelectClause(Expression selectClause) in B:\source\nhibernate-core\src\NHibernate\Linq\Visitors\QueryModelVisitor.cs:line 481
   at NHibernate.Linq.Visitors.QueryModelVisitor.VisitSelectClause(SelectClause selectClause, QueryModel queryModel) in B:\source\nhibernate-core\src\NHibernate\Linq\Visitors\QueryModelVisitor.cs:line 472
   at Remotion.Linq.Clauses.SelectClause.Accept(IQueryModelVisitor visitor, QueryModel queryModel)
   at Remotion.Linq.QueryModelVisitorBase.VisitQueryModel(QueryModel queryModel)
   at NHibernate.Linq.Visitors.QueryModelVisitor.Visit() in B:\source\nhibernate-core\src\NHibernate\Linq\Visitors\QueryModelVisitor.cs:line 172
   at NHibernate.Linq.Visitors.QueryModelVisitor.GenerateHqlQuery(QueryModel queryModel, VisitorParameters parameters, Boolean root, Nullable`1 rootReturnType) in B:\source\nhibernate-core\src\NHibernate\Linq\Visitors\QueryModelVisitor.cs:line 108
   at NHibernate.Linq.NhLinqExpression.Translate(ISessionFactoryImplementor sessionFactory, Boolean filter) in B:\source\nhibernate-core\src\NHibernate\Linq\NhLinqExpression.cs:line 97
   at NHibernate.Hql.Ast.ANTLR.ASTQueryTranslatorFactory.CreateQueryTranslators(IQueryExpression queryExpression, String collectionRole, Boolean shallow, IDictionary`2 filters, ISessionFactoryImplementor factory) in B:\source\nhibernate-core\src\NHibernate\Hql\Ast\ANTLR\ASTQueryTranslatorFactory.cs:line 21
   at NHibernate.Engine.Query.QueryExpressionPlan.CreateTranslators(IQueryExpression queryExpression, String collectionRole, Boolean shallow, IDictionary`2 enabledFilters, ISessionFactoryImplementor factory) in B:\source\nhibernate-core\src\NHibernate\Engine\Query\QueryExpressionPlan.cs:line 37
   at NHibernate.Engine.Query.QueryExpressionPlan..ctor(IQueryExpression queryExpression, Boolean shallow, IDictionary`2 enabledFilters, ISessionFactoryImplementor factory) in B:\source\nhibernate-core\src\NHibernate\Engine\Query\QueryExpressionPlan.cs:line 19
   at NHibernate.Engine.Query.QueryPlanCache.GetHQLQueryPlan(IQueryExpression queryExpression, Boolean shallow, IDictionary`2 enabledFilters) in B:\source\nhibernate-core\src\NHibernate\Engine\Query\QueryPlanCache.cs:line 76
   at NHibernate.Impl.AbstractSessionImpl.GetHQLQueryPlan(IQueryExpression queryExpression, Boolean shallow) in B:\source\nhibernate-core\src\NHibernate\Impl\AbstractSessionImpl.cs:line 611
   at NHibernate.Impl.AbstractSessionImpl.CreateQuery(IQueryExpression queryExpression) in B:\source\nhibernate-core\src\NHibernate\Impl\AbstractSessionImpl.cs:line 579
   at NHibernate.Linq.DefaultQueryProvider.PrepareQuery(Expression expression, IQuery& query) in B:\source\nhibernate-core\src\NHibernate\Linq\DefaultQueryProvider.cs:line 208
   at NHibernate.Linq.DefaultQueryProvider.Execute(Expression expression) in B:\source\nhibernate-core\src\NHibernate\Linq\DefaultQueryProvider.cs:line 94
   at NHibernate.Linq.DefaultQueryProvider.Execute[TResult](Expression expression) in B:\source\nhibernate-core\src\NHibernate\Linq\DefaultQueryProvider.cs:line 101
   at NHibernate.Test.Linq.ByMethod.DistinctTests.DistinctCountOnComplexAnonymousTypeProjection() in B:\source\nhibernate-core\src\NHibernate.Test\Linq\ByMethod\DistinctTests.cs:line 74
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
   at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)