Merge branch 'NH-3743'

Closes #398

Author: hazzik

src/NHibernate.Test/Linq/ByMethod/GroupByTests.cs

@@ -810,6 +810,19 @@ public void GroupByOrderByKeySelectToClass()
 		}
 
 
+		[Test(Description = "NH-3743")]
+		public void FetchBeforeGroupBy()
+		{
+			var result = db.Orders
+				.Fetch(x => x.Customer)
+				.GroupBy(x => x.Customer.CompanyName)
+				.OrderBy(x => x.Key)
+				.Select(x => new { P0 = x.Key, P1 = x.Count() })
+				.ToArray();
+
+			Assert.True(result.Any());
+		}
+
 		private class GroupInfo
 		{
 			public object Key { get; set; }

src/NHibernate/Linq/ReWriters/QueryReferenceExpressionFlattener.cs

@@ -4,6 +4,7 @@
 using Remotion.Linq;
 using Remotion.Linq.Clauses;
 using Remotion.Linq.Clauses.Expressions;
+using Remotion.Linq.EagerFetching;
 using Remotion.Linq.Parsing;
 
 namespace NHibernate.Linq.ReWriters
@@ -16,6 +17,8 @@ public class QueryReferenceExpressionFlattener : ExpressionTreeVisitor
 		{
 			typeof (CacheableResultOperator),
 			typeof (TimeoutResultOperator),
+			typeof (FetchOneRequest),
+			typeof (FetchManyRequest)
 		};
 
 		private QueryReferenceExpressionFlattener(QueryModel model)