From 6ee61faee5ca89a473e00526c3cf5aac31ea6f85 Mon Sep 17 00:00:00 2001
From: maca88 <bostjan.markezic@siol.net>
Date: Sun, 24 Jan 2021 16:40:35 +0100
Subject: [PATCH] Fix enum detection when using OfType for Linq provider

---
 .../Northwind/Entities/Animal.cs                    |  2 ++
 .../Northwind/Mappings/Animal.hbm.xml               |  5 ++++-
 .../Linq/ParameterTypeLocatorTests.cs               | 13 +++++++++++++
 src/NHibernate/Util/ExpressionsHelper.cs            |  7 +++++++
 4 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/src/NHibernate.DomainModel/Northwind/Entities/Animal.cs b/src/NHibernate.DomainModel/Northwind/Entities/Animal.cs
index 21fac97d4ae..384e6e760d5 100644
--- a/src/NHibernate.DomainModel/Northwind/Entities/Animal.cs
+++ b/src/NHibernate.DomainModel/Northwind/Entities/Animal.cs
@@ -19,6 +19,8 @@ public class Animal
     public abstract class Reptile : Animal
     {
         public virtual double BodyTemperature { get; set; }
+
+		public virtual EnumStoredAsString Enum1 { get; set; }
     }
 
     public class Lizard : Reptile { }
diff --git a/src/NHibernate.DomainModel/Northwind/Mappings/Animal.hbm.xml b/src/NHibernate.DomainModel/Northwind/Mappings/Animal.hbm.xml
index 12e6bcd1e23..7cf325b54aa 100644
--- a/src/NHibernate.DomainModel/Northwind/Mappings/Animal.hbm.xml
+++ b/src/NHibernate.DomainModel/Northwind/Mappings/Animal.hbm.xml
@@ -19,6 +19,9 @@
     <joined-subclass name="Reptile">
       <key column="Animal"/>
       <property name="BodyTemperature"/>
+      <property name="Enum1" type="NHibernate.DomainModel.Northwind.Entities.EnumStoredAsStringType, NHibernate.DomainModel"
+                formula="('Unspecified')" insert="false" update="false">
+      </property>
 
       <joined-subclass name="Lizard">
         <key column="Reptile"/>
@@ -39,4 +42,4 @@
       </joined-subclass>
     </joined-subclass>
   </class>
-</hibernate-mapping>
\ No newline at end of file
+</hibernate-mapping>
diff --git a/src/NHibernate.Test/Linq/ParameterTypeLocatorTests.cs b/src/NHibernate.Test/Linq/ParameterTypeLocatorTests.cs
index 48cc2e14048..50be6a9e470 100644
--- a/src/NHibernate.Test/Linq/ParameterTypeLocatorTests.cs
+++ b/src/NHibernate.Test/Linq/ParameterTypeLocatorTests.cs
@@ -84,6 +84,19 @@ public void EqualStringEnumTest()
 			);
 		}
 
+		[Test]
+		public void SubClassStringEnumTest()
+		{
+			AssertResults(
+				new Dictionary<string, Predicate<IType>>
+				{
+					{"0", o => o is EnumStoredAsStringType}
+				},
+				db.Animals.Where(o => o.Children.OfType<Reptile>().Any(r => r.Enum1 == EnumStoredAsString.Unspecified)),
+				db.Animals.Where(o => o.Children.OfType<Reptile>().Any(r => EnumStoredAsString.Unspecified == r.Enum1))
+			);
+		}
+
 		[Test]
 		public void EqualsMethodStringTest()
 		{
diff --git a/src/NHibernate/Util/ExpressionsHelper.cs b/src/NHibernate/Util/ExpressionsHelper.cs
index 6f9f290aa72..a5874cf94f0 100644
--- a/src/NHibernate/Util/ExpressionsHelper.cs
+++ b/src/NHibernate/Util/ExpressionsHelper.cs
@@ -16,6 +16,7 @@
 using NHibernate.Type;
 using Remotion.Linq.Clauses;
 using Remotion.Linq.Clauses.Expressions;
+using Remotion.Linq.Clauses.ResultOperators;
 using Remotion.Linq.Parsing;
 
 namespace NHibernate.Util
@@ -716,6 +717,12 @@ protected override Expression VisitQuerySourceReference(QuerySourceReferenceExpr
 
 			protected override Expression VisitSubQuery(SubQueryExpression expression)
 			{
+				var ofTypeOperator = expression.QueryModel.ResultOperators.OfType<OfTypeResultOperator>().FirstOrDefault();
+				if (ofTypeOperator != null)
+				{
+					_convertType = ofTypeOperator.SearchedItemType;
+				}
+
 				base.Visit(expression.QueryModel.SelectClause.Selector);
 				return expression;
 			}