Fix referencing nullable entity in correlated subquery

src/NHibernate.Test/Async/NHSpecificTest/GH3306NullableEntityCorrelatedSubquery/Fixture.cs

@@ -0,0 +1,69 @@
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by AsyncGenerator.
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+
+
+using System.Linq;
+using NUnit.Framework;
+using NHibernate.Linq;
+
+namespace NHibernate.Test.NHSpecificTest.GH3306NullableEntityCorrelatedSubquery
+{
+	using System.Threading.Tasks;
+	[TestFixture]
+	public class FixtureAsync : BugTestCase
+	{
+		private const string NAME_JOE = "Joe";
+		private const string NAME_ALLEN = "Allen";
+
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var tx = session.BeginTransaction())
+			{
+				var joe = new Customer { Name = NAME_JOE };
+				session.Save(joe);
+
+				var allen = new Customer { Name = NAME_ALLEN };
+				session.Save(allen);
+
+				var joeInvoice0 = new Invoice { Customer = joe, Number = 0 };
+				session.Save(joeInvoice0);
+
+				var allenInvoice1 = new Invoice { Customer = allen, Number = 1 };
+				session.Save(allenInvoice1);
+
+				tx.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var tx = session.BeginTransaction())
+			{
+				session.Delete("from Invoice");
+				session.Delete("from Customer");
+				tx.Commit();
+			}
+		}
+
+		[Test]
+		public async Task NullableEntityInCorrelatedSubqueryAsync()
+		{
+			using (var s = OpenSession())
+			{
+				var customers = s.Query<Customer>().Where(c => c.Name == NAME_JOE);
+				var results = await (s.Query<Invoice>()
+					.Where(i => customers.Any(c => c.Invoices.Any(ci => ci.Customer == i.Customer))).ToListAsync());
+
+				Assert.That(results.Count, Is.EqualTo(1));
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH3306NullableEntityCorrelatedSubquery/Fixture.cs

@@ -0,0 +1,57 @@
+using System.Linq;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH3306NullableEntityCorrelatedSubquery
+{
+	[TestFixture]
+	public class Fixture : BugTestCase
+	{
+		private const string NAME_JOE = "Joe";
+		private const string NAME_ALLEN = "Allen";
+
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var tx = session.BeginTransaction())
+			{
+				var joe = new Customer { Name = NAME_JOE };
+				session.Save(joe);
+
+				var allen = new Customer { Name = NAME_ALLEN };
+				session.Save(allen);
+
+				var joeInvoice0 = new Invoice { Customer = joe, Number = 0 };
+				session.Save(joeInvoice0);
+
+				var allenInvoice1 = new Invoice { Customer = allen, Number = 1 };
+				session.Save(allenInvoice1);
+
+				tx.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var tx = session.BeginTransaction())
+			{
+				session.Delete("from Invoice");
+				session.Delete("from Customer");
+				tx.Commit();
+			}
+		}
+
+		[Test]
+		public void NullableEntityInCorrelatedSubquery()
+		{
+			using (var s = OpenSession())
+			{
+				var customers = s.Query<Customer>().Where(c => c.Name == NAME_JOE);
+				var results = s.Query<Invoice>()
+					.Where(i => customers.Any(c => c.Invoices.Any(ci => ci.Customer == i.Customer))).ToList();
+
+				Assert.That(results.Count, Is.EqualTo(1));
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH3306NullableEntityCorrelatedSubquery/Mappings.hbm.xml

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
+									 assembly="NHibernate.Test"
+									 namespace="NHibernate.Test.NHSpecificTest.GH3306NullableEntityCorrelatedSubquery">
+
+  <class name="Customer" >
+    <id name="ID" type="Int32">
+      <generator class="native" />
+    </id>
+    <property name="Name" type="String" />
+
+    <set name="Invoices" inverse="true" >
+      <key column="CustomerID"/>
+      <one-to-many class="Invoice"/>
+    </set>
+  </class>
+
+  <class name="Invoice">
+    <id name="ID" type="Int32">
+      <generator class="native" />
+    </id>
+
+    <property name="Number" type="Int32" column="`Number`" />
+    <many-to-one name="Customer" not-found="ignore" column="CustomerID" class="Customer" />
+  </class>
+
+</hibernate-mapping>

src/NHibernate.Test/NHSpecificTest/GH3306NullableEntityCorrelatedSubquery/Model.cs

@@ -0,0 +1,18 @@
+using System.Collections.Generic;
+
+namespace NHibernate.Test.NHSpecificTest.GH3306NullableEntityCorrelatedSubquery
+{
+	public class Customer
+	{
+		public virtual int ID { get; protected set; }
+		public virtual ISet<Invoice> Invoices { get; set; }
+		public virtual string Name { get; set; }
+	}
+
+	public class Invoice
+	{
+		public virtual int ID { get; protected set; }
+		public virtual Customer Customer { get; set; }
+		public virtual int Number { get; set; }
+	}
+}

src/NHibernate/Hql/Ast/ANTLR/Tree/DotNode.cs

@@ -389,7 +389,7 @@ private void DereferenceEntity(EntityType entityType, bool implicitJoin, string
 			bool joinIsNeeded;
 
 			//For nullable entity comparisons we always need to add join (like not constrained one-to-one or not-found ignore associations)
-			bool comparisonWithNullableEntity = entityType.IsNullable && Walker.IsComparativeExpressionClause;
+			bool comparisonWithNullableEntity = entityType.IsNullable && Walker.IsComparativeExpressionClause && !IsCorrelatedSubselect;
 
 			if ( IsDotNode( parent ) ) 
 			{