Enhance nullability check for "==" and "!=" operators for LINQ provider

src/NHibernate.DomainModel/Northwind/Entities/AnotherEntityRequired.cs

@@ -0,0 +1,33 @@
+using System.Collections.Generic;
+
+namespace NHibernate.DomainModel.Northwind.Entities
+{
+	public class AnotherEntityRequired
+	{
+		public virtual int Id { get; set; }
+
+		public virtual string Output { get; set; }
+
+		public virtual string Input { get; set; }
+
+		public virtual Address Address { get; set; }
+
+		public virtual AnotherEntityNullability InputNullability { get; set; }
+
+		public virtual string NullableOutput { get; set; }
+
+		public virtual AnotherEntityRequired NullableAnotherEntityRequired { get; set; }
+
+		public virtual int? NullableAnotherEntityRequiredId { get; set; }
+
+		public virtual ISet<AnotherEntity> RelatedItems { get; set; } = new HashSet<AnotherEntity>();
+
+		public virtual bool? NullableBool { get; set; }
+	}
+
+	public enum AnotherEntityNullability
+	{
+		False = 0,
+		True = 1
+	}
+}

src/NHibernate.DomainModel/Northwind/Entities/User.cs

@@ -26,6 +26,8 @@ public interface IUser
 		Role Role { get; set; }
 		EnumStoredAsString Enum1 { get; set; }
 		EnumStoredAsInt32 Enum2 { get; set; }
+		IUser CreatedBy { get; set; }
+		IUser ModifiedBy { get; set; }
 	}
 
 	public class User : IUser, IEntity
@@ -50,6 +52,10 @@ public class User : IUser, IEntity
 
 		public virtual EnumStoredAsInt32 Enum2 { get; set; }
 
+		public virtual IUser CreatedBy { get; set; }
+
+		public virtual IUser ModifiedBy { get; set; }
+
 		public virtual int NotMapped { get; set; }
 
 		public virtual Role NotMappedRole { get; set; }

src/NHibernate.DomainModel/Northwind/Mappings/AnotherEntityRequired.hbm.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="NHibernate.DomainModel.Northwind.Entities" assembly="NHibernate.DomainModel">
+  <class name="AnotherEntityRequired" table="AnotherEntity" mutable="false" schema-action="none">
+    <id name="Id">
+      <generator class="native" />
+    </id>
+    <property name="Output" not-null="true" />
+    <property name="Input" not-null="true" />
+    <property name="NullableOutput" formula="Output" lazy="true" />
+    <property name="InputNullability" formula="case when Input is not null then 0 else 1 end" lazy="true" />
+    <property name="NullableAnotherEntityRequiredId" formula="Id" lazy="true" />
+    <property name="NullableBool" formula="null" lazy="true" />
+    <component name="Address" insert="false" update="false" lazy="true">
+      <property name="Street" formula="Input" access="field.camelcase-underscore" />
+      <property name="City" formula="Output" access="field.camelcase-underscore" />
+    </component>
+    <many-to-one name="NullableAnotherEntityRequired" formula="Id" />
+    <set name="RelatedItems" lazy="true" inverse="true">
+      <key column="Id"/>
+      <one-to-many class="AnotherEntity"/>
+    </set>
+  </class>
+</hibernate-mapping>

src/NHibernate.DomainModel/Northwind/Mappings/User.hbm.xml

@@ -7,11 +7,19 @@
       <generator class="assigned" />
     </id>
 
-    <property name="Name" type="AnsiString" />
+    <property name="Name" type="AnsiString" not-null="true" />
     <property name="InvalidLoginAttempts" type="Int32" />
     <property name="RegisteredAt" type="DateTime" />
     <property name="LastLoginDate" type="DateTime" />
 
+    <many-to-one name="CreatedBy" class="User" not-null="true" lazy="false">
+      <column name="CreatedById" not-null="true" />
+    </many-to-one>
+
+    <many-to-one name="ModifiedBy" class="User" lazy="false">
+      <column name="ModifiedById" />
+    </many-to-one>
+
     <property name="Enum1" type="NHibernate.DomainModel.Northwind.Entities.EnumStoredAsStringType, NHibernate.DomainModel">
       <column name="Enum1" length="12" />
     </property>

src/NHibernate.Test/DbScripts/MsSql2012DialectLinqReadonlyCreateScript.sql

@@ -3774,6 +3774,8 @@ CREATE TABLE [dbo].[Users](
 	[Property1] [varchar](255) NULL,
 	[Property2] [varchar](255) NULL,
 	[OtherProperty1] [varchar](255) NULL,
+	[CreatedById] [int] NOT NULL,
+	[ModifiedById] [int] NULL
 PRIMARY KEY CLUSTERED 
 (
 	[UserId] ASC
@@ -3783,9 +3785,9 @@ GO
 SET ANSI_PADDING OFF
 GO
 SET IDENTITY_INSERT [dbo].[Users] ON
-INSERT [dbo].[Users] ([UserId], [Name], [InvalidLoginAttempts], [RegisteredAt], [LastLoginDate], [Enum1], [Enum2], [RoleId], [Property1], [Property2], [OtherProperty1]) VALUES (1, N'ayende', 4, CAST(0x00009D9800000000 AS DateTime), NULL, N'Medium', 1, 1, N'test1', N'test2', N'othertest1')
-INSERT [dbo].[Users] ([UserId], [Name], [InvalidLoginAttempts], [RegisteredAt], [LastLoginDate], [Enum1], [Enum2], [RoleId], [Property1], [Property2], [OtherProperty1]) VALUES (2, N'rahien', 5, CAST(0x00008D3E00000000 AS DateTime), NULL, N'Small', 0, 2, NULL, N'test2', NULL)
-INSERT [dbo].[Users] ([UserId], [Name], [InvalidLoginAttempts], [RegisteredAt], [LastLoginDate], [Enum1], [Enum2], [Features], [RoleId], [Property1], [Property2], [OtherProperty1]) VALUES (3, N'nhibernate', 6, CAST(0x00008EAC00000000 AS DateTime), CAST(0x00009D970110B41C AS DateTime), N'Medium', 0, 8, NULL, NULL, NULL, NULL)
+INSERT [dbo].[Users] ([UserId], [Name], [InvalidLoginAttempts], [RegisteredAt], [LastLoginDate], [Enum1], [Enum2], [RoleId], [Property1], [Property2], [OtherProperty1], [CreatedById], [ModifiedById]) VALUES (1, N'ayende', 4, CAST(0x00009D9800000000 AS DateTime), NULL, N'Medium', 1, 1, N'test1', N'test2', N'othertest1', 1, NULL)
+INSERT [dbo].[Users] ([UserId], [Name], [InvalidLoginAttempts], [RegisteredAt], [LastLoginDate], [Enum1], [Enum2], [RoleId], [Property1], [Property2], [OtherProperty1], [CreatedById], [ModifiedById]) VALUES (2, N'rahien', 5, CAST(0x00008D3E00000000 AS DateTime), NULL, N'Small', 0, 2, NULL, N'test2', NULL, 1, NULL)
+INSERT [dbo].[Users] ([UserId], [Name], [InvalidLoginAttempts], [RegisteredAt], [LastLoginDate], [Enum1], [Enum2], [Features], [RoleId], [Property1], [Property2], [OtherProperty1], [CreatedById], [ModifiedById]) VALUES (3, N'nhibernate', 6, CAST(0x00008EAC00000000 AS DateTime), CAST(0x00009D970110B41C AS DateTime), N'Medium', 0, 8, NULL, NULL, NULL, NULL, 1, NULL)
 SET IDENTITY_INSERT [dbo].[Users] OFF
 /****** Object:  Table [dbo].[TimeSheetUsers]    Script Date: 06/17/2010 13:08:54 ******/
 SET ANSI_NULLS ON

src/NHibernate.Test/Linq/LinqTestCase.cs

@@ -29,6 +29,7 @@ protected override string[] Mappings
 					"Northwind.Mappings.Supplier.hbm.xml",
 					"Northwind.Mappings.Territory.hbm.xml",
 					"Northwind.Mappings.AnotherEntity.hbm.xml",
+					"Northwind.Mappings.AnotherEntityRequired.hbm.xml",
 					"Northwind.Mappings.Role.hbm.xml",
 					"Northwind.Mappings.User.hbm.xml",
 					"Northwind.Mappings.TimeSheet.hbm.xml",
@@ -69,4 +70,4 @@ public static void AssertByIds<TEntity, TId>(IEnumerable<TEntity> entities, TId[
 			Assert.That(entities.Select(x => entityIdGetter(x)), Is.EquivalentTo(expectedIds));
 		}
 	}
-}
+}

src/NHibernate.Test/Linq/NorthwindDbCreator.cs

@@ -70,6 +70,11 @@ public static void CreateMiscTestData(ISession session)
 				}
 			};
 
+			foreach (var user in users)
+			{
+				user.CreatedBy = users[0];
+			}
+
 			var timesheets = new[]
 			{
 				new Timesheet
@@ -3707,4 +3712,4 @@ static void CreateOrderLines22(IStatelessSession session, IDictionary<int, Order
 			orderLine = new OrderLine { Order = ordersById[11077], Product = productsByName["Original Frankfurter grüne Soße"], UnitPrice = 13.00M, Quantity = 2, Discount = 0M }; session.Insert(orderLine);
 		}
 	}
-}
+}