Linq: add enum Equals and object Equals support

src/NHibernate.Test/Async/Linq/FunctionTests.cs

@@ -459,6 +459,33 @@ where item.Discount.Equals(-1)
 			await (ObjectDumper.WriteAsync(query));
 		}
 
+		[Test]
+		public async Task WhereEnumEqualAsync()
+		{
+			var query = from item in db.PatientRecords
+						where item.Gender.Equals(Gender.Female)
+						select item;
+
+			await (ObjectDumper.WriteAsync(query));
+
+			query = from item in db.PatientRecords
+					where item.Gender.Equals(item.Gender)
+					select item;
+
+			await (ObjectDumper.WriteAsync(query));
+		}
+
+
+		[Test]
+		public async Task WhereObjectEqualAsync()
+		{
+			var query = from item in db.PatientRecords
+						where ((object) item.Gender).Equals(Gender.Female)
+						select item;
+
+			await (ObjectDumper.WriteAsync(query));
+		}
+
 		[Test]
 		public async Task WhereEquatableEqualAsync()
 		{

src/NHibernate.Test/Linq/FunctionTests.cs

@@ -491,6 +491,33 @@ where item.Discount.Equals(-1)
 			ObjectDumper.Write(query);
 		}
 
+		[Test]
+		public void WhereEnumEqual()
+		{
+			var query = from item in db.PatientRecords
+						where item.Gender.Equals(Gender.Female)
+						select item;
+
+			ObjectDumper.Write(query);
+
+			query = from item in db.PatientRecords
+					where item.Gender.Equals(item.Gender)
+					select item;
+
+			ObjectDumper.Write(query);
+		}
+
+
+		[Test]
+		public void WhereObjectEqual()
+		{
+			var query = from item in db.PatientRecords
+						where ((object) item.Gender).Equals(Gender.Female)
+						select item;
+
+			ObjectDumper.Write(query);
+		}
+
 		[Test]
 		public void WhereEquatableEqual()
 		{

src/NHibernate/Linq/Functions/DefaultLinqToHqlGeneratorsRegistry.cs

@@ -111,12 +111,12 @@ public virtual bool TryGetGenerator(MemberInfo property, out IHqlGeneratorForPro
 
 		public virtual void RegisterGenerator(MethodInfo method, IHqlGeneratorForMethod generator)
 		{
-			registeredMethods.Add(method, generator);
+			registeredMethods[method] = generator;
 		}
 
 		public virtual void RegisterGenerator(MemberInfo property, IHqlGeneratorForProperty generator)
 		{
-			registeredProperties.Add(property, generator);
+			registeredProperties[property] = generator;
 		}
 
 		public void RegisterGenerator(IRuntimeMethodHqlGenerator generator)

src/NHibernate/Linq/Functions/EqualsGenerator.cs

@@ -58,7 +58,10 @@ public class EqualsGenerator : BaseHqlGeneratorForMethod
 			ReflectHelper.GetMethodDefinition<IEquatable<DateTime>>(x => x.Equals(default(DateTime))),
 			ReflectHelper.GetMethodDefinition<IEquatable<DateTimeOffset>>(x => x.Equals(default(DateTimeOffset))),
 			ReflectHelper.GetMethodDefinition<IEquatable<TimeSpan>>(x => x.Equals(default(TimeSpan))),
-			ReflectHelper.GetMethodDefinition<IEquatable<bool>>(x => x.Equals(default(bool)))
+			ReflectHelper.GetMethodDefinition<IEquatable<bool>>(x => x.Equals(default(bool))),
+			ReflectHelper.GetMethodDefinition<object>(x => x.Equals(default(object))), // this covers also Enum.Equals
+			ReflectHelper.GetMethodDefinition<IEquatable<object>>(x => x.Equals(default(object))),
+			ReflectHelper.GetMethodDefinition<IEquatable<Enum>>(x => x.Equals(default(Enum)))
 		};
 
 		public EqualsGenerator()
@@ -72,7 +75,10 @@ public override HqlTreeNode BuildHql(MethodInfo method, Expression targetObject,
 		{
 			Expression lhs = arguments.Count == 1 ? targetObject : arguments[0];
 			Expression rhs = arguments.Count == 1 ? arguments[0] : arguments[1];
-
+			if (lhs.Type.IsEnum)
+			{
+				return visitor.Visit(Expression.Equal(lhs, Expression.Convert(rhs, lhs.Type)));
+			}
 			return visitor.Visit(Expression.Equal(lhs, rhs));
 		}
 	}