Fix InvalidCastException when casting a field of a type different than Enum's underlying type

Fixes #1121

Author: hazzik

src/NHibernate.Test/Async/NHSpecificTest/GH1121/Fixture.cs

@@ -0,0 +1,87 @@
+//------------------------------------------------------------------------------
+// <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.GH1121
+{
+	using System.Threading.Tasks;
+	[TestFixture]
+	public class FixtureAsync : BugTestCase
+	{
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.Save(new Entity
+				{
+					Name = "Bob",
+					Color = 2
+				});
+
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from Entity").ExecuteUpdate();
+
+				transaction.Commit();
+			}
+		}
+
+		[Test]
+		public async Task CanCastToDifferentTypeAsync()
+		{
+			using (var session = OpenSession())
+			using (session.BeginTransaction())
+			{
+				var result = await ((
+					from e in session.Query<Entity>()
+					where e.Name == "Bob"
+					select new
+					{
+						e.Id,
+						MyColor = (int) e.Color
+					}).ToListAsync());
+
+				Assert.That(result, Has.Count.EqualTo(1));
+				Assert.That(result[0].MyColor, Is.EqualTo(2));
+			}
+		}
+		
+		[Test]
+		public async Task CanCastEnumWithDifferentUnderlyingTypeAsync()
+		{
+			using (var session = OpenSession())
+			using (session.BeginTransaction())
+			{
+				var result = await ((
+					from e in session.Query<Entity>()
+					where e.Name == "Bob"
+					select new
+					{
+						e.Id,
+						MyColor = (Colors) e.Color
+					}).ToListAsync());
+
+				Assert.That(result, Has.Count.EqualTo(1));
+				Assert.That(result[0].MyColor, Is.EqualTo(Colors.Green));
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH1121/Entity.cs

@@ -0,0 +1,17 @@
+using System;
+
+namespace NHibernate.Test.NHSpecificTest.GH1121
+{
+	class Entity
+	{
+		public virtual Guid Id { get; set; }
+		public virtual string Name { get; set; }
+		public virtual long Color { get; set; }
+	}
+	public enum Colors
+	{
+		Red = 1,
+		Green = 2,
+		Blue = 3,
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH1121/Fixture.cs

@@ -0,0 +1,75 @@
+using System.Linq;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH1121
+{
+	[TestFixture]
+	public class Fixture : BugTestCase
+	{
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.Save(new Entity
+				{
+					Name = "Bob",
+					Color = 2
+				});
+
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from Entity").ExecuteUpdate();
+
+				transaction.Commit();
+			}
+		}
+
+		[Test]
+		public void CanCastToDifferentType()
+		{
+			using (var session = OpenSession())
+			using (session.BeginTransaction())
+			{
+				var result = (
+					from e in session.Query<Entity>()
+					where e.Name == "Bob"
+					select new
+					{
+						e.Id,
+						MyColor = (int) e.Color
+					}).ToList();
+
+				Assert.That(result, Has.Count.EqualTo(1));
+				Assert.That(result[0].MyColor, Is.EqualTo(2));
+			}
+		}
+		
+		[Test]
+		public void CanCastEnumWithDifferentUnderlyingType()
+		{
+			using (var session = OpenSession())
+			using (session.BeginTransaction())
+			{
+				var result = (
+					from e in session.Query<Entity>()
+					where e.Name == "Bob"
+					select new
+					{
+						e.Id,
+						MyColor = (Colors) e.Color
+					}).ToList();
+
+				Assert.That(result, Has.Count.EqualTo(1));
+				Assert.That(result[0].MyColor, Is.EqualTo(Colors.Green));
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH1121/Mappings.hbm.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="NHibernate.Test"
+                   namespace="NHibernate.Test.NHSpecificTest.GH1121">
+
+  <class name="Entity">
+    <id name="Id" generator="guid.comb"/>
+    <property name="Name"/>
+    <property name="Color"/>
+  </class>
+</hibernate-mapping>

src/NHibernate/Linq/Visitors/SelectClauseVisitor.cs

@@ -2,8 +2,10 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Linq.Expressions;
+using System.Reflection;
 using NHibernate.Hql.Ast;
 using NHibernate.Linq.Expressions;
+using NHibernate.Util;
 using Remotion.Linq.Parsing;
 
 namespace NHibernate.Linq.Visitors
@@ -83,12 +85,29 @@ public override Expression Visit(Expression expression)
 				// Pure HQL evaluation
 				_hqlTreeNodes.Add(_hqlVisitor.Visit(expression).AsExpression());
 
-				return Expression.Convert(Expression.ArrayIndex(_inputParameter, Expression.Constant(_iColumn++)), expression.Type);
+				return Convert(Expression.ArrayIndex(_inputParameter, Expression.Constant(_iColumn++)), expression.Type);
 			}
 
 			// Can't handle this node with HQL.  Just recurse down, and emit the expression
 			return base.Visit(expression);
 		}
+
+		private static readonly MethodInfo ConvertChangeType =
+			ReflectHelper.GetMethod(() => System.Convert.ChangeType(default(object), default(System.Type)));
+
+		private static Expression Convert(Expression expression, System.Type type)
+		{
+			//#1121
+			if (type.IsEnum)
+			{
+				expression = Expression.Call(
+					ConvertChangeType,
+					expression,
+					Expression.Constant(Enum.GetUnderlyingType(type)));
+			}
+
+			return Expression.Convert(expression, type);
+		}
 	}
 
 	// Since v5