Fix casting properties from object type in LINQ

src/NHibernate.Test/Async/NHSpecificTest/GH3005/FixtureByCode.cs

@@ -0,0 +1,71 @@
+//------------------------------------------------------------------------------
+// <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;
+using System.Linq;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Mapping.ByCode;
+using NUnit.Framework;
+using NHibernate.Linq;
+
+namespace NHibernate.Test.NHSpecificTest.GH3005
+{
+	using System.Threading.Tasks;
+	[TestFixture]
+	public class ByCodeFixtureAsync : TestCaseMappingByCode
+	{
+		protected override HbmMapping GetMappings()
+		{
+			var mapper = new ModelMapper();
+			mapper.Class<Entity>(rc =>
+			{
+				rc.Id(x => x.Id, m => m.Generator(Generators.GuidComb));
+				rc.Property(x => x.Name);
+				rc.Property(x => x.Duration);
+			});
+
+			return mapper.CompileMappingForAllExplicitlyAddedEntities();
+		}
+
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var e1 = new Entity { Name = "Bob", Duration = TimeSpan.FromMinutes(1) };
+				session.Save(e1);
+
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from System.Object").ExecuteUpdate();
+
+				transaction.Commit();
+			}
+		}
+
+		[Test]
+		public async Task CanCastFromObjectAsync()
+		{
+			using (var session = OpenSession())
+			{
+				var result = await (session.Query<Entity>().Select(x => (TimeSpan)(object)x.Duration).FirstOrDefaultAsync());
+
+				Assert.That(result, Is.EqualTo(TimeSpan.FromMinutes(1)));
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH3005/Entity.cs

@@ -0,0 +1,11 @@
+using System;
+
+namespace NHibernate.Test.NHSpecificTest.GH3005
+{
+	class Entity
+	{
+		public virtual Guid Id { get; set; }
+		public virtual string Name { get; set; }
+		public virtual TimeSpan Duration { get; set; }
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH3005/FixtureByCode.cs

@@ -0,0 +1,59 @@
+using System;
+using System.Linq;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Mapping.ByCode;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH3005
+{
+	[TestFixture]
+	public class ByCodeFixture : TestCaseMappingByCode
+	{
+		protected override HbmMapping GetMappings()
+		{
+			var mapper = new ModelMapper();
+			mapper.Class<Entity>(rc =>
+			{
+				rc.Id(x => x.Id, m => m.Generator(Generators.GuidComb));
+				rc.Property(x => x.Name);
+				rc.Property(x => x.Duration);
+			});
+
+			return mapper.CompileMappingForAllExplicitlyAddedEntities();
+		}
+
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var e1 = new Entity { Name = "Bob", Duration = TimeSpan.FromMinutes(1) };
+				session.Save(e1);
+
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from System.Object").ExecuteUpdate();
+
+				transaction.Commit();
+			}
+		}
+
+		[Test]
+		public void CanCastFromObject()
+		{
+			using (var session = OpenSession())
+			{
+				var result = session.Query<Entity>().Select(x => (TimeSpan)(object)x.Duration).FirstOrDefault();
+
+				Assert.That(result, Is.EqualTo(TimeSpan.FromMinutes(1)));
+			}
+		}
+	}
+}

src/NHibernate/Linq/Visitors/HqlGeneratorExpressionVisitor.cs

@@ -245,9 +245,11 @@ protected HqlTreeNode VisitNhAverage(NhAverageExpression expression)
 			// otherwise the result may be incorrect. In SQL Server avg always returns int
 			// when the argument is int.
 			var hqlExpression = VisitExpression(expression.Expression).AsExpression();
-			hqlExpression = IsCastRequired(expression.Expression, expression.Type, out _)
-				? (HqlExpression) _hqlTreeBuilder.Cast(hqlExpression, expression.Type)
-				: _hqlTreeBuilder.TransparentCast(hqlExpression, expression.Type);
+			hqlExpression = IsCastRequired(expression.Expression, expression.Type, out var needTransparentCast)
+				? _hqlTreeBuilder.Cast(hqlExpression, expression.Type)
+				: needTransparentCast
+					? _hqlTreeBuilder.TransparentCast(hqlExpression, expression.Type)
+					: hqlExpression;
 
 			// In Oracle the avg function can return a number with up to 40 digits which cannot be retrieved from the data reader due to the lack of such
 			// numeric type in .NET. In order to avoid that we have to add a cast to trim the number so that it can be converted into a .NET numeric type.
@@ -532,10 +534,10 @@ protected HqlTreeNode VisitUnaryExpression(UnaryExpression expression)
 						castType = expression.Type;
 					}
 
-					return IsCastRequired(expression.Operand, castType, out var existType) && castable
+					return IsCastRequired(expression.Operand, castType, out var needTransparentCast) && castable
 						? _hqlTreeBuilder.Cast(VisitExpression(expression.Operand).AsExpression(), castType)
 						// Make a transparent cast when an IType exists, so that it can be used to retrieve the value from the data reader
-						: existType && HqlIdent.SupportsType(castType)
+						: needTransparentCast 
 							? _hqlTreeBuilder.TransparentCast(VisitExpression(expression.Operand).AsExpression(), castType)
 							: VisitExpression(expression.Operand);
 			}
@@ -643,12 +645,16 @@ protected HqlTreeNode VisitNewArrayExpression(NewArrayExpression expression)
 			return _hqlTreeBuilder.ExpressionSubTreeHolder(expressionSubTree);
 		}
 
-		private bool IsCastRequired(Expression expression, System.Type toType, out bool existType)
+		private bool IsCastRequired(Expression expression, System.Type toType, out bool needTransparentCast)
 		{
-			existType = false;
-			return toType != typeof(object) &&
-			       expression.Type.UnwrapIfNullable() != toType.UnwrapIfNullable() &&
-			       IsCastRequired(ExpressionsHelper.GetType(_parameters, expression), TypeFactory.GetDefaultTypeFor(toType), out existType);
+			needTransparentCast =
+				toType != typeof(object)
+				&& expression.Type != typeof(object)
+				&& expression.Type != toType
+				&& HqlIdent.SupportsType(toType)
+				&& expression.Type.UnwrapIfNullable() != toType.UnwrapIfNullable();
+
+			return needTransparentCast && IsCastRequired(ExpressionsHelper.GetType(_parameters, expression), TypeFactory.GetDefaultTypeFor(toType), out needTransparentCast);
 		}
 
 		private bool IsCastRequired(IType type, IType toType, out bool existType)