Improve LINQ Contains subquery parameter detection

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

@@ -15,6 +15,7 @@
 using System.Linq;
 using System.Linq.Expressions;
 using log4net.Core;
+using NHibernate.Dialect;
 using NHibernate.Engine.Query;
 using NHibernate.Linq;
 using NHibernate.DomainModel.Northwind.Entities;
@@ -647,6 +648,9 @@ where sheet.Users.Contains(user)
 		[Test]
 		public async Task TimesheetsWithEnumerableContainsOnSelectAsync()
 		{
+			if (Dialect is MsSqlCeDialect)
+				Assert.Ignore("Dialect is not supported");
+
 			var value = (EnumStoredAsInt32) 1000;
 			var query = await ((from sheet in db.Timesheets
 			             where sheet.Users.Select(x => x.NullableEnum2 ?? value).Contains(value)
@@ -655,6 +659,24 @@ where sheet.Users.Select(x => x.NullableEnum2 ?? value).Contains(value)
 			Assert.That(query.Count, Is.EqualTo(1));
 		}
 
+		[Test]
+		public async Task ContainsSubqueryWithCoalesceStringEnumSelectAsync()
+		{
+			if (Dialect is MsSqlCeDialect || Dialect is SQLiteDialect)
+				Assert.Ignore("Dialect is not supported");
+
+			var results =
+				await (db.Timesheets.Where(
+					  o =>
+						  o.Users
+						   .Where(u => u.Id != 0.MappedAs(NHibernateUtil.Int32))
+						   .Select(u => u.Name == u.Name ? u.Enum1 : u.NullableEnum1.Value)
+						   .Contains(EnumStoredAsString.Small))
+				  .ToListAsync());
+
+			Assert.That(results.Count, Is.EqualTo(1));
+		}
+
 		[Test]
 		public async Task SearchOnObjectTypeWithExtensionMethodAsync()
 		{

src/NHibernate.Test/Linq/WhereTests.cs

@@ -5,6 +5,7 @@
 using System.Linq;
 using System.Linq.Expressions;
 using log4net.Core;
+using NHibernate.Dialect;
 using NHibernate.Engine.Query;
 using NHibernate.Linq;
 using NHibernate.DomainModel.Northwind.Entities;
@@ -648,6 +649,9 @@ where sheet.Users.Contains(user)
 		[Test]
 		public void TimesheetsWithEnumerableContainsOnSelect()
 		{
+			if (Dialect is MsSqlCeDialect)
+				Assert.Ignore("Dialect is not supported");
+
 			var value = (EnumStoredAsInt32) 1000;
 			var query = (from sheet in db.Timesheets
 			             where sheet.Users.Select(x => x.NullableEnum2 ?? value).Contains(value)
@@ -656,6 +660,24 @@ where sheet.Users.Select(x => x.NullableEnum2 ?? value).Contains(value)
 			Assert.That(query.Count, Is.EqualTo(1));
 		}
 
+		[Test]
+		public void ContainsSubqueryWithCoalesceStringEnumSelect()
+		{
+			if (Dialect is MsSqlCeDialect || Dialect is SQLiteDialect)
+				Assert.Ignore("Dialect is not supported");
+
+			var results =
+				db.Timesheets.Where(
+					  o =>
+						  o.Users
+						   .Where(u => u.Id != 0.MappedAs(NHibernateUtil.Int32))
+						   .Select(u => u.Name == u.Name ? u.Enum1 : u.NullableEnum1.Value)
+						   .Contains(EnumStoredAsString.Small))
+				  .ToList();
+
+			Assert.That(results.Count, Is.EqualTo(1));
+		}
+
 		[Test]
 		public void SearchOnObjectTypeWithExtensionMethod()
 		{

src/NHibernate/Linq/Visitors/ParameterTypeLocator.cs

@@ -288,42 +288,35 @@ protected override Expression VisitConstant(ConstantExpression node)
 
 			protected override Expression VisitSubQuery(SubQueryExpression node)
 			{
-				if (!TryLinkContainsMethod(node.QueryModel))
-				{
-					node.QueryModel.TransformExpressions(Visit);
-				}
+				TryLinkContainsMethod(node.QueryModel);
+				node.QueryModel.TransformExpressions(Visit);
 
 				return node;
 			}
 
-			private bool TryLinkContainsMethod(QueryModel queryModel)
+			private void TryLinkContainsMethod(QueryModel queryModel)
 			{
 				// ReLinq wraps all ResultOperatorExpressionNodeBase into a SubQueryExpression. In case of
 				// ContainsResultOperator where the constant expression is dislocated from the related expression,
 				// we have to manually link the related expressions.
 				if (queryModel.ResultOperators.Count != 1 ||
-					!(queryModel.ResultOperators[0] is ContainsResultOperator containsOperator) ||
-					!(queryModel.SelectClause.Selector is QuerySourceReferenceExpression querySourceReference) ||
-					!(querySourceReference.ReferencedQuerySource is MainFromClause mainFromClause))
+					!(queryModel.ResultOperators[0] is ContainsResultOperator containsOperator))
 				{
-					return false;
+					return;
 				}
 
-				var left = UnwrapUnary(Visit(mainFromClause.FromExpression));
+				Expression selector =
+					queryModel.SelectClause.Selector is QuerySourceReferenceExpression { ReferencedQuerySource: MainFromClause mainFromClause }
+						? mainFromClause.FromExpression
+						: queryModel.SelectClause.Selector;
+
+				var left = UnwrapUnary(Visit(selector));
 				var right = UnwrapUnary(Visit(containsOperator.Item));
-				// The constant is on the left side (e.g. db.Users.Where(o => users.Contains(o)))
-				// The constant is on the right side (e.g. db.Customers.Where(o => o.Orders.Contains(item)))
-				if (left.NodeType != ExpressionType.Constant && right.NodeType != ExpressionType.Constant)
-				{
-					return false;
-				}
 
 				// Copy all found MemberExpressions to the constant expression
 				// (e.g. values.Contains(o.Name != o.Name2 ? o.Enum1 : o.Enum2) -> copy o.Enum1 and o.Enum2)
 				AddRelatedExpression(null, left, right);
 				AddRelatedExpression(null, right, left);
-
-				return true;
 			}
 
 			private void VisitAssign(Expression leftNode, Expression rightNode)