Fix parameters inside evaluatable expressions for Linq provider

Author: maca88

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

@@ -125,6 +125,23 @@ public async Task UsingValueTypeParameterTwiceAsync()
 				1));
 		}
 
+		[Test]
+		public async Task UsingParameterInEvaluatableExpressionAsync()
+		{
+			var value = "test";
+			await (db.Orders.Where(o => string.Format("{0}", value) != o.ShippedTo).ToListAsync());
+			await (db.Orders.Where(o => $"{value}_" != o.ShippedTo).ToListAsync());
+			await (db.Orders.Where(o => string.Copy(value) != o.ShippedTo).ToListAsync());
+
+			var guid = Guid.Parse("2D7E6EB3-BD08-4A40-A4E7-5150F7895821");
+			await (db.Orders.Where(o => o.ShippedTo.Contains($"VALUE {guid}")).ToListAsync());
+
+			var names = new[] {"name"};
+			await (db.Users.Where(x => names.Length == 0 || names.Contains(x.Name)).ToListAsync());
+			names = new string[] { };
+			await (db.Users.Where(x => names.Length == 0 || names.Contains(x.Name)).ToListAsync());
+		}
+
 		[Test]
 		public async Task UsingNegateValueTypeParameterTwiceAsync()
 		{

src/NHibernate.Test/Linq/ParameterTests.cs

@@ -113,6 +113,23 @@ public void UsingValueTypeParameterTwice()
 				1);
 		}
 
+		[Test]
+		public void UsingParameterInEvaluatableExpression()
+		{
+			var value = "test";
+			db.Orders.Where(o => string.Format("{0}", value) != o.ShippedTo).ToList();
+			db.Orders.Where(o => $"{value}_" != o.ShippedTo).ToList();
+			db.Orders.Where(o => string.Copy(value) != o.ShippedTo).ToList();
+
+			var guid = Guid.Parse("2D7E6EB3-BD08-4A40-A4E7-5150F7895821");
+			db.Orders.Where(o => o.ShippedTo.Contains($"VALUE {guid}")).ToList();
+
+			var names = new[] {"name"};
+			db.Users.Where(x => names.Length == 0 || names.Contains(x.Name)).ToList();
+			names = new string[] { };
+			db.Users.Where(x => names.Length == 0 || names.Contains(x.Name)).ToList();
+		}
+
 		[Test]
 		public void ValidateMixingTwoParametersCacheKeys()
 		{

src/NHibernate/Linq/Visitors/NhPartialEvaluatingExpressionVisitor.cs

@@ -77,7 +77,12 @@ public override Expression Visit(Expression expression)
 			if (expression == null)
 				return null;
 
-			if (expression.NodeType == ExpressionType.Lambda || !_partialEvaluationInfo.IsEvaluatableExpression(expression))
+			if (expression.NodeType == ExpressionType.Lambda || !_partialEvaluationInfo.IsEvaluatableExpression(expression) ||
+				#region NH additions
+				// Variables should be evaluated only when they are part of an evaluatable expression (e.g. o => string.Format("...", variable))
+				expression is UnaryExpression unaryExpression &&
+				ExpressionsHelper.IsVariable(unaryExpression.Operand, out _, out _))
+				#endregion
 				return base.Visit(expression);
 
 			Expression evaluatedExpression;
@@ -211,11 +216,6 @@ public override bool IsEvaluatableConstant(ConstantExpression node)
 			return base.IsEvaluatableConstant(node);
 		}
 
-		public override bool IsEvaluatableUnary(UnaryExpression node)
-		{
-			return !ExpressionsHelper.IsVariable(node.Operand, out _, out _);
-		}
-
 		public override bool IsEvaluatableMember(MemberExpression node)
 		{
 			if (node == null)