Fix casting to unmapped interface in LINQ

src/NHibernate.DomainModel/Northwind/Entities/Animal.cs

@@ -16,7 +16,12 @@ public class Animal
 		public virtual Animal FatherOrMother => Father ?? Mother;
 	}
 
-    public abstract class Reptile : Animal
+	public interface IReptile
+	{
+		EnumStoredAsString Enum1 { get; }
+	}
+
+    public abstract class Reptile : Animal, IReptile
     {
         public virtual double BodyTemperature { get; set; }
 

src/NHibernate.Test/Async/NHSpecificTest/GH2858/FixtureByCode.cs

@@ -0,0 +1,187 @@
+//------------------------------------------------------------------------------
+// <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.Collections.Generic;
+using System.Linq;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Mapping.ByCode;
+using NUnit.Framework;
+using NHibernate.Linq;
+
+namespace NHibernate.Test.NHSpecificTest.GH2858
+{
+	using System.Threading.Tasks;
+	[TestFixture]
+	public class ByCodeFixtureAsync : TestCaseMappingByCode
+	{
+		protected override HbmMapping GetMappings()
+		{
+			var mapper = new ModelMapper();
+
+			mapper.Class<Department>(
+				rc =>
+				{
+					rc.Id(x => x.Id, m => m.Generator(Generators.GuidComb));
+					rc.Property(x => x.Name);
+				});
+			mapper.Class<Project>(
+				rc =>
+				{
+					rc.Id(x => x.Id, m => m.Generator(Generators.GuidComb));
+					rc.Property(x => x.Name);
+					rc.ManyToOne(x => x.Department, m => m.Column("DepartmentId"));
+				});
+			mapper.Class<Issue>(
+				rc =>
+				{
+					rc.Id(x => x.Id, m => m.Generator(Generators.GuidComb));
+					rc.Property(x => x.Name);
+					rc.IdBag(
+						x => x.Departments,
+						m => m.Table("IssuesToDepartments"),
+						r => r.ManyToMany());
+					rc.ManyToOne(x => x.Project, m => m.Column("ProjectId"));
+				});
+			mapper.Class<TimeChunk>(
+				rc =>
+				{
+					rc.Id(x => x.Id, m => m.Generator(Generators.GuidComb));
+					rc.ManyToOne(x => x.Issue, m => m.Column("IssueId"));
+					rc.Property(x => x.Seconds);
+				});
+
+			return mapper.CompileMappingForAllExplicitlyAddedEntities();
+		}
+
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var deptA = new Department {Name = "A"};
+				session.Save(deptA);
+				var deptB = new Department {Name = "B"};
+				session.Save(deptB);
+				var deptC = new Department {Name = "C"};
+				session.Save(deptC);
+				var deptD = new Department {Name = "D"};
+				session.Save(deptD);
+				var deptE = new Department {Name = "E"};
+				session.Save(deptE);
+
+				var projectX = new Project {Name = "X", Department = deptA};
+				session.Save(projectX);
+				var projectY = new Project {Name = "Y", Department = deptC};
+				session.Save(projectY);
+				var projectZ = new Project {Name = "Z", Department = deptE};
+				session.Save(projectZ);
+
+				var issue1 = new Issue {Name = "TEST-1", Project = projectX,};
+				session.Save(issue1);
+				var issue2 = new Issue {Name = "TEST-2", Project = projectX, Departments = {deptA},};
+				session.Save(issue2);
+				var issue3 = new Issue {Name = "TEST-3", Project = projectX, Departments = {deptA, deptB},};
+				session.Save(issue3);
+				var issue4 = new Issue {Name = "TEST-4", Project = projectY,};
+				session.Save(issue4);
+				var issue5 = new Issue {Name = "TEST-5", Project = projectY, Departments = {deptD}};
+				session.Save(issue5);
+
+				session.Save(new TimeChunk {Issue = issue1});
+				session.Save(new TimeChunk {Issue = issue1});
+				session.Save(new TimeChunk {Issue = issue2});
+				session.Save(new TimeChunk {Issue = issue2});
+				session.Save(new TimeChunk {Issue = issue3});
+				session.Save(new TimeChunk {Issue = issue3});
+				session.Save(new TimeChunk {Issue = issue4});
+				session.Save(new TimeChunk {Issue = issue4});
+				session.Save(new TimeChunk {Issue = issue5});
+				session.Save(new TimeChunk {Issue = issue5});
+
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.Delete("from System.Object");
+				transaction.Commit();
+			}
+		}
+
+		[Test(Description = "GH-2857")]
+		public async Task GroupLevelQueryAsync()
+		{
+			using (var session = OpenSession())
+			{
+				var query = session.Query<ITimeChunk>()
+									.Select(x => new object[] {(object) x})
+									.GroupBy(g => new object[] {(Guid?) (((ITimeChunk) g[0]).Issue.Project.Id)}, v => (ITimeChunk) v[0])
+									.Select(r => new object[] {r.Key, r.Sum(t => (int?) t.Seconds)});
+
+				var results = await (query.ToListAsync());
+				Assert.That(results, Has.Count.EqualTo(2));
+			}
+		}
+
+		[Test(Description = "GH-2857")]
+		public async Task GroupLevelQuery_SimplifiedAsync()
+		{
+			using (var session = OpenSession())
+			{
+				var query = session.Query<ITimeChunk>()
+									.Select(x => new object[] {x})
+									.GroupBy(g => new object[] {((ITimeChunk) g[0]).Issue.Project.Id}, v => (ITimeChunk) v[0])
+									.Select(r => new object[] {r.Key, r.Sum(t => (int?) t.Seconds)});
+
+				var results = await (query.ToListAsync());
+				Assert.That(results, Has.Count.EqualTo(2));
+			}
+		}
+
+		[Test]
+		public async Task SelectManySubQueryWithCoalesceAsync()
+		{
+			using (var session = OpenSession())
+			{
+				var usedDepartments = session.Query<ITimeChunk>()
+											.SelectMany(x => ((IEnumerable<object>) x.Issue.Departments).DefaultIfEmpty().Select(d => (object) ((Guid?) ((Guid?) (((IDepartment) d).Id) ?? x.Issue.Project.Department.Id))))
+											.Where(id => id != null)
+											.Select(id => (Guid?) id);
+
+				var result = session.Query<IDepartment>()
+									.Where(d => usedDepartments.Contains(d.Id))
+									.Select(d => new {d.Id, d.Name});
+
+				Assert.That(await (result.ToListAsync()), Has.Count.EqualTo(4));
+			}
+		}
+
+		[Test]
+		public async Task SelectManySubQueryWithCoalesce_SimplifiedAsync()
+		{
+			using (var session = OpenSession())
+			{
+				var usedDepartments = session.Query<ITimeChunk>()
+											.SelectMany(x => ((IEnumerable<object>) x.Issue.Departments).DefaultIfEmpty().Select(d => (Guid?) ((IDepartment) d).Id ?? x.Issue.Project.Department.Id));
+
+				var result = session.Query<IDepartment>()
+									.Where(d => usedDepartments.Contains(d.Id))
+									.Select(d => new {d.Id, d.Name});
+
+				Assert.That(await (result.ToListAsync()), Has.Count.EqualTo(4));
+			}
+		}
+	}
+}

src/NHibernate.Test/Linq/ParameterTypeLocatorTests.cs

@@ -97,6 +97,16 @@ public void SubClassStringEnumTest()
 			);
 		}
 
+		[Test]
+		public void SubClassAsUnamppedInterfaceStringEnumTest()
+		{
+			AssertResults(
+				new Dictionary<string, Predicate<IType>> {{"0", o => o is EnumStoredAsStringType}},
+				db.Animals.Where(o => o.Children.OfType<IReptile>().Any(r => r.Enum1 == EnumStoredAsString.Unspecified)),
+				db.Animals.Where(o => o.Children.OfType<IReptile>().Any(r => EnumStoredAsString.Unspecified == r.Enum1))
+				);
+		}
+
 		[Test]
 		public void EqualsMethodStringTest()
 		{

src/NHibernate.Test/Linq/TryGetMappedTests.cs

@@ -124,7 +124,7 @@ public void SelfCastNotMappedTest()
 				false,
 				typeof(A).FullName,
 				null,
-				o => o is SerializableType serializableType && serializableType.ReturnedClass == typeof(object));
+				o => o is EntityType entityType && entityType.ReturnedClass == typeof(A));
 		}
 
 		[Test]

src/NHibernate.Test/NHSpecificTest/GH2858/Entity.cs

@@ -0,0 +1,61 @@
+using System;
+using System.Collections.Generic;
+
+namespace NHibernate.Test.NHSpecificTest.GH2858
+{
+	public interface IDepartment
+	{
+		Guid Id { get; set; }
+		string Name { get; set; }
+	}
+
+	public class Department : IDepartment
+	{
+		public virtual Guid Id { get; set; }
+		public virtual string Name { get; set; }
+	}
+
+	public interface IProject
+	{
+		Guid Id { get; set; }
+		string Name { get; set; }
+		Department Department { get; set; }
+	}
+
+	public class Project : IProject
+	{
+		public virtual Guid Id { get; set; }
+		public virtual string Name { get; set; }
+		public virtual Department Department { get; set; }
+	}
+
+	public interface IIssue
+	{
+		Guid Id { get; set; }
+		string Name { get; set; }
+		Project Project { get; set; }
+		IList<Department> Departments { get; set; }
+	}
+
+	public class Issue : IIssue
+	{
+		public virtual Guid Id { get; set; }
+		public virtual string Name { get; set; }
+		public virtual IList<Department> Departments { get; set; } = new List<Department>();
+		public virtual Project Project { get; set; }
+	}
+
+	public interface ITimeChunk
+	{
+		Guid Id { get; set; }
+		Issue Issue { get; set; }
+		int Seconds { get; set; }
+	}
+
+	public class TimeChunk : ITimeChunk
+	{
+		public virtual Guid Id { get; set; }
+		public virtual Issue Issue { get; set; }
+		public virtual int Seconds { get; set; }
+	}
+}