Fix TryGetEntityName for custom entity names

Author: maca88

src/NHibernate/Async/Persister/Entity/IEntityPersister.cs

@@ -20,7 +20,6 @@
 using System.Collections.Generic;
 using NHibernate.Intercept;
 using NHibernate.Util;
-using System.Linq;
 
 namespace NHibernate.Persister.Entity
 {

src/NHibernate/Linq/Functions/ListIndexerGenerator.cs

@@ -12,20 +12,30 @@ namespace NHibernate.Linq.Functions
 {
 	internal class ListIndexerGenerator : BaseHqlGeneratorForMethod,IRuntimeMethodHqlGenerator
 	{
+		private static readonly HashSet<MethodInfo> _supportedMethods = new HashSet<MethodInfo>
+		{
+			ReflectHelper.GetMethodDefinition(() => Enumerable.ElementAt<object>(null, 0)),
+			ReflectHelper.GetMethodDefinition(() => Queryable.ElementAt<object>(null, 0))
+		};
+
 		public ListIndexerGenerator()
 		{
-			SupportedMethods = new[]
-			{
-				ReflectHelper.GetMethodDefinition(() => Enumerable.ElementAt<object>(null, 0)),
-				ReflectHelper.GetMethodDefinition(() => Queryable.ElementAt<object>(null, 0))
-			};
+			SupportedMethods = _supportedMethods;
 		}
 
 		public bool SupportsMethod(MethodInfo method)
 		{
-			return method != null &&
-			       method.Name == "get_Item" &&
-			       (method.IsMethodOf(typeof(IList)) || method.IsMethodOf(typeof(IList<>)));
+			return IsRuntimeMethodSupported(method);
+		}
+
+		public static bool IsMethodSupported(MethodInfo method)
+		{
+			if (method.IsGenericMethod)
+			{
+				method = method.GetGenericMethodDefinition();
+			}
+
+			return _supportedMethods.Contains(method) || IsRuntimeMethodSupported(method);
 		}
 
 		public IHqlGeneratorForMethod GetMethodGenerator(MethodInfo method)
@@ -40,5 +50,12 @@ public override HqlTreeNode BuildHql(MethodInfo method, Expression targetObject,
 
 			return treeBuilder.Index(collection, index);
 		}
+
+		private static bool IsRuntimeMethodSupported(MethodInfo method)
+		{
+			return method != null &&
+					method.Name == "get_Item" &&
+					(method.IsMethodOf(typeof(IList)) || method.IsMethodOf(typeof(IList<>)));
+		}
 	}
-}
+}

src/NHibernate/Linq/Visitors/NullableExpressionDetector.cs

@@ -163,8 +163,8 @@ private bool IsNullable(MemberExpression memberExpression, BinaryExpression equa
 			}
 
 			// We have to check the member mapping to determine if is nullable
-			var entityName = ExpressionsHelper.TryGetEntityName(_sessionFactory, memberExpression, out var memberPath);
-			if (entityName == null)
+			var entityName = ExpressionsHelper.TryGetEntityName(_sessionFactory, memberExpression, out var memberPath, out _);
+			if (entityName == null || memberPath == null)
 			{
 				return true; // Not mapped
 			}

src/NHibernate/Tuple/Entity/EntityMetamodel.cs

@@ -51,6 +51,7 @@ public class EntityMetamodel
 
 		private readonly Dictionary<string, int?> propertyIndexes = new Dictionary<string, int?>();
 		private readonly IDictionary<string, IType> _identifierPropertyTypes = new Dictionary<string, IType>();
+		private readonly IDictionary<string, IType> _propertyTypes = new Dictionary<string, IType>();
 		private readonly bool hasCollections;
 		private readonly bool hasMutableProperties;
 		private readonly bool hasLazyProperties;
@@ -418,15 +419,17 @@ private void MapPropertyToIndex(Mapping.Property prop, int i)
 
 		private void MapPropertyToIndex(string path, Mapping.Property prop, int i)
 		{
-			propertyIndexes[!string.IsNullOrEmpty(path) ? $"{path}.{prop.Name}" : prop.Name] = i;
+			var propPath = !string.IsNullOrEmpty(path) ? $"{path}.{prop.Name}" : prop.Name;
+			propertyIndexes[propPath] = i;
+			_propertyTypes[propPath] = prop.Type;
 			if (!(prop.Value is Mapping.Component comp))
 			{
 				return;
 			}
 
 			foreach (var subprop in comp.PropertyIterator)
 			{
-				MapPropertyToIndex(!string.IsNullOrEmpty(path) ? $"{path}.{prop.Name}" : prop.Name, subprop, i);
+				MapPropertyToIndex(propPath, subprop, i);
 			}
 		}
 
@@ -441,7 +444,7 @@ private void MapIdentifierPropertyTypes(string path, IType propertyType)
 			{
 				_identifierPropertyTypes[path] = propertyType;
 			}
-			
+
 			if (propertyType is IAbstractComponentType componentType)
 			{
 				for (var i = 0; i < componentType.PropertyNames.Length; i++)
@@ -572,6 +575,13 @@ internal IType GetIdentifierPropertyType(string memberPath)
 			return _identifierPropertyTypes.TryGetValue(memberPath, out var propertyType) ? propertyType : null;
 		}
 
+		internal IType GetPropertyType(string memberPath)
+		{
+			return _propertyTypes.TryGetValue(memberPath, out var propertyType)
+				? propertyType
+				: GetIdentifierPropertyType(memberPath);
+		}
+
 		public bool HasCollections
 		{
 			get { return hasCollections; }