fixup! Replace IObjectsFactory with IServiceProvider interface

Throw explicitly on an error case.

Author: fredericDelaporte

src/NHibernate/Util/ServiceProviderExtensions.cs

@@ -1,17 +1,28 @@
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+using NHibernate.Bytecode;
 
 namespace NHibernate.Util
 {
 	internal static class ServiceProviderExtensions
 	{
+		/// <summary>
+		/// Get a service, throwing if it cannot be resolved.
+		/// </summary>
+		/// <param name="serviceProvider">The service provider.</param>
+		/// <param name="serviceType">The service interface, base class or concrete implementation class.</param>
+		/// <returns>The service instance.</returns>
+		/// <exception cref="ArgumentNullException">thrown if <paramref name="serviceType"/> is <see langword="null" />.</exception>
+		/// <exception cref="HibernateServiceProviderException">thrown if the service cannot be resolved.</exception>
 		public static object GetInstance(this IServiceProvider serviceProvider, System.Type serviceType)
 		{
-			// 6.0 TODO throw a meaningful exception instead of using the Activator
-			return serviceProvider.GetService(serviceType) ?? Activator.CreateInstance(serviceType);
+			if (serviceType == null)
+				throw new ArgumentNullException(nameof(serviceType));
+			var service = serviceProvider.GetService(serviceType);
+
+			if (service == null)
+				throw new HibernateServiceProviderException(
+					$"Unable to resolve an instance for {serviceType.AssemblyQualifiedName}");
+			return service;
 		}
 	}
 }