LINQ projection of nullable enum with list fails

[gliljas]

Projecting a value based on a nullable enum works fine, but if a contained list is also included, thereby requiring a List Transformer, a cast exception is thrown:

NHibernate.Exceptions.GenericADOException : Could not execute query[SQL: SQL not available]
  ----> System.InvalidCastException : Specified cast is not valid.
at NHibernate.Impl.SessionImpl.List(IQueryExpression queryExpression, QueryParameters queryParameters, IList results, Object filterConnection) in D:\BuildAgent\work\30546188361a242\src\NHibernate\Impl\SessionImpl.cs:line 563
   at NHibernate.Impl.SessionImpl.List(IQueryExpression queryExpression, QueryParameters queryParameters, IList results) in D:\BuildAgent\work\30546188361a242\src\NHibernate\Impl\SessionImpl.cs:line 523
   at NHibernate.Impl.AbstractSessionImpl.List[T](IQueryExpression query, QueryParameters parameters) in D:\BuildAgent\work\30546188361a242\src\NHibernate\Impl\AbstractSessionImpl.cs:line 182
   at NHibernate.Impl.AbstractQueryImpl2.List[T]() in D:\BuildAgent\work\30546188361a242\src\NHibernate\Impl\AbstractQueryImpl2.cs:line 111
   at NHibernate.Linq.DefaultQueryProvider.ExecuteList[TResult](Expression expression) in D:\BuildAgent\work\30546188361a242\src\NHibernate\Linq\DefaultQueryProvider.cs:line 111
   at NHibernate.Linq.NhQueryable`1.System.Collections.Generic.IEnumerable<T>.GetEnumerator() in D:\BuildAgent\work\30546188361a242\src\NHibernate\Linq\NhQueryable.cs:line 65
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at NHibernate.Test.Linq.EnumTests.CanProjectWithListTransformation() in D:\BuildAgent\work\30546188361a242\src\NHibernate.Test\Linq\EnumTests.cs:line 199
--InvalidCastException
   at lambda_method(Closure , IGrouping`2 )
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at lambda_method(Closure , IEnumerable`1 )
   at NHibernate.Linq.ResultTransformer.TransformList(IList collection) in D:\BuildAgent\work\30546188361a242\src\NHibernate\Linq\ResultTransformer.cs:line 36
   at NHibernate.Loader.Hql.QueryLoader.GetResultList(IList results, IResultTransformer resultTransformer) in D:\BuildAgent\work\30546188361a242\src\NHibernate\Loader\Hql\QueryLoader.cs:line 343
   at NHibernate.Loader.Loader.ListIgnoreQueryCache(ISessionImplementor session, QueryParameters queryParameters) in D:\BuildAgent\work\30546188361a242\src\NHibernate\Loader\Loader.cs:line 1837
   at NHibernate.Loader.Loader.List(ISessionImplementor session, QueryParameters queryParameters, ISet`1 querySpaces) in D:\BuildAgent\work\30546188361a242\src\NHibernate\Loader\Loader.cs:line 1827
   at NHibernate.Loader.Hql.QueryLoader.List(ISessionImplementor session, QueryParameters queryParameters) in D:\BuildAgent\work\30546188361a242\src\NHibernate\Loader\Hql\QueryLoader.cs:line 325
   at NHibernate.Hql.Ast.ANTLR.QueryTranslatorImpl.List(ISessionImplementor session, QueryParameters queryParameters) in D:\BuildAgent\work\30546188361a242\src\NHibernate\Hql\Ast\ANTLR\QueryTranslatorImpl.cs:line 131
   at NHibernate.Engine.Query.HQLQueryPlan.PerformList(QueryParameters queryParameters, ISessionImplementor session, IList results) in D:\BuildAgent\work\30546188361a242\src\NHibernate\Engine\Query\HQLQueryPlan.cs:line 115
   at NHibernate.Impl.SessionImpl.List(IQueryExpression queryExpression, QueryParameters queryParameters, IList results, Object filterConnection) in D:\BuildAgent\work\30546188361a242\src\NHibernate\Impl\SessionImpl.cs:line 553

[fredericDelaporte]

From which version is this a regression? 5.2.x?

Regression introduced by 5.3 as the discussion in the PR allows to infer.

[fredericDelaporte]

Fixed by #2703.