Query: compilation error for complex query with SelectMany, optional navigation, subquery and string concat in projection

[maumar]

from l1 in ctx.LevelOne
from l2 in l1.OneToMany_Optional.Where(l => l.Id > 5).OrderByDescending(l => l.Name).DefaultIfEmpty()
select l1.Name + " " + l2 != null ? l2.Name : "NULL";

throws:

The operands for operator 'Add' do not match the parameters of method 'Concat'.
at System.Linq.Expressions.Expression.GetMethodBasedBinaryOperator(ExpressionType binaryType, Expression left, Expression right, MethodInfo method, Boolean liftToNull)
at System.Linq.Expressions.Expression.Add(Expression left, Expression right, MethodInfo method)
at System.Linq.Expressions.Expression.MakeBinary(ExpressionType binaryType, Expression left, Expression right, Boolean liftToNull, MethodInfo method, LambdaExpression conversion)
at System.Linq.Expressions.Expression.MakeBinary(ExpressionType binaryType, Expression left, Expression right, Boolean liftToNull, MethodInfo method)
at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.NavigationRewritingExpressionVisitor.VisitBinary(BinaryExpression node)
at System.Linq.Expressions.BinaryExpression.Accept(ExpressionVisitor visitor)
at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.NavigationRewritingExpressionVisitor.VisitBinary(BinaryExpression node)
at System.Linq.Expressions.BinaryExpression.Accept(ExpressionVisitor visitor)
at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.NavigationRewritingExpressionVisitor.VisitConditional(ConditionalExpression node)
at System.Linq.Expressions.ConditionalExpression.Accept(ExpressionVisitor visitor)
at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
at Remotion.Linq.Clauses.SelectClause.TransformExpressions(Func2 transformation) at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.ExpressionTransformingQueryModelVisitor1.VisitSelectClause(SelectClause selectClause, QueryModel queryModel)
at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.NavigationRewritingExpressionVisitor.NavigationRewritingQueryModelVisitor.VisitSelectClause(SelectClause selectClause, QueryModel queryModel)
at Remotion.Linq.Clauses.SelectClause.Accept(IQueryModelVisitor visitor, QueryModel queryModel)
at Remotion.Linq.QueryModelVisitorBase.VisitQueryModel(QueryModel queryModel)
at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.NavigationRewritingExpressionVisitor.Rewrite(QueryModel queryModel, QueryModel parentQueryModel)
at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.OptimizeQueryModel(QueryModel queryModel, ICollection1 includeResultOperators) at Microsoft.EntityFrameworkCore.Query.RelationalQueryModelVisitor.OptimizeQueryModel(QueryModel queryModel, ICollection1 includeResultOperators)
at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.CreateQueryExecutor[TResult](QueryModel queryModel)
at Microsoft.EntityFrameworkCore.Storage.Database.CompileQuery[TResult](QueryModel queryModel)
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileQueryCore[TResult](Expression query, INodeTypeProvider nodeTypeProvider, IDatabase database, ILogger logger, Type contextType)
at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass15_01.<Execute>b__0() at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQueryCore[TFunc](Object cacheKey, Func1 compiler)
at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func1 compiler) at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.Execute[TResult](Expression query) at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.Execute[TResult](Expression expression) at Remotion.Linq.QueryableBase1.GetEnumerator()
at System.Collections.Generic.List1..ctor(IEnumerable1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)

[maumar]

issue has been fixed in previous commit, test added in 75b17fd