Nested select operation require instantiation of local variable Follow

Hi, I have the following construct:

list<list<[enummember<MyEnum>, node<MyConcept>]>> result = 
   this.someCollection
      .select({\itemOuter => itemOuter.subCollection
         .select({\itemInner => [this.mapIndexToMyEnum[itemInner.index], itemInner.someLookupOfMyConceptInstance()]; 
                 }).toList; 
              }).toList;

This does not compile, with the following error message:
`: Type mismatch: cannot convert from IListSequence<IListSequence<Tuples._2<SEnumerationLiteral,SNode>>> to List<List<Tuples._2<SEnumerationLiteral,SNode>>> (line: 90)`

However, when I introduce a local variable for the result of the inner `select` operation, like so (basically hitting Ctrl+Alt+V at the inner "toList" operation), it does compile:

list<list<[enummember<MyEnum>, node<MyConcept>]>> listOuterResult = 
   this.someCollection 
      .select({\itemOuter => list<[enummember<MyEnum>, node<MyConcept>]> listInnerResult = itemOuter.subCollection 
         .select({\itemInner => [this.mapIndexToMyEnum[itemInner.index], itemInner.someLookupOfMyConceptInstance()]; 
                 }).toList; 
                 return listInnerResult;
              }).toList;

This is really annoying since it makes the code less readable by quite a bit. Any idea if this is a bug?