Q:

Is this a bug in resharper?

I have me some Resharper squiggles here.

and they tell me that I have a possible multiple enumeration of IEnumerable going on. However you can see that this is not true. final is explicitly declared as a list ( List<Point2D> ) and pointTangents is declared previously as  List<PointVector2D> 
Any idea on why Resharper might be telling me this?
Edit Experiments To See If I can replicate with simpler code
As you can see below there are no squiggles and no warnings even though Bar is declared to take IEnumerable as arg.

A:

Looks a lot like RSRP-429474 False-positive warning for possible multiple enumeration :

I have this code:
List<string> duplicateLabelsList = allResourcesLookup.SelectMany(x => x).Select(x => x.LoaderOptions.Label).Duplicates<string, string>().ToList(); ; 
if (duplicateLabelsList.Any()) 
throw new DuplicateResourceLoaderLabelsException(duplicateLabelsList);

For both usages of duplicateLabelsList, I'm being warned about
  possible multiple enumeration, despite the fact I've called ToList and
  therefore there should be no multiple enumeration.

which (currently) has a Fix Version of 9.2, which (currently) isn't yet released.

