UPDATE: I just double-checked and I see many errors like this: Unresolved variable someFieldName which are preceded by a RED round icon containing a '!'.

UPDATE: I just double-checked and I see many errors like this: Unresolved variable someFieldName which are preceded by a RED round icon containing a '!'. It certainly looks like an error because it is red and there are also other problems listed which are preceded by a yellow-background icon. So I think WebStorm thinks this is an error, not a warning.