Dart Function Returning Set<bool> Instead of bool - flutter

Question

I'm building a mobile client for a blog with a paid CMS that shows a number of articles all the time, plus a rotating article each week, and I've built a simple function to get the current week of the year and return a Boolean value if an article should be displayed this week:
bool displayArticle(StoredArticle article){
if (article.week < 0) {
return true;
}
DateTime now = DateTime.now();
DateTime janFirst = DateTime(now.year, 1, 1);
int weekNum = (now.difference(janFirst).inDays / 7).ceil();
if(article.week == weekNum || article.week == (weekNum - 1)){
return true;
}
return false;
}
I then use this function to filter a list of all the articles like so:
List<StoredArticle> articlessToDisplay = storedArticleObjs.where((article) => {
displayArticle(article)
}).toList();
This is all enclosed within a Stateful Widget.
However, using the function like this throws an error at the function call that The return type 'Set<bool>' isn't a 'bool', as required by the closure's context.
My first thought was that there was an issue with the displayArticle() function being a static member function to a stateful widget, but moving the function directly into the closure as follows did not impact the error.
List<StoredArticle> articlessToDisplay = storedArticleObjs.where((article) => {
if (article.week < 0) {
return true;
}
DateTime now = DateTime.now();
DateTime janFirst = DateTime(now.year, 1, 1);
int weekNum = (now.difference(janFirst).inDays / 7).ceil();
if(article.week == weekNum || article.week == (weekNum - 1)){
return true;
}
return false;
}).toList();
Next I thought it might be that the early return was confusing the inspector to belive it was returning multiple values, so I converted it to a single return function as follows, but that did nothing either.
bool displayArticle(StoredArticle article){
bool shouldDisplay = false;
if (article.week < 0) {
shouldDisplay = true;
}
DateTime now = DateTime.now();
DateTime janFirst = DateTime(now.year, 1, 1);
int weekNum = (now.difference(janFirst).inDays / 7).ceil();
if(article.week == weekNum || article.week == (weekNum - 1)){
shouldDisplay = true;
}
return shouldDisplay;
The only resources on similar issues have been referring to functions that return Future<T> instead of T. Putting aside the fact that my issue is with a Set<T> rather than a Future<T>, those errors have all been thrown by the return statement or the function definition rather than the function call.
I haven't been able to find any resources relating to this specific issue, though as I'm new to Flutter and Dart I suppose could be missing some specific terminology.
That being said, returning a set of the return type does not make any sense to me. Is this a quirk of implementation in a Stateful Widget?

Answer 1

The problem is that you have a few too many braces, and {"A"} is set-syntax in Dart.
You have:
storedArticleObjs.where((article) => {
displayArticle(article)
}).
Change that to:
storedArticleObjs.where((article) =>
displayArticle(article)
).
Note that the => function syntax doesn't use braces.
You could even probably write it more compactly using tear-offs like so:
storedArticleObjs.where(displayArticle).