[SR-6239] Cannot convert value to generic value

[swift-ci]

Previous ID	SR-6239
Radar	None
Original Reporter	robdashnash (JIRA User)
Type	Bug

Environment

macOS 10.13 Xcode Version 9.0.1 (9A1004) Swift 4 iMac (Retina 5K, 27-inch, 2017)

Additional Detail from JIRA

| | | |------------------|-----------------| |Votes | 0 | |Component/s | Compiler | |Labels | Bug, TypeChecker | |Assignee | @slavapestov | |Priority | Medium | md5: eb4d433304e40a585fd63cfdd5b2135d

Issue Description:

class Event: NSManagedObject {}

class FetchedResultsController<Entity: NSManagedObject>: NSObject {}

final class EventsFetchedResultsController: FetchedResultsController<Event> {}

struct Bubble<Entity: NSManagedObject> {
  let fetchedResultsController: FetchedResultsController<Entity>
}

var bubble: Bubble<Event> = Bubble<Event>(fetchedResultsController: EventsFetchedResultsController()) // Error: Cannot convert value of type 'EventsFetchedResultsController' to expected argument type 'FetchedResultsController<_>

[belkadan]

cc @xedin, @rudkx

[slavapestov]

Objective-C generics allow you to cast between different instantiations of the same generic type, but the cast warnings don't know this. I have some dupes of this and am planning on looking at it later.

[swift-ci]

Comment by Rob Nash (JIRA)

What does AM / PM mean in your comments ? : - 0