Holly Borla comments

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                                            Holly Borla

Assertion failed: ((!replacement || replacement->hasError() || gp->isParameterPack() == replacement->is<PackType>()) && "replacement for pack parameter must be a pack type"), function operator(), file SubstitutionMap.cpp, line 237.

Yep, this is fixed in Swift 6!

Swift 6 complete concurrency checking permits `async` functions of nonisolated classes to mutate their state

The bug is that this is valid ```swift group.addTask { @MainActor [c] in await c.mutateC() } ``` `c` is not `Sendable` and passing `c` to the generic executor on the...

Swift 6 complete concurrency checking permits `async` functions of nonisolated classes to mutate their state

cc @gottesmm, I believe this should be diagnosed by region isolation because a value from the main actor region is being sent outside the main actor.

Swift 6 complete concurrency checking permits `async` functions of nonisolated classes to mutate their state

@gottesmm `c` cannot become main actor isolated because it's a field of `self`. It should be invalid to transfer it. EDIT: I'm wrong, because the function that the send happens...

Overridden methods can't have different actor isolation from nonisolated overridden declaration

Yes that's right, SE-0470 is only for protocol conformances. I'm working on a proposal to apply similar techniques to subclasses to allow isolated overrides like this (using the basic approach...

Incorrect actor isolation assumption across Swift 5/6 module boundary leads to `dispatch_assert_queue` crashes

Yes, this is a deliberate language design choice. I was leaving this open to try to dig up documentation for why, and if it doesn't exist, I'll write it up.

Incorrect actor isolation assumption across Swift 5/6 module boundary leads to `dispatch_assert_queue` crashes

> So you know that this would lead to a runtime crash and still decide to not produce a warning or error? 🫣 I greatly appreciate your constructive feedback and...

Incorrect actor isolation assumption across Swift 5/6 module boundary leads to `dispatch_assert_queue` crashes

Perhaps my comment was misunderstood. The compiler does not and cannot know the code will crash at runtime, because it cannot see across module boundaries into the implementation of the...

Incorrect actor isolation assumption across Swift 5/6 module boundary leads to `dispatch_assert_queue` crashes

> I would love for this behavior to not crash and also not produce a warning. You can [disable the dynamic actor isolation checking](https://github.com/swiftlang/swift-evolution/blob/main/proposals/0423-dynamic-actor-isolation.md#disabling-dynamic-actor-isolation-checking) with `-disable-dynamic-actor-isolation`.

Incorrect actor isolation assumption across Swift 5/6 module boundary leads to `dispatch_assert_queue` crashes

>do you mind linking where the implicit behavior is documented, for future reference? (it's not easy to navigate Swift Concurrency rules) I added documentation for this behavior in the migration...