Combine PassthroughSubject is not Sendable

[jaredh159 (Jared Henderson)]

curious about this as well. per @Tony_Parker this post:

"PassthroughSubject" seems to be thread-unsafe, is this a bug or limitation?

In addition to obeying demand, the Publisher contract also includes a requirement that publishers do not send values concurrently with other values, completion, or subscription. We needed to decide if subjects should enforce this thread safety requirement on their own (adding to overhead by locking) or deferring it to the user of the subject. Ultimately we decided the subject needed to lock on its own, because the subject can receive input itself from two sources - its own upstream or the send(…

subjects lock internally... so, should they be marked Sendable? they don't seem to be as of Swift 6.0.3