AsyncStream and Actors

Using Swift
4

Would it kill the compiler to elaborate in its error message, here? Your explanation (@lukasa) makes sense, but there's really no way someone could be expected to deduce that from the compiler's output.

Cannot call mutating async function 'next()' on actor-isolated property 'frameIterator'

Why not?

  • Is "mutating async function" relevant or merely describing the type of next?
    • Is the crux of the problem that the method is mutating?
    • Is the crux of the problem that the method is async?
    • Is the crux of the problem that the method has some special isolation requirement?
  • Which actor is it referring to? ActorSource or the async iterator type itself?
  • Is the frameIterator stored property somehow not properly isolated to the ActorSource actor?
  • Is it something to do with the stored property being lazy?

I really wish the compiler would explain itself, rather than just make pithy statements.

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