[Pitch] Non-Escapable Types and Lifetime Dependency

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@tbkka It was initially proposed as @nonescaping modifier. However, it eventually became ~Escapable. Could you please expand on why? I feel like the initial notion is far superior and would allow much better composition, but I'm sure you had a good reason to express it as a property of type instead of a property of a function argument.

Also, are non-escaping closures ~Escaping (and subject to lifetime modifiers)? Will it be possible to write this:

func f(_ g: borrowing () -> Void) -> copy(g) () -> Void { // not sure about `copy`
  g
}

PS:

  • A copy(self) lifetime dependency with a borrowing or inout mutation-modifier

I believe it should be "borrowing or mutating"

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