[swift-evolution] History and future of Swift's parentheses

John McCall rjmccall at apple.com
Mon Jun 12 13:52:11 CDT 2017


> On Jun 12, 2017, at 2:36 PM, Jens Persson via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 
> On Mon, Jun 12, 2017 at 7:13 PM, Michael Ilseman <milseman at apple.com <mailto:milseman at apple.com>> wrote:
> 
> * Unless you’re proposing a change to the semantics of the language that could affect e.g. name mangling or the type metadata hierarchy, then that would be ABI-affecting. For example, proposing that all functions must only take a single tuple rather than multiple arguments could affect the runtime representation of function types. But even then, there are approaches to mitigate this, so such a proposal would likely present an ABI migration strategy.
> 
> 
> I think I understand (and understood), in very basic terms, the difference between source stability and binary stability, and I was thinking something like this:
> 
> What if there is a chance that the "uniform tuple concept" could be redesigned and reimplemented after all, handling inout, variadic, etc in some way, allowing named single element tuples, allowing A -> B to represent (possibly only "pure") functions with _any_number_ of args, and not just one, as in Swift 4, and so on.

We really do want to tie most of these features specifically to function calls.

John.

> 
> I'm still not entirely sure if this is ABI-affecting or not. But anyway, thank you for your calming words!
> 
> (I will try to not worry that (almost) everything parentheses-related in Swift will forever be stuck in a local optimum, because its current state and the history that lead to it is so confusing that it will stop all attempts at a substantially better solution and only allow minor changes/polishing.)
> 
> /Jens
> 
> 
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