[swift-evolution] Enums and Source Compatibility - defaults

[Zach Waldowski]

On Wed, Aug 9, 2017, at 08:42 PM, Jordan Rose via swift-evolution wrote:> - Consistency: switches on an enum in the same module can always be
>   exhaustive, so having it be different across modules is a bit
>   annoying. (But 'public' already acts like this.)
>From someone frequently working on teams or unfamiliar codebases, it’s
really heard to know whether “default: fatalError()” is a smell or not
without memorizing the  surface area of every API your app works with.
> … That brings us to one more concern: how different should binary
> frameworks be from source frameworks?
As few as possible. Realistically, I understand there must be  some, but
I feel like they need to be there for awfully good reasons. The
differences between app targets, framework/library targets, and
playgrounds feel arbitrary unless you understand parts of the language
very fully.
Some debugging techniques (or even just saving-time-rebuilding
techniques) involve using a binary framework and swapping it for another
binary with extra instrumentation or a source version for full
instrumentation, or vice-versa as you ossify a PoC feature into being
production-ready. It would be awful to break source compatibility as
this happens because an API you’re consuming changes behavior according
to the compiler. (I can hear my graybeard coworkers already - “It’s the
same code!”)
Sincerely,
  Zachary Waldowski
  zach at waldowski.me


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