[swift-evolution] Type-annotated throws

[Nur Ismail]

Hi,

Sounds like checked exceptions of Java with a similar syntax. With Java you
have to specify the exceptions a method can throw. However been lots of
debate over the years whether it's a good thing or bad thing, some like it,
but I think many more hate it.
Most other languages don't have it, and possibly for good reason.

Regards,

On Fri, Aug 26, 2016 at 5:43 PM, Rod Brown via swift-evolution <
swift-evolution at swift.org> wrote:

> (resent for Swift Evolution)
>
> I’m a big fan of this idea. Currently “throws” seems like a very limited
> API - you know it’s throwing out something, but you can only hope to guess
> what that is or create fallbacks. Definitely a big +1 from me. A fallback
> for compatibility could be “throws” assumes “throws Any” and can be a
> warning?
>
> While I am not deeply familiar with the implications, I do like think your
> line of reasoning has merit, and think this makes sense for Phase 1 of
> Swift 4.
>
> - Rod
>
>
> On 27 Aug 2016, at 1:39 AM, Félix Cloutier via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Hi all,
>
> Currently, a function that throws is assumed to throw anything. There was
> a proposal draft last December to restrict that. The general idea was that
> you'd write, for instance:
>
> enum Foo: ErrorProtocol {
>     case bar
>     case baz
> }
>
> func frob() throws Foo {
>     throw Foo.bar // throw .bar?
> }
>
>
> If you `catch Foo` (or every case of Foo), now that the compiler can
> verify that your catch is exhaustive, you no longer have to have a
> catch-all block at the end of the sequence.
>
> This impacts the metadata format and has implications on resilience, which
> leads me to believe that the discussion could qualify for the phase 1 of
> Swift 4. If this is the case, I'd be interested in pulling out the old
> discussions and seeing where we left that at.
>
> Félix
>
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