[swift-evolution] Proposal: partial initialization before returning nil from an initializer

[Keith Smiley]

It's currently the second bullet point in the CHANGELOG in the main repo
https://github.com/apple/swift/blob/master/CHANGELOG.md
On Thu, Dec 17, 2015 at 10:32 Kevin Wooten via swift-evolution <
swift-evolution at swift.org> wrote:

> Apologies, looks like that exists no longer in relevant branches, just saw
> that it was updated to describe new support of initializers.
>
> On Dec 17, 2015, at 9:25 AM, Kevin Wooten via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Bottom of that commit…
>
> utils/buildbot-release-notes.txt
>
>
> On Dec 17, 2015, at 9:23 AM, Félix Cloutier via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Oh, sweet.
>
> Is there a changelog anywhere? I really like LLVM's release notes and how
> they're updated during development.
>
> Félix
>
> Le 17 déc. 2015 à 11:20:08, Keith Smiley <keithbsmiley at gmail.com> a écrit
> :
>
> I believe this has already been fixed here:
> https://github.com/apple/swift/commit/f524802e129f17de16fa6f8c3f08e5bcf75cc581
> On Thu, Dec 17, 2015 at 10:01 Félix Cloutier <swift-evolution at swift.org>
> wrote:
>
>> Hi all,
>>
>> Initializers can now fail, but objects still need to be fully initialized
>> before you can return `nil` from them. For instance:
>>
>>         class Foo {
>>                 let bar: Int
>>                 init?(baz: Int) {
>>                         guard baz < 100 else {
>>                                 return nil
>>                         }
>>                         self.bar = baz
>>                 }
>>         }
>>
>> This trivial example causes the following error: "all stored properties
>> of a class instance must be initialized before returning nil from an
>> initializer".
>>
>> For integers, that's easy: you can simply set them to zero. However,
>> sometimes, you'd want initialization to fail because the arguments you
>> received don't allow you to properly initialize a member. In these cases,
>> you have to make the fields Optionals (implicitly unwrapped or not) to
>> overcome this.
>>
>> I remember that Chris said that this is a temporary issue and that it
>> would eventually be fixed. I'm starting this thread because I'd love to
>> have this with or before Swift 3 and I'd like to see who thinks this is big
>> enough of an issue to rival the proposals we already have.
>>
>> Félix
>>
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>>
>
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