[swift-evolution] /*Let it be*/ func() -> @discardable Bool {} /*Rather Than*/ @discardableResult func() -> Bool {}

[Xiaodi Wu]

No, I'm talking about the implicit discardability proposed by Brent, such
as for all Optional<@discardable T>.

He proposes that the @discardable syntax has a strong motivating advantage
because it can be extended in a way to mark _types_ so that return values
of those types are always implicitly @discardable. That is:

@discardable class A { ... }
// any return value of type A is implicitly discardable
// what happens if A : Error and I throw A?

class B : A { ... }
// is any return value of type B also implicitly discardable?


On Thu, Oct 19, 2017 at 01:02 Mike Kluev <mike.kluev at gmail.com> wrote:

> On 19 October 2017 at 05:04, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
>
>>
>> d) Does a class that override a `@discardable` type inherit that
>> annotation? If not, they it's kind of a weird exception to the inheritance
>> thing, no? If so, then we'd need a @nondiscardable annotation to do
>> type-level overrides of @discardable.
>>
>>
> the very current form of @discardableResult as a function attribute leads
> to these type of questions in the first place. if it was a type modifier -
> there would be no doubt:
>
> class A {
>     func foo() -> Bool {
>         ...
>     }
>
>     func bar() -> discardable Bool {
>         ...
>     }
> }
>
> class B: A {
>     override func foo() -> discardable Bool { // ok, types compatible
>        ...
>     }
>
>     override func bar() -> Bool { // error. types mismatch
>         ...
>     }
> }
>
> Mike
>
>
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