[swift-evolution] Keyword for protocol conformance

[Xiaodi Wu]

That's a good point. Since you're proposing an optional keyword, though,
aren't you describing a linter functionality?
On Mon, Aug 22, 2016 at 18:25 Charles Srstka <cocoadev at charlessoft.com>
wrote:

> On Aug 22, 2016, at 5:41 PM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
>
>
> There's been agreement even from the core team that the quality of
> diagnostics when conforming to a protocol is sub-par.
>
> The modified rule you propose has also been suggested before. The reason
> it doesn't help is that (1) if a method signature is mismatched
> accidentally due to a typo, you get a compilation error already because
> your type doesn't conform to the protocol (it's the quality of the error
> message that needs improvement);
>
>
> You don’t get any error at all if there’s a default value.
>
> protocol P {
> func doSomething()
> }
>
> extension P {
> func doSomething() { print(“Do This Thing”) }
> }
>
> struct S: P {
> func doSomthing() { print(“Do This Instead”) } // Whoops, doesn’t get
> called. And we don’t find out until mysterious behavior occurs at runtime.
> }
>
> If there were a way to tell the compiler that the function was meant to
> satisfy a protocol, we could prevent the mistake above from occurring.
>
> (2) otherwise, if your type fulfills all protocol requirements but also
> implements an additional method unnecessary for conformance, what is the
> harm that is being prevented by a compiler error?
>
>
> The fact that implementing protocol requirements that have default values
> is, in effect, stringly typed.
>
> Charles
>
>
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