----- Mail original -----
> De: "John Rose" <[email protected]>
> À: "Remi Forax" <[email protected]>
> Cc: "Gavin Bierman" <[email protected]>, "amber-spec-experts"
> <[email protected]>
> Envoyé: Jeudi 5 Septembre 2019 01:27:23
> Objet: Re: Draft JLS spec for records
> On Sep 3, 2019, at 5:02 AM, [email protected] wrote:
>>
>> Given that i've always find the syntax of the canonical constructor too
>> close to
>> the one of the real constructor (depending on the fact that parenthesis are
>> present or not),
>> i propose a new kind of initializer, the require initializer (obvisouly it
>> can
>> be another name than "require").
>>
>> An example of syntax:
>> record Foo(String s) {
>> require {
>> Objects.requireNonNull(s);
>> }
>> }
>>
>> I also believe we should make the instance initializer illegal in record
>> given
>> that a require initializer is a kind a better instance initializer because it
>> can access local variables.
>
> The reason those initializers cannot “see” constructor parameters is (as you
> noted later) the initializers are incorporated into every constructor, and
> thus
> cannot assume any particular set of parameter names.
>
> OTOH, if you are incorporating only into the canonical constructor of a
> record,
> you *can* assume all component names are in scope.
>
> In fact, OTOOH, in some sense *every* constructor of a record has *all*
> component names in scope, so the initializer of a record *could* have those
> names. It doesn’t even have to be a new kind of initializer, just a new power
> of the existing initializer in the restricted context of a record, where all
> components are always in scope.
>
> So (a) don’t add the keyword and (b) all instance initializers to access full
> context of a record’s components. Brian will immediately say that this makes
> a
> questionable syntax choice (yes, I plead guilty to that) into an attractive
> nuisance, so that’s a reason to maybe require a keyword to opt into the nice
> new features of IIs.
>
> OTO^3H, since the canonical constructor is central to a record in a special
> way,
> it makes perfect sense to (1) put all the juicy validation/normalization logic
> into the body of the main constructor, and (2) look for ways to slim down the
> syntax of that constructor so, in common cases, it looks as slim and friendly
> as an instance initializer. So:
>
> record Foo(String s) {
> constructor {
> Objects.requireNonNull(s);
> }
> }
it looks like JavaScript, are you, even subconsciously, trying to bridge the
gap between Java and JavaScript :)
>
> But that’s so close to the proposed CompactConstructorDeclaration syntax that
> we
> are now arguing about matters of taste.
given that we have determine that it really works more as a simplified
constructor than a block/initializer, i believe the compact constructor syntax
is fine.
>
> My taste-meter doesn’t budge for the missing parentheses of “Foo { }”, but the
> needle *does* twitch a little because of the obligation to say “public” before
> every compact constructor declaration. Surely that’s not necessary. Since
> interfaces *also* require certain members to be public, *and* they allow
> “public” to be elided, it seems like records should provide the same courtesy.
> I’m sure that’s already been discussed, but I’ll add my vote for eliding
> “public” at that point.
can someone explain me why we need the constructor to be public ?
>
> — John
Rémi
