[records] SafeVarargs and canonical constructors

[Gavin Bierman]

Spec now updated as per this suggestion (http://cr.openjdk.java.net/~gbierman/jep359/latest)

> On 29 Dec 2019, at 19:15, Remi Forax <forax at univ-mlv.fr> wrote:
> 
> Yes, i agree.
> 
> Rémi
> 
> De: "Brian Goetz" <brian.goetz at oracle.com>
> À: "Tagir Valeev" <amaembo at gmail.com>, "amber-spec-experts" <amber-spec-experts at openjdk.java.net>
> Envoyé: Dimanche 29 Décembre 2019 18:35:08
> Objet: Re: [records] SafeVarargs and canonical constructors
> This seems a very practical place to land here.
> 
> On 12/29/2019 12:32 PM, Tagir Valeev wrote:
> I have a proposal on how to solve SafeVarargs problem:
> 
> 1. Do not allow annotating record type with SafeVarargs
> 2. If the record type has explicit canonical/compact constructor, the
> heap pollution warning should be issued on the constructor, rather
> than on record header declaration
> 3. If explicit canonical/compact constructor is annotated with
> SafeVarargs, no warning should be issued.
> 
> So if one has a record declaration with potential heap pollution, and
> want to declare that varargs are safe, they must explicitly add an
> empty compact constructor and annotate it with SafeVarargs. Given that
> this case should be extremely rare in practice, such an amount of
> boilerplate doesn't look too big to me. On the other hand, such
> solution requires less changes in Java (e.g. no need to allow
> SafeVarargs on types).
> 
> What do you think?
> 
> With best regards,
> Tagir Valeev.
> 
> On Sat, Dec 28, 2019 at 1:10 PM Tagir Valeev <amaembo at gmail.com> <mailto:amaembo at gmail.com> wrote:
> Hello!
> 
> More questions about SafeVarargs:
> 
> 1. If we have a compact constructor declared, should the warning be
> issued at record header or at compact constructor declaration? To
> suppress the warning should I annotate a record type or compact
> constructor?
> 
> 2. The same if explicit canonical constructor is declared.
> 
> To me, it seems logical to put SafeVarargs at record type if compact
> constructor is present (because the variable arity parameter is not
> explicitly written in constructor declaration). However, if explicit
> canonical constructor is declared, it seems better to require
> SafeVarargs at constructor declaration, rather than a record
> declaration. Or place it in either place (but not at both).
> 
> What do you think?
> 
> With best regards,
> Tagir Valeev.
> 
> 

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