[records] SafeVarargs and canonical constructors

Tagir Valeev amaembo at gmail.com
Sun Dec 29 17:32:40 UTC 2019

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> 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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