Thanks Tagir. > On 11 Nov 2019, at 04:07, Tagir Valeev <amae...@gmail.com> wrote: > > Hello! > >>> Several points are unclear to me >>> 1. It's not explicitly specified whether an explicitly declared >>> canonical constructor must be 'public' like it's specified for compact >>> constructors. Does this mean that I can declare non-public canonical >>> constructor? >> >> The compact constructor _is_ a canonical constructor; its just an alternate >> notation for it, and its an error to declare it both ways (because its an >> error to declare the same member twice). The canonical constructor should >> be public (yes, Remi, we see you there), whether declared implicitly, >> explicitly with a full argument list, or explicitly with a compact ctor. > > Sure, this sounds consistent. I'm just saying that this part of the > current spec draft is incomplete. It says that implicit canonical ctor > is public; it says that compact ctor must be public but it says > nothing about explicit canonical ctor. And it's not evident that it > must be the same as in the implicit declaration (e.g. implicit default > ctor has the same access level as the class, but explicit one is > allowed to have the different one). Also, compact constructor rules > should not be taken into account for the explicit canonical > constructor: the compact constructor is a partial case, so it could be > more restrictive. My suggestion is to write this explicitly in 8.10.4: > > If the canonical constructor is explicitly declared, then it must > satisfy the following; otherwise a compile-time error occurs: > - The canonical constructor must be declared public.
Agreed. > ... > >>> 2. I see the restriction for not having a return statement quite >>> arbitrary. I understand it for compact constructors but see no reason >>> for this restriction in non-compact canonical constructors. Could >>> anybody provide a rationale behind this restriction? Sorry if it was >>> discussed; in this case, links to the discussion would also be >>> appreciated. >> >> Yes, it exists primarily for compact constructors and could be refined to >> mention only those. > > Great. > >>> 3. As it's already mentioned in 8.10.3, each record component implies >>> an implicitly declared private final field. And as 8.3.1.2 [2] says, >>> "A blank final instance variable must be definitely assigned and >>> moreover not definitely unassigned at the end of every constructor of >>> the class in which it is declared". Thus "Every field corresponding to >>> a record component of R must be definitely assigned and moreover not >>> definitely unassigned..." part seems redundant as it's covered by >>> normal constructor rules. Probably it's not harmful to specify this >>> explicitly though. >> >> Agreed. Ordinary DA should cover this, though its reasonable to remind the >> reader that DA applies to implicitly declared final fields too. >> > > So to summarize, my suggestion is to reformulate this part of 8.10.4, > as follows: > > If the canonical constructor is explicitly declared, then it must > satisfy the following; otherwise a compile-time error occurs: > - The canonical constructor must be declared public. > - The body of a canonical constructor must not contain an explicit > constructor invocation statement (8.8.7.1). > - Every field corresponding to a record component of R must be > definitely assigned and > moreover not definitely unassigned (16.9) at the end of the canonical > constructor. // or probably remove this item > - All the other rules for a constructor in a normal class declaration > must be satisfied (8.8). I think we should remove the third item. It’s not needed. > > And for compact constructor (8.10.5): > > A compact constructor declaration must satisfy all of the following > conditions; otherwise a compile-time error occurs. > - The compact constructor must be declared public. > - The body of a compact constructor must not contain an explicit > constructor invocation statement (8.8.7.1). > - The body of a compact constructor must not contain a return statement > (14.17). > - All the other rules for a constructor in a normal class declaration > must be satisfied (8.8). Agreed. > > With best regards, > Tagir Valeev.
