Fwd: Records feedback

[Brian Goetz]

Received on the -comments list.

A similar comment was made in the comments of this SO issue:
https://stackoverflow.com/questions/64131753/why-is-the-variable-arity-record-component-not-inferred-with-custom-constructor





-------- Forwarded Message --------
Subject: 	Records feedback
Date: 	Thu, 1 Oct 2020 15:09:38 -0500
From: 	David Aaron Kaye <kayedavi at gmail.com>
To: 	java-se-spec-comments at openjdk.java.net



Good afternoon,

I am very excited to see Records coming to Java. I have been playing around
with them since JDK 14. I noticed that in the proposal, JDK-8246771
<https://bugs.openjdk.java.net/browse/JDK-8246771>, it says

...if the canonical constructor is explicitly declared then its access
modifier must provide at least as much access as the record class


I have implemented a functional List:

public sealed interface List<A> permits Cons, Nil {
}

public record Cons<A>(A head, List<A> tail) implements List<A> {
}

@SuppressWarnings("rawtypes")
public record Nil<Nothing>() implements List<Nothing> {
public static final Nil instance = new Nil();

private Nil() {
}
}

I made the constructor private because I want this to be a singleton,
accessed from instance, but the current proposal does not allow me to do
that, and I get a compilation error on the private constructor. I could
prefer to be able to make the constructor private so that I can have a
record that is a singleton.

Thanks,

David Kaye
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