[lworld] RFR: 8279656: [lworld] Javac diagnostic compiler.err.primitive.class.must.not.implement.cloneable not valid anymore

[Srikanth Adayapalam]

On Sat, 15 Jan 2022 09:26:08 GMT, Srikanth Adayapalam <sadayapalam at openjdk.org> wrote:

>> Elides the restriction for `Cloneable`.
>
> test/langtools/tools/javac/valhalla/lworld-values/T8279656.java line 11:
> 
>> 9:     primitive class Primitive implements Cloneable {
>> 10:     }
>> 11: }
> 
> First I thought we may need a similar test in value-objects directory since value objects will get integrated ahead of and independently of primitive classes - but value objects are new and so were never restricted in the first place - so perhaps we don't need a test there after all.

According to the javadoc on Cloneable: 

By convention, classes that implement this interface should override
 * {@code Object.clone} (which is protected) with a public method.
 * See {@link java.lang.Object#clone()} for details on overriding this
 * method.


But elsewhere we forbid clone from being overridden in a primitive/value class - that restriction should be co-lifted.
ATM if I compile

primitive class X implements Cloneable {
    public X clone() {
        throw new Error("Not implemented yet");
    }
}


it results in

X.java:2: error: value classes may not override the method clone from Object
    public X clone() {
             ^
1 error

-------------

PR: https://git.openjdk.java.net/valhalla/pull/603