RFR: 8246778: Compiler implementation for Sealed Classes (Second Preview) [v6]

[Mandy Chung]

On Fri, 4 Dec 2020 16:22:28 GMT, Jan Lahoda <jlahoda at openjdk.org> wrote:

>> This pull request replaces https://github.com/openjdk/jdk/pull/1227.
>> 
>> From the original PR:
>> 
>>> Please review the code for the second iteration of sealed classes. In this iteration we are:
>>> 
>>>     * Enhancing narrowing reference conversion to allow for stricter checking of cast conversions with respect to sealed type hierarchies
>>> 
>>>     * Also local classes are not considered when determining implicitly declared permitted direct subclasses of a sealed class or sealed interface
>>> 
>>>     * renaming Class::permittedSubclasses to Class::getPermittedSubclasses, still in the same method, the return type has been changed to Class<?>[] instead of the previous ClassDesc[]
>>> 
>>>     * adding code to make sure that annotations can't be sealed
>>> 
>>>     * improving some tests
>>> 
>>> 
>>> TIA
>>> 
>>> Related specs:
>>> [Sealed Classes JSL](http://cr.openjdk.java.net/~gbierman/jep397/jep397-20201104/specs/sealed-classes-jls.html)
>>> [Sealed Classes JVMS](http://cr.openjdk.java.net/~gbierman/jep397/jep397-20201104/specs/sealed-classes-jvms.html)
>>> [Additional: Contextual Keywords](http://cr.openjdk.java.net/~gbierman/jep397/jep397-20201104/specs/contextual-keywords-jls.html)
>> 
>> This PR strives to reflect the review comments from 1227:
>>  * adjustments to javadoc of j.l.Class methods
>>  * package access checks in Class.getPermittedSubclasses()
>>  * fixed to the narrowing conversion/castability as pointed out by Maurizio
>
> Jan Lahoda has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Cleanup as suggested on the review.

Marked as reviewed by mchung (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/1483