RFR: JDK-8329624: Add visitors for preview language features

[Joe Darcy]

On Wed, 3 Apr 2024 21:05:20 GMT, Vicente Romero <vromero at openjdk.org> wrote:

>> When new language features are added, the javax.lang.model may need to be updated. For certain classes of features, the API update includes introducing a new set of concrete visitors to handle the language feature.
>> 
>> The API scaffolding to support the new feature tends to be considerably larger than the API specifically for the new feature.
>> 
>> To aid work in progress (such as https://github.com/openjdk/jdk/pull/18509) and anticipated in the future, I think it would be helpful to introduce a persistent set of preview visitors independent of any particular language change.
>
> src/java.compiler/share/classes/javax/lang/model/util/SimpleElementVisitorPreview.java line 2:
> 
>> 1: /*
>> 2:  * Copyright (c) 2019, 2024, Oracle and/or its affiliates. All rights reserved.
> 
> general, please check the copyright years

Starting with 2019 was intentional as I copied the corresponding FooVisitor14 file into FooVisitorPreview and then began editing.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18609#discussion_r1550538694