Summary
-------

Update `javax.land.model` API to support component local variables as part of a preview language feature.

Problem
-------
The Derived Record Creation feature contains new language structures to be modeled.

Solution
--------
Use the preview visitors to provide the necessary language model.

Specification
-------------

    diff --git a/src/java.compiler/share/classes/javax/lang/model/element/ElementKind.java b/src/java.compiler/share/classes/javax/lang/model/element/ElementKind.java
    index 4190e2acdab..91382fe6e90 100644
    --- a/src/java.compiler/share/classes/javax/lang/model/element/ElementKind.java
    +++ b/src/java.compiler/share/classes/javax/lang/model/element/ElementKind.java
    @@ -25,6 +25,8 @@
     
     package javax.lang.model.element;
     
    +import jdk.internal.javac.PreviewFeature;
    +
     /**
      * The {@code kind} of an element.
      *
    @@ -121,7 +123,14 @@ public enum ElementKind {
          * A binding variable in a pattern.
          * @since 16
          */
    -    BINDING_VARIABLE;
    +    BINDING_VARIABLE,
    +
    +    /**
    +     * A local component variable in a derived record creation expression.
    +     * @since 23
    +     */
    +    @PreviewFeature(feature=PreviewFeature.Feature.DERIVED_RECORD_CREATION, reflective=true)
    +    COMPONENT_LOCAL_VARIABLE;
     
         // Maintenance note: check if the default implementation of
         // Elements.getOutermostTypeElement needs updating when new kind
    @@ -200,7 +209,8 @@ public boolean isInitializer() {
          * Returns {@code true} if this is a kind of variable: including
          * {@code ENUM_CONSTANT}, {@code FIELD}, {@code PARAMETER},
          * {@code LOCAL_VARIABLE}, {@code EXCEPTION_PARAMETER},
    -     * {@code RESOURCE_VARIABLE}, and {@code BINDING_VARIABLE}.
    +     * {@code RESOURCE_VARIABLE}, {@code BINDING_VARIABLE}, and
    +     * {@code COMPONENT_LOCAL_VARIABLE}.
          *
          * @return {@code true} if this is a kind of variable
          * @since 19
    @@ -209,7 +219,7 @@ public boolean isVariable() {
             return switch(this) {
             case ENUM_CONSTANT, FIELD, PARAMETER,
                  LOCAL_VARIABLE, EXCEPTION_PARAMETER, RESOURCE_VARIABLE,
    -             BINDING_VARIABLE -> true;
    +             BINDING_VARIABLE, COMPONENT_LOCAL_VARIABLE -> true;
             default -> false;
             };
         }

    --- a/src/java.compiler/share/classes/javax/lang/model/util/ElementKindVisitor6.java
    +++ b/src/java.compiler/share/classes/javax/lang/model/util/ElementKindVisitor6.java
    @@ -1,5 +1,5 @@
     /*
    - * Copyright (c) 2005, 2023, Oracle and/or its affiliates. All rights reserved.
    + * Copyright (c) 2005, 2024, Oracle and/or its affiliates. All rights reserved.
      * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
      *
      * This code is free software; you can redistribute it and/or modify it
    @@ -25,6 +25,8 @@
     
     package javax.lang.model.util;
     
    +import jdk.internal.javac.PreviewFeature;
    +
     import javax.lang.model.element.*;
     import javax.annotation.processing.SupportedSourceVersion;
     import javax.lang.model.SourceVersion;
    @@ -264,6 +266,9 @@
             case BINDING_VARIABLE:
                 return visitVariableAsBindingVariable(e, p);
     
    +        case COMPONENT_LOCAL_VARIABLE:
    +            return visitVariableAsComponentLocalVariable(e, p);
    +
             default:
                 throw new AssertionError("Bad kind " + k + " for VariableElement" + e);
             }
    @@ -364,6 +369,22 @@
             return visitUnknown(e, p);
         }
     
    +    /**
    +     * Visits a {@code COMPONENT_LOCAL_VARIABLE} variable element.
    +     *
    +     * @implSpec This implementation calls {@code visitUnknown}.
    +     *
    +     * @param e the element to visit
    +     * @param p a visitor-specified parameter
    +     * @return  the result of {@code visitUnknown}
    +     *
    +     * @since 23
    +     */
    +    @PreviewFeature(feature=PreviewFeature.Feature.DERIVED_RECORD_CREATION, reflective=true)
    +    public R visitVariableAsComponentLocalVariable(VariableElement e, P p) {
    +        return visitUnknown(e, p);
    +    }
    +
         /**
          * {@inheritDoc ElementVisitor}
          *

    --- a/src/java.compiler/share/classes/javax/lang/model/util/ElementKindVisitorPreview.java
    +++ b/src/java.compiler/share/classes/javax/lang/model/util/ElementKindVisitorPreview.java
    @@ -86,4 +86,21 @@ protected ElementKindVisitorPreview() {
         protected ElementKindVisitorPreview(R defaultValue) {
             super(defaultValue);
         }
    +
    +    /**
    +     * {@inheritDoc ElementKindVisitor6}
    +     *
    +     * @implSpec This implementation calls {@code defaultAction}.
    +     *
    +     * @param e {@inheritDoc ElementKindVisitor6}
    +     * @param p {@inheritDoc ElementKindVisitor6}
    +     * @return  the result of {@code defaultAction}
    +     *
    +     * @since 23
    +     */
    +    @Override
    +    @PreviewFeature(feature=PreviewFeature.Feature.DERIVED_RECORD_CREATION, reflective=true)
    +    public R visitVariableAsComponentLocalVariable(VariableElement e, P p) {
    +        return defaultAction(e, p);
    +     }
     }