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 * Copyright (c) 2022, 2024, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * version 2 for more details (a copy is included in the LICENSE file that
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package java.lang.classfile.attribute;

import java.lang.classfile.Attribute;
import java.lang.classfile.ClassElement;
import java.lang.classfile.constantpool.ClassEntry;
import java.lang.constant.ClassDesc;

import jdk.internal.classfile.impl.BoundAttribute;
import jdk.internal.classfile.impl.TemporaryConstantPool;
import jdk.internal.classfile.impl.UnboundAttribute;
import jdk.internal.javac.PreviewFeature;

/**
 * Models the {@code ModuleMainClass} attribute (JVMS {@jvms 4.7.27}), which can
 * appear on classes that represent module descriptors.
 * Delivered as a {@link java.lang.classfile.ClassElement} when
 * traversing the elements of a {@link java.lang.classfile.ClassModel}.
 * <p>
 * The attribute does not permit multiple instances in a given location.
 * Subsequent occurrence of the attribute takes precedence during the attributed
 * element build or transformation.
 * <p>
 * The attribute was introduced in the Java SE Platform version 9.
 *
 * @since 22
 */
@PreviewFeature(feature = PreviewFeature.Feature.CLASSFILE_API)
public sealed interface ModuleMainClassAttribute
        extends Attribute<ModuleMainClassAttribute>, ClassElement
        permits BoundAttribute.BoundModuleMainClassAttribute, UnboundAttribute.UnboundModuleMainClassAttribute {

    /**
     * {@return main class for this module}
     */
    ClassEntry mainClass();

    /**
     * {@return a {@code ModuleMainClass} attribute}
     * @param mainClass the main class
     */
    static ModuleMainClassAttribute of(ClassEntry mainClass) {
        return new UnboundAttribute.UnboundModuleMainClassAttribute(mainClass);
    }

    /**
     * {@return a {@code ModuleMainClass} attribute}
     * @param mainClass the main class
     * @throws IllegalArgumentException if {@code mainClass} represents a primitive type
     */
    static ModuleMainClassAttribute of(ClassDesc mainClass) {
        return new UnboundAttribute.UnboundModuleMainClassAttribute(TemporaryConstantPool.INSTANCE.classEntry(mainClass));
    }
}
