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An unofficial backport of the JDK Classfile API to Java 17

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/*
 * Copyright (c) 2022, 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
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package io.github.dmlloyd.classfile.instruction;

import io.github.dmlloyd.classfile.CodeElement;
import io.github.dmlloyd.classfile.CodeModel;
import io.github.dmlloyd.classfile.Instruction;
import io.github.dmlloyd.classfile.Label;
import io.github.dmlloyd.classfile.Opcode;
import io.github.dmlloyd.classfile.impl.AbstractInstruction;
import io.github.dmlloyd.classfile.impl.Util;
import io.github.dmlloyd.classfile.extras.PreviewFeature;

/**
 * Models a branching instruction (conditional or unconditional) in the {@code
 * code} array of a {@code Code} attribute.  Corresponding opcodes will have a
 * {@code kind} of {@link Opcode.Kind#BRANCH}.  Delivered as a {@link
 * CodeElement} when traversing the elements of a {@link CodeModel}.
 *
 * @since 22
 */
@PreviewFeature(feature = PreviewFeature.Feature.CLASSFILE_API)
public sealed interface BranchInstruction extends Instruction
        permits AbstractInstruction.BoundBranchInstruction,
                AbstractInstruction.UnboundBranchInstruction {
    /**
     * {@return the target of the branch}
     */
    Label target();

    /**
     * {@return a branch instruction}
     *
     * @param op the opcode for the specific type of branch instruction,
     *           which must be of kind {@link Opcode.Kind#BRANCH}
     * @param target the target of the branch
     * @throws IllegalArgumentException if the opcode kind is not
     *         {@link Opcode.Kind#BRANCH}.
     */
    static BranchInstruction of(Opcode op, Label target) {
        Util.checkKind(op, Opcode.Kind.BRANCH);
        return new AbstractInstruction.UnboundBranchInstruction(op, target);
    }
}