MethodVisitor.java

/*
 * 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
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/*
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file:
 *
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2011 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package jdk.internal.org.objectweb.asm;

/**
 * A visitor to visit a Java method. The methods of this class must be called in the following
 * order: ( {@code visitParameter} )* [ {@code visitAnnotationDefault} ] ( {@code visitAnnotation} |
 * {@code visitAnnotableParameterCount} | {@code visitParameterAnnotation} {@code
 * visitTypeAnnotation} | {@code visitAttribute} )* [ {@code visitCode} ( {@code visitFrame} |
 * {@code visit<i>X</i>Insn} | {@code visitLabel} | {@code visitInsnAnnotation} | {@code
 * visitTryCatchBlock} | {@code visitTryCatchAnnotation} | {@code visitLocalVariable} | {@code
 * visitLocalVariableAnnotation} | {@code visitLineNumber} )* {@code visitMaxs} ] {@code visitEnd}.
 * In addition, the {@code visit<i>X</i>Insn} and {@code visitLabel} methods must be called in the
 * sequential order of the bytecode instructions of the visited code, {@code visitInsnAnnotation}
 * must be called <i>after</i> the annotated instruction, {@code visitTryCatchBlock} must be called
 * <i>before</i> the labels passed as arguments have been visited, {@code
 * visitTryCatchBlockAnnotation} must be called <i>after</i> the corresponding try catch block has
 * been visited, and the {@code visitLocalVariable}, {@code visitLocalVariableAnnotation} and {@code
 * visitLineNumber} methods must be called <i>after</i> the labels passed as arguments have been
 * visited.
 *
 * @author Eric Bruneton
 */
public abstract class MethodVisitor {

    private static final String REQUIRES_ASM5 = "This feature requires ASM5";

    /**
      * The ASM API version implemented by this visitor. The value of this field must be one of {@link
      * Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}.
      */
    protected final int api;

    /**
      * The method visitor to which this visitor must delegate method calls. May be {@literal null}.
      */
    protected MethodVisitor mv;

    /**
      * Constructs a new {@link MethodVisitor}.
      *
      * @param api the ASM API version implemented by this visitor. Must be one of {@link
      *     Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}.
      */
    public MethodVisitor(final int api) {
        this(api, null);
    }

    /**
      * Constructs a new {@link MethodVisitor}.
      *
      * @param api the ASM API version implemented by this visitor. Must be one of {@link
      *     Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}.
      * @param methodVisitor the method visitor to which this visitor must delegate method calls. May
      *     be null.
      */
    @SuppressWarnings("deprecation")
    public MethodVisitor(final int api, final MethodVisitor methodVisitor) {
        if (api != Opcodes.ASM8
                && api != Opcodes.ASM7
                && api != Opcodes.ASM6
                && api != Opcodes.ASM5
                && api != Opcodes.ASM4
                && api != Opcodes.ASM9_EXPERIMENTAL) {
            throw new IllegalArgumentException("Unsupported api " + api);
        }
        if (api == Opcodes.ASM9_EXPERIMENTAL) {
            Constants.checkAsmExperimental(this);
        }
        this.api = api;
        this.mv = methodVisitor;
    }

    // -----------------------------------------------------------------------------------------------
    // Parameters, annotations and non standard attributes
    // -----------------------------------------------------------------------------------------------

    /**
      * Visits a parameter of this method.
      *
      * @param name parameter name or {@literal null} if none is provided.
      * @param access the parameter's access flags, only {@code ACC_FINAL}, {@code ACC_SYNTHETIC}
      *     or/and {@code ACC_MANDATED} are allowed (see {@link Opcodes}).
      */
    public void visitParameter(final String name, final int access) {
        if (api < Opcodes.ASM5) {
            throw new UnsupportedOperationException(REQUIRES_ASM5);
        }
        if (mv != null) {
            mv.visitParameter(name, access);
        }
    }

    /**
      * Visits the default value of this annotation interface method.
      *
      * @return a visitor to the visit the actual default value of this annotation interface method, or
      *     {@literal null} if this visitor is not interested in visiting this default value. The
      *     'name' parameters passed to the methods of this annotation visitor are ignored. Moreover,
      *     exacly one visit method must be called on this annotation visitor, followed by visitEnd.
      */
    public AnnotationVisitor visitAnnotationDefault() {
        if (mv != null) {
            return mv.visitAnnotationDefault();
        }
        return null;
    }

    /**
      * Visits an annotation of this method.
      *
      * @param descriptor the class descriptor of the annotation class.
      * @param visible {@literal true} if the annotation is visible at runtime.
      * @return a visitor to visit the annotation values, or {@literal null} if this visitor is not
      *     interested in visiting this annotation.
      */
    public AnnotationVisitor visitAnnotation(final String descriptor, final boolean visible) {
        if (mv != null) {
            return mv.visitAnnotation(descriptor, visible);
        }
        return null;
    }

    /**
      * Visits an annotation on a type in the method signature.
      *
      * @param typeRef a reference to the annotated type. The sort of this type reference must be
      *     {@link TypeReference#METHOD_TYPE_PARAMETER}, {@link
      *     TypeReference#METHOD_TYPE_PARAMETER_BOUND}, {@link TypeReference#METHOD_RETURN}, {@link
      *     TypeReference#METHOD_RECEIVER}, {@link TypeReference#METHOD_FORMAL_PARAMETER} or {@link
      *     TypeReference#THROWS}. See {@link TypeReference}.
      * @param typePath the path to the annotated type argument, wildcard bound, array element type, or
      *     static inner type within 'typeRef'. May be {@literal null} if the annotation targets
      *     'typeRef' as a whole.
      * @param descriptor the class descriptor of the annotation class.
      * @param visible {@literal true} if the annotation is visible at runtime.
      * @return a visitor to visit the annotation values, or {@literal null} if this visitor is not
      *     interested in visiting this annotation.
      */
    public AnnotationVisitor visitTypeAnnotation(
            final int typeRef, final TypePath typePath, final String descriptor, final boolean visible) {
        if (api < Opcodes.ASM5) {
            throw new UnsupportedOperationException(REQUIRES_ASM5);
        }
        if (mv != null) {
            return mv.visitTypeAnnotation(typeRef, typePath, descriptor, visible);
        }
        return null;
    }

    /**
      * Visits the number of method parameters that can have annotations. By default (i.e. when this
      * method is not called), all the method parameters defined by the method descriptor can have
      * annotations.
      *
      * @param parameterCount the number of method parameters than can have annotations. This number
      *     must be less or equal than the number of parameter types in the method descriptor. It can
      *     be strictly less when a method has synthetic parameters and when these parameters are
      *     ignored when computing parameter indices for the purpose of parameter annotations (see
      *     https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.18).
      * @param visible {@literal true} to define the number of method parameters that can have
      *     annotations visible at runtime, {@literal false} to define the number of method parameters
      *     that can have annotations invisible at runtime.
      */
    public void visitAnnotableParameterCount(final int parameterCount, final boolean visible) {
        if (mv != null) {
            mv.visitAnnotableParameterCount(parameterCount, visible);
        }
    }

    /**
      * Visits an annotation of a parameter this method.
      *
      * @param parameter the parameter index. This index must be strictly smaller than the number of
      *     parameters in the method descriptor, and strictly smaller than the parameter count
      *     specified in {@link #visitAnnotableParameterCount}. Important note: <i>a parameter index i
      *     is not required to correspond to the i'th parameter descriptor in the method
      *     descriptor</i>, in particular in case of synthetic parameters (see
      *     https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.18).
      * @param descriptor the class descriptor of the annotation class.
      * @param visible {@literal true} if the annotation is visible at runtime.
      * @return a visitor to visit the annotation values, or {@literal null} if this visitor is not
      *     interested in visiting this annotation.
      */
    public AnnotationVisitor visitParameterAnnotation(
            final int parameter, final String descriptor, final boolean visible) {
        if (mv != null) {
            return mv.visitParameterAnnotation(parameter, descriptor, visible);
        }
        return null;
    }

    /**
      * Visits a non standard attribute of this method.
      *
      * @param attribute an attribute.
      */
    public void visitAttribute(final Attribute attribute) {
        if (mv != null) {
            mv.visitAttribute(attribute);
        }
    }

    /** Starts the visit of the method's code, if any (i.e. non abstract method). */
    public void visitCode() {
        if (mv != null) {
            mv.visitCode();
        }
    }

    /**
      * Visits the current state of the local variables and operand stack elements. This method must(*)
      * be called <i>just before</i> any instruction <b>i</b> that follows an unconditional branch
      * instruction such as GOTO or THROW, that is the target of a jump instruction, or that starts an
      * exception handler block. The visited types must describe the values of the local variables and
      * of the operand stack elements <i>just before</i> <b>i</b> is executed.<br>
      * <br>
      * (*) this is mandatory only for classes whose version is greater than or equal to {@link
      * Opcodes#V1_6}. <br>
      * <br>
      * The frames of a method must be given either in expanded form, or in compressed form (all frames
      * must use the same format, i.e. you must not mix expanded and compressed frames within a single
      * method):
      *
      * <ul>
      *   <li>In expanded form, all frames must have the F_NEW type.
      *   <li>In compressed form, frames are basically "deltas" from the state of the previous frame:
      *       <ul>
      *         <li>{@link Opcodes#F_SAME} representing frame with exactly the same locals as the
      *             previous frame and with the empty stack.
      *         <li>{@link Opcodes#F_SAME1} representing frame with exactly the same locals as the
      *             previous frame and with single value on the stack ( <code>numStack</code> is 1 and
      *             <code>stack[0]</code> contains value for the type of the stack item).
      *         <li>{@link Opcodes#F_APPEND} representing frame with current locals are the same as the
      *             locals in the previous frame, except that additional locals are defined (<code>
      *             numLocal</code> is 1, 2 or 3 and <code>local</code> elements contains values
      *             representing added types).
      *         <li>{@link Opcodes#F_CHOP} representing frame with current locals are the same as the
      *             locals in the previous frame, except that the last 1-3 locals are absent and with
      *             the empty stack (<code>numLocal</code> is 1, 2 or 3).
      *         <li>{@link Opcodes#F_FULL} representing complete frame data.
      *       </ul>
      * </ul>
      *
      * <br>
      * In both cases the first frame, corresponding to the method's parameters and access flags, is
      * implicit and must not be visited. Also, it is illegal to visit two or more frames for the same
      * code location (i.e., at least one instruction must be visited between two calls to visitFrame).
      *
      * @param type the type of this stack map frame. Must be {@link Opcodes#F_NEW} for expanded
      *     frames, or {@link Opcodes#F_FULL}, {@link Opcodes#F_APPEND}, {@link Opcodes#F_CHOP}, {@link
      *     Opcodes#F_SAME} or {@link Opcodes#F_APPEND}, {@link Opcodes#F_SAME1} for compressed frames.
      * @param numLocal the number of local variables in the visited frame.
      * @param local the local variable types in this frame. This array must not be modified. Primitive
      *     types are represented by {@link Opcodes#TOP}, {@link Opcodes#INTEGER}, {@link
      *     Opcodes#FLOAT}, {@link Opcodes#LONG}, {@link Opcodes#DOUBLE}, {@link Opcodes#NULL} or
      *     {@link Opcodes#UNINITIALIZED_THIS} (long and double are represented by a single element).
      *     Reference types are represented by String objects (representing internal names), and
      *     uninitialized types by Label objects (this label designates the NEW instruction that
      *     created this uninitialized value).
      * @param numStack the number of operand stack elements in the visited frame.
      * @param stack the operand stack types in this frame. This array must not be modified. Its
      *     content has the same format as the "local" array.
      * @throws IllegalStateException if a frame is visited just after another one, without any
      *     instruction between the two (unless this frame is a Opcodes#F_SAME frame, in which case it
      *     is silently ignored).
      */
    public void visitFrame(
            final int type,
            final int numLocal,
            final Object[] local,
            final int numStack,
            final Object[] stack) {
        if (mv != null) {
            mv.visitFrame(type, numLocal, local, numStack, stack);
        }
    }

    // -----------------------------------------------------------------------------------------------
    // Normal instructions
    // -----------------------------------------------------------------------------------------------

    /**
      * Visits a zero operand instruction.
      *
      * @param opcode the opcode of the instruction to be visited. This opcode is either NOP,
      *     ACONST_NULL, ICONST_M1, ICONST_0, ICONST_1, ICONST_2, ICONST_3, ICONST_4, ICONST_5,
      *     LCONST_0, LCONST_1, FCONST_0, FCONST_1, FCONST_2, DCONST_0, DCONST_1, IALOAD, LALOAD,
      *     FALOAD, DALOAD, AALOAD, BALOAD, CALOAD, SALOAD, IASTORE, LASTORE, FASTORE, DASTORE,
      *     AASTORE, BASTORE, CASTORE, SASTORE, POP, POP2, DUP, DUP_X1, DUP_X2, DUP2, DUP2_X1, DUP2_X2,
      *     SWAP, IADD, LADD, FADD, DADD, ISUB, LSUB, FSUB, DSUB, IMUL, LMUL, FMUL, DMUL, IDIV, LDIV,
      *     FDIV, DDIV, IREM, LREM, FREM, DREM, INEG, LNEG, FNEG, DNEG, ISHL, LSHL, ISHR, LSHR, IUSHR,
      *     LUSHR, IAND, LAND, IOR, LOR, IXOR, LXOR, I2L, I2F, I2D, L2I, L2F, L2D, F2I, F2L, F2D, D2I,
      *     D2L, D2F, I2B, I2C, I2S, LCMP, FCMPL, FCMPG, DCMPL, DCMPG, IRETURN, LRETURN, FRETURN,
      *     DRETURN, ARETURN, RETURN, ARRAYLENGTH, ATHROW, MONITORENTER, or MONITOREXIT.
      */
    public void visitInsn(final int opcode) {
        if (mv != null) {
            mv.visitInsn(opcode);
        }
    }

    /**
      * Visits an instruction with a single int operand.
      *
      * @param opcode the opcode of the instruction to be visited. This opcode is either BIPUSH, SIPUSH
      *     or NEWARRAY.
      * @param operand the operand of the instruction to be visited.<br>
      *     When opcode is BIPUSH, operand value should be between Byte.MIN_VALUE and Byte.MAX_VALUE.
      *     <br>
      *     When opcode is SIPUSH, operand value should be between Short.MIN_VALUE and Short.MAX_VALUE.
      *     <br>
      *     When opcode is NEWARRAY, operand value should be one of {@link Opcodes#T_BOOLEAN}, {@link
      *     Opcodes#T_CHAR}, {@link Opcodes#T_FLOAT}, {@link Opcodes#T_DOUBLE}, {@link Opcodes#T_BYTE},
      *     {@link Opcodes#T_SHORT}, {@link Opcodes#T_INT} or {@link Opcodes#T_LONG}.
      */
    public void visitIntInsn(final int opcode, final int operand) {
        if (mv != null) {
            mv.visitIntInsn(opcode, operand);
        }
    }

    /**
      * Visits a local variable instruction. A local variable instruction is an instruction that loads
      * or stores the value of a local variable.
      *
      * @param opcode the opcode of the local variable instruction to be visited. This opcode is either
      *     ILOAD, LLOAD, FLOAD, DLOAD, ALOAD, ISTORE, LSTORE, FSTORE, DSTORE, ASTORE or RET.
      * @param var the operand of the instruction to be visited. This operand is the index of a local
      *     variable.
      */
    public void visitVarInsn(final int opcode, final int var) {
        if (mv != null) {
            mv.visitVarInsn(opcode, var);
        }
    }

    /**
      * Visits a type instruction. A type instruction is an instruction that takes the internal name of
      * a class as parameter.
      *
      * @param opcode the opcode of the type instruction to be visited. This opcode is either NEW,
      *     ANEWARRAY, CHECKCAST or INSTANCEOF.
      * @param type the operand of the instruction to be visited. This operand must be the internal
      *     name of an object or array class (see {@link Type#getInternalName()}).
      */
    public void visitTypeInsn(final int opcode, final String type) {
        if (mv != null) {
            mv.visitTypeInsn(opcode, type);
        }
    }

    /**
      * Visits a field instruction. A field instruction is an instruction that loads or stores the
      * value of a field of an object.
      *
      * @param opcode the opcode of the type instruction to be visited. This opcode is either
      *     GETSTATIC, PUTSTATIC, GETFIELD or PUTFIELD.
      * @param owner the internal name of the field's owner class (see {@link Type#getInternalName()}).
      * @param name the field's name.
      * @param descriptor the field's descriptor (see {@link Type}).
      */
    public void visitFieldInsn(
            final int opcode, final String owner, final String name, final String descriptor) {
        if (mv != null) {
            mv.visitFieldInsn(opcode, owner, name, descriptor);
        }
    }

    /**
      * Visits a method instruction. A method instruction is an instruction that invokes a method.
      *
      * @param opcode the opcode of the type instruction to be visited. This opcode is either
      *     INVOKEVIRTUAL, INVOKESPECIAL, INVOKESTATIC or INVOKEINTERFACE.
      * @param owner the internal name of the method's owner class (see {@link
      *     Type#getInternalName()}).
      * @param name the method's name.
      * @param descriptor the method's descriptor (see {@link Type}).
      * @deprecated use {@link #visitMethodInsn(int, String, String, String, boolean)} instead.
      */
    @Deprecated
    public void visitMethodInsn(
            final int opcode, final String owner, final String name, final String descriptor) {
        int opcodeAndSource = opcode | (api < Opcodes.ASM5 ? Opcodes.SOURCE_DEPRECATED : 0);
        visitMethodInsn(opcodeAndSource, owner, name, descriptor, opcode == Opcodes.INVOKEINTERFACE);
    }

    /**
      * Visits a method instruction. A method instruction is an instruction that invokes a method.
      *
      * @param opcode the opcode of the type instruction to be visited. This opcode is either
      *     INVOKEVIRTUAL, INVOKESPECIAL, INVOKESTATIC or INVOKEINTERFACE.
      * @param owner the internal name of the method's owner class (see {@link
      *     Type#getInternalName()}).
      * @param name the method's name.
      * @param descriptor the method's descriptor (see {@link Type}).
      * @param isInterface if the method's owner class is an interface.
      */
    public void visitMethodInsn(
            final int opcode,
            final String owner,
            final String name,
            final String descriptor,
            final boolean isInterface) {
        if (api < Opcodes.ASM5 && (opcode & Opcodes.SOURCE_DEPRECATED) == 0) {
            if (isInterface != (opcode == Opcodes.INVOKEINTERFACE)) {
                throw new UnsupportedOperationException("INVOKESPECIAL/STATIC on interfaces requires ASM5");
            }
            visitMethodInsn(opcode, owner, name, descriptor);
            return;
        }
        if (mv != null) {
            mv.visitMethodInsn(opcode & ~Opcodes.SOURCE_MASK, owner, name, descriptor, isInterface);
        }
    }

    /**
      * Visits an invokedynamic instruction.
      *
      * @param name the method's name.
      * @param descriptor the method's descriptor (see {@link Type}).
      * @param bootstrapMethodHandle the bootstrap method.
      * @param bootstrapMethodArguments the bootstrap method constant arguments. Each argument must be
      *     an {@link Integer}, {@link Float}, {@link Long}, {@link Double}, {@link String}, {@link
      *     Type}, {@link Handle} or {@link ConstantDynamic} value. This method is allowed to modify
      *     the content of the array so a caller should expect that this array may change.
      */
    public void visitInvokeDynamicInsn(
            final String name,
            final String descriptor,
            final Handle bootstrapMethodHandle,
            final Object... bootstrapMethodArguments) {
        if (api < Opcodes.ASM5) {
            throw new UnsupportedOperationException(REQUIRES_ASM5);
        }
        if (mv != null) {
            mv.visitInvokeDynamicInsn(name, descriptor, bootstrapMethodHandle, bootstrapMethodArguments);
        }
    }

    /**
      * Visits a jump instruction. A jump instruction is an instruction that may jump to another
      * instruction.
      *
      * @param opcode the opcode of the type instruction to be visited. This opcode is either IFEQ,
      *     IFNE, IFLT, IFGE, IFGT, IFLE, IF_ICMPEQ, IF_ICMPNE, IF_ICMPLT, IF_ICMPGE, IF_ICMPGT,
      *     IF_ICMPLE, IF_ACMPEQ, IF_ACMPNE, GOTO, JSR, IFNULL or IFNONNULL.
      * @param label the operand of the instruction to be visited. This operand is a label that
      *     designates the instruction to which the jump instruction may jump.
      */
    public void visitJumpInsn(final int opcode, final Label label) {
        if (mv != null) {
            mv.visitJumpInsn(opcode, label);
        }
    }

    /**
      * Visits a label. A label designates the instruction that will be visited just after it.
      *
      * @param label a {@link Label} object.
      */
    public void visitLabel(final Label label) {
        if (mv != null) {
            mv.visitLabel(label);
        }
    }

    // -----------------------------------------------------------------------------------------------
    // Special instructions
    // -----------------------------------------------------------------------------------------------

    /**
      * Visits a LDC instruction. Note that new constant types may be added in future versions of the
      * Java Virtual Machine. To easily detect new constant types, implementations of this method
      * should check for unexpected constant types, like this:
      *
      * <pre>
      * if (cst instanceof Integer) {
      *     // ...
      * } else if (cst instanceof Float) {
      *     // ...
      * } else if (cst instanceof Long) {
      *     // ...
      * } else if (cst instanceof Double) {
      *     // ...
      * } else if (cst instanceof String) {
      *     // ...
      * } else if (cst instanceof Type) {
      *     int sort = ((Type) cst).getSort();
      *     if (sort == Type.OBJECT) {
      *         // ...
      *     } else if (sort == Type.ARRAY) {
      *         // ...
      *     } else if (sort == Type.METHOD) {
      *         // ...
      *     } else {
      *         // throw an exception
      *     }
      * } else if (cst instanceof Handle) {
      *     // ...
      * } else if (cst instanceof ConstantDynamic) {
      *     // ...
      * } else {
      *     // throw an exception
      * }
      * </pre>
      *
      * @param value the constant to be loaded on the stack. This parameter must be a non null {@link
      *     Integer}, a {@link Float}, a {@link Long}, a {@link Double}, a {@link String}, a {@link
      *     Type} of OBJECT or ARRAY sort for {@code .class} constants, for classes whose version is
      *     49, a {@link Type} of METHOD sort for MethodType, a {@link Handle} for MethodHandle
      *     constants, for classes whose version is 51 or a {@link ConstantDynamic} for a constant
      *     dynamic for classes whose version is 55.
      */
    public void visitLdcInsn(final Object value) {
        if (api < Opcodes.ASM5
                && (value instanceof Handle
                        || (value instanceof Type && ((Type) value).getSort() == Type.METHOD))) {
            throw new UnsupportedOperationException(REQUIRES_ASM5);
        }
        if (api < Opcodes.ASM7 && value instanceof ConstantDynamic) {
            throw new UnsupportedOperationException("This feature requires ASM7");
        }
        if (mv != null) {
            mv.visitLdcInsn(value);
        }
    }

    /**
      * Visits an IINC instruction.
      *
      * @param var index of the local variable to be incremented.
      * @param increment amount to increment the local variable by.
      */
    public void visitIincInsn(final int var, final int increment) {
        if (mv != null) {
            mv.visitIincInsn(var, increment);
        }
    }

    /**
      * Visits a TABLESWITCH instruction.
      *
      * @param min the minimum key value.
      * @param max the maximum key value.
      * @param dflt beginning of the default handler block.
      * @param labels beginnings of the handler blocks. {@code labels[i]} is the beginning of the
      *     handler block for the {@code min + i} key.
      */
    public void visitTableSwitchInsn(
            final int min, final int max, final Label dflt, final Label... labels) {
        if (mv != null) {
            mv.visitTableSwitchInsn(min, max, dflt, labels);
        }
    }

    /**
      * Visits a LOOKUPSWITCH instruction.
      *
      * @param dflt beginning of the default handler block.
      * @param keys the values of the keys.
      * @param labels beginnings of the handler blocks. {@code labels[i]} is the beginning of the
      *     handler block for the {@code keys[i]} key.
      */
    public void visitLookupSwitchInsn(final Label dflt, final int[] keys, final Label[] labels) {
        if (mv != null) {
            mv.visitLookupSwitchInsn(dflt, keys, labels);
        }
    }

    /**
      * Visits a MULTIANEWARRAY instruction.
      *
      * @param descriptor an array type descriptor (see {@link Type}).
      * @param numDimensions the number of dimensions of the array to allocate.
      */
    public void visitMultiANewArrayInsn(final String descriptor, final int numDimensions) {
        if (mv != null) {
            mv.visitMultiANewArrayInsn(descriptor, numDimensions);
        }
    }

    /**
      * Visits an annotation on an instruction. This method must be called just <i>after</i> the
      * annotated instruction. It can be called several times for the same instruction.
      *
      * @param typeRef a reference to the annotated type. The sort of this type reference must be
      *     {@link TypeReference#INSTANCEOF}, {@link TypeReference#NEW}, {@link
      *     TypeReference#CONSTRUCTOR_REFERENCE}, {@link TypeReference#METHOD_REFERENCE}, {@link
      *     TypeReference#CAST}, {@link TypeReference#CONSTRUCTOR_INVOCATION_TYPE_ARGUMENT}, {@link
      *     TypeReference#METHOD_INVOCATION_TYPE_ARGUMENT}, {@link
      *     TypeReference#CONSTRUCTOR_REFERENCE_TYPE_ARGUMENT}, or {@link
      *     TypeReference#METHOD_REFERENCE_TYPE_ARGUMENT}. See {@link TypeReference}.
      * @param typePath the path to the annotated type argument, wildcard bound, array element type, or
      *     static inner type within 'typeRef'. May be {@literal null} if the annotation targets
      *     'typeRef' as a whole.
      * @param descriptor the class descriptor of the annotation class.
      * @param visible {@literal true} if the annotation is visible at runtime.
      * @return a visitor to visit the annotation values, or {@literal null} if this visitor is not
      *     interested in visiting this annotation.
      */
    public AnnotationVisitor visitInsnAnnotation(
            final int typeRef, final TypePath typePath, final String descriptor, final boolean visible) {
        if (api < Opcodes.ASM5) {
            throw new UnsupportedOperationException(REQUIRES_ASM5);
        }
        if (mv != null) {
            return mv.visitInsnAnnotation(typeRef, typePath, descriptor, visible);
        }
        return null;
    }

    // -----------------------------------------------------------------------------------------------
    // Exceptions table entries, debug information, max stack and max locals
    // -----------------------------------------------------------------------------------------------

    /**
      * Visits a try catch block.
      *
      * @param start the beginning of the exception handler's scope (inclusive).
      * @param end the end of the exception handler's scope (exclusive).
      * @param handler the beginning of the exception handler's code.
      * @param type the internal name of the type of exceptions handled by the handler, or {@literal
      *     null} to catch any exceptions (for "finally" blocks).
      * @throws IllegalArgumentException if one of the labels has already been visited by this visitor
      *     (by the {@link #visitLabel} method).
      */
    public void visitTryCatchBlock(
            final Label start, final Label end, final Label handler, final String type) {
        if (mv != null) {
            mv.visitTryCatchBlock(start, end, handler, type);
        }
    }

    /**
      * Visits an annotation on an exception handler type. This method must be called <i>after</i> the
      * {@link #visitTryCatchBlock} for the annotated exception handler. It can be called several times
      * for the same exception handler.
      *
      * @param typeRef a reference to the annotated type. The sort of this type reference must be
      *     {@link TypeReference#EXCEPTION_PARAMETER}. See {@link TypeReference}.
      * @param typePath the path to the annotated type argument, wildcard bound, array element type, or
      *     static inner type within 'typeRef'. May be {@literal null} if the annotation targets
      *     'typeRef' as a whole.
      * @param descriptor the class descriptor of the annotation class.
      * @param visible {@literal true} if the annotation is visible at runtime.
      * @return a visitor to visit the annotation values, or {@literal null} if this visitor is not
      *     interested in visiting this annotation.
      */
    public AnnotationVisitor visitTryCatchAnnotation(
            final int typeRef, final TypePath typePath, final String descriptor, final boolean visible) {
        if (api < Opcodes.ASM5) {
            throw new UnsupportedOperationException(REQUIRES_ASM5);
        }
        if (mv != null) {
            return mv.visitTryCatchAnnotation(typeRef, typePath, descriptor, visible);
        }
        return null;
    }

    /**
      * Visits a local variable declaration.
      *
      * @param name the name of a local variable.
      * @param descriptor the type descriptor of this local variable.
      * @param signature the type signature of this local variable. May be {@literal null} if the local
      *     variable type does not use generic types.
      * @param start the first instruction corresponding to the scope of this local variable
      *     (inclusive).
      * @param end the last instruction corresponding to the scope of this local variable (exclusive).
      * @param index the local variable's index.
      * @throws IllegalArgumentException if one of the labels has not already been visited by this
      *     visitor (by the {@link #visitLabel} method).
      */
    public void visitLocalVariable(
            final String name,
            final String descriptor,
            final String signature,
            final Label start,
            final Label end,
            final int index) {
        if (mv != null) {
            mv.visitLocalVariable(name, descriptor, signature, start, end, index);
        }
    }

    /**
      * Visits an annotation on a local variable type.
      *
      * @param typeRef a reference to the annotated type. The sort of this type reference must be
      *     {@link TypeReference#LOCAL_VARIABLE} or {@link TypeReference#RESOURCE_VARIABLE}. See {@link
      *     TypeReference}.
      * @param typePath the path to the annotated type argument, wildcard bound, array element type, or
      *     static inner type within 'typeRef'. May be {@literal null} if the annotation targets
      *     'typeRef' as a whole.
      * @param start the fist instructions corresponding to the continuous ranges that make the scope
      *     of this local variable (inclusive).
      * @param end the last instructions corresponding to the continuous ranges that make the scope of
      *     this local variable (exclusive). This array must have the same size as the 'start' array.
      * @param index the local variable's index in each range. This array must have the same size as
      *     the 'start' array.
      * @param descriptor the class descriptor of the annotation class.
      * @param visible {@literal true} if the annotation is visible at runtime.
      * @return a visitor to visit the annotation values, or {@literal null} if this visitor is not
      *     interested in visiting this annotation.
      */
    public AnnotationVisitor visitLocalVariableAnnotation(
            final int typeRef,
            final TypePath typePath,
            final Label[] start,
            final Label[] end,
            final int[] index,
            final String descriptor,
            final boolean visible) {
        if (api < Opcodes.ASM5) {
            throw new UnsupportedOperationException(REQUIRES_ASM5);
        }
        if (mv != null) {
            return mv.visitLocalVariableAnnotation(
                    typeRef, typePath, start, end, index, descriptor, visible);
        }
        return null;
    }

    /**
      * Visits a line number declaration.
      *
      * @param line a line number. This number refers to the source file from which the class was
      *     compiled.
      * @param start the first instruction corresponding to this line number.
      * @throws IllegalArgumentException if {@code start} has not already been visited by this visitor
      *     (by the {@link #visitLabel} method).
      */
    public void visitLineNumber(final int line, final Label start) {
        if (mv != null) {
            mv.visitLineNumber(line, start);
        }
    }

    /**
      * Visits the maximum stack size and the maximum number of local variables of the method.
      *
      * @param maxStack maximum stack size of the method.
      * @param maxLocals maximum number of local variables for the method.
      */
    public void visitMaxs(final int maxStack, final int maxLocals) {
        if (mv != null) {
            mv.visitMaxs(maxStack, maxLocals);
        }
    }

    /**
      * Visits the end of the method. This method, which is the last one to be called, is used to
      * inform the visitor that all the annotations and attributes of the method have been visited.
      */
    public void visitEnd() {
        if (mv != null) {
            mv.visitEnd();
        }
    }
}