/*

 * Copyright (c) 2008, 2013, 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

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 * questions.

 */

package java.lang.invoke;

import sun.invoke.util.Wrapper;

import java.lang.ref.WeakReference;

import java.lang.ref.Reference;

import java.lang.ref.ReferenceQueue;

import java.util.Arrays;

import java.util.Collections;

import java.util.List;

import java.util.Objects;

import java.util.concurrent.ConcurrentMap;

import java.util.concurrent.ConcurrentHashMap;

import sun.invoke.util.BytecodeDescriptor;

import static java.lang.invoke.MethodHandleStatics.*;

import sun.invoke.util.VerifyType;

/**

 * A method type represents the arguments and return type accepted and

 * returned by a method handle, or the arguments and return type passed

 * and expected  by a method handle caller.  Method types must be properly

 * matched between a method handle and all its callers,

 * and the JVM's operations enforce this matching at, specifically

 * during calls to {@link MethodHandle#invokeExact MethodHandle.invokeExact}

 * and {@link MethodHandle#invoke MethodHandle.invoke}, and during execution

 * of {@code invokedynamic} instructions.

 * <p>

 * The structure is a return type accompanied by any number of parameter types.

 * The types (primitive, {@code void}, and reference) are represented by {@link Class} objects.

 * (For ease of exposition, we treat {@code void} as if it were a type.

 * In fact, it denotes the absence of a return type.)

 * <p>

 * All instances of {@code MethodType} are immutable.

 * Two instances are completely interchangeable if they compare equal.

 * Equality depends on pairwise correspondence of the return and parameter types and on nothing else.

 * <p>

 * This type can be created only by factory methods.

 * All factory methods may cache values, though caching is not guaranteed.

 * Some factory methods are static, while others are virtual methods which

 * modify precursor method types, e.g., by changing a selected parameter.

 * <p>

 * Factory methods which operate on groups of parameter types

 * are systematically presented in two versions, so that both Java arrays and

 * Java lists can be used to work with groups of parameter types.

 * The query methods {@code parameterArray} and {@code parameterList}

 * also provide a choice between arrays and lists.

 * <p>

 * {@code MethodType} objects are sometimes derived from bytecode instructions

 * such as {@code invokedynamic}, specifically from the type descriptor strings associated

 * with the instructions in a class file's constant pool.

 * <p>

 * Like classes and strings, method types can also be represented directly

 * in a class file's constant pool as constants.

 * A method type may be loaded by an {@code ldc} instruction which refers

 * to a suitable {@code CONSTANT_MethodType} constant pool entry.

 * The entry refers to a {@code CONSTANT_Utf8} spelling for the descriptor string.

 * (For full details on method type constants,

 * see sections 4.4.8 and 5.4.3.5 of the Java Virtual Machine Specification.)

 * <p>

 * When the JVM materializes a {@code MethodType} from a descriptor string,

 * all classes named in the descriptor must be accessible, and will be loaded.

 * (But the classes need not be initialized, as is the case with a {@code CONSTANT_Class}.)

 * This loading may occur at any time before the {@code MethodType} object is first derived.

 * @author John Rose, JSR 292 EG

 */

public final

class MethodType implements java.io.Serializable {

    private static final long serialVersionUID = 292L;  // {rtype, {ptype...}}

    // The rtype and ptypes fields define the structural identity of the method type:

    private final Class<?>   rtype;

    private final Class<?>[] ptypes;

    // The remaining fields are caches of various sorts:

    private @Stable MethodTypeForm form; // erased form, plus cached data about primitives

    private @Stable MethodType wrapAlt;  // alternative wrapped/unwrapped version

    private @Stable Invokers invokers;   // cache of handy higher-order adapters

    private @Stable String methodDescriptor;  // cache for toMethodDescriptorString

    /**

     * Check the given parameters for validity and store them into the final fields.

     */

    private MethodType(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {

        checkRtype(rtype);

        checkPtypes(ptypes);

        this.rtype = rtype;

        // defensively copy the array passed in by the user

        this.ptypes = trusted ? ptypes : Arrays.copyOf(ptypes, ptypes.length);

    }

    /**

     * Construct a temporary unchecked instance of MethodType for use only as a key to the intern table.

     * Does not check the given parameters for validity, and must be discarded after it is used as a searching key.

     * The parameters are reversed for this constructor, so that is is not accidentally used.

     */

    private MethodType(Class<?>[] ptypes, Class<?> rtype) {

        this.rtype = rtype;

        this.ptypes = ptypes;

    }

    /*trusted*/ MethodTypeForm form() { return form; }

    /*trusted*/ Class<?> rtype() { return rtype; }

    /*trusted*/ Class<?>[] ptypes() { return ptypes; }

    void setForm(MethodTypeForm f) { form = f; }

    /** This number, mandated by the JVM spec as 255,

     *  is the maximum number of <em>slots</em>

     *  that any Java method can receive in its argument list.

     *  It limits both JVM signatures and method type objects.

     *  The longest possible invocation will look like

     *  {@code staticMethod(arg1, arg2, ..., arg255)} or

     *  {@code x.virtualMethod(arg1, arg2, ..., arg254)}.

     */

    /*non-public*/ static final int MAX_JVM_ARITY = 255;  // this is mandated by the JVM spec.

    /** This number is the maximum arity of a method handle, 254.

     *  It is derived from the absolute JVM-imposed arity by subtracting one,

     *  which is the slot occupied by the method handle itself at the

     *  beginning of the argument list used to invoke the method handle.

     *  The longest possible invocation will look like

     *  {@code mh.invoke(arg1, arg2, ..., arg254)}.

     */

    // Issue:  Should we allow MH.invokeWithArguments to go to the full 255?

    /*non-public*/ static final int MAX_MH_ARITY = MAX_JVM_ARITY-1;  // deduct one for mh receiver

    /** This number is the maximum arity of a method handle invoker, 253.

     *  It is derived from the absolute JVM-imposed arity by subtracting two,

     *  which are the slots occupied by invoke method handle, and the

     *  target method handle, which are both at the beginning of the argument

     *  list used to invoke the target method handle.

     *  The longest possible invocation will look like

     *  {@code invokermh.invoke(targetmh, arg1, arg2, ..., arg253)}.

     */

    /*non-public*/ static final int MAX_MH_INVOKER_ARITY = MAX_MH_ARITY-1;  // deduct one more for invoker

    private static void checkRtype(Class<?> rtype) {

        Objects.requireNonNull(rtype);

    }

    private static void checkPtype(Class<?> ptype) {

        Objects.requireNonNull(ptype);

        if (ptype == void.class)

            throw newIllegalArgumentException("parameter type cannot be void");

    }

    /** Return number of extra slots (count of long/double args). */

    private static int checkPtypes(Class<?>[] ptypes) {

        int slots = 0;

        for (Class<?> ptype : ptypes) {

            checkPtype(ptype);

            if (ptype == double.class || ptype == long.class) {

                slots++;

            }

        }

        checkSlotCount(ptypes.length + slots);

        return slots;

    }

    static void checkSlotCount(int count) {

        assert((MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0);

        // MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work:

        if ((count & MAX_JVM_ARITY) != count)

            throw newIllegalArgumentException("bad parameter count "+count);

    }

    private static IndexOutOfBoundsException newIndexOutOfBoundsException(Object num) {

        if (num instanceof Integer)  num = "bad index: "+num;

        return new IndexOutOfBoundsException(num.toString());

    }

    static final ConcurrentWeakInternSet<MethodType> internTable = new ConcurrentWeakInternSet<>();

    static final Class<?>[] NO_PTYPES = {};

    /**

     * Finds or creates an instance of the given method type.

     * @param rtype  the return type

     * @param ptypes the parameter types

     * @return a method type with the given components

     * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null

     * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}

     */

    public static

    MethodType methodType(Class<?> rtype, Class<?>[] ptypes) {

        return makeImpl(rtype, ptypes, false);

    }

    /**

     * Finds or creates a method type with the given components.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param rtype  the return type

     * @param ptypes the parameter types

     * @return a method type with the given components

     * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null

     * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}

     */

    public static

    MethodType methodType(Class<?> rtype, List<Class<?>> ptypes) {

        boolean notrust = false;  // random List impl. could return evil ptypes array

        return makeImpl(rtype, listToArray(ptypes), notrust);

    }

    private static Class<?>[] listToArray(List<Class<?>> ptypes) {

        // sanity check the size before the toArray call, since size might be huge

        checkSlotCount(ptypes.size());

        return ptypes.toArray(NO_PTYPES);

    }

    /**

     * Finds or creates a method type with the given components.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * The leading parameter type is prepended to the remaining array.

     * @param rtype  the return type

     * @param ptype0 the first parameter type

     * @param ptypes the remaining parameter types

     * @return a method type with the given components

     * @throws NullPointerException if {@code rtype} or {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is null

     * @throws IllegalArgumentException if {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is {@code void.class}

     */

    public static

    MethodType methodType(Class<?> rtype, Class<?> ptype0, Class<?>... ptypes) {

        Class<?>[] ptypes1 = new Class<?>[1+ptypes.length];

        ptypes1[0] = ptype0;

        System.arraycopy(ptypes, 0, ptypes1, 1, ptypes.length);

        return makeImpl(rtype, ptypes1, true);

    }

    /**

     * Finds or creates a method type with the given components.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * The resulting method has no parameter types.

     * @param rtype  the return type

     * @return a method type with the given return value

     * @throws NullPointerException if {@code rtype} is null

     */

    public static

    MethodType methodType(Class<?> rtype) {

        return makeImpl(rtype, NO_PTYPES, true);

    }

    /**

     * Finds or creates a method type with the given components.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * The resulting method has the single given parameter type.

     * @param rtype  the return type

     * @param ptype0 the parameter type

     * @return a method type with the given return value and parameter type

     * @throws NullPointerException if {@code rtype} or {@code ptype0} is null

     * @throws IllegalArgumentException if {@code ptype0} is {@code void.class}

     */

    public static

    MethodType methodType(Class<?> rtype, Class<?> ptype0) {

        return makeImpl(rtype, new Class<?>[]{ ptype0 }, true);

    }

    /**

     * Finds or creates a method type with the given components.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * The resulting method has the same parameter types as {@code ptypes},

     * and the specified return type.

     * @param rtype  the return type

     * @param ptypes the method type which supplies the parameter types

     * @return a method type with the given components

     * @throws NullPointerException if {@code rtype} or {@code ptypes} is null

     */

    public static

    MethodType methodType(Class<?> rtype, MethodType ptypes) {

        return makeImpl(rtype, ptypes.ptypes, true);

    }

    /**

     * Sole factory method to find or create an interned method type.

     * @param rtype desired return type

     * @param ptypes desired parameter types

     * @param trusted whether the ptypes can be used without cloning

     * @return the unique method type of the desired structure

     */

    /*trusted*/ static

    MethodType makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {

        MethodType mt = internTable.get(new MethodType(ptypes, rtype));

        if (mt != null)

            return mt;

        if (ptypes.length == 0) {

            ptypes = NO_PTYPES; trusted = true;

        }

        mt = new MethodType(rtype, ptypes, trusted);

        // promote the object to the Real Thing, and reprobe

        mt.form = MethodTypeForm.findForm(mt);

        return internTable.add(mt);

    }

    private static final MethodType[] objectOnlyTypes = new MethodType[20];

    /**

     * Finds or creates a method type whose components are {@code Object} with an optional trailing {@code Object[]} array.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * All parameters and the return type will be {@code Object},

     * except the final array parameter if any, which will be {@code Object[]}.

     * @param objectArgCount number of parameters (excluding the final array parameter if any)

     * @param finalArray whether there will be a trailing array parameter, of type {@code Object[]}

     * @return a generally applicable method type, for all calls of the given fixed argument count and a collected array of further arguments

     * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 (or 254, if {@code finalArray} is true)

     * @see #genericMethodType(int)

     */

    public static

    MethodType genericMethodType(int objectArgCount, boolean finalArray) {

        MethodType mt;

        checkSlotCount(objectArgCount);

        int ivarargs = (!finalArray ? 0 : 1);

        int ootIndex = objectArgCount*2 + ivarargs;

        if (ootIndex < objectOnlyTypes.length) {

            mt = objectOnlyTypes[ootIndex];

            if (mt != null)  return mt;

        }

        Class<?>[] ptypes = new Class<?>[objectArgCount + ivarargs];

        Arrays.fill(ptypes, Object.class);

        if (ivarargs != 0)  ptypes[objectArgCount] = Object[].class;

        mt = makeImpl(Object.class, ptypes, true);

        if (ootIndex < objectOnlyTypes.length) {

            objectOnlyTypes[ootIndex] = mt;     // cache it here also!

        }

        return mt;

    }

    /**

     * Finds or creates a method type whose components are all {@code Object}.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * All parameters and the return type will be Object.

     * @param objectArgCount number of parameters

     * @return a generally applicable method type, for all calls of the given argument count

     * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255

     * @see #genericMethodType(int, boolean)

     */

    public static

    MethodType genericMethodType(int objectArgCount) {

        return genericMethodType(objectArgCount, false);

    }

    /**

     * Finds or creates a method type with a single different parameter type.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param num    the index (zero-based) of the parameter type to change

     * @param nptype a new parameter type to replace the old one with

     * @return the same type, except with the selected parameter changed

     * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}

     * @throws IllegalArgumentException if {@code nptype} is {@code void.class}

     * @throws NullPointerException if {@code nptype} is null

     */

    public MethodType changeParameterType(int num, Class<?> nptype) {

        if (parameterType(num) == nptype)  return this;

        checkPtype(nptype);

        Class<?>[] nptypes = ptypes.clone();

        nptypes[num] = nptype;

        return makeImpl(rtype, nptypes, true);

    }

    /**

     * Finds or creates a method type with additional parameter types.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param num    the position (zero-based) of the inserted parameter type(s)

     * @param ptypesToInsert zero or more new parameter types to insert into the parameter list

     * @return the same type, except with the selected parameter(s) inserted

     * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}

     * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}

     *                                  or if the resulting method type would have more than 255 parameter slots

     * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null

     */

    public MethodType insertParameterTypes(int num, Class<?>... ptypesToInsert) {

        int len = ptypes.length;

        if (num < 0 || num > len)

            throw newIndexOutOfBoundsException(num);

        int ins = checkPtypes(ptypesToInsert);

        checkSlotCount(parameterSlotCount() + ptypesToInsert.length + ins);

        int ilen = ptypesToInsert.length;

        if (ilen == 0)  return this;

        Class<?>[] nptypes = Arrays.copyOfRange(ptypes, 0, len+ilen);

        System.arraycopy(nptypes, num, nptypes, num+ilen, len-num);

        System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen);

        return makeImpl(rtype, nptypes, true);

    }

    /**

     * Finds or creates a method type with additional parameter types.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list

     * @return the same type, except with the selected parameter(s) appended

     * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}

     *                                  or if the resulting method type would have more than 255 parameter slots

     * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null

     */

    public MethodType appendParameterTypes(Class<?>... ptypesToInsert) {

        return insertParameterTypes(parameterCount(), ptypesToInsert);

    }

    /**

     * Finds or creates a method type with additional parameter types.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param num    the position (zero-based) of the inserted parameter type(s)

     * @param ptypesToInsert zero or more new parameter types to insert into the parameter list

     * @return the same type, except with the selected parameter(s) inserted

     * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}

     * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}

     *                                  or if the resulting method type would have more than 255 parameter slots

     * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null

     */

    public MethodType insertParameterTypes(int num, List<Class<?>> ptypesToInsert) {

        return insertParameterTypes(num, listToArray(ptypesToInsert));

    }

    /**

     * Finds or creates a method type with additional parameter types.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list

     * @return the same type, except with the selected parameter(s) appended

     * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}

     *                                  or if the resulting method type would have more than 255 parameter slots

     * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null

     */

    public MethodType appendParameterTypes(List<Class<?>> ptypesToInsert) {

        return insertParameterTypes(parameterCount(), ptypesToInsert);

    }

     /**

     * Finds or creates a method type with modified parameter types.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param start  the position (zero-based) of the first replaced parameter type(s)

     * @param end    the position (zero-based) after the last replaced parameter type(s)

     * @param ptypesToInsert zero or more new parameter types to insert into the parameter list

     * @return the same type, except with the selected parameter(s) replaced

     * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}

     *                                  or if {@code end} is negative or greater than {@code parameterCount()}

     *                                  or if {@code start} is greater than {@code end}

     * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}

     *                                  or if the resulting method type would have more than 255 parameter slots

     * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null

     */

    /*non-public*/ MethodType replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert) {

        if (start == end)

            return insertParameterTypes(start, ptypesToInsert);

        int len = ptypes.length;

        if (!(0 <= start && start <= end && end <= len))

            throw newIndexOutOfBoundsException("start="+start+" end="+end);

        int ilen = ptypesToInsert.length;

        if (ilen == 0)

            return dropParameterTypes(start, end);

        return dropParameterTypes(start, end).insertParameterTypes(start, ptypesToInsert);

    }

    /**

     * Finds or creates a method type with some parameter types omitted.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param start  the index (zero-based) of the first parameter type to remove

     * @param end    the index (greater than {@code start}) of the first parameter type after not to remove

     * @return the same type, except with the selected parameter(s) removed

     * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}

     *                                  or if {@code end} is negative or greater than {@code parameterCount()}

     *                                  or if {@code start} is greater than {@code end}

     */

    public MethodType dropParameterTypes(int start, int end) {

        int len = ptypes.length;

        if (!(0 <= start && start <= end && end <= len))

            throw newIndexOutOfBoundsException("start="+start+" end="+end);

        if (start == end)  return this;

        Class<?>[] nptypes;

        if (start == 0) {

            if (end == len) {

                // drop all parameters

                nptypes = NO_PTYPES;

            } else {

                // drop initial parameter(s)

                nptypes = Arrays.copyOfRange(ptypes, end, len);

            }

        } else {

            if (end == len) {

                // drop trailing parameter(s)

                nptypes = Arrays.copyOfRange(ptypes, 0, start);

            } else {

                int tail = len - end;

                nptypes = Arrays.copyOfRange(ptypes, 0, start + tail);

                System.arraycopy(ptypes, end, nptypes, start, tail);

            }

        }

        return makeImpl(rtype, nptypes, true);

    }

    /**

     * Finds or creates a method type with a different return type.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param nrtype a return parameter type to replace the old one with

     * @return the same type, except with the return type change

     * @throws NullPointerException if {@code nrtype} is null

     */

    public MethodType changeReturnType(Class<?> nrtype) {

        if (returnType() == nrtype)  return this;

        return makeImpl(nrtype, ptypes, true);

    }

    /**

     * Reports if this type contains a primitive argument or return value.

     * The return type {@code void} counts as a primitive.

     * @return true if any of the types are primitives

     */

    public boolean hasPrimitives() {

        return form.hasPrimitives();

    }

    /**

     * Reports if this type contains a wrapper argument or return value.

     * Wrappers are types which box primitive values, such as {@link Integer}.

     * The reference type {@code java.lang.Void} counts as a wrapper,

     * if it occurs as a return type.

     * @return true if any of the types are wrappers

     */

    public boolean hasWrappers() {

        return unwrap() != this;

    }

    /**

     * Erases all reference types to {@code Object}.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * All primitive types (including {@code void}) will remain unchanged.

     * @return a version of the original type with all reference types replaced

     */

    public MethodType erase() {

        return form.erasedType();

    }

    /**

     * Erases all reference types to {@code Object}, and all subword types to {@code int}.

     * This is the reduced type polymorphism used by private methods

     * such as {@link MethodHandle#invokeBasic invokeBasic}.

     * @return a version of the original type with all reference and subword types replaced

     */

    /*non-public*/ MethodType basicType() {

        return form.basicType();

    }

    /**

     * @return a version of the original type with MethodHandle prepended as the first argument

     */

    /*non-public*/ MethodType invokerType() {

        return insertParameterTypes(0, MethodHandle.class);

    }

    /**

     * Converts all types, both reference and primitive, to {@code Object}.

     * Convenience method for {@link #genericMethodType(int) genericMethodType}.

     * The expression {@code type.wrap().erase()} produces the same value

     * as {@code type.generic()}.

     * @return a version of the original type with all types replaced

     */

    public MethodType generic() {

        return genericMethodType(parameterCount());

    }

    /**

     * Converts all primitive types to their corresponding wrapper types.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * All reference types (including wrapper types) will remain unchanged.

     * A {@code void} return type is changed to the type {@code java.lang.Void}.

     * The expression {@code type.wrap().erase()} produces the same value

     * as {@code type.generic()}.

     * @return a version of the original type with all primitive types replaced

     */

    public MethodType wrap() {

        return hasPrimitives() ? wrapWithPrims(this) : this;

    }

    /**

     * Converts all wrapper types to their corresponding primitive types.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * All primitive types (including {@code void}) will remain unchanged.

     * A return type of {@code java.lang.Void} is changed to {@code void}.

     * @return a version of the original type with all wrapper types replaced

     */

    public MethodType unwrap() {

        MethodType noprims = !hasPrimitives() ? this : wrapWithPrims(this);

        return unwrapWithNoPrims(noprims);

    }

    private static MethodType wrapWithPrims(MethodType pt) {

        assert(pt.hasPrimitives());

        MethodType wt = pt.wrapAlt;

        if (wt == null) {

            // fill in lazily

            wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP, MethodTypeForm.WRAP);

            assert(wt != null);

            pt.wrapAlt = wt;

        }

        return wt;

    }

    private static MethodType unwrapWithNoPrims(MethodType wt) {

        assert(!wt.hasPrimitives());

        MethodType uwt = wt.wrapAlt;

        if (uwt == null) {

            // fill in lazily

            uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP, MethodTypeForm.UNWRAP);

            if (uwt == null)

                uwt = wt;    // type has no wrappers or prims at all

            wt.wrapAlt = uwt;

        }

        return uwt;

    }

    /**

     * Returns the parameter type at the specified index, within this method type.

     * @param num the index (zero-based) of the desired parameter type

     * @return the selected parameter type

     * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}

     */

    public Class<?> parameterType(int num) {

        return ptypes[num];

    }

    /**

     * Returns the number of parameter types in this method type.

     * @return the number of parameter types

     */

    public int parameterCount() {

        return ptypes.length;

    }

    /**

     * Returns the return type of this method type.

     * @return the return type

     */

    public Class<?> returnType() {

        return rtype;

    }

    /**

     * Presents the parameter types as a list (a convenience method).

     * The list will be immutable.

     * @return the parameter types (as an immutable list)

     */

    public List<Class<?>> parameterList() {

        return Collections.unmodifiableList(Arrays.asList(ptypes));

    }

    /*non-public*/ Class<?> lastParameterType() {

        int len = ptypes.length;

        return len == 0 ? void.class : ptypes[len-1];

    }

    /**

     * Presents the parameter types as an array (a convenience method).

     * Changes to the array will not result in changes to the type.

     * @return the parameter types (as a fresh copy if necessary)

     */

    public Class<?>[] parameterArray() {

        return ptypes.clone();

    }

    /**

     * Compares the specified object with this type for equality.

     * That is, it returns <tt>true</tt> if and only if the specified object

     * is also a method type with exactly the same parameters and return type.

     * @param x object to compare

     * @see Object#equals(Object)

     */

    @Override

    public boolean equals(Object x) {

        return this == x || x instanceof MethodType && equals((MethodType)x);

    }

    private boolean equals(MethodType that) {

        return this.rtype == that.rtype

            && Arrays.equals(this.ptypes, that.ptypes);

    }

    /**

     * Returns the hash code value for this method type.

     * It is defined to be the same as the hashcode of a List

     * whose elements are the return type followed by the

     * parameter types.

     * @return the hash code value for this method type

     * @see Object#hashCode()

     * @see #equals(Object)

     * @see List#hashCode()

     */

    @Override

    public int hashCode() {

      int hashCode = 31 + rtype.hashCode();

      for (Class<?> ptype : ptypes)

          hashCode = 31*hashCode + ptype.hashCode();

      return hashCode;

    }

    /**

     * Returns a string representation of the method type,

     * of the form {@code "(PT0,PT1...)RT"}.

     * The string representation of a method type is a

     * parenthesis enclosed, comma separated list of type names,

     * followed immediately by the return type.

     * <p>

     * Each type is represented by its

     * {@link java.lang.Class#getSimpleName simple name}.

     */

    @Override

    public String toString() {

        StringBuilder sb = new StringBuilder();

        sb.append("(");

        for (int i = 0; i < ptypes.length; i++) {

            if (i > 0)  sb.append(",");

            sb.append(ptypes[i].getSimpleName());

        }

        sb.append(")");

        sb.append(rtype.getSimpleName());

        return sb.toString();

    }

    /*non-public*/

    boolean isViewableAs(MethodType newType) {

        if (!VerifyType.isNullConversion(returnType(), newType.returnType()))

            return false;

        int argc = parameterCount();

        if (argc != newType.parameterCount())

            return false;

        for (int i = 0; i < argc; i++) {

            if (!VerifyType.isNullConversion(newType.parameterType(i), parameterType(i)))

                return false;

        }

        return true;

    }

    /*non-public*/

    boolean isCastableTo(MethodType newType) {

        int argc = parameterCount();

        if (argc != newType.parameterCount())

            return false;

        return true;

    }

    /*non-public*/

    boolean isConvertibleTo(MethodType newType) {

        if (!canConvert(returnType(), newType.returnType()))

            return false;

        int argc = parameterCount();

        if (argc != newType.parameterCount())

            return false;

        for (int i = 0; i < argc; i++) {

            if (!canConvert(newType.parameterType(i), parameterType(i)))

                return false;

        }

        return true;

    }

    /*non-public*/

    static boolean canConvert(Class<?> src, Class<?> dst) {

        // short-circuit a few cases:

        if (src == dst || dst == Object.class)  return true;

        // the remainder of this logic is documented in MethodHandle.asType

        if (src.isPrimitive()) {

            // can force void to an explicit null, a la reflect.Method.invoke

            // can also force void to a primitive zero, by analogy

            if (src == void.class)  return true;  //or !dst.isPrimitive()?

            Wrapper sw = Wrapper.forPrimitiveType(src);

            if (dst.isPrimitive()) {

                // P->P must widen

                return Wrapper.forPrimitiveType(dst).isConvertibleFrom(sw);

            } else {

                // P->R must box and widen

                return dst.isAssignableFrom(sw.wrapperType());

            }

        } else if (dst.isPrimitive()) {

            // any value can be dropped

            if (dst == void.class)  return true;

            Wrapper dw = Wrapper.forPrimitiveType(dst);

            // R->P must be able to unbox (from a dynamically chosen type) and widen

            // For example:

            //   Byte/Number/Comparable/Object -> dw:Byte -> byte.

            //   Character/Comparable/Object -> dw:Character -> char

            //   Boolean/Comparable/Object -> dw:Boolean -> boolean

            // This means that dw must be cast-compatible with src.

            if (src.isAssignableFrom(dw.wrapperType())) {

                return true;

            }

            // The above does not work if the source reference is strongly typed

            // to a wrapper whose primitive must be widened.  For example:

            //   Byte -> unbox:byte -> short/int/long/float/double

            //   Character -> unbox:char -> int/long/float/double

            if (Wrapper.isWrapperType(src) &&

                dw.isConvertibleFrom(Wrapper.forWrapperType(src))) {

                // can unbox from src and then widen to dst

                return true;

            }

            // We have already covered cases which arise due to runtime unboxing

            // of a reference type which covers several wrapper types:

            //   Object -> cast:Integer -> unbox:int -> long/float/double

            //   Serializable -> cast:Byte -> unbox:byte -> byte/short/int/long/float/double

            // An marginal case is Number -> dw:Character -> char, which would be OK if there were a

            // subclass of Number which wraps a value that can convert to char.

            // Since there is none, we don't need an extra check here to cover char or boolean.

            return false;

        } else {

            // R->R always works, since null is always valid dynamically

            return true;

        }

    }

    /// Queries which have to do with the bytecode architecture

    /** Reports the number of JVM stack slots required to invoke a method

     * of this type.  Note that (for historical reasons) the JVM requires

     * a second stack slot to pass long and double arguments.

     * So this method returns {@link #parameterCount() parameterCount} plus the

     * number of long and double parameters (if any).

     * <p>

     * This method is included for the benefit of applications that must

     * generate bytecodes that process method handles and invokedynamic.

     * @return the number of JVM stack slots for this type's parameters

     */

    /*non-public*/ int parameterSlotCount() {

        return form.parameterSlotCount();

    }

    /*non-public*/ Invokers invokers() {

        Invokers inv = invokers;

        if (inv != null)  return inv;

        invokers = inv = new Invokers(this);

        return inv;

    }

    /** Reports the number of JVM stack slots which carry all parameters including and after

     * the given position, which must be in the range of 0 to

     * {@code parameterCount} inclusive.  Successive parameters are

     * more shallowly stacked, and parameters are indexed in the bytecodes

     * according to their trailing edge.  Thus, to obtain the depth

     * in the outgoing call stack of parameter {@code N}, obtain

     * the {@code parameterSlotDepth} of its trailing edge

     * at position {@code N+1}.

     * <p>

     * Parameters of type {@code long} and {@code double} occupy

     * two stack slots (for historical reasons) and all others occupy one.

     * Therefore, the number returned is the number of arguments

     * <em>including</em> and <em>after</em> the given parameter,

     * <em>plus</em> the number of long or double arguments

     * at or after after the argument for the given parameter.

     * <p>

     * This method is included for the benefit of applications that must

     * generate bytecodes that process method handles and invokedynamic.

     * @param num an index (zero-based, inclusive) within the parameter types

     * @return the index of the (shallowest) JVM stack slot transmitting the

     *         given parameter

     * @throws IllegalArgumentException if {@code num} is negative or greater than {@code parameterCount()}

     */

    /*non-public*/ int parameterSlotDepth(int num) {

        if (num < 0 || num > ptypes.length)

            parameterType(num);  // force a range check

        return form.parameterToArgSlot(num-1);

    }

    /** Reports the number of JVM stack slots required to receive a return value

     * from a method of this type.

     * If the {@link #returnType() return type} is void, it will be zero,

     * else if the return type is long or double, it will be two, else one.

     * <p>

     * This method is included for the benefit of applications that must

     * generate bytecodes that process method handles and invokedynamic.

     * @return the number of JVM stack slots (0, 1, or 2) for this type's return value

     * Will be removed for PFD.

     */

    /*non-public*/ int returnSlotCount() {

        return form.returnSlotCount();

    }

    /**

     * Finds or creates an instance of a method type, given the spelling of its bytecode descriptor.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * Any class or interface name embedded in the descriptor string

     * will be resolved by calling {@link ClassLoader#loadClass(java.lang.String)}

     * on the given loader (or if it is null, on the system class loader).

     * <p>

     * Note that it is possible to encounter method types which cannot be

     * constructed by this method, because their component types are

     * not all reachable from a common class loader.

     * <p>

     * This method is included for the benefit of applications that must

     * generate bytecodes that process method handles and {@code invokedynamic}.

     * @param descriptor a bytecode-level type descriptor string "(T...)T"

     * @param loader the class loader in which to look up the types

     * @return a method type matching the bytecode-level type descriptor

     * @throws NullPointerException if the string is null

     * @throws IllegalArgumentException if the string is not well-formed

     * @throws TypeNotPresentException if a named type cannot be found

     */

    public static MethodType fromMethodDescriptorString(String descriptor, ClassLoader loader)

        throws IllegalArgumentException, TypeNotPresentException

    {

        if (!descriptor.startsWith("(") ||  // also generates NPE if needed

            descriptor.indexOf(')') < 0 ||

            descriptor.indexOf('.') >= 0)

            throw new IllegalArgumentException("not a method descriptor: "+descriptor);

        List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader);

        Class<?> rtype = types.remove(types.size() - 1);

        checkSlotCount(types.size());

        Class<?>[] ptypes = listToArray(types);

        return makeImpl(rtype, ptypes, true);

    }

    /**

     * Produces a bytecode descriptor representation of the method type.

     * <p>

     * Note that this is not a strict inverse of {@link #fromMethodDescriptorString fromMethodDescriptorString}.

     * Two distinct classes which share a common name but have different class loaders

     * will appear identical when viewed within descriptor strings.

     * <p>

     * This method is included for the benefit of applications that must

     * generate bytecodes that process method handles and {@code invokedynamic}.

     * {@link #fromMethodDescriptorString(java.lang.String, java.lang.ClassLoader) fromMethodDescriptorString},

     * because the latter requires a suitable class loader argument.

     * @return the bytecode type descriptor representation

     */

    public String toMethodDescriptorString() {

        String desc = methodDescriptor;

        if (desc == null) {

            desc = BytecodeDescriptor.unparse(this);

            methodDescriptor = desc;

        }

        return desc;

    }

    /*non-public*/ static String toFieldDescriptorString(Class<?> cls) {

        return BytecodeDescriptor.unparse(cls);

    }

    /// Serialization.

    /**

     * There are no serializable fields for {@code MethodType}.

     */

    private static final java.io.ObjectStreamField[] serialPersistentFields = { };

    /**

     * Save the {@code MethodType} instance to a stream.

     *

     * @serialData

     * For portability, the serialized format does not refer to named fields.

     * Instead, the return type and parameter type arrays are written directly

     * from the {@code writeObject} method, using two calls to {@code s.writeObject}

     * as follows:

     * <blockquote><pre>{@code

s.writeObject(this.returnType());

s.writeObject(this.parameterArray());

     * }</pre></blockquote>

     * <p>

     * The deserialized field values are checked as if they were

     * provided to the factory method {@link #methodType(Class,Class[]) methodType}.

     * For example, null values, or {@code void} parameter types,

     * will lead to exceptions during deserialization.

     * @param s the stream to write the object to

     * @throws java.io.IOException if there is a problem writing the object

     */

    private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {

        s.defaultWriteObject();  // requires serialPersistentFields to be an empty array

        s.writeObject(returnType());

        s.writeObject(parameterArray());

    }

    /**

     * Reconstitute the {@code MethodType} instance from a stream (that is,

     * deserialize it).

     * This instance is a scratch object with bogus final fields.

     * It provides the parameters to the factory method called by

     * {@link #readResolve readResolve}.

     * After that call it is discarded.

     * @param s the stream to read the object from

     * @throws java.io.IOException if there is a problem reading the object

     * @throws ClassNotFoundException if one of the component classes cannot be resolved

     * @see #MethodType()

     * @see #readResolve

     * @see #writeObject

     */

    private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {

        s.defaultReadObject();  // requires serialPersistentFields to be an empty array