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	/*
	* Copyright (c) 2008, 2017, 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 java.lang.invoke;

	import jdk.internal.vm.annotation.Stable;
	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.StringJoiner;
	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
	* @since 1.7
	*/
	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 @Stable Class<?> rtype;
	private final @Stable 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

	/**
	* Constructor that performs no copying or validation.
	* Should only be called from the factory method makeImpl
	*/
	private MethodType(Class<?> rtype, Class<?>[] ptypes) {
	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 {
	// MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work:
	assert((MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0);
	}
	static void checkSlotCount(int count) {
	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) {
	if (ptypes.length == 0) {
	ptypes = NO_PTYPES; trusted = true;
	}
	MethodType primordialMT = new MethodType(rtype, ptypes);
	MethodType mt = internTable.get(primordialMT);
	if (mt != null)
	return mt;

	// promote the object to the Real Thing, and reprobe
	MethodType.checkRtype(rtype);
	if (trusted) {
	MethodType.checkPtypes(ptypes);
	mt = primordialMT;
	} else {
	// Make defensive copy then validate
	ptypes = Arrays.copyOf(ptypes, ptypes.length);
	MethodType.checkPtypes(ptypes);
	mt = new MethodType(rtype, ptypes);
	}
	mt.form = MethodTypeForm.findForm(mt);
	return internTable.add(mt);
	}
	private static final @Stable 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 = new Class<?>[len + ilen];
	if (num > 0) {
	System.arraycopy(ptypes, 0, nptypes, 0, num);
	}
	System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen);
	if (num < len) {
	System.arraycopy(ptypes, num, nptypes, num+ilen, len-num);
	}
	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);
	}

	/** Replace the last arrayLength parameter types with the component type of arrayType.
	* @param arrayType any array type
	* @param pos position at which to spread
	* @param arrayLength the number of parameter types to change
	* @return the resulting type
	*/
	/non-public/ MethodType asSpreaderType(Class<?> arrayType, int pos, int arrayLength) {
	assert(parameterCount() >= arrayLength);
	int spreadPos = pos;
	if (arrayLength == 0) return this; // nothing to change
	if (arrayType == Object[].class) {
	if (isGeneric()) return this; // nothing to change
	if (spreadPos == 0) {
	// no leading arguments to preserve; go generic
	MethodType res = genericMethodType(arrayLength);
	if (rtype != Object.class) {
	res = res.changeReturnType(rtype);
	}
	return res;
	}
	}
	Class<?> elemType = arrayType.getComponentType();
	assert(elemType != null);
	for (int i = spreadPos; i < spreadPos + arrayLength; i++) {
	if (ptypes[i] != elemType) {
	Class<?>[] fixedPtypes = ptypes.clone();
	Arrays.fill(fixedPtypes, i, spreadPos + arrayLength, elemType);
	return methodType(rtype, fixedPtypes);
	}
	}
	return this; // arguments check out; no change
	}

	/** Return the leading parameter type, which must exist and be a reference.
	* @return the leading parameter type, after error checks
	*/
	/non-public/ Class<?> leadingReferenceParameter() {
	Class<?> ptype;
	if (ptypes.length == 0 \|\|
	(ptype = ptypes[0]).isPrimitive())
	throw newIllegalArgumentException("no leading reference parameter");
	return ptype;
	}

	/** Delete the last parameter type and replace it with arrayLength copies of the component type of arrayType.
	* @param arrayType any array type
	* @param pos position at which to insert parameters
	* @param arrayLength the number of parameter types to insert
	* @return the resulting type
	*/
	/non-public/ MethodType asCollectorType(Class<?> arrayType, int pos, int arrayLength) {
	assert(parameterCount() >= 1);
	assert(pos < ptypes.length);
	assert(ptypes[pos].isAssignableFrom(arrayType));
	MethodType res;
	if (arrayType == Object[].class) {
	res = genericMethodType(arrayLength);
	if (rtype != Object.class) {
	res = res.changeReturnType(rtype);
	}
	} else {
	Class<?> elemType = arrayType.getComponentType();
	assert(elemType != null);
	res = methodType(rtype, Collections.nCopies(arrayLength, elemType));
	}
	if (ptypes.length == 1) {
	return res;
	} else {
	// insert after (if need be), then before
	if (pos < ptypes.length - 1) {
	res = res.insertParameterTypes(arrayLength, Arrays.copyOfRange(ptypes, pos + 1, ptypes.length));
	}
	return res.insertParameterTypes(0, Arrays.copyOf(ptypes, pos));
	}
	}

	/**
	* 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();
	}

	private static final @Stable Class<?>[] METHOD_HANDLE_ARRAY
	= new Class<?>[] { MethodHandle.class };

	/**
	* @return a version of the original type with MethodHandle prepended as the first argument
	*/
	/non-public/ MethodType invokerType() {
	return insertParameterTypes(0, METHOD_HANDLE_ARRAY);
	}

	/**
	* 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());
	}

	/non-public/ boolean isGeneric() {
	return this == erase() && !hasPrimitives();
	}

	/**
	* 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.clone()));
	}

	/**
	* Returns the last parameter type of this method type.
	* If this type has no parameters, the sentinel value
	* {@code void.class} is returned instead.
	* @apiNote
	* <p>
	* The sentinel value is chosen so that reflective queries can be
	* made directly against the result value.
	* The sentinel value cannot be confused with a real parameter,
	* since {@code void} is never acceptable as a parameter type.
	* For variable arity invocation modes, the expression
	* {@link Class#getComponentType lastParameterType().getComponentType()}
	* is useful to query the type of the "varargs" parameter.
	* @return the last parameter type if any, else {@code void.class}
	* @since 10
	*/
	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 {@code true} 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() {
	StringJoiner sj = new StringJoiner(",", "(",
	")" + rtype.getSimpleName());
	for (int i = 0; i < ptypes.length; i++) {
	sj.add(ptypes[i].getSimpleName());
	}
	return sj.toString();
	}

	/** True if my parameter list is effectively identical to the given full list,
	* after skipping the given number of my own initial parameters.
	* In other words, after disregarding {@code skipPos} parameters,
	* my remaining parameter list is no longer than the {@code fullList}, and
	* is equal to the same-length initial sublist of {@code fullList}.
	*/
	/non-public/
	boolean effectivelyIdenticalParameters(int skipPos, List<Class<?>> fullList) {
	int myLen = ptypes.length, fullLen = fullList.size();
	if (skipPos > myLen \|\| myLen - skipPos > fullLen)
	return false;
	List<Class<?>> myList = Arrays.asList(ptypes);
	if (skipPos != 0) {
	myList = myList.subList(skipPos, myLen);
	myLen -= skipPos;
	}
	if (fullLen == myLen)
	return myList.equals(fullList);
	else
	return myList.equals(fullList.subList(0, myLen));
	}

	/** True if the old return type can always be viewed (w/o casting) under new return type,
	* and the new parameters can be viewed (w/o casting) under the old parameter types.
	*/
	/non-public/
	boolean isViewableAs(MethodType newType, boolean keepInterfaces) {
	if (!VerifyType.isNullConversion(returnType(), newType.returnType(), keepInterfaces))
	return false;
	if (form == newType.form && form.erasedType == this)
	return true; // my reference parameters are all Object
	if (ptypes == newType.ptypes)
	return true;
	int argc = parameterCount();
	if (argc != newType.parameterCount())
	return false;
	for (int i = 0; i < argc; i++) {
	if (!VerifyType.isNullConversion(newType.parameterType(i), parameterType(i), keepInterfaces))
	return false;
	}
	return true;
	}
	/non-public/
	boolean isConvertibleTo(MethodType newType) {
	MethodTypeForm oldForm = this.form();
	MethodTypeForm newForm = newType.form();
	if (oldForm == newForm)
	// same parameter count, same primitive/object mix
	return true;
	if (!canConvert(returnType(), newType.returnType()))
	return false;
	Class<?>[] srcTypes = newType.ptypes;
	Class<?>[] dstTypes = ptypes;
	if (srcTypes == dstTypes)
	return true;
	int argc;
	if ((argc = srcTypes.length) != dstTypes.length)
	return false;
	if (argc <= 1) {
	if (argc == 1 && !canConvert(srcTypes[0], dstTypes[0]))
	return false;
	return true;
	}
	if ((oldForm.primitiveParameterCount() == 0 && oldForm.erasedType == this) \|\|
	(newForm.primitiveParameterCount() == 0 && newForm.erasedType == newType)) {
	// Somewhat complicated test to avoid a loop of 2 or more trips.
	// If either type has only Object parameters, we know we can convert.
	assert(canConvertParameters(srcTypes, dstTypes));
	return true;
	}
	return canConvertParameters(srcTypes, dstTypes);
	}

	/** Returns true if MHs.explicitCastArguments produces the same result as MH.asType.
	* If the type conversion is impossible for either, the result should be false.
	*/
	/non-public/
	boolean explicitCastEquivalentToAsType(MethodType newType) {
	if (this == newType) return true;
	if (!explicitCastEquivalentToAsType(rtype, newType.rtype)) {
	return false;
	}
	Class<?>[] srcTypes = newType.ptypes;
	Class<?>[] dstTypes = ptypes;
	if (dstTypes == srcTypes) {
	return true;
	}
	assert(dstTypes.length == srcTypes.length);
	for (int i = 0; i < dstTypes.length; i++) {
	if (!explicitCastEquivalentToAsType(srcTypes[i], dstTypes[i])) {
	return false;
	}
	}
	return true;
	}

	/** Reports true if the src can be converted to the dst, by both asType and MHs.eCE,
	* and with the same effect.
	* MHs.eCA has the following "upgrades" to MH.asType:
	* 1. interfaces are unchecked (that is, treated as if aliased to Object)
	* Therefore, {@code Object->CharSequence} is possible in both cases but has different semantics
	* 2. the full matrix of primitive-to-primitive conversions is supported
	* Narrowing like {@code long->byte} and basic-typing like {@code boolean->int}
	* are not supported by asType, but anything supported by asType is equivalent
	* with MHs.eCE.
	* 3a. unboxing conversions can be followed by the full matrix of primitive conversions
	* 3b. unboxing of null is permitted (creates a zero primitive value)
	* Other than interfaces, reference-to-reference conversions are the same.
	* Boxing primitives to references is the same for both operators.
	*/
	private static boolean explicitCastEquivalentToAsType(Class<?> src, Class<?> dst) {
	if (src == dst \|\| dst == Object.class \|\| dst == void.class) return true;
	if (src.isPrimitive()) {
	// Could be a prim/prim conversion, where casting is a strict superset.
	// Or a boxing conversion, which is always to an exact wrapper class.
	return canConvert(src, dst);
	} else if (dst.isPrimitive()) {
	// Unboxing behavior is different between MHs.eCA & MH.asType (see 3b).
	return false;
	} else {
	// R->R always works, but we have to avoid a check-cast to an interface.
	return !dst.isInterface() \|\| dst.isAssignableFrom(src);
	}
	}

	private boolean canConvertParameters(Class<?>[] srcTypes, Class<?>[] dstTypes) {
	for (int i = 0; i < srcTypes.length; i++) {
	if (!canConvert(srcTypes[i], dstTypes[i])) {
	return false;
	}
	}
	return true;
	}

	/non-public/
	static boolean canConvert(Class<?> src, Class<?> dst) {
	// short-circuit a few cases:
	if (src == dst \|\| src == Object.class \|\| 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 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
	{
	return fromDescriptor(descriptor,
	(loader == null) ? ClassLoader.getSystemClassLoader() : loader);
	}

	/**
	* Same as {@link #fromMethodDescriptorString(String, ClassLoader)}, but
	* {@code null} ClassLoader means the bootstrap loader is used here.
	* <p>
	* IMPORTANT: This method is preferable for JDK internal use as it more
	* correctly interprets {@code null} ClassLoader than
	* {@link #fromMethodDescriptorString(String, ClassLoader)}.
	* Use of this method also avoids early initialization issues when system
	* ClassLoader is not initialized yet.
	*/
	static MethodType fromDescriptor(String descriptor, ClassLoader loader)
	throws IllegalArgumentException, TypeNotPresentException
	{
	if (!descriptor.startsWith("(") \|\| // also generates NPE if needed
	descriptor.indexOf(')') < 0 \|\|
	descriptor.indexOf('.') >= 0)
	throw newIllegalArgumentException("not a method descriptor: "+descriptor);
	List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader);
	Class<?> rtype = types.remove(types.size() - 1);
	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.unparseMethod(this.rtype, this.ptypes);
	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 #readResolve
	* @see #writeObject
	*/
	private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
	// Assign temporary defaults in case this object escapes
	MethodType_init(void.class, NO_PTYPES);

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

	Class<?> returnType = (Class<?>) s.readObject();
	Class<?>[] parameterArray = (Class<?>[]) s.readObject();
	parameterArray = parameterArray.clone(); // make sure it is unshared

	// Assign deserialized values
	MethodType_init(returnType, parameterArray);
	}

	// Initialization of state for deserialization only
	private void MethodType_init(Class<?> rtype, Class<?>[] ptypes) {
	// In order to communicate these values to readResolve, we must
	// store them into the implementation-specific final fields.
	checkRtype(rtype);
	checkPtypes(ptypes);
	UNSAFE.putObject(this, OffsetHolder.rtypeOffset, rtype);
	UNSAFE.putObject(this, OffsetHolder.ptypesOffset, ptypes);
	}

	// Support for resetting final fields while deserializing. Implement Holder
	// pattern to make the rarely needed offset calculation lazy.
	private static class OffsetHolder {
	static final long rtypeOffset
	= UNSAFE.objectFieldOffset(MethodType.class, "rtype");

	static final long ptypesOffset
	= UNSAFE.objectFieldOffset(MethodType.class, "ptypes");
	}

	/**
	* Resolves and initializes a {@code MethodType} object
	* after serialization.
	* @return the fully initialized {@code MethodType} object
	*/
	private Object readResolve() {
	// Do not use a trusted path for deserialization:
	// return makeImpl(rtype, ptypes, true);
	// Verify all operands, and make sure ptypes is unshared:
	try {
	return methodType(rtype, ptypes);
	} finally {
	// Re-assign defaults in case this object escapes
	MethodType_init(void.class, NO_PTYPES);
	}
	}

	/**
	* Simple implementation of weak concurrent intern set.
	*
	* @param <T> interned type
	*/
	private static class ConcurrentWeakInternSet<T> {

	private final ConcurrentMap<WeakEntry<T>, WeakEntry<T>> map;
	private final ReferenceQueue<T> stale;

	public ConcurrentWeakInternSet() {
	this.map = new ConcurrentHashMap<>(512);
	this.stale = new ReferenceQueue<>();
	}

	/**
	* Get the existing interned element.
	* This method returns null if no element is interned.
	*
	* @param elem element to look up
	* @return the interned element
	*/
	public T get(T elem) {
	if (elem == null) throw new NullPointerException();
	expungeStaleElements();

	WeakEntry<T> value = map.get(new WeakEntry<>(elem));
	if (value != null) {
	T res = value.get();
	if (res != null) {
	return res;
	}
	}
	return null;
	}

	/**
	* Interns the element.
	* Always returns non-null element, matching the one in the intern set.
	* Under the race against another add(), it can return <i>different</i>
	* element, if another thread beats us to interning it.
	*
	* @param elem element to add
	* @return element that was actually added
	*/
	public T add(T elem) {
	if (elem == null) throw new NullPointerException();

	// Playing double race here, and so spinloop is required.
	// First race is with two concurrent updaters.
	// Second race is with GC purging weak ref under our feet.
	// Hopefully, we almost always end up with a single pass.
	T interned;
	WeakEntry<T> e = new WeakEntry<>(elem, stale);
	do {
	expungeStaleElements();
	WeakEntry<T> exist = map.putIfAbsent(e, e);
	interned = (exist == null) ? elem : exist.get();
	} while (interned == null);
	return interned;
	}

	private void expungeStaleElements() {
	Reference<? extends T> reference;
	while ((reference = stale.poll()) != null) {
	map.remove(reference);
	}
	}

	private static class WeakEntry<T> extends WeakReference<T> {

	public final int hashcode;

	public WeakEntry(T key, ReferenceQueue<T> queue) {
	super(key, queue);
	hashcode = key.hashCode();
	}

	public WeakEntry(T key) {
	super(key);
	hashcode = key.hashCode();
	}

	@Override
	public boolean equals(Object obj) {
	if (obj instanceof WeakEntry) {
	Object that = ((WeakEntry) obj).get();
	Object mine = get();
	return (that == null \|\| mine == null) ? (this == obj) : mine.equals(that);
	}
	return false;
	}

	@Override
	public int hashCode() {
	return hashcode;
	}

	}
	}

	}

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