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	/*
	* 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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	*/

	package java.lang.invoke;


	import java.util.*;

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

	/**
	* A method handle is a typed, directly executable reference to an underlying method,
	* constructor, field, or similar low-level operation, with optional
	* transformations of arguments or return values.
	* These transformations are quite general, and include such patterns as
	* {@linkplain #asType conversion},
	* {@linkplain #bindTo insertion},
	* {@linkplain java.lang.invoke.MethodHandles#dropArguments deletion},
	* and {@linkplain java.lang.invoke.MethodHandles#filterArguments substitution}.
	*
	* <h1>Method handle contents</h1>
	* Method handles are dynamically and strongly typed according to their parameter and return types.
	* They are not distinguished by the name or the defining class of their underlying methods.
	* A method handle must be invoked using a symbolic type descriptor which matches
	* the method handle's own {@linkplain #type type descriptor}.
	* <p>
	* Every method handle reports its type descriptor via the {@link #type type} accessor.
	* This type descriptor is a {@link java.lang.invoke.MethodType MethodType} object,
	* whose structure is a series of classes, one of which is
	* the return type of the method (or {@code void.class} if none).
	* <p>
	* A method handle's type controls the types of invocations it accepts,
	* and the kinds of transformations that apply to it.
	* <p>
	* A method handle contains a pair of special invoker methods
	* called {@link #invokeExact invokeExact} and {@link #invoke invoke}.
	* Both invoker methods provide direct access to the method handle's
	* underlying method, constructor, field, or other operation,
	* as modified by transformations of arguments and return values.
	* Both invokers accept calls which exactly match the method handle's own type.
	* The plain, inexact invoker also accepts a range of other call types.
	* <p>
	* Method handles are immutable and have no visible state.
	* Of course, they can be bound to underlying methods or data which exhibit state.
	* With respect to the Java Memory Model, any method handle will behave
	* as if all of its (internal) fields are final variables. This means that any method
	* handle made visible to the application will always be fully formed.
	* This is true even if the method handle is published through a shared
	* variable in a data race.
	* <p>
	* Method handles cannot be subclassed by the user.
	* Implementations may (or may not) create internal subclasses of {@code MethodHandle}
	* which may be visible via the {@link java.lang.Object#getClass Object.getClass}
	* operation. The programmer should not draw conclusions about a method handle
	* from its specific class, as the method handle class hierarchy (if any)
	* may change from time to time or across implementations from different vendors.
	*
	* <h1>Method handle compilation</h1>
	* A Java method call expression naming {@code invokeExact} or {@code invoke}
	* can invoke a method handle from Java source code.
	* From the viewpoint of source code, these methods can take any arguments
	* and their result can be cast to any return type.
	* Formally this is accomplished by giving the invoker methods
	* {@code Object} return types and variable arity {@code Object} arguments,
	* but they have an additional quality called <em>signature polymorphism</em>
	* which connects this freedom of invocation directly to the JVM execution stack.
	* <p>
	* As is usual with virtual methods, source-level calls to {@code invokeExact}
	* and {@code invoke} compile to an {@code invokevirtual} instruction.
	* More unusually, the compiler must record the actual argument types,
	* and may not perform method invocation conversions on the arguments.
	* Instead, it must push them on the stack according to their own unconverted types.
	* The method handle object itself is pushed on the stack before the arguments.
	* The compiler then calls the method handle with a symbolic type descriptor which
	* describes the argument and return types.
	* <p>
	* To issue a complete symbolic type descriptor, the compiler must also determine
	* the return type. This is based on a cast on the method invocation expression,
	* if there is one, or else {@code Object} if the invocation is an expression
	* or else {@code void} if the invocation is a statement.
	* The cast may be to a primitive type (but not {@code void}).
	* <p>
	* As a corner case, an uncasted {@code null} argument is given
	* a symbolic type descriptor of {@code java.lang.Void}.
	* The ambiguity with the type {@code Void} is harmless, since there are no references of type
	* {@code Void} except the null reference.
	*
	* <h1>Method handle invocation</h1>
	* The first time a {@code invokevirtual} instruction is executed
	* it is linked, by symbolically resolving the names in the instruction
	* and verifying that the method call is statically legal.
	* This is true of calls to {@code invokeExact} and {@code invoke}.
	* In this case, the symbolic type descriptor emitted by the compiler is checked for
	* correct syntax and names it contains are resolved.
	* Thus, an {@code invokevirtual} instruction which invokes
	* a method handle will always link, as long
	* as the symbolic type descriptor is syntactically well-formed
	* and the types exist.
	* <p>
	* When the {@code invokevirtual} is executed after linking,
	* the receiving method handle's type is first checked by the JVM
	* to ensure that it matches the symbolic type descriptor.
	* If the type match fails, it means that the method which the
	* caller is invoking is not present on the individual
	* method handle being invoked.
	* <p>
	* In the case of {@code invokeExact}, the type descriptor of the invocation
	* (after resolving symbolic type names) must exactly match the method type
	* of the receiving method handle.
	* In the case of plain, inexact {@code invoke}, the resolved type descriptor
	* must be a valid argument to the receiver's {@link #asType asType} method.
	* Thus, plain {@code invoke} is more permissive than {@code invokeExact}.
	* <p>
	* After type matching, a call to {@code invokeExact} directly
	* and immediately invoke the method handle's underlying method
	* (or other behavior, as the case may be).
	* <p>
	* A call to plain {@code invoke} works the same as a call to
	* {@code invokeExact}, if the symbolic type descriptor specified by the caller
	* exactly matches the method handle's own type.
	* If there is a type mismatch, {@code invoke} attempts
	* to adjust the type of the receiving method handle,
	* as if by a call to {@link #asType asType},
	* to obtain an exactly invokable method handle {@code M2}.
	* This allows a more powerful negotiation of method type
	* between caller and callee.
	* <p>
	* (<em>Note:</em> The adjusted method handle {@code M2} is not directly observable,
	* and implementations are therefore not required to materialize it.)
	*
	* <h1>Invocation checking</h1>
	* In typical programs, method handle type matching will usually succeed.
	* But if a match fails, the JVM will throw a {@link WrongMethodTypeException},
	* either directly (in the case of {@code invokeExact}) or indirectly as if
	* by a failed call to {@code asType} (in the case of {@code invoke}).
	* <p>
	* Thus, a method type mismatch which might show up as a linkage error
	* in a statically typed program can show up as
	* a dynamic {@code WrongMethodTypeException}
	* in a program which uses method handles.
	* <p>
	* Because method types contain "live" {@code Class} objects,
	* method type matching takes into account both types names and class loaders.
	* Thus, even if a method handle {@code M} is created in one
	* class loader {@code L1} and used in another {@code L2},
	* method handle calls are type-safe, because the caller's symbolic type
	* descriptor, as resolved in {@code L2},
	* is matched against the original callee method's symbolic type descriptor,
	* as resolved in {@code L1}.
	* The resolution in {@code L1} happens when {@code M} is created
	* and its type is assigned, while the resolution in {@code L2} happens
	* when the {@code invokevirtual} instruction is linked.
	* <p>
	* Apart from the checking of type descriptors,
	* a method handle's capability to call its underlying method is unrestricted.
	* If a method handle is formed on a non-public method by a class
	* that has access to that method, the resulting handle can be used
	* in any place by any caller who receives a reference to it.
	* <p>
	* Unlike with the Core Reflection API, where access is checked every time
	* a reflective method is invoked,
	* method handle access checking is performed
	* <a href="MethodHandles.Lookup.html#access">when the method handle is created</a>.
	* In the case of {@code ldc} (see below), access checking is performed as part of linking
	* the constant pool entry underlying the constant method handle.
	* <p>
	* Thus, handles to non-public methods, or to methods in non-public classes,
	* should generally be kept secret.
	* They should not be passed to untrusted code unless their use from
	* the untrusted code would be harmless.
	*
	* <h1>Method handle creation</h1>
	* Java code can create a method handle that directly accesses
	* any method, constructor, or field that is accessible to that code.
	* This is done via a reflective, capability-based API called
	* {@link java.lang.invoke.MethodHandles.Lookup MethodHandles.Lookup}
	* For example, a static method handle can be obtained
	* from {@link java.lang.invoke.MethodHandles.Lookup#findStatic Lookup.findStatic}.
	* There are also conversion methods from Core Reflection API objects,
	* such as {@link java.lang.invoke.MethodHandles.Lookup#unreflect Lookup.unreflect}.
	* <p>
	* Like classes and strings, method handles that correspond to accessible
	* fields, methods, and constructors can also be represented directly
	* in a class file's constant pool as constants to be loaded by {@code ldc} bytecodes.
	* A new type of constant pool entry, {@code CONSTANT_MethodHandle},
	* refers directly to an associated {@code CONSTANT_Methodref},
	* {@code CONSTANT_InterfaceMethodref}, or {@code CONSTANT_Fieldref}
	* constant pool entry.
	* (For full details on method handle constants,
	* see sections 4.4.8 and 5.4.3.5 of the Java Virtual Machine Specification.)
	* <p>
	* Method handles produced by lookups or constant loads from methods or
	* constructors with the variable arity modifier bit ({@code 0x0080})
	* have a corresponding variable arity, as if they were defined with
	* the help of {@link #asVarargsCollector asVarargsCollector}.
	* <p>
	* A method reference may refer either to a static or non-static method.
	* In the non-static case, the method handle type includes an explicit
	* receiver argument, prepended before any other arguments.
	* In the method handle's type, the initial receiver argument is typed
	* according to the class under which the method was initially requested.
	* (E.g., if a non-static method handle is obtained via {@code ldc},
	* the type of the receiver is the class named in the constant pool entry.)
	* <p>
	* Method handle constants are subject to the same link-time access checks
	* their corresponding bytecode instructions, and the {@code ldc} instruction
	* will throw corresponding linkage errors if the bytecode behaviors would
	* throw such errors.
	* <p>
	* As a corollary of this, access to protected members is restricted
	* to receivers only of the accessing class, or one of its subclasses,
	* and the accessing class must in turn be a subclass (or package sibling)
	* of the protected member's defining class.
	* If a method reference refers to a protected non-static method or field
	* of a class outside the current package, the receiver argument will
	* be narrowed to the type of the accessing class.
	* <p>
	* When a method handle to a virtual method is invoked, the method is
	* always looked up in the receiver (that is, the first argument).
	* <p>
	* A non-virtual method handle to a specific virtual method implementation
	* can also be created. These do not perform virtual lookup based on
	* receiver type. Such a method handle simulates the effect of
	* an {@code invokespecial} instruction to the same method.
	*
	* <h1>Usage examples</h1>
	* Here are some examples of usage:
	* <blockquote><pre>{@code
	Object x, y; String s; int i;
	MethodType mt; MethodHandle mh;
	MethodHandles.Lookup lookup = MethodHandles.lookup();
	// mt is (char,char)String
	mt = MethodType.methodType(String.class, char.class, char.class);
	mh = lookup.findVirtual(String.class, "replace", mt);
	s = (String) mh.invokeExact("daddy",'d','n');
	// invokeExact(Ljava/lang/String;CC)Ljava/lang/String;
	assertEquals(s, "nanny");
	// weakly typed invocation (using MHs.invoke)
	s = (String) mh.invokeWithArguments("sappy", 'p', 'v');
	assertEquals(s, "savvy");
	// mt is (Object[])List
	mt = MethodType.methodType(java.util.List.class, Object[].class);
	mh = lookup.findStatic(java.util.Arrays.class, "asList", mt);
	assert(mh.isVarargsCollector());
	x = mh.invoke("one", "two");
	// invoke(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/Object;
	assertEquals(x, java.util.Arrays.asList("one","two"));
	// mt is (Object,Object,Object)Object
	mt = MethodType.genericMethodType(3);
	mh = mh.asType(mt);
	x = mh.invokeExact((Object)1, (Object)2, (Object)3);
	// invokeExact(Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;
	assertEquals(x, java.util.Arrays.asList(1,2,3));
	// mt is ()int
	mt = MethodType.methodType(int.class);
	mh = lookup.findVirtual(java.util.List.class, "size", mt);
	i = (int) mh.invokeExact(java.util.Arrays.asList(1,2,3));
	// invokeExact(Ljava/util/List;)I
	assert(i == 3);
	mt = MethodType.methodType(void.class, String.class);
	mh = lookup.findVirtual(java.io.PrintStream.class, "println", mt);
	mh.invokeExact(System.out, "Hello, world.");
	// invokeExact(Ljava/io/PrintStream;Ljava/lang/String;)V
	* }</pre></blockquote>
	* Each of the above calls to {@code invokeExact} or plain {@code invoke}
	* generates a single invokevirtual instruction with
	* the symbolic type descriptor indicated in the following comment.
	* In these examples, the helper method {@code assertEquals} is assumed to
	* be a method which calls {@link java.util.Objects#equals(Object,Object) Objects.equals}
	* on its arguments, and asserts that the result is true.
	*
	* <h1>Exceptions</h1>
	* The methods {@code invokeExact} and {@code invoke} are declared
	* to throw {@link java.lang.Throwable Throwable},
	* which is to say that there is no static restriction on what a method handle
	* can throw. Since the JVM does not distinguish between checked
	* and unchecked exceptions (other than by their class, of course),
	* there is no particular effect on bytecode shape from ascribing
	* checked exceptions to method handle invocations. But in Java source
	* code, methods which perform method handle calls must either explicitly
	* throw {@code Throwable}, or else must catch all
	* throwables locally, rethrowing only those which are legal in the context,
	* and wrapping ones which are illegal.
	*
	* <h1><a name="sigpoly"></a>Signature polymorphism</h1>
	* The unusual compilation and linkage behavior of
	* {@code invokeExact} and plain {@code invoke}
	* is referenced by the term <em>signature polymorphism</em>.
	* As defined in the Java Language Specification,
	* a signature polymorphic method is one which can operate with
	* any of a wide range of call signatures and return types.
	* <p>
	* In source code, a call to a signature polymorphic method will
	* compile, regardless of the requested symbolic type descriptor.
	* As usual, the Java compiler emits an {@code invokevirtual}
	* instruction with the given symbolic type descriptor against the named method.
	* The unusual part is that the symbolic type descriptor is derived from
	* the actual argument and return types, not from the method declaration.
	* <p>
	* When the JVM processes bytecode containing signature polymorphic calls,
	* it will successfully link any such call, regardless of its symbolic type descriptor.
	* (In order to retain type safety, the JVM will guard such calls with suitable
	* dynamic type checks, as described elsewhere.)
	* <p>
	* Bytecode generators, including the compiler back end, are required to emit
	* untransformed symbolic type descriptors for these methods.
	* Tools which determine symbolic linkage are required to accept such
	* untransformed descriptors, without reporting linkage errors.
	*
	* <h1>Interoperation between method handles and the Core Reflection API</h1>
	* Using factory methods in the {@link java.lang.invoke.MethodHandles.Lookup Lookup} API,
	* any class member represented by a Core Reflection API object
	* can be converted to a behaviorally equivalent method handle.
	* For example, a reflective {@link java.lang.reflect.Method Method} can
	* be converted to a method handle using
	* {@link java.lang.invoke.MethodHandles.Lookup#unreflect Lookup.unreflect}.
	* The resulting method handles generally provide more direct and efficient
	* access to the underlying class members.
	* <p>
	* As a special case,
	* when the Core Reflection API is used to view the signature polymorphic
	* methods {@code invokeExact} or plain {@code invoke} in this class,
	* they appear as ordinary non-polymorphic methods.
	* Their reflective appearance, as viewed by
	* {@link java.lang.Class#getDeclaredMethod Class.getDeclaredMethod},
	* is unaffected by their special status in this API.
	* For example, {@link java.lang.reflect.Method#getModifiers Method.getModifiers}
	* will report exactly those modifier bits required for any similarly
	* declared method, including in this case {@code native} and {@code varargs} bits.
	* <p>
	* As with any reflected method, these methods (when reflected) may be
	* invoked via {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}.
	* However, such reflective calls do not result in method handle invocations.
	* Such a call, if passed the required argument
	* (a single one, of type {@code Object[]}), will ignore the argument and
	* will throw an {@code UnsupportedOperationException}.
	* <p>
	* Since {@code invokevirtual} instructions can natively
	* invoke method handles under any symbolic type descriptor, this reflective view conflicts
	* with the normal presentation of these methods via bytecodes.
	* Thus, these two native methods, when reflectively viewed by
	* {@code Class.getDeclaredMethod}, may be regarded as placeholders only.
	* <p>
	* In order to obtain an invoker method for a particular type descriptor,
	* use {@link java.lang.invoke.MethodHandles#exactInvoker MethodHandles.exactInvoker},
	* or {@link java.lang.invoke.MethodHandles#invoker MethodHandles.invoker}.
	* The {@link java.lang.invoke.MethodHandles.Lookup#findVirtual Lookup.findVirtual}
	* API is also able to return a method handle
	* to call {@code invokeExact} or plain {@code invoke},
	* for any specified type descriptor .
	*
	* <h1>Interoperation between method handles and Java generics</h1>
	* A method handle can be obtained on a method, constructor, or field
	* which is declared with Java generic types.
	* As with the Core Reflection API, the type of the method handle
	* will constructed from the erasure of the source-level type.
	* When a method handle is invoked, the types of its arguments
	* or the return value cast type may be generic types or type instances.
	* If this occurs, the compiler will replace those
	* types by their erasures when it constructs the symbolic type descriptor
	* for the {@code invokevirtual} instruction.
	* <p>
	* Method handles do not represent
	* their function-like types in terms of Java parameterized (generic) types,
	* because there are three mismatches between function-like types and parameterized
	* Java types.
	* <ul>
	* <li>Method types range over all possible arities,
	* from no arguments to up to the <a href="MethodHandle.html#maxarity">maximum number</a> of allowed arguments.
	* Generics are not variadic, and so cannot represent this.</li>
	* <li>Method types can specify arguments of primitive types,
	* which Java generic types cannot range over.</li>
	* <li>Higher order functions over method handles (combinators) are
	* often generic across a wide range of function types, including
	* those of multiple arities. It is impossible to represent such
	* genericity with a Java type parameter.</li>
	* </ul>
	*
	* <h1><a name="maxarity"></a>Arity limits</h1>
	* The JVM imposes on all methods and constructors of any kind an absolute
	* limit of 255 stacked arguments. This limit can appear more restrictive
	* in certain cases:
	* <ul>
	* <li>A {@code long} or {@code double} argument counts (for purposes of arity limits) as two argument slots.
	* <li>A non-static method consumes an extra argument for the object on which the method is called.
	* <li>A constructor consumes an extra argument for the object which is being constructed.
	* <li>Since a method handle’s {@code invoke} method (or other signature-polymorphic method) is non-virtual,
	* it consumes an extra argument for the method handle itself, in addition to any non-virtual receiver object.
	* </ul>
	* These limits imply that certain method handles cannot be created, solely because of the JVM limit on stacked arguments.
	* For example, if a static JVM method accepts exactly 255 arguments, a method handle cannot be created for it.
	* Attempts to create method handles with impossible method types lead to an {@link IllegalArgumentException}.
	* In particular, a method handle’s type must not have an arity of the exact maximum 255.
	*
	* @see MethodType
	* @see MethodHandles
	* @author John Rose, JSR 292 EG
	*/
	public abstract class MethodHandle {
	static { MethodHandleImpl.initStatics(); }

	/**
	* Internal marker interface which distinguishes (to the Java compiler)
	* those methods which are <a href="MethodHandle.html#sigpoly">signature polymorphic</a>.
	*/
	@java.lang.annotation.Target({java.lang.annotation.ElementType.METHOD})
	@java.lang.annotation.Retention(java.lang.annotation.RetentionPolicy.RUNTIME)
	@interface PolymorphicSignature { }

	private final MethodType type;
	/private/ final LambdaForm form;
	// form is not private so that invokers can easily fetch it
	/private/ MethodHandle asTypeCache;
	// asTypeCache is not private so that invokers can easily fetch it
	/non-public/ byte customizationCount;
	// customizationCount should be accessible from invokers

	/**
	* Reports the type of this method handle.
	* Every invocation of this method handle via {@code invokeExact} must exactly match this type.
	* @return the method handle type
	*/
	public MethodType type() {
	return type;
	}

	/**
	* Package-private constructor for the method handle implementation hierarchy.
	* Method handle inheritance will be contained completely within
	* the {@code java.lang.invoke} package.
	*/
	// @param type type (permanently assigned) of the new method handle
	/non-public/ MethodHandle(MethodType type, LambdaForm form) {
	type.getClass(); // explicit NPE
	form.getClass(); // explicit NPE
	this.type = type;
	this.form = form.uncustomize();

	this.form.prepare(); // TO DO: Try to delay this step until just before invocation.
	}

	/**
	* Invokes the method handle, allowing any caller type descriptor, but requiring an exact type match.
	* The symbolic type descriptor at the call site of {@code invokeExact} must
	* exactly match this method handle's {@link #type type}.
	* No conversions are allowed on arguments or return values.
	* <p>
	* When this method is observed via the Core Reflection API,
	* it will appear as a single native method, taking an object array and returning an object.
	* If this native method is invoked directly via
	* {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}, via JNI,
	* or indirectly via {@link java.lang.invoke.MethodHandles.Lookup#unreflect Lookup.unreflect},
	* it will throw an {@code UnsupportedOperationException}.
	* @param args the signature-polymorphic parameter list, statically represented using varargs
	* @return the signature-polymorphic result, statically represented using {@code Object}
	* @throws WrongMethodTypeException if the target's type is not identical with the caller's symbolic type descriptor
	* @throws Throwable anything thrown by the underlying method propagates unchanged through the method handle call
	*/
	public final native @PolymorphicSignature Object invokeExact(Object... args) throws Throwable;

	/**
	* Invokes the method handle, allowing any caller type descriptor,
	* and optionally performing conversions on arguments and return values.
	* <p>
	* If the call site's symbolic type descriptor exactly matches this method handle's {@link #type type},
	* the call proceeds as if by {@link #invokeExact invokeExact}.
	* <p>
	* Otherwise, the call proceeds as if this method handle were first
	* adjusted by calling {@link #asType asType} to adjust this method handle
	* to the required type, and then the call proceeds as if by
	* {@link #invokeExact invokeExact} on the adjusted method handle.
	* <p>
	* There is no guarantee that the {@code asType} call is actually made.
	* If the JVM can predict the results of making the call, it may perform
	* adaptations directly on the caller's arguments,
	* and call the target method handle according to its own exact type.
	* <p>
	* The resolved type descriptor at the call site of {@code invoke} must
	* be a valid argument to the receivers {@code asType} method.
	* In particular, the caller must specify the same argument arity
	* as the callee's type,
	* if the callee is not a {@linkplain #asVarargsCollector variable arity collector}.
	* <p>
	* When this method is observed via the Core Reflection API,
	* it will appear as a single native method, taking an object array and returning an object.
	* If this native method is invoked directly via
	* {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}, via JNI,
	* or indirectly via {@link java.lang.invoke.MethodHandles.Lookup#unreflect Lookup.unreflect},
	* it will throw an {@code UnsupportedOperationException}.
	* @param args the signature-polymorphic parameter list, statically represented using varargs
	* @return the signature-polymorphic result, statically represented using {@code Object}
	* @throws WrongMethodTypeException if the target's type cannot be adjusted to the caller's symbolic type descriptor
	* @throws ClassCastException if the target's type can be adjusted to the caller, but a reference cast fails
	* @throws Throwable anything thrown by the underlying method propagates unchanged through the method handle call
	*/
	public final native @PolymorphicSignature Object invoke(Object... args) throws Throwable;

	/**
	* Private method for trusted invocation of a method handle respecting simplified signatures.
	* Type mismatches will not throw {@code WrongMethodTypeException}, but could crash the JVM.
	* <p>
	* The caller signature is restricted to the following basic types:
	* Object, int, long, float, double, and void return.
	* <p>
	* The caller is responsible for maintaining type correctness by ensuring
	* that the each outgoing argument value is a member of the range of the corresponding
	* callee argument type.
	* (The caller should therefore issue appropriate casts and integer narrowing
	* operations on outgoing argument values.)
	* The caller can assume that the incoming result value is part of the range
	* of the callee's return type.
	* @param args the signature-polymorphic parameter list, statically represented using varargs
	* @return the signature-polymorphic result, statically represented using {@code Object}
	*/
	/non-public/ final native @PolymorphicSignature Object invokeBasic(Object... args) throws Throwable;

	/**
	* Private method for trusted invocation of a MemberName of kind {@code REF_invokeVirtual}.
	* The caller signature is restricted to basic types as with {@code invokeBasic}.
	* The trailing (not leading) argument must be a MemberName.
	* @param args the signature-polymorphic parameter list, statically represented using varargs
	* @return the signature-polymorphic result, statically represented using {@code Object}
	*/
	/non-public/ static native @PolymorphicSignature Object linkToVirtual(Object... args) throws Throwable;

	/**
	* Private method for trusted invocation of a MemberName of kind {@code REF_invokeStatic}.
	* The caller signature is restricted to basic types as with {@code invokeBasic}.
	* The trailing (not leading) argument must be a MemberName.
	* @param args the signature-polymorphic parameter list, statically represented using varargs
	* @return the signature-polymorphic result, statically represented using {@code Object}
	*/
	/non-public/ static native @PolymorphicSignature Object linkToStatic(Object... args) throws Throwable;

	/**
	* Private method for trusted invocation of a MemberName of kind {@code REF_invokeSpecial}.
	* The caller signature is restricted to basic types as with {@code invokeBasic}.
	* The trailing (not leading) argument must be a MemberName.
	* @param args the signature-polymorphic parameter list, statically represented using varargs
	* @return the signature-polymorphic result, statically represented using {@code Object}
	*/
	/non-public/ static native @PolymorphicSignature Object linkToSpecial(Object... args) throws Throwable;

	/**
	* Private method for trusted invocation of a MemberName of kind {@code REF_invokeInterface}.
	* The caller signature is restricted to basic types as with {@code invokeBasic}.
	* The trailing (not leading) argument must be a MemberName.
	* @param args the signature-polymorphic parameter list, statically represented using varargs
	* @return the signature-polymorphic result, statically represented using {@code Object}
	*/
	/non-public/ static native @PolymorphicSignature Object linkToInterface(Object... args) throws Throwable;

	/**
	* Performs a variable arity invocation, passing the arguments in the given list
	* to the method handle, as if via an inexact {@link #invoke invoke} from a call site
	* which mentions only the type {@code Object}, and whose arity is the length
	* of the argument list.
	* <p>
	* Specifically, execution proceeds as if by the following steps,
	* although the methods are not guaranteed to be called if the JVM
	* can predict their effects.
	* <ul>
	* <li>Determine the length of the argument array as {@code N}.
	* For a null reference, {@code N=0}. </li>
	* <li>Determine the general type {@code TN} of {@code N} arguments as
	* as {@code TN=MethodType.genericMethodType(N)}.</li>
	* <li>Force the original target method handle {@code MH0} to the
	* required type, as {@code MH1 = MH0.asType(TN)}. </li>
	* <li>Spread the array into {@code N} separate arguments {@code A0, ...}. </li>
	* <li>Invoke the type-adjusted method handle on the unpacked arguments:
	* MH1.invokeExact(A0, ...). </li>
	* <li>Take the return value as an {@code Object} reference. </li>
	* </ul>
	* <p>
	* Because of the action of the {@code asType} step, the following argument
	* conversions are applied as necessary:
	* <ul>
	* <li>reference casting
	* <li>unboxing
	* <li>widening primitive conversions
	* </ul>
	* <p>
	* The result returned by the call is boxed if it is a primitive,
	* or forced to null if the return type is void.
	* <p>
	* This call is equivalent to the following code:
	* <blockquote><pre>{@code
	* MethodHandle invoker = MethodHandles.spreadInvoker(this.type(), 0);
	* Object result = invoker.invokeExact(this, arguments);
	* }</pre></blockquote>
	* <p>
	* Unlike the signature polymorphic methods {@code invokeExact} and {@code invoke},
	* {@code invokeWithArguments} can be accessed normally via the Core Reflection API and JNI.
	* It can therefore be used as a bridge between native or reflective code and method handles.
	*
	* @param arguments the arguments to pass to the target
	* @return the result returned by the target
	* @throws ClassCastException if an argument cannot be converted by reference casting
	* @throws WrongMethodTypeException if the target's type cannot be adjusted to take the given number of {@code Object} arguments
	* @throws Throwable anything thrown by the target method invocation
	* @see MethodHandles#spreadInvoker
	*/
	public Object invokeWithArguments(Object... arguments) throws Throwable {
	MethodType invocationType = MethodType.genericMethodType(arguments == null ? 0 : arguments.length);
	return invocationType.invokers().spreadInvoker(0).invokeExact(asType(invocationType), arguments);
	}

	/**
	* Performs a variable arity invocation, passing the arguments in the given array
	* to the method handle, as if via an inexact {@link #invoke invoke} from a call site
	* which mentions only the type {@code Object}, and whose arity is the length
	* of the argument array.
	* <p>
	* This method is also equivalent to the following code:
	* <blockquote><pre>{@code
	* invokeWithArguments(arguments.toArray()
	* }</pre></blockquote>
	*
	* @param arguments the arguments to pass to the target
	* @return the result returned by the target
	* @throws NullPointerException if {@code arguments} is a null reference
	* @throws ClassCastException if an argument cannot be converted by reference casting
	* @throws WrongMethodTypeException if the target's type cannot be adjusted to take the given number of {@code Object} arguments
	* @throws Throwable anything thrown by the target method invocation
	*/
	public Object invokeWithArguments(java.util.List<?> arguments) throws Throwable {
	return invokeWithArguments(arguments.toArray());
	}

	/**
	* Produces an adapter method handle which adapts the type of the
	* current method handle to a new type.
	* The resulting method handle is guaranteed to report a type
	* which is equal to the desired new type.
	* <p>
	* If the original type and new type are equal, returns {@code this}.
	* <p>
	* The new method handle, when invoked, will perform the following
	* steps:
	* <ul>
	* <li>Convert the incoming argument list to match the original
	* method handle's argument list.
	* <li>Invoke the original method handle on the converted argument list.
	* <li>Convert any result returned by the original method handle
	* to the return type of new method handle.
	* </ul>
	* <p>
	* This method provides the crucial behavioral difference between
	* {@link #invokeExact invokeExact} and plain, inexact {@link #invoke invoke}.
	* The two methods
	* perform the same steps when the caller's type descriptor exactly m atches
	* the callee's, but when the types differ, plain {@link #invoke invoke}
	* also calls {@code asType} (or some internal equivalent) in order
	* to match up the caller's and callee's types.
	* <p>
	* If the current method is a variable arity method handle
	* argument list conversion may involve the conversion and collection
	* of several arguments into an array, as
	* {@linkplain #asVarargsCollector described elsewhere}.
	* In every other case, all conversions are applied <em>pairwise</em>,
	* which means that each argument or return value is converted to
	* exactly one argument or return value (or no return value).
	* The applied conversions are defined by consulting the
	* the corresponding component types of the old and new
	* method handle types.
	* <p>
	* Let <em>T0</em> and <em>T1</em> be corresponding new and old parameter types,
	* or old and new return types. Specifically, for some valid index {@code i}, let
	* <em>T0</em>{@code =newType.parameterType(i)} and <em>T1</em>{@code =this.type().parameterType(i)}.
	* Or else, going the other way for return values, let
	* <em>T0</em>{@code =this.type().returnType()} and <em>T1</em>{@code =newType.returnType()}.
	* If the types are the same, the new method handle makes no change
	* to the corresponding argument or return value (if any).
	* Otherwise, one of the following conversions is applied
	* if possible:
	* <ul>
	* <li>If <em>T0</em> and <em>T1</em> are references, then a cast to <em>T1</em> is applied.
	* (The types do not need to be related in any particular way.
	* This is because a dynamic value of null can convert to any reference type.)
	* <li>If <em>T0</em> and <em>T1</em> are primitives, then a Java method invocation
	* conversion (JLS 5.3) is applied, if one exists.
	* (Specifically, <em>T0</em> must convert to <em>T1</em> by a widening primitive conversion.)
	* <li>If <em>T0</em> is a primitive and <em>T1</em> a reference,
	* a Java casting conversion (JLS 5.5) is applied if one exists.
	* (Specifically, the value is boxed from <em>T0</em> to its wrapper class,
	* which is then widened as needed to <em>T1</em>.)
	* <li>If <em>T0</em> is a reference and <em>T1</em> a primitive, an unboxing
	* conversion will be applied at runtime, possibly followed
	* by a Java method invocation conversion (JLS 5.3)
	* on the primitive value. (These are the primitive widening conversions.)
	* <em>T0</em> must be a wrapper class or a supertype of one.
	* (In the case where <em>T0</em> is Object, these are the conversions
	* allowed by {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}.)
	* The unboxing conversion must have a possibility of success, which means that
	* if <em>T0</em> is not itself a wrapper class, there must exist at least one
	* wrapper class <em>TW</em> which is a subtype of <em>T0</em> and whose unboxed
	* primitive value can be widened to <em>T1</em>.
	* <li>If the return type <em>T1</em> is marked as void, any returned value is discarded
	* <li>If the return type <em>T0</em> is void and <em>T1</em> a reference, a null value is introduced.
	* <li>If the return type <em>T0</em> is void and <em>T1</em> a primitive,
	* a zero value is introduced.
	* </ul>
	* (<em>Note:</em> Both <em>T0</em> and <em>T1</em> may be regarded as static types,
	* because neither corresponds specifically to the <em>dynamic type</em> of any
	* actual argument or return value.)
	* <p>
	* The method handle conversion cannot be made if any one of the required
	* pairwise conversions cannot be made.
	* <p>
	* At runtime, the conversions applied to reference arguments
	* or return values may require additional runtime checks which can fail.
	* An unboxing operation may fail because the original reference is null,
	* causing a {@link java.lang.NullPointerException NullPointerException}.
	* An unboxing operation or a reference cast may also fail on a reference
	* to an object of the wrong type,
	* causing a {@link java.lang.ClassCastException ClassCastException}.
	* Although an unboxing operation may accept several kinds of wrappers,
	* if none are available, a {@code ClassCastException} will be thrown.
	*
	* @param newType the expected type of the new method handle
	* @return a method handle which delegates to {@code this} after performing
	* any necessary argument conversions, and arranges for any
	* necessary return value conversions
	* @throws NullPointerException if {@code newType} is a null reference
	* @throws WrongMethodTypeException if the conversion cannot be made
	* @see MethodHandles#explicitCastArguments
	*/
	public MethodHandle asType(MethodType newType) {
	// Fast path alternative to a heavyweight {@code asType} call.
	// Return 'this' if the conversion will be a no-op.
	if (newType == type) {
	return this;
	}
	// Return 'this.asTypeCache' if the conversion is already memoized.
	MethodHandle atc = asTypeCached(newType);
	if (atc != null) {
	return atc;
	}
	return asTypeUncached(newType);
	}

	private MethodHandle asTypeCached(MethodType newType) {
	MethodHandle atc = asTypeCache;
	if (atc != null && newType == atc.type) {
	return atc;
	}
	return null;
	}

	/** Override this to change asType behavior. */
	/non-public/ MethodHandle asTypeUncached(MethodType newType) {
	if (!type.isConvertibleTo(newType))
	throw new WrongMethodTypeException("cannot convert "+this+" to "+newType);
	return asTypeCache = MethodHandleImpl.makePairwiseConvert(this, newType, true);
	}

	/**
	* Makes an <em>array-spreading</em> method handle, which accepts a trailing array argument
	* and spreads its elements as positional arguments.
	* The new method handle adapts, as its <i>target</i>,
	* the current method handle. The type of the adapter will be
	* the same as the type of the target, except that the final
	* {@code arrayLength} parameters of the target's type are replaced
	* by a single array parameter of type {@code arrayType}.
	* <p>
	* If the array element type differs from any of the corresponding
	* argument types on the original target,
	* the original target is adapted to take the array elements directly,
	* as if by a call to {@link #asType asType}.
	* <p>
	* When called, the adapter replaces a trailing array argument
	* by the array's elements, each as its own argument to the target.
	* (The order of the arguments is preserved.)
	* They are converted pairwise by casting and/or unboxing
	* to the types of the trailing parameters of the target.
	* Finally the target is called.
	* What the target eventually returns is returned unchanged by the adapter.
	* <p>
	* Before calling the target, the adapter verifies that the array
	* contains exactly enough elements to provide a correct argument count
	* to the target method handle.
	* (The array may also be null when zero elements are required.)
	* <p>
	* If, when the adapter is called, the supplied array argument does
	* not have the correct number of elements, the adapter will throw
	* an {@link IllegalArgumentException} instead of invoking the target.
	* <p>
	* Here are some simple examples of array-spreading method handles:
	* <blockquote><pre>{@code
	MethodHandle equals = publicLookup()
	.findVirtual(String.class, "equals", methodType(boolean.class, Object.class));
	assert( (boolean) equals.invokeExact("me", (Object)"me"));
	assert(!(boolean) equals.invokeExact("me", (Object)"thee"));
	// spread both arguments from a 2-array:
	MethodHandle eq2 = equals.asSpreader(Object[].class, 2);
	assert( (boolean) eq2.invokeExact(new Object[]{ "me", "me" }));
	assert(!(boolean) eq2.invokeExact(new Object[]{ "me", "thee" }));
	// try to spread from anything but a 2-array:
	for (int n = 0; n <= 10; n++) {
	Object[] badArityArgs = (n == 2 ? null : new Object[n]);
	try { assert((boolean) eq2.invokeExact(badArityArgs) && false); }
	catch (IllegalArgumentException ex) { } // OK
	}
	// spread both arguments from a String array:
	MethodHandle eq2s = equals.asSpreader(String[].class, 2);
	assert( (boolean) eq2s.invokeExact(new String[]{ "me", "me" }));
	assert(!(boolean) eq2s.invokeExact(new String[]{ "me", "thee" }));
	// spread second arguments from a 1-array:
	MethodHandle eq1 = equals.asSpreader(Object[].class, 1);
	assert( (boolean) eq1.invokeExact("me", new Object[]{ "me" }));
	assert(!(boolean) eq1.invokeExact("me", new Object[]{ "thee" }));
	// spread no arguments from a 0-array or null:
	MethodHandle eq0 = equals.asSpreader(Object[].class, 0);
	assert( (boolean) eq0.invokeExact("me", (Object)"me", new Object[0]));
	assert(!(boolean) eq0.invokeExact("me", (Object)"thee", (Object[])null));
	// asSpreader and asCollector are approximate inverses:
	for (int n = 0; n <= 2; n++) {
	for (Class<?> a : new Class<?>[]{Object[].class, String[].class, CharSequence[].class}) {
	MethodHandle equals2 = equals.asSpreader(a, n).asCollector(a, n);
	assert( (boolean) equals2.invokeWithArguments("me", "me"));
	assert(!(boolean) equals2.invokeWithArguments("me", "thee"));
	}
	}
	MethodHandle caToString = publicLookup()
	.findStatic(Arrays.class, "toString", methodType(String.class, char[].class));
	assertEquals("[A, B, C]", (String) caToString.invokeExact("ABC".toCharArray()));
	MethodHandle caString3 = caToString.asCollector(char[].class, 3);
	assertEquals("[A, B, C]", (String) caString3.invokeExact('A', 'B', 'C'));
	MethodHandle caToString2 = caString3.asSpreader(char[].class, 2);
	assertEquals("[A, B, C]", (String) caToString2.invokeExact('A', "BC".toCharArray()));
	* }</pre></blockquote>
	* @param arrayType usually {@code Object[]}, the type of the array argument from which to extract the spread arguments
	* @param arrayLength the number of arguments to spread from an incoming array argument
	* @return a new method handle which spreads its final array argument,
	* before calling the original method handle
	* @throws NullPointerException if {@code arrayType} is a null reference
	* @throws IllegalArgumentException if {@code arrayType} is not an array type,
	* or if target does not have at least
	* {@code arrayLength} parameter types,
	* or if {@code arrayLength} is negative,
	* or if the resulting method handle's type would have
	* <a href="MethodHandle.html#maxarity">too many parameters</a>
	* @throws WrongMethodTypeException if the implied {@code asType} call fails
	* @see #asCollector
	*/
	public MethodHandle asSpreader(Class<?> arrayType, int arrayLength) {
	MethodType postSpreadType = asSpreaderChecks(arrayType, arrayLength);
	int arity = type().parameterCount();
	int spreadArgPos = arity - arrayLength;
	MethodHandle afterSpread = this.asType(postSpreadType);
	BoundMethodHandle mh = afterSpread.rebind();
	LambdaForm lform = mh.editor().spreadArgumentsForm(1 + spreadArgPos, arrayType, arrayLength);
	MethodType preSpreadType = postSpreadType.replaceParameterTypes(spreadArgPos, arity, arrayType);
	return mh.copyWith(preSpreadType, lform);
	}

	/**
	* See if {@code asSpreader} can be validly called with the given arguments.
	* Return the type of the method handle call after spreading but before conversions.
	*/
	private MethodType asSpreaderChecks(Class<?> arrayType, int arrayLength) {
	spreadArrayChecks(arrayType, arrayLength);
	int nargs = type().parameterCount();
	if (nargs < arrayLength \|\| arrayLength < 0)
	throw newIllegalArgumentException("bad spread array length");
	Class<?> arrayElement = arrayType.getComponentType();
	MethodType mtype = type();
	boolean match = true, fail = false;
	for (int i = nargs - arrayLength; i < nargs; i++) {
	Class<?> ptype = mtype.parameterType(i);
	if (ptype != arrayElement) {
	match = false;
	if (!MethodType.canConvert(arrayElement, ptype)) {
	fail = true;
	break;
	}
	}
	}
	if (match) return mtype;
	MethodType needType = mtype.asSpreaderType(arrayType, arrayLength);
	if (!fail) return needType;
	// elicit an error:
	this.asType(needType);
	throw newInternalError("should not return", null);
	}

	private void spreadArrayChecks(Class<?> arrayType, int arrayLength) {
	Class<?> arrayElement = arrayType.getComponentType();
	if (arrayElement == null)
	throw newIllegalArgumentException("not an array type", arrayType);
	if ((arrayLength & 0x7F) != arrayLength) {
	if ((arrayLength & 0xFF) != arrayLength)
	throw newIllegalArgumentException("array length is not legal", arrayLength);
	assert(arrayLength >= 128);
	if (arrayElement == long.class \|\|
	arrayElement == double.class)
	throw newIllegalArgumentException("array length is not legal for long[] or double[]", arrayLength);
	}
	}

	/**
	* Makes an <em>array-collecting</em> method handle, which accepts a given number of trailing
	* positional arguments and collects them into an array argument.
	* The new method handle adapts, as its <i>target</i>,
	* the current method handle. The type of the adapter will be
	* the same as the type of the target, except that a single trailing
	* parameter (usually of type {@code arrayType}) is replaced by
	* {@code arrayLength} parameters whose type is element type of {@code arrayType}.
	* <p>
	* If the array type differs from the final argument type on the original target,
	* the original target is adapted to take the array type directly,
	* as if by a call to {@link #asType asType}.
	* <p>
	* When called, the adapter replaces its trailing {@code arrayLength}
	* arguments by a single new array of type {@code arrayType}, whose elements
	* comprise (in order) the replaced arguments.
	* Finally the target is called.
	* What the target eventually returns is returned unchanged by the adapter.
	* <p>
	* (The array may also be a shared constant when {@code arrayLength} is zero.)
	* <p>
	* (<em>Note:</em> The {@code arrayType} is often identical to the last
	* parameter type of the original target.
	* It is an explicit argument for symmetry with {@code asSpreader}, and also
	* to allow the target to use a simple {@code Object} as its last parameter type.)
	* <p>
	* In order to create a collecting adapter which is not restricted to a particular
	* number of collected arguments, use {@link #asVarargsCollector asVarargsCollector} instead.
	* <p>
	* Here are some examples of array-collecting method handles:
	* <blockquote><pre>{@code
	MethodHandle deepToString = publicLookup()
	.findStatic(Arrays.class, "deepToString", methodType(String.class, Object[].class));
	assertEquals("[won]", (String) deepToString.invokeExact(new Object[]{"won"}));
	MethodHandle ts1 = deepToString.asCollector(Object[].class, 1);
	assertEquals(methodType(String.class, Object.class), ts1.type());
	//assertEquals("[won]", (String) ts1.invokeExact( new Object[]{"won"})); //FAIL
	assertEquals("[[won]]", (String) ts1.invokeExact((Object) new Object[]{"won"}));
	// arrayType can be a subtype of Object[]
	MethodHandle ts2 = deepToString.asCollector(String[].class, 2);
	assertEquals(methodType(String.class, String.class, String.class), ts2.type());
	assertEquals("[two, too]", (String) ts2.invokeExact("two", "too"));
	MethodHandle ts0 = deepToString.asCollector(Object[].class, 0);
	assertEquals("[]", (String) ts0.invokeExact());
	// collectors can be nested, Lisp-style
	MethodHandle ts22 = deepToString.asCollector(Object[].class, 3).asCollector(String[].class, 2);
	assertEquals("[A, B, [C, D]]", ((String) ts22.invokeExact((Object)'A', (Object)"B", "C", "D")));
	// arrayType can be any primitive array type
	MethodHandle bytesToString = publicLookup()
	.findStatic(Arrays.class, "toString", methodType(String.class, byte[].class))
	.asCollector(byte[].class, 3);
	assertEquals("[1, 2, 3]", (String) bytesToString.invokeExact((byte)1, (byte)2, (byte)3));
	MethodHandle longsToString = publicLookup()
	.findStatic(Arrays.class, "toString", methodType(String.class, long[].class))
	.asCollector(long[].class, 1);
	assertEquals("[123]", (String) longsToString.invokeExact((long)123));
	* }</pre></blockquote>
	* @param arrayType often {@code Object[]}, the type of the array argument which will collect the arguments
	* @param arrayLength the number of arguments to collect into a new array argument
	* @return a new method handle which collects some trailing argument
	* into an array, before calling the original method handle
	* @throws NullPointerException if {@code arrayType} is a null reference
	* @throws IllegalArgumentException if {@code arrayType} is not an array type
	* or {@code arrayType} is not assignable to this method handle's trailing parameter type,
	* or {@code arrayLength} is not a legal array size,
	* or the resulting method handle's type would have
	* <a href="MethodHandle.html#maxarity">too many parameters</a>
	* @throws WrongMethodTypeException if the implied {@code asType} call fails
	* @see #asSpreader
	* @see #asVarargsCollector
	*/
	public MethodHandle asCollector(Class<?> arrayType, int arrayLength) {
	asCollectorChecks(arrayType, arrayLength);
	int collectArgPos = type().parameterCount() - 1;
	BoundMethodHandle mh = rebind();
	MethodType resultType = type().asCollectorType(arrayType, arrayLength);
	MethodHandle newArray = MethodHandleImpl.varargsArray(arrayType, arrayLength);
	LambdaForm lform = mh.editor().collectArgumentArrayForm(1 + collectArgPos, newArray);
	if (lform != null) {
	return mh.copyWith(resultType, lform);
	}
	lform = mh.editor().collectArgumentsForm(1 + collectArgPos, newArray.type().basicType());
	return mh.copyWithExtendL(resultType, lform, newArray);
	}

	/**
	* See if {@code asCollector} can be validly called with the given arguments.
	* Return false if the last parameter is not an exact match to arrayType.
	*/
	/non-public/ boolean asCollectorChecks(Class<?> arrayType, int arrayLength) {
	spreadArrayChecks(arrayType, arrayLength);
	int nargs = type().parameterCount();
	if (nargs != 0) {
	Class<?> lastParam = type().parameterType(nargs-1);
	if (lastParam == arrayType) return true;
	if (lastParam.isAssignableFrom(arrayType)) return false;
	}
	throw newIllegalArgumentException("array type not assignable to trailing argument", this, arrayType);
	}

	/**
	* Makes a <em>variable arity</em> adapter which is able to accept
	* any number of trailing positional arguments and collect them
	* into an array argument.
	* <p>
	* The type and behavior of the adapter will be the same as
	* the type and behavior of the target, except that certain
	* {@code invoke} and {@code asType} requests can lead to
	* trailing positional arguments being collected into target's
	* trailing parameter.
	* Also, the last parameter type of the adapter will be
	* {@code arrayType}, even if the target has a different
	* last parameter type.
	* <p>
	* This transformation may return {@code this} if the method handle is
	* already of variable arity and its trailing parameter type
	* is identical to {@code arrayType}.
	* <p>
	* When called with {@link #invokeExact invokeExact}, the adapter invokes
	* the target with no argument changes.
	* (<em>Note:</em> This behavior is different from a
	* {@linkplain #asCollector fixed arity collector},
	* since it accepts a whole array of indeterminate length,
	* rather than a fixed number of arguments.)
	* <p>
	* When called with plain, inexact {@link #invoke invoke}, if the caller
	* type is the same as the adapter, the adapter invokes the target as with
	* {@code invokeExact}.
	* (This is the normal behavior for {@code invoke} when types match.)
	* <p>
	* Otherwise, if the caller and adapter arity are the same, and the
	* trailing parameter type of the caller is a reference type identical to
	* or assignable to the trailing parameter type of the adapter,
	* the arguments and return values are converted pairwise,
	* as if by {@link #asType asType} on a fixed arity
	* method handle.
	* <p>
	* Otherwise, the arities differ, or the adapter's trailing parameter
	* type is not assignable from the corresponding caller type.
	* In this case, the adapter replaces all trailing arguments from
	* the original trailing argument position onward, by
	* a new array of type {@code arrayType}, whose elements
	* comprise (in order) the replaced arguments.
	* <p>
	* The caller type must provides as least enough arguments,
	* and of the correct type, to satisfy the target's requirement for
	* positional arguments before the trailing array argument.
	* Thus, the caller must supply, at a minimum, {@code N-1} arguments,
	* where {@code N} is the arity of the target.
	* Also, there must exist conversions from the incoming arguments
	* to the target's arguments.
	* As with other uses of plain {@code invoke}, if these basic
	* requirements are not fulfilled, a {@code WrongMethodTypeException}
	* may be thrown.
	* <p>
	* In all cases, what the target eventually returns is returned unchanged by the adapter.
	* <p>
	* In the final case, it is exactly as if the target method handle were
	* temporarily adapted with a {@linkplain #asCollector fixed arity collector}
	* to the arity required by the caller type.
	* (As with {@code asCollector}, if the array length is zero,
	* a shared constant may be used instead of a new array.
	* If the implied call to {@code asCollector} would throw
	* an {@code IllegalArgumentException} or {@code WrongMethodTypeException},
	* the call to the variable arity adapter must throw
	* {@code WrongMethodTypeException}.)
	* <p>
	* The behavior of {@link #asType asType} is also specialized for
	* variable arity adapters, to maintain the invariant that
	* plain, inexact {@code invoke} is always equivalent to an {@code asType}
	* call to adjust the target type, followed by {@code invokeExact}.
	* Therefore, a variable arity adapter responds
	* to an {@code asType} request by building a fixed arity collector,
	* if and only if the adapter and requested type differ either
	* in arity or trailing argument type.
	* The resulting fixed arity collector has its type further adjusted
	* (if necessary) to the requested type by pairwise conversion,
	* as if by another application of {@code asType}.
	* <p>
	* When a method handle is obtained by executing an {@code ldc} instruction
	* of a {@code CONSTANT_MethodHandle} constant, and the target method is marked
	* as a variable arity method (with the modifier bit {@code 0x0080}),
	* the method handle will accept multiple arities, as if the method handle
	* constant were created by means of a call to {@code asVarargsCollector}.
	* <p>
	* In order to create a collecting adapter which collects a predetermined
	* number of arguments, and whose type reflects this predetermined number,
	* use {@link #asCollector asCollector} instead.
	* <p>
	* No method handle transformations produce new method handles with
	* variable arity, unless they are documented as doing so.
	* Therefore, besides {@code asVarargsCollector},
	* all methods in {@code MethodHandle} and {@code MethodHandles}
	* will return a method handle with fixed arity,
	* except in the cases where they are specified to return their original
	* operand (e.g., {@code asType} of the method handle's own type).
	* <p>
	* Calling {@code asVarargsCollector} on a method handle which is already
	* of variable arity will produce a method handle with the same type and behavior.
	* It may (or may not) return the original variable arity method handle.
	* <p>
	* Here is an example, of a list-making variable arity method handle:
	* <blockquote><pre>{@code
	MethodHandle deepToString = publicLookup()
	.findStatic(Arrays.class, "deepToString", methodType(String.class, Object[].class));
	MethodHandle ts1 = deepToString.asVarargsCollector(Object[].class);
	assertEquals("[won]", (String) ts1.invokeExact( new Object[]{"won"}));
	assertEquals("[won]", (String) ts1.invoke( new Object[]{"won"}));
	assertEquals("[won]", (String) ts1.invoke( "won" ));
	assertEquals("[[won]]", (String) ts1.invoke((Object) new Object[]{"won"}));
	// findStatic of Arrays.asList(...) produces a variable arity method handle:
	MethodHandle asList = publicLookup()
	.findStatic(Arrays.class, "asList", methodType(List.class, Object[].class));
	assertEquals(methodType(List.class, Object[].class), asList.type());
	assert(asList.isVarargsCollector());
	assertEquals("[]", asList.invoke().toString());
	assertEquals("[1]", asList.invoke(1).toString());
	assertEquals("[two, too]", asList.invoke("two", "too").toString());
	String[] argv = { "three", "thee", "tee" };
	assertEquals("[three, thee, tee]", asList.invoke(argv).toString());
	assertEquals("[three, thee, tee]", asList.invoke((Object[])argv).toString());
	List ls = (List) asList.invoke((Object)argv);
	assertEquals(1, ls.size());
	assertEquals("[three, thee, tee]", Arrays.toString((Object[])ls.get(0)));
	* }</pre></blockquote>
	* <p style="font-size:smaller;">
	* <em>Discussion:</em>
	* These rules are designed as a dynamically-typed variation
	* of the Java rules for variable arity methods.
	* In both cases, callers to a variable arity method or method handle
	* can either pass zero or more positional arguments, or else pass
	* pre-collected arrays of any length. Users should be aware of the
	* special role of the final argument, and of the effect of a
	* type match on that final argument, which determines whether
	* or not a single trailing argument is interpreted as a whole
	* array or a single element of an array to be collected.
	* Note that the dynamic type of the trailing argument has no
	* effect on this decision, only a comparison between the symbolic
	* type descriptor of the call site and the type descriptor of the method handle.)
	*
	* @param arrayType often {@code Object[]}, the type of the array argument which will collect the arguments
	* @return a new method handle which can collect any number of trailing arguments
	* into an array, before calling the original method handle
	* @throws NullPointerException if {@code arrayType} is a null reference
	* @throws IllegalArgumentException if {@code arrayType} is not an array type
	* or {@code arrayType} is not assignable to this method handle's trailing parameter type
	* @see #asCollector
	* @see #isVarargsCollector
	* @see #asFixedArity
	*/
	public MethodHandle asVarargsCollector(Class<?> arrayType) {
	arrayType.getClass(); // explicit NPE
	boolean lastMatch = asCollectorChecks(arrayType, 0);
	if (isVarargsCollector() && lastMatch)
	return this;
	return MethodHandleImpl.makeVarargsCollector(this, arrayType);
	}

	/**
	* Determines if this method handle
	* supports {@linkplain #asVarargsCollector variable arity} calls.
	* Such method handles arise from the following sources:
	* <ul>
	* <li>a call to {@linkplain #asVarargsCollector asVarargsCollector}
	* <li>a call to a {@linkplain java.lang.invoke.MethodHandles.Lookup lookup method}
	* which resolves to a variable arity Java method or constructor
	* <li>an {@code ldc} instruction of a {@code CONSTANT_MethodHandle}
	* which resolves to a variable arity Java method or constructor
	* </ul>
	* @return true if this method handle accepts more than one arity of plain, inexact {@code invoke} calls
	* @see #asVarargsCollector
	* @see #asFixedArity
	*/
	public boolean isVarargsCollector() {
	return false;
	}

	/**
	* Makes a <em>fixed arity</em> method handle which is otherwise
	* equivalent to the current method handle.
	* <p>
	* If the current method handle is not of
	* {@linkplain #asVarargsCollector variable arity},
	* the current method handle is returned.
	* This is true even if the current method handle
	* could not be a valid input to {@code asVarargsCollector}.
	* <p>
	* Otherwise, the resulting fixed-arity method handle has the same
	* type and behavior of the current method handle,
	* except that {@link #isVarargsCollector isVarargsCollector}
	* will be false.
	* The fixed-arity method handle may (or may not) be the
	* a previous argument to {@code asVarargsCollector}.
	* <p>
	* Here is an example, of a list-making variable arity method handle:
	* <blockquote><pre>{@code
	MethodHandle asListVar = publicLookup()
	.findStatic(Arrays.class, "asList", methodType(List.class, Object[].class))
	.asVarargsCollector(Object[].class);
	MethodHandle asListFix = asListVar.asFixedArity();
	assertEquals("[1]", asListVar.invoke(1).toString());
	Exception caught = null;
	try { asListFix.invoke((Object)1); }
	catch (Exception ex) { caught = ex; }
	assert(caught instanceof ClassCastException);
	assertEquals("[two, too]", asListVar.invoke("two", "too").toString());
	try { asListFix.invoke("two", "too"); }
	catch (Exception ex) { caught = ex; }
	assert(caught instanceof WrongMethodTypeException);
	Object[] argv = { "three", "thee", "tee" };
	assertEquals("[three, thee, tee]", asListVar.invoke(argv).toString());
	assertEquals("[three, thee, tee]", asListFix.invoke(argv).toString());
	assertEquals(1, ((List) asListVar.invoke((Object)argv)).size());
	assertEquals("[three, thee, tee]", asListFix.invoke((Object)argv).toString());
	* }</pre></blockquote>
	*
	* @return a new method handle which accepts only a fixed number of arguments
	* @see #asVarargsCollector
	* @see #isVarargsCollector
	*/
	public MethodHandle asFixedArity() {
	assert(!isVarargsCollector());
	return this;
	}

	/**
	* Binds a value {@code x} to the first argument of a method handle, without invoking it.
	* The new method handle adapts, as its <i>target</i>,
	* the current method handle by binding it to the given argument.
	* The type of the bound handle will be
	* the same as the type of the target, except that a single leading
	* reference parameter will be omitted.
	* <p>
	* When called, the bound handle inserts the given value {@code x}
	* as a new leading argument to the target. The other arguments are
	* also passed unchanged.
	* What the target eventually returns is returned unchanged by the bound handle.
	* <p>
	* The reference {@code x} must be convertible to the first parameter
	* type of the target.
	* <p>
	* (<em>Note:</em> Because method handles are immutable, the target method handle
	* retains its original type and behavior.)
	* @param x the value to bind to the first argument of the target
	* @return a new method handle which prepends the given value to the incoming
	* argument list, before calling the original method handle
	* @throws IllegalArgumentException if the target does not have a
	* leading parameter type that is a reference type
	* @throws ClassCastException if {@code x} cannot be converted
	* to the leading parameter type of the target
	* @see MethodHandles#insertArguments
	*/
	public MethodHandle bindTo(Object x) {
	x = type.leadingReferenceParameter().cast(x); // throw CCE if needed
	return bindArgumentL(0, x);
	}

	/**
	* Returns a string representation of the method handle,
	* starting with the string {@code "MethodHandle"} and
	* ending with the string representation of the method handle's type.
	* In other words, this method returns a string equal to the value of:
	* <blockquote><pre>{@code
	* "MethodHandle" + type().toString()
	* }</pre></blockquote>
	* <p>
	* (<em>Note:</em> Future releases of this API may add further information
	* to the string representation.
	* Therefore, the present syntax should not be parsed by applications.)
	*
	* @return a string representation of the method handle
	*/
	@Override
	public String toString() {
	if (DEBUG_METHOD_HANDLE_NAMES) return "MethodHandle"+debugString();
	return standardString();
	}
	String standardString() {
	return "MethodHandle"+type;
	}
	/** Return a string with a several lines describing the method handle structure.
	* This string would be suitable for display in an IDE debugger.
	*/
	String debugString() {
	return type+" : "+internalForm()+internalProperties();
	}

	//// Implementation methods.
	//// Sub-classes can override these default implementations.
	//// All these methods assume arguments are already validated.

	// Other transforms to do: convert, explicitCast, permute, drop, filter, fold, GWT, catch

	BoundMethodHandle bindArgumentL(int pos, Object value) {
	return rebind().bindArgumentL(pos, value);
	}

	/non-public/
	MethodHandle setVarargs(MemberName member) throws IllegalAccessException {
	if (!member.isVarargs()) return this;
	Class<?> arrayType = type().lastParameterType();
	if (arrayType.isArray()) {
	return MethodHandleImpl.makeVarargsCollector(this, arrayType);
	}
	throw member.makeAccessException("cannot make variable arity", null);
	}

	/non-public/
	MethodHandle viewAsType(MethodType newType, boolean strict) {
	// No actual conversions, just a new view of the same method.
	// Note that this operation must not produce a DirectMethodHandle,
	// because retyped DMHs, like any transformed MHs,
	// cannot be cracked into MethodHandleInfo.
	assert viewAsTypeChecks(newType, strict);
	BoundMethodHandle mh = rebind();
	assert(!((MethodHandle)mh instanceof DirectMethodHandle));
	return mh.copyWith(newType, mh.form);
	}

	/non-public/
	boolean viewAsTypeChecks(MethodType newType, boolean strict) {
	if (strict) {
	assert(type().isViewableAs(newType, true))
	: Arrays.asList(this, newType);
	} else {
	assert(type().basicType().isViewableAs(newType.basicType(), true))
	: Arrays.asList(this, newType);
	}
	return true;
	}

	// Decoding

	/non-public/
	LambdaForm internalForm() {
	return form;
	}

	/non-public/
	MemberName internalMemberName() {
	return null; // DMH returns DMH.member
	}

	/non-public/
	Class<?> internalCallerClass() {
	return null; // caller-bound MH for @CallerSensitive method returns caller
	}

	/non-public/
	MethodHandleImpl.Intrinsic intrinsicName() {
	// no special intrinsic meaning to most MHs
	return MethodHandleImpl.Intrinsic.NONE;
	}

	/non-public/
	MethodHandle withInternalMemberName(MemberName member, boolean isInvokeSpecial) {
	if (member != null) {
	return MethodHandleImpl.makeWrappedMember(this, member, isInvokeSpecial);
	} else if (internalMemberName() == null) {
	// The required internaMemberName is null, and this MH (like most) doesn't have one.
	return this;
	} else {
	// The following case is rare. Mask the internalMemberName by wrapping the MH in a BMH.
	MethodHandle result = rebind();
	assert (result.internalMemberName() == null);
	return result;
	}
	}

	/non-public/
	boolean isInvokeSpecial() {
	return false; // DMH.Special returns true
	}

	/non-public/
	Object internalValues() {
	return null;
	}

	/non-public/
	Object internalProperties() {
	// Override to something to follow this.form, like "\n& FOO=bar"
	return "";
	}

	//// Method handle implementation methods.
	//// Sub-classes can override these default implementations.
	//// All these methods assume arguments are already validated.

	/non-public/
	abstract MethodHandle copyWith(MethodType mt, LambdaForm lf);

	/** Require this method handle to be a BMH, or else replace it with a "wrapper" BMH.
	* Many transforms are implemented only for BMHs.
	* @return a behaviorally equivalent BMH
	*/
	abstract BoundMethodHandle rebind();

	/**
	* Replace the old lambda form of this method handle with a new one.
	* The new one must be functionally equivalent to the old one.
	* Threads may continue running the old form indefinitely,
	* but it is likely that the new one will be preferred for new executions.
	* Use with discretion.
	*/
	/non-public/
	void updateForm(LambdaForm newForm) {
	assert(newForm.customized == null \|\| newForm.customized == this);
	if (form == newForm) return;
	newForm.prepare(); // as in MethodHandle.<init>
	UNSAFE.putObject(this, FORM_OFFSET, newForm);
	UNSAFE.fullFence();
	}

	/** Craft a LambdaForm customized for this particular MethodHandle */
	/non-public/
	void customize() {
	if (form.customized == null) {
	LambdaForm newForm = form.customize(this);
	updateForm(newForm);
	} else {
	assert(form.customized == this);
	}
	}

	private static final long FORM_OFFSET;
	static {
	try {
	FORM_OFFSET = UNSAFE.objectFieldOffset(MethodHandle.class.getDeclaredField("form"));
	} catch (ReflectiveOperationException ex) {
	throw newInternalError(ex);
	}
	}
	}

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