/*

 * Copyright (c) 2011, 2018, 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.perf.PerfCounter;

import jdk.internal.vm.annotation.DontInline;

import jdk.internal.vm.annotation.Stable;

import sun.invoke.util.Wrapper;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

import java.lang.reflect.Method;

import java.util.Arrays;

import java.util.HashMap;

import static java.lang.invoke.LambdaForm.BasicType.*;

import static java.lang.invoke.MethodHandleNatives.Constants.REF_invokeStatic;

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

/**

 * The symbolic, non-executable form of a method handle's invocation semantics.

 * It consists of a series of names.

 * The first N (N=arity) names are parameters,

 * while any remaining names are temporary values.

 * Each temporary specifies the application of a function to some arguments.

 * The functions are method handles, while the arguments are mixes of

 * constant values and local names.

 * The result of the lambda is defined as one of the names, often the last one.

 * <p>

 * Here is an approximate grammar:

 * <blockquote><pre>{@code

 * LambdaForm = "(" ArgName* ")=>{" TempName* Result "}"

 * ArgName = "a" N ":" T

 * TempName = "t" N ":" T "=" Function "(" Argument* ");"

 * Function = ConstantValue

 * Argument = NameRef | ConstantValue

 * Result = NameRef | "void"

 * NameRef = "a" N | "t" N

 * N = (any whole number)

 * T = "L" | "I" | "J" | "F" | "D" | "V"

 * }</pre></blockquote>

 * Names are numbered consecutively from left to right starting at zero.

 * (The letters are merely a taste of syntax sugar.)

 * Thus, the first temporary (if any) is always numbered N (where N=arity).

 * Every occurrence of a name reference in an argument list must refer to

 * a name previously defined within the same lambda.

 * A lambda has a void result if and only if its result index is -1.

 * If a temporary has the type "V", it cannot be the subject of a NameRef,

 * even though possesses a number.

 * Note that all reference types are erased to "L", which stands for {@code Object}.

 * All subword types (boolean, byte, short, char) are erased to "I" which is {@code int}.

 * The other types stand for the usual primitive types.

 * <p>

 * Function invocation closely follows the static rules of the Java verifier.

 * Arguments and return values must exactly match when their "Name" types are

 * considered.

 * Conversions are allowed only if they do not change the erased type.

 * <ul>

 * <li>L = Object: casts are used freely to convert into and out of reference types

 * <li>I = int: subword types are forcibly narrowed when passed as arguments (see {@code explicitCastArguments})

 * <li>J = long: no implicit conversions

 * <li>F = float: no implicit conversions

 * <li>D = double: no implicit conversions

 * <li>V = void: a function result may be void if and only if its Name is of type "V"

 * </ul>

 * Although implicit conversions are not allowed, explicit ones can easily be

 * encoded by using temporary expressions which call type-transformed identity functions.

 * <p>

 * Examples:

 * <blockquote><pre>{@code

 * (a0:J)=>{ a0 }

 *     == identity(long)

 * (a0:I)=>{ t1:V = System.out#println(a0); void }

 *     == System.out#println(int)

 * (a0:L)=>{ t1:V = System.out#println(a0); a0 }

 *     == identity, with printing side-effect

 * (a0:L, a1:L)=>{ t2:L = BoundMethodHandle#argument(a0);

 *                 t3:L = BoundMethodHandle#target(a0);

 *                 t4:L = MethodHandle#invoke(t3, t2, a1); t4 }

 *     == general invoker for unary insertArgument combination

 * (a0:L, a1:L)=>{ t2:L = FilterMethodHandle#filter(a0);

 *                 t3:L = MethodHandle#invoke(t2, a1);

 *                 t4:L = FilterMethodHandle#target(a0);

 *                 t5:L = MethodHandle#invoke(t4, t3); t5 }

 *     == general invoker for unary filterArgument combination

 * (a0:L, a1:L)=>{ ...(same as previous example)...

 *                 t5:L = MethodHandle#invoke(t4, t3, a1); t5 }

 *     == general invoker for unary/unary foldArgument combination

 * (a0:L, a1:I)=>{ t2:I = identity(long).asType((int)->long)(a1); t2 }

 *     == invoker for identity method handle which performs i2l

 * (a0:L, a1:L)=>{ t2:L = BoundMethodHandle#argument(a0);

 *                 t3:L = Class#cast(t2,a1); t3 }

 *     == invoker for identity method handle which performs cast

 * }</pre></blockquote>

 * <p>

 * @author John Rose, JSR 292 EG

 */

class LambdaForm {

    final int arity;

    final int result;

    final boolean forceInline;

    final MethodHandle customized;

    @Stable final Name[] names;

    final Kind kind;

    MemberName vmentry;   // low-level behavior, or null if not yet prepared

    private boolean isCompiled;

    // Either a LambdaForm cache (managed by LambdaFormEditor) or a link to uncustomized version (for customized LF)

    volatile Object transformCache;

    public static final int VOID_RESULT = -1, LAST_RESULT = -2;

    enum BasicType {

        L_TYPE('L', Object.class, Wrapper.OBJECT),  // all reference types

        I_TYPE('I', int.class,    Wrapper.INT),

        J_TYPE('J', long.class,   Wrapper.LONG),

        F_TYPE('F', float.class,  Wrapper.FLOAT),

        D_TYPE('D', double.class, Wrapper.DOUBLE),  // all primitive types

        V_TYPE('V', void.class,   Wrapper.VOID);    // not valid in all contexts

        static final @Stable BasicType[] ALL_TYPES = BasicType.values();

        static final @Stable BasicType[] ARG_TYPES = Arrays.copyOf(ALL_TYPES, ALL_TYPES.length-1);

        static final int ARG_TYPE_LIMIT = ARG_TYPES.length;

        static final int TYPE_LIMIT = ALL_TYPES.length;

        // Derived int constants, which (unlike the enums) can be constant folded.

        // We can remove them when JDK-8161245 is fixed.

        static final byte

                L_TYPE_NUM = (byte) L_TYPE.ordinal(),

                I_TYPE_NUM = (byte) I_TYPE.ordinal(),

                J_TYPE_NUM = (byte) J_TYPE.ordinal(),

                F_TYPE_NUM = (byte) F_TYPE.ordinal(),

                D_TYPE_NUM = (byte) D_TYPE.ordinal(),

                V_TYPE_NUM = (byte) V_TYPE.ordinal();

        final char btChar;

        final Class<?> btClass;

        final Wrapper btWrapper;

        private BasicType(char btChar, Class<?> btClass, Wrapper wrapper) {

            this.btChar = btChar;

            this.btClass = btClass;

            this.btWrapper = wrapper;

        }

        char basicTypeChar() {

            return btChar;

        }

        Class<?> basicTypeClass() {

            return btClass;

        }

        Wrapper basicTypeWrapper() {

            return btWrapper;

        }

        int basicTypeSlots() {

            return btWrapper.stackSlots();

        }

        static BasicType basicType(byte type) {

            return ALL_TYPES[type];

        }

        static BasicType basicType(char type) {

            switch (type) {

                case 'L': return L_TYPE;

                case 'I': return I_TYPE;

                case 'J': return J_TYPE;

                case 'F': return F_TYPE;

                case 'D': return D_TYPE;

                case 'V': return V_TYPE;

                // all subword types are represented as ints

                case 'Z':

                case 'B':

                case 'S':

                case 'C':

                    return I_TYPE;

                default:

                    throw newInternalError("Unknown type char: '"+type+"'");

            }

        }

        static BasicType basicType(Wrapper type) {

            char c = type.basicTypeChar();

            return basicType(c);

        }

        static BasicType basicType(Class<?> type) {

            if (!type.isPrimitive())  return L_TYPE;

            return basicType(Wrapper.forPrimitiveType(type));

        }

        static BasicType[] basicTypes(String types) {

            BasicType[] btypes = new BasicType[types.length()];

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

                btypes[i] = basicType(types.charAt(i));

            }

            return btypes;

        }

        static String basicTypeDesc(BasicType[] types) {

            if (types == null) {

                return null;

            }

            if (types.length == 0) {

                return "";

            }

            StringBuilder sb = new StringBuilder();

            for (BasicType bt : types) {

                sb.append(bt.basicTypeChar());

            }

            return sb.toString();

        }

        static int[] basicTypeOrds(BasicType[] types) {

            if (types == null) {

                return null;

            }

            int[] a = new int[types.length];

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

                a[i] = types[i].ordinal();

            }

            return a;

        }

        static char basicTypeChar(Class<?> type) {

            return basicType(type).btChar;

        }

        static byte[] basicTypesOrd(Class<?>[] types) {

            byte[] ords = new byte[types.length];

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

                ords[i] = (byte)basicType(types[i]).ordinal();

            }

            return ords;

        }

        static boolean isBasicTypeChar(char c) {

            return "LIJFDV".indexOf(c) >= 0;

        }

        static boolean isArgBasicTypeChar(char c) {

            return "LIJFD".indexOf(c) >= 0;

        }

        static { assert(checkBasicType()); }

        private static boolean checkBasicType() {

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

                assert ARG_TYPES[i].ordinal() == i;

                assert ARG_TYPES[i] == ALL_TYPES[i];

            }

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

                assert ALL_TYPES[i].ordinal() == i;

            }

            assert ALL_TYPES[TYPE_LIMIT - 1] == V_TYPE;

            assert !Arrays.asList(ARG_TYPES).contains(V_TYPE);

            return true;

        }

    }

    enum Kind {

        GENERIC("invoke"),

        ZERO("zero"),

        IDENTITY("identity"),

        BOUND_REINVOKER("BMH.reinvoke", "reinvoke"),

        REINVOKER("MH.reinvoke", "reinvoke"),

        DELEGATE("MH.delegate", "delegate"),

        EXACT_LINKER("MH.invokeExact_MT", "invokeExact_MT"),

        EXACT_INVOKER("MH.exactInvoker", "exactInvoker"),

        GENERIC_LINKER("MH.invoke_MT", "invoke_MT"),

        GENERIC_INVOKER("MH.invoker", "invoker"),

        LINK_TO_TARGET_METHOD("linkToTargetMethod"),

        LINK_TO_CALL_SITE("linkToCallSite"),

        DIRECT_INVOKE_VIRTUAL("DMH.invokeVirtual", "invokeVirtual"),

        DIRECT_INVOKE_SPECIAL("DMH.invokeSpecial", "invokeSpecial"),

        DIRECT_INVOKE_SPECIAL_IFC("DMH.invokeSpecialIFC", "invokeSpecialIFC"),

        DIRECT_INVOKE_STATIC("DMH.invokeStatic", "invokeStatic"),

        DIRECT_NEW_INVOKE_SPECIAL("DMH.newInvokeSpecial", "newInvokeSpecial"),

        DIRECT_INVOKE_INTERFACE("DMH.invokeInterface", "invokeInterface"),

        DIRECT_INVOKE_STATIC_INIT("DMH.invokeStaticInit", "invokeStaticInit"),

        GET_OBJECT("getObject"),

        PUT_OBJECT("putObject"),

        GET_OBJECT_VOLATILE("getObjectVolatile"),

        PUT_OBJECT_VOLATILE("putObjectVolatile"),

        GET_INT("getInt"),

        PUT_INT("putInt"),

        GET_INT_VOLATILE("getIntVolatile"),

        PUT_INT_VOLATILE("putIntVolatile"),

        GET_BOOLEAN("getBoolean"),

        PUT_BOOLEAN("putBoolean"),

        GET_BOOLEAN_VOLATILE("getBooleanVolatile"),

        PUT_BOOLEAN_VOLATILE("putBooleanVolatile"),

        GET_BYTE("getByte"),

        PUT_BYTE("putByte"),

        GET_BYTE_VOLATILE("getByteVolatile"),

        PUT_BYTE_VOLATILE("putByteVolatile"),

        GET_CHAR("getChar"),

        PUT_CHAR("putChar"),

        GET_CHAR_VOLATILE("getCharVolatile"),

        PUT_CHAR_VOLATILE("putCharVolatile"),

        GET_SHORT("getShort"),

        PUT_SHORT("putShort"),

        GET_SHORT_VOLATILE("getShortVolatile"),

        PUT_SHORT_VOLATILE("putShortVolatile"),

        GET_LONG("getLong"),

        PUT_LONG("putLong"),

        GET_LONG_VOLATILE("getLongVolatile"),

        PUT_LONG_VOLATILE("putLongVolatile"),

        GET_FLOAT("getFloat"),

        PUT_FLOAT("putFloat"),

        GET_FLOAT_VOLATILE("getFloatVolatile"),

        PUT_FLOAT_VOLATILE("putFloatVolatile"),

        GET_DOUBLE("getDouble"),

        PUT_DOUBLE("putDouble"),

        GET_DOUBLE_VOLATILE("getDoubleVolatile"),

        PUT_DOUBLE_VOLATILE("putDoubleVolatile"),

        TRY_FINALLY("tryFinally"),

        COLLECT("collect"),

        CONVERT("convert"),

        SPREAD("spread"),

        LOOP("loop"),

        FIELD("field"),

        GUARD("guard"),

        GUARD_WITH_CATCH("guardWithCatch"),

        VARHANDLE_EXACT_INVOKER("VH.exactInvoker"),

        VARHANDLE_INVOKER("VH.invoker", "invoker"),

        VARHANDLE_LINKER("VH.invoke_MT", "invoke_MT");

        final String defaultLambdaName;

        final String methodName;

        private Kind(String defaultLambdaName) {

            this(defaultLambdaName, defaultLambdaName);

        }

        private Kind(String defaultLambdaName, String methodName) {

            this.defaultLambdaName = defaultLambdaName;

            this.methodName = methodName;

        }

    }

    LambdaForm(int arity, Name[] names, int result) {

        this(arity, names, result, /*forceInline=*/true, /*customized=*/null, Kind.GENERIC);

    }

    LambdaForm(int arity, Name[] names, int result, Kind kind) {

        this(arity, names, result, /*forceInline=*/true, /*customized=*/null, kind);

    }

    LambdaForm(int arity, Name[] names, int result, boolean forceInline, MethodHandle customized) {

        this(arity, names, result, forceInline, customized, Kind.GENERIC);

    }

    LambdaForm(int arity, Name[] names, int result, boolean forceInline, MethodHandle customized, Kind kind) {

        assert(namesOK(arity, names));

        this.arity = arity;

        this.result = fixResult(result, names);

        this.names = names.clone();

        this.forceInline = forceInline;

        this.customized = customized;

        this.kind = kind;

        int maxOutArity = normalize();

        if (maxOutArity > MethodType.MAX_MH_INVOKER_ARITY) {

            // Cannot use LF interpreter on very high arity expressions.

            assert(maxOutArity <= MethodType.MAX_JVM_ARITY);

            compileToBytecode();

        }

    }

    LambdaForm(int arity, Name[] names) {

        this(arity, names, LAST_RESULT, /*forceInline=*/true, /*customized=*/null, Kind.GENERIC);

    }

    LambdaForm(int arity, Name[] names, Kind kind) {

        this(arity, names, LAST_RESULT, /*forceInline=*/true, /*customized=*/null, kind);

    }

    LambdaForm(int arity, Name[] names, boolean forceInline) {

        this(arity, names, LAST_RESULT, forceInline, /*customized=*/null, Kind.GENERIC);

    }

    LambdaForm(int arity, Name[] names, boolean forceInline, Kind kind) {

        this(arity, names, LAST_RESULT, forceInline, /*customized=*/null, kind);

    }

    LambdaForm(Name[] formals, Name[] temps, Name result) {

        this(formals.length, buildNames(formals, temps, result), LAST_RESULT, /*forceInline=*/true, /*customized=*/null);

    }

    LambdaForm(Name[] formals, Name[] temps, Name result, boolean forceInline) {

        this(formals.length, buildNames(formals, temps, result), LAST_RESULT, forceInline, /*customized=*/null);

    }

    private static Name[] buildNames(Name[] formals, Name[] temps, Name result) {

        int arity = formals.length;

        int length = arity + temps.length + (result == null ? 0 : 1);

        Name[] names = Arrays.copyOf(formals, length);

        System.arraycopy(temps, 0, names, arity, temps.length);

        if (result != null)

            names[length - 1] = result;

        return names;

    }

    private LambdaForm(MethodType mt) {

        // Make a blank lambda form, which returns a constant zero or null.

        // It is used as a template for managing the invocation of similar forms that are non-empty.

        // Called only from getPreparedForm.

        this.arity = mt.parameterCount();

        this.result = (mt.returnType() == void.class || mt.returnType() == Void.class) ? -1 : arity;

        this.names = buildEmptyNames(arity, mt, result == -1);

        this.forceInline = true;

        this.customized = null;

        this.kind = Kind.ZERO;

        assert(nameRefsAreLegal());

        assert(isEmpty());

        String sig = null;

        assert(isValidSignature(sig = basicTypeSignature()));

        assert(sig.equals(basicTypeSignature())) : sig + " != " + basicTypeSignature();

    }

    private static Name[] buildEmptyNames(int arity, MethodType mt, boolean isVoid) {

        Name[] names = arguments(isVoid ? 0 : 1, mt);

        if (!isVoid) {

            Name zero = new Name(constantZero(basicType(mt.returnType())));

            names[arity] = zero.newIndex(arity);

        }

        return names;

    }

    private static int fixResult(int result, Name[] names) {

        if (result == LAST_RESULT)

            result = names.length - 1;  // might still be void

        if (result >= 0 && names[result].type == V_TYPE)

            result = VOID_RESULT;

        return result;

    }

    static boolean debugNames() {

        return DEBUG_NAME_COUNTERS != null;

    }

    static void associateWithDebugName(LambdaForm form, String name) {

        assert (debugNames());

        synchronized (DEBUG_NAMES) {

            DEBUG_NAMES.put(form, name);

        }

    }

    String lambdaName() {

        if (DEBUG_NAMES != null) {

            synchronized (DEBUG_NAMES) {

                String name = DEBUG_NAMES.get(this);

                if (name == null) {

                    name = generateDebugName();

                }

                return name;

            }

        }

        return kind.defaultLambdaName;

    }

    private String generateDebugName() {

        assert (debugNames());

        String debugNameStem = kind.defaultLambdaName;

        Integer ctr = DEBUG_NAME_COUNTERS.getOrDefault(debugNameStem, 0);

        DEBUG_NAME_COUNTERS.put(debugNameStem, ctr + 1);

        StringBuilder buf = new StringBuilder(debugNameStem);

        int leadingZero = buf.length();

        buf.append((int) ctr);

        for (int i = buf.length() - leadingZero; i < 3; i++) {

            buf.insert(leadingZero, '0');

        }

        buf.append('_');

        buf.append(basicTypeSignature());

        String name = buf.toString();

        associateWithDebugName(this, name);

        return name;

    }

    private static boolean namesOK(int arity, Name[] names) {

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

            Name n = names[i];

            assert(n != null) : "n is null";

            if (i < arity)

                assert( n.isParam()) : n + " is not param at " + i;

            else

                assert(!n.isParam()) : n + " is param at " + i;

        }

        return true;

    }

    /** Customize LambdaForm for a particular MethodHandle */

    LambdaForm customize(MethodHandle mh) {

        LambdaForm customForm = new LambdaForm(arity, names, result, forceInline, mh, kind);

        if (COMPILE_THRESHOLD >= 0 && isCompiled) {

            // If shared LambdaForm has been compiled, compile customized version as well.

            customForm.compileToBytecode();

        }

        customForm.transformCache = this; // LambdaFormEditor should always use uncustomized form.

        return customForm;

    }

    /** Get uncustomized flavor of the LambdaForm */

    LambdaForm uncustomize() {

        if (customized == null) {

            return this;

        }

        assert(transformCache != null); // Customized LambdaForm should always has a link to uncustomized version.

        LambdaForm uncustomizedForm = (LambdaForm)transformCache;

        if (COMPILE_THRESHOLD >= 0 && isCompiled) {

            // If customized LambdaForm has been compiled, compile uncustomized version as well.

            uncustomizedForm.compileToBytecode();

        }

        return uncustomizedForm;

    }

    /** Renumber and/or replace params so that they are interned and canonically numbered.

     *  @return maximum argument list length among the names (since we have to pass over them anyway)

     */

    private int normalize() {

        Name[] oldNames = null;

        int maxOutArity = 0;

        int changesStart = 0;

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

            Name n = names[i];

            if (!n.initIndex(i)) {

                if (oldNames == null) {

                    oldNames = names.clone();

                    changesStart = i;

                }

                names[i] = n.cloneWithIndex(i);

            }

            if (n.arguments != null && maxOutArity < n.arguments.length)

                maxOutArity = n.arguments.length;

        }

        if (oldNames != null) {

            int startFixing = arity;

            if (startFixing <= changesStart)

                startFixing = changesStart+1;

            for (int i = startFixing; i < names.length; i++) {

                Name fixed = names[i].replaceNames(oldNames, names, changesStart, i);

                names[i] = fixed.newIndex(i);

            }

        }

        assert(nameRefsAreLegal());

        int maxInterned = Math.min(arity, INTERNED_ARGUMENT_LIMIT);

        boolean needIntern = false;

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

            Name n = names[i], n2 = internArgument(n);

            if (n != n2) {

                names[i] = n2;

                needIntern = true;

            }

        }

        if (needIntern) {

            for (int i = arity; i < names.length; i++) {

                names[i].internArguments();

            }

        }

        assert(nameRefsAreLegal());

        return maxOutArity;

    }

    /**

     * Check that all embedded Name references are localizable to this lambda,

     * and are properly ordered after their corresponding definitions.

     * <p>

     * Note that a Name can be local to multiple lambdas, as long as

     * it possesses the same index in each use site.

     * This allows Name references to be freely reused to construct

     * fresh lambdas, without confusion.

     */

    boolean nameRefsAreLegal() {

        assert(arity >= 0 && arity <= names.length);

        assert(result >= -1 && result < names.length);

        // Do all names possess an index consistent with their local definition order?

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

            Name n = names[i];

            assert(n.index() == i) : Arrays.asList(n.index(), i);

            assert(n.isParam());

        }

        // Also, do all local name references

        for (int i = arity; i < names.length; i++) {

            Name n = names[i];

            assert(n.index() == i);

            for (Object arg : n.arguments) {

                if (arg instanceof Name) {

                    Name n2 = (Name) arg;

                    int i2 = n2.index;

                    assert(0 <= i2 && i2 < names.length) : n.debugString() + ": 0 <= i2 && i2 < names.length: 0 <= " + i2 + " < " + names.length;

                    assert(names[i2] == n2) : Arrays.asList("-1-", i, "-2-", n.debugString(), "-3-", i2, "-4-", n2.debugString(), "-5-", names[i2].debugString(), "-6-", this);

                    assert(i2 < i);  // ref must come after def!

                }

            }

        }

        return true;

    }

    /** Invoke this form on the given arguments. */

    // final Object invoke(Object... args) throws Throwable {

    //     // NYI: fit this into the fast path?

    //     return interpretWithArguments(args);

    // }

    /** Report the return type. */

    BasicType returnType() {

        if (result < 0)  return V_TYPE;

        Name n = names[result];

        return n.type;

    }

    /** Report the N-th argument type. */

    BasicType parameterType(int n) {

        return parameter(n).type;

    }

    /** Report the N-th argument name. */

    Name parameter(int n) {

        assert(n < arity);

        Name param = names[n];

        assert(param.isParam());

        return param;

    }

    /** Report the N-th argument type constraint. */

    Object parameterConstraint(int n) {

        return parameter(n).constraint;

    }

    /** Report the arity. */

    int arity() {

        return arity;

    }

    /** Report the number of expressions (non-parameter names). */

    int expressionCount() {

        return names.length - arity;

    }

    /** Return the method type corresponding to my basic type signature. */

    MethodType methodType() {

        Class<?>[] ptypes = new Class<?>[arity];

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

            ptypes[i] = parameterType(i).btClass;

        }

        return MethodType.makeImpl(returnType().btClass, ptypes, true);

    }

    /** Return ABC_Z, where the ABC are parameter type characters, and Z is the return type character. */

    final String basicTypeSignature() {

        StringBuilder buf = new StringBuilder(arity() + 3);

        for (int i = 0, a = arity(); i < a; i++)

            buf.append(parameterType(i).basicTypeChar());

        return buf.append('_').append(returnType().basicTypeChar()).toString();

    }

    static int signatureArity(String sig) {

        assert(isValidSignature(sig));

        return sig.indexOf('_');

    }

    static BasicType signatureReturn(String sig) {

        return basicType(sig.charAt(signatureArity(sig) + 1));

    }

    static boolean isValidSignature(String sig) {

        int arity = sig.indexOf('_');

        if (arity < 0)  return false;  // must be of the form *_*

        int siglen = sig.length();

        if (siglen != arity + 2)  return false;  // *_X

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

            if (i == arity)  continue;  // skip '_'

            char c = sig.charAt(i);

            if (c == 'V')

                return (i == siglen - 1 && arity == siglen - 2);

            if (!isArgBasicTypeChar(c))  return false; // must be [LIJFD]

        }

        return true;  // [LIJFD]*_[LIJFDV]

    }

    static MethodType signatureType(String sig) {

        Class<?>[] ptypes = new Class<?>[signatureArity(sig)];

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

            ptypes[i] = basicType(sig.charAt(i)).btClass;

        Class<?> rtype = signatureReturn(sig).btClass;

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

    }

    static MethodType basicMethodType(MethodType mt) {

        return signatureType(basicTypeSignature(mt));

    }

    /**

     * Check if i-th name is a call to MethodHandleImpl.selectAlternative.

     */

    boolean isSelectAlternative(int pos) {

        // selectAlternative idiom:

        //   t_{n}:L=MethodHandleImpl.selectAlternative(...)

        //   t_{n+1}:?=MethodHandle.invokeBasic(t_{n}, ...)

        if (pos+1 >= names.length)  return false;

        Name name0 = names[pos];

        Name name1 = names[pos+1];

        return name0.refersTo(MethodHandleImpl.class, "selectAlternative") &&

                name1.isInvokeBasic() &&

                name1.lastUseIndex(name0) == 0 && // t_{n+1}:?=MethodHandle.invokeBasic(t_{n}, ...)

                lastUseIndex(name0) == pos+1;     // t_{n} is local: used only in t_{n+1}

    }

    private boolean isMatchingIdiom(int pos, String idiomName, int nArgs) {

        if (pos+2 >= names.length)  return false;

        Name name0 = names[pos];

        Name name1 = names[pos+1];

        Name name2 = names[pos+2];

        return name1.refersTo(MethodHandleImpl.class, idiomName) &&

                name0.isInvokeBasic() &&

                name2.isInvokeBasic() &&

                name1.lastUseIndex(name0) == nArgs && // t_{n+1}:L=MethodHandleImpl.<invoker>(<args>, t_{n});

                lastUseIndex(name0) == pos+1 &&       // t_{n} is local: used only in t_{n+1}

                name2.lastUseIndex(name1) == 1 &&     // t_{n+2}:?=MethodHandle.invokeBasic(*, t_{n+1})

                lastUseIndex(name1) == pos+2;         // t_{n+1} is local: used only in t_{n+2}

    }

    /**

     * Check if i-th name is a start of GuardWithCatch idiom.

     */

    boolean isGuardWithCatch(int pos) {

        // GuardWithCatch idiom:

        //   t_{n}:L=MethodHandle.invokeBasic(...)

        //   t_{n+1}:L=MethodHandleImpl.guardWithCatch(*, *, *, t_{n});

        //   t_{n+2}:?=MethodHandle.invokeBasic(*, t_{n+1})

        return isMatchingIdiom(pos, "guardWithCatch", 3);

    }

    /**

     * Check if i-th name is a start of the tryFinally idiom.

     */

    boolean isTryFinally(int pos) {

        // tryFinally idiom:

        //   t_{n}:L=MethodHandle.invokeBasic(...)

        //   t_{n+1}:L=MethodHandleImpl.tryFinally(*, *, t_{n})

        //   t_{n+2}:?=MethodHandle.invokeBasic(*, t_{n+1})

        return isMatchingIdiom(pos, "tryFinally", 2);

    }

    /**

     * Check if i-th name is a start of the loop idiom.

     */

    boolean isLoop(int pos) {

        // loop idiom:

        //   t_{n}:L=MethodHandle.invokeBasic(...)

        //   t_{n+1}:L=MethodHandleImpl.loop(types, *, t_{n})

        //   t_{n+2}:?=MethodHandle.invokeBasic(*, t_{n+1})

        return isMatchingIdiom(pos, "loop", 2);

    }

    /*

     * Code generation issues:

     *

     * Compiled LFs should be reusable in general.

     * The biggest issue is how to decide when to pull a name into

     * the bytecode, versus loading a reified form from the MH data.

     *

     * For example, an asType wrapper may require execution of a cast

     * after a call to a MH.  The target type of the cast can be placed

     * as a constant in the LF itself.  This will force the cast type

     * to be compiled into the bytecodes and native code for the MH.

     * Or, the target type of the cast can be erased in the LF, and

     * loaded from the MH data.  (Later on, if the MH as a whole is

     * inlined, the data will flow into the inlined instance of the LF,

     * as a constant, and the end result will be an optimal cast.)

     *

     * This erasure of cast types can be done with any use of

     * reference types.  It can also be done with whole method

     * handles.  Erasing a method handle might leave behind

     * LF code that executes correctly for any MH of a given

     * type, and load the required MH from the enclosing MH's data.

     * Or, the erasure might even erase the expected MT.

     *

     * Also, for direct MHs, the MemberName of the target

     * could be erased, and loaded from the containing direct MH.

     * As a simple case, a LF for all int-valued non-static

     * field getters would perform a cast on its input argument

     * (to non-constant base type derived from the MemberName)

     * and load an integer value from the input object

     * (at a non-constant offset also derived from the MemberName).

     * Such MN-erased LFs would be inlinable back to optimized

     * code, whenever a constant enclosing DMH is available

     * to supply a constant MN from its data.

     *

     * The main problem here is to keep LFs reasonably generic,

     * while ensuring that hot spots will inline good instances.

     * "Reasonably generic" means that we don't end up with

     * repeated versions of bytecode or machine code that do

     * not differ in their optimized form.  Repeated versions

     * of machine would have the undesirable overheads of

     * (a) redundant compilation work and (b) extra I$ pressure.

     * To control repeated versions, we need to be ready to

     * erase details from LFs and move them into MH data,

     * whevener those details are not relevant to significant

     * optimization.  "Significant" means optimization of

     * code that is actually hot.

     *

     * Achieving this may require dynamic splitting of MHs, by replacing

     * a generic LF with a more specialized one, on the same MH,

     * if (a) the MH is frequently executed and (b) the MH cannot

     * be inlined into a containing caller, such as an invokedynamic.

     *

     * Compiled LFs that are no longer used should be GC-able.

     * If they contain non-BCP references, they should be properly

     * interlinked with the class loader(s) that their embedded types

     * depend on.  This probably means that reusable compiled LFs

     * will be tabulated (indexed) on relevant class loaders,

     * or else that the tables that cache them will have weak links.

     */

    /**

     * Make this LF directly executable, as part of a MethodHandle.

     * Invariant:  Every MH which is invoked must prepare its LF

     * before invocation.

     * (In principle, the JVM could do this very lazily,

     * as a sort of pre-invocation linkage step.)

     */

    public void prepare() {

        if (COMPILE_THRESHOLD == 0 && !forceInterpretation() && !isCompiled) {

            compileToBytecode();

        }

        if (this.vmentry != null) {

            // already prepared (e.g., a primitive DMH invoker form)

            return;

        }

        MethodType mtype = methodType();

        LambdaForm prep = mtype.form().cachedLambdaForm(MethodTypeForm.LF_INTERPRET);

        if (prep == null) {

            assert (isValidSignature(basicTypeSignature()));

            prep = new LambdaForm(mtype);

            prep.vmentry = InvokerBytecodeGenerator.generateLambdaFormInterpreterEntryPoint(mtype);

            prep = mtype.form().setCachedLambdaForm(MethodTypeForm.LF_INTERPRET, prep);

        }

        this.vmentry = prep.vmentry;

        // TO DO: Maybe add invokeGeneric, invokeWithArguments

    }

    private static @Stable PerfCounter LF_FAILED;

    private static PerfCounter failedCompilationCounter() {

        if (LF_FAILED == null) {

            LF_FAILED = PerfCounter.newPerfCounter("java.lang.invoke.failedLambdaFormCompilations");

        }

        return LF_FAILED;

    }

    /** Generate optimizable bytecode for this form. */

    void compileToBytecode() {

        if (forceInterpretation()) {

            return; // this should not be compiled

        }

        if (vmentry != null && isCompiled) {

            return;  // already compiled somehow

        }

        // Obtain the invoker MethodType outside of the following try block.

        // This ensures that an IllegalArgumentException is directly thrown if the

        // type would have 256 or more parameters

        MethodType invokerType = methodType();

        assert(vmentry == null || vmentry.getMethodType().basicType().equals(invokerType));

        try {

            vmentry = InvokerBytecodeGenerator.generateCustomizedCode(this, invokerType);

            if (TRACE_INTERPRETER)

                traceInterpreter("compileToBytecode", this);

            isCompiled = true;

        } catch (InvokerBytecodeGenerator.BytecodeGenerationException bge) {

            // bytecode generation failed - mark this LambdaForm as to be run in interpretation mode only

            invocationCounter = -1;

            failedCompilationCounter().increment();

            if (LOG_LF_COMPILATION_FAILURE) {

                System.out.println("LambdaForm compilation failed: " + this);

                bge.printStackTrace(System.out);

            }

        } catch (Error e) {

            // Pass through any error

            throw e;

        } catch (Exception e) {

            // Wrap any exception

            throw newInternalError(this.toString(), e);

        }

    }

    // The next few routines are called only from assert expressions

    // They verify that the built-in invokers process the correct raw data types.

    private static boolean argumentTypesMatch(String sig, Object[] av) {

        int arity = signatureArity(sig);

        assert(av.length == arity) : "av.length == arity: av.length=" + av.length + ", arity=" + arity;

        assert(av[0] instanceof MethodHandle) : "av[0] not instace of MethodHandle: " + av[0];

        MethodHandle mh = (MethodHandle) av[0];

        MethodType mt = mh.type();

        assert(mt.parameterCount() == arity-1);

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

            Class<?> pt = (i == 0 ? MethodHandle.class : mt.parameterType(i-1));

            assert(valueMatches(basicType(sig.charAt(i)), pt, av[i]));

        }

        return true;

    }

    private static boolean valueMatches(BasicType tc, Class<?> type, Object x) {

        // The following line is needed because (...)void method handles can use non-void invokers

        if (type == void.class)  tc = V_TYPE;   // can drop any kind of value

        assert tc == basicType(type) : tc + " == basicType(" + type + ")=" + basicType(type);

        switch (tc) {

        case I_TYPE: assert checkInt(type, x)   : "checkInt(" + type + "," + x +")";   break;

        case J_TYPE: assert x instanceof Long   : "instanceof Long: " + x;             break;

        case F_TYPE: assert x instanceof Float  : "instanceof Float: " + x;            break;

        case D_TYPE: assert x instanceof Double : "instanceof Double: " + x;           break;

        case L_TYPE: assert checkRef(type, x)   : "checkRef(" + type + "," + x + ")";  break;

        case V_TYPE: break;  // allow anything here; will be dropped

        default:  assert(false);

        }

        return true;

    }

    private static boolean checkInt(Class<?> type, Object x) {

        assert(x instanceof Integer);

        if (type == int.class)  return true;

        Wrapper w = Wrapper.forBasicType(type);

        assert(w.isSubwordOrInt());

        Object x1 = Wrapper.INT.wrap(w.wrap(x));

        return x.equals(x1);

    }

    private static boolean checkRef(Class<?> type, Object x) {

        assert(!type.isPrimitive());

        if (x == null)  return true;

        if (type.isInterface())  return true;

        return type.isInstance(x);

    }

    /** If the invocation count hits the threshold we spin bytecodes and call that subsequently. */

    private static final int COMPILE_THRESHOLD;

    static {

        COMPILE_THRESHOLD = Math.max(-1, MethodHandleStatics.COMPILE_THRESHOLD);

    }

    private int invocationCounter = 0; // a value of -1 indicates LambdaForm interpretation mode forever

    private boolean forceInterpretation() {

        return invocationCounter == -1;

    }

    @Hidden

    @DontInline

    /** Interpretively invoke this form on the given arguments. */

    Object interpretWithArguments(Object... argumentValues) throws Throwable {

        if (TRACE_INTERPRETER)

            return interpretWithArgumentsTracing(argumentValues);

        checkInvocationCounter();

        assert(arityCheck(argumentValues));

        Object[] values = Arrays.copyOf(argumentValues, names.length);

        for (int i = argumentValues.length; i < values.length; i++) {

            values[i] = interpretName(names[i], values);

        }

        Object rv = (result < 0) ? null : values[result];

        assert(resultCheck(argumentValues, rv));

        return rv;

    }

    @Hidden

    @DontInline

    /** Evaluate a single Name within this form, applying its function to its arguments. */

    Object interpretName(Name name, Object[] values) throws Throwable {

        if (TRACE_INTERPRETER)

            traceInterpreter("| interpretName", name.debugString(), (Object[]) null);

        Object[] arguments = Arrays.copyOf(name.arguments, name.arguments.length, Object[].class);

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

            Object a = arguments[i];

            if (a instanceof Name) {

                int i2 = ((Name)a).index();

                assert(names[i2] == a);

                a = values[i2];

                arguments[i] = a;

            }

        }

        return name.function.invokeWithArguments(arguments);

    }

    private void checkInvocationCounter() {

        if (COMPILE_THRESHOLD != 0 &&

            !forceInterpretation() && invocationCounter < COMPILE_THRESHOLD) {

            invocationCounter++;  // benign race

            if (invocationCounter >= COMPILE_THRESHOLD) {

                // Replace vmentry with a bytecode version of this LF.

                compileToBytecode();

            }

        }

    }

    Object interpretWithArgumentsTracing(Object... argumentValues) throws Throwable {

        traceInterpreter("[ interpretWithArguments", this, argumentValues);

        if (!forceInterpretation() && invocationCounter < COMPILE_THRESHOLD) {

            int ctr = invocationCounter++;  // benign race

            traceInterpreter("| invocationCounter", ctr);

            if (invocationCounter >= COMPILE_THRESHOLD) {

                compileToBytecode();

            }

        }

        Object rval;

        try {

            assert(arityCheck(argumentValues));

            Object[] values = Arrays.copyOf(argumentValues, names.length);

            for (int i = argumentValues.length; i < values.length; i++) {

                values[i] = interpretName(names[i], values);

            }

            rval = (result < 0) ? null : values[result];

        } catch (Throwable ex) {

            traceInterpreter("] throw =>", ex);

            throw ex;

        }

        traceInterpreter("] return =>", rval);

        return rval;

    }

    static void traceInterpreter(String event, Object obj, Object... args) {

        if (TRACE_INTERPRETER) {

            System.out.println("LFI: "+event+" "+(obj != null ? obj : "")+(args != null && args.length != 0 ? Arrays.asList(args) : ""));

        }

    }

    static void traceInterpreter(String event, Object obj) {

        traceInterpreter(event, obj, (Object[])null);

    }

    private boolean arityCheck(Object[] argumentValues) {

        assert(argumentValues.length == arity) : arity+"!="+Arrays.asList(argumentValues)+".length";

        // also check that the leading (receiver) argument is somehow bound to this LF:

        assert(argumentValues[0] instanceof MethodHandle) : "not MH: " + argumentValues[0];

        MethodHandle mh = (MethodHandle) argumentValues[0];

        assert(mh.internalForm() == this);

        // note:  argument #0 could also be an interface wrapper, in the future

        argumentTypesMatch(basicTypeSignature(), argumentValues);

        return true;

    }

    private boolean resultCheck(Object[] argumentValues, Object result) {

        MethodHandle mh = (MethodHandle) argumentValues[0];

        MethodType mt = mh.type();

        assert(valueMatches(returnType(), mt.returnType(), result));

        return true;

    }

    private boolean isEmpty() {

        if (result < 0)

            return (names.length == arity);

        else if (result == arity && names.length == arity + 1)

            return names[arity].isConstantZero();

        else

            return false;

    }

    public String toString() {

        String lambdaName = lambdaName();

        StringBuilder buf = new StringBuilder(lambdaName + "=Lambda(");

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

            if (i == arity)  buf.append(")=>{");

            Name n = names[i];

            if (i >= arity)  buf.append("\n    ");

            buf.append(n.paramString());

            if (i < arity) {

                if (i+1 < arity)  buf.append(",");

                continue;

            }

            buf.append("=").append(n.exprString());

            buf.append(";");

        }

        if (arity == names.length)  buf.append(")=>{");

        buf.append(result < 0 ? "void" : names[result]).append("}");

        if (TRACE_INTERPRETER) {

            // Extra verbosity:

            buf.append(":").append(basicTypeSignature());

            buf.append("/").append(vmentry);

        }

        return buf.toString();

    }

    @Override

    public boolean equals(Object obj) {

        return obj instanceof LambdaForm && equals((LambdaForm)obj);

    }

    public boolean equals(LambdaForm that) {

        if (this.result != that.result)  return false;

        return Arrays.equals(this.names, that.names);

    }

    public int hashCode() {

        return result + 31 * Arrays.hashCode(names);

    }

    LambdaFormEditor editor() {

        return LambdaFormEditor.lambdaFormEditor(this);

    }

    boolean contains(Name name) {

        int pos = name.index();

        if (pos >= 0) {

            return pos < names.length && name.equals(names[pos]);

        }

        for (int i = arity; i < names.length; i++) {

            if (name.equals(names[i]))

                return true;

        }

        return false;

    }

    static class NamedFunction {

        final MemberName member;

        private @Stable MethodHandle resolvedHandle;

        @Stable MethodHandle invoker;

        private final MethodHandleImpl.Intrinsic intrinsicName;

        NamedFunction(MethodHandle resolvedHandle) {

            this(resolvedHandle.internalMemberName(), resolvedHandle, MethodHandleImpl.Intrinsic.NONE);

        }

        NamedFunction(MethodHandle resolvedHandle, MethodHandleImpl.Intrinsic intrinsic) {

            this(resolvedHandle.internalMemberName(), resolvedHandle, intrinsic);

        }

        NamedFunction(MemberName member, MethodHandle resolvedHandle) {

            this(member, resolvedHandle, MethodHandleImpl.Intrinsic.NONE);

        }

        NamedFunction(MemberName member, MethodHandle resolvedHandle, MethodHandleImpl.Intrinsic intrinsic) {

            this.member = member;

            this.resolvedHandle = resolvedHandle;

            this.intrinsicName = intrinsic;

            assert(resolvedHandle == null ||

                   resolvedHandle.intrinsicName() == MethodHandleImpl.Intrinsic.NONE ||

                   resolvedHandle.intrinsicName() == intrinsic) : resolvedHandle.intrinsicName() + " != " + intrinsic;

             // The following assert is almost always correct, but will fail for corner cases, such as PrivateInvokeTest.

             //assert(!isInvokeBasic(member));

        }

        NamedFunction(MethodType basicInvokerType) {

            assert(basicInvokerType == basicInvokerType.basicType()) : basicInvokerType;

            if (basicInvokerType.parameterSlotCount() < MethodType.MAX_MH_INVOKER_ARITY) {

                this.resolvedHandle = basicInvokerType.invokers().basicInvoker();

                this.member = resolvedHandle.internalMemberName();

            } else {

                // necessary to pass BigArityTest

                this.member = Invokers.invokeBasicMethod(basicInvokerType);

            }

            this.intrinsicName = MethodHandleImpl.Intrinsic.NONE;

            assert(isInvokeBasic(member));

        }

        private static boolean isInvokeBasic(MemberName member) {

            return member != null &&

                   member.getDeclaringClass() == MethodHandle.class &&

                  "invokeBasic".equals(member.getName());

        }

        // The next 2 constructors are used to break circular dependencies on MH.invokeStatic, etc.

        // Any LambdaForm containing such a member is not interpretable.

        // This is OK, since all such LFs are prepared with special primitive vmentry points.

        // And even without the resolvedHandle, the name can still be compiled and optimized.

        NamedFunction(Method method) {

            this(new MemberName(method));

        }

        NamedFunction(MemberName member) {

            this(member, null);

        }

        MethodHandle resolvedHandle() {

            if (resolvedHandle == null)  resolve();

            return resolvedHandle;

        }

        synchronized void resolve() {

            if (resolvedHandle == null) {

                resolvedHandle = DirectMethodHandle.make(member);

            }

        }

        @Override

        public boolean equals(Object other) {

            if (this == other) return true;

            if (other == null) return false;

            if (!(other instanceof NamedFunction)) return false;

            NamedFunction that = (NamedFunction) other;

            return this.member != null && this.member.equals(that.member);

        }

        @Override

        public int hashCode() {

            if (member != null)

                return member.hashCode();

            return super.hashCode();

        }

        static final MethodType INVOKER_METHOD_TYPE =

            MethodType.methodType(Object.class, MethodHandle.class, Object[].class);

        private static MethodHandle computeInvoker(MethodTypeForm typeForm) {

            typeForm = typeForm.basicType().form();  // normalize to basic type

            MethodHandle mh = typeForm.cachedMethodHandle(MethodTypeForm.MH_NF_INV);

            if (mh != null)  return mh;

            MemberName invoker = InvokerBytecodeGenerator.generateNamedFunctionInvoker(typeForm);  // this could take a while

            mh = DirectMethodHandle.make(invoker);

            MethodHandle mh2 = typeForm.cachedMethodHandle(MethodTypeForm.MH_NF_INV);

            if (mh2 != null)  return mh2;  // benign race

            if (!mh.type().equals(INVOKER_METHOD_TYPE))

                throw newInternalError(mh.debugString());

            return typeForm.setCachedMethodHandle(MethodTypeForm.MH_NF_INV, mh);

        }

        @Hidden

        Object invokeWithArguments(Object... arguments) throws Throwable {

            // If we have a cached invoker, call it right away.

            // NOTE: The invoker always returns a reference value.

            if (TRACE_INTERPRETER)  return invokeWithArgumentsTracing(arguments);

            return invoker().invokeBasic(resolvedHandle(), arguments);

        }

        @Hidden

        Object invokeWithArgumentsTracing(Object[] arguments) throws Throwable {

            Object rval;

            try {

                traceInterpreter("[ call", this, arguments);

                if (invoker == null) {

                    traceInterpreter("| getInvoker", this);

                    invoker();

                }

                // resolvedHandle might be uninitialized, ok for tracing

                if (resolvedHandle == null) {

                    traceInterpreter("| resolve", this);

                    resolvedHandle();

                }

                rval = invoker().invokeBasic(resolvedHandle(), arguments);

            } catch (Throwable ex) {

                traceInterpreter("] throw =>", ex);

                throw ex;

            }

            traceInterpreter("] return =>", rval);

            return rval;

        }

        private MethodHandle invoker() {

            if (invoker != null)  return invoker;

            // Get an invoker and cache it.

            return invoker = computeInvoker(methodType().form());

        }

        MethodType methodType() {

            if (resolvedHandle != null)

                return resolvedHandle.type();

            else

                // only for certain internal LFs during bootstrapping

                return member.getInvocationType();

        }

        MemberName member() {

            assert(assertMemberIsConsistent());

            return member;

        }

        // Called only from assert.

        private boolean assertMemberIsConsistent() {

            if (resolvedHandle instanceof DirectMethodHandle) {

                MemberName m = resolvedHandle.internalMemberName();

                assert(m.equals(member));

            }

            return true;

        }

        Class<?> memberDeclaringClassOrNull() {

            return (member == null) ? null : member.getDeclaringClass();