trunk/js/jsparse.cpp

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sw=4 et tw=99:
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla Communicator client code, released
 * March 31, 1998.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1998
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

/*
 * JS parser.
 *
 * This is a recursive-descent parser for the JavaScript language specified by
 * "The JavaScript 1.5 Language Specification".  It uses lexical and semantic
 * feedback to disambiguate non-LL(1) structures.  It generates trees of nodes
 * induced by the recursive parsing (not precise syntax trees, see jsparse.h).
 * After tree construction, it rewrites trees to fold constants and evaluate
 * compile-time expressions.  Finally, it calls js_EmitTree (see jsemit.h) to
 * generate bytecode.
 *
 * This parser attempts no error recovery.
 */
#include "jsstddef.h"
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "jstypes.h"
#include "jsarena.h" /* Added by JSIFY */
#include "jsutil.h" /* Added by JSIFY */
#include "jsapi.h"
#include "jsarray.h"
#include "jsatom.h"
#include "jscntxt.h"
#include "jsversion.h"
#include "jsemit.h"
#include "jsfun.h"
#include "jsinterp.h"
#include "jsiter.h"
#include "jslock.h"
#include "jsnum.h"
#include "jsobj.h"
#include "jsopcode.h"
#include "jsparse.h"
#include "jsscan.h"
#include "jsscope.h"
#include "jsscript.h"
#include "jsstr.h"
#include "jsstaticcheck.h"

#if JS_HAS_XML_SUPPORT
#include "jsxml.h"
#endif

#if JS_HAS_DESTRUCTURING
#include "jsdhash.h"
#endif

/*
 * Asserts to verify assumptions behind pn_ macros.
 */
JS_STATIC_ASSERT(offsetof(JSParseNode, pn_u.name.atom) ==
                 offsetof(JSParseNode, pn_u.apair.atom));
JS_STATIC_ASSERT(offsetof(JSParseNode, pn_u.name.slot) ==
                 offsetof(JSParseNode, pn_u.lexical.slot));

/*
 * JS parsers, from lowest to highest precedence.
 *
 * Each parser takes a context, a token stream, and a tree context struct.
 * Each returns a parse node tree or null on error.
 */

typedef JSParseNode *
JSParser(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc);

typedef JSParseNode *
JSMemberParser(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc,
               JSBool allowCallSyntax);

typedef JSParseNode *
JSPrimaryParser(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc,
                JSTokenType tt, JSBool afterDot);

typedef JSParseNode *
JSParenParser(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc,
              JSParseNode *pn1, JSBool *genexp);

static JSParser FunctionStmt;
static JSParser FunctionExpr;
static JSParser Statements;
static JSParser Statement;
static JSParser Variables;
static JSParser Expr;
static JSParser AssignExpr;
static JSParser CondExpr;
static JSParser OrExpr;
static JSParser AndExpr;
static JSParser BitOrExpr;
static JSParser BitXorExpr;
static JSParser BitAndExpr;
static JSParser EqExpr;
static JSParser RelExpr;
static JSParser ShiftExpr;
static JSParser AddExpr;
static JSParser MulExpr;
static JSParser UnaryExpr;
static JSMemberParser  MemberExpr;
static JSPrimaryParser PrimaryExpr;
static JSParenParser   ParenExpr;

/*
 * Insist that the next token be of type tt, or report errno and return null.
 * NB: this macro uses cx and ts from its lexical environment.
 */
#define MUST_MATCH_TOKEN(tt, errno)                                           \
    JS_BEGIN_MACRO                                                            \
        if (js_GetToken(cx, ts) != tt) {                                      \
            js_ReportCompileErrorNumber(cx, ts, NULL, JSREPORT_ERROR, errno); \
            return NULL;                                                      \
        }                                                                     \
    JS_END_MACRO

#ifdef METER_PARSENODES
static uint32 parsenodes = 0;
static uint32 maxparsenodes = 0;
static uint32 recyclednodes = 0;
#endif

JSBool
js_InitParseContext(JSContext *cx, JSParseContext *pc, JSPrincipals *principals,
                    JSStackFrame *callerFrame,
                    const jschar *base, size_t length,
                    FILE *fp, const char *filename, uintN lineno)
{
    JS_ASSERT_IF(callerFrame, callerFrame->script);

    pc->tempPoolMark = JS_ARENA_MARK(&cx->tempPool);
    if (!js_InitTokenStream(cx, TS(pc), base, length, fp, filename, lineno)) {
        JS_ARENA_RELEASE(&cx->tempPool, pc->tempPoolMark);
        return JS_FALSE;
    }
    if (principals)
        JSPRINCIPALS_HOLD(cx, principals);
    pc->principals = principals;
    pc->callerFrame = callerFrame;
    pc->nodeList = NULL;
    pc->traceListHead = NULL;

    /* Root atoms and objects allocated for the parsed tree. */
    JS_KEEP_ATOMS(cx->runtime);
    JS_PUSH_TEMP_ROOT_PARSE_CONTEXT(cx, pc, &pc->tempRoot);
    return JS_TRUE;
}

void
js_FinishParseContext(JSContext *cx, JSParseContext *pc)
{
    if (pc->principals)
        JSPRINCIPALS_DROP(cx, pc->principals);
    JS_ASSERT(pc->tempRoot.u.parseContext == pc);
    JS_POP_TEMP_ROOT(cx, &pc->tempRoot);
    JS_UNKEEP_ATOMS(cx->runtime);
    js_CloseTokenStream(cx, TS(pc));
    JS_ARENA_RELEASE(&cx->tempPool, pc->tempPoolMark);
}

void
js_InitCompilePrincipals(JSContext *cx, JSParseContext *pc,
                         JSPrincipals *principals)
{
    JS_ASSERT(!pc->principals);
    if (principals)
        JSPRINCIPALS_HOLD(cx, principals);
    pc->principals = principals;
}

JSParsedObjectBox *
js_NewParsedObjectBox(JSContext *cx, JSParseContext *pc, JSObject *obj)
{
    JSParsedObjectBox *pob;

    /*
     * We use JSContext.tempPool to allocate parsed objects and place them on
     * a list in JSTokenStream to ensure GC safety. Thus the tempPool arenas
     * containing the entries must be alive until we are done with scanning,
     * parsing and code generation for the whole script or top-level function.
     */
    JS_ASSERT(obj);
    JS_ARENA_ALLOCATE_TYPE(pob, JSParsedObjectBox, &cx->tempPool);
    if (!pob) {
        js_ReportOutOfScriptQuota(cx);
        return NULL;
    }
    pob->traceLink = pc->traceListHead;
    pob->emitLink = NULL;
    pob->object = obj;
    pc->traceListHead = pob;
    return pob;
}


void
js_TraceParseContext(JSTracer *trc, JSParseContext *pc)
{
    JSParsedObjectBox *pob;

    JS_ASSERT(pc->tempRoot.u.parseContext == pc);
    pob = pc->traceListHead;
    while (pob) {
        JS_CALL_OBJECT_TRACER(trc, pob->object, "parser.object");
        pob = pob->traceLink;
    }
}

static JSParseNode *
RecycleTree(JSParseNode *pn, JSTreeContext *tc)
{
    JSParseNode *next;

    if (!pn)
        return NULL;

    /* Catch back-to-back dup recycles. */
    JS_ASSERT(pn != tc->parseContext->nodeList);
    next = pn->pn_next;
    pn->pn_next = tc->parseContext->nodeList;
    tc->parseContext->nodeList = pn;
#ifdef METER_PARSENODES
    recyclednodes++;
#endif
    return next;
}

static JSParseNode *
NewOrRecycledNode(JSContext *cx, JSTreeContext *tc)
{
    JSParseNode *pn;

    pn = tc->parseContext->nodeList;
    if (!pn) {
        JS_ARENA_ALLOCATE_TYPE(pn, JSParseNode, &cx->tempPool);
        if (!pn)
            js_ReportOutOfScriptQuota(cx);
    } else {
        tc->parseContext->nodeList = pn->pn_next;

        /* Recycle immediate descendents only, to save work and working set. */
        switch (pn->pn_arity) {
          case PN_FUNC:
            RecycleTree(pn->pn_body, tc);
            break;
          case PN_LIST:
            if (pn->pn_head) {
                /* XXX check for dup recycles in the list */
                *pn->pn_tail = tc->parseContext->nodeList;
                tc->parseContext->nodeList = pn->pn_head;
#ifdef METER_PARSENODES
                recyclednodes += pn->pn_count;
#endif
            }
            break;
          case PN_TERNARY:
            RecycleTree(pn->pn_kid1, tc);
            RecycleTree(pn->pn_kid2, tc);
            RecycleTree(pn->pn_kid3, tc);
            break;
          case PN_BINARY:
            if (pn->pn_left != pn->pn_right)
                RecycleTree(pn->pn_left, tc);
            RecycleTree(pn->pn_right, tc);
            break;
          case PN_UNARY:
            RecycleTree(pn->pn_kid, tc);
            break;
          case PN_NAME:
            RecycleTree(pn->pn_expr, tc);
            break;
          case PN_NULLARY:
            break;
        }
    }
    if (pn) {
#ifdef METER_PARSENODES
        parsenodes++;
        if (parsenodes - recyclednodes > maxparsenodes)
            maxparsenodes = parsenodes - recyclednodes;
#endif
        memset(&pn->pn_u, 0, sizeof pn->pn_u);
        pn->pn_next = NULL;
    }
    return pn;
}

/*
 * Allocate a JSParseNode from cx's temporary arena.
 */
static JSParseNode *
NewParseNode(JSContext *cx, JSTokenStream *ts, JSParseNodeArity arity,
             JSTreeContext *tc)
{
    JSParseNode *pn;
    JSToken *tp;

    pn = NewOrRecycledNode(cx, tc);
    if (!pn)
        return NULL;
    tp = &CURRENT_TOKEN(ts);
    pn->pn_type = tp->type;
    pn->pn_pos = tp->pos;
    pn->pn_op = JSOP_NOP;
    pn->pn_arity = arity;
    return pn;
}

static JSParseNode *
NewBinary(JSContext *cx, JSTokenType tt,
          JSOp op, JSParseNode *left, JSParseNode *right,
          JSTreeContext *tc)
{
    JSParseNode *pn, *pn1, *pn2;

    if (!left || !right)
        return NULL;

    /*
     * Flatten a left-associative (left-heavy) tree of a given operator into
     * a list, to reduce js_FoldConstants and js_EmitTree recursion.
     */
    if (left->pn_type == tt &&
        left->pn_op == op &&
        (js_CodeSpec[op].format & JOF_LEFTASSOC)) {
        if (left->pn_arity != PN_LIST) {
            pn1 = left->pn_left, pn2 = left->pn_right;
            left->pn_arity = PN_LIST;
            PN_INIT_LIST_1(left, pn1);
            PN_APPEND(left, pn2);
            if (tt == TOK_PLUS) {
                if (pn1->pn_type == TOK_STRING)
                    left->pn_extra |= PNX_STRCAT;
                else if (pn1->pn_type != TOK_NUMBER)
                    left->pn_extra |= PNX_CANTFOLD;
                if (pn2->pn_type == TOK_STRING)
                    left->pn_extra |= PNX_STRCAT;
                else if (pn2->pn_type != TOK_NUMBER)
                    left->pn_extra |= PNX_CANTFOLD;
            }
        }
        PN_APPEND(left, right);
        left->pn_pos.end = right->pn_pos.end;
        if (tt == TOK_PLUS) {
            if (right->pn_type == TOK_STRING)
                left->pn_extra |= PNX_STRCAT;
            else if (right->pn_type != TOK_NUMBER)
                left->pn_extra |= PNX_CANTFOLD;
        }
        return left;
    }

    /*
     * Fold constant addition immediately, to conserve node space and, what's
     * more, so js_FoldConstants never sees mixed addition and concatenation
     * operations with more than one leading non-string operand in a PN_LIST
     * generated for expressions such as 1 + 2 + "pt" (which should evaluate
     * to "3pt", not "12pt").
     */
    if (tt == TOK_PLUS &&
        left->pn_type == TOK_NUMBER &&
        right->pn_type == TOK_NUMBER) {
        left->pn_dval += right->pn_dval;
        left->pn_pos.end = right->pn_pos.end;
        RecycleTree(right, tc);
        return left;
    }

    pn = NewOrRecycledNode(cx, tc);
    if (!pn)
        return NULL;
    pn->pn_type = tt;
    pn->pn_pos.begin = left->pn_pos.begin;
    pn->pn_pos.end = right->pn_pos.end;
    pn->pn_op = op;
    pn->pn_arity = PN_BINARY;
    pn->pn_left = left;
    pn->pn_right = right;
    return pn;
}

#if JS_HAS_GETTER_SETTER
static JSTokenType
CheckGetterOrSetter(JSContext *cx, JSTokenStream *ts, JSTokenType tt)
{
    JSAtom *atom;
    JSRuntime *rt;
    JSOp op;
    const char *name;

    JS_ASSERT(CURRENT_TOKEN(ts).type == TOK_NAME);
    atom = CURRENT_TOKEN(ts).t_atom;
    rt = cx->runtime;
    if (atom == rt->atomState.getterAtom)
        op = JSOP_GETTER;
    else if (atom == rt->atomState.setterAtom)
        op = JSOP_SETTER;
    else
        return TOK_NAME;
    if (js_PeekTokenSameLine(cx, ts) != tt)
        return TOK_NAME;
    (void) js_GetToken(cx, ts);
    if (CURRENT_TOKEN(ts).t_op != JSOP_NOP) {
        js_ReportCompileErrorNumber(cx, ts, NULL, JSREPORT_ERROR,
                                    JSMSG_BAD_GETTER_OR_SETTER,
                                    (op == JSOP_GETTER)
                                    ? js_getter_str
                                    : js_setter_str);
        return TOK_ERROR;
    }
    CURRENT_TOKEN(ts).t_op = op;
    if (JS_HAS_STRICT_OPTION(cx)) {
        name = js_AtomToPrintableString(cx, atom);
        if (!name ||
            !js_ReportCompileErrorNumber(cx, ts, NULL,
                                         JSREPORT_WARNING | JSREPORT_STRICT,
                                         JSMSG_DEPRECATED_USAGE,
                                         name)) {
            return TOK_ERROR;
        }
    }
    return tt;
}
#endif

/*
 * Parse a top-level JS script.
 */
JSParseNode *
js_ParseScript(JSContext *cx, JSObject *chain, JSParseContext *pc)
{
    JSTreeContext tc;
    JSParseNode *pn;

    /*
     * Protect atoms from being collected by a GC activation, which might
     * - nest on this thread due to out of memory (the so-called "last ditch"
     *   GC attempted within js_NewGCThing), or
     * - run for any reason on another thread if this thread is suspended on
     *   an object lock before it finishes generating bytecode into a script
     *   protected from the GC by a root or a stack frame reference.
     */
    TREE_CONTEXT_INIT(&tc, pc);
    tc.u.scopeChain = chain;
    pn = Statements(cx, TS(pc), &tc);
    if (pn) {
        if (!js_MatchToken(cx, TS(pc), TOK_EOF)) {
            js_ReportCompileErrorNumber(cx, TS(pc), NULL, JSREPORT_ERROR,
                                        JSMSG_SYNTAX_ERROR);
            pn = NULL;
        } else {
            pn->pn_type = TOK_LC;
            if (!js_FoldConstants(cx, pn, &tc))
                pn = NULL;
        }
    }

    TREE_CONTEXT_FINISH(cx, &tc);
    return pn;
}

/*
 * Compile a top-level script.
 */
extern JSScript *
js_CompileScript(JSContext *cx, JSObject *scopeChain, JSStackFrame *callerFrame,
                 JSPrincipals *principals, uint32 tcflags,
                 const jschar *chars, size_t length,
                 FILE *file, const char *filename, uintN lineno)
{
    JSParseContext pc;
    JSArenaPool codePool, notePool;
    JSCodeGenerator cg;
    JSTokenType tt;
    JSParseNode *pn;
    uint32 scriptGlobals;
    JSScript *script;
#ifdef METER_PARSENODES
    void *sbrk(ptrdiff_t), *before = sbrk(0);
#endif

    JS_ASSERT(!(tcflags & ~(TCF_COMPILE_N_GO | TCF_NO_SCRIPT_RVAL |
                            TCF_STATIC_DEPTH_MASK)));

    /*
     * The scripted callerFrame can only be given for compile-and-go scripts
     * and non-zero static depth requires callerFrame.
     */
    JS_ASSERT_IF(callerFrame, tcflags & TCF_COMPILE_N_GO);
    JS_ASSERT_IF(TCF_GET_STATIC_DEPTH(tcflags) != 0, callerFrame);

    if (!js_InitParseContext(cx, &pc, principals, callerFrame, chars, length,
                             file, filename, lineno)) {
        return NULL;
    }

    JS_INIT_ARENA_POOL(&codePool, "code", 1024, sizeof(jsbytecode),
                       &cx->scriptStackQuota);
    JS_INIT_ARENA_POOL(&notePool, "note", 1024, sizeof(jssrcnote),
                       &cx->scriptStackQuota);
    js_InitCodeGenerator(cx, &cg, &pc, &codePool, &notePool,
                         pc.tokenStream.lineno);

    MUST_FLOW_THROUGH("out");
    cg.treeContext.flags |= (uint16) tcflags;
    cg.treeContext.u.scopeChain = scopeChain;
    cg.staticDepth = TCF_GET_STATIC_DEPTH(tcflags);

    if ((tcflags & TCF_COMPILE_N_GO) && callerFrame && callerFrame->fun) {
        /*
         * An eval script in a caller frame needs to have its enclosing function
         * captured in case it uses an upvar reference, and someone wishes to
         * decompile it while running.
         */
        JSParsedObjectBox *pob = js_NewParsedObjectBox(cx, &pc, callerFrame->callee);
        pob->emitLink = cg.objectList.lastPob;
        cg.objectList.lastPob = pob;
        cg.objectList.length++;
    }

    /* Inline Statements() to emit as we go to save space. */
    for (;;) {
        pc.tokenStream.flags |= TSF_OPERAND;
        tt = js_PeekToken(cx, &pc.tokenStream);
        pc.tokenStream.flags &= ~TSF_OPERAND;
        if (tt <= TOK_EOF) {
            if (tt == TOK_EOF)
                break;
            JS_ASSERT(tt == TOK_ERROR);
            script = NULL;
            goto out;
        }

        pn = Statement(cx, &pc.tokenStream, &cg.treeContext);
        if (!pn) {
            script = NULL;
            goto out;
        }
        JS_ASSERT(!cg.treeContext.blockNode);

        if (!js_FoldConstants(cx, pn, &cg.treeContext) ||
            !js_EmitTree(cx, &cg, pn)) {
            script = NULL;
            goto out;
        }
        RecycleTree(pn, &cg.treeContext);
    }

    /*
     * Global variables and regexps shares the index space with locals. Due to
     * incremental code generation we need to patch the bytecode to adjust the
     * local references to skip the globals.
     */
    scriptGlobals = cg.treeContext.ngvars + cg.regexpList.length;
    if (scriptGlobals != 0) {
        jsbytecode *code, *end;
        JSOp op;
        const JSCodeSpec *cs;
        uintN len, slot;

        if (scriptGlobals >= SLOTNO_LIMIT)
            goto too_many_slots;
        code = CG_BASE(&cg);
        for (end = code + CG_OFFSET(&cg); code != end; code += len) {
            JS_ASSERT(code < end);
            op = (JSOp) *code;
            cs = &js_CodeSpec[op];
            len = (cs->length > 0)
                  ? (uintN) cs->length
                  : js_GetVariableBytecodeLength(code);
            if (JOF_TYPE(cs->format) == JOF_LOCAL ||
                (JOF_TYPE(cs->format) == JOF_SLOTATOM)) {
                /*
                 * JSOP_GETARGPROP also has JOF_SLOTATOM type, but it may be
                 * emitted only for a function.
                 */
                JS_ASSERT((JOF_TYPE(cs->format) == JOF_SLOTATOM) ==
                          (op == JSOP_GETLOCALPROP));
                slot = GET_SLOTNO(code);
                slot += scriptGlobals;
                if (slot >= SLOTNO_LIMIT)
                    goto too_many_slots;
                SET_SLOTNO(code, slot);
            }
        }
    }

#ifdef METER_PARSENODES
    printf("Parser growth: %d (%u nodes, %u max, %u unrecycled)\n",
           (char *)sbrk(0) - (char *)before,
           parsenodes,
           maxparsenodes,
           parsenodes - recyclednodes);
    before = sbrk(0);
#endif

    /*
     * Nowadays the threaded interpreter needs a stop instruction, so we
     * do have to emit that here.
     */
    if (js_Emit1(cx, &cg, JSOP_STOP) < 0) {
        script = NULL;
        goto out;
    }
#ifdef METER_PARSENODES
    printf("Code-gen growth: %d (%u bytecodes, %u srcnotes)\n",
           (char *)sbrk(0) - (char *)before, CG_OFFSET(cg), cg->noteCount);
#endif
#ifdef JS_ARENAMETER
    JS_DumpArenaStats(stdout);
#endif
    script = js_NewScriptFromCG(cx, &cg);

#ifdef JS_SCOPE_DEPTH_METER
    if (script) {
        JSObject *obj = scopeChain;
        uintN depth = 1;
        while ((obj = OBJ_GET_PARENT(cx, obj)) != NULL)
            ++depth;
        JS_BASIC_STATS_ACCUM(&cx->runtime->hostenvScopeDepthStats, depth);
    }
#endif

  out:
    js_FinishCodeGenerator(cx, &cg);
    JS_FinishArenaPool(&codePool);
    JS_FinishArenaPool(&notePool);
    js_FinishParseContext(cx, &pc);
    return script;

  too_many_slots:
    js_ReportCompileErrorNumber(cx, &pc.tokenStream, NULL,
                                JSREPORT_ERROR, JSMSG_TOO_MANY_LOCALS);
    script = NULL;
    goto out;
}

/*
 * Insist on a final return before control flows out of pn.  Try to be a bit
 * smart about loops: do {...; return e2;} while(0) at the end of a function
 * that contains an early return e1 will get a strict warning.  Similarly for
 * iloops: while (true){...} is treated as though ... returns.
 */
#define ENDS_IN_OTHER   0
#define ENDS_IN_RETURN  1
#define ENDS_IN_BREAK   2

static int
HasFinalReturn(JSParseNode *pn)
{
    JSParseNode *pn2, *pn3;
    uintN rv, rv2, hasDefault;

    switch (pn->pn_type) {
      case TOK_LC:
        if (!pn->pn_head)
            return ENDS_IN_OTHER;
        return HasFinalReturn(PN_LAST(pn));

      case TOK_IF:
        if (!pn->pn_kid3)
            return ENDS_IN_OTHER;
        return HasFinalReturn(pn->pn_kid2) & HasFinalReturn(pn->pn_kid3);

      case TOK_WHILE:
        pn2 = pn->pn_left;
        if (pn2->pn_type == TOK_PRIMARY && pn2->pn_op == JSOP_TRUE)
            return ENDS_IN_RETURN;
        if (pn2->pn_type == TOK_NUMBER && pn2->pn_dval)
            return ENDS_IN_RETURN;
        return ENDS_IN_OTHER;

      case TOK_DO:
        pn2 = pn->pn_right;
        if (pn2->pn_type == TOK_PRIMARY) {
            if (pn2->pn_op == JSOP_FALSE)
                return HasFinalReturn(pn->pn_left);
            if (pn2->pn_op == JSOP_TRUE)
                return ENDS_IN_RETURN;
        }
        if (pn2->pn_type == TOK_NUMBER) {
            if (pn2->pn_dval == 0)
                return HasFinalReturn(pn->pn_left);
            return ENDS_IN_RETURN;
        }
        return ENDS_IN_OTHER;

      case TOK_FOR:
        pn2 = pn->pn_left;
        if (pn2->pn_arity == PN_TERNARY && !pn2->pn_kid2)
            return ENDS_IN_RETURN;
        return ENDS_IN_OTHER;

      case TOK_SWITCH:
        rv = ENDS_IN_RETURN;
        hasDefault = ENDS_IN_OTHER;
        pn2 = pn->pn_right;
        if (pn2->pn_type == TOK_LEXICALSCOPE)
            pn2 = pn2->pn_expr;
        for (pn2 = pn2->pn_head; rv && pn2; pn2 = pn2->pn_next) {
            if (pn2->pn_type == TOK_DEFAULT)
                hasDefault = ENDS_IN_RETURN;
            pn3 = pn2->pn_right;
            JS_ASSERT(pn3->pn_type == TOK_LC);
            if (pn3->pn_head) {
                rv2 = HasFinalReturn(PN_LAST(pn3));
                if (rv2 == ENDS_IN_OTHER && pn2->pn_next)
                    /* Falling through to next case or default. */;
                else
                    rv &= rv2;
            }
        }
        /* If a final switch has no default case, we judge it harshly. */
        rv &= hasDefault;
        return rv;

      case TOK_BREAK:
        return ENDS_IN_BREAK;

      case TOK_WITH:
        return HasFinalReturn(pn->pn_right);

      case TOK_RETURN:
        return ENDS_IN_RETURN;

      case TOK_COLON:
      case TOK_LEXICALSCOPE:
        return HasFinalReturn(pn->pn_expr);

      case TOK_THROW:
        return ENDS_IN_RETURN;

      case TOK_TRY:
        /* If we have a finally block that returns, we are done. */
        if (pn->pn_kid3) {
            rv = HasFinalReturn(pn->pn_kid3);
            if (rv == ENDS_IN_RETURN)
                return rv;
        }

        /* Else check the try block and any and all catch statements. */
        rv = HasFinalReturn(pn->pn_kid1);
        if (pn->pn_kid2) {
            JS_ASSERT(pn->pn_kid2->pn_arity == PN_LIST);
            for (pn2 = pn->pn_kid2->pn_head; pn2; pn2 = pn2->pn_next)
                rv &= HasFinalReturn(pn2);
        }
        return rv;

      case TOK_CATCH:
        /* Check this catch block's body. */
        return HasFinalReturn(pn->pn_kid3);

      case TOK_LET:
        /* Non-binary let statements are let declarations. */
        if (pn->pn_arity != PN_BINARY)
            return ENDS_IN_OTHER;
        return HasFinalReturn(pn->pn_right);

      default:
        return ENDS_IN_OTHER;
    }
}

static JSBool
ReportBadReturn(JSContext *cx, JSTreeContext *tc, uintN flags, uintN errnum,
                uintN anonerrnum)
{
    const char *name;

    JS_ASSERT(tc->flags & TCF_IN_FUNCTION);
    if (tc->u.fun->atom) {
        name = js_AtomToPrintableString(cx, tc->u.fun->atom);
    } else {
        errnum = anonerrnum;
        name = NULL;
    }
    return js_ReportCompileErrorNumber(cx, TS(tc->parseContext), NULL, flags,
                                       errnum, name);
}

static JSBool
CheckFinalReturn(JSContext *cx, JSTreeContext *tc, JSParseNode *pn)
{
    JS_ASSERT(tc->flags & TCF_IN_FUNCTION);
    return HasFinalReturn(pn) == ENDS_IN_RETURN ||
           ReportBadReturn(cx, tc, JSREPORT_WARNING | JSREPORT_STRICT,
                           JSMSG_NO_RETURN_VALUE, JSMSG_ANON_NO_RETURN_VALUE);
}

static JSParseNode *
FunctionBody(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc)
{
    JSStmtInfo stmtInfo;
    uintN oldflags, firstLine;
    JSParseNode *pn;

    JS_ASSERT(tc->flags & TCF_IN_FUNCTION);
    js_PushStatement(tc, &stmtInfo, STMT_BLOCK, -1);
    stmtInfo.flags = SIF_BODY_BLOCK;

    oldflags = tc->flags;
    tc->flags &= ~(TCF_RETURN_EXPR | TCF_RETURN_VOID);

    /*
     * Save the body's first line, and store it in pn->pn_pos.begin.lineno
     * later, because we may have not peeked in ts yet, so Statements won't
     * acquire a valid pn->pn_pos.begin from the current token.
     */
    firstLine = ts->lineno;
#if JS_HAS_EXPR_CLOSURES
    if (CURRENT_TOKEN(ts).type == TOK_LC) {
        pn = Statements(cx, ts, tc);
    } else {
        pn = NewParseNode(cx, ts, PN_UNARY, tc);
        if (pn) {
            pn->pn_kid = AssignExpr(cx, ts, tc);
            if (!pn->pn_kid) {
                pn = NULL;
            } else {
                if (tc->flags & TCF_FUN_IS_GENERATOR) {
                    ReportBadReturn(cx, tc, JSREPORT_ERROR,
                                    JSMSG_BAD_GENERATOR_RETURN,
                                    JSMSG_BAD_ANON_GENERATOR_RETURN);
                    pn = NULL;
                } else {
                    pn->pn_type = TOK_RETURN;
                    pn->pn_op = JSOP_RETURN;
                    pn->pn_pos.end = pn->pn_kid->pn_pos.end;
                }
            }
        }
    }
#else
    pn = Statements(cx, ts, tc);
#endif

    if (pn) {
        js_PopStatement(tc);
        pn->pn_pos.begin.lineno = firstLine;

        /* Check for falling off the end of a function that returns a value. */
        if (JS_HAS_STRICT_OPTION(cx) && (tc->flags & TCF_RETURN_EXPR) &&
            !CheckFinalReturn(cx, tc, pn)) {
            pn = NULL;
        }
    }

    tc->flags = oldflags | (tc->flags & (TCF_FUN_FLAGS | TCF_HAS_DEFXMLNS));
    return pn;
}

/*
 * Compile a JS function body, which might appear as the value of an event
 * handler attribute in an HTML <INPUT> tag.
 */
JSBool
js_CompileFunctionBody(JSContext *cx, JSFunction *fun, JSPrincipals *principals,
                       const jschar *chars, size_t length,
                       const char *filename, uintN lineno)
{
    JSParseContext pc;
    JSArenaPool codePool, notePool;
    JSCodeGenerator funcg;
    JSParseNode *pn;

    if (!js_InitParseContext(cx, &pc, principals, NULL, chars, length, NULL,
                             filename, lineno)) {
        return JS_FALSE;
    }

    /* No early return from this point until js_FinishParseContext call. */
    JS_INIT_ARENA_POOL(&codePool, "code", 1024, sizeof(jsbytecode),
                       &cx->scriptStackQuota);
    JS_INIT_ARENA_POOL(&notePool, "note", 1024, sizeof(jssrcnote),
                       &cx->scriptStackQuota);
    js_InitCodeGenerator(cx, &funcg, &pc, &codePool, &notePool,
                         pc.tokenStream.lineno);
    funcg.treeContext.flags |= TCF_IN_FUNCTION;
    funcg.treeContext.u.fun = fun;

    /*
     * Farble the body so that it looks like a block statement to js_EmitTree,
     * which is called beneath FunctionBody; see Statements, further below in
     * this file.  FunctionBody pushes a STMT_BLOCK record around its call to
     * Statements, so Statements will not compile each statement as it loops
     * to save JSParseNode space -- it will not compile at all, only build a
     * JSParseNode tree.
     *
     * Therefore we must fold constants, allocate try notes, and generate code
     * for this function, including a stop opcode at the end.
     */
    CURRENT_TOKEN(&pc.tokenStream).type = TOK_LC;
    pn = FunctionBody(cx, &pc.tokenStream, &funcg.treeContext);
    if (pn) {
        if (!js_MatchToken(cx, &pc.tokenStream, TOK_EOF)) {
            js_ReportCompileErrorNumber(cx, &pc.tokenStream, NULL,
                                        JSREPORT_ERROR, JSMSG_SYNTAX_ERROR);
            pn = NULL;
        } else {
            if (!js_FoldConstants(cx, pn, &funcg.treeContext) ||
                !js_EmitFunctionScript(cx, &funcg, pn)) {
                pn = NULL;
            }
        }
    }

    /* Restore saved state and release code generation arenas. */
    js_FinishCodeGenerator(cx, &funcg);
    JS_FinishArenaPool(&codePool);
    JS_FinishArenaPool(&notePool);
    js_FinishParseContext(cx, &pc);
    return pn != NULL;
}

/*
 * Parameter block types for the several Binder functions.  We use a common
 * helper function signature in order to share code among destructuring and
 * simple variable declaration parsers.  In the destructuring case, the binder
 * function is called indirectly from the variable declaration parser by way
 * of CheckDestructuring and its friends.
 */
typedef struct BindData BindData;

typedef JSBool
(*Binder)(JSContext *cx, BindData *data, JSAtom *atom, JSTreeContext *tc);

struct BindData {
    JSParseNode             *pn;                /* error source coordinate */
    JSOp                    op;                 /* prolog bytecode or nop */
    Binder                  binder;             /* binder, discriminates u */
    union {
        struct {
            uintN           overflow;
        } let;
    } u;
};

static JSBool
BindArg(JSContext *cx, JSAtom *atom, JSTreeContext *tc)
{
    const char *name;

    /*
     * Check for a duplicate parameter name, a "feature" required by ECMA-262.
     */
    JS_ASSERT(tc->flags & TCF_IN_FUNCTION);
    if (js_LookupLocal(cx, tc->u.fun, atom, NULL) != JSLOCAL_NONE) {
        name = js_AtomToPrintableString(cx, atom);
        if (!name ||
            !js_ReportCompileErrorNumber(cx, TS(tc->parseContext), NULL,
                                         JSREPORT_WARNING | JSREPORT_STRICT,
                                         JSMSG_DUPLICATE_FORMAL,
                                         name)) {
            return JS_FALSE;
        }
    }

    return js_AddLocal(cx, tc->u.fun, atom, JSLOCAL_ARG);
}

static JSBool
BindLocalVariable(JSContext *cx, JSFunction *fun, JSAtom *atom,
                  JSLocalKind localKind)
{
    JS_ASSERT(localKind == JSLOCAL_VAR || localKind == JSLOCAL_CONST);

    /*
     * Don't bind a variable with the hidden name 'arguments', per ECMA-262.
     * Instead 'var arguments' always restates the predefined property of the
     * activation objects with unhidden name 'arguments'.  Assignment to such
     * a variable must be handled specially.
     */
    if (atom == cx->runtime->atomState.argumentsAtom)
        return JS_TRUE;

    return js_AddLocal(cx, fun, atom, localKind);
}

#if JS_HAS_DESTRUCTURING
/*
 * Forward declaration to maintain top-down presentation.
 */
static JSParseNode *
DestructuringExpr(JSContext *cx, BindData *data, JSTreeContext *tc,
                  JSTokenType tt);

static JSBool
BindDestructuringArg(JSContext *cx, BindData *data, JSAtom *atom,
                     JSTreeContext *tc)
{
    JSAtomListElement *ale;
    const char *name;

    JS_ASSERT(tc->flags & TCF_IN_FUNCTION);
    ATOM_LIST_SEARCH(ale, &tc->decls, atom);
    if (!ale) {
        ale = js_IndexAtom(cx, atom, &tc->decls);
        if (!ale)
            return JS_FALSE;
        ALE_SET_JSOP(ale, data->op);
    }

    if (js_LookupLocal(cx, tc->u.fun, atom, NULL) != JSLOCAL_NONE) {
        name = js_AtomToPrintableString(cx, atom);
        if (!name ||
            !js_ReportCompileErrorNumber(cx, TS(tc->parseContext), data->pn,
                                         JSREPORT_WARNING | JSREPORT_STRICT,
                                         JSMSG_DUPLICATE_FORMAL,
                                         name)) {
            return JS_FALSE;
        }
    } else {
        if (!BindLocalVariable(cx, tc->u.fun, atom, JSLOCAL_VAR))
            return JS_FALSE;
    }
    return JS_TRUE;
}
#endif /* JS_HAS_DESTRUCTURING */

static JSFunction *
NewCompilerFunction(JSContext *cx, JSTreeContext *tc, JSAtom *atom,
                    uintN lambda)
{
    JSObject *parent;
    JSFunction *fun;

    JS_ASSERT((lambda & ~JSFUN_LAMBDA) == 0);
    parent = (tc->flags & TCF_IN_FUNCTION)
             ? FUN_OBJECT(tc->u.fun)
             : tc->u.scopeChain;
    fun = js_NewFunction(cx, NULL, NULL, 0, JSFUN_INTERPRETED | lambda,
                         parent, atom);
    if (fun && !(tc->flags & TCF_COMPILE_N_GO)) {
        STOBJ_CLEAR_PARENT(FUN_OBJECT(fun));
        STOBJ_CLEAR_PROTO(FUN_OBJECT(fun));
    }
    return fun;
}

static JSParseNode *
FunctionDef(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc,
            uintN lambda)
{
    JSOp op, prevop;
    JSParseNode *pn, *body, *result;
    JSTokenType tt;
    JSAtom *funAtom;
    JSParsedObjectBox *funpob;
    JSAtomListElement *ale;
    JSFunction *fun;
    JSTreeContext funtc;
#if JS_HAS_DESTRUCTURING
    JSParseNode *item, *list = NULL;
#endif

    /* Make a TOK_FUNCTION node. */
#if JS_HAS_GETTER_SETTER
    op = CURRENT_TOKEN(ts).t_op;
#endif
    pn = NewParseNode(cx, ts, PN_FUNC, tc);
    if (!pn)
        return NULL;
#ifdef DEBUG
    pn->pn_index = (uint32) -1;
#endif

    /* Scan the optional function name into funAtom. */
    ts->flags |= TSF_KEYWORD_IS_NAME;
    tt = js_GetToken(cx, ts);
    ts->flags &= ~TSF_KEYWORD_IS_NAME;
    if (tt == TOK_NAME) {
        funAtom = CURRENT_TOKEN(ts).t_atom;
    } else {
        if (lambda == 0 && (cx->options & JSOPTION_ANONFUNFIX)) {
            js_ReportCompileErrorNumber(cx, ts, NULL, JSREPORT_ERROR,
                                        JSMSG_SYNTAX_ERROR);
            return NULL;
        }
        funAtom = NULL;
        js_UngetToken(ts);
    }

    /*
     * Record names for function statements in tc->decls so we know when to
     * avoid optimizing variable references that might name a function.
     */
    if (lambda == 0 && funAtom) {
        ATOM_LIST_SEARCH(ale, &tc->decls, funAtom);
        if (ale) {
            prevop = ALE_JSOP(ale);
            if (JS_HAS_STRICT_OPTION(cx) || prevop == JSOP_DEFCONST) {
                const char *name = js_AtomToPrintableString(cx, funAtom);
                if (!name ||
                    !js_ReportCompileErrorNumber(cx, ts, NULL,
                                                 (prevop != JSOP_DEFCONST)
                                                 ? JSREPORT_WARNING |
                                                   JSREPORT_STRICT
                                                 : JSREPORT_ERROR,
                                                 JSMSG_REDECLARED_VAR,
                                                 (prevop == JSOP_DEFFUN)
                                                 ? js_function_str
                                                 : (prevop == JSOP_DEFCONST)
                                                 ? js_const_str
                                                 : js_var_str,
                                                 name)) {
                    return NULL;
                }
            }
            if (!AT_TOP_LEVEL(tc) && prevop == JSOP_DEFVAR)
                tc->flags |= TCF_FUN_CLOSURE_VS_VAR;
        } else {
            ale = js_IndexAtom(cx, funAtom, &tc->decls);
            if (!ale)
                return NULL;
        }
        ALE_SET_JSOP(ale, JSOP_DEFFUN);

        /*
         * A function nested at top level inside another's body needs only a
         * local variable to bind its name to its value, and not an activation
         * object property (it might also need the activation property, if the
         * outer function contains with statements, e.g., but the stack slot
         * wins when jsemit.c's BindNameToSlot can optimize a JSOP_NAME into a
         * JSOP_GETLOCAL bytecode).
         */
        if (AT_TOP_LEVEL(tc) && (tc->flags & TCF_IN_FUNCTION)) {
            JSLocalKind localKind;

            /*
             * Define a property on the outer function so that BindNameToSlot
             * can properly optimize accesses. Note that we need a variable,
             * not an argument, for the function statement. Thus we add a
             * variable even if the parameter with the given name already
             * exists.
             */
            localKind = js_LookupLocal(cx, tc->u.fun, funAtom, NULL);
            if (localKind == JSLOCAL_NONE || localKind == JSLOCAL_ARG) {
                if (!js_AddLocal(cx, tc->u.fun, funAtom, JSLOCAL_VAR))
                    return NULL;
            }
        }
    }

    fun = NewCompilerFunction(cx, tc, funAtom, lambda);
    if (!fun)
        return NULL;

#if JS_HAS_GETTER_SETTER
    if (op != JSOP_NOP)
        fun->flags |= (op == JSOP_GETTER) ? JSPROP_GETTER : JSPROP_SETTER;
#endif

    /*
     * Create wrapping box for fun->object early to protect against a
     * last-ditch GC.
     */
    funpob = js_NewParsedObjectBox(cx, tc->parseContext, FUN_OBJECT(fun));
    if (!funpob)
        return NULL;

    /* Initialize early for possible flags mutation via DestructuringExpr. */
    TREE_CONTEXT_INIT(&funtc, tc->parseContext);
    funtc.flags |= TCF_IN_FUNCTION | (tc->flags & TCF_COMPILE_N_GO);
    funtc.u.fun = fun;

    /* Now parse formal argument list and compute fun->nargs. */
    MUST_MATCH_TOKEN(TOK_LP, JSMSG_PAREN_BEFORE_FORMAL);
    if (!js_MatchToken(cx, ts, TOK_RP)) {
        do {
            tt = js_GetToken(cx, ts);
            switch (tt) {
#if JS_HAS_DESTRUCTURING
              case TOK_LB:
              case TOK_LC:
              {
                BindData data;
                JSParseNode *lhs, *rhs;
                jsint slot;

                /*
                 * A destructuring formal parameter turns into one or more
                 * local variables initialized from properties of a single
                 * anonymous positional parameter, so here we must tweak our
                 * binder and its data.
                 */
                data.pn = NULL;
                data.op = JSOP_DEFVAR;
                data.binder = BindDestructuringArg;
                lhs = DestructuringExpr(cx, &data, &funtc, tt);
                if (!lhs)
                    return NULL;

                /*
                 * Adjust fun->nargs to count the single anonymous positional
                 * parameter that is to be destructured.
                 */
                slot = fun->nargs;
                if (!js_AddLocal(cx, fun, NULL, JSLOCAL_ARG))
                    return NULL;

                /*
                 * Synthesize a destructuring assignment from the single
                 * anonymous positional parameter into the destructuring
                 * left-hand-side expression and accumulate it in list.
                 */
                rhs = NewParseNode(cx, ts, PN_NAME, tc);
                if (!rhs)
                    return NULL;
                rhs->pn_type = TOK_NAME;
                rhs->pn_op = JSOP_GETARG;
                rhs->pn_atom = cx->runtime->atomState.emptyAtom;
                rhs->pn_slot = slot;

                item = NewBinary(cx, TOK_ASSIGN, JSOP_NOP, lhs, rhs, tc);
                if (!item)
                    return NULL;
                if (!list) {
                    list = NewParseNode(cx, ts, PN_LIST, tc);
                    if (!list)
                        return NULL;
                    list->pn_type = TOK_COMMA;
                    PN_INIT_LIST(list);
                }
                PN_APPEND(list, item);
                break;
              }
#endif /* JS_HAS_DESTRUCTURING */

              case TOK_NAME:
                if (!BindArg(cx, CURRENT_TOKEN(ts).t_atom, &funtc))
                    return NULL;
                break;

              default:
                js_ReportCompileErrorNumber(cx, ts, NULL, JSREPORT_ERROR,
                                            JSMSG_MISSING_FORMAL);
                return NULL;
            }
        } while (js_MatchToken(cx, ts, TOK_COMMA));

        MUST_MATCH_TOKEN(TOK_RP, JSMSG_PAREN_AFTER_FORMAL);
    }

#if JS_HAS_EXPR_CLOSURES
    ts->flags |= TSF_OPERAND;
    tt = js_GetToken(cx, ts);
    ts->flags &= ~TSF_OPERAND;
    if (tt != TOK_LC) {
        js_UngetToken(ts);
        fun->flags |= JSFUN_EXPR_CLOSURE;
    }
#else
    MUST_MATCH_TOKEN(TOK_LC, JSMSG_CURLY_BEFORE_BODY);
#endif
    pn->pn_pos.begin = CURRENT_TOKEN(ts).pos.begin;

    body = FunctionBody(cx, ts, &funtc);
    if (!body)
        return NULL;

#if JS_HAS_EXPR_CLOSURES
    if (tt == TOK_LC)
        MUST_MATCH_TOKEN(TOK_RC, JSMSG_CURLY_AFTER_BODY);
    else if (lambda == 0)
        js_MatchToken(cx, ts, TOK_SEMI);
#else
    MUST_MATCH_TOKEN(TOK_RC, JSMSG_CURLY_AFTER_BODY);
#endif
    pn->pn_pos.end = CURRENT_TOKEN(ts).pos.end;

#if JS_HAS_DESTRUCTURING
    /*
     * If there were destructuring formal parameters, prepend the initializing
     * comma expression that we synthesized to body.  If the body is a lexical
     * scope node, we must make a special TOK_SEQ node, to prepend the formal
     * parameter destructuring code without bracing the decompilation of the
     * function body's lexical scope.
     */
    if (list) {
        if (body->pn_arity != PN_LIST) {
            JSParseNode *block;

            block = NewParseNode(cx, ts, PN_LIST, tc);
            if (!block)
                return NULL;
            block->pn_type = TOK_SEQ;
            block->pn_pos = body->pn_pos;
            PN_INIT_LIST_1(block, body);

            body = block;
        }

        item = NewParseNode(cx, ts, PN_UNARY, tc);
        if (!item)
            return NULL;

        item->pn_type = TOK_SEMI;
        item->pn_pos.begin = item->pn_pos.end = body->pn_pos.begin;
        item->pn_kid = list;
        item->pn_next = body->pn_head;
        body->pn_head = item;
        if (body->pn_tail == &body->pn_head)
            body->pn_tail = &item->pn_next;
        ++body->pn_count;
    }
#endif

    /*
     * If we collected flags that indicate nested heavyweight functions, or
     * this function contains heavyweight-making statements (references to
     * __parent__ or __proto__; use of with, or eval; and assignment to 
     * arguments), flag the function as heavyweight (requiring a call object 
     * per invocation).
     */
    if (funtc.flags & TCF_FUN_HEAVYWEIGHT) {
        fun->flags |= JSFUN_HEAVYWEIGHT;
        tc->flags |= TCF_FUN_HEAVYWEIGHT;
    } else {
        /*
         * If this function is a named statement function not at top-level
         * (i.e. not a top-level function definiton or expression), then
         * our enclosing function, if any, must be heavyweight.
         *
         * The TCF_FUN_USES_NONLOCALS flag is set only by the code generator,
         * so it won't be set here.  Assert that it's not.  We have to check
         * it later, in js_EmitTree, after js_EmitFunctionScript has traversed
         * the function's body.
         */
        JS_ASSERT(!(funtc.flags & TCF_FUN_USES_NONLOCALS));
        if (lambda == 0 && funAtom && !AT_TOP_LEVEL(tc))
            tc->flags |= TCF_FUN_HEAVYWEIGHT;
    }

    result = pn;
    if (lambda != 0) {
        /*
         * ECMA ed. 3 standard: function expression, possibly anonymous.
         */
        op = funAtom ? JSOP_NAMEDFUNOBJ : JSOP_ANONFUNOBJ;
    } else if (!funAtom) {
        /*
         * If this anonymous function definition is *not* embedded within a
         * larger expression, we treat it as an expression statement, not as
         * a function declaration -- and not as a syntax error (as ECMA-262
         * Edition 3 would have it).  Backward compatibility must trump all,
         * unless JSOPTION_ANONFUNFIX is set.
         */
        result = NewParseNode(cx, ts, PN_UNARY, tc);
        if (!result)
            return NULL;
        result->pn_type = TOK_SEMI;
        result->pn_pos = pn->pn_pos;
        result->pn_kid = pn;
        op = JSOP_ANONFUNOBJ;
    } else if (!AT_TOP_LEVEL(tc)) {
        /*
         * ECMA ed. 3 extension: a function expression statement not at the
         * top level, e.g., in a compound statement such as the "then" part
         * of an "if" statement, binds a closure only if control reaches that
         * sub-statement.
         */
        op = JSOP_DEFFUN;
    } else {
        op = JSOP_NOP;
    }

    pn->pn_funpob = funpob;
    pn->pn_op = op;
    pn->pn_body = body;
    pn->pn_flags = funtc.flags & (TCF_FUN_FLAGS | TCF_HAS_DEFXMLNS | TCF_COMPILE_N_GO);
    TREE_CONTEXT_FINISH(cx, &funtc);
    return result;
}

static JSParseNode *
FunctionStmt(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc)
{
    return FunctionDef(cx, ts, tc, 0);
}

static JSParseNode *
FunctionExpr(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc)
{
    return FunctionDef(cx, ts, tc, JSFUN_LAMBDA);
}

/*
 * Parse the statements in a block, creating a TOK_LC node that lists the
 * statements' trees.  If called from block-parsing code, the caller must
 * match { before and } after.
 */
static JSParseNode *
Statements(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc)
{
    JSParseNode *pn, *pn2, *saveBlock;
    JSTokenType tt;

    JS_CHECK_RECURSION(cx, return NULL);

    pn = NewParseNode(cx, ts, PN_LIST, tc);
    if (!pn)
        return NULL;
    saveBlock = tc->blockNode;
    tc->blockNode = pn;
    PN_INIT_LIST(pn);

    for (;;) {
        ts->flags |= TSF_OPERAND;
        tt = js_PeekToken(cx, ts);
        ts->flags &= ~TSF_OPERAND;
        if (tt <= TOK_EOF || tt == TOK_RC) {
            if (tt == TOK_ERROR)
                return NULL;
            break;
        }
        pn2 = Statement(cx, ts, tc);
        if (!pn2) {
            if (ts->flags & TSF_EOF)
                ts->flags |= TSF_UNEXPECTED_EOF;
            return NULL;
        }

        if (pn2->pn_type == TOK_FUNCTION) {
            /*
             * PNX_FUNCDEFS notifies the emitter that the block contains top-
             * level function definitions that should be processed before the
             * rest of nodes.
             *
             * TCF_HAS_FUNCTION_STMT is for the TOK_LC case in Statement. It
             * is relevant only for function definitions not at top-level,
             * which we call function statements.
             */
            if (AT_TOP_LEVEL(tc))
                pn->pn_extra |= PNX_FUNCDEFS;
            else
                tc->flags |= TCF_HAS_FUNCTION_STMT;
        }
        PN_APPEND(pn, pn2);
    }

    /*
     * Handle the case where there was a let declaration under this block.  If
     * it replaced tc->blockNode with a new block node then we must refresh pn
     * and then restore tc->blockNode.
     */
    if (tc->blockNode != pn)
        pn = tc->blockNode;
    tc->blockNode = saveBlock;

    pn->pn_pos.end = CURRENT_TOKEN(ts).pos.end;
    return pn;
}

static JSParseNode *
Condition(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc)
{
    JSParseNode *pn;

    MUST_MATCH_TOKEN(TOK_LP, JSMSG_PAREN_BEFORE_COND);
    pn = ParenExpr(cx, ts, tc, NULL, NULL);
    if (!pn)
        return NULL;
    MUST_MATCH_TOKEN(TOK_RP, JSMSG_PAREN_AFTER_COND);

    /*
     * Check for (a = b) and warn about possible (a == b) mistype iff b's
     * operator has greater precedence than ==.
     */
    if (pn->pn_type == TOK_ASSIGN &&
        pn->pn_op == JSOP_NOP &&
        pn->pn_right->pn_type > TOK_EQOP)
    {
        if (!js_ReportCompileErrorNumber(cx, ts, NULL,
                                         JSREPORT_WARNING | JSREPORT_STRICT,
                                         JSMSG_EQUAL_AS_ASSIGN,
                                         "")) {
            return NULL;
        }
    }
    return pn;
}

static JSBool
MatchLabel(JSContext *cx, JSTokenStream *ts, JSParseNode *pn)
{
    JSAtom *label;
    JSTokenType tt;

    tt = js_PeekTokenSameLine(cx, ts);
    if (tt == TOK_ERROR)
        return JS_FALSE;
    if (tt == TOK_NAME) {
        (void) js_GetToken(cx, ts);
        label = CURRENT_TOKEN(ts).t_atom;
    } else {
        label = NULL;
    }
    pn->pn_atom = label;
    return JS_TRUE;
}

static JSBool
BindLet(JSContext *cx, BindData *data, JSAtom *atom, JSTreeContext *tc)
{
    JSObject *blockObj;
    JSScopeProperty *sprop;
    JSAtomListElement *ale;
    uintN n;

    blockObj = tc->blockChain;
    sprop = SCOPE_GET_PROPERTY(OBJ_SCOPE(blockObj), ATOM_TO_JSID(atom));
    ATOM_LIST_SEARCH(ale, &tc->decls, atom);
    if (sprop || (ale && ALE_JSOP(ale) == JSOP_DEFCONST)) {
        const char *name;

        if (sprop) {
            JS_ASSERT(sprop->flags & SPROP_HAS_SHORTID);
            JS_ASSERT((uint16)sprop->shortid < OBJ_BLOCK_COUNT(cx, blockObj));
        }

        name = js_AtomToPrintableString(cx, atom);
        if (name) {
            js_ReportCompileErrorNumber(cx, TS(tc->parseContext), data->pn,
                                        JSREPORT_ERROR, JSMSG_REDECLARED_VAR,
                                        (ale && ALE_JSOP(ale) == JSOP_DEFCONST)
                                        ? js_const_str
                                        : "variable",
                                        name);
        }
        return JS_FALSE;
    }

    n = OBJ_BLOCK_COUNT(cx, blockObj);
    if (n == JS_BIT(16)) {
        js_ReportCompileErrorNumber(cx, TS(tc->parseContext), data->pn,
                                    JSREPORT_ERROR, data->u.let.overflow);
        return JS_FALSE;
    }

    /* Use JSPROP_ENUMERATE to aid the disassembler. */
    return js_DefineNativeProperty(cx, blockObj, ATOM_TO_JSID(atom),
                                   JSVAL_VOID, NULL, NULL,
                                   JSPROP_ENUMERATE |
                                   JSPROP_PERMANENT |
                                   JSPROP_SHARED,
                                   SPROP_HAS_SHORTID, (int16) n, NULL);
}

static JSBool
BindVarOrConst(JSContext *cx, BindData *data, JSAtom *atom, JSTreeContext *tc)
{
    JSStmtInfo *stmt;
    JSAtomListElement *ale;
    JSOp op, prevop;
    const char *name;
    JSLocalKind localKind;

    stmt = js_LexicalLookup(tc, atom, NULL);
    ATOM_LIST_SEARCH(ale, &tc->decls, atom);
    op = data->op;
    if ((stmt && stmt->type != STMT_WITH) || ale) {
        prevop = ale ? ALE_JSOP(ale) : JSOP_DEFVAR;
        if (JS_HAS_STRICT_OPTION(cx)
            ? op != JSOP_DEFVAR || prevop != JSOP_DEFVAR
            : op == JSOP_DEFCONST || prevop == JSOP_DEFCONST) {
            name = js_AtomToPrintableString(cx, atom);
            if (!name ||
                !js_ReportCompileErrorNumber(cx, TS(tc->parseContext), data->pn,
                                             (op != JSOP_DEFCONST &&
                                              prevop != JSOP_DEFCONST)
                                             ? JSREPORT_WARNING |
                                               JSREPORT_STRICT
                                             : JSREPORT_ERROR,
                                             JSMSG_REDECLARED_VAR,
                                             (prevop == JSOP_DEFFUN)
                                             ? js_function_str
                                             : (prevop == JSOP_DEFCONST)
                                             ? js_const_str
                                             : js_var_str,
                                             name)) {
                return JS_FALSE;
            }
        }
        if (op == JSOP_DEFVAR && prevop == JSOP_DEFFUN)
            tc->flags |= TCF_FUN_CLOSURE_VS_VAR;
    }
    if (!ale) {
        ale = js_IndexAtom(cx, atom, &tc->decls);
        if (!ale)
            return JS_FALSE;
    }
    ALE_SET_JSOP(ale, op);

    if (!(tc->flags & TCF_IN_FUNCTION)) {
        /*
         * Don't lookup global variables or variables in an active frame at
         * compile time.
         */
        return JS_TRUE;
    }

    localKind = js_LookupLocal(cx, tc->u.fun, atom, NULL);
    if (localKind == JSLOCAL_NONE) {
        /*
         * Property not found in current variable scope: we have not seen this
         * variable before.  Define a new local variable by adding a property
         * to the function's scope, allocating one slot in the function's vars
         * frame. Any locals declared in with statement bodies are handled at
         * runtime, by script prolog JSOP_DEFVAR opcodes generated for
         * slot-less vars.
         */
        localKind = (data->op == JSOP_DEFCONST) ? JSLOCAL_CONST : JSLOCAL_VAR;
        if (!js_InWithStatement(tc) &&
            !BindLocalVariable(cx, tc->u.fun, atom, localKind)) {
            return JS_FALSE;
        }
    } else if (localKind == JSLOCAL_ARG) {
        name = js_AtomToPrintableString(cx, atom);
        if (!name)
            return JS_FALSE;

        if (op == JSOP_DEFCONST) {
            js_ReportCompileErrorNumber(cx, TS(tc->parseContext), data->pn,
                                        JSREPORT_ERROR, JSMSG_REDECLARED_PARAM,
                                        name);
            return JS_FALSE;
        }
        if (!js_ReportCompileErrorNumber(cx, TS(tc->parseContext), data->pn,
                                         JSREPORT_WARNING | JSREPORT_STRICT,
                                         JSMSG_VAR_HIDES_ARG, name)) {
            return JS_FALSE;
        }
    } else {
        /* Not an argument, must be a redeclared local var. */
        JS_ASSERT(localKind == JSLOCAL_VAR || localKind == JSLOCAL_CONST);
    }
    return JS_TRUE;
}

static JSBool
MakeSetCall(JSContext *cx, JSParseNode *pn, JSTreeContext *tc, uintN msg)
{
    JSParseNode *pn2;

    JS_ASSERT(pn->pn_arity == PN_LIST);
    JS_ASSERT(pn->pn_op == JSOP_CALL || pn->pn_op == JSOP_EVAL || pn->pn_op == JSOP_APPLY);
    pn2 = pn->pn_head;
    if (pn2->pn_type == TOK_FUNCTION && (pn2->pn_flags & TCF_GENEXP_LAMBDA)) {
        js_ReportCompileErrorNumber(cx, TS(tc->parseContext), pn,
                                    JSREPORT_ERROR, msg);
        return JS_FALSE;
    }
    pn->pn_op = JSOP_SETCALL;
    return JS_TRUE;
}

#if JS_HAS_DESTRUCTURING

static JSBool
BindDestructuringVar(JSContext *cx, BindData *data, JSParseNode *pn,
                     JSTreeContext *tc)
{
    JSAtom *atom;

    /*
     * Destructuring is a form of assignment, so just as for an initialized
     * simple variable, we must check for assignment to 'arguments' and flag
     * the enclosing function (if any) as heavyweight.
     */
    JS_ASSERT(pn->pn_type == TOK_NAME);
    atom = pn->pn_atom;
    if (atom == cx->runtime->atomState.argumentsAtom)
        tc->flags |= TCF_FUN_HEAVYWEIGHT;

    data->pn = pn;
    if (!data->binder(cx, data, atom, tc))
        return JS_FALSE;
    data->pn = NULL;

    /*
     * Select the appropriate name-setting opcode, which may be specialized
     * further for local variable and argument slot optimizations.  At this
     * point, we can't select the optimal final opcode, yet we must preserve
     * the CONST bit and convey "set", not "get".
     */
    if (data->op == JSOP_DEFCONST) {
        pn->pn_op = JSOP_SETCONST;
        pn->pn_const = JS_TRUE;
    } else {
        pn->pn_op = JSOP_SETNAME;
        pn->pn_const = JS_FALSE;
    }
    return JS_TRUE;
}

/*
 * Here, we are destructuring {... P: Q, ...} = R, where P is any id, Q is any
 * LHS expression except a destructuring initialiser, and R is on the stack.
 * Because R is already evaluated, the usual LHS-specialized bytecodes won't
 * work.  After pushing R[P] we need to evaluate Q's "reference base" QB and
 * then push its property name QN.  At this point the stack looks like
 *
 *   [... R, R[P], QB, QN]
 *
 * We need to set QB[QN] = R[P].  This is a job for JSOP_ENUMELEM, which takes
 * its operands with left-hand side above right-hand side:
 *
 *   [rval, lval, xval]
 *
 * and pops all three values, setting lval[xval] = rval.  But we cannot select
 * JSOP_ENUMELEM yet, because the LHS may turn out to be an arg or local var,
 * which can be optimized further.  So we select JSOP_SETNAME.
 */
static JSBool
BindDestructuringLHS(JSContext *cx, JSParseNode *pn, JSTreeContext *tc)
{
    while (pn->pn_type == TOK_RP)
        pn = pn->pn_kid;

    switch (pn->pn_type) {
      case TOK_NAME:
        if (pn->pn_atom == cx->runtime->atomState.argumentsAtom)
            tc->flags |= TCF_FUN_HEAVYWEIGHT;
        /* FALL THROUGH */
      case TOK_DOT:
      case TOK_LB:
        pn->pn_op = JSOP_SETNAME;
        break;

#if JS_HAS_LVALUE_RETURN
      case TOK_LP:
        if (!MakeSetCall(cx, pn, tc, JSMSG_BAD_LEFTSIDE_OF_ASS))
            return JS_FALSE;
        break;
#endif

#if JS_HAS_XML_SUPPORT
      case TOK_UNARYOP:
        if (pn->pn_op == JSOP_XMLNAME) {
            pn->pn_op = JSOP_BINDXMLNAME;
            break;
        }
        /* FALL THROUGH */
#endif

      default:
        js_ReportCompileErrorNumber(cx, TS(tc->parseContext), pn,
                                    JSREPORT_ERROR, JSMSG_BAD_LEFTSIDE_OF_ASS);
        return JS_FALSE;
    }

    return JS_TRUE;
}

typedef struct FindPropValData {
    uint32          numvars;    /* # of destructuring vars in left side */
    uint32          maxstep;    /* max # of steps searching right side */
    JSDHashTable    table;      /* hash table for O(1) right side search */
} FindPropValData;

typedef struct FindPropValEntry {
    JSDHashEntryHdr hdr;
    JSParseNode     *pnkey;
    JSParseNode     *pnval;
} FindPropValEntry;

#define ASSERT_VALID_PROPERTY_KEY(pnkey)                                      \
    JS_ASSERT((pnkey)->pn_arity == PN_NULLARY &&                              \
              ((pnkey)->pn_type == TOK_NUMBER ||                              \
               (pnkey)->pn_type == TOK_STRING ||                              \
               (pnkey)->pn_type == TOK_NAME))

static JSDHashNumber
HashFindPropValKey(JSDHashTable *table, const void *key)
{
    const JSParseNode *pnkey = (const JSParseNode *)key;

    ASSERT_VALID_PROPERTY_KEY(pnkey);
    return (pnkey->pn_type == TOK_NUMBER)
           ? (JSDHashNumber) (JSDOUBLE_HI32(pnkey->pn_dval) ^
                              JSDOUBLE_LO32(pnkey->pn_dval))
           : ATOM_HASH(pnkey->pn_atom);
}

static JSBool
MatchFindPropValEntry(JSDHashTable *table,
                      const JSDHashEntryHdr *entry,
                      const void *key)
{
    const FindPropValEntry *fpve = (const FindPropValEntry *)entry;
    const JSParseNode *pnkey = (const JSParseNode *)key;

    ASSERT_VALID_PROPERTY_KEY(pnkey);
    return pnkey->pn_type == fpve->pnkey->pn_type &&
           ((pnkey->pn_type == TOK_NUMBER)
            ? pnkey->pn_dval == fpve->pnkey->pn_dval
            : pnkey->pn_atom == fpve->pnkey->pn_atom);
}

static const JSDHashTableOps FindPropValOps = {
    JS_DHashAllocTable,
    JS_DHashFreeTable,
    HashFindPropValKey,
    MatchFindPropValEntry,
    JS_DHashMoveEntryStub,
    JS_DHashClearEntryStub,
    JS_DHashFinalizeStub,
    NULL
};

#define STEP_HASH_THRESHOLD     10
#define BIG_DESTRUCTURING        5
#define BIG_OBJECT_INIT         20

static JSParseNode *
FindPropertyValue(JSParseNode *pn, JSParseNode *pnid, FindPropValData *data)
{
    FindPropValEntry *entry;
    JSParseNode *pnhit, *pnhead, *pnprop, *pnkey;
    uint32 step;

    /* If we have a hash table, use it as the sole source of truth. */
    if (data->table.ops) {
        entry = (FindPropValEntry *)
                JS_DHashTableOperate(&data->table, pnid, JS_DHASH_LOOKUP);
        return JS_DHASH_ENTRY_IS_BUSY(&entry->hdr) ? entry->pnval : NULL;
    }

    /* If pn is not an object initialiser node, we can't do anything here. */
    if (pn->pn_type != TOK_RC)
        return NULL;

    /*
     * We must search all the way through pn's list, to handle the case of an
     * id duplicated for two or more property initialisers.
     */
    pnhit = NULL;
    step = 0;
    ASSERT_VALID_PROPERTY_KEY(pnid);
    pnhead = pn->pn_head;
    if (pnhead && pnhead->pn_type == TOK_DEFSHARP)
        pnhead = pnhead->pn_next;
    if (pnid->pn_type == TOK_NUMBER) {
        for (pnprop = pnhead; pnprop; pnprop = pnprop->pn_next) {
            JS_ASSERT(pnprop->pn_type == TOK_COLON);
            if (pnprop->pn_op == JSOP_NOP) {
                pnkey = pnprop->pn_left;
                ASSERT_VALID_PROPERTY_KEY(pnkey);
                if (pnkey->pn_type == TOK_NUMBER &&
                    pnkey->pn_dval == pnid->pn_dval) {
                    pnhit = pnprop;
                }
                ++step;
            }
        }
    } else {
        for (pnprop = pnhead; pnprop; pnprop = pnprop->pn_next) {
            JS_ASSERT(pnprop->pn_type == TOK_COLON);
            if (pnprop->pn_op == JSOP_NOP) {
                pnkey = pnprop->pn_left;
                ASSERT_VALID_PROPERTY_KEY(pnkey);
                if (pnkey->pn_type == pnid->pn_type &&
                    pnkey->pn_atom == pnid->pn_atom) {
                    pnhit = pnprop;
                }
                ++step;
            }
        }
    }
    if (!pnhit)
        return NULL;

    /* Hit via full search -- see whether it's time to create the hash table. */
    JS_ASSERT(!data->table.ops);
    if (step > data->maxstep) {
        data->maxstep = step;
        if (step >= STEP_HASH_THRESHOLD &&
            data->numvars >= BIG_DESTRUCTURING &&
            pn->pn_count >= BIG_OBJECT_INIT &&
            JS_DHashTableInit(&data->table, &FindPropValOps, pn,
                              sizeof(FindPropValEntry),
                              JS_DHASH_DEFAULT_CAPACITY(pn->pn_count)))
        {
            for (pn = pnhead; pn; pn = pn->pn_next) {
                JS_ASSERT(pnprop->pn_type == TOK_COLON);
                ASSERT_VALID_PROPERTY_KEY(pn->pn_left);
                entry = (FindPropValEntry *)
                        JS_DHashTableOperate(&data->table, pn->pn_left,
                                             JS_DHASH_ADD);
                entry->pnval = pn->pn_right;
            }
        }
    }
    return pnhit->pn_right;
}

/*
 * If data is null, the caller is AssignExpr and instead of binding variables,
 * we specialize lvalues in the propery value positions of the left-hand side.
 * If right is null, just check for well-formed lvalues.
 */
static JSBool
CheckDestructuring(JSContext *cx, BindData *data,
                   JSParseNode *left, JSParseNode *right,
                   JSTreeContext *tc)
{
    JSBool ok;
    FindPropValData fpvd;
    JSParseNode *lhs, *rhs, *pn, *pn2;

    if (left->pn_type == TOK_ARRAYCOMP) {
        js_ReportCompileErrorNumber(cx, TS(tc->parseContext), left,
                                    JSREPORT_ERROR, JSMSG_ARRAY_COMP_LEFTSIDE);
        return JS_FALSE;
    }

#if JS_HAS_DESTRUCTURING_SHORTHAND
    if (right && right->pn_arity == PN_LIST && (right->pn_extra & PNX_SHORTHAND)) {
        js_ReportCompileErrorNumber(cx, TS(tc->parseContext), right,
                                    JSREPORT_ERROR, JSMSG_BAD_OBJECT_INIT);
        return JS_FALSE;
    }
#endif

    fpvd.table.ops = NULL;
    lhs = left->pn_head;
    if (lhs && lhs->pn_type == TOK_DEFSHARP) {
        pn = lhs;
        goto no_var_name;
    }

    if (left->pn_type == TOK_RB) {
        rhs = (right && right->pn_type == left->pn_type)
              ? right->pn_head
              : NULL;

        while (lhs) {
            pn = lhs, pn2 = rhs;
            if (!data) {
                /* Skip parenthesization if not in a variable declaration. */
                while (pn->pn_type == TOK_RP)
                    pn = pn->pn_kid;
                if (pn2) {
                    while (pn2->pn_type == TOK_RP)
                        pn2 = pn2->pn_kid;
                }
            }

            /* Nullary comma is an elision; binary comma is an expression.*/
            if (pn->pn_type != TOK_COMMA || pn->pn_arity != PN_NULLARY) {
                if (pn->pn_type == TOK_RB || pn->pn_type == TOK_RC) {
                    ok = CheckDestructuring(cx, data, pn, pn2, tc);
                } else {
                    if (data) {
                        if (pn->pn_type != TOK_NAME)
                            goto no_var_name;

                        ok = BindDestructuringVar(cx, data, pn, tc);
                    } else {
                        ok = BindDestructuringLHS(cx, pn, tc);
                    }
                }
                if (!ok)
                    goto out;
            }

            lhs = lhs->pn_next;
            if (rhs)
                rhs = rhs->pn_next;
        }
    } else {
        JS_ASSERT(left->pn_type == TOK_RC);
        fpvd.numvars = left->pn_count;
        fpvd.maxstep = 0;
        rhs = NULL;

        while (lhs) {
            JS_ASSERT(lhs->pn_type == TOK_COLON);
            pn = lhs->pn_right;
            if (!data) {
                /* Skip parenthesization if not in a variable declaration. */
                while (pn->pn_type == TOK_RP)
                    pn = pn->pn_kid;
            }

            if (pn->pn_type == TOK_RB || pn->pn_type == TOK_RC) {
                if (right) {
                    rhs = FindPropertyValue(right, lhs->pn_left, &fpvd);
                    if (rhs && !data) {
                        while (rhs->pn_type == TOK_RP)
                            rhs = rhs->pn_kid;
                    }
                }

                ok = CheckDestructuring(cx, data, pn, rhs, tc);
            } else if (data) {
                if (pn->pn_type != TOK_NAME)
                    goto no_var_name;

                ok = BindDestructuringVar(cx, data, pn, tc);
            } else {
                ok = BindDestructuringLHS(cx, pn, tc);
            }
            if (!ok)
                goto out;

            lhs = lhs->pn_next;
        }
    }

    /*
     * The catch/finally handler implementation in the interpreter assumes
     * that any operation that introduces a new scope (like a "let" or "with"
     * block) increases the stack depth. This way, it is possible to restore
     * the scope chain based on stack depth of the handler alone. "let" with
     * an empty destructuring pattern like in
     *
     *   let [] = 1;
     *
     * would violate this assumption as the there would be no let locals to
     * store on the stack. To satisfy it we add an empty property to such
     * blocks so that OBJ_BLOCK_COUNT(cx, blockObj), which gives the number of
     * slots, would be always positive.
     *
     * Note that we add such a property even if the block has locals due to
     * later let declarations in it. We optimize for code simplicity here,
     * not the fastest runtime performance with empty [] or {}.
     */
    if (data &&
        data->binder == BindLet &&
        OBJ_BLOCK_COUNT(cx, tc->blockChain) == 0) {
        ok = js_DefineNativeProperty(cx, tc->blockChain,
                                     ATOM_TO_JSID(cx->runtime->
                                                  atomState.emptyAtom),
                                     JSVAL_VOID, NULL, NULL,
                                     JSPROP_ENUMERATE |
                                     JSPROP_PERMANENT |
                                     JSPROP_SHARED,
                                     SPROP_HAS_SHORTID, 0, NULL);
        if (!ok)
            goto out;
    }

    ok = JS_TRUE;

  out:
    if (fpvd.table.ops)
        JS_DHashTableFinish(&fpvd.table);
    return ok;

  no_var_name:
    js_ReportCompileErrorNumber(cx, TS(tc->parseContext), pn, JSREPORT_ERROR,
                                JSMSG_NO_VARIABLE_NAME);
    ok = JS_FALSE;
    goto out;
}

static JSParseNode *
DestructuringExpr(JSContext *cx, BindData *data, JSTreeContext *tc,
                  JSTokenType tt)
{
    JSParseNode *pn;

    pn = PrimaryExpr(cx, TS(tc->parseContext), tc, tt, JS_FALSE);
    if (!pn)
        return NULL;
    if (!CheckDestructuring(cx, data, pn, NULL, tc))
        return NULL;
    return pn;
}

// Currently used only #if JS_HAS_DESTRUCTURING, in Statement's TOK_FOR case.
static JSParseNode *
CloneParseTree(JSContext *cx, JSParseNode *opn, JSTreeContext *tc)
{
    JSParseNode *pn, *pn2, *opn2;

    pn = NewOrRecycledNode(cx, tc);
    if (!pn)
        return NULL;
    pn->pn_type = opn->pn_type;
    pn->pn_pos = opn->pn_pos;
    pn->pn_op = opn->pn_op;
    pn->pn_arity = opn->pn_arity;

    switch (pn->pn_arity) {
#define NULLCHECK(e)    JS_BEGIN_MACRO if (!(e)) return NULL; JS_END_MACRO

      case PN_FUNC:
        NULLCHECK(pn->pn_funpob =
                  js_NewParsedObjectBox(cx, tc->parseContext, opn->pn_funpob->object));
        NULLCHECK(pn->pn_body = CloneParseTree(cx, opn->pn_body, tc));
        pn->pn_flags = opn->pn_flags;
        pn->pn_index = opn->pn_index;
        break;

      case PN_LIST:
        PN_INIT_LIST(pn);
        for (opn2 = opn->pn_head; opn2; opn2 = opn2->pn_next) {
            NULLCHECK(pn2 = CloneParseTree(cx, opn2, tc));
            PN_APPEND(pn, pn2);
        }
        pn->pn_extra = opn->pn_extra;
        break;

      case PN_TERNARY:
        NULLCHECK(pn->pn_kid1 = CloneParseTree(cx, opn->pn_kid1, tc));
        NULLCHECK(pn->pn_kid2 = CloneParseTree(cx, opn->pn_kid2, tc));
        NULLCHECK(pn->pn_kid3 = CloneParseTree(cx, opn->pn_kid3, tc));
        break;

      case PN_BINARY:
        NULLCHECK(pn->pn_left = CloneParseTree(cx, opn->pn_left, tc));
        if (opn->pn_right != opn->pn_left)
            NULLCHECK(pn->pn_right = CloneParseTree(cx, opn->pn_right, tc));
        else
            pn->pn_right = pn->pn_left;
        pn->pn_val = opn->pn_val;
        pn->pn_iflags = opn->pn_iflags;
        break;

      case PN_UNARY:
        NULLCHECK(pn->pn_kid = CloneParseTree(cx, opn->pn_kid, tc));
        pn->pn_num = opn->pn_num;
        pn->pn_hidden = opn->pn_hidden;
        break;

      case PN_NAME:
        // PN_NAME could mean several arms in pn_u, so copy the whole thing.
        pn->pn_u = opn->pn_u;
        if (opn->pn_expr)
            NULLCHECK(pn->pn_expr = CloneParseTree(cx, opn->pn_expr, tc));
        break;

      case PN_NULLARY:
        // Even PN_NULLARY may have data (apair for E4X -- what a botch).
        pn->pn_u = opn->pn_u;
        break;

#undef NULLCHECK
    }
    return pn;
}

#endif /* JS_HAS_DESTRUCTURING */

extern const char js_with_statement_str[];

static JSParseNode *
ContainsStmt(JSParseNode *pn, JSTokenType tt)
{
    JSParseNode *pn2, *pnt;

    if (!pn)
        return NULL;
    if (pn->pn_type == tt)
        return pn;
    switch (pn->pn_arity) {
      case PN_LIST:
        for (pn2 = pn->pn_head; pn2; pn2 = pn2->pn_next) {
            pnt = ContainsStmt(pn2, tt);
            if (pnt)
                return pnt;
        }
        break;
      case PN_TERNARY:
        pnt = ContainsStmt(pn->pn_kid1, tt);
        if (pnt)
            return pnt;
        pnt = ContainsStmt(pn->pn_kid2, tt);
        if (pnt)
            return pnt;
        return ContainsStmt(pn->pn_kid3, tt);
      case PN_BINARY:
        /*
         * Limit recursion if pn is a binary expression, which can't contain a
         * var statement.
         */
        if (pn->pn_op != JSOP_NOP)
            return NULL;
        pnt = ContainsStmt(pn->pn_left, tt);
        if (pnt)
            return pnt;
        return ContainsStmt(pn->pn_right, tt);
      case PN_UNARY:
        if (pn->pn_op != JSOP_NOP)
            return NULL;
        return ContainsStmt(pn->pn_kid, tt);
      case PN_NAME:
        return ContainsStmt(pn->pn_expr, tt);
      default:;
    }
    return NULL;
}

static JSParseNode *
ReturnOrYield(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc,
              JSParser operandParser)
{
    JSTokenType tt, tt2;
    JSParseNode *pn, *pn2;

    tt = CURRENT_TOKEN(ts).type;
    if (tt == TOK_RETURN && !(tc->flags & TCF_IN_FUNCTION)) {
        js_ReportCompileErrorNumber(cx, ts, NULL, JSREPORT_ERROR,
                                    JSMSG_BAD_RETURN_OR_YIELD, js_return_str);
        return NULL;
    }

    pn = NewParseNode(cx, ts, PN_UNARY, tc);
    if (!pn)
        return NULL;

#if JS_HAS_GENERATORS
    if (tt == TOK_YIELD)
        tc->flags |= TCF_FUN_IS_GENERATOR;
#endif

    /* This is ugly, but we don't want to require a semicolon. */
    ts->flags |= TSF_OPERAND;
    tt2 = js_PeekTokenSameLine(cx, ts);
    ts->flags &= ~TSF_OPERAND;
    if (tt2 == TOK_ERROR)
        return NULL;

    if (tt2 != TOK_EOF && tt2 != TOK_EOL && tt2 != TOK_SEMI && tt2 != TOK_RC
#if JS_HAS_GENERATORS
        && (tt != TOK_YIELD ||
            (tt2 != tt && tt2 != TOK_RB && tt2 != TOK_RP &&
             tt2 != TOK_COLON && tt2 != TOK_COMMA))
#endif
        ) {
        pn2 = operandParser(cx, ts, tc);
        if (!pn2)
            return NULL;
#if JS_HAS_GENERATORS
        if (tt == TOK_RETURN)
#endif
            tc->flags |= TCF_RETURN_EXPR;
        pn->pn_pos.end = pn2->pn_pos.end;
        pn->pn_kid = pn2;
    } else {
#if JS_HAS_GENERATORS
        if (tt == TOK_RETURN)
#endif
            tc->flags |= TCF_RETURN_VOID;
    }

    if ((~tc->flags & (TCF_RETURN_EXPR | TCF_FUN_IS_GENERATOR)) == 0) {
        /* As in Python (see PEP-255), disallow return v; in generators. */
        ReportBadReturn(cx, tc, JSREPORT_ERROR,
                        JSMSG_BAD_GENERATOR_RETURN,
                        JSMSG_BAD_ANON_GENERATOR_RETURN);
        return NULL;
    }

    if (JS_HAS_STRICT_OPTION(cx) &&
        (~tc->flags & (TCF_RETURN_EXPR | TCF_RETURN_VOID)) == 0 &&
        !ReportBadReturn(cx, tc, JSREPORT_WARNING | JSREPORT_STRICT,
                         JSMSG_NO_RETURN_VALUE,
                         JSMSG_ANON_NO_RETURN_VALUE)) {
        return NULL;
    }

    return pn;
}

static JSParseNode *
PushLexicalScope(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc,
                 JSStmtInfo *stmtInfo)
{
    JSParseNode *pn;
    JSObject *obj;
    JSParsedObjectBox *blockpob;

    pn = NewParseNode(cx, ts, PN_NAME, tc);
    if (!pn)
        return NULL;

    obj = js_NewBlockObject(cx);
    if (!obj)
        return NULL;

    blockpob = js_NewParsedObjectBox(cx, tc->parseContext, obj);
    if (!blockpob)
        return NULL;

    js_PushBlockScope(tc, stmtInfo, obj, -1);
    pn->pn_type = TOK_LEXICALSCOPE;
    pn->pn_op = JSOP_LEAVEBLOCK;
    pn->pn_pob = blockpob;
    pn->pn_slot = -1;
    return pn;
}

#if JS_HAS_BLOCK_SCOPE

static JSParseNode *
LetBlock(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc, JSBool statement)
{
    JSParseNode *pn, *pnblock, *pnlet;
    JSStmtInfo stmtInfo;

    JS_ASSERT(CURRENT_TOKEN(ts).type == TOK_LET);

    /* Create the let binary node. */
    pnlet = NewParseNode(cx, ts, PN_BINARY, tc);
    if (!pnlet)
        return NULL;

    MUST_MATCH_TOKEN(TOK_LP, JSMSG_PAREN_BEFORE_LET);

    /* This is a let block or expression of the form: let (a, b, c) .... */
    pnblock = PushLexicalScope(cx, ts, tc, &stmtInfo);
    if (!pnblock)
        return NULL;
    pn = pnblock;
    pn->pn_expr = pnlet;

    pnlet->pn_left = Variables(cx, ts, tc);
    if (!pnlet->pn_left)
        return NULL;
    pnlet->pn_left->pn_extra = PNX_POPVAR;

    MUST_MATCH_TOKEN(TOK_RP, JSMSG_PAREN_AFTER_LET);

    ts->flags |= TSF_OPERAND;
    if (statement && !js_MatchToken(cx, ts, TOK_LC)) {
        /*
         * If this is really an expression in let statement guise, then we
         * need to wrap the TOK_LET node in a TOK_SEMI node so that we pop
         * the return value of the expression.
         */
        pn = NewParseNode(cx, ts, PN_UNARY, tc);
        if (!pn)
            return NULL;
        pn->pn_type = TOK_SEMI;
        pn->pn_num = -1;
        pn->pn_kid = pnblock;

        statement = JS_FALSE;
    }
    ts->flags &= ~TSF_OPERAND;

    if (statement) {
        pnlet->pn_right = Statements(cx, ts, tc);
        if (!pnlet->pn_right)
            return NULL;
        MUST_MATCH_TOKEN(TOK_RC, JSMSG_CURLY_AFTER_LET);
    } else {
        /*
         * Change pnblock's opcode to the variant that propagates the last
         * result down after popping the block, and clear statement.
         */
        pnblock->pn_op = JSOP_LEAVEBLOCKEXPR;
        pnlet->pn_right = AssignExpr(cx, ts, tc);
        if (!pnlet->pn_right)
            return NULL;
    }

    js_PopStatement(tc);
    return pn;
}

#endif /* JS_HAS_BLOCK_SCOPE */

static JSParseNode *
Statement(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc)
{
    JSTokenType tt;
    JSParseNode *pn, *pn1, *pn2, *pn3, *pn4;
    JSStmtInfo stmtInfo, *stmt, *stmt2;
    JSAtom *label;

    JS_CHECK_RECURSION(cx, return NULL);

    ts->flags |= TSF_OPERAND;
    tt = js_GetToken(cx, ts);
    ts->flags &= ~TSF_OPERAND;

#if JS_HAS_GETTER_SETTER
    if (tt == TOK_NAME) {
        tt = CheckGetterOrSetter(cx, ts, TOK_FUNCTION);
        if (tt == TOK_ERROR)
            return NULL;
    }
#endif

    switch (tt) {
      case TOK_FUNCTION:
#if JS_HAS_XML_SUPPORT
        ts->flags |= TSF_KEYWORD_IS_NAME;
        tt = js_PeekToken(cx, ts);
        ts->flags &= ~TSF_KEYWORD_IS_NAME;
        if (tt == TOK_DBLCOLON)
            goto expression;
#endif
        return FunctionStmt(cx, ts, tc);

      case TOK_IF:
        /* An IF node has three kids: condition, then, and optional else. */
        pn = NewParseNode(cx, ts, PN_TERNARY, tc);
        if (!pn)
            return NULL;
        pn1 = Condition(cx, ts, tc);
        if (!pn1)
            return NULL;
        js_PushStatement(tc, &stmtInfo, STMT_IF, -1);
        pn2 = Statement(cx, ts, tc);
        if (!pn2)
            return NULL;
        ts->flags |= TSF_OPERAND;
        if (js_MatchToken(cx, ts, TOK_ELSE)) {
            ts->flags &= ~TSF_OPERAND;
            stmtInfo.type = STMT_ELSE;
            pn3 = Statement(cx, ts, tc);
            if (!pn3)
                return NULL;
            pn->pn_pos.end = pn3->pn_pos.end;
        } else {
            ts->flags &= ~TSF_OPERAND;
            pn3 = NULL;
            pn->pn_pos.end = pn2->pn_pos.end;
        }
        js_PopStatement(tc);
        pn->pn_kid1 = pn1;
        pn->pn_kid2 = pn2;
        pn->pn_kid3 = pn3;
        return pn;

      case TOK_SWITCH:
      {
        JSParseNode *pn5, *saveBlock;
        JSBool seenDefault = JS_FALSE;

        pn = NewParseNode(cx, ts, PN_BINARY, tc);
        if (!pn)
            return NULL;
        MUST_MATCH_TOKEN(TOK_LP, JSMSG_PAREN_BEFORE_SWITCH);

        /* pn1 points to the switch's discriminant. */
        pn1 = ParenExpr(cx, ts, tc, NULL, NULL);
        if (!pn1)
            return NULL;

        MUST_MATCH_TOKEN(TOK_RP, JSMSG_PAREN_AFTER_SWITCH);
        MUST_MATCH_TOKEN(TOK_LC, JSMSG_CURLY_BEFORE_SWITCH);

        /* pn2 is a list of case nodes. The default case has pn_left == NULL */
        pn2 = NewParseNode(cx, ts, PN_LIST, tc);
        if (!pn2)
            return NULL;
        saveBlock = tc->blockNode;
        tc->blockNode = pn2;
        PN_INIT_LIST(pn2);

        js_PushStatement(tc, &stmtInfo, STMT_SWITCH, -1);

        while ((tt = js_GetToken(cx, ts)) != TOK_RC) {
            switch (tt) {
              case TOK_DEFAULT:
                if (seenDefault) {
                    js_ReportCompileErrorNumber(cx, ts, NULL, JSREPORT_ERROR,
                                                JSMSG_TOO_MANY_DEFAULTS);
                    return NULL;
                }
                seenDefault = JS_TRUE;
                /* FALL THROUGH */

              case TOK_CASE:
                pn3 = NewParseNode(cx, ts, PN_BINARY, tc);
                if (!pn3)
                    return NULL;
                if (tt == TOK_CASE) {
                    pn3->pn_left = Expr(cx, ts, tc);
                    if (!pn3->pn_left)
                        return NULL;
                }
                PN_APPEND(pn2, pn3);
                if (pn2->pn_count == JS_BIT(16)) {
                    js_ReportCompileErrorNumber(cx, ts, NULL, JSREPORT_ERROR,
                                                JSMSG_TOO_MANY_CASES);
                    return NULL;
                }
                break;

              case TOK_ERROR:
                return NULL;

              default:
                js_ReportCompileErrorNumber(cx, ts, NULL, JSREPORT_ERROR,
                                            JSMSG_BAD_SWITCH);
                return NULL;
            }
            MUST_MATCH_TOKEN(TOK_COLON, JSMSG_COLON_AFTER_CASE);

            pn4 = NewParseNode(cx, ts, PN_LIST, tc);
            if (!pn4)
                return NULL;
            pn4->pn_type = TOK_LC;
            PN_INIT_LIST(pn4);
            ts->flags |= TSF_OPERAND;
            while ((tt = js_PeekToken(cx, ts)) != TOK_RC &&
                   tt != TOK_CASE && tt != TOK_DEFAULT) {
                ts->flags &= ~TSF_OPERAND;
                if (tt == TOK_ERROR)
                    return NULL;
                pn5 = Statement(cx, ts, tc);
                if (!pn5)
                    return NULL;
                pn4->pn_pos.end = pn5->pn_pos.end;
                PN_APPEND(pn4, pn5);
                ts->flags |= TSF_OPERAND;
            }
            ts->flags &= ~TSF_OPERAND;

            /* Fix the PN_LIST so it doesn't begin at the TOK_COLON. */
            if (pn4->pn_head)
                pn4->pn_pos.begin = pn4->pn_head->pn_pos.begin;
            pn3->pn_pos.end = pn4->pn_pos.end;
            pn3->pn_right = pn4;
        }

        /*
         * Handle the case where there was a let declaration in any case in
         * the switch body, but not within an inner block.  If it replaced
         * tc->blockNode with a new block node then we must refresh pn2 and
         * then restore tc->blockNode.
         */
        if (tc->blockNode != pn2)
            pn2 = tc->blockNode;
        tc->blockNode = saveBlock;
        js_PopStatement(tc);

        pn->pn_pos.end = pn2->pn_pos.end = CURRENT_TOKEN(ts).pos.end;
        pn->pn_left = pn1;
        pn->pn_right = pn2;
        return pn;
      }

      case TOK_WHILE:
        pn = NewParseNode(cx, ts, PN_BINARY, tc);
        if (!pn)
            return NULL;
        js_PushStatement(tc, &stmtInfo, STMT_WHILE_LOOP, -1);
        pn2 = Condition(cx, ts, tc);
        if (!pn2)
            return NULL;
        pn->pn_left = pn2;
        pn2 = Statement(cx, ts, tc);
        if (!pn2)
            return NULL;
        js_PopStatement(tc);