jsparse.h

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sw=4 et tw=78:
 *
 * ***** 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
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 * Portions created by the Initial Developer are Copyright (C) 1998
 * the Initial Developer. All Rights Reserved.
 *
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 *
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 * either of the GNU General Public License Version 2 or later (the "GPL"),
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#ifndef jsparse_h___
#define jsparse_h___
/*
 * JS parser definitions.
 */
#include "jsversion.h"
#include "jsprvtd.h"
#include "jspubtd.h"
#include "jsatom.h"
#include "jsscan.h"

JS_BEGIN_EXTERN_C

/*
 * Parsing builds a tree of nodes that directs code generation.  This tree is
 * not a concrete syntax tree in all respects (for example, || and && are left
 * associative, but (A && B && C) translates into the right-associated tree
 * <A && <B && C>> so that code generation can emit a left-associative branch
 * around <B && C> when A is false).  Nodes are labeled by token type, with a
 * JSOp secondary label when needed:
 *
 * Label        Variant     Members
 * -----        -------     -------
 * <Definitions>
 * TOK_FUNCTION name        pn_funbox: ptr to JSFunctionBox holding function
 *                            object containing arg and var properties.  We
 *                            create the function object at parse (not emit)
 *                            time to specialize arg and var bytecodes early.
 *                          pn_body: TOK_UPVARS if the function's source body
 *                                   depends on outer names, else TOK_ARGSBODY
 *                                   if formal parameters, else TOK_LC node for
 *                                   function body statements
 *                          pn_cookie: static level and var index for function
 *                          pn_dflags: PND_* definition/use flags (see below)
 *                          pn_blockid: block id number
 * TOK_ARGSBODY list        list of formal parameters followed by TOK_LC node
 *                            for function body statements as final element
 *                          pn_count: 1 + number of formal parameters
 * TOK_UPVARS   nameset     pn_names: lexical dependencies (JSDefinitions)
 *                            defined in enclosing scopes, or ultimately not
 *                            defined (free variables, either global property
 *                            references or reference errors).
 *                          pn_argsbody: TOK_ARGSBODY or TOK_LC node
 *
 * <Statements>
 * TOK_LC       list        pn_head: list of pn_count statements
 * TOK_IF       ternary     pn_kid1: cond, pn_kid2: then, pn_kid3: else or null
 * TOK_SWITCH   binary      pn_left: discriminant
 *                          pn_right: list of TOK_CASE nodes, with at most one
 *                            TOK_DEFAULT node, or if there are let bindings
 *                            in the top level of the switch body's cases, a
 *                            TOK_LEXICALSCOPE node that contains the list of
 *                            TOK_CASE nodes.
 * TOK_CASE,    binary      pn_left: case expr or null if TOK_DEFAULT
 * TOK_DEFAULT              pn_right: TOK_LC node for this case's statements
 *                          pn_val: constant value if lookup or table switch
 * TOK_WHILE    binary      pn_left: cond, pn_right: body
 * TOK_DO       binary      pn_left: body, pn_right: cond
 * TOK_FOR      binary      pn_left: either
 *                            for/in loop: a binary TOK_IN node with
 *                              pn_left:  TOK_VAR or TOK_NAME to left of 'in'
 *                                if TOK_VAR, its pn_xflags may have PNX_POPVAR
 *                                and PNX_FORINVAR bits set
 *                              pn_right: object expr to right of 'in'
 *                            for(;;) loop: a ternary TOK_RESERVED node with
 *                              pn_kid1:  init expr before first ';'
 *                              pn_kid2:  cond expr before second ';'
 *                              pn_kid3:  update expr after second ';'
 *                              any kid may be null
 *                          pn_right: body
 * TOK_THROW    unary       pn_op: JSOP_THROW, pn_kid: exception
 * TOK_TRY      ternary     pn_kid1: try block
 *                          pn_kid2: null or TOK_RESERVED list of
 *                          TOK_LEXICALSCOPE nodes, each with pn_expr pointing
 *                          to a TOK_CATCH node
 *                          pn_kid3: null or finally block
 * TOK_CATCH    ternary     pn_kid1: TOK_NAME, TOK_RB, or TOK_RC catch var node
 *                                   (TOK_RB or TOK_RC if destructuring)
 *                          pn_kid2: null or the catch guard expression
 *                          pn_kid3: catch block statements
 * TOK_BREAK    name        pn_atom: label or null
 * TOK_CONTINUE name        pn_atom: label or null
 * TOK_WITH     binary      pn_left: head expr, pn_right: body
 * TOK_VAR      list        pn_head: list of TOK_NAME or TOK_ASSIGN nodes
 *                                   each name node has
 *                                     pn_used: false
 *                                     pn_atom: variable name
 *                                     pn_expr: initializer or null
 *                                   each assignment node has
 *                                     pn_left: TOK_NAME with pn_used true and
*                                               pn_lexdef (NOT pn_expr) set
 *                                     pn_right: initializer
 * TOK_RETURN   unary       pn_kid: return expr or null
 * TOK_SEMI     unary       pn_kid: expr or null statement
 * TOK_COLON    name        pn_atom: label, pn_expr: labeled statement
 *
 * <Expressions>
 * All left-associated binary trees of the same type are optimized into lists
 * to avoid recursion when processing expression chains.
 * TOK_COMMA    list        pn_head: list of pn_count comma-separated exprs
 * TOK_ASSIGN   binary      pn_left: lvalue, pn_right: rvalue
 *                          pn_op: JSOP_ADD for +=, etc.
 * TOK_HOOK     ternary     pn_kid1: cond, pn_kid2: then, pn_kid3: else
 * TOK_OR       binary      pn_left: first in || chain, pn_right: rest of chain
 * TOK_AND      binary      pn_left: first in && chain, pn_right: rest of chain
 * TOK_BITOR    binary      pn_left: left-assoc | expr, pn_right: ^ expr
 * TOK_BITXOR   binary      pn_left: left-assoc ^ expr, pn_right: & expr
 * TOK_BITAND   binary      pn_left: left-assoc & expr, pn_right: EQ expr
 * TOK_EQOP     binary      pn_left: left-assoc EQ expr, pn_right: REL expr
 *                          pn_op: JSOP_EQ, JSOP_NE,
 *                                 JSOP_STRICTEQ, JSOP_STRICTNE
 * TOK_RELOP    binary      pn_left: left-assoc REL expr, pn_right: SH expr
 *                          pn_op: JSOP_LT, JSOP_LE, JSOP_GT, JSOP_GE
 * TOK_SHOP     binary      pn_left: left-assoc SH expr, pn_right: ADD expr
 *                          pn_op: JSOP_LSH, JSOP_RSH, JSOP_URSH
 * TOK_PLUS,    binary      pn_left: left-assoc ADD expr, pn_right: MUL expr
 *                          pn_xflags: if a left-associated binary TOK_PLUS
 *                            tree has been flattened into a list (see above
 *                            under <Expressions>), pn_xflags will contain
 *                            PNX_STRCAT if at least one list element is a
 *                            string literal (TOK_STRING); if such a list has
 *                            any non-string, non-number term, pn_xflags will
 *                            contain PNX_CANTFOLD.
 *                          pn_
 * TOK_MINUS                pn_op: JSOP_ADD, JSOP_SUB
 * TOK_STAR,    binary      pn_left: left-assoc MUL expr, pn_right: UNARY expr
 * TOK_DIVOP                pn_op: JSOP_MUL, JSOP_DIV, JSOP_MOD
 * TOK_UNARYOP  unary       pn_kid: UNARY expr, pn_op: JSOP_NEG, JSOP_POS,
 *                          JSOP_NOT, JSOP_BITNOT, JSOP_TYPEOF, JSOP_VOID
 * TOK_INC,     unary       pn_kid: MEMBER expr
 * TOK_DEC
 * TOK_NEW      list        pn_head: list of ctor, arg1, arg2, ... argN
 *                          pn_count: 1 + N (where N is number of args)
 *                          ctor is a MEMBER expr
 * TOK_DELETE   unary       pn_kid: MEMBER expr
 * TOK_DOT,     name        pn_expr: MEMBER expr to left of .
 * TOK_DBLDOT               pn_atom: name to right of .
 * TOK_LB       binary      pn_left: MEMBER expr to left of [
 *                          pn_right: expr between [ and ]
 * TOK_LP       list        pn_head: list of call, arg1, arg2, ... argN
 *                          pn_count: 1 + N (where N is number of args)
 *                          call is a MEMBER expr naming a callable object
 * TOK_RB       list        pn_head: list of pn_count array element exprs
 *                          [,,] holes are represented by TOK_COMMA nodes
 *                          pn_xflags: PN_ENDCOMMA if extra comma at end
 * TOK_RC       list        pn_head: list of pn_count binary TOK_COLON nodes
 * TOK_COLON    binary      key-value pair in object initializer or
 *                          destructuring lhs
 *                          pn_left: property id, pn_right: value
 *                          var {x} = object destructuring shorthand shares
 *                          PN_NAME node for x on left and right of TOK_COLON
 *                          node in TOK_RC's list, has PNX_DESTRUCT flag
 * TOK_DEFSHARP unary       pn_num: jsint value of n in #n=
 *                          pn_kid: primary function, paren, name, object or
 *                                  array literal expressions
 * TOK_USESHARP nullary     pn_num: jsint value of n in #n#
 * TOK_RP       unary       pn_kid: parenthesized expression
 * TOK_NAME,    name        pn_atom: name, string, or object atom
 * TOK_STRING,              pn_op: JSOP_NAME, JSOP_STRING, or JSOP_OBJECT, or
 *                                 JSOP_REGEXP
 * TOK_REGEXP               If JSOP_NAME, pn_op may be JSOP_*ARG or JSOP_*VAR
 *                          with pn_cookie telling (staticLevel, slot) (see
 *                          jsscript.h's UPVAR macros) and pn_dflags telling
 *                          const-ness and static analysis results
 * TOK_NAME     name        If pn_used, TOK_NAME uses the lexdef member instead
 *                          of the expr member it overlays
 * TOK_NUMBER   dval        pn_dval: double value of numeric literal
 * TOK_PRIMARY  nullary     pn_op: JSOp bytecode
 *
 * <E4X node descriptions>
 * TOK_ANYNAME  nullary     pn_op: JSOP_ANYNAME
 *                          pn_atom: cx->runtime->atomState.starAtom
 * TOK_AT       unary       pn_op: JSOP_TOATTRNAME; pn_kid attribute id/expr
 * TOK_DBLCOLON binary      pn_op: JSOP_QNAME
 *                          pn_left: TOK_ANYNAME or TOK_NAME node
 *                          pn_right: TOK_STRING "*" node, or expr within []
 *              name        pn_op: JSOP_QNAMECONST
 *                          pn_expr: TOK_ANYNAME or TOK_NAME left operand
 *                          pn_atom: name on right of ::
 * TOK_XMLELEM  list        XML element node
 *                          pn_head: start tag, content1, ... contentN, end tag
 *                          pn_count: 2 + N where N is number of content nodes
 *                                    N may be > x.length() if {expr} embedded
 * TOK_XMLLIST  list        XML list node
 *                          pn_head: content1, ... contentN
 * TOK_XMLSTAGO, list       XML start, end, and point tag contents
 * TOK_XMLETAGC,            pn_head: tag name or {expr}, ... XML attrs ...
 * TOK_XMLPTAGO
 * TOK_XMLNAME  nullary     pn_atom: XML name, with no {expr} embedded
 * TOK_XMLNAME  list        pn_head: tag name or {expr}, ... name or {expr}
 * TOK_XMLATTR, nullary     pn_atom: attribute value string; pn_op: JSOP_STRING
 * TOK_XMLCDATA,
 * TOK_XMLCOMMENT
 * TOK_XMLPI    nullary     pn_atom: XML processing instruction target
 *                          pn_atom2: XML PI content, or null if no content
 * TOK_XMLTEXT  nullary     pn_atom: marked-up text, or null if empty string
 * TOK_LC       unary       {expr} in XML tag or content; pn_kid is expr
 *
 * So an XML tag with no {expr} and three attributes is a list with the form:
 *
 *    (tagname attrname1 attrvalue1 attrname2 attrvalue2 attrname2 attrvalue3)
 *
 * An XML tag with embedded expressions like so:
 *
 *    <name1{expr1} name2{expr2}name3={expr3}>
 *
 * would have the form:
 *
 *    ((name1 {expr1}) (name2 {expr2} name3) {expr3})
 *
 * where () bracket a list with elements separated by spaces, and {expr} is a
 * TOK_LC unary node with expr as its kid.
 *
 * Thus, the attribute name/value pairs occupy successive odd and even list
 * locations, where pn_head is the TOK_XMLNAME node at list location 0.  The
 * parser builds the same sort of structures for elements:
 *
 *    <a x={x}>Hi there!<b y={y}>How are you?</b><answer>{x + y}</answer></a>
 *
 * translates to:
 *
 *    ((a x {x}) 'Hi there!' ((b y {y}) 'How are you?') ((answer) {x + y}))
 *
 * <Non-E4X node descriptions, continued>
 *
 * Label              Variant   Members
 * -----              -------   -------
 * TOK_LEXICALSCOPE   name      pn_op: JSOP_LEAVEBLOCK or JSOP_LEAVEBLOCKEXPR
 *                              pn_objbox: block object in JSObjectBox holder
 *                              pn_expr: block body
 * TOK_ARRAYCOMP      list      pn_head: list of pn_count (1 or 2) elements
 *                              if pn_count is 2, first element is #n=[...]
 *                                last element is block enclosing for loop(s)
 *                                and optionally if-guarded TOK_ARRAYPUSH
 * TOK_ARRAYPUSH      unary     pn_op: JSOP_ARRAYCOMP
 *                              pn_kid: array comprehension expression
 */
typedef enum JSParseNodeArity {
    PN_NULLARY,                         /* 0 kids, only pn_atom/pn_dval/etc. */
    PN_UNARY,                           /* one kid, plus a couple of scalars */
    PN_BINARY,                          /* two kids, plus a couple of scalars */
    PN_TERNARY,                         /* three kids */
    PN_FUNC,                            /* function definition node */
    PN_LIST,                            /* generic singly linked list */
    PN_NAME,                            /* name use or definition node */
    PN_NAMESET                          /* JSAtomList + JSParseNode ptr */
} JSParseNodeArity;

struct JSDefinition;

struct JSParseNode {
    uint32              pn_type:16,     /* TOK_* type, see jsscan.h */
                        pn_op:8,        /* see JSOp enum and jsopcode.tbl */
                        pn_arity:6,     /* see JSParseNodeArity enum */
                        pn_used:1,      /* name node is on a use-chain */
                        pn_defn:1;      /* this node is a JSDefinition */

#define PN_OP(pn)    ((JSOp)(pn)->pn_op)
#define PN_TYPE(pn)  ((JSTokenType)(pn)->pn_type)

    JSTokenPos          pn_pos;         /* two 16-bit pairs here, for 64 bits */
    int32               pn_offset;      /* first generated bytecode offset */
    JSParseNode         *pn_next;       /* intrinsic link in parent PN_LIST */
    JSParseNode         *pn_link;       /* def/use link (alignment freebie) */
    union {
        struct {                        /* list of next-linked nodes */
            JSParseNode *head;          /* first node in list */
            JSParseNode **tail;         /* ptr to ptr to last node in list */
            uint32      count;          /* number of nodes in list */
            uint32      xflags:12,      /* extra flags, see below */
                        blockid:20;     /* see name variant below */
        } list;
        struct {                        /* ternary: if, for(;;), ?: */
            JSParseNode *kid1;          /* condition, discriminant, etc. */
            JSParseNode *kid2;          /* then-part, case list, etc. */
            JSParseNode *kid3;          /* else-part, default case, etc. */
        } ternary;
        struct {                        /* two kids if binary */
            JSParseNode *left;
            JSParseNode *right;
            jsval       val;            /* switch case value */
            uintN       iflags;         /* JSITER_* flags for TOK_FOR node */
        } binary;
        struct {                        /* one kid if unary */
            JSParseNode *kid;
            jsint       num;            /* -1 or sharp variable number */
            JSBool      hidden;         /* hidden genexp-induced JSOP_YIELD */
        } unary;
        struct {                        /* name, labeled statement, etc. */
            union {
                JSAtom        *atom;    /* lexical name or label atom */
                JSFunctionBox *funbox;  /* function object */
                JSObjectBox   *objbox;  /* block or regexp object */
            };
            union {
                JSParseNode  *expr;     /* function body, var initializer, or
                                           base object of TOK_DOT */
                JSDefinition *lexdef;   /* lexical definition for this use */
            };
            uint32      cookie;         /* upvar cookie with absolute frame
                                           level (not relative skip), possibly
                                           in current frame */
            uint32      dflags:12,      /* definition/use flags, see below */
                        blockid:20;     /* block number, for subset dominance
                                           computation */
        } name;
        struct {                        /* lexical dependencies + sub-tree */
            JSAtomSet   names;          /* set of names with JSDefinitions */
            JSParseNode *tree;          /* sub-tree containing name uses */
        } nameset;
        struct {                        /* PN_NULLARY variant for E4X */
            JSAtom      *atom;          /* first atom in pair */
            JSAtom      *atom2;         /* second atom in pair or null */
        } apair;
        jsdouble        dval;           /* aligned numeric literal value */
    } pn_u;

#define pn_funbox       pn_u.name.funbox
#define pn_body         pn_u.name.expr
#define pn_cookie       pn_u.name.cookie
#define pn_dflags       pn_u.name.dflags
#define pn_blockid      pn_u.name.blockid
#define pn_index        pn_u.name.blockid /* reuse as object table index */
#define pn_head         pn_u.list.head
#define pn_tail         pn_u.list.tail
#define pn_count        pn_u.list.count
#define pn_xflags       pn_u.list.xflags
#define pn_kid1         pn_u.ternary.kid1
#define pn_kid2         pn_u.ternary.kid2
#define pn_kid3         pn_u.ternary.kid3
#define pn_left         pn_u.binary.left
#define pn_right        pn_u.binary.right
#define pn_val          pn_u.binary.val
#define pn_iflags       pn_u.binary.iflags
#define pn_kid          pn_u.unary.kid
#define pn_num          pn_u.unary.num
#define pn_hidden       pn_u.unary.hidden
#define pn_atom         pn_u.name.atom
#define pn_objbox       pn_u.name.objbox
#define pn_expr         pn_u.name.expr
#define pn_lexdef       pn_u.name.lexdef
#define pn_names        pn_u.nameset.names
#define pn_tree         pn_u.nameset.tree
#define pn_dval         pn_u.dval
#define pn_atom2        pn_u.apair.atom2

    /*
     * The pn_expr and lexdef members are arms of an unsafe union. Unless you
     * know exactly what you're doing, use only the following methods to access
     * them. For less overhead and assertions for protection, use pn->expr()
     * and pn->lexdef(). Otherwise, use pn->maybeExpr() and pn->maybeLexDef().
     */
    JSParseNode  *expr() const {
        JS_ASSERT(!pn_used);
        JS_ASSERT(pn_arity == PN_NAME || pn_arity == PN_FUNC);
        return pn_expr;
    }

    JSDefinition *lexdef() const {
        JS_ASSERT(pn_used);
        JS_ASSERT(pn_arity == PN_NAME);
        return pn_lexdef;
    }

    JSParseNode  *maybeExpr()   { return pn_used ? NULL : expr(); }
    JSDefinition *maybeLexDef() { return pn_used ? lexdef() : NULL; }

/* PN_FUNC and PN_NAME pn_dflags bits. */
#define PND_LET         0x01            /* let (block-scoped) binding */
#define PND_CONST       0x02            /* const binding (orthogonal to let) */
#define PND_INITIALIZED 0x04            /* initialized declaration */
#define PND_ASSIGNED    0x08            /* set if ever LHS of assignment */
#define PND_TOPLEVEL    0x10            /* function at top of body or prog */
#define PND_BLOCKCHILD  0x20            /* use or def is direct block child */
#define PND_GVAR        0x40            /* gvar binding, can't close over
                                           because it could be deleted */
#define PND_PLACEHOLDER 0x80            /* placeholder definition for lexdep */
#define PND_FUNARG     0x100            /* downward or upward funarg usage */
#define PND_BOUND      0x200            /* bound to a stack or global slot */

/* PN_LIST pn_xflags bits. */
#define PNX_STRCAT      0x01            /* TOK_PLUS list has string term */
#define PNX_CANTFOLD    0x02            /* TOK_PLUS list has unfoldable term */
#define PNX_POPVAR      0x04            /* TOK_VAR last result needs popping */
#define PNX_FORINVAR    0x08            /* TOK_VAR is left kid of TOK_IN node,
                                           which is left kid of TOK_FOR */
#define PNX_ENDCOMMA    0x10            /* array literal has comma at end */
#define PNX_XMLROOT     0x20            /* top-most node in XML literal tree */
#define PNX_GROUPINIT   0x40            /* var [a, b] = [c, d]; unit list */
#define PNX_NEEDBRACES  0x80            /* braces necessary due to closure */
#define PNX_FUNCDEFS   0x100            /* contains top-level function
                                           statements */
#define PNX_DESTRUCT   0x200            /* destructuring special cases:
                                           1. shorthand syntax used, at present
                                              object destructuring ({x,y}) only;
                                           2. the first child of function body
                                              is code evaluating destructuring
                                              arguments */
#define PNX_HOLEY      0x400            /* array initialiser has holes */

    uintN frameLevel() const {
        JS_ASSERT(pn_arity == PN_FUNC || pn_arity == PN_NAME);
        return UPVAR_FRAME_SKIP(pn_cookie);
    }

    uintN frameSlot() const {
        JS_ASSERT(pn_arity == PN_FUNC || pn_arity == PN_NAME);
        return UPVAR_FRAME_SLOT(pn_cookie);
    }

    bool test(uintN flag) const {
        JS_ASSERT(pn_arity == PN_FUNC || pn_arity == PN_NAME);
        return !!(pn_dflags & flag);
    }

    bool isLet() const          { return test(PND_LET); }
    bool isConst() const        { return test(PND_CONST); }
    bool isInitialized() const  { return test(PND_INITIALIZED); }
    bool isTopLevel() const     { return test(PND_TOPLEVEL); }
    bool isBlockChild() const   { return test(PND_BLOCKCHILD); }
    bool isPlaceholder() const  { return test(PND_PLACEHOLDER); }

    /* Defined below, see after struct JSDefinition. */
    bool isAssigned() const;
    bool isFunArg() const;
    void setFunArg();

    void become(JSParseNode *pn2);
    void clear();

    /* True if pn is a parsenode representing a literal constant. */
    bool isLiteral() const {
        return PN_TYPE(this) == TOK_NUMBER ||
               PN_TYPE(this) == TOK_STRING ||
               (PN_TYPE(this) == TOK_PRIMARY && PN_OP(this) != JSOP_THIS);
    }

    /*
     * Compute a pointer to the last element in a singly-linked list. NB: list
     * must be non-empty for correct PN_LAST usage -- this is asserted!
     */
    JSParseNode *last() const {
        JS_ASSERT(pn_arity == PN_LIST);
        JS_ASSERT(pn_count != 0);
        return (JSParseNode *)((char *)pn_tail - offsetof(JSParseNode, pn_next));
    }

    void makeEmpty() {
        JS_ASSERT(pn_arity == PN_LIST);
        pn_head = NULL;
        pn_tail = &pn_head;
        pn_count = 0;
        pn_xflags = 0;
        pn_blockid = 0;
    }

    void initList(JSParseNode *pn) {
        JS_ASSERT(pn_arity == PN_LIST);
        pn_head = pn;
        pn_tail = &pn->pn_next;
        pn_count = 1;
        pn_xflags = 0;
        pn_blockid = 0;
    }

    void append(JSParseNode *pn) {
        JS_ASSERT(pn_arity == PN_LIST);
        *pn_tail = pn;
        pn_tail = &pn->pn_next;
        pn_count++;
    }
};

/*
 * JSDefinition is a degenerate subtype of the PN_FUNC and PN_NAME variants of
 * JSParseNode, allocated only for function, var, const, and let declarations
 * that define truly lexical bindings. This means that a child of a TOK_VAR
 * list may be a JSDefinition instead of a JSParseNode. The pn_defn bit is set
 * for all JSDefinitions, clear otherwise.
 *
 * Note that not all var declarations are definitions: JS allows multiple var
 * declarations in a function or script, but only the first creates the hoisted
 * binding. JS programmers do redeclare variables for good refactoring reasons,
 * for example:
 *
 *   function foo() {
 *       ...
 *       for (var i ...) ...;
 *       ...
 *       for (var i ...) ...;
 *       ...
 *   }
 *
 * Not all definitions bind lexical variables, alas. In global and eval code
 * var may re-declare a pre-existing property having any attributes, with or
 * without JSPROP_PERMANENT. In eval code, indeed, ECMA-262 Editions 1 through
 * 3 require function and var to bind deletable bindings. Global vars thus are
 * properties of the global object, so they can be aliased even if they can't
 * be deleted.
 *
 * Only bindings within function code may be treated as lexical, of course with
 * the caveat that hoisting means use before initialization is allowed. We deal
 * with use before declaration in one pass as follows (error checking elided):
 *
 *   for (each use of unqualified name x in parse order) {
 *       if (this use of x is a declaration) {
 *           if (x in tc->decls) {                          // redeclaring
 *               pn = allocate a PN_NAME JSParseNode;
 *           } else {                                       // defining
 *               dn = lookup x in tc->lexdeps;
 *               if (dn) {                                  // use before def
 *                   remove x from tc->lexdeps;
 *               } else {                                   // def before use
 *                   dn = allocate a PN_NAME JSDefinition;
 *                   map x to dn via tc->decls;
 *               }
 *               pn = dn;
 *           }
 *           insert pn into its parent TOK_VAR list;
 *       } else {
 *           pn = allocate a JSParseNode for this reference to x;
 *           dn = lookup x in tc's lexical scope chain;
 *           if (!dn) {
 *               dn = lookup x in tc->lexdeps;
 *               if (!dn) {
 *                   dn = pre-allocate a JSDefinition for x;
 *                   map x to dn in tc->lexdeps;
 *               }
 *           }
 *           append pn to dn's use chain;
 *       }
 *   }
 *
 * See jsemit.h for JSTreeContext and its top*Stmt, decls, and lexdeps members.
 *
 * Notes:
 *
 *  0. To avoid bloating JSParseNode, we steal a bit from pn_arity for pn_defn
 *     and set it on a JSParseNode instead of allocating a JSDefinition.
 *
 *  1. Due to hoisting, a definition cannot be eliminated even if its "Variable
 *     statement" (ECMA-262 12.2) can be proven to be dead code. RecycleTree in
 *     jsparse.cpp will not recycle a node whose pn_defn bit is set.
 *
 *  2. "lookup x in tc's lexical scope chain" gives up on def/use chaining if a
 *     with statement is found along the the scope chain, which includes tc,
 *     tc->parent, etc. Thus we eagerly connect an inner function's use of an
 *     outer's var x if the var x was parsed before the inner function.
 *
 *  3. A use may be eliminated as dead by the constant folder, which therefore
 *     must remove the dead name node from its singly-linked use chain, which
 *     would mean hashing to find the definition node and searching to update
 *     the pn_link pointing at the use to be removed. This is costly, so as for
 *     dead definitions, we do not recycle dead pn_used nodes.
 *
 * At the end of parsing a function body or global or eval program, tc->lexdeps
 * holds the lexical dependencies of the parsed unit. The name to def/use chain
 * mappings are then merged into the parent tc->lexdeps.
 *
 * Thus if a later var x is parsed in the outer function satisfying an earlier
 * inner function's use of x, we will remove dn from tc->lexdeps and re-use it
 * as the new definition node in the outer function's parse tree.
 *
 * When the compiler unwinds from the outermost tc, tc->lexdeps contains the
 * definition nodes with use chains for all free variables. These are either
 * global variables or reference errors.
 *
 * We analyze whether a binding is initialized, whether the bound names is ever
 * assigned apart from its initializer, and if the bound name definition or use
 * is in a direct child of a block. These PND_* flags allow a subset dominance
 * computation telling whether an initialized var dominates its uses. An inner
 * function using only such outer vars (and formal parameters) can be optimized
 * into a flat closure. See JSOP_{GET,CALL}DSLOT.
 *
 * Another important subset dominance relation: ... { var x = ...; ... x ... }
 * where x is not assigned after initialization and not used outside the block.
 * This style is common in the absence of 'let'. Even though the var x is not
 * at top level, we can tell its initialization dominates all uses cheaply,
 * because the above one-pass algorithm sees the definition before any uses,
 * and because all uses are contained in the same block as the definition.
 *
 * We also analyze function uses to flag upward/downward funargs, optimizing
 * Algol-like (not passed as funargs, only ever called) lightweight functions
 * using cx->display. See JSOP_{GET,CALL}UPVAR.
 *
 * This means that closure optimizations may be frustrated by with, eval, or
 * assignment to an outer var. Such hard cases require heavyweight functions
 * and JSOP_NAME, etc.
 */
#define dn_uses         pn_link

struct JSDefinition : public JSParseNode
{
    /*
     * We store definition pointers in PN_NAMESET JSAtomLists in the AST, but
     * due to redefinition these nodes may become uses of other definitions.
     * This is unusual, so we simply chase the pn_lexdef link to find the final
     * definition node. See methods called from JSCompiler::analyzeFunctions.
     *
     * FIXME: MakeAssignment mutates for want of a parent link...
     */
    JSDefinition *resolve() {
        JSParseNode *pn = this;
        while (!pn->pn_defn) {
            if (pn->pn_type == TOK_ASSIGN) {
                pn = pn->pn_left;
                continue;
            }
            pn = pn->lexdef();
        }
        return (JSDefinition *) pn;
    }

    bool test(uintN flag) const {
        JS_ASSERT(pn_defn);
        if (pn_dflags & flag)
            return true;
#ifdef DEBUG
        for (JSParseNode *pn = dn_uses; pn; pn = pn->pn_link) {
            JS_ASSERT(!pn->pn_defn);
            JS_ASSERT(!(pn->pn_dflags & flag));
        }
#endif
        return false;
    }

    bool isAssigned() const {
        return test(PND_ASSIGNED);
    }

    bool isFunArg() const {
        return test(PND_FUNARG);
    }

    bool isFreeVar() const {
        JS_ASSERT(pn_defn);
        return pn_cookie == FREE_UPVAR_COOKIE || test(PND_GVAR);
    }

    // Grr, windows.h or something under it #defines CONST...
#ifdef CONST
# undef CONST
#endif
    enum Kind { VAR, CONST, LET, FUNCTION, ARG, UNKNOWN };

    bool isBindingForm() { return int(kind()) <= int(LET); }

    static const char *kindString(Kind kind);

    Kind kind() {
        if (PN_TYPE(this) == TOK_FUNCTION)
            return FUNCTION;
        JS_ASSERT(PN_TYPE(this) == TOK_NAME);
        if (PN_OP(this) == JSOP_NOP)
            return UNKNOWN;
        if (PN_OP(this) == JSOP_GETARG)
            return ARG;
        if (isConst())
            return CONST;
        if (isLet())
            return LET;
        return VAR;
    }
};

/*
 * These two are overridden by JSDefinition and we cannot afford virtual
 * methods -- so we use the mighty 'if' statement!
 */
inline bool
JSParseNode::isAssigned() const
{
#ifdef DEBUG
    if (pn_defn)
        return ((JSDefinition *)this)->isAssigned();
#endif
    return test(PND_ASSIGNED);
}

inline bool
JSParseNode::isFunArg() const
{
#ifdef DEBUG
    if (pn_defn)
        return ((JSDefinition *)this)->isFunArg();
#endif
    return test(PND_FUNARG);
}

inline void
JSParseNode::setFunArg()
{
    /*
     * pn_defn NAND pn_used must be true, per this chart:
     *
     *   pn_defn pn_used
     *         0       0        anonymous function used implicitly, e.g. by
     *                          hidden yield in a genexp
     *         0       1        a use of a definition or placeholder
     *         1       0        a definition or placeholder
     *         1       1        error: this case must not be possible
     */
    JS_ASSERT(!(pn_defn & pn_used));
    if (pn_used)
        pn_lexdef->pn_dflags |= PND_FUNARG;
    pn_dflags |= PND_FUNARG;
}

struct JSObjectBox {
    JSObjectBox         *traceLink;
    JSObjectBox         *emitLink;
    JSObject            *object;
};

#define JSFB_LEVEL_BITS 14

struct JSFunctionBox : public JSObjectBox
{
    JSParseNode         *node;
    JSFunctionBox       *siblings;
    JSFunctionBox       *kids;
    JSFunctionBox       *parent;
    uint32              queued:1,
                        inLoop:1,               /* in a loop in parent function */
                        level:JSFB_LEVEL_BITS,
                        tcflags:16;
};

struct JSFunctionBoxQueue {
    JSFunctionBox       **vector;
    size_t              head, tail;
    size_t              lengthMask;

    size_t count()  { return head - tail; }
    size_t length() { return lengthMask + 1; }

    JSFunctionBoxQueue()
      : vector(NULL), head(0), tail(0), lengthMask(0) { }

    bool init(uint32 count) {
        lengthMask = JS_BITMASK(JS_CeilingLog2(count));
        vector = new JSFunctionBox*[length()];
        return !!vector;
    }

    ~JSFunctionBoxQueue() { delete[] vector; }

    void push(JSFunctionBox *funbox) {
        if (!funbox->queued) {
            JS_ASSERT(count() < length());
            vector[head++ & lengthMask] = funbox;
            funbox->queued = true;
        }
    }

    JSFunctionBox *pull() {
        if (tail == head)
            return NULL;
        JS_ASSERT(tail < head);
        JSFunctionBox *funbox = vector[tail++ & lengthMask];
        funbox->queued = false;
        return funbox;
    }
};

#define NUM_TEMP_FREELISTS      6U      /* 32 to 2048 byte size classes (32 bit) */

struct JSCompiler {
    JSContext           *context;
    JSAtomListElement   *aleFreeList;
    void                *tempFreeList[NUM_TEMP_FREELISTS];
    JSTokenStream       tokenStream;
    void                *tempPoolMark;  /* initial JSContext.tempPool mark */
    JSPrincipals        *principals;    /* principals associated with source */
    JSStackFrame        *callerFrame;   /* scripted caller frame for eval and dbgapi */
    JSParseNode         *nodeList;      /* list of recyclable parse-node structs */
    uint32              functionCount;  /* number of functions in current unit */
    JSObjectBox         *traceListHead; /* list of parsed object for GC tracing */
    JSTempValueRooter   tempRoot;       /* root to trace traceListHead */

    JSCompiler(JSContext *cx, JSPrincipals *prin = NULL, JSStackFrame *cfp = NULL)
      : context(cx), aleFreeList(NULL), principals(NULL), callerFrame(cfp),
        nodeList(NULL), functionCount(0), traceListHead(NULL)
    {
        memset(tempFreeList, 0, sizeof tempFreeList);
        setPrincipals(prin);
        JS_ASSERT_IF(cfp, cfp->script);
    }

    ~JSCompiler();

    /*
     * Initialize a compiler. Parameters are passed on to js_InitTokenStream.
     * The compiler owns the arena pool "tops-of-stack" space above the current
     * JSContext.tempPool mark. This means you cannot allocate from tempPool
     * and save the pointer beyond the next JSCompiler destructor invocation.
     */
    bool init(const jschar *base, size_t length,
              FILE *fp, const char *filename, uintN lineno);

    void setPrincipals(JSPrincipals *prin);

    /*
     * Parse a top-level JS script.
     */
    JSParseNode *parse(JSObject *chain);

#if JS_HAS_XML_SUPPORT
    JSParseNode *parseXMLText(JSObject *chain, bool allowList);
#endif

    /*
     * Allocate a new parsed object or function container from cx->tempPool.
     */
    JSObjectBox *newObjectBox(JSObject *obj);

    JSFunctionBox *newFunctionBox(JSObject *obj, JSParseNode *fn, JSTreeContext *tc);

    /*
     * Create a new function object given tree context (tc), optional name
     * (atom may be null) and lambda flag (JSFUN_LAMBDA or 0).
     */
    JSFunction *newFunction(JSTreeContext *tc, JSAtom *atom, uintN lambda);

    /*
     * Analyze the tree of functions nested within a single compilation unit,
     * starting at funbox, recursively walking its kids, then following its
     * siblings, their kids, etc.
     */
    bool analyzeFunctions(JSFunctionBox *funbox, uint16& tcflags);
    bool markFunArgs(JSFunctionBox *funbox, uintN tcflags);
    void setFunctionKinds(JSFunctionBox *funbox, uint16& tcflags);

    void trace(JSTracer *trc);

    static bool
    compileFunctionBody(JSContext *cx, JSFunction *fun, JSPrincipals *principals,
                        const jschar *chars, size_t length,
                        const char *filename, uintN lineno);

    static JSScript *
    compileScript(JSContext *cx, JSObject *scopeChain, JSStackFrame *callerFrame,
                  JSPrincipals *principals, uint32 tcflags,
                  const jschar *chars, size_t length,
                  FILE *file, const char *filename, uintN lineno,
                  JSString *source = NULL);
};

/*
 * Convenience macro to access JSCompiler.tokenStream as a pointer.
 */
#define TS(jsc) (&(jsc)->tokenStream)

extern JSBool
js_FoldConstants(JSContext *cx, JSParseNode *pn, JSTreeContext *tc,
                 bool inCond = false);

JS_END_EXTERN_C

#endif /* jsparse_h___ */