cocorobolx/skulpt/src/ast.js

//
// This is pretty much a straight port of ast.c from CPython 2.6.5.
//
// The previous version was easier to work with and more JS-ish, but having a
// somewhat different ast structure than cpython makes testing more difficult.
//
// This way, we can use a dump from the ast module on any arbitrary python
// code and know that we're the same up to ast level, at least.
//

var SYM = Sk.ParseTables.sym;
var TOK = Sk.Tokenizer.Tokens;
var COMP_GENEXP = 0;
var COMP_SETCOMP = 1;

/** @constructor */
function Compiling (encoding, filename, c_flags) {
    this.c_encoding = encoding;
    this.c_filename = filename;
    this.c_flags = c_flags || 0;
}

/**
 * @return {number}
 */
function NCH (n) {
    goog.asserts.assert(n !== undefined);
    if (n.children === null) {
        return 0;
    }
    return n.children.length;
}

function CHILD (n, i) {
    goog.asserts.assert(n !== undefined);
    goog.asserts.assert(i !== undefined);
    return n.children[i];
}

function REQ (n, type) {
    goog.asserts.assert(n.type === type, "node wasn't expected type");
}

function strobj (s) {
    goog.asserts.assert(typeof s === "string", "expecting string, got " + (typeof s));
    return new Sk.builtin.str(s);
}

/** @return {number} */
function numStmts (n) {
    var ch;
    var i;
    var cnt;
    switch (n.type) {
        case SYM.single_input:
            if (CHILD(n, 0).type === TOK.T_NEWLINE) {
                return 0;
            }
            else {
                return numStmts(CHILD(n, 0));
            }
        case SYM.file_input:
            cnt = 0;
            for (i = 0; i < NCH(n); ++i) {
                ch = CHILD(n, i);
                if (ch.type === SYM.stmt) {
                    cnt += numStmts(ch);
                }
            }
            return cnt;
        case SYM.stmt:
            return numStmts(CHILD(n, 0));
        case SYM.compound_stmt:
            return 1;
        case SYM.simple_stmt:
            return Math.floor(NCH(n) / 2); // div 2 is to remove count of ;s
        case SYM.suite:
            if (NCH(n) === 1) {
                return numStmts(CHILD(n, 0));
            }
            else {
                cnt = 0;
                for (i = 2; i < NCH(n) - 1; ++i) {
                    cnt += numStmts(CHILD(n, i));
                }
                return cnt;
            }
            break;
        default:
            goog.asserts.fail("Non-statement found");
    }
    return 0;
}

function forbiddenCheck (c, n, x, lineno) {
    if (x === "None") {
        throw new Sk.builtin.SyntaxError("assignment to None", c.c_filename, lineno);
    }
    if (x === "True" || x === "False") {
        throw new Sk.builtin.SyntaxError("assignment to True or False is forbidden", c.c_filename, lineno);
    }
}

/**
 * Set the context ctx for e, recursively traversing e.
 *
 * Only sets context for expr kinds that can appear in assignment context as
 * per the asdl file.
 */
function setContext (c, e, ctx, n) {
    var i;
    var exprName;
    var s;
    goog.asserts.assert(ctx !== AugStore && ctx !== AugLoad);
    s = null;
    exprName = null;

    switch (e.constructor) {
        case Attribute:
        case Name:
            if (ctx === Store) {
                forbiddenCheck(c, n, e.attr, n.lineno);
            }
            e.ctx = ctx;
            break;
        case Subscript:
            e.ctx = ctx;
            break;
        case List:
            e.ctx = ctx;
            s = e.elts;
            break;
        case Tuple:
            if (e.elts.length === 0) {
                throw new Sk.builtin.SyntaxError("can't assign to ()", c.c_filename, n.lineno);
            }
            e.ctx = ctx;
            s = e.elts;
            break;
        case Lambda:
            exprName = "lambda";
            break;
        case Call:
            exprName = "function call";
            break;
        case BoolOp:
        case BinOp:
        case UnaryOp:
            exprName = "operator";
            break;
        case GeneratorExp:
            exprName = "generator expression";
            break;
        case Yield:
            exprName = "yield expression";
            break;
        case ListComp:
            exprName = "list comprehension";
            break;
        case SetComp:
            exprName = "set comprehension";
            break;
        case DictComp:
            exprName = "dict comprehension";
            break;
        case Dict:
        case Set:
        case Num:
        case Str:
            exprName = "literal";
            break;
        case Compare:
            exprName = "comparison";
            break;
        case Repr:
            exprName = "repr";
            break;
        case IfExp:
            exprName = "conditional expression";
            break;
        default:
            goog.asserts.fail("unhandled expression in assignment");
    }
    if (exprName) {
        throw new Sk.builtin.SyntaxError("can't " + (ctx === Store ? "assign to" : "delete") + " " + exprName, c.c_filename, n.lineno);
    }

    if (s) {
        for (i = 0; i < s.length; ++i) {
            setContext(c, s[i], ctx, n);
        }
    }
}

var operatorMap = {};
(function () {
    operatorMap[TOK.T_VBAR] = BitOr;
    operatorMap[TOK.T_CIRCUMFLEX] = BitXor;
    operatorMap[TOK.T_AMPER] = BitAnd;
    operatorMap[TOK.T_LEFTSHIFT] = LShift;
    operatorMap[TOK.T_RIGHTSHIFT] = RShift;
    operatorMap[TOK.T_PLUS] = Add;
    operatorMap[TOK.T_MINUS] = Sub;
    operatorMap[TOK.T_STAR] = Mult;
    operatorMap[TOK.T_SLASH] = Div;
    operatorMap[TOK.T_DOUBLESLASH] = FloorDiv;
    operatorMap[TOK.T_PERCENT] = Mod;
}());

function getOperator (n) {
    goog.asserts.assert(operatorMap[n.type] !== undefined);
    return operatorMap[n.type];
}

function astForCompOp (c, n) {
    /* comp_op: '<'|'>'|'=='|'>='|'<='|'<>'|'!='|'in'|'not' 'in'|'is'
     |'is' 'not'
     */
    REQ(n, SYM.comp_op);
    if (NCH(n) === 1) {
        n = CHILD(n, 0);
        switch (n.type) {
            case TOK.T_LESS:
                return Lt;
            case TOK.T_GREATER:
                return Gt;
            case TOK.T_EQEQUAL:
                return Eq;
            case TOK.T_LESSEQUAL:
                return LtE;
            case TOK.T_GREATEREQUAL:
                return GtE;
            case TOK.T_NOTEQUAL:
                return NotEq;
            case TOK.T_NAME:
                if (n.value === "in") {
                    return In_;
                }
                if (n.value === "is") {
                    return Is;
                }
        }
    }
    else if (NCH(n) === 2) {
        if (CHILD(n, 0).type === TOK.T_NAME) {
            if (CHILD(n, 1).value === "in") {
                return NotIn;
            }
            if (CHILD(n, 0).value === "is") {
                return IsNot;
            }
        }
    }
    goog.asserts.fail("invalid comp_op");
}

function seqForTestlist (c, n) {
    /* testlist: test (',' test)* [','] */
    var i;
    var seq = [];
    goog.asserts.assert(n.type === SYM.testlist ||
        n.type === SYM.listmaker ||
        n.type === SYM.testlist_comp ||
        n.type === SYM.testlist_safe ||
        n.type === SYM.testlist1);
    for (i = 0; i < NCH(n); i += 2) {
        goog.asserts.assert(CHILD(n, i).type === SYM.test || CHILD(n, i).type === SYM.old_test);
        seq[i / 2] = astForExpr(c, CHILD(n, i));
    }
    return seq;
}

function astForSuite (c, n) {
    /* suite: simple_stmt | NEWLINE INDENT stmt+ DEDENT */
    var j;
    var num;
    var i;
    var end;
    var ch;
    var pos;
    var seq;
    REQ(n, SYM.suite);
    seq = [];
    pos = 0;
    if (CHILD(n, 0).type === SYM.simple_stmt) {
        n = CHILD(n, 0);
        /* simple_stmt always ends with an NEWLINE and may have a trailing
         * SEMI. */
        end = NCH(n) - 1;
        if (CHILD(n, end - 1).type === TOK.T_SEMI) {
            end -= 1;
        }
        for (i = 0; i < end; i += 2) // by 2 to skip ;
        {
            seq[pos++] = astForStmt(c, CHILD(n, i));
        }
    }
    else {
        for (i = 2; i < NCH(n) - 1; ++i) {
            ch = CHILD(n, i);
            REQ(ch, SYM.stmt);
            num = numStmts(ch);
            if (num === 1) {
                // small_stmt or compound_stmt w/ only 1 child
                seq[pos++] = astForStmt(c, ch);
            }
            else {
                ch = CHILD(ch, 0);
                REQ(ch, SYM.simple_stmt);
                for (j = 0; j < NCH(ch); j += 2) {
                    if (NCH(CHILD(ch, j)) === 0) {
                        goog.asserts.assert(j + 1 === NCH(ch));
                        break;
                    }
                    seq[pos++] = astForStmt(c, CHILD(ch, j));
                }
            }
        }
    }
    goog.asserts.assert(pos === numStmts(n));
    return seq;
}

function astForExceptClause (c, exc, body) {
    /* except_clause: 'except' [test [(',' | 'as') test]] */
    var e;
    REQ(exc, SYM.except_clause);
    REQ(body, SYM.suite);
    if (NCH(exc) === 1) {
        return new ExceptHandler(null, null, astForSuite(c, body), exc.lineno, exc.col_offset, exc.endlineno, exc.col_endoffset);
    }
    else if (NCH(exc) === 2) {
        return new ExceptHandler(astForExpr(c, CHILD(exc, 1)), null, astForSuite(c, body), exc.lineno, exc.col_offset, exc.endlineno, exc.col_endoffset);
    }
    else if (NCH(exc) === 4) {
        e = astForExpr(c, CHILD(exc, 3));
        setContext(c, e, Store, CHILD(exc, 3));
        return new ExceptHandler(astForExpr(c, CHILD(exc, 1)), e, astForSuite(c, body), exc.lineno, exc.col_offset, exc.endlineno, exc.col_endoffset);
    }
    goog.asserts.fail("wrong number of children for except clause");
}

function astForTryStmt (c, n) {
    var exceptSt;
    var i;
    var handlers;
    var nc = NCH(n);
    var nexcept = (nc - 3) / 3;
    var body, orelse = [],
        finally_ = null;

    REQ(n, SYM.try_stmt);
    body = astForSuite(c, CHILD(n, 2));
    if (CHILD(n, nc - 3).type === TOK.T_NAME) {
        if (CHILD(n, nc - 3).value === "finally") {
            if (nc >= 9 && CHILD(n, nc - 6).type === TOK.T_NAME) {
                /* we can assume it's an "else",
                 because nc >= 9 for try-else-finally and
                 it would otherwise have a type of except_clause */
                orelse = astForSuite(c, CHILD(n, nc - 4));
                nexcept--;
            }

            finally_ = astForSuite(c, CHILD(n, nc - 1));
            nexcept--;
        }
        else {
            /* we can assume it's an "else",
             otherwise it would have a type of except_clause */
            orelse = astForSuite(c, CHILD(n, nc - 1));
            nexcept--;
        }
    }
    else if (CHILD(n, nc - 3).type !== SYM.except_clause) {
        throw new Sk.builtin.SyntaxError("malformed 'try' statement", c.c_filename, n.lineno);
    }

    if (nexcept > 0) {
        handlers = [];
        for (i = 0; i < nexcept; ++i) {
            handlers[i] = astForExceptClause(c, CHILD(n, 3 + i * 3), CHILD(n, 5 + i * 3));
        }
        exceptSt = new TryExcept(body, handlers, orelse, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);

        if (!finally_) {
            return exceptSt;
        }

        /* if a 'finally' is present too, we nest the TryExcept within a
         TryFinally to emulate try ... except ... finally */
        body = [exceptSt];
    }

    goog.asserts.assert(finally_ !== null);
    return new TryFinally(body, finally_, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
}


function astForDottedName (c, n) {
    var i;
    var e;
    var id;
    var col_offset;
    var lineno;
    REQ(n, SYM.dotted_name);
    lineno = n.lineno;
    col_offset = n.col_offset;
    id = strobj(CHILD(n, 0).value);
    e = new Name(id, Load, lineno, col_offset, n.endlineno, n.col_endoffset);
    for (i = 2; i < NCH(n); i += 2) {
        id = strobj(CHILD(n, i).value);
        e = new Attribute(e, id, Load, lineno, col_offset, n.endlineno, n.col_endoffset);
    }
    return e;
}

function astForDecorator (c, n) {
    /* decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE */
    var nameExpr;
    REQ(n, SYM.decorator);
    REQ(CHILD(n, 0), TOK.T_AT);
    REQ(CHILD(n, NCH(n) - 1), TOK.T_NEWLINE);
    nameExpr = astForDottedName(c, CHILD(n, 1));
    if (NCH(n) === 3) // no args
    {
        return nameExpr;
    }
    else if (NCH(n) === 5) // call with no args
    {
        return new Call(nameExpr, [], [], null, null, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }
    else {
        return astForCall(c, CHILD(n, 3), nameExpr);
    }
}

function astForDecorators (c, n) {
    var i;
    var decoratorSeq;
    REQ(n, SYM.decorators);
    decoratorSeq = [];
    for (i = 0; i < NCH(n); ++i) {
        decoratorSeq[i] = astForDecorator(c, CHILD(n, i));
    }
    return decoratorSeq;
}

function astForDecorated (c, n) {
    var thing;
    var decoratorSeq;
    REQ(n, SYM.decorated);
    decoratorSeq = astForDecorators(c, CHILD(n, 0));
    goog.asserts.assert(CHILD(n, 1).type === SYM.funcdef || CHILD(n, 1).type === SYM.classdef);

    thing = null;
    if (CHILD(n, 1).type === SYM.funcdef) {
        thing = astForFuncdef(c, CHILD(n, 1), decoratorSeq);
    }
    else if (CHILD(n, 1) === SYM.classdef) {
        thing = astForClassdef(c, CHILD(n, 1), decoratorSeq);
    }
    if (thing) {
        thing.lineno = n.lineno;
        thing.col_offset = n.col_offset;
        thing.endlineno = n.endlineno;
        thing.col_endoffset = n.col_endoffset
    }
    return thing;
}

/* with_item: test ['as' expr] */
function astForWithItem (c, n, content) {
    var expr_ty, context_expr, optional_vars;
    REQ(n, SYM.with_item);
    context_expr = astForExpr(c, CHILD(n, 0));
    if (NCH(n) == 3) {
        optional_vars = astForExpr(c, CHILD(n, 2));
        setContext(c, optional_vars, Store, n);
    }

    return new With_(context_expr, optional_vars, content, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
}

function astForWithStmt (c, n) {
        /* with_stmt: 'with' with_item (',' with_item)* ':' suite */
    var i;
    var ret
    var inner;

    REQ(n, SYM.with_stmt)

    /* process the with items inside-out */
    i = NCH(n) -1 
    /* the suite of the innermost with item is the suite of the with stmt */
    inner = astForSuite(c, CHILD(n,i));

    while (true) {
        i-=2;
        ret = astForWithItem(c, CHILD(n, i), inner)
        /* was this the last item? */
        if (i == 1) {
            break;
        }

        inner = [ret];
    } 

    return ret
}

function astForExecStmt (c, n) {
    var expr1, globals = null, locals = null;
    var nchildren = NCH(n);
    goog.asserts.assert(nchildren === 2 || nchildren === 4 || nchildren === 6);

    /* exec_stmt: 'exec' expr ['in' test [',' test]] */
    REQ(n, SYM.exec_stmt);
    expr1 = astForExpr(c, CHILD(n, 1));
    if (nchildren >= 4) {
        globals = astForExpr(c, CHILD(n, 3));
    }
    if (nchildren === 6) {
        locals = astForExpr(c, CHILD(n, 5));
    }
    return new Exec(expr1, globals, locals, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
}

function astForIfStmt (c, n) {
    /* if_stmt: 'if' test ':' suite ('elif' test ':' suite)*
     ['else' ':' suite]
     */
    var off;
    var i;
    var orelse;
    var hasElse;
    var nElif;
    var decider;
    var s;
    REQ(n, SYM.if_stmt);
    if (NCH(n) === 4) {
        return new If_(
            astForExpr(c, CHILD(n, 1)),
            astForSuite(c, CHILD(n, 3)),
            [], n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }

    s = CHILD(n, 4).value;
    decider = s.charAt(2); // elSe or elIf
    if (decider === "s") {
        return new If_(
            astForExpr(c, CHILD(n, 1)),
            astForSuite(c, CHILD(n, 3)),
            astForSuite(c, CHILD(n, 6)),
            n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }
    else if (decider === "i") {
        nElif = NCH(n) - 4;
        hasElse = false;
        orelse = [];

        /* must reference the child nElif+1 since 'else' token is third, not
         * fourth child from the end. */
        if (CHILD(n, nElif + 1).type === TOK.T_NAME &&
            CHILD(n, nElif + 1).value.charAt(2) === "s") {
            hasElse = true;
            nElif -= 3;
        }
        nElif /= 4;

        if (hasElse) {
            orelse = [
                new If_(
                    astForExpr(c, CHILD(n, NCH(n) - 6)),
                    astForSuite(c, CHILD(n, NCH(n) - 4)),
                    astForSuite(c, CHILD(n, NCH(n) - 1)),
                    CHILD(n, NCH(n) - 6).lineno,
                    CHILD(n, NCH(n) - 6).col_offset,
                    CHILD(n, NCH(n) - 6).endlineno, 
                    CHILD(n, NCH(n) - 6).col_endoffset)];
            nElif--;
        }

        for (i = 0; i < nElif; ++i) {
            off = 5 + (nElif - i - 1) * 4;
            orelse = [
                new If_(
                    astForExpr(c, CHILD(n, off)),
                    astForSuite(c, CHILD(n, off + 2)),
                    orelse,
                    CHILD(n, off).lineno,
                    CHILD(n, off).col_offset,
                    CHILD(n, NCH(n) - 6).endlineno, 
                    CHILD(n, NCH(n) - 6).col_endoffset)];
        }
        return new If_(
            astForExpr(c, CHILD(n, 1)),
            astForSuite(c, CHILD(n, 3)),
            orelse, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }

    goog.asserts.fail("unexpected token in 'if' statement");
}

function astForExprlist (c, n, context) {
    var e;
    var i;
    var seq;
    REQ(n, SYM.exprlist);
    seq = [];
    for (i = 0; i < NCH(n); i += 2) {
        e = astForExpr(c, CHILD(n, i));
        seq[i / 2] = e;
        if (context) {
            setContext(c, e, context, CHILD(n, i));
        }
    }
    return seq;
}

function astForDelStmt (c, n) {
    /* del_stmt: 'del' exprlist */
    REQ(n, SYM.del_stmt);
    return new Delete_(astForExprlist(c, CHILD(n, 1), Del), n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
}

function astForGlobalStmt (c, n) {
    /* global_stmt: 'global' NAME (',' NAME)* */
    var i;
    var s = [];
    REQ(n, SYM.global_stmt);
    for (i = 1; i < NCH(n); i += 2) {
        s[(i - 1) / 2] = strobj(CHILD(n, i).value);
    }
    return new Global(s, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
}

function astForAssertStmt (c, n) {
    /* assert_stmt: 'assert' test [',' test] */
    REQ(n, SYM.assert_stmt);
    if (NCH(n) === 2) {
        return new Assert(astForExpr(c, CHILD(n, 1)), null, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }
    else if (NCH(n) === 4) {
        return new Assert(astForExpr(c, CHILD(n, 1)), astForExpr(c, CHILD(n, 3)), n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }
    goog.asserts.fail("improper number of parts to assert stmt");
}

function aliasForImportName (c, n) {
    /*
     import_as_name: NAME ['as' NAME]
     dotted_as_name: dotted_name ['as' NAME]
     dotted_name: NAME ('.' NAME)*
     */

    var i;
    var a;
    var name;
    var str;
    loop: while (true) {
        switch (n.type) {
            case SYM.import_as_name:
                str = null;
                name = strobj(CHILD(n, 0).value);
                if (NCH(n) === 3) {
                    str = CHILD(n, 2).value;
                }
                return new alias(name, str == null ? null : strobj(str));
            case SYM.dotted_as_name:
                if (NCH(n) === 1) {
                    n = CHILD(n, 0);
                    continue loop;
                }
                else {
                    a = aliasForImportName(c, CHILD(n, 0));
                    goog.asserts.assert(!a.asname);
                    a.asname = strobj(CHILD(n, 2).value);
                    return a;
                }
                break;
            case SYM.dotted_name:
                if (NCH(n) === 1) {
                    return new alias(strobj(CHILD(n, 0).value), null);
                }
                else {
                    // create a string of the form a.b.c
                    str = "";
                    for (i = 0; i < NCH(n); i += 2) {
                        str += CHILD(n, i).value + ".";
                    }
                    return new alias(strobj(str.substr(0, str.length - 1)), null);
                }
                break;
            case TOK.T_STAR:
                return new alias(strobj("*"), null);
            default:
                throw new Sk.builtin.SyntaxError("unexpected import name", c.c_filename, n.lineno);
        }
        break;
    }
}

function astForImportStmt (c, n) {
    /*
     import_stmt: import_name | import_from
     import_name: 'import' dotted_as_names
     import_from: 'from' ('.'* dotted_name | '.') 'import'
     ('*' | '(' import_as_names ')' | import_as_names)
     */
    var modname;
    var idx;
    var nchildren;
    var ndots;
    var mod;
    var i;
    var aliases;
    var col_offset;
    var lineno;
    REQ(n, SYM.import_stmt);
    lineno = n.lineno;
    col_offset = n.col_offset;
    var endlineno = n.endlineno;
    var col_endoffset = n.col_endoffset;
    n = CHILD(n, 0);
    if (n.type === SYM.import_name) {
        n = CHILD(n, 1);
        REQ(n, SYM.dotted_as_names);
        aliases = [];
        for (i = 0; i < NCH(n); i += 2) {
            aliases[i / 2] = aliasForImportName(c, CHILD(n, i));
        }
        return new Import_(aliases, lineno, col_offset, endlineno, col_endoffset);
    }
    else if (n.type === SYM.import_from) {
        mod = null;
        ndots = 0;

        for (idx = 1; idx < NCH(n); ++idx) {
            if (CHILD(n, idx).type === SYM.dotted_name) {
                mod = aliasForImportName(c, CHILD(n, idx));
                idx++;
                break;
            }
            else if (CHILD(n, idx).type !== TOK.T_DOT) {
                break;
            }
            ndots++;
        }
        ++idx; // skip the import keyword
        switch (CHILD(n, idx).type) {
            case TOK.T_STAR:
                // from ... import
                n = CHILD(n, idx);
                nchildren = 1;
                break;
            case TOK.T_LPAR:
                // from ... import (x, y, z)
                n = CHILD(n, idx + 1);
                nchildren = NCH(n);
                break;
            case SYM.import_as_names:
                // from ... import x, y, z
                n = CHILD(n, idx);
                nchildren = NCH(n);
                if (nchildren % 2 === 0) {
                    throw new Sk.builtin.SyntaxError("trailing comma not allowed without surrounding parentheses", c.c_filename, n.lineno);
                }
                break;
            default:
                throw new Sk.builtin.SyntaxError("Unexpected node-type in from-import", c.c_filename, n.lineno);
        }
        aliases = [];
        if (n.type === TOK.T_STAR) {
            aliases[0] = aliasForImportName(c, n);
        }
        else {
            for (i = 0; i < NCH(n); i += 2) {
                aliases[i / 2] = aliasForImportName(c, CHILD(n, i));
            }
        }
        modname = mod ? mod.name.v : "";
        return new ImportFrom(strobj(modname), aliases, ndots, lineno, col_offset, endlineno, col_endoffset);
    }
    throw new Sk.builtin.SyntaxError("unknown import statement", c.c_filename, n.lineno);
}

function astForTestlistComp(c, n) {
    /* testlist_comp: test ( comp_for | (',' test)* [','] ) */
    /* argument: test [comp_for] */
    goog.asserts.assert(n.type === SYM.testlist_comp || n.type === SYM.argument);
    if (NCH(n) > 1 && CHILD(n, 1).type === SYM.comp_for) {
        return astForGenExpr(c, n);
    }
    return astForTestlist(c, n);
}

function astForListcomp (c, n) {
    /* listmaker: test ( list_for | (',' test)* [','] )
     list_for: 'for' exprlist 'in' testlist_safe [list_iter]
     list_iter: list_for | list_if
     list_if: 'if' test [list_iter]
     testlist_safe: test [(',' test)+ [',']]
     */

    function countListFors (c, n) {
        var nfors = 0;
        var ch = CHILD(n, 1);
        count_list_for: while (true) {
            nfors++;
            REQ(ch, SYM.list_for);
            if (NCH(ch) === 5) {
                ch = CHILD(ch, 4);
            }
            else {
                return nfors;
            }
            count_list_iter: while (true) {
                REQ(ch, SYM.list_iter);
                ch = CHILD(ch, 0);
                if (ch.type === SYM.list_for) {
                    continue count_list_for;
                }
                else if (ch.type === SYM.list_if) {
                    if (NCH(ch) === 3) {
                        ch = CHILD(ch, 2);
                        continue count_list_iter;
                    }
                    else {
                        return nfors;
                    }
                }
                break;
            }
            break;
        }
    }

    function countListIfs (c, n) {
        var nifs = 0;
        while (true) {
            REQ(n, SYM.list_iter);
            if (CHILD(n, 0).type === SYM.list_for) {
                return nifs;
            }
            n = CHILD(n, 0);
            REQ(n, SYM.list_if);
            nifs++;
            if (NCH(n) == 2) {
                return nifs;
            }
            n = CHILD(n, 2);
        }
    }

    var j;
    var ifs;
    var nifs;
    var lc;
    var expression;
    var t;
    var forch;
    var i;
    var ch;
    var listcomps;
    var nfors;
    var elt;
    REQ(n, SYM.listmaker);
    goog.asserts.assert(NCH(n) > 1);
    elt = astForExpr(c, CHILD(n, 0));
    nfors = countListFors(c, n);
    listcomps = [];
    ch = CHILD(n, 1);
    for (i = 0; i < nfors; ++i) {
        REQ(ch, SYM.list_for);
        forch = CHILD(ch, 1);
        t = astForExprlist(c, forch, Store);
        expression = astForTestlist(c, CHILD(ch, 3));
        if (NCH(forch) === 1) {
            lc = new comprehension(t[0], expression, []);
        }
        else {
            lc = new comprehension(new Tuple(t, Store, ch.lineno, ch.col_offset, ch.endlineno, ch.col_endoffset), expression, []);
        }

        if (NCH(ch) === 5) {
            ch = CHILD(ch, 4);
            nifs = countListIfs(c, ch);
            ifs = [];
            for (j = 0; j < nifs; ++j) {
                REQ(ch, SYM.list_iter);
                ch = CHILD(ch, 0);
                REQ(ch, SYM.list_if);
                ifs[j] = astForExpr(c, CHILD(ch, 1));
                if (NCH(ch) === 3) {
                    ch = CHILD(ch, 2);
                }
            }
            if (ch.type === SYM.list_iter) {
                ch = CHILD(ch, 0);
            }
            lc.ifs = ifs;
        }
        listcomps[i] = lc;
    }
    return new ListComp(elt, listcomps, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
}

function astForFactor (c, n) {
    /* some random peephole thing that cpy does */
    var expression;
    var pnum;
    var patom;
    var ppower;
    var pfactor;
    if (CHILD(n, 0).type === TOK.T_MINUS && NCH(n) === 2) {
        pfactor = CHILD(n, 1);
        if (pfactor.type === SYM.factor && NCH(pfactor) === 1) {
            ppower = CHILD(pfactor, 0);
            if (ppower.type === SYM.power && NCH(ppower) === 1) {
                patom = CHILD(ppower, 0);
                if (patom.type === SYM.atom) {
                    pnum = CHILD(patom, 0);
                    if (pnum.type === TOK.T_NUMBER) {
                        pnum.value = "-" + pnum.value;
                        return astForAtom(c, patom);
                    }
                }
            }
        }
    }

    expression = astForExpr(c, CHILD(n, 1));
    switch (CHILD(n, 0).type) {
        case TOK.T_PLUS:
            return new UnaryOp(UAdd, expression, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
        case TOK.T_MINUS:
            return new UnaryOp(USub, expression, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
        case TOK.T_TILDE:
            return new UnaryOp(Invert, expression, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }

    goog.asserts.fail("unhandled factor");
}

function astForForStmt (c, n) {
    /* for_stmt: 'for' exprlist 'in' testlist ':' suite ['else' ':' suite] */
    var target;
    var _target;
    var nodeTarget;
    var seq = [];
    REQ(n, SYM.for_stmt);
    if (NCH(n) === 9) {
        seq = astForSuite(c, CHILD(n, 8));
    }
    nodeTarget = CHILD(n, 1);
    _target = astForExprlist(c, nodeTarget, Store);
    if (NCH(nodeTarget) === 1) {
        target = _target[0];
    }
    else {
        target = new Tuple(_target, Store, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }

    return new For_(target,
        astForTestlist(c, CHILD(n, 3)),
        astForSuite(c, CHILD(n, 5)),
        seq, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
}

function astForCall (c, n, func) {
    /*
      arglist: (argument ',')* (argument [',']| '*' test [',' '**' test]
               | '**' test)
      argument: test [comp_for] | test '=' test       # Really [keyword '='] test
    */
    var tmp;
    var k;
    var key;
    var e;
    var kwarg;
    var vararg;
    var keywords;
    var args;
    var ch;
    var i;
    var ngens;
    var nkeywords;
    var nargs;

    REQ(n, SYM.arglist);
    nargs = 0;
    nkeywords = 0;
    ngens = 0;
    for (i = 0; i < NCH(n); i++) {
        ch = CHILD(n, i);
        if (ch.type === SYM.argument) {
            if (NCH(ch) === 1) {
                nargs++;
            }
            else if (CHILD(ch, 1).type === SYM.comp_for) {
                ngens++;
            }
            else {
                nkeywords++;
            }
        }
    }
    if (ngens > 1 || (ngens && (nargs || nkeywords))) {
        throw new Sk.builtin.SyntaxError("Generator expression must be parenthesized if not sole argument", c.c_filename, n.lineno);
    }
    if (nargs + nkeywords + ngens > 255) {
        throw new Sk.builtin.SyntaxError("more than 255 arguments", c.c_filename, n.lineno);
    }
    args = [];
    keywords = [];
    nargs = 0;
    nkeywords = 0;
    vararg = null;
    kwarg = null;
    for (i = 0; i < NCH(n); i++) {
        ch = CHILD(n, i);
        if (ch.type === SYM.argument) {
            if (NCH(ch) === 1) {
                if (nkeywords) {
                    throw new Sk.builtin.SyntaxError("non-keyword arg after keyword arg", c.c_filename, n.lineno);
                }
                if (vararg) {
                    throw new Sk.builtin.SyntaxError("only named arguments may follow *expression", c.c_filename, n.lineno);
                }
                args[nargs++] = astForExpr(c, CHILD(ch, 0));
            }
            else if (CHILD(ch, 1).type === SYM.comp_for) {
                args[nargs++] = astForGenExpr(c, ch);
            }
            else {
                e = astForExpr(c, CHILD(ch, 0));
                if (e.constructor === Lambda) {
                    throw new Sk.builtin.SyntaxError("lambda cannot contain assignment", c.c_filename, n.lineno);
                }
                else if (e.constructor !== Name) {
                    throw new Sk.builtin.SyntaxError("keyword can't be an expression", c.c_filename, n.lineno);
                }
                key = e.id;
                forbiddenCheck(c, CHILD(ch, 0), key, n.lineno);
                for (k = 0; k < nkeywords; ++k) {
                    tmp = keywords[k].arg;
                    if (tmp === key) {
                        throw new Sk.builtin.SyntaxError("keyword argument repeated", c.c_filename, n.lineno);
                    }
                }
                keywords[nkeywords++] = new keyword(key, astForExpr(c, CHILD(ch, 2)));
            }
        }
        else if (ch.type === TOK.T_STAR) {
            vararg = astForExpr(c, CHILD(n, ++i));
        }
        else if (ch.type === TOK.T_DOUBLESTAR) {
            kwarg = astForExpr(c, CHILD(n, ++i));
        }
    }
    return new Call(func, args, keywords, vararg, kwarg, func.lineno, func.col_offset, func.endlineno, func.col_endoffset);
}

function astForTrailer (c, n, leftExpr) {
    /* trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME 
     subscriptlist: subscript (',' subscript)* [',']
     subscript: '.' '.' '.' | test | [test] ':' [test] [sliceop]
     */
    var e;
    var elts;
    var slc;
    var j;
    var slices;
    var simple;
    REQ(n, SYM.trailer);
    if (CHILD(n, 0).type === TOK.T_LPAR) {
        if (NCH(n) === 2) {
            return new Call(leftExpr, [], [], null, null, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
        }
        else {
            return astForCall(c, CHILD(n, 1), leftExpr);
        }
    }
    else if (CHILD(n, 0).type === TOK.T_DOT) {
        return new Attribute(leftExpr, strobj(CHILD(n, 1).value), Load, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }
    else {
        REQ(CHILD(n, 0), TOK.T_LSQB);
        REQ(CHILD(n, 2), TOK.T_RSQB);
        n = CHILD(n, 1);
        if (NCH(n) === 1) {
            return new Subscript(leftExpr, astForSlice(c, CHILD(n, 0)), Load, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
        }
        else {
            /* The grammar is ambiguous here. The ambiguity is resolved 
             by treating the sequence as a tuple literal if there are
             no slice features.
             */
            simple = true;
            slices = [];
            for (j = 0; j < NCH(n); j += 2) {
                slc = astForSlice(c, CHILD(n, j));
                if (slc.constructor !== Index) {
                    simple = false;
                }
                slices[j / 2] = slc;
            }
            if (!simple) {
                return new Subscript(leftExpr, new ExtSlice(slices), Load, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            }
            elts = [];
            for (j = 0; j < slices.length; ++j) {
                slc = slices[j];
                goog.asserts.assert(slc.constructor === Index && slc.value !== null && slc.value !== undefined);
                elts[j] = slc.value;
            }
            e = new Tuple(elts, Load, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            return new Subscript(leftExpr, new Index(e), Load, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
        }
    }
}

function astForFlowStmt (c, n) {
    /*
     flow_stmt: break_stmt | continue_stmt | return_stmt | raise_stmt
     | yield_stmt
     break_stmt: 'break'
     continue_stmt: 'continue'
     return_stmt: 'return' [testlist]
     yield_stmt: yield_expr
     yield_expr: 'yield' testlist
     raise_stmt: 'raise' [test [',' test [',' test]]]
     */
    var ch;
    REQ(n, SYM.flow_stmt);
    ch = CHILD(n, 0);
    switch (ch.type) {
        case SYM.break_stmt:
            return new Break_(n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
        case SYM.continue_stmt:
            return new Continue_(n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
        case SYM.yield_stmt:
            return new Expr(astForExpr(c, CHILD(ch, 0)), n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
        case SYM.return_stmt:
            if (NCH(ch) === 1) {
                return new Return_(null, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            }
            else {
                return new Return_(astForTestlist(c, CHILD(ch, 1)), n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            }
            break;
        case SYM.raise_stmt:
            if (NCH(ch) === 1) {
                return new Raise(null, null, null, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            }
            else if (NCH(ch) === 2) {
                return new Raise(astForExpr(c, CHILD(ch, 1)), null, null, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            }
            else if (NCH(ch) === 4) {
                return new Raise(
                    astForExpr(c, CHILD(ch, 1)),
                    astForExpr(c, CHILD(ch, 3)),
                    null, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            }
            else if (NCH(ch) === 6) {
                return new Raise(
                    astForExpr(c, CHILD(ch, 1)),
                    astForExpr(c, CHILD(ch, 3)),
                    astForExpr(c, CHILD(ch, 5)),
                    n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            }
            break;
        default:
            goog.asserts.fail("unexpected flow_stmt");
    }
    goog.asserts.fail("unhandled flow statement");
}

function astForArguments (c, n) {
    /* parameters: '(' [varargslist] ')'
     varargslist: (fpdef ['=' test] ',')* ('*' NAME [',' '**' NAME]
     | '**' NAME) | fpdef ['=' test] (',' fpdef ['=' test])* [',']
     */
    var parenthesized;
    var id;
    var complexArgs;
    var k;
    var j;
    var i;
    var foundDefault;
    var defaults;
    var args;
    var ch;
    var vararg = null;
    var kwarg = null;
    if (n.type === SYM.parameters) {
        if (NCH(n) === 2) // () as arglist
        {
            return new arguments_([], null, null, []);
        }
        n = CHILD(n, 1);
    }
    REQ(n, SYM.varargslist);

    args = [];
    defaults = [];

    /* fpdef: NAME | '(' fplist ')'
     fplist: fpdef (',' fpdef)* [',']
     */
    foundDefault = false;
    i = 0;
    j = 0; // index for defaults
    k = 0; // index for args
    while (i < NCH(n)) {
        ch = CHILD(n, i);
        switch (ch.type) {
            case SYM.fpdef:
                complexArgs = 0;
                parenthesized = 0;
                handle_fpdef: while (true) {
                    if (i + 1 < NCH(n) && CHILD(n, i + 1).type === TOK.T_EQUAL) {
                        defaults[j++] = astForExpr(c, CHILD(n, i + 2));
                        i += 2;
                        foundDefault = true;
                    }
                    else if (foundDefault) {
                        /* def f((x)=4): pass should raise an error.
                         def f((x, (y))): pass will just incur the tuple unpacking warning. */
                        if (parenthesized && !complexArgs) {
                            throw new Sk.builtin.SyntaxError("parenthesized arg with default", c.c_filename, n.lineno);
                        }
                        throw new Sk.builtin.SyntaxError("non-default argument follows default argument", c.c_filename, n.lineno);
                    }

                    if (NCH(ch) === 3) {
                        ch = CHILD(ch, 1);
                        // def foo((x)): is not complex, special case.
                        if (NCH(ch) !== 1) {
                            throw new Sk.builtin.SyntaxError("tuple parameter unpacking has been removed", c.c_filename, n.lineno);
                        }
                        else {
                            /* def foo((x)): setup for checking NAME below. */
                            /* Loop because there can be many parens and tuple
                             unpacking mixed in. */
                            parenthesized = true;
                            ch = CHILD(ch, 0);
                            goog.asserts.assert(ch.type === SYM.fpdef);
                            continue handle_fpdef;
                        }
                    }
                    if (CHILD(ch, 0).type === TOK.T_NAME) {
                        forbiddenCheck(c, n, CHILD(ch, 0).value, n.lineno);
                        id = strobj(CHILD(ch, 0).value);
                        args[k++] = new Name(id, Param, ch.lineno, ch.col_offset, n.endlineno, n.col_endoffset);
                    }
                    i += 2;
                    if (parenthesized) {
                        throw new Sk.builtin.SyntaxError("parenthesized argument names are invalid", c.c_filename, n.lineno);
                    }
                    break;
                }
                break;
            case TOK.T_STAR:
                forbiddenCheck(c, CHILD(n, i + 1), CHILD(n, i + 1).value, n.lineno);
                vararg = strobj(CHILD(n, i + 1).value);
                i += 3;
                break;
            case TOK.T_DOUBLESTAR:
                forbiddenCheck(c, CHILD(n, i + 1), CHILD(n, i + 1).value, n.lineno);
                kwarg = strobj(CHILD(n, i + 1).value);
                i += 3;
                break;
            default:
                goog.asserts.fail("unexpected node in varargslist");
        }
    }
    return new arguments_(args, vararg, kwarg, defaults);
}

function astForFuncdef (c, n, decoratorSeq) {
    /* funcdef: 'def' NAME parameters ':' suite */
    var body;
    var args;
    var name;
    REQ(n, SYM.funcdef);
    name = strobj(CHILD(n, 1).value);
    forbiddenCheck(c, CHILD(n, 1), CHILD(n, 1).value, n.lineno);
    args = astForArguments(c, CHILD(n, 2));
    body = astForSuite(c, CHILD(n, 4));
    return new FunctionDef(name, args, body, decoratorSeq, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
}

function astForClassBases (c, n) {
    /* testlist: test (',' test)* [','] */
    goog.asserts.assert(NCH(n) > 0);
    REQ(n, SYM.testlist);
    if (NCH(n) === 1) {
        return [ astForExpr(c, CHILD(n, 0)) ];
    }
    return seqForTestlist(c, n);
}

function astForClassdef (c, n, decoratorSeq) {
    /* classdef: 'class' NAME ['(' testlist ')'] ':' suite */
    var s;
    var bases;
    var classname;
    REQ(n, SYM.classdef);
    forbiddenCheck(c, n, CHILD(n, 1).value, n.lineno);
    classname = strobj(CHILD(n, 1).value);
    if (NCH(n) === 4) {
        return new ClassDef(classname, [], astForSuite(c, CHILD(n, 3)), decoratorSeq, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }
    if (CHILD(n, 3).type === TOK.T_RPAR) {
        return new ClassDef(classname, [], astForSuite(c, CHILD(n, 5)), decoratorSeq, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }

    bases = astForClassBases(c, CHILD(n, 3));
    s = astForSuite(c, CHILD(n, 6));
    return new ClassDef(classname, bases, s, decoratorSeq, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
}

function astForLambdef (c, n) {
    /* lambdef: 'lambda' [varargslist] ':' test */
    var args;
    var expression;
    if (NCH(n) === 3) {
        args = new arguments_([], null, null, []);
        expression = astForExpr(c, CHILD(n, 2));
    }
    else {
        args = astForArguments(c, CHILD(n, 1));
        expression = astForExpr(c, CHILD(n, 3));
    }
    return new Lambda(args, expression, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
}

function astForComprehension(c, n) {
    /* testlist_comp: test ( comp_for | (',' test)* [','] )
       argument: test [comp_for] | test '=' test       # Really [keyword '='] test */
    
    var j;
    var ifs;
    var nifs;
    var ge;
    var expression;
    var t;
    var forch;
    var i;
    var ch;
    var genexps;
    var nfors;
    var elt;
    var comps;
    var comp;

    function countCompFors(c, n) {
        var nfors = 0;
        count_comp_for: while (true) {
            nfors++;
            REQ(n, SYM.comp_for);
            if (NCH(n) === 5) {
                n = CHILD(n, 4);
            } else {
                return nfors;
            }
            count_comp_iter: while (true) {
                REQ(n, SYM.comp_iter);
                n = CHILD(n, 0);
                if (n.type === SYM.comp_for) {
                    continue count_comp_for;
                } else if (n.type === SYM.comp_if) {
                    if (NCH(n) === 3) {
                        n = CHILD(n, 2);
                        continue count_comp_iter;
                    } else {
                        return nfors;
                    }
                }
                break;
            }
            break;
        }
        goog.asserts.fail("logic error in countCompFors");
    }

    function countCompIfs(c, n) {
        var nifs = 0;
        while (true) {
            REQ(n, SYM.comp_iter);
            if (CHILD(n, 0).type === SYM.comp_for) {
                return nifs;
            }
            n = CHILD(n, 0);
            REQ(n, SYM.comp_if);
            nifs++;
            if (NCH(n) == 2) {
                return nifs;
            }
            n = CHILD(n, 2);
        }
    }

    nfors = countCompFors(c, n);
    comps = [];
    for (i = 0; i < nfors; ++i) {
        REQ(n, SYM.comp_for);
        forch = CHILD(n, 1);
        t = astForExprlist(c, forch, Store);
        expression = astForExpr(c, CHILD(n, 3));
        if (NCH(forch) === 1) {
            comp = new comprehension(t[0], expression, []);
        } else {
            comp = new comprehension(new Tuple(t, Store, n.lineno, n.col_offset, n.endlineno, n.col_endoffset), expression, []);
        }
        if (NCH(n) === 5) {
            n = CHILD(n, 4);
            nifs = countCompIfs(c, n);
            ifs = [];
            for (j = 0; j < nifs; ++j) {
                REQ(n, SYM.comp_iter);
                n = CHILD(n, 0);
                REQ(n, SYM.comp_if);
                expression = astForExpr(c, CHILD(n, 1));
                ifs[j] = expression;
                if (NCH(n) === 3) {
                    n = CHILD(n, 2);
                }
            }
            if (n.type === SYM.comp_iter) {
                n = CHILD(n, 0);
            }
            comp.ifs = ifs;
        }
        comps[i] = comp;
    }
    return comps;
}

function astForIterComp(c, n, type) {
    var elt, comps;
    goog.asserts.assert(NCH(n) > 1);
    elt = astForExpr(c, CHILD(n, 0));
    comps = astForComprehension(c, CHILD(n, 1));
    if (type === COMP_GENEXP) {
        return new GeneratorExp(elt, comps, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    } else if (type === COMP_SETCOMP) {
        return new SetComp(elt, comps, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }
}

function astForDictComp(c, n) {
    var key, value;
    var comps = [];
    goog.asserts.assert(NCH(n) > 3);
    REQ(CHILD(n, 1), TOK.T_COLON);
    key = astForExpr(c, CHILD(n, 0));
    value = astForExpr(c, CHILD(n, 2));
    comps = astForComprehension(c, CHILD(n, 3));
    return new DictComp(key, value, comps, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
}

function astForGenExpr(c, n) {
    goog.asserts.assert(n.type === SYM.testlist_comp || n.type === SYM.argument);
    return astForIterComp(c, n, COMP_GENEXP);
}

function astForSetComp(c, n) {
    goog.asserts.assert(n.type === SYM.dictorsetmaker);
    return astForIterComp(c, n, COMP_SETCOMP);
}

function astForWhileStmt (c, n) {
    /* while_stmt: 'while' test ':' suite ['else' ':' suite] */
    REQ(n, SYM.while_stmt);
    if (NCH(n) === 4) {
        return new While_(astForExpr(c, CHILD(n, 1)), astForSuite(c, CHILD(n, 3)), [], n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }
    else if (NCH(n) === 7) {
        return new While_(astForExpr(c, CHILD(n, 1)), astForSuite(c, CHILD(n, 3)), astForSuite(c, CHILD(n, 6)), n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }
    goog.asserts.fail("wrong number of tokens for 'while' stmt");
}

function astForAugassign (c, n) {
    REQ(n, SYM.augassign);
    n = CHILD(n, 0);
    switch (n.value.charAt(0)) {
        case "+":
            return Add;
        case "-":
            return Sub;
        case "/":
            if (n.value.charAt(1) === "/") {
                return FloorDiv;
            }
            return Div;
        case "%":
            return Mod;
        case "<":
            return LShift;
        case ">":
            return RShift;
        case "&":
            return BitAnd;
        case "^":
            return BitXor;
        case "|":
            return BitOr;
        case "*":
            if (n.value.charAt(1) === "*") {
                return Pow;
            }
            return Mult;
        default:
            goog.asserts.fail("invalid augassign");
    }
}

function astForBinop (c, n) {
    /* Must account for a sequence of expressions.
     How should A op B op C by represented?
     BinOp(BinOp(A, op, B), op, C).
     */
    var tmp;
    var newoperator;
    var nextOper;
    var i;
    var result = new BinOp(
        astForExpr(c, CHILD(n, 0)),
        getOperator(CHILD(n, 1)),
        astForExpr(c, CHILD(n, 2)),
        n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    var nops = (NCH(n) - 1) / 2;
    for (i = 1; i < nops; ++i) {
        nextOper = CHILD(n, i * 2 + 1);
        newoperator = getOperator(nextOper);
        tmp = astForExpr(c, CHILD(n, i * 2 + 2));
        result = new BinOp(result, newoperator, tmp, nextOper.lineno, nextOper.col_offset, n.endlineno, n.col_endoffset);
    }
    return result;

}


function astForTestlist(c, n) {
    /* this doesn't show up in Grammar.txt never did: testlist_gexp: test (',' test)* [','] */
    /* testlist_comp: test (',' test)* [','] */
    /* testlist: test (',' test)* [','] */
    /* testlist_safe: test (',' test)+ [','] */
    /* testlist1: test (',' test)* */
    goog.asserts.assert(NCH(n) > 0);
    if (n.type === SYM.testlist_comp) {
        if (NCH(n) > 1) {
            goog.asserts.assert(CHILD(n, 1).type !== SYM.comp_for);
        }
    }
    else {
        goog.asserts.assert(n.type === SYM.testlist || n.type === SYM.testlist_safe || n.type === SYM.testlist1);
    }

    if (NCH(n) === 1) {
        return astForExpr(c, CHILD(n, 0));
    }
    else {
        return new Tuple(seqForTestlist(c, n), Load, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }

}

function astForExprStmt (c, n) {
    var expression;
    var value;
    var e;
    var i;
    var targets;
    var expr2;
    var varName;
    var expr1;
    var ch;
    REQ(n, SYM.expr_stmt);
    /* expr_stmt: testlist (augassign (yield_expr|testlist) 
     | ('=' (yield_expr|testlist))*)
     testlist: test (',' test)* [',']
     augassign: '+=' | '-=' | '*=' | '/=' | '%=' | '&=' | '|=' | '^='
     | '<<=' | '>>=' | '**=' | '//='
     test: ... here starts the operator precendence dance
     */
    if (NCH(n) === 1) {
        return new Expr(astForTestlist(c, CHILD(n, 0)), n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }
    else if (CHILD(n, 1).type === SYM.augassign) {
        ch = CHILD(n, 0);
        expr1 = astForTestlist(c, ch);
        switch (expr1.constructor) {
            case GeneratorExp:
                throw new Sk.builtin.SyntaxError("augmented assignment to generator expression not possible", c.c_filename, n.lineno);
            case Yield:
                throw new Sk.builtin.SyntaxError("augmented assignment to yield expression not possible", c.c_filename, n.lineno);
            case Name:
                varName = expr1.id;
                forbiddenCheck(c, ch, varName, n.lineno);
                break;
            case Attribute:
            case Subscript:
                break;
            default:
                throw new Sk.builtin.SyntaxError("illegal expression for augmented assignment", c.c_filename, n.lineno);
        }
        setContext(c, expr1, Store, ch);

        ch = CHILD(n, 2);
        if (ch.type === SYM.testlist) {
            expr2 = astForTestlist(c, ch);
        }
        else {
            expr2 = astForExpr(c, ch);
        }

        return new AugAssign(expr1, astForAugassign(c, CHILD(n, 1)), expr2, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }
    else {
        // normal assignment
        REQ(CHILD(n, 1), TOK.T_EQUAL);
        targets = [];
        for (i = 0; i < NCH(n) - 2; i += 2) {
            ch = CHILD(n, i);
            if (ch.type === SYM.yield_expr) {
                throw new Sk.builtin.SyntaxError("assignment to yield expression not possible", c.c_filename, n.lineno);
            }
            e = astForTestlist(c, ch);
            setContext(c, e, Store, CHILD(n, i));
            targets[i / 2] = e;
        }
        value = CHILD(n, NCH(n) - 1);
        if (value.type === SYM.testlist) {
            expression = astForTestlist(c, value);
        }
        else {
            expression = astForExpr(c, value);
        }
        return new Assign(targets, expression, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }
}

function astForIfexpr (c, n) {
    /* test: or_test 'if' or_test 'else' test */
    goog.asserts.assert(NCH(n) === 5);
    return new IfExp(
        astForExpr(c, CHILD(n, 2)),
        astForExpr(c, CHILD(n, 0)),
        astForExpr(c, CHILD(n, 4)),
        n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
}

/**
 * s is a python-style string literal, including quote characters and u/r/b
 * prefixes. Returns decoded string object.
 */
function parsestr (c, s) {
    var encodeUtf8 = function (s) {
        return unescape(encodeURIComponent(s));
    };
    var decodeUtf8 = function (s) {
        return decodeURIComponent(escape(s));
    };
    var decodeEscape = function (s, quote) {
        var d3;
        var d2;
        var d1;
        var d0;
        var c;
        var i;
        var len = s.length;
        var ret = "";
        for (i = 0; i < len; ++i) {
            c = s.charAt(i);
            if (c === "\\") {
                ++i;
                c = s.charAt(i);
                if (c === "n") {
                    ret += "\n";
                }
                else if (c === "\\") {
                    ret += "\\";
                }
                else if (c === "t") {
                    ret += "\t";
                }
                else if (c === "r") {
                    ret += "\r";
                }
                else if (c === "b") {
                    ret += "\b";
                }
                else if (c === "f") {
                    ret += "\f";
                }
                else if (c === "v") {
                    ret += "\v";
                }
                else if (c === "0") {
                    ret += "\0";
                }
                else if (c === '"') {
                    ret += '"';
                }
                else if (c === '\'') {
                    ret += '\'';
                }
                else if (c === "\n") /* escaped newline, join lines */ {
                }
                else if (c === "x") {
                    d0 = s.charAt(++i);
                    d1 = s.charAt(++i);
                    ret += String.fromCharCode(parseInt(d0 + d1, 16));
                }
                else if (c === "u" || c === "U") {
                    d0 = s.charAt(++i);
                    d1 = s.charAt(++i);
                    d2 = s.charAt(++i);
                    d3 = s.charAt(++i);
                    ret += String.fromCharCode(parseInt(d0 + d1, 16), parseInt(d2 + d3, 16));
                }
                else {
                    // Leave it alone
                    ret += "\\" + c;
                    // goog.asserts.fail("unhandled escape: '" + c.charCodeAt(0) + "'");
                }
            }
            else {
                ret += c;
            }
        }
        return ret;
    };

    //print("parsestr", s);

    var quote = s.charAt(0);
    var rawmode = false;
    var unicode = false;

    // treats every sequence as unicodes even if they are not treated with uU prefix
    // kinda hacking though working for most purposes
    if((c.c_flags & Parser.CO_FUTURE_UNICODE_LITERALS || Sk.python3 === true)) {
        unicode = true;
    }

    if (quote === "u" || quote === "U") {
        s = s.substr(1);
        quote = s.charAt(0);
        unicode = true;
    }
    else if (quote === "r" || quote === "R") {
        s = s.substr(1);
        quote = s.charAt(0);
        rawmode = true;
    }
    goog.asserts.assert(quote !== "b" && quote !== "B", "todo; haven't done b'' strings yet");

    goog.asserts.assert(quote === "'" || quote === '"' && s.charAt(s.length - 1) === quote);
    s = s.substr(1, s.length - 2);
    if (unicode) {
        s = encodeUtf8(s);
    }

    if (s.length >= 4 && s.charAt(0) === quote && s.charAt(1) === quote) {
        goog.asserts.assert(s.charAt(s.length - 1) === quote && s.charAt(s.length - 2) === quote);
        s = s.substr(2, s.length - 4);
    }

    if (rawmode || s.indexOf("\\") === -1) {
        return strobj(decodeUtf8(s));
    }
    return strobj(decodeEscape(s, quote));
}

function parsestrplus (c, n) {
    var i;
    var ret;
    REQ(CHILD(n, 0), TOK.T_STRING);
    ret = new Sk.builtin.str("");
    for (i = 0; i < NCH(n); ++i) {
        try {
            ret = ret.sq$concat(parsestr(c, CHILD(n, i).value));
        } catch (x) {
            throw new Sk.builtin.SyntaxError("invalid string (possibly contains a unicode character)", c.c_filename, CHILD(n, i).lineno);
        }
    }
    return ret;
}

function parsenumber (c, s, lineno) {
    var neg;
    var val;
    var tmp;
    var end = s.charAt(s.length - 1);

    // call internal complex type constructor for complex strings
    if (end === "j" || end === "J") {
        return Sk.builtin.complex.complex_subtype_from_string(s);
    }

    // Handle longs
    if (end === "l" || end === "L") {
        return Sk.longFromStr(s.substr(0, s.length - 1), 0);
    }

    // todo; we don't currently distinguish between int and float so
    // str is wrong for these.
    if (s.indexOf(".") !== -1) {
        return new Sk.builtin.float_(parseFloat(s));
    }

    // Handle integers of various bases
    tmp = s;
    neg = false;
    if (s.charAt(0) === "-") {
        tmp = s.substr(1);
        neg = true;
    }

    if (tmp.charAt(0) === "0" && (tmp.charAt(1) === "x" || tmp.charAt(1) === "X")) {
        // Hex
        tmp = tmp.substring(2);
        val = parseInt(tmp, 16);
    } else if ((s.indexOf("e") !== -1) || (s.indexOf("E") !== -1)) {
        // Float with exponent (needed to make sure e/E wasn't hex first)
        return new Sk.builtin.float_(parseFloat(s));
    } else if (tmp.charAt(0) === "0" && (tmp.charAt(1) === "b" || tmp.charAt(1) === "B")) {
        // Binary
        tmp = tmp.substring(2);
        val = parseInt(tmp, 2);
    } else if (tmp.charAt(0) === "0") {
        if (tmp === "0") {
            // Zero
            val = 0;
        } else {
            // Octal
            tmp = tmp.substring(1);
            if ((tmp.charAt(0) === "o") || (tmp.charAt(0) === "O")) {
                tmp = tmp.substring(1);
            }
            val = parseInt(tmp, 8);
        }
    }
    else {
        // Decimal
        val = parseInt(tmp, 10);
    }

    // Convert to long
    if (val > Sk.builtin.int_.threshold$ &&
        Math.floor(val) === val &&
        (s.indexOf("e") === -1 && s.indexOf("E") === -1)) {
        return Sk.longFromStr(s, 0);
    }

    // Small enough, return parsed number
    if (neg) {
        return new Sk.builtin.int_(-val);
    } else {
        return new Sk.builtin.int_(val);
    }
}

function astForSlice (c, n) {
    var n2;
    var step;
    var upper;
    var lower;
    var ch;
    REQ(n, SYM.subscript);

    /*
     subscript: '.' '.' '.' | test | [test] ':' [test] [sliceop]
     sliceop: ':' [test]
     */
    ch = CHILD(n, 0);
    lower = null;
    upper = null;
    step = null;
    if (ch.type === TOK.T_DOT) {
        return new Ellipsis();
    }
    if (NCH(n) === 1 && ch.type === SYM.test) {
        return new Index(astForExpr(c, ch));
    }
    if (ch.type === SYM.test) {
        lower = astForExpr(c, ch);
    }
    if (ch.type === TOK.T_COLON) {
        if (NCH(n) > 1) {
            n2 = CHILD(n, 1);
            if (n2.type === SYM.test) {
                upper = astForExpr(c, n2);
            }
        }
    }
    else if (NCH(n) > 2) {
        n2 = CHILD(n, 2);
        if (n2.type === SYM.test) {
            upper = astForExpr(c, n2);
        }
    }

    ch = CHILD(n, NCH(n) - 1);
    if (ch.type === SYM.sliceop) {
        if (NCH(ch) === 1) {
            ch = CHILD(ch, 0);
            step = new Name(strobj("None"), Load, ch.lineno, ch.col_offset, ch.endlineno, ch.col_endoffset);
        }
        else {
            ch = CHILD(ch, 1);
            if (ch.type === SYM.test) {
                step = astForExpr(c, ch);
            }
        }
    }
    return new Slice(lower, upper, step);
}

function astForAtom(c, n) {
    /* atom: ('(' [yield_expr|testlist_comp] ')' |
       '[' [listmaker] ']' |
       '{' [dictorsetmaker] '}' |
       '`' testlist1 '`' |
       NAME | NUMBER | STRING+)
    */
    var i;
    var values;
    var keys;
    var size;
    var ch = CHILD(n, 0);
    var elts;
    switch (ch.type) {
        case TOK.T_NAME:
            // All names start in Load context, but may be changed later
            return new Name(strobj(ch.value), Load, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
        case TOK.T_STRING:
            return new Str(parsestrplus(c, n), n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
        case TOK.T_NUMBER:
            return new Num(parsenumber(c, ch.value, n.lineno), n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
        case TOK.T_LPAR: // various uses for parens
            ch = CHILD(n, 1);
            if (ch.type === TOK.T_RPAR) {
                return new Tuple([], Load, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            }
            if (ch.type === SYM.yield_expr) {
                return astForExpr(c, ch);
            }
            //            if (NCH(ch) > 1 && CHILD(ch, 1).type === SYM.comp_for) {
            //                return astForComprehension(c, ch);
            //            }
            return astForTestlistComp(c, ch);
        case TOK.T_LSQB: // list or listcomp
            ch = CHILD(n, 1);
            if (ch.type === TOK.T_RSQB) {
                return new List([], Load, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            }
            REQ(ch, SYM.listmaker);
            if (NCH(ch) === 1 || CHILD(ch, 1).type === TOK.T_COMMA) {
                return new List(seqForTestlist(c, ch), Load, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            } 
            return astForListcomp(c, ch);
            
        case TOK.T_LBRACE:
            /* dictorsetmaker: 
             *     (test ':' test (comp_for : (',' test ':' test)* [','])) |
             *     (test (comp_for | (',' test)* [',']))
             */
            keys = [];
            values = [];
            ch = CHILD(n, 1);
            if (n.type === TOK.T_RBRACE) {
                //it's an empty dict
                return new Dict([], null, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            } 
            else if (NCH(ch) === 1 || (NCH(ch) !== 0 && CHILD(ch, 1).type === TOK.T_COMMA)) {
                //it's a simple set
                elts = [];
                size = Math.floor((NCH(ch) + 1) / 2);
                for (i = 0; i < NCH(ch); i += 2) {
                    var expression = astForExpr(c, CHILD(ch, i));
                    elts[i / 2] = expression;
                }
                return new Set(elts, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            } 
            else if (NCH(ch) !== 0 && CHILD(ch, 1).type == SYM.comp_for) {
                //it's a set comprehension
                return astForSetComp(c, ch);
            } 
            else if (NCH(ch) > 3 && CHILD(ch, 3).type === SYM.comp_for) {
                //it's a dict compr. I think.
                return astForDictComp(c, ch);
            } 
            else {
                size = Math.floor((NCH(ch) + 1) / 4); // + 1 for no trailing comma case
                for (i = 0; i < NCH(ch); i += 4) {
                    keys[i / 4] = astForExpr(c, CHILD(ch, i));
                    values[i / 4] = astForExpr(c, CHILD(ch, i + 2));
                }
                return new Dict(keys, values, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            }
        case TOK.T_BACKQUOTE:
            //throw new Sk.builtin.SyntaxError("backquote not supported, use repr()", c.c_filename, n.lineno);
            return new Repr(astForTestlist(c, CHILD(n, 1)), n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
        default:
            goog.asserts.fail("unhandled atom", ch.type);

    }
}

function astForPower (c, n) {
    /* power: atom trailer* ('**' factor)*
     */
    var f;
    var tmp;
    var ch;
    var i;
    var e;
    REQ(n, SYM.power);
    e = astForAtom(c, CHILD(n, 0));
    if (NCH(n) === 1) {
        return e;
    }
    for (i = 1; i < NCH(n); ++i) {
        ch = CHILD(n, i);
        if (ch.type !== SYM.trailer) {
            break;
        }
        tmp = astForTrailer(c, ch, e);
        tmp.lineno = e.lineno;
        tmp.col_offset = e.col_offset;
        tmp.endlineno = e.endlineno;
        tmp.col_endoffset = e.col_endoffset;
        e = tmp;
    }
    if (CHILD(n, NCH(n) - 1).type === SYM.factor) {
        f = astForExpr(c, CHILD(n, NCH(n) - 1));
        e = new BinOp(e, Pow, f, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
    }
    return e;
}

function astForExpr (c, n) {
    /* handle the full range of simple expressions
     test: or_test ['if' or_test 'else' test] | lambdef
     or_test: and_test ('or' and_test)*
     and_test: not_test ('and' not_test)*
     not_test: 'not' not_test | comparison
     comparison: expr (comp_op expr)*
     expr: xor_expr ('|' xor_expr)*
     xor_expr: and_expr ('^' and_expr)*
     and_expr: shift_expr ('&' shift_expr)*
     shift_expr: arith_expr (('<<'|'>>') arith_expr)*
     arith_expr: term (('+'|'-') term)*
     term: factor (('*'|'/'|'%'|'//') factor)*
     factor: ('+'|'-'|'~') factor | power
     power: atom trailer* ('**' factor)*

     As well as modified versions that exist for backward compatibility,
     to explicitly allow:
     [ x for x in lambda: 0, lambda: 1 ]
     (which would be ambiguous without these extra rules)

     old_test: or_test | old_lambdef
     old_lambdef: 'lambda' [vararglist] ':' old_test

     */

    var exp;
    var cmps;
    var ops;
    var i;
    var seq;
    LOOP: while (true) {
        switch (n.type) {
            case SYM.test:
            case SYM.old_test:
                if (CHILD(n, 0).type === SYM.lambdef || CHILD(n, 0).type === SYM.old_lambdef) {
                    return astForLambdef(c, CHILD(n, 0));
                }
                else if (NCH(n) > 1) {
                    return astForIfexpr(c, n);
                }
            // fallthrough
            case SYM.or_test:
            case SYM.and_test:
                if (NCH(n) === 1) {
                    n = CHILD(n, 0);
                    continue LOOP;
                }
                seq = [];
                for (i = 0; i < NCH(n); i += 2) {
                    seq[i / 2] = astForExpr(c, CHILD(n, i));
                }
                if (CHILD(n, 1).value === "and") {
                    return new BoolOp(And, seq, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
                }
                goog.asserts.assert(CHILD(n, 1).value === "or");
                return new BoolOp(Or, seq, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            case SYM.not_test:
                if (NCH(n) === 1) {
                    n = CHILD(n, 0);
                    continue LOOP;
                }
                else {
                    return new UnaryOp(Not, astForExpr(c, CHILD(n, 1)), n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
                }
                break;
            case SYM.comparison:
                if (NCH(n) === 1) {
                    n = CHILD(n, 0);
                    continue LOOP;
                }
                else {
                    ops = [];
                    cmps = [];
                    for (i = 1; i < NCH(n); i += 2) {
                        ops[(i - 1) / 2] = astForCompOp(c, CHILD(n, i));
                        cmps[(i - 1) / 2] = astForExpr(c, CHILD(n, i + 1));
                    }
                    return new Compare(astForExpr(c, CHILD(n, 0)), ops, cmps, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
                }
                break;
            case SYM.expr:
            case SYM.xor_expr:
            case SYM.and_expr:
            case SYM.shift_expr:
            case SYM.arith_expr:
            case SYM.term:
                if (NCH(n) === 1) {
                    n = CHILD(n, 0);
                    continue LOOP;
                }
                return astForBinop(c, n);
            case SYM.yield_expr:
                exp = null;
                if (NCH(n) === 2) {
                    exp = astForTestlist(c, CHILD(n, 1));
                }
                return new Yield(exp, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            case SYM.factor:
                if (NCH(n) === 1) {
                    n = CHILD(n, 0);
                    continue LOOP;
                }
                return astForFactor(c, n);
            case SYM.power:
                return astForPower(c, n);
            default:
                goog.asserts.fail("unhandled expr", "n.type: %d", n.type);
        }
        break;
    }
}

function astForPrintStmt (c, n) {
    /* print_stmt: 'print' ( [ test (',' test)* [','] ]
     | '>>' test [ (',' test)+ [','] ] )
     */
    var nl;
    var i, j;
    var seq;
    var start = 1;
    var dest = null;
    REQ(n, SYM.print_stmt);
    if (NCH(n) >= 2 && CHILD(n, 1).type === TOK.T_RIGHTSHIFT) {
        dest = astForExpr(c, CHILD(n, 2));
        start = 4;
    }
    seq = [];
    for (i = start, j = 0; i < NCH(n); i += 2, ++j) {
        seq[j] = astForExpr(c, CHILD(n, i));
    }
    nl = (CHILD(n, NCH(n) - 1)).type === TOK.T_COMMA ? false : true;
    return new Print(dest, seq, nl, n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
}

function astForStmt(c, n) {
    var ch;
    if (n.type === SYM.stmt) {
        goog.asserts.assert(NCH(n) === 1);
        n = CHILD(n, 0);
    }
    if (n.type === SYM.simple_stmt) {
        goog.asserts.assert(numStmts(n) === 1);
        n = CHILD(n, 0);
    }
    if (n.type === SYM.small_stmt) {
        REQ(n, SYM.small_stmt);
        n = CHILD(n, 0);
        /* small_stmt: expr_stmt | print_stmt  | del_stmt | pass_stmt
         | flow_stmt | import_stmt | global_stmt | exec_stmt
         | assert_stmt
         */
        switch (n.type) {
            case SYM.expr_stmt:
                return astForExprStmt(c, n);
            case SYM.print_stmt:
                return astForPrintStmt(c, n);
            case SYM.del_stmt:
                return astForDelStmt(c, n);
            case SYM.pass_stmt:
                return new Pass(n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            case SYM.flow_stmt:
                return astForFlowStmt(c, n);
            case SYM.import_stmt:
                return astForImportStmt(c, n);
            case SYM.global_stmt:
                return astForGlobalStmt(c, n);
            case SYM.exec_stmt:
                return astForExecStmt(c, n);
            case SYM.assert_stmt:
                return astForAssertStmt(c, n);
            case SYM.debugger_stmt:
                return new Debugger_(n.lineno, n.col_offset, n.endlineno, n.col_endoffset);
            default:
                goog.asserts.fail("unhandled small_stmt");
        }
    }
    else {
        /* compound_stmt: if_stmt | while_stmt | for_stmt | try_stmt
                          | funcdef | classdef | decorated
         */
        ch = CHILD(n, 0);
        REQ(n, SYM.compound_stmt);
        switch (ch.type) {
            case SYM.if_stmt:
                return astForIfStmt(c, ch);
            case SYM.while_stmt:
                return astForWhileStmt(c, ch);
            case SYM.for_stmt:
                return astForForStmt(c, ch);
            case SYM.try_stmt:
                return astForTryStmt(c, ch);
            case SYM.with_stmt:
                return astForWithStmt(c, ch);
            case SYM.funcdef:
                return astForFuncdef(c, ch, []);
            case SYM.classdef:
                return astForClassdef(c, ch, []);
            case SYM.decorated:
                return astForDecorated(c, ch);
            default:
                goog.asserts.assert("unhandled compound_stmt");
        }
    }
}

Sk.astFromParse = function (n, filename, c_flags) {
    var j;
    var num;
    var ch;
    var i;
    var c = new Compiling("utf-8", filename, c_flags);
    var stmts = [];
    var k = 0;
    switch (n.type) {
        case SYM.file_input:
            for (i = 0; i < NCH(n) - 1; ++i) {
                ch = CHILD(n, i);
                if (n.type === TOK.T_NEWLINE) {
                    continue;
                }
                REQ(ch, SYM.stmt);
                num = numStmts(ch);
                if (num === 1) {
                    stmts[k++] = astForStmt(c, ch);
                }
                else {
                    ch = CHILD(ch, 0);
                    REQ(ch, SYM.simple_stmt);
                    for (j = 0; j < num; ++j) {
                        stmts[k++] = astForStmt(c, CHILD(ch, j * 2));
                    }
                }
            }
            return new Module(stmts);
        case SYM.eval_input:
            goog.asserts.fail("todo;");
        case SYM.single_input:
            goog.asserts.fail("todo;");
        default:
            goog.asserts.fail("todo;");
    }
};

Sk.astDump = function (node) {
    var spaces = function (n) // todo; blurgh
    {
        var i;
        var ret = "";
        for (i = 0; i < n; ++i) {
            ret += " ";
        }
        return ret;
    };

    var _format = function (node, indent) {
        var ret;
        var elemsstr;
        var x;
        var elems;
        var fieldstr;
        var field;
        var attrs;
        var fieldlen;
        var b;
        var a;
        var i;
        var fields;
        var namelen;
        if (node === null) {
            return indent + "None";
        }
        else if (node.prototype && node.prototype._astname !== undefined && node.prototype._isenum) {
            return indent + node.prototype._astname + "()";
        }
        else if (node._astname !== undefined) {
            namelen = spaces(node._astname.length + 1);
            fields = [];
            for (i = 0; i < node._fields.length; i += 2) // iter_fields
            {
                a = node._fields[i]; // field name
                b = node._fields[i + 1](node); // field getter func
                fieldlen = spaces(a.length + 1);
                fields.push([a, _format(b, indent + namelen + fieldlen)]);
            }
            attrs = [];
            for (i = 0; i < fields.length; ++i) {
                field = fields[i];
                attrs.push(field[0] + "=" + field[1].replace(/^\s+/, ""));
            }
            fieldstr = attrs.join(",\n" + indent + namelen);
            return indent + node._astname + "(" + fieldstr + ")";
        }
        else if (goog.isArrayLike(node)) {
            //Sk.debugout("arr", node.length);
            elems = [];
            for (i = 0; i < node.length; ++i) {
                x = node[i];
                elems.push(_format(x, indent + " "));
            }
            elemsstr = elems.join(",\n");
            return indent + "[" + elemsstr.replace(/^\s+/, "") + "]";
        }
        else {
            if (node === true) {
                ret = "True";
            }
            else if (node === false) {
                ret = "False";
            }
            else if (node instanceof Sk.builtin.lng) {
                ret = node.tp$str().v;
            }
            else if (node instanceof Sk.builtin.str) {
                ret = node["$r"]().v;
            }
            else {
                ret = "" + node;
            }
            return indent + ret;
        }
    };

    return _format(node, "");
};

goog.exportSymbol("Sk.astFromParse", Sk.astFromParse);
goog.exportSymbol("Sk.astDump", Sk.astDump);