func (p *parser) parseLoadStmt() *LoadStmt {
	loadPos := p.nextToken()  
	lparen := p.consume(LPAREN)
	if p.tok != STRING {
		p.in.errorf(p.in.pos, "first operand of load statement must be a string literal")
	}
	module := p.parsePrimary().(*Literal)
	var from, to []*Ident
	for p.tok != RPAREN && p.tok != EOF {
		p.consume(COMMA)
		if p.tok == RPAREN {
			break  
		}
		switch p.tok {
		case STRING:
			lit := p.parsePrimary().(*Literal)
			id := &Ident{
				NamePos: lit.TokenPos.add(`"`),
				Name:    lit.Value.(string),
			}
			to = append(to, id)
			from = append(from, id)
		case IDENT:
			// load("module", to="from")
			id := p.parseIdent()
			to = append(to, id)
			if p.tok != EQ {
				p.in.errorf(p.in.pos, `load operand must be "%[1]s" or %[1]s="originalname" (want '=' after %[1]s)`, id.Name)
			}
			p.consume(EQ)
			if p.tok != STRING {
				p.in.errorf(p.in.pos, `original name of loaded symbol must be quoted: %s="originalname"`, id.Name)
			}
			lit := p.parsePrimary().(*Literal)
			from = append(from, &Ident{
				NamePos: lit.TokenPos.add(`"`),
				Name:    lit.Value.(string),
			})
		case RPAREN:
			p.in.errorf(p.in.pos, "trailing comma in load statement")
		default:
			p.in.errorf(p.in.pos, `load operand must be "name" or localname="name" (got %#v)`, p.tok)
		}
	}
	rparen := p.consume(RPAREN)
	if len(to) == 0 {
		p.in.errorf(lparen, "load statement must import at least 1 symbol")
	}
	return &LoadStmt{
		Load:   loadPos,
		Module: module,
		To:     to,
		From:   from,
		Rparen: rparen,
	}
}
stmt = LOAD '(' STRING {',' (IDENT '=')? STRING} [','] ')'
package syntax
import log "log"
const debug = false
type Mode uint
const (
	RetainComments Mode = 1 << iota  
)
func Parse(filename string, src interface{}, mode Mode) (f *File, err error) {
	in, err := newScanner(filename, src, mode&RetainComments != 0)
	if err != nil {
		return nil, err
	}
	p := parser{in: in}
	defer p.in.recover(&err)
	p.nextToken()  
	f = p.parseFile()
	if f != nil {
		f.Path = filename
	}
	p.assignComments(f)
	return f, nil
}
func ParseExpr(filename string, src interface{}, mode Mode) (expr Expr, err error) {
	in, err := newScanner(filename, src, mode&RetainComments != 0)
	if err != nil {
		return nil, err
	}
	p := parser{in: in}
	defer p.in.recover(&err)
	p.nextToken()  
	expr = p.parseTest()
	if p.tok == NEWLINE {
		p.nextToken()
	}
	if p.tok != EOF {
		p.in.errorf(p.in.pos, "got %#v after expression, want EOF", p.tok)
	}
	p.assignComments(expr)
	return expr, nil
}
type parser struct {
	in     *scanner
	tok    Token
	tokval tokenValue
}
func (p *parser) nextToken() Position {
	oldpos := p.tokval.pos
	p.tok = p.in.nextToken(&p.tokval)
	if debug {
		log.Printf("nextToken: %-20s%+v\n", p.tok, p.tokval.pos)
	}
	return oldpos
}
func (p *parser) parseFile() *File {
	var stmts []Stmt
	for p.tok != EOF {
		if p.tok == NEWLINE {
			p.nextToken()
			continue
		}
		stmts = p.parseStmt(stmts)
	}
	return &File{Stmts: stmts}
}
func (p *parser) parseStmt(stmts []Stmt) []Stmt {
	if p.tok == DEF {
		return append(stmts, p.parseDefStmt())
	} else if p.tok == IF {
		return append(stmts, p.parseIfStmt())
	} else if p.tok == FOR {
		return append(stmts, p.parseForStmt())
	}
	return p.parseSimpleStmt(stmts)
}
func (p *parser) parseDefStmt() Stmt {
	defpos := p.nextToken()  
	id := p.parseIdent()
	p.consume(LPAREN)
	params := p.parseParams()
	p.consume(RPAREN)
	p.consume(COLON)
	body := p.parseSuite()
	return &DefStmt{
		Def:  defpos,
		Name: id,
		Function: Function{
			StartPos: defpos,
			Params:   params,
			Body:     body,
		},
	}
}
func (p *parser) parseIfStmt() Stmt {
	ifpos := p.nextToken()  
	cond := p.parseTest()
	p.consume(COLON)
	body := p.parseSuite()
	ifStmt := &IfStmt{
		If:   ifpos,
		Cond: cond,
		True: body,
	}
	tail := ifStmt
	for p.tok == ELIF {
		elifpos := p.nextToken()  
		cond := p.parseTest()
		p.consume(COLON)
		body := p.parseSuite()
		elif := &IfStmt{
			If:   elifpos,
			Cond: cond,
			True: body,
		}
		tail.ElsePos = elifpos
		tail.False = []Stmt{elif}
		tail = elif
	}
	if p.tok == ELSE {
		tail.ElsePos = p.nextToken()  
		p.consume(COLON)
		tail.False = p.parseSuite()
	}
	return ifStmt
}
func (p *parser) parseForStmt() Stmt {
	forpos := p.nextToken()  
	vars := p.parseForLoopVariables()
	p.consume(IN)
	x := p.parseExpr(false)
	p.consume(COLON)
	body := p.parseSuite()
	return &ForStmt{
		For:  forpos,
		Vars: vars,
		X:    x,
		Body: body,
	}
}
func (p *parser) parseForLoopVariables() Expr {
	v := p.parsePrimaryWithSuffix()
	if p.tok != COMMA {
		return v
	}
	list := []Expr{v}
	for p.tok == COMMA {
		p.nextToken()
		if terminatesExprList(p.tok) {
			break
		}
		list = append(list, p.parsePrimaryWithSuffix())
	}
	return &TupleExpr{List: list}
}
func (p *parser) parseSimpleStmt(stmts []Stmt) []Stmt {
	for {
		stmts = append(stmts, p.parseSmallStmt())
		if p.tok != SEMI {
			break
		}
		p.nextToken()  
		if p.tok == NEWLINE || p.tok == EOF {
			break
		}
	}
	if p.tok != EOF {
		p.consume(NEWLINE)
	}
	return stmts
}
func (p *parser) parseSmallStmt() Stmt {
	switch p.tok {
	case RETURN:
		pos := p.nextToken()  
		var result Expr
		if p.tok != EOF && p.tok != NEWLINE && p.tok != SEMI {
			result = p.parseExpr(false)
		}
		return &ReturnStmt{Return: pos, Result: result}
	case BREAK, CONTINUE, PASS:
		tok := p.tok
		pos := p.nextToken()  
		return &BranchStmt{Token: tok, TokenPos: pos}
	case LOAD:
		return p.parseLoadStmt()
	}
	x := p.parseExpr(false)
	switch p.tok {
	case EQ, PLUS_EQ, MINUS_EQ, STAR_EQ, SLASH_EQ, SLASHSLASH_EQ, PERCENT_EQ, AMP_EQ, PIPE_EQ, CIRCUMFLEX_EQ, LTLT_EQ, GTGT_EQ:
		op := p.tok
		pos := p.nextToken()  
		rhs := p.parseExpr(false)
		return &AssignStmt{OpPos: pos, Op: op, LHS: x, RHS: rhs}
	}
	return &ExprStmt{X: x}
}