wip

vendor/github.com/antonmedv/expr/parser/lexer/lexer.go

@@ -0,0 +1,205 @@
+package lexer
+
+import (
+	"fmt"
+	"strings"
+	"unicode/utf8"
+
+	"github.com/antonmedv/expr/file"
+)
+
+func Lex(source *file.Source) ([]Token, error) {
+	l := &lexer{
+		input:  source.Content(),
+		tokens: make([]Token, 0),
+	}
+
+	l.loc = file.Location{1, 0}
+	l.prev = l.loc
+	l.startLoc = l.loc
+
+	for state := root; state != nil; {
+		state = state(l)
+	}
+
+	if l.err != nil {
+		return nil, l.err.Bind(source)
+	}
+
+	return l.tokens, nil
+}
+
+type lexer struct {
+	input      string
+	state      stateFn
+	tokens     []Token
+	start, end int           // current position in input
+	width      int           // last rune with
+	startLoc   file.Location // start location
+	prev, loc  file.Location // prev location of end location, end location
+	err        *file.Error
+}
+
+const eof rune = -1
+
+func (l *lexer) next() rune {
+	if l.end >= len(l.input) {
+		l.width = 0
+		return eof
+	}
+	r, w := utf8.DecodeRuneInString(l.input[l.end:])
+	l.width = w
+	l.end += w
+
+	l.prev = l.loc
+	if r == '\n' {
+		l.loc.Line++
+		l.loc.Column = 0
+	} else {
+		l.loc.Column++
+	}
+
+	return r
+}
+
+func (l *lexer) peek() rune {
+	r := l.next()
+	l.backup()
+	return r
+}
+
+func (l *lexer) backup() {
+	l.end -= l.width
+	l.loc = l.prev
+}
+
+func (l *lexer) emit(t Kind) {
+	l.emitValue(t, l.word())
+}
+
+func (l *lexer) emitValue(t Kind, value string) {
+	l.tokens = append(l.tokens, Token{
+		Location: l.startLoc,
+		Kind:     t,
+		Value:    value,
+	})
+	l.start = l.end
+	l.startLoc = l.loc
+}
+
+func (l *lexer) emitEOF() {
+	l.tokens = append(l.tokens, Token{
+		Location: l.prev, // Point to previous position for better error messages.
+		Kind:     EOF,
+	})
+	l.start = l.end
+	l.startLoc = l.loc
+}
+
+func (l *lexer) word() string {
+	return l.input[l.start:l.end]
+}
+
+func (l *lexer) ignore() {
+	l.start = l.end
+	l.startLoc = l.loc
+}
+
+func (l *lexer) accept(valid string) bool {
+	if strings.ContainsRune(valid, l.next()) {
+		return true
+	}
+	l.backup()
+	return false
+}
+
+func (l *lexer) acceptRun(valid string) {
+	for strings.ContainsRune(valid, l.next()) {
+	}
+	l.backup()
+}
+
+func (l *lexer) acceptWord(word string) bool {
+	pos := l.end
+	loc := l.loc
+	prev := l.prev
+	for _, ch := range word {
+		if l.next() != ch {
+			l.end = pos
+			l.loc = loc
+			l.prev = prev
+			return false
+		}
+	}
+	return true
+}
+
+func (l *lexer) error(format string, args ...interface{}) stateFn {
+	if l.err == nil { // show first error
+		l.err = &file.Error{
+			Location: l.loc,
+			Message:  fmt.Sprintf(format, args...),
+		}
+	}
+	return nil
+}
+
+func digitVal(ch rune) int {
+	switch {
+	case '0' <= ch && ch <= '9':
+		return int(ch - '0')
+	case 'a' <= lower(ch) && lower(ch) <= 'f':
+		return int(lower(ch) - 'a' + 10)
+	}
+	return 16 // larger than any legal digit val
+}
+
+func lower(ch rune) rune { return ('a' - 'A') | ch } // returns lower-case ch iff ch is ASCII letter
+
+func (l *lexer) scanDigits(ch rune, base, n int) rune {
+	for n > 0 && digitVal(ch) < base {
+		ch = l.next()
+		n--
+	}
+	if n > 0 {
+		l.error("invalid char escape")
+	}
+	return ch
+}
+
+func (l *lexer) scanEscape(quote rune) rune {
+	ch := l.next() // read character after '/'
+	switch ch {
+	case 'a', 'b', 'f', 'n', 'r', 't', 'v', '\\', quote:
+		// nothing to do
+		ch = l.next()
+	case '0', '1', '2', '3', '4', '5', '6', '7':
+		ch = l.scanDigits(ch, 8, 3)
+	case 'x':
+		ch = l.scanDigits(l.next(), 16, 2)
+	case 'u':
+		ch = l.scanDigits(l.next(), 16, 4)
+	case 'U':
+		ch = l.scanDigits(l.next(), 16, 8)
+	default:
+		l.error("invalid char escape")
+	}
+	return ch
+}
+
+func (l *lexer) scanString(quote rune) (n int) {
+	ch := l.next() // read character after quote
+	for ch != quote {
+		if ch == '\n' || ch == eof {
+			l.error("literal not terminated")
+			return
+		}
+		if ch == '\\' {
+			ch = l.scanEscape(quote)
+		} else {
+			ch = l.next()
+		}
+		n++
+	}
+	return
+}

vendor/github.com/antonmedv/expr/parser/lexer/state.go

@@ -0,0 +1,134 @@
+package lexer
+
+import (
+	"strings"
+)
+
+type stateFn func(*lexer) stateFn
+
+func root(l *lexer) stateFn {
+	switch r := l.next(); {
+	case r == eof:
+		l.emitEOF()
+		return nil
+	case IsSpace(r):
+		l.ignore()
+		return root
+	case r == '\'' || r == '"':
+		l.scanString(r)
+		str, err := unescape(l.word())
+		if err != nil {
+			l.error("%v", err)
+		}
+		l.emitValue(String, str)
+	case '0' <= r && r <= '9':
+		l.backup()
+		return number
+	case strings.ContainsRune("([{", r):
+		l.emit(Bracket)
+	case strings.ContainsRune(")]}", r):
+		l.emit(Bracket)
+	case strings.ContainsRune("#,?:%+-/", r): // single rune operator
+		l.emit(Operator)
+	case strings.ContainsRune("&|!=*<>", r): // possible double rune operator
+		l.accept("&|=*")
+		l.emit(Operator)
+	case r == '.':
+		l.backup()
+		return dot
+	case IsAlphaNumeric(r):
+		l.backup()
+		return identifier
+	default:
+		return l.error("unrecognized character: %#U", r)
+	}
+	return root
+}
+
+func number(l *lexer) stateFn {
+	if !l.scanNumber() {
+		return l.error("bad number syntax: %q", l.word())
+	}
+	l.emit(Number)
+	return root
+}
+
+func (l *lexer) scanNumber() bool {
+	digits := "0123456789_"
+	// Is it hex?
+	if l.accept("0") {
+		// Note: Leading 0 does not mean octal in floats.
+		if l.accept("xX") {
+			digits = "0123456789abcdefABCDEF_"
+		} else if l.accept("oO") {
+			digits = "01234567_"
+		} else if l.accept("bB") {
+			digits = "01_"
+		}
+	}
+	l.acceptRun(digits)
+	loc, prev, end := l.loc, l.prev, l.end
+	if l.accept(".") {
+		// Lookup for .. operator: if after dot there is another dot (1..2), it maybe a range operator.
+		if l.peek() == '.' {
+			// We can't backup() here, as it would require two backups,
+			// and backup() func supports only one for now. So, save and
+			// restore it here.
+			l.loc, l.prev, l.end = loc, prev, end
+			return true
+		}
+		l.acceptRun(digits)
+	}
+	if l.accept("eE") {
+		l.accept("+-")
+		l.acceptRun(digits)
+	}
+	// Next thing mustn't be alphanumeric.
+	if IsAlphaNumeric(l.peek()) {
+		l.next()
+		return false
+	}
+	return true
+}
+
+func dot(l *lexer) stateFn {
+	l.next()
+	if l.accept("0123456789") {
+		l.backup()
+		return number
+	}
+	l.accept(".")
+	l.emit(Operator)
+	return root
+}
+
+func identifier(l *lexer) stateFn {
+loop:
+	for {
+		switch r := l.next(); {
+		case IsAlphaNumeric(r):
+			// absorb
+		default:
+			l.backup()
+			switch l.word() {
+			case "not":
+				return not
+			case "in", "or", "and", "matches", "contains", "startsWith", "endsWith":
+				l.emit(Operator)
+			default:
+				l.emit(Identifier)
+			}
+			break loop
+		}
+	}
+	return root
+}
+
+func not(l *lexer) stateFn {
+	if l.acceptWord(" in") {
+		l.emit(Operator)
+	} else {
+		l.emit(Operator)
+	}
+	return root
+}

vendor/github.com/antonmedv/expr/parser/lexer/token.go

@@ -0,0 +1,47 @@
+package lexer
+
+import (
+	"fmt"
+
+	"github.com/antonmedv/expr/file"
+)
+
+type Kind string
+
+const (
+	Identifier Kind = "Identifier"
+	Number          = "Number"
+	String          = "String"
+	Operator        = "Operator"
+	Bracket         = "Bracket"
+	EOF             = "EOF"
+)
+
+type Token struct {
+	file.Location
+	Kind  Kind
+	Value string
+}
+
+func (t Token) String() string {
+	if t.Value == "" {
+		return string(t.Kind)
+	}
+	return fmt.Sprintf("%s(%#v)", t.Kind, t.Value)
+}
+
+func (t Token) Is(kind Kind, values ...string) bool {
+	if len(values) == 0 {
+		return kind == t.Kind
+	}
+
+	for _, v := range values {
+		if v == t.Value {
+			goto found
+		}
+	}
+	return false
+
+found:
+	return kind == t.Kind
+}

vendor/github.com/antonmedv/expr/parser/lexer/utils.go

@@ -0,0 +1,194 @@
+package lexer
+
+import (
+	"fmt"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+)
+
+func IsSpace(r rune) bool {
+	return unicode.IsSpace(r)
+}
+
+func IsAlphaNumeric(r rune) bool {
+	return IsAlphabetic(r) || unicode.IsDigit(r)
+}
+
+func IsAlphabetic(r rune) bool {
+	return r == '_' || r == '$' || unicode.IsLetter(r)
+}
+
+var (
+	newlineNormalizer = strings.NewReplacer("\r\n", "\n", "\r", "\n")
+)
+
+// Unescape takes a quoted string, unquotes, and unescapes it.
+func unescape(value string) (string, error) {
+	// All strings normalize newlines to the \n representation.
+	value = newlineNormalizer.Replace(value)
+	n := len(value)
+
+	// Nothing to unescape / decode.
+	if n < 2 {
+		return value, fmt.Errorf("unable to unescape string")
+	}
+
+	// Quoted string of some form, must have same first and last char.
+	if value[0] != value[n-1] || (value[0] != '"' && value[0] != '\'') {
+		return value, fmt.Errorf("unable to unescape string")
+	}
+
+	value = value[1 : n-1]
+
+	// The string contains escape characters.
+	// The following logic is adapted from `strconv/quote.go`
+	var runeTmp [utf8.UTFMax]byte
+	buf := make([]byte, 0, 3*n/2)
+	for len(value) > 0 {
+		c, multibyte, rest, err := unescapeChar(value)
+		if err != nil {
+			return "", err
+		}
+		value = rest
+		if c < utf8.RuneSelf || !multibyte {
+			buf = append(buf, byte(c))
+		} else {
+			n := utf8.EncodeRune(runeTmp[:], c)
+			buf = append(buf, runeTmp[:n]...)
+		}
+	}
+	return string(buf), nil
+}
+
+// unescapeChar takes a string input and returns the following info:
+//
+//   value - the escaped unicode rune at the front of the string.
+//   multibyte - whether the rune value might require multiple bytes to represent.
+//   tail - the remainder of the input string.
+//   err - error value, if the character could not be unescaped.
+//
+// When multibyte is true the return value may still fit within a single byte,
+// but a multibyte conversion is attempted which is more expensive than when the
+// value is known to fit within one byte.
+func unescapeChar(s string) (value rune, multibyte bool, tail string, err error) {
+	// 1. Character is not an escape sequence.
+	switch c := s[0]; {
+	case c >= utf8.RuneSelf:
+		r, size := utf8.DecodeRuneInString(s)
+		return r, true, s[size:], nil
+	case c != '\\':
+		return rune(s[0]), false, s[1:], nil
+	}
+
+	// 2. Last character is the start of an escape sequence.
+	if len(s) <= 1 {
+		err = fmt.Errorf("unable to unescape string, found '\\' as last character")
+		return
+	}
+
+	c := s[1]
+	s = s[2:]
+	// 3. Common escape sequences shared with Google SQL
+	switch c {
+	case 'a':
+		value = '\a'
+	case 'b':
+		value = '\b'
+	case 'f':
+		value = '\f'
+	case 'n':
+		value = '\n'
+	case 'r':
+		value = '\r'
+	case 't':
+		value = '\t'
+	case 'v':
+		value = '\v'
+	case '\\':
+		value = '\\'
+	case '\'':
+		value = '\''
+	case '"':
+		value = '"'
+	case '`':
+		value = '`'
+	case '?':
+		value = '?'
+
+	// 4. Unicode escape sequences, reproduced from `strconv/quote.go`
+	case 'x', 'X', 'u', 'U':
+		n := 0
+		switch c {
+		case 'x', 'X':
+			n = 2
+		case 'u':
+			n = 4
+		case 'U':
+			n = 8
+		}
+		var v rune
+		if len(s) < n {
+			err = fmt.Errorf("unable to unescape string")
+			return
+		}
+		for j := 0; j < n; j++ {
+			x, ok := unhex(s[j])
+			if !ok {
+				err = fmt.Errorf("unable to unescape string")
+				return
+			}
+			v = v<<4 | x
+		}
+		s = s[n:]
+		if v > utf8.MaxRune {
+			err = fmt.Errorf("unable to unescape string")
+			return
+		}
+		value = v
+		multibyte = true
+
+	// 5. Octal escape sequences, must be three digits \[0-3][0-7][0-7]
+	case '0', '1', '2', '3':
+		if len(s) < 2 {
+			err = fmt.Errorf("unable to unescape octal sequence in string")
+			return
+		}
+		v := rune(c - '0')
+		for j := 0; j < 2; j++ {
+			x := s[j]
+			if x < '0' || x > '7' {
+				err = fmt.Errorf("unable to unescape octal sequence in string")
+				return
+			}
+			v = v*8 + rune(x-'0')
+		}
+		if v > utf8.MaxRune {
+			err = fmt.Errorf("unable to unescape string")
+			return
+		}
+		value = v
+		s = s[2:]
+		multibyte = true
+
+		// Unknown escape sequence.
+	default:
+		err = fmt.Errorf("unable to unescape string")
+	}
+
+	tail = s
+	return
+}
+
+func unhex(b byte) (rune, bool) {
+	c := rune(b)
+	switch {
+	case '0' <= c && c <= '9':
+		return c - '0', true
+	case 'a' <= c && c <= 'f':
+		return c - 'a' + 10, true
+	case 'A' <= c && c <= 'F':
+		return c - 'A' + 10, true
+	}
+	return 0, false
+}

vendor/github.com/antonmedv/expr/parser/parser.go

@@ -0,0 +1,579 @@
+package parser
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+	"unicode/utf8"
+
+	. "github.com/antonmedv/expr/ast"
+	"github.com/antonmedv/expr/file"
+	. "github.com/antonmedv/expr/parser/lexer"
+)
+
+type associativity int
+
+const (
+	left associativity = iota + 1
+	right
+)
+
+type operator struct {
+	precedence    int
+	associativity associativity
+}
+
+type builtin struct {
+	arity int
+}
+
+var unaryOperators = map[string]operator{
+	"not": {50, left},
+	"!":   {50, left},
+	"-":   {500, left},
+	"+":   {500, left},
+}
+
+var binaryOperators = map[string]operator{
+	"or":         {10, left},
+	"||":         {10, left},
+	"and":        {15, left},
+	"&&":         {15, left},
+	"==":         {20, left},
+	"!=":         {20, left},
+	"<":          {20, left},
+	">":          {20, left},
+	">=":         {20, left},
+	"<=":         {20, left},
+	"not in":     {20, left},
+	"in":         {20, left},
+	"matches":    {20, left},
+	"contains":   {20, left},
+	"startsWith": {20, left},
+	"endsWith":   {20, left},
+	"..":         {25, left},
+	"+":          {30, left},
+	"-":          {30, left},
+	"*":          {60, left},
+	"/":          {60, left},
+	"%":          {60, left},
+	"**":         {70, right},
+}
+
+var builtins = map[string]builtin{
+	"len":    {1},
+	"all":    {2},
+	"none":   {2},
+	"any":    {2},
+	"one":    {2},
+	"filter": {2},
+	"map":    {2},
+	"count":  {2},
+}
+
+type parser struct {
+	tokens  []Token
+	current Token
+	pos     int
+	err     *file.Error
+	depth   int // closure call depth
+}
+
+type Tree struct {
+	Node   Node
+	Source *file.Source
+}
+
+func Parse(input string) (*Tree, error) {
+	source := file.NewSource(input)
+
+	tokens, err := Lex(source)
+	if err != nil {
+		return nil, err
+	}
+
+	p := &parser{
+		tokens:  tokens,
+		current: tokens[0],
+	}
+
+	node := p.parseExpression(0)
+
+	if !p.current.Is(EOF) {
+		p.error("unexpected token %v", p.current)
+	}
+
+	if p.err != nil {
+		return nil, p.err.Bind(source)
+	}
+
+	return &Tree{
+		Node:   node,
+		Source: source,
+	}, nil
+}
+
+func (p *parser) error(format string, args ...interface{}) {
+	if p.err == nil { // show first error
+		p.err = &file.Error{
+			Location: p.current.Location,
+			Message:  fmt.Sprintf(format, args...),
+		}
+	}
+}
+
+func (p *parser) next() {
+	p.pos++
+	if p.pos >= len(p.tokens) {
+		p.error("unexpected end of expression")
+		return
+	}
+	p.current = p.tokens[p.pos]
+}
+
+func (p *parser) expect(kind Kind, values ...string) {
+	if p.current.Is(kind, values...) {
+		p.next()
+		return
+	}
+	p.error("unexpected token %v", p.current)
+}
+
+// parse functions
+
+func (p *parser) parseExpression(precedence int) Node {
+	nodeLeft := p.parsePrimary()
+
+	token := p.current
+	for token.Is(Operator) && p.err == nil {
+		if op, ok := binaryOperators[token.Value]; ok {
+			if op.precedence >= precedence {
+				p.next()
+
+				var nodeRight Node
+				if op.associativity == left {
+					nodeRight = p.parseExpression(op.precedence + 1)
+				} else {
+					nodeRight = p.parseExpression(op.precedence)
+				}
+
+				if token.Is(Operator, "matches") {
+					var r *regexp.Regexp
+					var err error
+
+					if s, ok := nodeRight.(*StringNode); ok {
+						r, err = regexp.Compile(s.Value)
+						if err != nil {
+							p.error("%v", err)
+						}
+					}
+					nodeLeft = &MatchesNode{
+						Regexp: r,
+						Left:   nodeLeft,
+						Right:  nodeRight,
+					}
+					nodeLeft.SetLocation(token.Location)
+				} else {
+					nodeLeft = &BinaryNode{
+						Operator: token.Value,
+						Left:     nodeLeft,
+						Right:    nodeRight,
+					}
+					nodeLeft.SetLocation(token.Location)
+				}
+				token = p.current
+				continue
+			}
+		}
+		break
+	}
+
+	if precedence == 0 {
+		nodeLeft = p.parseConditionalExpression(nodeLeft)
+	}
+
+	return nodeLeft
+}
+
+func (p *parser) parsePrimary() Node {
+	token := p.current
+
+	if token.Is(Operator) {
+		if op, ok := unaryOperators[token.Value]; ok {
+			p.next()
+			expr := p.parseExpression(op.precedence)
+			node := &UnaryNode{
+				Operator: token.Value,
+				Node:     expr,
+			}
+			node.SetLocation(token.Location)
+			return p.parsePostfixExpression(node)
+		}
+	}
+
+	if token.Is(Bracket, "(") {
+		p.next()
+		expr := p.parseExpression(0)
+		p.expect(Bracket, ")") // "an opened parenthesis is not properly closed"
+		return p.parsePostfixExpression(expr)
+	}
+
+	if p.depth > 0 {
+		if token.Is(Operator, "#") || token.Is(Operator, ".") {
+			if token.Is(Operator, "#") {
+				p.next()
+			}
+			node := &PointerNode{}
+			node.SetLocation(token.Location)
+			return p.parsePostfixExpression(node)
+		}
+	} else {
+		if token.Is(Operator, "#") || token.Is(Operator, ".") {
+			p.error("cannot use pointer accessor outside closure")
+		}
+	}
+
+	return p.parsePrimaryExpression()
+}
+
+func (p *parser) parseConditionalExpression(node Node) Node {
+	var expr1, expr2 Node
+	for p.current.Is(Operator, "?") && p.err == nil {
+		p.next()
+
+		if !p.current.Is(Operator, ":") {
+			expr1 = p.parseExpression(0)
+			p.expect(Operator, ":")
+			expr2 = p.parseExpression(0)
+		} else {
+			p.next()
+			expr1 = node
+			expr2 = p.parseExpression(0)
+		}
+
+		node = &ConditionalNode{
+			Cond: node,
+			Exp1: expr1,
+			Exp2: expr2,
+		}
+	}
+	return node
+}
+
+func (p *parser) parsePrimaryExpression() Node {
+	var node Node
+	token := p.current
+
+	switch token.Kind {
+
+	case Identifier:
+		p.next()
+		switch token.Value {
+		case "true":
+			node := &BoolNode{Value: true}
+			node.SetLocation(token.Location)
+			return node
+		case "false":
+			node := &BoolNode{Value: false}
+			node.SetLocation(token.Location)
+			return node
+		case "nil":
+			node := &NilNode{}
+			node.SetLocation(token.Location)
+			return node
+		default:
+			node = p.parseIdentifierExpression(token)
+		}
+
+	case Number:
+		p.next()
+		value := strings.Replace(token.Value, "_", "", -1)
+		if strings.ContainsAny(value, ".eE") {
+			number, err := strconv.ParseFloat(value, 64)
+			if err != nil {
+				p.error("invalid float literal: %v", err)
+			}
+			node := &FloatNode{Value: number}
+			node.SetLocation(token.Location)
+			return node
+		} else if strings.Contains(value, "x") {
+			number, err := strconv.ParseInt(value, 0, 64)
+			if err != nil {
+				p.error("invalid hex literal: %v", err)
+			}
+			node := &IntegerNode{Value: int(number)}
+			node.SetLocation(token.Location)
+			return node
+		} else {
+			number, err := strconv.ParseInt(value, 10, 64)
+			if err != nil {
+				p.error("invalid integer literal: %v", err)
+			}
+			node := &IntegerNode{Value: int(number)}
+			node.SetLocation(token.Location)
+			return node
+		}
+
+	case String:
+		p.next()
+		node := &StringNode{Value: token.Value}
+		node.SetLocation(token.Location)
+		return node
+
+	default:
+		if token.Is(Bracket, "[") {
+			node = p.parseArrayExpression(token)
+		} else if token.Is(Bracket, "{") {
+			node = p.parseMapExpression(token)
+		} else {
+			p.error("unexpected token %v", token)
+		}
+	}
+
+	return p.parsePostfixExpression(node)
+}
+
+func (p *parser) parseIdentifierExpression(token Token) Node {
+	var node Node
+	if p.current.Is(Bracket, "(") {
+		var arguments []Node
+
+		if b, ok := builtins[token.Value]; ok {
+			p.expect(Bracket, "(")
+			// TODO: Add builtins signatures.
+			if b.arity == 1 {
+				arguments = make([]Node, 1)
+				arguments[0] = p.parseExpression(0)
+			} else if b.arity == 2 {
+				arguments = make([]Node, 2)
+				arguments[0] = p.parseExpression(0)
+				p.expect(Operator, ",")
+				arguments[1] = p.parseClosure()
+			}
+			p.expect(Bracket, ")")
+
+			node = &BuiltinNode{
+				Name:      token.Value,
+				Arguments: arguments,
+			}
+			node.SetLocation(token.Location)
+		} else {
+			arguments = p.parseArguments()
+			node = &FunctionNode{
+				Name:      token.Value,
+				Arguments: arguments,
+			}
+			node.SetLocation(token.Location)
+		}
+	} else {
+		node = &IdentifierNode{Value: token.Value}
+		node.SetLocation(token.Location)
+	}
+	return node
+}
+
+func (p *parser) parseClosure() Node {
+	token := p.current
+	p.expect(Bracket, "{")
+
+	p.depth++
+	node := p.parseExpression(0)
+	p.depth--
+
+	p.expect(Bracket, "}")
+	closure := &ClosureNode{
+		Node: node,
+	}
+	closure.SetLocation(token.Location)
+	return closure
+}
+
+func (p *parser) parseArrayExpression(token Token) Node {
+	nodes := make([]Node, 0)
+
+	p.expect(Bracket, "[")
+	for !p.current.Is(Bracket, "]") && p.err == nil {
+		if len(nodes) > 0 {
+			p.expect(Operator, ",")
+			if p.current.Is(Bracket, "]") {
+				goto end
+			}
+		}
+		node := p.parseExpression(0)
+		nodes = append(nodes, node)
+	}
+end:
+	p.expect(Bracket, "]")
+
+	node := &ArrayNode{Nodes: nodes}
+	node.SetLocation(token.Location)
+	return node
+}
+
+func (p *parser) parseMapExpression(token Token) Node {
+	p.expect(Bracket, "{")
+
+	nodes := make([]Node, 0)
+	for !p.current.Is(Bracket, "}") && p.err == nil {
+		if len(nodes) > 0 {
+			p.expect(Operator, ",")
+			if p.current.Is(Bracket, "}") {
+				goto end
+			}
+			if p.current.Is(Operator, ",") {
+				p.error("unexpected token %v", p.current)
+			}
+		}
+
+		var key Node
+		// a map key can be:
+		//  * a number
+		//  * a string
+		//  * a identifier, which is equivalent to a string
+		//  * an expression, which must be enclosed in parentheses -- (1 + 2)
+		if p.current.Is(Number) || p.current.Is(String) || p.current.Is(Identifier) {
+			key = &StringNode{Value: p.current.Value}
+			key.SetLocation(token.Location)
+			p.next()
+		} else if p.current.Is(Bracket, "(") {
+			key = p.parseExpression(0)
+		} else {
+			p.error("a map key must be a quoted string, a number, a identifier, or an expression enclosed in parentheses (unexpected token %v)", p.current)
+		}
+
+		p.expect(Operator, ":")
+
+		node := p.parseExpression(0)
+		pair := &PairNode{Key: key, Value: node}
+		pair.SetLocation(token.Location)
+		nodes = append(nodes, pair)
+	}
+
+end:
+	p.expect(Bracket, "}")
+
+	node := &MapNode{Pairs: nodes}
+	node.SetLocation(token.Location)
+	return node
+}
+
+func (p *parser) parsePostfixExpression(node Node) Node {
+	token := p.current
+	for (token.Is(Operator) || token.Is(Bracket)) && p.err == nil {
+		if token.Value == "." {
+			p.next()
+
+			token = p.current
+			p.next()
+
+			if token.Kind != Identifier &&
+				// Operators like "not" and "matches" are valid methods or property names.
+				(token.Kind != Operator || !isValidIdentifier(token.Value)) {
+				p.error("expected name")
+			}
+
+			if p.current.Is(Bracket, "(") {
+				arguments := p.parseArguments()
+				node = &MethodNode{
+					Node:      node,
+					Method:    token.Value,
+					Arguments: arguments,
+				}
+				node.SetLocation(token.Location)
+			} else {
+				node = &PropertyNode{
+					Node:     node,
+					Property: token.Value,
+				}
+				node.SetLocation(token.Location)
+			}
+
+		} else if token.Value == "[" {
+			p.next()
+			var from, to Node
+
+			if p.current.Is(Operator, ":") { // slice without from [:1]
+				p.next()
+
+				if !p.current.Is(Bracket, "]") { // slice without from and to [:]
+					to = p.parseExpression(0)
+				}
+
+				node = &SliceNode{
+					Node: node,
+					To:   to,
+				}
+				node.SetLocation(token.Location)
+				p.expect(Bracket, "]")
+
+			} else {
+
+				from = p.parseExpression(0)
+
+				if p.current.Is(Operator, ":") {
+					p.next()
+
+					if !p.current.Is(Bracket, "]") { // slice without to [1:]
+						to = p.parseExpression(0)
+					}
+
+					node = &SliceNode{
+						Node: node,
+						From: from,
+						To:   to,
+					}
+					node.SetLocation(token.Location)
+					p.expect(Bracket, "]")
+
+				} else {
+					// Slice operator [:] was not found, it should by just index node.
+
+					node = &IndexNode{
+						Node:  node,
+						Index: from,
+					}
+					node.SetLocation(token.Location)
+					p.expect(Bracket, "]")
+				}
+			}
+
+		} else {
+			break
+		}
+
+		token = p.current
+	}
+	return node
+}
+
+func isValidIdentifier(str string) bool {
+	if len(str) == 0 {
+		return false
+	}
+	h, w := utf8.DecodeRuneInString(str)
+	if !IsAlphabetic(h) {
+		return false
+	}
+	for _, r := range str[w:] {
+		if !IsAlphaNumeric(r) {
+			return false
+		}
+	}
+	return true
+}
+
+func (p *parser) parseArguments() []Node {
+	p.expect(Bracket, "(")
+	nodes := make([]Node, 0)
+	for !p.current.Is(Bracket, ")") && p.err == nil {
+		if len(nodes) > 0 {
+			p.expect(Operator, ",")
+		}
+		node := p.parseExpression(0)
+		nodes = append(nodes, node)
+	}
+	p.expect(Bracket, ")")
+
+	return nodes
+}