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ladybird/Libraries/LibJS/Lexer.cpp
Timothy Flynn 00182a2405 LibJS: Port the JS lexer and parser to UTF-16 
This ports the lexer to UTF-16 and deals with the immediate fallout up
to the AST. The AST will be dealt with in upcoming commits.

The lexer will still accept UTF-8 strings as input, and will transcode
them to UTF-16 for lexing. This doesn't actually incur a new allocation,
as we were already converting the input StringView to a ByteString for
each lexer.

One immediate logical benefit here is that we do not need to know off-
hand how many UTF-8 bytes some special code points occupy. They all
happen to be a single UTF-16 code unit. So instead of advancing the
lexer by 3 positions in some cases, we can just always advance by 1.
2025-08-13 09:56:13 -04:00

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/*
* Copyright (c) 2020, Stephan Unverwerth <s.unverwerth@serenityos.org>
* Copyright (c) 2020-2021, Linus Groh <linusg@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/CharacterTypes.h>
#include <AK/Debug.h>
#include <AK/GenericLexer.h>
#include <AK/Utf16FlyString.h>
#include <LibJS/Lexer.h>
#include <LibUnicode/CharacterTypes.h>
namespace JS {
HashMap<Utf16FlyString, TokenType> Lexer::s_keywords;
static constexpr TokenType parse_two_char_token(Utf16View const& view)
{
if (view.length_in_code_units() != 2)
return TokenType::Invalid;
auto ch0 = view.code_unit_at(0);
auto ch1 = view.code_unit_at(1);
switch (ch0) {
case '=':
switch (ch1) {
case '>':
return TokenType::Arrow;
case '=':
return TokenType::EqualsEquals;
default:
return TokenType::Invalid;
}
case '+':
switch (ch1) {
case '=':
return TokenType::PlusEquals;
case '+':
return TokenType::PlusPlus;
default:
return TokenType::Invalid;
}
case '-':
switch (ch1) {
case '=':
return TokenType::MinusEquals;
case '-':
return TokenType::MinusMinus;
default:
return TokenType::Invalid;
}
case '*':
switch (ch1) {
case '=':
return TokenType::AsteriskEquals;
case '*':
return TokenType::DoubleAsterisk;
default:
return TokenType::Invalid;
}
case '/':
switch (ch1) {
case '=':
return TokenType::SlashEquals;
default:
return TokenType::Invalid;
}
case '%':
switch (ch1) {
case '=':
return TokenType::PercentEquals;
default:
return TokenType::Invalid;
}
case '&':
switch (ch1) {
case '=':
return TokenType::AmpersandEquals;
case '&':
return TokenType::DoubleAmpersand;
default:
return TokenType::Invalid;
}
case '|':
switch (ch1) {
case '=':
return TokenType::PipeEquals;
case '|':
return TokenType::DoublePipe;
default:
return TokenType::Invalid;
}
case '^':
switch (ch1) {
case '=':
return TokenType::CaretEquals;
default:
return TokenType::Invalid;
}
case '<':
switch (ch1) {
case '=':
return TokenType::LessThanEquals;
case '<':
return TokenType::ShiftLeft;
default:
return TokenType::Invalid;
}
case '>':
switch (ch1) {
case '=':
return TokenType::GreaterThanEquals;
case '>':
return TokenType::ShiftRight;
default:
return TokenType::Invalid;
}
case '?':
switch (ch1) {
case '?':
return TokenType::DoubleQuestionMark;
case '.':
return TokenType::QuestionMarkPeriod;
default:
return TokenType::Invalid;
}
case '!':
switch (ch1) {
case '=':
return TokenType::ExclamationMarkEquals;
default:
return TokenType::Invalid;
}
default:
return TokenType::Invalid;
}
}
static constexpr TokenType parse_three_char_token(Utf16View const& view)
{
if (view.length_in_code_units() != 3)
return TokenType::Invalid;
auto ch0 = view.code_unit_at(0);
auto ch1 = view.code_unit_at(1);
auto ch2 = view.code_unit_at(2);
switch (ch0) {
case '<':
if (ch1 == '<' && ch2 == '=')
return TokenType::ShiftLeftEquals;
return TokenType::Invalid;
case '>':
if (ch1 == '>' && ch2 == '=')
return TokenType::ShiftRightEquals;
if (ch1 == '>' && ch2 == '>')
return TokenType::UnsignedShiftRight;
return TokenType::Invalid;
case '=':
if (ch1 == '=' && ch2 == '=')
return TokenType::EqualsEqualsEquals;
return TokenType::Invalid;
case '!':
if (ch1 == '=' && ch2 == '=')
return TokenType::ExclamationMarkEqualsEquals;
return TokenType::Invalid;
case '.':
if (ch1 == '.' && ch2 == '.')
return TokenType::TripleDot;
return TokenType::Invalid;
case '*':
if (ch1 == '*' && ch2 == '=')
return TokenType::DoubleAsteriskEquals;
return TokenType::Invalid;
case '&':
if (ch1 == '&' && ch2 == '=')
return TokenType::DoubleAmpersandEquals;
return TokenType::Invalid;
case '|':
if (ch1 == '|' && ch2 == '=')
return TokenType::DoublePipeEquals;
return TokenType::Invalid;
case '?':
if (ch1 == '?' && ch2 == '=')
return TokenType::DoubleQuestionMarkEquals;
return TokenType::Invalid;
default:
return TokenType::Invalid;
}
}
static consteval Array<TokenType, 256> make_single_char_tokens_array()
{
Array<TokenType, 256> array;
array.fill(TokenType::Invalid);
array['&'] = TokenType::Ampersand;
array['*'] = TokenType::Asterisk;
array['['] = TokenType::BracketOpen;
array[']'] = TokenType::BracketClose;
array['^'] = TokenType::Caret;
array[':'] = TokenType::Colon;
array[','] = TokenType::Comma;
array['{'] = TokenType::CurlyOpen;
array['}'] = TokenType::CurlyClose;
array['='] = TokenType::Equals;
array['!'] = TokenType::ExclamationMark;
array['-'] = TokenType::Minus;
array['('] = TokenType::ParenOpen;
array[')'] = TokenType::ParenClose;
array['%'] = TokenType::Percent;
array['.'] = TokenType::Period;
array['|'] = TokenType::Pipe;
array['+'] = TokenType::Plus;
array['?'] = TokenType::QuestionMark;
array[';'] = TokenType::Semicolon;
array['/'] = TokenType::Slash;
array['~'] = TokenType::Tilde;
array['<'] = TokenType::LessThan;
array['>'] = TokenType::GreaterThan;
return array;
}
static constexpr auto s_single_char_tokens = make_single_char_tokens_array();
static Utf16String create_utf16_string_from_possibly_invalid_utf8_string(StringView source)
{
Utf8View utf8_source { source };
if (utf8_source.validate()) [[likely]]
return Utf16String::from_utf8_without_validation(source);
StringBuilder builder(StringBuilder::Mode::UTF16);
for (auto code_point : utf8_source) {
builder.append_code_point(code_point);
if (code_point == AK::UnicodeUtils::REPLACEMENT_CODE_POINT)
break;
}
return builder.to_utf16_string();
}
Lexer::Lexer(StringView source, StringView filename, size_t line_number, size_t line_column)
: Lexer(create_utf16_string_from_possibly_invalid_utf8_string(source), filename, line_number, line_column)
{
// FIXME: Remove this API once all callers are ported to UTF-16.
}
Lexer::Lexer(Utf16String source, StringView filename, size_t line_number, size_t line_column)
: m_source(move(source))
, m_current_token(TokenType::Eof, {}, {}, {}, 0, 0, 0)
, m_filename(String::from_utf8(filename).release_value_but_fixme_should_propagate_errors())
, m_line_number(line_number)
, m_line_column(line_column)
, m_parsed_identifiers(adopt_ref(*new ParsedIdentifiers))
{
if (s_keywords.is_empty()) {
s_keywords.set("async"_utf16_fly_string, TokenType::Async);
s_keywords.set("await"_utf16_fly_string, TokenType::Await);
s_keywords.set("break"_utf16_fly_string, TokenType::Break);
s_keywords.set("case"_utf16_fly_string, TokenType::Case);
s_keywords.set("catch"_utf16_fly_string, TokenType::Catch);
s_keywords.set("class"_utf16_fly_string, TokenType::Class);
s_keywords.set("const"_utf16_fly_string, TokenType::Const);
s_keywords.set("continue"_utf16_fly_string, TokenType::Continue);
s_keywords.set("debugger"_utf16_fly_string, TokenType::Debugger);
s_keywords.set("default"_utf16_fly_string, TokenType::Default);
s_keywords.set("delete"_utf16_fly_string, TokenType::Delete);
s_keywords.set("do"_utf16_fly_string, TokenType::Do);
s_keywords.set("else"_utf16_fly_string, TokenType::Else);
s_keywords.set("enum"_utf16_fly_string, TokenType::Enum);
s_keywords.set("export"_utf16_fly_string, TokenType::Export);
s_keywords.set("extends"_utf16_fly_string, TokenType::Extends);
s_keywords.set("false"_utf16_fly_string, TokenType::BoolLiteral);
s_keywords.set("finally"_utf16_fly_string, TokenType::Finally);
s_keywords.set("for"_utf16_fly_string, TokenType::For);
s_keywords.set("function"_utf16_fly_string, TokenType::Function);
s_keywords.set("if"_utf16_fly_string, TokenType::If);
s_keywords.set("import"_utf16_fly_string, TokenType::Import);
s_keywords.set("in"_utf16_fly_string, TokenType::In);
s_keywords.set("instanceof"_utf16_fly_string, TokenType::Instanceof);
s_keywords.set("let"_utf16_fly_string, TokenType::Let);
s_keywords.set("new"_utf16_fly_string, TokenType::New);
s_keywords.set("null"_utf16_fly_string, TokenType::NullLiteral);
s_keywords.set("return"_utf16_fly_string, TokenType::Return);
s_keywords.set("super"_utf16_fly_string, TokenType::Super);
s_keywords.set("switch"_utf16_fly_string, TokenType::Switch);
s_keywords.set("this"_utf16_fly_string, TokenType::This);
s_keywords.set("throw"_utf16_fly_string, TokenType::Throw);
s_keywords.set("true"_utf16_fly_string, TokenType::BoolLiteral);
s_keywords.set("try"_utf16_fly_string, TokenType::Try);
s_keywords.set("typeof"_utf16_fly_string, TokenType::Typeof);
s_keywords.set("var"_utf16_fly_string, TokenType::Var);
s_keywords.set("void"_utf16_fly_string, TokenType::Void);
s_keywords.set("while"_utf16_fly_string, TokenType::While);
s_keywords.set("with"_utf16_fly_string, TokenType::With);
s_keywords.set("yield"_utf16_fly_string, TokenType::Yield);
}
consume();
}
void Lexer::consume()
{
auto did_reach_eof = [this] {
if (m_position < m_source.length_in_code_units())
return false;
m_eof = true;
m_current_code_unit = '\0';
m_position = m_source.length_in_code_units() + 1;
m_line_column++;
return true;
};
if (m_position > m_source.length_in_code_units())
return;
if (did_reach_eof())
return;
if (is_line_terminator()) {
if constexpr (LEXER_DEBUG) {
StringView type;
if (m_current_code_unit == '\n')
type = "LINE FEED"sv;
else if (m_current_code_unit == '\r')
type = "CARRIAGE RETURN"sv;
else if (m_source.code_unit_at(m_position + 1) == LINE_SEPARATOR)
type = "LINE SEPARATOR"sv;
else
type = "PARAGRAPH SEPARATOR"sv;
dbgln("Found a line terminator: {}", type);
}
// If the previous character is \r and the current one \n we already updated line number
// and column - don't do it again. From https://tc39.es/ecma262/#sec-line-terminators:
// The sequence <CR><LF> is commonly used as a line terminator.
// It should be considered a single SourceCharacter for the purpose of reporting line numbers.
auto second_char_of_crlf = m_position > 1 && m_source.code_unit_at(m_position - 2) == '\r' && m_current_code_unit == '\n';
if (!second_char_of_crlf) {
m_line_number++;
m_line_column = 1;
dbgln_if(LEXER_DEBUG, "Incremented line number, now at: line {}, column 1", m_line_number);
} else {
dbgln_if(LEXER_DEBUG, "Previous was CR, this is LF - not incrementing line number again.");
}
} else {
if (AK::UnicodeUtils::is_utf16_high_surrogate(m_current_code_unit) && m_position < m_source.length_in_code_units()) {
if (AK::UnicodeUtils::is_utf16_low_surrogate(m_source.code_unit_at(m_position))) {
++m_position;
if (did_reach_eof())
return;
}
}
++m_line_column;
}
m_current_code_unit = m_source.code_unit_at(m_position++);
}
bool Lexer::consume_decimal_number()
{
if (!is_ascii_digit(m_current_code_unit))
return false;
while (is_ascii_digit(m_current_code_unit) || match_numeric_literal_separator_followed_by(is_ascii_digit)) {
consume();
}
return true;
}
bool Lexer::consume_exponent()
{
consume();
if (m_current_code_unit == '-' || m_current_code_unit == '+')
consume();
if (!is_ascii_digit(m_current_code_unit))
return false;
return consume_decimal_number();
}
static constexpr bool is_octal_digit(char16_t ch)
{
return ch >= '0' && ch <= '7';
}
bool Lexer::consume_octal_number()
{
consume();
if (!is_octal_digit(m_current_code_unit))
return false;
while (is_octal_digit(m_current_code_unit) || match_numeric_literal_separator_followed_by(is_octal_digit))
consume();
return true;
}
bool Lexer::consume_hexadecimal_number()
{
consume();
if (!is_ascii_hex_digit(m_current_code_unit))
return false;
while (is_ascii_hex_digit(m_current_code_unit) || match_numeric_literal_separator_followed_by(is_ascii_hex_digit))
consume();
return true;
}
static constexpr bool is_binary_digit(char16_t ch)
{
return ch == '0' || ch == '1';
}
bool Lexer::consume_binary_number()
{
consume();
if (!is_binary_digit(m_current_code_unit))
return false;
while (is_binary_digit(m_current_code_unit) || match_numeric_literal_separator_followed_by(is_binary_digit))
consume();
return true;
}
template<typename Callback>
bool Lexer::match_numeric_literal_separator_followed_by(Callback callback) const
{
if (m_position >= m_source.length_in_code_units())
return false;
return m_current_code_unit == '_'
&& callback(m_source.code_unit_at(m_position));
}
bool Lexer::match(char16_t a, char16_t b) const
{
if (m_position >= m_source.length_in_code_units())
return false;
return m_current_code_unit == a
&& m_source.code_unit_at(m_position) == b;
}
bool Lexer::match(char16_t a, char16_t b, char16_t c) const
{
if (m_position + 1 >= m_source.length_in_code_units())
return false;
return m_current_code_unit == a
&& m_source.code_unit_at(m_position) == b
&& m_source.code_unit_at(m_position + 1) == c;
}
bool Lexer::match(char16_t a, char16_t b, char16_t c, char16_t d) const
{
if (m_position + 2 >= m_source.length_in_code_units())
return false;
return m_current_code_unit == a
&& m_source.code_unit_at(m_position) == b
&& m_source.code_unit_at(m_position + 1) == c
&& m_source.code_unit_at(m_position + 2) == d;
}
bool Lexer::is_eof() const
{
return m_eof;
}
ALWAYS_INLINE bool Lexer::is_line_terminator() const
{
// OPTIMIZATION: Fast-path for ASCII characters.
if (m_current_code_unit == '\n' || m_current_code_unit == '\r')
return true;
if (is_ascii(m_current_code_unit))
return false;
return JS::is_line_terminator(current_code_point());
}
ALWAYS_INLINE u32 Lexer::current_code_point() const
{
if (m_position == 0)
return AK::UnicodeUtils::REPLACEMENT_CODE_POINT;
auto substring = m_source.substring_view(m_position - 1);
if (substring.is_empty())
return AK::UnicodeUtils::REPLACEMENT_CODE_POINT;
return *substring.begin();
}
bool Lexer::is_whitespace() const
{
// OPTIMIZATION: Fast-path for ASCII characters.
if (is_ascii_space(m_current_code_unit))
return true;
if (is_ascii(m_current_code_unit))
return false;
return JS::is_whitespace(current_code_point());
}
// UnicodeEscapeSequence :: https://tc39.es/ecma262/#prod-UnicodeEscapeSequence
// u Hex4Digits
// u{ CodePoint }
Optional<u32> Lexer::is_identifier_unicode_escape(size_t& identifier_length) const
{
Utf16GenericLexer lexer(source().substring_view(m_position - 1));
if (auto code_point_or_error = lexer.consume_escaped_code_point(false); !code_point_or_error.is_error()) {
identifier_length = lexer.tell();
return code_point_or_error.value();
}
return {};
}
// IdentifierStart :: https://tc39.es/ecma262/#prod-IdentifierStart
// UnicodeIDStart
// $
// _
// \ UnicodeEscapeSequence
Optional<u32> Lexer::is_identifier_start(size_t& identifier_length) const
{
u32 code_point = current_code_point();
identifier_length = 1;
if (code_point == '\\') {
if (auto maybe_code_point = is_identifier_unicode_escape(identifier_length); maybe_code_point.has_value())
code_point = *maybe_code_point;
else
return {};
}
if (is_ascii_alpha(code_point) || code_point == '_' || code_point == '$')
return code_point;
// Optimization: the first codepoint with the ID_Start property after A-Za-z is outside the
// ASCII range (0x00AA), so we can skip code_point_has_property() for any ASCII characters.
if (is_ascii(code_point))
return {};
if (Unicode::code_point_has_identifier_start_property(code_point))
return code_point;
return {};
}
// IdentifierPart :: https://tc39.es/ecma262/#prod-IdentifierPart
// UnicodeIDContinue
// $
// \ UnicodeEscapeSequence
// <ZWNJ>
// <ZWJ>
Optional<u32> Lexer::is_identifier_middle(size_t& identifier_length) const
{
u32 code_point = current_code_point();
identifier_length = 1;
if (code_point == '\\') {
if (auto maybe_code_point = is_identifier_unicode_escape(identifier_length); maybe_code_point.has_value())
code_point = *maybe_code_point;
else
return {};
}
if (is_ascii_alphanumeric(code_point) || (code_point == '$') || (code_point == ZERO_WIDTH_NON_JOINER) || (code_point == ZERO_WIDTH_JOINER))
return code_point;
// Optimization: the first codepoint with the ID_Continue property after A-Za-z0-9_ is outside the
// ASCII range (0x00AA), so we can skip code_point_has_property() for any ASCII characters.
if (code_point == '_')
return code_point;
if (is_ascii(code_point))
return {};
if (Unicode::code_point_has_identifier_continue_property(code_point))
return code_point;
return {};
}
bool Lexer::is_line_comment_start(bool line_has_token_yet) const
{
return match('/', '/')
|| (m_allow_html_comments && match('<', '!', '-', '-'))
// "-->" is considered a line comment start if the current line is only whitespace and/or
// other block comment(s); or in other words: the current line does not have a token or
// ongoing line comment yet
|| (m_allow_html_comments && !line_has_token_yet && match('-', '-', '>'))
// https://tc39.es/ecma262/#sec-hashbang
|| (match('#', '!') && m_position == 1);
}
bool Lexer::is_block_comment_start() const
{
return match('/', '*');
}
bool Lexer::is_block_comment_end() const
{
return match('*', '/');
}
bool Lexer::is_numeric_literal_start() const
{
return is_ascii_digit(m_current_code_unit) || (m_current_code_unit == '.' && m_position < m_source.length_in_code_units() && is_ascii_digit(m_source.code_unit_at(m_position)));
}
bool Lexer::slash_means_division() const
{
auto type = m_current_token.type();
return m_current_token.is_identifier_name()
|| type == TokenType::BigIntLiteral
|| type == TokenType::BracketClose
|| type == TokenType::CurlyClose
|| type == TokenType::MinusMinus
|| type == TokenType::NumericLiteral
|| type == TokenType::ParenClose
|| type == TokenType::PlusPlus
|| type == TokenType::PrivateIdentifier
|| type == TokenType::RegexLiteral
|| type == TokenType::StringLiteral
|| type == TokenType::TemplateLiteralEnd;
}
Token Lexer::next()
{
auto trivia_start = m_position;
auto in_template = !m_template_states.is_empty();
bool line_has_token_yet = m_line_column > 1;
bool unterminated_comment = false;
if (!in_template || m_template_states.last().in_expr) {
// consume whitespace and comments
while (true) {
if (is_line_terminator()) {
line_has_token_yet = false;
do {
consume();
} while (is_line_terminator());
} else if (is_whitespace()) {
do {
consume();
} while (is_whitespace());
} else if (is_line_comment_start(line_has_token_yet)) {
consume();
do {
consume();
} while (!is_eof() && !is_line_terminator());
} else if (is_block_comment_start()) {
size_t start_line_number = m_line_number;
consume();
do {
consume();
} while (!is_eof() && !is_block_comment_end());
if (is_eof())
unterminated_comment = true;
consume(); // consume *
if (is_eof())
unterminated_comment = true;
consume(); // consume /
if (start_line_number != m_line_number)
line_has_token_yet = false;
} else {
break;
}
}
}
size_t value_start = m_position;
size_t value_start_line_number = m_line_number;
size_t value_start_column_number = m_line_column;
auto token_type = TokenType::Invalid;
auto did_consume_whitespace_or_comments = trivia_start != value_start;
// This is being used to communicate info about invalid tokens to the parser, which then
// can turn that into more specific error messages - instead of us having to make up a
// bunch of Invalid* tokens (bad numeric literals, unterminated comments etc.)
StringView token_message;
Optional<Utf16FlyString> identifier;
size_t identifier_length = 0;
if (m_current_token.type() == TokenType::RegexLiteral && !is_eof() && is_ascii_alpha(m_current_code_unit) && !did_consume_whitespace_or_comments) {
token_type = TokenType::RegexFlags;
while (!is_eof() && is_ascii_alpha(m_current_code_unit))
consume();
} else if (m_current_code_unit == '`') {
consume();
if (!in_template) {
token_type = TokenType::TemplateLiteralStart;
m_template_states.append({ false, 0 });
} else {
if (m_template_states.last().in_expr) {
m_template_states.append({ false, 0 });
token_type = TokenType::TemplateLiteralStart;
} else {
m_template_states.take_last();
token_type = TokenType::TemplateLiteralEnd;
}
}
} else if (in_template && m_template_states.last().in_expr && m_template_states.last().open_bracket_count == 0 && m_current_code_unit == '}') {
consume();
token_type = TokenType::TemplateLiteralExprEnd;
m_template_states.last().in_expr = false;
} else if (in_template && !m_template_states.last().in_expr) {
if (is_eof()) {
token_type = TokenType::UnterminatedTemplateLiteral;
m_template_states.take_last();
} else if (match('$', '{')) {
token_type = TokenType::TemplateLiteralExprStart;
consume();
consume();
m_template_states.last().in_expr = true;
} else {
// TemplateCharacter ::
// $ [lookahead ≠ {]
// \ TemplateEscapeSequence
// \ NotEscapeSequence
// LineContinuation
// LineTerminatorSequence
// SourceCharacter but not one of ` or \ or $ or LineTerminator
while (!match('$', '{') && m_current_code_unit != '`' && !is_eof()) {
if (match('\\', '$') || match('\\', '`') || match('\\', '\\'))
consume();
consume();
}
if (is_eof() && !m_template_states.is_empty())
token_type = TokenType::UnterminatedTemplateLiteral;
else
token_type = TokenType::TemplateLiteralString;
}
} else if (m_current_code_unit == '#') {
// Note: This has some duplicated code with the identifier lexing below
consume();
auto code_point = is_identifier_start(identifier_length);
if (code_point.has_value()) {
StringBuilder builder(StringBuilder::Mode::UTF16);
builder.append_code_point('#');
do {
builder.append_code_point(*code_point);
for (size_t i = 0; i < identifier_length; ++i)
consume();
code_point = is_identifier_middle(identifier_length);
} while (code_point.has_value());
identifier = builder.to_utf16_string();
token_type = TokenType::PrivateIdentifier;
m_parsed_identifiers->identifiers.set(*identifier);
} else {
token_type = TokenType::Invalid;
token_message = "Start of private name '#' but not followed by valid identifier"sv;
}
} else if (auto code_point = is_identifier_start(identifier_length); code_point.has_value()) {
bool has_escaped_character = false;
// identifier or keyword
StringBuilder builder(StringBuilder::Mode::UTF16);
do {
builder.append_code_point(*code_point);
for (size_t i = 0; i < identifier_length; ++i)
consume();
has_escaped_character |= identifier_length > 1;
code_point = is_identifier_middle(identifier_length);
} while (code_point.has_value());
identifier = builder.to_utf16_string();
m_parsed_identifiers->identifiers.set(*identifier);
auto it = s_keywords.find(identifier->hash(), [&](auto& entry) { return entry.key == identifier; });
if (it == s_keywords.end())
token_type = TokenType::Identifier;
else
token_type = has_escaped_character ? TokenType::EscapedKeyword : it->value;
} else if (is_numeric_literal_start()) {
token_type = TokenType::NumericLiteral;
bool is_invalid_numeric_literal = false;
if (m_current_code_unit == '0') {
consume();
if (m_current_code_unit == '.') {
// decimal
consume();
while (is_ascii_digit(m_current_code_unit))
consume();
if (m_current_code_unit == 'e' || m_current_code_unit == 'E')
is_invalid_numeric_literal = !consume_exponent();
} else if (m_current_code_unit == 'e' || m_current_code_unit == 'E') {
is_invalid_numeric_literal = !consume_exponent();
} else if (m_current_code_unit == 'o' || m_current_code_unit == 'O') {
// octal
is_invalid_numeric_literal = !consume_octal_number();
if (m_current_code_unit == 'n') {
consume();
token_type = TokenType::BigIntLiteral;
}
} else if (m_current_code_unit == 'b' || m_current_code_unit == 'B') {
// binary
is_invalid_numeric_literal = !consume_binary_number();
if (m_current_code_unit == 'n') {
consume();
token_type = TokenType::BigIntLiteral;
}
} else if (m_current_code_unit == 'x' || m_current_code_unit == 'X') {
// hexadecimal
is_invalid_numeric_literal = !consume_hexadecimal_number();
if (m_current_code_unit == 'n') {
consume();
token_type = TokenType::BigIntLiteral;
}
} else if (m_current_code_unit == 'n') {
consume();
token_type = TokenType::BigIntLiteral;
} else if (is_ascii_digit(m_current_code_unit)) {
// octal without '0o' prefix. Forbidden in 'strict mode'
do {
consume();
} while (is_ascii_digit(m_current_code_unit));
}
} else {
// 1...9 or period
while (is_ascii_digit(m_current_code_unit) || match_numeric_literal_separator_followed_by(is_ascii_digit))
consume();
if (m_current_code_unit == 'n') {
consume();
token_type = TokenType::BigIntLiteral;
} else {
if (m_current_code_unit == '.') {
consume();
if (m_current_code_unit == '_')
is_invalid_numeric_literal = true;
while (is_ascii_digit(m_current_code_unit) || match_numeric_literal_separator_followed_by(is_ascii_digit)) {
consume();
}
}
if (m_current_code_unit == 'e' || m_current_code_unit == 'E')
is_invalid_numeric_literal = is_invalid_numeric_literal || !consume_exponent();
}
}
if (is_invalid_numeric_literal) {
token_type = TokenType::Invalid;
token_message = "Invalid numeric literal"sv;
}
} else if (m_current_code_unit == '"' || m_current_code_unit == '\'') {
auto stop_char = m_current_code_unit;
consume();
// Note: LS/PS line terminators are allowed in string literals.
while (m_current_code_unit != stop_char && m_current_code_unit != '\r' && m_current_code_unit != '\n' && !is_eof()) {
if (m_current_code_unit == '\\') {
consume();
if (m_current_code_unit == '\r' && m_position < m_source.length_in_code_units() && m_source.code_unit_at(m_position) == '\n') {
consume();
}
}
consume();
}
if (m_current_code_unit != stop_char) {
token_type = TokenType::UnterminatedStringLiteral;
} else {
consume();
token_type = TokenType::StringLiteral;
}
} else if (m_current_code_unit == '/' && !slash_means_division()) {
consume();
token_type = consume_regex_literal();
} else if (m_eof) {
if (unterminated_comment) {
token_type = TokenType::Invalid;
token_message = "Unterminated multi-line comment"sv;
} else {
token_type = TokenType::Eof;
}
} else {
bool found_token = false;
// There is only one four-char operator: >>>=
if (match('>', '>', '>', '=')) {
found_token = true;
token_type = TokenType::UnsignedShiftRightEquals;
consume();
consume();
consume();
consume();
}
if (!found_token && m_position + 1 < m_source.length_in_code_units()) {
auto three_chars_view = m_source.substring_view(m_position - 1, 3);
if (auto type = parse_three_char_token(three_chars_view); type != TokenType::Invalid) {
found_token = true;
token_type = type;
consume();
consume();
consume();
}
}
if (!found_token && m_position < m_source.length_in_code_units()) {
auto two_chars_view = m_source.substring_view(m_position - 1, 2);
if (auto type = parse_two_char_token(two_chars_view); type != TokenType::Invalid) {
// OptionalChainingPunctuator :: ?. [lookahead ∉ DecimalDigit]
if (!(type == TokenType::QuestionMarkPeriod && m_position + 1 < m_source.length_in_code_units() && is_ascii_digit(m_source.code_unit_at(m_position + 1)))) {
found_token = true;
token_type = type;
consume();
consume();
}
}
}
if (!found_token && is_ascii(m_current_code_unit)) {
if (auto type = s_single_char_tokens[static_cast<u8>(m_current_code_unit)]; type != TokenType::Invalid) {
found_token = true;
token_type = type;
consume();
}
}
if (!found_token) {
token_type = TokenType::Invalid;
consume();
}
}
if (!m_template_states.is_empty() && m_template_states.last().in_expr) {
if (token_type == TokenType::CurlyOpen) {
m_template_states.last().open_bracket_count++;
} else if (token_type == TokenType::CurlyClose) {
m_template_states.last().open_bracket_count--;
}
}
m_current_token = Token(
token_type,
token_message,
m_source.substring_view(trivia_start - 1, value_start - trivia_start),
m_source.substring_view(value_start - 1, m_position - value_start),
value_start_line_number,
value_start_column_number,
value_start - 1);
if (identifier.has_value())
m_current_token.set_identifier_value(identifier.release_value());
if constexpr (LEXER_DEBUG) {
dbgln("------------------------------");
dbgln("Token: {}", m_current_token.name());
dbgln("Trivia: _{}_", m_current_token.trivia());
dbgln("Value: _{}_", m_current_token.value());
dbgln("Line: {}, Column: {}", m_current_token.line_number(), m_current_token.line_column());
dbgln("------------------------------");
}
return m_current_token;
}
Token Lexer::force_slash_as_regex()
{
VERIFY(m_current_token.type() == TokenType::Slash || m_current_token.type() == TokenType::SlashEquals);
bool has_equals = m_current_token.type() == TokenType::SlashEquals;
VERIFY(m_position > 0);
size_t value_start = m_position - 1;
if (has_equals) {
VERIFY(m_source.code_unit_at(value_start - 1) == '=');
--value_start;
--m_position;
m_current_code_unit = '=';
}
TokenType token_type = consume_regex_literal();
m_current_token = Token(
token_type,
String {},
m_current_token.trivia(),
m_source.substring_view(value_start - 1, m_position - value_start),
m_current_token.line_number(),
m_current_token.line_column(),
value_start - 1);
if constexpr (LEXER_DEBUG) {
dbgln("------------------------------");
dbgln("Token: {}", m_current_token.name());
dbgln("Trivia: _{}_", m_current_token.trivia());
dbgln("Value: _{}_", m_current_token.value());
dbgln("Line: {}, Column: {}", m_current_token.line_number(), m_current_token.line_column());
dbgln("------------------------------");
}
return m_current_token;
}
TokenType Lexer::consume_regex_literal()
{
while (!is_eof()) {
if (is_line_terminator() || (!m_regex_is_in_character_class && m_current_code_unit == '/'))
break;
if (m_current_code_unit == '[') {
m_regex_is_in_character_class = true;
} else if (m_current_code_unit == ']') {
m_regex_is_in_character_class = false;
} else if (!m_regex_is_in_character_class && m_current_code_unit == '/') {
break;
}
if (match('\\', '/') || match('\\', '[') || match('\\', '\\') || (m_regex_is_in_character_class && match('\\', ']')))
consume();
consume();
}
if (m_current_code_unit == '/') {
consume();
return TokenType::RegexLiteral;
}
return TokenType::UnterminatedRegexLiteral;
}
// https://tc39.es/ecma262/#prod-SyntaxCharacter
bool is_syntax_character(u32 code_point)
{
// SyntaxCharacter :: one of
// ^ $ \ . * + ? ( ) [ ] { } |
static constexpr auto syntax_characters = "^$\\.*+?()[]{}|"sv;
return is_ascii(code_point) && syntax_characters.contains(static_cast<char>(code_point));
}
// https://tc39.es/ecma262/#prod-WhiteSpace
bool is_whitespace(u32 code_point)
{
// WhiteSpace ::
// <TAB>
// <VT>
// <FF>
// <ZWNBSP>
// <USP>
if (is_ascii_space(code_point))
return true;
if (code_point == NO_BREAK_SPACE || code_point == ZERO_WIDTH_NO_BREAK_SPACE)
return true;
return Unicode::code_point_has_space_separator_general_category(code_point);
}
// https://tc39.es/ecma262/#prod-LineTerminator
bool is_line_terminator(u32 code_point)
{
// LineTerminator ::
// <LF>
// <CR>
// <LS>
// <PS>
return code_point == '\n' || code_point == '\r' || code_point == LINE_SEPARATOR || code_point == PARAGRAPH_SEPARATOR;
}
}
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