Something went wrong. Try again.
we (web engine): Experimental web browser project to understand the limits of Claude
Something went wrong. Try again.
12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182838485868788899091929394959697989910010110210310410510610710810911011111211311411511611711811912012112212312412512612712812913013113213313413513613713813914014114214314414514614714814915015115215315415515615715815916016116216316416516616716816917017117217317417517617717817918018118218318418518618718818919019119219319419519619719819920020120220320420520620720820921021121221321421521621721821922022122222322422522622722822923023123223323423523623723823924024124224324424524624724824925025125225325425525625725825926026126226326426526626726826927027127227327427527627727827928028128228328428528628728828929029129229329429529629729829930030130230330430530630730830931031131231331431531631731831932032132232332432532632732832933033133233333433533633733833934034134234334434534634734834935035135235335435535635735835936036136236336436536636736836937037137237337437537637737837938038138238338438538638738838939039139239339439539639739839940040140240340440540640740840941041141241341441541641741841942042142242342442542642742842943043143243343443543643743843944044144244344444544644744844945045145245345445545645745845946046146246346446546646746846947047147247347447547647747847948048148248348448548648748848949049149249349449549649749849950050150250350450550650750850951051151251351451551651751851952052152252352452552652752852953053153253353453553653753853954054154254354454554654754854955055155255355455555655755855956056156256356456556656756856957057157257357457557657757857958058158258358458558658758858959059159259359459559659759859960060160260360460560660760860961061161261361461561661761861962062162262362462562662762862963063163263363463563663763863964064164264364464564664764864965065165265365465565665765865966066166266366466566666766866967067167267367467567667767867968068168268368468568668768868969069169269369469569669769869970070170270370470570670770870971071171271371471571671771871972072172272372472572672772872973073173273373473573673773873974074174274374474574674774874975075175275375475575675775875976076176276376476576676776876977077177277377477577677777877978078178278378478578678778878979079179279379479579679779879980080180280380480580680780880981081181281381481581681781881982082182282382482582682782882983083183283383483583683783883984084184284384484584684784884985085185285385485585685785885986086186286386486586686786886987087187287387487587687787887988088188288388488588688788888989089189289389489589689789889990090190290390490590690790890991091191291391491591691791891992092192292392492592692792892993093193293393493593693793893994094194294394494594694794894995095195295395495595695795895996096196296396496596696796896997097197297397497597697797897998098198298398498598698798898999099199299399499599699799899910001001100210031004100510061007100810091010101110121013101410151016101710181019102010211022102310241025102610271028102910301031103210331034103510361037103810391040104110421043104410451046104710481049105010511052105310541055105610571058105910601061106210631064106510661067106810691070107110721073107410751076107710781079108010811082108310841085108610871088108910901091109210931094109510961097109810991100110111021103110411051106110711081109111011111112111311141115111611171118111911201121112211231124112511261127112811291130113111321133113411351136113711381139114011411142114311441145114611471148114911501151115211531154115511561157115811591160116111621163116411651166116711681169117011711172117311741175117611771178117911801181118211831184118511861187118811891190119111921193119411951196119711981199120012011202120312041205120612071208120912101211121212131214121512161217121812191220122112221223122412251226122712281229123012311232123312341235123612371238123912401241124212431244124512461247124812491250125112521253125412551256125712581259126012611262126312641265126612671268126912701271127212731274127512761277127812791280128112821283128412851286128712881289129012911292129312941295129612971298129913001301130213031304130513061307130813091310131113121313131413151316131713181319132013211322132313241325132613271328132913301331133213331334133513361337133813391340134113421343134413451346134713481349135013511352135313541355135613571358135913601361136213631364136513661367136813691370137113721373137413751376137713781379138013811382138313841385138613871388138913901391139213931394139513961397139813991400140114021403140414051406140714081409141014111412141314141415141614171418141914201421142214231424142514261427142814291430143114321433143414351436143714381439144014411442144314441445144614471448144914501451145214531454145514561457145814591460146114621463146414651466146714681469147014711472147314741475147614771478147914801481148214831484148514861487148814891490149114921493149414951496149714981499150015011502150315041505150615071508150915101511151215131514151515161517151815191520152115221523152415251526152715281529153015311532153315341535153615371538153915401541154215431544154515461547154815491550155115521553155415551556155715581559156015611562156315641565156615671568156915701571157215731574157515761577157815791580158115821583158415851586158715881589159015911592159315941595159615971598159916001601160216031604160516061607160816091610161116121613161416151616161716181619162016211622162316241625162616271628162916301631163216331634163516361637163816391640164116421643164416451646164716481649165016511652165316541655165616571658165916601661166216631664166516661667166816691670167116721673167416751676167716781679168016811682168316841685168616871688168916901691169216931694169516961697169816991700170117021703170417051706170717081709171017111712171317141715171617171718171917201721172217231724172517261727172817291730173117321733173417351736173717381739174017411742174317441745174617471748174917501751175217531754175517561757175817591760176117621763176417651766176717681769177017711772177317741775177617771778177917801781178217831784178517861787178817891790179117921793179417951796179717981799180018011802180318041805180618071808180918101811181218131814181518161817181818191820182118221823182418251826182718281829183018311832183318341835183618371838183918401841184218431844184518461847184818491850185118521853185418551856185718581859186018611862186318641865186618671868186918701871187218731874187518761877187818791880188118821883188418851886188718881889189018911892189318941895189618971898189919001901190219031904190519061907190819091910191119121913191419151916191719181919192019211922192319241925192619271928192919301931193219331934193519361937193819391940194119421943194419451946194719481949195019511952195319541955195619571958195919601961196219631964196519661967196819691970197119721973197419751976197719781979198019811982198319841985198619871988198919901991199219931994199519961997199819992000200120022003200420052006200720082009201020112012201320142015201620172018201920202021202220232024202520262027202820292030203120322033203420352036203720382039204020412042204320442045204620472048204920502051205220532054205520562057205820592060206120622063206420652066206720682069207020712072207320742075207620772078207920802081208220832084208520862087208820892090209120922093209420952096209720982099210021012102210321042105210621072108210921102111211221132114211521162117211821192120212121222123212421252126212721282129213021312132213321342135213621372138213921402141214221432144214521462147214821492150215121522153215421552156215721582159216021612162216321642165216621672168216921702171217221732174217521762177217821792180218121822183218421852186218721882189219021912192219321942195219621972198219922002201220222032204220522062207220822092210221122122213221422152216221722182219222022212222222322242225222622272228222922302231223222332234223522362237223822392240224122422243224422452246224722482249225022512252225322542255225622572258225922602261226222632264226522662267226822692270227122722273227422752276227722782279228022812282228322842285228622872288228922902291229222932294229522962297229822992300230123022303230423052306230723082309231023112312231323142315231623172318231923202321232223232324232523262327232823292330233123322333233423352336233723382339234023412342234323442345234623472348234923502351235223532354235523562357235823592360236123622363236423652366236723682369237023712372237323742375237623772378237923802381238223832384238523862387238823892390239123922393239423952396239723982399240024012402240324042405240624072408240924102411241224132414241524162417241824192420242124222423242424252426242724282429243024312432243324342435243624372438243924402441244224432444244524462447244824492450245124522453245424552456245724582459246024612462246324642465246624672468246924702471247224732474247524762477247824792480248124822483248424852486248724882489249024912492249324942495249624972498249925002501250225032504250525062507250825092510251125122513251425152516251725182519252025212522252325242525252625272528252925302531253225332534253525362537253825392540254125422543254425452546254725482549255025512552255325542555255625572558255925602561256225632564256525662567256825692570257125722573257425752576257725782579258025812582258325842585258625872588258925902591259225932594259525962597259825992600260126022603260426052606260726082609261026112612261326142615261626172618261926202621262226232624262526262627262826292630263126322633263426352636263726382639264026412642264326442645264626472648264926502651265226532654265526562657265826592660266126622663266426652666266726682669267026712672267326742675267626772678267926802681268226832684268526862687268826892690269126922693269426952696269726982699270027012702270327042705270627072708270927102711271227132714271527162717271827192720272127222723272427252726272727282729273027312732273327342735273627372738273927402741274227432744274527462747274827492750275127522753275427552756275727582759276027612762276327642765276627672768276927702771277227732774277527762777277827792780278127822783278427852786278727882789279027912792279327942795279627972798279928002801280228032804280528062807280828092810281128122813281428152816281728182819282028212822282328242825282628272828282928302831283228332834283528362837283828392840284128422843284428452846284728482849285028512852285328542855285628572858285928602861286228632864286528662867286828692870287128722873287428752876287728782879288028812882288328842885288628872888288928902891289228932894289528962897289828992900290129022903290429052906290729082909291029112912291329142915291629172918291929202921292229232924292529262927292829292930293129322933293429352936293729382939294029412942294329442945294629472948294929502951295229532954295529562957295829592960296129622963296429652966296729682969297029712972297329742975297629772978297929802981298229832984298529862987298829892990299129922993299429952996299729982999300030013002300330043005300630073008300930103011301230133014301530163017301830193020302130223023302430253026302730283029303030313032303330343035303630373038303930403041304230433044304530463047304830493050305130523053305430553056305730583059306030613062306330643065306630673068306930703071307230733074307530763077307830793080308130823083308430853086308730883089309030913092309330943095309630973098309931003101310231033104310531063107310831093110311131123113311431153116311731183119312031213122312331243125312631273128312931303131313231333134313531363137313831393140314131423143314431453146314731483149315031513152315331543155315631573158315931603161316231633164316531663167316831693170317131723173317431753176317731783179318031813182318331843185318631873188318931903191319231933194319531963197319831993200320132023203320432053206320732083209321032113212321332143215321632173218321932203221322232233224322532263227322832293230323132323233323432353236323732383239324032413242324332443245324632473248324932503251325232533254325532563257325832593260326132623263326432653266326732683269327032713272327332743275327632773278327932803281328232833284328532863287328832893290329132923293329432953296329732983299330033013302330333043305330633073308330933103311331233133314331533163317331833193320332133223323332433253326332733283329333033313332333333343335333633373338333933403341334233433344334533463347334833493350335133523353335433553356335733583359336033613362336333643365336633673368336933703371337233733374337533763377337833793380338133823383338433853386338733883389339033913392339333943395339633973398339934003401340234033404340534063407340834093410341134123413341434153416341734183419342034213422342334243425342634273428342934303431343234333434343534363437343834393440344134423443344434453446344734483449345034513452345334543455345634573458345934603461346234633464346534663467346834693470347134723473347434753476347734783479348034813482348334843485348634873488348934903491349234933494349534963497349834993500350135023503350435053506350735083509351035113512351335143515351635173518351935203521352235233524352535263527352835293530353135323533353435353536353735383539354035413542354335443545354635473548354935503551355235533554355535563557355835593560356135623563356435653566356735683569357035713572357335743575357635773578357935803581358235833584358535863587358835893590359135923593359435953596359735983599360036013602360336043605360636073608360936103611361236133614361536163617361836193620362136223623362436253626362736283629363036313632363336343635363636373638363936403641364236433644364536463647364836493650365136523653365436553656365736583659366036613662366336643665366636673668366936703671367236733674367536763677367836793680368136823683368436853686368736883689369036913692369336943695369636973698369937003701370237033704370537063707370837093710371137123713371437153716371737183719372037213722372337243725372637273728372937303731373237333734373537363737373837393740374137423743374437453746374737483749375037513752375337543755375637573758375937603761376237633764376537663767376837693770377137723773377437753776377737783779378037813782378337843785378637873788378937903791379237933794379537963797379837993800380138023803380438053806380738083809381038113812381338143815381638173818381938203821382238233824382538263827382838293830383138323833383438353836383738383839384038413842384338443845384638473848384938503851385238533854385538563857385838593860386138623863386438653866386738683869387038713872387338743875387638773878387938803881388238833884388538863887388838893890389138923893389438953896389738983899390039013902390339043905390639073908390939103911391239133914391539163917391839193920392139223923392439253926392739283929393039313932393339343935393639373938393939403941394239433944394539463947394839493950395139523953395439553956395739583959396039613962396339643965396639673968396939703971397239733974397539763977397839793980398139823983398439853986398739883989399039913992399339943995399639973998399940004001400240034004400540064007400840094010401140124013401440154016401740184019402040214022402340244025402640274028402940304031403240334034403540364037403840394040404140424043404440454046404740484049405040514052405340544055405640574058405940604061406240634064406540664067406840694070407140724073407440754076407740784079408040814082408340844085408640874088408940904091409240934094409540964097409840994100410141024103410441054106410741084109411041114112411341144115411641174118411941204121412241234124412541264127412841294130413141324133413441354136413741384139414041414142414341444145414641474148414941504151415241534154415541564157415841594160416141624163416441654166416741684169417041714172417341744175417641774178//! Recursive-descent JavaScript parser with Pratt expression parsing.//!//! Transforms a token stream from the [`crate::lexer::Lexer`] into an//! [`crate::ast::Program`] AST.
use crate::ast::*;use crate::lexer::{LexError, Lexer, SourcePos, Span, Token, TokenKind};use std::fmt;
// ── Error ───────────────────────────────────────────────────
/// An error produced during parsing.#[derive(Debug, Clone, PartialEq)]pub struct ParseError { pub message: String, pub pos: SourcePos,}
impl fmt::Display for ParseError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!( f, "ParseError at {}:{}: {}", self.pos.line, self.pos.col, self.message ) }}
impl From<LexError> for ParseError { fn from(e: LexError) -> Self { ParseError { message: e.message, pos: e.pos, } }}
// ── Parser ──────────────────────────────────────────────────
pub struct Parser { tokens: Vec<Token>, pos: usize, /// When false, `in` is not treated as a binary operator (for-init disambiguation). allow_in: bool,}
impl Parser { /// Parse source as a script. pub fn parse(source: &str) -> Result<Program, ParseError> { let tokens = Lexer::tokenize(source)?; let mut parser = Parser { tokens, pos: 0, allow_in: true, }; parser.parse_program(SourceType::Script) }
/// Parse source as a module. pub fn parse_module(source: &str) -> Result<Program, ParseError> { let tokens = Lexer::tokenize(source)?; let mut parser = Parser { tokens, pos: 0, allow_in: true, }; parser.parse_program(SourceType::Module) }
// ── Token navigation ────────────────────────────────────
fn peek(&self) -> &Token { &self.tokens[self.pos.min(self.tokens.len() - 1)] }
fn peek_kind(&self) -> &TokenKind { &self.peek().kind }
fn peek_ahead(&self, offset: usize) -> &TokenKind { let idx = (self.pos + offset).min(self.tokens.len() - 1); &self.tokens[idx].kind }
fn at(&self, kind: &TokenKind) -> bool { std::mem::discriminant(self.peek_kind()) == std::mem::discriminant(kind) }
fn at_eof(&self) -> bool { matches!(self.peek_kind(), TokenKind::Eof) }
fn advance(&mut self) -> Token { let tok = self.tokens[self.pos.min(self.tokens.len() - 1)].clone(); if self.pos < self.tokens.len() - 1 { self.pos += 1; } tok }
fn eat(&mut self, kind: &TokenKind) -> bool { if self.at(kind) { self.advance(); true } else { false } }
fn expect(&mut self, kind: &TokenKind) -> Result<Token, ParseError> { if self.at(kind) { Ok(self.advance()) } else { Err(self.error(format!("expected {:?}, found {:?}", kind, self.peek_kind()))) } }
fn expect_semicolon(&mut self) -> Result<(), ParseError> { if self.eat(&TokenKind::Semicolon) { return Ok(()); } // ASI: insert semicolon before `}`, at EOF, or after newline if matches!(self.peek_kind(), TokenKind::RBrace | TokenKind::Eof) || self.peek().preceded_by_newline { return Ok(()); } Err(self.error(format!("expected `;`, found {:?}", self.peek_kind()))) }
fn expect_identifier(&mut self) -> Result<String, ParseError> { match self.peek_kind().clone() { TokenKind::Identifier(name) => { self.advance(); Ok(name) } kind if is_contextual_identifier(&kind) => { let name = format!("{kind}"); self.advance(); Ok(name) } _ => Err(self.error(format!("expected identifier, found {:?}", self.peek_kind()))), } }
/// Per ES5+, an "identifier name" allows any identifier OR any keyword. /// Used for property access after `.` and similar positions where reserved /// words are legal property names. fn expect_identifier_name(&mut self) -> Result<String, ParseError> { match self.peek_kind().clone() { TokenKind::Identifier(name) => { self.advance(); Ok(name) } kind if is_keyword(&kind) => { let name = format!("{kind}"); self.advance(); Ok(name) } _ => Err(self.error(format!( "expected identifier name, found {:?}", self.peek_kind() ))), } }
fn expect_module_export_name(&mut self) -> Result<(String, bool), ParseError> { match self.peek_kind().clone() { TokenKind::Identifier(name) => { self.advance(); Ok((name, true)) } TokenKind::String(name) => { self.advance(); Ok((name, false)) } kind if is_keyword(&kind) => { let binding_ok = is_contextual_identifier(&kind); let name = format!("{kind}"); self.advance(); Ok((name, binding_ok)) } _ => Err(self.error(format!( "expected module export name, found {:?}", self.peek_kind() ))), } }
fn start_span(&self) -> SourcePos { self.peek().span.start }
fn end_span(&self) -> SourcePos { if self.pos > 0 { self.tokens[self.pos - 1].span.end } else { self.peek().span.start } }
fn span_from(&self, start: SourcePos) -> Span { Span { start, end: self.end_span(), } }
fn error(&self, message: String) -> ParseError { ParseError { message, pos: self.peek().span.start, } }
// ── Program ─────────────────────────────────────────────
fn parse_program(&mut self, source_type: SourceType) -> Result<Program, ParseError> { let start = self.start_span(); let mut body = Vec::new(); while !self.at_eof() { body.push(self.parse_statement_list_item()?); } Ok(Program { body, source_type, span: self.span_from(start), }) }
fn parse_statement_list_item(&mut self) -> Result<Stmt, ParseError> { match self.peek_kind() { TokenKind::Function => self.parse_function_declaration(), TokenKind::Class => self.parse_class_declaration(), TokenKind::Var | TokenKind::Let | TokenKind::Const => { self.parse_variable_declaration_stmt() } TokenKind::Async if matches!(self.peek_ahead(1), TokenKind::Function) && !self.tokens[self.pos + 1].preceded_by_newline => { self.parse_async_function_declaration() } TokenKind::Import if !matches!(self.peek_ahead(1), TokenKind::LParen | TokenKind::Dot) => { self.parse_import_declaration() } TokenKind::Export => self.parse_export_declaration(), _ => self.parse_statement(), } }
// ── Statements ──────────────────────────────────────────
fn parse_statement(&mut self) -> Result<Stmt, ParseError> { match self.peek_kind() { TokenKind::LBrace => self.parse_block_stmt(), TokenKind::Semicolon => { let start = self.start_span(); self.advance(); Ok(Stmt { kind: StmtKind::Empty, span: self.span_from(start), }) } TokenKind::If => self.parse_if(), TokenKind::For => self.parse_for(), TokenKind::While => self.parse_while(), TokenKind::Do => self.parse_do_while(), TokenKind::Switch => self.parse_switch(), TokenKind::Try => self.parse_try(), TokenKind::Return => self.parse_return(), TokenKind::Throw => self.parse_throw(), TokenKind::Break => self.parse_break(), TokenKind::Continue => self.parse_continue(), TokenKind::With => self.parse_with(), TokenKind::Debugger => { let start = self.start_span(); self.advance(); self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::Debugger, span: self.span_from(start), }) } // Labeled statement: `ident: stmt` TokenKind::Identifier(_) if matches!(self.peek_ahead(1), TokenKind::Colon) => { self.parse_labeled() } // Variable declarations can also appear as statements TokenKind::Var | TokenKind::Let | TokenKind::Const => { self.parse_variable_declaration_stmt() } // Function/class declarations in statement position TokenKind::Function => self.parse_function_declaration(), TokenKind::Class => self.parse_class_declaration(), TokenKind::Async if matches!(self.peek_ahead(1), TokenKind::Function) && !self.tokens[self.pos + 1].preceded_by_newline => { self.parse_async_function_declaration() } _ => self.parse_expression_statement(), } }
fn parse_block_stmt(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); let body = self.parse_block_body()?; Ok(Stmt { kind: StmtKind::Block(body), span: self.span_from(start), }) }
fn parse_block_body(&mut self) -> Result<Vec<Stmt>, ParseError> { self.expect(&TokenKind::LBrace)?; let mut body = Vec::new(); while !self.at(&TokenKind::RBrace) && !self.at_eof() { body.push(self.parse_statement_list_item()?); } self.expect(&TokenKind::RBrace)?; Ok(body) }
fn parse_expression_statement(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); let expr = self.parse_expression()?; self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::Expr(expr), span: self.span_from(start), }) }
fn parse_if(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::If)?; self.expect(&TokenKind::LParen)?; let test = self.parse_expression()?; self.expect(&TokenKind::RParen)?; let consequent = Box::new(self.parse_statement()?); let alternate = if self.eat(&TokenKind::Else) { Some(Box::new(self.parse_statement()?)) } else { None }; Ok(Stmt { kind: StmtKind::If { test, consequent, alternate, }, span: self.span_from(start), }) }
fn parse_while(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::While)?; self.expect(&TokenKind::LParen)?; let test = self.parse_expression()?; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); Ok(Stmt { kind: StmtKind::While { test, body }, span: self.span_from(start), }) }
fn parse_do_while(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Do)?; let body = Box::new(self.parse_statement()?); self.expect(&TokenKind::While)?; self.expect(&TokenKind::LParen)?; let test = self.parse_expression()?; self.expect(&TokenKind::RParen)?; // ASI special case (ECMA-262 12.10.1): the terminating semicolon of a // `do-while` statement is inserted automatically whenever it is absent, // even without an intervening line terminator. So `do {} while (x) y` // and `do {} while (x) return 1` both parse, with `y`/`return` starting // a new statement. Consume an explicit `;` if present; otherwise rely on // unconditional ASI rather than requiring a newline. self.eat(&TokenKind::Semicolon); Ok(Stmt { kind: StmtKind::DoWhile { body, test }, span: self.span_from(start), }) }
fn parse_for(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::For)?; let is_await = self.eat(&TokenKind::Await); self.expect(&TokenKind::LParen)?;
// Check for for-in/for-of with var/let/const if matches!( self.peek_kind(), TokenKind::Var | TokenKind::Let | TokenKind::Const ) { let var_kind = match self.peek_kind() { TokenKind::Var => VarKind::Var, TokenKind::Let => VarKind::Let, TokenKind::Const => VarKind::Const, _ => unreachable!(), }; self.advance(); let pattern = self.parse_binding_pattern()?;
if self.eat(&TokenKind::In) { let right = self.parse_expression()?; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); return Ok(Stmt { kind: StmtKind::ForIn { left: ForInOfLeft::VarDecl { kind: var_kind, pattern, }, right, body, }, span: self.span_from(start), }); } if self.eat(&TokenKind::Of) { let right = self.parse_assignment_expression()?; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); return Ok(Stmt { kind: StmtKind::ForOf { left: ForInOfLeft::VarDecl { kind: var_kind, pattern, }, right, body, is_await, }, span: self.span_from(start), }); }
// Regular for: parse remaining declarators let mut declarators = vec![VarDeclarator { span: pattern.span, init: if self.eat(&TokenKind::Assign) { Some(self.parse_assignment_expression_no_in()?) } else { None }, pattern, }]; while self.eat(&TokenKind::Comma) { declarators.push(self.parse_var_declarator_no_in()?); } self.expect(&TokenKind::Semicolon)?; let test = if self.at(&TokenKind::Semicolon) { None } else { Some(self.parse_expression()?) }; self.expect(&TokenKind::Semicolon)?; let update = if self.at(&TokenKind::RParen) { None } else { Some(self.parse_expression()?) }; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); return Ok(Stmt { kind: StmtKind::For { init: Some(ForInit::VarDecl { kind: var_kind, declarators, }), test, update, body, }, span: self.span_from(start), }); }
// No var/let/const if self.eat(&TokenKind::Semicolon) { // for(; ...) let test = if self.at(&TokenKind::Semicolon) { None } else { Some(self.parse_expression()?) }; self.expect(&TokenKind::Semicolon)?; let update = if self.at(&TokenKind::RParen) { None } else { Some(self.parse_expression()?) }; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); return Ok(Stmt { kind: StmtKind::For { init: None, test, update, body, }, span: self.span_from(start), }); }
// Expression init — might be for-in/for-of let old_allow_in = self.allow_in; self.allow_in = false; let init_expr = self.parse_expression()?; self.allow_in = old_allow_in;
if self.eat(&TokenKind::In) { let pattern = self.expr_to_pattern(&init_expr)?; let right = self.parse_expression()?; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); return Ok(Stmt { kind: StmtKind::ForIn { left: ForInOfLeft::Pattern(pattern), right, body, }, span: self.span_from(start), }); } if self.eat(&TokenKind::Of) { let pattern = self.expr_to_pattern(&init_expr)?; let right = self.parse_assignment_expression()?; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); return Ok(Stmt { kind: StmtKind::ForOf { left: ForInOfLeft::Pattern(pattern), right, body, is_await, }, span: self.span_from(start), }); }
self.expect(&TokenKind::Semicolon)?; let test = if self.at(&TokenKind::Semicolon) { None } else { Some(self.parse_expression()?) }; self.expect(&TokenKind::Semicolon)?; let update = if self.at(&TokenKind::RParen) { None } else { Some(self.parse_expression()?) }; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); Ok(Stmt { kind: StmtKind::For { init: Some(ForInit::Expr(init_expr)), test, update, body, }, span: self.span_from(start), }) }
fn parse_switch(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Switch)?; self.expect(&TokenKind::LParen)?; let discriminant = self.parse_expression()?; self.expect(&TokenKind::RParen)?; self.expect(&TokenKind::LBrace)?; let mut cases = Vec::new(); while !self.at(&TokenKind::RBrace) && !self.at_eof() { let case_start = self.start_span(); let test = if self.eat(&TokenKind::Case) { Some(self.parse_expression()?) } else { self.expect(&TokenKind::Default)?; None }; self.expect(&TokenKind::Colon)?; let mut consequent = Vec::new(); while !matches!( self.peek_kind(), TokenKind::Case | TokenKind::Default | TokenKind::RBrace ) && !self.at_eof() { consequent.push(self.parse_statement_list_item()?); } cases.push(SwitchCase { test, consequent, span: self.span_from(case_start), }); } self.expect(&TokenKind::RBrace)?; Ok(Stmt { kind: StmtKind::Switch { discriminant, cases, }, span: self.span_from(start), }) }
fn parse_try(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Try)?; let block = self.parse_block_body()?;
let handler = if self.eat(&TokenKind::Catch) { let catch_start = self.start_span(); let param = if self.eat(&TokenKind::LParen) { let pat = self.parse_binding_pattern()?; self.expect(&TokenKind::RParen)?; Some(pat) } else { None }; let body = self.parse_block_body()?; Some(CatchClause { param, body, span: self.span_from(catch_start), }) } else { None };
let finalizer = if self.eat(&TokenKind::Finally) { Some(self.parse_block_body()?) } else { None };
if handler.is_none() && finalizer.is_none() { return Err(self.error("try requires catch or finally".into())); }
Ok(Stmt { kind: StmtKind::Try { block, handler, finalizer, }, span: self.span_from(start), }) }
fn parse_return(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Return)?; // Restricted production: newline after return inserts semicolon let argument = if matches!( self.peek_kind(), TokenKind::Semicolon | TokenKind::RBrace | TokenKind::Eof ) || self.peek().preceded_by_newline { None } else { Some(self.parse_expression()?) }; self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::Return(argument), span: self.span_from(start), }) }
fn parse_throw(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Throw)?; if self.peek().preceded_by_newline { return Err(ParseError { message: "newline not allowed after throw".into(), pos: self.peek().span.start, }); } let argument = self.parse_expression()?; self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::Throw(argument), span: self.span_from(start), }) }
fn parse_break(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Break)?; let label = if !self.peek().preceded_by_newline { if let TokenKind::Identifier(name) = self.peek_kind().clone() { self.advance(); Some(name) } else { None } } else { None }; self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::Break(label), span: self.span_from(start), }) }
fn parse_continue(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Continue)?; let label = if !self.peek().preceded_by_newline { if let TokenKind::Identifier(name) = self.peek_kind().clone() { self.advance(); Some(name) } else { None } } else { None }; self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::Continue(label), span: self.span_from(start), }) }
fn parse_labeled(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); let label = self.expect_identifier()?; self.expect(&TokenKind::Colon)?; let body = Box::new(self.parse_statement()?); Ok(Stmt { kind: StmtKind::Labeled { label, body }, span: self.span_from(start), }) }
fn parse_with(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::With)?; self.expect(&TokenKind::LParen)?; let object = self.parse_expression()?; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); Ok(Stmt { kind: StmtKind::With { object, body }, span: self.span_from(start), }) }
// ── Variable declarations ───────────────────────────────
fn parse_variable_declaration_stmt(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); let kind = match self.peek_kind() { TokenKind::Var => VarKind::Var, TokenKind::Let => VarKind::Let, TokenKind::Const => VarKind::Const, _ => return Err(self.error("expected var, let, or const".into())), }; self.advance(); let mut declarators = vec![self.parse_var_declarator()?]; while self.eat(&TokenKind::Comma) { declarators.push(self.parse_var_declarator()?); } self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::VarDecl { kind, declarators }, span: self.span_from(start), }) }
fn parse_var_declarator(&mut self) -> Result<VarDeclarator, ParseError> { let start = self.start_span(); let pattern = self.parse_binding_pattern()?; let init = if self.eat(&TokenKind::Assign) { Some(self.parse_assignment_expression()?) } else { None }; Ok(VarDeclarator { pattern, init, span: self.span_from(start), }) }
fn parse_var_declarator_no_in(&mut self) -> Result<VarDeclarator, ParseError> { let start = self.start_span(); let pattern = self.parse_binding_pattern()?; let init = if self.eat(&TokenKind::Assign) { Some(self.parse_assignment_expression_no_in()?) } else { None }; Ok(VarDeclarator { pattern, init, span: self.span_from(start), }) }
// ── Binding patterns (destructuring) ────────────────────
fn parse_binding_pattern(&mut self) -> Result<Pattern, ParseError> { match self.peek_kind() { TokenKind::LBracket => self.parse_array_pattern(), TokenKind::LBrace => self.parse_object_pattern(), _ => { let start = self.start_span(); let name = self.expect_identifier()?; Ok(Pattern { kind: PatternKind::Identifier(name), span: self.span_from(start), }) } } }
fn parse_array_pattern(&mut self) -> Result<Pattern, ParseError> { let start = self.start_span(); self.expect(&TokenKind::LBracket)?; let mut elements = Vec::new(); let mut rest = None; while !self.at(&TokenKind::RBracket) && !self.at_eof() { if self.eat(&TokenKind::Comma) { elements.push(None); continue; } if self.at(&TokenKind::Ellipsis) { self.advance(); rest = Some(Box::new(self.parse_binding_pattern()?)); self.eat(&TokenKind::Comma); // trailing comma after rest break; } let mut pat = self.parse_binding_pattern()?; if self.eat(&TokenKind::Assign) { let right = self.parse_assignment_expression()?; let span = Span { start: pat.span.start, end: right.span.end, }; pat = Pattern { kind: PatternKind::Assign { left: Box::new(pat), right: Box::new(right), }, span, }; } elements.push(Some(pat)); if !self.eat(&TokenKind::Comma) { break; } } self.expect(&TokenKind::RBracket)?; Ok(Pattern { kind: PatternKind::Array { elements, rest }, span: self.span_from(start), }) }
fn parse_object_pattern(&mut self) -> Result<Pattern, ParseError> { let start = self.start_span(); self.expect(&TokenKind::LBrace)?; let mut properties = Vec::new(); let mut rest = None; while !self.at(&TokenKind::RBrace) && !self.at_eof() { if self.at(&TokenKind::Ellipsis) { self.advance(); rest = Some(Box::new(self.parse_binding_pattern()?)); self.eat(&TokenKind::Comma); break; } let prop_start = self.start_span(); let (key, computed) = self.parse_property_name()?; if self.eat(&TokenKind::Colon) { // { key: pattern } let mut value = self.parse_binding_pattern()?; if self.eat(&TokenKind::Assign) { let right = self.parse_assignment_expression()?; let span = Span { start: value.span.start, end: right.span.end, }; value = Pattern { kind: PatternKind::Assign { left: Box::new(value), right: Box::new(right), }, span, }; } properties.push(ObjectPatternProp { key, value, computed, shorthand: false, span: self.span_from(prop_start), }); } else { // Shorthand: { name } or { name = default } let name = match &key { PropertyKey::Identifier(n) => n.clone(), _ => return Err(self.error("shorthand properties require identifier".into())), }; let ident_span = self.span_from(prop_start); let mut value = Pattern { kind: PatternKind::Identifier(name.clone()), span: ident_span, }; if self.eat(&TokenKind::Assign) { let right = self.parse_assignment_expression()?; let span = Span { start: value.span.start, end: right.span.end, }; value = Pattern { kind: PatternKind::Assign { left: Box::new(value), right: Box::new(right), }, span, }; } properties.push(ObjectPatternProp { key, value, computed, shorthand: true, span: self.span_from(prop_start), }); } if !self.eat(&TokenKind::Comma) { break; } } self.expect(&TokenKind::RBrace)?; Ok(Pattern { kind: PatternKind::Object { properties, rest }, span: self.span_from(start), }) }
// ── Function declarations ───────────────────────────────
fn parse_function_declaration(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Function)?; let is_generator = self.eat(&TokenKind::Star); let id = Some(self.expect_identifier()?); let (params, body) = self.parse_function_params_and_body()?; Ok(Stmt { kind: StmtKind::FunctionDecl(FunctionDef { id, params, body, is_async: false, is_generator, }), span: self.span_from(start), }) }
fn parse_async_function_declaration(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Async)?; self.expect(&TokenKind::Function)?; let is_generator = self.eat(&TokenKind::Star); let id = Some(self.expect_identifier()?); let (params, body) = self.parse_function_params_and_body()?; Ok(Stmt { kind: StmtKind::FunctionDecl(FunctionDef { id, params, body, is_async: true, is_generator, }), span: self.span_from(start), }) }
fn parse_function_params_and_body(&mut self) -> Result<(Vec<Pattern>, Vec<Stmt>), ParseError> { // Formal-parameter initializers and the function body are `[+In]` // regardless of an enclosing `for`-initializer NoIn context. self.with_in(|p| { p.expect(&TokenKind::LParen)?; let params = p.parse_formal_parameters()?; p.expect(&TokenKind::RParen)?; let body = p.parse_block_body()?; Ok((params, body)) }) }
fn parse_formal_parameters(&mut self) -> Result<Vec<Pattern>, ParseError> { // Parameter `Initializer`s are `[+In]`, independent of any enclosing // `for`-initializer NoIn context (reached directly via the arrow path). let old_allow_in = self.allow_in; self.allow_in = true; let result = self.parse_formal_parameters_inner(); self.allow_in = old_allow_in; result }
fn parse_formal_parameters_inner(&mut self) -> Result<Vec<Pattern>, ParseError> { let mut params = Vec::new(); while !self.at(&TokenKind::RParen) && !self.at_eof() { if self.at(&TokenKind::Ellipsis) { let start = self.start_span(); self.advance(); let inner = self.parse_binding_pattern()?; params.push(Pattern { kind: PatternKind::Rest(Box::new(inner)), span: self.span_from(start), }); self.eat(&TokenKind::Comma); break; } let mut pat = self.parse_binding_pattern()?; if self.eat(&TokenKind::Assign) { let right = self.parse_assignment_expression()?; let span = Span { start: pat.span.start, end: right.span.end, }; pat = Pattern { kind: PatternKind::Assign { left: Box::new(pat), right: Box::new(right), }, span, }; } params.push(pat); if !self.eat(&TokenKind::Comma) { break; } } Ok(params) }
// ── Class declarations ──────────────────────────────────
fn parse_class_declaration(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); let class_def = self.parse_class(true)?; Ok(Stmt { kind: StmtKind::ClassDecl(class_def), span: self.span_from(start), }) }
fn parse_class(&mut self, require_name: bool) -> Result<ClassDef, ParseError> { self.expect(&TokenKind::Class)?; let id = if require_name { Some(self.expect_identifier()?) } else if let TokenKind::Identifier(_) = self.peek_kind() { Some(self.expect_identifier()?) } else { None }; let super_class = if self.eat(&TokenKind::Extends) { Some(Box::new(self.parse_left_hand_side_expression()?)) } else { None }; let body = self.parse_class_body()?; Ok(ClassDef { id, super_class, body, }) }
fn parse_class_body(&mut self) -> Result<Vec<ClassMember>, ParseError> { self.expect(&TokenKind::LBrace)?; let mut members = Vec::new(); while !self.at(&TokenKind::RBrace) && !self.at_eof() { if self.eat(&TokenKind::Semicolon) { continue; } members.push(self.parse_class_member()?); } self.expect(&TokenKind::RBrace)?; Ok(members) }
fn parse_class_member(&mut self) -> Result<ClassMember, ParseError> { let start = self.start_span(); let is_static = self.eat(&TokenKind::Static);
// Check for getter/setter if let TokenKind::Identifier(ref name) = self.peek_kind().clone() { if (name == "get" || name == "set") && !matches!( self.peek_ahead(1), TokenKind::LParen | TokenKind::Assign | TokenKind::Semicolon ) { let kind = if name == "get" { MethodKind::Get } else { MethodKind::Set }; self.advance(); let (key, computed) = self.parse_property_name()?; let (params, body) = self.parse_function_params_and_body()?; return Ok(ClassMember { kind: ClassMemberKind::Method { key, value: FunctionDef { id: None, params, body, is_async: false, is_generator: false, }, kind, is_static, computed, }, span: self.span_from(start), }); } }
// Generator method let is_generator = self.eat(&TokenKind::Star);
// Async method let is_async = if !is_generator && matches!(self.peek_kind(), TokenKind::Async) && !matches!( self.peek_ahead(1), TokenKind::LParen | TokenKind::Assign | TokenKind::Semicolon ) { self.advance(); true } else { false };
let is_generator = is_generator || (is_async && self.eat(&TokenKind::Star));
let (key, computed) = self.parse_property_name()?;
// Check for constructor let method_kind = if !is_static && !computed && key == PropertyKey::Identifier("constructor".into()) { MethodKind::Constructor } else { MethodKind::Method };
if self.at(&TokenKind::LParen) { let (params, body) = self.parse_function_params_and_body()?; Ok(ClassMember { kind: ClassMemberKind::Method { key, value: FunctionDef { id: None, params, body, is_async, is_generator, }, kind: method_kind, is_static, computed, }, span: self.span_from(start), }) } else { // Class field let value = if self.eat(&TokenKind::Assign) { Some(self.parse_assignment_expression()?) } else { None }; self.expect_semicolon()?; Ok(ClassMember { kind: ClassMemberKind::Property { key, value, is_static, computed, }, span: self.span_from(start), }) } }
// ── Import / Export ─────────────────────────────────────
fn parse_import_declaration(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Import)?;
// `import "source"` — side-effect import if let TokenKind::String(source) = self.peek_kind().clone() { self.advance(); self.expect_semicolon()?; return Ok(Stmt { kind: StmtKind::Import { specifiers: vec![], source, }, span: self.span_from(start), }); }
let mut specifiers = Vec::new();
// `import * as ns from "source"` if self.eat(&TokenKind::Star) { self.expect_identifier_matching("as")?; let local = self.expect_identifier()?; specifiers.push(ImportSpecifier::Namespace(local)); } // `import { a, b as c } from "source"` else if self.at(&TokenKind::LBrace) { self.advance(); while !self.at(&TokenKind::RBrace) && !self.at_eof() { let (imported, imported_can_bind) = self.expect_module_export_name()?; let local = if self.eat_identifier_matching("as") { self.expect_identifier()? } else { if !imported_can_bind { return Err( self.error(format!("imported name {imported:?} requires `as` binding")) ); } imported.clone() }; specifiers.push(ImportSpecifier::Named { imported, local }); if !self.eat(&TokenKind::Comma) { break; } } self.expect(&TokenKind::RBrace)?; } // `import defaultExport from "source"` or `import defaultExport, { ... } from "source"` else { let default_name = self.expect_identifier()?; specifiers.push(ImportSpecifier::Default(default_name));
if self.eat(&TokenKind::Comma) { if self.eat(&TokenKind::Star) { self.expect_identifier_matching("as")?; let local = self.expect_identifier()?; specifiers.push(ImportSpecifier::Namespace(local)); } else { self.expect(&TokenKind::LBrace)?; while !self.at(&TokenKind::RBrace) && !self.at_eof() { let (imported, imported_can_bind) = self.expect_module_export_name()?; let local = if self.eat_identifier_matching("as") { self.expect_identifier()? } else { if !imported_can_bind { return Err(self.error(format!( "imported name {imported:?} requires `as` binding" ))); } imported.clone() }; specifiers.push(ImportSpecifier::Named { imported, local }); if !self.eat(&TokenKind::Comma) { break; } } self.expect(&TokenKind::RBrace)?; } } }
self.expect_identifier_matching("from")?; let source = match self.peek_kind().clone() { TokenKind::String(s) => { self.advance(); s } _ => return Err(self.error("expected module source string".into())), }; self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::Import { specifiers, source }, span: self.span_from(start), }) }
fn parse_export_declaration(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Export)?;
// `export default ...` if self.eat(&TokenKind::Default) { if matches!(self.peek_kind(), TokenKind::Function) { // Named function → declaration, anonymous → default expression let has_name = matches!(self.peek_ahead(1), TokenKind::Identifier(_)) || (matches!(self.peek_ahead(1), TokenKind::Star) && matches!(self.peek_ahead(2), TokenKind::Identifier(_))); if has_name { let decl = self.parse_function_declaration()?; return Ok(Stmt { kind: StmtKind::Export(ExportDecl::Declaration(Box::new(decl))), span: self.span_from(start), }); } let expr = self.parse_function_expression()?; return Ok(Stmt { kind: StmtKind::Export(ExportDecl::Default(expr)), span: self.span_from(start), }); } if matches!(self.peek_kind(), TokenKind::Class) { // Named class → declaration, anonymous → default expression if matches!(self.peek_ahead(1), TokenKind::Identifier(_)) { let decl = self.parse_class_declaration()?; return Ok(Stmt { kind: StmtKind::Export(ExportDecl::Declaration(Box::new(decl))), span: self.span_from(start), }); } let expr = self.parse_class_expression()?; return Ok(Stmt { kind: StmtKind::Export(ExportDecl::Default(expr)), span: self.span_from(start), }); } let expr = self.parse_assignment_expression()?; self.expect_semicolon()?; return Ok(Stmt { kind: StmtKind::Export(ExportDecl::Default(expr)), span: self.span_from(start), }); }
// `export * from "source"` if self.eat(&TokenKind::Star) { self.expect_identifier_matching("from")?; let source = match self.peek_kind().clone() { TokenKind::String(s) => { self.advance(); s } _ => return Err(self.error("expected module source string".into())), }; self.expect_semicolon()?; return Ok(Stmt { kind: StmtKind::Export(ExportDecl::AllFrom(source)), span: self.span_from(start), }); }
// `export { a, b as c } [from "source"]` if self.at(&TokenKind::LBrace) { self.advance(); let mut specifiers = Vec::new(); while !self.at(&TokenKind::RBrace) && !self.at_eof() { let (local, _) = self.expect_module_export_name()?; let exported = if self.eat_identifier_matching("as") { self.expect_module_export_name()?.0 } else { local.clone() }; specifiers.push(ExportSpecifier { local, exported }); if !self.eat(&TokenKind::Comma) { break; } } self.expect(&TokenKind::RBrace)?; let source = if self.eat_identifier_matching("from") { match self.peek_kind().clone() { TokenKind::String(s) => { self.advance(); Some(s) } _ => return Err(self.error("expected module source string".into())), } } else { None }; self.expect_semicolon()?; return Ok(Stmt { kind: StmtKind::Export(ExportDecl::Named { specifiers, source }), span: self.span_from(start), }); }
// `export var/let/const/function/class ...` let decl = self.parse_statement_list_item()?; Ok(Stmt { kind: StmtKind::Export(ExportDecl::Declaration(Box::new(decl))), span: self.span_from(start), }) }
// ── Helper for contextual keywords ──────────────────────
fn expect_identifier_matching(&mut self, expected: &str) -> Result<(), ParseError> { match self.peek_kind().clone() { TokenKind::Identifier(ref name) if name == expected => { self.advance(); Ok(()) } _ => Err(self.error(format!("expected '{}'", expected))), } }
fn eat_identifier_matching(&mut self, expected: &str) -> bool { if let TokenKind::Identifier(ref name) = self.peek_kind() { if name == expected { self.advance(); return true; } } false }
// ── Expressions ─────────────────────────────────────────
fn parse_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); let expr = self.parse_assignment_expression()?; if !self.at(&TokenKind::Comma) { return Ok(expr); } let mut exprs = vec![expr]; while self.eat(&TokenKind::Comma) { exprs.push(self.parse_assignment_expression()?); } Ok(Expr { kind: ExprKind::Sequence(exprs), span: self.span_from(start), }) }
fn parse_assignment_expression(&mut self) -> Result<Expr, ParseError> { // Check for `async (...) => ...` before treating `async(...)` as a call. if matches!(self.peek_kind(), TokenKind::Async) && !self.peek().preceded_by_newline && matches!(self.peek_ahead(1), TokenKind::LParen) && self.is_parenthesized_arrow_params(1) { let start = self.start_span(); self.advance(); // async self.expect(&TokenKind::LParen)?; let params = self.parse_formal_parameters()?; self.expect(&TokenKind::RParen)?; self.expect(&TokenKind::Arrow)?; return self.parse_arrow_body(start, params, true); }
// Check for `(...) => ...` before parsing the parenthesized expression. // This accepts rest parameters after earlier parameters, e.g. // `(value, ...rest) => rest`, which expression parsing cannot represent. if matches!(self.peek_kind(), TokenKind::LParen) && self.is_parenthesized_arrow_params(0) { let start = self.start_span(); self.expect(&TokenKind::LParen)?; let params = self.parse_formal_parameters()?; self.expect(&TokenKind::RParen)?; self.expect(&TokenKind::Arrow)?; return self.parse_arrow_body(start, params, false); }
// Check for arrow function: `x => ...` or `async x => ...` if let TokenKind::Identifier(ref name) = self.peek_kind().clone() { if matches!(self.peek_ahead(1), TokenKind::Arrow) && !self.peek().preceded_by_newline { let param_start = self.start_span(); let name = name.clone(); self.advance(); // identifier self.advance(); // => let params = vec![Pattern { kind: PatternKind::Identifier(name), span: self.span_from(param_start), }]; return self.parse_arrow_body(param_start, params, false); } }
// Check for `async x => ...` or `async (...)` arrow if matches!(self.peek_kind(), TokenKind::Async) && !self.peek().preceded_by_newline { if let TokenKind::Identifier(_) = self.peek_ahead(1) { if matches!(self.peek_ahead(2), TokenKind::Arrow) { let start = self.start_span(); self.advance(); // async let param_start = self.start_span(); let name = self.expect_identifier()?; self.advance(); // => let params = vec![Pattern { kind: PatternKind::Identifier(name), span: self.span_from(param_start), }]; return self.parse_arrow_body(start, params, true); } } }
let start = self.start_span(); let left = self.parse_conditional_expression()?;
// Check for arrow function after parenthesized expr: `(a, b) => ...` if matches!(self.peek_kind(), TokenKind::Arrow) && !self.peek().preceded_by_newline { self.advance(); // => let params = self.expr_to_params(&left)?; return self.parse_arrow_body(start, params, false); }
// Assignment if let Some(op) = self.peek_assign_op() { self.advance(); let right = self.parse_assignment_expression()?; return Ok(Expr { span: self.span_from(start), kind: ExprKind::Assignment { op, left: Box::new(left), right: Box::new(right), }, }); }
Ok(left) }
fn is_parenthesized_arrow_params(&self, paren_offset: usize) -> bool { let mut depth = 0usize; let mut idx = self.pos + paren_offset; while idx < self.tokens.len() { match &self.tokens[idx].kind { TokenKind::LParen | TokenKind::LBracket | TokenKind::LBrace => { depth += 1; } TokenKind::RParen | TokenKind::RBracket | TokenKind::RBrace => { if depth == 0 { return false; } depth -= 1; if depth == 0 { return matches!( self.tokens.get(idx + 1).map(|t| &t.kind), Some(TokenKind::Arrow) ); } } TokenKind::Eof => return false, _ => {} } idx += 1; } false }
fn parse_assignment_expression_no_in(&mut self) -> Result<Expr, ParseError> { let old = self.allow_in; self.allow_in = false; let result = self.parse_assignment_expression(); self.allow_in = old; result }
/// Run `f` with the grammar's `[In]` parameter forced on, restoring the /// previous value afterwards. The ECMAScript grammar only threads the /// NoIn restriction through the `for`-initializer expression spine; every /// nested bracketed production (call arguments, array/object literals, /// computed member access, template substitutions, function/arrow bodies) /// is evaluated with `[+In]`. Use this at those boundaries so that, e.g., /// `for (var x = f("k" in o); ;) {}` parses the `in` operator correctly. fn with_in<T>( &mut self, f: impl FnOnce(&mut Self) -> Result<T, ParseError>, ) -> Result<T, ParseError> { let old = self.allow_in; self.allow_in = true; let result = f(self); self.allow_in = old; result }
fn parse_arrow_body( &mut self, start: SourcePos, params: Vec<Pattern>, is_async: bool, ) -> Result<Expr, ParseError> { // A braced arrow body is `{ FunctionBody }` (`[+In]`); a concise // expression body is `ExpressionBody[?In]`, so it inherits the // enclosing NoIn context and must not reset `allow_in`. let body = if self.at(&TokenKind::LBrace) { ArrowBody::Block(self.with_in(|p| p.parse_block_body())?) } else { ArrowBody::Expr(Box::new(self.parse_assignment_expression()?)) }; Ok(Expr { kind: ExprKind::Arrow { params, body, is_async, }, span: self.span_from(start), }) }
fn parse_conditional_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); let expr = self.parse_binary_expression(0)?; if !self.eat(&TokenKind::Question) { return Ok(expr); } let consequent = self.parse_assignment_expression()?; self.expect(&TokenKind::Colon)?; let alternate = self.parse_assignment_expression()?; Ok(Expr { kind: ExprKind::Conditional { test: Box::new(expr), consequent: Box::new(consequent), alternate: Box::new(alternate), }, span: self.span_from(start), }) }
// ── Pratt expression parsing ────────────────────────────
fn parse_binary_expression(&mut self, min_bp: u8) -> Result<Expr, ParseError> { let start = self.start_span(); let mut left = self.parse_unary_expression()?;
while let Some((op, left_bp, right_bp)) = self.peek_binary_op() { if left_bp < min_bp { break; } self.advance();
let right = self.parse_binary_expression(right_bp)?; let span = self.span_from(start);
left = match op { BinOrLogical::Binary(op) => Expr { kind: ExprKind::Binary { op, left: Box::new(left), right: Box::new(right), }, span, }, BinOrLogical::Logical(op) => Expr { kind: ExprKind::Logical { op, left: Box::new(left), right: Box::new(right), }, span, }, }; }
Ok(left) }
fn parse_unary_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); match self.peek_kind() { TokenKind::Minus => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Unary { op: UnaryOp::Minus, argument: Box::new(arg), }, span: self.span_from(start), }) } TokenKind::Plus => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Unary { op: UnaryOp::Plus, argument: Box::new(arg), }, span: self.span_from(start), }) } TokenKind::Not => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Unary { op: UnaryOp::Not, argument: Box::new(arg), }, span: self.span_from(start), }) } TokenKind::Tilde => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Unary { op: UnaryOp::BitwiseNot, argument: Box::new(arg), }, span: self.span_from(start), }) } TokenKind::Typeof => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Unary { op: UnaryOp::Typeof, argument: Box::new(arg), }, span: self.span_from(start), }) } TokenKind::Void => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Unary { op: UnaryOp::Void, argument: Box::new(arg), }, span: self.span_from(start), }) } TokenKind::Delete => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Unary { op: UnaryOp::Delete, argument: Box::new(arg), }, span: self.span_from(start), }) } TokenKind::PlusPlus => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Update { op: UpdateOp::Increment, argument: Box::new(arg), prefix: true, }, span: self.span_from(start), }) } TokenKind::MinusMinus => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Update { op: UpdateOp::Decrement, argument: Box::new(arg), prefix: true, }, span: self.span_from(start), }) } TokenKind::Await => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Await(Box::new(arg)), span: self.span_from(start), }) } _ => self.parse_postfix_expression(), } }
fn parse_postfix_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); let mut expr = self.parse_call_expression()?;
if !self.peek().preceded_by_newline { if matches!(self.peek_kind(), TokenKind::PlusPlus) { self.advance(); expr = Expr { kind: ExprKind::Update { op: UpdateOp::Increment, argument: Box::new(expr), prefix: false, }, span: self.span_from(start), }; } else if matches!(self.peek_kind(), TokenKind::MinusMinus) { self.advance(); expr = Expr { kind: ExprKind::Update { op: UpdateOp::Decrement, argument: Box::new(expr), prefix: false, }, span: self.span_from(start), }; } }
Ok(expr) }
fn parse_call_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span();
let mut expr = if matches!(self.peek_kind(), TokenKind::New) { self.parse_new_expression()? } else { self.parse_primary_expression()? };
let mut saw_optional = false; loop { match self.peek_kind() { TokenKind::Dot => { self.advance(); let prop_start = self.start_span(); let property = self.parse_member_property_after_dot(prop_start)?; expr = Expr { kind: ExprKind::Member { object: Box::new(expr), property: Box::new(property), computed: false, }, span: self.span_from(start), }; } TokenKind::LBracket => { self.advance(); let prop = self.with_in(|p| p.parse_expression())?; self.expect(&TokenKind::RBracket)?; expr = Expr { kind: ExprKind::Member { object: Box::new(expr), property: Box::new(prop), computed: true, }, span: self.span_from(start), }; } TokenKind::LParen => { let arguments = self.parse_arguments()?; expr = Expr { kind: ExprKind::Call { callee: Box::new(expr), arguments, }, span: self.span_from(start), }; } TokenKind::QuestionDot => { self.advance(); saw_optional = true; // ?. can be followed by identifier, [expr], or (args) match self.peek_kind() { TokenKind::LBracket => { self.advance(); let prop = self.with_in(|p| p.parse_expression())?; self.expect(&TokenKind::RBracket)?; expr = Expr { kind: ExprKind::Member { object: Box::new(Expr { kind: ExprKind::OptionalChain { base: Box::new(expr.clone()), }, span: self.span_from(start), }), property: Box::new(prop), computed: true, }, span: self.span_from(start), }; } TokenKind::LParen => { let arguments = self.parse_arguments()?; expr = Expr { kind: ExprKind::Call { callee: Box::new(Expr { kind: ExprKind::OptionalChain { base: Box::new(expr.clone()), }, span: self.span_from(start), }), arguments, }, span: self.span_from(start), }; } _ => { let prop_start = self.start_span(); let property = self.parse_member_property_after_dot(prop_start)?; expr = Expr { kind: ExprKind::Member { object: Box::new(Expr { kind: ExprKind::OptionalChain { base: Box::new(expr.clone()), }, span: self.span_from(start), }), property: Box::new(property), computed: false, }, span: self.span_from(start), }; } } } TokenKind::TemplateFull(_) | TokenKind::TemplateHead(_) => { let quasi = self.parse_template_literal()?; expr = Expr { kind: ExprKind::TaggedTemplate { tag: Box::new(expr), quasi: Box::new(quasi), }, span: self.span_from(start), }; } _ => break, } }
if saw_optional { expr = Expr { kind: ExprKind::OptionalChainExpr { chain: Box::new(expr), }, span: self.span_from(start), }; }
Ok(expr) }
fn parse_new_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); self.expect(&TokenKind::New)?;
if self.eat(&TokenKind::Dot) { let name = self.expect_identifier_name()?; if name != "target" { return Err(self.error(format!("expected new.target, found new.{name}"))); } return Ok(Expr { kind: ExprKind::NewTarget, span: self.span_from(start), }); }
// new new Foo() → new (new Foo()) if matches!(self.peek_kind(), TokenKind::New) { let callee = self.parse_new_expression()?; return Ok(Expr { kind: ExprKind::New { callee: Box::new(callee), arguments: vec![], }, span: self.span_from(start), }); }
let callee = self.parse_primary_expression()?; // Allow member access on the callee let callee = self.parse_member_chain(start, callee)?; let arguments = if self.at(&TokenKind::LParen) { self.parse_arguments()? } else { vec![] }; Ok(Expr { kind: ExprKind::New { callee: Box::new(callee), arguments, }, span: self.span_from(start), }) }
fn parse_member_chain(&mut self, start: SourcePos, mut expr: Expr) -> Result<Expr, ParseError> { loop { match self.peek_kind() { TokenKind::Dot => { self.advance(); let prop_start = self.start_span(); let property = self.parse_member_property_after_dot(prop_start)?; expr = Expr { kind: ExprKind::Member { object: Box::new(expr), property: Box::new(property), computed: false, }, span: self.span_from(start), }; } TokenKind::LBracket => { self.advance(); let prop = self.with_in(|p| p.parse_expression())?; self.expect(&TokenKind::RBracket)?; expr = Expr { kind: ExprKind::Member { object: Box::new(expr), property: Box::new(prop), computed: true, }, span: self.span_from(start), }; } _ => break, } } Ok(expr) }
/// Parse the property that follows a `.` (or `?.`) in a member access. /// Returns a `PrivateName` expression for `obj.#x`, otherwise an /// `Identifier` (keywords are permitted as property names). fn parse_member_property_after_dot( &mut self, prop_start: SourcePos, ) -> Result<Expr, ParseError> { if let TokenKind::PrivateName(name) = self.peek_kind().clone() { self.advance(); return Ok(Expr { kind: ExprKind::PrivateName(name), span: self.span_from(prop_start), }); } let name = self.expect_identifier_name()?; Ok(Expr { kind: ExprKind::Identifier(name), span: self.span_from(prop_start), }) }
fn parse_left_hand_side_expression(&mut self) -> Result<Expr, ParseError> { self.parse_call_expression() }
fn parse_arguments(&mut self) -> Result<Vec<Expr>, ParseError> { // `Arguments` evaluates each `AssignmentExpression` with `[+In]`. self.with_in(|p| { p.expect(&TokenKind::LParen)?; let mut args = Vec::new(); while !p.at(&TokenKind::RParen) && !p.at_eof() { if p.at(&TokenKind::Ellipsis) { let start = p.start_span(); p.advance(); let arg = p.parse_assignment_expression()?; args.push(Expr { kind: ExprKind::Spread(Box::new(arg)), span: p.span_from(start), }); } else { args.push(p.parse_assignment_expression()?); } if !p.eat(&TokenKind::Comma) { break; } } p.expect(&TokenKind::RParen)?; Ok(args) }) }
// ── Primary expressions ─────────────────────────────────
fn parse_primary_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); match self.peek_kind().clone() { TokenKind::Number(n) => { self.advance(); Ok(Expr { kind: ExprKind::Number(n), span: self.span_from(start), }) } TokenKind::String(s) => { self.advance(); Ok(Expr { kind: ExprKind::String(s), span: self.span_from(start), }) } TokenKind::True => { self.advance(); Ok(Expr { kind: ExprKind::Bool(true), span: self.span_from(start), }) } TokenKind::False => { self.advance(); Ok(Expr { kind: ExprKind::Bool(false), span: self.span_from(start), }) } TokenKind::Null => { self.advance(); Ok(Expr { kind: ExprKind::Null, span: self.span_from(start), }) } TokenKind::This => { self.advance(); Ok(Expr { kind: ExprKind::This, span: self.span_from(start), }) } TokenKind::Identifier(name) => { self.advance(); Ok(Expr { kind: ExprKind::Identifier(name), span: self.span_from(start), }) } // A leading private name is only legal as the left operand of an // `in` expression (`#x in obj`); the binary-expression parser // continues from here and the compiler rejects other uses. TokenKind::PrivateName(name) => { self.advance(); Ok(Expr { kind: ExprKind::PrivateName(name), span: self.span_from(start), }) } kind if is_contextual_identifier(&kind) && !matches!(kind, TokenKind::Async) => { let name = format!("{kind}"); self.advance(); Ok(Expr { kind: ExprKind::Identifier(name), span: self.span_from(start), }) } TokenKind::LParen => self.parse_parenthesized_expression(), TokenKind::LBracket => self.parse_array_expression(), TokenKind::LBrace => self.parse_object_expression(), TokenKind::Function => self.parse_function_expression(), TokenKind::Class => self.parse_class_expression(), TokenKind::Async => { // async function expression if matches!(self.peek_ahead(1), TokenKind::Function) && !self.tokens[self.pos + 1].preceded_by_newline { return self.parse_async_function_expression(); } // Otherwise treat 'async' as an identifier self.advance(); Ok(Expr { kind: ExprKind::Identifier("async".into()), span: self.span_from(start), }) } TokenKind::TemplateFull(_) | TokenKind::TemplateHead(_) => { self.parse_template_literal() } TokenKind::RegExp { pattern, flags } => { self.advance(); Ok(Expr { kind: ExprKind::RegExp { pattern, flags }, span: self.span_from(start), }) } TokenKind::Yield => { self.advance(); let delegate = self.eat(&TokenKind::Star); let argument = if !self.peek().preceded_by_newline && !matches!( self.peek_kind(), TokenKind::Semicolon | TokenKind::RBrace | TokenKind::RParen | TokenKind::RBracket | TokenKind::Colon | TokenKind::Comma | TokenKind::Eof ) { Some(Box::new(self.parse_assignment_expression()?)) } else { None }; Ok(Expr { kind: ExprKind::Yield { argument, delegate }, span: self.span_from(start), }) } TokenKind::Super => { self.advance(); Ok(Expr { kind: ExprKind::Super, span: self.span_from(start), }) } TokenKind::Import => { self.advance(); if self.at(&TokenKind::Dot) { // `import.meta` — leave as a bare identifier so the member // access evaluates against the (currently absent) global, // yielding `undefined` rather than a dynamic import. Ok(Expr { kind: ExprKind::Identifier("import".into()), span: self.span_from(start), }) } else { // Dynamic `import(specifier)`. The trailing `(...)` is parsed // by the call-expression suffix logic, producing a call to // the `__we_dynamic_import` runtime helper which returns a // Promise for the imported module namespace. Ok(Expr { kind: ExprKind::Identifier("__we_dynamic_import".into()), span: self.span_from(start), }) } } _ => Err(self.error(format!("unexpected token {:?}", self.peek_kind()))), } }
fn parse_parenthesized_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); self.expect(&TokenKind::LParen)?;
// Empty parens: `() => ...` if self.at(&TokenKind::RParen) { self.advance(); // Must be arrow if !matches!(self.peek_kind(), TokenKind::Arrow) { return Err(self.error("unexpected empty parentheses".into())); } // Arrow will be handled by caller return Ok(Expr { kind: ExprKind::Sequence(vec![]), span: self.span_from(start), }); }
// `(...rest) => ...` if self.at(&TokenKind::Ellipsis) { // This must be an arrow parameter list with rest let rest_start = self.start_span(); self.advance(); let rest_pat = self.parse_binding_pattern()?; self.expect(&TokenKind::RParen)?; // Must be followed by => if !matches!(self.peek_kind(), TokenKind::Arrow) { return Err(self.error("expected '=>'".into())); } let _ = rest_pat; // Will be handled as pattern // Return a marker that the arrow handler will convert return Ok(Expr { kind: ExprKind::Spread(Box::new(Expr { kind: match rest_pat.kind { PatternKind::Identifier(name) => ExprKind::Identifier(name), _ => { return Err(ParseError { message: "complex rest pattern in arrow".into(), pos: rest_start, }) } }, span: rest_pat.span, })), span: self.span_from(start), }); }
// `in` is disallowed at the top level of a regular `for` initializer // so `for (x in y)` can be parsed as for-in. Parentheses start a nested // expression where `in` is valid again, e.g. `for (x = ("k" in obj);;)`. let old_allow_in = self.allow_in; self.allow_in = true; let expr = self.parse_expression(); self.allow_in = old_allow_in; let expr = expr?; self.expect(&TokenKind::RParen)?; Ok(expr) }
fn parse_array_expression(&mut self) -> Result<Expr, ParseError> { // `ArrayLiteral` evaluates each element `AssignmentExpression` with `[+In]`. self.with_in(|p| { let start = p.start_span(); p.expect(&TokenKind::LBracket)?; let mut elements = Vec::new(); while !p.at(&TokenKind::RBracket) && !p.at_eof() { if p.eat(&TokenKind::Comma) { elements.push(None); continue; } if p.at(&TokenKind::Ellipsis) { let spread_start = p.start_span(); p.advance(); let arg = p.parse_assignment_expression()?; elements.push(Some(ArrayElement::Spread(Expr { kind: ExprKind::Spread(Box::new(arg)), span: p.span_from(spread_start), }))); } else { let elem = p.parse_assignment_expression()?; elements.push(Some(ArrayElement::Expr(elem))); } if !p.eat(&TokenKind::Comma) { break; } } p.expect(&TokenKind::RBracket)?; Ok(Expr { kind: ExprKind::Array(elements), span: p.span_from(start), }) }) }
fn parse_object_expression(&mut self) -> Result<Expr, ParseError> { // Object literal computed keys and property values are `[+In]`. self.with_in(|p| { let start = p.start_span(); p.expect(&TokenKind::LBrace)?; let mut properties = Vec::new(); while !p.at(&TokenKind::RBrace) && !p.at_eof() { let prop = p.parse_object_property()?; properties.push(prop); if !p.eat(&TokenKind::Comma) { break; } } p.expect(&TokenKind::RBrace)?; Ok(Expr { kind: ExprKind::Object(properties), span: p.span_from(start), }) }) }
fn parse_object_property(&mut self) -> Result<Property, ParseError> { let prop_start = self.start_span();
// Spread: `...expr` if self.at(&TokenKind::Ellipsis) { self.advance(); let arg = self.parse_assignment_expression()?; return Ok(Property { key: PropertyKey::Identifier("".into()), value: Some(arg), kind: PropertyKind::Init, computed: false, shorthand: false, method: false, span: self.span_from(prop_start), }); }
// Getter/setter: `get name() {}` or `set name(v) {}` if let TokenKind::Identifier(ref name) = self.peek_kind().clone() { if (name == "get" || name == "set") && !matches!( self.peek_ahead(1), TokenKind::Colon | TokenKind::Comma | TokenKind::RBrace | TokenKind::LParen | TokenKind::Assign ) { let kind = if name == "get" { PropertyKind::Get } else { PropertyKind::Set }; self.advance(); let (key, computed) = self.parse_property_name()?; let (params, body) = self.parse_function_params_and_body()?; return Ok(Property { key, value: Some(Expr { kind: ExprKind::Function(FunctionDef { id: None, params, body, is_async: false, is_generator: false, }), span: self.span_from(prop_start), }), kind, computed, shorthand: false, method: true, span: self.span_from(prop_start), }); } }
// Generator method: `*name() {}` if self.eat(&TokenKind::Star) { let (key, computed) = self.parse_property_name()?; let (params, body) = self.parse_function_params_and_body()?; return Ok(Property { key, value: Some(Expr { kind: ExprKind::Function(FunctionDef { id: None, params, body, is_async: false, is_generator: true, }), span: self.span_from(prop_start), }), kind: PropertyKind::Init, computed, shorthand: false, method: true, span: self.span_from(prop_start), }); }
// Async method: `async name() {}` let is_async = if matches!(self.peek_kind(), TokenKind::Async) && !matches!( self.peek_ahead(1), TokenKind::Colon | TokenKind::Comma | TokenKind::RBrace | TokenKind::Assign ) && !self .tokens .get(self.pos + 1) .is_none_or(|t| t.preceded_by_newline) { self.advance(); true } else { false };
let is_generator = is_async && self.eat(&TokenKind::Star);
let (key, computed) = self.parse_property_name()?;
// Method shorthand: `name() {}` or `name(params) {}` if self.at(&TokenKind::LParen) { let (params, body) = self.parse_function_params_and_body()?; return Ok(Property { key, value: Some(Expr { kind: ExprKind::Function(FunctionDef { id: None, params, body, is_async, is_generator, }), span: self.span_from(prop_start), }), kind: PropertyKind::Init, computed, shorthand: false, method: true, span: self.span_from(prop_start), }); }
// Shorthand: `{ name }` or `{ name = default }` if !computed && matches!( self.peek_kind(), TokenKind::Comma | TokenKind::RBrace | TokenKind::Assign ) { let name = match &key { PropertyKey::Identifier(n) => n.clone(), _ => return Err(self.error("expected identifier for shorthand property".into())), }; let value = if self.eat(&TokenKind::Assign) { let default = self.parse_assignment_expression()?; Some(Expr { kind: ExprKind::Assignment { op: AssignOp::Assign, left: Box::new(Expr { kind: ExprKind::Identifier(name.clone()), span: self.span_from(prop_start), }), right: Box::new(default), }, span: self.span_from(prop_start), }) } else { Some(Expr { kind: ExprKind::Identifier(name), span: self.span_from(prop_start), }) }; return Ok(Property { key, value, kind: PropertyKind::Init, computed, shorthand: true, method: false, span: self.span_from(prop_start), }); }
// Regular: `key: value` self.expect(&TokenKind::Colon)?; let value = self.parse_assignment_expression()?; Ok(Property { key, value: Some(value), kind: PropertyKind::Init, computed, shorthand: false, method: false, span: self.span_from(prop_start), }) }
fn parse_property_name(&mut self) -> Result<(PropertyKey, bool), ParseError> { match self.peek_kind().clone() { TokenKind::Identifier(name) => { self.advance(); Ok((PropertyKey::Identifier(name), false)) } TokenKind::PrivateName(name) => { self.advance(); Ok((PropertyKey::PrivateName(name), false)) } TokenKind::String(s) => { self.advance(); Ok((PropertyKey::String(s), false)) } TokenKind::Number(n) => { self.advance(); Ok((PropertyKey::Number(n), false)) } TokenKind::LBracket => { self.advance(); let expr = self.parse_assignment_expression()?; self.expect(&TokenKind::RBracket)?; Ok((PropertyKey::Computed(expr), true)) } // Keywords can also be property names _ if is_keyword(self.peek_kind()) => { let name = format!("{}", self.peek_kind()); self.advance(); Ok((PropertyKey::Identifier(name), false)) } _ => Err(self.error(format!( "expected property name, found {:?}", self.peek_kind() ))), } }
fn parse_function_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Function)?; let is_generator = self.eat(&TokenKind::Star); let id = if let TokenKind::Identifier(_) = self.peek_kind() { Some(self.expect_identifier()?) } else { None }; let (params, body) = self.parse_function_params_and_body()?; Ok(Expr { kind: ExprKind::Function(FunctionDef { id, params, body, is_async: false, is_generator, }), span: self.span_from(start), }) }
fn parse_async_function_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Async)?; self.expect(&TokenKind::Function)?; let is_generator = self.eat(&TokenKind::Star); let id = if let TokenKind::Identifier(_) = self.peek_kind() { Some(self.expect_identifier()?) } else { None }; let (params, body) = self.parse_function_params_and_body()?; Ok(Expr { kind: ExprKind::Function(FunctionDef { id, params, body, is_async: true, is_generator, }), span: self.span_from(start), }) }
fn parse_class_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); let class_def = self.parse_class(false)?; Ok(Expr { kind: ExprKind::Class(class_def), span: self.span_from(start), }) }
fn parse_template_literal(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); match self.peek_kind().clone() { TokenKind::TemplateFull(s) => { self.advance(); Ok(Expr { kind: ExprKind::TemplateLiteral { quasis: vec![s], expressions: vec![], }, span: self.span_from(start), }) } TokenKind::TemplateHead(s) => { self.advance(); let mut quasis = vec![s]; let mut expressions = Vec::new(); loop { // Template substitutions are `${ Expression[+In] }`. expressions.push(self.with_in(|p| p.parse_expression())?); match self.peek_kind().clone() { TokenKind::TemplateMiddle(s) => { self.advance(); quasis.push(s); } TokenKind::TemplateTail(s) => { self.advance(); quasis.push(s); break; } _ => { return Err(self.error("expected template continuation or tail".into())); } } } Ok(Expr { kind: ExprKind::TemplateLiteral { quasis, expressions, }, span: self.span_from(start), }) } _ => Err(self.error("expected template literal".into())), } }
// ── Operator tables ─────────────────────────────────────
fn peek_binary_op(&self) -> Option<(BinOrLogical, u8, u8)> { let kind = self.peek_kind(); let (op, left_bp, right_bp) = match kind { TokenKind::Or => (BinOrLogical::Logical(LogicalOp::Or), 2, 3), TokenKind::And => (BinOrLogical::Logical(LogicalOp::And), 4, 5), TokenKind::Nullish => (BinOrLogical::Logical(LogicalOp::Nullish), 6, 7), TokenKind::Pipe => (BinOrLogical::Binary(BinaryOp::BitOr), 8, 9), TokenKind::Caret => (BinOrLogical::Binary(BinaryOp::BitXor), 10, 11), TokenKind::Amp => (BinOrLogical::Binary(BinaryOp::BitAnd), 12, 13), TokenKind::Eq => (BinOrLogical::Binary(BinaryOp::Eq), 14, 15), TokenKind::Ne => (BinOrLogical::Binary(BinaryOp::Ne), 14, 15), TokenKind::StrictEq => (BinOrLogical::Binary(BinaryOp::StrictEq), 14, 15), TokenKind::StrictNe => (BinOrLogical::Binary(BinaryOp::StrictNe), 14, 15), TokenKind::Lt => (BinOrLogical::Binary(BinaryOp::Lt), 16, 17), TokenKind::Gt => (BinOrLogical::Binary(BinaryOp::Gt), 16, 17), TokenKind::Le => (BinOrLogical::Binary(BinaryOp::Le), 16, 17), TokenKind::Ge => (BinOrLogical::Binary(BinaryOp::Ge), 16, 17), TokenKind::Instanceof => (BinOrLogical::Binary(BinaryOp::Instanceof), 16, 17), TokenKind::In if self.allow_in => (BinOrLogical::Binary(BinaryOp::In), 16, 17), TokenKind::Shl => (BinOrLogical::Binary(BinaryOp::Shl), 18, 19), TokenKind::Shr => (BinOrLogical::Binary(BinaryOp::Shr), 18, 19), TokenKind::Ushr => (BinOrLogical::Binary(BinaryOp::Ushr), 18, 19), TokenKind::Plus => (BinOrLogical::Binary(BinaryOp::Add), 20, 21), TokenKind::Minus => (BinOrLogical::Binary(BinaryOp::Sub), 20, 21), TokenKind::Star => (BinOrLogical::Binary(BinaryOp::Mul), 22, 23), TokenKind::Slash => (BinOrLogical::Binary(BinaryOp::Div), 22, 23), TokenKind::Percent => (BinOrLogical::Binary(BinaryOp::Rem), 22, 23), TokenKind::Exp => (BinOrLogical::Binary(BinaryOp::Exp), 25, 24), // right-assoc _ => return None, }; Some((op, left_bp, right_bp)) }
fn peek_assign_op(&self) -> Option<AssignOp> { match self.peek_kind() { TokenKind::Assign => Some(AssignOp::Assign), TokenKind::PlusAssign => Some(AssignOp::AddAssign), TokenKind::MinusAssign => Some(AssignOp::SubAssign), TokenKind::StarAssign => Some(AssignOp::MulAssign), TokenKind::SlashAssign => Some(AssignOp::DivAssign), TokenKind::PercentAssign => Some(AssignOp::RemAssign), TokenKind::ExpAssign => Some(AssignOp::ExpAssign), TokenKind::ShlAssign => Some(AssignOp::ShlAssign), TokenKind::ShrAssign => Some(AssignOp::ShrAssign), TokenKind::UshrAssign => Some(AssignOp::UshrAssign), TokenKind::AmpAssign => Some(AssignOp::BitAndAssign), TokenKind::PipeAssign => Some(AssignOp::BitOrAssign), TokenKind::CaretAssign => Some(AssignOp::BitXorAssign), TokenKind::AndAssign => Some(AssignOp::AndAssign), TokenKind::OrAssign => Some(AssignOp::OrAssign), TokenKind::NullishAssign => Some(AssignOp::NullishAssign), _ => None, } }
// ── Expression ↔ Pattern conversion ─────────────────────
fn expr_to_pattern(&self, expr: &Expr) -> Result<Pattern, ParseError> { let span = expr.span; match &expr.kind { ExprKind::Identifier(name) => Ok(Pattern { kind: PatternKind::Identifier(name.clone()), span, }), ExprKind::Array(elements) => { let mut pats = Vec::new(); let mut rest = None; for elem in elements { match elem { None => pats.push(None), Some(ArrayElement::Spread(e)) => { if let ExprKind::Spread(inner) = &e.kind { rest = Some(Box::new(self.expr_to_pattern(inner)?)); } else { rest = Some(Box::new(self.expr_to_pattern(e)?)); } } Some(ArrayElement::Expr(e)) => { pats.push(Some(self.expr_to_pattern(e)?)); } } } Ok(Pattern { kind: PatternKind::Array { elements: pats, rest, }, span, }) } ExprKind::Object(properties) => { let mut pats = Vec::new(); let mut rest = None; for prop in properties { if prop.key == PropertyKey::Identifier("".into()) { if let Some(val) = &prop.value { // Spread property rest = Some(Box::new(self.expr_to_pattern(val)?)); } continue; } let value = if let Some(val) = &prop.value { self.expr_to_pattern(val)? } else { continue; }; pats.push(ObjectPatternProp { key: prop.key.clone(), value, computed: prop.computed, shorthand: prop.shorthand, span: prop.span, }); } Ok(Pattern { kind: PatternKind::Object { properties: pats, rest, }, span, }) } ExprKind::Assignment { op: AssignOp::Assign, left, right, } => { let left_pat = self.expr_to_pattern(left)?; Ok(Pattern { kind: PatternKind::Assign { left: Box::new(left_pat), right: right.clone(), }, span, }) } ExprKind::Spread(inner) => self.expr_to_pattern(inner), _ => Err(ParseError { message: "invalid destructuring pattern".into(), pos: span.start, }), } }
fn expr_to_params(&self, expr: &Expr) -> Result<Vec<Pattern>, ParseError> { match &expr.kind { ExprKind::Sequence(exprs) if exprs.is_empty() => Ok(vec![]), ExprKind::Sequence(exprs) => { let mut params = Vec::new(); for e in exprs { if let ExprKind::Spread(inner) = &e.kind { let pat = self.expr_to_pattern(inner)?; params.push(Pattern { kind: PatternKind::Rest(Box::new(pat)), span: e.span, }); } else { params.push(self.expr_to_pattern(e)?); } } Ok(params) } ExprKind::Spread(inner) => { let pat = self.expr_to_pattern(inner)?; Ok(vec![Pattern { kind: PatternKind::Rest(Box::new(pat)), span: expr.span, }]) } _ => { // Single expression as single parameter Ok(vec![self.expr_to_pattern(expr)?]) } } }}
// ── Helpers ─────────────────────────────────────────────────
/// Distinguishes binary operators from logical operators in Pratt parsing.enum BinOrLogical { Binary(BinaryOp), Logical(LogicalOp),}
/// Returns true if the token kind is a keyword (used for property name parsing).fn is_keyword(kind: &TokenKind) -> bool { matches!( kind, TokenKind::Await | TokenKind::Break | TokenKind::Case | TokenKind::Catch | TokenKind::Class | TokenKind::Const | TokenKind::Continue | TokenKind::Debugger | TokenKind::Default | TokenKind::Delete | TokenKind::Do | TokenKind::Else | TokenKind::Export | TokenKind::Extends | TokenKind::Finally | TokenKind::For | TokenKind::Function | TokenKind::If | TokenKind::Import | TokenKind::In | TokenKind::Instanceof | TokenKind::Let | TokenKind::New | TokenKind::Of | TokenKind::Return | TokenKind::Static | TokenKind::Super | TokenKind::Switch | TokenKind::This | TokenKind::Throw | TokenKind::Try | TokenKind::Typeof | TokenKind::Var | TokenKind::Void | TokenKind::While | TokenKind::With | TokenKind::Yield | TokenKind::Async | TokenKind::True | TokenKind::False | TokenKind::Null )}
fn is_contextual_identifier(kind: &TokenKind) -> bool { matches!(kind, TokenKind::Async | TokenKind::Of)}
// ── Tests ───────────────────────────────────────────────────
#[cfg(test)]mod tests { use super::*;
fn parse(src: &str) -> Program { Parser::parse(src).unwrap() }
fn parse_expr(src: &str) -> Expr { let prog = parse(src); match &prog.body[0].kind { StmtKind::Expr(e) => e.clone(), _ => panic!("expected expression statement, got {:?}", prog.body[0].kind), } }
fn parse_stmt(src: &str) -> Stmt { let prog = parse(src); prog.body[0].clone() }
#[test] fn test_in_after_string_outside_for_init() { // `in` after a string literal at statement level (regression for the // tradera.net webpack chunk; isu issue 362). for src in [ "a&&\"dotAll\"in js&&b;", "\"dotAll\" in js;", "x=(\"dotAll\" in js);", "h=t,ps&&\"dotAll\"in js&&(n=1),r=e;", ] { assert!(Parser::parse(src).is_ok(), "should parse: {src}"); } }
#[test] fn test_no_in_does_not_leak_into_nested_contexts() { // The `for`-initializer NoIn restriction must not propagate into the // bracketed productions nested inside it, which the grammar always // evaluates with `[+In]` (isu issue 362). for src in [ "for(var x=f(\"k\" in o);;){}", // call arguments "for(var x=[\"k\" in o];;){}", // array element "for(var x=o[\"k\" in p];;){}", // computed member "for(var x={a:(\"k\" in o)};;){}", // object value "for(var x={[\"k\" in o]:1};;){}", // computed key "for(var x=`${\"k\" in o}`;;){}", // template substitution "for(var x=function(){return \"k\" in o};;){}", // function body "for(var x=(a=\"k\" in o)=>a;;){}", // arrow param default "for(var f=function(a=\"k\" in o){};;){}", // function param default "for(var x=f(\"k\" in o), y=2;;){}", // multi-declarator "for(x=f(\"k\" in o);;){}", // no-var expression init ] { assert!(Parser::parse(src).is_ok(), "should parse: {src}"); } }
#[test] fn test_top_level_for_in_still_parses() { // The NoIn restriction at the for-init spine must remain so `for (k in // obj)` is still recognised as a for-in statement. assert!(matches!( parse_stmt("for (k in obj) {}").kind, StmtKind::ForIn { .. } )); assert!(matches!( parse_stmt("for (var k in obj) {}").kind, StmtKind::ForIn { .. } )); }
// ── Literals ────────────────────────────────────────
#[test] fn test_number_literal() { let expr = parse_expr("42"); assert_eq!(expr.kind, ExprKind::Number(42.0)); }
#[test] fn test_string_literal() { let expr = parse_expr("\"hello\""); assert_eq!(expr.kind, ExprKind::String("hello".into())); }
#[test] fn test_boolean_literals() { assert_eq!(parse_expr("true").kind, ExprKind::Bool(true)); assert_eq!(parse_expr("false").kind, ExprKind::Bool(false)); }
#[test] fn test_null_literal() { assert_eq!(parse_expr("null").kind, ExprKind::Null); }
#[test] fn test_this() { assert_eq!(parse_expr("this").kind, ExprKind::This); }
#[test] fn test_identifier() { assert_eq!(parse_expr("foo").kind, ExprKind::Identifier("foo".into())); }
#[test] fn test_contextual_identifier_of_expression() { let expr = parse_expr("of(e, t)"); match expr.kind { ExprKind::Call { callee, arguments, .. } => { assert_eq!(callee.kind, ExprKind::Identifier("of".into())); assert_eq!(arguments.len(), 2); } _ => panic!("expected call"), } }
#[test] fn test_regexp() { let expr = parse_expr("x = /test/gi"); match &expr.kind { ExprKind::Assignment { right, .. } => { assert_eq!( right.kind, ExprKind::RegExp { pattern: "test".into(), flags: "gi".into() } ); } _ => panic!("expected assignment"), } }
#[test] fn test_regexp_after_function_declaration() { Parser::parse("function f(){}/iPhone|iPad/.test(navigator.userAgent);").unwrap(); }
#[test] fn test_regexp_after_control_flow_header() { // isu #361: the for-of body is an expression statement beginning with a // RegExp literal; `/` after the header `)` must lex as a regex. Parser::parse("for(let t of Object.keys(e))/didomi/gi.test(t)||0;").unwrap(); Parser::parse("if(a)/re/.test(x);").unwrap(); Parser::parse("while(a)/re/g.exec(x);").unwrap(); }
#[test] fn test_async_function_expression_object_function_property() { Parser::parse( "let f = async function(e) { return { reference: function(e, t, a) { return 1; } }; };", ) .unwrap(); }
// ── Binary expressions ──────────────────────────────
#[test] fn test_addition() { let expr = parse_expr("1 + 2"); match expr.kind { ExprKind::Binary { op, left, right } => { assert_eq!(op, BinaryOp::Add); assert_eq!(left.kind, ExprKind::Number(1.0)); assert_eq!(right.kind, ExprKind::Number(2.0)); } _ => panic!("expected binary"), } }
#[test] fn test_precedence() { // 1 + 2 * 3 should be 1 + (2 * 3) let expr = parse_expr("1 + 2 * 3"); match expr.kind { ExprKind::Binary { op: BinaryOp::Add, left, right, } => { assert_eq!(left.kind, ExprKind::Number(1.0)); match right.kind { ExprKind::Binary { op: BinaryOp::Mul, .. } => {} _ => panic!("expected multiply on right"), } } _ => panic!("expected binary add"), } }
#[test] fn test_exponentiation_right_assoc() { // 2 ** 3 ** 2 should be 2 ** (3 ** 2) let expr = parse_expr("2 ** 3 ** 2"); match expr.kind { ExprKind::Binary { op: BinaryOp::Exp, left, right, } => { assert_eq!(left.kind, ExprKind::Number(2.0)); match right.kind { ExprKind::Binary { op: BinaryOp::Exp, .. } => {} _ => panic!("expected exp on right"), } } _ => panic!("expected binary exp"), } }
#[test] fn test_comparison() { let expr = parse_expr("a === b"); match expr.kind { ExprKind::Binary { op: BinaryOp::StrictEq, .. } => {} _ => panic!("expected strict eq"), } }
#[test] fn test_logical_operators() { let expr = parse_expr("a && b || c"); // Should be (a && b) || c because && has higher precedence match expr.kind { ExprKind::Logical { op: LogicalOp::Or, .. } => {} _ => panic!("expected logical or"), } }
// ── Unary expressions ───────────────────────────────
#[test] fn test_unary_minus() { let expr = parse_expr("-x"); match expr.kind { ExprKind::Unary { op: UnaryOp::Minus, argument, } => { assert_eq!(argument.kind, ExprKind::Identifier("x".into())); } _ => panic!("expected unary minus"), } }
#[test] fn test_typeof() { let expr = parse_expr("typeof x"); match expr.kind { ExprKind::Unary { op: UnaryOp::Typeof, .. } => {} _ => panic!("expected typeof"), } }
#[test] fn test_prefix_increment() { let expr = parse_expr("++x"); match expr.kind { ExprKind::Update { op: UpdateOp::Increment, prefix: true, .. } => {} _ => panic!("expected prefix increment"), } }
#[test] fn test_postfix_decrement() { let expr = parse_expr("x--"); match expr.kind { ExprKind::Update { op: UpdateOp::Decrement, prefix: false, .. } => {} _ => panic!("expected postfix decrement"), } }
// ── Conditional expression ──────────────────────────
#[test] fn test_ternary() { let expr = parse_expr("a ? b : c"); match expr.kind { ExprKind::Conditional { test, consequent, alternate, } => { assert_eq!(test.kind, ExprKind::Identifier("a".into())); assert_eq!(consequent.kind, ExprKind::Identifier("b".into())); assert_eq!(alternate.kind, ExprKind::Identifier("c".into())); } _ => panic!("expected conditional"), } }
// ── Assignment ──────────────────────────────────────
#[test] fn test_assignment() { let expr = parse_expr("x = 42"); match expr.kind { ExprKind::Assignment { op: AssignOp::Assign, left, right, } => { assert_eq!(left.kind, ExprKind::Identifier("x".into())); assert_eq!(right.kind, ExprKind::Number(42.0)); } _ => panic!("expected assignment"), } }
#[test] fn test_compound_assignment() { let expr = parse_expr("x += 1"); match expr.kind { ExprKind::Assignment { op: AssignOp::AddAssign, .. } => {} _ => panic!("expected add-assign"), } }
// ── Member expressions ──────────────────────────────
#[test] fn test_dot_access() { let expr = parse_expr("a.b"); match expr.kind { ExprKind::Member { computed: false, .. } => {} _ => panic!("expected member access"), } }
#[test] fn test_bracket_access() { let expr = parse_expr("a[0]"); match expr.kind { ExprKind::Member { computed: true, .. } => {} _ => panic!("expected computed member"), } }
// ── Call expressions ────────────────────────────────
#[test] fn test_function_call() { let expr = parse_expr("foo(1, 2)"); match expr.kind { ExprKind::Call { callee, arguments, .. } => { assert_eq!(callee.kind, ExprKind::Identifier("foo".into())); assert_eq!(arguments.len(), 2); } _ => panic!("expected call"), } }
#[test] fn test_method_call() { let expr = parse_expr("obj.method()"); match expr.kind { ExprKind::Call { callee, .. } => match callee.kind { ExprKind::Member { .. } => {} _ => panic!("expected member callee"), }, _ => panic!("expected call"), } }
#[test] fn test_new_expression() { let expr = parse_expr("new Foo(1)"); match expr.kind { ExprKind::New { callee, arguments, .. } => { assert_eq!(callee.kind, ExprKind::Identifier("Foo".into())); assert_eq!(arguments.len(), 1); } _ => panic!("expected new"), } }
#[test] fn test_new_expression_member_chain() { // new MemberExpression Arguments is itself a MemberExpression, so // `.forEach` after it must parse as a member access on the new'd object. // Regression: Reddit's bot-check inline script uses // `new URLSearchParams(document.location.search).forEach(...)`. let expr = parse_expr("new URLSearchParams(s).forEach(cb)"); match expr.kind { ExprKind::Call { callee, arguments, .. } => { assert_eq!(arguments.len(), 1); match callee.kind { ExprKind::Member { object, property, computed, } => { assert!(!computed); assert_eq!(property.kind, ExprKind::Identifier("forEach".into())); match object.kind { ExprKind::New { callee: new_callee, arguments: new_args, } => { assert_eq!( new_callee.kind, ExprKind::Identifier("URLSearchParams".into()) ); assert_eq!(new_args.len(), 1); } _ => panic!("expected new inside member"), } } _ => panic!("expected member callee"), } } _ => panic!("expected call expression"), } }
#[test] fn test_new_expression_computed_member() { let expr = parse_expr("new Foo()[0]"); match expr.kind { ExprKind::Member { object, computed, .. } => { assert!(computed); assert!(matches!(object.kind, ExprKind::New { .. })); } _ => panic!("expected member"), } }
#[test] fn test_new_expression_call_chain() { // new X(a)(b) → call the constructed object let expr = parse_expr("new Foo()()"); match expr.kind { ExprKind::Call { callee, .. } => { assert!(matches!(callee.kind, ExprKind::New { .. })); } _ => panic!("expected call"), } }
#[test] fn test_new_target() { let expr = parse_expr("new.target"); assert!(matches!(expr.kind, ExprKind::NewTarget)); }
// ── Array and object literals ───────────────────────
#[test] fn test_array_literal() { let expr = parse_expr("[1, 2, 3]"); match expr.kind { ExprKind::Array(elements) => { assert_eq!(elements.len(), 3); } _ => panic!("expected array"), } }
#[test] fn test_object_literal() { let expr = parse_expr("({a: 1, b: 2})"); match expr.kind { ExprKind::Object(props) => { assert_eq!(props.len(), 2); assert_eq!(props[0].key, PropertyKey::Identifier("a".into())); } _ => panic!("expected object"), } }
#[test] fn test_shorthand_property() { let expr = parse_expr("({x, y})"); match expr.kind { ExprKind::Object(props) => { assert!(props[0].shorthand); assert!(props[1].shorthand); } _ => panic!("expected object"), } }
#[test] fn test_computed_property() { let expr = parse_expr("({[key]: value})"); match expr.kind { ExprKind::Object(props) => { assert!(props[0].computed); } _ => panic!("expected object"), } }
// ── Arrow functions ─────────────────────────────────
#[test] fn test_arrow_single_param() { let expr = parse_expr("x => x + 1"); match expr.kind { ExprKind::Arrow { params, body: ArrowBody::Expr(_), is_async: false, } => { assert_eq!(params.len(), 1); } _ => panic!("expected arrow"), } }
#[test] fn test_arrow_multi_param() { let expr = parse_expr("(a, b) => a + b"); match expr.kind { ExprKind::Arrow { params, .. } => { assert_eq!(params.len(), 2); } _ => panic!("expected arrow"), } }
#[test] fn test_arrow_rest_after_param() { let expr = parse_expr("(value, ...rest) => rest"); match expr.kind { ExprKind::Arrow { params, .. } => { assert_eq!(params.len(), 2); assert!(matches!( ¶ms[1].kind, PatternKind::Rest(inner) if matches!(&inner.kind, PatternKind::Identifier(n) if n == "rest") )); } _ => panic!("expected arrow"), } }
#[test] fn test_async_parenthesized_arrow() { let expr = parse_expr("async (value) => value"); match expr.kind { ExprKind::Arrow { params, is_async, .. } => { assert!(is_async); assert_eq!(params.len(), 1); } _ => panic!("expected async arrow"), } }
#[test] fn test_async_empty_parenthesized_arrow_without_space() { let expr = parse_expr("async()=>value"); match expr.kind { ExprKind::Arrow { params, is_async, .. } => { assert!(is_async); assert!(params.is_empty()); } _ => panic!("expected async arrow"), } }
#[test] fn test_async_parenthesized_arrow_without_space() { let expr = parse_expr("async(value)=>value"); match expr.kind { ExprKind::Arrow { params, is_async, .. } => { assert!(is_async); assert_eq!(params.len(), 1); } _ => panic!("expected async arrow"), } }
#[test] fn test_arrow_body_block() { let expr = parse_expr("() => { return 1; }"); match expr.kind { ExprKind::Arrow { body: ArrowBody::Block(stmts), .. } => { assert_eq!(stmts.len(), 1); } _ => panic!("expected arrow with block body"), } }
// ── Template literals ───────────────────────────────
#[test] fn test_template_no_subst() { let expr = parse_expr("`hello`"); match expr.kind { ExprKind::TemplateLiteral { quasis, expressions, } => { assert_eq!(quasis, vec!["hello"]); assert!(expressions.is_empty()); } _ => panic!("expected template literal"), } }
#[test] fn test_template_with_subst() { let expr = parse_expr("`hello ${name}!`"); match expr.kind { ExprKind::TemplateLiteral { quasis, expressions, } => { assert_eq!(quasis, vec!["hello ", "!"]); assert_eq!(expressions.len(), 1); } _ => panic!("expected template literal"), } }
// ── Spread ──────────────────────────────────────────
#[test] fn test_spread_in_call() { let expr = parse_expr("foo(...args)"); match expr.kind { ExprKind::Call { arguments, .. } => { assert_eq!(arguments.len(), 1); assert!(matches!(arguments[0].kind, ExprKind::Spread(_))); } _ => panic!("expected call"), } }
// ── Variable declarations ───────────────────────────
#[test] fn test_var_decl() { let stmt = parse_stmt("var x = 42;"); match stmt.kind { StmtKind::VarDecl { kind, declarators } => { assert_eq!(kind, VarKind::Var); assert_eq!(declarators.len(), 1); assert!(matches!( declarators[0].pattern.kind, PatternKind::Identifier(ref n) if n == "x" )); assert!(declarators[0].init.is_some()); } _ => panic!("expected var decl"), } }
#[test] fn test_const_decl() { let stmt = parse_stmt("const [a, b] = arr;"); match stmt.kind { StmtKind::VarDecl { kind: VarKind::Const, declarators, } => { assert!(matches!( declarators[0].pattern.kind, PatternKind::Array { .. } )); } _ => panic!("expected const decl"), } }
#[test] fn test_destructuring_object() { let stmt = parse_stmt("let { a, b: c } = obj;"); match stmt.kind { StmtKind::VarDecl { declarators, .. } => match &declarators[0].pattern.kind { PatternKind::Object { properties, .. } => { assert_eq!(properties.len(), 2); assert!(properties[0].shorthand); assert!(!properties[1].shorthand); } _ => panic!("expected object pattern"), }, _ => panic!("expected var decl"), } }
// ── Function declaration ────────────────────────────
#[test] fn test_function_decl() { let stmt = parse_stmt("function add(a, b) { return a + b; }"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert_eq!(def.id, Some("add".into())); assert_eq!(def.params.len(), 2); assert!(!def.is_async); assert!(!def.is_generator); assert_eq!(def.body.len(), 1); } _ => panic!("expected function decl"), } }
#[test] fn test_function_decl_contextual_name_of() { let stmt = parse_stmt("function of(value) { return value; }"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert_eq!(def.id, Some("of".into())); assert_eq!(def.params.len(), 1); } _ => panic!("expected function decl"), } }
#[test] fn test_generator_function() { let stmt = parse_stmt("function* gen() { yield 1; }"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert!(def.is_generator); } _ => panic!("expected function decl"), } }
#[test] fn test_async_function() { let stmt = parse_stmt("async function fetch() { await get(); }"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert!(def.is_async); } _ => panic!("expected function decl"), } }
#[test] fn test_default_params() { let stmt = parse_stmt("function f(a, b = 10) {}"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert_eq!(def.params.len(), 2); assert!(matches!(def.params[1].kind, PatternKind::Assign { .. })); } _ => panic!("expected function decl"), } }
#[test] fn test_rest_params() { let stmt = parse_stmt("function f(...args) {}"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert_eq!(def.params.len(), 1); assert!(matches!( &def.params[0].kind, PatternKind::Rest(inner) if matches!(&inner.kind, PatternKind::Identifier(n) if n == "args") )); } _ => panic!("expected function decl"), } }
// ── Class declaration ───────────────────────────────
#[test] fn test_class_decl() { let stmt = parse_stmt("class Foo { constructor() {} method() {} }"); match stmt.kind { StmtKind::ClassDecl(def) => { assert_eq!(def.id, Some("Foo".into())); assert_eq!(def.body.len(), 2); } _ => panic!("expected class decl"), } }
#[test] fn test_class_extends() { let stmt = parse_stmt("class Bar extends Foo {}"); match stmt.kind { StmtKind::ClassDecl(def) => { assert!(def.super_class.is_some()); } _ => panic!("expected class decl"), } }
#[test] fn test_class_getter_setter() { let stmt = parse_stmt("class C { get x() { return 1; } set x(v) {} }"); match stmt.kind { StmtKind::ClassDecl(def) => { assert_eq!(def.body.len(), 2); match &def.body[0].kind { ClassMemberKind::Method { kind, .. } => { assert_eq!(*kind, MethodKind::Get); } _ => panic!("expected getter"), } } _ => panic!("expected class decl"), } }
// ── Control flow statements ─────────────────────────
#[test] fn test_if_else() { let stmt = parse_stmt("if (x) { a(); } else { b(); }"); match stmt.kind { StmtKind::If { alternate, .. } => { assert!(alternate.is_some()); } _ => panic!("expected if"), } }
#[test] fn test_for_loop() { let stmt = parse_stmt("for (let i = 0; i < 10; i++) {}"); match stmt.kind { StmtKind::For { init, test, update, .. } => { assert!(init.is_some()); assert!(test.is_some()); assert!(update.is_some()); } _ => panic!("expected for"), } }
#[test] fn test_for_in() { let stmt = parse_stmt("for (const key in obj) {}"); assert!(matches!(stmt.kind, StmtKind::ForIn { .. })); }
#[test] fn test_for_initializer_allows_parenthesized_in_expression() { let stmt = parse_stmt("for (s = (t in f) ? f[t] : null, h = 0; h < c; h++) {}"); assert!(matches!(stmt.kind, StmtKind::For { .. })); }
#[test] fn test_for_initializer_allows_parenthesized_in_expression_minified() { // Minified equivalent of test_for_initializer_allows_parenthesized_in_expression // (no whitespace, expression-statement body). Mirrors a pattern found in // production code (e.g., bing.com's minified bundles). let stmt = parse_stmt("for(s=(t in f)?f[t]:null,h=0;h<c;h++)r=u[h];"); assert!(matches!(stmt.kind, StmtKind::For { .. })); }
#[test] fn test_for_of() { let stmt = parse_stmt("for (const item of arr) {}"); assert!(matches!(stmt.kind, StmtKind::ForOf { .. })); }
#[test] fn test_while_loop() { let stmt = parse_stmt("while (true) {}"); assert!(matches!(stmt.kind, StmtKind::While { .. })); }
#[test] fn test_do_while() { let stmt = parse_stmt("do {} while (true);"); assert!(matches!(stmt.kind, StmtKind::DoWhile { .. })); }
#[test] fn test_do_while_asi_no_semicolon_no_newline() { // ECMA-262 12.10.1: the terminating semicolon of a do-while is inserted // automatically even with no intervening line terminator, so the token // following `)` begins a new statement. Minifiers (e.g. Next.js chunks) // emit `do{...}while(cond)return x` on a single line. Regression for // isu issue 344 (tradera.com static chunk parse error). let prog = parse("function f(){do{}while(x)return 1}"); match &prog.body[0].kind { StmtKind::FunctionDecl(func) => { let body = &func.body; assert!(matches!(body[0].kind, StmtKind::DoWhile { .. })); assert!(matches!(body[1].kind, StmtKind::Return(_))); } other => panic!("expected function, got {other:?}"), } }
#[test] fn test_do_while_asi_followed_by_expr_statement() { let prog = parse("do {} while (x) y"); assert_eq!(prog.body.len(), 2); assert!(matches!(prog.body[0].kind, StmtKind::DoWhile { .. })); assert!(matches!(prog.body[1].kind, StmtKind::Expr(_))); }
#[test] fn test_switch() { let stmt = parse_stmt("switch (x) { case 1: break; default: break; }"); match stmt.kind { StmtKind::Switch { cases, .. } => { assert_eq!(cases.len(), 2); assert!(cases[0].test.is_some()); assert!(cases[1].test.is_none()); // default } _ => panic!("expected switch"), } }
#[test] fn test_try_catch() { let stmt = parse_stmt("try { f(); } catch (e) { g(); }"); match stmt.kind { StmtKind::Try { handler, finalizer, .. } => { assert!(handler.is_some()); assert!(finalizer.is_none()); } _ => panic!("expected try"), } }
#[test] fn test_try_catch_finally() { let stmt = parse_stmt("try {} catch (e) {} finally {}"); match stmt.kind { StmtKind::Try { handler, finalizer, .. } => { assert!(handler.is_some()); assert!(finalizer.is_some()); } _ => panic!("expected try"), } }
#[test] fn test_return() { let stmt = parse_stmt("function f() { return 42; }"); match stmt.kind { StmtKind::FunctionDecl(def) => match &def.body[0].kind { StmtKind::Return(Some(expr)) => { assert_eq!(expr.kind, ExprKind::Number(42.0)); } _ => panic!("expected return"), }, _ => panic!("expected function"), } }
#[test] fn test_throw() { let stmt = parse_stmt("function f() { throw new Error(); }"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert!(matches!(def.body[0].kind, StmtKind::Throw(_))); } _ => panic!("expected function"), } }
#[test] fn test_break_continue() { let prog = parse("while (true) { break; continue; }"); let while_stmt = &prog.body[0]; match &while_stmt.kind { StmtKind::While { body, .. } => match &body.kind { StmtKind::Block(stmts) => { assert!(matches!(stmts[0].kind, StmtKind::Break(None))); assert!(matches!(stmts[1].kind, StmtKind::Continue(None))); } _ => panic!("expected block"), }, _ => panic!("expected while"), } }
#[test] fn test_labeled_statement() { let stmt = parse_stmt("outer: for (;;) {}"); match stmt.kind { StmtKind::Labeled { label, .. } => { assert_eq!(label, "outer"); } _ => panic!("expected labeled"), } }
// ── Import / Export ─────────────────────────────────
#[test] fn test_import_default() { let stmt = parse_stmt("import foo from \"mod\";"); match stmt.kind { StmtKind::Import { specifiers, source } => { assert_eq!(source, "mod"); assert_eq!(specifiers.len(), 1); assert!(matches!(&specifiers[0], ImportSpecifier::Default(n) if n == "foo")); } _ => panic!("expected import"), } }
#[test] fn test_import_named() { let prog = Parser::parse_module("import { a, b as c } from \"mod\";").unwrap(); match &prog.body[0].kind { StmtKind::Import { specifiers, .. } => { assert_eq!(specifiers.len(), 2); } _ => panic!("expected import"), } }
#[test] fn test_import_default_as_named_export() { let prog = Parser::parse_module("import { default as React } from \"react\";").unwrap(); match &prog.body[0].kind { StmtKind::Import { specifiers, .. } => { assert!( matches!(&specifiers[0], ImportSpecifier::Named { imported, local } if imported == "default" && local == "React") ); } _ => panic!("expected import"), } }
#[test] fn test_import_namespace() { let prog = Parser::parse_module("import * as ns from \"mod\";").unwrap(); match &prog.body[0].kind { StmtKind::Import { specifiers, .. } => { assert!(matches!(&specifiers[0], ImportSpecifier::Namespace(n) if n == "ns")); } _ => panic!("expected import"), } }
#[test] fn test_export_default() { let prog = Parser::parse_module("export default 42;").unwrap(); match &prog.body[0].kind { StmtKind::Export(ExportDecl::Default(expr)) => { assert_eq!(expr.kind, ExprKind::Number(42.0)); } _ => panic!("expected export default"), } }
#[test] fn test_export_named() { let prog = Parser::parse_module("export { a, b as c };").unwrap(); match &prog.body[0].kind { StmtKind::Export(ExportDecl::Named { specifiers, .. }) => { assert_eq!(specifiers.len(), 2); } _ => panic!("expected export named"), } }
#[test] fn test_export_named_as_default() { let prog = Parser::parse_module("export { value as default };").unwrap(); match &prog.body[0].kind { StmtKind::Export(ExportDecl::Named { specifiers, .. }) => { assert_eq!(specifiers.len(), 1); assert_eq!(specifiers[0].local, "value"); assert_eq!(specifiers[0].exported, "default"); } _ => panic!("expected export named"), } }
#[test] fn test_export_declaration() { let prog = Parser::parse_module("export const x = 1;").unwrap(); match &prog.body[0].kind { StmtKind::Export(ExportDecl::Declaration(_)) => {} _ => panic!("expected export declaration"), } }
#[test] fn test_export_default_anonymous_function() { let prog = Parser::parse_module("export default function() {}").unwrap(); match &prog.body[0].kind { StmtKind::Export(ExportDecl::Default(expr)) => { assert!(matches!(expr.kind, ExprKind::Function(ref def) if def.id.is_none())); } _ => panic!("expected export default anonymous function"), } }
#[test] fn test_export_default_anonymous_class() { let prog = Parser::parse_module("export default class {}").unwrap(); match &prog.body[0].kind { StmtKind::Export(ExportDecl::Default(expr)) => { assert!(matches!(expr.kind, ExprKind::Class(ref def) if def.id.is_none())); } _ => panic!("expected export default anonymous class"), } }
#[test] fn test_export_default_anonymous_generator() { let prog = Parser::parse_module("export default function*() {}").unwrap(); match &prog.body[0].kind { StmtKind::Export(ExportDecl::Default(expr)) => { assert!(matches!( expr.kind, ExprKind::Function(ref def) if def.id.is_none() && def.is_generator )); } _ => panic!("expected export default anonymous generator"), } }
// ── ASI (Automatic Semicolon Insertion) ─────────────
#[test] fn test_asi_newline() { let prog = parse("let x = 1\nlet y = 2"); assert_eq!(prog.body.len(), 2); }
#[test] fn test_asi_before_rbrace() { let stmt = parse_stmt("function f() { return 1 }"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert_eq!(def.body.len(), 1); } _ => panic!("expected function"), } }
// ── Complex programs ────────────────────────────────
#[test] fn test_fibonacci() { let src = r#" function fib(n) { if (n <= 1) return n; return fib(n - 1) + fib(n - 2); } "#; let prog = parse(src); assert_eq!(prog.body.len(), 1); assert!(matches!(prog.body[0].kind, StmtKind::FunctionDecl(_))); }
#[test] fn test_class_with_methods() { let src = r#" class Animal { constructor(name) { this.name = name; } speak() { return this.name; } static create(name) { return new Animal(name); } } "#; let prog = parse(src); assert_eq!(prog.body.len(), 1); match &prog.body[0].kind { StmtKind::ClassDecl(def) => { assert_eq!(def.body.len(), 3); } _ => panic!("expected class"), } }
#[test] fn test_for_of_destructuring() { let stmt = parse_stmt("for (const [k, v] of map) {}"); match stmt.kind { StmtKind::ForOf { left, .. } => match left { ForInOfLeft::VarDecl { pattern, .. } => { assert!(matches!(pattern.kind, PatternKind::Array { .. })); } _ => panic!("expected var decl"), }, _ => panic!("expected for-of"), } }
#[test] fn test_multiple_statements() { let src = "let x = 1; let y = 2; x + y;"; let prog = parse(src); assert_eq!(prog.body.len(), 3); }
// ── Error cases ─────────────────────────────────────
#[test] fn test_error_unexpected_token() { assert!(Parser::parse(")").is_err()); }
#[test] fn test_error_unterminated_block() { assert!(Parser::parse("{ let x = 1;").is_err()); }
#[test] fn test_error_missing_paren() { assert!(Parser::parse("if x {}").is_err()); }}