Reduced boilerplate code in the parser (#2410)

This PR adds an `OrAbrupt` trait, with the `or_abrupt()` function. This function is equivalent to the previous `?.ok_or(ParseError::AbruptEnd)`, but it's cleaner. It's implemented for the parser cursor results types.

It also adds an `advance()` function to the parser cursor (which might be possible to optimize further), that just advances the cursor without returning any token. This shows a clearer intent in many places where it's being used.

I also used `ParseResult` in more places, since we were not using it in many places.

boa_engine/src/syntax/parser/cursor/buffered_lexer/mod.rs

@@ -1,6 +1,6 @@
 use crate::syntax::{
     lexer::{InputElement, Lexer, Token, TokenKind},
-    parser::error::ParseError,
+    parser::{error::ParseError, ParseResult},
 };
 use boa_ast::Position;
 use boa_interner::Interner;
@@ -83,7 +83,7 @@ where
         &mut self,
         start: Position,
         interner: &mut Interner,
-    ) -> Result<Token, ParseError> {
+    ) -> ParseResult<Token> {
         let _timer = Profiler::global().start_event("cursor::lex_regex()", "Parsing");
         self.set_goal(InputElement::RegExp);
         self.lexer
@@ -97,7 +97,7 @@ where
         &mut self,
         start: Position,
         interner: &mut Interner,
-    ) -> Result<Token, ParseError> {
+    ) -> ParseResult<Token> {
         self.lexer
             .lex_template(start, interner)
             .map_err(ParseError::from)
@@ -116,7 +116,7 @@ where
     /// Fills the peeking buffer with the next token.
     ///
     /// It will not fill two line terminators one after the other.
-    fn fill(&mut self, interner: &mut Interner) -> Result<(), ParseError> {
+    fn fill(&mut self, interner: &mut Interner) -> ParseResult<()> {
         debug_assert!(
             self.write_index < PEEK_BUF_SIZE,
             "write index went out of bounds"
@@ -166,12 +166,12 @@ where
     ///
     /// This follows iterator semantics in that a `peek(0, false)` followed by a `next(false)` will
     /// return the same value. Note that because a `peek(n, false)` may return a line terminator a
-    // subsequent `next(true)` may not return the same value.
+    /// subsequent `next(true)` may not return the same value.
     pub(super) fn next(
         &mut self,
         skip_line_terminators: bool,
         interner: &mut Interner,
-    ) -> Result<Option<Token>, ParseError> {
+    ) -> ParseResult<Option<Token>> {
         if self.read_index == self.write_index {
             self.fill(interner)?;
         }
@@ -217,7 +217,7 @@ where
         skip_n: usize,
         skip_line_terminators: bool,
         interner: &mut Interner,
-    ) -> Result<Option<&Token>, ParseError> {
+    ) -> ParseResult<Option<&Token>> {
         assert!(
             skip_n <= MAX_PEEK_SKIP,
             "you cannot skip more than {} elements",

boa_engine/src/syntax/parser/cursor/mod.rs

@@ -1,7 +1,7 @@
 //! Cursor implementation for the parser.
 mod buffered_lexer;
 
-use super::{statement::PrivateElement, ParseError};
+use super::{statement::PrivateElement, OrAbrupt, ParseError, ParseResult};
 use crate::syntax::lexer::{InputElement, Lexer, Token, TokenKind};
 use boa_ast::{Position, Punctuator};
 use boa_interner::{Interner, Sym};
@@ -54,7 +54,7 @@ where
         &mut self,
         start: Position,
         interner: &mut Interner,
-    ) -> Result<Token, ParseError> {
+    ) -> ParseResult<Token> {
         self.buffered_lexer.lex_regex(start, interner)
     }
 
@@ -63,35 +63,55 @@ where
         &mut self,
         start: Position,
         interner: &mut Interner,
-    ) -> Result<Token, ParseError> {
+    ) -> ParseResult<Token> {
         self.buffered_lexer.lex_template(start, interner)
     }
 
+    /// Advances the cursor and returns the next token.
     #[inline]
-    pub(super) fn next(&mut self, interner: &mut Interner) -> Result<Option<Token>, ParseError> {
+    pub(super) fn next(&mut self, interner: &mut Interner) -> ParseResult<Option<Token>> {
         self.buffered_lexer.next(true, interner)
     }
 
+    /// Advances the cursor without returning the next token.
+    ///
+    /// # Panics
+    ///
+    /// This function will panic if there is no further token in the cursor.
+    #[inline]
+    #[track_caller]
+    #[allow(clippy::let_underscore_drop)]
+    pub(super) fn advance(&mut self, interner: &mut Interner) {
+        let _ = self
+            .next(interner)
+            .expect("tried to advance cursor, but the buffer was empty");
+    }
+
+    /// Peeks a future token, without consuming it or advancing the cursor.
+    ///
+    /// You can skip some tokens with the `skip_n` option.
     #[inline]
     pub(super) fn peek(
         &mut self,
         skip_n: usize,
         interner: &mut Interner,
-    ) -> Result<Option<&Token>, ParseError> {
+    ) -> ParseResult<Option<&Token>> {
         self.buffered_lexer.peek(skip_n, true, interner)
     }
 
+    /// Gets the current strict mode for the cursor.
     #[inline]
     pub(super) fn strict_mode(&self) -> bool {
         self.buffered_lexer.strict_mode()
     }
 
+    /// Sets the strict mode to strict or non-strict.
     #[inline]
     pub(super) fn set_strict_mode(&mut self, strict_mode: bool) {
         self.buffered_lexer.set_strict_mode(strict_mode);
     }
 
-    /// Returns if the cursor is currently in a arrow function declaration.
+    /// Returns if the cursor is currently in an arrow function declaration.
     #[inline]
     pub(super) fn arrow(&self) -> bool {
         self.arrow
@@ -116,7 +136,7 @@ where
         &mut self,
         identifier: Sym,
         position: Position,
-    ) -> Result<(), ParseError> {
+    ) -> ParseResult<()> {
         if let Some(env) = self.private_environments_stack.last_mut() {
             env.entry(identifier).or_insert(position);
             Ok(())
@@ -136,7 +156,7 @@ where
     pub(super) fn pop_private_environment(
         &mut self,
         identifiers: &FxHashMap<Sym, PrivateElement>,
-    ) -> Result<(), ParseError> {
+    ) -> ParseResult<()> {
         let last = self
             .private_environments_stack
             .pop()
@@ -163,11 +183,11 @@ where
         kind: K,
         context: &'static str,
         interner: &mut Interner,
-    ) -> Result<Token, ParseError>
+    ) -> ParseResult<Token>
     where
         K: Into<TokenKind>,
     {
-        let next_token = self.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+        let next_token = self.next(interner).or_abrupt()?;
         let kind = kind.into();
 
         if next_token.kind() == &kind {
@@ -191,7 +211,7 @@ where
     pub(super) fn peek_semicolon(
         &mut self,
         interner: &mut Interner,
-    ) -> Result<SemicolonResult<'_>, ParseError> {
+    ) -> ParseResult<SemicolonResult<'_>> {
         match self.buffered_lexer.peek(0, false, interner)? {
             Some(tk) => match tk.kind() {
                 TokenKind::Punctuator(Punctuator::Semicolon | Punctuator::CloseBlock)
@@ -212,7 +232,7 @@ where
         &mut self,
         context: &'static str,
         interner: &mut Interner,
-    ) -> Result<(), ParseError> {
+    ) -> ParseResult<()> {
         match self.peek_semicolon(interner)? {
             SemicolonResult::Found(Some(tk)) => match *tk.kind() {
                 TokenKind::Punctuator(Punctuator::Semicolon) | TokenKind::LineTerminator => {
@@ -243,19 +263,20 @@ where
         skip_n: usize,
         context: &'static str,
         interner: &mut Interner,
-    ) -> Result<&Token, ParseError> {
-        if let Some(t) = self.buffered_lexer.peek(skip_n, false, interner)? {
-            if t.kind() == &TokenKind::LineTerminator {
-                Err(ParseError::unexpected(
-                    t.to_string(interner),
-                    t.span(),
-                    context,
-                ))
-            } else {
-                Ok(t)
-            }
+    ) -> ParseResult<&Token> {
+        let tok = self
+            .buffered_lexer
+            .peek(skip_n, false, interner)
+            .or_abrupt()?;
+
+        if tok.kind() == &TokenKind::LineTerminator {
+            Err(ParseError::unexpected(
+                tok.to_string(interner),
+                tok.span(),
+                context,
+            ))
         } else {
-            Err(ParseError::AbruptEnd)
+            Ok(tok)
         }
     }
 
@@ -265,7 +286,7 @@ where
         &mut self,
         skip_n: usize,
         interner: &mut Interner,
-    ) -> Result<Option<bool>, ParseError> {
+    ) -> ParseResult<Option<bool>> {
         if let Some(t) = self.buffered_lexer.peek(skip_n, false, interner)? {
             Ok(Some(t.kind() == &TokenKind::LineTerminator))
         } else {
@@ -283,7 +304,7 @@ where
         &mut self,
         kind: K,
         interner: &mut Interner,
-    ) -> Result<Option<Token>, ParseError>
+    ) -> ParseResult<Option<Token>>
     where
         K: Into<TokenKind>,
     {

boa_engine/src/syntax/parser/error.rs

@@ -12,13 +12,15 @@ pub(crate) trait ErrorContext {
     fn context(self, context: &'static str) -> Self;
 }
 
-impl<T> ErrorContext for Result<T, ParseError> {
+impl<T> ErrorContext for ParseResult<T> {
+    #[inline]
     fn context(self, context: &'static str) -> Self {
         self.map_err(|e| e.context(context))
     }
 }
 
 impl From<LexError> for ParseError {
+    #[inline]
     fn from(e: LexError) -> Self {
         Self::lex(e)
     }

boa_engine/src/syntax/parser/expression/assignment/arrow_function.rs

@@ -14,7 +14,8 @@ use crate::syntax::{
         error::{ErrorContext, ParseError, ParseResult},
         expression::BindingIdentifier,
         function::{FormalParameters, FunctionBody},
-        name_in_lexically_declared_names, AllowAwait, AllowIn, AllowYield, Cursor, TokenParser,
+        name_in_lexically_declared_names, AllowAwait, AllowIn, AllowYield, Cursor, OrAbrupt,
+        TokenParser,
     },
 };
 use ast::operations::{bound_names, top_level_lexically_declared_names};
@@ -78,7 +79,7 @@ where
 
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("ArrowFunction", "Parsing");
-        let next_token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let next_token = cursor.peek(0, interner).or_abrupt()?;
 
         let (params, params_start_position) = if let TokenKind::Punctuator(Punctuator::OpenParen) =
             &next_token.kind()
@@ -191,13 +192,9 @@ where
     type Output = StatementList;
 
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
-        match cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .kind()
-        {
+        match cursor.peek(0, interner).or_abrupt()?.kind() {
             TokenKind::Punctuator(Punctuator::OpenBlock) => {
-                let _next = cursor.next(interner)?;
+                cursor.advance(interner);
                 let body = FunctionBody::new(false, false).parse(cursor, interner)?;
                 cursor.expect(Punctuator::CloseBlock, "arrow function", interner)?;
                 Ok(body)

boa_engine/src/syntax/parser/expression/assignment/async_arrow_function.rs

@@ -14,7 +14,7 @@ use crate::syntax::{
         error::{ErrorContext, ParseError, ParseResult},
         expression::BindingIdentifier,
         function::{FormalParameters, FunctionBody},
-        name_in_lexically_declared_names, AllowIn, AllowYield, Cursor, TokenParser,
+        name_in_lexically_declared_names, AllowIn, AllowYield, Cursor, OrAbrupt, TokenParser,
     },
 };
 use ast::{
@@ -76,7 +76,7 @@ where
         cursor.expect((Keyword::Async, false), "async arrow function", interner)?;
         cursor.peek_expect_no_lineterminator(0, "async arrow function", interner)?;
 
-        let next_token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let next_token = cursor.peek(0, interner).or_abrupt()?;
         let (params, params_start_position) = if let TokenKind::Punctuator(Punctuator::OpenParen) =
             &next_token.kind()
         {
@@ -180,13 +180,9 @@ where
     type Output = StatementList;
 
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
-        match cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .kind()
-        {
+        match cursor.peek(0, interner).or_abrupt()?.kind() {
             TokenKind::Punctuator(Punctuator::OpenBlock) => {
-                cursor.next(interner)?;
+                cursor.advance(interner);
                 let body = FunctionBody::new(false, true).parse(cursor, interner)?;
                 cursor.expect(Punctuator::CloseBlock, "async arrow function", interner)?;
                 Ok(body)

boa_engine/src/syntax/parser/expression/assignment/conditional.rs

@@ -79,7 +79,7 @@ where
 
         if let Some(tok) = cursor.peek(0, interner)? {
             if tok.kind() == &TokenKind::Punctuator(Punctuator::Question) {
-                cursor.next(interner)?.expect("? character vanished"); // Consume the token.
+                cursor.advance(interner);
                 let then_clause =
                     AssignmentExpression::new(None, true, self.allow_yield, self.allow_await)
                         .parse(cursor, interner)?;

boa_engine/src/syntax/parser/expression/assignment/exponentiation.rs

@@ -7,12 +7,11 @@
 //! [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Exponentiation
 //! [spec]: https://tc39.es/ecma262/#sec-exp-operator
 
-use super::ParseError;
 use crate::syntax::{
     lexer::TokenKind,
     parser::{
         expression::{unary::UnaryExpression, update::UpdateExpression},
-        AllowAwait, AllowYield, Cursor, ParseResult, TokenParser,
+        AllowAwait, AllowYield, Cursor, OrAbrupt, ParseResult, TokenParser,
     },
 };
 use boa_ast::{
@@ -70,7 +69,7 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("ExponentiationExpression", "Parsing");
 
-        let next = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let next = cursor.peek(0, interner).or_abrupt()?;
         match next.kind() {
             TokenKind::Keyword((Keyword::Delete | Keyword::Void | Keyword::TypeOf, _))
             | TokenKind::Punctuator(
@@ -90,7 +89,7 @@ where
             .parse(cursor, interner)?;
         if let Some(tok) = cursor.peek(0, interner)? {
             if let TokenKind::Punctuator(Punctuator::Exp) = tok.kind() {
-                cursor.next(interner)?.expect("** token vanished"); // Consume the token.
+                cursor.advance(interner);
                 return Ok(Binary::new(
                     ArithmeticOp::Exp.into(),
                     lhs,

boa_engine/src/syntax/parser/expression/assignment/mod.rs

@@ -22,17 +22,16 @@ use crate::syntax::{
             conditional::ConditionalExpression,
             r#yield::YieldExpression,
         },
-        name_in_lexically_declared_names, AllowAwait, AllowIn, AllowYield, Cursor, ParseError,
-        ParseResult, TokenParser,
+        name_in_lexically_declared_names, AllowAwait, AllowIn, AllowYield, Cursor, OrAbrupt,
+        ParseError, ParseResult, TokenParser,
     },
 };
-use ast::operations::{bound_names, contains, top_level_lexically_declared_names, ContainsSymbol};
 use boa_ast::{
-    self as ast,
     expression::{
         operator::assign::{Assign, AssignOp, AssignTarget},
         Identifier,
     },
+    operations::{bound_names, contains, top_level_lexically_declared_names, ContainsSymbol},
     Expression, Keyword, Punctuator,
 };
 use boa_interner::Interner;
@@ -102,11 +101,7 @@ where
         let _timer = Profiler::global().start_event("AssignmentExpression", "Parsing");
         cursor.set_goal(InputElement::RegExp);
 
-        match cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .kind()
-        {
+        match cursor.peek(0, interner).or_abrupt()?.kind() {
             // [+Yield]YieldExpression[?In, ?Await]
             TokenKind::Keyword((Keyword::Yield, _)) if self.allow_yield.0 => {
                 return YieldExpression::new(self.allow_in, self.allow_await)
@@ -118,10 +113,7 @@ where
 
                 // Because we already peeked the identifier token, there may be a line terminator before the identifier token.
                 // In that case we have to skip an additional token on the next peek.
-                let skip_n = if cursor
-                    .peek_is_line_terminator(0, interner)?
-                    .ok_or(ParseError::AbruptEnd)?
-                {
+                let skip_n = if cursor.peek_is_line_terminator(0, interner).or_abrupt()? {
                     2
                 } else {
                     1
@@ -143,23 +135,17 @@ where
             }
             //  AsyncArrowFunction[?In, ?Yield, ?Await]
             TokenKind::Keyword((Keyword::Async, _)) => {
-                let skip_n = if cursor
-                    .peek_is_line_terminator(0, interner)?
-                    .ok_or(ParseError::AbruptEnd)?
-                {
+                let skip_n = if cursor.peek_is_line_terminator(0, interner).or_abrupt()? {
                     2
                 } else {
                     1
                 };
 
                 if !cursor
-                    .peek_is_line_terminator(skip_n, interner)?
-                    .ok_or(ParseError::AbruptEnd)?
+                    .peek_is_line_terminator(skip_n, interner)
+                    .or_abrupt()?
                     && matches!(
-                        cursor
-                            .peek(1, interner)?
-                            .ok_or(ParseError::AbruptEnd)?
-                            .kind(),
+                        cursor.peek(1, interner).or_abrupt()?.kind(),
                         TokenKind::Identifier(_)
                             | TokenKind::Keyword((Keyword::Yield | Keyword::Await, _))
                             | TokenKind::Punctuator(Punctuator::OpenParen)
@@ -177,11 +163,7 @@ where
 
         cursor.set_goal(InputElement::Div);
 
-        let position = cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .span()
-            .start();
+        let position = cursor.peek(0, interner).or_abrupt()?.span().start();
         let mut lhs = ConditionalExpression::new(
             self.name,
             self.allow_in,
@@ -247,7 +229,7 @@ where
                 position,
             )?;
 
-            return Ok(ast::function::ArrowFunction::new(self.name, parameters, body).into());
+            return Ok(boa_ast::function::ArrowFunction::new(self.name, parameters, body).into());
         }
 
         // Review if we are trying to assign to an invalid left hand side expression.
@@ -260,7 +242,7 @@ where
                         }
                     }
 
-                    cursor.next(interner)?.expect("= token vanished");
+                    cursor.advance(interner);
                     cursor.set_goal(InputElement::RegExp);
 
                     if let Some(target) =
@@ -285,7 +267,7 @@ where
                         }
                     }
 
-                    cursor.next(interner)?.expect("token vanished");
+                    cursor.advance(interner);
                     if let Some(target) =
                         AssignTarget::from_expression(&lhs, cursor.strict_mode(), false)
                     {

boa_engine/src/syntax/parser/expression/assignment/yield.rs

@@ -10,7 +10,7 @@
 use super::AssignmentExpression;
 use crate::syntax::{
     lexer::TokenKind,
-    parser::{AllowAwait, AllowIn, Cursor, ParseError, ParseResult, TokenParser},
+    parser::{AllowAwait, AllowIn, Cursor, OrAbrupt, ParseResult, TokenParser},
 };
 use boa_ast::{expression::Yield, Expression, Keyword, Punctuator};
 use boa_interner::Interner;
@@ -67,10 +67,10 @@ where
             return Ok(Yield::new(None, false).into());
         }
 
-        let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let token = cursor.peek(0, interner).or_abrupt()?;
         match token.kind() {
             TokenKind::Punctuator(Punctuator::Mul) => {
-                cursor.next(interner)?.expect("token disappeared");
+                cursor.advance(interner);
                 let expr = AssignmentExpression::new(None, self.allow_in, true, self.allow_await)
                     .parse(cursor, interner)?;
                 Ok(Yield::new(Some(expr), true).into())

boa_engine/src/syntax/parser/expression/identifiers.rs

@@ -7,7 +7,9 @@
 
 use crate::syntax::{
     lexer::{Error as LexError, TokenKind},
-    parser::{cursor::Cursor, AllowAwait, AllowYield, ParseError, ParseResult, TokenParser},
+    parser::{
+        cursor::Cursor, AllowAwait, AllowYield, OrAbrupt, ParseError, ParseResult, TokenParser,
+    },
 };
 use boa_ast::{expression::Identifier, Keyword};
 use boa_interner::{Interner, Sym};
@@ -61,7 +63,7 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("IdentifierReference", "Parsing");
 
-        let token = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+        let token = cursor.next(interner).or_abrupt()?;
 
         match token.kind() {
             TokenKind::Identifier(ident)
@@ -153,7 +155,7 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("BindingIdentifier", "Parsing");
 
-        let next_token = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+        let next_token = cursor.next(interner).or_abrupt()?;
 
         match next_token.kind() {
             TokenKind::Identifier(Sym::ARGUMENTS) if cursor.strict_mode() => {

boa_engine/src/syntax/parser/expression/left_hand_side/arguments.rs

@@ -10,8 +10,8 @@
 use crate::syntax::{
     lexer::{InputElement, TokenKind},
     parser::{
-        expression::AssignmentExpression, AllowAwait, AllowYield, Cursor, ParseError, ParseResult,
-        TokenParser,
+        expression::AssignmentExpression, AllowAwait, AllowYield, Cursor, OrAbrupt, ParseError,
+        ParseResult, TokenParser,
     },
 };
 use boa_ast::{expression::Spread, Expression, Punctuator};
@@ -60,11 +60,11 @@ where
         let mut args = Vec::new();
         loop {
             cursor.set_goal(InputElement::RegExp);
-            let next_token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+            let next_token = cursor.peek(0, interner).or_abrupt()?;
 
             match next_token.kind() {
                 TokenKind::Punctuator(Punctuator::CloseParen) => {
-                    cursor.next(interner)?.expect(") token vanished"); // Consume the token.
+                    cursor.advance(interner);
                     break;
                 }
                 TokenKind::Punctuator(Punctuator::Comma) => {

boa_engine/src/syntax/parser/expression/left_hand_side/call.rs

@@ -12,7 +12,7 @@ use crate::syntax::{
     lexer::TokenKind,
     parser::{
         expression::{left_hand_side::template::TaggedTemplateLiteral, Expression},
-        AllowAwait, AllowYield, Cursor, ParseError, ParseResult, TokenParser,
+        AllowAwait, AllowYield, Cursor, OrAbrupt, ParseError, ParseResult, TokenParser,
     },
 };
 use boa_ast::{
@@ -68,7 +68,7 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("CallExpression", "Parsing");
 
-        let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let token = cursor.peek(0, interner).or_abrupt()?;
 
         let mut lhs = if token.kind() == &TokenKind::Punctuator(Punctuator::OpenParen) {
             let args =
@@ -93,9 +93,9 @@ where
                     lhs = ast::Expression::from(Call::new(lhs, args));
                 }
                 TokenKind::Punctuator(Punctuator::Dot) => {
-                    cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?; // We move the parser forward.
+                    cursor.advance(interner);
 
-                    let access = match cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?.kind() {
+                    let access = match cursor.next(interner).or_abrupt()?.kind() {
                         TokenKind::Identifier(name) => SimplePropertyAccess::new(lhs, *name).into(),
                         TokenKind::Keyword((kw, _)) => {
                             SimplePropertyAccess::new(lhs, kw.to_sym(interner)).into()
@@ -124,7 +124,7 @@ where
                     lhs = ast::Expression::PropertyAccess(access);
                 }
                 TokenKind::Punctuator(Punctuator::OpenBracket) => {
-                    let _next = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?; // We move the parser.
+                    cursor.advance(interner);
                     let idx = Expression::new(None, true, self.allow_yield, self.allow_await)
                         .parse(cursor, interner)?;
                     cursor.expect(Punctuator::CloseBracket, "call expression", interner)?;

boa_engine/src/syntax/parser/expression/left_hand_side/member.rs

@@ -12,7 +12,7 @@ use crate::syntax::{
         expression::{
             left_hand_side::template::TaggedTemplateLiteral, primary::PrimaryExpression, Expression,
         },
-        AllowAwait, AllowYield, Cursor, ParseError, ParseResult, TokenParser,
+        AllowAwait, AllowYield, Cursor, OrAbrupt, ParseError, ParseResult, TokenParser,
     },
 };
 use boa_ast::{
@@ -69,7 +69,7 @@ where
 
         cursor.set_goal(InputElement::RegExp);
 
-        let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let token = cursor.peek(0, interner).or_abrupt()?;
         let mut lhs = match token.kind() {
             TokenKind::Keyword((Keyword::New | Keyword::Super, true)) => {
                 return Err(ParseError::general(
@@ -78,10 +78,10 @@ where
                 ));
             }
             TokenKind::Keyword((Keyword::New, false)) => {
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
 
                 if cursor.next_if(Punctuator::Dot, interner)?.is_some() {
-                    let token = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+                    let token = cursor.next(interner).or_abrupt()?;
                     match token.kind() {
                         TokenKind::Identifier(Sym::TARGET) => {
                             return Ok(ast::Expression::NewTarget)
@@ -108,11 +108,11 @@ where
                 ast::Expression::from(New::from(call_node))
             }
             TokenKind::Keyword((Keyword::Super, _)) => {
-                cursor.next(interner).expect("token disappeared");
-                let token = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+                cursor.advance(interner);
+                let token = cursor.next(interner).or_abrupt()?;
                 match token.kind() {
                     TokenKind::Punctuator(Punctuator::Dot) => {
-                        let token = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+                        let token = cursor.next(interner).or_abrupt()?;
                         let field = match token.kind() {
                             TokenKind::Identifier(name) => {
                                 SuperPropertyAccess::new(PropertyAccessField::from(*name))
@@ -173,7 +173,7 @@ where
                         .next(interner)?
                         .expect("dot punctuator token disappeared"); // We move the parser forward.
 
-                    let token = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+                    let token = cursor.next(interner).or_abrupt()?;
 
                     let access = match token.kind() {
                         TokenKind::Identifier(name) => SimplePropertyAccess::new(lhs, *name).into(),

boa_engine/src/syntax/parser/expression/left_hand_side/mod.rs

@@ -101,7 +101,7 @@ where
         cursor.set_goal(InputElement::TemplateTail);
 
         let mut lhs = if is_super_call(cursor, interner)? {
-            cursor.next(interner).expect("token disappeared");
+            cursor.advance(interner);
             let args =
                 Arguments::new(self.allow_yield, self.allow_await).parse(cursor, interner)?;
             SuperCall::new(args).into()

boa_engine/src/syntax/parser/expression/left_hand_side/optional/mod.rs

@@ -9,8 +9,8 @@ use boa_profiler::Profiler;
 use crate::syntax::{
     lexer::{Token, TokenKind},
     parser::{
-        cursor::Cursor, expression::Expression, AllowAwait, AllowYield, ParseError, ParseResult,
-        TokenParser,
+        cursor::Cursor, expression::Expression, AllowAwait, AllowYield, OrAbrupt, ParseError,
+        ParseResult, TokenParser,
     },
 };
 
@@ -105,13 +105,13 @@ where
         while let Some(token) = cursor.peek(0, interner)? {
             let shorted = match token.kind() {
                 TokenKind::Punctuator(Punctuator::Optional) => {
-                    cursor.next(interner).expect("token disappeared");
+                    cursor.advance(interner);
                     true
                 }
                 TokenKind::Punctuator(Punctuator::OpenParen | Punctuator::OpenBracket) => false,
                 TokenKind::Punctuator(Punctuator::Dot) => {
-                    cursor.next(interner).expect("token disappeared");
-                    let field = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+                    cursor.advance(interner);
+                    let field = cursor.next(interner).or_abrupt()?;
 
                     let item = parse_const_access(cursor, &field, interner)?;
 
@@ -127,7 +127,7 @@ where
                 _ => break,
             };
 
-            let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+            let token = cursor.peek(0, interner).or_abrupt()?;
 
             let item = match token.kind() {
                 TokenKind::Punctuator(Punctuator::OpenParen) => {

boa_engine/src/syntax/parser/expression/left_hand_side/template.rs

@@ -1,8 +1,8 @@
 use crate::syntax::{
     lexer::TokenKind,
     parser::{
-        cursor::Cursor, expression::Expression, AllowAwait, AllowYield, ParseError, ParseResult,
-        TokenParser,
+        cursor::Cursor, expression::Expression, AllowAwait, AllowYield, OrAbrupt, ParseError,
+        ParseResult, TokenParser,
     },
 };
 use boa_ast::{self as ast, expression::TaggedTemplate, Position, Punctuator};
@@ -58,7 +58,7 @@ where
         let mut cookeds = Vec::new();
         let mut exprs = Vec::new();
 
-        let mut token = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+        let mut token = cursor.next(interner).or_abrupt()?;
 
         loop {
             match token.kind() {

boa_engine/src/syntax/parser/expression/mod.rs

@@ -23,10 +23,9 @@ use crate::syntax::{
     lexer::{InputElement, TokenKind},
     parser::{
         expression::assignment::ExponentiationExpression, AllowAwait, AllowIn, AllowYield, Cursor,
-        ParseError, ParseResult, TokenParser,
+        OrAbrupt, ParseError, ParseResult, TokenParser,
     },
 };
-
 use boa_ast::{
     self as ast,
     expression::{
@@ -43,6 +42,7 @@ use boa_profiler::Profiler;
 use std::io::Read;
 
 pub(super) use self::{assignment::AssignmentExpression, primary::Initializer};
+
 pub(in crate::syntax::parser) use {
     identifiers::{BindingIdentifier, LabelIdentifier},
     left_hand_side::LeftHandSideExpression,
@@ -88,7 +88,7 @@ macro_rules! expression {
                 while let Some(tok) = cursor.peek(0, interner)? {
                     match *tok.kind() {
                         TokenKind::Punctuator(op) if $( op == $op )||* => {
-                            let _next = cursor.next(interner).expect("token disappeared");
+                            cursor.advance(interner);
                             lhs = Binary::new(
                                 op.as_binary_op().expect("Could not get binary operation."),
                                 lhs,
@@ -159,25 +159,19 @@ where
         while let Some(tok) = cursor.peek(0, interner)? {
             match *tok.kind() {
                 TokenKind::Punctuator(Punctuator::Comma) => {
-                    if cursor
-                        .peek(1, interner)?
-                        .ok_or(ParseError::AbruptEnd)?
-                        .kind()
+                    if cursor.peek(1, interner).or_abrupt()?.kind()
                         == &TokenKind::Punctuator(Punctuator::CloseParen)
                     {
                         return Ok(lhs);
                     }
 
-                    if cursor
-                        .peek(1, interner)?
-                        .ok_or(ParseError::AbruptEnd)?
-                        .kind()
+                    if cursor.peek(1, interner).or_abrupt()?.kind()
                         == &TokenKind::Punctuator(Punctuator::Spread)
                     {
                         return Ok(lhs);
                     }
 
-                    let _next = cursor.next(interner).expect("token disappeared");
+                    cursor.advance(interner);
 
                     lhs = Binary::new(
                         Punctuator::Comma
@@ -291,7 +285,7 @@ where
                             "logical expression (cannot use '??' without parentheses within '||' or '&&')",
                         ));
                     }
-                    let _next = cursor.next(interner)?.expect("'&&' expected");
+                    cursor.advance(interner);
                     previous = PreviousExpr::Logical;
                     let rhs = BitwiseORExpression::new(
                         self.name,
@@ -312,7 +306,7 @@ where
                             "logical expression (cannot use '??' without parentheses within '||' or '&&')",
                         ));
                     }
-                    let _next = cursor.next(interner)?.expect("'||' expected");
+                    cursor.advance(interner);
                     previous = PreviousExpr::Logical;
                     let rhs = Self::with_previous(
                         self.name,
@@ -334,7 +328,7 @@ where
                             "cannot use '??' unparenthesized within '||' or '&&'",
                         ));
                     }
-                    let _next = cursor.next(interner)?.expect("'??' expected");
+                    cursor.advance(interner);
                     previous = PreviousExpr::Coalesce;
                     let rhs = BitwiseORExpression::new(
                         self.name,
@@ -580,7 +574,7 @@ where
                         || op == Punctuator::LessThanOrEq
                         || op == Punctuator::GreaterThanOrEq =>
                 {
-                    let _next = cursor.next(interner).expect("token disappeared");
+                    cursor.advance(interner);
                     lhs = Binary::new(
                         op.as_binary_op().expect("Could not get binary operation."),
                         lhs,
@@ -599,7 +593,7 @@ where
                     if op == Keyword::InstanceOf
                         || (op == Keyword::In && self.allow_in == AllowIn(true)) =>
                 {
-                    let _next = cursor.next(interner).expect("token disappeared");
+                    cursor.advance(interner);
                     lhs = Binary::new(
                         op.as_binary_op().expect("Could not get binary operation."),
                         lhs,
@@ -742,7 +736,7 @@ expression!(
 );
 
 /// Returns an error if `arguments` or `eval` are used as identifier in strict mode.
-fn check_strict_arguments_or_eval(ident: Identifier, position: Position) -> Result<(), ParseError> {
+fn check_strict_arguments_or_eval(ident: Identifier, position: Position) -> ParseResult<()> {
     match ident.sym() {
         Sym::ARGUMENTS => Err(ParseError::general(
             "unexpected identifier 'arguments' in strict mode",

boa_engine/src/syntax/parser/expression/primary/array_initializer/mod.rs

@@ -13,8 +13,8 @@ mod tests;
 use crate::syntax::{
     lexer::TokenKind,
     parser::{
-        expression::AssignmentExpression, AllowAwait, AllowYield, Cursor, ParseError, ParseResult,
-        TokenParser,
+        expression::AssignmentExpression, AllowAwait, AllowYield, Cursor, OrAbrupt, ParseError,
+        ParseResult, TokenParser,
     },
 };
 use boa_ast::{
@@ -67,17 +67,17 @@ where
         let mut last_spread = false;
 
         loop {
-            let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+            let token = cursor.peek(0, interner).or_abrupt()?;
             match token.kind() {
                 TokenKind::Punctuator(Punctuator::CloseBracket) => {
-                    cursor.next(interner).expect("token disappeared");
+                    cursor.advance(interner);
                     break;
                 }
                 TokenKind::Punctuator(Punctuator::Comma) if next_comma => {
-                    cursor.next(interner).expect("token disappeared");
+                    cursor.advance(interner);
 
                     if last_spread {
-                        let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+                        let token = cursor.peek(0, interner).or_abrupt()?;
                         if token.kind() == &TokenKind::Punctuator(Punctuator::CloseBracket) {
                             has_trailing_comma_spread = true;
                         }
@@ -86,7 +86,7 @@ where
                     next_comma = false;
                 }
                 TokenKind::Punctuator(Punctuator::Comma) => {
-                    cursor.next(interner).expect("token disappeared");
+                    cursor.advance(interner);
                     elements.push(None);
                 }
                 TokenKind::Punctuator(Punctuator::Spread) if next_comma => {
@@ -97,7 +97,7 @@ where
                     ));
                 }
                 TokenKind::Punctuator(Punctuator::Spread) => {
-                    cursor.next(interner).expect("token disappeared");
+                    cursor.advance(interner);
                     let node =
                         AssignmentExpression::new(None, true, self.allow_yield, self.allow_await)
                             .parse(cursor, interner)?;

boa_engine/src/syntax/parser/expression/primary/async_function_expression/mod.rs

@@ -6,7 +6,8 @@ use crate::syntax::{
     parser::{
         expression::BindingIdentifier,
         function::{FormalParameters, FunctionBody},
-        name_in_lexically_declared_names, AllowYield, Cursor, ParseError, ParseResult, TokenParser,
+        name_in_lexically_declared_names, AllowYield, Cursor, OrAbrupt, ParseError, ParseResult,
+        TokenParser,
     },
 };
 use boa_ast::{
@@ -62,11 +63,7 @@ where
             interner,
         )?;
 
-        let (name, has_binding_identifier) = match cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .kind()
-        {
+        let (name, has_binding_identifier) = match cursor.peek(0, interner).or_abrupt()?.kind() {
             TokenKind::Punctuator(Punctuator::OpenParen) => (self.name, false),
             _ => (
                 Some(BindingIdentifier::new(self.allow_yield, true).parse(cursor, interner)?),

boa_engine/src/syntax/parser/expression/primary/async_generator_expression/mod.rs

@@ -15,7 +15,7 @@ use crate::syntax::{
     parser::{
         expression::BindingIdentifier,
         function::{FormalParameters, FunctionBody},
-        name_in_lexically_declared_names, Cursor, ParseError, ParseResult, TokenParser,
+        name_in_lexically_declared_names, Cursor, OrAbrupt, ParseError, ParseResult, TokenParser,
     },
 };
 use boa_ast::{
@@ -71,11 +71,7 @@ where
             interner,
         )?;
 
-        let (name, has_binding_identifier) = match cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .kind()
-        {
+        let (name, has_binding_identifier) = match cursor.peek(0, interner).or_abrupt()?.kind() {
             TokenKind::Punctuator(Punctuator::OpenParen) => (self.name, false),
             _ => (
                 Some(BindingIdentifier::new(true, true).parse(cursor, interner)?),

boa_engine/src/syntax/parser/expression/primary/class_expression/mod.rs

@@ -2,7 +2,7 @@ use crate::syntax::{
     lexer::TokenKind,
     parser::{
         expression::BindingIdentifier, statement::ClassTail, AllowAwait, AllowYield, Cursor,
-        ParseError, ParseResult, TokenParser,
+        OrAbrupt, ParseError, ParseResult, TokenParser,
     },
 };
 use boa_ast::{expression::Identifier, function::Class, Keyword};
@@ -50,7 +50,7 @@ where
         let strict = cursor.strict_mode();
         cursor.set_strict_mode(true);
 
-        let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let token = cursor.peek(0, interner).or_abrupt()?;
         let name = match token.kind() {
             TokenKind::Identifier(_) | TokenKind::Keyword((Keyword::Yield | Keyword::Await, _)) => {
                 BindingIdentifier::new(self.allow_yield, self.allow_await)

boa_engine/src/syntax/parser/expression/primary/function_expression/mod.rs

@@ -15,7 +15,7 @@ use crate::syntax::{
     parser::{
         expression::BindingIdentifier,
         function::{FormalParameters, FunctionBody},
-        name_in_lexically_declared_names, Cursor, ParseError, ParseResult, TokenParser,
+        name_in_lexically_declared_names, Cursor, OrAbrupt, ParseError, ParseResult, TokenParser,
     },
 };
 use boa_ast::{
@@ -60,11 +60,7 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("FunctionExpression", "Parsing");
 
-        let (name, has_binding_identifier) = match cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .kind()
-        {
+        let (name, has_binding_identifier) = match cursor.peek(0, interner).or_abrupt()?.kind() {
             TokenKind::Identifier(_)
             | TokenKind::Keyword((
                 Keyword::Yield | Keyword::Await | Keyword::Async | Keyword::Of,

boa_engine/src/syntax/parser/expression/primary/generator_expression/mod.rs

@@ -15,7 +15,7 @@ use crate::syntax::{
     parser::{
         expression::BindingIdentifier,
         function::{FormalParameters, FunctionBody},
-        name_in_lexically_declared_names, Cursor, ParseError, ParseResult, TokenParser,
+        name_in_lexically_declared_names, Cursor, OrAbrupt, ParseError, ParseResult, TokenParser,
     },
 };
 use boa_ast::{
@@ -66,11 +66,7 @@ where
             interner,
         )?;
 
-        let (name, has_binding_identifier) = match cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .kind()
-        {
+        let (name, has_binding_identifier) = match cursor.peek(0, interner).or_abrupt()?.kind() {
             TokenKind::Punctuator(Punctuator::OpenParen) => (self.name, false),
             _ => (
                 Some(BindingIdentifier::new(true, false).parse(cursor, interner)?),

boa_engine/src/syntax/parser/expression/primary/mod.rs

@@ -34,7 +34,7 @@ use crate::syntax::{
             BindingIdentifier, Expression,
         },
         statement::{ArrayBindingPattern, ObjectBindingPattern},
-        AllowAwait, AllowYield, Cursor, ParseError, ParseResult, TokenParser,
+        AllowAwait, AllowYield, Cursor, OrAbrupt, ParseError, ParseResult, TokenParser,
     },
 };
 use boa_ast::{
@@ -98,7 +98,7 @@ where
 
         // TODO: tok currently consumes the token instead of peeking, so the token
         // isn't passed and consumed by parsers according to spec (EX: GeneratorExpression)
-        let tok = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let tok = cursor.peek(0, interner).or_abrupt()?;
         let tok_position = tok.span().start();
 
         match tok.kind() {
@@ -107,12 +107,12 @@ where
                 tok_position,
             )),
             TokenKind::Keyword((Keyword::This, false)) => {
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 Ok(ast::Expression::This)
             }
             TokenKind::Keyword((Keyword::Function, _)) => {
-                cursor.next(interner).expect("token disappeared");
-                let next_token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+                cursor.advance(interner);
+                let next_token = cursor.peek(0, interner).or_abrupt()?;
                 if next_token.kind() == &TokenKind::Punctuator(Punctuator::Mul) {
                     GeneratorExpression::new(self.name)
                         .parse(cursor, interner)
@@ -124,7 +124,7 @@ where
                 }
             }
             TokenKind::Keyword((Keyword::Class, _)) => {
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 ClassExpression::new(self.name, self.allow_yield, self.allow_await)
                     .parse(cursor, interner)
                     .map(Into::into)
@@ -139,7 +139,7 @@ where
                         ))
                     }
                     Some(TokenKind::Keyword((Keyword::Function, _))) => {
-                        cursor.next(interner).expect("token disappeared");
+                        cursor.advance(interner);
                         match cursor.peek(1, interner)?.map(Token::kind) {
                             Some(TokenKind::Punctuator(Punctuator::Mul)) => {
                                 AsyncGeneratorExpression::new(self.name)
@@ -157,7 +157,7 @@ where
                 }
             }
             TokenKind::Punctuator(Punctuator::OpenParen) => {
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 cursor.set_goal(InputElement::RegExp);
                 let expr = CoverParenthesizedExpressionAndArrowParameterList::new(
                     self.name,
@@ -168,14 +168,14 @@ where
                 Ok(expr)
             }
             TokenKind::Punctuator(Punctuator::OpenBracket) => {
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 cursor.set_goal(InputElement::RegExp);
                 ArrayLiteral::new(self.allow_yield, self.allow_await)
                     .parse(cursor, interner)
                     .map(Into::into)
             }
             TokenKind::Punctuator(Punctuator::OpenBlock) => {
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 cursor.set_goal(InputElement::RegExp);
                 ObjectLiteral::new(self.allow_yield, self.allow_await)
                     .parse(cursor, interner)
@@ -183,11 +183,11 @@ where
             }
             TokenKind::BooleanLiteral(boolean) => {
                 let node = Literal::from(*boolean).into();
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 Ok(node)
             }
             TokenKind::NullLiteral => {
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 Ok(Literal::Null.into())
             }
             TokenKind::Identifier(_)
@@ -199,7 +199,7 @@ where
                 .map(Into::into),
             TokenKind::StringLiteral(lit) => {
                 let node = Literal::from(*lit).into();
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 Ok(node)
             }
             TokenKind::TemplateNoSubstitution(template_string) => {
@@ -209,22 +209,22 @@ where
                         .map_err(ParseError::lex)?,
                 )
                 .into();
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 Ok(node)
             }
             TokenKind::NumericLiteral(Numeric::Integer(num)) => {
                 let node = Literal::from(*num).into();
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 Ok(node)
             }
             TokenKind::NumericLiteral(Numeric::Rational(num)) => {
                 let node = Literal::from(*num).into();
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 Ok(node)
             }
             TokenKind::NumericLiteral(Numeric::BigInt(num)) => {
                 let node = Literal::from(num.clone()).into();
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 Ok(node)
             }
             TokenKind::RegularExpressionLiteral(body, flags) => {
@@ -232,12 +232,12 @@ where
                     Identifier::new(Sym::REGEXP).into(),
                     vec![Literal::from(*body).into(), Literal::from(*flags).into()].into(),
                 )));
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 Ok(node)
             }
             TokenKind::Punctuator(Punctuator::Div) => {
                 let position = tok.span().start();
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 let tok = cursor.lex_regex(position, interner)?;
 
                 if let TokenKind::RegularExpressionLiteral(body, flags) = *tok.kind() {
@@ -263,7 +263,7 @@ where
                         .to_owned_cooked(interner)
                         .map_err(ParseError::lex)?,
                 );
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 parser.parse(cursor, interner).map(Into::into)
             }
             _ => Err(ParseError::unexpected(
@@ -324,24 +324,21 @@ where
             "Parsing",
         );
 
-        let start_span = cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .span();
+        let start_span = cursor.peek(0, interner).or_abrupt()?.span();
 
         let mut expressions = Vec::new();
         let mut tailing_comma = None;
 
-        let next = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let next = cursor.peek(0, interner).or_abrupt()?;
         let span = match next.kind() {
             TokenKind::Punctuator(Punctuator::CloseParen) => {
                 let span = next.span();
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 span
             }
             TokenKind::Punctuator(Punctuator::Spread) => {
-                cursor.next(interner).expect("token disappeared");
-                let next = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+                cursor.advance(interner);
+                let next = cursor.peek(0, interner).or_abrupt()?;
                 match next.kind() {
                     TokenKind::Punctuator(Punctuator::OpenBlock) => {
                         let bindings =
@@ -375,27 +372,26 @@ where
                         .parse(cursor, interner)?;
                 expressions.push(InnerExpression::Expression(expression));
 
-                let next = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+                let next = cursor.peek(0, interner).or_abrupt()?;
                 match next.kind() {
                     TokenKind::Punctuator(Punctuator::CloseParen) => {
                         let span = next.span();
-                        cursor.next(interner).expect("token disappeared");
+                        cursor.advance(interner);
                         span
                     }
                     TokenKind::Punctuator(Punctuator::Comma) => {
-                        cursor.next(interner).expect("token disappeared");
-                        let next = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+                        cursor.advance(interner);
+                        let next = cursor.peek(0, interner).or_abrupt()?;
                         match next.kind() {
                             TokenKind::Punctuator(Punctuator::CloseParen) => {
                                 let span = next.span();
                                 tailing_comma = Some(next.span());
-                                cursor.next(interner).expect("token disappeared");
+                                cursor.advance(interner);
                                 span
                             }
                             TokenKind::Punctuator(Punctuator::Spread) => {
-                                cursor.next(interner).expect("token disappeared");
-                                let next =
-                                    cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+                                cursor.advance(interner);
+                                let next = cursor.peek(0, interner).or_abrupt()?;
                                 match next.kind() {
                                     TokenKind::Punctuator(Punctuator::OpenBlock) => {
                                         let bindings = ObjectBindingPattern::new(
@@ -456,9 +452,7 @@ where
         let is_arrow = if let Some(TokenKind::Punctuator(Punctuator::Arrow)) =
             cursor.peek(0, interner)?.map(Token::kind)
         {
-            !cursor
-                .peek_is_line_terminator(0, interner)?
-                .ok_or(ParseError::AbruptEnd)?
+            !cursor.peek_is_line_terminator(0, interner).or_abrupt()?
         } else {
             false
         };
@@ -557,7 +551,7 @@ fn expression_to_formal_parameters(
     parameters: &mut Vec<FormalParameter>,
     strict: bool,
     span: Span,
-) -> Result<(), ParseError> {
+) -> ParseResult<()> {
     match node {
         ast::Expression::Identifier(identifier) if strict && *identifier == Sym::EVAL => {
             return Err(ParseError::general(

boa_engine/src/syntax/parser/expression/primary/object_initializer/mod.rs

@@ -15,8 +15,8 @@ use crate::syntax::{
     parser::{
         expression::{identifiers::IdentifierReference, AssignmentExpression},
         function::{FormalParameter, FormalParameters, FunctionBody, UniqueFormalParameters},
-        name_in_lexically_declared_names, AllowAwait, AllowIn, AllowYield, Cursor, ParseError,
-        ParseResult, TokenParser,
+        name_in_lexically_declared_names, AllowAwait, AllowIn, AllowYield, Cursor, OrAbrupt,
+        ParseError, ParseResult, TokenParser,
     },
 };
 use boa_ast::{
@@ -89,7 +89,7 @@ where
             }
 
             if cursor.next_if(Punctuator::Comma, interner)?.is_none() {
-                let next_token = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+                let next_token = cursor.next(interner).or_abrupt()?;
                 return Err(ParseError::expected(
                     [",".to_owned(), "}".to_owned()],
                     next_token.to_string(interner),
@@ -138,11 +138,7 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("PropertyDefinition", "Parsing");
 
-        match cursor
-            .peek(1, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .kind()
-        {
+        match cursor.peek(1, interner).or_abrupt()?.kind() {
             TokenKind::Punctuator(Punctuator::CloseBlock | Punctuator::Comma) => {
                 let ident = IdentifierReference::new(self.allow_yield, self.allow_await)
                     .parse(cursor, interner)?;
@@ -167,13 +163,10 @@ where
 
         //Async [AsyncMethod, AsyncGeneratorMethod] object methods
         let is_keyword = !matches!(
-            cursor
-                .peek(1, interner)?
-                .ok_or(ParseError::AbruptEnd)?
-                .kind(),
+            cursor.peek(1, interner).or_abrupt()?.kind(),
             TokenKind::Punctuator(Punctuator::OpenParen | Punctuator::Colon)
         );
-        let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let token = cursor.peek(0, interner).or_abrupt()?;
         match token.kind() {
             TokenKind::Keyword((Keyword::Async, true)) if is_keyword => {
                 return Err(ParseError::general(
@@ -182,10 +175,10 @@ where
                 ));
             }
             TokenKind::Keyword((Keyword::Async, false)) if is_keyword => {
-                cursor.next(interner)?.expect("token disappeared");
+                cursor.advance(interner);
                 cursor.peek_expect_no_lineterminator(0, "Async object methods", interner)?;
 
-                let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+                let token = cursor.peek(0, interner).or_abrupt()?;
                 let position = token.span().start();
 
                 if let TokenKind::Punctuator(Punctuator::Mul) = token.kind() {
@@ -238,17 +231,8 @@ where
             _ => {}
         }
 
-        if cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .kind()
-            == &TokenKind::Punctuator(Punctuator::Mul)
-        {
-            let position = cursor
-                .peek(0, interner)?
-                .ok_or(ParseError::AbruptEnd)?
-                .span()
-                .start();
+        if cursor.peek(0, interner).or_abrupt()?.kind() == &TokenKind::Punctuator(Punctuator::Mul) {
+            let position = cursor.peek(0, interner).or_abrupt()?.span().start();
             let (class_element_name, method) =
                 GeneratorMethod::new(self.allow_yield, self.allow_await).parse(cursor, interner)?;
 
@@ -283,20 +267,13 @@ where
             return Ok(property::PropertyDefinition::Property(property_name, value));
         }
 
-        let ordinary_method = cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .kind()
+        let ordinary_method = cursor.peek(0, interner).or_abrupt()?.kind()
             == &TokenKind::Punctuator(Punctuator::OpenParen);
 
         match property_name {
             // MethodDefinition[?Yield, ?Await] -> get ClassElementName[?Yield, ?Await] ( ) { FunctionBody[~Yield, ~Await] }
             property::PropertyName::Literal(str) if str == Sym::GET && !ordinary_method => {
-                let position = cursor
-                    .peek(0, interner)?
-                    .ok_or(ParseError::AbruptEnd)?
-                    .span()
-                    .start();
+                let position = cursor.peek(0, interner).or_abrupt()?.span().start();
 
                 property_name = PropertyName::new(self.allow_yield, self.allow_await)
                     .parse(cursor, interner)?;
@@ -507,10 +484,10 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("PropertyName", "Parsing");
 
-        let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let token = cursor.peek(0, interner).or_abrupt()?;
         let name = match token.kind() {
             TokenKind::Punctuator(Punctuator::OpenBracket) => {
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 let node =
                     AssignmentExpression::new(None, false, self.allow_yield, self.allow_await)
                         .parse(cursor, interner)?;
@@ -534,7 +511,7 @@ where
             },
             _ => return Err(ParseError::AbruptEnd),
         };
-        cursor.next(interner).expect("token disappeared");
+        cursor.advance(interner);
         Ok(name)
     }
 }
@@ -574,14 +551,10 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("ClassElementName", "Parsing");
 
-        match cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .kind()
-        {
+        match cursor.peek(0, interner).or_abrupt()?.kind() {
             TokenKind::PrivateIdentifier(ident) => {
                 let ident = *ident;
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 Ok(property::ClassElementName::PrivateIdentifier(ident))
             }
             _ => Ok(property::ClassElementName::PropertyName(
@@ -682,11 +655,7 @@ where
         let class_element_name =
             ClassElementName::new(self.allow_yield, self.allow_await).parse(cursor, interner)?;
 
-        let params_start_position = cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .span()
-            .start();
+        let params_start_position = cursor.peek(0, interner).or_abrupt()?.span().start();
 
         let params = UniqueFormalParameters::new(true, false).parse(cursor, interner)?;
 
@@ -778,11 +747,7 @@ where
         let name =
             ClassElementName::new(self.allow_yield, self.allow_await).parse(cursor, interner)?;
 
-        let params_start_position = cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .span()
-            .start();
+        let params_start_position = cursor.peek(0, interner).or_abrupt()?.span().start();
 
         let params = UniqueFormalParameters::new(true, true).parse(cursor, interner)?;
 
@@ -888,11 +853,7 @@ where
         let class_element_name =
             ClassElementName::new(self.allow_yield, self.allow_await).parse(cursor, interner)?;
 
-        let params_start_position = cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .span()
-            .start();
+        let params_start_position = cursor.peek(0, interner).or_abrupt()?.span().start();
 
         let params = UniqueFormalParameters::new(false, true).parse(cursor, interner)?;
 

boa_engine/src/syntax/parser/expression/unary.rs

@@ -11,7 +11,7 @@ use crate::syntax::{
     lexer::{Error as LexError, TokenKind},
     parser::{
         expression::{await_expr::AwaitExpression, update::UpdateExpression},
-        AllowAwait, AllowYield, Cursor, ParseError, ParseResult, TokenParser,
+        AllowAwait, AllowYield, Cursor, OrAbrupt, ParseError, ParseResult, TokenParser,
     },
 };
 use boa_ast::{
@@ -66,19 +66,15 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("UnaryExpression", "Parsing");
 
-        let tok = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let tok = cursor.peek(0, interner).or_abrupt()?;
         let token_start = tok.span().start();
         match tok.kind() {
             TokenKind::Keyword((Keyword::Delete | Keyword::Void | Keyword::TypeOf, true)) => Err(
                 ParseError::general("Keyword must not contain escaped characters", token_start),
             ),
             TokenKind::Keyword((Keyword::Delete, false)) => {
-                cursor.next(interner)?.expect("Delete keyword vanished");
-                let position = cursor
-                    .peek(0, interner)?
-                    .ok_or(ParseError::AbruptEnd)?
-                    .span()
-                    .start();
+                cursor.advance(interner);
+                let position = cursor.peek(0, interner).or_abrupt()?.span().start();
                 let val = self.parse(cursor, interner)?;
 
                 match val {
@@ -100,27 +96,27 @@ where
                 Ok(Unary::new(UnaryOp::Delete, val).into())
             }
             TokenKind::Keyword((Keyword::Void, false)) => {
-                cursor.next(interner)?.expect("Void keyword vanished"); // Consume the token.
+                cursor.advance(interner);
                 Ok(Unary::new(UnaryOp::Void, self.parse(cursor, interner)?).into())
             }
             TokenKind::Keyword((Keyword::TypeOf, false)) => {
-                cursor.next(interner)?.expect("TypeOf keyword vanished"); // Consume the token.
+                cursor.advance(interner);
                 Ok(Unary::new(UnaryOp::TypeOf, self.parse(cursor, interner)?).into())
             }
             TokenKind::Punctuator(Punctuator::Add) => {
-                cursor.next(interner)?.expect("+ token vanished"); // Consume the token.
+                cursor.advance(interner);
                 Ok(Unary::new(UnaryOp::Plus, self.parse(cursor, interner)?).into())
             }
             TokenKind::Punctuator(Punctuator::Sub) => {
-                cursor.next(interner)?.expect("- token vanished"); // Consume the token.
+                cursor.advance(interner);
                 Ok(Unary::new(UnaryOp::Minus, self.parse(cursor, interner)?).into())
             }
             TokenKind::Punctuator(Punctuator::Neg) => {
-                cursor.next(interner)?.expect("~ token vanished"); // Consume the token.
+                cursor.advance(interner);
                 Ok(Unary::new(UnaryOp::Tilde, self.parse(cursor, interner)?).into())
             }
             TokenKind::Punctuator(Punctuator::Not) => {
-                cursor.next(interner)?.expect("! token vanished"); // Consume the token.
+                cursor.advance(interner);
                 Ok(Unary::new(UnaryOp::Not, self.parse(cursor, interner)?).into())
             }
             TokenKind::Keyword((Keyword::Await, true)) if self.allow_await.0 => {

boa_engine/src/syntax/parser/expression/update.rs

@@ -9,7 +9,7 @@ use super::{check_strict_arguments_or_eval, left_hand_side::LeftHandSideExpressi
 use crate::syntax::{
     lexer::{Error as LexError, TokenKind},
     parser::{
-        expression::unary::UnaryExpression, AllowAwait, AllowYield, Cursor, ParseError,
+        expression::unary::UnaryExpression, AllowAwait, AllowYield, Cursor, OrAbrupt, ParseError,
         ParseResult, TokenParser,
     },
 };
@@ -62,7 +62,7 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("UpdateExpression", "Parsing");
 
-        let tok = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let tok = cursor.peek(0, interner).or_abrupt()?;
         let position = tok.span().start();
         match tok.kind() {
             TokenKind::Punctuator(Punctuator::Inc) => {

boa_engine/src/syntax/parser/function/mod.rs

@@ -29,7 +29,7 @@ use boa_macros::utf16;
 use boa_profiler::Profiler;
 use std::io::Read;
 
-use super::ParseResult;
+use super::{OrAbrupt, ParseResult};
 
 /// Formal parameters parsing.
 ///
@@ -71,7 +71,7 @@ where
 
         let mut params = Vec::new();
 
-        let next_token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let next_token = cursor.peek(0, interner).or_abrupt()?;
         if next_token.kind() == &TokenKind::Punctuator(Punctuator::CloseParen) {
             return Ok(FormalParameterList::default());
         }
@@ -99,10 +99,7 @@ where
 
             params.push(next_param);
 
-            if cursor
-                .peek(0, interner)?
-                .ok_or(ParseError::AbruptEnd)?
-                .kind()
+            if cursor.peek(0, interner).or_abrupt()?.kind()
                 == &TokenKind::Punctuator(Punctuator::CloseParen)
             {
                 break;
@@ -118,10 +115,7 @@ where
             }
 
             cursor.expect(Punctuator::Comma, "parameter list", interner)?;
-            if cursor
-                .peek(0, interner)?
-                .ok_or(ParseError::AbruptEnd)?
-                .kind()
+            if cursor.peek(0, interner).or_abrupt()?.kind()
                 == &TokenKind::Punctuator(Punctuator::CloseParen)
             {
                 break;
@@ -353,10 +347,7 @@ where
                 TokenKind::Punctuator(Punctuator::OpenBlock) => {
                     let bindings = ObjectBindingPattern::new(self.allow_yield, self.allow_await)
                         .parse(cursor, interner)?;
-                    let init = if *cursor
-                        .peek(0, interner)?
-                        .ok_or(ParseError::AbruptEnd)?
-                        .kind()
+                    let init = if *cursor.peek(0, interner).or_abrupt()?.kind()
                         == TokenKind::Punctuator(Punctuator::Assign)
                     {
                         Some(
@@ -372,10 +363,7 @@ where
                 TokenKind::Punctuator(Punctuator::OpenBracket) => {
                     let bindings = ArrayBindingPattern::new(self.allow_yield, self.allow_await)
                         .parse(cursor, interner)?;
-                    let init = if *cursor
-                        .peek(0, interner)?
-                        .ok_or(ParseError::AbruptEnd)?
-                        .kind()
+                    let init = if *cursor.peek(0, interner).or_abrupt()?.kind()
                         == TokenKind::Punctuator(Punctuator::Assign)
                     {
                         Some(
@@ -391,10 +379,7 @@ where
                 _ => {
                     let ident = BindingIdentifier::new(self.allow_yield, self.allow_await)
                         .parse(cursor, interner)?;
-                    let init = if *cursor
-                        .peek(0, interner)?
-                        .ok_or(ParseError::AbruptEnd)?
-                        .kind()
+                    let init = if *cursor.peek(0, interner).or_abrupt()?.kind()
                         == TokenKind::Punctuator(Punctuator::Assign)
                     {
                         Some(

boa_engine/src/syntax/parser/mod.rs

@@ -133,7 +133,7 @@ impl<R> Parser<R> {
     /// The resulting `StatementList` can be compiled into boa bytecode and executed in the boa vm.
     ///
     /// [spec]: https://tc39.es/ecma262/#prod-Script
-    pub fn parse_all(&mut self, context: &mut Context) -> Result<StatementList, ParseError>
+    pub fn parse_all(&mut self, context: &mut Context) -> ParseResult<StatementList>
     where
         R: Read,
     {
@@ -149,7 +149,7 @@ impl<R> Parser<R> {
         &mut self,
         direct: bool,
         context: &mut Context,
-    ) -> Result<StatementList, ParseError>
+    ) -> ParseResult<StatementList>
     where
         R: Read,
     {
@@ -241,7 +241,7 @@ impl<R> Parser<R> {
         interner: &mut Interner,
         allow_yield: bool,
         allow_await: bool,
-    ) -> Result<StatementList, ParseError>
+    ) -> ParseResult<StatementList>
     where
         R: Read,
     {
@@ -256,7 +256,7 @@ impl<R> Parser<R> {
         interner: &mut Interner,
         allow_yield: bool,
         allow_await: bool,
-    ) -> Result<FormalParameterList, ParseError>
+    ) -> ParseResult<FormalParameterList>
     where
         R: Read,
     {
@@ -285,7 +285,7 @@ impl Script {
         self,
         cursor: &mut Cursor<R>,
         context: &mut Context,
-    ) -> Result<StatementList, ParseError> {
+    ) -> ParseResult<StatementList> {
         let mut strict = cursor.strict_mode();
         match cursor.peek(0, context.interner_mut())? {
             Some(tok) => {
@@ -393,7 +393,7 @@ fn name_in_lexically_declared_names(
     bound_names: &[Identifier],
     lexical_names: &[Identifier],
     position: Position,
-) -> Result<(), ParseError> {
+) -> ParseResult<()> {
     for name in bound_names {
         if lexical_names.contains(name) {
             return Err(ParseError::General {
@@ -404,3 +404,16 @@ fn name_in_lexically_declared_names(
     }
     Ok(())
 }
+
+/// Trait to reduce boilerplate in the parser.
+trait OrAbrupt<T> {
+    /// Will convert an `Ok(None)` to a [`ParseError::AbruptEnd`] or return the inner type if not.
+    fn or_abrupt(self) -> ParseResult<T>;
+}
+
+impl<T> OrAbrupt<T> for ParseResult<Option<T>> {
+    #[inline]
+    fn or_abrupt(self) -> ParseResult<T> {
+        self?.ok_or(ParseError::AbruptEnd)
+    }
+}

boa_engine/src/syntax/parser/statement/block/mod.rs

@@ -13,7 +13,9 @@ mod tests;
 use super::StatementList;
 use crate::syntax::{
     lexer::TokenKind,
-    parser::{AllowAwait, AllowReturn, AllowYield, Cursor, ParseError, ParseResult, TokenParser},
+    parser::{
+        AllowAwait, AllowReturn, AllowYield, Cursor, OrAbrupt, ParseError, ParseResult, TokenParser,
+    },
 };
 use boa_ast::{
     operations::{lexically_declared_names_legacy, var_declared_names},
@@ -77,15 +79,11 @@ where
         cursor.expect(Punctuator::OpenBlock, "block", interner)?;
         if let Some(tk) = cursor.peek(0, interner)? {
             if tk.kind() == &TokenKind::Punctuator(Punctuator::CloseBlock) {
-                cursor.next(interner)?.expect("} token vanished");
+                cursor.advance(interner);
                 return Ok(statement::Block::from(vec![]));
             }
         }
-        let position = cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .span()
-            .start();
+        let position = cursor.peek(0, interner).or_abrupt()?.span().start();
         let statement_list = StatementList::new(
             self.allow_yield,
             self.allow_await,

boa_engine/src/syntax/parser/statement/break_stm/mod.rs

@@ -64,7 +64,7 @@ where
         let label = if let SemicolonResult::Found(tok) = cursor.peek_semicolon(interner)? {
             match tok {
                 Some(tok) if tok.kind() == &TokenKind::Punctuator(Punctuator::Semicolon) => {
-                    let _next = cursor.next(interner)?;
+                    cursor.advance(interner);
                 }
                 _ => {}
             }

boa_engine/src/syntax/parser/statement/continue_stm/mod.rs

@@ -64,11 +64,11 @@ where
         let label = if let SemicolonResult::Found(tok) = cursor.peek_semicolon(interner)? {
             if let Some(token) = tok {
                 if token.kind() == &TokenKind::Punctuator(Punctuator::Semicolon) {
-                    cursor.next(interner)?;
+                    cursor.advance(interner);
                 } else if token.kind() == &TokenKind::LineTerminator {
                     if let Some(token) = cursor.peek(0, interner)? {
                         if token.kind() == &TokenKind::Punctuator(Punctuator::Semicolon) {
-                            cursor.next(interner)?;
+                            cursor.advance(interner);
                         }
                     }
                 }

boa_engine/src/syntax/parser/statement/declaration/hoistable/class_decl/mod.rs

@@ -10,7 +10,8 @@ use crate::syntax::{
         },
         function::{FormalParameters, FunctionBody, UniqueFormalParameters, FUNCTION_BREAK_TOKENS},
         statement::StatementList,
-        AllowAwait, AllowDefault, AllowYield, Cursor, ParseError, ParseResult, TokenParser,
+        AllowAwait, AllowDefault, AllowYield, Cursor, OrAbrupt, ParseError, ParseResult,
+        TokenParser,
     },
 };
 use ast::operations::{lexically_declared_names, var_declared_names};
@@ -68,7 +69,7 @@ where
         let strict = cursor.strict_mode();
         cursor.set_strict_mode(true);
 
-        let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let token = cursor.peek(0, interner).or_abrupt()?;
         let name = match token.kind() {
             TokenKind::Identifier(_) | TokenKind::Keyword((Keyword::Yield | Keyword::Await, _)) => {
                 BindingIdentifier::new(self.allow_yield, self.allow_await)
@@ -130,7 +131,7 @@ where
     type Output = Class;
 
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
-        let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let token = cursor.peek(0, interner).or_abrupt()?;
         let super_ref = match token.kind() {
             TokenKind::Keyword((Keyword::Extends, true)) => {
                 return Err(ParseError::general(
@@ -149,22 +150,15 @@ where
         // Temporarily disable strict mode because "strict" may be parsed as a keyword.
         let strict = cursor.strict_mode();
         cursor.set_strict_mode(false);
-        let is_close_block = cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .kind()
+        let is_close_block = cursor.peek(0, interner).or_abrupt()?.kind()
             == &TokenKind::Punctuator(Punctuator::CloseBlock);
         cursor.set_strict_mode(strict);
 
         if is_close_block {
-            cursor.next(interner).expect("token disappeared");
+            cursor.advance(interner);
             Ok(Class::new(Some(self.name), super_ref, None, Box::default()))
         } else {
-            let body_start = cursor
-                .peek(0, interner)?
-                .ok_or(ParseError::AbruptEnd)?
-                .span()
-                .start();
+            let body_start = cursor.peek(0, interner).or_abrupt()?.span().start();
             let (constructor, elements) =
                 ClassBody::new(self.name, self.allow_yield, self.allow_await)
                     .parse(cursor, interner)?;
@@ -290,7 +284,7 @@ where
         let strict = cursor.strict_mode();
         cursor.set_strict_mode(false);
         loop {
-            let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+            let token = cursor.peek(0, interner).or_abrupt()?;
             let position = token.span().start();
             match token.kind() {
                 TokenKind::Punctuator(Punctuator::CloseBlock) => break,
@@ -550,14 +544,14 @@ where
     type Output = (Option<Function>, Option<function::ClassElement>);
 
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
-        let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let token = cursor.peek(0, interner).or_abrupt()?;
         let r#static = match token.kind() {
             TokenKind::Punctuator(Punctuator::Semicolon) => {
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 return Ok((None, None));
             }
             TokenKind::Identifier(Sym::STATIC) => {
-                let token = cursor.peek(1, interner)?.ok_or(ParseError::AbruptEnd)?;
+                let token = cursor.peek(1, interner).or_abrupt()?;
                 match token.kind() {
                     TokenKind::Identifier(_)
                     | TokenKind::StringLiteral(_)
@@ -569,7 +563,7 @@ where
                         Punctuator::OpenBracket | Punctuator::Mul | Punctuator::OpenBlock,
                     ) => {
                         // this "static" is a keyword.
-                        cursor.next(interner).expect("token disappeared");
+                        cursor.advance(interner);
                         true
                     }
                     _ => false,
@@ -579,10 +573,7 @@ where
         };
 
         let is_keyword = !matches!(
-            cursor
-                .peek(1, interner)?
-                .ok_or(ParseError::AbruptEnd)?
-                .kind(),
+            cursor.peek(1, interner).or_abrupt()?.kind(),
             TokenKind::Punctuator(
                 Punctuator::Assign
                     | Punctuator::CloseBlock
@@ -591,11 +582,11 @@ where
             )
         );
 
-        let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let token = cursor.peek(0, interner).or_abrupt()?;
         let position = token.span().start();
         let element = match token.kind() {
             TokenKind::Identifier(Sym::CONSTRUCTOR) if !r#static => {
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 let strict = cursor.strict_mode();
                 cursor.set_strict_mode(true);
 
@@ -620,7 +611,7 @@ where
                 return Ok((Some(Function::new(Some(self.name), parameters, body)), None));
             }
             TokenKind::Punctuator(Punctuator::OpenBlock) if r#static => {
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 let statement_list = if cursor
                     .next_if(TokenKind::Punctuator(Punctuator::CloseBlock), interner)?
                     .is_some()
@@ -629,11 +620,7 @@ where
                 } else {
                     let strict = cursor.strict_mode();
                     cursor.set_strict_mode(true);
-                    let position = cursor
-                        .peek(0, interner)?
-                        .ok_or(ParseError::AbruptEnd)?
-                        .span()
-                        .start();
+                    let position = cursor.peek(0, interner).or_abrupt()?.span().start();
                     let statement_list =
                         StatementList::new(false, true, false, &FUNCTION_BREAK_TOKENS)
                             .parse(cursor, interner)?;
@@ -668,7 +655,7 @@ where
                 function::ClassElement::StaticBlock(statement_list)
             }
             TokenKind::Punctuator(Punctuator::Mul) => {
-                let token = cursor.peek(1, interner)?.ok_or(ParseError::AbruptEnd)?;
+                let token = cursor.peek(1, interner).or_abrupt()?;
                 let name_position = token.span().start();
                 if let TokenKind::Identifier(Sym::CONSTRUCTOR) = token.kind() {
                     return Err(ParseError::general(
@@ -717,12 +704,12 @@ where
                 ));
             }
             TokenKind::Keyword((Keyword::Async, false)) if is_keyword => {
-                cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
                 cursor.peek_expect_no_lineterminator(0, "Async object methods", interner)?;
-                let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+                let token = cursor.peek(0, interner).or_abrupt()?;
                 match token.kind() {
                     TokenKind::Punctuator(Punctuator::Mul) => {
-                        let token = cursor.peek(1, interner)?.ok_or(ParseError::AbruptEnd)?;
+                        let token = cursor.peek(1, interner).or_abrupt()?;
                         let name_position = token.span().start();
                         match token.kind() {
                             TokenKind::Identifier(Sym::CONSTRUCTOR)
@@ -820,8 +807,8 @@ where
                 }
             }
             TokenKind::Identifier(Sym::GET) if is_keyword => {
-                cursor.next(interner).expect("token disappeared");
-                let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+                cursor.advance(interner);
+                let token = cursor.peek(0, interner).or_abrupt()?;
                 match token.kind() {
                     TokenKind::PrivateIdentifier(Sym::CONSTRUCTOR) => {
                         return Err(ParseError::general(
@@ -831,7 +818,7 @@ where
                     }
                     TokenKind::PrivateIdentifier(name) => {
                         let name = *name;
-                        cursor.next(interner).expect("token disappeared");
+                        cursor.advance(interner);
                         let strict = cursor.strict_mode();
                         cursor.set_strict_mode(true);
                         let params =
@@ -941,8 +928,8 @@ where
                 }
             }
             TokenKind::Identifier(Sym::SET) if is_keyword => {
-                cursor.next(interner).expect("token disappeared");
-                let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+                cursor.advance(interner);
+                let token = cursor.peek(0, interner).or_abrupt()?;
                 match token.kind() {
                     TokenKind::PrivateIdentifier(Sym::CONSTRUCTOR) => {
                         return Err(ParseError::general(
@@ -952,7 +939,7 @@ where
                     }
                     TokenKind::PrivateIdentifier(name) => {
                         let name = *name;
-                        cursor.next(interner).expect("token disappeared");
+                        cursor.advance(interner);
                         let strict = cursor.strict_mode();
                         cursor.set_strict_mode(true);
                         let params =
@@ -1066,11 +1053,11 @@ where
             }
             TokenKind::PrivateIdentifier(name) => {
                 let name = *name;
-                cursor.next(interner).expect("token disappeared");
-                let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+                cursor.advance(interner);
+                let token = cursor.peek(0, interner).or_abrupt()?;
                 match token.kind() {
                     TokenKind::Punctuator(Punctuator::Assign) => {
-                        cursor.next(interner).expect("token disappeared");
+                        cursor.advance(interner);
                         let strict = cursor.strict_mode();
                         cursor.set_strict_mode(true);
                         let rhs = AssignmentExpression::new(
@@ -1141,7 +1128,7 @@ where
                 let name_position = token.span().start();
                 let name = PropertyName::new(self.allow_yield, self.allow_await)
                     .parse(cursor, interner)?;
-                let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+                let token = cursor.peek(0, interner).or_abrupt()?;
                 match token.kind() {
                     TokenKind::Punctuator(Punctuator::Assign) => {
                         if let Some(name) = name.prop_name() {
@@ -1159,7 +1146,7 @@ where
                                 ));
                             }
                         }
-                        cursor.next(interner).expect("token disappeared");
+                        cursor.advance(interner);
                         let strict = cursor.strict_mode();
                         cursor.set_strict_mode(true);
                         let rhs = AssignmentExpression::new(

boa_engine/src/syntax/parser/statement/declaration/hoistable/mod.rs

@@ -26,7 +26,8 @@ use crate::syntax::{
         function::{FormalParameters, FunctionBody},
         name_in_lexically_declared_names,
         statement::LexError,
-        AllowAwait, AllowDefault, AllowYield, Cursor, ParseError, ParseResult, TokenParser,
+        AllowAwait, AllowDefault, AllowYield, Cursor, OrAbrupt, ParseError, ParseResult,
+        TokenParser,
     },
 };
 use boa_ast::{
@@ -78,7 +79,7 @@ where
 
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("HoistableDeclaration", "Parsing");
-        let tok = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let tok = cursor.peek(0, interner).or_abrupt()?;
 
         match tok.kind() {
             TokenKind::Keyword((Keyword::Function | Keyword::Async | Keyword::Class, true)) => {
@@ -88,7 +89,7 @@ where
                 ))
             }
             TokenKind::Keyword((Keyword::Function, false)) => {
-                let next_token = cursor.peek(1, interner)?.ok_or(ParseError::AbruptEnd)?;
+                let next_token = cursor.peek(1, interner).or_abrupt()?;
                 if let TokenKind::Punctuator(Punctuator::Mul) = next_token.kind() {
                     GeneratorDeclaration::new(self.allow_yield, self.allow_await, self.is_default)
                         .parse(cursor, interner)
@@ -100,7 +101,7 @@ where
                 }
             }
             TokenKind::Keyword((Keyword::Async, false)) => {
-                let next_token = cursor.peek(2, interner)?.ok_or(ParseError::AbruptEnd)?;
+                let next_token = cursor.peek(2, interner).or_abrupt()?;
                 if let TokenKind::Punctuator(Punctuator::Mul) = next_token.kind() {
                     AsyncGeneratorDeclaration::new(
                         self.allow_yield,
@@ -142,8 +143,8 @@ fn parse_callable_declaration<R: Read, C: CallableDeclaration>(
     c: &C,
     cursor: &mut Cursor<R>,
     interner: &mut Interner,
-) -> Result<(Identifier, FormalParameterList, StatementList), ParseError> {
-    let next_token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+) -> ParseResult<(Identifier, FormalParameterList, StatementList)> {
+    let next_token = cursor.peek(0, interner).or_abrupt()?;
     let name = match next_token.kind() {
         TokenKind::Punctuator(Punctuator::OpenParen) => {
             if !c.is_default() {

boa_engine/src/syntax/parser/statement/declaration/lexical.rs

@@ -13,7 +13,7 @@ use crate::syntax::{
         cursor::{Cursor, SemicolonResult},
         expression::Initializer,
         statement::{ArrayBindingPattern, BindingIdentifier, ObjectBindingPattern},
-        AllowAwait, AllowIn, AllowYield, ParseError, ParseResult, TokenParser,
+        AllowAwait, AllowIn, AllowYield, OrAbrupt, ParseError, ParseResult, TokenParser,
     },
 };
 use ast::operations::bound_names;
@@ -66,7 +66,7 @@ where
 
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("LexicalDeclaration", "Parsing");
-        let tok = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+        let tok = cursor.next(interner).or_abrupt()?;
 
         match tok.kind() {
             TokenKind::Keyword((Keyword::Const | Keyword::Let, true)) => Err(ParseError::general(
@@ -159,7 +159,7 @@ where
                 if init_is_some || self.loop_init {
                     decls.push(decl);
                 } else {
-                    let next = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+                    let next = cursor.next(interner).or_abrupt()?;
                     return Err(ParseError::general(
                         "Expected initializer for const declaration",
                         next.span().start(),
@@ -190,11 +190,11 @@ where
                     if tk.kind() == &TokenKind::Punctuator(Punctuator::Comma) =>
                 {
                     // We discard the comma
-                    let _comma = cursor.next(interner)?;
+                    cursor.advance(interner);
                 }
                 SemicolonResult::NotFound(_) if self.loop_init => break,
                 SemicolonResult::NotFound(_) => {
-                    let next = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+                    let next = cursor.next(interner).or_abrupt()?;
                     return Err(ParseError::expected(
                         [";".to_owned(), "line terminator".to_owned()],
                         next.to_string(interner),
@@ -254,7 +254,7 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("LexicalBinding", "Parsing");
 
-        let peek_token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let peek_token = cursor.peek(0, interner).or_abrupt()?;
         let position = peek_token.span().start();
 
         match peek_token.kind() {

boa_engine/src/syntax/parser/statement/declaration/mod.rs

@@ -20,7 +20,7 @@ pub(in crate::syntax::parser) use lexical::LexicalDeclaration;
 
 use crate::syntax::{
     lexer::TokenKind,
-    parser::{AllowAwait, AllowYield, Cursor, ParseError, ParseResult, TokenParser},
+    parser::{AllowAwait, AllowYield, Cursor, OrAbrupt, ParseResult, TokenParser},
 };
 use boa_ast::{self as ast, Keyword};
 use boa_interner::Interner;
@@ -60,7 +60,7 @@ where
 
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("Declaration", "Parsing");
-        let tok = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let tok = cursor.peek(0, interner).or_abrupt()?;
 
         match tok.kind() {
             TokenKind::Keyword((Keyword::Function | Keyword::Async | Keyword::Class, _)) => {

boa_engine/src/syntax/parser/statement/expression/mod.rs

@@ -1,7 +1,7 @@
 use crate::syntax::{
     lexer::TokenKind,
     parser::{
-        expression::Expression, AllowAwait, AllowYield, Cursor, ParseError, ParseResult,
+        expression::Expression, AllowAwait, AllowYield, Cursor, OrAbrupt, ParseError, ParseResult,
         TokenParser,
     },
 };
@@ -45,7 +45,7 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("ExpressionStatement", "Parsing");
 
-        let next_token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let next_token = cursor.peek(0, interner).or_abrupt()?;
         match next_token.kind() {
             TokenKind::Keyword((
                 Keyword::Function | Keyword::Class | Keyword::Async | Keyword::Let,
@@ -63,7 +63,7 @@ where
                 ));
             }
             TokenKind::Keyword((Keyword::Async, false)) => {
-                let next_token = cursor.peek(1, interner)?.ok_or(ParseError::AbruptEnd)?;
+                let next_token = cursor.peek(1, interner).or_abrupt()?;
                 match next_token.kind() {
                     TokenKind::Keyword((Keyword::Function, true)) => {
                         return Err(ParseError::general(
@@ -81,7 +81,7 @@ where
                 }
             }
             TokenKind::Keyword((Keyword::Let, false)) => {
-                let next_token = cursor.peek(1, interner)?.ok_or(ParseError::AbruptEnd)?;
+                let next_token = cursor.peek(1, interner).or_abrupt()?;
                 if next_token.kind() == &TokenKind::Punctuator(Punctuator::OpenBracket) {
                     return Err(ParseError::general(
                         "expected statement",

boa_engine/src/syntax/parser/statement/if_stm/mod.rs

@@ -5,7 +5,7 @@ use crate::syntax::{
     lexer::TokenKind,
     parser::{
         expression::Expression, statement::declaration::FunctionDeclaration, AllowAwait,
-        AllowReturn, AllowYield, Cursor, ParseError, ParseResult, TokenParser,
+        AllowReturn, AllowYield, Cursor, OrAbrupt, ParseError, ParseResult, TokenParser,
     },
 };
 use boa_ast::{
@@ -72,7 +72,7 @@ where
             .end();
 
         let strict = cursor.strict_mode();
-        let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let token = cursor.peek(0, interner).or_abrupt()?;
         let then_node = match token.kind() {
             TokenKind::Keyword((Keyword::Function, _)) => {
                 // FunctionDeclarations in IfStatement Statement Clauses
@@ -108,10 +108,10 @@ where
                     ));
                 }
                 TokenKind::Keyword((Keyword::Else, false)) => {
-                    cursor.next(interner)?.expect("token disappeared");
+                    cursor.advance(interner);
 
                     let strict = cursor.strict_mode();
-                    let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+                    let token = cursor.peek(0, interner).or_abrupt()?;
                     let position = token.span().start();
                     let stmt = match token.kind() {
                         TokenKind::Keyword((Keyword::Function, _)) => {

boa_engine/src/syntax/parser/statement/iteration/do_while_statement.rs

@@ -11,7 +11,7 @@ use crate::syntax::{
     lexer::TokenKind,
     parser::{
         expression::Expression, statement::Statement, AllowAwait, AllowReturn, AllowYield, Cursor,
-        ParseError, ParseResult, TokenParser,
+        OrAbrupt, ParseError, ParseResult, TokenParser,
     },
 };
 use boa_ast::{statement::DoWhileLoop, Keyword, Punctuator};
@@ -65,11 +65,7 @@ where
 
         cursor.expect((Keyword::Do, false), "do while statement", interner)?;
 
-        let position = cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .span()
-            .start();
+        let position = cursor.peek(0, interner).or_abrupt()?.span().start();
 
         let body = Statement::new(self.allow_yield, self.allow_await, self.allow_return)
             .parse(cursor, interner)?;
@@ -79,7 +75,7 @@ where
             return Err(ParseError::wrong_labelled_function_declaration(position));
         }
 
-        let next_token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let next_token = cursor.peek(0, interner).or_abrupt()?;
         match next_token.kind() {
             TokenKind::Keyword((Keyword::While, true)) => {
                 return Err(ParseError::general(
@@ -112,7 +108,7 @@ where
         // https://tc39.es/ecma262/#sec-automatic-semicolon-insertion
         if let Some(tok) = cursor.peek(0, interner)? {
             if let TokenKind::Punctuator(Punctuator::Semicolon) = *tok.kind() {
-                cursor.next(interner)?;
+                cursor.advance(interner);
             }
         }
 

boa_engine/src/syntax/parser/statement/iteration/for_statement.rs

@@ -13,7 +13,8 @@ use crate::syntax::{
         expression::Expression,
         statement::declaration::LexicalDeclaration,
         statement::{variable::VariableDeclarationList, Statement},
-        AllowAwait, AllowReturn, AllowYield, Cursor, ParseError, ParseResult, TokenParser,
+        AllowAwait, AllowReturn, AllowYield, Cursor, OrAbrupt, ParseError, ParseResult,
+        TokenParser,
     },
 };
 use ast::operations::{bound_names, var_declared_names};
@@ -77,7 +78,7 @@ where
 
         let mut r#await = false;
 
-        let next = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+        let next = cursor.next(interner).or_abrupt()?;
         let init_position = match next.kind() {
             TokenKind::Punctuator(Punctuator::OpenParen) => next.span().end(),
             TokenKind::Keyword((Keyword::Await, _)) if !self.allow_await.0 => {
@@ -103,13 +104,9 @@ where
             }
         };
 
-        let init = match cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .kind()
-        {
+        let init = match cursor.peek(0, interner).or_abrupt()?.kind() {
             TokenKind::Keyword((Keyword::Var, _)) => {
-                let _next = cursor.next(interner)?;
+                cursor.advance(interner);
                 Some(
                     VariableDeclarationList::new(false, self.allow_yield, self.allow_await)
                         .parse(cursor, interner)?
@@ -122,11 +119,7 @@ where
                     .into(),
             ),
             TokenKind::Keyword((Keyword::Async, false)) => {
-                match cursor
-                    .peek(1, interner)?
-                    .ok_or(ParseError::AbruptEnd)?
-                    .kind()
-                {
+                match cursor.peek(1, interner).or_abrupt()?.kind() {
                     TokenKind::Keyword((Keyword::Of, _)) => {
                         return Err(ParseError::lex(LexError::Syntax(
                             "invalid left-hand side expression 'async' of a for-of loop".into(),
@@ -148,7 +141,7 @@ where
             ),
         };
 
-        let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let token = cursor.peek(0, interner).or_abrupt()?;
         let position = token.span().start();
         let init = match (init, token.kind()) {
             (Some(_), TokenKind::Keyword((Keyword::In | Keyword::Of, true))) => {
@@ -168,17 +161,13 @@ where
                 let init =
                     initializer_to_iterable_loop_initializer(init, position, cursor.strict_mode())?;
 
-                let _next = cursor.next(interner)?;
+                cursor.advance(interner);
                 let expr = Expression::new(None, true, self.allow_yield, self.allow_await)
                     .parse(cursor, interner)?;
 
                 cursor.expect(Punctuator::CloseParen, "for in/of statement", interner)?;
 
-                let position = cursor
-                    .peek(0, interner)?
-                    .ok_or(ParseError::AbruptEnd)?
-                    .span()
-                    .start();
+                let position = cursor.peek(0, interner).or_abrupt()?.span().start();
 
                 let body = Statement::new(self.allow_yield, self.allow_await, self.allow_return)
                     .parse(cursor, interner)?;
@@ -266,11 +255,7 @@ where
             Some(step)
         };
 
-        let position = cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .span()
-            .start();
+        let position = cursor.peek(0, interner).or_abrupt()?.span().start();
 
         let body = Statement::new(self.allow_yield, self.allow_await, self.allow_return)
             .parse(cursor, interner)?;
@@ -304,7 +289,7 @@ fn initializer_to_iterable_loop_initializer(
     initializer: ForLoopInitializer,
     position: Position,
     strict: bool,
-) -> Result<IterableLoopInitializer, ParseError> {
+) -> ParseResult<IterableLoopInitializer> {
     match initializer {
         ForLoopInitializer::Expression(expr) => match expr {
             ast::Expression::Identifier(ident)

boa_engine/src/syntax/parser/statement/iteration/while_statement.rs

@@ -1,6 +1,6 @@
 use crate::syntax::parser::{
     expression::Expression, statement::Statement, AllowAwait, AllowReturn, AllowYield, Cursor,
-    ParseError, ParseResult, TokenParser,
+    OrAbrupt, ParseError, ParseResult, TokenParser,
 };
 use boa_ast::{statement::WhileLoop, Keyword, Punctuator};
 use boa_interner::Interner;
@@ -59,11 +59,7 @@ where
 
         cursor.expect(Punctuator::CloseParen, "while statement", interner)?;
 
-        let position = cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .span()
-            .start();
+        let position = cursor.peek(0, interner).or_abrupt()?.span().start();
 
         let body = Statement::new(self.allow_yield, self.allow_await, self.allow_return)
             .parse(cursor, interner)?;

boa_engine/src/syntax/parser/statement/labelled_stm/mod.rs

@@ -5,7 +5,7 @@ use crate::syntax::{
         error::ParseError,
         expression::LabelIdentifier,
         statement::{AllowAwait, AllowReturn, Statement},
-        AllowYield, ParseResult, TokenParser,
+        AllowYield, OrAbrupt, ParseResult, TokenParser,
     },
 };
 use boa_ast::{self as ast, Keyword, Punctuator};
@@ -61,7 +61,7 @@ where
         cursor.expect(Punctuator::Colon, "Labelled Statement", interner)?;
 
         let strict = cursor.strict_mode();
-        let next_token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let next_token = cursor.peek(0, interner).or_abrupt()?;
 
         let labelled_item = match next_token.kind() {
             // Early Error: It is a Syntax Error if any strict mode source code matches this rule.

boa_engine/src/syntax/parser/statement/mod.rs

@@ -37,8 +37,8 @@ use self::{
     variable::VariableStatement,
 };
 use super::{
-    expression::PropertyName, AllowAwait, AllowReturn, AllowYield, Cursor, ParseError, ParseResult,
-    TokenParser,
+    expression::PropertyName, AllowAwait, AllowReturn, AllowYield, Cursor, OrAbrupt, ParseError,
+    ParseResult, TokenParser,
 };
 use crate::syntax::{
     lexer::{Error as LexError, InputElement, Token, TokenKind},
@@ -114,7 +114,7 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("Statement", "Parsing");
         // TODO: add BreakableStatement and divide Whiles, fors and so on to another place.
-        let tok = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let tok = cursor.peek(0, interner).or_abrupt()?;
 
         match tok.kind() {
             TokenKind::Keyword((Keyword::If, _)) => {
@@ -187,7 +187,7 @@ where
             }
             TokenKind::Punctuator(Punctuator::Semicolon) => {
                 // parse the EmptyStatement
-                cursor.next(interner).expect("semicolon disappeared");
+                cursor.advance(interner);
                 Ok(ast::Statement::Empty)
             }
             TokenKind::Identifier(_) => {
@@ -336,7 +336,7 @@ where
 
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("StatementListItem", "Parsing");
-        let tok = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let tok = cursor.peek(0, interner).or_abrupt()?;
 
         match *tok.kind() {
             TokenKind::Keyword((
@@ -409,12 +409,9 @@ where
         let mut property_names = Vec::new();
 
         loop {
-            let next_token_is_colon = *cursor
-                .peek(1, interner)?
-                .ok_or(ParseError::AbruptEnd)?
-                .kind()
+            let next_token_is_colon = *cursor.peek(1, interner).or_abrupt()?.kind()
                 == TokenKind::Punctuator(Punctuator::Colon);
-            let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+            let token = cursor.peek(0, interner).or_abrupt()?;
             match token.kind() {
                 TokenKind::Punctuator(Punctuator::CloseBlock) => {
                     cursor.expect(
@@ -655,11 +652,7 @@ where
         let mut last_elision_or_first = true;
 
         loop {
-            match cursor
-                .peek(0, interner)?
-                .ok_or(ParseError::AbruptEnd)?
-                .kind()
-            {
+            match cursor.peek(0, interner).or_abrupt()?.kind() {
                 TokenKind::Punctuator(Punctuator::CloseBracket) => {
                     cursor.expect(
                         TokenKind::Punctuator(Punctuator::CloseBracket),
@@ -688,11 +681,7 @@ where
                         interner,
                     )?;
 
-                    match cursor
-                        .peek(0, interner)?
-                        .ok_or(ParseError::AbruptEnd)?
-                        .kind()
-                    {
+                    match cursor.peek(0, interner).or_abrupt()?.kind() {
                         TokenKind::Punctuator(Punctuator::OpenBlock) => {
                             let bindings =
                                 ObjectBindingPattern::new(self.allow_yield, self.allow_await)
@@ -732,11 +721,7 @@ where
                     let bindings = ObjectBindingPattern::new(self.allow_yield, self.allow_await)
                         .parse(cursor, interner)?;
 
-                    match cursor
-                        .peek(0, interner)?
-                        .ok_or(ParseError::AbruptEnd)?
-                        .kind()
-                    {
+                    match cursor.peek(0, interner).or_abrupt()?.kind() {
                         TokenKind::Punctuator(Punctuator::Assign) => {
                             let default_init =
                                 Initializer::new(None, true, self.allow_yield, self.allow_await)
@@ -760,11 +745,7 @@ where
                     let bindings =
                         Self::new(self.allow_yield, self.allow_await).parse(cursor, interner)?;
 
-                    match cursor
-                        .peek(0, interner)?
-                        .ok_or(ParseError::AbruptEnd)?
-                        .kind()
-                    {
+                    match cursor.peek(0, interner).or_abrupt()?.kind() {
                         TokenKind::Punctuator(Punctuator::Assign) => {
                             let default_init =
                                 Initializer::new(None, true, self.allow_yield, self.allow_await)
@@ -787,11 +768,7 @@ where
 
                     let ident = BindingIdentifier::new(self.allow_yield, self.allow_await)
                         .parse(cursor, interner)?;
-                    match cursor
-                        .peek(0, interner)?
-                        .ok_or(ParseError::AbruptEnd)?
-                        .kind()
-                    {
+                    match cursor.peek(0, interner).or_abrupt()?.kind() {
                         TokenKind::Punctuator(Punctuator::Assign) => {
                             let default_init = Initializer::new(
                                 Some(ident),

boa_engine/src/syntax/parser/statement/return_stm/mod.rs

@@ -52,7 +52,7 @@ where
         if let SemicolonResult::Found(tok) = cursor.peek_semicolon(interner)? {
             match tok {
                 Some(tok) if tok.kind() == &TokenKind::Punctuator(Punctuator::Semicolon) => {
-                    let _next = cursor.next(interner)?;
+                    cursor.advance(interner);
                 }
                 _ => {}
             }

boa_engine/src/syntax/parser/statement/switch/mod.rs

@@ -5,7 +5,7 @@ use crate::syntax::{
     lexer::TokenKind,
     parser::{
         expression::Expression, statement::StatementList, AllowAwait, AllowReturn, AllowYield,
-        Cursor, ParseError, ParseResult, TokenParser,
+        Cursor, OrAbrupt, ParseError, ParseResult, TokenParser,
     },
 };
 use ast::operations::{lexically_declared_names_legacy, var_declared_names};
@@ -69,11 +69,7 @@ where
 
         cursor.expect(Punctuator::CloseParen, "switch statement", interner)?;
 
-        let position = cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .span()
-            .start();
+        let position = cursor.peek(0, interner).or_abrupt()?.span().start();
 
         let (cases, default) =
             CaseBlock::new(self.allow_yield, self.allow_await, self.allow_return)
@@ -156,7 +152,7 @@ where
         let mut default = None;
 
         loop {
-            let token = cursor.next(interner)?.ok_or(ParseError::AbruptEnd)?;
+            let token = cursor.next(interner).or_abrupt()?;
             match token.kind() {
                 TokenKind::Keyword((Keyword::Case | Keyword::Default, true)) => {
                     return Err(ParseError::general(

boa_engine/src/syntax/parser/statement/throw/mod.rs

@@ -54,7 +54,7 @@ where
             .parse(cursor, interner)?;
         if let Some(tok) = cursor.peek(0, interner)? {
             if tok.kind() == &TokenKind::Punctuator(Punctuator::Semicolon) {
-                let _next = cursor.next(interner).expect("token disappeared");
+                cursor.advance(interner);
             }
         }
 

boa_engine/src/syntax/parser/statement/try_stm/catch.rs

@@ -2,7 +2,8 @@ use crate::syntax::{
     lexer::TokenKind,
     parser::{
         statement::{block::Block, ArrayBindingPattern, BindingIdentifier, ObjectBindingPattern},
-        AllowAwait, AllowReturn, AllowYield, Cursor, ParseError, ParseResult, TokenParser,
+        AllowAwait, AllowReturn, AllowYield, Cursor, OrAbrupt, ParseError, ParseResult,
+        TokenParser,
     },
 };
 use boa_ast::{
@@ -55,11 +56,7 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("Catch", "Parsing");
         cursor.expect((Keyword::Catch, false), "try statement", interner)?;
-        let position = cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .span()
-            .start();
+        let position = cursor.peek(0, interner).or_abrupt()?.span().start();
         let catch_param = if cursor.next_if(Punctuator::OpenParen, interner)?.is_some() {
             let catch_param =
                 CatchParameter::new(self.allow_yield, self.allow_await).parse(cursor, interner)?;
@@ -88,11 +85,7 @@ where
             })
             .transpose()?;
 
-        let position = cursor
-            .peek(0, interner)?
-            .ok_or(ParseError::AbruptEnd)?
-            .span()
-            .start();
+        let position = cursor.peek(0, interner).or_abrupt()?.span().start();
         let catch_block = Block::new(self.allow_yield, self.allow_await, self.allow_return)
             .parse(cursor, interner)?;
 
@@ -161,7 +154,7 @@ where
     type Output = Binding;
 
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
-        let token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let token = cursor.peek(0, interner).or_abrupt()?;
 
         match token.kind() {
             TokenKind::Punctuator(Punctuator::OpenBlock) => {

boa_engine/src/syntax/parser/statement/try_stm/mod.rs

@@ -8,7 +8,9 @@ use self::{catch::Catch, finally::Finally};
 use super::block::Block;
 use crate::syntax::{
     lexer::TokenKind,
-    parser::{AllowAwait, AllowReturn, AllowYield, Cursor, ParseError, ParseResult, TokenParser},
+    parser::{
+        AllowAwait, AllowReturn, AllowYield, Cursor, OrAbrupt, ParseError, ParseResult, TokenParser,
+    },
 };
 use boa_ast::{
     statement::{ErrorHandler, Try},
@@ -63,7 +65,7 @@ where
         let try_clause = Block::new(self.allow_yield, self.allow_await, self.allow_return)
             .parse(cursor, interner)?;
 
-        let next_token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let next_token = cursor.peek(0, interner).or_abrupt()?;
         match next_token.kind() {
             TokenKind::Keyword((Keyword::Catch | Keyword::Finally, true)) => {
                 return Err(ParseError::general(

boa_engine/src/syntax/parser/statement/variable/mod.rs

@@ -6,7 +6,7 @@ use crate::syntax::{
         cursor::Cursor,
         expression::Initializer,
         statement::{ArrayBindingPattern, BindingIdentifier, ObjectBindingPattern},
-        AllowAwait, AllowIn, AllowYield, ParseError, ParseResult, TokenParser,
+        AllowAwait, AllowIn, AllowYield, OrAbrupt, ParseResult, TokenParser,
     },
 };
 use boa_ast::{
@@ -163,7 +163,7 @@ where
     type Output = Variable;
 
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
-        let peek_token = cursor.peek(0, interner)?.ok_or(ParseError::AbruptEnd)?;
+        let peek_token = cursor.peek(0, interner).or_abrupt()?;
 
         match peek_token.kind() {
             TokenKind::Punctuator(Punctuator::OpenBlock) => {