1 use super::pat::{CommaRecoveryMode, RecoverColon, RecoverComma, PARAM_EXPECTED};
2 use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
4 AttrWrapper, BlockMode, ClosureSpans, ForceCollect, Parser, PathStyle, Restrictions, TokenType,
6 use super::{SemiColonMode, SeqSep, TokenExpectType, TrailingToken};
7 use crate::maybe_recover_from_interpolated_ty_qpath;
9 use ast::token::DelimToken;
10 use rustc_ast::ptr::P;
11 use rustc_ast::token::{self, Token, TokenKind};
12 use rustc_ast::tokenstream::Spacing;
13 use rustc_ast::util::classify;
14 use rustc_ast::util::literal::LitError;
15 use rustc_ast::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
16 use rustc_ast::{self as ast, AttrStyle, AttrVec, CaptureBy, ExprField, Lit, UnOp, DUMMY_NODE_ID};
17 use rustc_ast::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, MacCall, Param, Ty, TyKind};
18 use rustc_ast::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits};
19 use rustc_ast_pretty::pprust;
20 use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, PResult};
21 use rustc_session::lint::builtin::BREAK_WITH_LABEL_AND_LOOP;
22 use rustc_session::lint::BuiltinLintDiagnostics;
23 use rustc_span::source_map::{self, Span, Spanned};
24 use rustc_span::symbol::{kw, sym, Ident, Symbol};
25 use rustc_span::{BytePos, Pos};
28 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
29 /// dropped into the token stream, which happens while parsing the result of
30 /// macro expansion). Placement of these is not as complex as I feared it would
31 /// be. The important thing is to make sure that lookahead doesn't balk at
32 /// `token::Interpolated` tokens.
33 macro_rules! maybe_whole_expr {
35 if let token::Interpolated(nt) = &$p.token.kind {
37 token::NtExpr(e) | token::NtLiteral(e) => {
42 token::NtPath(path) => {
43 let path = path.clone();
47 ExprKind::Path(None, path),
51 token::NtBlock(block) => {
52 let block = block.clone();
56 ExprKind::Block(block, None),
67 pub(super) enum LhsExpr {
69 AttributesParsed(AttrWrapper),
70 AlreadyParsed(P<Expr>),
73 impl From<Option<AttrWrapper>> for LhsExpr {
74 /// Converts `Some(attrs)` into `LhsExpr::AttributesParsed(attrs)`
75 /// and `None` into `LhsExpr::NotYetParsed`.
77 /// This conversion does not allocate.
78 fn from(o: Option<AttrWrapper>) -> Self {
79 if let Some(attrs) = o { LhsExpr::AttributesParsed(attrs) } else { LhsExpr::NotYetParsed }
83 impl From<P<Expr>> for LhsExpr {
84 /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed(expr)`.
86 /// This conversion does not allocate.
87 fn from(expr: P<Expr>) -> Self {
88 LhsExpr::AlreadyParsed(expr)
93 /// Parses an expression.
95 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
96 self.current_closure.take();
98 self.parse_expr_res(Restrictions::empty(), None)
101 /// Parses an expression, forcing tokens to be collected
102 pub fn parse_expr_force_collect(&mut self) -> PResult<'a, P<Expr>> {
103 self.collect_tokens_no_attrs(|this| this.parse_expr())
106 pub fn parse_anon_const_expr(&mut self) -> PResult<'a, AnonConst> {
107 self.parse_expr().map(|value| AnonConst { id: DUMMY_NODE_ID, value })
110 fn parse_expr_catch_underscore(&mut self) -> PResult<'a, P<Expr>> {
111 match self.parse_expr() {
112 Ok(expr) => Ok(expr),
113 Err(mut err) => match self.token.ident() {
114 Some((Ident { name: kw::Underscore, .. }, false))
115 if self.look_ahead(1, |t| t == &token::Comma) =>
117 // Special-case handling of `foo(_, _, _)`
120 Ok(self.mk_expr(self.prev_token.span, ExprKind::Err, AttrVec::new()))
127 /// Parses a sequence of expressions delimited by parentheses.
128 fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
129 self.parse_paren_comma_seq(|p| p.parse_expr_catch_underscore()).map(|(r, _)| r)
132 /// Parses an expression, subject to the given restrictions.
134 pub(super) fn parse_expr_res(
137 already_parsed_attrs: Option<AttrWrapper>,
138 ) -> PResult<'a, P<Expr>> {
139 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
142 /// Parses an associative expression.
144 /// This parses an expression accounting for associativity and precedence of the operators in
149 already_parsed_attrs: Option<AttrWrapper>,
150 ) -> PResult<'a, P<Expr>> {
151 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
154 /// Parses an associative expression with operators of at least `min_prec` precedence.
155 pub(super) fn parse_assoc_expr_with(
159 ) -> PResult<'a, P<Expr>> {
160 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
163 let attrs = match lhs {
164 LhsExpr::AttributesParsed(attrs) => Some(attrs),
167 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind) {
168 return self.parse_prefix_range_expr(attrs);
170 self.parse_prefix_expr(attrs)?
173 let last_type_ascription_set = self.last_type_ascription.is_some();
175 if !self.should_continue_as_assoc_expr(&lhs) {
176 self.last_type_ascription = None;
180 self.expected_tokens.push(TokenType::Operator);
181 while let Some(op) = self.check_assoc_op() {
182 // Adjust the span for interpolated LHS to point to the `$lhs` token
183 // and not to what it refers to.
184 let lhs_span = match self.prev_token.kind {
185 TokenKind::Interpolated(..) => self.prev_token.span,
189 let cur_op_span = self.token.span;
190 let restrictions = if op.node.is_assign_like() {
191 self.restrictions & Restrictions::NO_STRUCT_LITERAL
195 let prec = op.node.precedence();
199 // Check for deprecated `...` syntax
200 if self.token == token::DotDotDot && op.node == AssocOp::DotDotEq {
201 self.err_dotdotdot_syntax(self.token.span);
204 if self.token == token::LArrow {
205 self.err_larrow_operator(self.token.span);
209 if op.node.is_comparison() {
210 if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
215 // Look for JS' `===` and `!==` and recover
216 if (op.node == AssocOp::Equal || op.node == AssocOp::NotEqual)
217 && self.token.kind == token::Eq
218 && self.prev_token.span.hi() == self.token.span.lo()
220 let sp = op.span.to(self.token.span);
221 let sugg = match op.node {
222 AssocOp::Equal => "==",
223 AssocOp::NotEqual => "!=",
226 self.struct_span_err(sp, &format!("invalid comparison operator `{sugg}=`"))
227 .span_suggestion_short(
229 &format!("`{s}=` is not a valid comparison operator, use `{s}`", s = sugg),
231 Applicability::MachineApplicable,
237 // Look for PHP's `<>` and recover
238 if op.node == AssocOp::Less
239 && self.token.kind == token::Gt
240 && self.prev_token.span.hi() == self.token.span.lo()
242 let sp = op.span.to(self.token.span);
243 self.struct_span_err(sp, "invalid comparison operator `<>`")
244 .span_suggestion_short(
246 "`<>` is not a valid comparison operator, use `!=`",
248 Applicability::MachineApplicable,
254 // Look for C++'s `<=>` and recover
255 if op.node == AssocOp::LessEqual
256 && self.token.kind == token::Gt
257 && self.prev_token.span.hi() == self.token.span.lo()
259 let sp = op.span.to(self.token.span);
260 self.struct_span_err(sp, "invalid comparison operator `<=>`")
263 "`<=>` is not a valid comparison operator, use `std::cmp::Ordering`",
271 if op == AssocOp::As {
272 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
274 } else if op == AssocOp::Colon {
275 lhs = self.parse_assoc_op_ascribe(lhs, lhs_span)?;
277 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
278 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
279 // generalise it to the Fixity::None code.
280 lhs = self.parse_range_expr(prec, lhs, op, cur_op_span)?;
284 let fixity = op.fixity();
285 let prec_adjustment = match fixity {
288 // We currently have no non-associative operators that are not handled above by
289 // the special cases. The code is here only for future convenience.
292 let rhs = self.with_res(restrictions - Restrictions::STMT_EXPR, |this| {
293 this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
296 let span = self.mk_expr_sp(&lhs, lhs_span, rhs.span);
309 | AssocOp::ShiftRight
315 | AssocOp::GreaterEqual => {
316 let ast_op = op.to_ast_binop().unwrap();
317 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
318 self.mk_expr(span, binary, AttrVec::new())
321 self.mk_expr(span, ExprKind::Assign(lhs, rhs, cur_op_span), AttrVec::new())
323 AssocOp::AssignOp(k) => {
325 token::Plus => BinOpKind::Add,
326 token::Minus => BinOpKind::Sub,
327 token::Star => BinOpKind::Mul,
328 token::Slash => BinOpKind::Div,
329 token::Percent => BinOpKind::Rem,
330 token::Caret => BinOpKind::BitXor,
331 token::And => BinOpKind::BitAnd,
332 token::Or => BinOpKind::BitOr,
333 token::Shl => BinOpKind::Shl,
334 token::Shr => BinOpKind::Shr,
336 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
337 self.mk_expr(span, aopexpr, AttrVec::new())
339 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
340 self.span_bug(span, "AssocOp should have been handled by special case")
344 if let Fixity::None = fixity {
348 if last_type_ascription_set {
349 self.last_type_ascription = None;
354 fn should_continue_as_assoc_expr(&mut self, lhs: &Expr) -> bool {
355 match (self.expr_is_complete(lhs), AssocOp::from_token(&self.token)) {
356 // Semi-statement forms are odd:
357 // See https://github.com/rust-lang/rust/issues/29071
358 (true, None) => false,
359 (false, _) => true, // Continue parsing the expression.
360 // An exhaustive check is done in the following block, but these are checked first
361 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
362 // want to keep their span info to improve diagnostics in these cases in a later stage.
363 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
364 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
365 (true, Some(AssocOp::Add)) // `{ 42 } + 42
366 // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
367 // `if x { a } else { b } && if y { c } else { d }`
368 if !self.look_ahead(1, |t| t.is_used_keyword()) => {
369 // These cases are ambiguous and can't be identified in the parser alone.
370 let sp = self.sess.source_map().start_point(self.token.span);
371 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
374 (true, Some(AssocOp::LAnd)) |
375 (true, Some(AssocOp::LOr)) |
376 (true, Some(AssocOp::BitOr)) => {
377 // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }`. Separated from the
378 // above due to #74233.
379 // These cases are ambiguous and can't be identified in the parser alone.
381 // Bitwise AND is left out because guessing intent is hard. We can make
382 // suggestions based on the assumption that double-refs are rarely intentional,
383 // and closures are distinct enough that they don't get mixed up with their
385 let sp = self.sess.source_map().start_point(self.token.span);
386 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
389 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => false,
391 self.error_found_expr_would_be_stmt(lhs);
397 /// We've found an expression that would be parsed as a statement,
398 /// but the next token implies this should be parsed as an expression.
399 /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
400 fn error_found_expr_would_be_stmt(&self, lhs: &Expr) {
401 let mut err = self.struct_span_err(
403 &format!("expected expression, found `{}`", pprust::token_to_string(&self.token),),
405 err.span_label(self.token.span, "expected expression");
406 self.sess.expr_parentheses_needed(&mut err, lhs.span);
410 /// Possibly translate the current token to an associative operator.
411 /// The method does not advance the current token.
413 /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
414 fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
415 let (op, span) = match (AssocOp::from_token(&self.token), self.token.ident()) {
416 // When parsing const expressions, stop parsing when encountering `>`.
421 | AssocOp::GreaterEqual
422 | AssocOp::AssignOp(token::BinOpToken::Shr),
425 ) if self.restrictions.contains(Restrictions::CONST_EXPR) => {
428 (Some(op), _) => (op, self.token.span),
429 (None, Some((Ident { name: sym::and, span }, false))) => {
430 self.error_bad_logical_op("and", "&&", "conjunction");
431 (AssocOp::LAnd, span)
433 (None, Some((Ident { name: sym::or, span }, false))) => {
434 self.error_bad_logical_op("or", "||", "disjunction");
439 Some(source_map::respan(span, op))
442 /// Error on `and` and `or` suggesting `&&` and `||` respectively.
443 fn error_bad_logical_op(&self, bad: &str, good: &str, english: &str) {
444 self.struct_span_err(self.token.span, &format!("`{bad}` is not a logical operator"))
445 .span_suggestion_short(
447 &format!("use `{good}` to perform logical {english}"),
449 Applicability::MachineApplicable,
451 .note("unlike in e.g., python and PHP, `&&` and `||` are used for logical operators")
455 /// Checks if this expression is a successfully parsed statement.
456 fn expr_is_complete(&self, e: &Expr) -> bool {
457 self.restrictions.contains(Restrictions::STMT_EXPR)
458 && !classify::expr_requires_semi_to_be_stmt(e)
461 /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
462 /// The other two variants are handled in `parse_prefix_range_expr` below.
469 ) -> PResult<'a, P<Expr>> {
470 let rhs = if self.is_at_start_of_range_notation_rhs() {
471 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
475 let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
476 let span = self.mk_expr_sp(&lhs, lhs.span, rhs_span);
478 if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
479 let range = self.mk_range(Some(lhs), rhs, limits);
480 Ok(self.mk_expr(span, range, AttrVec::new()))
483 fn is_at_start_of_range_notation_rhs(&self) -> bool {
484 if self.token.can_begin_expr() {
485 // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
486 if self.token == token::OpenDelim(token::Brace) {
487 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
495 /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
496 fn parse_prefix_range_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
497 // Check for deprecated `...` syntax.
498 if self.token == token::DotDotDot {
499 self.err_dotdotdot_syntax(self.token.span);
503 [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind),
504 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
508 let limits = match self.token.kind {
509 token::DotDot => RangeLimits::HalfOpen,
510 _ => RangeLimits::Closed,
512 let op = AssocOp::from_token(&self.token);
513 // FIXME: `parse_prefix_range_expr` is called when the current
514 // token is `DotDot`, `DotDotDot`, or `DotDotEq`. If we haven't already
515 // parsed attributes, then trying to parse them here will always fail.
516 // We should figure out how we want attributes on range expressions to work.
517 let attrs = self.parse_or_use_outer_attributes(attrs)?;
518 self.collect_tokens_for_expr(attrs, |this, attrs| {
519 let lo = this.token.span;
521 let (span, opt_end) = if this.is_at_start_of_range_notation_rhs() {
522 // RHS must be parsed with more associativity than the dots.
523 this.parse_assoc_expr_with(op.unwrap().precedence() + 1, LhsExpr::NotYetParsed)
524 .map(|x| (lo.to(x.span), Some(x)))?
528 let range = this.mk_range(None, opt_end, limits);
529 Ok(this.mk_expr(span, range, attrs.into()))
533 /// Parses a prefix-unary-operator expr.
534 fn parse_prefix_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
535 let attrs = self.parse_or_use_outer_attributes(attrs)?;
536 let lo = self.token.span;
538 macro_rules! make_it {
539 ($this:ident, $attrs:expr, |this, _| $body:expr) => {
540 $this.collect_tokens_for_expr($attrs, |$this, attrs| {
541 let (hi, ex) = $body?;
542 Ok($this.mk_expr(lo.to(hi), ex, attrs.into()))
549 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
550 match this.token.uninterpolate().kind {
551 token::Not => make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Not)), // `!expr`
552 token::Tilde => make_it!(this, attrs, |this, _| this.recover_tilde_expr(lo)), // `~expr`
553 token::BinOp(token::Minus) => {
554 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Neg))
556 token::BinOp(token::Star) => {
557 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Deref))
559 token::BinOp(token::And) | token::AndAnd => {
560 make_it!(this, attrs, |this, _| this.parse_borrow_expr(lo))
562 token::BinOp(token::Plus) if this.look_ahead(1, |tok| tok.is_numeric_lit()) => {
563 let mut err = this.struct_span_err(lo, "leading `+` is not supported");
564 err.span_label(lo, "unexpected `+`");
566 // a block on the LHS might have been intended to be an expression instead
567 if let Some(sp) = this.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
568 this.sess.expr_parentheses_needed(&mut err, *sp);
570 err.span_suggestion_verbose(
572 "try removing the `+`",
574 Applicability::MachineApplicable,
580 this.parse_prefix_expr(None)
582 token::Ident(..) if this.token.is_keyword(kw::Box) => {
583 make_it!(this, attrs, |this, _| this.parse_box_expr(lo))
585 token::Ident(..) if this.is_mistaken_not_ident_negation() => {
586 make_it!(this, attrs, |this, _| this.recover_not_expr(lo))
588 _ => return this.parse_dot_or_call_expr(Some(attrs)),
592 fn parse_prefix_expr_common(&mut self, lo: Span) -> PResult<'a, (Span, P<Expr>)> {
594 let expr = self.parse_prefix_expr(None);
595 let (span, expr) = self.interpolated_or_expr_span(expr)?;
596 Ok((lo.to(span), expr))
599 fn parse_unary_expr(&mut self, lo: Span, op: UnOp) -> PResult<'a, (Span, ExprKind)> {
600 let (span, expr) = self.parse_prefix_expr_common(lo)?;
601 Ok((span, self.mk_unary(op, expr)))
604 // Recover on `!` suggesting for bitwise negation instead.
605 fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
606 self.struct_span_err(lo, "`~` cannot be used as a unary operator")
607 .span_suggestion_short(
609 "use `!` to perform bitwise not",
611 Applicability::MachineApplicable,
615 self.parse_unary_expr(lo, UnOp::Not)
618 /// Parse `box expr`.
619 fn parse_box_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
620 let (span, expr) = self.parse_prefix_expr_common(lo)?;
621 self.sess.gated_spans.gate(sym::box_syntax, span);
622 Ok((span, ExprKind::Box(expr)))
625 fn is_mistaken_not_ident_negation(&self) -> bool {
626 let token_cannot_continue_expr = |t: &Token| match t.uninterpolate().kind {
627 // These tokens can start an expression after `!`, but
628 // can't continue an expression after an ident
629 token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
630 token::Literal(..) | token::Pound => true,
631 _ => t.is_whole_expr(),
633 self.token.is_ident_named(sym::not) && self.look_ahead(1, token_cannot_continue_expr)
636 /// Recover on `not expr` in favor of `!expr`.
637 fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
639 let not_token = self.look_ahead(1, |t| t.clone());
640 self.struct_span_err(
642 &format!("unexpected {} after identifier", super::token_descr(¬_token)),
644 .span_suggestion_short(
645 // Span the `not` plus trailing whitespace to avoid
646 // trailing whitespace after the `!` in our suggestion
647 self.sess.source_map().span_until_non_whitespace(lo.to(not_token.span)),
648 "use `!` to perform logical negation",
650 Applicability::MachineApplicable,
655 self.parse_unary_expr(lo, UnOp::Not)
658 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
659 fn interpolated_or_expr_span(
661 expr: PResult<'a, P<Expr>>,
662 ) -> PResult<'a, (Span, P<Expr>)> {
665 match self.prev_token.kind {
666 TokenKind::Interpolated(..) => self.prev_token.span,
674 fn parse_assoc_op_cast(
678 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
679 ) -> PResult<'a, P<Expr>> {
680 let mk_expr = |this: &mut Self, lhs: P<Expr>, rhs: P<Ty>| {
682 this.mk_expr_sp(&lhs, lhs_span, rhs.span),
688 // Save the state of the parser before parsing type normally, in case there is a
689 // LessThan comparison after this cast.
690 let parser_snapshot_before_type = self.clone();
691 let cast_expr = match self.parse_as_cast_ty() {
692 Ok(rhs) => mk_expr(self, lhs, rhs),
694 // Rewind to before attempting to parse the type with generics, to recover
695 // from situations like `x as usize < y` in which we first tried to parse
696 // `usize < y` as a type with generic arguments.
697 let parser_snapshot_after_type = mem::replace(self, parser_snapshot_before_type);
699 // Check for typo of `'a: loop { break 'a }` with a missing `'`.
700 match (&lhs.kind, &self.token.kind) {
703 ExprKind::Path(None, ast::Path { segments, .. }),
704 TokenKind::Ident(kw::For | kw::Loop | kw::While, false),
705 ) if segments.len() == 1 => {
706 let snapshot = self.clone();
708 ident: Ident::from_str_and_span(
709 &format!("'{}", segments[0].ident),
710 segments[0].ident.span,
713 match self.parse_labeled_expr(label, AttrVec::new(), false) {
716 self.struct_span_err(label.ident.span, "malformed loop label")
719 "use the correct loop label format",
720 label.ident.to_string(),
721 Applicability::MachineApplicable,
735 match self.parse_path(PathStyle::Expr) {
737 let (op_noun, op_verb) = match self.token.kind {
738 token::Lt => ("comparison", "comparing"),
739 token::BinOp(token::Shl) => ("shift", "shifting"),
741 // We can end up here even without `<` being the next token, for
742 // example because `parse_ty_no_plus` returns `Err` on keywords,
743 // but `parse_path` returns `Ok` on them due to error recovery.
744 // Return original error and parser state.
745 *self = parser_snapshot_after_type;
746 return Err(type_err);
750 // Successfully parsed the type path leaving a `<` yet to parse.
753 // Report non-fatal diagnostics, keep `x as usize` as an expression
754 // in AST and continue parsing.
756 "`<` is interpreted as a start of generic arguments for `{}`, not a {}",
757 pprust::path_to_string(&path),
760 let span_after_type = parser_snapshot_after_type.token.span;
762 mk_expr(self, lhs, self.mk_ty(path.span, TyKind::Path(None, path)));
764 self.struct_span_err(self.token.span, &msg)
766 self.look_ahead(1, |t| t.span).to(span_after_type),
767 "interpreted as generic arguments",
769 .span_label(self.token.span, format!("not interpreted as {op_noun}"))
770 .multipart_suggestion(
771 &format!("try {op_verb} the cast value"),
773 (expr.span.shrink_to_lo(), "(".to_string()),
774 (expr.span.shrink_to_hi(), ")".to_string()),
776 Applicability::MachineApplicable,
783 // Couldn't parse as a path, return original error and parser state.
785 *self = parser_snapshot_after_type;
786 return Err(type_err);
792 self.parse_and_disallow_postfix_after_cast(cast_expr)
795 /// Parses a postfix operators such as `.`, `?`, or index (`[]`) after a cast,
796 /// then emits an error and returns the newly parsed tree.
797 /// The resulting parse tree for `&x as T[0]` has a precedence of `((&x) as T)[0]`.
798 fn parse_and_disallow_postfix_after_cast(
801 ) -> PResult<'a, P<Expr>> {
802 // Save the memory location of expr before parsing any following postfix operators.
803 // This will be compared with the memory location of the output expression.
804 // If they different we can assume we parsed another expression because the existing expression is not reallocated.
805 let addr_before = &*cast_expr as *const _ as usize;
806 let span = cast_expr.span;
807 let with_postfix = self.parse_dot_or_call_expr_with_(cast_expr, span)?;
808 let changed = addr_before != &*with_postfix as *const _ as usize;
810 // Check if an illegal postfix operator has been added after the cast.
811 // If the resulting expression is not a cast, or has a different memory location, it is an illegal postfix operator.
812 if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) || changed {
814 "casts cannot be followed by {}",
815 match with_postfix.kind {
816 ExprKind::Index(_, _) => "indexing",
817 ExprKind::Try(_) => "`?`",
818 ExprKind::Field(_, _) => "a field access",
819 ExprKind::MethodCall(_, _, _) => "a method call",
820 ExprKind::Call(_, _) => "a function call",
821 ExprKind::Await(_) => "`.await`",
822 ExprKind::Err => return Ok(with_postfix),
823 _ => unreachable!("parse_dot_or_call_expr_with_ shouldn't produce this"),
826 let mut err = self.struct_span_err(span, &msg);
827 // If type ascription is "likely an error", the user will already be getting a useful
828 // help message, and doesn't need a second.
829 if self.last_type_ascription.map_or(false, |last_ascription| last_ascription.1) {
830 self.maybe_annotate_with_ascription(&mut err, false);
832 let suggestions = vec![
833 (span.shrink_to_lo(), "(".to_string()),
834 (span.shrink_to_hi(), ")".to_string()),
836 err.multipart_suggestion(
837 "try surrounding the expression in parentheses",
839 Applicability::MachineApplicable,
847 fn parse_assoc_op_ascribe(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
848 let maybe_path = self.could_ascription_be_path(&lhs.kind);
849 self.last_type_ascription = Some((self.prev_token.span, maybe_path));
850 let lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
851 self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
855 /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
856 fn parse_borrow_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
858 let has_lifetime = self.token.is_lifetime() && self.look_ahead(1, |t| t != &token::Colon);
859 let lifetime = has_lifetime.then(|| self.expect_lifetime()); // For recovery, see below.
860 let (borrow_kind, mutbl) = self.parse_borrow_modifiers(lo);
861 let expr = self.parse_prefix_expr(None);
862 let (hi, expr) = self.interpolated_or_expr_span(expr)?;
863 let span = lo.to(hi);
864 if let Some(lt) = lifetime {
865 self.error_remove_borrow_lifetime(span, lt.ident.span);
867 Ok((span, ExprKind::AddrOf(borrow_kind, mutbl, expr)))
870 fn error_remove_borrow_lifetime(&self, span: Span, lt_span: Span) {
871 self.struct_span_err(span, "borrow expressions cannot be annotated with lifetimes")
872 .span_label(lt_span, "annotated with lifetime here")
875 "remove the lifetime annotation",
877 Applicability::MachineApplicable,
882 /// Parse `mut?` or `raw [ const | mut ]`.
883 fn parse_borrow_modifiers(&mut self, lo: Span) -> (ast::BorrowKind, ast::Mutability) {
884 if self.check_keyword(kw::Raw) && self.look_ahead(1, Token::is_mutability) {
885 // `raw [ const | mut ]`.
886 let found_raw = self.eat_keyword(kw::Raw);
888 let mutability = self.parse_const_or_mut().unwrap();
889 self.sess.gated_spans.gate(sym::raw_ref_op, lo.to(self.prev_token.span));
890 (ast::BorrowKind::Raw, mutability)
893 (ast::BorrowKind::Ref, self.parse_mutability())
897 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
898 fn parse_dot_or_call_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
899 let attrs = self.parse_or_use_outer_attributes(attrs)?;
900 self.collect_tokens_for_expr(attrs, |this, attrs| {
901 let base = this.parse_bottom_expr();
902 let (span, base) = this.interpolated_or_expr_span(base)?;
903 this.parse_dot_or_call_expr_with(base, span, attrs)
907 pub(super) fn parse_dot_or_call_expr_with(
911 mut attrs: Vec<ast::Attribute>,
912 ) -> PResult<'a, P<Expr>> {
913 // Stitch the list of outer attributes onto the return value.
914 // A little bit ugly, but the best way given the current code
916 self.parse_dot_or_call_expr_with_(e0, lo).map(|expr| {
917 expr.map(|mut expr| {
918 attrs.extend::<Vec<_>>(expr.attrs.into());
919 expr.attrs = attrs.into();
925 fn parse_dot_or_call_expr_with_(&mut self, mut e: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
927 if self.eat(&token::Question) {
929 e = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Try(e), AttrVec::new());
932 if self.eat(&token::Dot) {
934 e = self.parse_dot_suffix_expr(lo, e)?;
937 if self.expr_is_complete(&e) {
940 e = match self.token.kind {
941 token::OpenDelim(token::Paren) => self.parse_fn_call_expr(lo, e),
942 token::OpenDelim(token::Bracket) => self.parse_index_expr(lo, e)?,
948 fn look_ahead_type_ascription_as_field(&mut self) -> bool {
949 self.look_ahead(1, |t| t.is_ident())
950 && self.look_ahead(2, |t| t == &token::Colon)
951 && self.look_ahead(3, |t| t.can_begin_expr())
954 fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
955 match self.token.uninterpolate().kind {
956 token::Ident(..) => self.parse_dot_suffix(base, lo),
957 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
958 Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix, None))
960 token::Literal(token::Lit { kind: token::Float, symbol, suffix }) => {
961 Ok(self.parse_tuple_field_access_expr_float(lo, base, symbol, suffix))
964 self.error_unexpected_after_dot();
970 fn error_unexpected_after_dot(&self) {
971 // FIXME Could factor this out into non_fatal_unexpected or something.
972 let actual = pprust::token_to_string(&self.token);
973 self.struct_span_err(self.token.span, &format!("unexpected token: `{actual}`")).emit();
976 // We need an identifier or integer, but the next token is a float.
977 // Break the float into components to extract the identifier or integer.
978 // FIXME: With current `TokenCursor` it's hard to break tokens into more than 2
979 // parts unless those parts are processed immediately. `TokenCursor` should either
980 // support pushing "future tokens" (would be also helpful to `break_and_eat`), or
981 // we should break everything including floats into more basic proc-macro style
982 // tokens in the lexer (probably preferable).
983 fn parse_tuple_field_access_expr_float(
988 suffix: Option<Symbol>,
991 enum FloatComponent {
995 use FloatComponent::*;
997 let float_str = float.as_str();
998 let mut components = Vec::new();
999 let mut ident_like = String::new();
1000 for c in float_str.chars() {
1001 if c == '_' || c.is_ascii_alphanumeric() {
1003 } else if matches!(c, '.' | '+' | '-') {
1004 if !ident_like.is_empty() {
1005 components.push(IdentLike(mem::take(&mut ident_like)));
1007 components.push(Punct(c));
1009 panic!("unexpected character in a float token: {:?}", c)
1012 if !ident_like.is_empty() {
1013 components.push(IdentLike(ident_like));
1016 // With proc macros the span can refer to anything, the source may be too short,
1017 // or too long, or non-ASCII. It only makes sense to break our span into components
1018 // if its underlying text is identical to our float literal.
1019 let span = self.token.span;
1020 let can_take_span_apart =
1021 || self.span_to_snippet(span).as_deref() == Ok(float_str).as_deref();
1023 match &*components {
1026 self.parse_tuple_field_access_expr(lo, base, Symbol::intern(&i), suffix, None)
1029 [IdentLike(i), Punct('.')] => {
1030 let (ident_span, dot_span) = if can_take_span_apart() {
1031 let (span, ident_len) = (span.data(), BytePos::from_usize(i.len()));
1032 let ident_span = span.with_hi(span.lo + ident_len);
1033 let dot_span = span.with_lo(span.lo + ident_len);
1034 (ident_span, dot_span)
1038 assert!(suffix.is_none());
1039 let symbol = Symbol::intern(&i);
1040 self.token = Token::new(token::Ident(symbol, false), ident_span);
1041 let next_token = (Token::new(token::Dot, dot_span), self.token_spacing);
1042 self.parse_tuple_field_access_expr(lo, base, symbol, None, Some(next_token))
1045 [IdentLike(i1), Punct('.'), IdentLike(i2)] => {
1046 let (ident1_span, dot_span, ident2_span) = if can_take_span_apart() {
1047 let (span, ident1_len) = (span.data(), BytePos::from_usize(i1.len()));
1048 let ident1_span = span.with_hi(span.lo + ident1_len);
1050 .with_lo(span.lo + ident1_len)
1051 .with_hi(span.lo + ident1_len + BytePos(1));
1052 let ident2_span = self.token.span.with_lo(span.lo + ident1_len + BytePos(1));
1053 (ident1_span, dot_span, ident2_span)
1057 let symbol1 = Symbol::intern(&i1);
1058 self.token = Token::new(token::Ident(symbol1, false), ident1_span);
1059 // This needs to be `Spacing::Alone` to prevent regressions.
1060 // See issue #76399 and PR #76285 for more details
1061 let next_token1 = (Token::new(token::Dot, dot_span), Spacing::Alone);
1063 self.parse_tuple_field_access_expr(lo, base, symbol1, None, Some(next_token1));
1064 let symbol2 = Symbol::intern(&i2);
1065 let next_token2 = Token::new(token::Ident(symbol2, false), ident2_span);
1066 self.bump_with((next_token2, self.token_spacing)); // `.`
1067 self.parse_tuple_field_access_expr(lo, base1, symbol2, suffix, None)
1069 // 1e+ | 1e- (recovered)
1070 [IdentLike(_), Punct('+' | '-')] |
1072 [IdentLike(_), Punct('+' | '-'), IdentLike(_)] |
1074 [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-')] |
1076 [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-'), IdentLike(_)] => {
1077 // See the FIXME about `TokenCursor` above.
1078 self.error_unexpected_after_dot();
1081 _ => panic!("unexpected components in a float token: {:?}", components),
1085 fn parse_tuple_field_access_expr(
1090 suffix: Option<Symbol>,
1091 next_token: Option<(Token, Spacing)>,
1094 Some(next_token) => self.bump_with(next_token),
1095 None => self.bump(),
1097 let span = self.prev_token.span;
1098 let field = ExprKind::Field(base, Ident::new(field, span));
1099 self.expect_no_suffix(span, "a tuple index", suffix);
1100 self.mk_expr(lo.to(span), field, AttrVec::new())
1103 /// Parse a function call expression, `expr(...)`.
1104 fn parse_fn_call_expr(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
1105 let snapshot = if self.token.kind == token::OpenDelim(token::Paren)
1106 && self.look_ahead_type_ascription_as_field()
1108 Some((self.clone(), fun.kind.clone()))
1112 let open_paren = self.token.span;
1114 let mut seq = self.parse_paren_expr_seq().map(|args| {
1115 self.mk_expr(lo.to(self.prev_token.span), self.mk_call(fun, args), AttrVec::new())
1118 self.maybe_recover_struct_lit_bad_delims(lo, open_paren, &mut seq, snapshot)
1122 self.recover_seq_parse_error(token::Paren, lo, seq)
1125 /// If we encounter a parser state that looks like the user has written a `struct` literal with
1126 /// parentheses instead of braces, recover the parser state and provide suggestions.
1127 #[instrument(skip(self, seq, snapshot), level = "trace")]
1128 fn maybe_recover_struct_lit_bad_delims(
1132 seq: &mut PResult<'a, P<Expr>>,
1133 snapshot: Option<(Self, ExprKind)>,
1134 ) -> Option<P<Expr>> {
1135 match (seq.as_mut(), snapshot) {
1136 (Err(err), Some((mut snapshot, ExprKind::Path(None, path)))) => {
1137 let name = pprust::path_to_string(&path);
1138 snapshot.bump(); // `(`
1139 match snapshot.parse_struct_fields(path, false, token::Paren) {
1140 Ok((fields, ..)) if snapshot.eat(&token::CloseDelim(token::Paren)) => {
1141 // We are certain we have `Enum::Foo(a: 3, b: 4)`, suggest
1142 // `Enum::Foo { a: 3, b: 4 }` or `Enum::Foo(3, 4)`.
1144 let close_paren = self.prev_token.span;
1145 let span = lo.to(self.prev_token.span);
1146 if !fields.is_empty() {
1147 let replacement_err = self.struct_span_err(
1149 "invalid `struct` delimiters or `fn` call arguments",
1151 mem::replace(err, replacement_err).cancel();
1153 err.multipart_suggestion(
1154 &format!("if `{name}` is a struct, use braces as delimiters"),
1156 (open_paren, " { ".to_string()),
1157 (close_paren, " }".to_string()),
1159 Applicability::MaybeIncorrect,
1161 err.multipart_suggestion(
1162 &format!("if `{name}` is a function, use the arguments directly"),
1165 .map(|field| (field.span.until(field.expr.span), String::new()))
1167 Applicability::MaybeIncorrect,
1173 return Some(self.mk_expr_err(span));
1186 /// Parse an indexing expression `expr[...]`.
1187 fn parse_index_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
1189 let index = self.parse_expr()?;
1190 self.expect(&token::CloseDelim(token::Bracket))?;
1191 Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_index(base, index), AttrVec::new()))
1194 /// Assuming we have just parsed `.`, continue parsing into an expression.
1195 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
1196 if self.token.uninterpolated_span().rust_2018() && self.eat_keyword(kw::Await) {
1197 return Ok(self.mk_await_expr(self_arg, lo));
1200 let fn_span_lo = self.token.span;
1201 let mut segment = self.parse_path_segment(PathStyle::Expr, None)?;
1202 self.check_trailing_angle_brackets(&segment, &[&token::OpenDelim(token::Paren)]);
1203 self.check_turbofish_missing_angle_brackets(&mut segment);
1205 if self.check(&token::OpenDelim(token::Paren)) {
1206 // Method call `expr.f()`
1207 let mut args = self.parse_paren_expr_seq()?;
1208 args.insert(0, self_arg);
1210 let fn_span = fn_span_lo.to(self.prev_token.span);
1211 let span = lo.to(self.prev_token.span);
1212 Ok(self.mk_expr(span, ExprKind::MethodCall(segment, args, fn_span), AttrVec::new()))
1214 // Field access `expr.f`
1215 if let Some(args) = segment.args {
1216 self.struct_span_err(
1218 "field expressions cannot have generic arguments",
1223 let span = lo.to(self.prev_token.span);
1224 Ok(self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), AttrVec::new()))
1228 /// At the bottom (top?) of the precedence hierarchy,
1229 /// Parses things like parenthesized exprs, macros, `return`, etc.
1231 /// N.B., this does not parse outer attributes, and is private because it only works
1232 /// correctly if called from `parse_dot_or_call_expr()`.
1233 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
1234 maybe_recover_from_interpolated_ty_qpath!(self, true);
1235 maybe_whole_expr!(self);
1237 // Outer attributes are already parsed and will be
1238 // added to the return value after the fact.
1240 // Therefore, prevent sub-parser from parsing
1241 // attributes by giving them an empty "already-parsed" list.
1242 let attrs = AttrVec::new();
1244 // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
1245 let lo = self.token.span;
1246 if let token::Literal(_) = self.token.kind {
1247 // This match arm is a special-case of the `_` match arm below and
1248 // could be removed without changing functionality, but it's faster
1249 // to have it here, especially for programs with large constants.
1250 self.parse_lit_expr(attrs)
1251 } else if self.check(&token::OpenDelim(token::Paren)) {
1252 self.parse_tuple_parens_expr(attrs)
1253 } else if self.check(&token::OpenDelim(token::Brace)) {
1254 self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs)
1255 } else if self.check(&token::BinOp(token::Or)) || self.check(&token::OrOr) {
1256 self.parse_closure_expr(attrs).map_err(|mut err| {
1257 // If the input is something like `if a { 1 } else { 2 } | if a { 3 } else { 4 }`
1258 // then suggest parens around the lhs.
1259 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
1260 self.sess.expr_parentheses_needed(&mut err, *sp);
1264 } else if self.check(&token::OpenDelim(token::Bracket)) {
1265 self.parse_array_or_repeat_expr(attrs, token::Bracket)
1266 } else if self.check_path() {
1267 self.parse_path_start_expr(attrs)
1268 } else if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
1269 self.parse_closure_expr(attrs)
1270 } else if self.eat_keyword(kw::If) {
1271 self.parse_if_expr(attrs)
1272 } else if self.check_keyword(kw::For) {
1273 if self.choose_generics_over_qpath(1) {
1274 // NOTE(Centril, eddyb): DO NOT REMOVE! Beyond providing parser recovery,
1275 // this is an insurance policy in case we allow qpaths in (tuple-)struct patterns.
1276 // When `for <Foo as Bar>::Proj in $expr $block` is wanted,
1277 // you can disambiguate in favor of a pattern with `(...)`.
1278 self.recover_quantified_closure_expr(attrs)
1280 assert!(self.eat_keyword(kw::For));
1281 self.parse_for_expr(None, self.prev_token.span, attrs)
1283 } else if self.eat_keyword(kw::While) {
1284 self.parse_while_expr(None, self.prev_token.span, attrs)
1285 } else if let Some(label) = self.eat_label() {
1286 self.parse_labeled_expr(label, attrs, true)
1287 } else if self.eat_keyword(kw::Loop) {
1288 let sp = self.prev_token.span;
1289 self.parse_loop_expr(None, self.prev_token.span, attrs).map_err(|mut err| {
1290 err.span_label(sp, "while parsing this `loop` expression");
1293 } else if self.eat_keyword(kw::Continue) {
1294 let kind = ExprKind::Continue(self.eat_label());
1295 Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
1296 } else if self.eat_keyword(kw::Match) {
1297 let match_sp = self.prev_token.span;
1298 self.parse_match_expr(attrs).map_err(|mut err| {
1299 err.span_label(match_sp, "while parsing this `match` expression");
1302 } else if self.eat_keyword(kw::Unsafe) {
1303 let sp = self.prev_token.span;
1304 self.parse_block_expr(None, lo, BlockCheckMode::Unsafe(ast::UserProvided), attrs)
1305 .map_err(|mut err| {
1306 err.span_label(sp, "while parsing this `unsafe` expression");
1309 } else if self.check_inline_const(0) {
1310 self.parse_const_block(lo.to(self.token.span), false)
1311 } else if self.is_do_catch_block() {
1312 self.recover_do_catch(attrs)
1313 } else if self.is_try_block() {
1314 self.expect_keyword(kw::Try)?;
1315 self.parse_try_block(lo, attrs)
1316 } else if self.eat_keyword(kw::Return) {
1317 self.parse_return_expr(attrs)
1318 } else if self.eat_keyword(kw::Break) {
1319 self.parse_break_expr(attrs)
1320 } else if self.eat_keyword(kw::Yield) {
1321 self.parse_yield_expr(attrs)
1322 } else if self.eat_keyword(kw::Let) {
1323 self.parse_let_expr(attrs)
1324 } else if self.eat_keyword(kw::Underscore) {
1325 Ok(self.mk_expr(self.prev_token.span, ExprKind::Underscore, attrs))
1326 } else if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
1327 // Don't complain about bare semicolons after unclosed braces
1328 // recovery in order to keep the error count down. Fixing the
1329 // delimiters will possibly also fix the bare semicolon found in
1330 // expression context. For example, silence the following error:
1332 // error: expected expression, found `;`
1336 // | ^ expected expression
1338 Ok(self.mk_expr_err(self.token.span))
1339 } else if self.token.uninterpolated_span().rust_2018() {
1340 // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
1341 if self.check_keyword(kw::Async) {
1342 if self.is_async_block() {
1343 // Check for `async {` and `async move {`.
1344 self.parse_async_block(attrs)
1346 self.parse_closure_expr(attrs)
1348 } else if self.eat_keyword(kw::Await) {
1349 self.recover_incorrect_await_syntax(lo, self.prev_token.span, attrs)
1351 self.parse_lit_expr(attrs)
1354 self.parse_lit_expr(attrs)
1358 fn parse_lit_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1359 let lo = self.token.span;
1360 match self.parse_opt_lit() {
1362 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Lit(literal), attrs);
1363 self.maybe_recover_from_bad_qpath(expr, true)
1365 None => self.try_macro_suggestion(),
1369 fn parse_tuple_parens_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1370 let lo = self.token.span;
1371 self.expect(&token::OpenDelim(token::Paren))?;
1372 let (es, trailing_comma) = match self.parse_seq_to_end(
1373 &token::CloseDelim(token::Paren),
1374 SeqSep::trailing_allowed(token::Comma),
1375 |p| p.parse_expr_catch_underscore(),
1378 Err(err) => return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err))),
1380 let kind = if es.len() == 1 && !trailing_comma {
1381 // `(e)` is parenthesized `e`.
1382 ExprKind::Paren(es.into_iter().next().unwrap())
1384 // `(e,)` is a tuple with only one field, `e`.
1387 let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
1388 self.maybe_recover_from_bad_qpath(expr, true)
1391 fn parse_array_or_repeat_expr(
1394 close_delim: token::DelimToken,
1395 ) -> PResult<'a, P<Expr>> {
1396 let lo = self.token.span;
1397 self.bump(); // `[` or other open delim
1399 let close = &token::CloseDelim(close_delim);
1400 let kind = if self.eat(close) {
1402 ExprKind::Array(Vec::new())
1405 let first_expr = self.parse_expr()?;
1406 if self.eat(&token::Semi) {
1407 // Repeating array syntax: `[ 0; 512 ]`
1408 let count = self.parse_anon_const_expr()?;
1409 self.expect(close)?;
1410 ExprKind::Repeat(first_expr, count)
1411 } else if self.eat(&token::Comma) {
1412 // Vector with two or more elements.
1413 let sep = SeqSep::trailing_allowed(token::Comma);
1414 let (remaining_exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
1415 let mut exprs = vec![first_expr];
1416 exprs.extend(remaining_exprs);
1417 ExprKind::Array(exprs)
1419 // Vector with one element
1420 self.expect(close)?;
1421 ExprKind::Array(vec![first_expr])
1424 let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
1425 self.maybe_recover_from_bad_qpath(expr, true)
1428 fn parse_path_start_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1429 let (qself, path) = if self.eat_lt() {
1430 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
1433 (None, self.parse_path(PathStyle::Expr)?)
1437 // `!`, as an operator, is prefix, so we know this isn't that.
1438 let (hi, kind) = if self.eat(&token::Not) {
1439 // MACRO INVOCATION expression
1440 if qself.is_some() {
1441 self.struct_span_err(path.span, "macros cannot use qualified paths").emit();
1445 args: self.parse_mac_args()?,
1446 prior_type_ascription: self.last_type_ascription,
1448 (self.prev_token.span, ExprKind::MacCall(mac))
1449 } else if self.check(&token::OpenDelim(token::Brace)) {
1450 if let Some(expr) = self.maybe_parse_struct_expr(qself.as_ref(), &path, &attrs) {
1451 if qself.is_some() {
1452 self.sess.gated_spans.gate(sym::more_qualified_paths, path.span);
1456 (path.span, ExprKind::Path(qself, path))
1459 (path.span, ExprKind::Path(qself, path))
1462 let expr = self.mk_expr(lo.to(hi), kind, attrs);
1463 self.maybe_recover_from_bad_qpath(expr, true)
1466 /// Parse `'label: $expr`. The label is already parsed.
1467 fn parse_labeled_expr(
1471 mut consume_colon: bool,
1472 ) -> PResult<'a, P<Expr>> {
1473 let lo = label.ident.span;
1474 let label = Some(label);
1475 let ate_colon = self.eat(&token::Colon);
1476 let expr = if self.eat_keyword(kw::While) {
1477 self.parse_while_expr(label, lo, attrs)
1478 } else if self.eat_keyword(kw::For) {
1479 self.parse_for_expr(label, lo, attrs)
1480 } else if self.eat_keyword(kw::Loop) {
1481 self.parse_loop_expr(label, lo, attrs)
1482 } else if self.check(&token::OpenDelim(token::Brace)) || self.token.is_whole_block() {
1483 self.parse_block_expr(label, lo, BlockCheckMode::Default, attrs)
1484 } else if !ate_colon && (self.check(&TokenKind::Comma) || self.check(&TokenKind::Gt)) {
1485 // We're probably inside of a `Path<'a>` that needs a turbofish
1486 let msg = "expected `while`, `for`, `loop` or `{` after a label";
1487 self.struct_span_err(self.token.span, msg).span_label(self.token.span, msg).emit();
1488 consume_colon = false;
1489 Ok(self.mk_expr_err(lo))
1491 let msg = "expected `while`, `for`, `loop` or `{` after a label";
1492 self.struct_span_err(self.token.span, msg).span_label(self.token.span, msg).emit();
1493 // Continue as an expression in an effort to recover on `'label: non_block_expr`.
1497 if !ate_colon && consume_colon {
1498 self.error_labeled_expr_must_be_followed_by_colon(lo, expr.span);
1504 fn error_labeled_expr_must_be_followed_by_colon(&self, lo: Span, span: Span) {
1505 self.struct_span_err(span, "labeled expression must be followed by `:`")
1506 .span_label(lo, "the label")
1507 .span_suggestion_short(
1509 "add `:` after the label",
1511 Applicability::MachineApplicable,
1513 .note("labels are used before loops and blocks, allowing e.g., `break 'label` to them")
1517 /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
1518 fn recover_do_catch(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1519 let lo = self.token.span;
1521 self.bump(); // `do`
1522 self.bump(); // `catch`
1524 let span_dc = lo.to(self.prev_token.span);
1525 self.struct_span_err(span_dc, "found removed `do catch` syntax")
1528 "replace with the new syntax",
1530 Applicability::MachineApplicable,
1532 .note("following RFC #2388, the new non-placeholder syntax is `try`")
1535 self.parse_try_block(lo, attrs)
1538 /// Parse an expression if the token can begin one.
1539 fn parse_expr_opt(&mut self) -> PResult<'a, Option<P<Expr>>> {
1540 Ok(if self.token.can_begin_expr() { Some(self.parse_expr()?) } else { None })
1543 /// Parse `"return" expr?`.
1544 fn parse_return_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1545 let lo = self.prev_token.span;
1546 let kind = ExprKind::Ret(self.parse_expr_opt()?);
1547 let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
1548 self.maybe_recover_from_bad_qpath(expr, true)
1551 /// Parse `"break" (('label (:? expr)?) | expr?)` with `"break"` token already eaten.
1552 /// If the label is followed immediately by a `:` token, the label and `:` are
1553 /// parsed as part of the expression (i.e. a labeled loop). The language team has
1554 /// decided in #87026 to require parentheses as a visual aid to avoid confusion if
1555 /// the break expression of an unlabeled break is a labeled loop (as in
1556 /// `break 'lbl: loop {}`); a labeled break with an unlabeled loop as its value
1557 /// expression only gets a warning for compatibility reasons; and a labeled break
1558 /// with a labeled loop does not even get a warning because there is no ambiguity.
1559 fn parse_break_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1560 let lo = self.prev_token.span;
1561 let mut label = self.eat_label();
1562 let kind = if label.is_some() && self.token == token::Colon {
1563 // The value expression can be a labeled loop, see issue #86948, e.g.:
1564 // `loop { break 'label: loop { break 'label 42; }; }`
1565 let lexpr = self.parse_labeled_expr(label.take().unwrap(), AttrVec::new(), true)?;
1566 self.struct_span_err(
1568 "parentheses are required around this expression to avoid confusion with a labeled break expression",
1570 .multipart_suggestion(
1571 "wrap the expression in parentheses",
1573 (lexpr.span.shrink_to_lo(), "(".to_string()),
1574 (lexpr.span.shrink_to_hi(), ")".to_string()),
1576 Applicability::MachineApplicable,
1580 } else if self.token != token::OpenDelim(token::Brace)
1581 || !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1583 let expr = self.parse_expr_opt()?;
1584 if let Some(ref expr) = expr {
1588 ExprKind::While(_, _, None)
1589 | ExprKind::ForLoop(_, _, _, None)
1590 | ExprKind::Loop(_, None)
1591 | ExprKind::Block(_, None)
1594 self.sess.buffer_lint_with_diagnostic(
1595 BREAK_WITH_LABEL_AND_LOOP,
1598 "this labeled break expression is easy to confuse with an unlabeled break with a labeled value expression",
1599 BuiltinLintDiagnostics::BreakWithLabelAndLoop(expr.span),
1607 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Break(label, kind), attrs);
1608 self.maybe_recover_from_bad_qpath(expr, true)
1611 /// Parse `"yield" expr?`.
1612 fn parse_yield_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1613 let lo = self.prev_token.span;
1614 let kind = ExprKind::Yield(self.parse_expr_opt()?);
1615 let span = lo.to(self.prev_token.span);
1616 self.sess.gated_spans.gate(sym::generators, span);
1617 let expr = self.mk_expr(span, kind, attrs);
1618 self.maybe_recover_from_bad_qpath(expr, true)
1621 /// Returns a string literal if the next token is a string literal.
1622 /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
1623 /// and returns `None` if the next token is not literal at all.
1624 pub fn parse_str_lit(&mut self) -> Result<ast::StrLit, Option<Lit>> {
1625 match self.parse_opt_lit() {
1626 Some(lit) => match lit.kind {
1627 ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
1629 symbol: lit.token.symbol,
1630 suffix: lit.token.suffix,
1634 _ => Err(Some(lit)),
1640 pub(super) fn parse_lit(&mut self) -> PResult<'a, Lit> {
1641 self.parse_opt_lit().ok_or_else(|| {
1642 if let token::Interpolated(inner) = &self.token.kind {
1643 let expr = match inner.as_ref() {
1644 token::NtExpr(expr) => Some(expr),
1645 token::NtLiteral(expr) => Some(expr),
1648 if let Some(expr) = expr {
1649 if matches!(expr.kind, ExprKind::Err) {
1652 .struct_span_err(self.token.span, &"invalid interpolated expression");
1653 err.downgrade_to_delayed_bug();
1658 let msg = format!("unexpected token: {}", super::token_descr(&self.token));
1659 self.struct_span_err(self.token.span, &msg)
1663 /// Matches `lit = true | false | token_lit`.
1664 /// Returns `None` if the next token is not a literal.
1665 pub(super) fn parse_opt_lit(&mut self) -> Option<Lit> {
1666 let mut recovered = None;
1667 if self.token == token::Dot {
1668 // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
1669 // dot would follow an optional literal, so we do this unconditionally.
1670 recovered = self.look_ahead(1, |next_token| {
1671 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
1674 if self.token.span.hi() == next_token.span.lo() {
1675 let s = String::from("0.") + symbol.as_str();
1676 let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
1677 return Some(Token::new(kind, self.token.span.to(next_token.span)));
1682 if let Some(token) = &recovered {
1684 self.error_float_lits_must_have_int_part(&token);
1688 let token = recovered.as_ref().unwrap_or(&self.token);
1689 match Lit::from_token(token) {
1694 Err(LitError::NotLiteral) => None,
1696 let span = token.span;
1697 let token::Literal(lit) = token.kind else {
1701 self.report_lit_error(err, lit, span);
1702 // Pack possible quotes and prefixes from the original literal into
1703 // the error literal's symbol so they can be pretty-printed faithfully.
1704 let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
1705 let symbol = Symbol::intern(&suffixless_lit.to_string());
1706 let lit = token::Lit::new(token::Err, symbol, lit.suffix);
1707 Some(Lit::from_lit_token(lit, span).unwrap_or_else(|_| unreachable!()))
1712 fn error_float_lits_must_have_int_part(&self, token: &Token) {
1713 self.struct_span_err(token.span, "float literals must have an integer part")
1716 "must have an integer part",
1717 pprust::token_to_string(token).into(),
1718 Applicability::MachineApplicable,
1723 fn report_lit_error(&self, err: LitError, lit: token::Lit, span: Span) {
1724 // Checks if `s` looks like i32 or u1234 etc.
1725 fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
1726 s.len() > 1 && s.starts_with(first_chars) && s[1..].chars().all(|c| c.is_ascii_digit())
1729 // Try to lowercase the prefix if it's a valid base prefix.
1730 fn fix_base_capitalisation(s: &str) -> Option<String> {
1731 if let Some(stripped) = s.strip_prefix('B') {
1732 Some(format!("0b{stripped}"))
1733 } else if let Some(stripped) = s.strip_prefix('O') {
1734 Some(format!("0o{stripped}"))
1735 } else if let Some(stripped) = s.strip_prefix('X') {
1736 Some(format!("0x{stripped}"))
1742 let token::Lit { kind, suffix, .. } = lit;
1744 // `NotLiteral` is not an error by itself, so we don't report
1745 // it and give the parser opportunity to try something else.
1746 LitError::NotLiteral => {}
1747 // `LexerError` *is* an error, but it was already reported
1748 // by lexer, so here we don't report it the second time.
1749 LitError::LexerError => {}
1750 LitError::InvalidSuffix => {
1751 self.expect_no_suffix(
1753 &format!("{} {} literal", kind.article(), kind.descr()),
1757 LitError::InvalidIntSuffix => {
1758 let suf = suffix.expect("suffix error with no suffix");
1759 let suf = suf.as_str();
1760 if looks_like_width_suffix(&['i', 'u'], &suf) {
1761 // If it looks like a width, try to be helpful.
1762 let msg = format!("invalid width `{}` for integer literal", &suf[1..]);
1763 self.struct_span_err(span, &msg)
1764 .help("valid widths are 8, 16, 32, 64 and 128")
1766 } else if let Some(fixed) = fix_base_capitalisation(suf) {
1767 let msg = "invalid base prefix for number literal";
1769 self.struct_span_err(span, &msg)
1770 .note("base prefixes (`0xff`, `0b1010`, `0o755`) are lowercase")
1773 "try making the prefix lowercase",
1775 Applicability::MaybeIncorrect,
1779 let msg = format!("invalid suffix `{suf}` for number literal");
1780 self.struct_span_err(span, &msg)
1781 .span_label(span, format!("invalid suffix `{suf}`"))
1782 .help("the suffix must be one of the numeric types (`u32`, `isize`, `f32`, etc.)")
1786 LitError::InvalidFloatSuffix => {
1787 let suf = suffix.expect("suffix error with no suffix");
1788 let suf = suf.as_str();
1789 if looks_like_width_suffix(&['f'], suf) {
1790 // If it looks like a width, try to be helpful.
1791 let msg = format!("invalid width `{}` for float literal", &suf[1..]);
1792 self.struct_span_err(span, &msg).help("valid widths are 32 and 64").emit();
1794 let msg = format!("invalid suffix `{suf}` for float literal");
1795 self.struct_span_err(span, &msg)
1796 .span_label(span, format!("invalid suffix `{suf}`"))
1797 .help("valid suffixes are `f32` and `f64`")
1801 LitError::NonDecimalFloat(base) => {
1802 let descr = match base {
1803 16 => "hexadecimal",
1806 _ => unreachable!(),
1808 self.struct_span_err(span, &format!("{descr} float literal is not supported"))
1809 .span_label(span, "not supported")
1812 LitError::IntTooLarge => {
1813 self.struct_span_err(span, "integer literal is too large").emit();
1818 pub(super) fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<Symbol>) {
1819 if let Some(suf) = suffix {
1820 let mut err = if kind == "a tuple index"
1821 && [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suf)
1823 // #59553: warn instead of reject out of hand to allow the fix to percolate
1824 // through the ecosystem when people fix their macros
1828 .struct_span_warn(sp, &format!("suffixes on {kind} are invalid"));
1830 "`{}` is *temporarily* accepted on tuple index fields as it was \
1831 incorrectly accepted on stable for a few releases",
1835 "on proc macros, you'll want to use `syn::Index::from` or \
1836 `proc_macro::Literal::*_unsuffixed` for code that will desugar \
1837 to tuple field access",
1840 "see issue #60210 <https://github.com/rust-lang/rust/issues/60210> \
1841 for more information",
1845 self.struct_span_err(sp, &format!("suffixes on {kind} are invalid"))
1848 err.span_label(sp, format!("invalid suffix `{suf}`"));
1853 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1854 /// Keep this in sync with `Token::can_begin_literal_maybe_minus`.
1855 pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1856 maybe_whole_expr!(self);
1858 let lo = self.token.span;
1859 let minus_present = self.eat(&token::BinOp(token::Minus));
1860 let lit = self.parse_lit()?;
1861 let expr = self.mk_expr(lit.span, ExprKind::Lit(lit), AttrVec::new());
1865 lo.to(self.prev_token.span),
1866 self.mk_unary(UnOp::Neg, expr),
1874 fn is_array_like_block(&mut self) -> bool {
1875 self.look_ahead(1, |t| matches!(t.kind, TokenKind::Ident(..) | TokenKind::Literal(_)))
1876 && self.look_ahead(2, |t| t == &token::Comma)
1877 && self.look_ahead(3, |t| t.can_begin_expr())
1880 /// Emits a suggestion if it looks like the user meant an array but
1881 /// accidentally used braces, causing the code to be interpreted as a block
1883 fn maybe_suggest_brackets_instead_of_braces(
1887 ) -> Option<P<Expr>> {
1888 let mut snapshot = self.clone();
1889 match snapshot.parse_array_or_repeat_expr(attrs, token::Brace) {
1891 let hi = snapshot.prev_token.span;
1892 self.struct_span_err(
1894 "this code is interpreted as a block expression, not an array",
1896 .multipart_suggestion(
1897 "try using [] instead of {}",
1898 vec![(lo, "[".to_owned()), (hi, "]".to_owned())],
1899 Applicability::MaybeIncorrect,
1901 .note("to define an array, one would use square brackets instead of curly braces")
1905 Some(self.mk_expr_err(arr.span))
1914 /// Parses a block or unsafe block.
1915 pub(super) fn parse_block_expr(
1917 opt_label: Option<Label>,
1919 blk_mode: BlockCheckMode,
1921 ) -> PResult<'a, P<Expr>> {
1922 if self.is_array_like_block() {
1923 if let Some(arr) = self.maybe_suggest_brackets_instead_of_braces(lo, attrs.clone()) {
1928 if let Some(label) = opt_label {
1929 self.sess.gated_spans.gate(sym::label_break_value, label.ident.span);
1932 if self.token.is_whole_block() {
1933 self.struct_span_err(self.token.span, "cannot use a `block` macro fragment here")
1934 .span_label(lo.to(self.token.span), "the `block` fragment is within this context")
1938 let (inner_attrs, blk) = self.parse_block_common(lo, blk_mode)?;
1939 attrs.extend(inner_attrs);
1940 Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs))
1943 /// Recover on an explicitly quantified closure expression, e.g., `for<'a> |x: &'a u8| *x + 1`.
1944 fn recover_quantified_closure_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1945 let lo = self.token.span;
1946 let _ = self.parse_late_bound_lifetime_defs()?;
1947 let span_for = lo.to(self.prev_token.span);
1948 let closure = self.parse_closure_expr(attrs)?;
1950 self.struct_span_err(span_for, "cannot introduce explicit parameters for a closure")
1951 .span_label(closure.span, "the parameters are attached to this closure")
1954 "remove the parameters",
1956 Applicability::MachineApplicable,
1960 Ok(self.mk_expr_err(lo.to(closure.span)))
1963 /// Parses a closure expression (e.g., `move |args| expr`).
1964 fn parse_closure_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1965 let lo = self.token.span;
1968 if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
1970 let asyncness = if self.token.uninterpolated_span().rust_2018() {
1971 self.parse_asyncness()
1976 let capture_clause = self.parse_capture_clause()?;
1977 let decl = self.parse_fn_block_decl()?;
1978 let decl_hi = self.prev_token.span;
1979 let mut body = match decl.output {
1980 FnRetTy::Default(_) => {
1981 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
1982 self.parse_expr_res(restrictions, None)?
1985 // If an explicit return type is given, require a block to appear (RFC 968).
1986 let body_lo = self.token.span;
1987 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, AttrVec::new())?
1991 if let Async::Yes { span, .. } = asyncness {
1992 // Feature-gate `async ||` closures.
1993 self.sess.gated_spans.gate(sym::async_closure, span);
1996 if self.token.kind == TokenKind::Semi && self.token_cursor.frame.delim == DelimToken::Paren
1998 // It is likely that the closure body is a block but where the
1999 // braces have been removed. We will recover and eat the next
2000 // statements later in the parsing process.
2001 body = self.mk_expr_err(body.span);
2004 let body_span = body.span;
2006 let closure = self.mk_expr(
2008 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
2012 // Disable recovery for closure body
2014 ClosureSpans { whole_closure: closure.span, closing_pipe: decl_hi, body: body_span };
2015 self.current_closure = Some(spans);
2020 /// Parses an optional `move` prefix to a closure-like construct.
2021 fn parse_capture_clause(&mut self) -> PResult<'a, CaptureBy> {
2022 if self.eat_keyword(kw::Move) {
2023 // Check for `move async` and recover
2024 if self.check_keyword(kw::Async) {
2025 let move_async_span = self.token.span.with_lo(self.prev_token.span.data().lo);
2026 Err(self.incorrect_move_async_order_found(move_async_span))
2028 Ok(CaptureBy::Value)
2035 /// Parses the `|arg, arg|` header of a closure.
2036 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
2037 let inputs = if self.eat(&token::OrOr) {
2040 self.expect(&token::BinOp(token::Or))?;
2042 .parse_seq_to_before_tokens(
2043 &[&token::BinOp(token::Or), &token::OrOr],
2044 SeqSep::trailing_allowed(token::Comma),
2045 TokenExpectType::NoExpect,
2046 |p| p.parse_fn_block_param(),
2053 self.parse_ret_ty(AllowPlus::Yes, RecoverQPath::Yes, RecoverReturnSign::Yes)?;
2055 Ok(P(FnDecl { inputs, output }))
2058 /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
2059 fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
2060 let lo = self.token.span;
2061 let attrs = self.parse_outer_attributes()?;
2062 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2063 let pat = this.parse_pat_no_top_alt(PARAM_EXPECTED)?;
2064 let ty = if this.eat(&token::Colon) {
2067 this.mk_ty(this.prev_token.span, TyKind::Infer)
2072 attrs: attrs.into(),
2075 span: lo.to(this.token.span),
2077 is_placeholder: false,
2079 TrailingToken::MaybeComma,
2084 /// Parses an `if` expression (`if` token already eaten).
2085 fn parse_if_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
2086 let lo = self.prev_token.span;
2087 let cond = self.parse_cond_expr()?;
2089 let missing_then_block_binop_span = || {
2091 ExprKind::Binary(Spanned { span: binop_span, .. }, _, ref right)
2092 if let ExprKind::Block(..) = right.kind => Some(binop_span),
2097 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
2098 // verify that the last statement is either an implicit return (no `;`) or an explicit
2099 // return. This won't catch blocks with an explicit `return`, but that would be caught by
2100 // the dead code lint.
2101 let thn = if self.token.is_keyword(kw::Else) || !cond.returns() {
2102 if let Some(binop_span) = missing_then_block_binop_span() {
2103 self.error_missing_if_then_block(lo, None, Some(binop_span)).emit();
2104 self.mk_block_err(cond.span)
2106 self.error_missing_if_cond(lo, cond.span)
2109 let attrs = self.parse_outer_attributes()?.take_for_recovery(); // For recovery.
2110 let not_block = self.token != token::OpenDelim(token::Brace);
2111 let block = self.parse_block().map_err(|err| {
2113 self.error_missing_if_then_block(lo, Some(err), missing_then_block_binop_span())
2118 self.error_on_if_block_attrs(lo, false, block.span, &attrs);
2121 let els = if self.eat_keyword(kw::Else) { Some(self.parse_else_expr()?) } else { None };
2122 Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::If(cond, thn, els), attrs))
2125 fn error_missing_if_then_block(
2128 err: Option<DiagnosticBuilder<'a, ErrorGuaranteed>>,
2129 binop_span: Option<Span>,
2130 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
2131 let msg = "this `if` expression has a condition, but no block";
2133 let mut err = if let Some(mut err) = err {
2134 err.span_label(if_span, msg);
2137 self.struct_span_err(if_span, msg)
2140 if let Some(binop_span) = binop_span {
2141 err.span_help(binop_span, "maybe you forgot the right operand of the condition?");
2147 fn error_missing_if_cond(&self, lo: Span, span: Span) -> P<ast::Block> {
2148 let sp = self.sess.source_map().next_point(lo);
2149 self.struct_span_err(sp, "missing condition for `if` expression")
2150 .span_label(sp, "expected if condition here")
2152 self.mk_block_err(span)
2155 /// Parses the condition of a `if` or `while` expression.
2156 fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
2157 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2159 if let ExprKind::Let(..) = cond.kind {
2160 // Remove the last feature gating of a `let` expression since it's stable.
2161 self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
2167 /// Parses a `let $pat = $expr` pseudo-expression.
2168 /// The `let` token has already been eaten.
2169 fn parse_let_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
2170 let lo = self.prev_token.span;
2171 let pat = self.parse_pat_allow_top_alt(
2175 CommaRecoveryMode::LikelyTuple,
2177 self.expect(&token::Eq)?;
2178 let expr = self.with_res(self.restrictions | Restrictions::NO_STRUCT_LITERAL, |this| {
2179 this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
2181 let span = lo.to(expr.span);
2182 self.sess.gated_spans.gate(sym::let_chains, span);
2183 Ok(self.mk_expr(span, ExprKind::Let(pat, expr, span), attrs))
2186 /// Parses an `else { ... }` expression (`else` token already eaten).
2187 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
2188 let ctx_span = self.prev_token.span; // `else`
2189 let attrs = self.parse_outer_attributes()?.take_for_recovery(); // For recovery.
2190 let expr = if self.eat_keyword(kw::If) {
2191 self.parse_if_expr(AttrVec::new())?
2193 let blk = self.parse_block()?;
2194 self.mk_expr(blk.span, ExprKind::Block(blk, None), AttrVec::new())
2196 self.error_on_if_block_attrs(ctx_span, true, expr.span, &attrs);
2200 fn error_on_if_block_attrs(
2205 attrs: &[ast::Attribute],
2207 let (span, last) = match attrs {
2209 [x0 @ xn] | [x0, .., xn] => (x0.span.to(xn.span), xn.span),
2211 let ctx = if is_ctx_else { "else" } else { "if" };
2212 self.struct_span_err(last, "outer attributes are not allowed on `if` and `else` branches")
2213 .span_label(branch_span, "the attributes are attached to this branch")
2214 .span_label(ctx_span, format!("the branch belongs to this `{ctx}`"))
2217 "remove the attributes",
2219 Applicability::MachineApplicable,
2224 /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
2227 opt_label: Option<Label>,
2230 ) -> PResult<'a, P<Expr>> {
2231 // Record whether we are about to parse `for (`.
2232 // This is used below for recovery in case of `for ( $stuff ) $block`
2233 // in which case we will suggest `for $stuff $block`.
2234 let begin_paren = match self.token.kind {
2235 token::OpenDelim(token::Paren) => Some(self.token.span),
2239 let pat = self.parse_pat_allow_top_alt(
2243 CommaRecoveryMode::LikelyTuple,
2245 if !self.eat_keyword(kw::In) {
2246 self.error_missing_in_for_loop();
2248 self.check_for_for_in_in_typo(self.prev_token.span);
2249 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2251 let pat = self.recover_parens_around_for_head(pat, begin_paren);
2253 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
2254 attrs.extend(iattrs);
2256 let kind = ExprKind::ForLoop(pat, expr, loop_block, opt_label);
2257 Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
2260 fn error_missing_in_for_loop(&mut self) {
2261 let (span, msg, sugg) = if self.token.is_ident_named(sym::of) {
2262 // Possibly using JS syntax (#75311).
2263 let span = self.token.span;
2265 (span, "try using `in` here instead", "in")
2267 (self.prev_token.span.between(self.token.span), "try adding `in` here", " in ")
2269 self.struct_span_err(span, "missing `in` in `for` loop")
2270 .span_suggestion_short(
2274 // Has been misleading, at least in the past (closed Issue #48492).
2275 Applicability::MaybeIncorrect,
2280 /// Parses a `while` or `while let` expression (`while` token already eaten).
2281 fn parse_while_expr(
2283 opt_label: Option<Label>,
2286 ) -> PResult<'a, P<Expr>> {
2287 let cond = self.parse_cond_expr().map_err(|mut err| {
2288 err.span_label(lo, "while parsing the condition of this `while` expression");
2291 let (iattrs, body) = self.parse_inner_attrs_and_block().map_err(|mut err| {
2292 err.span_label(lo, "while parsing the body of this `while` expression");
2293 err.span_label(cond.span, "this `while` condition successfully parsed");
2296 attrs.extend(iattrs);
2297 Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::While(cond, body, opt_label), attrs))
2300 /// Parses `loop { ... }` (`loop` token already eaten).
2303 opt_label: Option<Label>,
2306 ) -> PResult<'a, P<Expr>> {
2307 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
2308 attrs.extend(iattrs);
2309 Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::Loop(body, opt_label), attrs))
2312 crate fn eat_label(&mut self) -> Option<Label> {
2313 self.token.lifetime().map(|ident| {
2319 /// Parses a `match ... { ... }` expression (`match` token already eaten).
2320 fn parse_match_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
2321 let match_span = self.prev_token.span;
2322 let lo = self.prev_token.span;
2323 let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2324 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
2325 if self.token == token::Semi {
2326 e.span_suggestion_short(
2328 "try removing this `match`",
2330 Applicability::MaybeIncorrect, // speculative
2333 if self.maybe_recover_unexpected_block_label() {
2340 attrs.extend(self.parse_inner_attributes()?);
2342 let mut arms: Vec<Arm> = Vec::new();
2343 while self.token != token::CloseDelim(token::Brace) {
2344 match self.parse_arm() {
2345 Ok(arm) => arms.push(arm),
2347 // Recover by skipping to the end of the block.
2349 self.recover_stmt();
2350 let span = lo.to(self.token.span);
2351 if self.token == token::CloseDelim(token::Brace) {
2354 return Ok(self.mk_expr(span, ExprKind::Match(scrutinee, arms), attrs));
2358 let hi = self.token.span;
2360 Ok(self.mk_expr(lo.to(hi), ExprKind::Match(scrutinee, arms), attrs))
2363 /// Attempt to recover from match arm body with statements and no surrounding braces.
2364 fn parse_arm_body_missing_braces(
2366 first_expr: &P<Expr>,
2368 ) -> Option<P<Expr>> {
2369 if self.token.kind != token::Semi {
2372 let start_snapshot = self.clone();
2373 let semi_sp = self.token.span;
2376 vec![self.mk_stmt(first_expr.span, ast::StmtKind::Expr(first_expr.clone()))];
2377 let err = |this: &mut Parser<'_>, stmts: Vec<ast::Stmt>| {
2378 let span = stmts[0].span.to(stmts[stmts.len() - 1].span);
2379 let mut err = this.struct_span_err(span, "`match` arm body without braces");
2380 let (these, s, are) =
2381 if stmts.len() > 1 { ("these", "s", "are") } else { ("this", "", "is") };
2385 "{these} statement{s} {are} not surrounded by a body",
2391 err.span_label(arrow_span, "while parsing the `match` arm starting here");
2392 if stmts.len() > 1 {
2393 err.multipart_suggestion(
2394 &format!("surround the statement{s} with a body"),
2396 (span.shrink_to_lo(), "{ ".to_string()),
2397 (span.shrink_to_hi(), " }".to_string()),
2399 Applicability::MachineApplicable,
2402 err.span_suggestion(
2404 "use a comma to end a `match` arm expression",
2406 Applicability::MachineApplicable,
2410 this.mk_expr_err(span)
2412 // We might have either a `,` -> `;` typo, or a block without braces. We need
2413 // a more subtle parsing strategy.
2415 if self.token.kind == token::CloseDelim(token::Brace) {
2416 // We have reached the closing brace of the `match` expression.
2417 return Some(err(self, stmts));
2419 if self.token.kind == token::Comma {
2420 *self = start_snapshot;
2423 let pre_pat_snapshot = self.clone();
2424 match self.parse_pat_no_top_alt(None) {
2426 if self.token.kind == token::FatArrow {
2428 *self = pre_pat_snapshot;
2429 return Some(err(self, stmts));
2437 *self = pre_pat_snapshot;
2438 match self.parse_stmt_without_recovery(true, ForceCollect::No) {
2439 // Consume statements for as long as possible.
2444 *self = start_snapshot;
2447 // We couldn't parse either yet another statement missing it's
2448 // enclosing block nor the next arm's pattern or closing brace.
2451 *self = start_snapshot;
2459 pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
2460 fn check_let_expr(expr: &Expr) -> (bool, bool) {
2462 ExprKind::Binary(_, ref lhs, ref rhs) => {
2463 let lhs_rslt = check_let_expr(lhs);
2464 let rhs_rslt = check_let_expr(rhs);
2465 (lhs_rslt.0 || rhs_rslt.0, false)
2467 ExprKind::Let(..) => (true, true),
2471 let attrs = self.parse_outer_attributes()?;
2472 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2473 let lo = this.token.span;
2474 let pat = this.parse_pat_allow_top_alt(
2478 CommaRecoveryMode::EitherTupleOrPipe,
2480 let guard = if this.eat_keyword(kw::If) {
2481 let if_span = this.prev_token.span;
2482 let cond = this.parse_expr()?;
2483 let (has_let_expr, does_not_have_bin_op) = check_let_expr(&cond);
2485 if does_not_have_bin_op {
2486 // Remove the last feature gating of a `let` expression since it's stable.
2487 this.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
2489 let span = if_span.to(cond.span);
2490 this.sess.gated_spans.gate(sym::if_let_guard, span);
2496 let arrow_span = this.token.span;
2497 if let Err(mut err) = this.expect(&token::FatArrow) {
2498 // We might have a `=>` -> `=` or `->` typo (issue #89396).
2499 if TokenKind::FatArrow
2501 .map_or(false, |similar_tokens| similar_tokens.contains(&this.token.kind))
2503 err.span_suggestion(
2505 "try using a fat arrow here",
2507 Applicability::MaybeIncorrect,
2515 let arm_start_span = this.token.span;
2517 let expr = this.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
2518 err.span_label(arrow_span, "while parsing the `match` arm starting here");
2522 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
2523 && this.token != token::CloseDelim(token::Brace);
2525 let hi = this.prev_token.span;
2528 let sm = this.sess.source_map();
2529 if let Some(body) = this.parse_arm_body_missing_braces(&expr, arrow_span) {
2530 let span = body.span;
2533 attrs: attrs.into(),
2539 is_placeholder: false,
2541 TrailingToken::None,
2544 this.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)]).map_err(
2546 match (sm.span_to_lines(expr.span), sm.span_to_lines(arm_start_span)) {
2547 (Ok(ref expr_lines), Ok(ref arm_start_lines))
2548 if arm_start_lines.lines[0].end_col
2549 == expr_lines.lines[0].end_col
2550 && expr_lines.lines.len() == 2
2551 && this.token == token::FatArrow =>
2553 // We check whether there's any trailing code in the parse span,
2554 // if there isn't, we very likely have the following:
2557 // | -- - missing comma
2561 // | - ^^ self.token.span
2563 // | parsed until here as `"y" & X`
2564 err.span_suggestion_short(
2565 arm_start_span.shrink_to_hi(),
2566 "missing a comma here to end this `match` arm",
2568 Applicability::MachineApplicable,
2574 "while parsing the `match` arm starting here",
2582 this.eat(&token::Comma);
2587 attrs: attrs.into(),
2593 is_placeholder: false,
2595 TrailingToken::None,
2600 /// Parses a `try {...}` expression (`try` token already eaten).
2601 fn parse_try_block(&mut self, span_lo: Span, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
2602 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
2603 attrs.extend(iattrs);
2604 if self.eat_keyword(kw::Catch) {
2605 let mut error = self.struct_span_err(
2606 self.prev_token.span,
2607 "keyword `catch` cannot follow a `try` block",
2609 error.help("try using `match` on the result of the `try` block instead");
2613 let span = span_lo.to(body.span);
2614 self.sess.gated_spans.gate(sym::try_blocks, span);
2615 Ok(self.mk_expr(span, ExprKind::TryBlock(body), attrs))
2619 fn is_do_catch_block(&self) -> bool {
2620 self.token.is_keyword(kw::Do)
2621 && self.is_keyword_ahead(1, &[kw::Catch])
2622 && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
2623 && !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
2626 fn is_try_block(&self) -> bool {
2627 self.token.is_keyword(kw::Try)
2628 && self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
2629 && self.token.uninterpolated_span().rust_2018()
2632 /// Parses an `async move? {...}` expression.
2633 fn parse_async_block(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
2634 let lo = self.token.span;
2635 self.expect_keyword(kw::Async)?;
2636 let capture_clause = self.parse_capture_clause()?;
2637 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
2638 attrs.extend(iattrs);
2639 let kind = ExprKind::Async(capture_clause, DUMMY_NODE_ID, body);
2640 Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
2643 fn is_async_block(&self) -> bool {
2644 self.token.is_keyword(kw::Async)
2647 self.is_keyword_ahead(1, &[kw::Move])
2648 && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
2651 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
2655 fn is_certainly_not_a_block(&self) -> bool {
2656 self.look_ahead(1, |t| t.is_ident())
2658 // `{ ident, ` cannot start a block.
2659 self.look_ahead(2, |t| t == &token::Comma)
2660 || self.look_ahead(2, |t| t == &token::Colon)
2662 // `{ ident: token, ` cannot start a block.
2663 self.look_ahead(4, |t| t == &token::Comma) ||
2664 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
2665 self.look_ahead(3, |t| !t.can_begin_type())
2670 fn maybe_parse_struct_expr(
2672 qself: Option<&ast::QSelf>,
2675 ) -> Option<PResult<'a, P<Expr>>> {
2676 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
2677 if struct_allowed || self.is_certainly_not_a_block() {
2678 if let Err(err) = self.expect(&token::OpenDelim(token::Brace)) {
2679 return Some(Err(err));
2681 let expr = self.parse_struct_expr(qself.cloned(), path.clone(), attrs.clone(), true);
2682 if let (Ok(expr), false) = (&expr, struct_allowed) {
2683 // This is a struct literal, but we don't can't accept them here.
2684 self.error_struct_lit_not_allowed_here(path.span, expr.span);
2691 fn error_struct_lit_not_allowed_here(&self, lo: Span, sp: Span) {
2692 self.struct_span_err(sp, "struct literals are not allowed here")
2693 .multipart_suggestion(
2694 "surround the struct literal with parentheses",
2695 vec![(lo.shrink_to_lo(), "(".to_string()), (sp.shrink_to_hi(), ")".to_string())],
2696 Applicability::MachineApplicable,
2701 pub(super) fn parse_struct_fields(
2705 close_delim: token::DelimToken,
2706 ) -> PResult<'a, (Vec<ExprField>, ast::StructRest, bool)> {
2707 let mut fields = Vec::new();
2708 let mut base = ast::StructRest::None;
2709 let mut recover_async = false;
2711 let mut async_block_err = |e: &mut Diagnostic, span: Span| {
2712 recover_async = true;
2713 e.span_label(span, "`async` blocks are only allowed in Rust 2018 or later");
2714 e.help_use_latest_edition();
2717 while self.token != token::CloseDelim(close_delim) {
2718 if self.eat(&token::DotDot) {
2719 let exp_span = self.prev_token.span;
2720 // We permit `.. }` on the left-hand side of a destructuring assignment.
2721 if self.check(&token::CloseDelim(close_delim)) {
2722 base = ast::StructRest::Rest(self.prev_token.span.shrink_to_hi());
2725 match self.parse_expr() {
2726 Ok(e) => base = ast::StructRest::Base(e),
2727 Err(mut e) if recover => {
2729 self.recover_stmt();
2731 Err(e) => return Err(e),
2733 self.recover_struct_comma_after_dotdot(exp_span);
2737 let recovery_field = self.find_struct_error_after_field_looking_code();
2738 let parsed_field = match self.parse_expr_field() {
2741 if pth == kw::Async {
2742 async_block_err(&mut e, pth.span);
2744 e.span_label(pth.span, "while parsing this struct");
2748 // If the next token is a comma, then try to parse
2749 // what comes next as additional fields, rather than
2750 // bailing out until next `}`.
2751 if self.token != token::Comma {
2752 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2753 if self.token != token::Comma {
2761 match self.expect_one_of(&[token::Comma], &[token::CloseDelim(close_delim)]) {
2763 if let Some(f) = parsed_field.or(recovery_field) {
2764 // Only include the field if there's no parse error for the field name.
2769 if pth == kw::Async {
2770 async_block_err(&mut e, pth.span);
2772 e.span_label(pth.span, "while parsing this struct");
2773 if let Some(f) = recovery_field {
2776 self.prev_token.span.shrink_to_hi(),
2777 "try adding a comma",
2779 Applicability::MachineApplicable,
2787 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2788 self.eat(&token::Comma);
2792 Ok((fields, base, recover_async))
2795 /// Precondition: already parsed the '{'.
2796 pub(super) fn parse_struct_expr(
2798 qself: Option<ast::QSelf>,
2802 ) -> PResult<'a, P<Expr>> {
2804 let (fields, base, recover_async) =
2805 self.parse_struct_fields(pth.clone(), recover, token::Brace)?;
2806 let span = lo.to(self.token.span);
2807 self.expect(&token::CloseDelim(token::Brace))?;
2808 let expr = if recover_async {
2811 ExprKind::Struct(P(ast::StructExpr { qself, path: pth, fields, rest: base }))
2813 Ok(self.mk_expr(span, expr, attrs))
2816 /// Use in case of error after field-looking code: `S { foo: () with a }`.
2817 fn find_struct_error_after_field_looking_code(&self) -> Option<ExprField> {
2818 match self.token.ident() {
2819 Some((ident, is_raw))
2820 if (is_raw || !ident.is_reserved())
2821 && self.look_ahead(1, |t| *t == token::Colon) =>
2823 Some(ast::ExprField {
2825 span: self.token.span,
2826 expr: self.mk_expr_err(self.token.span),
2827 is_shorthand: false,
2828 attrs: AttrVec::new(),
2830 is_placeholder: false,
2837 fn recover_struct_comma_after_dotdot(&mut self, span: Span) {
2838 if self.token != token::Comma {
2841 self.struct_span_err(
2842 span.to(self.prev_token.span),
2843 "cannot use a comma after the base struct",
2845 .span_suggestion_short(
2847 "remove this comma",
2849 Applicability::MachineApplicable,
2851 .note("the base struct must always be the last field")
2853 self.recover_stmt();
2856 /// Parses `ident (COLON expr)?`.
2857 fn parse_expr_field(&mut self) -> PResult<'a, ExprField> {
2858 let attrs = self.parse_outer_attributes()?;
2859 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2860 let lo = this.token.span;
2862 // Check if a colon exists one ahead. This means we're parsing a fieldname.
2863 let is_shorthand = !this.look_ahead(1, |t| t == &token::Colon || t == &token::Eq);
2864 let (ident, expr) = if is_shorthand {
2865 // Mimic `x: x` for the `x` field shorthand.
2866 let ident = this.parse_ident_common(false)?;
2867 let path = ast::Path::from_ident(ident);
2868 (ident, this.mk_expr(ident.span, ExprKind::Path(None, path), AttrVec::new()))
2870 let ident = this.parse_field_name()?;
2871 this.error_on_eq_field_init(ident);
2873 (ident, this.parse_expr()?)
2879 span: lo.to(expr.span),
2882 attrs: attrs.into(),
2884 is_placeholder: false,
2886 TrailingToken::MaybeComma,
2891 /// Check for `=`. This means the source incorrectly attempts to
2892 /// initialize a field with an eq rather than a colon.
2893 fn error_on_eq_field_init(&self, field_name: Ident) {
2894 if self.token != token::Eq {
2898 self.struct_span_err(self.token.span, "expected `:`, found `=`")
2900 field_name.span.shrink_to_hi().to(self.token.span),
2901 "replace equals symbol with a colon",
2903 Applicability::MachineApplicable,
2908 fn err_dotdotdot_syntax(&self, span: Span) {
2909 self.struct_span_err(span, "unexpected token: `...`")
2912 "use `..` for an exclusive range",
2914 Applicability::MaybeIncorrect,
2918 "or `..=` for an inclusive range",
2920 Applicability::MaybeIncorrect,
2925 fn err_larrow_operator(&self, span: Span) {
2926 self.struct_span_err(span, "unexpected token: `<-`")
2929 "if you meant to write a comparison against a negative value, add a \
2930 space in between `<` and `-`",
2932 Applicability::MaybeIncorrect,
2937 fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
2938 ExprKind::AssignOp(binop, lhs, rhs)
2943 start: Option<P<Expr>>,
2944 end: Option<P<Expr>>,
2945 limits: RangeLimits,
2947 if end.is_none() && limits == RangeLimits::Closed {
2948 self.inclusive_range_with_incorrect_end(self.prev_token.span);
2951 ExprKind::Range(start, end, limits)
2955 fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
2956 ExprKind::Unary(unop, expr)
2959 fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
2960 ExprKind::Binary(binop, lhs, rhs)
2963 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
2964 ExprKind::Index(expr, idx)
2967 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
2968 ExprKind::Call(f, args)
2971 fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> P<Expr> {
2972 let span = lo.to(self.prev_token.span);
2973 let await_expr = self.mk_expr(span, ExprKind::Await(self_arg), AttrVec::new());
2974 self.recover_from_await_method_call();
2978 crate fn mk_expr(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
2979 P(Expr { kind, span, attrs, id: DUMMY_NODE_ID, tokens: None })
2982 pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> {
2983 self.mk_expr(span, ExprKind::Err, AttrVec::new())
2986 /// Create expression span ensuring the span of the parent node
2987 /// is larger than the span of lhs and rhs, including the attributes.
2988 fn mk_expr_sp(&self, lhs: &P<Expr>, lhs_span: Span, rhs_span: Span) -> Span {
2991 .find(|a| a.style == AttrStyle::Outer)
2992 .map_or(lhs_span, |a| a.span)
2996 fn collect_tokens_for_expr(
2999 f: impl FnOnce(&mut Self, Vec<ast::Attribute>) -> PResult<'a, P<Expr>>,
3000 ) -> PResult<'a, P<Expr>> {
3001 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
3002 let res = f(this, attrs)?;
3003 let trailing = if this.restrictions.contains(Restrictions::STMT_EXPR)
3004 && this.token.kind == token::Semi
3008 // FIXME - pass this through from the place where we know
3009 // we need a comma, rather than assuming that `#[attr] expr,`
3010 // always captures a trailing comma
3011 TrailingToken::MaybeComma