1 use super::diagnostics::SnapshotParser;
2 use super::pat::{CommaRecoveryMode, RecoverColon, RecoverComma, PARAM_EXPECTED};
3 use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
5 AttrWrapper, BlockMode, ClosureSpans, ForceCollect, Parser, PathStyle, Restrictions,
6 SemiColonMode, SeqSep, TokenExpectType, TokenType, TrailingToken,
8 use crate::maybe_recover_from_interpolated_ty_qpath;
10 use ast::token::DelimToken;
11 use rustc_ast::ptr::P;
12 use rustc_ast::token::{self, Token, TokenKind};
13 use rustc_ast::tokenstream::Spacing;
14 use rustc_ast::util::classify;
15 use rustc_ast::util::literal::LitError;
16 use rustc_ast::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
17 use rustc_ast::{self as ast, AttrStyle, AttrVec, CaptureBy, ExprField, Lit, UnOp, DUMMY_NODE_ID};
18 use rustc_ast::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, MacCall, Param, Ty, TyKind};
19 use rustc_ast::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits};
20 use rustc_ast_pretty::pprust;
21 use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, PResult};
22 use rustc_session::lint::builtin::BREAK_WITH_LABEL_AND_LOOP;
23 use rustc_session::lint::BuiltinLintDiagnostics;
24 use rustc_span::source_map::{self, Span, Spanned};
25 use rustc_span::symbol::{kw, sym, Ident, Symbol};
26 use rustc_span::{BytePos, Pos};
29 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
30 /// dropped into the token stream, which happens while parsing the result of
31 /// macro expansion). Placement of these is not as complex as I feared it would
32 /// be. The important thing is to make sure that lookahead doesn't balk at
33 /// `token::Interpolated` tokens.
34 macro_rules! maybe_whole_expr {
36 if let token::Interpolated(nt) = &$p.token.kind {
38 token::NtExpr(e) | token::NtLiteral(e) => {
43 token::NtPath(path) => {
44 let path = path.clone();
48 ExprKind::Path(None, path),
52 token::NtBlock(block) => {
53 let block = block.clone();
57 ExprKind::Block(block, None),
68 pub(super) enum LhsExpr {
70 AttributesParsed(AttrWrapper),
71 AlreadyParsed(P<Expr>),
74 impl From<Option<AttrWrapper>> for LhsExpr {
75 /// Converts `Some(attrs)` into `LhsExpr::AttributesParsed(attrs)`
76 /// and `None` into `LhsExpr::NotYetParsed`.
78 /// This conversion does not allocate.
79 fn from(o: Option<AttrWrapper>) -> Self {
80 if let Some(attrs) = o { LhsExpr::AttributesParsed(attrs) } else { LhsExpr::NotYetParsed }
84 impl From<P<Expr>> for LhsExpr {
85 /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed(expr)`.
87 /// This conversion does not allocate.
88 fn from(expr: P<Expr>) -> Self {
89 LhsExpr::AlreadyParsed(expr)
94 /// Parses an expression.
96 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
97 self.current_closure.take();
99 self.parse_expr_res(Restrictions::empty(), None)
102 /// Parses an expression, forcing tokens to be collected
103 pub fn parse_expr_force_collect(&mut self) -> PResult<'a, P<Expr>> {
104 self.collect_tokens_no_attrs(|this| this.parse_expr())
107 pub fn parse_anon_const_expr(&mut self) -> PResult<'a, AnonConst> {
108 self.parse_expr().map(|value| AnonConst { id: DUMMY_NODE_ID, value })
111 fn parse_expr_catch_underscore(&mut self) -> PResult<'a, P<Expr>> {
112 match self.parse_expr() {
113 Ok(expr) => Ok(expr),
114 Err(mut err) => match self.token.ident() {
115 Some((Ident { name: kw::Underscore, .. }, false))
116 if self.look_ahead(1, |t| t == &token::Comma) =>
118 // Special-case handling of `foo(_, _, _)`
121 Ok(self.mk_expr(self.prev_token.span, ExprKind::Err, AttrVec::new()))
128 /// Parses a sequence of expressions delimited by parentheses.
129 fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
130 self.parse_paren_comma_seq(|p| p.parse_expr_catch_underscore()).map(|(r, _)| r)
133 /// Parses an expression, subject to the given restrictions.
135 pub(super) fn parse_expr_res(
138 already_parsed_attrs: Option<AttrWrapper>,
139 ) -> PResult<'a, P<Expr>> {
140 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
143 /// Parses an associative expression.
145 /// This parses an expression accounting for associativity and precedence of the operators in
150 already_parsed_attrs: Option<AttrWrapper>,
151 ) -> PResult<'a, P<Expr>> {
152 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
155 /// Parses an associative expression with operators of at least `min_prec` precedence.
156 pub(super) fn parse_assoc_expr_with(
160 ) -> PResult<'a, P<Expr>> {
161 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
164 let attrs = match lhs {
165 LhsExpr::AttributesParsed(attrs) => Some(attrs),
168 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind) {
169 return self.parse_prefix_range_expr(attrs);
171 self.parse_prefix_expr(attrs)?
174 let last_type_ascription_set = self.last_type_ascription.is_some();
176 if !self.should_continue_as_assoc_expr(&lhs) {
177 self.last_type_ascription = None;
181 self.expected_tokens.push(TokenType::Operator);
182 while let Some(op) = self.check_assoc_op() {
183 // Adjust the span for interpolated LHS to point to the `$lhs` token
184 // and not to what it refers to.
185 let lhs_span = match self.prev_token.kind {
186 TokenKind::Interpolated(..) => self.prev_token.span,
190 let cur_op_span = self.token.span;
191 let restrictions = if op.node.is_assign_like() {
192 self.restrictions & Restrictions::NO_STRUCT_LITERAL
196 let prec = op.node.precedence();
200 // Check for deprecated `...` syntax
201 if self.token == token::DotDotDot && op.node == AssocOp::DotDotEq {
202 self.err_dotdotdot_syntax(self.token.span);
205 if self.token == token::LArrow {
206 self.err_larrow_operator(self.token.span);
210 if op.node.is_comparison() {
211 if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
216 // Look for JS' `===` and `!==` and recover
217 if (op.node == AssocOp::Equal || op.node == AssocOp::NotEqual)
218 && self.token.kind == token::Eq
219 && self.prev_token.span.hi() == self.token.span.lo()
221 let sp = op.span.to(self.token.span);
222 let sugg = match op.node {
223 AssocOp::Equal => "==",
224 AssocOp::NotEqual => "!=",
227 self.struct_span_err(sp, &format!("invalid comparison operator `{sugg}=`"))
228 .span_suggestion_short(
230 &format!("`{s}=` is not a valid comparison operator, use `{s}`", s = sugg),
232 Applicability::MachineApplicable,
238 // Look for PHP's `<>` and recover
239 if op.node == AssocOp::Less
240 && self.token.kind == token::Gt
241 && self.prev_token.span.hi() == self.token.span.lo()
243 let sp = op.span.to(self.token.span);
244 self.struct_span_err(sp, "invalid comparison operator `<>`")
245 .span_suggestion_short(
247 "`<>` is not a valid comparison operator, use `!=`",
249 Applicability::MachineApplicable,
255 // Look for C++'s `<=>` and recover
256 if op.node == AssocOp::LessEqual
257 && self.token.kind == token::Gt
258 && self.prev_token.span.hi() == self.token.span.lo()
260 let sp = op.span.to(self.token.span);
261 self.struct_span_err(sp, "invalid comparison operator `<=>`")
264 "`<=>` is not a valid comparison operator, use `std::cmp::Ordering`",
272 if op == AssocOp::As {
273 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
275 } else if op == AssocOp::Colon {
276 lhs = self.parse_assoc_op_ascribe(lhs, lhs_span)?;
278 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
279 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
280 // generalise it to the Fixity::None code.
281 lhs = self.parse_range_expr(prec, lhs, op, cur_op_span)?;
285 let fixity = op.fixity();
286 let prec_adjustment = match fixity {
289 // We currently have no non-associative operators that are not handled above by
290 // the special cases. The code is here only for future convenience.
293 let rhs = self.with_res(restrictions - Restrictions::STMT_EXPR, |this| {
294 this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
297 let span = self.mk_expr_sp(&lhs, lhs_span, rhs.span);
310 | AssocOp::ShiftRight
316 | AssocOp::GreaterEqual => {
317 let ast_op = op.to_ast_binop().unwrap();
318 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
319 self.mk_expr(span, binary, AttrVec::new())
322 self.mk_expr(span, ExprKind::Assign(lhs, rhs, cur_op_span), AttrVec::new())
324 AssocOp::AssignOp(k) => {
326 token::Plus => BinOpKind::Add,
327 token::Minus => BinOpKind::Sub,
328 token::Star => BinOpKind::Mul,
329 token::Slash => BinOpKind::Div,
330 token::Percent => BinOpKind::Rem,
331 token::Caret => BinOpKind::BitXor,
332 token::And => BinOpKind::BitAnd,
333 token::Or => BinOpKind::BitOr,
334 token::Shl => BinOpKind::Shl,
335 token::Shr => BinOpKind::Shr,
337 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
338 self.mk_expr(span, aopexpr, AttrVec::new())
340 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
341 self.span_bug(span, "AssocOp should have been handled by special case")
345 if let Fixity::None = fixity {
349 if last_type_ascription_set {
350 self.last_type_ascription = None;
355 fn should_continue_as_assoc_expr(&mut self, lhs: &Expr) -> bool {
356 match (self.expr_is_complete(lhs), AssocOp::from_token(&self.token)) {
357 // Semi-statement forms are odd:
358 // See https://github.com/rust-lang/rust/issues/29071
359 (true, None) => false,
360 (false, _) => true, // Continue parsing the expression.
361 // An exhaustive check is done in the following block, but these are checked first
362 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
363 // want to keep their span info to improve diagnostics in these cases in a later stage.
364 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
365 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
366 (true, Some(AssocOp::Add)) // `{ 42 } + 42
367 // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
368 // `if x { a } else { b } && if y { c } else { d }`
369 if !self.look_ahead(1, |t| t.is_used_keyword()) => {
370 // These cases are ambiguous and can't be identified in the parser alone.
371 let sp = self.sess.source_map().start_point(self.token.span);
372 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
375 (true, Some(AssocOp::LAnd)) |
376 (true, Some(AssocOp::LOr)) |
377 (true, Some(AssocOp::BitOr)) => {
378 // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }`. Separated from the
379 // above due to #74233.
380 // These cases are ambiguous and can't be identified in the parser alone.
382 // Bitwise AND is left out because guessing intent is hard. We can make
383 // suggestions based on the assumption that double-refs are rarely intentional,
384 // and closures are distinct enough that they don't get mixed up with their
386 let sp = self.sess.source_map().start_point(self.token.span);
387 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
390 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => false,
392 self.error_found_expr_would_be_stmt(lhs);
398 /// We've found an expression that would be parsed as a statement,
399 /// but the next token implies this should be parsed as an expression.
400 /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
401 fn error_found_expr_would_be_stmt(&self, lhs: &Expr) {
402 let mut err = self.struct_span_err(
404 &format!("expected expression, found `{}`", pprust::token_to_string(&self.token),),
406 err.span_label(self.token.span, "expected expression");
407 self.sess.expr_parentheses_needed(&mut err, lhs.span);
411 /// Possibly translate the current token to an associative operator.
412 /// The method does not advance the current token.
414 /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
415 fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
416 let (op, span) = match (AssocOp::from_token(&self.token), self.token.ident()) {
417 // When parsing const expressions, stop parsing when encountering `>`.
422 | AssocOp::GreaterEqual
423 | AssocOp::AssignOp(token::BinOpToken::Shr),
426 ) if self.restrictions.contains(Restrictions::CONST_EXPR) => {
429 (Some(op), _) => (op, self.token.span),
430 (None, Some((Ident { name: sym::and, span }, false))) => {
431 self.error_bad_logical_op("and", "&&", "conjunction");
432 (AssocOp::LAnd, span)
434 (None, Some((Ident { name: sym::or, span }, false))) => {
435 self.error_bad_logical_op("or", "||", "disjunction");
440 Some(source_map::respan(span, op))
443 /// Error on `and` and `or` suggesting `&&` and `||` respectively.
444 fn error_bad_logical_op(&self, bad: &str, good: &str, english: &str) {
445 self.struct_span_err(self.token.span, &format!("`{bad}` is not a logical operator"))
446 .span_suggestion_short(
448 &format!("use `{good}` to perform logical {english}"),
450 Applicability::MachineApplicable,
452 .note("unlike in e.g., python and PHP, `&&` and `||` are used for logical operators")
456 /// Checks if this expression is a successfully parsed statement.
457 fn expr_is_complete(&self, e: &Expr) -> bool {
458 self.restrictions.contains(Restrictions::STMT_EXPR)
459 && !classify::expr_requires_semi_to_be_stmt(e)
462 /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
463 /// The other two variants are handled in `parse_prefix_range_expr` below.
470 ) -> PResult<'a, P<Expr>> {
471 let rhs = if self.is_at_start_of_range_notation_rhs() {
472 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
476 let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
477 let span = self.mk_expr_sp(&lhs, lhs.span, rhs_span);
479 if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
480 let range = self.mk_range(Some(lhs), rhs, limits);
481 Ok(self.mk_expr(span, range, AttrVec::new()))
484 fn is_at_start_of_range_notation_rhs(&self) -> bool {
485 if self.token.can_begin_expr() {
486 // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
487 if self.token == token::OpenDelim(token::Brace) {
488 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
496 /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
497 fn parse_prefix_range_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
498 // Check for deprecated `...` syntax.
499 if self.token == token::DotDotDot {
500 self.err_dotdotdot_syntax(self.token.span);
504 [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind),
505 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
509 let limits = match self.token.kind {
510 token::DotDot => RangeLimits::HalfOpen,
511 _ => RangeLimits::Closed,
513 let op = AssocOp::from_token(&self.token);
514 // FIXME: `parse_prefix_range_expr` is called when the current
515 // token is `DotDot`, `DotDotDot`, or `DotDotEq`. If we haven't already
516 // parsed attributes, then trying to parse them here will always fail.
517 // We should figure out how we want attributes on range expressions to work.
518 let attrs = self.parse_or_use_outer_attributes(attrs)?;
519 self.collect_tokens_for_expr(attrs, |this, attrs| {
520 let lo = this.token.span;
522 let (span, opt_end) = if this.is_at_start_of_range_notation_rhs() {
523 // RHS must be parsed with more associativity than the dots.
524 this.parse_assoc_expr_with(op.unwrap().precedence() + 1, LhsExpr::NotYetParsed)
525 .map(|x| (lo.to(x.span), Some(x)))?
529 let range = this.mk_range(None, opt_end, limits);
530 Ok(this.mk_expr(span, range, attrs.into()))
534 /// Parses a prefix-unary-operator expr.
535 fn parse_prefix_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
536 let attrs = self.parse_or_use_outer_attributes(attrs)?;
537 let lo = self.token.span;
539 macro_rules! make_it {
540 ($this:ident, $attrs:expr, |this, _| $body:expr) => {
541 $this.collect_tokens_for_expr($attrs, |$this, attrs| {
542 let (hi, ex) = $body?;
543 Ok($this.mk_expr(lo.to(hi), ex, attrs.into()))
550 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
551 match this.token.uninterpolate().kind {
552 token::Not => make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Not)), // `!expr`
553 token::Tilde => make_it!(this, attrs, |this, _| this.recover_tilde_expr(lo)), // `~expr`
554 token::BinOp(token::Minus) => {
555 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Neg))
557 token::BinOp(token::Star) => {
558 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Deref))
560 token::BinOp(token::And) | token::AndAnd => {
561 make_it!(this, attrs, |this, _| this.parse_borrow_expr(lo))
563 token::BinOp(token::Plus) if this.look_ahead(1, |tok| tok.is_numeric_lit()) => {
564 let mut err = this.struct_span_err(lo, "leading `+` is not supported");
565 err.span_label(lo, "unexpected `+`");
567 // a block on the LHS might have been intended to be an expression instead
568 if let Some(sp) = this.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
569 this.sess.expr_parentheses_needed(&mut err, *sp);
571 err.span_suggestion_verbose(
573 "try removing the `+`",
575 Applicability::MachineApplicable,
581 this.parse_prefix_expr(None)
583 token::Ident(..) if this.token.is_keyword(kw::Box) => {
584 make_it!(this, attrs, |this, _| this.parse_box_expr(lo))
586 token::Ident(..) if this.is_mistaken_not_ident_negation() => {
587 make_it!(this, attrs, |this, _| this.recover_not_expr(lo))
589 _ => return this.parse_dot_or_call_expr(Some(attrs)),
593 fn parse_prefix_expr_common(&mut self, lo: Span) -> PResult<'a, (Span, P<Expr>)> {
595 let expr = self.parse_prefix_expr(None);
596 let (span, expr) = self.interpolated_or_expr_span(expr)?;
597 Ok((lo.to(span), expr))
600 fn parse_unary_expr(&mut self, lo: Span, op: UnOp) -> PResult<'a, (Span, ExprKind)> {
601 let (span, expr) = self.parse_prefix_expr_common(lo)?;
602 Ok((span, self.mk_unary(op, expr)))
605 // Recover on `!` suggesting for bitwise negation instead.
606 fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
607 self.struct_span_err(lo, "`~` cannot be used as a unary operator")
608 .span_suggestion_short(
610 "use `!` to perform bitwise not",
612 Applicability::MachineApplicable,
616 self.parse_unary_expr(lo, UnOp::Not)
619 /// Parse `box expr`.
620 fn parse_box_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
621 let (span, expr) = self.parse_prefix_expr_common(lo)?;
622 self.sess.gated_spans.gate(sym::box_syntax, span);
623 Ok((span, ExprKind::Box(expr)))
626 fn is_mistaken_not_ident_negation(&self) -> bool {
627 let token_cannot_continue_expr = |t: &Token| match t.uninterpolate().kind {
628 // These tokens can start an expression after `!`, but
629 // can't continue an expression after an ident
630 token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
631 token::Literal(..) | token::Pound => true,
632 _ => t.is_whole_expr(),
634 self.token.is_ident_named(sym::not) && self.look_ahead(1, token_cannot_continue_expr)
637 /// Recover on `not expr` in favor of `!expr`.
638 fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
640 let not_token = self.look_ahead(1, |t| t.clone());
641 self.struct_span_err(
643 &format!("unexpected {} after identifier", super::token_descr(¬_token)),
645 .span_suggestion_short(
646 // Span the `not` plus trailing whitespace to avoid
647 // trailing whitespace after the `!` in our suggestion
648 self.sess.source_map().span_until_non_whitespace(lo.to(not_token.span)),
649 "use `!` to perform logical negation",
651 Applicability::MachineApplicable,
656 self.parse_unary_expr(lo, UnOp::Not)
659 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
660 fn interpolated_or_expr_span(
662 expr: PResult<'a, P<Expr>>,
663 ) -> PResult<'a, (Span, P<Expr>)> {
666 match self.prev_token.kind {
667 TokenKind::Interpolated(..) => self.prev_token.span,
675 fn parse_assoc_op_cast(
679 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
680 ) -> PResult<'a, P<Expr>> {
681 let mk_expr = |this: &mut Self, lhs: P<Expr>, rhs: P<Ty>| {
683 this.mk_expr_sp(&lhs, lhs_span, rhs.span),
689 // Save the state of the parser before parsing type normally, in case there is a
690 // LessThan comparison after this cast.
691 let parser_snapshot_before_type = self.clone();
692 let cast_expr = match self.parse_as_cast_ty() {
693 Ok(rhs) => mk_expr(self, lhs, rhs),
695 // Rewind to before attempting to parse the type with generics, to recover
696 // from situations like `x as usize < y` in which we first tried to parse
697 // `usize < y` as a type with generic arguments.
698 let parser_snapshot_after_type = mem::replace(self, parser_snapshot_before_type);
700 // Check for typo of `'a: loop { break 'a }` with a missing `'`.
701 match (&lhs.kind, &self.token.kind) {
704 ExprKind::Path(None, ast::Path { segments, .. }),
705 TokenKind::Ident(kw::For | kw::Loop | kw::While, false),
706 ) if segments.len() == 1 => {
707 let snapshot = self.create_snapshot_for_diagnostic();
709 ident: Ident::from_str_and_span(
710 &format!("'{}", segments[0].ident),
711 segments[0].ident.span,
714 match self.parse_labeled_expr(label, AttrVec::new(), false) {
717 self.struct_span_err(label.ident.span, "malformed loop label")
720 "use the correct loop label format",
721 label.ident.to_string(),
722 Applicability::MachineApplicable,
729 self.restore_snapshot(snapshot);
736 match self.parse_path(PathStyle::Expr) {
738 let (op_noun, op_verb) = match self.token.kind {
739 token::Lt => ("comparison", "comparing"),
740 token::BinOp(token::Shl) => ("shift", "shifting"),
742 // We can end up here even without `<` being the next token, for
743 // example because `parse_ty_no_plus` returns `Err` on keywords,
744 // but `parse_path` returns `Ok` on them due to error recovery.
745 // Return original error and parser state.
746 *self = parser_snapshot_after_type;
747 return Err(type_err);
751 // Successfully parsed the type path leaving a `<` yet to parse.
754 // Report non-fatal diagnostics, keep `x as usize` as an expression
755 // in AST and continue parsing.
757 "`<` is interpreted as a start of generic arguments for `{}`, not a {}",
758 pprust::path_to_string(&path),
761 let span_after_type = parser_snapshot_after_type.token.span;
763 mk_expr(self, lhs, self.mk_ty(path.span, TyKind::Path(None, path)));
765 self.struct_span_err(self.token.span, &msg)
767 self.look_ahead(1, |t| t.span).to(span_after_type),
768 "interpreted as generic arguments",
770 .span_label(self.token.span, format!("not interpreted as {op_noun}"))
771 .multipart_suggestion(
772 &format!("try {op_verb} the cast value"),
774 (expr.span.shrink_to_lo(), "(".to_string()),
775 (expr.span.shrink_to_hi(), ")".to_string()),
777 Applicability::MachineApplicable,
784 // Couldn't parse as a path, return original error and parser state.
786 *self = parser_snapshot_after_type;
787 return Err(type_err);
793 self.parse_and_disallow_postfix_after_cast(cast_expr)
796 /// Parses a postfix operators such as `.`, `?`, or index (`[]`) after a cast,
797 /// then emits an error and returns the newly parsed tree.
798 /// The resulting parse tree for `&x as T[0]` has a precedence of `((&x) as T)[0]`.
799 fn parse_and_disallow_postfix_after_cast(
802 ) -> PResult<'a, P<Expr>> {
803 let span = cast_expr.span;
804 let maybe_ascription_span = if let ExprKind::Type(ascripted_expr, _) = &cast_expr.kind {
805 Some(ascripted_expr.span.shrink_to_hi().with_hi(span.hi()))
810 // Save the memory location of expr before parsing any following postfix operators.
811 // This will be compared with the memory location of the output expression.
812 // If they different we can assume we parsed another expression because the existing expression is not reallocated.
813 let addr_before = &*cast_expr as *const _ as usize;
814 let with_postfix = self.parse_dot_or_call_expr_with_(cast_expr, span)?;
815 let changed = addr_before != &*with_postfix as *const _ as usize;
817 // Check if an illegal postfix operator has been added after the cast.
818 // If the resulting expression is not a cast, or has a different memory location, it is an illegal postfix operator.
819 if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) || changed {
821 "casts cannot be followed by {}",
822 match with_postfix.kind {
823 ExprKind::Index(_, _) => "indexing",
824 ExprKind::Try(_) => "`?`",
825 ExprKind::Field(_, _) => "a field access",
826 ExprKind::MethodCall(_, _, _) => "a method call",
827 ExprKind::Call(_, _) => "a function call",
828 ExprKind::Await(_) => "`.await`",
829 ExprKind::Err => return Ok(with_postfix),
830 _ => unreachable!("parse_dot_or_call_expr_with_ shouldn't produce this"),
833 let mut err = self.struct_span_err(span, &msg);
835 let suggest_parens = |err: &mut DiagnosticBuilder<'_, _>| {
836 let suggestions = vec![
837 (span.shrink_to_lo(), "(".to_string()),
838 (span.shrink_to_hi(), ")".to_string()),
840 err.multipart_suggestion(
841 "try surrounding the expression in parentheses",
843 Applicability::MachineApplicable,
847 // If type ascription is "likely an error", the user will already be getting a useful
848 // help message, and doesn't need a second.
849 if self.last_type_ascription.map_or(false, |last_ascription| last_ascription.1) {
850 self.maybe_annotate_with_ascription(&mut err, false);
851 } else if let Some(ascription_span) = maybe_ascription_span {
852 let is_nightly = self.sess.unstable_features.is_nightly_build();
854 suggest_parens(&mut err);
859 "{}remove the type ascription",
860 if is_nightly { "alternatively, " } else { "" }
864 Applicability::MaybeIncorrect
866 Applicability::MachineApplicable
870 suggest_parens(&mut err);
877 fn parse_assoc_op_ascribe(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
878 let maybe_path = self.could_ascription_be_path(&lhs.kind);
879 self.last_type_ascription = Some((self.prev_token.span, maybe_path));
880 let lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
881 self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
885 /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
886 fn parse_borrow_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
888 let has_lifetime = self.token.is_lifetime() && self.look_ahead(1, |t| t != &token::Colon);
889 let lifetime = has_lifetime.then(|| self.expect_lifetime()); // For recovery, see below.
890 let (borrow_kind, mutbl) = self.parse_borrow_modifiers(lo);
891 let expr = self.parse_prefix_expr(None);
892 let (hi, expr) = self.interpolated_or_expr_span(expr)?;
893 let span = lo.to(hi);
894 if let Some(lt) = lifetime {
895 self.error_remove_borrow_lifetime(span, lt.ident.span);
897 Ok((span, ExprKind::AddrOf(borrow_kind, mutbl, expr)))
900 fn error_remove_borrow_lifetime(&self, span: Span, lt_span: Span) {
901 self.struct_span_err(span, "borrow expressions cannot be annotated with lifetimes")
902 .span_label(lt_span, "annotated with lifetime here")
905 "remove the lifetime annotation",
907 Applicability::MachineApplicable,
912 /// Parse `mut?` or `raw [ const | mut ]`.
913 fn parse_borrow_modifiers(&mut self, lo: Span) -> (ast::BorrowKind, ast::Mutability) {
914 if self.check_keyword(kw::Raw) && self.look_ahead(1, Token::is_mutability) {
915 // `raw [ const | mut ]`.
916 let found_raw = self.eat_keyword(kw::Raw);
918 let mutability = self.parse_const_or_mut().unwrap();
919 self.sess.gated_spans.gate(sym::raw_ref_op, lo.to(self.prev_token.span));
920 (ast::BorrowKind::Raw, mutability)
923 (ast::BorrowKind::Ref, self.parse_mutability())
927 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
928 fn parse_dot_or_call_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
929 let attrs = self.parse_or_use_outer_attributes(attrs)?;
930 self.collect_tokens_for_expr(attrs, |this, attrs| {
931 let base = this.parse_bottom_expr();
932 let (span, base) = this.interpolated_or_expr_span(base)?;
933 this.parse_dot_or_call_expr_with(base, span, attrs)
937 pub(super) fn parse_dot_or_call_expr_with(
941 mut attrs: Vec<ast::Attribute>,
942 ) -> PResult<'a, P<Expr>> {
943 // Stitch the list of outer attributes onto the return value.
944 // A little bit ugly, but the best way given the current code
946 self.parse_dot_or_call_expr_with_(e0, lo).map(|expr| {
947 expr.map(|mut expr| {
948 attrs.extend::<Vec<_>>(expr.attrs.into());
949 expr.attrs = attrs.into();
955 fn parse_dot_or_call_expr_with_(&mut self, mut e: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
957 if self.eat(&token::Question) {
959 e = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Try(e), AttrVec::new());
962 if self.eat(&token::Dot) {
964 e = self.parse_dot_suffix_expr(lo, e)?;
967 if self.expr_is_complete(&e) {
970 e = match self.token.kind {
971 token::OpenDelim(token::Paren) => self.parse_fn_call_expr(lo, e),
972 token::OpenDelim(token::Bracket) => self.parse_index_expr(lo, e)?,
978 fn look_ahead_type_ascription_as_field(&mut self) -> bool {
979 self.look_ahead(1, |t| t.is_ident())
980 && self.look_ahead(2, |t| t == &token::Colon)
981 && self.look_ahead(3, |t| t.can_begin_expr())
984 fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
985 match self.token.uninterpolate().kind {
986 token::Ident(..) => self.parse_dot_suffix(base, lo),
987 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
988 Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix, None))
990 token::Literal(token::Lit { kind: token::Float, symbol, suffix }) => {
991 Ok(self.parse_tuple_field_access_expr_float(lo, base, symbol, suffix))
994 self.error_unexpected_after_dot();
1000 fn error_unexpected_after_dot(&self) {
1001 // FIXME Could factor this out into non_fatal_unexpected or something.
1002 let actual = pprust::token_to_string(&self.token);
1003 self.struct_span_err(self.token.span, &format!("unexpected token: `{actual}`")).emit();
1006 // We need an identifier or integer, but the next token is a float.
1007 // Break the float into components to extract the identifier or integer.
1008 // FIXME: With current `TokenCursor` it's hard to break tokens into more than 2
1009 // parts unless those parts are processed immediately. `TokenCursor` should either
1010 // support pushing "future tokens" (would be also helpful to `break_and_eat`), or
1011 // we should break everything including floats into more basic proc-macro style
1012 // tokens in the lexer (probably preferable).
1013 fn parse_tuple_field_access_expr_float(
1018 suffix: Option<Symbol>,
1021 enum FloatComponent {
1025 use FloatComponent::*;
1027 let float_str = float.as_str();
1028 let mut components = Vec::new();
1029 let mut ident_like = String::new();
1030 for c in float_str.chars() {
1031 if c == '_' || c.is_ascii_alphanumeric() {
1033 } else if matches!(c, '.' | '+' | '-') {
1034 if !ident_like.is_empty() {
1035 components.push(IdentLike(mem::take(&mut ident_like)));
1037 components.push(Punct(c));
1039 panic!("unexpected character in a float token: {:?}", c)
1042 if !ident_like.is_empty() {
1043 components.push(IdentLike(ident_like));
1046 // With proc macros the span can refer to anything, the source may be too short,
1047 // or too long, or non-ASCII. It only makes sense to break our span into components
1048 // if its underlying text is identical to our float literal.
1049 let span = self.token.span;
1050 let can_take_span_apart =
1051 || self.span_to_snippet(span).as_deref() == Ok(float_str).as_deref();
1053 match &*components {
1056 self.parse_tuple_field_access_expr(lo, base, Symbol::intern(&i), suffix, None)
1059 [IdentLike(i), Punct('.')] => {
1060 let (ident_span, dot_span) = if can_take_span_apart() {
1061 let (span, ident_len) = (span.data(), BytePos::from_usize(i.len()));
1062 let ident_span = span.with_hi(span.lo + ident_len);
1063 let dot_span = span.with_lo(span.lo + ident_len);
1064 (ident_span, dot_span)
1068 assert!(suffix.is_none());
1069 let symbol = Symbol::intern(&i);
1070 self.token = Token::new(token::Ident(symbol, false), ident_span);
1071 let next_token = (Token::new(token::Dot, dot_span), self.token_spacing);
1072 self.parse_tuple_field_access_expr(lo, base, symbol, None, Some(next_token))
1075 [IdentLike(i1), Punct('.'), IdentLike(i2)] => {
1076 let (ident1_span, dot_span, ident2_span) = if can_take_span_apart() {
1077 let (span, ident1_len) = (span.data(), BytePos::from_usize(i1.len()));
1078 let ident1_span = span.with_hi(span.lo + ident1_len);
1080 .with_lo(span.lo + ident1_len)
1081 .with_hi(span.lo + ident1_len + BytePos(1));
1082 let ident2_span = self.token.span.with_lo(span.lo + ident1_len + BytePos(1));
1083 (ident1_span, dot_span, ident2_span)
1087 let symbol1 = Symbol::intern(&i1);
1088 self.token = Token::new(token::Ident(symbol1, false), ident1_span);
1089 // This needs to be `Spacing::Alone` to prevent regressions.
1090 // See issue #76399 and PR #76285 for more details
1091 let next_token1 = (Token::new(token::Dot, dot_span), Spacing::Alone);
1093 self.parse_tuple_field_access_expr(lo, base, symbol1, None, Some(next_token1));
1094 let symbol2 = Symbol::intern(&i2);
1095 let next_token2 = Token::new(token::Ident(symbol2, false), ident2_span);
1096 self.bump_with((next_token2, self.token_spacing)); // `.`
1097 self.parse_tuple_field_access_expr(lo, base1, symbol2, suffix, None)
1099 // 1e+ | 1e- (recovered)
1100 [IdentLike(_), Punct('+' | '-')] |
1102 [IdentLike(_), Punct('+' | '-'), IdentLike(_)] |
1104 [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-')] |
1106 [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-'), IdentLike(_)] => {
1107 // See the FIXME about `TokenCursor` above.
1108 self.error_unexpected_after_dot();
1111 _ => panic!("unexpected components in a float token: {:?}", components),
1115 fn parse_tuple_field_access_expr(
1120 suffix: Option<Symbol>,
1121 next_token: Option<(Token, Spacing)>,
1124 Some(next_token) => self.bump_with(next_token),
1125 None => self.bump(),
1127 let span = self.prev_token.span;
1128 let field = ExprKind::Field(base, Ident::new(field, span));
1129 self.expect_no_suffix(span, "a tuple index", suffix);
1130 self.mk_expr(lo.to(span), field, AttrVec::new())
1133 /// Parse a function call expression, `expr(...)`.
1134 fn parse_fn_call_expr(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
1135 let snapshot = if self.token.kind == token::OpenDelim(token::Paren)
1136 && self.look_ahead_type_ascription_as_field()
1138 Some((self.create_snapshot_for_diagnostic(), fun.kind.clone()))
1142 let open_paren = self.token.span;
1144 let mut seq = self.parse_paren_expr_seq().map(|args| {
1145 self.mk_expr(lo.to(self.prev_token.span), self.mk_call(fun, args), AttrVec::new())
1148 self.maybe_recover_struct_lit_bad_delims(lo, open_paren, &mut seq, snapshot)
1152 self.recover_seq_parse_error(token::Paren, lo, seq)
1155 /// If we encounter a parser state that looks like the user has written a `struct` literal with
1156 /// parentheses instead of braces, recover the parser state and provide suggestions.
1157 #[instrument(skip(self, seq, snapshot), level = "trace")]
1158 fn maybe_recover_struct_lit_bad_delims(
1162 seq: &mut PResult<'a, P<Expr>>,
1163 snapshot: Option<(SnapshotParser<'a>, ExprKind)>,
1164 ) -> Option<P<Expr>> {
1165 match (seq.as_mut(), snapshot) {
1166 (Err(err), Some((mut snapshot, ExprKind::Path(None, path)))) => {
1167 let name = pprust::path_to_string(&path);
1168 snapshot.bump(); // `(`
1169 match snapshot.parse_struct_fields(path, false, token::Paren) {
1170 Ok((fields, ..)) if snapshot.eat(&token::CloseDelim(token::Paren)) => {
1171 // We are certain we have `Enum::Foo(a: 3, b: 4)`, suggest
1172 // `Enum::Foo { a: 3, b: 4 }` or `Enum::Foo(3, 4)`.
1173 self.restore_snapshot(snapshot);
1174 let close_paren = self.prev_token.span;
1175 let span = lo.to(self.prev_token.span);
1176 if !fields.is_empty() {
1177 let replacement_err = self.struct_span_err(
1179 "invalid `struct` delimiters or `fn` call arguments",
1181 mem::replace(err, replacement_err).cancel();
1183 err.multipart_suggestion(
1184 &format!("if `{name}` is a struct, use braces as delimiters"),
1186 (open_paren, " { ".to_string()),
1187 (close_paren, " }".to_string()),
1189 Applicability::MaybeIncorrect,
1191 err.multipart_suggestion(
1192 &format!("if `{name}` is a function, use the arguments directly"),
1195 .map(|field| (field.span.until(field.expr.span), String::new()))
1197 Applicability::MaybeIncorrect,
1203 return Some(self.mk_expr_err(span));
1216 /// Parse an indexing expression `expr[...]`.
1217 fn parse_index_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
1219 let index = self.parse_expr()?;
1220 self.expect(&token::CloseDelim(token::Bracket))?;
1221 Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_index(base, index), AttrVec::new()))
1224 /// Assuming we have just parsed `.`, continue parsing into an expression.
1225 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
1226 if self.token.uninterpolated_span().rust_2018() && self.eat_keyword(kw::Await) {
1227 return Ok(self.mk_await_expr(self_arg, lo));
1230 let fn_span_lo = self.token.span;
1231 let mut segment = self.parse_path_segment(PathStyle::Expr, None)?;
1232 self.check_trailing_angle_brackets(&segment, &[&token::OpenDelim(token::Paren)]);
1233 self.check_turbofish_missing_angle_brackets(&mut segment);
1235 if self.check(&token::OpenDelim(token::Paren)) {
1236 // Method call `expr.f()`
1237 let mut args = self.parse_paren_expr_seq()?;
1238 args.insert(0, self_arg);
1240 let fn_span = fn_span_lo.to(self.prev_token.span);
1241 let span = lo.to(self.prev_token.span);
1242 Ok(self.mk_expr(span, ExprKind::MethodCall(segment, args, fn_span), AttrVec::new()))
1244 // Field access `expr.f`
1245 if let Some(args) = segment.args {
1246 self.struct_span_err(
1248 "field expressions cannot have generic arguments",
1253 let span = lo.to(self.prev_token.span);
1254 Ok(self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), AttrVec::new()))
1258 /// At the bottom (top?) of the precedence hierarchy,
1259 /// Parses things like parenthesized exprs, macros, `return`, etc.
1261 /// N.B., this does not parse outer attributes, and is private because it only works
1262 /// correctly if called from `parse_dot_or_call_expr()`.
1263 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
1264 maybe_recover_from_interpolated_ty_qpath!(self, true);
1265 maybe_whole_expr!(self);
1267 // Outer attributes are already parsed and will be
1268 // added to the return value after the fact.
1270 // Therefore, prevent sub-parser from parsing
1271 // attributes by giving them an empty "already-parsed" list.
1272 let attrs = AttrVec::new();
1274 // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
1275 let lo = self.token.span;
1276 if let token::Literal(_) = self.token.kind {
1277 // This match arm is a special-case of the `_` match arm below and
1278 // could be removed without changing functionality, but it's faster
1279 // to have it here, especially for programs with large constants.
1280 self.parse_lit_expr(attrs)
1281 } else if self.check(&token::OpenDelim(token::Paren)) {
1282 self.parse_tuple_parens_expr(attrs)
1283 } else if self.check(&token::OpenDelim(token::Brace)) {
1284 self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs)
1285 } else if self.check(&token::BinOp(token::Or)) || self.check(&token::OrOr) {
1286 self.parse_closure_expr(attrs).map_err(|mut err| {
1287 // If the input is something like `if a { 1 } else { 2 } | if a { 3 } else { 4 }`
1288 // then suggest parens around the lhs.
1289 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
1290 self.sess.expr_parentheses_needed(&mut err, *sp);
1294 } else if self.check(&token::OpenDelim(token::Bracket)) {
1295 self.parse_array_or_repeat_expr(attrs, token::Bracket)
1296 } else if self.check_path() {
1297 self.parse_path_start_expr(attrs)
1298 } else if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
1299 self.parse_closure_expr(attrs)
1300 } else if self.eat_keyword(kw::If) {
1301 self.parse_if_expr(attrs)
1302 } else if self.check_keyword(kw::For) {
1303 if self.choose_generics_over_qpath(1) {
1304 // NOTE(Centril, eddyb): DO NOT REMOVE! Beyond providing parser recovery,
1305 // this is an insurance policy in case we allow qpaths in (tuple-)struct patterns.
1306 // When `for <Foo as Bar>::Proj in $expr $block` is wanted,
1307 // you can disambiguate in favor of a pattern with `(...)`.
1308 self.recover_quantified_closure_expr(attrs)
1310 assert!(self.eat_keyword(kw::For));
1311 self.parse_for_expr(None, self.prev_token.span, attrs)
1313 } else if self.eat_keyword(kw::While) {
1314 self.parse_while_expr(None, self.prev_token.span, attrs)
1315 } else if let Some(label) = self.eat_label() {
1316 self.parse_labeled_expr(label, attrs, true)
1317 } else if self.eat_keyword(kw::Loop) {
1318 let sp = self.prev_token.span;
1319 self.parse_loop_expr(None, self.prev_token.span, attrs).map_err(|mut err| {
1320 err.span_label(sp, "while parsing this `loop` expression");
1323 } else if self.eat_keyword(kw::Continue) {
1324 let kind = ExprKind::Continue(self.eat_label());
1325 Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
1326 } else if self.eat_keyword(kw::Match) {
1327 let match_sp = self.prev_token.span;
1328 self.parse_match_expr(attrs).map_err(|mut err| {
1329 err.span_label(match_sp, "while parsing this `match` expression");
1332 } else if self.eat_keyword(kw::Unsafe) {
1333 let sp = self.prev_token.span;
1334 self.parse_block_expr(None, lo, BlockCheckMode::Unsafe(ast::UserProvided), attrs)
1335 .map_err(|mut err| {
1336 err.span_label(sp, "while parsing this `unsafe` expression");
1339 } else if self.check_inline_const(0) {
1340 self.parse_const_block(lo.to(self.token.span), false)
1341 } else if self.is_do_catch_block() {
1342 self.recover_do_catch(attrs)
1343 } else if self.is_try_block() {
1344 self.expect_keyword(kw::Try)?;
1345 self.parse_try_block(lo, attrs)
1346 } else if self.eat_keyword(kw::Return) {
1347 self.parse_return_expr(attrs)
1348 } else if self.eat_keyword(kw::Break) {
1349 self.parse_break_expr(attrs)
1350 } else if self.eat_keyword(kw::Yield) {
1351 self.parse_yield_expr(attrs)
1352 } else if self.eat_keyword(kw::Let) {
1353 self.parse_let_expr(attrs)
1354 } else if self.eat_keyword(kw::Underscore) {
1355 Ok(self.mk_expr(self.prev_token.span, ExprKind::Underscore, attrs))
1356 } else if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
1357 // Don't complain about bare semicolons after unclosed braces
1358 // recovery in order to keep the error count down. Fixing the
1359 // delimiters will possibly also fix the bare semicolon found in
1360 // expression context. For example, silence the following error:
1362 // error: expected expression, found `;`
1366 // | ^ expected expression
1368 Ok(self.mk_expr_err(self.token.span))
1369 } else if self.token.uninterpolated_span().rust_2018() {
1370 // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
1371 if self.check_keyword(kw::Async) {
1372 if self.is_async_block() {
1373 // Check for `async {` and `async move {`.
1374 self.parse_async_block(attrs)
1376 self.parse_closure_expr(attrs)
1378 } else if self.eat_keyword(kw::Await) {
1379 self.recover_incorrect_await_syntax(lo, self.prev_token.span, attrs)
1381 self.parse_lit_expr(attrs)
1384 self.parse_lit_expr(attrs)
1388 fn parse_lit_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1389 let lo = self.token.span;
1390 match self.parse_opt_lit() {
1392 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Lit(literal), attrs);
1393 self.maybe_recover_from_bad_qpath(expr, true)
1395 None => self.try_macro_suggestion(),
1399 fn parse_tuple_parens_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1400 let lo = self.token.span;
1401 self.expect(&token::OpenDelim(token::Paren))?;
1402 let (es, trailing_comma) = match self.parse_seq_to_end(
1403 &token::CloseDelim(token::Paren),
1404 SeqSep::trailing_allowed(token::Comma),
1405 |p| p.parse_expr_catch_underscore(),
1408 Err(err) => return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err))),
1410 let kind = if es.len() == 1 && !trailing_comma {
1411 // `(e)` is parenthesized `e`.
1412 ExprKind::Paren(es.into_iter().next().unwrap())
1414 // `(e,)` is a tuple with only one field, `e`.
1417 let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
1418 self.maybe_recover_from_bad_qpath(expr, true)
1421 fn parse_array_or_repeat_expr(
1424 close_delim: token::DelimToken,
1425 ) -> PResult<'a, P<Expr>> {
1426 let lo = self.token.span;
1427 self.bump(); // `[` or other open delim
1429 let close = &token::CloseDelim(close_delim);
1430 let kind = if self.eat(close) {
1432 ExprKind::Array(Vec::new())
1435 let first_expr = self.parse_expr()?;
1436 if self.eat(&token::Semi) {
1437 // Repeating array syntax: `[ 0; 512 ]`
1438 let count = self.parse_anon_const_expr()?;
1439 self.expect(close)?;
1440 ExprKind::Repeat(first_expr, count)
1441 } else if self.eat(&token::Comma) {
1442 // Vector with two or more elements.
1443 let sep = SeqSep::trailing_allowed(token::Comma);
1444 let (remaining_exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
1445 let mut exprs = vec![first_expr];
1446 exprs.extend(remaining_exprs);
1447 ExprKind::Array(exprs)
1449 // Vector with one element
1450 self.expect(close)?;
1451 ExprKind::Array(vec![first_expr])
1454 let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
1455 self.maybe_recover_from_bad_qpath(expr, true)
1458 fn parse_path_start_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1459 let (qself, path) = if self.eat_lt() {
1460 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
1463 (None, self.parse_path(PathStyle::Expr)?)
1467 // `!`, as an operator, is prefix, so we know this isn't that.
1468 let (hi, kind) = if self.eat(&token::Not) {
1469 // MACRO INVOCATION expression
1470 if qself.is_some() {
1471 self.struct_span_err(path.span, "macros cannot use qualified paths").emit();
1475 args: self.parse_mac_args()?,
1476 prior_type_ascription: self.last_type_ascription,
1478 (self.prev_token.span, ExprKind::MacCall(mac))
1479 } else if self.check(&token::OpenDelim(token::Brace)) {
1480 if let Some(expr) = self.maybe_parse_struct_expr(qself.as_ref(), &path, &attrs) {
1481 if qself.is_some() {
1482 self.sess.gated_spans.gate(sym::more_qualified_paths, path.span);
1486 (path.span, ExprKind::Path(qself, path))
1489 (path.span, ExprKind::Path(qself, path))
1492 let expr = self.mk_expr(lo.to(hi), kind, attrs);
1493 self.maybe_recover_from_bad_qpath(expr, true)
1496 /// Parse `'label: $expr`. The label is already parsed.
1497 fn parse_labeled_expr(
1501 mut consume_colon: bool,
1502 ) -> PResult<'a, P<Expr>> {
1503 let lo = label.ident.span;
1504 let label = Some(label);
1505 let ate_colon = self.eat(&token::Colon);
1506 let expr = if self.eat_keyword(kw::While) {
1507 self.parse_while_expr(label, lo, attrs)
1508 } else if self.eat_keyword(kw::For) {
1509 self.parse_for_expr(label, lo, attrs)
1510 } else if self.eat_keyword(kw::Loop) {
1511 self.parse_loop_expr(label, lo, attrs)
1512 } else if self.check(&token::OpenDelim(token::Brace)) || self.token.is_whole_block() {
1513 self.parse_block_expr(label, lo, BlockCheckMode::Default, attrs)
1514 } else if !ate_colon && (self.check(&TokenKind::Comma) || self.check(&TokenKind::Gt)) {
1515 // We're probably inside of a `Path<'a>` that needs a turbofish
1516 let msg = "expected `while`, `for`, `loop` or `{` after a label";
1517 self.struct_span_err(self.token.span, msg).span_label(self.token.span, msg).emit();
1518 consume_colon = false;
1519 Ok(self.mk_expr_err(lo))
1521 let msg = "expected `while`, `for`, `loop` or `{` after a label";
1522 self.struct_span_err(self.token.span, msg).span_label(self.token.span, msg).emit();
1523 // Continue as an expression in an effort to recover on `'label: non_block_expr`.
1527 if !ate_colon && consume_colon {
1528 self.error_labeled_expr_must_be_followed_by_colon(lo, expr.span);
1534 fn error_labeled_expr_must_be_followed_by_colon(&self, lo: Span, span: Span) {
1535 self.struct_span_err(span, "labeled expression must be followed by `:`")
1536 .span_label(lo, "the label")
1537 .span_suggestion_short(
1539 "add `:` after the label",
1541 Applicability::MachineApplicable,
1543 .note("labels are used before loops and blocks, allowing e.g., `break 'label` to them")
1547 /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
1548 fn recover_do_catch(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1549 let lo = self.token.span;
1551 self.bump(); // `do`
1552 self.bump(); // `catch`
1554 let span_dc = lo.to(self.prev_token.span);
1555 self.struct_span_err(span_dc, "found removed `do catch` syntax")
1558 "replace with the new syntax",
1560 Applicability::MachineApplicable,
1562 .note("following RFC #2388, the new non-placeholder syntax is `try`")
1565 self.parse_try_block(lo, attrs)
1568 /// Parse an expression if the token can begin one.
1569 fn parse_expr_opt(&mut self) -> PResult<'a, Option<P<Expr>>> {
1570 Ok(if self.token.can_begin_expr() { Some(self.parse_expr()?) } else { None })
1573 /// Parse `"return" expr?`.
1574 fn parse_return_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1575 let lo = self.prev_token.span;
1576 let kind = ExprKind::Ret(self.parse_expr_opt()?);
1577 let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
1578 self.maybe_recover_from_bad_qpath(expr, true)
1581 /// Parse `"break" (('label (:? expr)?) | expr?)` with `"break"` token already eaten.
1582 /// If the label is followed immediately by a `:` token, the label and `:` are
1583 /// parsed as part of the expression (i.e. a labeled loop). The language team has
1584 /// decided in #87026 to require parentheses as a visual aid to avoid confusion if
1585 /// the break expression of an unlabeled break is a labeled loop (as in
1586 /// `break 'lbl: loop {}`); a labeled break with an unlabeled loop as its value
1587 /// expression only gets a warning for compatibility reasons; and a labeled break
1588 /// with a labeled loop does not even get a warning because there is no ambiguity.
1589 fn parse_break_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1590 let lo = self.prev_token.span;
1591 let mut label = self.eat_label();
1592 let kind = if label.is_some() && self.token == token::Colon {
1593 // The value expression can be a labeled loop, see issue #86948, e.g.:
1594 // `loop { break 'label: loop { break 'label 42; }; }`
1595 let lexpr = self.parse_labeled_expr(label.take().unwrap(), AttrVec::new(), true)?;
1596 self.struct_span_err(
1598 "parentheses are required around this expression to avoid confusion with a labeled break expression",
1600 .multipart_suggestion(
1601 "wrap the expression in parentheses",
1603 (lexpr.span.shrink_to_lo(), "(".to_string()),
1604 (lexpr.span.shrink_to_hi(), ")".to_string()),
1606 Applicability::MachineApplicable,
1610 } else if self.token != token::OpenDelim(token::Brace)
1611 || !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1613 let expr = self.parse_expr_opt()?;
1614 if let Some(ref expr) = expr {
1618 ExprKind::While(_, _, None)
1619 | ExprKind::ForLoop(_, _, _, None)
1620 | ExprKind::Loop(_, None)
1621 | ExprKind::Block(_, None)
1624 self.sess.buffer_lint_with_diagnostic(
1625 BREAK_WITH_LABEL_AND_LOOP,
1628 "this labeled break expression is easy to confuse with an unlabeled break with a labeled value expression",
1629 BuiltinLintDiagnostics::BreakWithLabelAndLoop(expr.span),
1637 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Break(label, kind), attrs);
1638 self.maybe_recover_from_bad_qpath(expr, true)
1641 /// Parse `"yield" expr?`.
1642 fn parse_yield_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1643 let lo = self.prev_token.span;
1644 let kind = ExprKind::Yield(self.parse_expr_opt()?);
1645 let span = lo.to(self.prev_token.span);
1646 self.sess.gated_spans.gate(sym::generators, span);
1647 let expr = self.mk_expr(span, kind, attrs);
1648 self.maybe_recover_from_bad_qpath(expr, true)
1651 /// Returns a string literal if the next token is a string literal.
1652 /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
1653 /// and returns `None` if the next token is not literal at all.
1654 pub fn parse_str_lit(&mut self) -> Result<ast::StrLit, Option<Lit>> {
1655 match self.parse_opt_lit() {
1656 Some(lit) => match lit.kind {
1657 ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
1659 symbol: lit.token.symbol,
1660 suffix: lit.token.suffix,
1664 _ => Err(Some(lit)),
1670 pub(super) fn parse_lit(&mut self) -> PResult<'a, Lit> {
1671 self.parse_opt_lit().ok_or_else(|| {
1672 if let token::Interpolated(inner) = &self.token.kind {
1673 let expr = match inner.as_ref() {
1674 token::NtExpr(expr) => Some(expr),
1675 token::NtLiteral(expr) => Some(expr),
1678 if let Some(expr) = expr {
1679 if matches!(expr.kind, ExprKind::Err) {
1682 .struct_span_err(self.token.span, &"invalid interpolated expression");
1683 err.downgrade_to_delayed_bug();
1688 let msg = format!("unexpected token: {}", super::token_descr(&self.token));
1689 self.struct_span_err(self.token.span, &msg)
1693 /// Matches `lit = true | false | token_lit`.
1694 /// Returns `None` if the next token is not a literal.
1695 pub(super) fn parse_opt_lit(&mut self) -> Option<Lit> {
1696 let mut recovered = None;
1697 if self.token == token::Dot {
1698 // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
1699 // dot would follow an optional literal, so we do this unconditionally.
1700 recovered = self.look_ahead(1, |next_token| {
1701 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
1704 if self.token.span.hi() == next_token.span.lo() {
1705 let s = String::from("0.") + symbol.as_str();
1706 let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
1707 return Some(Token::new(kind, self.token.span.to(next_token.span)));
1712 if let Some(token) = &recovered {
1714 self.error_float_lits_must_have_int_part(&token);
1718 let token = recovered.as_ref().unwrap_or(&self.token);
1719 match Lit::from_token(token) {
1724 Err(LitError::NotLiteral) => None,
1726 let span = token.span;
1727 let token::Literal(lit) = token.kind else {
1731 self.report_lit_error(err, lit, span);
1732 // Pack possible quotes and prefixes from the original literal into
1733 // the error literal's symbol so they can be pretty-printed faithfully.
1734 let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
1735 let symbol = Symbol::intern(&suffixless_lit.to_string());
1736 let lit = token::Lit::new(token::Err, symbol, lit.suffix);
1737 Some(Lit::from_lit_token(lit, span).unwrap_or_else(|_| unreachable!()))
1742 fn error_float_lits_must_have_int_part(&self, token: &Token) {
1743 self.struct_span_err(token.span, "float literals must have an integer part")
1746 "must have an integer part",
1747 pprust::token_to_string(token).into(),
1748 Applicability::MachineApplicable,
1753 fn report_lit_error(&self, err: LitError, lit: token::Lit, span: Span) {
1754 // Checks if `s` looks like i32 or u1234 etc.
1755 fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
1756 s.len() > 1 && s.starts_with(first_chars) && s[1..].chars().all(|c| c.is_ascii_digit())
1759 // Try to lowercase the prefix if it's a valid base prefix.
1760 fn fix_base_capitalisation(s: &str) -> Option<String> {
1761 if let Some(stripped) = s.strip_prefix('B') {
1762 Some(format!("0b{stripped}"))
1763 } else if let Some(stripped) = s.strip_prefix('O') {
1764 Some(format!("0o{stripped}"))
1765 } else if let Some(stripped) = s.strip_prefix('X') {
1766 Some(format!("0x{stripped}"))
1772 let token::Lit { kind, suffix, .. } = lit;
1774 // `NotLiteral` is not an error by itself, so we don't report
1775 // it and give the parser opportunity to try something else.
1776 LitError::NotLiteral => {}
1777 // `LexerError` *is* an error, but it was already reported
1778 // by lexer, so here we don't report it the second time.
1779 LitError::LexerError => {}
1780 LitError::InvalidSuffix => {
1781 self.expect_no_suffix(
1783 &format!("{} {} literal", kind.article(), kind.descr()),
1787 LitError::InvalidIntSuffix => {
1788 let suf = suffix.expect("suffix error with no suffix");
1789 let suf = suf.as_str();
1790 if looks_like_width_suffix(&['i', 'u'], &suf) {
1791 // If it looks like a width, try to be helpful.
1792 let msg = format!("invalid width `{}` for integer literal", &suf[1..]);
1793 self.struct_span_err(span, &msg)
1794 .help("valid widths are 8, 16, 32, 64 and 128")
1796 } else if let Some(fixed) = fix_base_capitalisation(suf) {
1797 let msg = "invalid base prefix for number literal";
1799 self.struct_span_err(span, &msg)
1800 .note("base prefixes (`0xff`, `0b1010`, `0o755`) are lowercase")
1803 "try making the prefix lowercase",
1805 Applicability::MaybeIncorrect,
1809 let msg = format!("invalid suffix `{suf}` for number literal");
1810 self.struct_span_err(span, &msg)
1811 .span_label(span, format!("invalid suffix `{suf}`"))
1812 .help("the suffix must be one of the numeric types (`u32`, `isize`, `f32`, etc.)")
1816 LitError::InvalidFloatSuffix => {
1817 let suf = suffix.expect("suffix error with no suffix");
1818 let suf = suf.as_str();
1819 if looks_like_width_suffix(&['f'], suf) {
1820 // If it looks like a width, try to be helpful.
1821 let msg = format!("invalid width `{}` for float literal", &suf[1..]);
1822 self.struct_span_err(span, &msg).help("valid widths are 32 and 64").emit();
1824 let msg = format!("invalid suffix `{suf}` for float literal");
1825 self.struct_span_err(span, &msg)
1826 .span_label(span, format!("invalid suffix `{suf}`"))
1827 .help("valid suffixes are `f32` and `f64`")
1831 LitError::NonDecimalFloat(base) => {
1832 let descr = match base {
1833 16 => "hexadecimal",
1836 _ => unreachable!(),
1838 self.struct_span_err(span, &format!("{descr} float literal is not supported"))
1839 .span_label(span, "not supported")
1842 LitError::IntTooLarge => {
1843 self.struct_span_err(span, "integer literal is too large").emit();
1848 pub(super) fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<Symbol>) {
1849 if let Some(suf) = suffix {
1850 let mut err = if kind == "a tuple index"
1851 && [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suf)
1853 // #59553: warn instead of reject out of hand to allow the fix to percolate
1854 // through the ecosystem when people fix their macros
1858 .struct_span_warn(sp, &format!("suffixes on {kind} are invalid"));
1860 "`{}` is *temporarily* accepted on tuple index fields as it was \
1861 incorrectly accepted on stable for a few releases",
1865 "on proc macros, you'll want to use `syn::Index::from` or \
1866 `proc_macro::Literal::*_unsuffixed` for code that will desugar \
1867 to tuple field access",
1870 "see issue #60210 <https://github.com/rust-lang/rust/issues/60210> \
1871 for more information",
1875 self.struct_span_err(sp, &format!("suffixes on {kind} are invalid"))
1878 err.span_label(sp, format!("invalid suffix `{suf}`"));
1883 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1884 /// Keep this in sync with `Token::can_begin_literal_maybe_minus`.
1885 pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1886 maybe_whole_expr!(self);
1888 let lo = self.token.span;
1889 let minus_present = self.eat(&token::BinOp(token::Minus));
1890 let lit = self.parse_lit()?;
1891 let expr = self.mk_expr(lit.span, ExprKind::Lit(lit), AttrVec::new());
1895 lo.to(self.prev_token.span),
1896 self.mk_unary(UnOp::Neg, expr),
1904 fn is_array_like_block(&mut self) -> bool {
1905 self.look_ahead(1, |t| matches!(t.kind, TokenKind::Ident(..) | TokenKind::Literal(_)))
1906 && self.look_ahead(2, |t| t == &token::Comma)
1907 && self.look_ahead(3, |t| t.can_begin_expr())
1910 /// Emits a suggestion if it looks like the user meant an array but
1911 /// accidentally used braces, causing the code to be interpreted as a block
1913 fn maybe_suggest_brackets_instead_of_braces(
1917 ) -> Option<P<Expr>> {
1918 let mut snapshot = self.create_snapshot_for_diagnostic();
1919 match snapshot.parse_array_or_repeat_expr(attrs, token::Brace) {
1921 let hi = snapshot.prev_token.span;
1922 self.struct_span_err(
1924 "this code is interpreted as a block expression, not an array",
1926 .multipart_suggestion(
1927 "try using [] instead of {}",
1928 vec![(lo, "[".to_owned()), (hi, "]".to_owned())],
1929 Applicability::MaybeIncorrect,
1931 .note("to define an array, one would use square brackets instead of curly braces")
1934 self.restore_snapshot(snapshot);
1935 Some(self.mk_expr_err(arr.span))
1944 /// Parses a block or unsafe block.
1945 pub(super) fn parse_block_expr(
1947 opt_label: Option<Label>,
1949 blk_mode: BlockCheckMode,
1951 ) -> PResult<'a, P<Expr>> {
1952 if self.is_array_like_block() {
1953 if let Some(arr) = self.maybe_suggest_brackets_instead_of_braces(lo, attrs.clone()) {
1958 if let Some(label) = opt_label {
1959 self.sess.gated_spans.gate(sym::label_break_value, label.ident.span);
1962 if self.token.is_whole_block() {
1963 self.struct_span_err(self.token.span, "cannot use a `block` macro fragment here")
1964 .span_label(lo.to(self.token.span), "the `block` fragment is within this context")
1968 let (inner_attrs, blk) = self.parse_block_common(lo, blk_mode)?;
1969 attrs.extend(inner_attrs);
1970 Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs))
1973 /// Recover on an explicitly quantified closure expression, e.g., `for<'a> |x: &'a u8| *x + 1`.
1974 fn recover_quantified_closure_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1975 let lo = self.token.span;
1976 let _ = self.parse_late_bound_lifetime_defs()?;
1977 let span_for = lo.to(self.prev_token.span);
1978 let closure = self.parse_closure_expr(attrs)?;
1980 self.struct_span_err(span_for, "cannot introduce explicit parameters for a closure")
1981 .span_label(closure.span, "the parameters are attached to this closure")
1984 "remove the parameters",
1986 Applicability::MachineApplicable,
1990 Ok(self.mk_expr_err(lo.to(closure.span)))
1993 /// Parses a closure expression (e.g., `move |args| expr`).
1994 fn parse_closure_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1995 let lo = self.token.span;
1998 if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
2000 let asyncness = if self.token.uninterpolated_span().rust_2018() {
2001 self.parse_asyncness()
2006 let capture_clause = self.parse_capture_clause()?;
2007 let decl = self.parse_fn_block_decl()?;
2008 let decl_hi = self.prev_token.span;
2009 let mut body = match decl.output {
2010 FnRetTy::Default(_) => {
2011 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
2012 self.parse_expr_res(restrictions, None)?
2015 // If an explicit return type is given, require a block to appear (RFC 968).
2016 let body_lo = self.token.span;
2017 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, AttrVec::new())?
2021 if let Async::Yes { span, .. } = asyncness {
2022 // Feature-gate `async ||` closures.
2023 self.sess.gated_spans.gate(sym::async_closure, span);
2026 if self.token.kind == TokenKind::Semi && self.token_cursor.frame.delim == DelimToken::Paren
2028 // It is likely that the closure body is a block but where the
2029 // braces have been removed. We will recover and eat the next
2030 // statements later in the parsing process.
2031 body = self.mk_expr_err(body.span);
2034 let body_span = body.span;
2036 let closure = self.mk_expr(
2038 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
2042 // Disable recovery for closure body
2044 ClosureSpans { whole_closure: closure.span, closing_pipe: decl_hi, body: body_span };
2045 self.current_closure = Some(spans);
2050 /// Parses an optional `move` prefix to a closure-like construct.
2051 fn parse_capture_clause(&mut self) -> PResult<'a, CaptureBy> {
2052 if self.eat_keyword(kw::Move) {
2053 // Check for `move async` and recover
2054 if self.check_keyword(kw::Async) {
2055 let move_async_span = self.token.span.with_lo(self.prev_token.span.data().lo);
2056 Err(self.incorrect_move_async_order_found(move_async_span))
2058 Ok(CaptureBy::Value)
2065 /// Parses the `|arg, arg|` header of a closure.
2066 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
2067 let inputs = if self.eat(&token::OrOr) {
2070 self.expect(&token::BinOp(token::Or))?;
2072 .parse_seq_to_before_tokens(
2073 &[&token::BinOp(token::Or), &token::OrOr],
2074 SeqSep::trailing_allowed(token::Comma),
2075 TokenExpectType::NoExpect,
2076 |p| p.parse_fn_block_param(),
2083 self.parse_ret_ty(AllowPlus::Yes, RecoverQPath::Yes, RecoverReturnSign::Yes)?;
2085 Ok(P(FnDecl { inputs, output }))
2088 /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
2089 fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
2090 let lo = self.token.span;
2091 let attrs = self.parse_outer_attributes()?;
2092 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2093 let pat = this.parse_pat_no_top_alt(PARAM_EXPECTED)?;
2094 let ty = if this.eat(&token::Colon) {
2097 this.mk_ty(this.prev_token.span, TyKind::Infer)
2102 attrs: attrs.into(),
2105 span: lo.to(this.token.span),
2107 is_placeholder: false,
2109 TrailingToken::MaybeComma,
2114 /// Parses an `if` expression (`if` token already eaten).
2115 fn parse_if_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
2116 let lo = self.prev_token.span;
2117 let cond = self.parse_cond_expr()?;
2119 let missing_then_block_binop_span = || {
2121 ExprKind::Binary(Spanned { span: binop_span, .. }, _, ref right)
2122 if let ExprKind::Block(..) = right.kind => Some(binop_span),
2127 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
2128 // verify that the last statement is either an implicit return (no `;`) or an explicit
2129 // return. This won't catch blocks with an explicit `return`, but that would be caught by
2130 // the dead code lint.
2131 let thn = if self.token.is_keyword(kw::Else) || !cond.returns() {
2132 if let Some(binop_span) = missing_then_block_binop_span() {
2133 self.error_missing_if_then_block(lo, None, Some(binop_span)).emit();
2134 self.mk_block_err(cond.span)
2136 self.error_missing_if_cond(lo, cond.span)
2139 let attrs = self.parse_outer_attributes()?.take_for_recovery(); // For recovery.
2140 let not_block = self.token != token::OpenDelim(token::Brace);
2141 let block = self.parse_block().map_err(|err| {
2143 self.error_missing_if_then_block(lo, Some(err), missing_then_block_binop_span())
2148 self.error_on_if_block_attrs(lo, false, block.span, &attrs);
2151 let els = if self.eat_keyword(kw::Else) { Some(self.parse_else_expr()?) } else { None };
2152 Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::If(cond, thn, els), attrs))
2155 fn error_missing_if_then_block(
2158 err: Option<DiagnosticBuilder<'a, ErrorGuaranteed>>,
2159 binop_span: Option<Span>,
2160 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
2161 let msg = "this `if` expression has a condition, but no block";
2163 let mut err = if let Some(mut err) = err {
2164 err.span_label(if_span, msg);
2167 self.struct_span_err(if_span, msg)
2170 if let Some(binop_span) = binop_span {
2171 err.span_help(binop_span, "maybe you forgot the right operand of the condition?");
2177 fn error_missing_if_cond(&self, lo: Span, span: Span) -> P<ast::Block> {
2178 let sp = self.sess.source_map().next_point(lo);
2179 self.struct_span_err(sp, "missing condition for `if` expression")
2180 .span_label(sp, "expected if condition here")
2182 self.mk_block_err(span)
2185 /// Parses the condition of a `if` or `while` expression.
2186 fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
2187 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2189 if let ExprKind::Let(..) = cond.kind {
2190 // Remove the last feature gating of a `let` expression since it's stable.
2191 self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
2197 /// Parses a `let $pat = $expr` pseudo-expression.
2198 /// The `let` token has already been eaten.
2199 fn parse_let_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
2200 let lo = self.prev_token.span;
2201 let pat = self.parse_pat_allow_top_alt(
2205 CommaRecoveryMode::LikelyTuple,
2207 self.expect(&token::Eq)?;
2208 let expr = self.with_res(self.restrictions | Restrictions::NO_STRUCT_LITERAL, |this| {
2209 this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
2211 let span = lo.to(expr.span);
2212 self.sess.gated_spans.gate(sym::let_chains, span);
2213 Ok(self.mk_expr(span, ExprKind::Let(pat, expr, span), attrs))
2216 /// Parses an `else { ... }` expression (`else` token already eaten).
2217 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
2218 let ctx_span = self.prev_token.span; // `else`
2219 let attrs = self.parse_outer_attributes()?.take_for_recovery(); // For recovery.
2220 let expr = if self.eat_keyword(kw::If) {
2221 self.parse_if_expr(AttrVec::new())?
2223 let blk = self.parse_block()?;
2224 self.mk_expr(blk.span, ExprKind::Block(blk, None), AttrVec::new())
2226 self.error_on_if_block_attrs(ctx_span, true, expr.span, &attrs);
2230 fn error_on_if_block_attrs(
2235 attrs: &[ast::Attribute],
2237 let (span, last) = match attrs {
2239 [x0 @ xn] | [x0, .., xn] => (x0.span.to(xn.span), xn.span),
2241 let ctx = if is_ctx_else { "else" } else { "if" };
2242 self.struct_span_err(last, "outer attributes are not allowed on `if` and `else` branches")
2243 .span_label(branch_span, "the attributes are attached to this branch")
2244 .span_label(ctx_span, format!("the branch belongs to this `{ctx}`"))
2247 "remove the attributes",
2249 Applicability::MachineApplicable,
2254 /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
2257 opt_label: Option<Label>,
2260 ) -> PResult<'a, P<Expr>> {
2261 // Record whether we are about to parse `for (`.
2262 // This is used below for recovery in case of `for ( $stuff ) $block`
2263 // in which case we will suggest `for $stuff $block`.
2264 let begin_paren = match self.token.kind {
2265 token::OpenDelim(token::Paren) => Some(self.token.span),
2269 let pat = self.parse_pat_allow_top_alt(
2273 CommaRecoveryMode::LikelyTuple,
2275 if !self.eat_keyword(kw::In) {
2276 self.error_missing_in_for_loop();
2278 self.check_for_for_in_in_typo(self.prev_token.span);
2279 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2281 let pat = self.recover_parens_around_for_head(pat, begin_paren);
2283 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
2284 attrs.extend(iattrs);
2286 let kind = ExprKind::ForLoop(pat, expr, loop_block, opt_label);
2287 Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
2290 fn error_missing_in_for_loop(&mut self) {
2291 let (span, msg, sugg) = if self.token.is_ident_named(sym::of) {
2292 // Possibly using JS syntax (#75311).
2293 let span = self.token.span;
2295 (span, "try using `in` here instead", "in")
2297 (self.prev_token.span.between(self.token.span), "try adding `in` here", " in ")
2299 self.struct_span_err(span, "missing `in` in `for` loop")
2300 .span_suggestion_short(
2304 // Has been misleading, at least in the past (closed Issue #48492).
2305 Applicability::MaybeIncorrect,
2310 /// Parses a `while` or `while let` expression (`while` token already eaten).
2311 fn parse_while_expr(
2313 opt_label: Option<Label>,
2316 ) -> PResult<'a, P<Expr>> {
2317 let cond = self.parse_cond_expr().map_err(|mut err| {
2318 err.span_label(lo, "while parsing the condition of this `while` expression");
2321 let (iattrs, body) = self.parse_inner_attrs_and_block().map_err(|mut err| {
2322 err.span_label(lo, "while parsing the body of this `while` expression");
2323 err.span_label(cond.span, "this `while` condition successfully parsed");
2326 attrs.extend(iattrs);
2327 Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::While(cond, body, opt_label), attrs))
2330 /// Parses `loop { ... }` (`loop` token already eaten).
2333 opt_label: Option<Label>,
2336 ) -> PResult<'a, P<Expr>> {
2337 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
2338 attrs.extend(iattrs);
2339 Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::Loop(body, opt_label), attrs))
2342 crate fn eat_label(&mut self) -> Option<Label> {
2343 self.token.lifetime().map(|ident| {
2349 /// Parses a `match ... { ... }` expression (`match` token already eaten).
2350 fn parse_match_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
2351 let match_span = self.prev_token.span;
2352 let lo = self.prev_token.span;
2353 let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2354 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
2355 if self.token == token::Semi {
2356 e.span_suggestion_short(
2358 "try removing this `match`",
2360 Applicability::MaybeIncorrect, // speculative
2363 if self.maybe_recover_unexpected_block_label() {
2370 attrs.extend(self.parse_inner_attributes()?);
2372 let mut arms: Vec<Arm> = Vec::new();
2373 while self.token != token::CloseDelim(token::Brace) {
2374 match self.parse_arm() {
2375 Ok(arm) => arms.push(arm),
2377 // Recover by skipping to the end of the block.
2379 self.recover_stmt();
2380 let span = lo.to(self.token.span);
2381 if self.token == token::CloseDelim(token::Brace) {
2384 return Ok(self.mk_expr(span, ExprKind::Match(scrutinee, arms), attrs));
2388 let hi = self.token.span;
2390 Ok(self.mk_expr(lo.to(hi), ExprKind::Match(scrutinee, arms), attrs))
2393 /// Attempt to recover from match arm body with statements and no surrounding braces.
2394 fn parse_arm_body_missing_braces(
2396 first_expr: &P<Expr>,
2398 ) -> Option<P<Expr>> {
2399 if self.token.kind != token::Semi {
2402 let start_snapshot = self.create_snapshot_for_diagnostic();
2403 let semi_sp = self.token.span;
2406 vec![self.mk_stmt(first_expr.span, ast::StmtKind::Expr(first_expr.clone()))];
2407 let err = |this: &mut Parser<'_>, stmts: Vec<ast::Stmt>| {
2408 let span = stmts[0].span.to(stmts[stmts.len() - 1].span);
2409 let mut err = this.struct_span_err(span, "`match` arm body without braces");
2410 let (these, s, are) =
2411 if stmts.len() > 1 { ("these", "s", "are") } else { ("this", "", "is") };
2415 "{these} statement{s} {are} not surrounded by a body",
2421 err.span_label(arrow_span, "while parsing the `match` arm starting here");
2422 if stmts.len() > 1 {
2423 err.multipart_suggestion(
2424 &format!("surround the statement{s} with a body"),
2426 (span.shrink_to_lo(), "{ ".to_string()),
2427 (span.shrink_to_hi(), " }".to_string()),
2429 Applicability::MachineApplicable,
2432 err.span_suggestion(
2434 "use a comma to end a `match` arm expression",
2436 Applicability::MachineApplicable,
2440 this.mk_expr_err(span)
2442 // We might have either a `,` -> `;` typo, or a block without braces. We need
2443 // a more subtle parsing strategy.
2445 if self.token.kind == token::CloseDelim(token::Brace) {
2446 // We have reached the closing brace of the `match` expression.
2447 return Some(err(self, stmts));
2449 if self.token.kind == token::Comma {
2450 self.restore_snapshot(start_snapshot);
2453 let pre_pat_snapshot = self.create_snapshot_for_diagnostic();
2454 match self.parse_pat_no_top_alt(None) {
2456 if self.token.kind == token::FatArrow {
2458 self.restore_snapshot(pre_pat_snapshot);
2459 return Some(err(self, stmts));
2467 self.restore_snapshot(pre_pat_snapshot);
2468 match self.parse_stmt_without_recovery(true, ForceCollect::No) {
2469 // Consume statements for as long as possible.
2474 self.restore_snapshot(start_snapshot);
2477 // We couldn't parse either yet another statement missing it's
2478 // enclosing block nor the next arm's pattern or closing brace.
2481 self.restore_snapshot(start_snapshot);
2489 pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
2490 fn check_let_expr(expr: &Expr) -> (bool, bool) {
2492 ExprKind::Binary(_, ref lhs, ref rhs) => {
2493 let lhs_rslt = check_let_expr(lhs);
2494 let rhs_rslt = check_let_expr(rhs);
2495 (lhs_rslt.0 || rhs_rslt.0, false)
2497 ExprKind::Let(..) => (true, true),
2501 let attrs = self.parse_outer_attributes()?;
2502 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2503 let lo = this.token.span;
2504 let pat = this.parse_pat_allow_top_alt(
2508 CommaRecoveryMode::EitherTupleOrPipe,
2510 let guard = if this.eat_keyword(kw::If) {
2511 let if_span = this.prev_token.span;
2512 let cond = this.parse_expr()?;
2513 let (has_let_expr, does_not_have_bin_op) = check_let_expr(&cond);
2515 if does_not_have_bin_op {
2516 // Remove the last feature gating of a `let` expression since it's stable.
2517 this.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
2519 let span = if_span.to(cond.span);
2520 this.sess.gated_spans.gate(sym::if_let_guard, span);
2526 let arrow_span = this.token.span;
2527 if let Err(mut err) = this.expect(&token::FatArrow) {
2528 // We might have a `=>` -> `=` or `->` typo (issue #89396).
2529 if TokenKind::FatArrow
2531 .map_or(false, |similar_tokens| similar_tokens.contains(&this.token.kind))
2533 err.span_suggestion(
2535 "try using a fat arrow here",
2537 Applicability::MaybeIncorrect,
2545 let arm_start_span = this.token.span;
2547 let expr = this.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
2548 err.span_label(arrow_span, "while parsing the `match` arm starting here");
2552 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
2553 && this.token != token::CloseDelim(token::Brace);
2555 let hi = this.prev_token.span;
2558 let sm = this.sess.source_map();
2559 if let Some(body) = this.parse_arm_body_missing_braces(&expr, arrow_span) {
2560 let span = body.span;
2563 attrs: attrs.into(),
2569 is_placeholder: false,
2571 TrailingToken::None,
2574 this.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)]).map_err(
2576 match (sm.span_to_lines(expr.span), sm.span_to_lines(arm_start_span)) {
2577 (Ok(ref expr_lines), Ok(ref arm_start_lines))
2578 if arm_start_lines.lines[0].end_col
2579 == expr_lines.lines[0].end_col
2580 && expr_lines.lines.len() == 2
2581 && this.token == token::FatArrow =>
2583 // We check whether there's any trailing code in the parse span,
2584 // if there isn't, we very likely have the following:
2587 // | -- - missing comma
2591 // | - ^^ self.token.span
2593 // | parsed until here as `"y" & X`
2594 err.span_suggestion_short(
2595 arm_start_span.shrink_to_hi(),
2596 "missing a comma here to end this `match` arm",
2598 Applicability::MachineApplicable,
2604 "while parsing the `match` arm starting here",
2612 this.eat(&token::Comma);
2617 attrs: attrs.into(),
2623 is_placeholder: false,
2625 TrailingToken::None,
2630 /// Parses a `try {...}` expression (`try` token already eaten).
2631 fn parse_try_block(&mut self, span_lo: Span, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
2632 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
2633 attrs.extend(iattrs);
2634 if self.eat_keyword(kw::Catch) {
2635 let mut error = self.struct_span_err(
2636 self.prev_token.span,
2637 "keyword `catch` cannot follow a `try` block",
2639 error.help("try using `match` on the result of the `try` block instead");
2643 let span = span_lo.to(body.span);
2644 self.sess.gated_spans.gate(sym::try_blocks, span);
2645 Ok(self.mk_expr(span, ExprKind::TryBlock(body), attrs))
2649 fn is_do_catch_block(&self) -> bool {
2650 self.token.is_keyword(kw::Do)
2651 && self.is_keyword_ahead(1, &[kw::Catch])
2652 && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
2653 && !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
2656 fn is_try_block(&self) -> bool {
2657 self.token.is_keyword(kw::Try)
2658 && self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
2659 && self.token.uninterpolated_span().rust_2018()
2662 /// Parses an `async move? {...}` expression.
2663 fn parse_async_block(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
2664 let lo = self.token.span;
2665 self.expect_keyword(kw::Async)?;
2666 let capture_clause = self.parse_capture_clause()?;
2667 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
2668 attrs.extend(iattrs);
2669 let kind = ExprKind::Async(capture_clause, DUMMY_NODE_ID, body);
2670 Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
2673 fn is_async_block(&self) -> bool {
2674 self.token.is_keyword(kw::Async)
2677 self.is_keyword_ahead(1, &[kw::Move])
2678 && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
2681 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
2685 fn is_certainly_not_a_block(&self) -> bool {
2686 self.look_ahead(1, |t| t.is_ident())
2688 // `{ ident, ` cannot start a block.
2689 self.look_ahead(2, |t| t == &token::Comma)
2690 || self.look_ahead(2, |t| t == &token::Colon)
2692 // `{ ident: token, ` cannot start a block.
2693 self.look_ahead(4, |t| t == &token::Comma) ||
2694 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
2695 self.look_ahead(3, |t| !t.can_begin_type())
2700 fn maybe_parse_struct_expr(
2702 qself: Option<&ast::QSelf>,
2705 ) -> Option<PResult<'a, P<Expr>>> {
2706 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
2707 if struct_allowed || self.is_certainly_not_a_block() {
2708 if let Err(err) = self.expect(&token::OpenDelim(token::Brace)) {
2709 return Some(Err(err));
2711 let expr = self.parse_struct_expr(qself.cloned(), path.clone(), attrs.clone(), true);
2712 if let (Ok(expr), false) = (&expr, struct_allowed) {
2713 // This is a struct literal, but we don't can't accept them here.
2714 self.error_struct_lit_not_allowed_here(path.span, expr.span);
2721 fn error_struct_lit_not_allowed_here(&self, lo: Span, sp: Span) {
2722 self.struct_span_err(sp, "struct literals are not allowed here")
2723 .multipart_suggestion(
2724 "surround the struct literal with parentheses",
2725 vec![(lo.shrink_to_lo(), "(".to_string()), (sp.shrink_to_hi(), ")".to_string())],
2726 Applicability::MachineApplicable,
2731 pub(super) fn parse_struct_fields(
2735 close_delim: token::DelimToken,
2736 ) -> PResult<'a, (Vec<ExprField>, ast::StructRest, bool)> {
2737 let mut fields = Vec::new();
2738 let mut base = ast::StructRest::None;
2739 let mut recover_async = false;
2741 let mut async_block_err = |e: &mut Diagnostic, span: Span| {
2742 recover_async = true;
2743 e.span_label(span, "`async` blocks are only allowed in Rust 2018 or later");
2744 e.help_use_latest_edition();
2747 while self.token != token::CloseDelim(close_delim) {
2748 if self.eat(&token::DotDot) {
2749 let exp_span = self.prev_token.span;
2750 // We permit `.. }` on the left-hand side of a destructuring assignment.
2751 if self.check(&token::CloseDelim(close_delim)) {
2752 base = ast::StructRest::Rest(self.prev_token.span.shrink_to_hi());
2755 match self.parse_expr() {
2756 Ok(e) => base = ast::StructRest::Base(e),
2757 Err(mut e) if recover => {
2759 self.recover_stmt();
2761 Err(e) => return Err(e),
2763 self.recover_struct_comma_after_dotdot(exp_span);
2767 let recovery_field = self.find_struct_error_after_field_looking_code();
2768 let parsed_field = match self.parse_expr_field() {
2771 if pth == kw::Async {
2772 async_block_err(&mut e, pth.span);
2774 e.span_label(pth.span, "while parsing this struct");
2778 // If the next token is a comma, then try to parse
2779 // what comes next as additional fields, rather than
2780 // bailing out until next `}`.
2781 if self.token != token::Comma {
2782 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2783 if self.token != token::Comma {
2791 match self.expect_one_of(&[token::Comma], &[token::CloseDelim(close_delim)]) {
2793 if let Some(f) = parsed_field.or(recovery_field) {
2794 // Only include the field if there's no parse error for the field name.
2799 if pth == kw::Async {
2800 async_block_err(&mut e, pth.span);
2802 e.span_label(pth.span, "while parsing this struct");
2803 if let Some(f) = recovery_field {
2806 self.prev_token.span.shrink_to_hi(),
2807 "try adding a comma",
2809 Applicability::MachineApplicable,
2817 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2818 self.eat(&token::Comma);
2822 Ok((fields, base, recover_async))
2825 /// Precondition: already parsed the '{'.
2826 pub(super) fn parse_struct_expr(
2828 qself: Option<ast::QSelf>,
2832 ) -> PResult<'a, P<Expr>> {
2834 let (fields, base, recover_async) =
2835 self.parse_struct_fields(pth.clone(), recover, token::Brace)?;
2836 let span = lo.to(self.token.span);
2837 self.expect(&token::CloseDelim(token::Brace))?;
2838 let expr = if recover_async {
2841 ExprKind::Struct(P(ast::StructExpr { qself, path: pth, fields, rest: base }))
2843 Ok(self.mk_expr(span, expr, attrs))
2846 /// Use in case of error after field-looking code: `S { foo: () with a }`.
2847 fn find_struct_error_after_field_looking_code(&self) -> Option<ExprField> {
2848 match self.token.ident() {
2849 Some((ident, is_raw))
2850 if (is_raw || !ident.is_reserved())
2851 && self.look_ahead(1, |t| *t == token::Colon) =>
2853 Some(ast::ExprField {
2855 span: self.token.span,
2856 expr: self.mk_expr_err(self.token.span),
2857 is_shorthand: false,
2858 attrs: AttrVec::new(),
2860 is_placeholder: false,
2867 fn recover_struct_comma_after_dotdot(&mut self, span: Span) {
2868 if self.token != token::Comma {
2871 self.struct_span_err(
2872 span.to(self.prev_token.span),
2873 "cannot use a comma after the base struct",
2875 .span_suggestion_short(
2877 "remove this comma",
2879 Applicability::MachineApplicable,
2881 .note("the base struct must always be the last field")
2883 self.recover_stmt();
2886 /// Parses `ident (COLON expr)?`.
2887 fn parse_expr_field(&mut self) -> PResult<'a, ExprField> {
2888 let attrs = self.parse_outer_attributes()?;
2889 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2890 let lo = this.token.span;
2892 // Check if a colon exists one ahead. This means we're parsing a fieldname.
2893 let is_shorthand = !this.look_ahead(1, |t| t == &token::Colon || t == &token::Eq);
2894 let (ident, expr) = if is_shorthand {
2895 // Mimic `x: x` for the `x` field shorthand.
2896 let ident = this.parse_ident_common(false)?;
2897 let path = ast::Path::from_ident(ident);
2898 (ident, this.mk_expr(ident.span, ExprKind::Path(None, path), AttrVec::new()))
2900 let ident = this.parse_field_name()?;
2901 this.error_on_eq_field_init(ident);
2903 (ident, this.parse_expr()?)
2909 span: lo.to(expr.span),
2912 attrs: attrs.into(),
2914 is_placeholder: false,
2916 TrailingToken::MaybeComma,
2921 /// Check for `=`. This means the source incorrectly attempts to
2922 /// initialize a field with an eq rather than a colon.
2923 fn error_on_eq_field_init(&self, field_name: Ident) {
2924 if self.token != token::Eq {
2928 self.struct_span_err(self.token.span, "expected `:`, found `=`")
2930 field_name.span.shrink_to_hi().to(self.token.span),
2931 "replace equals symbol with a colon",
2933 Applicability::MachineApplicable,
2938 fn err_dotdotdot_syntax(&self, span: Span) {
2939 self.struct_span_err(span, "unexpected token: `...`")
2942 "use `..` for an exclusive range",
2944 Applicability::MaybeIncorrect,
2948 "or `..=` for an inclusive range",
2950 Applicability::MaybeIncorrect,
2955 fn err_larrow_operator(&self, span: Span) {
2956 self.struct_span_err(span, "unexpected token: `<-`")
2959 "if you meant to write a comparison against a negative value, add a \
2960 space in between `<` and `-`",
2962 Applicability::MaybeIncorrect,
2967 fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
2968 ExprKind::AssignOp(binop, lhs, rhs)
2973 start: Option<P<Expr>>,
2974 end: Option<P<Expr>>,
2975 limits: RangeLimits,
2977 if end.is_none() && limits == RangeLimits::Closed {
2978 self.inclusive_range_with_incorrect_end(self.prev_token.span);
2981 ExprKind::Range(start, end, limits)
2985 fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
2986 ExprKind::Unary(unop, expr)
2989 fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
2990 ExprKind::Binary(binop, lhs, rhs)
2993 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
2994 ExprKind::Index(expr, idx)
2997 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
2998 ExprKind::Call(f, args)
3001 fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> P<Expr> {
3002 let span = lo.to(self.prev_token.span);
3003 let await_expr = self.mk_expr(span, ExprKind::Await(self_arg), AttrVec::new());
3004 self.recover_from_await_method_call();
3008 crate fn mk_expr(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
3009 P(Expr { kind, span, attrs, id: DUMMY_NODE_ID, tokens: None })
3012 pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> {
3013 self.mk_expr(span, ExprKind::Err, AttrVec::new())
3016 /// Create expression span ensuring the span of the parent node
3017 /// is larger than the span of lhs and rhs, including the attributes.
3018 fn mk_expr_sp(&self, lhs: &P<Expr>, lhs_span: Span, rhs_span: Span) -> Span {
3021 .find(|a| a.style == AttrStyle::Outer)
3022 .map_or(lhs_span, |a| a.span)
3026 fn collect_tokens_for_expr(
3029 f: impl FnOnce(&mut Self, Vec<ast::Attribute>) -> PResult<'a, P<Expr>>,
3030 ) -> PResult<'a, P<Expr>> {
3031 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
3032 let res = f(this, attrs)?;
3033 let trailing = if this.restrictions.contains(Restrictions::STMT_EXPR)
3034 && this.token.kind == token::Semi
3038 // FIXME - pass this through from the place where we know
3039 // we need a comma, rather than assuming that `#[attr] expr,`
3040 // always captures a trailing comma
3041 TrailingToken::MaybeComma