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,
9 ArrayBracketsInsteadOfSpaces, ArrayBracketsInsteadOfSpacesSugg, AsyncMoveOrderIncorrect,
10 BracesForStructLiteral, CatchAfterTry, CommaAfterBaseStruct, ComparisonInterpretedAsGeneric,
11 ComparisonOrShiftInterpretedAsGenericSugg, DoCatchSyntaxRemoved, DotDotDot, EqFieldInit,
12 ExpectedElseBlock, ExpectedEqForLetExpr, ExpectedExpressionFoundLet,
13 FieldExpressionWithGeneric, FloatLiteralRequiresIntegerPart, FoundExprWouldBeStmt,
14 IfExpressionMissingCondition, IfExpressionMissingThenBlock, IfExpressionMissingThenBlockSub,
15 InvalidBlockMacroSegment, InvalidComparisonOperator, InvalidComparisonOperatorSub,
16 InvalidInterpolatedExpression, InvalidLiteralSuffixOnTupleIndex, InvalidLogicalOperator,
17 InvalidLogicalOperatorSub, LabeledLoopInBreak, LeadingPlusNotSupported, LeftArrowOperator,
18 LifetimeInBorrowExpression, MacroInvocationWithQualifiedPath, MalformedLoopLabel,
19 MatchArmBodyWithoutBraces, MatchArmBodyWithoutBracesSugg, MissingCommaAfterMatchArm,
20 MissingDotDot, MissingInInForLoop, MissingInInForLoopSub, MissingSemicolonBeforeArray,
21 NoFieldsForFnCall, NotAsNegationOperator, NotAsNegationOperatorSub,
22 OuterAttributeNotAllowedOnIfElse, ParenthesesWithStructFields,
23 RequireColonAfterLabeledExpression, ShiftInterpretedAsGeneric, StructLiteralNotAllowedHere,
24 StructLiteralNotAllowedHereSugg, TildeAsUnaryOperator, UnexpectedIfWithIf,
25 UnexpectedTokenAfterLabel, UnexpectedTokenAfterLabelSugg, WrapExpressionInParentheses,
27 use crate::maybe_recover_from_interpolated_ty_qpath;
29 use rustc_ast::ptr::P;
30 use rustc_ast::token::{self, Delimiter, Token, TokenKind};
31 use rustc_ast::tokenstream::Spacing;
32 use rustc_ast::util::case::Case;
33 use rustc_ast::util::classify;
34 use rustc_ast::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
35 use rustc_ast::visit::Visitor;
36 use rustc_ast::{self as ast, AttrStyle, AttrVec, CaptureBy, ExprField, UnOp, DUMMY_NODE_ID};
37 use rustc_ast::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, MacCall, Param, Ty, TyKind};
38 use rustc_ast::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits};
39 use rustc_ast::{ClosureBinder, MetaItemLit, StmtKind};
40 use rustc_ast_pretty::pprust;
42 Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, IntoDiagnostic, PResult,
45 use rustc_session::errors::{report_lit_error, ExprParenthesesNeeded};
46 use rustc_session::lint::builtin::BREAK_WITH_LABEL_AND_LOOP;
47 use rustc_session::lint::BuiltinLintDiagnostics;
48 use rustc_span::source_map::{self, Span, Spanned};
49 use rustc_span::symbol::{kw, sym, Ident, Symbol};
50 use rustc_span::{BytePos, Pos};
52 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
53 /// dropped into the token stream, which happens while parsing the result of
54 /// macro expansion). Placement of these is not as complex as I feared it would
55 /// be. The important thing is to make sure that lookahead doesn't balk at
56 /// `token::Interpolated` tokens.
57 macro_rules! maybe_whole_expr {
59 if let token::Interpolated(nt) = &$p.token.kind {
61 token::NtExpr(e) | token::NtLiteral(e) => {
66 token::NtPath(path) => {
67 let path = (**path).clone();
69 return Ok($p.mk_expr($p.prev_token.span, ExprKind::Path(None, path)));
71 token::NtBlock(block) => {
72 let block = block.clone();
74 return Ok($p.mk_expr($p.prev_token.span, ExprKind::Block(block, None)));
83 pub(super) enum LhsExpr {
85 AttributesParsed(AttrWrapper),
86 AlreadyParsed { expr: P<Expr>, starts_statement: bool },
89 impl From<Option<AttrWrapper>> for LhsExpr {
90 /// Converts `Some(attrs)` into `LhsExpr::AttributesParsed(attrs)`
91 /// and `None` into `LhsExpr::NotYetParsed`.
93 /// This conversion does not allocate.
94 fn from(o: Option<AttrWrapper>) -> Self {
95 if let Some(attrs) = o { LhsExpr::AttributesParsed(attrs) } else { LhsExpr::NotYetParsed }
99 impl From<P<Expr>> for LhsExpr {
100 /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed { expr, starts_statement: false }`.
102 /// This conversion does not allocate.
103 fn from(expr: P<Expr>) -> Self {
104 LhsExpr::AlreadyParsed { expr, starts_statement: false }
108 impl<'a> Parser<'a> {
109 /// Parses an expression.
111 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
112 self.current_closure.take();
114 self.parse_expr_res(Restrictions::empty(), None)
117 /// Parses an expression, forcing tokens to be collected
118 pub fn parse_expr_force_collect(&mut self) -> PResult<'a, P<Expr>> {
119 self.collect_tokens_no_attrs(|this| this.parse_expr())
122 pub fn parse_anon_const_expr(&mut self) -> PResult<'a, AnonConst> {
123 self.parse_expr().map(|value| AnonConst { id: DUMMY_NODE_ID, value })
126 fn parse_expr_catch_underscore(&mut self) -> PResult<'a, P<Expr>> {
127 match self.parse_expr() {
128 Ok(expr) => Ok(expr),
129 Err(mut err) => match self.token.ident() {
130 Some((Ident { name: kw::Underscore, .. }, false))
131 if self.may_recover() && self.look_ahead(1, |t| t == &token::Comma) =>
133 // Special-case handling of `foo(_, _, _)`
136 Ok(self.mk_expr(self.prev_token.span, ExprKind::Err))
143 /// Parses a sequence of expressions delimited by parentheses.
144 fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
145 self.parse_paren_comma_seq(|p| p.parse_expr_catch_underscore()).map(|(r, _)| r)
148 /// Parses an expression, subject to the given restrictions.
150 pub(super) fn parse_expr_res(
153 already_parsed_attrs: Option<AttrWrapper>,
154 ) -> PResult<'a, P<Expr>> {
155 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
158 /// Parses an associative expression.
160 /// This parses an expression accounting for associativity and precedence of the operators in
165 already_parsed_attrs: Option<AttrWrapper>,
166 ) -> PResult<'a, P<Expr>> {
167 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
170 /// Parses an associative expression with operators of at least `min_prec` precedence.
171 pub(super) fn parse_assoc_expr_with(
175 ) -> PResult<'a, P<Expr>> {
176 let mut starts_stmt = false;
177 let mut lhs = if let LhsExpr::AlreadyParsed { expr, starts_statement } = lhs {
178 starts_stmt = starts_statement;
181 let attrs = match lhs {
182 LhsExpr::AttributesParsed(attrs) => Some(attrs),
185 if self.token.is_range_separator() {
186 return self.parse_prefix_range_expr(attrs);
188 self.parse_prefix_expr(attrs)?
191 let last_type_ascription_set = self.last_type_ascription.is_some();
193 if !self.should_continue_as_assoc_expr(&lhs) {
194 self.last_type_ascription = None;
198 self.expected_tokens.push(TokenType::Operator);
199 while let Some(op) = self.check_assoc_op() {
200 // Adjust the span for interpolated LHS to point to the `$lhs` token
201 // and not to what it refers to.
202 let lhs_span = match self.prev_token.kind {
203 TokenKind::Interpolated(..) => self.prev_token.span,
207 let cur_op_span = self.token.span;
208 let restrictions = if op.node.is_assign_like() {
209 self.restrictions & Restrictions::NO_STRUCT_LITERAL
213 let prec = op.node.precedence();
217 // Check for deprecated `...` syntax
218 if self.token == token::DotDotDot && op.node == AssocOp::DotDotEq {
219 self.err_dotdotdot_syntax(self.token.span);
222 if self.token == token::LArrow {
223 self.err_larrow_operator(self.token.span);
227 if op.node.is_comparison() {
228 if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
233 // Look for JS' `===` and `!==` and recover
234 if (op.node == AssocOp::Equal || op.node == AssocOp::NotEqual)
235 && self.token.kind == token::Eq
236 && self.prev_token.span.hi() == self.token.span.lo()
238 let sp = op.span.to(self.token.span);
239 let sugg = match op.node {
240 AssocOp::Equal => "==",
241 AssocOp::NotEqual => "!=",
245 let invalid = format!("{}=", &sugg);
246 self.sess.emit_err(InvalidComparisonOperator {
248 invalid: invalid.clone(),
249 sub: InvalidComparisonOperatorSub::Correctable {
258 // Look for PHP's `<>` and recover
259 if op.node == AssocOp::Less
260 && self.token.kind == token::Gt
261 && self.prev_token.span.hi() == self.token.span.lo()
263 let sp = op.span.to(self.token.span);
264 self.sess.emit_err(InvalidComparisonOperator {
266 invalid: "<>".into(),
267 sub: InvalidComparisonOperatorSub::Correctable {
269 invalid: "<>".into(),
270 correct: "!=".into(),
276 // Look for C++'s `<=>` and recover
277 if op.node == AssocOp::LessEqual
278 && self.token.kind == token::Gt
279 && self.prev_token.span.hi() == self.token.span.lo()
281 let sp = op.span.to(self.token.span);
282 self.sess.emit_err(InvalidComparisonOperator {
284 invalid: "<=>".into(),
285 sub: InvalidComparisonOperatorSub::Spaceship(sp),
290 if self.prev_token == token::BinOp(token::Plus)
291 && self.token == token::BinOp(token::Plus)
292 && self.prev_token.span.between(self.token.span).is_empty()
294 let op_span = self.prev_token.span.to(self.token.span);
295 // Eat the second `+`
297 lhs = self.recover_from_postfix_increment(lhs, op_span, starts_stmt)?;
303 if op == AssocOp::As {
304 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
306 } else if op == AssocOp::Colon {
307 lhs = self.parse_assoc_op_ascribe(lhs, lhs_span)?;
309 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
310 // If we didn't have to handle `x..`/`x..=`, it would be pretty easy to
311 // generalise it to the Fixity::None code.
312 lhs = self.parse_range_expr(prec, lhs, op, cur_op_span)?;
316 let fixity = op.fixity();
317 let prec_adjustment = match fixity {
320 // We currently have no non-associative operators that are not handled above by
321 // the special cases. The code is here only for future convenience.
324 let rhs = self.with_res(restrictions - Restrictions::STMT_EXPR, |this| {
325 this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
328 let span = self.mk_expr_sp(&lhs, lhs_span, rhs.span);
341 | AssocOp::ShiftRight
347 | AssocOp::GreaterEqual => {
348 let ast_op = op.to_ast_binop().unwrap();
349 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
350 self.mk_expr(span, binary)
352 AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs, cur_op_span)),
353 AssocOp::AssignOp(k) => {
355 token::Plus => BinOpKind::Add,
356 token::Minus => BinOpKind::Sub,
357 token::Star => BinOpKind::Mul,
358 token::Slash => BinOpKind::Div,
359 token::Percent => BinOpKind::Rem,
360 token::Caret => BinOpKind::BitXor,
361 token::And => BinOpKind::BitAnd,
362 token::Or => BinOpKind::BitOr,
363 token::Shl => BinOpKind::Shl,
364 token::Shr => BinOpKind::Shr,
366 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
367 self.mk_expr(span, aopexpr)
369 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
370 self.span_bug(span, "AssocOp should have been handled by special case")
374 if let Fixity::None = fixity {
378 if last_type_ascription_set {
379 self.last_type_ascription = None;
384 fn should_continue_as_assoc_expr(&mut self, lhs: &Expr) -> bool {
385 match (self.expr_is_complete(lhs), AssocOp::from_token(&self.token)) {
386 // Semi-statement forms are odd:
387 // See https://github.com/rust-lang/rust/issues/29071
388 (true, None) => false,
389 (false, _) => true, // Continue parsing the expression.
390 // An exhaustive check is done in the following block, but these are checked first
391 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
392 // want to keep their span info to improve diagnostics in these cases in a later stage.
393 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
394 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
395 (true, Some(AssocOp::Add)) | // `{ 42 } + 42` (unary plus)
396 (true, Some(AssocOp::LAnd)) | // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }`
397 (true, Some(AssocOp::LOr)) | // `{ 42 } || 42` ("logical or" or closure)
398 (true, Some(AssocOp::BitOr)) // `{ 42 } | 42` or `{ 42 } |x| 42`
400 // These cases are ambiguous and can't be identified in the parser alone.
402 // Bitwise AND is left out because guessing intent is hard. We can make
403 // suggestions based on the assumption that double-refs are rarely intentional,
404 // and closures are distinct enough that they don't get mixed up with their
406 let sp = self.sess.source_map().start_point(self.token.span);
407 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
410 (true, Some(op)) if !op.can_continue_expr_unambiguously() => false,
412 self.error_found_expr_would_be_stmt(lhs);
418 /// We've found an expression that would be parsed as a statement,
419 /// but the next token implies this should be parsed as an expression.
420 /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
421 fn error_found_expr_would_be_stmt(&self, lhs: &Expr) {
422 self.sess.emit_err(FoundExprWouldBeStmt {
423 span: self.token.span,
424 token: self.token.clone(),
425 suggestion: ExprParenthesesNeeded::surrounding(lhs.span),
429 /// Possibly translate the current token to an associative operator.
430 /// The method does not advance the current token.
432 /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
433 fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
434 let (op, span) = match (AssocOp::from_token(&self.token), self.token.ident()) {
435 // When parsing const expressions, stop parsing when encountering `>`.
440 | AssocOp::GreaterEqual
441 | AssocOp::AssignOp(token::BinOpToken::Shr),
444 ) if self.restrictions.contains(Restrictions::CONST_EXPR) => {
447 (Some(op), _) => (op, self.token.span),
448 (None, Some((Ident { name: sym::and, span }, false))) if self.may_recover() => {
449 self.sess.emit_err(InvalidLogicalOperator {
450 span: self.token.span,
451 incorrect: "and".into(),
452 sub: InvalidLogicalOperatorSub::Conjunction(self.token.span),
454 (AssocOp::LAnd, span)
456 (None, Some((Ident { name: sym::or, span }, false))) if self.may_recover() => {
457 self.sess.emit_err(InvalidLogicalOperator {
458 span: self.token.span,
459 incorrect: "or".into(),
460 sub: InvalidLogicalOperatorSub::Disjunction(self.token.span),
466 Some(source_map::respan(span, op))
469 /// Checks if this expression is a successfully parsed statement.
470 fn expr_is_complete(&self, e: &Expr) -> bool {
471 self.restrictions.contains(Restrictions::STMT_EXPR)
472 && !classify::expr_requires_semi_to_be_stmt(e)
475 /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
476 /// The other two variants are handled in `parse_prefix_range_expr` below.
483 ) -> PResult<'a, P<Expr>> {
484 let rhs = if self.is_at_start_of_range_notation_rhs() {
485 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
489 let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
490 let span = self.mk_expr_sp(&lhs, lhs.span, rhs_span);
492 if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
493 let range = self.mk_range(Some(lhs), rhs, limits);
494 Ok(self.mk_expr(span, range))
497 fn is_at_start_of_range_notation_rhs(&self) -> bool {
498 if self.token.can_begin_expr() {
499 // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
500 if self.token == token::OpenDelim(Delimiter::Brace) {
501 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
509 /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
510 fn parse_prefix_range_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
511 // Check for deprecated `...` syntax.
512 if self.token == token::DotDotDot {
513 self.err_dotdotdot_syntax(self.token.span);
517 self.token.is_range_separator(),
518 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
522 let limits = match self.token.kind {
523 token::DotDot => RangeLimits::HalfOpen,
524 _ => RangeLimits::Closed,
526 let op = AssocOp::from_token(&self.token);
527 // FIXME: `parse_prefix_range_expr` is called when the current
528 // token is `DotDot`, `DotDotDot`, or `DotDotEq`. If we haven't already
529 // parsed attributes, then trying to parse them here will always fail.
530 // We should figure out how we want attributes on range expressions to work.
531 let attrs = self.parse_or_use_outer_attributes(attrs)?;
532 self.collect_tokens_for_expr(attrs, |this, attrs| {
533 let lo = this.token.span;
535 let (span, opt_end) = if this.is_at_start_of_range_notation_rhs() {
536 // RHS must be parsed with more associativity than the dots.
537 this.parse_assoc_expr_with(op.unwrap().precedence() + 1, LhsExpr::NotYetParsed)
538 .map(|x| (lo.to(x.span), Some(x)))?
542 let range = this.mk_range(None, opt_end, limits);
543 Ok(this.mk_expr_with_attrs(span, range, attrs))
547 /// Parses a prefix-unary-operator expr.
548 fn parse_prefix_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
549 let attrs = self.parse_or_use_outer_attributes(attrs)?;
550 let lo = self.token.span;
552 macro_rules! make_it {
553 ($this:ident, $attrs:expr, |this, _| $body:expr) => {
554 $this.collect_tokens_for_expr($attrs, |$this, attrs| {
555 let (hi, ex) = $body?;
556 Ok($this.mk_expr_with_attrs(lo.to(hi), ex, attrs))
563 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
564 match this.token.uninterpolate().kind {
566 token::Not => make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Not)),
568 token::Tilde => make_it!(this, attrs, |this, _| this.recover_tilde_expr(lo)),
570 token::BinOp(token::Minus) => {
571 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Neg))
574 token::BinOp(token::Star) => {
575 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Deref))
577 // `&expr` and `&&expr`
578 token::BinOp(token::And) | token::AndAnd => {
579 make_it!(this, attrs, |this, _| this.parse_borrow_expr(lo))
582 token::BinOp(token::Plus) if this.look_ahead(1, |tok| tok.is_numeric_lit()) => {
584 LeadingPlusNotSupported { span: lo, remove_plus: None, add_parentheses: None };
586 // a block on the LHS might have been intended to be an expression instead
587 if let Some(sp) = this.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
588 err.add_parentheses = Some(ExprParenthesesNeeded::surrounding(*sp));
590 err.remove_plus = Some(lo);
592 this.sess.emit_err(err);
595 this.parse_prefix_expr(None)
597 // Recover from `++x`:
598 token::BinOp(token::Plus)
599 if this.look_ahead(1, |t| *t == token::BinOp(token::Plus)) =>
601 let starts_stmt = this.prev_token == token::Semi
602 || this.prev_token == token::CloseDelim(Delimiter::Brace);
603 let pre_span = this.token.span.to(this.look_ahead(1, |t| t.span));
608 let operand_expr = this.parse_dot_or_call_expr(Default::default())?;
609 this.recover_from_prefix_increment(operand_expr, pre_span, starts_stmt)
611 token::Ident(..) if this.token.is_keyword(kw::Box) => {
612 make_it!(this, attrs, |this, _| this.parse_box_expr(lo))
614 token::Ident(..) if this.may_recover() && this.is_mistaken_not_ident_negation() => {
615 make_it!(this, attrs, |this, _| this.recover_not_expr(lo))
617 _ => return this.parse_dot_or_call_expr(Some(attrs)),
621 fn parse_prefix_expr_common(&mut self, lo: Span) -> PResult<'a, (Span, P<Expr>)> {
623 let expr = self.parse_prefix_expr(None);
624 let (span, expr) = self.interpolated_or_expr_span(expr)?;
625 Ok((lo.to(span), expr))
628 fn parse_unary_expr(&mut self, lo: Span, op: UnOp) -> PResult<'a, (Span, ExprKind)> {
629 let (span, expr) = self.parse_prefix_expr_common(lo)?;
630 Ok((span, self.mk_unary(op, expr)))
633 /// Recover on `~expr` in favor of `!expr`.
634 fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
635 self.sess.emit_err(TildeAsUnaryOperator(lo));
637 self.parse_unary_expr(lo, UnOp::Not)
640 /// Parse `box expr`.
641 fn parse_box_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
642 let (span, expr) = self.parse_prefix_expr_common(lo)?;
643 self.sess.gated_spans.gate(sym::box_syntax, span);
644 Ok((span, ExprKind::Box(expr)))
647 fn is_mistaken_not_ident_negation(&self) -> bool {
648 let token_cannot_continue_expr = |t: &Token| match t.uninterpolate().kind {
649 // These tokens can start an expression after `!`, but
650 // can't continue an expression after an ident
651 token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
652 token::Literal(..) | token::Pound => true,
653 _ => t.is_whole_expr(),
655 self.token.is_ident_named(sym::not) && self.look_ahead(1, token_cannot_continue_expr)
658 /// Recover on `not expr` in favor of `!expr`.
659 fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
660 let negated_token = self.look_ahead(1, |t| t.clone());
662 let sub_diag = if negated_token.is_numeric_lit() {
663 NotAsNegationOperatorSub::SuggestNotBitwise
664 } else if negated_token.is_bool_lit() {
665 NotAsNegationOperatorSub::SuggestNotLogical
667 NotAsNegationOperatorSub::SuggestNotDefault
670 self.sess.emit_err(NotAsNegationOperator {
671 negated: negated_token.span,
672 negated_desc: super::token_descr(&negated_token),
673 // Span the `not` plus trailing whitespace to avoid
674 // trailing whitespace after the `!` in our suggestion
676 self.sess.source_map().span_until_non_whitespace(lo.to(negated_token.span)),
680 self.parse_unary_expr(lo, UnOp::Not)
683 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
684 fn interpolated_or_expr_span(
686 expr: PResult<'a, P<Expr>>,
687 ) -> PResult<'a, (Span, P<Expr>)> {
690 match self.prev_token.kind {
691 TokenKind::Interpolated(..) => self.prev_token.span,
699 fn parse_assoc_op_cast(
703 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
704 ) -> PResult<'a, P<Expr>> {
705 let mk_expr = |this: &mut Self, lhs: P<Expr>, rhs: P<Ty>| {
706 this.mk_expr(this.mk_expr_sp(&lhs, lhs_span, rhs.span), expr_kind(lhs, rhs))
709 // Save the state of the parser before parsing type normally, in case there is a
710 // LessThan comparison after this cast.
711 let parser_snapshot_before_type = self.clone();
712 let cast_expr = match self.parse_as_cast_ty() {
713 Ok(rhs) => mk_expr(self, lhs, rhs),
715 if !self.may_recover() {
716 return Err(type_err);
719 // Rewind to before attempting to parse the type with generics, to recover
720 // from situations like `x as usize < y` in which we first tried to parse
721 // `usize < y` as a type with generic arguments.
722 let parser_snapshot_after_type = mem::replace(self, parser_snapshot_before_type);
724 // Check for typo of `'a: loop { break 'a }` with a missing `'`.
725 match (&lhs.kind, &self.token.kind) {
728 ExprKind::Path(None, ast::Path { segments, .. }),
729 TokenKind::Ident(kw::For | kw::Loop | kw::While, false),
730 ) if segments.len() == 1 => {
731 let snapshot = self.create_snapshot_for_diagnostic();
733 ident: Ident::from_str_and_span(
734 &format!("'{}", segments[0].ident),
735 segments[0].ident.span,
738 match self.parse_labeled_expr(label, false) {
741 self.sess.emit_err(MalformedLoopLabel {
742 span: label.ident.span,
743 correct_label: label.ident,
749 self.restore_snapshot(snapshot);
756 match self.parse_path(PathStyle::Expr) {
758 let span_after_type = parser_snapshot_after_type.token.span;
762 self.mk_ty(path.span, TyKind::Path(None, path.clone())),
765 let args_span = self.look_ahead(1, |t| t.span).to(span_after_type);
766 let suggestion = ComparisonOrShiftInterpretedAsGenericSugg {
767 left: expr.span.shrink_to_lo(),
768 right: expr.span.shrink_to_hi(),
771 match self.token.kind {
772 token::Lt => self.sess.emit_err(ComparisonInterpretedAsGeneric {
773 comparison: self.token.span,
778 token::BinOp(token::Shl) => {
779 self.sess.emit_err(ShiftInterpretedAsGeneric {
780 shift: self.token.span,
787 // We can end up here even without `<` being the next token, for
788 // example because `parse_ty_no_plus` returns `Err` on keywords,
789 // but `parse_path` returns `Ok` on them due to error recovery.
790 // Return original error and parser state.
791 *self = parser_snapshot_after_type;
792 return Err(type_err);
796 // Successfully parsed the type path leaving a `<` yet to parse.
799 // Keep `x as usize` as an expression in AST and continue parsing.
803 // Couldn't parse as a path, return original error and parser state.
805 *self = parser_snapshot_after_type;
806 return Err(type_err);
812 self.parse_and_disallow_postfix_after_cast(cast_expr)
815 /// Parses a postfix operators such as `.`, `?`, or index (`[]`) after a cast,
816 /// then emits an error and returns the newly parsed tree.
817 /// The resulting parse tree for `&x as T[0]` has a precedence of `((&x) as T)[0]`.
818 fn parse_and_disallow_postfix_after_cast(
821 ) -> PResult<'a, P<Expr>> {
822 let span = cast_expr.span;
823 let (cast_kind, maybe_ascription_span) =
824 if let ExprKind::Type(ascripted_expr, _) = &cast_expr.kind {
825 ("type ascription", Some(ascripted_expr.span.shrink_to_hi().with_hi(span.hi())))
830 let with_postfix = self.parse_dot_or_call_expr_with_(cast_expr, span)?;
832 // Check if an illegal postfix operator has been added after the cast.
833 // If the resulting expression is not a cast, it is an illegal postfix operator.
834 if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) {
836 "{cast_kind} cannot be followed by {}",
837 match with_postfix.kind {
838 ExprKind::Index(_, _) => "indexing",
839 ExprKind::Try(_) => "`?`",
840 ExprKind::Field(_, _) => "a field access",
841 ExprKind::MethodCall(_) => "a method call",
842 ExprKind::Call(_, _) => "a function call",
843 ExprKind::Await(_) => "`.await`",
844 ExprKind::Err => return Ok(with_postfix),
845 _ => unreachable!("parse_dot_or_call_expr_with_ shouldn't produce this"),
848 let mut err = self.struct_span_err(span, &msg);
850 let suggest_parens = |err: &mut Diagnostic| {
851 let suggestions = vec![
852 (span.shrink_to_lo(), "(".to_string()),
853 (span.shrink_to_hi(), ")".to_string()),
855 err.multipart_suggestion(
856 "try surrounding the expression in parentheses",
858 Applicability::MachineApplicable,
862 // If type ascription is "likely an error", the user will already be getting a useful
863 // help message, and doesn't need a second.
864 if self.last_type_ascription.map_or(false, |last_ascription| last_ascription.1) {
865 self.maybe_annotate_with_ascription(&mut err, false);
866 } else if let Some(ascription_span) = maybe_ascription_span {
867 let is_nightly = self.sess.unstable_features.is_nightly_build();
869 suggest_parens(&mut err);
874 "{}remove the type ascription",
875 if is_nightly { "alternatively, " } else { "" }
879 Applicability::MaybeIncorrect
881 Applicability::MachineApplicable
885 suggest_parens(&mut err);
892 fn parse_assoc_op_ascribe(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
893 let maybe_path = self.could_ascription_be_path(&lhs.kind);
894 self.last_type_ascription = Some((self.prev_token.span, maybe_path));
895 let lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
896 self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
900 /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
901 fn parse_borrow_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
903 let has_lifetime = self.token.is_lifetime() && self.look_ahead(1, |t| t != &token::Colon);
904 let lifetime = has_lifetime.then(|| self.expect_lifetime()); // For recovery, see below.
905 let (borrow_kind, mutbl) = self.parse_borrow_modifiers(lo);
906 let expr = if self.token.is_range_separator() {
907 self.parse_prefix_range_expr(None)
909 self.parse_prefix_expr(None)
911 let (hi, expr) = self.interpolated_or_expr_span(expr)?;
912 let span = lo.to(hi);
913 if let Some(lt) = lifetime {
914 self.error_remove_borrow_lifetime(span, lt.ident.span);
916 Ok((span, ExprKind::AddrOf(borrow_kind, mutbl, expr)))
919 fn error_remove_borrow_lifetime(&self, span: Span, lt_span: Span) {
920 self.sess.emit_err(LifetimeInBorrowExpression { span, lifetime_span: lt_span });
923 /// Parse `mut?` or `raw [ const | mut ]`.
924 fn parse_borrow_modifiers(&mut self, lo: Span) -> (ast::BorrowKind, ast::Mutability) {
925 if self.check_keyword(kw::Raw) && self.look_ahead(1, Token::is_mutability) {
926 // `raw [ const | mut ]`.
927 let found_raw = self.eat_keyword(kw::Raw);
929 let mutability = self.parse_const_or_mut().unwrap();
930 self.sess.gated_spans.gate(sym::raw_ref_op, lo.to(self.prev_token.span));
931 (ast::BorrowKind::Raw, mutability)
934 (ast::BorrowKind::Ref, self.parse_mutability())
938 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
939 fn parse_dot_or_call_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
940 let attrs = self.parse_or_use_outer_attributes(attrs)?;
941 self.collect_tokens_for_expr(attrs, |this, attrs| {
942 let base = this.parse_bottom_expr();
943 let (span, base) = this.interpolated_or_expr_span(base)?;
944 this.parse_dot_or_call_expr_with(base, span, attrs)
948 pub(super) fn parse_dot_or_call_expr_with(
952 mut attrs: ast::AttrVec,
953 ) -> PResult<'a, P<Expr>> {
954 // Stitch the list of outer attributes onto the return value.
955 // A little bit ugly, but the best way given the current code
957 let res = self.parse_dot_or_call_expr_with_(e0, lo);
958 if attrs.is_empty() {
962 expr.map(|mut expr| {
963 attrs.extend(expr.attrs);
971 fn parse_dot_or_call_expr_with_(&mut self, mut e: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
973 let has_question = if self.prev_token.kind == TokenKind::Ident(kw::Return, false) {
974 // we are using noexpect here because we don't expect a `?` directly after a `return`
975 // which could be suggested otherwise
976 self.eat_noexpect(&token::Question)
978 self.eat(&token::Question)
982 e = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Try(e));
985 let has_dot = if self.prev_token.kind == TokenKind::Ident(kw::Return, false) {
986 // we are using noexpect here because we don't expect a `.` directly after a `return`
987 // which could be suggested otherwise
988 self.eat_noexpect(&token::Dot)
990 self.eat(&token::Dot)
994 e = self.parse_dot_suffix_expr(lo, e)?;
997 if self.expr_is_complete(&e) {
1000 e = match self.token.kind {
1001 token::OpenDelim(Delimiter::Parenthesis) => self.parse_fn_call_expr(lo, e),
1002 token::OpenDelim(Delimiter::Bracket) => self.parse_index_expr(lo, e)?,
1008 fn look_ahead_type_ascription_as_field(&mut self) -> bool {
1009 self.look_ahead(1, |t| t.is_ident())
1010 && self.look_ahead(2, |t| t == &token::Colon)
1011 && self.look_ahead(3, |t| t.can_begin_expr())
1014 fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
1015 match self.token.uninterpolate().kind {
1016 token::Ident(..) => self.parse_dot_suffix(base, lo),
1017 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
1018 Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix, None))
1020 token::Literal(token::Lit { kind: token::Float, symbol, suffix }) => {
1021 Ok(self.parse_tuple_field_access_expr_float(lo, base, symbol, suffix))
1024 self.error_unexpected_after_dot();
1030 fn error_unexpected_after_dot(&self) {
1031 // FIXME Could factor this out into non_fatal_unexpected or something.
1032 let actual = pprust::token_to_string(&self.token);
1033 self.struct_span_err(self.token.span, &format!("unexpected token: `{actual}`")).emit();
1036 // We need an identifier or integer, but the next token is a float.
1037 // Break the float into components to extract the identifier or integer.
1038 // FIXME: With current `TokenCursor` it's hard to break tokens into more than 2
1039 // parts unless those parts are processed immediately. `TokenCursor` should either
1040 // support pushing "future tokens" (would be also helpful to `break_and_eat`), or
1041 // we should break everything including floats into more basic proc-macro style
1042 // tokens in the lexer (probably preferable).
1043 fn parse_tuple_field_access_expr_float(
1048 suffix: Option<Symbol>,
1051 enum FloatComponent {
1055 use FloatComponent::*;
1057 let float_str = float.as_str();
1058 let mut components = Vec::new();
1059 let mut ident_like = String::new();
1060 for c in float_str.chars() {
1061 if c == '_' || c.is_ascii_alphanumeric() {
1063 } else if matches!(c, '.' | '+' | '-') {
1064 if !ident_like.is_empty() {
1065 components.push(IdentLike(mem::take(&mut ident_like)));
1067 components.push(Punct(c));
1069 panic!("unexpected character in a float token: {:?}", c)
1072 if !ident_like.is_empty() {
1073 components.push(IdentLike(ident_like));
1076 // With proc macros the span can refer to anything, the source may be too short,
1077 // or too long, or non-ASCII. It only makes sense to break our span into components
1078 // if its underlying text is identical to our float literal.
1079 let span = self.token.span;
1080 let can_take_span_apart =
1081 || self.span_to_snippet(span).as_deref() == Ok(float_str).as_deref();
1083 match &*components {
1086 self.parse_tuple_field_access_expr(lo, base, Symbol::intern(&i), suffix, None)
1089 [IdentLike(i), Punct('.')] => {
1090 let (ident_span, dot_span) = if can_take_span_apart() {
1091 let (span, ident_len) = (span.data(), BytePos::from_usize(i.len()));
1092 let ident_span = span.with_hi(span.lo + ident_len);
1093 let dot_span = span.with_lo(span.lo + ident_len);
1094 (ident_span, dot_span)
1098 assert!(suffix.is_none());
1099 let symbol = Symbol::intern(&i);
1100 self.token = Token::new(token::Ident(symbol, false), ident_span);
1101 let next_token = (Token::new(token::Dot, dot_span), self.token_spacing);
1102 self.parse_tuple_field_access_expr(lo, base, symbol, None, Some(next_token))
1105 [IdentLike(i1), Punct('.'), IdentLike(i2)] => {
1106 let (ident1_span, dot_span, ident2_span) = if can_take_span_apart() {
1107 let (span, ident1_len) = (span.data(), BytePos::from_usize(i1.len()));
1108 let ident1_span = span.with_hi(span.lo + ident1_len);
1110 .with_lo(span.lo + ident1_len)
1111 .with_hi(span.lo + ident1_len + BytePos(1));
1112 let ident2_span = self.token.span.with_lo(span.lo + ident1_len + BytePos(1));
1113 (ident1_span, dot_span, ident2_span)
1117 let symbol1 = Symbol::intern(&i1);
1118 self.token = Token::new(token::Ident(symbol1, false), ident1_span);
1119 // This needs to be `Spacing::Alone` to prevent regressions.
1120 // See issue #76399 and PR #76285 for more details
1121 let next_token1 = (Token::new(token::Dot, dot_span), Spacing::Alone);
1123 self.parse_tuple_field_access_expr(lo, base, symbol1, None, Some(next_token1));
1124 let symbol2 = Symbol::intern(&i2);
1125 let next_token2 = Token::new(token::Ident(symbol2, false), ident2_span);
1126 self.bump_with((next_token2, self.token_spacing)); // `.`
1127 self.parse_tuple_field_access_expr(lo, base1, symbol2, suffix, None)
1129 // 1e+ | 1e- (recovered)
1130 [IdentLike(_), Punct('+' | '-')] |
1132 [IdentLike(_), Punct('+' | '-'), IdentLike(_)] |
1134 [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-')] |
1136 [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-'), IdentLike(_)] => {
1137 // See the FIXME about `TokenCursor` above.
1138 self.error_unexpected_after_dot();
1141 _ => panic!("unexpected components in a float token: {:?}", components),
1145 fn parse_tuple_field_access_expr(
1150 suffix: Option<Symbol>,
1151 next_token: Option<(Token, Spacing)>,
1154 Some(next_token) => self.bump_with(next_token),
1155 None => self.bump(),
1157 let span = self.prev_token.span;
1158 let field = ExprKind::Field(base, Ident::new(field, span));
1159 if let Some(suffix) = suffix {
1160 self.expect_no_tuple_index_suffix(span, suffix);
1162 self.mk_expr(lo.to(span), field)
1165 /// Parse a function call expression, `expr(...)`.
1166 fn parse_fn_call_expr(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
1167 let snapshot = if self.token.kind == token::OpenDelim(Delimiter::Parenthesis)
1168 && self.look_ahead_type_ascription_as_field()
1170 Some((self.create_snapshot_for_diagnostic(), fun.kind.clone()))
1174 let open_paren = self.token.span;
1177 .parse_paren_expr_seq()
1178 .map(|args| self.mk_expr(lo.to(self.prev_token.span), self.mk_call(fun, args)));
1180 self.maybe_recover_struct_lit_bad_delims(lo, open_paren, &mut seq, snapshot)
1184 self.recover_seq_parse_error(Delimiter::Parenthesis, lo, seq)
1187 /// If we encounter a parser state that looks like the user has written a `struct` literal with
1188 /// parentheses instead of braces, recover the parser state and provide suggestions.
1189 #[instrument(skip(self, seq, snapshot), level = "trace")]
1190 fn maybe_recover_struct_lit_bad_delims(
1194 seq: &mut PResult<'a, P<Expr>>,
1195 snapshot: Option<(SnapshotParser<'a>, ExprKind)>,
1196 ) -> Option<P<Expr>> {
1197 if !self.may_recover() {
1201 match (seq.as_mut(), snapshot) {
1202 (Err(err), Some((mut snapshot, ExprKind::Path(None, path)))) => {
1203 snapshot.bump(); // `(`
1204 match snapshot.parse_struct_fields(path.clone(), false, Delimiter::Parenthesis) {
1206 if snapshot.eat(&token::CloseDelim(Delimiter::Parenthesis)) =>
1208 // We are certain we have `Enum::Foo(a: 3, b: 4)`, suggest
1209 // `Enum::Foo { a: 3, b: 4 }` or `Enum::Foo(3, 4)`.
1210 self.restore_snapshot(snapshot);
1211 let close_paren = self.prev_token.span;
1212 let span = lo.to(self.prev_token.span);
1213 if !fields.is_empty() {
1214 let mut replacement_err = ParenthesesWithStructFields {
1217 braces_for_struct: BracesForStructLiteral {
1219 second: close_paren,
1221 no_fields_for_fn: NoFieldsForFnCall {
1224 .map(|field| field.span.until(field.expr.span))
1228 .into_diagnostic(&self.sess.span_diagnostic);
1229 replacement_err.emit();
1231 let old_err = mem::replace(err, replacement_err);
1236 return Some(self.mk_expr_err(span));
1249 /// Parse an indexing expression `expr[...]`.
1250 fn parse_index_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
1251 let prev_span = self.prev_token.span;
1252 let open_delim_span = self.token.span;
1254 let index = self.parse_expr()?;
1255 self.suggest_missing_semicolon_before_array(prev_span, open_delim_span)?;
1256 self.expect(&token::CloseDelim(Delimiter::Bracket))?;
1257 Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_index(base, index)))
1260 /// Assuming we have just parsed `.`, continue parsing into an expression.
1261 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
1262 if self.token.uninterpolated_span().rust_2018() && self.eat_keyword(kw::Await) {
1263 return Ok(self.mk_await_expr(self_arg, lo));
1266 let fn_span_lo = self.token.span;
1267 let mut seg = self.parse_path_segment(PathStyle::Expr, None)?;
1268 self.check_trailing_angle_brackets(&seg, &[&token::OpenDelim(Delimiter::Parenthesis)]);
1269 self.check_turbofish_missing_angle_brackets(&mut seg);
1271 if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
1272 // Method call `expr.f()`
1273 let args = self.parse_paren_expr_seq()?;
1274 let fn_span = fn_span_lo.to(self.prev_token.span);
1275 let span = lo.to(self.prev_token.span);
1278 ExprKind::MethodCall(Box::new(ast::MethodCall {
1286 // Field access `expr.f`
1287 if let Some(args) = seg.args {
1288 self.sess.emit_err(FieldExpressionWithGeneric(args.span()));
1291 let span = lo.to(self.prev_token.span);
1292 Ok(self.mk_expr(span, ExprKind::Field(self_arg, seg.ident)))
1296 /// At the bottom (top?) of the precedence hierarchy,
1297 /// Parses things like parenthesized exprs, macros, `return`, etc.
1299 /// N.B., this does not parse outer attributes, and is private because it only works
1300 /// correctly if called from `parse_dot_or_call_expr()`.
1301 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
1302 maybe_recover_from_interpolated_ty_qpath!(self, true);
1303 maybe_whole_expr!(self);
1305 // Outer attributes are already parsed and will be
1306 // added to the return value after the fact.
1308 // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
1309 let lo = self.token.span;
1310 if let token::Literal(_) = self.token.kind {
1311 // This match arm is a special-case of the `_` match arm below and
1312 // could be removed without changing functionality, but it's faster
1313 // to have it here, especially for programs with large constants.
1314 self.parse_lit_expr()
1315 } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
1316 self.parse_tuple_parens_expr()
1317 } else if self.check(&token::OpenDelim(Delimiter::Brace)) {
1318 self.parse_block_expr(None, lo, BlockCheckMode::Default)
1319 } else if self.check(&token::BinOp(token::Or)) || self.check(&token::OrOr) {
1320 self.parse_closure_expr().map_err(|mut err| {
1321 // If the input is something like `if a { 1 } else { 2 } | if a { 3 } else { 4 }`
1322 // then suggest parens around the lhs.
1323 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
1324 err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
1328 } else if self.check(&token::OpenDelim(Delimiter::Bracket)) {
1329 self.parse_array_or_repeat_expr(Delimiter::Bracket)
1330 } else if self.check_path() {
1331 self.parse_path_start_expr()
1332 } else if self.check_keyword(kw::Move)
1333 || self.check_keyword(kw::Static)
1334 || self.check_const_closure()
1336 self.parse_closure_expr()
1337 } else if self.eat_keyword(kw::If) {
1338 self.parse_if_expr()
1339 } else if self.check_keyword(kw::For) {
1340 if self.choose_generics_over_qpath(1) {
1341 self.parse_closure_expr()
1343 assert!(self.eat_keyword(kw::For));
1344 self.parse_for_expr(None, self.prev_token.span)
1346 } else if self.eat_keyword(kw::While) {
1347 self.parse_while_expr(None, self.prev_token.span)
1348 } else if let Some(label) = self.eat_label() {
1349 self.parse_labeled_expr(label, true)
1350 } else if self.eat_keyword(kw::Loop) {
1351 let sp = self.prev_token.span;
1352 self.parse_loop_expr(None, self.prev_token.span).map_err(|mut err| {
1353 err.span_label(sp, "while parsing this `loop` expression");
1356 } else if self.eat_keyword(kw::Match) {
1357 let match_sp = self.prev_token.span;
1358 self.parse_match_expr().map_err(|mut err| {
1359 err.span_label(match_sp, "while parsing this `match` expression");
1362 } else if self.eat_keyword(kw::Unsafe) {
1363 let sp = self.prev_token.span;
1364 self.parse_block_expr(None, lo, BlockCheckMode::Unsafe(ast::UserProvided)).map_err(
1366 err.span_label(sp, "while parsing this `unsafe` expression");
1370 } else if self.check_inline_const(0) {
1371 self.parse_const_block(lo.to(self.token.span), false)
1372 } else if self.may_recover() && self.is_do_catch_block() {
1373 self.recover_do_catch()
1374 } else if self.is_try_block() {
1375 self.expect_keyword(kw::Try)?;
1376 self.parse_try_block(lo)
1377 } else if self.eat_keyword(kw::Return) {
1378 self.parse_return_expr()
1379 } else if self.eat_keyword(kw::Continue) {
1380 self.parse_continue_expr(lo)
1381 } else if self.eat_keyword(kw::Break) {
1382 self.parse_break_expr()
1383 } else if self.eat_keyword(kw::Yield) {
1384 self.parse_yield_expr()
1385 } else if self.is_do_yeet() {
1386 self.parse_yeet_expr()
1387 } else if self.check_keyword(kw::Let) {
1388 self.parse_let_expr()
1389 } else if self.eat_keyword(kw::Underscore) {
1390 Ok(self.mk_expr(self.prev_token.span, ExprKind::Underscore))
1391 } else if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
1392 // Don't complain about bare semicolons after unclosed braces
1393 // recovery in order to keep the error count down. Fixing the
1394 // delimiters will possibly also fix the bare semicolon found in
1395 // expression context. For example, silence the following error:
1397 // error: expected expression, found `;`
1401 // | ^ expected expression
1403 Ok(self.mk_expr_err(self.token.span))
1404 } else if self.token.uninterpolated_span().rust_2018() {
1405 // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
1406 if self.check_keyword(kw::Async) {
1407 if self.is_async_block() {
1408 // Check for `async {` and `async move {`.
1409 self.parse_async_block()
1411 self.parse_closure_expr()
1413 } else if self.eat_keyword(kw::Await) {
1414 self.recover_incorrect_await_syntax(lo, self.prev_token.span)
1416 self.parse_lit_expr()
1419 self.parse_lit_expr()
1423 fn parse_lit_expr(&mut self) -> PResult<'a, P<Expr>> {
1424 let lo = self.token.span;
1425 match self.parse_opt_token_lit() {
1426 Some((token_lit, _)) => {
1427 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Lit(token_lit));
1428 self.maybe_recover_from_bad_qpath(expr)
1430 None => self.try_macro_suggestion(),
1434 fn parse_tuple_parens_expr(&mut self) -> PResult<'a, P<Expr>> {
1435 let lo = self.token.span;
1436 self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
1437 let (es, trailing_comma) = match self.parse_seq_to_end(
1438 &token::CloseDelim(Delimiter::Parenthesis),
1439 SeqSep::trailing_allowed(token::Comma),
1440 |p| p.parse_expr_catch_underscore(),
1444 return Ok(self.recover_seq_parse_error(Delimiter::Parenthesis, lo, Err(err)));
1447 let kind = if es.len() == 1 && !trailing_comma {
1448 // `(e)` is parenthesized `e`.
1449 ExprKind::Paren(es.into_iter().next().unwrap())
1451 // `(e,)` is a tuple with only one field, `e`.
1454 let expr = self.mk_expr(lo.to(self.prev_token.span), kind);
1455 self.maybe_recover_from_bad_qpath(expr)
1458 fn parse_array_or_repeat_expr(&mut self, close_delim: Delimiter) -> PResult<'a, P<Expr>> {
1459 let lo = self.token.span;
1460 self.bump(); // `[` or other open delim
1462 let close = &token::CloseDelim(close_delim);
1463 let kind = if self.eat(close) {
1465 ExprKind::Array(Vec::new())
1468 let first_expr = self.parse_expr()?;
1469 if self.eat(&token::Semi) {
1470 // Repeating array syntax: `[ 0; 512 ]`
1471 let count = self.parse_anon_const_expr()?;
1472 self.expect(close)?;
1473 ExprKind::Repeat(first_expr, count)
1474 } else if self.eat(&token::Comma) {
1475 // Vector with two or more elements.
1476 let sep = SeqSep::trailing_allowed(token::Comma);
1477 let (mut exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
1478 exprs.insert(0, first_expr);
1479 ExprKind::Array(exprs)
1481 // Vector with one element
1482 self.expect(close)?;
1483 ExprKind::Array(vec![first_expr])
1486 let expr = self.mk_expr(lo.to(self.prev_token.span), kind);
1487 self.maybe_recover_from_bad_qpath(expr)
1490 fn parse_path_start_expr(&mut self) -> PResult<'a, P<Expr>> {
1491 let (qself, path) = if self.eat_lt() {
1492 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
1495 (None, self.parse_path(PathStyle::Expr)?)
1498 // `!`, as an operator, is prefix, so we know this isn't that.
1499 let (span, kind) = if self.eat(&token::Not) {
1500 // MACRO INVOCATION expression
1501 if qself.is_some() {
1502 self.sess.emit_err(MacroInvocationWithQualifiedPath(path.span));
1505 let mac = P(MacCall {
1507 args: self.parse_delim_args()?,
1508 prior_type_ascription: self.last_type_ascription,
1510 (lo.to(self.prev_token.span), ExprKind::MacCall(mac))
1511 } else if self.check(&token::OpenDelim(Delimiter::Brace))
1512 && let Some(expr) = self.maybe_parse_struct_expr(&qself, &path)
1514 if qself.is_some() {
1515 self.sess.gated_spans.gate(sym::more_qualified_paths, path.span);
1519 (path.span, ExprKind::Path(qself, path))
1522 let expr = self.mk_expr(span, kind);
1523 self.maybe_recover_from_bad_qpath(expr)
1526 /// Parse `'label: $expr`. The label is already parsed.
1527 fn parse_labeled_expr(
1530 mut consume_colon: bool,
1531 ) -> PResult<'a, P<Expr>> {
1532 let lo = label_.ident.span;
1533 let label = Some(label_);
1534 let ate_colon = self.eat(&token::Colon);
1535 let expr = if self.eat_keyword(kw::While) {
1536 self.parse_while_expr(label, lo)
1537 } else if self.eat_keyword(kw::For) {
1538 self.parse_for_expr(label, lo)
1539 } else if self.eat_keyword(kw::Loop) {
1540 self.parse_loop_expr(label, lo)
1541 } else if self.check_noexpect(&token::OpenDelim(Delimiter::Brace))
1542 || self.token.is_whole_block()
1544 self.parse_block_expr(label, lo, BlockCheckMode::Default)
1545 } else if !ate_colon
1546 && self.may_recover()
1547 && (matches!(self.token.kind, token::CloseDelim(_) | token::Comma)
1548 || self.token.is_op())
1551 self.recover_unclosed_char(label_.ident, Parser::mk_token_lit_char, |self_| {
1552 self_.sess.create_err(UnexpectedTokenAfterLabel {
1553 span: self_.token.span,
1555 enclose_in_block: None,
1558 consume_colon = false;
1559 Ok(self.mk_expr(lo, ExprKind::Lit(lit)))
1560 } else if !ate_colon
1561 && (self.check_noexpect(&TokenKind::Comma) || self.check_noexpect(&TokenKind::Gt))
1563 // We're probably inside of a `Path<'a>` that needs a turbofish
1564 self.sess.emit_err(UnexpectedTokenAfterLabel {
1565 span: self.token.span,
1567 enclose_in_block: None,
1569 consume_colon = false;
1570 Ok(self.mk_expr_err(lo))
1572 let mut err = UnexpectedTokenAfterLabel {
1573 span: self.token.span,
1575 enclose_in_block: None,
1578 // Continue as an expression in an effort to recover on `'label: non_block_expr`.
1579 let expr = self.parse_expr().map(|expr| {
1580 let span = expr.span;
1582 let found_labeled_breaks = {
1583 struct FindLabeledBreaksVisitor(bool);
1585 impl<'ast> Visitor<'ast> for FindLabeledBreaksVisitor {
1586 fn visit_expr_post(&mut self, ex: &'ast Expr) {
1587 if let ExprKind::Break(Some(_label), _) = ex.kind {
1593 let mut vis = FindLabeledBreaksVisitor(false);
1594 vis.visit_expr(&expr);
1598 // Suggestion involves adding a labeled block.
1600 // If there are no breaks that may use this label, suggest removing the label and
1601 // recover to the unmodified expression.
1602 if !found_labeled_breaks {
1603 err.remove_label = Some(lo.until(span));
1608 err.enclose_in_block = Some(UnexpectedTokenAfterLabelSugg {
1609 left: span.shrink_to_lo(),
1610 right: span.shrink_to_hi(),
1613 // Replace `'label: non_block_expr` with `'label: {non_block_expr}` in order to suppress future errors about `break 'label`.
1614 let stmt = self.mk_stmt(span, StmtKind::Expr(expr));
1615 let blk = self.mk_block(vec![stmt], BlockCheckMode::Default, span);
1616 self.mk_expr(span, ExprKind::Block(blk, label))
1619 self.sess.emit_err(err);
1623 if !ate_colon && consume_colon {
1624 self.sess.emit_err(RequireColonAfterLabeledExpression {
1627 label_end: lo.shrink_to_hi(),
1634 /// Emit an error when a char is parsed as a lifetime because of a missing quote.
1635 pub(super) fn recover_unclosed_char<L>(
1638 mk_lit_char: impl FnOnce(Symbol, Span) -> L,
1639 err: impl FnOnce(&Self) -> DiagnosticBuilder<'a, ErrorGuaranteed>,
1641 if let Some(mut diag) =
1642 self.sess.span_diagnostic.steal_diagnostic(lifetime.span, StashKey::LifetimeIsChar)
1644 diag.span_suggestion_verbose(
1645 lifetime.span.shrink_to_hi(),
1646 "add `'` to close the char literal",
1648 Applicability::MaybeIncorrect,
1653 .span_suggestion_verbose(
1654 lifetime.span.shrink_to_hi(),
1655 "add `'` to close the char literal",
1657 Applicability::MaybeIncorrect,
1661 let name = lifetime.without_first_quote().name;
1662 mk_lit_char(name, lifetime.span)
1665 /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
1666 fn recover_do_catch(&mut self) -> PResult<'a, P<Expr>> {
1667 let lo = self.token.span;
1669 self.bump(); // `do`
1670 self.bump(); // `catch`
1672 let span = lo.to(self.prev_token.span);
1673 self.sess.emit_err(DoCatchSyntaxRemoved { span });
1675 self.parse_try_block(lo)
1678 /// Parse an expression if the token can begin one.
1679 fn parse_expr_opt(&mut self) -> PResult<'a, Option<P<Expr>>> {
1680 Ok(if self.token.can_begin_expr() { Some(self.parse_expr()?) } else { None })
1683 /// Parse `"return" expr?`.
1684 fn parse_return_expr(&mut self) -> PResult<'a, P<Expr>> {
1685 let lo = self.prev_token.span;
1686 let kind = ExprKind::Ret(self.parse_expr_opt()?);
1687 let expr = self.mk_expr(lo.to(self.prev_token.span), kind);
1688 self.maybe_recover_from_bad_qpath(expr)
1691 /// Parse `"do" "yeet" expr?`.
1692 fn parse_yeet_expr(&mut self) -> PResult<'a, P<Expr>> {
1693 let lo = self.token.span;
1695 self.bump(); // `do`
1696 self.bump(); // `yeet`
1698 let kind = ExprKind::Yeet(self.parse_expr_opt()?);
1700 let span = lo.to(self.prev_token.span);
1701 self.sess.gated_spans.gate(sym::yeet_expr, span);
1702 let expr = self.mk_expr(span, kind);
1703 self.maybe_recover_from_bad_qpath(expr)
1706 /// Parse `"break" (('label (:? expr)?) | expr?)` with `"break"` token already eaten.
1707 /// If the label is followed immediately by a `:` token, the label and `:` are
1708 /// parsed as part of the expression (i.e. a labeled loop). The language team has
1709 /// decided in #87026 to require parentheses as a visual aid to avoid confusion if
1710 /// the break expression of an unlabeled break is a labeled loop (as in
1711 /// `break 'lbl: loop {}`); a labeled break with an unlabeled loop as its value
1712 /// expression only gets a warning for compatibility reasons; and a labeled break
1713 /// with a labeled loop does not even get a warning because there is no ambiguity.
1714 fn parse_break_expr(&mut self) -> PResult<'a, P<Expr>> {
1715 let lo = self.prev_token.span;
1716 let mut label = self.eat_label();
1717 let kind = if self.token == token::Colon && let Some(label) = label.take() {
1718 // The value expression can be a labeled loop, see issue #86948, e.g.:
1719 // `loop { break 'label: loop { break 'label 42; }; }`
1720 let lexpr = self.parse_labeled_expr(label, true)?;
1721 self.sess.emit_err(LabeledLoopInBreak {
1723 sub: WrapExpressionInParentheses {
1724 left: lexpr.span.shrink_to_lo(),
1725 right: lexpr.span.shrink_to_hi(),
1729 } else if self.token != token::OpenDelim(Delimiter::Brace)
1730 || !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1732 let mut expr = self.parse_expr_opt()?;
1733 if let Some(expr) = &mut expr {
1737 ExprKind::While(_, _, None)
1738 | ExprKind::ForLoop(_, _, _, None)
1739 | ExprKind::Loop(_, None, _)
1740 | ExprKind::Block(_, None)
1743 self.sess.buffer_lint_with_diagnostic(
1744 BREAK_WITH_LABEL_AND_LOOP,
1747 "this labeled break expression is easy to confuse with an unlabeled break with a labeled value expression",
1748 BuiltinLintDiagnostics::BreakWithLabelAndLoop(expr.span),
1752 // Recover `break label aaaaa`
1753 if self.may_recover()
1754 && let ExprKind::Path(None, p) = &expr.kind
1755 && let [segment] = &*p.segments
1756 && let &ast::PathSegment { ident, args: None, .. } = segment
1757 && let Some(next) = self.parse_expr_opt()?
1759 label = Some(self.recover_ident_into_label(ident));
1768 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Break(label, kind));
1769 self.maybe_recover_from_bad_qpath(expr)
1772 /// Parse `"continue" label?`.
1773 fn parse_continue_expr(&mut self, lo: Span) -> PResult<'a, P<Expr>> {
1774 let mut label = self.eat_label();
1776 // Recover `continue label` -> `continue 'label`
1777 if self.may_recover()
1779 && let Some((ident, _)) = self.token.ident()
1782 label = Some(self.recover_ident_into_label(ident));
1785 let kind = ExprKind::Continue(label);
1786 Ok(self.mk_expr(lo.to(self.prev_token.span), kind))
1789 /// Parse `"yield" expr?`.
1790 fn parse_yield_expr(&mut self) -> PResult<'a, P<Expr>> {
1791 let lo = self.prev_token.span;
1792 let kind = ExprKind::Yield(self.parse_expr_opt()?);
1793 let span = lo.to(self.prev_token.span);
1794 self.sess.gated_spans.gate(sym::generators, span);
1795 let expr = self.mk_expr(span, kind);
1796 self.maybe_recover_from_bad_qpath(expr)
1799 /// Returns a string literal if the next token is a string literal.
1800 /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
1801 /// and returns `None` if the next token is not literal at all.
1802 pub fn parse_str_lit(&mut self) -> Result<ast::StrLit, Option<MetaItemLit>> {
1803 match self.parse_opt_meta_item_lit() {
1804 Some(lit) => match lit.kind {
1805 ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
1812 _ => Err(Some(lit)),
1818 pub(crate) fn mk_token_lit_char(name: Symbol, span: Span) -> (token::Lit, Span) {
1819 (token::Lit { symbol: name, suffix: None, kind: token::Char }, span)
1822 fn mk_meta_item_lit_char(name: Symbol, span: Span) -> MetaItemLit {
1826 kind: ast::LitKind::Char(name.as_str().chars().next().unwrap_or('_')),
1831 fn handle_missing_lit<L>(
1833 mk_lit_char: impl FnOnce(Symbol, Span) -> L,
1834 ) -> PResult<'a, L> {
1835 if let token::Interpolated(inner) = &self.token.kind {
1836 let expr = match inner.as_ref() {
1837 token::NtExpr(expr) => Some(expr),
1838 token::NtLiteral(expr) => Some(expr),
1841 if let Some(expr) = expr {
1842 if matches!(expr.kind, ExprKind::Err) {
1843 let mut err = InvalidInterpolatedExpression { span: self.token.span }
1844 .into_diagnostic(&self.sess.span_diagnostic);
1845 err.downgrade_to_delayed_bug();
1850 let token = self.token.clone();
1851 let err = |self_: &Self| {
1852 let msg = format!("unexpected token: {}", super::token_descr(&token));
1853 self_.struct_span_err(token.span, &msg)
1855 // On an error path, eagerly consider a lifetime to be an unclosed character lit
1856 if self.token.is_lifetime() {
1857 let lt = self.expect_lifetime();
1858 Ok(self.recover_unclosed_char(lt.ident, mk_lit_char, err))
1864 pub(super) fn parse_token_lit(&mut self) -> PResult<'a, (token::Lit, Span)> {
1865 self.parse_opt_token_lit()
1867 .or_else(|()| self.handle_missing_lit(Parser::mk_token_lit_char))
1870 pub(super) fn parse_meta_item_lit(&mut self) -> PResult<'a, MetaItemLit> {
1871 self.parse_opt_meta_item_lit()
1873 .or_else(|()| self.handle_missing_lit(Parser::mk_meta_item_lit_char))
1876 fn recover_after_dot(&mut self) -> Option<Token> {
1877 let mut recovered = None;
1878 if self.token == token::Dot {
1879 // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
1880 // dot would follow an optional literal, so we do this unconditionally.
1881 recovered = self.look_ahead(1, |next_token| {
1882 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
1885 if self.token.span.hi() == next_token.span.lo() {
1886 let s = String::from("0.") + symbol.as_str();
1887 let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
1888 return Some(Token::new(kind, self.token.span.to(next_token.span)));
1893 if let Some(token) = &recovered {
1895 self.sess.emit_err(FloatLiteralRequiresIntegerPart {
1897 correct: pprust::token_to_string(token).into_owned(),
1905 /// Matches `lit = true | false | token_lit`.
1906 /// Returns `None` if the next token is not a literal.
1907 pub(super) fn parse_opt_token_lit(&mut self) -> Option<(token::Lit, Span)> {
1908 let recovered = self.recover_after_dot();
1909 let token = recovered.as_ref().unwrap_or(&self.token);
1910 let span = token.span;
1911 token::Lit::from_token(token).map(|token_lit| {
1917 /// Matches `lit = true | false | token_lit`.
1918 /// Returns `None` if the next token is not a literal.
1919 pub(super) fn parse_opt_meta_item_lit(&mut self) -> Option<MetaItemLit> {
1920 let recovered = self.recover_after_dot();
1921 let token = recovered.as_ref().unwrap_or(&self.token);
1922 match token::Lit::from_token(token) {
1923 Some(token_lit) => {
1924 match MetaItemLit::from_token_lit(token_lit, token.span) {
1930 let span = token.span;
1931 let token::Literal(lit) = token.kind else {
1935 report_lit_error(&self.sess, err, lit, span);
1936 // Pack possible quotes and prefixes from the original literal into
1937 // the error literal's symbol so they can be pretty-printed faithfully.
1938 let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
1939 let symbol = Symbol::intern(&suffixless_lit.to_string());
1940 let lit = token::Lit::new(token::Err, symbol, lit.suffix);
1942 MetaItemLit::from_token_lit(lit, span)
1943 .unwrap_or_else(|_| unreachable!()),
1952 pub(super) fn expect_no_tuple_index_suffix(&self, span: Span, suffix: Symbol) {
1953 if [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suffix) {
1954 // #59553: warn instead of reject out of hand to allow the fix to percolate
1955 // through the ecosystem when people fix their macros
1956 self.sess.emit_warning(InvalidLiteralSuffixOnTupleIndex {
1959 exception: Some(()),
1962 self.sess.emit_err(InvalidLiteralSuffixOnTupleIndex { span, suffix, exception: None });
1966 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1967 /// Keep this in sync with `Token::can_begin_literal_maybe_minus`.
1968 pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1969 maybe_whole_expr!(self);
1971 let lo = self.token.span;
1972 let minus_present = self.eat(&token::BinOp(token::Minus));
1973 let (token_lit, span) = self.parse_token_lit()?;
1974 let expr = self.mk_expr(span, ExprKind::Lit(token_lit));
1977 Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_unary(UnOp::Neg, expr)))
1983 fn is_array_like_block(&mut self) -> bool {
1984 self.look_ahead(1, |t| matches!(t.kind, TokenKind::Ident(..) | TokenKind::Literal(_)))
1985 && self.look_ahead(2, |t| t == &token::Comma)
1986 && self.look_ahead(3, |t| t.can_begin_expr())
1989 /// Emits a suggestion if it looks like the user meant an array but
1990 /// accidentally used braces, causing the code to be interpreted as a block
1992 fn maybe_suggest_brackets_instead_of_braces(&mut self, lo: Span) -> Option<P<Expr>> {
1993 let mut snapshot = self.create_snapshot_for_diagnostic();
1994 match snapshot.parse_array_or_repeat_expr(Delimiter::Brace) {
1996 self.sess.emit_err(ArrayBracketsInsteadOfSpaces {
1998 sub: ArrayBracketsInsteadOfSpacesSugg {
2000 right: snapshot.prev_token.span,
2004 self.restore_snapshot(snapshot);
2005 Some(self.mk_expr_err(arr.span))
2014 fn suggest_missing_semicolon_before_array(
2017 open_delim_span: Span,
2018 ) -> PResult<'a, ()> {
2019 if !self.may_recover() {
2023 if self.token.kind == token::Comma {
2024 if !self.sess.source_map().is_multiline(prev_span.until(self.token.span)) {
2027 let mut snapshot = self.create_snapshot_for_diagnostic();
2029 match snapshot.parse_seq_to_before_end(
2030 &token::CloseDelim(Delimiter::Bracket),
2031 SeqSep::trailing_allowed(token::Comma),
2035 // When the close delim is `)`, `token.kind` is expected to be `token::CloseDelim(Delimiter::Parenthesis)`,
2036 // but the actual `token.kind` is `token::CloseDelim(Delimiter::Bracket)`.
2037 // This is because the `token.kind` of the close delim is treated as the same as
2038 // that of the open delim in `TokenTreesReader::parse_token_tree`, even if the delimiters of them are different.
2039 // Therefore, `token.kind` should not be compared here.
2041 .span_to_snippet(snapshot.token.span)
2042 .map_or(false, |snippet| snippet == "]") =>
2044 return Err(MissingSemicolonBeforeArray {
2045 open_delim: open_delim_span,
2046 semicolon: prev_span.shrink_to_hi(),
2047 }.into_diagnostic(&self.sess.span_diagnostic));
2050 Err(err) => err.cancel(),
2056 /// Parses a block or unsafe block.
2057 pub(super) fn parse_block_expr(
2059 opt_label: Option<Label>,
2061 blk_mode: BlockCheckMode,
2062 ) -> PResult<'a, P<Expr>> {
2063 if self.may_recover() && self.is_array_like_block() {
2064 if let Some(arr) = self.maybe_suggest_brackets_instead_of_braces(lo) {
2069 if self.token.is_whole_block() {
2070 self.sess.emit_err(InvalidBlockMacroSegment {
2071 span: self.token.span,
2072 context: lo.to(self.token.span),
2076 let (attrs, blk) = self.parse_block_common(lo, blk_mode, true)?;
2077 Ok(self.mk_expr_with_attrs(blk.span, ExprKind::Block(blk, opt_label), attrs))
2080 /// Parse a block which takes no attributes and has no label
2081 fn parse_simple_block(&mut self) -> PResult<'a, P<Expr>> {
2082 let blk = self.parse_block()?;
2083 Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None)))
2086 /// Parses a closure expression (e.g., `move |args| expr`).
2087 fn parse_closure_expr(&mut self) -> PResult<'a, P<Expr>> {
2088 let lo = self.token.span;
2090 let binder = if self.check_keyword(kw::For) {
2091 let lo = self.token.span;
2092 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
2093 let span = lo.to(self.prev_token.span);
2095 self.sess.gated_spans.gate(sym::closure_lifetime_binder, span);
2097 ClosureBinder::For { span, generic_params: P::from_vec(lifetime_defs) }
2099 ClosureBinder::NotPresent
2102 let constness = self.parse_constness(Case::Sensitive);
2105 if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
2107 let asyncness = if self.token.uninterpolated_span().rust_2018() {
2108 self.parse_asyncness(Case::Sensitive)
2113 let capture_clause = self.parse_capture_clause()?;
2114 let (fn_decl, fn_arg_span) = self.parse_fn_block_decl()?;
2115 let decl_hi = self.prev_token.span;
2116 let mut body = match fn_decl.output {
2117 FnRetTy::Default(_) => {
2118 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
2119 self.parse_expr_res(restrictions, None)?
2122 // If an explicit return type is given, require a block to appear (RFC 968).
2123 let body_lo = self.token.span;
2124 self.parse_block_expr(None, body_lo, BlockCheckMode::Default)?
2128 if let Async::Yes { span, .. } = asyncness {
2129 // Feature-gate `async ||` closures.
2130 self.sess.gated_spans.gate(sym::async_closure, span);
2133 if self.token.kind == TokenKind::Semi
2134 && matches!(self.token_cursor.frame.delim_sp, Some((Delimiter::Parenthesis, _)))
2135 && self.may_recover()
2137 // It is likely that the closure body is a block but where the
2138 // braces have been removed. We will recover and eat the next
2139 // statements later in the parsing process.
2140 body = self.mk_expr_err(body.span);
2143 let body_span = body.span;
2145 let closure = self.mk_expr(
2147 ExprKind::Closure(Box::new(ast::Closure {
2155 fn_decl_span: lo.to(decl_hi),
2160 // Disable recovery for closure body
2162 ClosureSpans { whole_closure: closure.span, closing_pipe: decl_hi, body: body_span };
2163 self.current_closure = Some(spans);
2168 /// Parses an optional `move` prefix to a closure-like construct.
2169 fn parse_capture_clause(&mut self) -> PResult<'a, CaptureBy> {
2170 if self.eat_keyword(kw::Move) {
2171 // Check for `move async` and recover
2172 if self.check_keyword(kw::Async) {
2173 let move_async_span = self.token.span.with_lo(self.prev_token.span.data().lo);
2174 Err(AsyncMoveOrderIncorrect { span: move_async_span }
2175 .into_diagnostic(&self.sess.span_diagnostic))
2177 Ok(CaptureBy::Value)
2184 /// Parses the `|arg, arg|` header of a closure.
2185 fn parse_fn_block_decl(&mut self) -> PResult<'a, (P<FnDecl>, Span)> {
2186 let arg_start = self.token.span.lo();
2188 let inputs = if self.eat(&token::OrOr) {
2191 self.expect(&token::BinOp(token::Or))?;
2193 .parse_seq_to_before_tokens(
2194 &[&token::BinOp(token::Or), &token::OrOr],
2195 SeqSep::trailing_allowed(token::Comma),
2196 TokenExpectType::NoExpect,
2197 |p| p.parse_fn_block_param(),
2203 let arg_span = self.prev_token.span.with_lo(arg_start);
2205 self.parse_ret_ty(AllowPlus::Yes, RecoverQPath::Yes, RecoverReturnSign::Yes)?;
2207 Ok((P(FnDecl { inputs, output }), arg_span))
2210 /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
2211 fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
2212 let lo = self.token.span;
2213 let attrs = self.parse_outer_attributes()?;
2214 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2215 let pat = this.parse_pat_no_top_alt(PARAM_EXPECTED)?;
2216 let ty = if this.eat(&token::Colon) {
2219 this.mk_ty(this.prev_token.span, TyKind::Infer)
2227 span: lo.to(this.prev_token.span),
2229 is_placeholder: false,
2231 TrailingToken::MaybeComma,
2236 /// Parses an `if` expression (`if` token already eaten).
2237 fn parse_if_expr(&mut self) -> PResult<'a, P<Expr>> {
2238 let lo = self.prev_token.span;
2239 let cond = self.parse_cond_expr()?;
2240 self.parse_if_after_cond(lo, cond)
2243 fn parse_if_after_cond(&mut self, lo: Span, mut cond: P<Expr>) -> PResult<'a, P<Expr>> {
2244 let cond_span = cond.span;
2245 // Tries to interpret `cond` as either a missing expression if it's a block,
2246 // or as an unfinished expression if it's a binop and the RHS is a block.
2247 // We could probably add more recoveries here too...
2248 let mut recover_block_from_condition = |this: &mut Self| {
2249 let block = match &mut cond.kind {
2250 ExprKind::Binary(Spanned { span: binop_span, .. }, _, right)
2251 if let ExprKind::Block(_, None) = right.kind => {
2252 self.sess.emit_err(IfExpressionMissingThenBlock {
2254 sub: IfExpressionMissingThenBlockSub::UnfinishedCondition(
2255 cond_span.shrink_to_lo().to(*binop_span)
2258 std::mem::replace(right, this.mk_expr_err(binop_span.shrink_to_hi()))
2260 ExprKind::Block(_, None) => {
2261 self.sess.emit_err(IfExpressionMissingCondition {
2262 if_span: lo.shrink_to_hi(),
2263 block_span: self.sess.source_map().start_point(cond_span),
2265 std::mem::replace(&mut cond, this.mk_expr_err(cond_span.shrink_to_hi()))
2271 if let ExprKind::Block(block, _) = &block.kind {
2278 let thn = if self.token.is_keyword(kw::Else) {
2279 if let Some(block) = recover_block_from_condition(self) {
2282 self.sess.emit_err(IfExpressionMissingThenBlock {
2284 sub: IfExpressionMissingThenBlockSub::AddThenBlock(cond_span.shrink_to_hi()),
2286 self.mk_block_err(cond_span.shrink_to_hi())
2289 let attrs = self.parse_outer_attributes()?; // For recovery.
2290 let block = if self.check(&token::OpenDelim(Delimiter::Brace)) {
2293 if let Some(block) = recover_block_from_condition(self) {
2296 self.error_on_extra_if(&cond)?;
2297 // Parse block, which will always fail, but we can add a nice note to the error
2298 self.parse_block().map_err(|mut err| {
2301 "the `if` expression is missing a block after this condition",
2307 self.error_on_if_block_attrs(lo, false, block.span, attrs);
2310 let els = if self.eat_keyword(kw::Else) { Some(self.parse_else_expr()?) } else { None };
2311 Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::If(cond, thn, els)))
2314 /// Parses the condition of a `if` or `while` expression.
2315 fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
2317 self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL | Restrictions::ALLOW_LET, None)?;
2319 if let ExprKind::Let(..) = cond.kind {
2320 // Remove the last feature gating of a `let` expression since it's stable.
2321 self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
2327 /// Parses a `let $pat = $expr` pseudo-expression.
2328 fn parse_let_expr(&mut self) -> PResult<'a, P<Expr>> {
2329 // This is a *approximate* heuristic that detects if `let` chains are
2330 // being parsed in the right position. It's approximate because it
2331 // doesn't deny all invalid `let` expressions, just completely wrong usages.
2332 let not_in_chain = !matches!(
2333 self.prev_token.kind,
2334 TokenKind::AndAnd | TokenKind::Ident(kw::If, _) | TokenKind::Ident(kw::While, _)
2336 if !self.restrictions.contains(Restrictions::ALLOW_LET) || not_in_chain {
2337 self.sess.emit_err(ExpectedExpressionFoundLet { span: self.token.span });
2340 self.bump(); // Eat `let` token
2341 let lo = self.prev_token.span;
2342 let pat = self.parse_pat_allow_top_alt(
2346 CommaRecoveryMode::LikelyTuple,
2348 if self.token == token::EqEq {
2349 self.sess.emit_err(ExpectedEqForLetExpr {
2350 span: self.token.span,
2351 sugg_span: self.token.span,
2355 self.expect(&token::Eq)?;
2357 let expr = self.with_res(self.restrictions | Restrictions::NO_STRUCT_LITERAL, |this| {
2358 this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
2360 let span = lo.to(expr.span);
2361 self.sess.gated_spans.gate(sym::let_chains, span);
2362 Ok(self.mk_expr(span, ExprKind::Let(pat, expr, span)))
2365 /// Parses an `else { ... }` expression (`else` token already eaten).
2366 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
2367 let else_span = self.prev_token.span; // `else`
2368 let attrs = self.parse_outer_attributes()?; // For recovery.
2369 let expr = if self.eat_keyword(kw::If) {
2370 self.parse_if_expr()?
2371 } else if self.check(&TokenKind::OpenDelim(Delimiter::Brace)) {
2372 self.parse_simple_block()?
2374 let snapshot = self.create_snapshot_for_diagnostic();
2375 let first_tok = super::token_descr(&self.token);
2376 let first_tok_span = self.token.span;
2377 match self.parse_expr() {
2379 // If it's not a free-standing expression, and is followed by a block,
2380 // then it's very likely the condition to an `else if`.
2381 if self.check(&TokenKind::OpenDelim(Delimiter::Brace))
2382 && classify::expr_requires_semi_to_be_stmt(&cond) =>
2384 self.sess.emit_err(ExpectedElseBlock {
2388 condition_start: cond.span.shrink_to_lo(),
2390 self.parse_if_after_cond(cond.span.shrink_to_lo(), cond)?
2394 self.restore_snapshot(snapshot);
2395 self.parse_simple_block()?
2398 self.restore_snapshot(snapshot);
2399 self.parse_simple_block()?
2403 self.error_on_if_block_attrs(else_span, true, expr.span, attrs);
2407 fn error_on_if_block_attrs(
2414 if attrs.is_empty() {
2418 let attrs: &[ast::Attribute] = &attrs.take_for_recovery(self.sess);
2419 let (attributes, last) = match attrs {
2421 [x0 @ xn] | [x0, .., xn] => (x0.span.to(xn.span), xn.span),
2423 let ctx = if is_ctx_else { "else" } else { "if" };
2424 self.sess.emit_err(OuterAttributeNotAllowedOnIfElse {
2428 ctx: ctx.to_string(),
2433 fn error_on_extra_if(&mut self, cond: &P<Expr>) -> PResult<'a, ()> {
2434 if let ExprKind::Binary(Spanned { span: binop_span, node: binop}, _, right) = &cond.kind &&
2435 let BinOpKind::And = binop &&
2436 let ExprKind::If(cond, ..) = &right.kind {
2437 Err(self.sess.create_err(UnexpectedIfWithIf(binop_span.shrink_to_hi().to(cond.span.shrink_to_lo()))))
2443 /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
2444 fn parse_for_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2445 // Record whether we are about to parse `for (`.
2446 // This is used below for recovery in case of `for ( $stuff ) $block`
2447 // in which case we will suggest `for $stuff $block`.
2448 let begin_paren = match self.token.kind {
2449 token::OpenDelim(Delimiter::Parenthesis) => Some(self.token.span),
2453 let pat = self.parse_pat_allow_top_alt(
2457 CommaRecoveryMode::LikelyTuple,
2459 if !self.eat_keyword(kw::In) {
2460 self.error_missing_in_for_loop();
2462 self.check_for_for_in_in_typo(self.prev_token.span);
2463 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2465 let pat = self.recover_parens_around_for_head(pat, begin_paren);
2467 let (attrs, loop_block) = self.parse_inner_attrs_and_block()?;
2469 let kind = ExprKind::ForLoop(pat, expr, loop_block, opt_label);
2470 Ok(self.mk_expr_with_attrs(lo.to(self.prev_token.span), kind, attrs))
2473 fn error_missing_in_for_loop(&mut self) {
2474 let (span, sub): (_, fn(_) -> _) = if self.token.is_ident_named(sym::of) {
2475 // Possibly using JS syntax (#75311).
2476 let span = self.token.span;
2478 (span, MissingInInForLoopSub::InNotOf)
2480 (self.prev_token.span.between(self.token.span), MissingInInForLoopSub::AddIn)
2483 self.sess.emit_err(MissingInInForLoop { span, sub: sub(span) });
2486 /// Parses a `while` or `while let` expression (`while` token already eaten).
2487 fn parse_while_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2488 let cond = self.parse_cond_expr().map_err(|mut err| {
2489 err.span_label(lo, "while parsing the condition of this `while` expression");
2492 let (attrs, body) = self.parse_inner_attrs_and_block().map_err(|mut err| {
2493 err.span_label(lo, "while parsing the body of this `while` expression");
2494 err.span_label(cond.span, "this `while` condition successfully parsed");
2497 Ok(self.mk_expr_with_attrs(
2498 lo.to(self.prev_token.span),
2499 ExprKind::While(cond, body, opt_label),
2504 /// Parses `loop { ... }` (`loop` token already eaten).
2505 fn parse_loop_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2506 let loop_span = self.prev_token.span;
2507 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2508 Ok(self.mk_expr_with_attrs(
2509 lo.to(self.prev_token.span),
2510 ExprKind::Loop(body, opt_label, loop_span),
2515 pub(crate) fn eat_label(&mut self) -> Option<Label> {
2516 self.token.lifetime().map(|ident| {
2522 /// Parses a `match ... { ... }` expression (`match` token already eaten).
2523 fn parse_match_expr(&mut self) -> PResult<'a, P<Expr>> {
2524 let match_span = self.prev_token.span;
2525 let lo = self.prev_token.span;
2526 let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2527 if let Err(mut e) = self.expect(&token::OpenDelim(Delimiter::Brace)) {
2528 if self.token == token::Semi {
2529 e.span_suggestion_short(
2531 "try removing this `match`",
2533 Applicability::MaybeIncorrect, // speculative
2536 if self.maybe_recover_unexpected_block_label() {
2543 let attrs = self.parse_inner_attributes()?;
2545 let mut arms: Vec<Arm> = Vec::new();
2546 while self.token != token::CloseDelim(Delimiter::Brace) {
2547 match self.parse_arm() {
2548 Ok(arm) => arms.push(arm),
2550 // Recover by skipping to the end of the block.
2552 self.recover_stmt();
2553 let span = lo.to(self.token.span);
2554 if self.token == token::CloseDelim(Delimiter::Brace) {
2557 return Ok(self.mk_expr_with_attrs(
2559 ExprKind::Match(scrutinee, arms),
2565 let hi = self.token.span;
2567 Ok(self.mk_expr_with_attrs(lo.to(hi), ExprKind::Match(scrutinee, arms), attrs))
2570 /// Attempt to recover from match arm body with statements and no surrounding braces.
2571 fn parse_arm_body_missing_braces(
2573 first_expr: &P<Expr>,
2575 ) -> Option<P<Expr>> {
2576 if self.token.kind != token::Semi {
2579 let start_snapshot = self.create_snapshot_for_diagnostic();
2580 let semi_sp = self.token.span;
2583 vec![self.mk_stmt(first_expr.span, ast::StmtKind::Expr(first_expr.clone()))];
2584 let err = |this: &Parser<'_>, stmts: Vec<ast::Stmt>| {
2585 let span = stmts[0].span.to(stmts[stmts.len() - 1].span);
2587 this.sess.emit_err(MatchArmBodyWithoutBraces {
2590 num_statements: stmts.len(),
2591 sub: if stmts.len() > 1 {
2592 MatchArmBodyWithoutBracesSugg::AddBraces {
2593 left: span.shrink_to_lo(),
2594 right: span.shrink_to_hi(),
2597 MatchArmBodyWithoutBracesSugg::UseComma { semicolon: semi_sp }
2600 this.mk_expr_err(span)
2602 // We might have either a `,` -> `;` typo, or a block without braces. We need
2603 // a more subtle parsing strategy.
2605 if self.token.kind == token::CloseDelim(Delimiter::Brace) {
2606 // We have reached the closing brace of the `match` expression.
2607 return Some(err(self, stmts));
2609 if self.token.kind == token::Comma {
2610 self.restore_snapshot(start_snapshot);
2613 let pre_pat_snapshot = self.create_snapshot_for_diagnostic();
2614 match self.parse_pat_no_top_alt(None) {
2616 if self.token.kind == token::FatArrow {
2618 self.restore_snapshot(pre_pat_snapshot);
2619 return Some(err(self, stmts));
2627 self.restore_snapshot(pre_pat_snapshot);
2628 match self.parse_stmt_without_recovery(true, ForceCollect::No) {
2629 // Consume statements for as long as possible.
2634 self.restore_snapshot(start_snapshot);
2637 // We couldn't parse either yet another statement missing it's
2638 // enclosing block nor the next arm's pattern or closing brace.
2641 self.restore_snapshot(start_snapshot);
2649 pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
2650 // Used to check the `let_chains` and `if_let_guard` features mostly by scanning
2652 fn check_let_expr(expr: &Expr) -> (bool, bool) {
2654 ExprKind::Binary(BinOp { node: BinOpKind::And, .. }, lhs, rhs) => {
2655 let lhs_rslt = check_let_expr(lhs);
2656 let rhs_rslt = check_let_expr(rhs);
2657 (lhs_rslt.0 || rhs_rslt.0, false)
2659 ExprKind::Let(..) => (true, true),
2663 let attrs = self.parse_outer_attributes()?;
2664 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2665 let lo = this.token.span;
2666 let pat = this.parse_pat_allow_top_alt(
2670 CommaRecoveryMode::EitherTupleOrPipe,
2672 let guard = if this.eat_keyword(kw::If) {
2673 let if_span = this.prev_token.span;
2674 let cond = this.parse_expr_res(Restrictions::ALLOW_LET, None)?;
2675 let (has_let_expr, does_not_have_bin_op) = check_let_expr(&cond);
2677 if does_not_have_bin_op {
2678 // Remove the last feature gating of a `let` expression since it's stable.
2679 this.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
2681 let span = if_span.to(cond.span);
2682 this.sess.gated_spans.gate(sym::if_let_guard, span);
2688 let arrow_span = this.token.span;
2689 if let Err(mut err) = this.expect(&token::FatArrow) {
2690 // We might have a `=>` -> `=` or `->` typo (issue #89396).
2691 if TokenKind::FatArrow
2693 .map_or(false, |similar_tokens| similar_tokens.contains(&this.token.kind))
2695 err.span_suggestion(
2697 "try using a fat arrow here",
2699 Applicability::MaybeIncorrect,
2707 let arm_start_span = this.token.span;
2709 let expr = this.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
2710 err.span_label(arrow_span, "while parsing the `match` arm starting here");
2714 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
2715 && this.token != token::CloseDelim(Delimiter::Brace);
2717 let hi = this.prev_token.span;
2720 let sm = this.sess.source_map();
2721 if let Some(body) = this.parse_arm_body_missing_braces(&expr, arrow_span) {
2722 let span = body.span;
2731 is_placeholder: false,
2733 TrailingToken::None,
2736 this.expect_one_of(&[token::Comma], &[token::CloseDelim(Delimiter::Brace)])
2737 .or_else(|mut err| {
2738 if this.token == token::FatArrow {
2739 if let Ok(expr_lines) = sm.span_to_lines(expr.span)
2740 && let Ok(arm_start_lines) = sm.span_to_lines(arm_start_span)
2741 && arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
2742 && expr_lines.lines.len() == 2
2744 // We check whether there's any trailing code in the parse span,
2745 // if there isn't, we very likely have the following:
2748 // | -- - missing comma
2752 // | - ^^ self.token.span
2754 // | parsed until here as `"y" & X`
2755 err.span_suggestion_short(
2756 arm_start_span.shrink_to_hi(),
2757 "missing a comma here to end this `match` arm",
2759 Applicability::MachineApplicable,
2764 // FIXME(compiler-errors): We could also recover `; PAT =>` here
2766 // Try to parse a following `PAT =>`, if successful
2767 // then we should recover.
2768 let mut snapshot = this.create_snapshot_for_diagnostic();
2769 let pattern_follows = snapshot
2770 .parse_pat_allow_top_alt(
2774 CommaRecoveryMode::EitherTupleOrPipe,
2776 .map_err(|err| err.cancel())
2778 if pattern_follows && snapshot.check(&TokenKind::FatArrow) {
2780 this.sess.emit_err(MissingCommaAfterMatchArm {
2781 span: hi.shrink_to_hi(),
2786 err.span_label(arrow_span, "while parsing the `match` arm starting here");
2790 this.eat(&token::Comma);
2801 is_placeholder: false,
2803 TrailingToken::None,
2808 /// Parses a `try {...}` expression (`try` token already eaten).
2809 fn parse_try_block(&mut self, span_lo: Span) -> PResult<'a, P<Expr>> {
2810 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2811 if self.eat_keyword(kw::Catch) {
2812 Err(CatchAfterTry { span: self.prev_token.span }
2813 .into_diagnostic(&self.sess.span_diagnostic))
2815 let span = span_lo.to(body.span);
2816 self.sess.gated_spans.gate(sym::try_blocks, span);
2817 Ok(self.mk_expr_with_attrs(span, ExprKind::TryBlock(body), attrs))
2821 fn is_do_catch_block(&self) -> bool {
2822 self.token.is_keyword(kw::Do)
2823 && self.is_keyword_ahead(1, &[kw::Catch])
2824 && self.look_ahead(2, |t| *t == token::OpenDelim(Delimiter::Brace))
2825 && !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
2828 fn is_do_yeet(&self) -> bool {
2829 self.token.is_keyword(kw::Do) && self.is_keyword_ahead(1, &[kw::Yeet])
2832 fn is_try_block(&self) -> bool {
2833 self.token.is_keyword(kw::Try)
2834 && self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace))
2835 && self.token.uninterpolated_span().rust_2018()
2838 /// Parses an `async move? {...}` expression.
2839 fn parse_async_block(&mut self) -> PResult<'a, P<Expr>> {
2840 let lo = self.token.span;
2841 self.expect_keyword(kw::Async)?;
2842 let capture_clause = self.parse_capture_clause()?;
2843 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2844 let kind = ExprKind::Async(capture_clause, DUMMY_NODE_ID, body);
2845 Ok(self.mk_expr_with_attrs(lo.to(self.prev_token.span), kind, attrs))
2848 fn is_async_block(&self) -> bool {
2849 self.token.is_keyword(kw::Async)
2852 self.is_keyword_ahead(1, &[kw::Move])
2853 && self.look_ahead(2, |t| *t == token::OpenDelim(Delimiter::Brace))
2856 self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace))
2860 fn is_certainly_not_a_block(&self) -> bool {
2861 self.look_ahead(1, |t| t.is_ident())
2863 // `{ ident, ` cannot start a block.
2864 self.look_ahead(2, |t| t == &token::Comma)
2865 || self.look_ahead(2, |t| t == &token::Colon)
2867 // `{ ident: token, ` cannot start a block.
2868 self.look_ahead(4, |t| t == &token::Comma) ||
2869 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
2870 self.look_ahead(3, |t| !t.can_begin_type())
2875 fn maybe_parse_struct_expr(
2877 qself: &Option<P<ast::QSelf>>,
2879 ) -> Option<PResult<'a, P<Expr>>> {
2880 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
2881 if struct_allowed || self.is_certainly_not_a_block() {
2882 if let Err(err) = self.expect(&token::OpenDelim(Delimiter::Brace)) {
2883 return Some(Err(err));
2885 let expr = self.parse_struct_expr(qself.clone(), path.clone(), true);
2886 if let (Ok(expr), false) = (&expr, struct_allowed) {
2887 // This is a struct literal, but we don't can't accept them here.
2888 self.sess.emit_err(StructLiteralNotAllowedHere {
2890 sub: StructLiteralNotAllowedHereSugg {
2891 left: path.span.shrink_to_lo(),
2892 right: expr.span.shrink_to_hi(),
2901 pub(super) fn parse_struct_fields(
2905 close_delim: Delimiter,
2906 ) -> PResult<'a, (Vec<ExprField>, ast::StructRest, bool)> {
2907 let mut fields = Vec::new();
2908 let mut base = ast::StructRest::None;
2909 let mut recover_async = false;
2911 let mut async_block_err = |e: &mut Diagnostic, span: Span| {
2912 recover_async = true;
2913 e.span_label(span, "`async` blocks are only allowed in Rust 2018 or later");
2914 e.help_use_latest_edition();
2917 while self.token != token::CloseDelim(close_delim) {
2918 if self.eat(&token::DotDot) || self.recover_struct_field_dots(close_delim) {
2919 let exp_span = self.prev_token.span;
2920 // We permit `.. }` on the left-hand side of a destructuring assignment.
2921 if self.check(&token::CloseDelim(close_delim)) {
2922 base = ast::StructRest::Rest(self.prev_token.span.shrink_to_hi());
2925 match self.parse_expr() {
2926 Ok(e) => base = ast::StructRest::Base(e),
2927 Err(mut e) if recover => {
2929 self.recover_stmt();
2931 Err(e) => return Err(e),
2933 self.recover_struct_comma_after_dotdot(exp_span);
2937 let recovery_field = self.find_struct_error_after_field_looking_code();
2938 let parsed_field = match self.parse_expr_field() {
2941 if pth == kw::Async {
2942 async_block_err(&mut e, pth.span);
2944 e.span_label(pth.span, "while parsing this struct");
2948 // If the next token is a comma, then try to parse
2949 // what comes next as additional fields, rather than
2950 // bailing out until next `}`.
2951 if self.token != token::Comma {
2952 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2953 if self.token != token::Comma {
2961 let is_shorthand = parsed_field.as_ref().map_or(false, |f| f.is_shorthand);
2962 // A shorthand field can be turned into a full field with `:`.
2963 // We should point this out.
2964 self.check_or_expected(!is_shorthand, TokenType::Token(token::Colon));
2966 match self.expect_one_of(&[token::Comma], &[token::CloseDelim(close_delim)]) {
2968 if let Some(f) = parsed_field.or(recovery_field) {
2969 // Only include the field if there's no parse error for the field name.
2974 if pth == kw::Async {
2975 async_block_err(&mut e, pth.span);
2977 e.span_label(pth.span, "while parsing this struct");
2978 if let Some(f) = recovery_field {
2981 self.prev_token.span.shrink_to_hi(),
2982 "try adding a comma",
2984 Applicability::MachineApplicable,
2986 } else if is_shorthand
2987 && (AssocOp::from_token(&self.token).is_some()
2988 || matches!(&self.token.kind, token::OpenDelim(_))
2989 || self.token.kind == token::Dot)
2991 // Looks like they tried to write a shorthand, complex expression.
2992 let ident = parsed_field.expect("is_shorthand implies Some").ident;
2994 ident.span.shrink_to_lo(),
2995 "try naming a field",
2996 &format!("{ident}: "),
2997 Applicability::HasPlaceholders,
3005 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
3006 self.eat(&token::Comma);
3010 Ok((fields, base, recover_async))
3013 /// Precondition: already parsed the '{'.
3014 pub(super) fn parse_struct_expr(
3016 qself: Option<P<ast::QSelf>>,
3019 ) -> PResult<'a, P<Expr>> {
3021 let (fields, base, recover_async) =
3022 self.parse_struct_fields(pth.clone(), recover, Delimiter::Brace)?;
3023 let span = lo.to(self.token.span);
3024 self.expect(&token::CloseDelim(Delimiter::Brace))?;
3025 let expr = if recover_async {
3028 ExprKind::Struct(P(ast::StructExpr { qself, path: pth, fields, rest: base }))
3030 Ok(self.mk_expr(span, expr))
3033 /// Use in case of error after field-looking code: `S { foo: () with a }`.
3034 fn find_struct_error_after_field_looking_code(&self) -> Option<ExprField> {
3035 match self.token.ident() {
3036 Some((ident, is_raw))
3037 if (is_raw || !ident.is_reserved())
3038 && self.look_ahead(1, |t| *t == token::Colon) =>
3040 Some(ast::ExprField {
3042 span: self.token.span,
3043 expr: self.mk_expr_err(self.token.span),
3044 is_shorthand: false,
3045 attrs: AttrVec::new(),
3047 is_placeholder: false,
3054 fn recover_struct_comma_after_dotdot(&mut self, span: Span) {
3055 if self.token != token::Comma {
3058 self.sess.emit_err(CommaAfterBaseStruct {
3059 span: span.to(self.prev_token.span),
3060 comma: self.token.span,
3062 self.recover_stmt();
3065 fn recover_struct_field_dots(&mut self, close_delim: Delimiter) -> bool {
3066 if !self.look_ahead(1, |t| *t == token::CloseDelim(close_delim))
3067 && self.eat(&token::DotDotDot)
3069 // recover from typo of `...`, suggest `..`
3070 let span = self.prev_token.span;
3071 self.sess.emit_err(MissingDotDot { token_span: span, sugg_span: span });
3077 /// Converts an ident into 'label and emits an "expected a label, found an identifier" error.
3078 fn recover_ident_into_label(&mut self, ident: Ident) -> Label {
3079 // Convert `label` -> `'label`,
3080 // so that nameres doesn't complain about non-existing label
3081 let label = format!("'{}", ident.name);
3082 let ident = Ident { name: Symbol::intern(&label), span: ident.span };
3084 self.struct_span_err(ident.span, "expected a label, found an identifier")
3087 "labels start with a tick",
3089 Applicability::MachineApplicable,
3096 /// Parses `ident (COLON expr)?`.
3097 fn parse_expr_field(&mut self) -> PResult<'a, ExprField> {
3098 let attrs = self.parse_outer_attributes()?;
3099 self.recover_diff_marker();
3100 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
3101 let lo = this.token.span;
3103 // Check if a colon exists one ahead. This means we're parsing a fieldname.
3104 let is_shorthand = !this.look_ahead(1, |t| t == &token::Colon || t == &token::Eq);
3105 let (ident, expr) = if is_shorthand {
3106 // Mimic `x: x` for the `x` field shorthand.
3107 let ident = this.parse_ident_common(false)?;
3108 let path = ast::Path::from_ident(ident);
3109 (ident, this.mk_expr(ident.span, ExprKind::Path(None, path)))
3111 let ident = this.parse_field_name()?;
3112 this.error_on_eq_field_init(ident);
3114 (ident, this.parse_expr()?)
3120 span: lo.to(expr.span),
3125 is_placeholder: false,
3127 TrailingToken::MaybeComma,
3132 /// Check for `=`. This means the source incorrectly attempts to
3133 /// initialize a field with an eq rather than a colon.
3134 fn error_on_eq_field_init(&self, field_name: Ident) {
3135 if self.token != token::Eq {
3139 self.sess.emit_err(EqFieldInit {
3140 span: self.token.span,
3141 eq: field_name.span.shrink_to_hi().to(self.token.span),
3145 fn err_dotdotdot_syntax(&self, span: Span) {
3146 self.sess.emit_err(DotDotDot { span });
3149 fn err_larrow_operator(&self, span: Span) {
3150 self.sess.emit_err(LeftArrowOperator { span });
3153 fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
3154 ExprKind::AssignOp(binop, lhs, rhs)
3159 start: Option<P<Expr>>,
3160 end: Option<P<Expr>>,
3161 limits: RangeLimits,
3163 if end.is_none() && limits == RangeLimits::Closed {
3164 self.inclusive_range_with_incorrect_end(self.prev_token.span);
3167 ExprKind::Range(start, end, limits)
3171 fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
3172 ExprKind::Unary(unop, expr)
3175 fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
3176 ExprKind::Binary(binop, lhs, rhs)
3179 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
3180 ExprKind::Index(expr, idx)
3183 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
3184 ExprKind::Call(f, args)
3187 fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> P<Expr> {
3188 let span = lo.to(self.prev_token.span);
3189 let await_expr = self.mk_expr(span, ExprKind::Await(self_arg));
3190 self.recover_from_await_method_call();
3194 pub(crate) fn mk_expr_with_attrs(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
3195 P(Expr { kind, span, attrs, id: DUMMY_NODE_ID, tokens: None })
3198 pub(crate) fn mk_expr(&self, span: Span, kind: ExprKind) -> P<Expr> {
3199 P(Expr { kind, span, attrs: AttrVec::new(), id: DUMMY_NODE_ID, tokens: None })
3202 pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> {
3203 self.mk_expr(span, ExprKind::Err)
3206 /// Create expression span ensuring the span of the parent node
3207 /// is larger than the span of lhs and rhs, including the attributes.
3208 fn mk_expr_sp(&self, lhs: &P<Expr>, lhs_span: Span, rhs_span: Span) -> Span {
3211 .find(|a| a.style == AttrStyle::Outer)
3212 .map_or(lhs_span, |a| a.span)
3216 fn collect_tokens_for_expr(
3219 f: impl FnOnce(&mut Self, ast::AttrVec) -> PResult<'a, P<Expr>>,
3220 ) -> PResult<'a, P<Expr>> {
3221 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
3222 let res = f(this, attrs)?;
3223 let trailing = if this.restrictions.contains(Restrictions::STMT_EXPR)
3224 && this.token.kind == token::Semi
3227 } else if this.token.kind == token::Gt {
3230 // FIXME - pass this through from the place where we know
3231 // we need a comma, rather than assuming that `#[attr] expr,`
3232 // always captures a trailing comma
3233 TrailingToken::MaybeComma