1 use super::diagnostics::SnapshotParser;
2 use super::pat::{CommaRecoveryMode, Expected, RecoverColon, RecoverComma};
3 use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
5 AttrWrapper, BlockMode, ClosureSpans, ForceCollect, Parser, PathStyle, Restrictions,
6 SemiColonMode, SeqSep, TokenExpectType, TokenType, TrailingToken,
9 ArrayBracketsInsteadOfSpaces, ArrayBracketsInsteadOfSpacesSugg, AsyncBlockIn2015,
10 AsyncMoveOrderIncorrect, BracesForStructLiteral, CatchAfterTry, CommaAfterBaseStruct,
11 ComparisonInterpretedAsGeneric, ComparisonOrShiftInterpretedAsGenericSugg,
12 DoCatchSyntaxRemoved, DotDotDot, EqFieldInit, ExpectedElseBlock, ExpectedEqForLetExpr,
13 ExpectedExpressionFoundLet, FieldExpressionWithGeneric, FloatLiteralRequiresIntegerPart,
14 FoundExprWouldBeStmt, HelpUseLatestEdition, IfExpressionLetSomeSub,
15 IfExpressionMissingCondition, IfExpressionMissingThenBlock, IfExpressionMissingThenBlockSub,
16 InvalidBlockMacroSegment, InvalidComparisonOperator, InvalidComparisonOperatorSub,
17 InvalidInterpolatedExpression, InvalidLiteralSuffixOnTupleIndex, InvalidLogicalOperator,
18 InvalidLogicalOperatorSub, LabeledLoopInBreak, LeadingPlusNotSupported, LeftArrowOperator,
19 LifetimeInBorrowExpression, MacroInvocationWithQualifiedPath, MalformedLoopLabel,
20 MatchArmBodyWithoutBraces, MatchArmBodyWithoutBracesSugg, MissingCommaAfterMatchArm,
21 MissingDotDot, MissingInInForLoop, MissingInInForLoopSub, MissingSemicolonBeforeArray,
22 NoFieldsForFnCall, NotAsNegationOperator, NotAsNegationOperatorSub,
23 OuterAttributeNotAllowedOnIfElse, ParenthesesWithStructFields,
24 RequireColonAfterLabeledExpression, ShiftInterpretedAsGeneric, StructLiteralNotAllowedHere,
25 StructLiteralNotAllowedHereSugg, TildeAsUnaryOperator, UnexpectedIfWithIf,
26 UnexpectedTokenAfterLabel, UnexpectedTokenAfterLabelSugg, WrapExpressionInParentheses,
28 use crate::maybe_recover_from_interpolated_ty_qpath;
30 use rustc_ast::ptr::P;
31 use rustc_ast::token::{self, Delimiter, Token, TokenKind};
32 use rustc_ast::tokenstream::Spacing;
33 use rustc_ast::util::case::Case;
34 use rustc_ast::util::classify;
35 use rustc_ast::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
36 use rustc_ast::visit::Visitor;
37 use rustc_ast::{self as ast, AttrStyle, AttrVec, CaptureBy, ExprField, UnOp, DUMMY_NODE_ID};
38 use rustc_ast::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, MacCall, Param, Ty, TyKind};
39 use rustc_ast::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits};
40 use rustc_ast::{ClosureBinder, MetaItemLit, StmtKind};
41 use rustc_ast_pretty::pprust;
43 AddToDiagnostic, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, IntoDiagnostic,
46 use rustc_session::errors::{report_lit_error, ExprParenthesesNeeded};
47 use rustc_session::lint::builtin::BREAK_WITH_LABEL_AND_LOOP;
48 use rustc_session::lint::BuiltinLintDiagnostics;
49 use rustc_span::source_map::{self, Span, Spanned};
50 use rustc_span::symbol::{kw, sym, Ident, Symbol};
51 use rustc_span::{BytePos, Pos};
53 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
54 /// dropped into the token stream, which happens while parsing the result of
55 /// macro expansion). Placement of these is not as complex as I feared it would
56 /// be. The important thing is to make sure that lookahead doesn't balk at
57 /// `token::Interpolated` tokens.
58 macro_rules! maybe_whole_expr {
60 if let token::Interpolated(nt) = &$p.token.kind {
62 token::NtExpr(e) | token::NtLiteral(e) => {
67 token::NtPath(path) => {
68 let path = (**path).clone();
70 return Ok($p.mk_expr($p.prev_token.span, ExprKind::Path(None, path)));
72 token::NtBlock(block) => {
73 let block = block.clone();
75 return Ok($p.mk_expr($p.prev_token.span, ExprKind::Block(block, None)));
84 pub(super) enum LhsExpr {
86 AttributesParsed(AttrWrapper),
87 AlreadyParsed { expr: P<Expr>, starts_statement: bool },
90 impl From<Option<AttrWrapper>> for LhsExpr {
91 /// Converts `Some(attrs)` into `LhsExpr::AttributesParsed(attrs)`
92 /// and `None` into `LhsExpr::NotYetParsed`.
94 /// This conversion does not allocate.
95 fn from(o: Option<AttrWrapper>) -> Self {
96 if let Some(attrs) = o { LhsExpr::AttributesParsed(attrs) } else { LhsExpr::NotYetParsed }
100 impl From<P<Expr>> for LhsExpr {
101 /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed { expr, starts_statement: false }`.
103 /// This conversion does not allocate.
104 fn from(expr: P<Expr>) -> Self {
105 LhsExpr::AlreadyParsed { expr, starts_statement: false }
109 impl<'a> Parser<'a> {
110 /// Parses an expression.
112 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
113 self.current_closure.take();
115 self.parse_expr_res(Restrictions::empty(), None)
118 /// Parses an expression, forcing tokens to be collected
119 pub fn parse_expr_force_collect(&mut self) -> PResult<'a, P<Expr>> {
120 self.collect_tokens_no_attrs(|this| this.parse_expr())
123 pub fn parse_anon_const_expr(&mut self) -> PResult<'a, AnonConst> {
124 self.parse_expr().map(|value| AnonConst { id: DUMMY_NODE_ID, value })
127 fn parse_expr_catch_underscore(&mut self) -> PResult<'a, P<Expr>> {
128 match self.parse_expr() {
129 Ok(expr) => Ok(expr),
130 Err(mut err) => match self.token.ident() {
131 Some((Ident { name: kw::Underscore, .. }, false))
132 if self.may_recover() && self.look_ahead(1, |t| t == &token::Comma) =>
134 // Special-case handling of `foo(_, _, _)`
137 Ok(self.mk_expr(self.prev_token.span, ExprKind::Err))
144 /// Parses a sequence of expressions delimited by parentheses.
145 fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
146 self.parse_paren_comma_seq(|p| p.parse_expr_catch_underscore()).map(|(r, _)| r)
149 /// Parses an expression, subject to the given restrictions.
151 pub(super) fn parse_expr_res(
154 already_parsed_attrs: Option<AttrWrapper>,
155 ) -> PResult<'a, P<Expr>> {
156 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
159 /// Parses an associative expression.
161 /// This parses an expression accounting for associativity and precedence of the operators in
166 already_parsed_attrs: Option<AttrWrapper>,
167 ) -> PResult<'a, P<Expr>> {
168 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
171 /// Parses an associative expression with operators of at least `min_prec` precedence.
172 pub(super) fn parse_assoc_expr_with(
176 ) -> PResult<'a, P<Expr>> {
177 let mut starts_stmt = false;
178 let mut lhs = if let LhsExpr::AlreadyParsed { expr, starts_statement } = lhs {
179 starts_stmt = starts_statement;
182 let attrs = match lhs {
183 LhsExpr::AttributesParsed(attrs) => Some(attrs),
186 if self.token.is_range_separator() {
187 return self.parse_prefix_range_expr(attrs);
189 self.parse_prefix_expr(attrs)?
192 let last_type_ascription_set = self.last_type_ascription.is_some();
194 if !self.should_continue_as_assoc_expr(&lhs) {
195 self.last_type_ascription = None;
199 self.expected_tokens.push(TokenType::Operator);
200 while let Some(op) = self.check_assoc_op() {
201 // Adjust the span for interpolated LHS to point to the `$lhs` token
202 // and not to what it refers to.
203 let lhs_span = match self.prev_token.kind {
204 TokenKind::Interpolated(..) => self.prev_token.span,
208 let cur_op_span = self.token.span;
209 let restrictions = if op.node.is_assign_like() {
210 self.restrictions & Restrictions::NO_STRUCT_LITERAL
214 let prec = op.node.precedence();
218 // Check for deprecated `...` syntax
219 if self.token == token::DotDotDot && op.node == AssocOp::DotDotEq {
220 self.err_dotdotdot_syntax(self.token.span);
223 if self.token == token::LArrow {
224 self.err_larrow_operator(self.token.span);
228 if op.node.is_comparison() {
229 if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
234 // Look for JS' `===` and `!==` and recover
235 if (op.node == AssocOp::Equal || op.node == AssocOp::NotEqual)
236 && self.token.kind == token::Eq
237 && self.prev_token.span.hi() == self.token.span.lo()
239 let sp = op.span.to(self.token.span);
240 let sugg = match op.node {
241 AssocOp::Equal => "==",
242 AssocOp::NotEqual => "!=",
246 let invalid = format!("{}=", &sugg);
247 self.sess.emit_err(InvalidComparisonOperator {
249 invalid: invalid.clone(),
250 sub: InvalidComparisonOperatorSub::Correctable {
259 // Look for PHP's `<>` and recover
260 if op.node == AssocOp::Less
261 && self.token.kind == token::Gt
262 && self.prev_token.span.hi() == self.token.span.lo()
264 let sp = op.span.to(self.token.span);
265 self.sess.emit_err(InvalidComparisonOperator {
267 invalid: "<>".into(),
268 sub: InvalidComparisonOperatorSub::Correctable {
270 invalid: "<>".into(),
271 correct: "!=".into(),
277 // Look for C++'s `<=>` and recover
278 if op.node == AssocOp::LessEqual
279 && self.token.kind == token::Gt
280 && self.prev_token.span.hi() == self.token.span.lo()
282 let sp = op.span.to(self.token.span);
283 self.sess.emit_err(InvalidComparisonOperator {
285 invalid: "<=>".into(),
286 sub: InvalidComparisonOperatorSub::Spaceship(sp),
291 if self.prev_token == token::BinOp(token::Plus)
292 && self.token == token::BinOp(token::Plus)
293 && self.prev_token.span.between(self.token.span).is_empty()
295 let op_span = self.prev_token.span.to(self.token.span);
296 // Eat the second `+`
298 lhs = self.recover_from_postfix_increment(lhs, op_span, starts_stmt)?;
304 if op == AssocOp::As {
305 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
307 } else if op == AssocOp::Colon {
308 lhs = self.parse_assoc_op_ascribe(lhs, lhs_span)?;
310 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
311 // If we didn't have to handle `x..`/`x..=`, it would be pretty easy to
312 // generalise it to the Fixity::None code.
313 lhs = self.parse_range_expr(prec, lhs, op, cur_op_span)?;
317 let fixity = op.fixity();
318 let prec_adjustment = match fixity {
321 // We currently have no non-associative operators that are not handled above by
322 // the special cases. The code is here only for future convenience.
325 let rhs = self.with_res(restrictions - Restrictions::STMT_EXPR, |this| {
326 this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
329 let span = self.mk_expr_sp(&lhs, lhs_span, rhs.span);
342 | AssocOp::ShiftRight
348 | AssocOp::GreaterEqual => {
349 let ast_op = op.to_ast_binop().unwrap();
350 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
351 self.mk_expr(span, binary)
353 AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs, cur_op_span)),
354 AssocOp::AssignOp(k) => {
356 token::Plus => BinOpKind::Add,
357 token::Minus => BinOpKind::Sub,
358 token::Star => BinOpKind::Mul,
359 token::Slash => BinOpKind::Div,
360 token::Percent => BinOpKind::Rem,
361 token::Caret => BinOpKind::BitXor,
362 token::And => BinOpKind::BitAnd,
363 token::Or => BinOpKind::BitOr,
364 token::Shl => BinOpKind::Shl,
365 token::Shr => BinOpKind::Shr,
367 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
368 self.mk_expr(span, aopexpr)
370 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
371 self.span_bug(span, "AssocOp should have been handled by special case")
375 if let Fixity::None = fixity {
379 if last_type_ascription_set {
380 self.last_type_ascription = None;
385 fn should_continue_as_assoc_expr(&mut self, lhs: &Expr) -> bool {
386 match (self.expr_is_complete(lhs), AssocOp::from_token(&self.token)) {
387 // Semi-statement forms are odd:
388 // See https://github.com/rust-lang/rust/issues/29071
389 (true, None) => false,
390 (false, _) => true, // Continue parsing the expression.
391 // An exhaustive check is done in the following block, but these are checked first
392 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
393 // want to keep their span info to improve diagnostics in these cases in a later stage.
394 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
395 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
396 (true, Some(AssocOp::Add)) | // `{ 42 } + 42` (unary plus)
397 (true, Some(AssocOp::LAnd)) | // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }`
398 (true, Some(AssocOp::LOr)) | // `{ 42 } || 42` ("logical or" or closure)
399 (true, Some(AssocOp::BitOr)) // `{ 42 } | 42` or `{ 42 } |x| 42`
401 // These cases are ambiguous and can't be identified in the parser alone.
403 // Bitwise AND is left out because guessing intent is hard. We can make
404 // suggestions based on the assumption that double-refs are rarely intentional,
405 // and closures are distinct enough that they don't get mixed up with their
407 let sp = self.sess.source_map().start_point(self.token.span);
408 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
411 (true, Some(op)) if !op.can_continue_expr_unambiguously() => false,
413 self.error_found_expr_would_be_stmt(lhs);
419 /// We've found an expression that would be parsed as a statement,
420 /// but the next token implies this should be parsed as an expression.
421 /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
422 fn error_found_expr_would_be_stmt(&self, lhs: &Expr) {
423 self.sess.emit_err(FoundExprWouldBeStmt {
424 span: self.token.span,
425 token: self.token.clone(),
426 suggestion: ExprParenthesesNeeded::surrounding(lhs.span),
430 /// Possibly translate the current token to an associative operator.
431 /// The method does not advance the current token.
433 /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
434 fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
435 let (op, span) = match (AssocOp::from_token(&self.token), self.token.ident()) {
436 // When parsing const expressions, stop parsing when encountering `>`.
441 | AssocOp::GreaterEqual
442 | AssocOp::AssignOp(token::BinOpToken::Shr),
445 ) if self.restrictions.contains(Restrictions::CONST_EXPR) => {
448 (Some(op), _) => (op, self.token.span),
449 (None, Some((Ident { name: sym::and, span }, false))) if self.may_recover() => {
450 self.sess.emit_err(InvalidLogicalOperator {
451 span: self.token.span,
452 incorrect: "and".into(),
453 sub: InvalidLogicalOperatorSub::Conjunction(self.token.span),
455 (AssocOp::LAnd, span)
457 (None, Some((Ident { name: sym::or, span }, false))) if self.may_recover() => {
458 self.sess.emit_err(InvalidLogicalOperator {
459 span: self.token.span,
460 incorrect: "or".into(),
461 sub: InvalidLogicalOperatorSub::Disjunction(self.token.span),
467 Some(source_map::respan(span, op))
470 /// Checks if this expression is a successfully parsed statement.
471 fn expr_is_complete(&self, e: &Expr) -> bool {
472 self.restrictions.contains(Restrictions::STMT_EXPR)
473 && !classify::expr_requires_semi_to_be_stmt(e)
476 /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
477 /// The other two variants are handled in `parse_prefix_range_expr` below.
484 ) -> PResult<'a, P<Expr>> {
485 let rhs = if self.is_at_start_of_range_notation_rhs() {
486 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
490 let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
491 let span = self.mk_expr_sp(&lhs, lhs.span, rhs_span);
493 if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
494 let range = self.mk_range(Some(lhs), rhs, limits);
495 Ok(self.mk_expr(span, range))
498 fn is_at_start_of_range_notation_rhs(&self) -> bool {
499 if self.token.can_begin_expr() {
500 // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
501 if self.token == token::OpenDelim(Delimiter::Brace) {
502 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
510 /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
511 fn parse_prefix_range_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
512 // Check for deprecated `...` syntax.
513 if self.token == token::DotDotDot {
514 self.err_dotdotdot_syntax(self.token.span);
518 self.token.is_range_separator(),
519 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
523 let limits = match self.token.kind {
524 token::DotDot => RangeLimits::HalfOpen,
525 _ => RangeLimits::Closed,
527 let op = AssocOp::from_token(&self.token);
528 // FIXME: `parse_prefix_range_expr` is called when the current
529 // token is `DotDot`, `DotDotDot`, or `DotDotEq`. If we haven't already
530 // parsed attributes, then trying to parse them here will always fail.
531 // We should figure out how we want attributes on range expressions to work.
532 let attrs = self.parse_or_use_outer_attributes(attrs)?;
533 self.collect_tokens_for_expr(attrs, |this, attrs| {
534 let lo = this.token.span;
536 let (span, opt_end) = if this.is_at_start_of_range_notation_rhs() {
537 // RHS must be parsed with more associativity than the dots.
538 this.parse_assoc_expr_with(op.unwrap().precedence() + 1, LhsExpr::NotYetParsed)
539 .map(|x| (lo.to(x.span), Some(x)))?
543 let range = this.mk_range(None, opt_end, limits);
544 Ok(this.mk_expr_with_attrs(span, range, attrs))
548 /// Parses a prefix-unary-operator expr.
549 fn parse_prefix_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
550 let attrs = self.parse_or_use_outer_attributes(attrs)?;
551 let lo = self.token.span;
553 macro_rules! make_it {
554 ($this:ident, $attrs:expr, |this, _| $body:expr) => {
555 $this.collect_tokens_for_expr($attrs, |$this, attrs| {
556 let (hi, ex) = $body?;
557 Ok($this.mk_expr_with_attrs(lo.to(hi), ex, attrs))
564 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
565 match this.token.uninterpolate().kind {
567 token::Not => make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Not)),
569 token::Tilde => make_it!(this, attrs, |this, _| this.recover_tilde_expr(lo)),
571 token::BinOp(token::Minus) => {
572 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Neg))
575 token::BinOp(token::Star) => {
576 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Deref))
578 // `&expr` and `&&expr`
579 token::BinOp(token::And) | token::AndAnd => {
580 make_it!(this, attrs, |this, _| this.parse_borrow_expr(lo))
583 token::BinOp(token::Plus) if this.look_ahead(1, |tok| tok.is_numeric_lit()) => {
585 LeadingPlusNotSupported { span: lo, remove_plus: None, add_parentheses: None };
587 // a block on the LHS might have been intended to be an expression instead
588 if let Some(sp) = this.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
589 err.add_parentheses = Some(ExprParenthesesNeeded::surrounding(*sp));
591 err.remove_plus = Some(lo);
593 this.sess.emit_err(err);
596 this.parse_prefix_expr(None)
598 // Recover from `++x`:
599 token::BinOp(token::Plus)
600 if this.look_ahead(1, |t| *t == token::BinOp(token::Plus)) =>
602 let starts_stmt = this.prev_token == token::Semi
603 || this.prev_token == token::CloseDelim(Delimiter::Brace);
604 let pre_span = this.token.span.to(this.look_ahead(1, |t| t.span));
609 let operand_expr = this.parse_dot_or_call_expr(Default::default())?;
610 this.recover_from_prefix_increment(operand_expr, pre_span, starts_stmt)
612 token::Ident(..) if this.token.is_keyword(kw::Box) => {
613 make_it!(this, attrs, |this, _| this.parse_box_expr(lo))
615 token::Ident(..) if this.may_recover() && this.is_mistaken_not_ident_negation() => {
616 make_it!(this, attrs, |this, _| this.recover_not_expr(lo))
618 _ => return this.parse_dot_or_call_expr(Some(attrs)),
622 fn parse_prefix_expr_common(&mut self, lo: Span) -> PResult<'a, (Span, P<Expr>)> {
624 let expr = self.parse_prefix_expr(None);
625 let (span, expr) = self.interpolated_or_expr_span(expr)?;
626 Ok((lo.to(span), expr))
629 fn parse_unary_expr(&mut self, lo: Span, op: UnOp) -> PResult<'a, (Span, ExprKind)> {
630 let (span, expr) = self.parse_prefix_expr_common(lo)?;
631 Ok((span, self.mk_unary(op, expr)))
634 /// Recover on `~expr` in favor of `!expr`.
635 fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
636 self.sess.emit_err(TildeAsUnaryOperator(lo));
638 self.parse_unary_expr(lo, UnOp::Not)
641 /// Parse `box expr`.
642 fn parse_box_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
643 let (span, expr) = self.parse_prefix_expr_common(lo)?;
644 self.sess.gated_spans.gate(sym::box_syntax, span);
645 Ok((span, ExprKind::Box(expr)))
648 fn is_mistaken_not_ident_negation(&self) -> bool {
649 let token_cannot_continue_expr = |t: &Token| match t.uninterpolate().kind {
650 // These tokens can start an expression after `!`, but
651 // can't continue an expression after an ident
652 token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
653 token::Literal(..) | token::Pound => true,
654 _ => t.is_whole_expr(),
656 self.token.is_ident_named(sym::not) && self.look_ahead(1, token_cannot_continue_expr)
659 /// Recover on `not expr` in favor of `!expr`.
660 fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
661 let negated_token = self.look_ahead(1, |t| t.clone());
663 let sub_diag = if negated_token.is_numeric_lit() {
664 NotAsNegationOperatorSub::SuggestNotBitwise
665 } else if negated_token.is_bool_lit() {
666 NotAsNegationOperatorSub::SuggestNotLogical
668 NotAsNegationOperatorSub::SuggestNotDefault
671 self.sess.emit_err(NotAsNegationOperator {
672 negated: negated_token.span,
673 negated_desc: super::token_descr(&negated_token),
674 // Span the `not` plus trailing whitespace to avoid
675 // trailing whitespace after the `!` in our suggestion
677 self.sess.source_map().span_until_non_whitespace(lo.to(negated_token.span)),
681 self.parse_unary_expr(lo, UnOp::Not)
684 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
685 fn interpolated_or_expr_span(
687 expr: PResult<'a, P<Expr>>,
688 ) -> PResult<'a, (Span, P<Expr>)> {
691 match self.prev_token.kind {
692 TokenKind::Interpolated(..) => self.prev_token.span,
700 fn parse_assoc_op_cast(
704 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
705 ) -> PResult<'a, P<Expr>> {
706 let mk_expr = |this: &mut Self, lhs: P<Expr>, rhs: P<Ty>| {
707 this.mk_expr(this.mk_expr_sp(&lhs, lhs_span, rhs.span), expr_kind(lhs, rhs))
710 // Save the state of the parser before parsing type normally, in case there is a
711 // LessThan comparison after this cast.
712 let parser_snapshot_before_type = self.clone();
713 let cast_expr = match self.parse_as_cast_ty() {
714 Ok(rhs) => mk_expr(self, lhs, rhs),
716 if !self.may_recover() {
717 return Err(type_err);
720 // Rewind to before attempting to parse the type with generics, to recover
721 // from situations like `x as usize < y` in which we first tried to parse
722 // `usize < y` as a type with generic arguments.
723 let parser_snapshot_after_type = mem::replace(self, parser_snapshot_before_type);
725 // Check for typo of `'a: loop { break 'a }` with a missing `'`.
726 match (&lhs.kind, &self.token.kind) {
729 ExprKind::Path(None, ast::Path { segments, .. }),
730 TokenKind::Ident(kw::For | kw::Loop | kw::While, false),
731 ) if segments.len() == 1 => {
732 let snapshot = self.create_snapshot_for_diagnostic();
734 ident: Ident::from_str_and_span(
735 &format!("'{}", segments[0].ident),
736 segments[0].ident.span,
739 match self.parse_labeled_expr(label, false) {
742 self.sess.emit_err(MalformedLoopLabel {
743 span: label.ident.span,
744 correct_label: label.ident,
750 self.restore_snapshot(snapshot);
757 match self.parse_path(PathStyle::Expr) {
759 let span_after_type = parser_snapshot_after_type.token.span;
763 self.mk_ty(path.span, TyKind::Path(None, path.clone())),
766 let args_span = self.look_ahead(1, |t| t.span).to(span_after_type);
767 let suggestion = ComparisonOrShiftInterpretedAsGenericSugg {
768 left: expr.span.shrink_to_lo(),
769 right: expr.span.shrink_to_hi(),
772 match self.token.kind {
773 token::Lt => self.sess.emit_err(ComparisonInterpretedAsGeneric {
774 comparison: self.token.span,
779 token::BinOp(token::Shl) => {
780 self.sess.emit_err(ShiftInterpretedAsGeneric {
781 shift: self.token.span,
788 // We can end up here even without `<` being the next token, for
789 // example because `parse_ty_no_plus` returns `Err` on keywords,
790 // but `parse_path` returns `Ok` on them due to error recovery.
791 // Return original error and parser state.
792 *self = parser_snapshot_after_type;
793 return Err(type_err);
797 // Successfully parsed the type path leaving a `<` yet to parse.
800 // Keep `x as usize` as an expression in AST and continue parsing.
804 // Couldn't parse as a path, return original error and parser state.
806 *self = parser_snapshot_after_type;
807 return Err(type_err);
813 self.parse_and_disallow_postfix_after_cast(cast_expr)
816 /// Parses a postfix operators such as `.`, `?`, or index (`[]`) after a cast,
817 /// then emits an error and returns the newly parsed tree.
818 /// The resulting parse tree for `&x as T[0]` has a precedence of `((&x) as T)[0]`.
819 fn parse_and_disallow_postfix_after_cast(
822 ) -> PResult<'a, P<Expr>> {
823 let span = cast_expr.span;
824 let (cast_kind, maybe_ascription_span) =
825 if let ExprKind::Type(ascripted_expr, _) = &cast_expr.kind {
826 ("type ascription", Some(ascripted_expr.span.shrink_to_hi().with_hi(span.hi())))
831 let with_postfix = self.parse_dot_or_call_expr_with_(cast_expr, span)?;
833 // Check if an illegal postfix operator has been added after the cast.
834 // If the resulting expression is not a cast, it is an illegal postfix operator.
835 if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) {
837 "{cast_kind} cannot be followed by {}",
838 match with_postfix.kind {
839 ExprKind::Index(_, _) => "indexing",
840 ExprKind::Try(_) => "`?`",
841 ExprKind::Field(_, _) => "a field access",
842 ExprKind::MethodCall(_) => "a method call",
843 ExprKind::Call(_, _) => "a function call",
844 ExprKind::Await(_) => "`.await`",
845 ExprKind::Err => return Ok(with_postfix),
846 _ => unreachable!("parse_dot_or_call_expr_with_ shouldn't produce this"),
849 let mut err = self.struct_span_err(span, &msg);
851 let suggest_parens = |err: &mut Diagnostic| {
852 let suggestions = vec![
853 (span.shrink_to_lo(), "(".to_string()),
854 (span.shrink_to_hi(), ")".to_string()),
856 err.multipart_suggestion(
857 "try surrounding the expression in parentheses",
859 Applicability::MachineApplicable,
863 // If type ascription is "likely an error", the user will already be getting a useful
864 // help message, and doesn't need a second.
865 if self.last_type_ascription.map_or(false, |last_ascription| last_ascription.1) {
866 self.maybe_annotate_with_ascription(&mut err, false);
867 } else if let Some(ascription_span) = maybe_ascription_span {
868 let is_nightly = self.sess.unstable_features.is_nightly_build();
870 suggest_parens(&mut err);
875 "{}remove the type ascription",
876 if is_nightly { "alternatively, " } else { "" }
880 Applicability::MaybeIncorrect
882 Applicability::MachineApplicable
886 suggest_parens(&mut err);
893 fn parse_assoc_op_ascribe(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
894 let maybe_path = self.could_ascription_be_path(&lhs.kind);
895 self.last_type_ascription = Some((self.prev_token.span, maybe_path));
896 let lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
897 self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
901 /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
902 fn parse_borrow_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
904 let has_lifetime = self.token.is_lifetime() && self.look_ahead(1, |t| t != &token::Colon);
905 let lifetime = has_lifetime.then(|| self.expect_lifetime()); // For recovery, see below.
906 let (borrow_kind, mutbl) = self.parse_borrow_modifiers(lo);
907 let expr = if self.token.is_range_separator() {
908 self.parse_prefix_range_expr(None)
910 self.parse_prefix_expr(None)
912 let (hi, expr) = self.interpolated_or_expr_span(expr)?;
913 let span = lo.to(hi);
914 if let Some(lt) = lifetime {
915 self.error_remove_borrow_lifetime(span, lt.ident.span);
917 Ok((span, ExprKind::AddrOf(borrow_kind, mutbl, expr)))
920 fn error_remove_borrow_lifetime(&self, span: Span, lt_span: Span) {
921 self.sess.emit_err(LifetimeInBorrowExpression { span, lifetime_span: lt_span });
924 /// Parse `mut?` or `raw [ const | mut ]`.
925 fn parse_borrow_modifiers(&mut self, lo: Span) -> (ast::BorrowKind, ast::Mutability) {
926 if self.check_keyword(kw::Raw) && self.look_ahead(1, Token::is_mutability) {
927 // `raw [ const | mut ]`.
928 let found_raw = self.eat_keyword(kw::Raw);
930 let mutability = self.parse_const_or_mut().unwrap();
931 self.sess.gated_spans.gate(sym::raw_ref_op, lo.to(self.prev_token.span));
932 (ast::BorrowKind::Raw, mutability)
935 (ast::BorrowKind::Ref, self.parse_mutability())
939 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
940 fn parse_dot_or_call_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
941 let attrs = self.parse_or_use_outer_attributes(attrs)?;
942 self.collect_tokens_for_expr(attrs, |this, attrs| {
943 let base = this.parse_bottom_expr();
944 let (span, base) = this.interpolated_or_expr_span(base)?;
945 this.parse_dot_or_call_expr_with(base, span, attrs)
949 pub(super) fn parse_dot_or_call_expr_with(
953 mut attrs: ast::AttrVec,
954 ) -> PResult<'a, P<Expr>> {
955 // Stitch the list of outer attributes onto the return value.
956 // A little bit ugly, but the best way given the current code
958 let res = self.parse_dot_or_call_expr_with_(e0, lo);
959 if attrs.is_empty() {
963 expr.map(|mut expr| {
964 attrs.extend(expr.attrs);
972 fn parse_dot_or_call_expr_with_(&mut self, mut e: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
974 let has_question = if self.prev_token.kind == TokenKind::Ident(kw::Return, false) {
975 // we are using noexpect here because we don't expect a `?` directly after a `return`
976 // which could be suggested otherwise
977 self.eat_noexpect(&token::Question)
979 self.eat(&token::Question)
983 e = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Try(e));
986 let has_dot = if self.prev_token.kind == TokenKind::Ident(kw::Return, false) {
987 // we are using noexpect here because we don't expect a `.` directly after a `return`
988 // which could be suggested otherwise
989 self.eat_noexpect(&token::Dot)
991 self.eat(&token::Dot)
995 e = self.parse_dot_suffix_expr(lo, e)?;
998 if self.expr_is_complete(&e) {
1001 e = match self.token.kind {
1002 token::OpenDelim(Delimiter::Parenthesis) => self.parse_fn_call_expr(lo, e),
1003 token::OpenDelim(Delimiter::Bracket) => self.parse_index_expr(lo, e)?,
1009 fn look_ahead_type_ascription_as_field(&mut self) -> bool {
1010 self.look_ahead(1, |t| t.is_ident())
1011 && self.look_ahead(2, |t| t == &token::Colon)
1012 && self.look_ahead(3, |t| t.can_begin_expr())
1015 fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
1016 match self.token.uninterpolate().kind {
1017 token::Ident(..) => self.parse_dot_suffix(base, lo),
1018 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
1019 Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix, None))
1021 token::Literal(token::Lit { kind: token::Float, symbol, suffix }) => {
1022 Ok(self.parse_tuple_field_access_expr_float(lo, base, symbol, suffix))
1025 self.error_unexpected_after_dot();
1031 fn error_unexpected_after_dot(&self) {
1032 // FIXME Could factor this out into non_fatal_unexpected or something.
1033 let actual = pprust::token_to_string(&self.token);
1034 self.struct_span_err(self.token.span, &format!("unexpected token: `{actual}`")).emit();
1037 // We need an identifier or integer, but the next token is a float.
1038 // Break the float into components to extract the identifier or integer.
1039 // FIXME: With current `TokenCursor` it's hard to break tokens into more than 2
1040 // parts unless those parts are processed immediately. `TokenCursor` should either
1041 // support pushing "future tokens" (would be also helpful to `break_and_eat`), or
1042 // we should break everything including floats into more basic proc-macro style
1043 // tokens in the lexer (probably preferable).
1044 fn parse_tuple_field_access_expr_float(
1049 suffix: Option<Symbol>,
1052 enum FloatComponent {
1056 use FloatComponent::*;
1058 let float_str = float.as_str();
1059 let mut components = Vec::new();
1060 let mut ident_like = String::new();
1061 for c in float_str.chars() {
1062 if c == '_' || c.is_ascii_alphanumeric() {
1064 } else if matches!(c, '.' | '+' | '-') {
1065 if !ident_like.is_empty() {
1066 components.push(IdentLike(mem::take(&mut ident_like)));
1068 components.push(Punct(c));
1070 panic!("unexpected character in a float token: {:?}", c)
1073 if !ident_like.is_empty() {
1074 components.push(IdentLike(ident_like));
1077 // With proc macros the span can refer to anything, the source may be too short,
1078 // or too long, or non-ASCII. It only makes sense to break our span into components
1079 // if its underlying text is identical to our float literal.
1080 let span = self.token.span;
1081 let can_take_span_apart =
1082 || self.span_to_snippet(span).as_deref() == Ok(float_str).as_deref();
1084 match &*components {
1087 self.parse_tuple_field_access_expr(lo, base, Symbol::intern(&i), suffix, None)
1090 [IdentLike(i), Punct('.')] => {
1091 let (ident_span, dot_span) = if can_take_span_apart() {
1092 let (span, ident_len) = (span.data(), BytePos::from_usize(i.len()));
1093 let ident_span = span.with_hi(span.lo + ident_len);
1094 let dot_span = span.with_lo(span.lo + ident_len);
1095 (ident_span, dot_span)
1099 assert!(suffix.is_none());
1100 let symbol = Symbol::intern(&i);
1101 self.token = Token::new(token::Ident(symbol, false), ident_span);
1102 let next_token = (Token::new(token::Dot, dot_span), self.token_spacing);
1103 self.parse_tuple_field_access_expr(lo, base, symbol, None, Some(next_token))
1106 [IdentLike(i1), Punct('.'), IdentLike(i2)] => {
1107 let (ident1_span, dot_span, ident2_span) = if can_take_span_apart() {
1108 let (span, ident1_len) = (span.data(), BytePos::from_usize(i1.len()));
1109 let ident1_span = span.with_hi(span.lo + ident1_len);
1111 .with_lo(span.lo + ident1_len)
1112 .with_hi(span.lo + ident1_len + BytePos(1));
1113 let ident2_span = self.token.span.with_lo(span.lo + ident1_len + BytePos(1));
1114 (ident1_span, dot_span, ident2_span)
1118 let symbol1 = Symbol::intern(&i1);
1119 self.token = Token::new(token::Ident(symbol1, false), ident1_span);
1120 // This needs to be `Spacing::Alone` to prevent regressions.
1121 // See issue #76399 and PR #76285 for more details
1122 let next_token1 = (Token::new(token::Dot, dot_span), Spacing::Alone);
1124 self.parse_tuple_field_access_expr(lo, base, symbol1, None, Some(next_token1));
1125 let symbol2 = Symbol::intern(&i2);
1126 let next_token2 = Token::new(token::Ident(symbol2, false), ident2_span);
1127 self.bump_with((next_token2, self.token_spacing)); // `.`
1128 self.parse_tuple_field_access_expr(lo, base1, symbol2, suffix, None)
1130 // 1e+ | 1e- (recovered)
1131 [IdentLike(_), Punct('+' | '-')] |
1133 [IdentLike(_), Punct('+' | '-'), IdentLike(_)] |
1135 [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-')] |
1137 [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-'), IdentLike(_)] => {
1138 // See the FIXME about `TokenCursor` above.
1139 self.error_unexpected_after_dot();
1142 _ => panic!("unexpected components in a float token: {:?}", components),
1146 fn parse_tuple_field_access_expr(
1151 suffix: Option<Symbol>,
1152 next_token: Option<(Token, Spacing)>,
1155 Some(next_token) => self.bump_with(next_token),
1156 None => self.bump(),
1158 let span = self.prev_token.span;
1159 let field = ExprKind::Field(base, Ident::new(field, span));
1160 if let Some(suffix) = suffix {
1161 self.expect_no_tuple_index_suffix(span, suffix);
1163 self.mk_expr(lo.to(span), field)
1166 /// Parse a function call expression, `expr(...)`.
1167 fn parse_fn_call_expr(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
1168 let snapshot = if self.token.kind == token::OpenDelim(Delimiter::Parenthesis)
1169 && self.look_ahead_type_ascription_as_field()
1171 Some((self.create_snapshot_for_diagnostic(), fun.kind.clone()))
1175 let open_paren = self.token.span;
1178 .parse_paren_expr_seq()
1179 .map(|args| self.mk_expr(lo.to(self.prev_token.span), self.mk_call(fun, args)));
1181 self.maybe_recover_struct_lit_bad_delims(lo, open_paren, &mut seq, snapshot)
1185 self.recover_seq_parse_error(Delimiter::Parenthesis, lo, seq)
1188 /// If we encounter a parser state that looks like the user has written a `struct` literal with
1189 /// parentheses instead of braces, recover the parser state and provide suggestions.
1190 #[instrument(skip(self, seq, snapshot), level = "trace")]
1191 fn maybe_recover_struct_lit_bad_delims(
1195 seq: &mut PResult<'a, P<Expr>>,
1196 snapshot: Option<(SnapshotParser<'a>, ExprKind)>,
1197 ) -> Option<P<Expr>> {
1198 if !self.may_recover() {
1202 match (seq.as_mut(), snapshot) {
1203 (Err(err), Some((mut snapshot, ExprKind::Path(None, path)))) => {
1204 snapshot.bump(); // `(`
1205 match snapshot.parse_struct_fields(path.clone(), false, Delimiter::Parenthesis) {
1207 if snapshot.eat(&token::CloseDelim(Delimiter::Parenthesis)) =>
1209 // We are certain we have `Enum::Foo(a: 3, b: 4)`, suggest
1210 // `Enum::Foo { a: 3, b: 4 }` or `Enum::Foo(3, 4)`.
1211 self.restore_snapshot(snapshot);
1212 let close_paren = self.prev_token.span;
1213 let span = lo.to(self.prev_token.span);
1214 if !fields.is_empty() {
1215 let mut replacement_err = ParenthesesWithStructFields {
1218 braces_for_struct: BracesForStructLiteral {
1220 second: close_paren,
1222 no_fields_for_fn: NoFieldsForFnCall {
1225 .map(|field| field.span.until(field.expr.span))
1229 .into_diagnostic(&self.sess.span_diagnostic);
1230 replacement_err.emit();
1232 let old_err = mem::replace(err, replacement_err);
1237 return Some(self.mk_expr_err(span));
1250 /// Parse an indexing expression `expr[...]`.
1251 fn parse_index_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
1252 let prev_span = self.prev_token.span;
1253 let open_delim_span = self.token.span;
1255 let index = self.parse_expr()?;
1256 self.suggest_missing_semicolon_before_array(prev_span, open_delim_span)?;
1257 self.expect(&token::CloseDelim(Delimiter::Bracket))?;
1258 Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_index(base, index)))
1261 /// Assuming we have just parsed `.`, continue parsing into an expression.
1262 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
1263 if self.token.uninterpolated_span().rust_2018() && self.eat_keyword(kw::Await) {
1264 return Ok(self.mk_await_expr(self_arg, lo));
1267 let fn_span_lo = self.token.span;
1268 let mut seg = self.parse_path_segment(PathStyle::Expr, None)?;
1269 self.check_trailing_angle_brackets(&seg, &[&token::OpenDelim(Delimiter::Parenthesis)]);
1270 self.check_turbofish_missing_angle_brackets(&mut seg);
1272 if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
1273 // Method call `expr.f()`
1274 let args = self.parse_paren_expr_seq()?;
1275 let fn_span = fn_span_lo.to(self.prev_token.span);
1276 let span = lo.to(self.prev_token.span);
1279 ExprKind::MethodCall(Box::new(ast::MethodCall {
1287 // Field access `expr.f`
1288 if let Some(args) = seg.args {
1289 self.sess.emit_err(FieldExpressionWithGeneric(args.span()));
1292 let span = lo.to(self.prev_token.span);
1293 Ok(self.mk_expr(span, ExprKind::Field(self_arg, seg.ident)))
1297 /// At the bottom (top?) of the precedence hierarchy,
1298 /// Parses things like parenthesized exprs, macros, `return`, etc.
1300 /// N.B., this does not parse outer attributes, and is private because it only works
1301 /// correctly if called from `parse_dot_or_call_expr()`.
1302 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
1303 maybe_recover_from_interpolated_ty_qpath!(self, true);
1304 maybe_whole_expr!(self);
1306 // Outer attributes are already parsed and will be
1307 // added to the return value after the fact.
1309 // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
1310 let lo = self.token.span;
1311 if let token::Literal(_) = self.token.kind {
1312 // This match arm is a special-case of the `_` match arm below and
1313 // could be removed without changing functionality, but it's faster
1314 // to have it here, especially for programs with large constants.
1315 self.parse_lit_expr()
1316 } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
1317 self.parse_tuple_parens_expr()
1318 } else if self.check(&token::OpenDelim(Delimiter::Brace)) {
1319 self.parse_block_expr(None, lo, BlockCheckMode::Default)
1320 } else if self.check(&token::BinOp(token::Or)) || self.check(&token::OrOr) {
1321 self.parse_closure_expr().map_err(|mut err| {
1322 // If the input is something like `if a { 1 } else { 2 } | if a { 3 } else { 4 }`
1323 // then suggest parens around the lhs.
1324 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
1325 err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
1329 } else if self.check(&token::OpenDelim(Delimiter::Bracket)) {
1330 self.parse_array_or_repeat_expr(Delimiter::Bracket)
1331 } else if self.check_path() {
1332 self.parse_path_start_expr()
1333 } else if self.check_keyword(kw::Move)
1334 || self.check_keyword(kw::Static)
1335 || self.check_const_closure()
1337 self.parse_closure_expr()
1338 } else if self.eat_keyword(kw::If) {
1339 self.parse_if_expr()
1340 } else if self.check_keyword(kw::For) {
1341 if self.choose_generics_over_qpath(1) {
1342 self.parse_closure_expr()
1344 assert!(self.eat_keyword(kw::For));
1345 self.parse_for_expr(None, self.prev_token.span)
1347 } else if self.eat_keyword(kw::While) {
1348 self.parse_while_expr(None, self.prev_token.span)
1349 } else if let Some(label) = self.eat_label() {
1350 self.parse_labeled_expr(label, true)
1351 } else if self.eat_keyword(kw::Loop) {
1352 let sp = self.prev_token.span;
1353 self.parse_loop_expr(None, self.prev_token.span).map_err(|mut err| {
1354 err.span_label(sp, "while parsing this `loop` expression");
1357 } else if self.eat_keyword(kw::Match) {
1358 let match_sp = self.prev_token.span;
1359 self.parse_match_expr().map_err(|mut err| {
1360 err.span_label(match_sp, "while parsing this `match` expression");
1363 } else if self.eat_keyword(kw::Unsafe) {
1364 let sp = self.prev_token.span;
1365 self.parse_block_expr(None, lo, BlockCheckMode::Unsafe(ast::UserProvided)).map_err(
1367 err.span_label(sp, "while parsing this `unsafe` expression");
1371 } else if self.check_inline_const(0) {
1372 self.parse_const_block(lo.to(self.token.span), false)
1373 } else if self.may_recover() && self.is_do_catch_block() {
1374 self.recover_do_catch()
1375 } else if self.is_try_block() {
1376 self.expect_keyword(kw::Try)?;
1377 self.parse_try_block(lo)
1378 } else if self.eat_keyword(kw::Return) {
1379 self.parse_return_expr()
1380 } else if self.eat_keyword(kw::Continue) {
1381 self.parse_continue_expr(lo)
1382 } else if self.eat_keyword(kw::Break) {
1383 self.parse_break_expr()
1384 } else if self.eat_keyword(kw::Yield) {
1385 self.parse_yield_expr()
1386 } else if self.is_do_yeet() {
1387 self.parse_yeet_expr()
1388 } else if self.check_keyword(kw::Let) {
1389 self.parse_let_expr()
1390 } else if self.eat_keyword(kw::Underscore) {
1391 Ok(self.mk_expr(self.prev_token.span, ExprKind::Underscore))
1392 } else if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
1393 // Don't complain about bare semicolons after unclosed braces
1394 // recovery in order to keep the error count down. Fixing the
1395 // delimiters will possibly also fix the bare semicolon found in
1396 // expression context. For example, silence the following error:
1398 // error: expected expression, found `;`
1402 // | ^ expected expression
1404 Ok(self.mk_expr_err(self.token.span))
1405 } else if self.token.uninterpolated_span().rust_2018() {
1406 // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
1407 if self.check_keyword(kw::Async) {
1408 if self.is_async_block() {
1409 // Check for `async {` and `async move {`.
1410 self.parse_async_block()
1412 self.parse_closure_expr()
1414 } else if self.eat_keyword(kw::Await) {
1415 self.recover_incorrect_await_syntax(lo, self.prev_token.span)
1417 self.parse_lit_expr()
1420 self.parse_lit_expr()
1424 fn parse_lit_expr(&mut self) -> PResult<'a, P<Expr>> {
1425 let lo = self.token.span;
1426 match self.parse_opt_token_lit() {
1427 Some((token_lit, _)) => {
1428 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Lit(token_lit));
1429 self.maybe_recover_from_bad_qpath(expr)
1431 None => self.try_macro_suggestion(),
1435 fn parse_tuple_parens_expr(&mut self) -> PResult<'a, P<Expr>> {
1436 let lo = self.token.span;
1437 self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
1438 let (es, trailing_comma) = match self.parse_seq_to_end(
1439 &token::CloseDelim(Delimiter::Parenthesis),
1440 SeqSep::trailing_allowed(token::Comma),
1441 |p| p.parse_expr_catch_underscore(),
1445 return Ok(self.recover_seq_parse_error(Delimiter::Parenthesis, lo, Err(err)));
1448 let kind = if es.len() == 1 && !trailing_comma {
1449 // `(e)` is parenthesized `e`.
1450 ExprKind::Paren(es.into_iter().next().unwrap())
1452 // `(e,)` is a tuple with only one field, `e`.
1455 let expr = self.mk_expr(lo.to(self.prev_token.span), kind);
1456 self.maybe_recover_from_bad_qpath(expr)
1459 fn parse_array_or_repeat_expr(&mut self, close_delim: Delimiter) -> PResult<'a, P<Expr>> {
1460 let lo = self.token.span;
1461 self.bump(); // `[` or other open delim
1463 let close = &token::CloseDelim(close_delim);
1464 let kind = if self.eat(close) {
1466 ExprKind::Array(Vec::new())
1469 let first_expr = self.parse_expr()?;
1470 if self.eat(&token::Semi) {
1471 // Repeating array syntax: `[ 0; 512 ]`
1472 let count = self.parse_anon_const_expr()?;
1473 self.expect(close)?;
1474 ExprKind::Repeat(first_expr, count)
1475 } else if self.eat(&token::Comma) {
1476 // Vector with two or more elements.
1477 let sep = SeqSep::trailing_allowed(token::Comma);
1478 let (mut exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
1479 exprs.insert(0, first_expr);
1480 ExprKind::Array(exprs)
1482 // Vector with one element
1483 self.expect(close)?;
1484 ExprKind::Array(vec![first_expr])
1487 let expr = self.mk_expr(lo.to(self.prev_token.span), kind);
1488 self.maybe_recover_from_bad_qpath(expr)
1491 fn parse_path_start_expr(&mut self) -> PResult<'a, P<Expr>> {
1492 let (qself, path) = if self.eat_lt() {
1493 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
1496 (None, self.parse_path(PathStyle::Expr)?)
1499 // `!`, as an operator, is prefix, so we know this isn't that.
1500 let (span, kind) = if self.eat(&token::Not) {
1501 // MACRO INVOCATION expression
1502 if qself.is_some() {
1503 self.sess.emit_err(MacroInvocationWithQualifiedPath(path.span));
1506 let mac = P(MacCall {
1508 args: self.parse_delim_args()?,
1509 prior_type_ascription: self.last_type_ascription,
1511 (lo.to(self.prev_token.span), ExprKind::MacCall(mac))
1512 } else if self.check(&token::OpenDelim(Delimiter::Brace))
1513 && let Some(expr) = self.maybe_parse_struct_expr(&qself, &path)
1515 if qself.is_some() {
1516 self.sess.gated_spans.gate(sym::more_qualified_paths, path.span);
1520 (path.span, ExprKind::Path(qself, path))
1523 let expr = self.mk_expr(span, kind);
1524 self.maybe_recover_from_bad_qpath(expr)
1527 /// Parse `'label: $expr`. The label is already parsed.
1528 fn parse_labeled_expr(
1531 mut consume_colon: bool,
1532 ) -> PResult<'a, P<Expr>> {
1533 let lo = label_.ident.span;
1534 let label = Some(label_);
1535 let ate_colon = self.eat(&token::Colon);
1536 let expr = if self.eat_keyword(kw::While) {
1537 self.parse_while_expr(label, lo)
1538 } else if self.eat_keyword(kw::For) {
1539 self.parse_for_expr(label, lo)
1540 } else if self.eat_keyword(kw::Loop) {
1541 self.parse_loop_expr(label, lo)
1542 } else if self.check_noexpect(&token::OpenDelim(Delimiter::Brace))
1543 || self.token.is_whole_block()
1545 self.parse_block_expr(label, lo, BlockCheckMode::Default)
1546 } else if !ate_colon
1547 && self.may_recover()
1548 && (matches!(self.token.kind, token::CloseDelim(_) | token::Comma)
1549 || self.token.is_op())
1552 self.recover_unclosed_char(label_.ident, Parser::mk_token_lit_char, |self_| {
1553 self_.sess.create_err(UnexpectedTokenAfterLabel {
1554 span: self_.token.span,
1556 enclose_in_block: None,
1559 consume_colon = false;
1560 Ok(self.mk_expr(lo, ExprKind::Lit(lit)))
1561 } else if !ate_colon
1562 && (self.check_noexpect(&TokenKind::Comma) || self.check_noexpect(&TokenKind::Gt))
1564 // We're probably inside of a `Path<'a>` that needs a turbofish
1565 self.sess.emit_err(UnexpectedTokenAfterLabel {
1566 span: self.token.span,
1568 enclose_in_block: None,
1570 consume_colon = false;
1571 Ok(self.mk_expr_err(lo))
1573 let mut err = UnexpectedTokenAfterLabel {
1574 span: self.token.span,
1576 enclose_in_block: None,
1579 // Continue as an expression in an effort to recover on `'label: non_block_expr`.
1580 let expr = self.parse_expr().map(|expr| {
1581 let span = expr.span;
1583 let found_labeled_breaks = {
1584 struct FindLabeledBreaksVisitor(bool);
1586 impl<'ast> Visitor<'ast> for FindLabeledBreaksVisitor {
1587 fn visit_expr_post(&mut self, ex: &'ast Expr) {
1588 if let ExprKind::Break(Some(_label), _) = ex.kind {
1594 let mut vis = FindLabeledBreaksVisitor(false);
1595 vis.visit_expr(&expr);
1599 // Suggestion involves adding a labeled block.
1601 // If there are no breaks that may use this label, suggest removing the label and
1602 // recover to the unmodified expression.
1603 if !found_labeled_breaks {
1604 err.remove_label = Some(lo.until(span));
1609 err.enclose_in_block = Some(UnexpectedTokenAfterLabelSugg {
1610 left: span.shrink_to_lo(),
1611 right: span.shrink_to_hi(),
1614 // Replace `'label: non_block_expr` with `'label: {non_block_expr}` in order to suppress future errors about `break 'label`.
1615 let stmt = self.mk_stmt(span, StmtKind::Expr(expr));
1616 let blk = self.mk_block(vec![stmt], BlockCheckMode::Default, span);
1617 self.mk_expr(span, ExprKind::Block(blk, label))
1620 self.sess.emit_err(err);
1624 if !ate_colon && consume_colon {
1625 self.sess.emit_err(RequireColonAfterLabeledExpression {
1628 label_end: lo.shrink_to_hi(),
1635 /// Emit an error when a char is parsed as a lifetime because of a missing quote.
1636 pub(super) fn recover_unclosed_char<L>(
1639 mk_lit_char: impl FnOnce(Symbol, Span) -> L,
1640 err: impl FnOnce(&Self) -> DiagnosticBuilder<'a, ErrorGuaranteed>,
1642 if let Some(mut diag) =
1643 self.sess.span_diagnostic.steal_diagnostic(lifetime.span, StashKey::LifetimeIsChar)
1645 diag.span_suggestion_verbose(
1646 lifetime.span.shrink_to_hi(),
1647 "add `'` to close the char literal",
1649 Applicability::MaybeIncorrect,
1654 .span_suggestion_verbose(
1655 lifetime.span.shrink_to_hi(),
1656 "add `'` to close the char literal",
1658 Applicability::MaybeIncorrect,
1662 let name = lifetime.without_first_quote().name;
1663 mk_lit_char(name, lifetime.span)
1666 /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
1667 fn recover_do_catch(&mut self) -> PResult<'a, P<Expr>> {
1668 let lo = self.token.span;
1670 self.bump(); // `do`
1671 self.bump(); // `catch`
1673 let span = lo.to(self.prev_token.span);
1674 self.sess.emit_err(DoCatchSyntaxRemoved { span });
1676 self.parse_try_block(lo)
1679 /// Parse an expression if the token can begin one.
1680 fn parse_expr_opt(&mut self) -> PResult<'a, Option<P<Expr>>> {
1681 Ok(if self.token.can_begin_expr() { Some(self.parse_expr()?) } else { None })
1684 /// Parse `"return" expr?`.
1685 fn parse_return_expr(&mut self) -> PResult<'a, P<Expr>> {
1686 let lo = self.prev_token.span;
1687 let kind = ExprKind::Ret(self.parse_expr_opt()?);
1688 let expr = self.mk_expr(lo.to(self.prev_token.span), kind);
1689 self.maybe_recover_from_bad_qpath(expr)
1692 /// Parse `"do" "yeet" expr?`.
1693 fn parse_yeet_expr(&mut self) -> PResult<'a, P<Expr>> {
1694 let lo = self.token.span;
1696 self.bump(); // `do`
1697 self.bump(); // `yeet`
1699 let kind = ExprKind::Yeet(self.parse_expr_opt()?);
1701 let span = lo.to(self.prev_token.span);
1702 self.sess.gated_spans.gate(sym::yeet_expr, span);
1703 let expr = self.mk_expr(span, kind);
1704 self.maybe_recover_from_bad_qpath(expr)
1707 /// Parse `"break" (('label (:? expr)?) | expr?)` with `"break"` token already eaten.
1708 /// If the label is followed immediately by a `:` token, the label and `:` are
1709 /// parsed as part of the expression (i.e. a labeled loop). The language team has
1710 /// decided in #87026 to require parentheses as a visual aid to avoid confusion if
1711 /// the break expression of an unlabeled break is a labeled loop (as in
1712 /// `break 'lbl: loop {}`); a labeled break with an unlabeled loop as its value
1713 /// expression only gets a warning for compatibility reasons; and a labeled break
1714 /// with a labeled loop does not even get a warning because there is no ambiguity.
1715 fn parse_break_expr(&mut self) -> PResult<'a, P<Expr>> {
1716 let lo = self.prev_token.span;
1717 let mut label = self.eat_label();
1718 let kind = if self.token == token::Colon && let Some(label) = label.take() {
1719 // The value expression can be a labeled loop, see issue #86948, e.g.:
1720 // `loop { break 'label: loop { break 'label 42; }; }`
1721 let lexpr = self.parse_labeled_expr(label, true)?;
1722 self.sess.emit_err(LabeledLoopInBreak {
1724 sub: WrapExpressionInParentheses {
1725 left: lexpr.span.shrink_to_lo(),
1726 right: lexpr.span.shrink_to_hi(),
1730 } else if self.token != token::OpenDelim(Delimiter::Brace)
1731 || !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1733 let mut expr = self.parse_expr_opt()?;
1734 if let Some(expr) = &mut expr {
1738 ExprKind::While(_, _, None)
1739 | ExprKind::ForLoop(_, _, _, None)
1740 | ExprKind::Loop(_, None, _)
1741 | ExprKind::Block(_, None)
1744 self.sess.buffer_lint_with_diagnostic(
1745 BREAK_WITH_LABEL_AND_LOOP,
1748 "this labeled break expression is easy to confuse with an unlabeled break with a labeled value expression",
1749 BuiltinLintDiagnostics::BreakWithLabelAndLoop(expr.span),
1753 // Recover `break label aaaaa`
1754 if self.may_recover()
1755 && let ExprKind::Path(None, p) = &expr.kind
1756 && let [segment] = &*p.segments
1757 && let &ast::PathSegment { ident, args: None, .. } = segment
1758 && let Some(next) = self.parse_expr_opt()?
1760 label = Some(self.recover_ident_into_label(ident));
1769 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Break(label, kind));
1770 self.maybe_recover_from_bad_qpath(expr)
1773 /// Parse `"continue" label?`.
1774 fn parse_continue_expr(&mut self, lo: Span) -> PResult<'a, P<Expr>> {
1775 let mut label = self.eat_label();
1777 // Recover `continue label` -> `continue 'label`
1778 if self.may_recover()
1780 && let Some((ident, _)) = self.token.ident()
1783 label = Some(self.recover_ident_into_label(ident));
1786 let kind = ExprKind::Continue(label);
1787 Ok(self.mk_expr(lo.to(self.prev_token.span), kind))
1790 /// Parse `"yield" expr?`.
1791 fn parse_yield_expr(&mut self) -> PResult<'a, P<Expr>> {
1792 let lo = self.prev_token.span;
1793 let kind = ExprKind::Yield(self.parse_expr_opt()?);
1794 let span = lo.to(self.prev_token.span);
1795 self.sess.gated_spans.gate(sym::generators, span);
1796 let expr = self.mk_expr(span, kind);
1797 self.maybe_recover_from_bad_qpath(expr)
1800 /// Returns a string literal if the next token is a string literal.
1801 /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
1802 /// and returns `None` if the next token is not literal at all.
1803 pub fn parse_str_lit(&mut self) -> Result<ast::StrLit, Option<MetaItemLit>> {
1804 match self.parse_opt_meta_item_lit() {
1805 Some(lit) => match lit.kind {
1806 ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
1813 _ => Err(Some(lit)),
1819 pub(crate) fn mk_token_lit_char(name: Symbol, span: Span) -> (token::Lit, Span) {
1820 (token::Lit { symbol: name, suffix: None, kind: token::Char }, span)
1823 fn mk_meta_item_lit_char(name: Symbol, span: Span) -> MetaItemLit {
1827 kind: ast::LitKind::Char(name.as_str().chars().next().unwrap_or('_')),
1832 fn handle_missing_lit<L>(
1834 mk_lit_char: impl FnOnce(Symbol, Span) -> L,
1835 ) -> PResult<'a, L> {
1836 if let token::Interpolated(inner) = &self.token.kind {
1837 let expr = match inner.as_ref() {
1838 token::NtExpr(expr) => Some(expr),
1839 token::NtLiteral(expr) => Some(expr),
1842 if let Some(expr) = expr {
1843 if matches!(expr.kind, ExprKind::Err) {
1844 let mut err = InvalidInterpolatedExpression { span: self.token.span }
1845 .into_diagnostic(&self.sess.span_diagnostic);
1846 err.downgrade_to_delayed_bug();
1851 let token = self.token.clone();
1852 let err = |self_: &Self| {
1853 let msg = format!("unexpected token: {}", super::token_descr(&token));
1854 self_.struct_span_err(token.span, &msg)
1856 // On an error path, eagerly consider a lifetime to be an unclosed character lit
1857 if self.token.is_lifetime() {
1858 let lt = self.expect_lifetime();
1859 Ok(self.recover_unclosed_char(lt.ident, mk_lit_char, err))
1865 pub(super) fn parse_token_lit(&mut self) -> PResult<'a, (token::Lit, Span)> {
1866 self.parse_opt_token_lit()
1868 .or_else(|()| self.handle_missing_lit(Parser::mk_token_lit_char))
1871 pub(super) fn parse_meta_item_lit(&mut self) -> PResult<'a, MetaItemLit> {
1872 self.parse_opt_meta_item_lit()
1874 .or_else(|()| self.handle_missing_lit(Parser::mk_meta_item_lit_char))
1877 fn recover_after_dot(&mut self) -> Option<Token> {
1878 let mut recovered = None;
1879 if self.token == token::Dot {
1880 // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
1881 // dot would follow an optional literal, so we do this unconditionally.
1882 recovered = self.look_ahead(1, |next_token| {
1883 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
1886 // If this integer looks like a float, then recover as such.
1888 // We will never encounter the exponent part of a floating
1889 // point literal here, since there's no use of the exponent
1890 // syntax that also constitutes a valid integer, so we need
1891 // not check for that.
1892 if suffix.map_or(true, |s| s == sym::f32 || s == sym::f64)
1893 && symbol.as_str().chars().all(|c| c.is_numeric() || c == '_')
1894 && self.token.span.hi() == next_token.span.lo()
1896 let s = String::from("0.") + symbol.as_str();
1897 let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
1898 return Some(Token::new(kind, self.token.span.to(next_token.span)));
1903 if let Some(token) = &recovered {
1905 self.sess.emit_err(FloatLiteralRequiresIntegerPart {
1907 correct: pprust::token_to_string(token).into_owned(),
1915 /// Matches `lit = true | false | token_lit`.
1916 /// Returns `None` if the next token is not a literal.
1917 pub(super) fn parse_opt_token_lit(&mut self) -> Option<(token::Lit, Span)> {
1918 let recovered = self.recover_after_dot();
1919 let token = recovered.as_ref().unwrap_or(&self.token);
1920 let span = token.span;
1921 token::Lit::from_token(token).map(|token_lit| {
1927 /// Matches `lit = true | false | token_lit`.
1928 /// Returns `None` if the next token is not a literal.
1929 pub(super) fn parse_opt_meta_item_lit(&mut self) -> Option<MetaItemLit> {
1930 let recovered = self.recover_after_dot();
1931 let token = recovered.as_ref().unwrap_or(&self.token);
1932 match token::Lit::from_token(token) {
1933 Some(token_lit) => {
1934 match MetaItemLit::from_token_lit(token_lit, token.span) {
1940 let span = token.span;
1941 let token::Literal(lit) = token.kind else {
1945 report_lit_error(&self.sess, err, lit, span);
1946 // Pack possible quotes and prefixes from the original literal into
1947 // the error literal's symbol so they can be pretty-printed faithfully.
1948 let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
1949 let symbol = Symbol::intern(&suffixless_lit.to_string());
1950 let lit = token::Lit::new(token::Err, symbol, lit.suffix);
1952 MetaItemLit::from_token_lit(lit, span)
1953 .unwrap_or_else(|_| unreachable!()),
1962 pub(super) fn expect_no_tuple_index_suffix(&self, span: Span, suffix: Symbol) {
1963 if [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suffix) {
1964 // #59553: warn instead of reject out of hand to allow the fix to percolate
1965 // through the ecosystem when people fix their macros
1966 self.sess.emit_warning(InvalidLiteralSuffixOnTupleIndex {
1969 exception: Some(()),
1972 self.sess.emit_err(InvalidLiteralSuffixOnTupleIndex { span, suffix, exception: None });
1976 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1977 /// Keep this in sync with `Token::can_begin_literal_maybe_minus`.
1978 pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1979 maybe_whole_expr!(self);
1981 let lo = self.token.span;
1982 let minus_present = self.eat(&token::BinOp(token::Minus));
1983 let (token_lit, span) = self.parse_token_lit()?;
1984 let expr = self.mk_expr(span, ExprKind::Lit(token_lit));
1987 Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_unary(UnOp::Neg, expr)))
1993 fn is_array_like_block(&mut self) -> bool {
1994 self.look_ahead(1, |t| matches!(t.kind, TokenKind::Ident(..) | TokenKind::Literal(_)))
1995 && self.look_ahead(2, |t| t == &token::Comma)
1996 && self.look_ahead(3, |t| t.can_begin_expr())
1999 /// Emits a suggestion if it looks like the user meant an array but
2000 /// accidentally used braces, causing the code to be interpreted as a block
2002 fn maybe_suggest_brackets_instead_of_braces(&mut self, lo: Span) -> Option<P<Expr>> {
2003 let mut snapshot = self.create_snapshot_for_diagnostic();
2004 match snapshot.parse_array_or_repeat_expr(Delimiter::Brace) {
2006 self.sess.emit_err(ArrayBracketsInsteadOfSpaces {
2008 sub: ArrayBracketsInsteadOfSpacesSugg {
2010 right: snapshot.prev_token.span,
2014 self.restore_snapshot(snapshot);
2015 Some(self.mk_expr_err(arr.span))
2024 fn suggest_missing_semicolon_before_array(
2027 open_delim_span: Span,
2028 ) -> PResult<'a, ()> {
2029 if !self.may_recover() {
2033 if self.token.kind == token::Comma {
2034 if !self.sess.source_map().is_multiline(prev_span.until(self.token.span)) {
2037 let mut snapshot = self.create_snapshot_for_diagnostic();
2039 match snapshot.parse_seq_to_before_end(
2040 &token::CloseDelim(Delimiter::Bracket),
2041 SeqSep::trailing_allowed(token::Comma),
2045 // When the close delim is `)`, `token.kind` is expected to be `token::CloseDelim(Delimiter::Parenthesis)`,
2046 // but the actual `token.kind` is `token::CloseDelim(Delimiter::Bracket)`.
2047 // This is because the `token.kind` of the close delim is treated as the same as
2048 // that of the open delim in `TokenTreesReader::parse_token_tree`, even if the delimiters of them are different.
2049 // Therefore, `token.kind` should not be compared here.
2051 .span_to_snippet(snapshot.token.span)
2052 .map_or(false, |snippet| snippet == "]") =>
2054 return Err(MissingSemicolonBeforeArray {
2055 open_delim: open_delim_span,
2056 semicolon: prev_span.shrink_to_hi(),
2057 }.into_diagnostic(&self.sess.span_diagnostic));
2060 Err(err) => err.cancel(),
2066 /// Parses a block or unsafe block.
2067 pub(super) fn parse_block_expr(
2069 opt_label: Option<Label>,
2071 blk_mode: BlockCheckMode,
2072 ) -> PResult<'a, P<Expr>> {
2073 if self.may_recover() && self.is_array_like_block() {
2074 if let Some(arr) = self.maybe_suggest_brackets_instead_of_braces(lo) {
2079 if self.token.is_whole_block() {
2080 self.sess.emit_err(InvalidBlockMacroSegment {
2081 span: self.token.span,
2082 context: lo.to(self.token.span),
2086 let (attrs, blk) = self.parse_block_common(lo, blk_mode, true)?;
2087 Ok(self.mk_expr_with_attrs(blk.span, ExprKind::Block(blk, opt_label), attrs))
2090 /// Parse a block which takes no attributes and has no label
2091 fn parse_simple_block(&mut self) -> PResult<'a, P<Expr>> {
2092 let blk = self.parse_block()?;
2093 Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None)))
2096 /// Parses a closure expression (e.g., `move |args| expr`).
2097 fn parse_closure_expr(&mut self) -> PResult<'a, P<Expr>> {
2098 let lo = self.token.span;
2100 let binder = if self.check_keyword(kw::For) {
2101 let lo = self.token.span;
2102 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
2103 let span = lo.to(self.prev_token.span);
2105 self.sess.gated_spans.gate(sym::closure_lifetime_binder, span);
2107 ClosureBinder::For { span, generic_params: P::from_vec(lifetime_defs) }
2109 ClosureBinder::NotPresent
2112 let constness = self.parse_constness(Case::Sensitive);
2115 if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
2117 let asyncness = if self.token.uninterpolated_span().rust_2018() {
2118 self.parse_asyncness(Case::Sensitive)
2123 let capture_clause = self.parse_capture_clause()?;
2124 let (fn_decl, fn_arg_span) = self.parse_fn_block_decl()?;
2125 let decl_hi = self.prev_token.span;
2126 let mut body = match fn_decl.output {
2127 FnRetTy::Default(_) => {
2128 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
2129 self.parse_expr_res(restrictions, None)?
2132 // If an explicit return type is given, require a block to appear (RFC 968).
2133 let body_lo = self.token.span;
2134 self.parse_block_expr(None, body_lo, BlockCheckMode::Default)?
2138 if let Async::Yes { span, .. } = asyncness {
2139 // Feature-gate `async ||` closures.
2140 self.sess.gated_spans.gate(sym::async_closure, span);
2143 if self.token.kind == TokenKind::Semi
2144 && matches!(self.token_cursor.frame.delim_sp, Some((Delimiter::Parenthesis, _)))
2145 && self.may_recover()
2147 // It is likely that the closure body is a block but where the
2148 // braces have been removed. We will recover and eat the next
2149 // statements later in the parsing process.
2150 body = self.mk_expr_err(body.span);
2153 let body_span = body.span;
2155 let closure = self.mk_expr(
2157 ExprKind::Closure(Box::new(ast::Closure {
2165 fn_decl_span: lo.to(decl_hi),
2170 // Disable recovery for closure body
2172 ClosureSpans { whole_closure: closure.span, closing_pipe: decl_hi, body: body_span };
2173 self.current_closure = Some(spans);
2178 /// Parses an optional `move` prefix to a closure-like construct.
2179 fn parse_capture_clause(&mut self) -> PResult<'a, CaptureBy> {
2180 if self.eat_keyword(kw::Move) {
2181 // Check for `move async` and recover
2182 if self.check_keyword(kw::Async) {
2183 let move_async_span = self.token.span.with_lo(self.prev_token.span.data().lo);
2184 Err(AsyncMoveOrderIncorrect { span: move_async_span }
2185 .into_diagnostic(&self.sess.span_diagnostic))
2187 Ok(CaptureBy::Value)
2194 /// Parses the `|arg, arg|` header of a closure.
2195 fn parse_fn_block_decl(&mut self) -> PResult<'a, (P<FnDecl>, Span)> {
2196 let arg_start = self.token.span.lo();
2198 let inputs = if self.eat(&token::OrOr) {
2201 self.expect(&token::BinOp(token::Or))?;
2203 .parse_seq_to_before_tokens(
2204 &[&token::BinOp(token::Or), &token::OrOr],
2205 SeqSep::trailing_allowed(token::Comma),
2206 TokenExpectType::NoExpect,
2207 |p| p.parse_fn_block_param(),
2213 let arg_span = self.prev_token.span.with_lo(arg_start);
2215 self.parse_ret_ty(AllowPlus::Yes, RecoverQPath::Yes, RecoverReturnSign::Yes)?;
2217 Ok((P(FnDecl { inputs, output }), arg_span))
2220 /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
2221 fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
2222 let lo = self.token.span;
2223 let attrs = self.parse_outer_attributes()?;
2224 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2225 let pat = this.parse_pat_no_top_alt(Some(Expected::ParameterName))?;
2226 let ty = if this.eat(&token::Colon) {
2229 this.mk_ty(this.prev_token.span, TyKind::Infer)
2237 span: lo.to(this.prev_token.span),
2239 is_placeholder: false,
2241 TrailingToken::MaybeComma,
2246 /// Parses an `if` expression (`if` token already eaten).
2247 fn parse_if_expr(&mut self) -> PResult<'a, P<Expr>> {
2248 let lo = self.prev_token.span;
2249 let cond = self.parse_cond_expr()?;
2250 self.parse_if_after_cond(lo, cond)
2253 fn parse_if_after_cond(&mut self, lo: Span, mut cond: P<Expr>) -> PResult<'a, P<Expr>> {
2254 let cond_span = cond.span;
2255 // Tries to interpret `cond` as either a missing expression if it's a block,
2256 // or as an unfinished expression if it's a binop and the RHS is a block.
2257 // We could probably add more recoveries here too...
2258 let mut recover_block_from_condition = |this: &mut Self| {
2259 let block = match &mut cond.kind {
2260 ExprKind::Binary(Spanned { span: binop_span, .. }, _, right)
2261 if let ExprKind::Block(_, None) = right.kind => {
2262 self.sess.emit_err(IfExpressionMissingThenBlock {
2264 missing_then_block_sub:
2265 IfExpressionMissingThenBlockSub::UnfinishedCondition(cond_span.shrink_to_lo().to(*binop_span)),
2269 std::mem::replace(right, this.mk_expr_err(binop_span.shrink_to_hi()))
2271 ExprKind::Block(_, None) => {
2272 self.sess.emit_err(IfExpressionMissingCondition {
2273 if_span: lo.shrink_to_hi(),
2274 block_span: self.sess.source_map().start_point(cond_span),
2276 std::mem::replace(&mut cond, this.mk_expr_err(cond_span.shrink_to_hi()))
2282 if let ExprKind::Block(block, _) = &block.kind {
2289 let thn = if self.token.is_keyword(kw::Else) {
2290 if let Some(block) = recover_block_from_condition(self) {
2293 let let_else_sub = matches!(cond.kind, ExprKind::Let(..))
2294 .then(|| IfExpressionLetSomeSub { if_span: lo.until(cond_span) });
2296 self.sess.emit_err(IfExpressionMissingThenBlock {
2298 missing_then_block_sub: IfExpressionMissingThenBlockSub::AddThenBlock(
2299 cond_span.shrink_to_hi(),
2303 self.mk_block_err(cond_span.shrink_to_hi())
2306 let attrs = self.parse_outer_attributes()?; // For recovery.
2307 let block = if self.check(&token::OpenDelim(Delimiter::Brace)) {
2310 if let Some(block) = recover_block_from_condition(self) {
2313 self.error_on_extra_if(&cond)?;
2314 // Parse block, which will always fail, but we can add a nice note to the error
2315 self.parse_block().map_err(|mut err| {
2318 "the `if` expression is missing a block after this condition",
2324 self.error_on_if_block_attrs(lo, false, block.span, attrs);
2327 let els = if self.eat_keyword(kw::Else) { Some(self.parse_else_expr()?) } else { None };
2328 Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::If(cond, thn, els)))
2331 /// Parses the condition of a `if` or `while` expression.
2332 fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
2334 self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL | Restrictions::ALLOW_LET, None)?;
2336 if let ExprKind::Let(..) = cond.kind {
2337 // Remove the last feature gating of a `let` expression since it's stable.
2338 self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
2344 /// Parses a `let $pat = $expr` pseudo-expression.
2345 fn parse_let_expr(&mut self) -> PResult<'a, P<Expr>> {
2346 // This is a *approximate* heuristic that detects if `let` chains are
2347 // being parsed in the right position. It's approximate because it
2348 // doesn't deny all invalid `let` expressions, just completely wrong usages.
2349 let not_in_chain = !matches!(
2350 self.prev_token.kind,
2351 TokenKind::AndAnd | TokenKind::Ident(kw::If, _) | TokenKind::Ident(kw::While, _)
2353 if !self.restrictions.contains(Restrictions::ALLOW_LET) || not_in_chain {
2354 self.sess.emit_err(ExpectedExpressionFoundLet { span: self.token.span });
2357 self.bump(); // Eat `let` token
2358 let lo = self.prev_token.span;
2359 let pat = self.parse_pat_allow_top_alt(
2363 CommaRecoveryMode::LikelyTuple,
2365 if self.token == token::EqEq {
2366 self.sess.emit_err(ExpectedEqForLetExpr {
2367 span: self.token.span,
2368 sugg_span: self.token.span,
2372 self.expect(&token::Eq)?;
2374 let expr = self.with_res(self.restrictions | Restrictions::NO_STRUCT_LITERAL, |this| {
2375 this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
2377 let span = lo.to(expr.span);
2378 self.sess.gated_spans.gate(sym::let_chains, span);
2379 Ok(self.mk_expr(span, ExprKind::Let(pat, expr, span)))
2382 /// Parses an `else { ... }` expression (`else` token already eaten).
2383 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
2384 let else_span = self.prev_token.span; // `else`
2385 let attrs = self.parse_outer_attributes()?; // For recovery.
2386 let expr = if self.eat_keyword(kw::If) {
2387 self.parse_if_expr()?
2388 } else if self.check(&TokenKind::OpenDelim(Delimiter::Brace)) {
2389 self.parse_simple_block()?
2391 let snapshot = self.create_snapshot_for_diagnostic();
2392 let first_tok = super::token_descr(&self.token);
2393 let first_tok_span = self.token.span;
2394 match self.parse_expr() {
2396 // If it's not a free-standing expression, and is followed by a block,
2397 // then it's very likely the condition to an `else if`.
2398 if self.check(&TokenKind::OpenDelim(Delimiter::Brace))
2399 && classify::expr_requires_semi_to_be_stmt(&cond) =>
2401 self.sess.emit_err(ExpectedElseBlock {
2405 condition_start: cond.span.shrink_to_lo(),
2407 self.parse_if_after_cond(cond.span.shrink_to_lo(), cond)?
2411 self.restore_snapshot(snapshot);
2412 self.parse_simple_block()?
2415 self.restore_snapshot(snapshot);
2416 self.parse_simple_block()?
2420 self.error_on_if_block_attrs(else_span, true, expr.span, attrs);
2424 fn error_on_if_block_attrs(
2431 if attrs.is_empty() {
2435 let attrs: &[ast::Attribute] = &attrs.take_for_recovery(self.sess);
2436 let (attributes, last) = match attrs {
2438 [x0 @ xn] | [x0, .., xn] => (x0.span.to(xn.span), xn.span),
2440 let ctx = if is_ctx_else { "else" } else { "if" };
2441 self.sess.emit_err(OuterAttributeNotAllowedOnIfElse {
2445 ctx: ctx.to_string(),
2450 fn error_on_extra_if(&mut self, cond: &P<Expr>) -> PResult<'a, ()> {
2451 if let ExprKind::Binary(Spanned { span: binop_span, node: binop}, _, right) = &cond.kind &&
2452 let BinOpKind::And = binop &&
2453 let ExprKind::If(cond, ..) = &right.kind {
2454 Err(self.sess.create_err(UnexpectedIfWithIf(binop_span.shrink_to_hi().to(cond.span.shrink_to_lo()))))
2460 /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
2461 fn parse_for_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2462 // Record whether we are about to parse `for (`.
2463 // This is used below for recovery in case of `for ( $stuff ) $block`
2464 // in which case we will suggest `for $stuff $block`.
2465 let begin_paren = match self.token.kind {
2466 token::OpenDelim(Delimiter::Parenthesis) => Some(self.token.span),
2470 let pat = self.parse_pat_allow_top_alt(
2474 CommaRecoveryMode::LikelyTuple,
2476 if !self.eat_keyword(kw::In) {
2477 self.error_missing_in_for_loop();
2479 self.check_for_for_in_in_typo(self.prev_token.span);
2480 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2482 let pat = self.recover_parens_around_for_head(pat, begin_paren);
2484 let (attrs, loop_block) = self.parse_inner_attrs_and_block()?;
2486 let kind = ExprKind::ForLoop(pat, expr, loop_block, opt_label);
2487 Ok(self.mk_expr_with_attrs(lo.to(self.prev_token.span), kind, attrs))
2490 fn error_missing_in_for_loop(&mut self) {
2491 let (span, sub): (_, fn(_) -> _) = if self.token.is_ident_named(sym::of) {
2492 // Possibly using JS syntax (#75311).
2493 let span = self.token.span;
2495 (span, MissingInInForLoopSub::InNotOf)
2497 (self.prev_token.span.between(self.token.span), MissingInInForLoopSub::AddIn)
2500 self.sess.emit_err(MissingInInForLoop { span, sub: sub(span) });
2503 /// Parses a `while` or `while let` expression (`while` token already eaten).
2504 fn parse_while_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2505 let cond = self.parse_cond_expr().map_err(|mut err| {
2506 err.span_label(lo, "while parsing the condition of this `while` expression");
2509 let (attrs, body) = self.parse_inner_attrs_and_block().map_err(|mut err| {
2510 err.span_label(lo, "while parsing the body of this `while` expression");
2511 err.span_label(cond.span, "this `while` condition successfully parsed");
2514 Ok(self.mk_expr_with_attrs(
2515 lo.to(self.prev_token.span),
2516 ExprKind::While(cond, body, opt_label),
2521 /// Parses `loop { ... }` (`loop` token already eaten).
2522 fn parse_loop_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2523 let loop_span = self.prev_token.span;
2524 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2525 Ok(self.mk_expr_with_attrs(
2526 lo.to(self.prev_token.span),
2527 ExprKind::Loop(body, opt_label, loop_span),
2532 pub(crate) fn eat_label(&mut self) -> Option<Label> {
2533 self.token.lifetime().map(|ident| {
2539 /// Parses a `match ... { ... }` expression (`match` token already eaten).
2540 fn parse_match_expr(&mut self) -> PResult<'a, P<Expr>> {
2541 let match_span = self.prev_token.span;
2542 let lo = self.prev_token.span;
2543 let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2544 if let Err(mut e) = self.expect(&token::OpenDelim(Delimiter::Brace)) {
2545 if self.token == token::Semi {
2546 e.span_suggestion_short(
2548 "try removing this `match`",
2550 Applicability::MaybeIncorrect, // speculative
2553 if self.maybe_recover_unexpected_block_label() {
2560 let attrs = self.parse_inner_attributes()?;
2562 let mut arms: Vec<Arm> = Vec::new();
2563 while self.token != token::CloseDelim(Delimiter::Brace) {
2564 match self.parse_arm() {
2565 Ok(arm) => arms.push(arm),
2567 // Recover by skipping to the end of the block.
2569 self.recover_stmt();
2570 let span = lo.to(self.token.span);
2571 if self.token == token::CloseDelim(Delimiter::Brace) {
2574 return Ok(self.mk_expr_with_attrs(
2576 ExprKind::Match(scrutinee, arms),
2582 let hi = self.token.span;
2584 Ok(self.mk_expr_with_attrs(lo.to(hi), ExprKind::Match(scrutinee, arms), attrs))
2587 /// Attempt to recover from match arm body with statements and no surrounding braces.
2588 fn parse_arm_body_missing_braces(
2590 first_expr: &P<Expr>,
2592 ) -> Option<P<Expr>> {
2593 if self.token.kind != token::Semi {
2596 let start_snapshot = self.create_snapshot_for_diagnostic();
2597 let semi_sp = self.token.span;
2600 vec![self.mk_stmt(first_expr.span, ast::StmtKind::Expr(first_expr.clone()))];
2601 let err = |this: &Parser<'_>, stmts: Vec<ast::Stmt>| {
2602 let span = stmts[0].span.to(stmts[stmts.len() - 1].span);
2604 this.sess.emit_err(MatchArmBodyWithoutBraces {
2607 num_statements: stmts.len(),
2608 sub: if stmts.len() > 1 {
2609 MatchArmBodyWithoutBracesSugg::AddBraces {
2610 left: span.shrink_to_lo(),
2611 right: span.shrink_to_hi(),
2614 MatchArmBodyWithoutBracesSugg::UseComma { semicolon: semi_sp }
2617 this.mk_expr_err(span)
2619 // We might have either a `,` -> `;` typo, or a block without braces. We need
2620 // a more subtle parsing strategy.
2622 if self.token.kind == token::CloseDelim(Delimiter::Brace) {
2623 // We have reached the closing brace of the `match` expression.
2624 return Some(err(self, stmts));
2626 if self.token.kind == token::Comma {
2627 self.restore_snapshot(start_snapshot);
2630 let pre_pat_snapshot = self.create_snapshot_for_diagnostic();
2631 match self.parse_pat_no_top_alt(None) {
2633 if self.token.kind == token::FatArrow {
2635 self.restore_snapshot(pre_pat_snapshot);
2636 return Some(err(self, stmts));
2644 self.restore_snapshot(pre_pat_snapshot);
2645 match self.parse_stmt_without_recovery(true, ForceCollect::No) {
2646 // Consume statements for as long as possible.
2651 self.restore_snapshot(start_snapshot);
2654 // We couldn't parse either yet another statement missing it's
2655 // enclosing block nor the next arm's pattern or closing brace.
2658 self.restore_snapshot(start_snapshot);
2666 pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
2667 // Used to check the `let_chains` and `if_let_guard` features mostly by scanning
2669 fn check_let_expr(expr: &Expr) -> (bool, bool) {
2671 ExprKind::Binary(BinOp { node: BinOpKind::And, .. }, lhs, rhs) => {
2672 let lhs_rslt = check_let_expr(lhs);
2673 let rhs_rslt = check_let_expr(rhs);
2674 (lhs_rslt.0 || rhs_rslt.0, false)
2676 ExprKind::Let(..) => (true, true),
2680 let attrs = self.parse_outer_attributes()?;
2681 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2682 let lo = this.token.span;
2683 let pat = this.parse_pat_allow_top_alt(
2687 CommaRecoveryMode::EitherTupleOrPipe,
2689 let guard = if this.eat_keyword(kw::If) {
2690 let if_span = this.prev_token.span;
2691 let cond = this.parse_expr_res(Restrictions::ALLOW_LET, None)?;
2692 let (has_let_expr, does_not_have_bin_op) = check_let_expr(&cond);
2694 if does_not_have_bin_op {
2695 // Remove the last feature gating of a `let` expression since it's stable.
2696 this.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
2698 let span = if_span.to(cond.span);
2699 this.sess.gated_spans.gate(sym::if_let_guard, span);
2705 let arrow_span = this.token.span;
2706 if let Err(mut err) = this.expect(&token::FatArrow) {
2707 // We might have a `=>` -> `=` or `->` typo (issue #89396).
2708 if TokenKind::FatArrow
2710 .map_or(false, |similar_tokens| similar_tokens.contains(&this.token.kind))
2712 err.span_suggestion(
2714 "try using a fat arrow here",
2716 Applicability::MaybeIncorrect,
2721 (&this.prev_token.kind, &this.token.kind),
2722 (token::DotDotEq, token::Gt)
2724 // `error_inclusive_range_match_arrow` handles cases like `0..=> {}`,
2725 // so we supress the error here
2732 let arm_start_span = this.token.span;
2734 let expr = this.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
2735 err.span_label(arrow_span, "while parsing the `match` arm starting here");
2739 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
2740 && this.token != token::CloseDelim(Delimiter::Brace);
2742 let hi = this.prev_token.span;
2745 let sm = this.sess.source_map();
2746 if let Some(body) = this.parse_arm_body_missing_braces(&expr, arrow_span) {
2747 let span = body.span;
2756 is_placeholder: false,
2758 TrailingToken::None,
2761 this.expect_one_of(&[token::Comma], &[token::CloseDelim(Delimiter::Brace)])
2762 .or_else(|mut err| {
2763 if this.token == token::FatArrow {
2764 if let Ok(expr_lines) = sm.span_to_lines(expr.span)
2765 && let Ok(arm_start_lines) = sm.span_to_lines(arm_start_span)
2766 && arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
2767 && expr_lines.lines.len() == 2
2769 // We check whether there's any trailing code in the parse span,
2770 // if there isn't, we very likely have the following:
2773 // | -- - missing comma
2777 // | - ^^ self.token.span
2779 // | parsed until here as `"y" & X`
2780 err.span_suggestion_short(
2781 arm_start_span.shrink_to_hi(),
2782 "missing a comma here to end this `match` arm",
2784 Applicability::MachineApplicable,
2789 // FIXME(compiler-errors): We could also recover `; PAT =>` here
2791 // Try to parse a following `PAT =>`, if successful
2792 // then we should recover.
2793 let mut snapshot = this.create_snapshot_for_diagnostic();
2794 let pattern_follows = snapshot
2795 .parse_pat_allow_top_alt(
2799 CommaRecoveryMode::EitherTupleOrPipe,
2801 .map_err(|err| err.cancel())
2803 if pattern_follows && snapshot.check(&TokenKind::FatArrow) {
2805 this.sess.emit_err(MissingCommaAfterMatchArm {
2806 span: hi.shrink_to_hi(),
2811 err.span_label(arrow_span, "while parsing the `match` arm starting here");
2815 this.eat(&token::Comma);
2826 is_placeholder: false,
2828 TrailingToken::None,
2833 /// Parses a `try {...}` expression (`try` token already eaten).
2834 fn parse_try_block(&mut self, span_lo: Span) -> PResult<'a, P<Expr>> {
2835 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2836 if self.eat_keyword(kw::Catch) {
2837 Err(CatchAfterTry { span: self.prev_token.span }
2838 .into_diagnostic(&self.sess.span_diagnostic))
2840 let span = span_lo.to(body.span);
2841 self.sess.gated_spans.gate(sym::try_blocks, span);
2842 Ok(self.mk_expr_with_attrs(span, ExprKind::TryBlock(body), attrs))
2846 fn is_do_catch_block(&self) -> bool {
2847 self.token.is_keyword(kw::Do)
2848 && self.is_keyword_ahead(1, &[kw::Catch])
2849 && self.look_ahead(2, |t| *t == token::OpenDelim(Delimiter::Brace))
2850 && !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
2853 fn is_do_yeet(&self) -> bool {
2854 self.token.is_keyword(kw::Do) && self.is_keyword_ahead(1, &[kw::Yeet])
2857 fn is_try_block(&self) -> bool {
2858 self.token.is_keyword(kw::Try)
2859 && self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace))
2860 && self.token.uninterpolated_span().rust_2018()
2863 /// Parses an `async move? {...}` expression.
2864 fn parse_async_block(&mut self) -> PResult<'a, P<Expr>> {
2865 let lo = self.token.span;
2866 self.expect_keyword(kw::Async)?;
2867 let capture_clause = self.parse_capture_clause()?;
2868 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2869 let kind = ExprKind::Async(capture_clause, DUMMY_NODE_ID, body);
2870 Ok(self.mk_expr_with_attrs(lo.to(self.prev_token.span), kind, attrs))
2873 fn is_async_block(&self) -> bool {
2874 self.token.is_keyword(kw::Async)
2877 self.is_keyword_ahead(1, &[kw::Move])
2878 && self.look_ahead(2, |t| *t == token::OpenDelim(Delimiter::Brace))
2881 self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace))
2885 fn is_certainly_not_a_block(&self) -> bool {
2886 self.look_ahead(1, |t| t.is_ident())
2888 // `{ ident, ` cannot start a block.
2889 self.look_ahead(2, |t| t == &token::Comma)
2890 || self.look_ahead(2, |t| t == &token::Colon)
2892 // `{ ident: token, ` cannot start a block.
2893 self.look_ahead(4, |t| t == &token::Comma) ||
2894 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
2895 self.look_ahead(3, |t| !t.can_begin_type())
2900 fn maybe_parse_struct_expr(
2902 qself: &Option<P<ast::QSelf>>,
2904 ) -> Option<PResult<'a, P<Expr>>> {
2905 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
2906 if struct_allowed || self.is_certainly_not_a_block() {
2907 if let Err(err) = self.expect(&token::OpenDelim(Delimiter::Brace)) {
2908 return Some(Err(err));
2910 let expr = self.parse_struct_expr(qself.clone(), path.clone(), true);
2911 if let (Ok(expr), false) = (&expr, struct_allowed) {
2912 // This is a struct literal, but we don't can't accept them here.
2913 self.sess.emit_err(StructLiteralNotAllowedHere {
2915 sub: StructLiteralNotAllowedHereSugg {
2916 left: path.span.shrink_to_lo(),
2917 right: expr.span.shrink_to_hi(),
2926 pub(super) fn parse_struct_fields(
2930 close_delim: Delimiter,
2931 ) -> PResult<'a, (Vec<ExprField>, ast::StructRest, bool)> {
2932 let mut fields = Vec::new();
2933 let mut base = ast::StructRest::None;
2934 let mut recover_async = false;
2936 let mut async_block_err = |e: &mut Diagnostic, span: Span| {
2937 recover_async = true;
2938 AsyncBlockIn2015 { span }.add_to_diagnostic(e);
2939 HelpUseLatestEdition::new().add_to_diagnostic(e);
2942 while self.token != token::CloseDelim(close_delim) {
2943 if self.eat(&token::DotDot) || self.recover_struct_field_dots(close_delim) {
2944 let exp_span = self.prev_token.span;
2945 // We permit `.. }` on the left-hand side of a destructuring assignment.
2946 if self.check(&token::CloseDelim(close_delim)) {
2947 base = ast::StructRest::Rest(self.prev_token.span.shrink_to_hi());
2950 match self.parse_expr() {
2951 Ok(e) => base = ast::StructRest::Base(e),
2952 Err(mut e) if recover => {
2954 self.recover_stmt();
2956 Err(e) => return Err(e),
2958 self.recover_struct_comma_after_dotdot(exp_span);
2962 let recovery_field = self.find_struct_error_after_field_looking_code();
2963 let parsed_field = match self.parse_expr_field() {
2966 if pth == kw::Async {
2967 async_block_err(&mut e, pth.span);
2969 e.span_label(pth.span, "while parsing this struct");
2973 // If the next token is a comma, then try to parse
2974 // what comes next as additional fields, rather than
2975 // bailing out until next `}`.
2976 if self.token != token::Comma {
2977 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2978 if self.token != token::Comma {
2986 let is_shorthand = parsed_field.as_ref().map_or(false, |f| f.is_shorthand);
2987 // A shorthand field can be turned into a full field with `:`.
2988 // We should point this out.
2989 self.check_or_expected(!is_shorthand, TokenType::Token(token::Colon));
2991 match self.expect_one_of(&[token::Comma], &[token::CloseDelim(close_delim)]) {
2993 if let Some(f) = parsed_field.or(recovery_field) {
2994 // Only include the field if there's no parse error for the field name.
2999 if pth == kw::Async {
3000 async_block_err(&mut e, pth.span);
3002 e.span_label(pth.span, "while parsing this struct");
3003 if let Some(f) = recovery_field {
3006 self.prev_token.span.shrink_to_hi(),
3007 "try adding a comma",
3009 Applicability::MachineApplicable,
3011 } else if is_shorthand
3012 && (AssocOp::from_token(&self.token).is_some()
3013 || matches!(&self.token.kind, token::OpenDelim(_))
3014 || self.token.kind == token::Dot)
3016 // Looks like they tried to write a shorthand, complex expression.
3017 let ident = parsed_field.expect("is_shorthand implies Some").ident;
3019 ident.span.shrink_to_lo(),
3020 "try naming a field",
3021 &format!("{ident}: "),
3022 Applicability::HasPlaceholders,
3030 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
3031 self.eat(&token::Comma);
3035 Ok((fields, base, recover_async))
3038 /// Precondition: already parsed the '{'.
3039 pub(super) fn parse_struct_expr(
3041 qself: Option<P<ast::QSelf>>,
3044 ) -> PResult<'a, P<Expr>> {
3046 let (fields, base, recover_async) =
3047 self.parse_struct_fields(pth.clone(), recover, Delimiter::Brace)?;
3048 let span = lo.to(self.token.span);
3049 self.expect(&token::CloseDelim(Delimiter::Brace))?;
3050 let expr = if recover_async {
3053 ExprKind::Struct(P(ast::StructExpr { qself, path: pth, fields, rest: base }))
3055 Ok(self.mk_expr(span, expr))
3058 /// Use in case of error after field-looking code: `S { foo: () with a }`.
3059 fn find_struct_error_after_field_looking_code(&self) -> Option<ExprField> {
3060 match self.token.ident() {
3061 Some((ident, is_raw))
3062 if (is_raw || !ident.is_reserved())
3063 && self.look_ahead(1, |t| *t == token::Colon) =>
3065 Some(ast::ExprField {
3067 span: self.token.span,
3068 expr: self.mk_expr_err(self.token.span),
3069 is_shorthand: false,
3070 attrs: AttrVec::new(),
3072 is_placeholder: false,
3079 fn recover_struct_comma_after_dotdot(&mut self, span: Span) {
3080 if self.token != token::Comma {
3083 self.sess.emit_err(CommaAfterBaseStruct {
3084 span: span.to(self.prev_token.span),
3085 comma: self.token.span,
3087 self.recover_stmt();
3090 fn recover_struct_field_dots(&mut self, close_delim: Delimiter) -> bool {
3091 if !self.look_ahead(1, |t| *t == token::CloseDelim(close_delim))
3092 && self.eat(&token::DotDotDot)
3094 // recover from typo of `...`, suggest `..`
3095 let span = self.prev_token.span;
3096 self.sess.emit_err(MissingDotDot { token_span: span, sugg_span: span });
3102 /// Converts an ident into 'label and emits an "expected a label, found an identifier" error.
3103 fn recover_ident_into_label(&mut self, ident: Ident) -> Label {
3104 // Convert `label` -> `'label`,
3105 // so that nameres doesn't complain about non-existing label
3106 let label = format!("'{}", ident.name);
3107 let ident = Ident { name: Symbol::intern(&label), span: ident.span };
3109 self.struct_span_err(ident.span, "expected a label, found an identifier")
3112 "labels start with a tick",
3114 Applicability::MachineApplicable,
3121 /// Parses `ident (COLON expr)?`.
3122 fn parse_expr_field(&mut self) -> PResult<'a, ExprField> {
3123 let attrs = self.parse_outer_attributes()?;
3124 self.recover_diff_marker();
3125 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
3126 let lo = this.token.span;
3128 // Check if a colon exists one ahead. This means we're parsing a fieldname.
3129 let is_shorthand = !this.look_ahead(1, |t| t == &token::Colon || t == &token::Eq);
3130 let (ident, expr) = if is_shorthand {
3131 // Mimic `x: x` for the `x` field shorthand.
3132 let ident = this.parse_ident_common(false)?;
3133 let path = ast::Path::from_ident(ident);
3134 (ident, this.mk_expr(ident.span, ExprKind::Path(None, path)))
3136 let ident = this.parse_field_name()?;
3137 this.error_on_eq_field_init(ident);
3139 (ident, this.parse_expr()?)
3145 span: lo.to(expr.span),
3150 is_placeholder: false,
3152 TrailingToken::MaybeComma,
3157 /// Check for `=`. This means the source incorrectly attempts to
3158 /// initialize a field with an eq rather than a colon.
3159 fn error_on_eq_field_init(&self, field_name: Ident) {
3160 if self.token != token::Eq {
3164 self.sess.emit_err(EqFieldInit {
3165 span: self.token.span,
3166 eq: field_name.span.shrink_to_hi().to(self.token.span),
3170 fn err_dotdotdot_syntax(&self, span: Span) {
3171 self.sess.emit_err(DotDotDot { span });
3174 fn err_larrow_operator(&self, span: Span) {
3175 self.sess.emit_err(LeftArrowOperator { span });
3178 fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
3179 ExprKind::AssignOp(binop, lhs, rhs)
3184 start: Option<P<Expr>>,
3185 end: Option<P<Expr>>,
3186 limits: RangeLimits,
3188 if end.is_none() && limits == RangeLimits::Closed {
3189 self.inclusive_range_with_incorrect_end();
3192 ExprKind::Range(start, end, limits)
3196 fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
3197 ExprKind::Unary(unop, expr)
3200 fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
3201 ExprKind::Binary(binop, lhs, rhs)
3204 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
3205 ExprKind::Index(expr, idx)
3208 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
3209 ExprKind::Call(f, args)
3212 fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> P<Expr> {
3213 let span = lo.to(self.prev_token.span);
3214 let await_expr = self.mk_expr(span, ExprKind::Await(self_arg));
3215 self.recover_from_await_method_call();
3219 pub(crate) fn mk_expr_with_attrs(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
3220 P(Expr { kind, span, attrs, id: DUMMY_NODE_ID, tokens: None })
3223 pub(crate) fn mk_expr(&self, span: Span, kind: ExprKind) -> P<Expr> {
3224 P(Expr { kind, span, attrs: AttrVec::new(), id: DUMMY_NODE_ID, tokens: None })
3227 pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> {
3228 self.mk_expr(span, ExprKind::Err)
3231 /// Create expression span ensuring the span of the parent node
3232 /// is larger than the span of lhs and rhs, including the attributes.
3233 fn mk_expr_sp(&self, lhs: &P<Expr>, lhs_span: Span, rhs_span: Span) -> Span {
3236 .find(|a| a.style == AttrStyle::Outer)
3237 .map_or(lhs_span, |a| a.span)
3241 fn collect_tokens_for_expr(
3244 f: impl FnOnce(&mut Self, ast::AttrVec) -> PResult<'a, P<Expr>>,
3245 ) -> PResult<'a, P<Expr>> {
3246 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
3247 let res = f(this, attrs)?;
3248 let trailing = if this.restrictions.contains(Restrictions::STMT_EXPR)
3249 && this.token.kind == token::Semi
3252 } else if this.token.kind == token::Gt {
3255 // FIXME - pass this through from the place where we know
3256 // we need a comma, rather than assuming that `#[attr] expr,`
3257 // always captures a trailing comma
3258 TrailingToken::MaybeComma