1 use super::diagnostics::SnapshotParser;
2 use super::pat::{CommaRecoveryMode, RecoverColon, RecoverComma, PARAM_EXPECTED};
3 use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
5 AttrWrapper, BlockMode, ClosureSpans, ForceCollect, Parser, PathStyle, Restrictions,
6 SemiColonMode, SeqSep, TokenExpectType, TokenType, TrailingToken,
9 ArrayBracketsInsteadOfSpaces, ArrayBracketsInsteadOfSpacesSugg, AsyncMoveOrderIncorrect,
10 BracesForStructLiteral, CatchAfterTry, CommaAfterBaseStruct, ComparisonInterpretedAsGeneric,
11 ComparisonOrShiftInterpretedAsGenericSugg, DoCatchSyntaxRemoved, DotDotDot, EqFieldInit,
12 ExpectedElseBlock, ExpectedEqForLetExpr, ExpectedExpressionFoundLet,
13 FieldExpressionWithGeneric, FloatLiteralRequiresIntegerPart, FoundExprWouldBeStmt,
14 IfExpressionMissingCondition, IfExpressionMissingThenBlock, IfExpressionMissingThenBlockSub,
15 InvalidBlockMacroSegment, InvalidComparisonOperator, InvalidComparisonOperatorSub,
16 InvalidInterpolatedExpression, InvalidLiteralSuffixOnTupleIndex, InvalidLogicalOperator,
17 InvalidLogicalOperatorSub, LabeledLoopInBreak, LeadingPlusNotSupported, LeftArrowOperator,
18 LifetimeInBorrowExpression, MacroInvocationWithQualifiedPath, MalformedLoopLabel,
19 MatchArmBodyWithoutBraces, MatchArmBodyWithoutBracesSugg, MissingCommaAfterMatchArm,
20 MissingDotDot, MissingInInForLoop, MissingInInForLoopSub, MissingSemicolonBeforeArray,
21 NoFieldsForFnCall, NotAsNegationOperator, NotAsNegationOperatorSub,
22 OuterAttributeNotAllowedOnIfElse, ParenthesesWithStructFields,
23 RequireColonAfterLabeledExpression, ShiftInterpretedAsGeneric, StructLiteralNotAllowedHere,
24 StructLiteralNotAllowedHereSugg, TildeAsUnaryOperator, UnexpectedIfWithIf,
25 UnexpectedTokenAfterLabel, UnexpectedTokenAfterLabelSugg, WrapExpressionInParentheses,
27 use crate::maybe_recover_from_interpolated_ty_qpath;
29 use rustc_ast::ptr::P;
30 use rustc_ast::token::{self, Delimiter, Token, TokenKind};
31 use rustc_ast::tokenstream::Spacing;
32 use rustc_ast::util::case::Case;
33 use rustc_ast::util::classify;
34 use rustc_ast::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
35 use rustc_ast::visit::Visitor;
36 use rustc_ast::{self as ast, AttrStyle, AttrVec, CaptureBy, ExprField, UnOp, DUMMY_NODE_ID};
37 use rustc_ast::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, MacCall, Param, Ty, TyKind};
38 use rustc_ast::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits};
39 use rustc_ast::{ClosureBinder, MetaItemLit, StmtKind};
40 use rustc_ast_pretty::pprust;
42 Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, IntoDiagnostic, PResult,
45 use rustc_session::errors::{report_lit_error, ExprParenthesesNeeded};
46 use rustc_session::lint::builtin::BREAK_WITH_LABEL_AND_LOOP;
47 use rustc_session::lint::BuiltinLintDiagnostics;
48 use rustc_span::source_map::{self, Span, Spanned};
49 use rustc_span::symbol::{kw, sym, Ident, Symbol};
50 use rustc_span::{BytePos, Pos};
52 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
53 /// dropped into the token stream, which happens while parsing the result of
54 /// macro expansion). Placement of these is not as complex as I feared it would
55 /// be. The important thing is to make sure that lookahead doesn't balk at
56 /// `token::Interpolated` tokens.
57 macro_rules! maybe_whole_expr {
59 if let token::Interpolated(nt) = &$p.token.kind {
61 token::NtExpr(e) | token::NtLiteral(e) => {
66 token::NtPath(path) => {
67 let path = (**path).clone();
69 return Ok($p.mk_expr($p.prev_token.span, ExprKind::Path(None, path)));
71 token::NtBlock(block) => {
72 let block = block.clone();
74 return Ok($p.mk_expr($p.prev_token.span, ExprKind::Block(block, None)));
83 pub(super) enum LhsExpr {
85 AttributesParsed(AttrWrapper),
86 AlreadyParsed { expr: P<Expr>, starts_statement: bool },
89 impl From<Option<AttrWrapper>> for LhsExpr {
90 /// Converts `Some(attrs)` into `LhsExpr::AttributesParsed(attrs)`
91 /// and `None` into `LhsExpr::NotYetParsed`.
93 /// This conversion does not allocate.
94 fn from(o: Option<AttrWrapper>) -> Self {
95 if let Some(attrs) = o { LhsExpr::AttributesParsed(attrs) } else { LhsExpr::NotYetParsed }
99 impl From<P<Expr>> for LhsExpr {
100 /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed { expr, starts_statement: false }`.
102 /// This conversion does not allocate.
103 fn from(expr: P<Expr>) -> Self {
104 LhsExpr::AlreadyParsed { expr, starts_statement: false }
108 impl<'a> Parser<'a> {
109 /// Parses an expression.
111 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
112 self.current_closure.take();
114 self.parse_expr_res(Restrictions::empty(), None)
117 /// Parses an expression, forcing tokens to be collected
118 pub fn parse_expr_force_collect(&mut self) -> PResult<'a, P<Expr>> {
119 self.collect_tokens_no_attrs(|this| this.parse_expr())
122 pub fn parse_anon_const_expr(&mut self) -> PResult<'a, AnonConst> {
123 self.parse_expr().map(|value| AnonConst { id: DUMMY_NODE_ID, value })
126 fn parse_expr_catch_underscore(&mut self) -> PResult<'a, P<Expr>> {
127 match self.parse_expr() {
128 Ok(expr) => Ok(expr),
129 Err(mut err) => match self.token.ident() {
130 Some((Ident { name: kw::Underscore, .. }, false))
131 if self.may_recover() && self.look_ahead(1, |t| t == &token::Comma) =>
133 // Special-case handling of `foo(_, _, _)`
136 Ok(self.mk_expr(self.prev_token.span, ExprKind::Err))
143 /// Parses a sequence of expressions delimited by parentheses.
144 fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
145 self.parse_paren_comma_seq(|p| p.parse_expr_catch_underscore()).map(|(r, _)| r)
148 /// Parses an expression, subject to the given restrictions.
150 pub(super) fn parse_expr_res(
153 already_parsed_attrs: Option<AttrWrapper>,
154 ) -> PResult<'a, P<Expr>> {
155 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
158 /// Parses an associative expression.
160 /// This parses an expression accounting for associativity and precedence of the operators in
165 already_parsed_attrs: Option<AttrWrapper>,
166 ) -> PResult<'a, P<Expr>> {
167 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
170 /// Parses an associative expression with operators of at least `min_prec` precedence.
171 pub(super) fn parse_assoc_expr_with(
175 ) -> PResult<'a, P<Expr>> {
176 let mut starts_stmt = false;
177 let mut lhs = if let LhsExpr::AlreadyParsed { expr, starts_statement } = lhs {
178 starts_stmt = starts_statement;
181 let attrs = match lhs {
182 LhsExpr::AttributesParsed(attrs) => Some(attrs),
185 if self.token.is_range_separator() {
186 return self.parse_prefix_range_expr(attrs);
188 self.parse_prefix_expr(attrs)?
191 let last_type_ascription_set = self.last_type_ascription.is_some();
193 if !self.should_continue_as_assoc_expr(&lhs) {
194 self.last_type_ascription = None;
198 self.expected_tokens.push(TokenType::Operator);
199 while let Some(op) = self.check_assoc_op() {
200 // Adjust the span for interpolated LHS to point to the `$lhs` token
201 // and not to what it refers to.
202 let lhs_span = match self.prev_token.kind {
203 TokenKind::Interpolated(..) => self.prev_token.span,
207 let cur_op_span = self.token.span;
208 let restrictions = if op.node.is_assign_like() {
209 self.restrictions & Restrictions::NO_STRUCT_LITERAL
213 let prec = op.node.precedence();
217 // Check for deprecated `...` syntax
218 if self.token == token::DotDotDot && op.node == AssocOp::DotDotEq {
219 self.err_dotdotdot_syntax(self.token.span);
222 if self.token == token::LArrow {
223 self.err_larrow_operator(self.token.span);
227 if op.node.is_comparison() {
228 if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
233 // Look for JS' `===` and `!==` and recover
234 if (op.node == AssocOp::Equal || op.node == AssocOp::NotEqual)
235 && self.token.kind == token::Eq
236 && self.prev_token.span.hi() == self.token.span.lo()
238 let sp = op.span.to(self.token.span);
239 let sugg = match op.node {
240 AssocOp::Equal => "==",
241 AssocOp::NotEqual => "!=",
245 let invalid = format!("{}=", &sugg);
246 self.sess.emit_err(InvalidComparisonOperator {
248 invalid: invalid.clone(),
249 sub: InvalidComparisonOperatorSub::Correctable {
258 // Look for PHP's `<>` and recover
259 if op.node == AssocOp::Less
260 && self.token.kind == token::Gt
261 && self.prev_token.span.hi() == self.token.span.lo()
263 let sp = op.span.to(self.token.span);
264 self.sess.emit_err(InvalidComparisonOperator {
266 invalid: "<>".into(),
267 sub: InvalidComparisonOperatorSub::Correctable {
269 invalid: "<>".into(),
270 correct: "!=".into(),
276 // Look for C++'s `<=>` and recover
277 if op.node == AssocOp::LessEqual
278 && self.token.kind == token::Gt
279 && self.prev_token.span.hi() == self.token.span.lo()
281 let sp = op.span.to(self.token.span);
282 self.sess.emit_err(InvalidComparisonOperator {
284 invalid: "<=>".into(),
285 sub: InvalidComparisonOperatorSub::Spaceship(sp),
290 if self.prev_token == token::BinOp(token::Plus)
291 && self.token == token::BinOp(token::Plus)
292 && self.prev_token.span.between(self.token.span).is_empty()
294 let op_span = self.prev_token.span.to(self.token.span);
295 // Eat the second `+`
297 lhs = self.recover_from_postfix_increment(lhs, op_span, starts_stmt)?;
303 if op == AssocOp::As {
304 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
306 } else if op == AssocOp::Colon {
307 lhs = self.parse_assoc_op_ascribe(lhs, lhs_span)?;
309 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
310 // If we didn't have to handle `x..`/`x..=`, it would be pretty easy to
311 // generalise it to the Fixity::None code.
312 lhs = self.parse_range_expr(prec, lhs, op, cur_op_span)?;
316 let fixity = op.fixity();
317 let prec_adjustment = match fixity {
320 // We currently have no non-associative operators that are not handled above by
321 // the special cases. The code is here only for future convenience.
324 let rhs = self.with_res(restrictions - Restrictions::STMT_EXPR, |this| {
325 this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
328 let span = self.mk_expr_sp(&lhs, lhs_span, rhs.span);
341 | AssocOp::ShiftRight
347 | AssocOp::GreaterEqual => {
348 let ast_op = op.to_ast_binop().unwrap();
349 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
350 self.mk_expr(span, binary)
352 AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs, cur_op_span)),
353 AssocOp::AssignOp(k) => {
355 token::Plus => BinOpKind::Add,
356 token::Minus => BinOpKind::Sub,
357 token::Star => BinOpKind::Mul,
358 token::Slash => BinOpKind::Div,
359 token::Percent => BinOpKind::Rem,
360 token::Caret => BinOpKind::BitXor,
361 token::And => BinOpKind::BitAnd,
362 token::Or => BinOpKind::BitOr,
363 token::Shl => BinOpKind::Shl,
364 token::Shr => BinOpKind::Shr,
366 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
367 self.mk_expr(span, aopexpr)
369 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
370 self.span_bug(span, "AssocOp should have been handled by special case")
374 if let Fixity::None = fixity {
378 if last_type_ascription_set {
379 self.last_type_ascription = None;
384 fn should_continue_as_assoc_expr(&mut self, lhs: &Expr) -> bool {
385 match (self.expr_is_complete(lhs), AssocOp::from_token(&self.token)) {
386 // Semi-statement forms are odd:
387 // See https://github.com/rust-lang/rust/issues/29071
388 (true, None) => false,
389 (false, _) => true, // Continue parsing the expression.
390 // An exhaustive check is done in the following block, but these are checked first
391 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
392 // want to keep their span info to improve diagnostics in these cases in a later stage.
393 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
394 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
395 (true, Some(AssocOp::Add)) | // `{ 42 } + 42` (unary plus)
396 (true, Some(AssocOp::LAnd)) | // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }`
397 (true, Some(AssocOp::LOr)) | // `{ 42 } || 42` ("logical or" or closure)
398 (true, Some(AssocOp::BitOr)) // `{ 42 } | 42` or `{ 42 } |x| 42`
400 // These cases are ambiguous and can't be identified in the parser alone.
402 // Bitwise AND is left out because guessing intent is hard. We can make
403 // suggestions based on the assumption that double-refs are rarely intentional,
404 // and closures are distinct enough that they don't get mixed up with their
406 let sp = self.sess.source_map().start_point(self.token.span);
407 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
410 (true, Some(op)) if !op.can_continue_expr_unambiguously() => false,
412 self.error_found_expr_would_be_stmt(lhs);
418 /// We've found an expression that would be parsed as a statement,
419 /// but the next token implies this should be parsed as an expression.
420 /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
421 fn error_found_expr_would_be_stmt(&self, lhs: &Expr) {
422 self.sess.emit_err(FoundExprWouldBeStmt {
423 span: self.token.span,
424 token: self.token.clone(),
425 suggestion: ExprParenthesesNeeded::surrounding(lhs.span),
429 /// Possibly translate the current token to an associative operator.
430 /// The method does not advance the current token.
432 /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
433 fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
434 let (op, span) = match (AssocOp::from_token(&self.token), self.token.ident()) {
435 // When parsing const expressions, stop parsing when encountering `>`.
440 | AssocOp::GreaterEqual
441 | AssocOp::AssignOp(token::BinOpToken::Shr),
444 ) if self.restrictions.contains(Restrictions::CONST_EXPR) => {
447 (Some(op), _) => (op, self.token.span),
448 (None, Some((Ident { name: sym::and, span }, false))) if self.may_recover() => {
449 self.sess.emit_err(InvalidLogicalOperator {
450 span: self.token.span,
451 incorrect: "and".into(),
452 sub: InvalidLogicalOperatorSub::Conjunction(self.token.span),
454 (AssocOp::LAnd, span)
456 (None, Some((Ident { name: sym::or, span }, false))) if self.may_recover() => {
457 self.sess.emit_err(InvalidLogicalOperator {
458 span: self.token.span,
459 incorrect: "or".into(),
460 sub: InvalidLogicalOperatorSub::Disjunction(self.token.span),
466 Some(source_map::respan(span, op))
469 /// Checks if this expression is a successfully parsed statement.
470 fn expr_is_complete(&self, e: &Expr) -> bool {
471 self.restrictions.contains(Restrictions::STMT_EXPR)
472 && !classify::expr_requires_semi_to_be_stmt(e)
475 /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
476 /// The other two variants are handled in `parse_prefix_range_expr` below.
483 ) -> PResult<'a, P<Expr>> {
484 let rhs = if self.is_at_start_of_range_notation_rhs() {
485 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
489 let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
490 let span = self.mk_expr_sp(&lhs, lhs.span, rhs_span);
492 if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
493 let range = self.mk_range(Some(lhs), rhs, limits);
494 Ok(self.mk_expr(span, range))
497 fn is_at_start_of_range_notation_rhs(&self) -> bool {
498 if self.token.can_begin_expr() {
499 // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
500 if self.token == token::OpenDelim(Delimiter::Brace) {
501 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
509 /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
510 fn parse_prefix_range_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
511 // Check for deprecated `...` syntax.
512 if self.token == token::DotDotDot {
513 self.err_dotdotdot_syntax(self.token.span);
517 self.token.is_range_separator(),
518 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
522 let limits = match self.token.kind {
523 token::DotDot => RangeLimits::HalfOpen,
524 _ => RangeLimits::Closed,
526 let op = AssocOp::from_token(&self.token);
527 // FIXME: `parse_prefix_range_expr` is called when the current
528 // token is `DotDot`, `DotDotDot`, or `DotDotEq`. If we haven't already
529 // parsed attributes, then trying to parse them here will always fail.
530 // We should figure out how we want attributes on range expressions to work.
531 let attrs = self.parse_or_use_outer_attributes(attrs)?;
532 self.collect_tokens_for_expr(attrs, |this, attrs| {
533 let lo = this.token.span;
535 let (span, opt_end) = if this.is_at_start_of_range_notation_rhs() {
536 // RHS must be parsed with more associativity than the dots.
537 this.parse_assoc_expr_with(op.unwrap().precedence() + 1, LhsExpr::NotYetParsed)
538 .map(|x| (lo.to(x.span), Some(x)))?
542 let range = this.mk_range(None, opt_end, limits);
543 Ok(this.mk_expr_with_attrs(span, range, attrs))
547 /// Parses a prefix-unary-operator expr.
548 fn parse_prefix_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
549 let attrs = self.parse_or_use_outer_attributes(attrs)?;
550 let lo = self.token.span;
552 macro_rules! make_it {
553 ($this:ident, $attrs:expr, |this, _| $body:expr) => {
554 $this.collect_tokens_for_expr($attrs, |$this, attrs| {
555 let (hi, ex) = $body?;
556 Ok($this.mk_expr_with_attrs(lo.to(hi), ex, attrs))
563 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
564 match this.token.uninterpolate().kind {
566 token::Not => make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Not)),
568 token::Tilde => make_it!(this, attrs, |this, _| this.recover_tilde_expr(lo)),
570 token::BinOp(token::Minus) => {
571 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Neg))
574 token::BinOp(token::Star) => {
575 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Deref))
577 // `&expr` and `&&expr`
578 token::BinOp(token::And) | token::AndAnd => {
579 make_it!(this, attrs, |this, _| this.parse_borrow_expr(lo))
582 token::BinOp(token::Plus) if this.look_ahead(1, |tok| tok.is_numeric_lit()) => {
584 LeadingPlusNotSupported { span: lo, remove_plus: None, add_parentheses: None };
586 // a block on the LHS might have been intended to be an expression instead
587 if let Some(sp) = this.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
588 err.add_parentheses = Some(ExprParenthesesNeeded::surrounding(*sp));
590 err.remove_plus = Some(lo);
592 this.sess.emit_err(err);
595 this.parse_prefix_expr(None)
597 // Recover from `++x`:
598 token::BinOp(token::Plus)
599 if this.look_ahead(1, |t| *t == token::BinOp(token::Plus)) =>
601 let starts_stmt = this.prev_token == token::Semi
602 || this.prev_token == token::CloseDelim(Delimiter::Brace);
603 let pre_span = this.token.span.to(this.look_ahead(1, |t| t.span));
608 let operand_expr = this.parse_dot_or_call_expr(Default::default())?;
609 this.recover_from_prefix_increment(operand_expr, pre_span, starts_stmt)
611 token::Ident(..) if this.token.is_keyword(kw::Box) => {
612 make_it!(this, attrs, |this, _| this.parse_box_expr(lo))
614 token::Ident(..) if this.may_recover() && this.is_mistaken_not_ident_negation() => {
615 make_it!(this, attrs, |this, _| this.recover_not_expr(lo))
617 _ => return this.parse_dot_or_call_expr(Some(attrs)),
621 fn parse_prefix_expr_common(&mut self, lo: Span) -> PResult<'a, (Span, P<Expr>)> {
623 let expr = self.parse_prefix_expr(None);
624 let (span, expr) = self.interpolated_or_expr_span(expr)?;
625 Ok((lo.to(span), expr))
628 fn parse_unary_expr(&mut self, lo: Span, op: UnOp) -> PResult<'a, (Span, ExprKind)> {
629 let (span, expr) = self.parse_prefix_expr_common(lo)?;
630 Ok((span, self.mk_unary(op, expr)))
633 /// Recover on `~expr` in favor of `!expr`.
634 fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
635 self.sess.emit_err(TildeAsUnaryOperator(lo));
637 self.parse_unary_expr(lo, UnOp::Not)
640 /// Parse `box expr`.
641 fn parse_box_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
642 let (span, expr) = self.parse_prefix_expr_common(lo)?;
643 self.sess.gated_spans.gate(sym::box_syntax, span);
644 Ok((span, ExprKind::Box(expr)))
647 fn is_mistaken_not_ident_negation(&self) -> bool {
648 let token_cannot_continue_expr = |t: &Token| match t.uninterpolate().kind {
649 // These tokens can start an expression after `!`, but
650 // can't continue an expression after an ident
651 token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
652 token::Literal(..) | token::Pound => true,
653 _ => t.is_whole_expr(),
655 self.token.is_ident_named(sym::not) && self.look_ahead(1, token_cannot_continue_expr)
658 /// Recover on `not expr` in favor of `!expr`.
659 fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
660 let negated_token = self.look_ahead(1, |t| t.clone());
662 let sub_diag = if negated_token.is_numeric_lit() {
663 NotAsNegationOperatorSub::SuggestNotBitwise
664 } else if negated_token.is_bool_lit() {
665 NotAsNegationOperatorSub::SuggestNotLogical
667 NotAsNegationOperatorSub::SuggestNotDefault
670 self.sess.emit_err(NotAsNegationOperator {
671 negated: negated_token.span,
672 negated_desc: super::token_descr(&negated_token),
673 // Span the `not` plus trailing whitespace to avoid
674 // trailing whitespace after the `!` in our suggestion
676 self.sess.source_map().span_until_non_whitespace(lo.to(negated_token.span)),
680 self.parse_unary_expr(lo, UnOp::Not)
683 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
684 fn interpolated_or_expr_span(
686 expr: PResult<'a, P<Expr>>,
687 ) -> PResult<'a, (Span, P<Expr>)> {
690 match self.prev_token.kind {
691 TokenKind::Interpolated(..) => self.prev_token.span,
699 fn parse_assoc_op_cast(
703 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
704 ) -> PResult<'a, P<Expr>> {
705 let mk_expr = |this: &mut Self, lhs: P<Expr>, rhs: P<Ty>| {
706 this.mk_expr(this.mk_expr_sp(&lhs, lhs_span, rhs.span), expr_kind(lhs, rhs))
709 // Save the state of the parser before parsing type normally, in case there is a
710 // LessThan comparison after this cast.
711 let parser_snapshot_before_type = self.clone();
712 let cast_expr = match self.parse_as_cast_ty() {
713 Ok(rhs) => mk_expr(self, lhs, rhs),
715 if !self.may_recover() {
716 return Err(type_err);
719 // Rewind to before attempting to parse the type with generics, to recover
720 // from situations like `x as usize < y` in which we first tried to parse
721 // `usize < y` as a type with generic arguments.
722 let parser_snapshot_after_type = mem::replace(self, parser_snapshot_before_type);
724 // Check for typo of `'a: loop { break 'a }` with a missing `'`.
725 match (&lhs.kind, &self.token.kind) {
728 ExprKind::Path(None, ast::Path { segments, .. }),
729 TokenKind::Ident(kw::For | kw::Loop | kw::While, false),
730 ) if segments.len() == 1 => {
731 let snapshot = self.create_snapshot_for_diagnostic();
733 ident: Ident::from_str_and_span(
734 &format!("'{}", segments[0].ident),
735 segments[0].ident.span,
738 match self.parse_labeled_expr(label, false) {
741 self.sess.emit_err(MalformedLoopLabel {
742 span: label.ident.span,
743 correct_label: label.ident,
749 self.restore_snapshot(snapshot);
756 match self.parse_path(PathStyle::Expr) {
758 let span_after_type = parser_snapshot_after_type.token.span;
762 self.mk_ty(path.span, TyKind::Path(None, path.clone())),
765 let args_span = self.look_ahead(1, |t| t.span).to(span_after_type);
766 let suggestion = ComparisonOrShiftInterpretedAsGenericSugg {
767 left: expr.span.shrink_to_lo(),
768 right: expr.span.shrink_to_hi(),
771 match self.token.kind {
772 token::Lt => self.sess.emit_err(ComparisonInterpretedAsGeneric {
773 comparison: self.token.span,
778 token::BinOp(token::Shl) => {
779 self.sess.emit_err(ShiftInterpretedAsGeneric {
780 shift: self.token.span,
787 // We can end up here even without `<` being the next token, for
788 // example because `parse_ty_no_plus` returns `Err` on keywords,
789 // but `parse_path` returns `Ok` on them due to error recovery.
790 // Return original error and parser state.
791 *self = parser_snapshot_after_type;
792 return Err(type_err);
796 // Successfully parsed the type path leaving a `<` yet to parse.
799 // Keep `x as usize` as an expression in AST and continue parsing.
803 // Couldn't parse as a path, return original error and parser state.
805 *self = parser_snapshot_after_type;
806 return Err(type_err);
812 self.parse_and_disallow_postfix_after_cast(cast_expr)
815 /// Parses a postfix operators such as `.`, `?`, or index (`[]`) after a cast,
816 /// then emits an error and returns the newly parsed tree.
817 /// The resulting parse tree for `&x as T[0]` has a precedence of `((&x) as T)[0]`.
818 fn parse_and_disallow_postfix_after_cast(
821 ) -> PResult<'a, P<Expr>> {
822 let span = cast_expr.span;
823 let (cast_kind, maybe_ascription_span) =
824 if let ExprKind::Type(ascripted_expr, _) = &cast_expr.kind {
825 ("type ascription", Some(ascripted_expr.span.shrink_to_hi().with_hi(span.hi())))
830 let with_postfix = self.parse_dot_or_call_expr_with_(cast_expr, span)?;
832 // Check if an illegal postfix operator has been added after the cast.
833 // If the resulting expression is not a cast, it is an illegal postfix operator.
834 if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) {
836 "{cast_kind} cannot be followed by {}",
837 match with_postfix.kind {
838 ExprKind::Index(_, _) => "indexing",
839 ExprKind::Try(_) => "`?`",
840 ExprKind::Field(_, _) => "a field access",
841 ExprKind::MethodCall(_) => "a method call",
842 ExprKind::Call(_, _) => "a function call",
843 ExprKind::Await(_) => "`.await`",
844 ExprKind::Err => return Ok(with_postfix),
845 _ => unreachable!("parse_dot_or_call_expr_with_ shouldn't produce this"),
848 let mut err = self.struct_span_err(span, &msg);
850 let suggest_parens = |err: &mut Diagnostic| {
851 let suggestions = vec![
852 (span.shrink_to_lo(), "(".to_string()),
853 (span.shrink_to_hi(), ")".to_string()),
855 err.multipart_suggestion(
856 "try surrounding the expression in parentheses",
858 Applicability::MachineApplicable,
862 // If type ascription is "likely an error", the user will already be getting a useful
863 // help message, and doesn't need a second.
864 if self.last_type_ascription.map_or(false, |last_ascription| last_ascription.1) {
865 self.maybe_annotate_with_ascription(&mut err, false);
866 } else if let Some(ascription_span) = maybe_ascription_span {
867 let is_nightly = self.sess.unstable_features.is_nightly_build();
869 suggest_parens(&mut err);
874 "{}remove the type ascription",
875 if is_nightly { "alternatively, " } else { "" }
879 Applicability::MaybeIncorrect
881 Applicability::MachineApplicable
885 suggest_parens(&mut err);
892 fn parse_assoc_op_ascribe(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
893 let maybe_path = self.could_ascription_be_path(&lhs.kind);
894 self.last_type_ascription = Some((self.prev_token.span, maybe_path));
895 let lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
896 self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
900 /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
901 fn parse_borrow_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
903 let has_lifetime = self.token.is_lifetime() && self.look_ahead(1, |t| t != &token::Colon);
904 let lifetime = has_lifetime.then(|| self.expect_lifetime()); // For recovery, see below.
905 let (borrow_kind, mutbl) = self.parse_borrow_modifiers(lo);
906 let expr = if self.token.is_range_separator() {
907 self.parse_prefix_range_expr(None)
909 self.parse_prefix_expr(None)
911 let (hi, expr) = self.interpolated_or_expr_span(expr)?;
912 let span = lo.to(hi);
913 if let Some(lt) = lifetime {
914 self.error_remove_borrow_lifetime(span, lt.ident.span);
916 Ok((span, ExprKind::AddrOf(borrow_kind, mutbl, expr)))
919 fn error_remove_borrow_lifetime(&self, span: Span, lt_span: Span) {
920 self.sess.emit_err(LifetimeInBorrowExpression { span, lifetime_span: lt_span });
923 /// Parse `mut?` or `raw [ const | mut ]`.
924 fn parse_borrow_modifiers(&mut self, lo: Span) -> (ast::BorrowKind, ast::Mutability) {
925 if self.check_keyword(kw::Raw) && self.look_ahead(1, Token::is_mutability) {
926 // `raw [ const | mut ]`.
927 let found_raw = self.eat_keyword(kw::Raw);
929 let mutability = self.parse_const_or_mut().unwrap();
930 self.sess.gated_spans.gate(sym::raw_ref_op, lo.to(self.prev_token.span));
931 (ast::BorrowKind::Raw, mutability)
934 (ast::BorrowKind::Ref, self.parse_mutability())
938 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
939 fn parse_dot_or_call_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
940 let attrs = self.parse_or_use_outer_attributes(attrs)?;
941 self.collect_tokens_for_expr(attrs, |this, attrs| {
942 let base = this.parse_bottom_expr();
943 let (span, base) = this.interpolated_or_expr_span(base)?;
944 this.parse_dot_or_call_expr_with(base, span, attrs)
948 pub(super) fn parse_dot_or_call_expr_with(
952 mut attrs: ast::AttrVec,
953 ) -> PResult<'a, P<Expr>> {
954 // Stitch the list of outer attributes onto the return value.
955 // A little bit ugly, but the best way given the current code
957 let res = self.parse_dot_or_call_expr_with_(e0, lo);
958 if attrs.is_empty() {
962 expr.map(|mut expr| {
963 attrs.extend(expr.attrs);
971 fn parse_dot_or_call_expr_with_(&mut self, mut e: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
973 let has_question = if self.prev_token.kind == TokenKind::Ident(kw::Return, false) {
974 // we are using noexpect here because we don't expect a `?` directly after a `return`
975 // which could be suggested otherwise
976 self.eat_noexpect(&token::Question)
978 self.eat(&token::Question)
982 e = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Try(e));
985 let has_dot = if self.prev_token.kind == TokenKind::Ident(kw::Return, false) {
986 // we are using noexpect here because we don't expect a `.` directly after a `return`
987 // which could be suggested otherwise
988 self.eat_noexpect(&token::Dot)
990 self.eat(&token::Dot)
994 e = self.parse_dot_suffix_expr(lo, e)?;
997 if self.expr_is_complete(&e) {
1000 e = match self.token.kind {
1001 token::OpenDelim(Delimiter::Parenthesis) => self.parse_fn_call_expr(lo, e),
1002 token::OpenDelim(Delimiter::Bracket) => self.parse_index_expr(lo, e)?,
1008 fn look_ahead_type_ascription_as_field(&mut self) -> bool {
1009 self.look_ahead(1, |t| t.is_ident())
1010 && self.look_ahead(2, |t| t == &token::Colon)
1011 && self.look_ahead(3, |t| t.can_begin_expr())
1014 fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
1015 match self.token.uninterpolate().kind {
1016 token::Ident(..) => self.parse_dot_suffix(base, lo),
1017 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
1018 Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix, None))
1020 token::Literal(token::Lit { kind: token::Float, symbol, suffix }) => {
1021 Ok(self.parse_tuple_field_access_expr_float(lo, base, symbol, suffix))
1024 self.error_unexpected_after_dot();
1030 fn error_unexpected_after_dot(&self) {
1031 // FIXME Could factor this out into non_fatal_unexpected or something.
1032 let actual = pprust::token_to_string(&self.token);
1033 self.struct_span_err(self.token.span, &format!("unexpected token: `{actual}`")).emit();
1036 // We need an identifier or integer, but the next token is a float.
1037 // Break the float into components to extract the identifier or integer.
1038 // FIXME: With current `TokenCursor` it's hard to break tokens into more than 2
1039 // parts unless those parts are processed immediately. `TokenCursor` should either
1040 // support pushing "future tokens" (would be also helpful to `break_and_eat`), or
1041 // we should break everything including floats into more basic proc-macro style
1042 // tokens in the lexer (probably preferable).
1043 fn parse_tuple_field_access_expr_float(
1048 suffix: Option<Symbol>,
1051 enum FloatComponent {
1055 use FloatComponent::*;
1057 let float_str = float.as_str();
1058 let mut components = Vec::new();
1059 let mut ident_like = String::new();
1060 for c in float_str.chars() {
1061 if c == '_' || c.is_ascii_alphanumeric() {
1063 } else if matches!(c, '.' | '+' | '-') {
1064 if !ident_like.is_empty() {
1065 components.push(IdentLike(mem::take(&mut ident_like)));
1067 components.push(Punct(c));
1069 panic!("unexpected character in a float token: {:?}", c)
1072 if !ident_like.is_empty() {
1073 components.push(IdentLike(ident_like));
1076 // With proc macros the span can refer to anything, the source may be too short,
1077 // or too long, or non-ASCII. It only makes sense to break our span into components
1078 // if its underlying text is identical to our float literal.
1079 let span = self.token.span;
1080 let can_take_span_apart =
1081 || self.span_to_snippet(span).as_deref() == Ok(float_str).as_deref();
1083 match &*components {
1086 self.parse_tuple_field_access_expr(lo, base, Symbol::intern(&i), suffix, None)
1089 [IdentLike(i), Punct('.')] => {
1090 let (ident_span, dot_span) = if can_take_span_apart() {
1091 let (span, ident_len) = (span.data(), BytePos::from_usize(i.len()));
1092 let ident_span = span.with_hi(span.lo + ident_len);
1093 let dot_span = span.with_lo(span.lo + ident_len);
1094 (ident_span, dot_span)
1098 assert!(suffix.is_none());
1099 let symbol = Symbol::intern(&i);
1100 self.token = Token::new(token::Ident(symbol, false), ident_span);
1101 let next_token = (Token::new(token::Dot, dot_span), self.token_spacing);
1102 self.parse_tuple_field_access_expr(lo, base, symbol, None, Some(next_token))
1105 [IdentLike(i1), Punct('.'), IdentLike(i2)] => {
1106 let (ident1_span, dot_span, ident2_span) = if can_take_span_apart() {
1107 let (span, ident1_len) = (span.data(), BytePos::from_usize(i1.len()));
1108 let ident1_span = span.with_hi(span.lo + ident1_len);
1110 .with_lo(span.lo + ident1_len)
1111 .with_hi(span.lo + ident1_len + BytePos(1));
1112 let ident2_span = self.token.span.with_lo(span.lo + ident1_len + BytePos(1));
1113 (ident1_span, dot_span, ident2_span)
1117 let symbol1 = Symbol::intern(&i1);
1118 self.token = Token::new(token::Ident(symbol1, false), ident1_span);
1119 // This needs to be `Spacing::Alone` to prevent regressions.
1120 // See issue #76399 and PR #76285 for more details
1121 let next_token1 = (Token::new(token::Dot, dot_span), Spacing::Alone);
1123 self.parse_tuple_field_access_expr(lo, base, symbol1, None, Some(next_token1));
1124 let symbol2 = Symbol::intern(&i2);
1125 let next_token2 = Token::new(token::Ident(symbol2, false), ident2_span);
1126 self.bump_with((next_token2, self.token_spacing)); // `.`
1127 self.parse_tuple_field_access_expr(lo, base1, symbol2, suffix, None)
1129 // 1e+ | 1e- (recovered)
1130 [IdentLike(_), Punct('+' | '-')] |
1132 [IdentLike(_), Punct('+' | '-'), IdentLike(_)] |
1134 [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-')] |
1136 [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-'), IdentLike(_)] => {
1137 // See the FIXME about `TokenCursor` above.
1138 self.error_unexpected_after_dot();
1141 _ => panic!("unexpected components in a float token: {:?}", components),
1145 fn parse_tuple_field_access_expr(
1150 suffix: Option<Symbol>,
1151 next_token: Option<(Token, Spacing)>,
1154 Some(next_token) => self.bump_with(next_token),
1155 None => self.bump(),
1157 let span = self.prev_token.span;
1158 let field = ExprKind::Field(base, Ident::new(field, span));
1159 if let Some(suffix) = suffix {
1160 self.expect_no_tuple_index_suffix(span, suffix);
1162 self.mk_expr(lo.to(span), field)
1165 /// Parse a function call expression, `expr(...)`.
1166 fn parse_fn_call_expr(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
1167 let snapshot = if self.token.kind == token::OpenDelim(Delimiter::Parenthesis)
1168 && self.look_ahead_type_ascription_as_field()
1170 Some((self.create_snapshot_for_diagnostic(), fun.kind.clone()))
1174 let open_paren = self.token.span;
1177 .parse_paren_expr_seq()
1178 .map(|args| self.mk_expr(lo.to(self.prev_token.span), self.mk_call(fun, args)));
1180 self.maybe_recover_struct_lit_bad_delims(lo, open_paren, &mut seq, snapshot)
1184 self.recover_seq_parse_error(Delimiter::Parenthesis, lo, seq)
1187 /// If we encounter a parser state that looks like the user has written a `struct` literal with
1188 /// parentheses instead of braces, recover the parser state and provide suggestions.
1189 #[instrument(skip(self, seq, snapshot), level = "trace")]
1190 fn maybe_recover_struct_lit_bad_delims(
1194 seq: &mut PResult<'a, P<Expr>>,
1195 snapshot: Option<(SnapshotParser<'a>, ExprKind)>,
1196 ) -> Option<P<Expr>> {
1197 if !self.may_recover() {
1201 match (seq.as_mut(), snapshot) {
1202 (Err(err), Some((mut snapshot, ExprKind::Path(None, path)))) => {
1203 snapshot.bump(); // `(`
1204 match snapshot.parse_struct_fields(path.clone(), false, Delimiter::Parenthesis) {
1206 if snapshot.eat(&token::CloseDelim(Delimiter::Parenthesis)) =>
1208 // We are certain we have `Enum::Foo(a: 3, b: 4)`, suggest
1209 // `Enum::Foo { a: 3, b: 4 }` or `Enum::Foo(3, 4)`.
1210 self.restore_snapshot(snapshot);
1211 let close_paren = self.prev_token.span;
1212 let span = lo.to(self.prev_token.span);
1213 if !fields.is_empty() {
1214 let mut replacement_err = ParenthesesWithStructFields {
1217 braces_for_struct: BracesForStructLiteral {
1219 second: close_paren,
1221 no_fields_for_fn: NoFieldsForFnCall {
1224 .map(|field| field.span.until(field.expr.span))
1228 .into_diagnostic(&self.sess.span_diagnostic);
1229 replacement_err.emit();
1231 let old_err = mem::replace(err, replacement_err);
1236 return Some(self.mk_expr_err(span));
1249 /// Parse an indexing expression `expr[...]`.
1250 fn parse_index_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
1251 let prev_span = self.prev_token.span;
1252 let open_delim_span = self.token.span;
1254 let index = self.parse_expr()?;
1255 self.suggest_missing_semicolon_before_array(prev_span, open_delim_span)?;
1256 self.expect(&token::CloseDelim(Delimiter::Bracket))?;
1257 Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_index(base, index)))
1260 /// Assuming we have just parsed `.`, continue parsing into an expression.
1261 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
1262 if self.token.uninterpolated_span().rust_2018() && self.eat_keyword(kw::Await) {
1263 return Ok(self.mk_await_expr(self_arg, lo));
1266 let fn_span_lo = self.token.span;
1267 let mut seg = self.parse_path_segment(PathStyle::Expr, None)?;
1268 self.check_trailing_angle_brackets(&seg, &[&token::OpenDelim(Delimiter::Parenthesis)]);
1269 self.check_turbofish_missing_angle_brackets(&mut seg);
1271 if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
1272 // Method call `expr.f()`
1273 let args = self.parse_paren_expr_seq()?;
1274 let fn_span = fn_span_lo.to(self.prev_token.span);
1275 let span = lo.to(self.prev_token.span);
1278 ExprKind::MethodCall(Box::new(ast::MethodCall {
1286 // Field access `expr.f`
1287 if let Some(args) = seg.args {
1288 self.sess.emit_err(FieldExpressionWithGeneric(args.span()));
1291 let span = lo.to(self.prev_token.span);
1292 Ok(self.mk_expr(span, ExprKind::Field(self_arg, seg.ident)))
1296 /// At the bottom (top?) of the precedence hierarchy,
1297 /// Parses things like parenthesized exprs, macros, `return`, etc.
1299 /// N.B., this does not parse outer attributes, and is private because it only works
1300 /// correctly if called from `parse_dot_or_call_expr()`.
1301 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
1302 maybe_recover_from_interpolated_ty_qpath!(self, true);
1303 maybe_whole_expr!(self);
1305 // Outer attributes are already parsed and will be
1306 // added to the return value after the fact.
1308 // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
1309 let lo = self.token.span;
1310 if let token::Literal(_) = self.token.kind {
1311 // This match arm is a special-case of the `_` match arm below and
1312 // could be removed without changing functionality, but it's faster
1313 // to have it here, especially for programs with large constants.
1314 self.parse_lit_expr()
1315 } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
1316 self.parse_tuple_parens_expr()
1317 } else if self.check(&token::OpenDelim(Delimiter::Brace)) {
1318 self.parse_block_expr(None, lo, BlockCheckMode::Default)
1319 } else if self.check(&token::BinOp(token::Or)) || self.check(&token::OrOr) {
1320 self.parse_closure_expr().map_err(|mut err| {
1321 // If the input is something like `if a { 1 } else { 2 } | if a { 3 } else { 4 }`
1322 // then suggest parens around the lhs.
1323 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
1324 err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
1328 } else if self.check(&token::OpenDelim(Delimiter::Bracket)) {
1329 self.parse_array_or_repeat_expr(Delimiter::Bracket)
1330 } else if self.check_path() {
1331 self.parse_path_start_expr()
1332 } else if self.check_keyword(kw::Move)
1333 || self.check_keyword(kw::Static)
1334 || self.check_const_closure()
1336 self.parse_closure_expr()
1337 } else if self.eat_keyword(kw::If) {
1338 self.parse_if_expr()
1339 } else if self.check_keyword(kw::For) {
1340 if self.choose_generics_over_qpath(1) {
1341 self.parse_closure_expr()
1343 assert!(self.eat_keyword(kw::For));
1344 self.parse_for_expr(None, self.prev_token.span)
1346 } else if self.eat_keyword(kw::While) {
1347 self.parse_while_expr(None, self.prev_token.span)
1348 } else if let Some(label) = self.eat_label() {
1349 self.parse_labeled_expr(label, true)
1350 } else if self.eat_keyword(kw::Loop) {
1351 let sp = self.prev_token.span;
1352 self.parse_loop_expr(None, self.prev_token.span).map_err(|mut err| {
1353 err.span_label(sp, "while parsing this `loop` expression");
1356 } else if self.eat_keyword(kw::Continue) {
1357 let kind = ExprKind::Continue(self.eat_label());
1358 Ok(self.mk_expr(lo.to(self.prev_token.span), kind))
1359 } else if self.eat_keyword(kw::Match) {
1360 let match_sp = self.prev_token.span;
1361 self.parse_match_expr().map_err(|mut err| {
1362 err.span_label(match_sp, "while parsing this `match` expression");
1365 } else if self.eat_keyword(kw::Unsafe) {
1366 let sp = self.prev_token.span;
1367 self.parse_block_expr(None, lo, BlockCheckMode::Unsafe(ast::UserProvided)).map_err(
1369 err.span_label(sp, "while parsing this `unsafe` expression");
1373 } else if self.check_inline_const(0) {
1374 self.parse_const_block(lo.to(self.token.span), false)
1375 } else if self.may_recover() && self.is_do_catch_block() {
1376 self.recover_do_catch()
1377 } else if self.is_try_block() {
1378 self.expect_keyword(kw::Try)?;
1379 self.parse_try_block(lo)
1380 } else if self.eat_keyword(kw::Return) {
1381 self.parse_return_expr()
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 label.is_some() && self.token == token::Colon {
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.take().unwrap(), 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 expr = self.parse_expr_opt()?;
1734 if let Some(expr) = &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),
1757 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Break(label, kind));
1758 self.maybe_recover_from_bad_qpath(expr)
1761 /// Parse `"yield" expr?`.
1762 fn parse_yield_expr(&mut self) -> PResult<'a, P<Expr>> {
1763 let lo = self.prev_token.span;
1764 let kind = ExprKind::Yield(self.parse_expr_opt()?);
1765 let span = lo.to(self.prev_token.span);
1766 self.sess.gated_spans.gate(sym::generators, span);
1767 let expr = self.mk_expr(span, kind);
1768 self.maybe_recover_from_bad_qpath(expr)
1771 /// Returns a string literal if the next token is a string literal.
1772 /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
1773 /// and returns `None` if the next token is not literal at all.
1774 pub fn parse_str_lit(&mut self) -> Result<ast::StrLit, Option<MetaItemLit>> {
1775 match self.parse_opt_meta_item_lit() {
1776 Some(lit) => match lit.kind {
1777 ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
1784 _ => Err(Some(lit)),
1790 pub(crate) fn mk_token_lit_char(name: Symbol, span: Span) -> (token::Lit, Span) {
1791 (token::Lit { symbol: name, suffix: None, kind: token::Char }, span)
1794 fn mk_meta_item_lit_char(name: Symbol, span: Span) -> MetaItemLit {
1798 kind: ast::LitKind::Char(name.as_str().chars().next().unwrap_or('_')),
1803 fn handle_missing_lit<L>(
1805 mk_lit_char: impl FnOnce(Symbol, Span) -> L,
1806 ) -> PResult<'a, L> {
1807 if let token::Interpolated(inner) = &self.token.kind {
1808 let expr = match inner.as_ref() {
1809 token::NtExpr(expr) => Some(expr),
1810 token::NtLiteral(expr) => Some(expr),
1813 if let Some(expr) = expr {
1814 if matches!(expr.kind, ExprKind::Err) {
1815 let mut err = InvalidInterpolatedExpression { span: self.token.span }
1816 .into_diagnostic(&self.sess.span_diagnostic);
1817 err.downgrade_to_delayed_bug();
1822 let token = self.token.clone();
1823 let err = |self_: &Self| {
1824 let msg = format!("unexpected token: {}", super::token_descr(&token));
1825 self_.struct_span_err(token.span, &msg)
1827 // On an error path, eagerly consider a lifetime to be an unclosed character lit
1828 if self.token.is_lifetime() {
1829 let lt = self.expect_lifetime();
1830 Ok(self.recover_unclosed_char(lt.ident, mk_lit_char, err))
1836 pub(super) fn parse_token_lit(&mut self) -> PResult<'a, (token::Lit, Span)> {
1837 self.parse_opt_token_lit()
1839 .or_else(|()| self.handle_missing_lit(Parser::mk_token_lit_char))
1842 pub(super) fn parse_meta_item_lit(&mut self) -> PResult<'a, MetaItemLit> {
1843 self.parse_opt_meta_item_lit()
1845 .or_else(|()| self.handle_missing_lit(Parser::mk_meta_item_lit_char))
1848 fn recover_after_dot(&mut self) -> Option<Token> {
1849 let mut recovered = None;
1850 if self.token == token::Dot {
1851 // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
1852 // dot would follow an optional literal, so we do this unconditionally.
1853 recovered = self.look_ahead(1, |next_token| {
1854 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
1857 if self.token.span.hi() == next_token.span.lo() {
1858 let s = String::from("0.") + symbol.as_str();
1859 let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
1860 return Some(Token::new(kind, self.token.span.to(next_token.span)));
1865 if let Some(token) = &recovered {
1867 self.sess.emit_err(FloatLiteralRequiresIntegerPart {
1869 correct: pprust::token_to_string(token).into_owned(),
1877 /// Matches `lit = true | false | token_lit`.
1878 /// Returns `None` if the next token is not a literal.
1879 pub(super) fn parse_opt_token_lit(&mut self) -> Option<(token::Lit, Span)> {
1880 let recovered = self.recover_after_dot();
1881 let token = recovered.as_ref().unwrap_or(&self.token);
1882 let span = token.span;
1883 token::Lit::from_token(token).map(|token_lit| {
1889 /// Matches `lit = true | false | token_lit`.
1890 /// Returns `None` if the next token is not a literal.
1891 pub(super) fn parse_opt_meta_item_lit(&mut self) -> Option<MetaItemLit> {
1892 let recovered = self.recover_after_dot();
1893 let token = recovered.as_ref().unwrap_or(&self.token);
1894 match token::Lit::from_token(token) {
1895 Some(token_lit) => {
1896 match MetaItemLit::from_token_lit(token_lit, token.span) {
1902 let span = token.span;
1903 let token::Literal(lit) = token.kind else {
1907 report_lit_error(&self.sess, err, lit, span);
1908 // Pack possible quotes and prefixes from the original literal into
1909 // the error literal's symbol so they can be pretty-printed faithfully.
1910 let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
1911 let symbol = Symbol::intern(&suffixless_lit.to_string());
1912 let lit = token::Lit::new(token::Err, symbol, lit.suffix);
1914 MetaItemLit::from_token_lit(lit, span)
1915 .unwrap_or_else(|_| unreachable!()),
1924 pub(super) fn expect_no_tuple_index_suffix(&self, span: Span, suffix: Symbol) {
1925 if [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suffix) {
1926 // #59553: warn instead of reject out of hand to allow the fix to percolate
1927 // through the ecosystem when people fix their macros
1928 self.sess.emit_warning(InvalidLiteralSuffixOnTupleIndex {
1931 exception: Some(()),
1934 self.sess.emit_err(InvalidLiteralSuffixOnTupleIndex { span, suffix, exception: None });
1938 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1939 /// Keep this in sync with `Token::can_begin_literal_maybe_minus`.
1940 pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1941 maybe_whole_expr!(self);
1943 let lo = self.token.span;
1944 let minus_present = self.eat(&token::BinOp(token::Minus));
1945 let (token_lit, span) = self.parse_token_lit()?;
1946 let expr = self.mk_expr(span, ExprKind::Lit(token_lit));
1949 Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_unary(UnOp::Neg, expr)))
1955 fn is_array_like_block(&mut self) -> bool {
1956 self.look_ahead(1, |t| matches!(t.kind, TokenKind::Ident(..) | TokenKind::Literal(_)))
1957 && self.look_ahead(2, |t| t == &token::Comma)
1958 && self.look_ahead(3, |t| t.can_begin_expr())
1961 /// Emits a suggestion if it looks like the user meant an array but
1962 /// accidentally used braces, causing the code to be interpreted as a block
1964 fn maybe_suggest_brackets_instead_of_braces(&mut self, lo: Span) -> Option<P<Expr>> {
1965 let mut snapshot = self.create_snapshot_for_diagnostic();
1966 match snapshot.parse_array_or_repeat_expr(Delimiter::Brace) {
1968 self.sess.emit_err(ArrayBracketsInsteadOfSpaces {
1970 sub: ArrayBracketsInsteadOfSpacesSugg {
1972 right: snapshot.prev_token.span,
1976 self.restore_snapshot(snapshot);
1977 Some(self.mk_expr_err(arr.span))
1986 fn suggest_missing_semicolon_before_array(
1989 open_delim_span: Span,
1990 ) -> PResult<'a, ()> {
1991 if !self.may_recover() {
1995 if self.token.kind == token::Comma {
1996 if !self.sess.source_map().is_multiline(prev_span.until(self.token.span)) {
1999 let mut snapshot = self.create_snapshot_for_diagnostic();
2001 match snapshot.parse_seq_to_before_end(
2002 &token::CloseDelim(Delimiter::Bracket),
2003 SeqSep::trailing_allowed(token::Comma),
2007 // When the close delim is `)`, `token.kind` is expected to be `token::CloseDelim(Delimiter::Parenthesis)`,
2008 // but the actual `token.kind` is `token::CloseDelim(Delimiter::Bracket)`.
2009 // This is because the `token.kind` of the close delim is treated as the same as
2010 // that of the open delim in `TokenTreesReader::parse_token_tree`, even if the delimiters of them are different.
2011 // Therefore, `token.kind` should not be compared here.
2013 .span_to_snippet(snapshot.token.span)
2014 .map_or(false, |snippet| snippet == "]") =>
2016 return Err(MissingSemicolonBeforeArray {
2017 open_delim: open_delim_span,
2018 semicolon: prev_span.shrink_to_hi(),
2019 }.into_diagnostic(&self.sess.span_diagnostic));
2022 Err(err) => err.cancel(),
2028 /// Parses a block or unsafe block.
2029 pub(super) fn parse_block_expr(
2031 opt_label: Option<Label>,
2033 blk_mode: BlockCheckMode,
2034 ) -> PResult<'a, P<Expr>> {
2035 if self.may_recover() && self.is_array_like_block() {
2036 if let Some(arr) = self.maybe_suggest_brackets_instead_of_braces(lo) {
2041 if self.token.is_whole_block() {
2042 self.sess.emit_err(InvalidBlockMacroSegment {
2043 span: self.token.span,
2044 context: lo.to(self.token.span),
2048 let (attrs, blk) = self.parse_block_common(lo, blk_mode, true)?;
2049 Ok(self.mk_expr_with_attrs(blk.span, ExprKind::Block(blk, opt_label), attrs))
2052 /// Parse a block which takes no attributes and has no label
2053 fn parse_simple_block(&mut self) -> PResult<'a, P<Expr>> {
2054 let blk = self.parse_block()?;
2055 Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None)))
2058 /// Parses a closure expression (e.g., `move |args| expr`).
2059 fn parse_closure_expr(&mut self) -> PResult<'a, P<Expr>> {
2060 let lo = self.token.span;
2062 let binder = if self.check_keyword(kw::For) {
2063 let lo = self.token.span;
2064 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
2065 let span = lo.to(self.prev_token.span);
2067 self.sess.gated_spans.gate(sym::closure_lifetime_binder, span);
2069 ClosureBinder::For { span, generic_params: P::from_vec(lifetime_defs) }
2071 ClosureBinder::NotPresent
2074 let constness = self.parse_constness(Case::Sensitive);
2077 if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
2079 let asyncness = if self.token.uninterpolated_span().rust_2018() {
2080 self.parse_asyncness(Case::Sensitive)
2085 let capture_clause = self.parse_capture_clause()?;
2086 let (fn_decl, fn_arg_span) = self.parse_fn_block_decl()?;
2087 let decl_hi = self.prev_token.span;
2088 let mut body = match fn_decl.output {
2089 FnRetTy::Default(_) => {
2090 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
2091 self.parse_expr_res(restrictions, None)?
2094 // If an explicit return type is given, require a block to appear (RFC 968).
2095 let body_lo = self.token.span;
2096 self.parse_block_expr(None, body_lo, BlockCheckMode::Default)?
2100 if let Async::Yes { span, .. } = asyncness {
2101 // Feature-gate `async ||` closures.
2102 self.sess.gated_spans.gate(sym::async_closure, span);
2105 if self.token.kind == TokenKind::Semi
2106 && matches!(self.token_cursor.frame.delim_sp, Some((Delimiter::Parenthesis, _)))
2107 && self.may_recover()
2109 // It is likely that the closure body is a block but where the
2110 // braces have been removed. We will recover and eat the next
2111 // statements later in the parsing process.
2112 body = self.mk_expr_err(body.span);
2115 let body_span = body.span;
2117 let closure = self.mk_expr(
2119 ExprKind::Closure(Box::new(ast::Closure {
2127 fn_decl_span: lo.to(decl_hi),
2132 // Disable recovery for closure body
2134 ClosureSpans { whole_closure: closure.span, closing_pipe: decl_hi, body: body_span };
2135 self.current_closure = Some(spans);
2140 /// Parses an optional `move` prefix to a closure-like construct.
2141 fn parse_capture_clause(&mut self) -> PResult<'a, CaptureBy> {
2142 if self.eat_keyword(kw::Move) {
2143 // Check for `move async` and recover
2144 if self.check_keyword(kw::Async) {
2145 let move_async_span = self.token.span.with_lo(self.prev_token.span.data().lo);
2146 Err(AsyncMoveOrderIncorrect { span: move_async_span }
2147 .into_diagnostic(&self.sess.span_diagnostic))
2149 Ok(CaptureBy::Value)
2156 /// Parses the `|arg, arg|` header of a closure.
2157 fn parse_fn_block_decl(&mut self) -> PResult<'a, (P<FnDecl>, Span)> {
2158 let arg_start = self.token.span.lo();
2160 let inputs = if self.eat(&token::OrOr) {
2163 self.expect(&token::BinOp(token::Or))?;
2165 .parse_seq_to_before_tokens(
2166 &[&token::BinOp(token::Or), &token::OrOr],
2167 SeqSep::trailing_allowed(token::Comma),
2168 TokenExpectType::NoExpect,
2169 |p| p.parse_fn_block_param(),
2175 let arg_span = self.prev_token.span.with_lo(arg_start);
2177 self.parse_ret_ty(AllowPlus::Yes, RecoverQPath::Yes, RecoverReturnSign::Yes)?;
2179 Ok((P(FnDecl { inputs, output }), arg_span))
2182 /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
2183 fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
2184 let lo = self.token.span;
2185 let attrs = self.parse_outer_attributes()?;
2186 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2187 let pat = this.parse_pat_no_top_alt(PARAM_EXPECTED)?;
2188 let ty = if this.eat(&token::Colon) {
2191 this.mk_ty(this.prev_token.span, TyKind::Infer)
2199 span: lo.to(this.prev_token.span),
2201 is_placeholder: false,
2203 TrailingToken::MaybeComma,
2208 /// Parses an `if` expression (`if` token already eaten).
2209 fn parse_if_expr(&mut self) -> PResult<'a, P<Expr>> {
2210 let lo = self.prev_token.span;
2211 let cond = self.parse_cond_expr()?;
2212 self.parse_if_after_cond(lo, cond)
2215 fn parse_if_after_cond(&mut self, lo: Span, mut cond: P<Expr>) -> PResult<'a, P<Expr>> {
2216 let cond_span = cond.span;
2217 // Tries to interpret `cond` as either a missing expression if it's a block,
2218 // or as an unfinished expression if it's a binop and the RHS is a block.
2219 // We could probably add more recoveries here too...
2220 let mut recover_block_from_condition = |this: &mut Self| {
2221 let block = match &mut cond.kind {
2222 ExprKind::Binary(Spanned { span: binop_span, .. }, _, right)
2223 if let ExprKind::Block(_, None) = right.kind => {
2224 self.sess.emit_err(IfExpressionMissingThenBlock {
2226 sub: IfExpressionMissingThenBlockSub::UnfinishedCondition(
2227 cond_span.shrink_to_lo().to(*binop_span)
2230 std::mem::replace(right, this.mk_expr_err(binop_span.shrink_to_hi()))
2232 ExprKind::Block(_, None) => {
2233 self.sess.emit_err(IfExpressionMissingCondition {
2234 if_span: lo.shrink_to_hi(),
2235 block_span: self.sess.source_map().start_point(cond_span),
2237 std::mem::replace(&mut cond, this.mk_expr_err(cond_span.shrink_to_hi()))
2243 if let ExprKind::Block(block, _) = &block.kind {
2250 let thn = if self.token.is_keyword(kw::Else) {
2251 if let Some(block) = recover_block_from_condition(self) {
2254 self.sess.emit_err(IfExpressionMissingThenBlock {
2256 sub: IfExpressionMissingThenBlockSub::AddThenBlock(cond_span.shrink_to_hi()),
2258 self.mk_block_err(cond_span.shrink_to_hi())
2261 let attrs = self.parse_outer_attributes()?; // For recovery.
2262 let block = if self.check(&token::OpenDelim(Delimiter::Brace)) {
2265 if let Some(block) = recover_block_from_condition(self) {
2268 self.error_on_extra_if(&cond)?;
2269 // Parse block, which will always fail, but we can add a nice note to the error
2270 self.parse_block().map_err(|mut err| {
2273 "the `if` expression is missing a block after this condition",
2279 self.error_on_if_block_attrs(lo, false, block.span, attrs);
2282 let els = if self.eat_keyword(kw::Else) { Some(self.parse_else_expr()?) } else { None };
2283 Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::If(cond, thn, els)))
2286 /// Parses the condition of a `if` or `while` expression.
2287 fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
2289 self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL | Restrictions::ALLOW_LET, None)?;
2291 if let ExprKind::Let(..) = cond.kind {
2292 // Remove the last feature gating of a `let` expression since it's stable.
2293 self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
2299 /// Parses a `let $pat = $expr` pseudo-expression.
2300 fn parse_let_expr(&mut self) -> PResult<'a, P<Expr>> {
2301 // This is a *approximate* heuristic that detects if `let` chains are
2302 // being parsed in the right position. It's approximate because it
2303 // doesn't deny all invalid `let` expressions, just completely wrong usages.
2304 let not_in_chain = !matches!(
2305 self.prev_token.kind,
2306 TokenKind::AndAnd | TokenKind::Ident(kw::If, _) | TokenKind::Ident(kw::While, _)
2308 if !self.restrictions.contains(Restrictions::ALLOW_LET) || not_in_chain {
2309 self.sess.emit_err(ExpectedExpressionFoundLet { span: self.token.span });
2312 self.bump(); // Eat `let` token
2313 let lo = self.prev_token.span;
2314 let pat = self.parse_pat_allow_top_alt(
2318 CommaRecoveryMode::LikelyTuple,
2320 if self.token == token::EqEq {
2321 self.sess.emit_err(ExpectedEqForLetExpr {
2322 span: self.token.span,
2323 sugg_span: self.token.span,
2327 self.expect(&token::Eq)?;
2329 let expr = self.with_res(self.restrictions | Restrictions::NO_STRUCT_LITERAL, |this| {
2330 this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
2332 let span = lo.to(expr.span);
2333 self.sess.gated_spans.gate(sym::let_chains, span);
2334 Ok(self.mk_expr(span, ExprKind::Let(pat, expr, span)))
2337 /// Parses an `else { ... }` expression (`else` token already eaten).
2338 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
2339 let else_span = self.prev_token.span; // `else`
2340 let attrs = self.parse_outer_attributes()?; // For recovery.
2341 let expr = if self.eat_keyword(kw::If) {
2342 self.parse_if_expr()?
2343 } else if self.check(&TokenKind::OpenDelim(Delimiter::Brace)) {
2344 self.parse_simple_block()?
2346 let snapshot = self.create_snapshot_for_diagnostic();
2347 let first_tok = super::token_descr(&self.token);
2348 let first_tok_span = self.token.span;
2349 match self.parse_expr() {
2351 // If it's not a free-standing expression, and is followed by a block,
2352 // then it's very likely the condition to an `else if`.
2353 if self.check(&TokenKind::OpenDelim(Delimiter::Brace))
2354 && classify::expr_requires_semi_to_be_stmt(&cond) =>
2356 self.sess.emit_err(ExpectedElseBlock {
2360 condition_start: cond.span.shrink_to_lo(),
2362 self.parse_if_after_cond(cond.span.shrink_to_lo(), cond)?
2366 self.restore_snapshot(snapshot);
2367 self.parse_simple_block()?
2370 self.restore_snapshot(snapshot);
2371 self.parse_simple_block()?
2375 self.error_on_if_block_attrs(else_span, true, expr.span, attrs);
2379 fn error_on_if_block_attrs(
2386 if attrs.is_empty() {
2390 let attrs: &[ast::Attribute] = &attrs.take_for_recovery(self.sess);
2391 let (attributes, last) = match attrs {
2393 [x0 @ xn] | [x0, .., xn] => (x0.span.to(xn.span), xn.span),
2395 let ctx = if is_ctx_else { "else" } else { "if" };
2396 self.sess.emit_err(OuterAttributeNotAllowedOnIfElse {
2400 ctx: ctx.to_string(),
2405 fn error_on_extra_if(&mut self, cond: &P<Expr>) -> PResult<'a, ()> {
2406 if let ExprKind::Binary(Spanned { span: binop_span, node: binop}, _, right) = &cond.kind &&
2407 let BinOpKind::And = binop &&
2408 let ExprKind::If(cond, ..) = &right.kind {
2409 Err(self.sess.create_err(UnexpectedIfWithIf(binop_span.shrink_to_hi().to(cond.span.shrink_to_lo()))))
2415 /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
2416 fn parse_for_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2417 // Record whether we are about to parse `for (`.
2418 // This is used below for recovery in case of `for ( $stuff ) $block`
2419 // in which case we will suggest `for $stuff $block`.
2420 let begin_paren = match self.token.kind {
2421 token::OpenDelim(Delimiter::Parenthesis) => Some(self.token.span),
2425 let pat = self.parse_pat_allow_top_alt(
2429 CommaRecoveryMode::LikelyTuple,
2431 if !self.eat_keyword(kw::In) {
2432 self.error_missing_in_for_loop();
2434 self.check_for_for_in_in_typo(self.prev_token.span);
2435 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2437 let pat = self.recover_parens_around_for_head(pat, begin_paren);
2439 let (attrs, loop_block) = self.parse_inner_attrs_and_block()?;
2441 let kind = ExprKind::ForLoop(pat, expr, loop_block, opt_label);
2442 Ok(self.mk_expr_with_attrs(lo.to(self.prev_token.span), kind, attrs))
2445 fn error_missing_in_for_loop(&mut self) {
2446 let (span, sub): (_, fn(_) -> _) = if self.token.is_ident_named(sym::of) {
2447 // Possibly using JS syntax (#75311).
2448 let span = self.token.span;
2450 (span, MissingInInForLoopSub::InNotOf)
2452 (self.prev_token.span.between(self.token.span), MissingInInForLoopSub::AddIn)
2455 self.sess.emit_err(MissingInInForLoop { span, sub: sub(span) });
2458 /// Parses a `while` or `while let` expression (`while` token already eaten).
2459 fn parse_while_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2460 let cond = self.parse_cond_expr().map_err(|mut err| {
2461 err.span_label(lo, "while parsing the condition of this `while` expression");
2464 let (attrs, body) = self.parse_inner_attrs_and_block().map_err(|mut err| {
2465 err.span_label(lo, "while parsing the body of this `while` expression");
2466 err.span_label(cond.span, "this `while` condition successfully parsed");
2469 Ok(self.mk_expr_with_attrs(
2470 lo.to(self.prev_token.span),
2471 ExprKind::While(cond, body, opt_label),
2476 /// Parses `loop { ... }` (`loop` token already eaten).
2477 fn parse_loop_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2478 let loop_span = self.prev_token.span;
2479 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2480 Ok(self.mk_expr_with_attrs(
2481 lo.to(self.prev_token.span),
2482 ExprKind::Loop(body, opt_label, loop_span),
2487 pub(crate) fn eat_label(&mut self) -> Option<Label> {
2488 self.token.lifetime().map(|ident| {
2494 /// Parses a `match ... { ... }` expression (`match` token already eaten).
2495 fn parse_match_expr(&mut self) -> PResult<'a, P<Expr>> {
2496 let match_span = self.prev_token.span;
2497 let lo = self.prev_token.span;
2498 let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2499 if let Err(mut e) = self.expect(&token::OpenDelim(Delimiter::Brace)) {
2500 if self.token == token::Semi {
2501 e.span_suggestion_short(
2503 "try removing this `match`",
2505 Applicability::MaybeIncorrect, // speculative
2508 if self.maybe_recover_unexpected_block_label() {
2515 let attrs = self.parse_inner_attributes()?;
2517 let mut arms: Vec<Arm> = Vec::new();
2518 while self.token != token::CloseDelim(Delimiter::Brace) {
2519 match self.parse_arm() {
2520 Ok(arm) => arms.push(arm),
2522 // Recover by skipping to the end of the block.
2524 self.recover_stmt();
2525 let span = lo.to(self.token.span);
2526 if self.token == token::CloseDelim(Delimiter::Brace) {
2529 return Ok(self.mk_expr_with_attrs(
2531 ExprKind::Match(scrutinee, arms),
2537 let hi = self.token.span;
2539 Ok(self.mk_expr_with_attrs(lo.to(hi), ExprKind::Match(scrutinee, arms), attrs))
2542 /// Attempt to recover from match arm body with statements and no surrounding braces.
2543 fn parse_arm_body_missing_braces(
2545 first_expr: &P<Expr>,
2547 ) -> Option<P<Expr>> {
2548 if self.token.kind != token::Semi {
2551 let start_snapshot = self.create_snapshot_for_diagnostic();
2552 let semi_sp = self.token.span;
2555 vec![self.mk_stmt(first_expr.span, ast::StmtKind::Expr(first_expr.clone()))];
2556 let err = |this: &Parser<'_>, stmts: Vec<ast::Stmt>| {
2557 let span = stmts[0].span.to(stmts[stmts.len() - 1].span);
2559 this.sess.emit_err(MatchArmBodyWithoutBraces {
2562 num_statements: stmts.len(),
2563 sub: if stmts.len() > 1 {
2564 MatchArmBodyWithoutBracesSugg::AddBraces {
2565 left: span.shrink_to_lo(),
2566 right: span.shrink_to_hi(),
2569 MatchArmBodyWithoutBracesSugg::UseComma { semicolon: semi_sp }
2572 this.mk_expr_err(span)
2574 // We might have either a `,` -> `;` typo, or a block without braces. We need
2575 // a more subtle parsing strategy.
2577 if self.token.kind == token::CloseDelim(Delimiter::Brace) {
2578 // We have reached the closing brace of the `match` expression.
2579 return Some(err(self, stmts));
2581 if self.token.kind == token::Comma {
2582 self.restore_snapshot(start_snapshot);
2585 let pre_pat_snapshot = self.create_snapshot_for_diagnostic();
2586 match self.parse_pat_no_top_alt(None) {
2588 if self.token.kind == token::FatArrow {
2590 self.restore_snapshot(pre_pat_snapshot);
2591 return Some(err(self, stmts));
2599 self.restore_snapshot(pre_pat_snapshot);
2600 match self.parse_stmt_without_recovery(true, ForceCollect::No) {
2601 // Consume statements for as long as possible.
2606 self.restore_snapshot(start_snapshot);
2609 // We couldn't parse either yet another statement missing it's
2610 // enclosing block nor the next arm's pattern or closing brace.
2613 self.restore_snapshot(start_snapshot);
2621 pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
2622 // Used to check the `let_chains` and `if_let_guard` features mostly by scanning
2624 fn check_let_expr(expr: &Expr) -> (bool, bool) {
2626 ExprKind::Binary(BinOp { node: BinOpKind::And, .. }, lhs, rhs) => {
2627 let lhs_rslt = check_let_expr(lhs);
2628 let rhs_rslt = check_let_expr(rhs);
2629 (lhs_rslt.0 || rhs_rslt.0, false)
2631 ExprKind::Let(..) => (true, true),
2635 let attrs = self.parse_outer_attributes()?;
2636 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2637 let lo = this.token.span;
2638 let pat = this.parse_pat_allow_top_alt(
2642 CommaRecoveryMode::EitherTupleOrPipe,
2644 let guard = if this.eat_keyword(kw::If) {
2645 let if_span = this.prev_token.span;
2646 let cond = this.parse_expr_res(Restrictions::ALLOW_LET, None)?;
2647 let (has_let_expr, does_not_have_bin_op) = check_let_expr(&cond);
2649 if does_not_have_bin_op {
2650 // Remove the last feature gating of a `let` expression since it's stable.
2651 this.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
2653 let span = if_span.to(cond.span);
2654 this.sess.gated_spans.gate(sym::if_let_guard, span);
2660 let arrow_span = this.token.span;
2661 if let Err(mut err) = this.expect(&token::FatArrow) {
2662 // We might have a `=>` -> `=` or `->` typo (issue #89396).
2663 if TokenKind::FatArrow
2665 .map_or(false, |similar_tokens| similar_tokens.contains(&this.token.kind))
2667 err.span_suggestion(
2669 "try using a fat arrow here",
2671 Applicability::MaybeIncorrect,
2679 let arm_start_span = this.token.span;
2681 let expr = this.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
2682 err.span_label(arrow_span, "while parsing the `match` arm starting here");
2686 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
2687 && this.token != token::CloseDelim(Delimiter::Brace);
2689 let hi = this.prev_token.span;
2692 let sm = this.sess.source_map();
2693 if let Some(body) = this.parse_arm_body_missing_braces(&expr, arrow_span) {
2694 let span = body.span;
2703 is_placeholder: false,
2705 TrailingToken::None,
2708 this.expect_one_of(&[token::Comma], &[token::CloseDelim(Delimiter::Brace)])
2709 .or_else(|mut err| {
2710 if this.token == token::FatArrow {
2711 if let Ok(expr_lines) = sm.span_to_lines(expr.span)
2712 && let Ok(arm_start_lines) = sm.span_to_lines(arm_start_span)
2713 && arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
2714 && expr_lines.lines.len() == 2
2716 // We check whether there's any trailing code in the parse span,
2717 // if there isn't, we very likely have the following:
2720 // | -- - missing comma
2724 // | - ^^ self.token.span
2726 // | parsed until here as `"y" & X`
2727 err.span_suggestion_short(
2728 arm_start_span.shrink_to_hi(),
2729 "missing a comma here to end this `match` arm",
2731 Applicability::MachineApplicable,
2736 // FIXME(compiler-errors): We could also recover `; PAT =>` here
2738 // Try to parse a following `PAT =>`, if successful
2739 // then we should recover.
2740 let mut snapshot = this.create_snapshot_for_diagnostic();
2741 let pattern_follows = snapshot
2742 .parse_pat_allow_top_alt(
2746 CommaRecoveryMode::EitherTupleOrPipe,
2748 .map_err(|err| err.cancel())
2750 if pattern_follows && snapshot.check(&TokenKind::FatArrow) {
2752 this.sess.emit_err(MissingCommaAfterMatchArm {
2753 span: hi.shrink_to_hi(),
2758 err.span_label(arrow_span, "while parsing the `match` arm starting here");
2762 this.eat(&token::Comma);
2773 is_placeholder: false,
2775 TrailingToken::None,
2780 /// Parses a `try {...}` expression (`try` token already eaten).
2781 fn parse_try_block(&mut self, span_lo: Span) -> PResult<'a, P<Expr>> {
2782 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2783 if self.eat_keyword(kw::Catch) {
2784 Err(CatchAfterTry { span: self.prev_token.span }
2785 .into_diagnostic(&self.sess.span_diagnostic))
2787 let span = span_lo.to(body.span);
2788 self.sess.gated_spans.gate(sym::try_blocks, span);
2789 Ok(self.mk_expr_with_attrs(span, ExprKind::TryBlock(body), attrs))
2793 fn is_do_catch_block(&self) -> bool {
2794 self.token.is_keyword(kw::Do)
2795 && self.is_keyword_ahead(1, &[kw::Catch])
2796 && self.look_ahead(2, |t| *t == token::OpenDelim(Delimiter::Brace))
2797 && !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
2800 fn is_do_yeet(&self) -> bool {
2801 self.token.is_keyword(kw::Do) && self.is_keyword_ahead(1, &[kw::Yeet])
2804 fn is_try_block(&self) -> bool {
2805 self.token.is_keyword(kw::Try)
2806 && self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace))
2807 && self.token.uninterpolated_span().rust_2018()
2810 /// Parses an `async move? {...}` expression.
2811 fn parse_async_block(&mut self) -> PResult<'a, P<Expr>> {
2812 let lo = self.token.span;
2813 self.expect_keyword(kw::Async)?;
2814 let capture_clause = self.parse_capture_clause()?;
2815 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2816 let kind = ExprKind::Async(capture_clause, DUMMY_NODE_ID, body);
2817 Ok(self.mk_expr_with_attrs(lo.to(self.prev_token.span), kind, attrs))
2820 fn is_async_block(&self) -> bool {
2821 self.token.is_keyword(kw::Async)
2824 self.is_keyword_ahead(1, &[kw::Move])
2825 && self.look_ahead(2, |t| *t == token::OpenDelim(Delimiter::Brace))
2828 self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace))
2832 fn is_certainly_not_a_block(&self) -> bool {
2833 self.look_ahead(1, |t| t.is_ident())
2835 // `{ ident, ` cannot start a block.
2836 self.look_ahead(2, |t| t == &token::Comma)
2837 || self.look_ahead(2, |t| t == &token::Colon)
2839 // `{ ident: token, ` cannot start a block.
2840 self.look_ahead(4, |t| t == &token::Comma) ||
2841 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
2842 self.look_ahead(3, |t| !t.can_begin_type())
2847 fn maybe_parse_struct_expr(
2849 qself: &Option<P<ast::QSelf>>,
2851 ) -> Option<PResult<'a, P<Expr>>> {
2852 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
2853 if struct_allowed || self.is_certainly_not_a_block() {
2854 if let Err(err) = self.expect(&token::OpenDelim(Delimiter::Brace)) {
2855 return Some(Err(err));
2857 let expr = self.parse_struct_expr(qself.clone(), path.clone(), true);
2858 if let (Ok(expr), false) = (&expr, struct_allowed) {
2859 // This is a struct literal, but we don't can't accept them here.
2860 self.sess.emit_err(StructLiteralNotAllowedHere {
2862 sub: StructLiteralNotAllowedHereSugg {
2863 left: path.span.shrink_to_lo(),
2864 right: expr.span.shrink_to_hi(),
2873 pub(super) fn parse_struct_fields(
2877 close_delim: Delimiter,
2878 ) -> PResult<'a, (Vec<ExprField>, ast::StructRest, bool)> {
2879 let mut fields = Vec::new();
2880 let mut base = ast::StructRest::None;
2881 let mut recover_async = false;
2883 let mut async_block_err = |e: &mut Diagnostic, span: Span| {
2884 recover_async = true;
2885 e.span_label(span, "`async` blocks are only allowed in Rust 2018 or later");
2886 e.help_use_latest_edition();
2889 while self.token != token::CloseDelim(close_delim) {
2890 if self.eat(&token::DotDot) || self.recover_struct_field_dots(close_delim) {
2891 let exp_span = self.prev_token.span;
2892 // We permit `.. }` on the left-hand side of a destructuring assignment.
2893 if self.check(&token::CloseDelim(close_delim)) {
2894 base = ast::StructRest::Rest(self.prev_token.span.shrink_to_hi());
2897 match self.parse_expr() {
2898 Ok(e) => base = ast::StructRest::Base(e),
2899 Err(mut e) if recover => {
2901 self.recover_stmt();
2903 Err(e) => return Err(e),
2905 self.recover_struct_comma_after_dotdot(exp_span);
2909 let recovery_field = self.find_struct_error_after_field_looking_code();
2910 let parsed_field = match self.parse_expr_field() {
2913 if pth == kw::Async {
2914 async_block_err(&mut e, pth.span);
2916 e.span_label(pth.span, "while parsing this struct");
2920 // If the next token is a comma, then try to parse
2921 // what comes next as additional fields, rather than
2922 // bailing out until next `}`.
2923 if self.token != token::Comma {
2924 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2925 if self.token != token::Comma {
2933 let is_shorthand = parsed_field.as_ref().map_or(false, |f| f.is_shorthand);
2934 // A shorthand field can be turned into a full field with `:`.
2935 // We should point this out.
2936 self.check_or_expected(!is_shorthand, TokenType::Token(token::Colon));
2938 match self.expect_one_of(&[token::Comma], &[token::CloseDelim(close_delim)]) {
2940 if let Some(f) = parsed_field.or(recovery_field) {
2941 // Only include the field if there's no parse error for the field name.
2946 if pth == kw::Async {
2947 async_block_err(&mut e, pth.span);
2949 e.span_label(pth.span, "while parsing this struct");
2950 if let Some(f) = recovery_field {
2953 self.prev_token.span.shrink_to_hi(),
2954 "try adding a comma",
2956 Applicability::MachineApplicable,
2958 } else if is_shorthand
2959 && (AssocOp::from_token(&self.token).is_some()
2960 || matches!(&self.token.kind, token::OpenDelim(_))
2961 || self.token.kind == token::Dot)
2963 // Looks like they tried to write a shorthand, complex expression.
2964 let ident = parsed_field.expect("is_shorthand implies Some").ident;
2966 ident.span.shrink_to_lo(),
2967 "try naming a field",
2968 &format!("{ident}: "),
2969 Applicability::HasPlaceholders,
2977 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2978 self.eat(&token::Comma);
2982 Ok((fields, base, recover_async))
2985 /// Precondition: already parsed the '{'.
2986 pub(super) fn parse_struct_expr(
2988 qself: Option<P<ast::QSelf>>,
2991 ) -> PResult<'a, P<Expr>> {
2993 let (fields, base, recover_async) =
2994 self.parse_struct_fields(pth.clone(), recover, Delimiter::Brace)?;
2995 let span = lo.to(self.token.span);
2996 self.expect(&token::CloseDelim(Delimiter::Brace))?;
2997 let expr = if recover_async {
3000 ExprKind::Struct(P(ast::StructExpr { qself, path: pth, fields, rest: base }))
3002 Ok(self.mk_expr(span, expr))
3005 /// Use in case of error after field-looking code: `S { foo: () with a }`.
3006 fn find_struct_error_after_field_looking_code(&self) -> Option<ExprField> {
3007 match self.token.ident() {
3008 Some((ident, is_raw))
3009 if (is_raw || !ident.is_reserved())
3010 && self.look_ahead(1, |t| *t == token::Colon) =>
3012 Some(ast::ExprField {
3014 span: self.token.span,
3015 expr: self.mk_expr_err(self.token.span),
3016 is_shorthand: false,
3017 attrs: AttrVec::new(),
3019 is_placeholder: false,
3026 fn recover_struct_comma_after_dotdot(&mut self, span: Span) {
3027 if self.token != token::Comma {
3030 self.sess.emit_err(CommaAfterBaseStruct {
3031 span: span.to(self.prev_token.span),
3032 comma: self.token.span,
3034 self.recover_stmt();
3037 fn recover_struct_field_dots(&mut self, close_delim: Delimiter) -> bool {
3038 if !self.look_ahead(1, |t| *t == token::CloseDelim(close_delim))
3039 && self.eat(&token::DotDotDot)
3041 // recover from typo of `...`, suggest `..`
3042 let span = self.prev_token.span;
3043 self.sess.emit_err(MissingDotDot { token_span: span, sugg_span: span });
3049 /// Parses `ident (COLON expr)?`.
3050 fn parse_expr_field(&mut self) -> PResult<'a, ExprField> {
3051 let attrs = self.parse_outer_attributes()?;
3052 self.recover_diff_marker();
3053 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
3054 let lo = this.token.span;
3056 // Check if a colon exists one ahead. This means we're parsing a fieldname.
3057 let is_shorthand = !this.look_ahead(1, |t| t == &token::Colon || t == &token::Eq);
3058 let (ident, expr) = if is_shorthand {
3059 // Mimic `x: x` for the `x` field shorthand.
3060 let ident = this.parse_ident_common(false)?;
3061 let path = ast::Path::from_ident(ident);
3062 (ident, this.mk_expr(ident.span, ExprKind::Path(None, path)))
3064 let ident = this.parse_field_name()?;
3065 this.error_on_eq_field_init(ident);
3067 (ident, this.parse_expr()?)
3073 span: lo.to(expr.span),
3078 is_placeholder: false,
3080 TrailingToken::MaybeComma,
3085 /// Check for `=`. This means the source incorrectly attempts to
3086 /// initialize a field with an eq rather than a colon.
3087 fn error_on_eq_field_init(&self, field_name: Ident) {
3088 if self.token != token::Eq {
3092 self.sess.emit_err(EqFieldInit {
3093 span: self.token.span,
3094 eq: field_name.span.shrink_to_hi().to(self.token.span),
3098 fn err_dotdotdot_syntax(&self, span: Span) {
3099 self.sess.emit_err(DotDotDot { span });
3102 fn err_larrow_operator(&self, span: Span) {
3103 self.sess.emit_err(LeftArrowOperator { span });
3106 fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
3107 ExprKind::AssignOp(binop, lhs, rhs)
3112 start: Option<P<Expr>>,
3113 end: Option<P<Expr>>,
3114 limits: RangeLimits,
3116 if end.is_none() && limits == RangeLimits::Closed {
3117 self.inclusive_range_with_incorrect_end(self.prev_token.span);
3120 ExprKind::Range(start, end, limits)
3124 fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
3125 ExprKind::Unary(unop, expr)
3128 fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
3129 ExprKind::Binary(binop, lhs, rhs)
3132 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
3133 ExprKind::Index(expr, idx)
3136 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
3137 ExprKind::Call(f, args)
3140 fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> P<Expr> {
3141 let span = lo.to(self.prev_token.span);
3142 let await_expr = self.mk_expr(span, ExprKind::Await(self_arg));
3143 self.recover_from_await_method_call();
3147 pub(crate) fn mk_expr_with_attrs(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
3148 P(Expr { kind, span, attrs, id: DUMMY_NODE_ID, tokens: None })
3151 pub(crate) fn mk_expr(&self, span: Span, kind: ExprKind) -> P<Expr> {
3152 P(Expr { kind, span, attrs: AttrVec::new(), id: DUMMY_NODE_ID, tokens: None })
3155 pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> {
3156 self.mk_expr(span, ExprKind::Err)
3159 /// Create expression span ensuring the span of the parent node
3160 /// is larger than the span of lhs and rhs, including the attributes.
3161 fn mk_expr_sp(&self, lhs: &P<Expr>, lhs_span: Span, rhs_span: Span) -> Span {
3164 .find(|a| a.style == AttrStyle::Outer)
3165 .map_or(lhs_span, |a| a.span)
3169 fn collect_tokens_for_expr(
3172 f: impl FnOnce(&mut Self, ast::AttrVec) -> PResult<'a, P<Expr>>,
3173 ) -> PResult<'a, P<Expr>> {
3174 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
3175 let res = f(this, attrs)?;
3176 let trailing = if this.restrictions.contains(Restrictions::STMT_EXPR)
3177 && this.token.kind == token::Semi
3180 } else if this.token.kind == token::Gt {
3183 // FIXME - pass this through from the place where we know
3184 // we need a comma, rather than assuming that `#[attr] expr,`
3185 // always captures a trailing comma
3186 TrailingToken::MaybeComma