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 BinaryFloatLiteralNotSupported, BracesForStructLiteral, CatchAfterTry, CommaAfterBaseStruct,
11 ComparisonInterpretedAsGeneric, ComparisonOrShiftInterpretedAsGenericSugg,
12 DoCatchSyntaxRemoved, DotDotDot, EqFieldInit, ExpectedElseBlock, ExpectedEqForLetExpr,
13 ExpectedExpressionFoundLet, FieldExpressionWithGeneric, FloatLiteralRequiresIntegerPart,
14 FoundExprWouldBeStmt, HexadecimalFloatLiteralNotSupported, IfExpressionMissingCondition,
15 IfExpressionMissingThenBlock, IfExpressionMissingThenBlockSub, IntLiteralTooLarge,
16 InvalidBlockMacroSegment, InvalidComparisonOperator, InvalidComparisonOperatorSub,
17 InvalidFloatLiteralSuffix, InvalidFloatLiteralWidth, InvalidIntLiteralWidth,
18 InvalidInterpolatedExpression, InvalidLiteralSuffix, InvalidLiteralSuffixOnTupleIndex,
19 InvalidLogicalOperator, InvalidLogicalOperatorSub, InvalidNumLiteralBasePrefix,
20 InvalidNumLiteralSuffix, LabeledLoopInBreak, LeadingPlusNotSupported, LeftArrowOperator,
21 LifetimeInBorrowExpression, MacroInvocationWithQualifiedPath, MalformedLoopLabel,
22 MatchArmBodyWithoutBraces, MatchArmBodyWithoutBracesSugg, MissingCommaAfterMatchArm,
23 MissingDotDot, MissingInInForLoop, MissingInInForLoopSub, MissingSemicolonBeforeArray,
24 NoFieldsForFnCall, NotAsNegationOperator, NotAsNegationOperatorSub,
25 OctalFloatLiteralNotSupported, OuterAttributeNotAllowedOnIfElse, ParenthesesWithStructFields,
26 RequireColonAfterLabeledExpression, ShiftInterpretedAsGeneric, StructLiteralNotAllowedHere,
27 StructLiteralNotAllowedHereSugg, TildeAsUnaryOperator, UnexpectedTokenAfterLabel,
28 UnexpectedTokenAfterLabelSugg, WrapExpressionInParentheses,
30 use crate::maybe_recover_from_interpolated_ty_qpath;
33 use rustc_ast::ptr::P;
34 use rustc_ast::token::{self, Delimiter, Token, TokenKind};
35 use rustc_ast::tokenstream::Spacing;
36 use rustc_ast::util::case::Case;
37 use rustc_ast::util::classify;
38 use rustc_ast::util::literal::LitError;
39 use rustc_ast::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
40 use rustc_ast::visit::Visitor;
41 use rustc_ast::{self as ast, AttrStyle, AttrVec, CaptureBy, ExprField, Lit, UnOp, DUMMY_NODE_ID};
42 use rustc_ast::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, MacCall, Param, Ty, TyKind};
43 use rustc_ast::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits};
44 use rustc_ast::{ClosureBinder, StmtKind};
45 use rustc_ast_pretty::pprust;
47 Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, IntoDiagnostic, PResult,
50 use rustc_session::errors::ExprParenthesesNeeded;
51 use rustc_session::lint::builtin::BREAK_WITH_LABEL_AND_LOOP;
52 use rustc_session::lint::BuiltinLintDiagnostics;
53 use rustc_span::source_map::{self, Span, Spanned};
54 use rustc_span::symbol::{kw, sym, Ident, Symbol};
55 use rustc_span::{BytePos, Pos};
57 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
58 /// dropped into the token stream, which happens while parsing the result of
59 /// macro expansion). Placement of these is not as complex as I feared it would
60 /// be. The important thing is to make sure that lookahead doesn't balk at
61 /// `token::Interpolated` tokens.
62 macro_rules! maybe_whole_expr {
64 if let token::Interpolated(nt) = &$p.token.kind {
66 token::NtExpr(e) | token::NtLiteral(e) => {
71 token::NtPath(path) => {
72 let path = (**path).clone();
74 return Ok($p.mk_expr($p.prev_token.span, ExprKind::Path(None, path)));
76 token::NtBlock(block) => {
77 let block = block.clone();
79 return Ok($p.mk_expr($p.prev_token.span, ExprKind::Block(block, None)));
88 pub(super) enum LhsExpr {
90 AttributesParsed(AttrWrapper),
91 AlreadyParsed(P<Expr>),
94 impl From<Option<AttrWrapper>> for LhsExpr {
95 /// Converts `Some(attrs)` into `LhsExpr::AttributesParsed(attrs)`
96 /// and `None` into `LhsExpr::NotYetParsed`.
98 /// This conversion does not allocate.
99 fn from(o: Option<AttrWrapper>) -> Self {
100 if let Some(attrs) = o { LhsExpr::AttributesParsed(attrs) } else { LhsExpr::NotYetParsed }
104 impl From<P<Expr>> for LhsExpr {
105 /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed(expr)`.
107 /// This conversion does not allocate.
108 fn from(expr: P<Expr>) -> Self {
109 LhsExpr::AlreadyParsed(expr)
113 impl<'a> Parser<'a> {
114 /// Parses an expression.
116 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
117 self.current_closure.take();
119 self.parse_expr_res(Restrictions::empty(), None)
122 /// Parses an expression, forcing tokens to be collected
123 pub fn parse_expr_force_collect(&mut self) -> PResult<'a, P<Expr>> {
124 self.collect_tokens_no_attrs(|this| this.parse_expr())
127 pub fn parse_anon_const_expr(&mut self) -> PResult<'a, AnonConst> {
128 self.parse_expr().map(|value| AnonConst { id: DUMMY_NODE_ID, value })
131 fn parse_expr_catch_underscore(&mut self) -> PResult<'a, P<Expr>> {
132 match self.parse_expr() {
133 Ok(expr) => Ok(expr),
134 Err(mut err) => match self.token.ident() {
135 Some((Ident { name: kw::Underscore, .. }, false))
136 if self.may_recover() && self.look_ahead(1, |t| t == &token::Comma) =>
138 // Special-case handling of `foo(_, _, _)`
141 Ok(self.mk_expr(self.prev_token.span, ExprKind::Err))
148 /// Parses a sequence of expressions delimited by parentheses.
149 fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
150 self.parse_paren_comma_seq(|p| p.parse_expr_catch_underscore()).map(|(r, _)| r)
153 /// Parses an expression, subject to the given restrictions.
155 pub(super) fn parse_expr_res(
158 already_parsed_attrs: Option<AttrWrapper>,
159 ) -> PResult<'a, P<Expr>> {
160 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
163 /// Parses an associative expression.
165 /// This parses an expression accounting for associativity and precedence of the operators in
170 already_parsed_attrs: Option<AttrWrapper>,
171 ) -> PResult<'a, P<Expr>> {
172 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
175 /// Parses an associative expression with operators of at least `min_prec` precedence.
176 pub(super) fn parse_assoc_expr_with(
180 ) -> PResult<'a, P<Expr>> {
181 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
184 let attrs = match lhs {
185 LhsExpr::AttributesParsed(attrs) => Some(attrs),
188 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind) {
189 return self.parse_prefix_range_expr(attrs);
191 self.parse_prefix_expr(attrs)?
194 let last_type_ascription_set = self.last_type_ascription.is_some();
196 if !self.should_continue_as_assoc_expr(&lhs) {
197 self.last_type_ascription = None;
201 self.expected_tokens.push(TokenType::Operator);
202 while let Some(op) = self.check_assoc_op() {
203 // Adjust the span for interpolated LHS to point to the `$lhs` token
204 // and not to what it refers to.
205 let lhs_span = match self.prev_token.kind {
206 TokenKind::Interpolated(..) => self.prev_token.span,
210 let cur_op_span = self.token.span;
211 let restrictions = if op.node.is_assign_like() {
212 self.restrictions & Restrictions::NO_STRUCT_LITERAL
216 let prec = op.node.precedence();
220 // Check for deprecated `...` syntax
221 if self.token == token::DotDotDot && op.node == AssocOp::DotDotEq {
222 self.err_dotdotdot_syntax(self.token.span);
225 if self.token == token::LArrow {
226 self.err_larrow_operator(self.token.span);
230 if op.node.is_comparison() {
231 if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
236 // Look for JS' `===` and `!==` and recover
237 if (op.node == AssocOp::Equal || op.node == AssocOp::NotEqual)
238 && self.token.kind == token::Eq
239 && self.prev_token.span.hi() == self.token.span.lo()
241 let sp = op.span.to(self.token.span);
242 let sugg = match op.node {
243 AssocOp::Equal => "==",
244 AssocOp::NotEqual => "!=",
248 let invalid = format!("{}=", &sugg);
249 self.sess.emit_err(InvalidComparisonOperator {
251 invalid: invalid.clone(),
252 sub: InvalidComparisonOperatorSub::Correctable {
261 // Look for PHP's `<>` and recover
262 if op.node == AssocOp::Less
263 && self.token.kind == token::Gt
264 && self.prev_token.span.hi() == self.token.span.lo()
266 let sp = op.span.to(self.token.span);
267 self.sess.emit_err(InvalidComparisonOperator {
269 invalid: "<>".into(),
270 sub: InvalidComparisonOperatorSub::Correctable {
272 invalid: "<>".into(),
273 correct: "!=".into(),
279 // Look for C++'s `<=>` and recover
280 if op.node == AssocOp::LessEqual
281 && self.token.kind == token::Gt
282 && self.prev_token.span.hi() == self.token.span.lo()
284 let sp = op.span.to(self.token.span);
285 self.sess.emit_err(InvalidComparisonOperator {
287 invalid: "<=>".into(),
288 sub: InvalidComparisonOperatorSub::Spaceship(sp),
293 if self.prev_token == token::BinOp(token::Plus)
294 && self.token == token::BinOp(token::Plus)
295 && self.prev_token.span.between(self.token.span).is_empty()
297 let op_span = self.prev_token.span.to(self.token.span);
298 // Eat the second `+`
300 lhs = self.recover_from_postfix_increment(lhs, op_span)?;
306 if op == AssocOp::As {
307 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
309 } else if op == AssocOp::Colon {
310 lhs = self.parse_assoc_op_ascribe(lhs, lhs_span)?;
312 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
313 // If we didn't have to handle `x..`/`x..=`, it would be pretty easy to
314 // generalise it to the Fixity::None code.
315 lhs = self.parse_range_expr(prec, lhs, op, cur_op_span)?;
319 let fixity = op.fixity();
320 let prec_adjustment = match fixity {
323 // We currently have no non-associative operators that are not handled above by
324 // the special cases. The code is here only for future convenience.
327 let rhs = self.with_res(restrictions - Restrictions::STMT_EXPR, |this| {
328 this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
331 let span = self.mk_expr_sp(&lhs, lhs_span, rhs.span);
344 | AssocOp::ShiftRight
350 | AssocOp::GreaterEqual => {
351 let ast_op = op.to_ast_binop().unwrap();
352 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
353 self.mk_expr(span, binary)
355 AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs, cur_op_span)),
356 AssocOp::AssignOp(k) => {
358 token::Plus => BinOpKind::Add,
359 token::Minus => BinOpKind::Sub,
360 token::Star => BinOpKind::Mul,
361 token::Slash => BinOpKind::Div,
362 token::Percent => BinOpKind::Rem,
363 token::Caret => BinOpKind::BitXor,
364 token::And => BinOpKind::BitAnd,
365 token::Or => BinOpKind::BitOr,
366 token::Shl => BinOpKind::Shl,
367 token::Shr => BinOpKind::Shr,
369 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
370 self.mk_expr(span, aopexpr)
372 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
373 self.span_bug(span, "AssocOp should have been handled by special case")
377 if let Fixity::None = fixity {
381 if last_type_ascription_set {
382 self.last_type_ascription = None;
387 fn should_continue_as_assoc_expr(&mut self, lhs: &Expr) -> bool {
388 match (self.expr_is_complete(lhs), AssocOp::from_token(&self.token)) {
389 // Semi-statement forms are odd:
390 // See https://github.com/rust-lang/rust/issues/29071
391 (true, None) => false,
392 (false, _) => true, // Continue parsing the expression.
393 // An exhaustive check is done in the following block, but these are checked first
394 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
395 // want to keep their span info to improve diagnostics in these cases in a later stage.
396 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
397 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
398 (true, Some(AssocOp::Add)) // `{ 42 } + 42
399 // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
400 // `if x { a } else { b } && if y { c } else { d }`
401 if !self.look_ahead(1, |t| t.is_used_keyword()) => {
402 // These cases are ambiguous and can't be identified in the parser alone.
403 let sp = self.sess.source_map().start_point(self.token.span);
404 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
407 (true, Some(AssocOp::LAnd)) |
408 (true, Some(AssocOp::LOr)) |
409 (true, Some(AssocOp::BitOr)) => {
410 // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }`. Separated from the
411 // above due to #74233.
412 // These cases are ambiguous and can't be identified in the parser alone.
414 // Bitwise AND is left out because guessing intent is hard. We can make
415 // suggestions based on the assumption that double-refs are rarely intentional,
416 // and closures are distinct enough that they don't get mixed up with their
418 let sp = self.sess.source_map().start_point(self.token.span);
419 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
422 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => false,
424 self.error_found_expr_would_be_stmt(lhs);
430 /// We've found an expression that would be parsed as a statement,
431 /// but the next token implies this should be parsed as an expression.
432 /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
433 fn error_found_expr_would_be_stmt(&self, lhs: &Expr) {
434 self.sess.emit_err(FoundExprWouldBeStmt {
435 span: self.token.span,
436 token: self.token.clone(),
437 suggestion: ExprParenthesesNeeded::surrounding(lhs.span),
441 /// Possibly translate the current token to an associative operator.
442 /// The method does not advance the current token.
444 /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
445 fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
446 let (op, span) = match (AssocOp::from_token(&self.token), self.token.ident()) {
447 // When parsing const expressions, stop parsing when encountering `>`.
452 | AssocOp::GreaterEqual
453 | AssocOp::AssignOp(token::BinOpToken::Shr),
456 ) if self.restrictions.contains(Restrictions::CONST_EXPR) => {
459 (Some(op), _) => (op, self.token.span),
460 (None, Some((Ident { name: sym::and, span }, false))) if self.may_recover() => {
461 self.sess.emit_err(InvalidLogicalOperator {
462 span: self.token.span,
463 incorrect: "and".into(),
464 sub: InvalidLogicalOperatorSub::Conjunction(self.token.span),
466 (AssocOp::LAnd, span)
468 (None, Some((Ident { name: sym::or, span }, false))) if self.may_recover() => {
469 self.sess.emit_err(InvalidLogicalOperator {
470 span: self.token.span,
471 incorrect: "or".into(),
472 sub: InvalidLogicalOperatorSub::Disjunction(self.token.span),
478 Some(source_map::respan(span, op))
481 /// Checks if this expression is a successfully parsed statement.
482 fn expr_is_complete(&self, e: &Expr) -> bool {
483 self.restrictions.contains(Restrictions::STMT_EXPR)
484 && !classify::expr_requires_semi_to_be_stmt(e)
487 /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
488 /// The other two variants are handled in `parse_prefix_range_expr` below.
495 ) -> PResult<'a, P<Expr>> {
496 let rhs = if self.is_at_start_of_range_notation_rhs() {
497 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
501 let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
502 let span = self.mk_expr_sp(&lhs, lhs.span, rhs_span);
504 if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
505 let range = self.mk_range(Some(lhs), rhs, limits);
506 Ok(self.mk_expr(span, range))
509 fn is_at_start_of_range_notation_rhs(&self) -> bool {
510 if self.token.can_begin_expr() {
511 // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
512 if self.token == token::OpenDelim(Delimiter::Brace) {
513 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
521 /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
522 fn parse_prefix_range_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
523 // Check for deprecated `...` syntax.
524 if self.token == token::DotDotDot {
525 self.err_dotdotdot_syntax(self.token.span);
529 [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind),
530 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
534 let limits = match self.token.kind {
535 token::DotDot => RangeLimits::HalfOpen,
536 _ => RangeLimits::Closed,
538 let op = AssocOp::from_token(&self.token);
539 // FIXME: `parse_prefix_range_expr` is called when the current
540 // token is `DotDot`, `DotDotDot`, or `DotDotEq`. If we haven't already
541 // parsed attributes, then trying to parse them here will always fail.
542 // We should figure out how we want attributes on range expressions to work.
543 let attrs = self.parse_or_use_outer_attributes(attrs)?;
544 self.collect_tokens_for_expr(attrs, |this, attrs| {
545 let lo = this.token.span;
547 let (span, opt_end) = if this.is_at_start_of_range_notation_rhs() {
548 // RHS must be parsed with more associativity than the dots.
549 this.parse_assoc_expr_with(op.unwrap().precedence() + 1, LhsExpr::NotYetParsed)
550 .map(|x| (lo.to(x.span), Some(x)))?
554 let range = this.mk_range(None, opt_end, limits);
555 Ok(this.mk_expr_with_attrs(span, range, attrs))
559 /// Parses a prefix-unary-operator expr.
560 fn parse_prefix_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
561 let attrs = self.parse_or_use_outer_attributes(attrs)?;
562 let lo = self.token.span;
564 macro_rules! make_it {
565 ($this:ident, $attrs:expr, |this, _| $body:expr) => {
566 $this.collect_tokens_for_expr($attrs, |$this, attrs| {
567 let (hi, ex) = $body?;
568 Ok($this.mk_expr_with_attrs(lo.to(hi), ex, attrs))
575 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
576 match this.token.uninterpolate().kind {
577 token::Not => make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Not)), // `!expr`
578 token::Tilde => make_it!(this, attrs, |this, _| this.recover_tilde_expr(lo)), // `~expr`
579 token::BinOp(token::Minus) => {
580 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Neg))
582 token::BinOp(token::Star) => {
583 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Deref))
585 token::BinOp(token::And) | token::AndAnd => {
586 make_it!(this, attrs, |this, _| this.parse_borrow_expr(lo))
588 token::BinOp(token::Plus) if this.look_ahead(1, |tok| tok.is_numeric_lit()) => {
590 LeadingPlusNotSupported { span: lo, remove_plus: None, add_parentheses: None };
592 // a block on the LHS might have been intended to be an expression instead
593 if let Some(sp) = this.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
594 err.add_parentheses = Some(ExprParenthesesNeeded::surrounding(*sp));
596 err.remove_plus = Some(lo);
598 this.sess.emit_err(err);
601 this.parse_prefix_expr(None)
603 // Recover from `++x`:
604 token::BinOp(token::Plus)
605 if this.look_ahead(1, |t| *t == token::BinOp(token::Plus)) =>
607 let prev_is_semi = this.prev_token == token::Semi;
608 let pre_span = this.token.span.to(this.look_ahead(1, |t| t.span));
613 let operand_expr = this.parse_dot_or_call_expr(Default::default())?;
614 this.recover_from_prefix_increment(operand_expr, pre_span, prev_is_semi)
616 token::Ident(..) if this.token.is_keyword(kw::Box) => {
617 make_it!(this, attrs, |this, _| this.parse_box_expr(lo))
619 token::Ident(..) if this.may_recover() && this.is_mistaken_not_ident_negation() => {
620 make_it!(this, attrs, |this, _| this.recover_not_expr(lo))
622 _ => return this.parse_dot_or_call_expr(Some(attrs)),
626 fn parse_prefix_expr_common(&mut self, lo: Span) -> PResult<'a, (Span, P<Expr>)> {
628 let expr = self.parse_prefix_expr(None);
629 let (span, expr) = self.interpolated_or_expr_span(expr)?;
630 Ok((lo.to(span), expr))
633 fn parse_unary_expr(&mut self, lo: Span, op: UnOp) -> PResult<'a, (Span, ExprKind)> {
634 let (span, expr) = self.parse_prefix_expr_common(lo)?;
635 Ok((span, self.mk_unary(op, expr)))
638 // Recover on `!` suggesting for bitwise negation instead.
639 fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
640 self.sess.emit_err(TildeAsUnaryOperator(lo));
642 self.parse_unary_expr(lo, UnOp::Not)
645 /// Parse `box expr`.
646 fn parse_box_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
647 let (span, expr) = self.parse_prefix_expr_common(lo)?;
648 self.sess.gated_spans.gate(sym::box_syntax, span);
649 Ok((span, ExprKind::Box(expr)))
652 fn is_mistaken_not_ident_negation(&self) -> bool {
653 let token_cannot_continue_expr = |t: &Token| match t.uninterpolate().kind {
654 // These tokens can start an expression after `!`, but
655 // can't continue an expression after an ident
656 token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
657 token::Literal(..) | token::Pound => true,
658 _ => t.is_whole_expr(),
660 self.token.is_ident_named(sym::not) && self.look_ahead(1, token_cannot_continue_expr)
663 /// Recover on `not expr` in favor of `!expr`.
664 fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
666 let negated_token = self.look_ahead(1, |t| t.clone());
668 let sub_diag = if negated_token.is_numeric_lit() {
669 NotAsNegationOperatorSub::SuggestNotBitwise
670 } else if negated_token.is_bool_lit() {
671 NotAsNegationOperatorSub::SuggestNotLogical
673 NotAsNegationOperatorSub::SuggestNotDefault
676 self.sess.emit_err(NotAsNegationOperator {
677 negated: negated_token.span,
678 negated_desc: super::token_descr(&negated_token),
679 // Span the `not` plus trailing whitespace to avoid
680 // trailing whitespace after the `!` in our suggestion
682 self.sess.source_map().span_until_non_whitespace(lo.to(negated_token.span)),
687 self.parse_unary_expr(lo, UnOp::Not)
690 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
691 fn interpolated_or_expr_span(
693 expr: PResult<'a, P<Expr>>,
694 ) -> PResult<'a, (Span, P<Expr>)> {
697 match self.prev_token.kind {
698 TokenKind::Interpolated(..) => self.prev_token.span,
706 fn parse_assoc_op_cast(
710 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
711 ) -> PResult<'a, P<Expr>> {
712 let mk_expr = |this: &mut Self, lhs: P<Expr>, rhs: P<Ty>| {
713 this.mk_expr(this.mk_expr_sp(&lhs, lhs_span, rhs.span), expr_kind(lhs, rhs))
716 // Save the state of the parser before parsing type normally, in case there is a
717 // LessThan comparison after this cast.
718 let parser_snapshot_before_type = self.clone();
719 let cast_expr = match self.parse_as_cast_ty() {
720 Ok(rhs) => mk_expr(self, lhs, rhs),
722 if !self.may_recover() {
723 return Err(type_err);
726 // Rewind to before attempting to parse the type with generics, to recover
727 // from situations like `x as usize < y` in which we first tried to parse
728 // `usize < y` as a type with generic arguments.
729 let parser_snapshot_after_type = mem::replace(self, parser_snapshot_before_type);
731 // Check for typo of `'a: loop { break 'a }` with a missing `'`.
732 match (&lhs.kind, &self.token.kind) {
735 ExprKind::Path(None, ast::Path { segments, .. }),
736 TokenKind::Ident(kw::For | kw::Loop | kw::While, false),
737 ) if segments.len() == 1 => {
738 let snapshot = self.create_snapshot_for_diagnostic();
740 ident: Ident::from_str_and_span(
741 &format!("'{}", segments[0].ident),
742 segments[0].ident.span,
745 match self.parse_labeled_expr(label, false) {
748 self.sess.emit_err(MalformedLoopLabel {
749 span: label.ident.span,
750 correct_label: label.ident,
756 self.restore_snapshot(snapshot);
763 match self.parse_path(PathStyle::Expr) {
765 let span_after_type = parser_snapshot_after_type.token.span;
769 self.mk_ty(path.span, TyKind::Path(None, path.clone())),
772 let args_span = self.look_ahead(1, |t| t.span).to(span_after_type);
773 let suggestion = ComparisonOrShiftInterpretedAsGenericSugg {
774 left: expr.span.shrink_to_lo(),
775 right: expr.span.shrink_to_hi(),
778 match self.token.kind {
779 token::Lt => self.sess.emit_err(ComparisonInterpretedAsGeneric {
780 comparison: self.token.span,
785 token::BinOp(token::Shl) => {
786 self.sess.emit_err(ShiftInterpretedAsGeneric {
787 shift: self.token.span,
794 // We can end up here even without `<` being the next token, for
795 // example because `parse_ty_no_plus` returns `Err` on keywords,
796 // but `parse_path` returns `Ok` on them due to error recovery.
797 // Return original error and parser state.
798 *self = parser_snapshot_after_type;
799 return Err(type_err);
803 // Successfully parsed the type path leaving a `<` yet to parse.
806 // Keep `x as usize` as an expression in AST and continue parsing.
810 // Couldn't parse as a path, return original error and parser state.
812 *self = parser_snapshot_after_type;
813 return Err(type_err);
819 self.parse_and_disallow_postfix_after_cast(cast_expr)
822 /// Parses a postfix operators such as `.`, `?`, or index (`[]`) after a cast,
823 /// then emits an error and returns the newly parsed tree.
824 /// The resulting parse tree for `&x as T[0]` has a precedence of `((&x) as T)[0]`.
825 fn parse_and_disallow_postfix_after_cast(
828 ) -> PResult<'a, P<Expr>> {
829 let span = cast_expr.span;
830 let (cast_kind, maybe_ascription_span) =
831 if let ExprKind::Type(ascripted_expr, _) = &cast_expr.kind {
832 ("type ascription", Some(ascripted_expr.span.shrink_to_hi().with_hi(span.hi())))
837 let with_postfix = self.parse_dot_or_call_expr_with_(cast_expr, span)?;
839 // Check if an illegal postfix operator has been added after the cast.
840 // If the resulting expression is not a cast, it is an illegal postfix operator.
841 if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) {
843 "{cast_kind} cannot be followed by {}",
844 match with_postfix.kind {
845 ExprKind::Index(_, _) => "indexing",
846 ExprKind::Try(_) => "`?`",
847 ExprKind::Field(_, _) => "a field access",
848 ExprKind::MethodCall(_, _, _, _) => "a method call",
849 ExprKind::Call(_, _) => "a function call",
850 ExprKind::Await(_) => "`.await`",
851 ExprKind::Err => return Ok(with_postfix),
852 _ => unreachable!("parse_dot_or_call_expr_with_ shouldn't produce this"),
855 let mut err = self.struct_span_err(span, &msg);
857 let suggest_parens = |err: &mut Diagnostic| {
858 let suggestions = vec![
859 (span.shrink_to_lo(), "(".to_string()),
860 (span.shrink_to_hi(), ")".to_string()),
862 err.multipart_suggestion(
863 "try surrounding the expression in parentheses",
865 Applicability::MachineApplicable,
869 // If type ascription is "likely an error", the user will already be getting a useful
870 // help message, and doesn't need a second.
871 if self.last_type_ascription.map_or(false, |last_ascription| last_ascription.1) {
872 self.maybe_annotate_with_ascription(&mut err, false);
873 } else if let Some(ascription_span) = maybe_ascription_span {
874 let is_nightly = self.sess.unstable_features.is_nightly_build();
876 suggest_parens(&mut err);
881 "{}remove the type ascription",
882 if is_nightly { "alternatively, " } else { "" }
886 Applicability::MaybeIncorrect
888 Applicability::MachineApplicable
892 suggest_parens(&mut err);
899 fn parse_assoc_op_ascribe(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
900 let maybe_path = self.could_ascription_be_path(&lhs.kind);
901 self.last_type_ascription = Some((self.prev_token.span, maybe_path));
902 let lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
903 self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
907 /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
908 fn parse_borrow_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
910 let has_lifetime = self.token.is_lifetime() && self.look_ahead(1, |t| t != &token::Colon);
911 let lifetime = has_lifetime.then(|| self.expect_lifetime()); // For recovery, see below.
912 let (borrow_kind, mutbl) = self.parse_borrow_modifiers(lo);
913 let expr = self.parse_prefix_expr(None);
914 let (hi, expr) = self.interpolated_or_expr_span(expr)?;
915 let span = lo.to(hi);
916 if let Some(lt) = lifetime {
917 self.error_remove_borrow_lifetime(span, lt.ident.span);
919 Ok((span, ExprKind::AddrOf(borrow_kind, mutbl, expr)))
922 fn error_remove_borrow_lifetime(&self, span: Span, lt_span: Span) {
923 self.sess.emit_err(LifetimeInBorrowExpression { span, lifetime_span: lt_span });
926 /// Parse `mut?` or `raw [ const | mut ]`.
927 fn parse_borrow_modifiers(&mut self, lo: Span) -> (ast::BorrowKind, ast::Mutability) {
928 if self.check_keyword(kw::Raw) && self.look_ahead(1, Token::is_mutability) {
929 // `raw [ const | mut ]`.
930 let found_raw = self.eat_keyword(kw::Raw);
932 let mutability = self.parse_const_or_mut().unwrap();
933 self.sess.gated_spans.gate(sym::raw_ref_op, lo.to(self.prev_token.span));
934 (ast::BorrowKind::Raw, mutability)
937 (ast::BorrowKind::Ref, self.parse_mutability())
941 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
942 fn parse_dot_or_call_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
943 let attrs = self.parse_or_use_outer_attributes(attrs)?;
944 self.collect_tokens_for_expr(attrs, |this, attrs| {
945 let base = this.parse_bottom_expr();
946 let (span, base) = this.interpolated_or_expr_span(base)?;
947 this.parse_dot_or_call_expr_with(base, span, attrs)
951 pub(super) fn parse_dot_or_call_expr_with(
955 mut attrs: ast::AttrVec,
956 ) -> PResult<'a, P<Expr>> {
957 // Stitch the list of outer attributes onto the return value.
958 // A little bit ugly, but the best way given the current code
960 let res = self.parse_dot_or_call_expr_with_(e0, lo);
961 if attrs.is_empty() {
965 expr.map(|mut expr| {
966 attrs.extend(expr.attrs);
974 fn parse_dot_or_call_expr_with_(&mut self, mut e: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
976 let has_question = if self.prev_token.kind == TokenKind::Ident(kw::Return, false) {
977 // we are using noexpect here because we don't expect a `?` directly after a `return`
978 // which could be suggested otherwise
979 self.eat_noexpect(&token::Question)
981 self.eat(&token::Question)
985 e = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Try(e));
988 let has_dot = if self.prev_token.kind == TokenKind::Ident(kw::Return, false) {
989 // we are using noexpect here because we don't expect a `.` directly after a `return`
990 // which could be suggested otherwise
991 self.eat_noexpect(&token::Dot)
993 self.eat(&token::Dot)
997 e = self.parse_dot_suffix_expr(lo, e)?;
1000 if self.expr_is_complete(&e) {
1003 e = match self.token.kind {
1004 token::OpenDelim(Delimiter::Parenthesis) => self.parse_fn_call_expr(lo, e),
1005 token::OpenDelim(Delimiter::Bracket) => self.parse_index_expr(lo, e)?,
1011 fn look_ahead_type_ascription_as_field(&mut self) -> bool {
1012 self.look_ahead(1, |t| t.is_ident())
1013 && self.look_ahead(2, |t| t == &token::Colon)
1014 && self.look_ahead(3, |t| t.can_begin_expr())
1017 fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
1018 match self.token.uninterpolate().kind {
1019 token::Ident(..) => self.parse_dot_suffix(base, lo),
1020 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
1021 Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix, None))
1023 token::Literal(token::Lit { kind: token::Float, symbol, suffix }) => {
1024 Ok(self.parse_tuple_field_access_expr_float(lo, base, symbol, suffix))
1027 self.error_unexpected_after_dot();
1033 fn error_unexpected_after_dot(&self) {
1034 // FIXME Could factor this out into non_fatal_unexpected or something.
1035 let actual = pprust::token_to_string(&self.token);
1036 self.struct_span_err(self.token.span, &format!("unexpected token: `{actual}`")).emit();
1039 // We need an identifier or integer, but the next token is a float.
1040 // Break the float into components to extract the identifier or integer.
1041 // FIXME: With current `TokenCursor` it's hard to break tokens into more than 2
1042 // parts unless those parts are processed immediately. `TokenCursor` should either
1043 // support pushing "future tokens" (would be also helpful to `break_and_eat`), or
1044 // we should break everything including floats into more basic proc-macro style
1045 // tokens in the lexer (probably preferable).
1046 fn parse_tuple_field_access_expr_float(
1051 suffix: Option<Symbol>,
1054 enum FloatComponent {
1058 use FloatComponent::*;
1060 let float_str = float.as_str();
1061 let mut components = Vec::new();
1062 let mut ident_like = String::new();
1063 for c in float_str.chars() {
1064 if c == '_' || c.is_ascii_alphanumeric() {
1066 } else if matches!(c, '.' | '+' | '-') {
1067 if !ident_like.is_empty() {
1068 components.push(IdentLike(mem::take(&mut ident_like)));
1070 components.push(Punct(c));
1072 panic!("unexpected character in a float token: {:?}", c)
1075 if !ident_like.is_empty() {
1076 components.push(IdentLike(ident_like));
1079 // With proc macros the span can refer to anything, the source may be too short,
1080 // or too long, or non-ASCII. It only makes sense to break our span into components
1081 // if its underlying text is identical to our float literal.
1082 let span = self.token.span;
1083 let can_take_span_apart =
1084 || self.span_to_snippet(span).as_deref() == Ok(float_str).as_deref();
1086 match &*components {
1089 self.parse_tuple_field_access_expr(lo, base, Symbol::intern(&i), suffix, None)
1092 [IdentLike(i), Punct('.')] => {
1093 let (ident_span, dot_span) = if can_take_span_apart() {
1094 let (span, ident_len) = (span.data(), BytePos::from_usize(i.len()));
1095 let ident_span = span.with_hi(span.lo + ident_len);
1096 let dot_span = span.with_lo(span.lo + ident_len);
1097 (ident_span, dot_span)
1101 assert!(suffix.is_none());
1102 let symbol = Symbol::intern(&i);
1103 self.token = Token::new(token::Ident(symbol, false), ident_span);
1104 let next_token = (Token::new(token::Dot, dot_span), self.token_spacing);
1105 self.parse_tuple_field_access_expr(lo, base, symbol, None, Some(next_token))
1108 [IdentLike(i1), Punct('.'), IdentLike(i2)] => {
1109 let (ident1_span, dot_span, ident2_span) = if can_take_span_apart() {
1110 let (span, ident1_len) = (span.data(), BytePos::from_usize(i1.len()));
1111 let ident1_span = span.with_hi(span.lo + ident1_len);
1113 .with_lo(span.lo + ident1_len)
1114 .with_hi(span.lo + ident1_len + BytePos(1));
1115 let ident2_span = self.token.span.with_lo(span.lo + ident1_len + BytePos(1));
1116 (ident1_span, dot_span, ident2_span)
1120 let symbol1 = Symbol::intern(&i1);
1121 self.token = Token::new(token::Ident(symbol1, false), ident1_span);
1122 // This needs to be `Spacing::Alone` to prevent regressions.
1123 // See issue #76399 and PR #76285 for more details
1124 let next_token1 = (Token::new(token::Dot, dot_span), Spacing::Alone);
1126 self.parse_tuple_field_access_expr(lo, base, symbol1, None, Some(next_token1));
1127 let symbol2 = Symbol::intern(&i2);
1128 let next_token2 = Token::new(token::Ident(symbol2, false), ident2_span);
1129 self.bump_with((next_token2, self.token_spacing)); // `.`
1130 self.parse_tuple_field_access_expr(lo, base1, symbol2, suffix, None)
1132 // 1e+ | 1e- (recovered)
1133 [IdentLike(_), Punct('+' | '-')] |
1135 [IdentLike(_), Punct('+' | '-'), IdentLike(_)] |
1137 [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-')] |
1139 [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-'), IdentLike(_)] => {
1140 // See the FIXME about `TokenCursor` above.
1141 self.error_unexpected_after_dot();
1144 _ => panic!("unexpected components in a float token: {:?}", components),
1148 fn parse_tuple_field_access_expr(
1153 suffix: Option<Symbol>,
1154 next_token: Option<(Token, Spacing)>,
1157 Some(next_token) => self.bump_with(next_token),
1158 None => self.bump(),
1160 let span = self.prev_token.span;
1161 let field = ExprKind::Field(base, Ident::new(field, span));
1162 if let Some(suffix) = suffix {
1163 self.expect_no_tuple_index_suffix(span, suffix);
1165 self.mk_expr(lo.to(span), field)
1168 /// Parse a function call expression, `expr(...)`.
1169 fn parse_fn_call_expr(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
1170 let snapshot = if self.token.kind == token::OpenDelim(Delimiter::Parenthesis)
1171 && self.look_ahead_type_ascription_as_field()
1173 Some((self.create_snapshot_for_diagnostic(), fun.kind.clone()))
1177 let open_paren = self.token.span;
1180 .parse_paren_expr_seq()
1181 .map(|args| self.mk_expr(lo.to(self.prev_token.span), self.mk_call(fun, args)));
1183 self.maybe_recover_struct_lit_bad_delims(lo, open_paren, &mut seq, snapshot)
1187 self.recover_seq_parse_error(Delimiter::Parenthesis, lo, seq)
1190 /// If we encounter a parser state that looks like the user has written a `struct` literal with
1191 /// parentheses instead of braces, recover the parser state and provide suggestions.
1192 #[instrument(skip(self, seq, snapshot), level = "trace")]
1193 fn maybe_recover_struct_lit_bad_delims(
1197 seq: &mut PResult<'a, P<Expr>>,
1198 snapshot: Option<(SnapshotParser<'a>, ExprKind)>,
1199 ) -> Option<P<Expr>> {
1200 if !self.may_recover() {
1204 match (seq.as_mut(), snapshot) {
1205 (Err(err), Some((mut snapshot, ExprKind::Path(None, path)))) => {
1206 snapshot.bump(); // `(`
1207 match snapshot.parse_struct_fields(path.clone(), false, Delimiter::Parenthesis) {
1209 if snapshot.eat(&token::CloseDelim(Delimiter::Parenthesis)) =>
1211 // We are certain we have `Enum::Foo(a: 3, b: 4)`, suggest
1212 // `Enum::Foo { a: 3, b: 4 }` or `Enum::Foo(3, 4)`.
1213 self.restore_snapshot(snapshot);
1214 let close_paren = self.prev_token.span;
1215 let span = lo.to(self.prev_token.span);
1216 if !fields.is_empty() {
1217 let mut replacement_err = ParenthesesWithStructFields {
1220 braces_for_struct: BracesForStructLiteral {
1222 second: close_paren,
1224 no_fields_for_fn: NoFieldsForFnCall {
1227 .map(|field| field.span.until(field.expr.span))
1231 .into_diagnostic(&self.sess.span_diagnostic);
1232 replacement_err.emit();
1234 let old_err = mem::replace(err, replacement_err);
1239 return Some(self.mk_expr_err(span));
1252 /// Parse an indexing expression `expr[...]`.
1253 fn parse_index_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
1254 let prev_span = self.prev_token.span;
1255 let open_delim_span = self.token.span;
1257 let index = self.parse_expr()?;
1258 self.suggest_missing_semicolon_before_array(prev_span, open_delim_span)?;
1259 self.expect(&token::CloseDelim(Delimiter::Bracket))?;
1260 Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_index(base, index)))
1263 /// Assuming we have just parsed `.`, continue parsing into an expression.
1264 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
1265 if self.token.uninterpolated_span().rust_2018() && self.eat_keyword(kw::Await) {
1266 return Ok(self.mk_await_expr(self_arg, lo));
1269 let fn_span_lo = self.token.span;
1270 let mut segment = self.parse_path_segment(PathStyle::Expr, None)?;
1271 self.check_trailing_angle_brackets(&segment, &[&token::OpenDelim(Delimiter::Parenthesis)]);
1272 self.check_turbofish_missing_angle_brackets(&mut segment);
1274 if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
1275 // Method call `expr.f()`
1276 let args = self.parse_paren_expr_seq()?;
1277 let fn_span = fn_span_lo.to(self.prev_token.span);
1278 let span = lo.to(self.prev_token.span);
1279 Ok(self.mk_expr(span, ExprKind::MethodCall(segment, self_arg, args, fn_span)))
1281 // Field access `expr.f`
1282 if let Some(args) = segment.args {
1283 self.sess.emit_err(FieldExpressionWithGeneric(args.span()));
1286 let span = lo.to(self.prev_token.span);
1287 Ok(self.mk_expr(span, ExprKind::Field(self_arg, segment.ident)))
1291 /// At the bottom (top?) of the precedence hierarchy,
1292 /// Parses things like parenthesized exprs, macros, `return`, etc.
1294 /// N.B., this does not parse outer attributes, and is private because it only works
1295 /// correctly if called from `parse_dot_or_call_expr()`.
1296 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
1297 maybe_recover_from_interpolated_ty_qpath!(self, true);
1298 maybe_whole_expr!(self);
1300 // Outer attributes are already parsed and will be
1301 // added to the return value after the fact.
1303 // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
1304 let lo = self.token.span;
1305 if let token::Literal(_) = self.token.kind {
1306 // This match arm is a special-case of the `_` match arm below and
1307 // could be removed without changing functionality, but it's faster
1308 // to have it here, especially for programs with large constants.
1309 self.parse_lit_expr()
1310 } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
1311 self.parse_tuple_parens_expr()
1312 } else if self.check(&token::OpenDelim(Delimiter::Brace)) {
1313 self.parse_block_expr(None, lo, BlockCheckMode::Default)
1314 } else if self.check(&token::BinOp(token::Or)) || self.check(&token::OrOr) {
1315 self.parse_closure_expr().map_err(|mut err| {
1316 // If the input is something like `if a { 1 } else { 2 } | if a { 3 } else { 4 }`
1317 // then suggest parens around the lhs.
1318 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
1319 err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
1323 } else if self.check(&token::OpenDelim(Delimiter::Bracket)) {
1324 self.parse_array_or_repeat_expr(Delimiter::Bracket)
1325 } else if self.check_path() {
1326 self.parse_path_start_expr()
1327 } else if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
1328 self.parse_closure_expr()
1329 } else if self.eat_keyword(kw::If) {
1330 self.parse_if_expr()
1331 } else if self.check_keyword(kw::For) {
1332 if self.choose_generics_over_qpath(1) {
1333 self.parse_closure_expr()
1335 assert!(self.eat_keyword(kw::For));
1336 self.parse_for_expr(None, self.prev_token.span)
1338 } else if self.eat_keyword(kw::While) {
1339 self.parse_while_expr(None, self.prev_token.span)
1340 } else if let Some(label) = self.eat_label() {
1341 self.parse_labeled_expr(label, true)
1342 } else if self.eat_keyword(kw::Loop) {
1343 let sp = self.prev_token.span;
1344 self.parse_loop_expr(None, self.prev_token.span).map_err(|mut err| {
1345 err.span_label(sp, "while parsing this `loop` expression");
1348 } else if self.eat_keyword(kw::Continue) {
1349 let kind = ExprKind::Continue(self.eat_label());
1350 Ok(self.mk_expr(lo.to(self.prev_token.span), kind))
1351 } else if self.eat_keyword(kw::Match) {
1352 let match_sp = self.prev_token.span;
1353 self.parse_match_expr().map_err(|mut err| {
1354 err.span_label(match_sp, "while parsing this `match` expression");
1357 } else if self.eat_keyword(kw::Unsafe) {
1358 let sp = self.prev_token.span;
1359 self.parse_block_expr(None, lo, BlockCheckMode::Unsafe(ast::UserProvided)).map_err(
1361 err.span_label(sp, "while parsing this `unsafe` expression");
1365 } else if self.check_inline_const(0) {
1366 self.parse_const_block(lo.to(self.token.span), false)
1367 } else if self.may_recover() && self.is_do_catch_block() {
1368 self.recover_do_catch()
1369 } else if self.is_try_block() {
1370 self.expect_keyword(kw::Try)?;
1371 self.parse_try_block(lo)
1372 } else if self.eat_keyword(kw::Return) {
1373 self.parse_return_expr()
1374 } else if self.eat_keyword(kw::Break) {
1375 self.parse_break_expr()
1376 } else if self.eat_keyword(kw::Yield) {
1377 self.parse_yield_expr()
1378 } else if self.is_do_yeet() {
1379 self.parse_yeet_expr()
1380 } else if self.check_keyword(kw::Let) {
1381 self.parse_let_expr()
1382 } else if self.eat_keyword(kw::Underscore) {
1383 Ok(self.mk_expr(self.prev_token.span, ExprKind::Underscore))
1384 } else if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
1385 // Don't complain about bare semicolons after unclosed braces
1386 // recovery in order to keep the error count down. Fixing the
1387 // delimiters will possibly also fix the bare semicolon found in
1388 // expression context. For example, silence the following error:
1390 // error: expected expression, found `;`
1394 // | ^ expected expression
1396 Ok(self.mk_expr_err(self.token.span))
1397 } else if self.token.uninterpolated_span().rust_2018() {
1398 // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
1399 if self.check_keyword(kw::Async) {
1400 if self.is_async_block() {
1401 // Check for `async {` and `async move {`.
1402 self.parse_async_block()
1404 self.parse_closure_expr()
1406 } else if self.eat_keyword(kw::Await) {
1407 self.recover_incorrect_await_syntax(lo, self.prev_token.span)
1409 self.parse_lit_expr()
1412 self.parse_lit_expr()
1416 fn parse_lit_expr(&mut self) -> PResult<'a, P<Expr>> {
1417 let lo = self.token.span;
1418 match self.parse_opt_lit() {
1420 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Lit(literal));
1421 self.maybe_recover_from_bad_qpath(expr)
1423 None => self.try_macro_suggestion(),
1427 fn parse_tuple_parens_expr(&mut self) -> PResult<'a, P<Expr>> {
1428 let lo = self.token.span;
1429 self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
1430 let (es, trailing_comma) = match self.parse_seq_to_end(
1431 &token::CloseDelim(Delimiter::Parenthesis),
1432 SeqSep::trailing_allowed(token::Comma),
1433 |p| p.parse_expr_catch_underscore(),
1437 return Ok(self.recover_seq_parse_error(Delimiter::Parenthesis, lo, Err(err)));
1440 let kind = if es.len() == 1 && !trailing_comma {
1441 // `(e)` is parenthesized `e`.
1442 ExprKind::Paren(es.into_iter().next().unwrap())
1444 // `(e,)` is a tuple with only one field, `e`.
1447 let expr = self.mk_expr(lo.to(self.prev_token.span), kind);
1448 self.maybe_recover_from_bad_qpath(expr)
1451 fn parse_array_or_repeat_expr(&mut self, close_delim: Delimiter) -> PResult<'a, P<Expr>> {
1452 let lo = self.token.span;
1453 self.bump(); // `[` or other open delim
1455 let close = &token::CloseDelim(close_delim);
1456 let kind = if self.eat(close) {
1458 ExprKind::Array(Vec::new())
1461 let first_expr = self.parse_expr()?;
1462 if self.eat(&token::Semi) {
1463 // Repeating array syntax: `[ 0; 512 ]`
1464 let count = self.parse_anon_const_expr()?;
1465 self.expect(close)?;
1466 ExprKind::Repeat(first_expr, count)
1467 } else if self.eat(&token::Comma) {
1468 // Vector with two or more elements.
1469 let sep = SeqSep::trailing_allowed(token::Comma);
1470 let (remaining_exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
1471 let mut exprs = vec![first_expr];
1472 exprs.extend(remaining_exprs);
1473 ExprKind::Array(exprs)
1475 // Vector with one element
1476 self.expect(close)?;
1477 ExprKind::Array(vec![first_expr])
1480 let expr = self.mk_expr(lo.to(self.prev_token.span), kind);
1481 self.maybe_recover_from_bad_qpath(expr)
1484 fn parse_path_start_expr(&mut self) -> PResult<'a, P<Expr>> {
1485 let (qself, path) = if self.eat_lt() {
1486 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
1489 (None, self.parse_path(PathStyle::Expr)?)
1492 // `!`, as an operator, is prefix, so we know this isn't that.
1493 let (span, kind) = if self.eat(&token::Not) {
1494 // MACRO INVOCATION expression
1495 if qself.is_some() {
1496 self.sess.emit_err(MacroInvocationWithQualifiedPath(path.span));
1499 let mac = P(MacCall {
1501 args: self.parse_mac_args()?,
1502 prior_type_ascription: self.last_type_ascription,
1504 (lo.to(self.prev_token.span), ExprKind::MacCall(mac))
1505 } else if self.check(&token::OpenDelim(Delimiter::Brace)) &&
1506 let Some(expr) = self.maybe_parse_struct_expr(qself.as_ref(), &path) {
1507 if qself.is_some() {
1508 self.sess.gated_spans.gate(sym::more_qualified_paths, path.span);
1512 (path.span, ExprKind::Path(qself, path))
1515 let expr = self.mk_expr(span, kind);
1516 self.maybe_recover_from_bad_qpath(expr)
1519 /// Parse `'label: $expr`. The label is already parsed.
1520 fn parse_labeled_expr(
1523 mut consume_colon: bool,
1524 ) -> PResult<'a, P<Expr>> {
1525 let lo = label_.ident.span;
1526 let label = Some(label_);
1527 let ate_colon = self.eat(&token::Colon);
1528 let expr = if self.eat_keyword(kw::While) {
1529 self.parse_while_expr(label, lo)
1530 } else if self.eat_keyword(kw::For) {
1531 self.parse_for_expr(label, lo)
1532 } else if self.eat_keyword(kw::Loop) {
1533 self.parse_loop_expr(label, lo)
1534 } else if self.check_noexpect(&token::OpenDelim(Delimiter::Brace))
1535 || self.token.is_whole_block()
1537 self.parse_block_expr(label, lo, BlockCheckMode::Default)
1538 } else if !ate_colon
1539 && self.may_recover()
1540 && (matches!(self.token.kind, token::CloseDelim(_) | token::Comma)
1541 || self.token.is_op())
1543 let lit = self.recover_unclosed_char(label_.ident, |self_| {
1544 self_.sess.create_err(UnexpectedTokenAfterLabel {
1545 span: self_.token.span,
1547 enclose_in_block: None,
1550 consume_colon = false;
1551 Ok(self.mk_expr(lo, ExprKind::Lit(lit)))
1552 } else if !ate_colon
1553 && (self.check_noexpect(&TokenKind::Comma) || self.check_noexpect(&TokenKind::Gt))
1555 // We're probably inside of a `Path<'a>` that needs a turbofish
1556 self.sess.emit_err(UnexpectedTokenAfterLabel {
1557 span: self.token.span,
1559 enclose_in_block: None,
1561 consume_colon = false;
1562 Ok(self.mk_expr_err(lo))
1564 let mut err = UnexpectedTokenAfterLabel {
1565 span: self.token.span,
1567 enclose_in_block: None,
1570 // Continue as an expression in an effort to recover on `'label: non_block_expr`.
1571 let expr = self.parse_expr().map(|expr| {
1572 let span = expr.span;
1574 let found_labeled_breaks = {
1575 struct FindLabeledBreaksVisitor(bool);
1577 impl<'ast> Visitor<'ast> for FindLabeledBreaksVisitor {
1578 fn visit_expr_post(&mut self, ex: &'ast Expr) {
1579 if let ExprKind::Break(Some(_label), _) = ex.kind {
1585 let mut vis = FindLabeledBreaksVisitor(false);
1586 vis.visit_expr(&expr);
1590 // Suggestion involves adding a (as of time of writing this, unstable) labeled block.
1592 // If there are no breaks that may use this label, suggest removing the label and
1593 // recover to the unmodified expression.
1594 if !found_labeled_breaks {
1595 err.remove_label = Some(lo.until(span));
1600 err.enclose_in_block = Some(UnexpectedTokenAfterLabelSugg {
1601 left: span.shrink_to_lo(),
1602 right: span.shrink_to_hi(),
1605 // Replace `'label: non_block_expr` with `'label: {non_block_expr}` in order to suppress future errors about `break 'label`.
1606 let stmt = self.mk_stmt(span, StmtKind::Expr(expr));
1607 let blk = self.mk_block(vec![stmt], BlockCheckMode::Default, span);
1608 self.mk_expr(span, ExprKind::Block(blk, label))
1611 self.sess.emit_err(err);
1615 if !ate_colon && consume_colon {
1616 self.sess.emit_err(RequireColonAfterLabeledExpression {
1619 label_end: lo.shrink_to_hi(),
1626 /// Emit an error when a char is parsed as a lifetime because of a missing quote
1627 pub(super) fn recover_unclosed_char(
1630 err: impl FnOnce(&mut Self) -> DiagnosticBuilder<'a, ErrorGuaranteed>,
1632 if let Some(mut diag) =
1633 self.sess.span_diagnostic.steal_diagnostic(lifetime.span, StashKey::LifetimeIsChar)
1635 diag.span_suggestion_verbose(
1636 lifetime.span.shrink_to_hi(),
1637 "add `'` to close the char literal",
1639 Applicability::MaybeIncorrect,
1644 .span_suggestion_verbose(
1645 lifetime.span.shrink_to_hi(),
1646 "add `'` to close the char literal",
1648 Applicability::MaybeIncorrect,
1653 token_lit: token::Lit::new(token::LitKind::Char, lifetime.name, None),
1654 kind: ast::LitKind::Char(lifetime.name.as_str().chars().next().unwrap_or('_')),
1655 span: lifetime.span,
1659 /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
1660 fn recover_do_catch(&mut self) -> PResult<'a, P<Expr>> {
1661 let lo = self.token.span;
1663 self.bump(); // `do`
1664 self.bump(); // `catch`
1666 let span = lo.to(self.prev_token.span);
1667 self.sess.emit_err(DoCatchSyntaxRemoved { span });
1669 self.parse_try_block(lo)
1672 /// Parse an expression if the token can begin one.
1673 fn parse_expr_opt(&mut self) -> PResult<'a, Option<P<Expr>>> {
1674 Ok(if self.token.can_begin_expr() { Some(self.parse_expr()?) } else { None })
1677 /// Parse `"return" expr?`.
1678 fn parse_return_expr(&mut self) -> PResult<'a, P<Expr>> {
1679 let lo = self.prev_token.span;
1680 let kind = ExprKind::Ret(self.parse_expr_opt()?);
1681 let expr = self.mk_expr(lo.to(self.prev_token.span), kind);
1682 self.maybe_recover_from_bad_qpath(expr)
1685 /// Parse `"do" "yeet" expr?`.
1686 fn parse_yeet_expr(&mut self) -> PResult<'a, P<Expr>> {
1687 let lo = self.token.span;
1689 self.bump(); // `do`
1690 self.bump(); // `yeet`
1692 let kind = ExprKind::Yeet(self.parse_expr_opt()?);
1694 let span = lo.to(self.prev_token.span);
1695 self.sess.gated_spans.gate(sym::yeet_expr, span);
1696 let expr = self.mk_expr(span, kind);
1697 self.maybe_recover_from_bad_qpath(expr)
1700 /// Parse `"break" (('label (:? expr)?) | expr?)` with `"break"` token already eaten.
1701 /// If the label is followed immediately by a `:` token, the label and `:` are
1702 /// parsed as part of the expression (i.e. a labeled loop). The language team has
1703 /// decided in #87026 to require parentheses as a visual aid to avoid confusion if
1704 /// the break expression of an unlabeled break is a labeled loop (as in
1705 /// `break 'lbl: loop {}`); a labeled break with an unlabeled loop as its value
1706 /// expression only gets a warning for compatibility reasons; and a labeled break
1707 /// with a labeled loop does not even get a warning because there is no ambiguity.
1708 fn parse_break_expr(&mut self) -> PResult<'a, P<Expr>> {
1709 let lo = self.prev_token.span;
1710 let mut label = self.eat_label();
1711 let kind = if label.is_some() && self.token == token::Colon {
1712 // The value expression can be a labeled loop, see issue #86948, e.g.:
1713 // `loop { break 'label: loop { break 'label 42; }; }`
1714 let lexpr = self.parse_labeled_expr(label.take().unwrap(), true)?;
1715 self.sess.emit_err(LabeledLoopInBreak {
1717 sub: WrapExpressionInParentheses {
1718 left: lexpr.span.shrink_to_lo(),
1719 right: lexpr.span.shrink_to_hi(),
1723 } else if self.token != token::OpenDelim(Delimiter::Brace)
1724 || !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1726 let expr = self.parse_expr_opt()?;
1727 if let Some(ref expr) = expr {
1731 ExprKind::While(_, _, None)
1732 | ExprKind::ForLoop(_, _, _, None)
1733 | ExprKind::Loop(_, None)
1734 | ExprKind::Block(_, None)
1737 self.sess.buffer_lint_with_diagnostic(
1738 BREAK_WITH_LABEL_AND_LOOP,
1741 "this labeled break expression is easy to confuse with an unlabeled break with a labeled value expression",
1742 BuiltinLintDiagnostics::BreakWithLabelAndLoop(expr.span),
1750 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Break(label, kind));
1751 self.maybe_recover_from_bad_qpath(expr)
1754 /// Parse `"yield" expr?`.
1755 fn parse_yield_expr(&mut self) -> PResult<'a, P<Expr>> {
1756 let lo = self.prev_token.span;
1757 let kind = ExprKind::Yield(self.parse_expr_opt()?);
1758 let span = lo.to(self.prev_token.span);
1759 self.sess.gated_spans.gate(sym::generators, span);
1760 let expr = self.mk_expr(span, kind);
1761 self.maybe_recover_from_bad_qpath(expr)
1764 /// Returns a string literal if the next token is a string literal.
1765 /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
1766 /// and returns `None` if the next token is not literal at all.
1767 pub fn parse_str_lit(&mut self) -> Result<ast::StrLit, Option<Lit>> {
1768 match self.parse_opt_lit() {
1769 Some(lit) => match lit.kind {
1770 ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
1772 symbol: lit.token_lit.symbol,
1773 suffix: lit.token_lit.suffix,
1777 _ => Err(Some(lit)),
1783 pub(super) fn parse_lit(&mut self) -> PResult<'a, Lit> {
1784 self.parse_opt_lit().ok_or(()).or_else(|()| {
1785 if let token::Interpolated(inner) = &self.token.kind {
1786 let expr = match inner.as_ref() {
1787 token::NtExpr(expr) => Some(expr),
1788 token::NtLiteral(expr) => Some(expr),
1791 if let Some(expr) = expr {
1792 if matches!(expr.kind, ExprKind::Err) {
1793 let mut err = InvalidInterpolatedExpression { span: self.token.span }
1794 .into_diagnostic(&self.sess.span_diagnostic);
1795 err.downgrade_to_delayed_bug();
1800 let token = self.token.clone();
1801 let err = |self_: &mut Self| {
1802 let msg = format!("unexpected token: {}", super::token_descr(&token));
1803 self_.struct_span_err(token.span, &msg)
1805 // On an error path, eagerly consider a lifetime to be an unclosed character lit
1806 if self.token.is_lifetime() {
1807 let lt = self.expect_lifetime();
1808 Ok(self.recover_unclosed_char(lt.ident, err))
1815 /// Matches `lit = true | false | token_lit`.
1816 /// Returns `None` if the next token is not a literal.
1817 pub(super) fn parse_opt_lit(&mut self) -> Option<Lit> {
1818 let mut recovered = None;
1819 if self.token == token::Dot {
1820 // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
1821 // dot would follow an optional literal, so we do this unconditionally.
1822 recovered = self.look_ahead(1, |next_token| {
1823 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
1826 if self.token.span.hi() == next_token.span.lo() {
1827 let s = String::from("0.") + symbol.as_str();
1828 let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
1829 return Some(Token::new(kind, self.token.span.to(next_token.span)));
1834 if let Some(token) = &recovered {
1836 self.sess.emit_err(FloatLiteralRequiresIntegerPart {
1838 correct: pprust::token_to_string(token).into_owned(),
1843 let token = recovered.as_ref().unwrap_or(&self.token);
1844 match Lit::from_token(token) {
1849 Err(LitError::NotLiteral) => None,
1851 let span = token.span;
1852 let token::Literal(lit) = token.kind else {
1856 self.report_lit_error(err, lit, span);
1857 // Pack possible quotes and prefixes from the original literal into
1858 // the error literal's symbol so they can be pretty-printed faithfully.
1859 let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
1860 let symbol = Symbol::intern(&suffixless_lit.to_string());
1861 let lit = token::Lit::new(token::Err, symbol, lit.suffix);
1862 Some(Lit::from_token_lit(lit, span).unwrap_or_else(|_| unreachable!()))
1867 fn report_lit_error(&self, err: LitError, lit: token::Lit, span: Span) {
1868 // Checks if `s` looks like i32 or u1234 etc.
1869 fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
1870 s.len() > 1 && s.starts_with(first_chars) && s[1..].chars().all(|c| c.is_ascii_digit())
1873 // Try to lowercase the prefix if it's a valid base prefix.
1874 fn fix_base_capitalisation(s: &str) -> Option<String> {
1875 if let Some(stripped) = s.strip_prefix('B') {
1876 Some(format!("0b{stripped}"))
1877 } else if let Some(stripped) = s.strip_prefix('O') {
1878 Some(format!("0o{stripped}"))
1879 } else if let Some(stripped) = s.strip_prefix('X') {
1880 Some(format!("0x{stripped}"))
1886 let token::Lit { kind, suffix, .. } = lit;
1888 // `NotLiteral` is not an error by itself, so we don't report
1889 // it and give the parser opportunity to try something else.
1890 LitError::NotLiteral => {}
1891 // `LexerError` *is* an error, but it was already reported
1892 // by lexer, so here we don't report it the second time.
1893 LitError::LexerError => {}
1894 LitError::InvalidSuffix => {
1895 if let Some(suffix) = suffix {
1896 self.sess.emit_err(InvalidLiteralSuffix {
1898 kind: format!("{}", kind.descr()),
1903 LitError::InvalidIntSuffix => {
1904 let suf = suffix.expect("suffix error with no suffix");
1905 let suf = suf.as_str();
1906 if looks_like_width_suffix(&['i', 'u'], &suf) {
1907 // If it looks like a width, try to be helpful.
1908 self.sess.emit_err(InvalidIntLiteralWidth { span, width: suf[1..].into() });
1909 } else if let Some(fixed) = fix_base_capitalisation(suf) {
1910 self.sess.emit_err(InvalidNumLiteralBasePrefix { span, fixed });
1912 self.sess.emit_err(InvalidNumLiteralSuffix { span, suffix: suf.to_string() });
1915 LitError::InvalidFloatSuffix => {
1916 let suf = suffix.expect("suffix error with no suffix");
1917 let suf = suf.as_str();
1918 if looks_like_width_suffix(&['f'], suf) {
1919 // If it looks like a width, try to be helpful.
1921 .emit_err(InvalidFloatLiteralWidth { span, width: suf[1..].to_string() });
1923 self.sess.emit_err(InvalidFloatLiteralSuffix { span, suffix: suf.to_string() });
1926 LitError::NonDecimalFloat(base) => {
1928 16 => self.sess.emit_err(HexadecimalFloatLiteralNotSupported { span }),
1929 8 => self.sess.emit_err(OctalFloatLiteralNotSupported { span }),
1930 2 => self.sess.emit_err(BinaryFloatLiteralNotSupported { span }),
1931 _ => unreachable!(),
1934 LitError::IntTooLarge => {
1935 self.sess.emit_err(IntLiteralTooLarge { span });
1940 pub(super) fn expect_no_tuple_index_suffix(&self, span: Span, suffix: Symbol) {
1941 if [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suffix) {
1942 // #59553: warn instead of reject out of hand to allow the fix to percolate
1943 // through the ecosystem when people fix their macros
1944 self.sess.emit_warning(InvalidLiteralSuffixOnTupleIndex {
1947 exception: Some(()),
1950 self.sess.emit_err(InvalidLiteralSuffixOnTupleIndex { span, suffix, exception: None });
1954 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1955 /// Keep this in sync with `Token::can_begin_literal_maybe_minus`.
1956 pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1957 maybe_whole_expr!(self);
1959 let lo = self.token.span;
1960 let minus_present = self.eat(&token::BinOp(token::Minus));
1961 let lit = self.parse_lit()?;
1962 let expr = self.mk_expr(lit.span, ExprKind::Lit(lit));
1965 Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_unary(UnOp::Neg, expr)))
1971 fn is_array_like_block(&mut self) -> bool {
1972 self.look_ahead(1, |t| matches!(t.kind, TokenKind::Ident(..) | TokenKind::Literal(_)))
1973 && self.look_ahead(2, |t| t == &token::Comma)
1974 && self.look_ahead(3, |t| t.can_begin_expr())
1977 /// Emits a suggestion if it looks like the user meant an array but
1978 /// accidentally used braces, causing the code to be interpreted as a block
1980 fn maybe_suggest_brackets_instead_of_braces(&mut self, lo: Span) -> Option<P<Expr>> {
1981 let mut snapshot = self.create_snapshot_for_diagnostic();
1982 match snapshot.parse_array_or_repeat_expr(Delimiter::Brace) {
1984 self.sess.emit_err(ArrayBracketsInsteadOfSpaces {
1986 sub: ArrayBracketsInsteadOfSpacesSugg {
1988 right: snapshot.prev_token.span,
1992 self.restore_snapshot(snapshot);
1993 Some(self.mk_expr_err(arr.span))
2002 fn suggest_missing_semicolon_before_array(
2005 open_delim_span: Span,
2006 ) -> PResult<'a, ()> {
2007 if !self.may_recover() {
2011 if self.token.kind == token::Comma {
2012 if !self.sess.source_map().is_multiline(prev_span.until(self.token.span)) {
2015 let mut snapshot = self.create_snapshot_for_diagnostic();
2017 match snapshot.parse_seq_to_before_end(
2018 &token::CloseDelim(Delimiter::Bracket),
2019 SeqSep::trailing_allowed(token::Comma),
2023 // When the close delim is `)`, `token.kind` is expected to be `token::CloseDelim(Delimiter::Parenthesis)`,
2024 // but the actual `token.kind` is `token::CloseDelim(Delimiter::Bracket)`.
2025 // This is because the `token.kind` of the close delim is treated as the same as
2026 // that of the open delim in `TokenTreesReader::parse_token_tree`, even if the delimiters of them are different.
2027 // Therefore, `token.kind` should not be compared here.
2029 .span_to_snippet(snapshot.token.span)
2030 .map_or(false, |snippet| snippet == "]") =>
2032 return Err(MissingSemicolonBeforeArray {
2033 open_delim: open_delim_span,
2034 semicolon: prev_span.shrink_to_hi(),
2035 }.into_diagnostic(&self.sess.span_diagnostic));
2038 Err(err) => err.cancel(),
2044 /// Parses a block or unsafe block.
2045 pub(super) fn parse_block_expr(
2047 opt_label: Option<Label>,
2049 blk_mode: BlockCheckMode,
2050 ) -> PResult<'a, P<Expr>> {
2051 if self.may_recover() && self.is_array_like_block() {
2052 if let Some(arr) = self.maybe_suggest_brackets_instead_of_braces(lo) {
2057 if self.token.is_whole_block() {
2058 self.sess.emit_err(InvalidBlockMacroSegment {
2059 span: self.token.span,
2060 context: lo.to(self.token.span),
2064 let (attrs, blk) = self.parse_block_common(lo, blk_mode)?;
2065 Ok(self.mk_expr_with_attrs(blk.span, ExprKind::Block(blk, opt_label), attrs))
2068 /// Parse a block which takes no attributes and has no label
2069 fn parse_simple_block(&mut self) -> PResult<'a, P<Expr>> {
2070 let blk = self.parse_block()?;
2071 Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None)))
2074 /// Parses a closure expression (e.g., `move |args| expr`).
2075 fn parse_closure_expr(&mut self) -> PResult<'a, P<Expr>> {
2076 let lo = self.token.span;
2078 let binder = if self.check_keyword(kw::For) {
2079 let lo = self.token.span;
2080 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
2081 let span = lo.to(self.prev_token.span);
2083 self.sess.gated_spans.gate(sym::closure_lifetime_binder, span);
2085 ClosureBinder::For { span, generic_params: P::from_vec(lifetime_defs) }
2087 ClosureBinder::NotPresent
2091 if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
2093 let asyncness = if self.token.uninterpolated_span().rust_2018() {
2094 self.parse_asyncness(Case::Sensitive)
2099 let capture_clause = self.parse_capture_clause()?;
2100 let decl = self.parse_fn_block_decl()?;
2101 let decl_hi = self.prev_token.span;
2102 let mut body = match decl.output {
2103 FnRetTy::Default(_) => {
2104 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
2105 self.parse_expr_res(restrictions, None)?
2108 // If an explicit return type is given, require a block to appear (RFC 968).
2109 let body_lo = self.token.span;
2110 self.parse_block_expr(None, body_lo, BlockCheckMode::Default)?
2114 if let Async::Yes { span, .. } = asyncness {
2115 // Feature-gate `async ||` closures.
2116 self.sess.gated_spans.gate(sym::async_closure, span);
2119 if self.token.kind == TokenKind::Semi
2120 && matches!(self.token_cursor.frame.delim_sp, Some((Delimiter::Parenthesis, _)))
2121 // HACK: This is needed so we can detect whether we're inside a macro,
2122 // where regular assumptions about what tokens can follow other tokens
2123 // don't necessarily apply.
2124 && self.may_recover()
2125 // FIXME(Nilstrieb): Remove this check once `may_recover` actually stops recovery
2126 && self.subparser_name.is_none()
2128 // It is likely that the closure body is a block but where the
2129 // braces have been removed. We will recover and eat the next
2130 // statements later in the parsing process.
2131 body = self.mk_expr_err(body.span);
2134 let body_span = body.span;
2136 let closure = self.mk_expr(
2149 // Disable recovery for closure body
2151 ClosureSpans { whole_closure: closure.span, closing_pipe: decl_hi, body: body_span };
2152 self.current_closure = Some(spans);
2157 /// Parses an optional `move` prefix to a closure-like construct.
2158 fn parse_capture_clause(&mut self) -> PResult<'a, CaptureBy> {
2159 if self.eat_keyword(kw::Move) {
2160 // Check for `move async` and recover
2161 if self.check_keyword(kw::Async) {
2162 let move_async_span = self.token.span.with_lo(self.prev_token.span.data().lo);
2163 Err(AsyncMoveOrderIncorrect { span: move_async_span }
2164 .into_diagnostic(&self.sess.span_diagnostic))
2166 Ok(CaptureBy::Value)
2173 /// Parses the `|arg, arg|` header of a closure.
2174 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
2175 let inputs = if self.eat(&token::OrOr) {
2178 self.expect(&token::BinOp(token::Or))?;
2180 .parse_seq_to_before_tokens(
2181 &[&token::BinOp(token::Or), &token::OrOr],
2182 SeqSep::trailing_allowed(token::Comma),
2183 TokenExpectType::NoExpect,
2184 |p| p.parse_fn_block_param(),
2191 self.parse_ret_ty(AllowPlus::Yes, RecoverQPath::Yes, RecoverReturnSign::Yes)?;
2193 Ok(P(FnDecl { inputs, output }))
2196 /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
2197 fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
2198 let lo = self.token.span;
2199 let attrs = self.parse_outer_attributes()?;
2200 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2201 let pat = this.parse_pat_no_top_alt(PARAM_EXPECTED)?;
2202 let ty = if this.eat(&token::Colon) {
2205 this.mk_ty(this.prev_token.span, TyKind::Infer)
2213 span: lo.to(this.prev_token.span),
2215 is_placeholder: false,
2217 TrailingToken::MaybeComma,
2222 /// Parses an `if` expression (`if` token already eaten).
2223 fn parse_if_expr(&mut self) -> PResult<'a, P<Expr>> {
2224 let lo = self.prev_token.span;
2225 let cond = self.parse_cond_expr()?;
2226 self.parse_if_after_cond(lo, cond)
2229 fn parse_if_after_cond(&mut self, lo: Span, mut cond: P<Expr>) -> PResult<'a, P<Expr>> {
2230 let cond_span = cond.span;
2231 // Tries to interpret `cond` as either a missing expression if it's a block,
2232 // or as an unfinished expression if it's a binop and the RHS is a block.
2233 // We could probably add more recoveries here too...
2234 let mut recover_block_from_condition = |this: &mut Self| {
2235 let block = match &mut cond.kind {
2236 ExprKind::Binary(Spanned { span: binop_span, .. }, _, right)
2237 if let ExprKind::Block(_, None) = right.kind => {
2238 self.sess.emit_err(IfExpressionMissingThenBlock {
2240 sub: IfExpressionMissingThenBlockSub::UnfinishedCondition(
2241 cond_span.shrink_to_lo().to(*binop_span)
2244 std::mem::replace(right, this.mk_expr_err(binop_span.shrink_to_hi()))
2246 ExprKind::Block(_, None) => {
2247 self.sess.emit_err(IfExpressionMissingCondition {
2248 if_span: lo.shrink_to_hi(),
2249 block_span: self.sess.source_map().start_point(cond_span),
2251 std::mem::replace(&mut cond, this.mk_expr_err(cond_span.shrink_to_hi()))
2257 if let ExprKind::Block(block, _) = &block.kind {
2264 let thn = if self.token.is_keyword(kw::Else) {
2265 if let Some(block) = recover_block_from_condition(self) {
2268 self.sess.emit_err(IfExpressionMissingThenBlock {
2270 sub: IfExpressionMissingThenBlockSub::AddThenBlock(cond_span.shrink_to_hi()),
2272 self.mk_block_err(cond_span.shrink_to_hi())
2275 let attrs = self.parse_outer_attributes()?.take_for_recovery(); // For recovery.
2276 let block = if self.check(&token::OpenDelim(Delimiter::Brace)) {
2279 if let Some(block) = recover_block_from_condition(self) {
2282 // Parse block, which will always fail, but we can add a nice note to the error
2283 self.parse_block().map_err(|mut err| {
2286 "the `if` expression is missing a block after this condition",
2292 self.error_on_if_block_attrs(lo, false, block.span, &attrs);
2295 let els = if self.eat_keyword(kw::Else) { Some(self.parse_else_expr()?) } else { None };
2296 Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::If(cond, thn, els)))
2299 /// Parses the condition of a `if` or `while` expression.
2300 fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
2302 self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL | Restrictions::ALLOW_LET, None)?;
2304 if let ExprKind::Let(..) = cond.kind {
2305 // Remove the last feature gating of a `let` expression since it's stable.
2306 self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
2312 /// Parses a `let $pat = $expr` pseudo-expression.
2313 fn parse_let_expr(&mut self) -> PResult<'a, P<Expr>> {
2314 // This is a *approximate* heuristic that detects if `let` chains are
2315 // being parsed in the right position. It's approximate because it
2316 // doesn't deny all invalid `let` expressions, just completely wrong usages.
2317 let not_in_chain = !matches!(
2318 self.prev_token.kind,
2319 TokenKind::AndAnd | TokenKind::Ident(kw::If, _) | TokenKind::Ident(kw::While, _)
2321 if !self.restrictions.contains(Restrictions::ALLOW_LET) || not_in_chain {
2322 self.sess.emit_err(ExpectedExpressionFoundLet { span: self.token.span });
2325 self.bump(); // Eat `let` token
2326 let lo = self.prev_token.span;
2327 let pat = self.parse_pat_allow_top_alt(
2331 CommaRecoveryMode::LikelyTuple,
2333 if self.token == token::EqEq {
2334 self.sess.emit_err(ExpectedEqForLetExpr {
2335 span: self.token.span,
2336 sugg_span: self.token.span,
2340 self.expect(&token::Eq)?;
2342 let expr = self.with_res(self.restrictions | Restrictions::NO_STRUCT_LITERAL, |this| {
2343 this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
2345 let span = lo.to(expr.span);
2346 self.sess.gated_spans.gate(sym::let_chains, span);
2347 Ok(self.mk_expr(span, ExprKind::Let(pat, expr, span)))
2350 /// Parses an `else { ... }` expression (`else` token already eaten).
2351 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
2352 let else_span = self.prev_token.span; // `else`
2353 let attrs = self.parse_outer_attributes()?.take_for_recovery(); // For recovery.
2354 let expr = if self.eat_keyword(kw::If) {
2355 self.parse_if_expr()?
2356 } else if self.check(&TokenKind::OpenDelim(Delimiter::Brace)) {
2357 self.parse_simple_block()?
2359 let snapshot = self.create_snapshot_for_diagnostic();
2360 let first_tok = super::token_descr(&self.token);
2361 let first_tok_span = self.token.span;
2362 match self.parse_expr() {
2364 // If it's not a free-standing expression, and is followed by a block,
2365 // then it's very likely the condition to an `else if`.
2366 if self.check(&TokenKind::OpenDelim(Delimiter::Brace))
2367 && classify::expr_requires_semi_to_be_stmt(&cond) =>
2369 self.sess.emit_err(ExpectedElseBlock {
2373 condition_start: cond.span.shrink_to_lo(),
2375 self.parse_if_after_cond(cond.span.shrink_to_lo(), cond)?
2379 self.restore_snapshot(snapshot);
2380 self.parse_simple_block()?
2383 self.restore_snapshot(snapshot);
2384 self.parse_simple_block()?
2388 self.error_on_if_block_attrs(else_span, true, expr.span, &attrs);
2392 fn error_on_if_block_attrs(
2397 attrs: &[ast::Attribute],
2399 let (attributes, last) = match attrs {
2401 [x0 @ xn] | [x0, .., xn] => (x0.span.to(xn.span), xn.span),
2403 let ctx = if is_ctx_else { "else" } else { "if" };
2404 self.sess.emit_err(OuterAttributeNotAllowedOnIfElse {
2408 ctx: ctx.to_string(),
2413 /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
2414 fn parse_for_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2415 // Record whether we are about to parse `for (`.
2416 // This is used below for recovery in case of `for ( $stuff ) $block`
2417 // in which case we will suggest `for $stuff $block`.
2418 let begin_paren = match self.token.kind {
2419 token::OpenDelim(Delimiter::Parenthesis) => Some(self.token.span),
2423 let pat = self.parse_pat_allow_top_alt(
2427 CommaRecoveryMode::LikelyTuple,
2429 if !self.eat_keyword(kw::In) {
2430 self.error_missing_in_for_loop();
2432 self.check_for_for_in_in_typo(self.prev_token.span);
2433 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2435 let pat = self.recover_parens_around_for_head(pat, begin_paren);
2437 let (attrs, loop_block) = self.parse_inner_attrs_and_block()?;
2439 let kind = ExprKind::ForLoop(pat, expr, loop_block, opt_label);
2440 Ok(self.mk_expr_with_attrs(lo.to(self.prev_token.span), kind, attrs))
2443 fn error_missing_in_for_loop(&mut self) {
2444 let (span, sub): (_, fn(_) -> _) = if self.token.is_ident_named(sym::of) {
2445 // Possibly using JS syntax (#75311).
2446 let span = self.token.span;
2448 (span, MissingInInForLoopSub::InNotOf)
2450 (self.prev_token.span.between(self.token.span), MissingInInForLoopSub::AddIn)
2453 self.sess.emit_err(MissingInInForLoop { span, sub: sub(span) });
2456 /// Parses a `while` or `while let` expression (`while` token already eaten).
2457 fn parse_while_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2458 let cond = self.parse_cond_expr().map_err(|mut err| {
2459 err.span_label(lo, "while parsing the condition of this `while` expression");
2462 let (attrs, body) = self.parse_inner_attrs_and_block().map_err(|mut err| {
2463 err.span_label(lo, "while parsing the body of this `while` expression");
2464 err.span_label(cond.span, "this `while` condition successfully parsed");
2467 Ok(self.mk_expr_with_attrs(
2468 lo.to(self.prev_token.span),
2469 ExprKind::While(cond, body, opt_label),
2474 /// Parses `loop { ... }` (`loop` token already eaten).
2475 fn parse_loop_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2476 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2477 Ok(self.mk_expr_with_attrs(
2478 lo.to(self.prev_token.span),
2479 ExprKind::Loop(body, opt_label),
2484 pub(crate) fn eat_label(&mut self) -> Option<Label> {
2485 self.token.lifetime().map(|ident| {
2491 /// Parses a `match ... { ... }` expression (`match` token already eaten).
2492 fn parse_match_expr(&mut self) -> PResult<'a, P<Expr>> {
2493 let match_span = self.prev_token.span;
2494 let lo = self.prev_token.span;
2495 let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2496 if let Err(mut e) = self.expect(&token::OpenDelim(Delimiter::Brace)) {
2497 if self.token == token::Semi {
2498 e.span_suggestion_short(
2500 "try removing this `match`",
2502 Applicability::MaybeIncorrect, // speculative
2505 if self.maybe_recover_unexpected_block_label() {
2512 let attrs = self.parse_inner_attributes()?;
2514 let mut arms: Vec<Arm> = Vec::new();
2515 while self.token != token::CloseDelim(Delimiter::Brace) {
2516 match self.parse_arm() {
2517 Ok(arm) => arms.push(arm),
2519 // Recover by skipping to the end of the block.
2521 self.recover_stmt();
2522 let span = lo.to(self.token.span);
2523 if self.token == token::CloseDelim(Delimiter::Brace) {
2526 return Ok(self.mk_expr_with_attrs(
2528 ExprKind::Match(scrutinee, arms),
2534 let hi = self.token.span;
2536 Ok(self.mk_expr_with_attrs(lo.to(hi), ExprKind::Match(scrutinee, arms), attrs))
2539 /// Attempt to recover from match arm body with statements and no surrounding braces.
2540 fn parse_arm_body_missing_braces(
2542 first_expr: &P<Expr>,
2544 ) -> Option<P<Expr>> {
2545 if self.token.kind != token::Semi {
2548 let start_snapshot = self.create_snapshot_for_diagnostic();
2549 let semi_sp = self.token.span;
2552 vec![self.mk_stmt(first_expr.span, ast::StmtKind::Expr(first_expr.clone()))];
2553 let err = |this: &Parser<'_>, stmts: Vec<ast::Stmt>| {
2554 let span = stmts[0].span.to(stmts[stmts.len() - 1].span);
2556 this.sess.emit_err(MatchArmBodyWithoutBraces {
2559 num_statements: stmts.len(),
2560 sub: if stmts.len() > 1 {
2561 MatchArmBodyWithoutBracesSugg::AddBraces {
2562 left: span.shrink_to_lo(),
2563 right: span.shrink_to_hi(),
2566 MatchArmBodyWithoutBracesSugg::UseComma { semicolon: semi_sp }
2569 this.mk_expr_err(span)
2571 // We might have either a `,` -> `;` typo, or a block without braces. We need
2572 // a more subtle parsing strategy.
2574 if self.token.kind == token::CloseDelim(Delimiter::Brace) {
2575 // We have reached the closing brace of the `match` expression.
2576 return Some(err(self, stmts));
2578 if self.token.kind == token::Comma {
2579 self.restore_snapshot(start_snapshot);
2582 let pre_pat_snapshot = self.create_snapshot_for_diagnostic();
2583 match self.parse_pat_no_top_alt(None) {
2585 if self.token.kind == token::FatArrow {
2587 self.restore_snapshot(pre_pat_snapshot);
2588 return Some(err(self, stmts));
2596 self.restore_snapshot(pre_pat_snapshot);
2597 match self.parse_stmt_without_recovery(true, ForceCollect::No) {
2598 // Consume statements for as long as possible.
2603 self.restore_snapshot(start_snapshot);
2606 // We couldn't parse either yet another statement missing it's
2607 // enclosing block nor the next arm's pattern or closing brace.
2610 self.restore_snapshot(start_snapshot);
2618 pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
2619 // Used to check the `let_chains` and `if_let_guard` features mostly by scanning
2621 fn check_let_expr(expr: &Expr) -> (bool, bool) {
2623 ExprKind::Binary(BinOp { node: BinOpKind::And, .. }, ref lhs, ref rhs) => {
2624 let lhs_rslt = check_let_expr(lhs);
2625 let rhs_rslt = check_let_expr(rhs);
2626 (lhs_rslt.0 || rhs_rslt.0, false)
2628 ExprKind::Let(..) => (true, true),
2632 let attrs = self.parse_outer_attributes()?;
2633 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2634 let lo = this.token.span;
2635 let pat = this.parse_pat_allow_top_alt(
2639 CommaRecoveryMode::EitherTupleOrPipe,
2641 let guard = if this.eat_keyword(kw::If) {
2642 let if_span = this.prev_token.span;
2643 let cond = this.parse_expr_res(Restrictions::ALLOW_LET, None)?;
2644 let (has_let_expr, does_not_have_bin_op) = check_let_expr(&cond);
2646 if does_not_have_bin_op {
2647 // Remove the last feature gating of a `let` expression since it's stable.
2648 this.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
2650 let span = if_span.to(cond.span);
2651 this.sess.gated_spans.gate(sym::if_let_guard, span);
2657 let arrow_span = this.token.span;
2658 if let Err(mut err) = this.expect(&token::FatArrow) {
2659 // We might have a `=>` -> `=` or `->` typo (issue #89396).
2660 if TokenKind::FatArrow
2662 .map_or(false, |similar_tokens| similar_tokens.contains(&this.token.kind))
2664 err.span_suggestion(
2666 "try using a fat arrow here",
2668 Applicability::MaybeIncorrect,
2676 let arm_start_span = this.token.span;
2678 let expr = this.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
2679 err.span_label(arrow_span, "while parsing the `match` arm starting here");
2683 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
2684 && this.token != token::CloseDelim(Delimiter::Brace);
2686 let hi = this.prev_token.span;
2689 let sm = this.sess.source_map();
2690 if let Some(body) = this.parse_arm_body_missing_braces(&expr, arrow_span) {
2691 let span = body.span;
2700 is_placeholder: false,
2702 TrailingToken::None,
2705 this.expect_one_of(&[token::Comma], &[token::CloseDelim(Delimiter::Brace)])
2706 .or_else(|mut err| {
2707 if this.token == token::FatArrow {
2708 if let Ok(expr_lines) = sm.span_to_lines(expr.span)
2709 && let Ok(arm_start_lines) = sm.span_to_lines(arm_start_span)
2710 && arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
2711 && expr_lines.lines.len() == 2
2713 // We check whether there's any trailing code in the parse span,
2714 // if there isn't, we very likely have the following:
2717 // | -- - missing comma
2721 // | - ^^ self.token.span
2723 // | parsed until here as `"y" & X`
2724 err.span_suggestion_short(
2725 arm_start_span.shrink_to_hi(),
2726 "missing a comma here to end this `match` arm",
2728 Applicability::MachineApplicable,
2733 // FIXME(compiler-errors): We could also recover `; PAT =>` here
2735 // Try to parse a following `PAT =>`, if successful
2736 // then we should recover.
2737 let mut snapshot = this.create_snapshot_for_diagnostic();
2738 let pattern_follows = snapshot
2739 .parse_pat_allow_top_alt(
2743 CommaRecoveryMode::EitherTupleOrPipe,
2745 .map_err(|err| err.cancel())
2747 if pattern_follows && snapshot.check(&TokenKind::FatArrow) {
2749 this.sess.emit_err(MissingCommaAfterMatchArm {
2750 span: hi.shrink_to_hi(),
2755 err.span_label(arrow_span, "while parsing the `match` arm starting here");
2759 this.eat(&token::Comma);
2770 is_placeholder: false,
2772 TrailingToken::None,
2777 /// Parses a `try {...}` expression (`try` token already eaten).
2778 fn parse_try_block(&mut self, span_lo: Span) -> PResult<'a, P<Expr>> {
2779 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2780 if self.eat_keyword(kw::Catch) {
2781 Err(CatchAfterTry { span: self.prev_token.span }
2782 .into_diagnostic(&self.sess.span_diagnostic))
2784 let span = span_lo.to(body.span);
2785 self.sess.gated_spans.gate(sym::try_blocks, span);
2786 Ok(self.mk_expr_with_attrs(span, ExprKind::TryBlock(body), attrs))
2790 fn is_do_catch_block(&self) -> bool {
2791 self.token.is_keyword(kw::Do)
2792 && self.is_keyword_ahead(1, &[kw::Catch])
2793 && self.look_ahead(2, |t| *t == token::OpenDelim(Delimiter::Brace))
2794 && !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
2797 fn is_do_yeet(&self) -> bool {
2798 self.token.is_keyword(kw::Do) && self.is_keyword_ahead(1, &[kw::Yeet])
2801 fn is_try_block(&self) -> bool {
2802 self.token.is_keyword(kw::Try)
2803 && self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace))
2804 && self.token.uninterpolated_span().rust_2018()
2807 /// Parses an `async move? {...}` expression.
2808 fn parse_async_block(&mut self) -> PResult<'a, P<Expr>> {
2809 let lo = self.token.span;
2810 self.expect_keyword(kw::Async)?;
2811 let capture_clause = self.parse_capture_clause()?;
2812 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2813 let kind = ExprKind::Async(capture_clause, DUMMY_NODE_ID, body);
2814 Ok(self.mk_expr_with_attrs(lo.to(self.prev_token.span), kind, attrs))
2817 fn is_async_block(&self) -> bool {
2818 self.token.is_keyword(kw::Async)
2821 self.is_keyword_ahead(1, &[kw::Move])
2822 && self.look_ahead(2, |t| *t == token::OpenDelim(Delimiter::Brace))
2825 self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace))
2829 fn is_certainly_not_a_block(&self) -> bool {
2830 self.look_ahead(1, |t| t.is_ident())
2832 // `{ ident, ` cannot start a block.
2833 self.look_ahead(2, |t| t == &token::Comma)
2834 || self.look_ahead(2, |t| t == &token::Colon)
2836 // `{ ident: token, ` cannot start a block.
2837 self.look_ahead(4, |t| t == &token::Comma) ||
2838 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
2839 self.look_ahead(3, |t| !t.can_begin_type())
2844 fn maybe_parse_struct_expr(
2846 qself: Option<&ast::QSelf>,
2848 ) -> Option<PResult<'a, P<Expr>>> {
2849 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
2850 if struct_allowed || self.is_certainly_not_a_block() {
2851 if let Err(err) = self.expect(&token::OpenDelim(Delimiter::Brace)) {
2852 return Some(Err(err));
2854 let expr = self.parse_struct_expr(qself.cloned(), path.clone(), true);
2855 if let (Ok(expr), false) = (&expr, struct_allowed) {
2856 // This is a struct literal, but we don't can't accept them here.
2857 self.sess.emit_err(StructLiteralNotAllowedHere {
2859 sub: StructLiteralNotAllowedHereSugg {
2860 left: path.span.shrink_to_lo(),
2861 right: expr.span.shrink_to_hi(),
2870 pub(super) fn parse_struct_fields(
2874 close_delim: Delimiter,
2875 ) -> PResult<'a, (Vec<ExprField>, ast::StructRest, bool)> {
2876 let mut fields = Vec::new();
2877 let mut base = ast::StructRest::None;
2878 let mut recover_async = false;
2880 let mut async_block_err = |e: &mut Diagnostic, span: Span| {
2881 recover_async = true;
2882 e.span_label(span, "`async` blocks are only allowed in Rust 2018 or later");
2883 e.help_use_latest_edition();
2886 while self.token != token::CloseDelim(close_delim) {
2887 if self.eat(&token::DotDot) || self.recover_struct_field_dots(close_delim) {
2888 let exp_span = self.prev_token.span;
2889 // We permit `.. }` on the left-hand side of a destructuring assignment.
2890 if self.check(&token::CloseDelim(close_delim)) {
2891 base = ast::StructRest::Rest(self.prev_token.span.shrink_to_hi());
2894 match self.parse_expr() {
2895 Ok(e) => base = ast::StructRest::Base(e),
2896 Err(mut e) if recover => {
2898 self.recover_stmt();
2900 Err(e) => return Err(e),
2902 self.recover_struct_comma_after_dotdot(exp_span);
2906 let recovery_field = self.find_struct_error_after_field_looking_code();
2907 let parsed_field = match self.parse_expr_field() {
2910 if pth == kw::Async {
2911 async_block_err(&mut e, pth.span);
2913 e.span_label(pth.span, "while parsing this struct");
2917 // If the next token is a comma, then try to parse
2918 // what comes next as additional fields, rather than
2919 // bailing out until next `}`.
2920 if self.token != token::Comma {
2921 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2922 if self.token != token::Comma {
2930 let is_shorthand = parsed_field.as_ref().map_or(false, |f| f.is_shorthand);
2931 // A shorthand field can be turned into a full field with `:`.
2932 // We should point this out.
2933 self.check_or_expected(!is_shorthand, TokenType::Token(token::Colon));
2935 match self.expect_one_of(&[token::Comma], &[token::CloseDelim(close_delim)]) {
2937 if let Some(f) = parsed_field.or(recovery_field) {
2938 // Only include the field if there's no parse error for the field name.
2943 if pth == kw::Async {
2944 async_block_err(&mut e, pth.span);
2946 e.span_label(pth.span, "while parsing this struct");
2947 if let Some(f) = recovery_field {
2950 self.prev_token.span.shrink_to_hi(),
2951 "try adding a comma",
2953 Applicability::MachineApplicable,
2955 } else if is_shorthand
2956 && (AssocOp::from_token(&self.token).is_some()
2957 || matches!(&self.token.kind, token::OpenDelim(_))
2958 || self.token.kind == token::Dot)
2960 // Looks like they tried to write a shorthand, complex expression.
2961 let ident = parsed_field.expect("is_shorthand implies Some").ident;
2963 ident.span.shrink_to_lo(),
2964 "try naming a field",
2965 &format!("{ident}: "),
2966 Applicability::HasPlaceholders,
2974 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2975 self.eat(&token::Comma);
2979 Ok((fields, base, recover_async))
2982 /// Precondition: already parsed the '{'.
2983 pub(super) fn parse_struct_expr(
2985 qself: Option<ast::QSelf>,
2988 ) -> PResult<'a, P<Expr>> {
2990 let (fields, base, recover_async) =
2991 self.parse_struct_fields(pth.clone(), recover, Delimiter::Brace)?;
2992 let span = lo.to(self.token.span);
2993 self.expect(&token::CloseDelim(Delimiter::Brace))?;
2994 let expr = if recover_async {
2997 ExprKind::Struct(P(ast::StructExpr { qself, path: pth, fields, rest: base }))
2999 Ok(self.mk_expr(span, expr))
3002 /// Use in case of error after field-looking code: `S { foo: () with a }`.
3003 fn find_struct_error_after_field_looking_code(&self) -> Option<ExprField> {
3004 match self.token.ident() {
3005 Some((ident, is_raw))
3006 if (is_raw || !ident.is_reserved())
3007 && self.look_ahead(1, |t| *t == token::Colon) =>
3009 Some(ast::ExprField {
3011 span: self.token.span,
3012 expr: self.mk_expr_err(self.token.span),
3013 is_shorthand: false,
3014 attrs: AttrVec::new(),
3016 is_placeholder: false,
3023 fn recover_struct_comma_after_dotdot(&mut self, span: Span) {
3024 if self.token != token::Comma {
3027 self.sess.emit_err(CommaAfterBaseStruct {
3028 span: span.to(self.prev_token.span),
3029 comma: self.token.span,
3031 self.recover_stmt();
3034 fn recover_struct_field_dots(&mut self, close_delim: Delimiter) -> bool {
3035 if !self.look_ahead(1, |t| *t == token::CloseDelim(close_delim))
3036 && self.eat(&token::DotDotDot)
3038 // recover from typo of `...`, suggest `..`
3039 let span = self.prev_token.span;
3040 self.sess.emit_err(MissingDotDot { token_span: span, sugg_span: span });
3046 /// Parses `ident (COLON expr)?`.
3047 fn parse_expr_field(&mut self) -> PResult<'a, ExprField> {
3048 let attrs = self.parse_outer_attributes()?;
3049 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
3050 let lo = this.token.span;
3052 // Check if a colon exists one ahead. This means we're parsing a fieldname.
3053 let is_shorthand = !this.look_ahead(1, |t| t == &token::Colon || t == &token::Eq);
3054 let (ident, expr) = if is_shorthand {
3055 // Mimic `x: x` for the `x` field shorthand.
3056 let ident = this.parse_ident_common(false)?;
3057 let path = ast::Path::from_ident(ident);
3058 (ident, this.mk_expr(ident.span, ExprKind::Path(None, path)))
3060 let ident = this.parse_field_name()?;
3061 this.error_on_eq_field_init(ident);
3063 (ident, this.parse_expr()?)
3069 span: lo.to(expr.span),
3074 is_placeholder: false,
3076 TrailingToken::MaybeComma,
3081 /// Check for `=`. This means the source incorrectly attempts to
3082 /// initialize a field with an eq rather than a colon.
3083 fn error_on_eq_field_init(&self, field_name: Ident) {
3084 if self.token != token::Eq {
3088 self.sess.emit_err(EqFieldInit {
3089 span: self.token.span,
3090 eq: field_name.span.shrink_to_hi().to(self.token.span),
3094 fn err_dotdotdot_syntax(&self, span: Span) {
3095 self.sess.emit_err(DotDotDot { span });
3098 fn err_larrow_operator(&self, span: Span) {
3099 self.sess.emit_err(LeftArrowOperator { span });
3102 fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
3103 ExprKind::AssignOp(binop, lhs, rhs)
3108 start: Option<P<Expr>>,
3109 end: Option<P<Expr>>,
3110 limits: RangeLimits,
3112 if end.is_none() && limits == RangeLimits::Closed {
3113 self.inclusive_range_with_incorrect_end(self.prev_token.span);
3116 ExprKind::Range(start, end, limits)
3120 fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
3121 ExprKind::Unary(unop, expr)
3124 fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
3125 ExprKind::Binary(binop, lhs, rhs)
3128 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
3129 ExprKind::Index(expr, idx)
3132 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
3133 ExprKind::Call(f, args)
3136 fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> P<Expr> {
3137 let span = lo.to(self.prev_token.span);
3138 let await_expr = self.mk_expr(span, ExprKind::Await(self_arg));
3139 self.recover_from_await_method_call();
3143 pub(crate) fn mk_expr_with_attrs(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
3144 P(Expr { kind, span, attrs, id: DUMMY_NODE_ID, tokens: None })
3147 pub(crate) fn mk_expr(&self, span: Span, kind: ExprKind) -> P<Expr> {
3148 P(Expr { kind, span, attrs: AttrVec::new(), id: DUMMY_NODE_ID, tokens: None })
3151 pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> {
3152 self.mk_expr(span, ExprKind::Err)
3155 /// Create expression span ensuring the span of the parent node
3156 /// is larger than the span of lhs and rhs, including the attributes.
3157 fn mk_expr_sp(&self, lhs: &P<Expr>, lhs_span: Span, rhs_span: Span) -> Span {
3160 .find(|a| a.style == AttrStyle::Outer)
3161 .map_or(lhs_span, |a| a.span)
3165 fn collect_tokens_for_expr(
3168 f: impl FnOnce(&mut Self, ast::AttrVec) -> PResult<'a, P<Expr>>,
3169 ) -> PResult<'a, P<Expr>> {
3170 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
3171 let res = f(this, attrs)?;
3172 let trailing = if this.restrictions.contains(Restrictions::STMT_EXPR)
3173 && this.token.kind == token::Semi
3176 } else if this.token.kind == token::Gt {
3179 // FIXME - pass this through from the place where we know
3180 // we need a comma, rather than assuming that `#[attr] expr,`
3181 // always captures a trailing comma
3182 TrailingToken::MaybeComma