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::classify;
37 use rustc_ast::util::literal::LitError;
38 use rustc_ast::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
39 use rustc_ast::visit::Visitor;
40 use rustc_ast::{self as ast, AttrStyle, AttrVec, CaptureBy, ExprField, Lit, UnOp, DUMMY_NODE_ID};
41 use rustc_ast::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, MacCall, Param, Ty, TyKind};
42 use rustc_ast::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits};
43 use rustc_ast::{ClosureBinder, StmtKind};
44 use rustc_ast_pretty::pprust;
46 Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, IntoDiagnostic, PResult,
49 use rustc_session::errors::ExprParenthesesNeeded;
50 use rustc_session::lint::builtin::BREAK_WITH_LABEL_AND_LOOP;
51 use rustc_session::lint::BuiltinLintDiagnostics;
52 use rustc_span::source_map::{self, Span, Spanned};
53 use rustc_span::symbol::{kw, sym, Ident, Symbol};
54 use rustc_span::{BytePos, Pos};
56 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
57 /// dropped into the token stream, which happens while parsing the result of
58 /// macro expansion). Placement of these is not as complex as I feared it would
59 /// be. The important thing is to make sure that lookahead doesn't balk at
60 /// `token::Interpolated` tokens.
61 macro_rules! maybe_whole_expr {
63 if let token::Interpolated(nt) = &$p.token.kind {
65 token::NtExpr(e) | token::NtLiteral(e) => {
70 token::NtPath(path) => {
71 let path = (**path).clone();
73 return Ok($p.mk_expr($p.prev_token.span, ExprKind::Path(None, path)));
75 token::NtBlock(block) => {
76 let block = block.clone();
78 return Ok($p.mk_expr($p.prev_token.span, ExprKind::Block(block, None)));
87 pub(super) enum LhsExpr {
89 AttributesParsed(AttrWrapper),
90 AlreadyParsed(P<Expr>),
93 impl From<Option<AttrWrapper>> for LhsExpr {
94 /// Converts `Some(attrs)` into `LhsExpr::AttributesParsed(attrs)`
95 /// and `None` into `LhsExpr::NotYetParsed`.
97 /// This conversion does not allocate.
98 fn from(o: Option<AttrWrapper>) -> Self {
99 if let Some(attrs) = o { LhsExpr::AttributesParsed(attrs) } else { LhsExpr::NotYetParsed }
103 impl From<P<Expr>> for LhsExpr {
104 /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed(expr)`.
106 /// This conversion does not allocate.
107 fn from(expr: P<Expr>) -> Self {
108 LhsExpr::AlreadyParsed(expr)
112 impl<'a> Parser<'a> {
113 /// Parses an expression.
115 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
116 self.current_closure.take();
118 self.parse_expr_res(Restrictions::empty(), None)
121 /// Parses an expression, forcing tokens to be collected
122 pub fn parse_expr_force_collect(&mut self) -> PResult<'a, P<Expr>> {
123 self.collect_tokens_no_attrs(|this| this.parse_expr())
126 pub fn parse_anon_const_expr(&mut self) -> PResult<'a, AnonConst> {
127 self.parse_expr().map(|value| AnonConst { id: DUMMY_NODE_ID, value })
130 fn parse_expr_catch_underscore(&mut self) -> PResult<'a, P<Expr>> {
131 match self.parse_expr() {
132 Ok(expr) => Ok(expr),
133 Err(mut err) => match self.token.ident() {
134 Some((Ident { name: kw::Underscore, .. }, false))
135 if self.may_recover() && self.look_ahead(1, |t| t == &token::Comma) =>
137 // Special-case handling of `foo(_, _, _)`
140 Ok(self.mk_expr(self.prev_token.span, ExprKind::Err))
147 /// Parses a sequence of expressions delimited by parentheses.
148 fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
149 self.parse_paren_comma_seq(|p| p.parse_expr_catch_underscore()).map(|(r, _)| r)
152 /// Parses an expression, subject to the given restrictions.
154 pub(super) fn parse_expr_res(
157 already_parsed_attrs: Option<AttrWrapper>,
158 ) -> PResult<'a, P<Expr>> {
159 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
162 /// Parses an associative expression.
164 /// This parses an expression accounting for associativity and precedence of the operators in
169 already_parsed_attrs: Option<AttrWrapper>,
170 ) -> PResult<'a, P<Expr>> {
171 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
174 /// Parses an associative expression with operators of at least `min_prec` precedence.
175 pub(super) fn parse_assoc_expr_with(
179 ) -> PResult<'a, P<Expr>> {
180 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
183 let attrs = match lhs {
184 LhsExpr::AttributesParsed(attrs) => Some(attrs),
187 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind) {
188 return self.parse_prefix_range_expr(attrs);
190 self.parse_prefix_expr(attrs)?
193 let last_type_ascription_set = self.last_type_ascription.is_some();
195 if !self.should_continue_as_assoc_expr(&lhs) {
196 self.last_type_ascription = None;
200 self.expected_tokens.push(TokenType::Operator);
201 while let Some(op) = self.check_assoc_op() {
202 // Adjust the span for interpolated LHS to point to the `$lhs` token
203 // and not to what it refers to.
204 let lhs_span = match self.prev_token.kind {
205 TokenKind::Interpolated(..) => self.prev_token.span,
209 let cur_op_span = self.token.span;
210 let restrictions = if op.node.is_assign_like() {
211 self.restrictions & Restrictions::NO_STRUCT_LITERAL
215 let prec = op.node.precedence();
219 // Check for deprecated `...` syntax
220 if self.token == token::DotDotDot && op.node == AssocOp::DotDotEq {
221 self.err_dotdotdot_syntax(self.token.span);
224 if self.token == token::LArrow {
225 self.err_larrow_operator(self.token.span);
229 if op.node.is_comparison() {
230 if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
235 // Look for JS' `===` and `!==` and recover
236 if (op.node == AssocOp::Equal || op.node == AssocOp::NotEqual)
237 && self.token.kind == token::Eq
238 && self.prev_token.span.hi() == self.token.span.lo()
240 let sp = op.span.to(self.token.span);
241 let sugg = match op.node {
242 AssocOp::Equal => "==",
243 AssocOp::NotEqual => "!=",
247 let invalid = format!("{}=", &sugg);
248 self.sess.emit_err(InvalidComparisonOperator {
250 invalid: invalid.clone(),
251 sub: InvalidComparisonOperatorSub::Correctable {
260 // Look for PHP's `<>` and recover
261 if op.node == AssocOp::Less
262 && self.token.kind == token::Gt
263 && self.prev_token.span.hi() == self.token.span.lo()
265 let sp = op.span.to(self.token.span);
266 self.sess.emit_err(InvalidComparisonOperator {
268 invalid: "<>".into(),
269 sub: InvalidComparisonOperatorSub::Correctable {
271 invalid: "<>".into(),
272 correct: "!=".into(),
278 // Look for C++'s `<=>` and recover
279 if op.node == AssocOp::LessEqual
280 && self.token.kind == token::Gt
281 && self.prev_token.span.hi() == self.token.span.lo()
283 let sp = op.span.to(self.token.span);
284 self.sess.emit_err(InvalidComparisonOperator {
286 invalid: "<=>".into(),
287 sub: InvalidComparisonOperatorSub::Spaceship(sp),
292 if self.prev_token == token::BinOp(token::Plus)
293 && self.token == token::BinOp(token::Plus)
294 && self.prev_token.span.between(self.token.span).is_empty()
296 let op_span = self.prev_token.span.to(self.token.span);
297 // Eat the second `+`
299 lhs = self.recover_from_postfix_increment(lhs, op_span)?;
305 if op == AssocOp::As {
306 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
308 } else if op == AssocOp::Colon {
309 lhs = self.parse_assoc_op_ascribe(lhs, lhs_span)?;
311 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
312 // If we didn't have to handle `x..`/`x..=`, it would be pretty easy to
313 // generalise it to the Fixity::None code.
314 lhs = self.parse_range_expr(prec, lhs, op, cur_op_span)?;
318 let fixity = op.fixity();
319 let prec_adjustment = match fixity {
322 // We currently have no non-associative operators that are not handled above by
323 // the special cases. The code is here only for future convenience.
326 let rhs = self.with_res(restrictions - Restrictions::STMT_EXPR, |this| {
327 this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
330 let span = self.mk_expr_sp(&lhs, lhs_span, rhs.span);
343 | AssocOp::ShiftRight
349 | AssocOp::GreaterEqual => {
350 let ast_op = op.to_ast_binop().unwrap();
351 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
352 self.mk_expr(span, binary)
354 AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs, cur_op_span)),
355 AssocOp::AssignOp(k) => {
357 token::Plus => BinOpKind::Add,
358 token::Minus => BinOpKind::Sub,
359 token::Star => BinOpKind::Mul,
360 token::Slash => BinOpKind::Div,
361 token::Percent => BinOpKind::Rem,
362 token::Caret => BinOpKind::BitXor,
363 token::And => BinOpKind::BitAnd,
364 token::Or => BinOpKind::BitOr,
365 token::Shl => BinOpKind::Shl,
366 token::Shr => BinOpKind::Shr,
368 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
369 self.mk_expr(span, aopexpr)
371 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
372 self.span_bug(span, "AssocOp should have been handled by special case")
376 if let Fixity::None = fixity {
380 if last_type_ascription_set {
381 self.last_type_ascription = None;
386 fn should_continue_as_assoc_expr(&mut self, lhs: &Expr) -> bool {
387 match (self.expr_is_complete(lhs), AssocOp::from_token(&self.token)) {
388 // Semi-statement forms are odd:
389 // See https://github.com/rust-lang/rust/issues/29071
390 (true, None) => false,
391 (false, _) => true, // Continue parsing the expression.
392 // An exhaustive check is done in the following block, but these are checked first
393 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
394 // want to keep their span info to improve diagnostics in these cases in a later stage.
395 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
396 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
397 (true, Some(AssocOp::Add)) // `{ 42 } + 42
398 // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
399 // `if x { a } else { b } && if y { c } else { d }`
400 if !self.look_ahead(1, |t| t.is_used_keyword()) => {
401 // These cases are ambiguous and can't be identified in the parser alone.
402 let sp = self.sess.source_map().start_point(self.token.span);
403 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
406 (true, Some(AssocOp::LAnd)) |
407 (true, Some(AssocOp::LOr)) |
408 (true, Some(AssocOp::BitOr)) => {
409 // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }`. Separated from the
410 // above due to #74233.
411 // These cases are ambiguous and can't be identified in the parser alone.
413 // Bitwise AND is left out because guessing intent is hard. We can make
414 // suggestions based on the assumption that double-refs are rarely intentional,
415 // and closures are distinct enough that they don't get mixed up with their
417 let sp = self.sess.source_map().start_point(self.token.span);
418 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
421 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => false,
423 self.error_found_expr_would_be_stmt(lhs);
429 /// We've found an expression that would be parsed as a statement,
430 /// but the next token implies this should be parsed as an expression.
431 /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
432 fn error_found_expr_would_be_stmt(&self, lhs: &Expr) {
433 self.sess.emit_err(FoundExprWouldBeStmt {
434 span: self.token.span,
435 token: self.token.clone(),
436 suggestion: ExprParenthesesNeeded::surrounding(lhs.span),
440 /// Possibly translate the current token to an associative operator.
441 /// The method does not advance the current token.
443 /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
444 fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
445 let (op, span) = match (AssocOp::from_token(&self.token), self.token.ident()) {
446 // When parsing const expressions, stop parsing when encountering `>`.
451 | AssocOp::GreaterEqual
452 | AssocOp::AssignOp(token::BinOpToken::Shr),
455 ) if self.restrictions.contains(Restrictions::CONST_EXPR) => {
458 (Some(op), _) => (op, self.token.span),
459 (None, Some((Ident { name: sym::and, span }, false))) if self.may_recover() => {
460 self.sess.emit_err(InvalidLogicalOperator {
461 span: self.token.span,
462 incorrect: "and".into(),
463 sub: InvalidLogicalOperatorSub::Conjunction(self.token.span),
465 (AssocOp::LAnd, span)
467 (None, Some((Ident { name: sym::or, span }, false))) if self.may_recover() => {
468 self.sess.emit_err(InvalidLogicalOperator {
469 span: self.token.span,
470 incorrect: "or".into(),
471 sub: InvalidLogicalOperatorSub::Disjunction(self.token.span),
477 Some(source_map::respan(span, op))
480 /// Checks if this expression is a successfully parsed statement.
481 fn expr_is_complete(&self, e: &Expr) -> bool {
482 self.restrictions.contains(Restrictions::STMT_EXPR)
483 && !classify::expr_requires_semi_to_be_stmt(e)
486 /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
487 /// The other two variants are handled in `parse_prefix_range_expr` below.
494 ) -> PResult<'a, P<Expr>> {
495 let rhs = if self.is_at_start_of_range_notation_rhs() {
496 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
500 let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
501 let span = self.mk_expr_sp(&lhs, lhs.span, rhs_span);
503 if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
504 let range = self.mk_range(Some(lhs), rhs, limits);
505 Ok(self.mk_expr(span, range))
508 fn is_at_start_of_range_notation_rhs(&self) -> bool {
509 if self.token.can_begin_expr() {
510 // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
511 if self.token == token::OpenDelim(Delimiter::Brace) {
512 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
520 /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
521 fn parse_prefix_range_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
522 // Check for deprecated `...` syntax.
523 if self.token == token::DotDotDot {
524 self.err_dotdotdot_syntax(self.token.span);
528 [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind),
529 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
533 let limits = match self.token.kind {
534 token::DotDot => RangeLimits::HalfOpen,
535 _ => RangeLimits::Closed,
537 let op = AssocOp::from_token(&self.token);
538 // FIXME: `parse_prefix_range_expr` is called when the current
539 // token is `DotDot`, `DotDotDot`, or `DotDotEq`. If we haven't already
540 // parsed attributes, then trying to parse them here will always fail.
541 // We should figure out how we want attributes on range expressions to work.
542 let attrs = self.parse_or_use_outer_attributes(attrs)?;
543 self.collect_tokens_for_expr(attrs, |this, attrs| {
544 let lo = this.token.span;
546 let (span, opt_end) = if this.is_at_start_of_range_notation_rhs() {
547 // RHS must be parsed with more associativity than the dots.
548 this.parse_assoc_expr_with(op.unwrap().precedence() + 1, LhsExpr::NotYetParsed)
549 .map(|x| (lo.to(x.span), Some(x)))?
553 let range = this.mk_range(None, opt_end, limits);
554 Ok(this.mk_expr_with_attrs(span, range, attrs))
558 /// Parses a prefix-unary-operator expr.
559 fn parse_prefix_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
560 let attrs = self.parse_or_use_outer_attributes(attrs)?;
561 let lo = self.token.span;
563 macro_rules! make_it {
564 ($this:ident, $attrs:expr, |this, _| $body:expr) => {
565 $this.collect_tokens_for_expr($attrs, |$this, attrs| {
566 let (hi, ex) = $body?;
567 Ok($this.mk_expr_with_attrs(lo.to(hi), ex, attrs))
574 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
575 match this.token.uninterpolate().kind {
576 token::Not => make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Not)), // `!expr`
577 token::Tilde => make_it!(this, attrs, |this, _| this.recover_tilde_expr(lo)), // `~expr`
578 token::BinOp(token::Minus) => {
579 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Neg))
581 token::BinOp(token::Star) => {
582 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Deref))
584 token::BinOp(token::And) | token::AndAnd => {
585 make_it!(this, attrs, |this, _| this.parse_borrow_expr(lo))
587 token::BinOp(token::Plus) if this.look_ahead(1, |tok| tok.is_numeric_lit()) => {
589 LeadingPlusNotSupported { span: lo, remove_plus: None, add_parentheses: None };
591 // a block on the LHS might have been intended to be an expression instead
592 if let Some(sp) = this.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
593 err.add_parentheses = Some(ExprParenthesesNeeded::surrounding(*sp));
595 err.remove_plus = Some(lo);
597 this.sess.emit_err(err);
600 this.parse_prefix_expr(None)
602 // Recover from `++x`:
603 token::BinOp(token::Plus)
604 if this.look_ahead(1, |t| *t == token::BinOp(token::Plus)) =>
606 let prev_is_semi = this.prev_token == token::Semi;
607 let pre_span = this.token.span.to(this.look_ahead(1, |t| t.span));
612 let operand_expr = this.parse_dot_or_call_expr(Default::default())?;
613 this.recover_from_prefix_increment(operand_expr, pre_span, prev_is_semi)
615 token::Ident(..) if this.token.is_keyword(kw::Box) => {
616 make_it!(this, attrs, |this, _| this.parse_box_expr(lo))
618 token::Ident(..) if this.may_recover() && this.is_mistaken_not_ident_negation() => {
619 make_it!(this, attrs, |this, _| this.recover_not_expr(lo))
621 _ => return this.parse_dot_or_call_expr(Some(attrs)),
625 fn parse_prefix_expr_common(&mut self, lo: Span) -> PResult<'a, (Span, P<Expr>)> {
627 let expr = self.parse_prefix_expr(None);
628 let (span, expr) = self.interpolated_or_expr_span(expr)?;
629 Ok((lo.to(span), expr))
632 fn parse_unary_expr(&mut self, lo: Span, op: UnOp) -> PResult<'a, (Span, ExprKind)> {
633 let (span, expr) = self.parse_prefix_expr_common(lo)?;
634 Ok((span, self.mk_unary(op, expr)))
637 // Recover on `!` suggesting for bitwise negation instead.
638 fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
639 self.sess.emit_err(TildeAsUnaryOperator(lo));
641 self.parse_unary_expr(lo, UnOp::Not)
644 /// Parse `box expr`.
645 fn parse_box_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
646 let (span, expr) = self.parse_prefix_expr_common(lo)?;
647 self.sess.gated_spans.gate(sym::box_syntax, span);
648 Ok((span, ExprKind::Box(expr)))
651 fn is_mistaken_not_ident_negation(&self) -> bool {
652 let token_cannot_continue_expr = |t: &Token| match t.uninterpolate().kind {
653 // These tokens can start an expression after `!`, but
654 // can't continue an expression after an ident
655 token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
656 token::Literal(..) | token::Pound => true,
657 _ => t.is_whole_expr(),
659 self.token.is_ident_named(sym::not) && self.look_ahead(1, token_cannot_continue_expr)
662 /// Recover on `not expr` in favor of `!expr`.
663 fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
665 let negated_token = self.look_ahead(1, |t| t.clone());
667 let sub_diag = if negated_token.is_numeric_lit() {
668 NotAsNegationOperatorSub::SuggestNotBitwise
669 } else if negated_token.is_bool_lit() {
670 NotAsNegationOperatorSub::SuggestNotLogical
672 NotAsNegationOperatorSub::SuggestNotDefault
675 self.sess.emit_err(NotAsNegationOperator {
676 negated: negated_token.span,
677 negated_desc: super::token_descr(&negated_token),
678 // Span the `not` plus trailing whitespace to avoid
679 // trailing whitespace after the `!` in our suggestion
681 self.sess.source_map().span_until_non_whitespace(lo.to(negated_token.span)),
686 self.parse_unary_expr(lo, UnOp::Not)
689 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
690 fn interpolated_or_expr_span(
692 expr: PResult<'a, P<Expr>>,
693 ) -> PResult<'a, (Span, P<Expr>)> {
696 match self.prev_token.kind {
697 TokenKind::Interpolated(..) => self.prev_token.span,
705 fn parse_assoc_op_cast(
709 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
710 ) -> PResult<'a, P<Expr>> {
711 let mk_expr = |this: &mut Self, lhs: P<Expr>, rhs: P<Ty>| {
712 this.mk_expr(this.mk_expr_sp(&lhs, lhs_span, rhs.span), expr_kind(lhs, rhs))
715 // Save the state of the parser before parsing type normally, in case there is a
716 // LessThan comparison after this cast.
717 let parser_snapshot_before_type = self.clone();
718 let cast_expr = match self.parse_as_cast_ty() {
719 Ok(rhs) => mk_expr(self, lhs, rhs),
721 if !self.may_recover() {
722 return Err(type_err);
725 // Rewind to before attempting to parse the type with generics, to recover
726 // from situations like `x as usize < y` in which we first tried to parse
727 // `usize < y` as a type with generic arguments.
728 let parser_snapshot_after_type = mem::replace(self, parser_snapshot_before_type);
730 // Check for typo of `'a: loop { break 'a }` with a missing `'`.
731 match (&lhs.kind, &self.token.kind) {
734 ExprKind::Path(None, ast::Path { segments, .. }),
735 TokenKind::Ident(kw::For | kw::Loop | kw::While, false),
736 ) if segments.len() == 1 => {
737 let snapshot = self.create_snapshot_for_diagnostic();
739 ident: Ident::from_str_and_span(
740 &format!("'{}", segments[0].ident),
741 segments[0].ident.span,
744 match self.parse_labeled_expr(label, false) {
747 self.sess.emit_err(MalformedLoopLabel {
748 span: label.ident.span,
749 correct_label: label.ident,
755 self.restore_snapshot(snapshot);
762 match self.parse_path(PathStyle::Expr) {
764 let span_after_type = parser_snapshot_after_type.token.span;
768 self.mk_ty(path.span, TyKind::Path(None, path.clone())),
771 let args_span = self.look_ahead(1, |t| t.span).to(span_after_type);
772 let suggestion = ComparisonOrShiftInterpretedAsGenericSugg {
773 left: expr.span.shrink_to_lo(),
774 right: expr.span.shrink_to_hi(),
777 match self.token.kind {
778 token::Lt => self.sess.emit_err(ComparisonInterpretedAsGeneric {
779 comparison: self.token.span,
784 token::BinOp(token::Shl) => {
785 self.sess.emit_err(ShiftInterpretedAsGeneric {
786 shift: self.token.span,
793 // We can end up here even without `<` being the next token, for
794 // example because `parse_ty_no_plus` returns `Err` on keywords,
795 // but `parse_path` returns `Ok` on them due to error recovery.
796 // Return original error and parser state.
797 *self = parser_snapshot_after_type;
798 return Err(type_err);
802 // Successfully parsed the type path leaving a `<` yet to parse.
805 // Keep `x as usize` as an expression in AST and continue parsing.
809 // Couldn't parse as a path, return original error and parser state.
811 *self = parser_snapshot_after_type;
812 return Err(type_err);
818 self.parse_and_disallow_postfix_after_cast(cast_expr)
821 /// Parses a postfix operators such as `.`, `?`, or index (`[]`) after a cast,
822 /// then emits an error and returns the newly parsed tree.
823 /// The resulting parse tree for `&x as T[0]` has a precedence of `((&x) as T)[0]`.
824 fn parse_and_disallow_postfix_after_cast(
827 ) -> PResult<'a, P<Expr>> {
828 let span = cast_expr.span;
829 let (cast_kind, maybe_ascription_span) =
830 if let ExprKind::Type(ascripted_expr, _) = &cast_expr.kind {
831 ("type ascription", Some(ascripted_expr.span.shrink_to_hi().with_hi(span.hi())))
836 let with_postfix = self.parse_dot_or_call_expr_with_(cast_expr, span)?;
838 // Check if an illegal postfix operator has been added after the cast.
839 // If the resulting expression is not a cast, it is an illegal postfix operator.
840 if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) {
842 "{cast_kind} cannot be followed by {}",
843 match with_postfix.kind {
844 ExprKind::Index(_, _) => "indexing",
845 ExprKind::Try(_) => "`?`",
846 ExprKind::Field(_, _) => "a field access",
847 ExprKind::MethodCall(_, _, _, _) => "a method call",
848 ExprKind::Call(_, _) => "a function call",
849 ExprKind::Await(_) => "`.await`",
850 ExprKind::Err => return Ok(with_postfix),
851 _ => unreachable!("parse_dot_or_call_expr_with_ shouldn't produce this"),
854 let mut err = self.struct_span_err(span, &msg);
856 let suggest_parens = |err: &mut Diagnostic| {
857 let suggestions = vec![
858 (span.shrink_to_lo(), "(".to_string()),
859 (span.shrink_to_hi(), ")".to_string()),
861 err.multipart_suggestion(
862 "try surrounding the expression in parentheses",
864 Applicability::MachineApplicable,
868 // If type ascription is "likely an error", the user will already be getting a useful
869 // help message, and doesn't need a second.
870 if self.last_type_ascription.map_or(false, |last_ascription| last_ascription.1) {
871 self.maybe_annotate_with_ascription(&mut err, false);
872 } else if let Some(ascription_span) = maybe_ascription_span {
873 let is_nightly = self.sess.unstable_features.is_nightly_build();
875 suggest_parens(&mut err);
880 "{}remove the type ascription",
881 if is_nightly { "alternatively, " } else { "" }
885 Applicability::MaybeIncorrect
887 Applicability::MachineApplicable
891 suggest_parens(&mut err);
898 fn parse_assoc_op_ascribe(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
899 let maybe_path = self.could_ascription_be_path(&lhs.kind);
900 self.last_type_ascription = Some((self.prev_token.span, maybe_path));
901 let lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
902 self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
906 /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
907 fn parse_borrow_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
909 let has_lifetime = self.token.is_lifetime() && self.look_ahead(1, |t| t != &token::Colon);
910 let lifetime = has_lifetime.then(|| self.expect_lifetime()); // For recovery, see below.
911 let (borrow_kind, mutbl) = self.parse_borrow_modifiers(lo);
912 let expr = self.parse_prefix_expr(None);
913 let (hi, expr) = self.interpolated_or_expr_span(expr)?;
914 let span = lo.to(hi);
915 if let Some(lt) = lifetime {
916 self.error_remove_borrow_lifetime(span, lt.ident.span);
918 Ok((span, ExprKind::AddrOf(borrow_kind, mutbl, expr)))
921 fn error_remove_borrow_lifetime(&self, span: Span, lt_span: Span) {
922 self.sess.emit_err(LifetimeInBorrowExpression { span, lifetime_span: lt_span });
925 /// Parse `mut?` or `raw [ const | mut ]`.
926 fn parse_borrow_modifiers(&mut self, lo: Span) -> (ast::BorrowKind, ast::Mutability) {
927 if self.check_keyword(kw::Raw) && self.look_ahead(1, Token::is_mutability) {
928 // `raw [ const | mut ]`.
929 let found_raw = self.eat_keyword(kw::Raw);
931 let mutability = self.parse_const_or_mut().unwrap();
932 self.sess.gated_spans.gate(sym::raw_ref_op, lo.to(self.prev_token.span));
933 (ast::BorrowKind::Raw, mutability)
936 (ast::BorrowKind::Ref, self.parse_mutability())
940 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
941 fn parse_dot_or_call_expr(&mut self, attrs: Option<AttrWrapper>) -> PResult<'a, P<Expr>> {
942 let attrs = self.parse_or_use_outer_attributes(attrs)?;
943 self.collect_tokens_for_expr(attrs, |this, attrs| {
944 let base = this.parse_bottom_expr();
945 let (span, base) = this.interpolated_or_expr_span(base)?;
946 this.parse_dot_or_call_expr_with(base, span, attrs)
950 pub(super) fn parse_dot_or_call_expr_with(
954 mut attrs: ast::AttrVec,
955 ) -> PResult<'a, P<Expr>> {
956 // Stitch the list of outer attributes onto the return value.
957 // A little bit ugly, but the best way given the current code
959 let res = self.parse_dot_or_call_expr_with_(e0, lo);
960 if attrs.is_empty() {
964 expr.map(|mut expr| {
965 attrs.extend(expr.attrs);
973 fn parse_dot_or_call_expr_with_(&mut self, mut e: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
975 let has_question = if self.prev_token.kind == TokenKind::Ident(kw::Return, false) {
976 // we are using noexpect here because we don't expect a `?` directly after a `return`
977 // which could be suggested otherwise
978 self.eat_noexpect(&token::Question)
980 self.eat(&token::Question)
984 e = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Try(e));
987 let has_dot = if self.prev_token.kind == TokenKind::Ident(kw::Return, false) {
988 // we are using noexpect here because we don't expect a `.` directly after a `return`
989 // which could be suggested otherwise
990 self.eat_noexpect(&token::Dot)
992 self.eat(&token::Dot)
996 e = self.parse_dot_suffix_expr(lo, e)?;
999 if self.expr_is_complete(&e) {
1002 e = match self.token.kind {
1003 token::OpenDelim(Delimiter::Parenthesis) => self.parse_fn_call_expr(lo, e),
1004 token::OpenDelim(Delimiter::Bracket) => self.parse_index_expr(lo, e)?,
1010 fn look_ahead_type_ascription_as_field(&mut self) -> bool {
1011 self.look_ahead(1, |t| t.is_ident())
1012 && self.look_ahead(2, |t| t == &token::Colon)
1013 && self.look_ahead(3, |t| t.can_begin_expr())
1016 fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
1017 match self.token.uninterpolate().kind {
1018 token::Ident(..) => self.parse_dot_suffix(base, lo),
1019 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
1020 Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix, None))
1022 token::Literal(token::Lit { kind: token::Float, symbol, suffix }) => {
1023 Ok(self.parse_tuple_field_access_expr_float(lo, base, symbol, suffix))
1026 self.error_unexpected_after_dot();
1032 fn error_unexpected_after_dot(&self) {
1033 // FIXME Could factor this out into non_fatal_unexpected or something.
1034 let actual = pprust::token_to_string(&self.token);
1035 self.struct_span_err(self.token.span, &format!("unexpected token: `{actual}`")).emit();
1038 // We need an identifier or integer, but the next token is a float.
1039 // Break the float into components to extract the identifier or integer.
1040 // FIXME: With current `TokenCursor` it's hard to break tokens into more than 2
1041 // parts unless those parts are processed immediately. `TokenCursor` should either
1042 // support pushing "future tokens" (would be also helpful to `break_and_eat`), or
1043 // we should break everything including floats into more basic proc-macro style
1044 // tokens in the lexer (probably preferable).
1045 fn parse_tuple_field_access_expr_float(
1050 suffix: Option<Symbol>,
1053 enum FloatComponent {
1057 use FloatComponent::*;
1059 let float_str = float.as_str();
1060 let mut components = Vec::new();
1061 let mut ident_like = String::new();
1062 for c in float_str.chars() {
1063 if c == '_' || c.is_ascii_alphanumeric() {
1065 } else if matches!(c, '.' | '+' | '-') {
1066 if !ident_like.is_empty() {
1067 components.push(IdentLike(mem::take(&mut ident_like)));
1069 components.push(Punct(c));
1071 panic!("unexpected character in a float token: {:?}", c)
1074 if !ident_like.is_empty() {
1075 components.push(IdentLike(ident_like));
1078 // With proc macros the span can refer to anything, the source may be too short,
1079 // or too long, or non-ASCII. It only makes sense to break our span into components
1080 // if its underlying text is identical to our float literal.
1081 let span = self.token.span;
1082 let can_take_span_apart =
1083 || self.span_to_snippet(span).as_deref() == Ok(float_str).as_deref();
1085 match &*components {
1088 self.parse_tuple_field_access_expr(lo, base, Symbol::intern(&i), suffix, None)
1091 [IdentLike(i), Punct('.')] => {
1092 let (ident_span, dot_span) = if can_take_span_apart() {
1093 let (span, ident_len) = (span.data(), BytePos::from_usize(i.len()));
1094 let ident_span = span.with_hi(span.lo + ident_len);
1095 let dot_span = span.with_lo(span.lo + ident_len);
1096 (ident_span, dot_span)
1100 assert!(suffix.is_none());
1101 let symbol = Symbol::intern(&i);
1102 self.token = Token::new(token::Ident(symbol, false), ident_span);
1103 let next_token = (Token::new(token::Dot, dot_span), self.token_spacing);
1104 self.parse_tuple_field_access_expr(lo, base, symbol, None, Some(next_token))
1107 [IdentLike(i1), Punct('.'), IdentLike(i2)] => {
1108 let (ident1_span, dot_span, ident2_span) = if can_take_span_apart() {
1109 let (span, ident1_len) = (span.data(), BytePos::from_usize(i1.len()));
1110 let ident1_span = span.with_hi(span.lo + ident1_len);
1112 .with_lo(span.lo + ident1_len)
1113 .with_hi(span.lo + ident1_len + BytePos(1));
1114 let ident2_span = self.token.span.with_lo(span.lo + ident1_len + BytePos(1));
1115 (ident1_span, dot_span, ident2_span)
1119 let symbol1 = Symbol::intern(&i1);
1120 self.token = Token::new(token::Ident(symbol1, false), ident1_span);
1121 // This needs to be `Spacing::Alone` to prevent regressions.
1122 // See issue #76399 and PR #76285 for more details
1123 let next_token1 = (Token::new(token::Dot, dot_span), Spacing::Alone);
1125 self.parse_tuple_field_access_expr(lo, base, symbol1, None, Some(next_token1));
1126 let symbol2 = Symbol::intern(&i2);
1127 let next_token2 = Token::new(token::Ident(symbol2, false), ident2_span);
1128 self.bump_with((next_token2, self.token_spacing)); // `.`
1129 self.parse_tuple_field_access_expr(lo, base1, symbol2, suffix, None)
1131 // 1e+ | 1e- (recovered)
1132 [IdentLike(_), Punct('+' | '-')] |
1134 [IdentLike(_), Punct('+' | '-'), IdentLike(_)] |
1136 [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-')] |
1138 [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-'), IdentLike(_)] => {
1139 // See the FIXME about `TokenCursor` above.
1140 self.error_unexpected_after_dot();
1143 _ => panic!("unexpected components in a float token: {:?}", components),
1147 fn parse_tuple_field_access_expr(
1152 suffix: Option<Symbol>,
1153 next_token: Option<(Token, Spacing)>,
1156 Some(next_token) => self.bump_with(next_token),
1157 None => self.bump(),
1159 let span = self.prev_token.span;
1160 let field = ExprKind::Field(base, Ident::new(field, span));
1161 if let Some(suffix) = suffix {
1162 self.expect_no_tuple_index_suffix(span, suffix);
1164 self.mk_expr(lo.to(span), field)
1167 /// Parse a function call expression, `expr(...)`.
1168 fn parse_fn_call_expr(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
1169 let snapshot = if self.token.kind == token::OpenDelim(Delimiter::Parenthesis)
1170 && self.look_ahead_type_ascription_as_field()
1172 Some((self.create_snapshot_for_diagnostic(), fun.kind.clone()))
1176 let open_paren = self.token.span;
1179 .parse_paren_expr_seq()
1180 .map(|args| self.mk_expr(lo.to(self.prev_token.span), self.mk_call(fun, args)));
1182 self.maybe_recover_struct_lit_bad_delims(lo, open_paren, &mut seq, snapshot)
1186 self.recover_seq_parse_error(Delimiter::Parenthesis, lo, seq)
1189 /// If we encounter a parser state that looks like the user has written a `struct` literal with
1190 /// parentheses instead of braces, recover the parser state and provide suggestions.
1191 #[instrument(skip(self, seq, snapshot), level = "trace")]
1192 fn maybe_recover_struct_lit_bad_delims(
1196 seq: &mut PResult<'a, P<Expr>>,
1197 snapshot: Option<(SnapshotParser<'a>, ExprKind)>,
1198 ) -> Option<P<Expr>> {
1199 if !self.may_recover() {
1203 match (seq.as_mut(), snapshot) {
1204 (Err(err), Some((mut snapshot, ExprKind::Path(None, path)))) => {
1205 snapshot.bump(); // `(`
1206 match snapshot.parse_struct_fields(path.clone(), false, Delimiter::Parenthesis) {
1208 if snapshot.eat(&token::CloseDelim(Delimiter::Parenthesis)) =>
1210 // We are certain we have `Enum::Foo(a: 3, b: 4)`, suggest
1211 // `Enum::Foo { a: 3, b: 4 }` or `Enum::Foo(3, 4)`.
1212 self.restore_snapshot(snapshot);
1213 let close_paren = self.prev_token.span;
1214 let span = lo.to(self.prev_token.span);
1215 if !fields.is_empty() {
1216 let mut replacement_err = ParenthesesWithStructFields {
1219 braces_for_struct: BracesForStructLiteral {
1221 second: close_paren,
1223 no_fields_for_fn: NoFieldsForFnCall {
1226 .map(|field| field.span.until(field.expr.span))
1230 .into_diagnostic(&self.sess.span_diagnostic);
1231 replacement_err.emit();
1233 let old_err = mem::replace(err, replacement_err);
1238 return Some(self.mk_expr_err(span));
1251 /// Parse an indexing expression `expr[...]`.
1252 fn parse_index_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
1253 let prev_span = self.prev_token.span;
1254 let open_delim_span = self.token.span;
1256 let index = self.parse_expr()?;
1257 self.suggest_missing_semicolon_before_array(prev_span, open_delim_span)?;
1258 self.expect(&token::CloseDelim(Delimiter::Bracket))?;
1259 Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_index(base, index)))
1262 /// Assuming we have just parsed `.`, continue parsing into an expression.
1263 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
1264 if self.token.uninterpolated_span().rust_2018() && self.eat_keyword(kw::Await) {
1265 return Ok(self.mk_await_expr(self_arg, lo));
1268 let fn_span_lo = self.token.span;
1269 let mut segment = self.parse_path_segment(PathStyle::Expr, None)?;
1270 self.check_trailing_angle_brackets(&segment, &[&token::OpenDelim(Delimiter::Parenthesis)]);
1271 self.check_turbofish_missing_angle_brackets(&mut segment);
1273 if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
1274 // Method call `expr.f()`
1275 let args = self.parse_paren_expr_seq()?;
1276 let fn_span = fn_span_lo.to(self.prev_token.span);
1277 let span = lo.to(self.prev_token.span);
1278 Ok(self.mk_expr(span, ExprKind::MethodCall(segment, self_arg, args, fn_span)))
1280 // Field access `expr.f`
1281 if let Some(args) = segment.args {
1282 self.sess.emit_err(FieldExpressionWithGeneric(args.span()));
1285 let span = lo.to(self.prev_token.span);
1286 Ok(self.mk_expr(span, ExprKind::Field(self_arg, segment.ident)))
1290 /// At the bottom (top?) of the precedence hierarchy,
1291 /// Parses things like parenthesized exprs, macros, `return`, etc.
1293 /// N.B., this does not parse outer attributes, and is private because it only works
1294 /// correctly if called from `parse_dot_or_call_expr()`.
1295 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
1296 maybe_recover_from_interpolated_ty_qpath!(self, true);
1297 maybe_whole_expr!(self);
1299 // Outer attributes are already parsed and will be
1300 // added to the return value after the fact.
1302 // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
1303 let lo = self.token.span;
1304 if let token::Literal(_) = self.token.kind {
1305 // This match arm is a special-case of the `_` match arm below and
1306 // could be removed without changing functionality, but it's faster
1307 // to have it here, especially for programs with large constants.
1308 self.parse_lit_expr()
1309 } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
1310 self.parse_tuple_parens_expr()
1311 } else if self.check(&token::OpenDelim(Delimiter::Brace)) {
1312 self.parse_block_expr(None, lo, BlockCheckMode::Default)
1313 } else if self.check(&token::BinOp(token::Or)) || self.check(&token::OrOr) {
1314 self.parse_closure_expr().map_err(|mut err| {
1315 // If the input is something like `if a { 1 } else { 2 } | if a { 3 } else { 4 }`
1316 // then suggest parens around the lhs.
1317 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
1318 err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
1322 } else if self.check(&token::OpenDelim(Delimiter::Bracket)) {
1323 self.parse_array_or_repeat_expr(Delimiter::Bracket)
1324 } else if self.check_path() {
1325 self.parse_path_start_expr()
1326 } else if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
1327 self.parse_closure_expr()
1328 } else if self.eat_keyword(kw::If) {
1329 self.parse_if_expr()
1330 } else if self.check_keyword(kw::For) {
1331 if self.choose_generics_over_qpath(1) {
1332 self.parse_closure_expr()
1334 assert!(self.eat_keyword(kw::For));
1335 self.parse_for_expr(None, self.prev_token.span)
1337 } else if self.eat_keyword(kw::While) {
1338 self.parse_while_expr(None, self.prev_token.span)
1339 } else if let Some(label) = self.eat_label() {
1340 self.parse_labeled_expr(label, true)
1341 } else if self.eat_keyword(kw::Loop) {
1342 let sp = self.prev_token.span;
1343 self.parse_loop_expr(None, self.prev_token.span).map_err(|mut err| {
1344 err.span_label(sp, "while parsing this `loop` expression");
1347 } else if self.eat_keyword(kw::Continue) {
1348 let kind = ExprKind::Continue(self.eat_label());
1349 Ok(self.mk_expr(lo.to(self.prev_token.span), kind))
1350 } else if self.eat_keyword(kw::Match) {
1351 let match_sp = self.prev_token.span;
1352 self.parse_match_expr().map_err(|mut err| {
1353 err.span_label(match_sp, "while parsing this `match` expression");
1356 } else if self.eat_keyword(kw::Unsafe) {
1357 let sp = self.prev_token.span;
1358 self.parse_block_expr(None, lo, BlockCheckMode::Unsafe(ast::UserProvided)).map_err(
1360 err.span_label(sp, "while parsing this `unsafe` expression");
1364 } else if self.check_inline_const(0) {
1365 self.parse_const_block(lo.to(self.token.span), false)
1366 } else if self.may_recover() && self.is_do_catch_block() {
1367 self.recover_do_catch()
1368 } else if self.is_try_block() {
1369 self.expect_keyword(kw::Try)?;
1370 self.parse_try_block(lo)
1371 } else if self.eat_keyword(kw::Return) {
1372 self.parse_return_expr()
1373 } else if self.eat_keyword(kw::Break) {
1374 self.parse_break_expr()
1375 } else if self.eat_keyword(kw::Yield) {
1376 self.parse_yield_expr()
1377 } else if self.is_do_yeet() {
1378 self.parse_yeet_expr()
1379 } else if self.check_keyword(kw::Let) {
1380 self.parse_let_expr()
1381 } else if self.eat_keyword(kw::Underscore) {
1382 Ok(self.mk_expr(self.prev_token.span, ExprKind::Underscore))
1383 } else if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
1384 // Don't complain about bare semicolons after unclosed braces
1385 // recovery in order to keep the error count down. Fixing the
1386 // delimiters will possibly also fix the bare semicolon found in
1387 // expression context. For example, silence the following error:
1389 // error: expected expression, found `;`
1393 // | ^ expected expression
1395 Ok(self.mk_expr_err(self.token.span))
1396 } else if self.token.uninterpolated_span().rust_2018() {
1397 // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
1398 if self.check_keyword(kw::Async) {
1399 if self.is_async_block() {
1400 // Check for `async {` and `async move {`.
1401 self.parse_async_block()
1403 self.parse_closure_expr()
1405 } else if self.eat_keyword(kw::Await) {
1406 self.recover_incorrect_await_syntax(lo, self.prev_token.span)
1408 self.parse_lit_expr()
1411 self.parse_lit_expr()
1415 fn parse_lit_expr(&mut self) -> PResult<'a, P<Expr>> {
1416 let lo = self.token.span;
1417 match self.parse_opt_lit() {
1419 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Lit(literal));
1420 self.maybe_recover_from_bad_qpath(expr)
1422 None => self.try_macro_suggestion(),
1426 fn parse_tuple_parens_expr(&mut self) -> PResult<'a, P<Expr>> {
1427 let lo = self.token.span;
1428 self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
1429 let (es, trailing_comma) = match self.parse_seq_to_end(
1430 &token::CloseDelim(Delimiter::Parenthesis),
1431 SeqSep::trailing_allowed(token::Comma),
1432 |p| p.parse_expr_catch_underscore(),
1436 return Ok(self.recover_seq_parse_error(Delimiter::Parenthesis, lo, Err(err)));
1439 let kind = if es.len() == 1 && !trailing_comma {
1440 // `(e)` is parenthesized `e`.
1441 ExprKind::Paren(es.into_iter().next().unwrap())
1443 // `(e,)` is a tuple with only one field, `e`.
1446 let expr = self.mk_expr(lo.to(self.prev_token.span), kind);
1447 self.maybe_recover_from_bad_qpath(expr)
1450 fn parse_array_or_repeat_expr(&mut self, close_delim: Delimiter) -> PResult<'a, P<Expr>> {
1451 let lo = self.token.span;
1452 self.bump(); // `[` or other open delim
1454 let close = &token::CloseDelim(close_delim);
1455 let kind = if self.eat(close) {
1457 ExprKind::Array(Vec::new())
1460 let first_expr = self.parse_expr()?;
1461 if self.eat(&token::Semi) {
1462 // Repeating array syntax: `[ 0; 512 ]`
1463 let count = self.parse_anon_const_expr()?;
1464 self.expect(close)?;
1465 ExprKind::Repeat(first_expr, count)
1466 } else if self.eat(&token::Comma) {
1467 // Vector with two or more elements.
1468 let sep = SeqSep::trailing_allowed(token::Comma);
1469 let (remaining_exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
1470 let mut exprs = vec![first_expr];
1471 exprs.extend(remaining_exprs);
1472 ExprKind::Array(exprs)
1474 // Vector with one element
1475 self.expect(close)?;
1476 ExprKind::Array(vec![first_expr])
1479 let expr = self.mk_expr(lo.to(self.prev_token.span), kind);
1480 self.maybe_recover_from_bad_qpath(expr)
1483 fn parse_path_start_expr(&mut self) -> PResult<'a, P<Expr>> {
1484 let (qself, path) = if self.eat_lt() {
1485 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
1488 (None, self.parse_path(PathStyle::Expr)?)
1491 // `!`, as an operator, is prefix, so we know this isn't that.
1492 let (span, kind) = if self.eat(&token::Not) {
1493 // MACRO INVOCATION expression
1494 if qself.is_some() {
1495 self.sess.emit_err(MacroInvocationWithQualifiedPath(path.span));
1498 let mac = P(MacCall {
1500 args: self.parse_mac_args()?,
1501 prior_type_ascription: self.last_type_ascription,
1503 (lo.to(self.prev_token.span), ExprKind::MacCall(mac))
1504 } else if self.check(&token::OpenDelim(Delimiter::Brace)) &&
1505 let Some(expr) = self.maybe_parse_struct_expr(qself.as_ref(), &path) {
1506 if qself.is_some() {
1507 self.sess.gated_spans.gate(sym::more_qualified_paths, path.span);
1511 (path.span, ExprKind::Path(qself, path))
1514 let expr = self.mk_expr(span, kind);
1515 self.maybe_recover_from_bad_qpath(expr)
1518 /// Parse `'label: $expr`. The label is already parsed.
1519 fn parse_labeled_expr(
1522 mut consume_colon: bool,
1523 ) -> PResult<'a, P<Expr>> {
1524 let lo = label_.ident.span;
1525 let label = Some(label_);
1526 let ate_colon = self.eat(&token::Colon);
1527 let expr = if self.eat_keyword(kw::While) {
1528 self.parse_while_expr(label, lo)
1529 } else if self.eat_keyword(kw::For) {
1530 self.parse_for_expr(label, lo)
1531 } else if self.eat_keyword(kw::Loop) {
1532 self.parse_loop_expr(label, lo)
1533 } else if self.check_noexpect(&token::OpenDelim(Delimiter::Brace))
1534 || self.token.is_whole_block()
1536 self.parse_block_expr(label, lo, BlockCheckMode::Default)
1537 } else if !ate_colon
1538 && self.may_recover()
1539 && (matches!(self.token.kind, token::CloseDelim(_) | token::Comma)
1540 || self.token.is_op())
1542 let lit = self.recover_unclosed_char(label_.ident, |self_| {
1543 self_.sess.create_err(UnexpectedTokenAfterLabel {
1544 span: self_.token.span,
1546 enclose_in_block: None,
1549 consume_colon = false;
1550 Ok(self.mk_expr(lo, ExprKind::Lit(lit)))
1551 } else if !ate_colon
1552 && (self.check_noexpect(&TokenKind::Comma) || self.check_noexpect(&TokenKind::Gt))
1554 // We're probably inside of a `Path<'a>` that needs a turbofish
1555 self.sess.emit_err(UnexpectedTokenAfterLabel {
1556 span: self.token.span,
1558 enclose_in_block: None,
1560 consume_colon = false;
1561 Ok(self.mk_expr_err(lo))
1563 let mut err = UnexpectedTokenAfterLabel {
1564 span: self.token.span,
1566 enclose_in_block: None,
1569 // Continue as an expression in an effort to recover on `'label: non_block_expr`.
1570 let expr = self.parse_expr().map(|expr| {
1571 let span = expr.span;
1573 let found_labeled_breaks = {
1574 struct FindLabeledBreaksVisitor(bool);
1576 impl<'ast> Visitor<'ast> for FindLabeledBreaksVisitor {
1577 fn visit_expr_post(&mut self, ex: &'ast Expr) {
1578 if let ExprKind::Break(Some(_label), _) = ex.kind {
1584 let mut vis = FindLabeledBreaksVisitor(false);
1585 vis.visit_expr(&expr);
1589 // Suggestion involves adding a (as of time of writing this, unstable) labeled block.
1591 // If there are no breaks that may use this label, suggest removing the label and
1592 // recover to the unmodified expression.
1593 if !found_labeled_breaks {
1594 err.remove_label = Some(lo.until(span));
1599 err.enclose_in_block = Some(UnexpectedTokenAfterLabelSugg {
1600 left: span.shrink_to_lo(),
1601 right: span.shrink_to_hi(),
1604 // Replace `'label: non_block_expr` with `'label: {non_block_expr}` in order to suppress future errors about `break 'label`.
1605 let stmt = self.mk_stmt(span, StmtKind::Expr(expr));
1606 let blk = self.mk_block(vec![stmt], BlockCheckMode::Default, span);
1607 self.mk_expr(span, ExprKind::Block(blk, label))
1610 self.sess.emit_err(err);
1614 if !ate_colon && consume_colon {
1615 self.sess.emit_err(RequireColonAfterLabeledExpression {
1618 label_end: lo.shrink_to_hi(),
1625 /// Emit an error when a char is parsed as a lifetime because of a missing quote
1626 pub(super) fn recover_unclosed_char(
1629 err: impl FnOnce(&mut Self) -> DiagnosticBuilder<'a, ErrorGuaranteed>,
1631 if let Some(mut diag) =
1632 self.sess.span_diagnostic.steal_diagnostic(lifetime.span, StashKey::LifetimeIsChar)
1634 diag.span_suggestion_verbose(
1635 lifetime.span.shrink_to_hi(),
1636 "add `'` to close the char literal",
1638 Applicability::MaybeIncorrect,
1643 .span_suggestion_verbose(
1644 lifetime.span.shrink_to_hi(),
1645 "add `'` to close the char literal",
1647 Applicability::MaybeIncorrect,
1652 token_lit: token::Lit::new(token::LitKind::Char, lifetime.name, None),
1653 kind: ast::LitKind::Char(lifetime.name.as_str().chars().next().unwrap_or('_')),
1654 span: lifetime.span,
1658 /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
1659 fn recover_do_catch(&mut self) -> PResult<'a, P<Expr>> {
1660 let lo = self.token.span;
1662 self.bump(); // `do`
1663 self.bump(); // `catch`
1665 let span = lo.to(self.prev_token.span);
1666 self.sess.emit_err(DoCatchSyntaxRemoved { span });
1668 self.parse_try_block(lo)
1671 /// Parse an expression if the token can begin one.
1672 fn parse_expr_opt(&mut self) -> PResult<'a, Option<P<Expr>>> {
1673 Ok(if self.token.can_begin_expr() { Some(self.parse_expr()?) } else { None })
1676 /// Parse `"return" expr?`.
1677 fn parse_return_expr(&mut self) -> PResult<'a, P<Expr>> {
1678 let lo = self.prev_token.span;
1679 let kind = ExprKind::Ret(self.parse_expr_opt()?);
1680 let expr = self.mk_expr(lo.to(self.prev_token.span), kind);
1681 self.maybe_recover_from_bad_qpath(expr)
1684 /// Parse `"do" "yeet" expr?`.
1685 fn parse_yeet_expr(&mut self) -> PResult<'a, P<Expr>> {
1686 let lo = self.token.span;
1688 self.bump(); // `do`
1689 self.bump(); // `yeet`
1691 let kind = ExprKind::Yeet(self.parse_expr_opt()?);
1693 let span = lo.to(self.prev_token.span);
1694 self.sess.gated_spans.gate(sym::yeet_expr, span);
1695 let expr = self.mk_expr(span, kind);
1696 self.maybe_recover_from_bad_qpath(expr)
1699 /// Parse `"break" (('label (:? expr)?) | expr?)` with `"break"` token already eaten.
1700 /// If the label is followed immediately by a `:` token, the label and `:` are
1701 /// parsed as part of the expression (i.e. a labeled loop). The language team has
1702 /// decided in #87026 to require parentheses as a visual aid to avoid confusion if
1703 /// the break expression of an unlabeled break is a labeled loop (as in
1704 /// `break 'lbl: loop {}`); a labeled break with an unlabeled loop as its value
1705 /// expression only gets a warning for compatibility reasons; and a labeled break
1706 /// with a labeled loop does not even get a warning because there is no ambiguity.
1707 fn parse_break_expr(&mut self) -> PResult<'a, P<Expr>> {
1708 let lo = self.prev_token.span;
1709 let mut label = self.eat_label();
1710 let kind = if label.is_some() && self.token == token::Colon {
1711 // The value expression can be a labeled loop, see issue #86948, e.g.:
1712 // `loop { break 'label: loop { break 'label 42; }; }`
1713 let lexpr = self.parse_labeled_expr(label.take().unwrap(), true)?;
1714 self.sess.emit_err(LabeledLoopInBreak {
1716 sub: WrapExpressionInParentheses {
1717 left: lexpr.span.shrink_to_lo(),
1718 right: lexpr.span.shrink_to_hi(),
1722 } else if self.token != token::OpenDelim(Delimiter::Brace)
1723 || !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1725 let expr = self.parse_expr_opt()?;
1726 if let Some(ref expr) = expr {
1730 ExprKind::While(_, _, None)
1731 | ExprKind::ForLoop(_, _, _, None)
1732 | ExprKind::Loop(_, None)
1733 | ExprKind::Block(_, None)
1736 self.sess.buffer_lint_with_diagnostic(
1737 BREAK_WITH_LABEL_AND_LOOP,
1740 "this labeled break expression is easy to confuse with an unlabeled break with a labeled value expression",
1741 BuiltinLintDiagnostics::BreakWithLabelAndLoop(expr.span),
1749 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Break(label, kind));
1750 self.maybe_recover_from_bad_qpath(expr)
1753 /// Parse `"yield" expr?`.
1754 fn parse_yield_expr(&mut self) -> PResult<'a, P<Expr>> {
1755 let lo = self.prev_token.span;
1756 let kind = ExprKind::Yield(self.parse_expr_opt()?);
1757 let span = lo.to(self.prev_token.span);
1758 self.sess.gated_spans.gate(sym::generators, span);
1759 let expr = self.mk_expr(span, kind);
1760 self.maybe_recover_from_bad_qpath(expr)
1763 /// Returns a string literal if the next token is a string literal.
1764 /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
1765 /// and returns `None` if the next token is not literal at all.
1766 pub fn parse_str_lit(&mut self) -> Result<ast::StrLit, Option<Lit>> {
1767 match self.parse_opt_lit() {
1768 Some(lit) => match lit.kind {
1769 ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
1771 symbol: lit.token_lit.symbol,
1772 suffix: lit.token_lit.suffix,
1776 _ => Err(Some(lit)),
1782 pub(super) fn parse_lit(&mut self) -> PResult<'a, Lit> {
1783 self.parse_opt_lit().ok_or(()).or_else(|()| {
1784 if let token::Interpolated(inner) = &self.token.kind {
1785 let expr = match inner.as_ref() {
1786 token::NtExpr(expr) => Some(expr),
1787 token::NtLiteral(expr) => Some(expr),
1790 if let Some(expr) = expr {
1791 if matches!(expr.kind, ExprKind::Err) {
1792 let mut err = InvalidInterpolatedExpression { span: self.token.span }
1793 .into_diagnostic(&self.sess.span_diagnostic);
1794 err.downgrade_to_delayed_bug();
1799 let token = self.token.clone();
1800 let err = |self_: &mut Self| {
1801 let msg = format!("unexpected token: {}", super::token_descr(&token));
1802 self_.struct_span_err(token.span, &msg)
1804 // On an error path, eagerly consider a lifetime to be an unclosed character lit
1805 if self.token.is_lifetime() {
1806 let lt = self.expect_lifetime();
1807 Ok(self.recover_unclosed_char(lt.ident, err))
1814 /// Matches `lit = true | false | token_lit`.
1815 /// Returns `None` if the next token is not a literal.
1816 pub(super) fn parse_opt_lit(&mut self) -> Option<Lit> {
1817 let mut recovered = None;
1818 if self.token == token::Dot {
1819 // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
1820 // dot would follow an optional literal, so we do this unconditionally.
1821 recovered = self.look_ahead(1, |next_token| {
1822 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
1825 if self.token.span.hi() == next_token.span.lo() {
1826 let s = String::from("0.") + symbol.as_str();
1827 let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
1828 return Some(Token::new(kind, self.token.span.to(next_token.span)));
1833 if let Some(token) = &recovered {
1835 self.sess.emit_err(FloatLiteralRequiresIntegerPart {
1837 correct: pprust::token_to_string(token).into_owned(),
1842 let token = recovered.as_ref().unwrap_or(&self.token);
1843 match Lit::from_token(token) {
1848 Err(LitError::NotLiteral) => None,
1850 let span = token.span;
1851 let token::Literal(lit) = token.kind else {
1855 self.report_lit_error(err, lit, span);
1856 // Pack possible quotes and prefixes from the original literal into
1857 // the error literal's symbol so they can be pretty-printed faithfully.
1858 let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
1859 let symbol = Symbol::intern(&suffixless_lit.to_string());
1860 let lit = token::Lit::new(token::Err, symbol, lit.suffix);
1861 Some(Lit::from_token_lit(lit, span).unwrap_or_else(|_| unreachable!()))
1866 fn report_lit_error(&self, err: LitError, lit: token::Lit, span: Span) {
1867 // Checks if `s` looks like i32 or u1234 etc.
1868 fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
1869 s.len() > 1 && s.starts_with(first_chars) && s[1..].chars().all(|c| c.is_ascii_digit())
1872 // Try to lowercase the prefix if it's a valid base prefix.
1873 fn fix_base_capitalisation(s: &str) -> Option<String> {
1874 if let Some(stripped) = s.strip_prefix('B') {
1875 Some(format!("0b{stripped}"))
1876 } else if let Some(stripped) = s.strip_prefix('O') {
1877 Some(format!("0o{stripped}"))
1878 } else if let Some(stripped) = s.strip_prefix('X') {
1879 Some(format!("0x{stripped}"))
1885 let token::Lit { kind, suffix, .. } = lit;
1887 // `NotLiteral` is not an error by itself, so we don't report
1888 // it and give the parser opportunity to try something else.
1889 LitError::NotLiteral => {}
1890 // `LexerError` *is* an error, but it was already reported
1891 // by lexer, so here we don't report it the second time.
1892 LitError::LexerError => {}
1893 LitError::InvalidSuffix => {
1894 if let Some(suffix) = suffix {
1895 self.sess.emit_err(InvalidLiteralSuffix {
1897 kind: format!("{}", kind.descr()),
1902 LitError::InvalidIntSuffix => {
1903 let suf = suffix.expect("suffix error with no suffix");
1904 let suf = suf.as_str();
1905 if looks_like_width_suffix(&['i', 'u'], &suf) {
1906 // If it looks like a width, try to be helpful.
1907 self.sess.emit_err(InvalidIntLiteralWidth { span, width: suf[1..].into() });
1908 } else if let Some(fixed) = fix_base_capitalisation(suf) {
1909 self.sess.emit_err(InvalidNumLiteralBasePrefix { span, fixed });
1911 self.sess.emit_err(InvalidNumLiteralSuffix { span, suffix: suf.to_string() });
1914 LitError::InvalidFloatSuffix => {
1915 let suf = suffix.expect("suffix error with no suffix");
1916 let suf = suf.as_str();
1917 if looks_like_width_suffix(&['f'], suf) {
1918 // If it looks like a width, try to be helpful.
1920 .emit_err(InvalidFloatLiteralWidth { span, width: suf[1..].to_string() });
1922 self.sess.emit_err(InvalidFloatLiteralSuffix { span, suffix: suf.to_string() });
1925 LitError::NonDecimalFloat(base) => {
1927 16 => self.sess.emit_err(HexadecimalFloatLiteralNotSupported { span }),
1928 8 => self.sess.emit_err(OctalFloatLiteralNotSupported { span }),
1929 2 => self.sess.emit_err(BinaryFloatLiteralNotSupported { span }),
1930 _ => unreachable!(),
1933 LitError::IntTooLarge => {
1934 self.sess.emit_err(IntLiteralTooLarge { span });
1939 pub(super) fn expect_no_tuple_index_suffix(&self, span: Span, suffix: Symbol) {
1940 if [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suffix) {
1941 // #59553: warn instead of reject out of hand to allow the fix to percolate
1942 // through the ecosystem when people fix their macros
1943 self.sess.emit_warning(InvalidLiteralSuffixOnTupleIndex {
1946 exception: Some(()),
1949 self.sess.emit_err(InvalidLiteralSuffixOnTupleIndex { span, suffix, exception: None });
1953 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1954 /// Keep this in sync with `Token::can_begin_literal_maybe_minus`.
1955 pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1956 maybe_whole_expr!(self);
1958 let lo = self.token.span;
1959 let minus_present = self.eat(&token::BinOp(token::Minus));
1960 let lit = self.parse_lit()?;
1961 let expr = self.mk_expr(lit.span, ExprKind::Lit(lit));
1964 Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_unary(UnOp::Neg, expr)))
1970 fn is_array_like_block(&mut self) -> bool {
1971 self.look_ahead(1, |t| matches!(t.kind, TokenKind::Ident(..) | TokenKind::Literal(_)))
1972 && self.look_ahead(2, |t| t == &token::Comma)
1973 && self.look_ahead(3, |t| t.can_begin_expr())
1976 /// Emits a suggestion if it looks like the user meant an array but
1977 /// accidentally used braces, causing the code to be interpreted as a block
1979 fn maybe_suggest_brackets_instead_of_braces(&mut self, lo: Span) -> Option<P<Expr>> {
1980 let mut snapshot = self.create_snapshot_for_diagnostic();
1981 match snapshot.parse_array_or_repeat_expr(Delimiter::Brace) {
1983 self.sess.emit_err(ArrayBracketsInsteadOfSpaces {
1985 sub: ArrayBracketsInsteadOfSpacesSugg {
1987 right: snapshot.prev_token.span,
1991 self.restore_snapshot(snapshot);
1992 Some(self.mk_expr_err(arr.span))
2001 fn suggest_missing_semicolon_before_array(
2004 open_delim_span: Span,
2005 ) -> PResult<'a, ()> {
2006 if !self.may_recover() {
2010 if self.token.kind == token::Comma {
2011 if !self.sess.source_map().is_multiline(prev_span.until(self.token.span)) {
2014 let mut snapshot = self.create_snapshot_for_diagnostic();
2016 match snapshot.parse_seq_to_before_end(
2017 &token::CloseDelim(Delimiter::Bracket),
2018 SeqSep::trailing_allowed(token::Comma),
2022 // When the close delim is `)`, `token.kind` is expected to be `token::CloseDelim(Delimiter::Parenthesis)`,
2023 // but the actual `token.kind` is `token::CloseDelim(Delimiter::Bracket)`.
2024 // This is because the `token.kind` of the close delim is treated as the same as
2025 // that of the open delim in `TokenTreesReader::parse_token_tree`, even if the delimiters of them are different.
2026 // Therefore, `token.kind` should not be compared here.
2028 .span_to_snippet(snapshot.token.span)
2029 .map_or(false, |snippet| snippet == "]") =>
2031 return Err(MissingSemicolonBeforeArray {
2032 open_delim: open_delim_span,
2033 semicolon: prev_span.shrink_to_hi(),
2034 }.into_diagnostic(&self.sess.span_diagnostic));
2037 Err(err) => err.cancel(),
2043 /// Parses a block or unsafe block.
2044 pub(super) fn parse_block_expr(
2046 opt_label: Option<Label>,
2048 blk_mode: BlockCheckMode,
2049 ) -> PResult<'a, P<Expr>> {
2050 if self.may_recover() && self.is_array_like_block() {
2051 if let Some(arr) = self.maybe_suggest_brackets_instead_of_braces(lo) {
2056 if self.token.is_whole_block() {
2057 self.sess.emit_err(InvalidBlockMacroSegment {
2058 span: self.token.span,
2059 context: lo.to(self.token.span),
2063 let (attrs, blk) = self.parse_block_common(lo, blk_mode)?;
2064 Ok(self.mk_expr_with_attrs(blk.span, ExprKind::Block(blk, opt_label), attrs))
2067 /// Parse a block which takes no attributes and has no label
2068 fn parse_simple_block(&mut self) -> PResult<'a, P<Expr>> {
2069 let blk = self.parse_block()?;
2070 Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None)))
2073 /// Parses a closure expression (e.g., `move |args| expr`).
2074 fn parse_closure_expr(&mut self) -> PResult<'a, P<Expr>> {
2075 let lo = self.token.span;
2077 let binder = if self.check_keyword(kw::For) {
2078 let lo = self.token.span;
2079 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
2080 let span = lo.to(self.prev_token.span);
2082 self.sess.gated_spans.gate(sym::closure_lifetime_binder, span);
2084 ClosureBinder::For { span, generic_params: P::from_vec(lifetime_defs) }
2086 ClosureBinder::NotPresent
2090 if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
2092 let asyncness = if self.token.uninterpolated_span().rust_2018() {
2093 self.parse_asyncness()
2098 let capture_clause = self.parse_capture_clause()?;
2099 let decl = self.parse_fn_block_decl()?;
2100 let decl_hi = self.prev_token.span;
2101 let mut body = match decl.output {
2102 FnRetTy::Default(_) => {
2103 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
2104 self.parse_expr_res(restrictions, None)?
2107 // If an explicit return type is given, require a block to appear (RFC 968).
2108 let body_lo = self.token.span;
2109 self.parse_block_expr(None, body_lo, BlockCheckMode::Default)?
2113 if let Async::Yes { span, .. } = asyncness {
2114 // Feature-gate `async ||` closures.
2115 self.sess.gated_spans.gate(sym::async_closure, span);
2118 if self.token.kind == TokenKind::Semi
2119 && matches!(self.token_cursor.frame.delim_sp, Some((Delimiter::Parenthesis, _)))
2120 // HACK: This is needed so we can detect whether we're inside a macro,
2121 // where regular assumptions about what tokens can follow other tokens
2122 // don't necessarily apply.
2123 && self.may_recover()
2124 // FIXME(Nilstrieb): Remove this check once `may_recover` actually stops recovery
2125 && self.subparser_name.is_none()
2127 // It is likely that the closure body is a block but where the
2128 // braces have been removed. We will recover and eat the next
2129 // statements later in the parsing process.
2130 body = self.mk_expr_err(body.span);
2133 let body_span = body.span;
2135 let closure = self.mk_expr(
2148 // Disable recovery for closure body
2150 ClosureSpans { whole_closure: closure.span, closing_pipe: decl_hi, body: body_span };
2151 self.current_closure = Some(spans);
2156 /// Parses an optional `move` prefix to a closure-like construct.
2157 fn parse_capture_clause(&mut self) -> PResult<'a, CaptureBy> {
2158 if self.eat_keyword(kw::Move) {
2159 // Check for `move async` and recover
2160 if self.check_keyword(kw::Async) {
2161 let move_async_span = self.token.span.with_lo(self.prev_token.span.data().lo);
2162 Err(AsyncMoveOrderIncorrect { span: move_async_span }
2163 .into_diagnostic(&self.sess.span_diagnostic))
2165 Ok(CaptureBy::Value)
2172 /// Parses the `|arg, arg|` header of a closure.
2173 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
2174 let inputs = if self.eat(&token::OrOr) {
2177 self.expect(&token::BinOp(token::Or))?;
2179 .parse_seq_to_before_tokens(
2180 &[&token::BinOp(token::Or), &token::OrOr],
2181 SeqSep::trailing_allowed(token::Comma),
2182 TokenExpectType::NoExpect,
2183 |p| p.parse_fn_block_param(),
2190 self.parse_ret_ty(AllowPlus::Yes, RecoverQPath::Yes, RecoverReturnSign::Yes)?;
2192 Ok(P(FnDecl { inputs, output }))
2195 /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
2196 fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
2197 let lo = self.token.span;
2198 let attrs = self.parse_outer_attributes()?;
2199 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2200 let pat = this.parse_pat_no_top_alt(PARAM_EXPECTED)?;
2201 let ty = if this.eat(&token::Colon) {
2204 this.mk_ty(this.prev_token.span, TyKind::Infer)
2212 span: lo.to(this.prev_token.span),
2214 is_placeholder: false,
2216 TrailingToken::MaybeComma,
2221 /// Parses an `if` expression (`if` token already eaten).
2222 fn parse_if_expr(&mut self) -> PResult<'a, P<Expr>> {
2223 let lo = self.prev_token.span;
2224 let cond = self.parse_cond_expr()?;
2225 self.parse_if_after_cond(lo, cond)
2228 fn parse_if_after_cond(&mut self, lo: Span, mut cond: P<Expr>) -> PResult<'a, P<Expr>> {
2229 let cond_span = cond.span;
2230 // Tries to interpret `cond` as either a missing expression if it's a block,
2231 // or as an unfinished expression if it's a binop and the RHS is a block.
2232 // We could probably add more recoveries here too...
2233 let mut recover_block_from_condition = |this: &mut Self| {
2234 let block = match &mut cond.kind {
2235 ExprKind::Binary(Spanned { span: binop_span, .. }, _, right)
2236 if let ExprKind::Block(_, None) = right.kind => {
2237 self.sess.emit_err(IfExpressionMissingThenBlock {
2239 sub: IfExpressionMissingThenBlockSub::UnfinishedCondition(
2240 cond_span.shrink_to_lo().to(*binop_span)
2243 std::mem::replace(right, this.mk_expr_err(binop_span.shrink_to_hi()))
2245 ExprKind::Block(_, None) => {
2246 self.sess.emit_err(IfExpressionMissingCondition {
2247 if_span: lo.shrink_to_hi(),
2248 block_span: self.sess.source_map().start_point(cond_span),
2250 std::mem::replace(&mut cond, this.mk_expr_err(cond_span.shrink_to_hi()))
2256 if let ExprKind::Block(block, _) = &block.kind {
2263 let thn = if self.token.is_keyword(kw::Else) {
2264 if let Some(block) = recover_block_from_condition(self) {
2267 self.sess.emit_err(IfExpressionMissingThenBlock {
2269 sub: IfExpressionMissingThenBlockSub::AddThenBlock(cond_span.shrink_to_hi()),
2271 self.mk_block_err(cond_span.shrink_to_hi())
2274 let attrs = self.parse_outer_attributes()?.take_for_recovery(); // For recovery.
2275 let block = if self.check(&token::OpenDelim(Delimiter::Brace)) {
2278 if let Some(block) = recover_block_from_condition(self) {
2281 // Parse block, which will always fail, but we can add a nice note to the error
2282 self.parse_block().map_err(|mut err| {
2285 "the `if` expression is missing a block after this condition",
2291 self.error_on_if_block_attrs(lo, false, block.span, &attrs);
2294 let els = if self.eat_keyword(kw::Else) { Some(self.parse_else_expr()?) } else { None };
2295 Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::If(cond, thn, els)))
2298 /// Parses the condition of a `if` or `while` expression.
2299 fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
2301 self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL | Restrictions::ALLOW_LET, None)?;
2303 if let ExprKind::Let(..) = cond.kind {
2304 // Remove the last feature gating of a `let` expression since it's stable.
2305 self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
2311 /// Parses a `let $pat = $expr` pseudo-expression.
2312 fn parse_let_expr(&mut self) -> PResult<'a, P<Expr>> {
2313 // This is a *approximate* heuristic that detects if `let` chains are
2314 // being parsed in the right position. It's approximate because it
2315 // doesn't deny all invalid `let` expressions, just completely wrong usages.
2316 let not_in_chain = !matches!(
2317 self.prev_token.kind,
2318 TokenKind::AndAnd | TokenKind::Ident(kw::If, _) | TokenKind::Ident(kw::While, _)
2320 if !self.restrictions.contains(Restrictions::ALLOW_LET) || not_in_chain {
2321 self.sess.emit_err(ExpectedExpressionFoundLet { span: self.token.span });
2324 self.bump(); // Eat `let` token
2325 let lo = self.prev_token.span;
2326 let pat = self.parse_pat_allow_top_alt(
2330 CommaRecoveryMode::LikelyTuple,
2332 if self.token == token::EqEq {
2333 self.sess.emit_err(ExpectedEqForLetExpr {
2334 span: self.token.span,
2335 sugg_span: self.token.span,
2339 self.expect(&token::Eq)?;
2341 let expr = self.with_res(self.restrictions | Restrictions::NO_STRUCT_LITERAL, |this| {
2342 this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
2344 let span = lo.to(expr.span);
2345 self.sess.gated_spans.gate(sym::let_chains, span);
2346 Ok(self.mk_expr(span, ExprKind::Let(pat, expr, span)))
2349 /// Parses an `else { ... }` expression (`else` token already eaten).
2350 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
2351 let else_span = self.prev_token.span; // `else`
2352 let attrs = self.parse_outer_attributes()?.take_for_recovery(); // For recovery.
2353 let expr = if self.eat_keyword(kw::If) {
2354 self.parse_if_expr()?
2355 } else if self.check(&TokenKind::OpenDelim(Delimiter::Brace)) {
2356 self.parse_simple_block()?
2358 let snapshot = self.create_snapshot_for_diagnostic();
2359 let first_tok = super::token_descr(&self.token);
2360 let first_tok_span = self.token.span;
2361 match self.parse_expr() {
2363 // If it's not a free-standing expression, and is followed by a block,
2364 // then it's very likely the condition to an `else if`.
2365 if self.check(&TokenKind::OpenDelim(Delimiter::Brace))
2366 && classify::expr_requires_semi_to_be_stmt(&cond) =>
2368 self.sess.emit_err(ExpectedElseBlock {
2372 condition_start: cond.span.shrink_to_lo(),
2374 self.parse_if_after_cond(cond.span.shrink_to_lo(), cond)?
2378 self.restore_snapshot(snapshot);
2379 self.parse_simple_block()?
2382 self.restore_snapshot(snapshot);
2383 self.parse_simple_block()?
2387 self.error_on_if_block_attrs(else_span, true, expr.span, &attrs);
2391 fn error_on_if_block_attrs(
2396 attrs: &[ast::Attribute],
2398 let (attributes, last) = match attrs {
2400 [x0 @ xn] | [x0, .., xn] => (x0.span.to(xn.span), xn.span),
2402 let ctx = if is_ctx_else { "else" } else { "if" };
2403 self.sess.emit_err(OuterAttributeNotAllowedOnIfElse {
2407 ctx: ctx.to_string(),
2412 /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
2413 fn parse_for_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2414 // Record whether we are about to parse `for (`.
2415 // This is used below for recovery in case of `for ( $stuff ) $block`
2416 // in which case we will suggest `for $stuff $block`.
2417 let begin_paren = match self.token.kind {
2418 token::OpenDelim(Delimiter::Parenthesis) => Some(self.token.span),
2422 let pat = self.parse_pat_allow_top_alt(
2426 CommaRecoveryMode::LikelyTuple,
2428 if !self.eat_keyword(kw::In) {
2429 self.error_missing_in_for_loop();
2431 self.check_for_for_in_in_typo(self.prev_token.span);
2432 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2434 let pat = self.recover_parens_around_for_head(pat, begin_paren);
2436 let (attrs, loop_block) = self.parse_inner_attrs_and_block()?;
2438 let kind = ExprKind::ForLoop(pat, expr, loop_block, opt_label);
2439 Ok(self.mk_expr_with_attrs(lo.to(self.prev_token.span), kind, attrs))
2442 fn error_missing_in_for_loop(&mut self) {
2443 let (span, sub): (_, fn(_) -> _) = if self.token.is_ident_named(sym::of) {
2444 // Possibly using JS syntax (#75311).
2445 let span = self.token.span;
2447 (span, MissingInInForLoopSub::InNotOf)
2449 (self.prev_token.span.between(self.token.span), MissingInInForLoopSub::AddIn)
2452 self.sess.emit_err(MissingInInForLoop { span, sub: sub(span) });
2455 /// Parses a `while` or `while let` expression (`while` token already eaten).
2456 fn parse_while_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2457 let cond = self.parse_cond_expr().map_err(|mut err| {
2458 err.span_label(lo, "while parsing the condition of this `while` expression");
2461 let (attrs, body) = self.parse_inner_attrs_and_block().map_err(|mut err| {
2462 err.span_label(lo, "while parsing the body of this `while` expression");
2463 err.span_label(cond.span, "this `while` condition successfully parsed");
2466 Ok(self.mk_expr_with_attrs(
2467 lo.to(self.prev_token.span),
2468 ExprKind::While(cond, body, opt_label),
2473 /// Parses `loop { ... }` (`loop` token already eaten).
2474 fn parse_loop_expr(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
2475 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2476 Ok(self.mk_expr_with_attrs(
2477 lo.to(self.prev_token.span),
2478 ExprKind::Loop(body, opt_label),
2483 pub(crate) fn eat_label(&mut self) -> Option<Label> {
2484 self.token.lifetime().map(|ident| {
2490 /// Parses a `match ... { ... }` expression (`match` token already eaten).
2491 fn parse_match_expr(&mut self) -> PResult<'a, P<Expr>> {
2492 let match_span = self.prev_token.span;
2493 let lo = self.prev_token.span;
2494 let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
2495 if let Err(mut e) = self.expect(&token::OpenDelim(Delimiter::Brace)) {
2496 if self.token == token::Semi {
2497 e.span_suggestion_short(
2499 "try removing this `match`",
2501 Applicability::MaybeIncorrect, // speculative
2504 if self.maybe_recover_unexpected_block_label() {
2511 let attrs = self.parse_inner_attributes()?;
2513 let mut arms: Vec<Arm> = Vec::new();
2514 while self.token != token::CloseDelim(Delimiter::Brace) {
2515 match self.parse_arm() {
2516 Ok(arm) => arms.push(arm),
2518 // Recover by skipping to the end of the block.
2520 self.recover_stmt();
2521 let span = lo.to(self.token.span);
2522 if self.token == token::CloseDelim(Delimiter::Brace) {
2525 return Ok(self.mk_expr_with_attrs(
2527 ExprKind::Match(scrutinee, arms),
2533 let hi = self.token.span;
2535 Ok(self.mk_expr_with_attrs(lo.to(hi), ExprKind::Match(scrutinee, arms), attrs))
2538 /// Attempt to recover from match arm body with statements and no surrounding braces.
2539 fn parse_arm_body_missing_braces(
2541 first_expr: &P<Expr>,
2543 ) -> Option<P<Expr>> {
2544 if self.token.kind != token::Semi {
2547 let start_snapshot = self.create_snapshot_for_diagnostic();
2548 let semi_sp = self.token.span;
2551 vec![self.mk_stmt(first_expr.span, ast::StmtKind::Expr(first_expr.clone()))];
2552 let err = |this: &Parser<'_>, stmts: Vec<ast::Stmt>| {
2553 let span = stmts[0].span.to(stmts[stmts.len() - 1].span);
2555 this.sess.emit_err(MatchArmBodyWithoutBraces {
2558 num_statements: stmts.len(),
2559 sub: if stmts.len() > 1 {
2560 MatchArmBodyWithoutBracesSugg::AddBraces {
2561 left: span.shrink_to_lo(),
2562 right: span.shrink_to_hi(),
2565 MatchArmBodyWithoutBracesSugg::UseComma { semicolon: semi_sp }
2568 this.mk_expr_err(span)
2570 // We might have either a `,` -> `;` typo, or a block without braces. We need
2571 // a more subtle parsing strategy.
2573 if self.token.kind == token::CloseDelim(Delimiter::Brace) {
2574 // We have reached the closing brace of the `match` expression.
2575 return Some(err(self, stmts));
2577 if self.token.kind == token::Comma {
2578 self.restore_snapshot(start_snapshot);
2581 let pre_pat_snapshot = self.create_snapshot_for_diagnostic();
2582 match self.parse_pat_no_top_alt(None) {
2584 if self.token.kind == token::FatArrow {
2586 self.restore_snapshot(pre_pat_snapshot);
2587 return Some(err(self, stmts));
2595 self.restore_snapshot(pre_pat_snapshot);
2596 match self.parse_stmt_without_recovery(true, ForceCollect::No) {
2597 // Consume statements for as long as possible.
2602 self.restore_snapshot(start_snapshot);
2605 // We couldn't parse either yet another statement missing it's
2606 // enclosing block nor the next arm's pattern or closing brace.
2609 self.restore_snapshot(start_snapshot);
2617 pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
2618 // Used to check the `let_chains` and `if_let_guard` features mostly by scanning
2620 fn check_let_expr(expr: &Expr) -> (bool, bool) {
2622 ExprKind::Binary(BinOp { node: BinOpKind::And, .. }, ref lhs, ref rhs) => {
2623 let lhs_rslt = check_let_expr(lhs);
2624 let rhs_rslt = check_let_expr(rhs);
2625 (lhs_rslt.0 || rhs_rslt.0, false)
2627 ExprKind::Let(..) => (true, true),
2631 let attrs = self.parse_outer_attributes()?;
2632 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2633 let lo = this.token.span;
2634 let pat = this.parse_pat_allow_top_alt(
2638 CommaRecoveryMode::EitherTupleOrPipe,
2640 let guard = if this.eat_keyword(kw::If) {
2641 let if_span = this.prev_token.span;
2642 let cond = this.parse_expr_res(Restrictions::ALLOW_LET, None)?;
2643 let (has_let_expr, does_not_have_bin_op) = check_let_expr(&cond);
2645 if does_not_have_bin_op {
2646 // Remove the last feature gating of a `let` expression since it's stable.
2647 this.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
2649 let span = if_span.to(cond.span);
2650 this.sess.gated_spans.gate(sym::if_let_guard, span);
2656 let arrow_span = this.token.span;
2657 if let Err(mut err) = this.expect(&token::FatArrow) {
2658 // We might have a `=>` -> `=` or `->` typo (issue #89396).
2659 if TokenKind::FatArrow
2661 .map_or(false, |similar_tokens| similar_tokens.contains(&this.token.kind))
2663 err.span_suggestion(
2665 "try using a fat arrow here",
2667 Applicability::MaybeIncorrect,
2675 let arm_start_span = this.token.span;
2677 let expr = this.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
2678 err.span_label(arrow_span, "while parsing the `match` arm starting here");
2682 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
2683 && this.token != token::CloseDelim(Delimiter::Brace);
2685 let hi = this.prev_token.span;
2688 let sm = this.sess.source_map();
2689 if let Some(body) = this.parse_arm_body_missing_braces(&expr, arrow_span) {
2690 let span = body.span;
2699 is_placeholder: false,
2701 TrailingToken::None,
2704 this.expect_one_of(&[token::Comma], &[token::CloseDelim(Delimiter::Brace)])
2705 .or_else(|mut err| {
2706 if this.token == token::FatArrow {
2707 if let Ok(expr_lines) = sm.span_to_lines(expr.span)
2708 && let Ok(arm_start_lines) = sm.span_to_lines(arm_start_span)
2709 && arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
2710 && expr_lines.lines.len() == 2
2712 // We check whether there's any trailing code in the parse span,
2713 // if there isn't, we very likely have the following:
2716 // | -- - missing comma
2720 // | - ^^ self.token.span
2722 // | parsed until here as `"y" & X`
2723 err.span_suggestion_short(
2724 arm_start_span.shrink_to_hi(),
2725 "missing a comma here to end this `match` arm",
2727 Applicability::MachineApplicable,
2732 // FIXME(compiler-errors): We could also recover `; PAT =>` here
2734 // Try to parse a following `PAT =>`, if successful
2735 // then we should recover.
2736 let mut snapshot = this.create_snapshot_for_diagnostic();
2737 let pattern_follows = snapshot
2738 .parse_pat_allow_top_alt(
2742 CommaRecoveryMode::EitherTupleOrPipe,
2744 .map_err(|err| err.cancel())
2746 if pattern_follows && snapshot.check(&TokenKind::FatArrow) {
2748 this.sess.emit_err(MissingCommaAfterMatchArm {
2749 span: hi.shrink_to_hi(),
2754 err.span_label(arrow_span, "while parsing the `match` arm starting here");
2758 this.eat(&token::Comma);
2769 is_placeholder: false,
2771 TrailingToken::None,
2776 /// Parses a `try {...}` expression (`try` token already eaten).
2777 fn parse_try_block(&mut self, span_lo: Span) -> PResult<'a, P<Expr>> {
2778 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2779 if self.eat_keyword(kw::Catch) {
2780 Err(CatchAfterTry { span: self.prev_token.span }
2781 .into_diagnostic(&self.sess.span_diagnostic))
2783 let span = span_lo.to(body.span);
2784 self.sess.gated_spans.gate(sym::try_blocks, span);
2785 Ok(self.mk_expr_with_attrs(span, ExprKind::TryBlock(body), attrs))
2789 fn is_do_catch_block(&self) -> bool {
2790 self.token.is_keyword(kw::Do)
2791 && self.is_keyword_ahead(1, &[kw::Catch])
2792 && self.look_ahead(2, |t| *t == token::OpenDelim(Delimiter::Brace))
2793 && !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
2796 fn is_do_yeet(&self) -> bool {
2797 self.token.is_keyword(kw::Do) && self.is_keyword_ahead(1, &[kw::Yeet])
2800 fn is_try_block(&self) -> bool {
2801 self.token.is_keyword(kw::Try)
2802 && self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace))
2803 && self.token.uninterpolated_span().rust_2018()
2806 /// Parses an `async move? {...}` expression.
2807 fn parse_async_block(&mut self) -> PResult<'a, P<Expr>> {
2808 let lo = self.token.span;
2809 self.expect_keyword(kw::Async)?;
2810 let capture_clause = self.parse_capture_clause()?;
2811 let (attrs, body) = self.parse_inner_attrs_and_block()?;
2812 let kind = ExprKind::Async(capture_clause, DUMMY_NODE_ID, body);
2813 Ok(self.mk_expr_with_attrs(lo.to(self.prev_token.span), kind, attrs))
2816 fn is_async_block(&self) -> bool {
2817 self.token.is_keyword(kw::Async)
2820 self.is_keyword_ahead(1, &[kw::Move])
2821 && self.look_ahead(2, |t| *t == token::OpenDelim(Delimiter::Brace))
2824 self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace))
2828 fn is_certainly_not_a_block(&self) -> bool {
2829 self.look_ahead(1, |t| t.is_ident())
2831 // `{ ident, ` cannot start a block.
2832 self.look_ahead(2, |t| t == &token::Comma)
2833 || self.look_ahead(2, |t| t == &token::Colon)
2835 // `{ ident: token, ` cannot start a block.
2836 self.look_ahead(4, |t| t == &token::Comma) ||
2837 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
2838 self.look_ahead(3, |t| !t.can_begin_type())
2843 fn maybe_parse_struct_expr(
2845 qself: Option<&ast::QSelf>,
2847 ) -> Option<PResult<'a, P<Expr>>> {
2848 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
2849 if struct_allowed || self.is_certainly_not_a_block() {
2850 if let Err(err) = self.expect(&token::OpenDelim(Delimiter::Brace)) {
2851 return Some(Err(err));
2853 let expr = self.parse_struct_expr(qself.cloned(), path.clone(), true);
2854 if let (Ok(expr), false) = (&expr, struct_allowed) {
2855 // This is a struct literal, but we don't can't accept them here.
2856 self.sess.emit_err(StructLiteralNotAllowedHere {
2858 sub: StructLiteralNotAllowedHereSugg {
2859 left: path.span.shrink_to_lo(),
2860 right: expr.span.shrink_to_hi(),
2869 pub(super) fn parse_struct_fields(
2873 close_delim: Delimiter,
2874 ) -> PResult<'a, (Vec<ExprField>, ast::StructRest, bool)> {
2875 let mut fields = Vec::new();
2876 let mut base = ast::StructRest::None;
2877 let mut recover_async = false;
2879 let mut async_block_err = |e: &mut Diagnostic, span: Span| {
2880 recover_async = true;
2881 e.span_label(span, "`async` blocks are only allowed in Rust 2018 or later");
2882 e.help_use_latest_edition();
2885 while self.token != token::CloseDelim(close_delim) {
2886 if self.eat(&token::DotDot) || self.recover_struct_field_dots(close_delim) {
2887 let exp_span = self.prev_token.span;
2888 // We permit `.. }` on the left-hand side of a destructuring assignment.
2889 if self.check(&token::CloseDelim(close_delim)) {
2890 base = ast::StructRest::Rest(self.prev_token.span.shrink_to_hi());
2893 match self.parse_expr() {
2894 Ok(e) => base = ast::StructRest::Base(e),
2895 Err(mut e) if recover => {
2897 self.recover_stmt();
2899 Err(e) => return Err(e),
2901 self.recover_struct_comma_after_dotdot(exp_span);
2905 let recovery_field = self.find_struct_error_after_field_looking_code();
2906 let parsed_field = match self.parse_expr_field() {
2909 if pth == kw::Async {
2910 async_block_err(&mut e, pth.span);
2912 e.span_label(pth.span, "while parsing this struct");
2916 // If the next token is a comma, then try to parse
2917 // what comes next as additional fields, rather than
2918 // bailing out until next `}`.
2919 if self.token != token::Comma {
2920 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2921 if self.token != token::Comma {
2929 let is_shorthand = parsed_field.as_ref().map_or(false, |f| f.is_shorthand);
2930 // A shorthand field can be turned into a full field with `:`.
2931 // We should point this out.
2932 self.check_or_expected(!is_shorthand, TokenType::Token(token::Colon));
2934 match self.expect_one_of(&[token::Comma], &[token::CloseDelim(close_delim)]) {
2936 if let Some(f) = parsed_field.or(recovery_field) {
2937 // Only include the field if there's no parse error for the field name.
2942 if pth == kw::Async {
2943 async_block_err(&mut e, pth.span);
2945 e.span_label(pth.span, "while parsing this struct");
2946 if let Some(f) = recovery_field {
2949 self.prev_token.span.shrink_to_hi(),
2950 "try adding a comma",
2952 Applicability::MachineApplicable,
2954 } else if is_shorthand
2955 && (AssocOp::from_token(&self.token).is_some()
2956 || matches!(&self.token.kind, token::OpenDelim(_))
2957 || self.token.kind == token::Dot)
2959 // Looks like they tried to write a shorthand, complex expression.
2960 let ident = parsed_field.expect("is_shorthand implies Some").ident;
2962 ident.span.shrink_to_lo(),
2963 "try naming a field",
2964 &format!("{ident}: "),
2965 Applicability::HasPlaceholders,
2973 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2974 self.eat(&token::Comma);
2978 Ok((fields, base, recover_async))
2981 /// Precondition: already parsed the '{'.
2982 pub(super) fn parse_struct_expr(
2984 qself: Option<ast::QSelf>,
2987 ) -> PResult<'a, P<Expr>> {
2989 let (fields, base, recover_async) =
2990 self.parse_struct_fields(pth.clone(), recover, Delimiter::Brace)?;
2991 let span = lo.to(self.token.span);
2992 self.expect(&token::CloseDelim(Delimiter::Brace))?;
2993 let expr = if recover_async {
2996 ExprKind::Struct(P(ast::StructExpr { qself, path: pth, fields, rest: base }))
2998 Ok(self.mk_expr(span, expr))
3001 /// Use in case of error after field-looking code: `S { foo: () with a }`.
3002 fn find_struct_error_after_field_looking_code(&self) -> Option<ExprField> {
3003 match self.token.ident() {
3004 Some((ident, is_raw))
3005 if (is_raw || !ident.is_reserved())
3006 && self.look_ahead(1, |t| *t == token::Colon) =>
3008 Some(ast::ExprField {
3010 span: self.token.span,
3011 expr: self.mk_expr_err(self.token.span),
3012 is_shorthand: false,
3013 attrs: AttrVec::new(),
3015 is_placeholder: false,
3022 fn recover_struct_comma_after_dotdot(&mut self, span: Span) {
3023 if self.token != token::Comma {
3026 self.sess.emit_err(CommaAfterBaseStruct {
3027 span: span.to(self.prev_token.span),
3028 comma: self.token.span,
3030 self.recover_stmt();
3033 fn recover_struct_field_dots(&mut self, close_delim: Delimiter) -> bool {
3034 if !self.look_ahead(1, |t| *t == token::CloseDelim(close_delim))
3035 && self.eat(&token::DotDotDot)
3037 // recover from typo of `...`, suggest `..`
3038 let span = self.prev_token.span;
3039 self.sess.emit_err(MissingDotDot { token_span: span, sugg_span: span });
3045 /// Parses `ident (COLON expr)?`.
3046 fn parse_expr_field(&mut self) -> PResult<'a, ExprField> {
3047 let attrs = self.parse_outer_attributes()?;
3048 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
3049 let lo = this.token.span;
3051 // Check if a colon exists one ahead. This means we're parsing a fieldname.
3052 let is_shorthand = !this.look_ahead(1, |t| t == &token::Colon || t == &token::Eq);
3053 let (ident, expr) = if is_shorthand {
3054 // Mimic `x: x` for the `x` field shorthand.
3055 let ident = this.parse_ident_common(false)?;
3056 let path = ast::Path::from_ident(ident);
3057 (ident, this.mk_expr(ident.span, ExprKind::Path(None, path)))
3059 let ident = this.parse_field_name()?;
3060 this.error_on_eq_field_init(ident);
3062 (ident, this.parse_expr()?)
3068 span: lo.to(expr.span),
3073 is_placeholder: false,
3075 TrailingToken::MaybeComma,
3080 /// Check for `=`. This means the source incorrectly attempts to
3081 /// initialize a field with an eq rather than a colon.
3082 fn error_on_eq_field_init(&self, field_name: Ident) {
3083 if self.token != token::Eq {
3087 self.sess.emit_err(EqFieldInit {
3088 span: self.token.span,
3089 eq: field_name.span.shrink_to_hi().to(self.token.span),
3093 fn err_dotdotdot_syntax(&self, span: Span) {
3094 self.sess.emit_err(DotDotDot { span });
3097 fn err_larrow_operator(&self, span: Span) {
3098 self.sess.emit_err(LeftArrowOperator { span });
3101 fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
3102 ExprKind::AssignOp(binop, lhs, rhs)
3107 start: Option<P<Expr>>,
3108 end: Option<P<Expr>>,
3109 limits: RangeLimits,
3111 if end.is_none() && limits == RangeLimits::Closed {
3112 self.inclusive_range_with_incorrect_end(self.prev_token.span);
3115 ExprKind::Range(start, end, limits)
3119 fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
3120 ExprKind::Unary(unop, expr)
3123 fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
3124 ExprKind::Binary(binop, lhs, rhs)
3127 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
3128 ExprKind::Index(expr, idx)
3131 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
3132 ExprKind::Call(f, args)
3135 fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> P<Expr> {
3136 let span = lo.to(self.prev_token.span);
3137 let await_expr = self.mk_expr(span, ExprKind::Await(self_arg));
3138 self.recover_from_await_method_call();
3142 pub(crate) fn mk_expr_with_attrs(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
3143 P(Expr { kind, span, attrs, id: DUMMY_NODE_ID, tokens: None })
3146 pub(crate) fn mk_expr(&self, span: Span, kind: ExprKind) -> P<Expr> {
3147 P(Expr { kind, span, attrs: AttrVec::new(), id: DUMMY_NODE_ID, tokens: None })
3150 pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> {
3151 self.mk_expr(span, ExprKind::Err)
3154 /// Create expression span ensuring the span of the parent node
3155 /// is larger than the span of lhs and rhs, including the attributes.
3156 fn mk_expr_sp(&self, lhs: &P<Expr>, lhs_span: Span, rhs_span: Span) -> Span {
3159 .find(|a| a.style == AttrStyle::Outer)
3160 .map_or(lhs_span, |a| a.span)
3164 fn collect_tokens_for_expr(
3167 f: impl FnOnce(&mut Self, ast::AttrVec) -> PResult<'a, P<Expr>>,
3168 ) -> PResult<'a, P<Expr>> {
3169 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
3170 let res = f(this, attrs)?;
3171 let trailing = if this.restrictions.contains(Restrictions::STMT_EXPR)
3172 && this.token.kind == token::Semi
3175 } else if this.token.kind == token::Gt {
3178 // FIXME - pass this through from the place where we know
3179 // we need a comma, rather than assuming that `#[attr] expr,`
3180 // always captures a trailing comma
3181 TrailingToken::MaybeComma