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
,
8 use crate::maybe_recover_from_interpolated_ty_qpath
;
10 use ast
::token
::DelimToken
;
11 use rustc_ast
::ptr
::P
;
12 use rustc_ast
::token
::{self, Token, TokenKind}
;
13 use rustc_ast
::tokenstream
::Spacing
;
14 use rustc_ast
::util
::classify
;
15 use rustc_ast
::util
::literal
::LitError
;
16 use rustc_ast
::util
::parser
::{prec_let_scrutinee_needs_par, AssocOp, Fixity}
;
17 use rustc_ast
::{self as ast, AttrStyle, AttrVec, CaptureBy, ExprField, Lit, UnOp, DUMMY_NODE_ID}
;
18 use rustc_ast
::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, MacCall, Param, Ty, TyKind}
;
19 use rustc_ast
::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits}
;
20 use rustc_ast_pretty
::pprust
;
21 use rustc_errors
::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, PResult}
;
22 use rustc_session
::lint
::builtin
::BREAK_WITH_LABEL_AND_LOOP
;
23 use rustc_session
::lint
::BuiltinLintDiagnostics
;
24 use rustc_span
::source_map
::{self, Span, Spanned}
;
25 use rustc_span
::symbol
::{kw, sym, Ident, Symbol}
;
26 use rustc_span
::{BytePos, Pos}
;
29 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
30 /// dropped into the token stream, which happens while parsing the result of
31 /// macro expansion). Placement of these is not as complex as I feared it would
32 /// be. The important thing is to make sure that lookahead doesn't balk at
33 /// `token::Interpolated` tokens.
34 macro_rules
! maybe_whole_expr
{
36 if let token
::Interpolated(nt
) = &$p
.token
.kind
{
38 token
::NtExpr(e
) | token
::NtLiteral(e
) => {
43 token
::NtPath(path
) => {
44 let path
= path
.clone();
48 ExprKind
::Path(None
, path
),
52 token
::NtBlock(block
) => {
53 let block
= block
.clone();
57 ExprKind
::Block(block
, None
),
68 pub(super) enum LhsExpr
{
70 AttributesParsed(AttrWrapper
),
71 AlreadyParsed(P
<Expr
>),
74 impl From
<Option
<AttrWrapper
>> for LhsExpr
{
75 /// Converts `Some(attrs)` into `LhsExpr::AttributesParsed(attrs)`
76 /// and `None` into `LhsExpr::NotYetParsed`.
78 /// This conversion does not allocate.
79 fn from(o
: Option
<AttrWrapper
>) -> Self {
80 if let Some(attrs
) = o { LhsExpr::AttributesParsed(attrs) }
else { LhsExpr::NotYetParsed }
84 impl From
<P
<Expr
>> for LhsExpr
{
85 /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed(expr)`.
87 /// This conversion does not allocate.
88 fn from(expr
: P
<Expr
>) -> Self {
89 LhsExpr
::AlreadyParsed(expr
)
94 /// Parses an expression.
96 pub fn parse_expr(&mut self) -> PResult
<'a
, P
<Expr
>> {
97 self.current_closure
.take();
99 self.parse_expr_res(Restrictions
::empty(), None
)
102 /// Parses an expression, forcing tokens to be collected
103 pub fn parse_expr_force_collect(&mut self) -> PResult
<'a
, P
<Expr
>> {
104 self.collect_tokens_no_attrs(|this
| this
.parse_expr())
107 pub fn parse_anon_const_expr(&mut self) -> PResult
<'a
, AnonConst
> {
108 self.parse_expr().map(|value
| AnonConst { id: DUMMY_NODE_ID, value }
)
111 fn parse_expr_catch_underscore(&mut self) -> PResult
<'a
, P
<Expr
>> {
112 match self.parse_expr() {
113 Ok(expr
) => Ok(expr
),
114 Err(mut err
) => match self.token
.ident() {
115 Some((Ident { name: kw::Underscore, .. }
, false))
116 if self.look_ahead(1, |t
| t
== &token
::Comma
) =>
118 // Special-case handling of `foo(_, _, _)`
121 Ok(self.mk_expr(self.prev_token
.span
, ExprKind
::Err
, AttrVec
::new()))
128 /// Parses a sequence of expressions delimited by parentheses.
129 fn parse_paren_expr_seq(&mut self) -> PResult
<'a
, Vec
<P
<Expr
>>> {
130 self.parse_paren_comma_seq(|p
| p
.parse_expr_catch_underscore()).map(|(r
, _
)| r
)
133 /// Parses an expression, subject to the given restrictions.
135 pub(super) fn parse_expr_res(
138 already_parsed_attrs
: Option
<AttrWrapper
>,
139 ) -> PResult
<'a
, P
<Expr
>> {
140 self.with_res(r
, |this
| this
.parse_assoc_expr(already_parsed_attrs
))
143 /// Parses an associative expression.
145 /// This parses an expression accounting for associativity and precedence of the operators in
150 already_parsed_attrs
: Option
<AttrWrapper
>,
151 ) -> PResult
<'a
, P
<Expr
>> {
152 self.parse_assoc_expr_with(0, already_parsed_attrs
.into())
155 /// Parses an associative expression with operators of at least `min_prec` precedence.
156 pub(super) fn parse_assoc_expr_with(
160 ) -> PResult
<'a
, P
<Expr
>> {
161 let mut lhs
= if let LhsExpr
::AlreadyParsed(expr
) = lhs
{
164 let attrs
= match lhs
{
165 LhsExpr
::AttributesParsed(attrs
) => Some(attrs
),
168 if [token
::DotDot
, token
::DotDotDot
, token
::DotDotEq
].contains(&self.token
.kind
) {
169 return self.parse_prefix_range_expr(attrs
);
171 self.parse_prefix_expr(attrs
)?
174 let last_type_ascription_set
= self.last_type_ascription
.is_some();
176 if !self.should_continue_as_assoc_expr(&lhs
) {
177 self.last_type_ascription
= None
;
181 self.expected_tokens
.push(TokenType
::Operator
);
182 while let Some(op
) = self.check_assoc_op() {
183 // Adjust the span for interpolated LHS to point to the `$lhs` token
184 // and not to what it refers to.
185 let lhs_span
= match self.prev_token
.kind
{
186 TokenKind
::Interpolated(..) => self.prev_token
.span
,
190 let cur_op_span
= self.token
.span
;
191 let restrictions
= if op
.node
.is_assign_like() {
192 self.restrictions
& Restrictions
::NO_STRUCT_LITERAL
196 let prec
= op
.node
.precedence();
200 // Check for deprecated `...` syntax
201 if self.token
== token
::DotDotDot
&& op
.node
== AssocOp
::DotDotEq
{
202 self.err_dotdotdot_syntax(self.token
.span
);
205 if self.token
== token
::LArrow
{
206 self.err_larrow_operator(self.token
.span
);
210 if op
.node
.is_comparison() {
211 if let Some(expr
) = self.check_no_chained_comparison(&lhs
, &op
)?
{
216 // Look for JS' `===` and `!==` and recover
217 if (op
.node
== AssocOp
::Equal
|| op
.node
== AssocOp
::NotEqual
)
218 && self.token
.kind
== token
::Eq
219 && self.prev_token
.span
.hi() == self.token
.span
.lo()
221 let sp
= op
.span
.to(self.token
.span
);
222 let sugg
= match op
.node
{
223 AssocOp
::Equal
=> "==",
224 AssocOp
::NotEqual
=> "!=",
227 self.struct_span_err(sp
, &format
!("invalid comparison operator `{sugg}=`"))
228 .span_suggestion_short(
230 &format
!("`{s}=` is not a valid comparison operator, use `{s}`", s
= sugg
),
232 Applicability
::MachineApplicable
,
238 // Look for PHP's `<>` and recover
239 if op
.node
== AssocOp
::Less
240 && self.token
.kind
== token
::Gt
241 && self.prev_token
.span
.hi() == self.token
.span
.lo()
243 let sp
= op
.span
.to(self.token
.span
);
244 self.struct_span_err(sp
, "invalid comparison operator `<>`")
245 .span_suggestion_short(
247 "`<>` is not a valid comparison operator, use `!=`",
249 Applicability
::MachineApplicable
,
255 // Look for C++'s `<=>` and recover
256 if op
.node
== AssocOp
::LessEqual
257 && self.token
.kind
== token
::Gt
258 && self.prev_token
.span
.hi() == self.token
.span
.lo()
260 let sp
= op
.span
.to(self.token
.span
);
261 self.struct_span_err(sp
, "invalid comparison operator `<=>`")
264 "`<=>` is not a valid comparison operator, use `std::cmp::Ordering`",
270 if self.prev_token
== token
::BinOp(token
::Plus
)
271 && self.token
== token
::BinOp(token
::Plus
)
272 && self.prev_token
.span
.between(self.token
.span
).is_empty()
274 let op_span
= self.prev_token
.span
.to(self.token
.span
);
275 // Eat the second `+`
277 lhs
= self.recover_from_postfix_increment(lhs
, op_span
)?
;
283 if op
== AssocOp
::As
{
284 lhs
= self.parse_assoc_op_cast(lhs
, lhs_span
, ExprKind
::Cast
)?
;
286 } else if op
== AssocOp
::Colon
{
287 lhs
= self.parse_assoc_op_ascribe(lhs
, lhs_span
)?
;
289 } else if op
== AssocOp
::DotDot
|| op
== AssocOp
::DotDotEq
{
290 // If we didn't have to handle `x..`/`x..=`, it would be pretty easy to
291 // generalise it to the Fixity::None code.
292 lhs
= self.parse_range_expr(prec
, lhs
, op
, cur_op_span
)?
;
296 let fixity
= op
.fixity();
297 let prec_adjustment
= match fixity
{
300 // We currently have no non-associative operators that are not handled above by
301 // the special cases. The code is here only for future convenience.
304 let rhs
= self.with_res(restrictions
- Restrictions
::STMT_EXPR
, |this
| {
305 this
.parse_assoc_expr_with(prec
+ prec_adjustment
, LhsExpr
::NotYetParsed
)
308 let span
= self.mk_expr_sp(&lhs
, lhs_span
, rhs
.span
);
321 | AssocOp
::ShiftRight
327 | AssocOp
::GreaterEqual
=> {
328 let ast_op
= op
.to_ast_binop().unwrap();
329 let binary
= self.mk_binary(source_map
::respan(cur_op_span
, ast_op
), lhs
, rhs
);
330 self.mk_expr(span
, binary
, AttrVec
::new())
333 self.mk_expr(span
, ExprKind
::Assign(lhs
, rhs
, cur_op_span
), AttrVec
::new())
335 AssocOp
::AssignOp(k
) => {
337 token
::Plus
=> BinOpKind
::Add
,
338 token
::Minus
=> BinOpKind
::Sub
,
339 token
::Star
=> BinOpKind
::Mul
,
340 token
::Slash
=> BinOpKind
::Div
,
341 token
::Percent
=> BinOpKind
::Rem
,
342 token
::Caret
=> BinOpKind
::BitXor
,
343 token
::And
=> BinOpKind
::BitAnd
,
344 token
::Or
=> BinOpKind
::BitOr
,
345 token
::Shl
=> BinOpKind
::Shl
,
346 token
::Shr
=> BinOpKind
::Shr
,
348 let aopexpr
= self.mk_assign_op(source_map
::respan(cur_op_span
, aop
), lhs
, rhs
);
349 self.mk_expr(span
, aopexpr
, AttrVec
::new())
351 AssocOp
::As
| AssocOp
::Colon
| AssocOp
::DotDot
| AssocOp
::DotDotEq
=> {
352 self.span_bug(span
, "AssocOp should have been handled by special case")
356 if let Fixity
::None
= fixity
{
360 if last_type_ascription_set
{
361 self.last_type_ascription
= None
;
366 fn should_continue_as_assoc_expr(&mut self, lhs
: &Expr
) -> bool
{
367 match (self.expr_is_complete(lhs
), AssocOp
::from_token(&self.token
)) {
368 // Semi-statement forms are odd:
369 // See https://github.com/rust-lang/rust/issues/29071
370 (true, None
) => false,
371 (false, _
) => true, // Continue parsing the expression.
372 // An exhaustive check is done in the following block, but these are checked first
373 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
374 // want to keep their span info to improve diagnostics in these cases in a later stage.
375 (true, Some(AssocOp
::Multiply
)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
376 (true, Some(AssocOp
::Subtract
)) | // `{ 42 } -5`
377 (true, Some(AssocOp
::Add
)) // `{ 42 } + 42
378 // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
379 // `if x { a } else { b } && if y { c } else { d }`
380 if !self.look_ahead(1, |t
| t
.is_used_keyword()) => {
381 // These cases are ambiguous and can't be identified in the parser alone.
382 let sp
= self.sess
.source_map().start_point(self.token
.span
);
383 self.sess
.ambiguous_block_expr_parse
.borrow_mut().insert(sp
, lhs
.span
);
386 (true, Some(AssocOp
::LAnd
)) |
387 (true, Some(AssocOp
::LOr
)) |
388 (true, Some(AssocOp
::BitOr
)) => {
389 // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }`. Separated from the
390 // above due to #74233.
391 // These cases are ambiguous and can't be identified in the parser alone.
393 // Bitwise AND is left out because guessing intent is hard. We can make
394 // suggestions based on the assumption that double-refs are rarely intentional,
395 // and closures are distinct enough that they don't get mixed up with their
397 let sp
= self.sess
.source_map().start_point(self.token
.span
);
398 self.sess
.ambiguous_block_expr_parse
.borrow_mut().insert(sp
, lhs
.span
);
401 (true, Some(ref op
)) if !op
.can_continue_expr_unambiguously() => false,
403 self.error_found_expr_would_be_stmt(lhs
);
409 /// We've found an expression that would be parsed as a statement,
410 /// but the next token implies this should be parsed as an expression.
411 /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
412 fn error_found_expr_would_be_stmt(&self, lhs
: &Expr
) {
413 let mut err
= self.struct_span_err(
415 &format
!("expected expression, found `{}`", pprust
::token_to_string(&self.token
),),
417 err
.span_label(self.token
.span
, "expected expression");
418 self.sess
.expr_parentheses_needed(&mut err
, lhs
.span
);
422 /// Possibly translate the current token to an associative operator.
423 /// The method does not advance the current token.
425 /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
426 fn check_assoc_op(&self) -> Option
<Spanned
<AssocOp
>> {
427 let (op
, span
) = match (AssocOp
::from_token(&self.token
), self.token
.ident()) {
428 // When parsing const expressions, stop parsing when encountering `>`.
433 | AssocOp
::GreaterEqual
434 | AssocOp
::AssignOp(token
::BinOpToken
::Shr
),
437 ) if self.restrictions
.contains(Restrictions
::CONST_EXPR
) => {
440 (Some(op
), _
) => (op
, self.token
.span
),
441 (None
, Some((Ident { name: sym::and, span }
, false))) => {
442 self.error_bad_logical_op("and", "&&", "conjunction");
443 (AssocOp
::LAnd
, span
)
445 (None
, Some((Ident { name: sym::or, span }
, false))) => {
446 self.error_bad_logical_op("or", "||", "disjunction");
451 Some(source_map
::respan(span
, op
))
454 /// Error on `and` and `or` suggesting `&&` and `||` respectively.
455 fn error_bad_logical_op(&self, bad
: &str, good
: &str, english
: &str) {
456 self.struct_span_err(self.token
.span
, &format
!("`{bad}` is not a logical operator"))
457 .span_suggestion_short(
459 &format
!("use `{good}` to perform logical {english}"),
461 Applicability
::MachineApplicable
,
463 .note("unlike in e.g., python and PHP, `&&` and `||` are used for logical operators")
467 /// Checks if this expression is a successfully parsed statement.
468 fn expr_is_complete(&self, e
: &Expr
) -> bool
{
469 self.restrictions
.contains(Restrictions
::STMT_EXPR
)
470 && !classify
::expr_requires_semi_to_be_stmt(e
)
473 /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
474 /// The other two variants are handled in `parse_prefix_range_expr` below.
481 ) -> PResult
<'a
, P
<Expr
>> {
482 let rhs
= if self.is_at_start_of_range_notation_rhs() {
483 Some(self.parse_assoc_expr_with(prec
+ 1, LhsExpr
::NotYetParsed
)?
)
487 let rhs_span
= rhs
.as_ref().map_or(cur_op_span
, |x
| x
.span
);
488 let span
= self.mk_expr_sp(&lhs
, lhs
.span
, rhs_span
);
490 if op
== AssocOp
::DotDot { RangeLimits::HalfOpen }
else { RangeLimits::Closed }
;
491 let range
= self.mk_range(Some(lhs
), rhs
, limits
);
492 Ok(self.mk_expr(span
, range
, AttrVec
::new()))
495 fn is_at_start_of_range_notation_rhs(&self) -> bool
{
496 if self.token
.can_begin_expr() {
497 // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
498 if self.token
== token
::OpenDelim(token
::Brace
) {
499 return !self.restrictions
.contains(Restrictions
::NO_STRUCT_LITERAL
);
507 /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
508 fn parse_prefix_range_expr(&mut self, attrs
: Option
<AttrWrapper
>) -> PResult
<'a
, P
<Expr
>> {
509 // Check for deprecated `...` syntax.
510 if self.token
== token
::DotDotDot
{
511 self.err_dotdotdot_syntax(self.token
.span
);
515 [token
::DotDot
, token
::DotDotDot
, token
::DotDotEq
].contains(&self.token
.kind
),
516 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
520 let limits
= match self.token
.kind
{
521 token
::DotDot
=> RangeLimits
::HalfOpen
,
522 _
=> RangeLimits
::Closed
,
524 let op
= AssocOp
::from_token(&self.token
);
525 // FIXME: `parse_prefix_range_expr` is called when the current
526 // token is `DotDot`, `DotDotDot`, or `DotDotEq`. If we haven't already
527 // parsed attributes, then trying to parse them here will always fail.
528 // We should figure out how we want attributes on range expressions to work.
529 let attrs
= self.parse_or_use_outer_attributes(attrs
)?
;
530 self.collect_tokens_for_expr(attrs
, |this
, attrs
| {
531 let lo
= this
.token
.span
;
533 let (span
, opt_end
) = if this
.is_at_start_of_range_notation_rhs() {
534 // RHS must be parsed with more associativity than the dots.
535 this
.parse_assoc_expr_with(op
.unwrap().precedence() + 1, LhsExpr
::NotYetParsed
)
536 .map(|x
| (lo
.to(x
.span
), Some(x
)))?
540 let range
= this
.mk_range(None
, opt_end
, limits
);
541 Ok(this
.mk_expr(span
, range
, attrs
.into()))
545 /// Parses a prefix-unary-operator expr.
546 fn parse_prefix_expr(&mut self, attrs
: Option
<AttrWrapper
>) -> PResult
<'a
, P
<Expr
>> {
547 let attrs
= self.parse_or_use_outer_attributes(attrs
)?
;
548 let lo
= self.token
.span
;
550 macro_rules
! make_it
{
551 ($this
:ident
, $attrs
:expr
, |this
, _
| $body
:expr
) => {
552 $this
.collect_tokens_for_expr($attrs
, |$this
, attrs
| {
553 let (hi
, ex
) = $body?
;
554 Ok($this
.mk_expr(lo
.to(hi
), ex
, attrs
.into()))
561 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
562 match this
.token
.uninterpolate().kind
{
563 token
::Not
=> make_it
!(this
, attrs
, |this
, _
| this
.parse_unary_expr(lo
, UnOp
::Not
)), // `!expr`
564 token
::Tilde
=> make_it
!(this
, attrs
, |this
, _
| this
.recover_tilde_expr(lo
)), // `~expr`
565 token
::BinOp(token
::Minus
) => {
566 make_it
!(this
, attrs
, |this
, _
| this
.parse_unary_expr(lo
, UnOp
::Neg
))
568 token
::BinOp(token
::Star
) => {
569 make_it
!(this
, attrs
, |this
, _
| this
.parse_unary_expr(lo
, UnOp
::Deref
))
571 token
::BinOp(token
::And
) | token
::AndAnd
=> {
572 make_it
!(this
, attrs
, |this
, _
| this
.parse_borrow_expr(lo
))
574 token
::BinOp(token
::Plus
) if this
.look_ahead(1, |tok
| tok
.is_numeric_lit()) => {
575 let mut err
= this
.struct_span_err(lo
, "leading `+` is not supported");
576 err
.span_label(lo
, "unexpected `+`");
578 // a block on the LHS might have been intended to be an expression instead
579 if let Some(sp
) = this
.sess
.ambiguous_block_expr_parse
.borrow().get(&lo
) {
580 this
.sess
.expr_parentheses_needed(&mut err
, *sp
);
582 err
.span_suggestion_verbose(
584 "try removing the `+`",
586 Applicability
::MachineApplicable
,
592 this
.parse_prefix_expr(None
)
594 // Recover from `++x`:
595 token
::BinOp(token
::Plus
)
596 if this
.look_ahead(1, |t
| *t
== token
::BinOp(token
::Plus
)) =>
598 let prev_is_semi
= this
.prev_token
== token
::Semi
;
599 let pre_span
= this
.token
.span
.to(this
.look_ahead(1, |t
| t
.span
));
604 let operand_expr
= this
.parse_dot_or_call_expr(Default
::default())?
;
605 this
.recover_from_prefix_increment(operand_expr
, pre_span
, prev_is_semi
)
607 token
::Ident(..) if this
.token
.is_keyword(kw
::Box
) => {
608 make_it
!(this
, attrs
, |this
, _
| this
.parse_box_expr(lo
))
610 token
::Ident(..) if this
.is_mistaken_not_ident_negation() => {
611 make_it
!(this
, attrs
, |this
, _
| this
.recover_not_expr(lo
))
613 _
=> return this
.parse_dot_or_call_expr(Some(attrs
)),
617 fn parse_prefix_expr_common(&mut self, lo
: Span
) -> PResult
<'a
, (Span
, P
<Expr
>)> {
619 let expr
= self.parse_prefix_expr(None
);
620 let (span
, expr
) = self.interpolated_or_expr_span(expr
)?
;
621 Ok((lo
.to(span
), expr
))
624 fn parse_unary_expr(&mut self, lo
: Span
, op
: UnOp
) -> PResult
<'a
, (Span
, ExprKind
)> {
625 let (span
, expr
) = self.parse_prefix_expr_common(lo
)?
;
626 Ok((span
, self.mk_unary(op
, expr
)))
629 // Recover on `!` suggesting for bitwise negation instead.
630 fn recover_tilde_expr(&mut self, lo
: Span
) -> PResult
<'a
, (Span
, ExprKind
)> {
631 self.struct_span_err(lo
, "`~` cannot be used as a unary operator")
632 .span_suggestion_short(
634 "use `!` to perform bitwise not",
636 Applicability
::MachineApplicable
,
640 self.parse_unary_expr(lo
, UnOp
::Not
)
643 /// Parse `box expr`.
644 fn parse_box_expr(&mut self, lo
: Span
) -> PResult
<'a
, (Span
, ExprKind
)> {
645 let (span
, expr
) = self.parse_prefix_expr_common(lo
)?
;
646 self.sess
.gated_spans
.gate(sym
::box_syntax
, span
);
647 Ok((span
, ExprKind
::Box(expr
)))
650 fn is_mistaken_not_ident_negation(&self) -> bool
{
651 let token_cannot_continue_expr
= |t
: &Token
| match t
.uninterpolate().kind
{
652 // These tokens can start an expression after `!`, but
653 // can't continue an expression after an ident
654 token
::Ident(name
, is_raw
) => token
::ident_can_begin_expr(name
, t
.span
, is_raw
),
655 token
::Literal(..) | token
::Pound
=> true,
656 _
=> t
.is_whole_expr(),
658 self.token
.is_ident_named(sym
::not
) && self.look_ahead(1, token_cannot_continue_expr
)
661 /// Recover on `not expr` in favor of `!expr`.
662 fn recover_not_expr(&mut self, lo
: Span
) -> PResult
<'a
, (Span
, ExprKind
)> {
664 let not_token
= self.look_ahead(1, |t
| t
.clone());
665 self.struct_span_err(
667 &format
!("unexpected {} after identifier", super::token_descr(¬_token
)),
669 .span_suggestion_short(
670 // Span the `not` plus trailing whitespace to avoid
671 // trailing whitespace after the `!` in our suggestion
672 self.sess
.source_map().span_until_non_whitespace(lo
.to(not_token
.span
)),
673 "use `!` to perform logical negation",
675 Applicability
::MachineApplicable
,
680 self.parse_unary_expr(lo
, UnOp
::Not
)
683 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
684 fn interpolated_or_expr_span(
686 expr
: PResult
<'a
, P
<Expr
>>,
687 ) -> PResult
<'a
, (Span
, P
<Expr
>)> {
690 match self.prev_token
.kind
{
691 TokenKind
::Interpolated(..) => self.prev_token
.span
,
699 fn parse_assoc_op_cast(
703 expr_kind
: fn(P
<Expr
>, P
<Ty
>) -> ExprKind
,
704 ) -> PResult
<'a
, P
<Expr
>> {
705 let mk_expr
= |this
: &mut Self, lhs
: P
<Expr
>, rhs
: P
<Ty
>| {
707 this
.mk_expr_sp(&lhs
, lhs_span
, rhs
.span
),
713 // Save the state of the parser before parsing type normally, in case there is a
714 // LessThan comparison after this cast.
715 let parser_snapshot_before_type
= self.clone();
716 let cast_expr
= match self.parse_as_cast_ty() {
717 Ok(rhs
) => mk_expr(self, lhs
, rhs
),
719 // Rewind to before attempting to parse the type with generics, to recover
720 // from situations like `x as usize < y` in which we first tried to parse
721 // `usize < y` as a type with generic arguments.
722 let parser_snapshot_after_type
= mem
::replace(self, parser_snapshot_before_type
);
724 // Check for typo of `'a: loop { break 'a }` with a missing `'`.
725 match (&lhs
.kind
, &self.token
.kind
) {
728 ExprKind
::Path(None
, ast
::Path { segments, .. }
),
729 TokenKind
::Ident(kw
::For
| kw
::Loop
| kw
::While
, false),
730 ) if segments
.len() == 1 => {
731 let snapshot
= self.create_snapshot_for_diagnostic();
733 ident
: Ident
::from_str_and_span(
734 &format
!("'{}", segments
[0].ident
),
735 segments
[0].ident
.span
,
738 match self.parse_labeled_expr(label
, AttrVec
::new(), false) {
741 self.struct_span_err(label
.ident
.span
, "malformed loop label")
744 "use the correct loop label format",
745 label
.ident
.to_string(),
746 Applicability
::MachineApplicable
,
753 self.restore_snapshot(snapshot
);
760 match self.parse_path(PathStyle
::Expr
) {
762 let (op_noun
, op_verb
) = match self.token
.kind
{
763 token
::Lt
=> ("comparison", "comparing"),
764 token
::BinOp(token
::Shl
) => ("shift", "shifting"),
766 // We can end up here even without `<` being the next token, for
767 // example because `parse_ty_no_plus` returns `Err` on keywords,
768 // but `parse_path` returns `Ok` on them due to error recovery.
769 // Return original error and parser state.
770 *self = parser_snapshot_after_type
;
771 return Err(type_err
);
775 // Successfully parsed the type path leaving a `<` yet to parse.
778 // Report non-fatal diagnostics, keep `x as usize` as an expression
779 // in AST and continue parsing.
781 "`<` is interpreted as a start of generic arguments for `{}`, not a {}",
782 pprust
::path_to_string(&path
),
785 let span_after_type
= parser_snapshot_after_type
.token
.span
;
787 mk_expr(self, lhs
, self.mk_ty(path
.span
, TyKind
::Path(None
, path
)));
789 self.struct_span_err(self.token
.span
, &msg
)
791 self.look_ahead(1, |t
| t
.span
).to(span_after_type
),
792 "interpreted as generic arguments",
794 .span_label(self.token
.span
, format
!("not interpreted as {op_noun}"))
795 .multipart_suggestion(
796 &format
!("try {op_verb} the cast value"),
798 (expr
.span
.shrink_to_lo(), "(".to_string()),
799 (expr
.span
.shrink_to_hi(), ")".to_string()),
801 Applicability
::MachineApplicable
,
808 // Couldn't parse as a path, return original error and parser state.
810 *self = parser_snapshot_after_type
;
811 return Err(type_err
);
817 self.parse_and_disallow_postfix_after_cast(cast_expr
)
820 /// Parses a postfix operators such as `.`, `?`, or index (`[]`) after a cast,
821 /// then emits an error and returns the newly parsed tree.
822 /// The resulting parse tree for `&x as T[0]` has a precedence of `((&x) as T)[0]`.
823 fn parse_and_disallow_postfix_after_cast(
826 ) -> PResult
<'a
, P
<Expr
>> {
827 let span
= cast_expr
.span
;
828 let maybe_ascription_span
= if let ExprKind
::Type(ascripted_expr
, _
) = &cast_expr
.kind
{
829 Some(ascripted_expr
.span
.shrink_to_hi().with_hi(span
.hi()))
834 // Save the memory location of expr before parsing any following postfix operators.
835 // This will be compared with the memory location of the output expression.
836 // If they different we can assume we parsed another expression because the existing expression is not reallocated.
837 let addr_before
= &*cast_expr
as *const _
as usize;
838 let with_postfix
= self.parse_dot_or_call_expr_with_(cast_expr
, span
)?
;
839 let changed
= addr_before
!= &*with_postfix
as *const _
as usize;
841 // Check if an illegal postfix operator has been added after the cast.
842 // If the resulting expression is not a cast, or has a different memory location, it is an illegal postfix operator.
843 if !matches
!(with_postfix
.kind
, ExprKind
::Cast(_
, _
) | ExprKind
::Type(_
, _
)) || changed
{
845 "casts cannot be followed by {}",
846 match with_postfix
.kind
{
847 ExprKind
::Index(_
, _
) => "indexing",
848 ExprKind
::Try(_
) => "`?`",
849 ExprKind
::Field(_
, _
) => "a field access",
850 ExprKind
::MethodCall(_
, _
, _
) => "a method call",
851 ExprKind
::Call(_
, _
) => "a function call",
852 ExprKind
::Await(_
) => "`.await`",
853 ExprKind
::Err
=> return Ok(with_postfix
),
854 _
=> unreachable
!("parse_dot_or_call_expr_with_ shouldn't produce this"),
857 let mut err
= self.struct_span_err(span
, &msg
);
859 let suggest_parens
= |err
: &mut DiagnosticBuilder
<'_
, _
>| {
860 let suggestions
= vec
![
861 (span
.shrink_to_lo(), "(".to_string()),
862 (span
.shrink_to_hi(), ")".to_string()),
864 err
.multipart_suggestion(
865 "try surrounding the expression in parentheses",
867 Applicability
::MachineApplicable
,
871 // If type ascription is "likely an error", the user will already be getting a useful
872 // help message, and doesn't need a second.
873 if self.last_type_ascription
.map_or(false, |last_ascription
| last_ascription
.1) {
874 self.maybe_annotate_with_ascription(&mut err
, false);
875 } else if let Some(ascription_span
) = maybe_ascription_span
{
876 let is_nightly
= self.sess
.unstable_features
.is_nightly_build();
878 suggest_parens(&mut err
);
883 "{}remove the type ascription",
884 if is_nightly { "alternatively, " }
else { "" }
888 Applicability
::MaybeIncorrect
890 Applicability
::MachineApplicable
894 suggest_parens(&mut err
);
901 fn parse_assoc_op_ascribe(&mut self, lhs
: P
<Expr
>, lhs_span
: Span
) -> PResult
<'a
, P
<Expr
>> {
902 let maybe_path
= self.could_ascription_be_path(&lhs
.kind
);
903 self.last_type_ascription
= Some((self.prev_token
.span
, maybe_path
));
904 let lhs
= self.parse_assoc_op_cast(lhs
, lhs_span
, ExprKind
::Type
)?
;
905 self.sess
.gated_spans
.gate(sym
::type_ascription
, lhs
.span
);
909 /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
910 fn parse_borrow_expr(&mut self, lo
: Span
) -> PResult
<'a
, (Span
, ExprKind
)> {
912 let has_lifetime
= self.token
.is_lifetime() && self.look_ahead(1, |t
| t
!= &token
::Colon
);
913 let lifetime
= has_lifetime
.then(|| self.expect_lifetime()); // For recovery, see below.
914 let (borrow_kind
, mutbl
) = self.parse_borrow_modifiers(lo
);
915 let expr
= self.parse_prefix_expr(None
);
916 let (hi
, expr
) = self.interpolated_or_expr_span(expr
)?
;
917 let span
= lo
.to(hi
);
918 if let Some(lt
) = lifetime
{
919 self.error_remove_borrow_lifetime(span
, lt
.ident
.span
);
921 Ok((span
, ExprKind
::AddrOf(borrow_kind
, mutbl
, expr
)))
924 fn error_remove_borrow_lifetime(&self, span
: Span
, lt_span
: Span
) {
925 self.struct_span_err(span
, "borrow expressions cannot be annotated with lifetimes")
926 .span_label(lt_span
, "annotated with lifetime here")
929 "remove the lifetime annotation",
931 Applicability
::MachineApplicable
,
936 /// Parse `mut?` or `raw [ const | mut ]`.
937 fn parse_borrow_modifiers(&mut self, lo
: Span
) -> (ast
::BorrowKind
, ast
::Mutability
) {
938 if self.check_keyword(kw
::Raw
) && self.look_ahead(1, Token
::is_mutability
) {
939 // `raw [ const | mut ]`.
940 let found_raw
= self.eat_keyword(kw
::Raw
);
942 let mutability
= self.parse_const_or_mut().unwrap();
943 self.sess
.gated_spans
.gate(sym
::raw_ref_op
, lo
.to(self.prev_token
.span
));
944 (ast
::BorrowKind
::Raw
, mutability
)
947 (ast
::BorrowKind
::Ref
, self.parse_mutability())
951 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
952 fn parse_dot_or_call_expr(&mut self, attrs
: Option
<AttrWrapper
>) -> PResult
<'a
, P
<Expr
>> {
953 let attrs
= self.parse_or_use_outer_attributes(attrs
)?
;
954 self.collect_tokens_for_expr(attrs
, |this
, attrs
| {
955 let base
= this
.parse_bottom_expr();
956 let (span
, base
) = this
.interpolated_or_expr_span(base
)?
;
957 this
.parse_dot_or_call_expr_with(base
, span
, attrs
)
961 pub(super) fn parse_dot_or_call_expr_with(
965 mut attrs
: Vec
<ast
::Attribute
>,
966 ) -> PResult
<'a
, P
<Expr
>> {
967 // Stitch the list of outer attributes onto the return value.
968 // A little bit ugly, but the best way given the current code
970 self.parse_dot_or_call_expr_with_(e0
, lo
).map(|expr
| {
971 expr
.map(|mut expr
| {
972 attrs
.extend
::<Vec
<_
>>(expr
.attrs
.into());
973 expr
.attrs
= attrs
.into();
979 fn parse_dot_or_call_expr_with_(&mut self, mut e
: P
<Expr
>, lo
: Span
) -> PResult
<'a
, P
<Expr
>> {
981 if self.eat(&token
::Question
) {
983 e
= self.mk_expr(lo
.to(self.prev_token
.span
), ExprKind
::Try(e
), AttrVec
::new());
986 if self.eat(&token
::Dot
) {
988 e
= self.parse_dot_suffix_expr(lo
, e
)?
;
991 if self.expr_is_complete(&e
) {
994 e
= match self.token
.kind
{
995 token
::OpenDelim(token
::Paren
) => self.parse_fn_call_expr(lo
, e
),
996 token
::OpenDelim(token
::Bracket
) => self.parse_index_expr(lo
, e
)?
,
1002 fn look_ahead_type_ascription_as_field(&mut self) -> bool
{
1003 self.look_ahead(1, |t
| t
.is_ident())
1004 && self.look_ahead(2, |t
| t
== &token
::Colon
)
1005 && self.look_ahead(3, |t
| t
.can_begin_expr())
1008 fn parse_dot_suffix_expr(&mut self, lo
: Span
, base
: P
<Expr
>) -> PResult
<'a
, P
<Expr
>> {
1009 match self.token
.uninterpolate().kind
{
1010 token
::Ident(..) => self.parse_dot_suffix(base
, lo
),
1011 token
::Literal(token
::Lit { kind: token::Integer, symbol, suffix }
) => {
1012 Ok(self.parse_tuple_field_access_expr(lo
, base
, symbol
, suffix
, None
))
1014 token
::Literal(token
::Lit { kind: token::Float, symbol, suffix }
) => {
1015 Ok(self.parse_tuple_field_access_expr_float(lo
, base
, symbol
, suffix
))
1018 self.error_unexpected_after_dot();
1024 fn error_unexpected_after_dot(&self) {
1025 // FIXME Could factor this out into non_fatal_unexpected or something.
1026 let actual
= pprust
::token_to_string(&self.token
);
1027 self.struct_span_err(self.token
.span
, &format
!("unexpected token: `{actual}`")).emit();
1030 // We need an identifier or integer, but the next token is a float.
1031 // Break the float into components to extract the identifier or integer.
1032 // FIXME: With current `TokenCursor` it's hard to break tokens into more than 2
1033 // parts unless those parts are processed immediately. `TokenCursor` should either
1034 // support pushing "future tokens" (would be also helpful to `break_and_eat`), or
1035 // we should break everything including floats into more basic proc-macro style
1036 // tokens in the lexer (probably preferable).
1037 fn parse_tuple_field_access_expr_float(
1042 suffix
: Option
<Symbol
>,
1045 enum FloatComponent
{
1049 use FloatComponent
::*;
1051 let float_str
= float
.as_str();
1052 let mut components
= Vec
::new();
1053 let mut ident_like
= String
::new();
1054 for c
in float_str
.chars() {
1055 if c
== '_'
|| c
.is_ascii_alphanumeric() {
1057 } else if matches
!(c
, '
.'
| '
+'
| '
-'
) {
1058 if !ident_like
.is_empty() {
1059 components
.push(IdentLike(mem
::take(&mut ident_like
)));
1061 components
.push(Punct(c
));
1063 panic
!("unexpected character in a float token: {:?}", c
)
1066 if !ident_like
.is_empty() {
1067 components
.push(IdentLike(ident_like
));
1070 // With proc macros the span can refer to anything, the source may be too short,
1071 // or too long, or non-ASCII. It only makes sense to break our span into components
1072 // if its underlying text is identical to our float literal.
1073 let span
= self.token
.span
;
1074 let can_take_span_apart
=
1075 || self.span_to_snippet(span
).as_deref() == Ok(float_str
).as_deref();
1077 match &*components
{
1080 self.parse_tuple_field_access_expr(lo
, base
, Symbol
::intern(&i
), suffix
, None
)
1083 [IdentLike(i
), Punct('
.'
)] => {
1084 let (ident_span
, dot_span
) = if can_take_span_apart() {
1085 let (span
, ident_len
) = (span
.data(), BytePos
::from_usize(i
.len()));
1086 let ident_span
= span
.with_hi(span
.lo
+ ident_len
);
1087 let dot_span
= span
.with_lo(span
.lo
+ ident_len
);
1088 (ident_span
, dot_span
)
1092 assert
!(suffix
.is_none());
1093 let symbol
= Symbol
::intern(&i
);
1094 self.token
= Token
::new(token
::Ident(symbol
, false), ident_span
);
1095 let next_token
= (Token
::new(token
::Dot
, dot_span
), self.token_spacing
);
1096 self.parse_tuple_field_access_expr(lo
, base
, symbol
, None
, Some(next_token
))
1099 [IdentLike(i1
), Punct('
.'
), IdentLike(i2
)] => {
1100 let (ident1_span
, dot_span
, ident2_span
) = if can_take_span_apart() {
1101 let (span
, ident1_len
) = (span
.data(), BytePos
::from_usize(i1
.len()));
1102 let ident1_span
= span
.with_hi(span
.lo
+ ident1_len
);
1104 .with_lo(span
.lo
+ ident1_len
)
1105 .with_hi(span
.lo
+ ident1_len
+ BytePos(1));
1106 let ident2_span
= self.token
.span
.with_lo(span
.lo
+ ident1_len
+ BytePos(1));
1107 (ident1_span
, dot_span
, ident2_span
)
1111 let symbol1
= Symbol
::intern(&i1
);
1112 self.token
= Token
::new(token
::Ident(symbol1
, false), ident1_span
);
1113 // This needs to be `Spacing::Alone` to prevent regressions.
1114 // See issue #76399 and PR #76285 for more details
1115 let next_token1
= (Token
::new(token
::Dot
, dot_span
), Spacing
::Alone
);
1117 self.parse_tuple_field_access_expr(lo
, base
, symbol1
, None
, Some(next_token1
));
1118 let symbol2
= Symbol
::intern(&i2
);
1119 let next_token2
= Token
::new(token
::Ident(symbol2
, false), ident2_span
);
1120 self.bump_with((next_token2
, self.token_spacing
)); // `.`
1121 self.parse_tuple_field_access_expr(lo
, base1
, symbol2
, suffix
, None
)
1123 // 1e+ | 1e- (recovered)
1124 [IdentLike(_
), Punct('
+'
| '
-'
)] |
1126 [IdentLike(_
), Punct('
+'
| '
-'
), IdentLike(_
)] |
1128 [IdentLike(_
), Punct('
.'
), IdentLike(_
), Punct('
+'
| '
-'
)] |
1130 [IdentLike(_
), Punct('
.'
), IdentLike(_
), Punct('
+'
| '
-'
), IdentLike(_
)] => {
1131 // See the FIXME about `TokenCursor` above.
1132 self.error_unexpected_after_dot();
1135 _
=> panic
!("unexpected components in a float token: {:?}", components
),
1139 fn parse_tuple_field_access_expr(
1144 suffix
: Option
<Symbol
>,
1145 next_token
: Option
<(Token
, Spacing
)>,
1148 Some(next_token
) => self.bump_with(next_token
),
1149 None
=> self.bump(),
1151 let span
= self.prev_token
.span
;
1152 let field
= ExprKind
::Field(base
, Ident
::new(field
, span
));
1153 self.expect_no_suffix(span
, "a tuple index", suffix
);
1154 self.mk_expr(lo
.to(span
), field
, AttrVec
::new())
1157 /// Parse a function call expression, `expr(...)`.
1158 fn parse_fn_call_expr(&mut self, lo
: Span
, fun
: P
<Expr
>) -> P
<Expr
> {
1159 let snapshot
= if self.token
.kind
== token
::OpenDelim(token
::Paren
)
1160 && self.look_ahead_type_ascription_as_field()
1162 Some((self.create_snapshot_for_diagnostic(), fun
.kind
.clone()))
1166 let open_paren
= self.token
.span
;
1168 let mut seq
= self.parse_paren_expr_seq().map(|args
| {
1169 self.mk_expr(lo
.to(self.prev_token
.span
), self.mk_call(fun
, args
), AttrVec
::new())
1172 self.maybe_recover_struct_lit_bad_delims(lo
, open_paren
, &mut seq
, snapshot
)
1176 self.recover_seq_parse_error(token
::Paren
, lo
, seq
)
1179 /// If we encounter a parser state that looks like the user has written a `struct` literal with
1180 /// parentheses instead of braces, recover the parser state and provide suggestions.
1181 #[instrument(skip(self, seq, snapshot), level = "trace")]
1182 fn maybe_recover_struct_lit_bad_delims(
1186 seq
: &mut PResult
<'a
, P
<Expr
>>,
1187 snapshot
: Option
<(SnapshotParser
<'a
>, ExprKind
)>,
1188 ) -> Option
<P
<Expr
>> {
1189 match (seq
.as_mut(), snapshot
) {
1190 (Err(err
), Some((mut snapshot
, ExprKind
::Path(None
, path
)))) => {
1191 let name
= pprust
::path_to_string(&path
);
1192 snapshot
.bump(); // `(`
1193 match snapshot
.parse_struct_fields(path
, false, token
::Paren
) {
1194 Ok((fields
, ..)) if snapshot
.eat(&token
::CloseDelim(token
::Paren
)) => {
1195 // We are certain we have `Enum::Foo(a: 3, b: 4)`, suggest
1196 // `Enum::Foo { a: 3, b: 4 }` or `Enum::Foo(3, 4)`.
1197 self.restore_snapshot(snapshot
);
1198 let close_paren
= self.prev_token
.span
;
1199 let span
= lo
.to(self.prev_token
.span
);
1200 if !fields
.is_empty() {
1201 let replacement_err
= self.struct_span_err(
1203 "invalid `struct` delimiters or `fn` call arguments",
1205 mem
::replace(err
, replacement_err
).cancel();
1207 err
.multipart_suggestion(
1208 &format
!("if `{name}` is a struct, use braces as delimiters"),
1210 (open_paren
, " { ".to_string()),
1211 (close_paren
, " }".to_string()),
1213 Applicability
::MaybeIncorrect
,
1215 err
.multipart_suggestion(
1216 &format
!("if `{name}` is a function, use the arguments directly"),
1219 .map(|field
| (field
.span
.until(field
.expr
.span
), String
::new()))
1221 Applicability
::MaybeIncorrect
,
1227 return Some(self.mk_expr_err(span
));
1240 /// Parse an indexing expression `expr[...]`.
1241 fn parse_index_expr(&mut self, lo
: Span
, base
: P
<Expr
>) -> PResult
<'a
, P
<Expr
>> {
1243 let index
= self.parse_expr()?
;
1244 self.expect(&token
::CloseDelim(token
::Bracket
))?
;
1245 Ok(self.mk_expr(lo
.to(self.prev_token
.span
), self.mk_index(base
, index
), AttrVec
::new()))
1248 /// Assuming we have just parsed `.`, continue parsing into an expression.
1249 fn parse_dot_suffix(&mut self, self_arg
: P
<Expr
>, lo
: Span
) -> PResult
<'a
, P
<Expr
>> {
1250 if self.token
.uninterpolated_span().rust_2018() && self.eat_keyword(kw
::Await
) {
1251 return Ok(self.mk_await_expr(self_arg
, lo
));
1254 let fn_span_lo
= self.token
.span
;
1255 let mut segment
= self.parse_path_segment(PathStyle
::Expr
, None
)?
;
1256 self.check_trailing_angle_brackets(&segment
, &[&token
::OpenDelim(token
::Paren
)]);
1257 self.check_turbofish_missing_angle_brackets(&mut segment
);
1259 if self.check(&token
::OpenDelim(token
::Paren
)) {
1260 // Method call `expr.f()`
1261 let mut args
= self.parse_paren_expr_seq()?
;
1262 args
.insert(0, self_arg
);
1264 let fn_span
= fn_span_lo
.to(self.prev_token
.span
);
1265 let span
= lo
.to(self.prev_token
.span
);
1266 Ok(self.mk_expr(span
, ExprKind
::MethodCall(segment
, args
, fn_span
), AttrVec
::new()))
1268 // Field access `expr.f`
1269 if let Some(args
) = segment
.args
{
1270 self.struct_span_err(
1272 "field expressions cannot have generic arguments",
1277 let span
= lo
.to(self.prev_token
.span
);
1278 Ok(self.mk_expr(span
, ExprKind
::Field(self_arg
, segment
.ident
), AttrVec
::new()))
1282 /// At the bottom (top?) of the precedence hierarchy,
1283 /// Parses things like parenthesized exprs, macros, `return`, etc.
1285 /// N.B., this does not parse outer attributes, and is private because it only works
1286 /// correctly if called from `parse_dot_or_call_expr()`.
1287 fn parse_bottom_expr(&mut self) -> PResult
<'a
, P
<Expr
>> {
1288 maybe_recover_from_interpolated_ty_qpath
!(self, true);
1289 maybe_whole_expr
!(self);
1291 // Outer attributes are already parsed and will be
1292 // added to the return value after the fact.
1294 // Therefore, prevent sub-parser from parsing
1295 // attributes by giving them an empty "already-parsed" list.
1296 let attrs
= AttrVec
::new();
1298 // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
1299 let lo
= self.token
.span
;
1300 if let token
::Literal(_
) = self.token
.kind
{
1301 // This match arm is a special-case of the `_` match arm below and
1302 // could be removed without changing functionality, but it's faster
1303 // to have it here, especially for programs with large constants.
1304 self.parse_lit_expr(attrs
)
1305 } else if self.check(&token
::OpenDelim(token
::Paren
)) {
1306 self.parse_tuple_parens_expr(attrs
)
1307 } else if self.check(&token
::OpenDelim(token
::Brace
)) {
1308 self.parse_block_expr(None
, lo
, BlockCheckMode
::Default
, attrs
)
1309 } else if self.check(&token
::BinOp(token
::Or
)) || self.check(&token
::OrOr
) {
1310 self.parse_closure_expr(attrs
).map_err(|mut err
| {
1311 // If the input is something like `if a { 1 } else { 2 } | if a { 3 } else { 4 }`
1312 // then suggest parens around the lhs.
1313 if let Some(sp
) = self.sess
.ambiguous_block_expr_parse
.borrow().get(&lo
) {
1314 self.sess
.expr_parentheses_needed(&mut err
, *sp
);
1318 } else if self.check(&token
::OpenDelim(token
::Bracket
)) {
1319 self.parse_array_or_repeat_expr(attrs
, token
::Bracket
)
1320 } else if self.check_path() {
1321 self.parse_path_start_expr(attrs
)
1322 } else if self.check_keyword(kw
::Move
) || self.check_keyword(kw
::Static
) {
1323 self.parse_closure_expr(attrs
)
1324 } else if self.eat_keyword(kw
::If
) {
1325 self.parse_if_expr(attrs
)
1326 } else if self.check_keyword(kw
::For
) {
1327 if self.choose_generics_over_qpath(1) {
1328 // NOTE(Centril, eddyb): DO NOT REMOVE! Beyond providing parser recovery,
1329 // this is an insurance policy in case we allow qpaths in (tuple-)struct patterns.
1330 // When `for <Foo as Bar>::Proj in $expr $block` is wanted,
1331 // you can disambiguate in favor of a pattern with `(...)`.
1332 self.recover_quantified_closure_expr(attrs
)
1334 assert
!(self.eat_keyword(kw
::For
));
1335 self.parse_for_expr(None
, self.prev_token
.span
, attrs
)
1337 } else if self.eat_keyword(kw
::While
) {
1338 self.parse_while_expr(None
, self.prev_token
.span
, attrs
)
1339 } else if let Some(label
) = self.eat_label() {
1340 self.parse_labeled_expr(label
, attrs
, 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
, attrs
).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
, attrs
))
1350 } else if self.eat_keyword(kw
::Match
) {
1351 let match_sp
= self.prev_token
.span
;
1352 self.parse_match_expr(attrs
).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
), attrs
)
1359 .map_err(|mut err
| {
1360 err
.span_label(sp
, "while parsing this `unsafe` expression");
1363 } else if self.check_inline_const(0) {
1364 self.parse_const_block(lo
.to(self.token
.span
), false)
1365 } else if self.is_do_catch_block() {
1366 self.recover_do_catch(attrs
)
1367 } else if self.is_try_block() {
1368 self.expect_keyword(kw
::Try
)?
;
1369 self.parse_try_block(lo
, attrs
)
1370 } else if self.eat_keyword(kw
::Return
) {
1371 self.parse_return_expr(attrs
)
1372 } else if self.eat_keyword(kw
::Break
) {
1373 self.parse_break_expr(attrs
)
1374 } else if self.eat_keyword(kw
::Yield
) {
1375 self.parse_yield_expr(attrs
)
1376 } else if self.eat_keyword(kw
::Let
) {
1377 self.parse_let_expr(attrs
)
1378 } else if self.eat_keyword(kw
::Underscore
) {
1379 Ok(self.mk_expr(self.prev_token
.span
, ExprKind
::Underscore
, attrs
))
1380 } else if !self.unclosed_delims
.is_empty() && self.check(&token
::Semi
) {
1381 // Don't complain about bare semicolons after unclosed braces
1382 // recovery in order to keep the error count down. Fixing the
1383 // delimiters will possibly also fix the bare semicolon found in
1384 // expression context. For example, silence the following error:
1386 // error: expected expression, found `;`
1390 // | ^ expected expression
1392 Ok(self.mk_expr_err(self.token
.span
))
1393 } else if self.token
.uninterpolated_span().rust_2018() {
1394 // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
1395 if self.check_keyword(kw
::Async
) {
1396 if self.is_async_block() {
1397 // Check for `async {` and `async move {`.
1398 self.parse_async_block(attrs
)
1400 self.parse_closure_expr(attrs
)
1402 } else if self.eat_keyword(kw
::Await
) {
1403 self.recover_incorrect_await_syntax(lo
, self.prev_token
.span
, attrs
)
1405 self.parse_lit_expr(attrs
)
1408 self.parse_lit_expr(attrs
)
1412 fn parse_lit_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1413 let lo
= self.token
.span
;
1414 match self.parse_opt_lit() {
1416 let expr
= self.mk_expr(lo
.to(self.prev_token
.span
), ExprKind
::Lit(literal
), attrs
);
1417 self.maybe_recover_from_bad_qpath(expr
, true)
1419 None
=> self.try_macro_suggestion(),
1423 fn parse_tuple_parens_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1424 let lo
= self.token
.span
;
1425 self.expect(&token
::OpenDelim(token
::Paren
))?
;
1426 let (es
, trailing_comma
) = match self.parse_seq_to_end(
1427 &token
::CloseDelim(token
::Paren
),
1428 SeqSep
::trailing_allowed(token
::Comma
),
1429 |p
| p
.parse_expr_catch_underscore(),
1432 Err(err
) => return Ok(self.recover_seq_parse_error(token
::Paren
, lo
, Err(err
))),
1434 let kind
= if es
.len() == 1 && !trailing_comma
{
1435 // `(e)` is parenthesized `e`.
1436 ExprKind
::Paren(es
.into_iter().next().unwrap())
1438 // `(e,)` is a tuple with only one field, `e`.
1441 let expr
= self.mk_expr(lo
.to(self.prev_token
.span
), kind
, attrs
);
1442 self.maybe_recover_from_bad_qpath(expr
, true)
1445 fn parse_array_or_repeat_expr(
1448 close_delim
: token
::DelimToken
,
1449 ) -> PResult
<'a
, P
<Expr
>> {
1450 let lo
= self.token
.span
;
1451 self.bump(); // `[` or other open delim
1453 let close
= &token
::CloseDelim(close_delim
);
1454 let kind
= if self.eat(close
) {
1456 ExprKind
::Array(Vec
::new())
1459 let first_expr
= self.parse_expr()?
;
1460 if self.eat(&token
::Semi
) {
1461 // Repeating array syntax: `[ 0; 512 ]`
1462 let count
= self.parse_anon_const_expr()?
;
1463 self.expect(close
)?
;
1464 ExprKind
::Repeat(first_expr
, count
)
1465 } else if self.eat(&token
::Comma
) {
1466 // Vector with two or more elements.
1467 let sep
= SeqSep
::trailing_allowed(token
::Comma
);
1468 let (remaining_exprs
, _
) = self.parse_seq_to_end(close
, sep
, |p
| p
.parse_expr())?
;
1469 let mut exprs
= vec
![first_expr
];
1470 exprs
.extend(remaining_exprs
);
1471 ExprKind
::Array(exprs
)
1473 // Vector with one element
1474 self.expect(close
)?
;
1475 ExprKind
::Array(vec
![first_expr
])
1478 let expr
= self.mk_expr(lo
.to(self.prev_token
.span
), kind
, attrs
);
1479 self.maybe_recover_from_bad_qpath(expr
, true)
1482 fn parse_path_start_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1483 let (qself
, path
) = if self.eat_lt() {
1484 let (qself
, path
) = self.parse_qpath(PathStyle
::Expr
)?
;
1487 (None
, self.parse_path(PathStyle
::Expr
)?
)
1491 // `!`, as an operator, is prefix, so we know this isn't that.
1492 let (hi
, kind
) = if self.eat(&token
::Not
) {
1493 // MACRO INVOCATION expression
1494 if qself
.is_some() {
1495 self.struct_span_err(path
.span
, "macros cannot use qualified paths").emit();
1499 args
: self.parse_mac_args()?
,
1500 prior_type_ascription
: self.last_type_ascription
,
1502 (self.prev_token
.span
, ExprKind
::MacCall(mac
))
1503 } else if self.check(&token
::OpenDelim(token
::Brace
)) {
1504 if let Some(expr
) = self.maybe_parse_struct_expr(qself
.as_ref(), &path
, &attrs
) {
1505 if qself
.is_some() {
1506 self.sess
.gated_spans
.gate(sym
::more_qualified_paths
, path
.span
);
1510 (path
.span
, ExprKind
::Path(qself
, path
))
1513 (path
.span
, ExprKind
::Path(qself
, path
))
1516 let expr
= self.mk_expr(lo
.to(hi
), kind
, attrs
);
1517 self.maybe_recover_from_bad_qpath(expr
, true)
1520 /// Parse `'label: $expr`. The label is already parsed.
1521 fn parse_labeled_expr(
1525 mut consume_colon
: bool
,
1526 ) -> PResult
<'a
, P
<Expr
>> {
1527 let lo
= label
.ident
.span
;
1528 let label
= Some(label
);
1529 let ate_colon
= self.eat(&token
::Colon
);
1530 let expr
= if self.eat_keyword(kw
::While
) {
1531 self.parse_while_expr(label
, lo
, attrs
)
1532 } else if self.eat_keyword(kw
::For
) {
1533 self.parse_for_expr(label
, lo
, attrs
)
1534 } else if self.eat_keyword(kw
::Loop
) {
1535 self.parse_loop_expr(label
, lo
, attrs
)
1536 } else if self.check(&token
::OpenDelim(token
::Brace
)) || self.token
.is_whole_block() {
1537 self.parse_block_expr(label
, lo
, BlockCheckMode
::Default
, attrs
)
1538 } else if !ate_colon
&& (self.check(&TokenKind
::Comma
) || self.check(&TokenKind
::Gt
)) {
1539 // We're probably inside of a `Path<'a>` that needs a turbofish
1540 let msg
= "expected `while`, `for`, `loop` or `{` after a label";
1541 self.struct_span_err(self.token
.span
, msg
).span_label(self.token
.span
, msg
).emit();
1542 consume_colon
= false;
1543 Ok(self.mk_expr_err(lo
))
1545 let msg
= "expected `while`, `for`, `loop` or `{` after a label";
1546 self.struct_span_err(self.token
.span
, msg
).span_label(self.token
.span
, msg
).emit();
1547 // Continue as an expression in an effort to recover on `'label: non_block_expr`.
1551 if !ate_colon
&& consume_colon
{
1552 self.error_labeled_expr_must_be_followed_by_colon(lo
, expr
.span
);
1558 fn error_labeled_expr_must_be_followed_by_colon(&self, lo
: Span
, span
: Span
) {
1559 self.struct_span_err(span
, "labeled expression must be followed by `:`")
1560 .span_label(lo
, "the label")
1561 .span_suggestion_short(
1563 "add `:` after the label",
1565 Applicability
::MachineApplicable
,
1567 .note("labels are used before loops and blocks, allowing e.g., `break 'label` to them")
1571 /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
1572 fn recover_do_catch(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1573 let lo
= self.token
.span
;
1575 self.bump(); // `do`
1576 self.bump(); // `catch`
1578 let span_dc
= lo
.to(self.prev_token
.span
);
1579 self.struct_span_err(span_dc
, "found removed `do catch` syntax")
1582 "replace with the new syntax",
1584 Applicability
::MachineApplicable
,
1586 .note("following RFC #2388, the new non-placeholder syntax is `try`")
1589 self.parse_try_block(lo
, attrs
)
1592 /// Parse an expression if the token can begin one.
1593 fn parse_expr_opt(&mut self) -> PResult
<'a
, Option
<P
<Expr
>>> {
1594 Ok(if self.token
.can_begin_expr() { Some(self.parse_expr()?) }
else { None }
)
1597 /// Parse `"return" expr?`.
1598 fn parse_return_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1599 let lo
= self.prev_token
.span
;
1600 let kind
= ExprKind
::Ret(self.parse_expr_opt()?
);
1601 let expr
= self.mk_expr(lo
.to(self.prev_token
.span
), kind
, attrs
);
1602 self.maybe_recover_from_bad_qpath(expr
, true)
1605 /// Parse `"break" (('label (:? expr)?) | expr?)` with `"break"` token already eaten.
1606 /// If the label is followed immediately by a `:` token, the label and `:` are
1607 /// parsed as part of the expression (i.e. a labeled loop). The language team has
1608 /// decided in #87026 to require parentheses as a visual aid to avoid confusion if
1609 /// the break expression of an unlabeled break is a labeled loop (as in
1610 /// `break 'lbl: loop {}`); a labeled break with an unlabeled loop as its value
1611 /// expression only gets a warning for compatibility reasons; and a labeled break
1612 /// with a labeled loop does not even get a warning because there is no ambiguity.
1613 fn parse_break_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1614 let lo
= self.prev_token
.span
;
1615 let mut label
= self.eat_label();
1616 let kind
= if label
.is_some() && self.token
== token
::Colon
{
1617 // The value expression can be a labeled loop, see issue #86948, e.g.:
1618 // `loop { break 'label: loop { break 'label 42; }; }`
1619 let lexpr
= self.parse_labeled_expr(label
.take().unwrap(), AttrVec
::new(), true)?
;
1620 self.struct_span_err(
1622 "parentheses are required around this expression to avoid confusion with a labeled break expression",
1624 .multipart_suggestion(
1625 "wrap the expression in parentheses",
1627 (lexpr
.span
.shrink_to_lo(), "(".to_string()),
1628 (lexpr
.span
.shrink_to_hi(), ")".to_string()),
1630 Applicability
::MachineApplicable
,
1634 } else if self.token
!= token
::OpenDelim(token
::Brace
)
1635 || !self.restrictions
.contains(Restrictions
::NO_STRUCT_LITERAL
)
1637 let expr
= self.parse_expr_opt()?
;
1638 if let Some(ref expr
) = expr
{
1642 ExprKind
::While(_
, _
, None
)
1643 | ExprKind
::ForLoop(_
, _
, _
, None
)
1644 | ExprKind
::Loop(_
, None
)
1645 | ExprKind
::Block(_
, None
)
1648 self.sess
.buffer_lint_with_diagnostic(
1649 BREAK_WITH_LABEL_AND_LOOP
,
1652 "this labeled break expression is easy to confuse with an unlabeled break with a labeled value expression",
1653 BuiltinLintDiagnostics
::BreakWithLabelAndLoop(expr
.span
),
1661 let expr
= self.mk_expr(lo
.to(self.prev_token
.span
), ExprKind
::Break(label
, kind
), attrs
);
1662 self.maybe_recover_from_bad_qpath(expr
, true)
1665 /// Parse `"yield" expr?`.
1666 fn parse_yield_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1667 let lo
= self.prev_token
.span
;
1668 let kind
= ExprKind
::Yield(self.parse_expr_opt()?
);
1669 let span
= lo
.to(self.prev_token
.span
);
1670 self.sess
.gated_spans
.gate(sym
::generators
, span
);
1671 let expr
= self.mk_expr(span
, kind
, attrs
);
1672 self.maybe_recover_from_bad_qpath(expr
, true)
1675 /// Returns a string literal if the next token is a string literal.
1676 /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
1677 /// and returns `None` if the next token is not literal at all.
1678 pub fn parse_str_lit(&mut self) -> Result
<ast
::StrLit
, Option
<Lit
>> {
1679 match self.parse_opt_lit() {
1680 Some(lit
) => match lit
.kind
{
1681 ast
::LitKind
::Str(symbol_unescaped
, style
) => Ok(ast
::StrLit
{
1683 symbol
: lit
.token
.symbol
,
1684 suffix
: lit
.token
.suffix
,
1688 _
=> Err(Some(lit
)),
1694 pub(super) fn parse_lit(&mut self) -> PResult
<'a
, Lit
> {
1695 self.parse_opt_lit().ok_or_else(|| {
1696 if let token
::Interpolated(inner
) = &self.token
.kind
{
1697 let expr
= match inner
.as_ref() {
1698 token
::NtExpr(expr
) => Some(expr
),
1699 token
::NtLiteral(expr
) => Some(expr
),
1702 if let Some(expr
) = expr
{
1703 if matches
!(expr
.kind
, ExprKind
::Err
) {
1706 .struct_span_err(self.token
.span
, &"invalid interpolated expression");
1707 err
.downgrade_to_delayed_bug();
1712 let msg
= format
!("unexpected token: {}", super::token_descr(&self.token
));
1713 self.struct_span_err(self.token
.span
, &msg
)
1717 /// Matches `lit = true | false | token_lit`.
1718 /// Returns `None` if the next token is not a literal.
1719 pub(super) fn parse_opt_lit(&mut self) -> Option
<Lit
> {
1720 let mut recovered
= None
;
1721 if self.token
== token
::Dot
{
1722 // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
1723 // dot would follow an optional literal, so we do this unconditionally.
1724 recovered
= self.look_ahead(1, |next_token
| {
1725 if let token
::Literal(token
::Lit { kind: token::Integer, symbol, suffix }
) =
1728 if self.token
.span
.hi() == next_token
.span
.lo() {
1729 let s
= String
::from("0.") + symbol
.as_str();
1730 let kind
= TokenKind
::lit(token
::Float
, Symbol
::intern(&s
), suffix
);
1731 return Some(Token
::new(kind
, self.token
.span
.to(next_token
.span
)));
1736 if let Some(token
) = &recovered
{
1738 self.error_float_lits_must_have_int_part(&token
);
1742 let token
= recovered
.as_ref().unwrap_or(&self.token
);
1743 match Lit
::from_token(token
) {
1748 Err(LitError
::NotLiteral
) => None
,
1750 let span
= token
.span
;
1751 let token
::Literal(lit
) = token
.kind
else {
1755 self.report_lit_error(err
, lit
, span
);
1756 // Pack possible quotes and prefixes from the original literal into
1757 // the error literal's symbol so they can be pretty-printed faithfully.
1758 let suffixless_lit
= token
::Lit
::new(lit
.kind
, lit
.symbol
, None
);
1759 let symbol
= Symbol
::intern(&suffixless_lit
.to_string());
1760 let lit
= token
::Lit
::new(token
::Err
, symbol
, lit
.suffix
);
1761 Some(Lit
::from_lit_token(lit
, span
).unwrap_or_else(|_
| unreachable
!()))
1766 fn error_float_lits_must_have_int_part(&self, token
: &Token
) {
1767 self.struct_span_err(token
.span
, "float literals must have an integer part")
1770 "must have an integer part",
1771 pprust
::token_to_string(token
).into(),
1772 Applicability
::MachineApplicable
,
1777 fn report_lit_error(&self, err
: LitError
, lit
: token
::Lit
, span
: Span
) {
1778 // Checks if `s` looks like i32 or u1234 etc.
1779 fn looks_like_width_suffix(first_chars
: &[char], s
: &str) -> bool
{
1780 s
.len() > 1 && s
.starts_with(first_chars
) && s
[1..].chars().all(|c
| c
.is_ascii_digit())
1783 // Try to lowercase the prefix if it's a valid base prefix.
1784 fn fix_base_capitalisation(s
: &str) -> Option
<String
> {
1785 if let Some(stripped
) = s
.strip_prefix('B'
) {
1786 Some(format
!("0b{stripped}"))
1787 } else if let Some(stripped
) = s
.strip_prefix('O'
) {
1788 Some(format
!("0o{stripped}"))
1789 } else if let Some(stripped
) = s
.strip_prefix('X'
) {
1790 Some(format
!("0x{stripped}"))
1796 let token
::Lit { kind, suffix, .. }
= lit
;
1798 // `NotLiteral` is not an error by itself, so we don't report
1799 // it and give the parser opportunity to try something else.
1800 LitError
::NotLiteral
=> {}
1801 // `LexerError` *is* an error, but it was already reported
1802 // by lexer, so here we don't report it the second time.
1803 LitError
::LexerError
=> {}
1804 LitError
::InvalidSuffix
=> {
1805 self.expect_no_suffix(
1807 &format
!("{} {} literal", kind
.article(), kind
.descr()),
1811 LitError
::InvalidIntSuffix
=> {
1812 let suf
= suffix
.expect("suffix error with no suffix");
1813 let suf
= suf
.as_str();
1814 if looks_like_width_suffix(&['i'
, 'u'
], &suf
) {
1815 // If it looks like a width, try to be helpful.
1816 let msg
= format
!("invalid width `{}` for integer literal", &suf
[1..]);
1817 self.struct_span_err(span
, &msg
)
1818 .help("valid widths are 8, 16, 32, 64 and 128")
1820 } else if let Some(fixed
) = fix_base_capitalisation(suf
) {
1821 let msg
= "invalid base prefix for number literal";
1823 self.struct_span_err(span
, &msg
)
1824 .note("base prefixes (`0xff`, `0b1010`, `0o755`) are lowercase")
1827 "try making the prefix lowercase",
1829 Applicability
::MaybeIncorrect
,
1833 let msg
= format
!("invalid suffix `{suf}` for number literal");
1834 self.struct_span_err(span
, &msg
)
1835 .span_label(span
, format
!("invalid suffix `{suf}`"))
1836 .help("the suffix must be one of the numeric types (`u32`, `isize`, `f32`, etc.)")
1840 LitError
::InvalidFloatSuffix
=> {
1841 let suf
= suffix
.expect("suffix error with no suffix");
1842 let suf
= suf
.as_str();
1843 if looks_like_width_suffix(&['f'
], suf
) {
1844 // If it looks like a width, try to be helpful.
1845 let msg
= format
!("invalid width `{}` for float literal", &suf
[1..]);
1846 self.struct_span_err(span
, &msg
).help("valid widths are 32 and 64").emit();
1848 let msg
= format
!("invalid suffix `{suf}` for float literal");
1849 self.struct_span_err(span
, &msg
)
1850 .span_label(span
, format
!("invalid suffix `{suf}`"))
1851 .help("valid suffixes are `f32` and `f64`")
1855 LitError
::NonDecimalFloat(base
) => {
1856 let descr
= match base
{
1857 16 => "hexadecimal",
1860 _
=> unreachable
!(),
1862 self.struct_span_err(span
, &format
!("{descr} float literal is not supported"))
1863 .span_label(span
, "not supported")
1866 LitError
::IntTooLarge
=> {
1867 self.struct_span_err(span
, "integer literal is too large").emit();
1872 pub(super) fn expect_no_suffix(&self, sp
: Span
, kind
: &str, suffix
: Option
<Symbol
>) {
1873 if let Some(suf
) = suffix
{
1874 let mut err
= if kind
== "a tuple index"
1875 && [sym
::i32, sym
::u32, sym
::isize, sym
::usize].contains(&suf
)
1877 // #59553: warn instead of reject out of hand to allow the fix to percolate
1878 // through the ecosystem when people fix their macros
1882 .struct_span_warn(sp
, &format
!("suffixes on {kind} are invalid"));
1884 "`{}` is *temporarily* accepted on tuple index fields as it was \
1885 incorrectly accepted on stable for a few releases",
1889 "on proc macros, you'll want to use `syn::Index::from` or \
1890 `proc_macro::Literal::*_unsuffixed` for code that will desugar \
1891 to tuple field access",
1894 "see issue #60210 <https://github.com/rust-lang/rust/issues/60210> \
1895 for more information",
1899 self.struct_span_err(sp
, &format
!("suffixes on {kind} are invalid"))
1902 err
.span_label(sp
, format
!("invalid suffix `{suf}`"));
1907 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1908 /// Keep this in sync with `Token::can_begin_literal_maybe_minus`.
1909 pub fn parse_literal_maybe_minus(&mut self) -> PResult
<'a
, P
<Expr
>> {
1910 maybe_whole_expr
!(self);
1912 let lo
= self.token
.span
;
1913 let minus_present
= self.eat(&token
::BinOp(token
::Minus
));
1914 let lit
= self.parse_lit()?
;
1915 let expr
= self.mk_expr(lit
.span
, ExprKind
::Lit(lit
), AttrVec
::new());
1919 lo
.to(self.prev_token
.span
),
1920 self.mk_unary(UnOp
::Neg
, expr
),
1928 fn is_array_like_block(&mut self) -> bool
{
1929 self.look_ahead(1, |t
| matches
!(t
.kind
, TokenKind
::Ident(..) | TokenKind
::Literal(_
)))
1930 && self.look_ahead(2, |t
| t
== &token
::Comma
)
1931 && self.look_ahead(3, |t
| t
.can_begin_expr())
1934 /// Emits a suggestion if it looks like the user meant an array but
1935 /// accidentally used braces, causing the code to be interpreted as a block
1937 fn maybe_suggest_brackets_instead_of_braces(
1941 ) -> Option
<P
<Expr
>> {
1942 let mut snapshot
= self.create_snapshot_for_diagnostic();
1943 match snapshot
.parse_array_or_repeat_expr(attrs
, token
::Brace
) {
1945 let hi
= snapshot
.prev_token
.span
;
1946 self.struct_span_err(arr
.span
, "this is a block expression, not an array")
1947 .multipart_suggestion(
1948 "to make an array, use square brackets instead of curly braces",
1949 vec
![(lo
, "[".to_owned()), (hi
, "]".to_owned())],
1950 Applicability
::MaybeIncorrect
,
1954 self.restore_snapshot(snapshot
);
1955 Some(self.mk_expr_err(arr
.span
))
1964 /// Parses a block or unsafe block.
1965 pub(super) fn parse_block_expr(
1967 opt_label
: Option
<Label
>,
1969 blk_mode
: BlockCheckMode
,
1971 ) -> PResult
<'a
, P
<Expr
>> {
1972 if self.is_array_like_block() {
1973 if let Some(arr
) = self.maybe_suggest_brackets_instead_of_braces(lo
, attrs
.clone()) {
1978 if let Some(label
) = opt_label
{
1979 self.sess
.gated_spans
.gate(sym
::label_break_value
, label
.ident
.span
);
1982 if self.token
.is_whole_block() {
1983 self.struct_span_err(self.token
.span
, "cannot use a `block` macro fragment here")
1984 .span_label(lo
.to(self.token
.span
), "the `block` fragment is within this context")
1988 let (inner_attrs
, blk
) = self.parse_block_common(lo
, blk_mode
)?
;
1989 attrs
.extend(inner_attrs
);
1990 Ok(self.mk_expr(blk
.span
, ExprKind
::Block(blk
, opt_label
), attrs
))
1993 /// Recover on an explicitly quantified closure expression, e.g., `for<'a> |x: &'a u8| *x + 1`.
1994 fn recover_quantified_closure_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1995 let lo
= self.token
.span
;
1996 let _
= self.parse_late_bound_lifetime_defs()?
;
1997 let span_for
= lo
.to(self.prev_token
.span
);
1998 let closure
= self.parse_closure_expr(attrs
)?
;
2000 self.struct_span_err(span_for
, "cannot introduce explicit parameters for a closure")
2001 .span_label(closure
.span
, "the parameters are attached to this closure")
2004 "remove the parameters",
2006 Applicability
::MachineApplicable
,
2010 Ok(self.mk_expr_err(lo
.to(closure
.span
)))
2013 /// Parses a closure expression (e.g., `move |args| expr`).
2014 fn parse_closure_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
2015 let lo
= self.token
.span
;
2018 if self.eat_keyword(kw
::Static
) { Movability::Static }
else { Movability::Movable }
;
2020 let asyncness
= if self.token
.uninterpolated_span().rust_2018() {
2021 self.parse_asyncness()
2026 let capture_clause
= self.parse_capture_clause()?
;
2027 let decl
= self.parse_fn_block_decl()?
;
2028 let decl_hi
= self.prev_token
.span
;
2029 let mut body
= match decl
.output
{
2030 FnRetTy
::Default(_
) => {
2031 let restrictions
= self.restrictions
- Restrictions
::STMT_EXPR
;
2032 self.parse_expr_res(restrictions
, None
)?
2035 // If an explicit return type is given, require a block to appear (RFC 968).
2036 let body_lo
= self.token
.span
;
2037 self.parse_block_expr(None
, body_lo
, BlockCheckMode
::Default
, AttrVec
::new())?
2041 if let Async
::Yes { span, .. }
= asyncness
{
2042 // Feature-gate `async ||` closures.
2043 self.sess
.gated_spans
.gate(sym
::async_closure
, span
);
2046 if self.token
.kind
== TokenKind
::Semi
&& self.token_cursor
.frame
.delim
== DelimToken
::Paren
2048 // It is likely that the closure body is a block but where the
2049 // braces have been removed. We will recover and eat the next
2050 // statements later in the parsing process.
2051 body
= self.mk_expr_err(body
.span
);
2054 let body_span
= body
.span
;
2056 let closure
= self.mk_expr(
2058 ExprKind
::Closure(capture_clause
, asyncness
, movability
, decl
, body
, lo
.to(decl_hi
)),
2062 // Disable recovery for closure body
2064 ClosureSpans { whole_closure: closure.span, closing_pipe: decl_hi, body: body_span }
;
2065 self.current_closure
= Some(spans
);
2070 /// Parses an optional `move` prefix to a closure-like construct.
2071 fn parse_capture_clause(&mut self) -> PResult
<'a
, CaptureBy
> {
2072 if self.eat_keyword(kw
::Move
) {
2073 // Check for `move async` and recover
2074 if self.check_keyword(kw
::Async
) {
2075 let move_async_span
= self.token
.span
.with_lo(self.prev_token
.span
.data().lo
);
2076 Err(self.incorrect_move_async_order_found(move_async_span
))
2078 Ok(CaptureBy
::Value
)
2085 /// Parses the `|arg, arg|` header of a closure.
2086 fn parse_fn_block_decl(&mut self) -> PResult
<'a
, P
<FnDecl
>> {
2087 let inputs
= if self.eat(&token
::OrOr
) {
2090 self.expect(&token
::BinOp(token
::Or
))?
;
2092 .parse_seq_to_before_tokens(
2093 &[&token
::BinOp(token
::Or
), &token
::OrOr
],
2094 SeqSep
::trailing_allowed(token
::Comma
),
2095 TokenExpectType
::NoExpect
,
2096 |p
| p
.parse_fn_block_param(),
2103 self.parse_ret_ty(AllowPlus
::Yes
, RecoverQPath
::Yes
, RecoverReturnSign
::Yes
)?
;
2105 Ok(P(FnDecl { inputs, output }
))
2108 /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
2109 fn parse_fn_block_param(&mut self) -> PResult
<'a
, Param
> {
2110 let lo
= self.token
.span
;
2111 let attrs
= self.parse_outer_attributes()?
;
2112 self.collect_tokens_trailing_token(attrs
, ForceCollect
::No
, |this
, attrs
| {
2113 let pat
= this
.parse_pat_no_top_alt(PARAM_EXPECTED
)?
;
2114 let ty
= if this
.eat(&token
::Colon
) {
2117 this
.mk_ty(this
.prev_token
.span
, TyKind
::Infer
)
2122 attrs
: attrs
.into(),
2125 span
: lo
.to(this
.token
.span
),
2127 is_placeholder
: false,
2129 TrailingToken
::MaybeComma
,
2134 /// Parses an `if` expression (`if` token already eaten).
2135 fn parse_if_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
2136 let lo
= self.prev_token
.span
;
2137 let cond
= self.parse_cond_expr()?
;
2139 let missing_then_block_binop_span
= || {
2141 ExprKind
::Binary(Spanned { span: binop_span, .. }
, _
, ref right
)
2142 if let ExprKind
::Block(..) = right
.kind
=> Some(binop_span
),
2147 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
2148 // verify that the last statement is either an implicit return (no `;`) or an explicit
2149 // return. This won't catch blocks with an explicit `return`, but that would be caught by
2150 // the dead code lint.
2151 let thn
= if self.token
.is_keyword(kw
::Else
) || !cond
.returns() {
2152 if let Some(binop_span
) = missing_then_block_binop_span() {
2153 self.error_missing_if_then_block(lo
, None
, Some(binop_span
)).emit();
2154 self.mk_block_err(cond
.span
)
2156 self.error_missing_if_cond(lo
, cond
.span
)
2159 let attrs
= self.parse_outer_attributes()?
.take_for_recovery(); // For recovery.
2160 let not_block
= self.token
!= token
::OpenDelim(token
::Brace
);
2161 let block
= self.parse_block().map_err(|err
| {
2163 self.error_missing_if_then_block(lo
, Some(err
), missing_then_block_binop_span())
2168 self.error_on_if_block_attrs(lo
, false, block
.span
, &attrs
);
2171 let els
= if self.eat_keyword(kw
::Else
) { Some(self.parse_else_expr()?) }
else { None }
;
2172 Ok(self.mk_expr(lo
.to(self.prev_token
.span
), ExprKind
::If(cond
, thn
, els
), attrs
))
2175 fn error_missing_if_then_block(
2178 err
: Option
<DiagnosticBuilder
<'a
, ErrorGuaranteed
>>,
2179 binop_span
: Option
<Span
>,
2180 ) -> DiagnosticBuilder
<'a
, ErrorGuaranteed
> {
2181 let msg
= "this `if` expression has a condition, but no block";
2183 let mut err
= if let Some(mut err
) = err
{
2184 err
.span_label(if_span
, msg
);
2187 self.struct_span_err(if_span
, msg
)
2190 if let Some(binop_span
) = binop_span
{
2191 err
.span_help(binop_span
, "maybe you forgot the right operand of the condition?");
2197 fn error_missing_if_cond(&self, lo
: Span
, span
: Span
) -> P
<ast
::Block
> {
2198 let sp
= self.sess
.source_map().next_point(lo
);
2199 self.struct_span_err(sp
, "missing condition for `if` expression")
2200 .span_label(sp
, "expected if condition here")
2202 self.mk_block_err(span
)
2205 /// Parses the condition of a `if` or `while` expression.
2206 fn parse_cond_expr(&mut self) -> PResult
<'a
, P
<Expr
>> {
2207 let cond
= self.parse_expr_res(Restrictions
::NO_STRUCT_LITERAL
, None
)?
;
2209 if let ExprKind
::Let(..) = cond
.kind
{
2210 // Remove the last feature gating of a `let` expression since it's stable.
2211 self.sess
.gated_spans
.ungate_last(sym
::let_chains
, cond
.span
);
2217 /// Parses a `let $pat = $expr` pseudo-expression.
2218 /// The `let` token has already been eaten.
2219 fn parse_let_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
2220 let lo
= self.prev_token
.span
;
2221 let pat
= self.parse_pat_allow_top_alt(
2225 CommaRecoveryMode
::LikelyTuple
,
2227 self.expect(&token
::Eq
)?
;
2228 let expr
= self.with_res(self.restrictions
| Restrictions
::NO_STRUCT_LITERAL
, |this
| {
2229 this
.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None
.into())
2231 let span
= lo
.to(expr
.span
);
2232 self.sess
.gated_spans
.gate(sym
::let_chains
, span
);
2233 Ok(self.mk_expr(span
, ExprKind
::Let(pat
, expr
, span
), attrs
))
2236 /// Parses an `else { ... }` expression (`else` token already eaten).
2237 fn parse_else_expr(&mut self) -> PResult
<'a
, P
<Expr
>> {
2238 let ctx_span
= self.prev_token
.span
; // `else`
2239 let attrs
= self.parse_outer_attributes()?
.take_for_recovery(); // For recovery.
2240 let expr
= if self.eat_keyword(kw
::If
) {
2241 self.parse_if_expr(AttrVec
::new())?
2243 let blk
= self.parse_block()?
;
2244 self.mk_expr(blk
.span
, ExprKind
::Block(blk
, None
), AttrVec
::new())
2246 self.error_on_if_block_attrs(ctx_span
, true, expr
.span
, &attrs
);
2250 fn error_on_if_block_attrs(
2255 attrs
: &[ast
::Attribute
],
2257 let (span
, last
) = match attrs
{
2259 [x0 @ xn
] | [x0
, .., xn
] => (x0
.span
.to(xn
.span
), xn
.span
),
2261 let ctx
= if is_ctx_else { "else" }
else { "if" }
;
2262 self.struct_span_err(last
, "outer attributes are not allowed on `if` and `else` branches")
2263 .span_label(branch_span
, "the attributes are attached to this branch")
2264 .span_label(ctx_span
, format
!("the branch belongs to this `{ctx}`"))
2267 "remove the attributes",
2269 Applicability
::MachineApplicable
,
2274 /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
2277 opt_label
: Option
<Label
>,
2280 ) -> PResult
<'a
, P
<Expr
>> {
2281 // Record whether we are about to parse `for (`.
2282 // This is used below for recovery in case of `for ( $stuff ) $block`
2283 // in which case we will suggest `for $stuff $block`.
2284 let begin_paren
= match self.token
.kind
{
2285 token
::OpenDelim(token
::Paren
) => Some(self.token
.span
),
2289 let pat
= self.parse_pat_allow_top_alt(
2293 CommaRecoveryMode
::LikelyTuple
,
2295 if !self.eat_keyword(kw
::In
) {
2296 self.error_missing_in_for_loop();
2298 self.check_for_for_in_in_typo(self.prev_token
.span
);
2299 let expr
= self.parse_expr_res(Restrictions
::NO_STRUCT_LITERAL
, None
)?
;
2301 let pat
= self.recover_parens_around_for_head(pat
, begin_paren
);
2303 let (iattrs
, loop_block
) = self.parse_inner_attrs_and_block()?
;
2304 attrs
.extend(iattrs
);
2306 let kind
= ExprKind
::ForLoop(pat
, expr
, loop_block
, opt_label
);
2307 Ok(self.mk_expr(lo
.to(self.prev_token
.span
), kind
, attrs
))
2310 fn error_missing_in_for_loop(&mut self) {
2311 let (span
, msg
, sugg
) = if self.token
.is_ident_named(sym
::of
) {
2312 // Possibly using JS syntax (#75311).
2313 let span
= self.token
.span
;
2315 (span
, "try using `in` here instead", "in")
2317 (self.prev_token
.span
.between(self.token
.span
), "try adding `in` here", " in ")
2319 self.struct_span_err(span
, "missing `in` in `for` loop")
2320 .span_suggestion_short(
2324 // Has been misleading, at least in the past (closed Issue #48492).
2325 Applicability
::MaybeIncorrect
,
2330 /// Parses a `while` or `while let` expression (`while` token already eaten).
2331 fn parse_while_expr(
2333 opt_label
: Option
<Label
>,
2336 ) -> PResult
<'a
, P
<Expr
>> {
2337 let cond
= self.parse_cond_expr().map_err(|mut err
| {
2338 err
.span_label(lo
, "while parsing the condition of this `while` expression");
2341 let (iattrs
, body
) = self.parse_inner_attrs_and_block().map_err(|mut err
| {
2342 err
.span_label(lo
, "while parsing the body of this `while` expression");
2343 err
.span_label(cond
.span
, "this `while` condition successfully parsed");
2346 attrs
.extend(iattrs
);
2347 Ok(self.mk_expr(lo
.to(self.prev_token
.span
), ExprKind
::While(cond
, body
, opt_label
), attrs
))
2350 /// Parses `loop { ... }` (`loop` token already eaten).
2353 opt_label
: Option
<Label
>,
2356 ) -> PResult
<'a
, P
<Expr
>> {
2357 let (iattrs
, body
) = self.parse_inner_attrs_and_block()?
;
2358 attrs
.extend(iattrs
);
2359 Ok(self.mk_expr(lo
.to(self.prev_token
.span
), ExprKind
::Loop(body
, opt_label
), attrs
))
2362 crate fn eat_label(&mut self) -> Option
<Label
> {
2363 self.token
.lifetime().map(|ident
| {
2369 /// Parses a `match ... { ... }` expression (`match` token already eaten).
2370 fn parse_match_expr(&mut self, mut attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
2371 let match_span
= self.prev_token
.span
;
2372 let lo
= self.prev_token
.span
;
2373 let scrutinee
= self.parse_expr_res(Restrictions
::NO_STRUCT_LITERAL
, None
)?
;
2374 if let Err(mut e
) = self.expect(&token
::OpenDelim(token
::Brace
)) {
2375 if self.token
== token
::Semi
{
2376 e
.span_suggestion_short(
2378 "try removing this `match`",
2380 Applicability
::MaybeIncorrect
, // speculative
2383 if self.maybe_recover_unexpected_block_label() {
2390 attrs
.extend(self.parse_inner_attributes()?
);
2392 let mut arms
: Vec
<Arm
> = Vec
::new();
2393 while self.token
!= token
::CloseDelim(token
::Brace
) {
2394 match self.parse_arm() {
2395 Ok(arm
) => arms
.push(arm
),
2397 // Recover by skipping to the end of the block.
2399 self.recover_stmt();
2400 let span
= lo
.to(self.token
.span
);
2401 if self.token
== token
::CloseDelim(token
::Brace
) {
2404 return Ok(self.mk_expr(span
, ExprKind
::Match(scrutinee
, arms
), attrs
));
2408 let hi
= self.token
.span
;
2410 Ok(self.mk_expr(lo
.to(hi
), ExprKind
::Match(scrutinee
, arms
), attrs
))
2413 /// Attempt to recover from match arm body with statements and no surrounding braces.
2414 fn parse_arm_body_missing_braces(
2416 first_expr
: &P
<Expr
>,
2418 ) -> Option
<P
<Expr
>> {
2419 if self.token
.kind
!= token
::Semi
{
2422 let start_snapshot
= self.create_snapshot_for_diagnostic();
2423 let semi_sp
= self.token
.span
;
2426 vec
![self.mk_stmt(first_expr
.span
, ast
::StmtKind
::Expr(first_expr
.clone()))];
2427 let err
= |this
: &mut Parser
<'_
>, stmts
: Vec
<ast
::Stmt
>| {
2428 let span
= stmts
[0].span
.to(stmts
[stmts
.len() - 1].span
);
2429 let mut err
= this
.struct_span_err(span
, "`match` arm body without braces");
2430 let (these
, s
, are
) =
2431 if stmts
.len() > 1 { ("these", "s", "are") }
else { ("this", "", "is") }
;
2435 "{these} statement{s} {are} not surrounded by a body",
2441 err
.span_label(arrow_span
, "while parsing the `match` arm starting here");
2442 if stmts
.len() > 1 {
2443 err
.multipart_suggestion(
2444 &format
!("surround the statement{s} with a body"),
2446 (span
.shrink_to_lo(), "{ ".to_string()),
2447 (span
.shrink_to_hi(), " }".to_string()),
2449 Applicability
::MachineApplicable
,
2452 err
.span_suggestion(
2454 "use a comma to end a `match` arm expression",
2456 Applicability
::MachineApplicable
,
2460 this
.mk_expr_err(span
)
2462 // We might have either a `,` -> `;` typo, or a block without braces. We need
2463 // a more subtle parsing strategy.
2465 if self.token
.kind
== token
::CloseDelim(token
::Brace
) {
2466 // We have reached the closing brace of the `match` expression.
2467 return Some(err(self, stmts
));
2469 if self.token
.kind
== token
::Comma
{
2470 self.restore_snapshot(start_snapshot
);
2473 let pre_pat_snapshot
= self.create_snapshot_for_diagnostic();
2474 match self.parse_pat_no_top_alt(None
) {
2476 if self.token
.kind
== token
::FatArrow
{
2478 self.restore_snapshot(pre_pat_snapshot
);
2479 return Some(err(self, stmts
));
2487 self.restore_snapshot(pre_pat_snapshot
);
2488 match self.parse_stmt_without_recovery(true, ForceCollect
::No
) {
2489 // Consume statements for as long as possible.
2494 self.restore_snapshot(start_snapshot
);
2497 // We couldn't parse either yet another statement missing it's
2498 // enclosing block nor the next arm's pattern or closing brace.
2501 self.restore_snapshot(start_snapshot
);
2509 pub(super) fn parse_arm(&mut self) -> PResult
<'a
, Arm
> {
2510 fn check_let_expr(expr
: &Expr
) -> (bool
, bool
) {
2512 ExprKind
::Binary(_
, ref lhs
, ref rhs
) => {
2513 let lhs_rslt
= check_let_expr(lhs
);
2514 let rhs_rslt
= check_let_expr(rhs
);
2515 (lhs_rslt
.0 || rhs_rslt
.0, false)
2517 ExprKind
::Let(..) => (true, true),
2521 let attrs
= self.parse_outer_attributes()?
;
2522 self.collect_tokens_trailing_token(attrs
, ForceCollect
::No
, |this
, attrs
| {
2523 let lo
= this
.token
.span
;
2524 let pat
= this
.parse_pat_allow_top_alt(
2528 CommaRecoveryMode
::EitherTupleOrPipe
,
2530 let guard
= if this
.eat_keyword(kw
::If
) {
2531 let if_span
= this
.prev_token
.span
;
2532 let cond
= this
.parse_expr()?
;
2533 let (has_let_expr
, does_not_have_bin_op
) = check_let_expr(&cond
);
2535 if does_not_have_bin_op
{
2536 // Remove the last feature gating of a `let` expression since it's stable.
2537 this
.sess
.gated_spans
.ungate_last(sym
::let_chains
, cond
.span
);
2539 let span
= if_span
.to(cond
.span
);
2540 this
.sess
.gated_spans
.gate(sym
::if_let_guard
, span
);
2546 let arrow_span
= this
.token
.span
;
2547 if let Err(mut err
) = this
.expect(&token
::FatArrow
) {
2548 // We might have a `=>` -> `=` or `->` typo (issue #89396).
2549 if TokenKind
::FatArrow
2551 .map_or(false, |similar_tokens
| similar_tokens
.contains(&this
.token
.kind
))
2553 err
.span_suggestion(
2555 "try using a fat arrow here",
2557 Applicability
::MaybeIncorrect
,
2565 let arm_start_span
= this
.token
.span
;
2567 let expr
= this
.parse_expr_res(Restrictions
::STMT_EXPR
, None
).map_err(|mut err
| {
2568 err
.span_label(arrow_span
, "while parsing the `match` arm starting here");
2572 let require_comma
= classify
::expr_requires_semi_to_be_stmt(&expr
)
2573 && this
.token
!= token
::CloseDelim(token
::Brace
);
2575 let hi
= this
.prev_token
.span
;
2578 let sm
= this
.sess
.source_map();
2579 if let Some(body
) = this
.parse_arm_body_missing_braces(&expr
, arrow_span
) {
2580 let span
= body
.span
;
2583 attrs
: attrs
.into(),
2589 is_placeholder
: false,
2591 TrailingToken
::None
,
2594 this
.expect_one_of(&[token
::Comma
], &[token
::CloseDelim(token
::Brace
)]).map_err(
2596 match (sm
.span_to_lines(expr
.span
), sm
.span_to_lines(arm_start_span
)) {
2597 (Ok(ref expr_lines
), Ok(ref arm_start_lines
))
2598 if arm_start_lines
.lines
[0].end_col
2599 == expr_lines
.lines
[0].end_col
2600 && expr_lines
.lines
.len() == 2
2601 && this
.token
== token
::FatArrow
=>
2603 // We check whether there's any trailing code in the parse span,
2604 // if there isn't, we very likely have the following:
2607 // | -- - missing comma
2611 // | - ^^ self.token.span
2613 // | parsed until here as `"y" & X`
2614 err
.span_suggestion_short(
2615 arm_start_span
.shrink_to_hi(),
2616 "missing a comma here to end this `match` arm",
2618 Applicability
::MachineApplicable
,
2624 "while parsing the `match` arm starting here",
2632 this
.eat(&token
::Comma
);
2637 attrs
: attrs
.into(),
2643 is_placeholder
: false,
2645 TrailingToken
::None
,
2650 /// Parses a `try {...}` expression (`try` token already eaten).
2651 fn parse_try_block(&mut self, span_lo
: Span
, mut attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
2652 let (iattrs
, body
) = self.parse_inner_attrs_and_block()?
;
2653 attrs
.extend(iattrs
);
2654 if self.eat_keyword(kw
::Catch
) {
2655 let mut error
= self.struct_span_err(
2656 self.prev_token
.span
,
2657 "keyword `catch` cannot follow a `try` block",
2659 error
.help("try using `match` on the result of the `try` block instead");
2663 let span
= span_lo
.to(body
.span
);
2664 self.sess
.gated_spans
.gate(sym
::try_blocks
, span
);
2665 Ok(self.mk_expr(span
, ExprKind
::TryBlock(body
), attrs
))
2669 fn is_do_catch_block(&self) -> bool
{
2670 self.token
.is_keyword(kw
::Do
)
2671 && self.is_keyword_ahead(1, &[kw
::Catch
])
2672 && self.look_ahead(2, |t
| *t
== token
::OpenDelim(token
::Brace
))
2673 && !self.restrictions
.contains(Restrictions
::NO_STRUCT_LITERAL
)
2676 fn is_try_block(&self) -> bool
{
2677 self.token
.is_keyword(kw
::Try
)
2678 && self.look_ahead(1, |t
| *t
== token
::OpenDelim(token
::Brace
))
2679 && self.token
.uninterpolated_span().rust_2018()
2682 /// Parses an `async move? {...}` expression.
2683 fn parse_async_block(&mut self, mut attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
2684 let lo
= self.token
.span
;
2685 self.expect_keyword(kw
::Async
)?
;
2686 let capture_clause
= self.parse_capture_clause()?
;
2687 let (iattrs
, body
) = self.parse_inner_attrs_and_block()?
;
2688 attrs
.extend(iattrs
);
2689 let kind
= ExprKind
::Async(capture_clause
, DUMMY_NODE_ID
, body
);
2690 Ok(self.mk_expr(lo
.to(self.prev_token
.span
), kind
, attrs
))
2693 fn is_async_block(&self) -> bool
{
2694 self.token
.is_keyword(kw
::Async
)
2697 self.is_keyword_ahead(1, &[kw
::Move
])
2698 && self.look_ahead(2, |t
| *t
== token
::OpenDelim(token
::Brace
))
2701 self.look_ahead(1, |t
| *t
== token
::OpenDelim(token
::Brace
))
2705 fn is_certainly_not_a_block(&self) -> bool
{
2706 self.look_ahead(1, |t
| t
.is_ident())
2708 // `{ ident, ` cannot start a block.
2709 self.look_ahead(2, |t
| t
== &token
::Comma
)
2710 || self.look_ahead(2, |t
| t
== &token
::Colon
)
2712 // `{ ident: token, ` cannot start a block.
2713 self.look_ahead(4, |t
| t
== &token
::Comma
) ||
2714 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
2715 self.look_ahead(3, |t
| !t
.can_begin_type())
2720 fn maybe_parse_struct_expr(
2722 qself
: Option
<&ast
::QSelf
>,
2725 ) -> Option
<PResult
<'a
, P
<Expr
>>> {
2726 let struct_allowed
= !self.restrictions
.contains(Restrictions
::NO_STRUCT_LITERAL
);
2727 if struct_allowed
|| self.is_certainly_not_a_block() {
2728 if let Err(err
) = self.expect(&token
::OpenDelim(token
::Brace
)) {
2729 return Some(Err(err
));
2731 let expr
= self.parse_struct_expr(qself
.cloned(), path
.clone(), attrs
.clone(), true);
2732 if let (Ok(expr
), false) = (&expr
, struct_allowed
) {
2733 // This is a struct literal, but we don't can't accept them here.
2734 self.error_struct_lit_not_allowed_here(path
.span
, expr
.span
);
2741 fn error_struct_lit_not_allowed_here(&self, lo
: Span
, sp
: Span
) {
2742 self.struct_span_err(sp
, "struct literals are not allowed here")
2743 .multipart_suggestion(
2744 "surround the struct literal with parentheses",
2745 vec
![(lo
.shrink_to_lo(), "(".to_string()), (sp
.shrink_to_hi(), ")".to_string())],
2746 Applicability
::MachineApplicable
,
2751 pub(super) fn parse_struct_fields(
2755 close_delim
: token
::DelimToken
,
2756 ) -> PResult
<'a
, (Vec
<ExprField
>, ast
::StructRest
, bool
)> {
2757 let mut fields
= Vec
::new();
2758 let mut base
= ast
::StructRest
::None
;
2759 let mut recover_async
= false;
2761 let mut async_block_err
= |e
: &mut Diagnostic
, span
: Span
| {
2762 recover_async
= true;
2763 e
.span_label(span
, "`async` blocks are only allowed in Rust 2018 or later");
2764 e
.help_use_latest_edition();
2767 while self.token
!= token
::CloseDelim(close_delim
) {
2768 if self.eat(&token
::DotDot
) {
2769 let exp_span
= self.prev_token
.span
;
2770 // We permit `.. }` on the left-hand side of a destructuring assignment.
2771 if self.check(&token
::CloseDelim(close_delim
)) {
2772 base
= ast
::StructRest
::Rest(self.prev_token
.span
.shrink_to_hi());
2775 match self.parse_expr() {
2776 Ok(e
) => base
= ast
::StructRest
::Base(e
),
2777 Err(mut e
) if recover
=> {
2779 self.recover_stmt();
2781 Err(e
) => return Err(e
),
2783 self.recover_struct_comma_after_dotdot(exp_span
);
2787 let recovery_field
= self.find_struct_error_after_field_looking_code();
2788 let parsed_field
= match self.parse_expr_field() {
2791 if pth
== kw
::Async
{
2792 async_block_err(&mut e
, pth
.span
);
2794 e
.span_label(pth
.span
, "while parsing this struct");
2798 // If the next token is a comma, then try to parse
2799 // what comes next as additional fields, rather than
2800 // bailing out until next `}`.
2801 if self.token
!= token
::Comma
{
2802 self.recover_stmt_(SemiColonMode
::Comma
, BlockMode
::Ignore
);
2803 if self.token
!= token
::Comma
{
2811 match self.expect_one_of(&[token
::Comma
], &[token
::CloseDelim(close_delim
)]) {
2813 if let Some(f
) = parsed_field
.or(recovery_field
) {
2814 // Only include the field if there's no parse error for the field name.
2819 if pth
== kw
::Async
{
2820 async_block_err(&mut e
, pth
.span
);
2822 e
.span_label(pth
.span
, "while parsing this struct");
2823 if let Some(f
) = recovery_field
{
2826 self.prev_token
.span
.shrink_to_hi(),
2827 "try adding a comma",
2829 Applicability
::MachineApplicable
,
2837 self.recover_stmt_(SemiColonMode
::Comma
, BlockMode
::Ignore
);
2838 self.eat(&token
::Comma
);
2842 Ok((fields
, base
, recover_async
))
2845 /// Precondition: already parsed the '{'.
2846 pub(super) fn parse_struct_expr(
2848 qself
: Option
<ast
::QSelf
>,
2852 ) -> PResult
<'a
, P
<Expr
>> {
2854 let (fields
, base
, recover_async
) =
2855 self.parse_struct_fields(pth
.clone(), recover
, token
::Brace
)?
;
2856 let span
= lo
.to(self.token
.span
);
2857 self.expect(&token
::CloseDelim(token
::Brace
))?
;
2858 let expr
= if recover_async
{
2861 ExprKind
::Struct(P(ast
::StructExpr { qself, path: pth, fields, rest: base }
))
2863 Ok(self.mk_expr(span
, expr
, attrs
))
2866 /// Use in case of error after field-looking code: `S { foo: () with a }`.
2867 fn find_struct_error_after_field_looking_code(&self) -> Option
<ExprField
> {
2868 match self.token
.ident() {
2869 Some((ident
, is_raw
))
2870 if (is_raw
|| !ident
.is_reserved())
2871 && self.look_ahead(1, |t
| *t
== token
::Colon
) =>
2873 Some(ast
::ExprField
{
2875 span
: self.token
.span
,
2876 expr
: self.mk_expr_err(self.token
.span
),
2877 is_shorthand
: false,
2878 attrs
: AttrVec
::new(),
2880 is_placeholder
: false,
2887 fn recover_struct_comma_after_dotdot(&mut self, span
: Span
) {
2888 if self.token
!= token
::Comma
{
2891 self.struct_span_err(
2892 span
.to(self.prev_token
.span
),
2893 "cannot use a comma after the base struct",
2895 .span_suggestion_short(
2897 "remove this comma",
2899 Applicability
::MachineApplicable
,
2901 .note("the base struct must always be the last field")
2903 self.recover_stmt();
2906 /// Parses `ident (COLON expr)?`.
2907 fn parse_expr_field(&mut self) -> PResult
<'a
, ExprField
> {
2908 let attrs
= self.parse_outer_attributes()?
;
2909 self.collect_tokens_trailing_token(attrs
, ForceCollect
::No
, |this
, attrs
| {
2910 let lo
= this
.token
.span
;
2912 // Check if a colon exists one ahead. This means we're parsing a fieldname.
2913 let is_shorthand
= !this
.look_ahead(1, |t
| t
== &token
::Colon
|| t
== &token
::Eq
);
2914 let (ident
, expr
) = if is_shorthand
{
2915 // Mimic `x: x` for the `x` field shorthand.
2916 let ident
= this
.parse_ident_common(false)?
;
2917 let path
= ast
::Path
::from_ident(ident
);
2918 (ident
, this
.mk_expr(ident
.span
, ExprKind
::Path(None
, path
), AttrVec
::new()))
2920 let ident
= this
.parse_field_name()?
;
2921 this
.error_on_eq_field_init(ident
);
2923 (ident
, this
.parse_expr()?
)
2929 span
: lo
.to(expr
.span
),
2932 attrs
: attrs
.into(),
2934 is_placeholder
: false,
2936 TrailingToken
::MaybeComma
,
2941 /// Check for `=`. This means the source incorrectly attempts to
2942 /// initialize a field with an eq rather than a colon.
2943 fn error_on_eq_field_init(&self, field_name
: Ident
) {
2944 if self.token
!= token
::Eq
{
2948 self.struct_span_err(self.token
.span
, "expected `:`, found `=`")
2950 field_name
.span
.shrink_to_hi().to(self.token
.span
),
2951 "replace equals symbol with a colon",
2953 Applicability
::MachineApplicable
,
2958 fn err_dotdotdot_syntax(&self, span
: Span
) {
2959 self.struct_span_err(span
, "unexpected token: `...`")
2962 "use `..` for an exclusive range",
2964 Applicability
::MaybeIncorrect
,
2968 "or `..=` for an inclusive range",
2970 Applicability
::MaybeIncorrect
,
2975 fn err_larrow_operator(&self, span
: Span
) {
2976 self.struct_span_err(span
, "unexpected token: `<-`")
2979 "if you meant to write a comparison against a negative value, add a \
2980 space in between `<` and `-`",
2982 Applicability
::MaybeIncorrect
,
2987 fn mk_assign_op(&self, binop
: BinOp
, lhs
: P
<Expr
>, rhs
: P
<Expr
>) -> ExprKind
{
2988 ExprKind
::AssignOp(binop
, lhs
, rhs
)
2993 start
: Option
<P
<Expr
>>,
2994 end
: Option
<P
<Expr
>>,
2995 limits
: RangeLimits
,
2997 if end
.is_none() && limits
== RangeLimits
::Closed
{
2998 self.inclusive_range_with_incorrect_end(self.prev_token
.span
);
3001 ExprKind
::Range(start
, end
, limits
)
3005 fn mk_unary(&self, unop
: UnOp
, expr
: P
<Expr
>) -> ExprKind
{
3006 ExprKind
::Unary(unop
, expr
)
3009 fn mk_binary(&self, binop
: BinOp
, lhs
: P
<Expr
>, rhs
: P
<Expr
>) -> ExprKind
{
3010 ExprKind
::Binary(binop
, lhs
, rhs
)
3013 fn mk_index(&self, expr
: P
<Expr
>, idx
: P
<Expr
>) -> ExprKind
{
3014 ExprKind
::Index(expr
, idx
)
3017 fn mk_call(&self, f
: P
<Expr
>, args
: Vec
<P
<Expr
>>) -> ExprKind
{
3018 ExprKind
::Call(f
, args
)
3021 fn mk_await_expr(&mut self, self_arg
: P
<Expr
>, lo
: Span
) -> P
<Expr
> {
3022 let span
= lo
.to(self.prev_token
.span
);
3023 let await_expr
= self.mk_expr(span
, ExprKind
::Await(self_arg
), AttrVec
::new());
3024 self.recover_from_await_method_call();
3028 crate fn mk_expr(&self, span
: Span
, kind
: ExprKind
, attrs
: AttrVec
) -> P
<Expr
> {
3029 P(Expr { kind, span, attrs, id: DUMMY_NODE_ID, tokens: None }
)
3032 pub(super) fn mk_expr_err(&self, span
: Span
) -> P
<Expr
> {
3033 self.mk_expr(span
, ExprKind
::Err
, AttrVec
::new())
3036 /// Create expression span ensuring the span of the parent node
3037 /// is larger than the span of lhs and rhs, including the attributes.
3038 fn mk_expr_sp(&self, lhs
: &P
<Expr
>, lhs_span
: Span
, rhs_span
: Span
) -> Span
{
3041 .find(|a
| a
.style
== AttrStyle
::Outer
)
3042 .map_or(lhs_span
, |a
| a
.span
)
3046 fn collect_tokens_for_expr(
3049 f
: impl FnOnce(&mut Self, Vec
<ast
::Attribute
>) -> PResult
<'a
, P
<Expr
>>,
3050 ) -> PResult
<'a
, P
<Expr
>> {
3051 self.collect_tokens_trailing_token(attrs
, ForceCollect
::No
, |this
, attrs
| {
3052 let res
= f(this
, attrs
)?
;
3053 let trailing
= if this
.restrictions
.contains(Restrictions
::STMT_EXPR
)
3054 && this
.token
.kind
== token
::Semi
3058 // FIXME - pass this through from the place where we know
3059 // we need a comma, rather than assuming that `#[attr] expr,`
3060 // always captures a trailing comma
3061 TrailingToken
::MaybeComma