1 use super::pat
::{RecoverColon, RecoverComma, PARAM_EXPECTED}
;
2 use super::ty
::{AllowPlus, RecoverQPath, RecoverReturnSign}
;
4 AttrWrapper
, BlockMode
, ClosureSpans
, ForceCollect
, Parser
, PathStyle
, Restrictions
, TokenType
,
6 use super::{SemiColonMode, SeqSep, TokenExpectType, TrailingToken}
;
7 use crate::maybe_recover_from_interpolated_ty_qpath
;
9 use ast
::token
::DelimToken
;
10 use rustc_ast
::ptr
::P
;
11 use rustc_ast
::token
::{self, Token, TokenKind}
;
12 use rustc_ast
::tokenstream
::Spacing
;
13 use rustc_ast
::util
::classify
;
14 use rustc_ast
::util
::literal
::LitError
;
15 use rustc_ast
::util
::parser
::{prec_let_scrutinee_needs_par, AssocOp, Fixity}
;
16 use rustc_ast
::{self as ast, AttrStyle, AttrVec, CaptureBy, ExprField, Lit, UnOp, DUMMY_NODE_ID}
;
17 use rustc_ast
::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, MacCall, Param, Ty, TyKind}
;
18 use rustc_ast
::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits}
;
19 use rustc_ast_pretty
::pprust
;
20 use rustc_errors
::{Applicability, DiagnosticBuilder, PResult}
;
21 use rustc_session
::lint
::builtin
::BREAK_WITH_LABEL_AND_LOOP
;
22 use rustc_session
::lint
::BuiltinLintDiagnostics
;
23 use rustc_span
::edition
::LATEST_STABLE_EDITION
;
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 if (op
.node
== AssocOp
::Equal
|| op
.node
== AssocOp
::NotEqual
)
217 && self.token
.kind
== token
::Eq
218 && self.prev_token
.span
.hi() == self.token
.span
.lo()
220 // Look for JS' `===` and `!==` and recover 😇
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
,
240 if op
== AssocOp
::As
{
241 lhs
= self.parse_assoc_op_cast(lhs
, lhs_span
, ExprKind
::Cast
)?
;
243 } else if op
== AssocOp
::Colon
{
244 lhs
= self.parse_assoc_op_ascribe(lhs
, lhs_span
)?
;
246 } else if op
== AssocOp
::DotDot
|| op
== AssocOp
::DotDotEq
{
247 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
248 // generalise it to the Fixity::None code.
249 lhs
= self.parse_range_expr(prec
, lhs
, op
, cur_op_span
)?
;
253 let fixity
= op
.fixity();
254 let prec_adjustment
= match fixity
{
257 // We currently have no non-associative operators that are not handled above by
258 // the special cases. The code is here only for future convenience.
261 let rhs
= self.with_res(restrictions
- Restrictions
::STMT_EXPR
, |this
| {
262 this
.parse_assoc_expr_with(prec
+ prec_adjustment
, LhsExpr
::NotYetParsed
)
265 let span
= self.mk_expr_sp(&lhs
, lhs_span
, rhs
.span
);
278 | AssocOp
::ShiftRight
284 | AssocOp
::GreaterEqual
=> {
285 let ast_op
= op
.to_ast_binop().unwrap();
286 let binary
= self.mk_binary(source_map
::respan(cur_op_span
, ast_op
), lhs
, rhs
);
287 self.mk_expr(span
, binary
, AttrVec
::new())
290 self.mk_expr(span
, ExprKind
::Assign(lhs
, rhs
, cur_op_span
), AttrVec
::new())
292 AssocOp
::AssignOp(k
) => {
294 token
::Plus
=> BinOpKind
::Add
,
295 token
::Minus
=> BinOpKind
::Sub
,
296 token
::Star
=> BinOpKind
::Mul
,
297 token
::Slash
=> BinOpKind
::Div
,
298 token
::Percent
=> BinOpKind
::Rem
,
299 token
::Caret
=> BinOpKind
::BitXor
,
300 token
::And
=> BinOpKind
::BitAnd
,
301 token
::Or
=> BinOpKind
::BitOr
,
302 token
::Shl
=> BinOpKind
::Shl
,
303 token
::Shr
=> BinOpKind
::Shr
,
305 let aopexpr
= self.mk_assign_op(source_map
::respan(cur_op_span
, aop
), lhs
, rhs
);
306 self.mk_expr(span
, aopexpr
, AttrVec
::new())
308 AssocOp
::As
| AssocOp
::Colon
| AssocOp
::DotDot
| AssocOp
::DotDotEq
=> {
309 self.span_bug(span
, "AssocOp should have been handled by special case")
313 if let Fixity
::None
= fixity
{
317 if last_type_ascription_set
{
318 self.last_type_ascription
= None
;
323 fn should_continue_as_assoc_expr(&mut self, lhs
: &Expr
) -> bool
{
324 match (self.expr_is_complete(lhs
), AssocOp
::from_token(&self.token
)) {
325 // Semi-statement forms are odd:
326 // See https://github.com/rust-lang/rust/issues/29071
327 (true, None
) => false,
328 (false, _
) => true, // Continue parsing the expression.
329 // An exhaustive check is done in the following block, but these are checked first
330 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
331 // want to keep their span info to improve diagnostics in these cases in a later stage.
332 (true, Some(AssocOp
::Multiply
)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
333 (true, Some(AssocOp
::Subtract
)) | // `{ 42 } -5`
334 (true, Some(AssocOp
::Add
)) // `{ 42 } + 42
335 // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
336 // `if x { a } else { b } && if y { c } else { d }`
337 if !self.look_ahead(1, |t
| t
.is_used_keyword()) => {
338 // These cases are ambiguous and can't be identified in the parser alone.
339 let sp
= self.sess
.source_map().start_point(self.token
.span
);
340 self.sess
.ambiguous_block_expr_parse
.borrow_mut().insert(sp
, lhs
.span
);
343 (true, Some(AssocOp
::LAnd
)) => {
344 // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }`. Separated from the
345 // above due to #74233.
346 // These cases are ambiguous and can't be identified in the parser alone.
347 let sp
= self.sess
.source_map().start_point(self.token
.span
);
348 self.sess
.ambiguous_block_expr_parse
.borrow_mut().insert(sp
, lhs
.span
);
351 (true, Some(ref op
)) if !op
.can_continue_expr_unambiguously() => false,
353 self.error_found_expr_would_be_stmt(lhs
);
359 /// We've found an expression that would be parsed as a statement,
360 /// but the next token implies this should be parsed as an expression.
361 /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
362 fn error_found_expr_would_be_stmt(&self, lhs
: &Expr
) {
363 let mut err
= self.struct_span_err(
365 &format
!("expected expression, found `{}`", pprust
::token_to_string(&self.token
),),
367 err
.span_label(self.token
.span
, "expected expression");
368 self.sess
.expr_parentheses_needed(&mut err
, lhs
.span
);
372 /// Possibly translate the current token to an associative operator.
373 /// The method does not advance the current token.
375 /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
376 fn check_assoc_op(&self) -> Option
<Spanned
<AssocOp
>> {
377 let (op
, span
) = match (AssocOp
::from_token(&self.token
), self.token
.ident()) {
378 // When parsing const expressions, stop parsing when encountering `>`.
383 | AssocOp
::GreaterEqual
384 | AssocOp
::AssignOp(token
::BinOpToken
::Shr
),
387 ) if self.restrictions
.contains(Restrictions
::CONST_EXPR
) => {
390 (Some(op
), _
) => (op
, self.token
.span
),
391 (None
, Some((Ident { name: sym::and, span }
, false))) => {
392 self.error_bad_logical_op("and", "&&", "conjunction");
393 (AssocOp
::LAnd
, span
)
395 (None
, Some((Ident { name: sym::or, span }
, false))) => {
396 self.error_bad_logical_op("or", "||", "disjunction");
401 Some(source_map
::respan(span
, op
))
404 /// Error on `and` and `or` suggesting `&&` and `||` respectively.
405 fn error_bad_logical_op(&self, bad
: &str, good
: &str, english
: &str) {
406 self.struct_span_err(self.token
.span
, &format
!("`{}` is not a logical operator", bad
))
407 .span_suggestion_short(
409 &format
!("use `{}` to perform logical {}", good
, english
),
411 Applicability
::MachineApplicable
,
413 .note("unlike in e.g., python and PHP, `&&` and `||` are used for logical operators")
417 /// Checks if this expression is a successfully parsed statement.
418 fn expr_is_complete(&self, e
: &Expr
) -> bool
{
419 self.restrictions
.contains(Restrictions
::STMT_EXPR
)
420 && !classify
::expr_requires_semi_to_be_stmt(e
)
423 /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
424 /// The other two variants are handled in `parse_prefix_range_expr` below.
431 ) -> PResult
<'a
, P
<Expr
>> {
432 let rhs
= if self.is_at_start_of_range_notation_rhs() {
433 Some(self.parse_assoc_expr_with(prec
+ 1, LhsExpr
::NotYetParsed
)?
)
437 let rhs_span
= rhs
.as_ref().map_or(cur_op_span
, |x
| x
.span
);
438 let span
= self.mk_expr_sp(&lhs
, lhs
.span
, rhs_span
);
440 if op
== AssocOp
::DotDot { RangeLimits::HalfOpen }
else { RangeLimits::Closed }
;
441 let range
= self.mk_range(Some(lhs
), rhs
, limits
);
442 Ok(self.mk_expr(span
, range
, AttrVec
::new()))
445 fn is_at_start_of_range_notation_rhs(&self) -> bool
{
446 if self.token
.can_begin_expr() {
447 // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
448 if self.token
== token
::OpenDelim(token
::Brace
) {
449 return !self.restrictions
.contains(Restrictions
::NO_STRUCT_LITERAL
);
457 /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
458 fn parse_prefix_range_expr(&mut self, attrs
: Option
<AttrWrapper
>) -> PResult
<'a
, P
<Expr
>> {
459 // Check for deprecated `...` syntax.
460 if self.token
== token
::DotDotDot
{
461 self.err_dotdotdot_syntax(self.token
.span
);
465 [token
::DotDot
, token
::DotDotDot
, token
::DotDotEq
].contains(&self.token
.kind
),
466 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
470 let limits
= match self.token
.kind
{
471 token
::DotDot
=> RangeLimits
::HalfOpen
,
472 _
=> RangeLimits
::Closed
,
474 let op
= AssocOp
::from_token(&self.token
);
475 // FIXME: `parse_prefix_range_expr` is called when the current
476 // token is `DotDot`, `DotDotDot`, or `DotDotEq`. If we haven't already
477 // parsed attributes, then trying to parse them here will always fail.
478 // We should figure out how we want attributes on range expressions to work.
479 let attrs
= self.parse_or_use_outer_attributes(attrs
)?
;
480 self.collect_tokens_for_expr(attrs
, |this
, attrs
| {
481 let lo
= this
.token
.span
;
483 let (span
, opt_end
) = if this
.is_at_start_of_range_notation_rhs() {
484 // RHS must be parsed with more associativity than the dots.
485 this
.parse_assoc_expr_with(op
.unwrap().precedence() + 1, LhsExpr
::NotYetParsed
)
486 .map(|x
| (lo
.to(x
.span
), Some(x
)))?
490 let range
= this
.mk_range(None
, opt_end
, limits
);
491 Ok(this
.mk_expr(span
, range
, attrs
.into()))
495 /// Parses a prefix-unary-operator expr.
496 fn parse_prefix_expr(&mut self, attrs
: Option
<AttrWrapper
>) -> PResult
<'a
, P
<Expr
>> {
497 let attrs
= self.parse_or_use_outer_attributes(attrs
)?
;
498 let lo
= self.token
.span
;
500 macro_rules
! make_it
{
501 ($this
:ident
, $attrs
:expr
, |this
, _
| $body
:expr
) => {
502 $this
.collect_tokens_for_expr($attrs
, |$this
, attrs
| {
503 let (hi
, ex
) = $body?
;
504 Ok($this
.mk_expr(lo
.to(hi
), ex
, attrs
.into()))
511 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
512 match this
.token
.uninterpolate().kind
{
513 token
::Not
=> make_it
!(this
, attrs
, |this
, _
| this
.parse_unary_expr(lo
, UnOp
::Not
)), // `!expr`
514 token
::Tilde
=> make_it
!(this
, attrs
, |this
, _
| this
.recover_tilde_expr(lo
)), // `~expr`
515 token
::BinOp(token
::Minus
) => {
516 make_it
!(this
, attrs
, |this
, _
| this
.parse_unary_expr(lo
, UnOp
::Neg
))
518 token
::BinOp(token
::Star
) => {
519 make_it
!(this
, attrs
, |this
, _
| this
.parse_unary_expr(lo
, UnOp
::Deref
))
521 token
::BinOp(token
::And
) | token
::AndAnd
=> {
522 make_it
!(this
, attrs
, |this
, _
| this
.parse_borrow_expr(lo
))
524 token
::BinOp(token
::Plus
) if this
.look_ahead(1, |tok
| tok
.is_numeric_lit()) => {
525 let mut err
= this
.struct_span_err(lo
, "leading `+` is not supported");
526 err
.span_label(lo
, "unexpected `+`");
528 // a block on the LHS might have been intended to be an expression instead
529 if let Some(sp
) = this
.sess
.ambiguous_block_expr_parse
.borrow().get(&lo
) {
530 this
.sess
.expr_parentheses_needed(&mut err
, *sp
);
532 err
.span_suggestion_verbose(
534 "try removing the `+`",
536 Applicability
::MachineApplicable
,
542 this
.parse_prefix_expr(None
)
544 token
::Ident(..) if this
.token
.is_keyword(kw
::Box
) => {
545 make_it
!(this
, attrs
, |this
, _
| this
.parse_box_expr(lo
))
547 token
::Ident(..) if this
.is_mistaken_not_ident_negation() => {
548 make_it
!(this
, attrs
, |this
, _
| this
.recover_not_expr(lo
))
550 _
=> return this
.parse_dot_or_call_expr(Some(attrs
)),
554 fn parse_prefix_expr_common(&mut self, lo
: Span
) -> PResult
<'a
, (Span
, P
<Expr
>)> {
556 let expr
= self.parse_prefix_expr(None
);
557 let (span
, expr
) = self.interpolated_or_expr_span(expr
)?
;
558 Ok((lo
.to(span
), expr
))
561 fn parse_unary_expr(&mut self, lo
: Span
, op
: UnOp
) -> PResult
<'a
, (Span
, ExprKind
)> {
562 let (span
, expr
) = self.parse_prefix_expr_common(lo
)?
;
563 Ok((span
, self.mk_unary(op
, expr
)))
566 // Recover on `!` suggesting for bitwise negation instead.
567 fn recover_tilde_expr(&mut self, lo
: Span
) -> PResult
<'a
, (Span
, ExprKind
)> {
568 self.struct_span_err(lo
, "`~` cannot be used as a unary operator")
569 .span_suggestion_short(
571 "use `!` to perform bitwise not",
573 Applicability
::MachineApplicable
,
577 self.parse_unary_expr(lo
, UnOp
::Not
)
580 /// Parse `box expr`.
581 fn parse_box_expr(&mut self, lo
: Span
) -> PResult
<'a
, (Span
, ExprKind
)> {
582 let (span
, expr
) = self.parse_prefix_expr_common(lo
)?
;
583 self.sess
.gated_spans
.gate(sym
::box_syntax
, span
);
584 Ok((span
, ExprKind
::Box(expr
)))
587 fn is_mistaken_not_ident_negation(&self) -> bool
{
588 let token_cannot_continue_expr
= |t
: &Token
| match t
.uninterpolate().kind
{
589 // These tokens can start an expression after `!`, but
590 // can't continue an expression after an ident
591 token
::Ident(name
, is_raw
) => token
::ident_can_begin_expr(name
, t
.span
, is_raw
),
592 token
::Literal(..) | token
::Pound
=> true,
593 _
=> t
.is_whole_expr(),
595 self.token
.is_ident_named(sym
::not
) && self.look_ahead(1, token_cannot_continue_expr
)
598 /// Recover on `not expr` in favor of `!expr`.
599 fn recover_not_expr(&mut self, lo
: Span
) -> PResult
<'a
, (Span
, ExprKind
)> {
601 let not_token
= self.look_ahead(1, |t
| t
.clone());
602 self.struct_span_err(
604 &format
!("unexpected {} after identifier", super::token_descr(¬_token
)),
606 .span_suggestion_short(
607 // Span the `not` plus trailing whitespace to avoid
608 // trailing whitespace after the `!` in our suggestion
609 self.sess
.source_map().span_until_non_whitespace(lo
.to(not_token
.span
)),
610 "use `!` to perform logical negation",
612 Applicability
::MachineApplicable
,
617 self.parse_unary_expr(lo
, UnOp
::Not
)
620 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
621 fn interpolated_or_expr_span(
623 expr
: PResult
<'a
, P
<Expr
>>,
624 ) -> PResult
<'a
, (Span
, P
<Expr
>)> {
627 match self.prev_token
.kind
{
628 TokenKind
::Interpolated(..) => self.prev_token
.span
,
636 fn parse_assoc_op_cast(
640 expr_kind
: fn(P
<Expr
>, P
<Ty
>) -> ExprKind
,
641 ) -> PResult
<'a
, P
<Expr
>> {
642 let mk_expr
= |this
: &mut Self, lhs
: P
<Expr
>, rhs
: P
<Ty
>| {
644 this
.mk_expr_sp(&lhs
, lhs_span
, rhs
.span
),
650 // Save the state of the parser before parsing type normally, in case there is a
651 // LessThan comparison after this cast.
652 let parser_snapshot_before_type
= self.clone();
653 let cast_expr
= match self.parse_ty_no_plus() {
654 Ok(rhs
) => mk_expr(self, lhs
, rhs
),
655 Err(mut type_err
) => {
656 // Rewind to before attempting to parse the type with generics, to recover
657 // from situations like `x as usize < y` in which we first tried to parse
658 // `usize < y` as a type with generic arguments.
659 let parser_snapshot_after_type
= mem
::replace(self, parser_snapshot_before_type
);
661 // Check for typo of `'a: loop { break 'a }` with a missing `'`.
662 match (&lhs
.kind
, &self.token
.kind
) {
665 ExprKind
::Path(None
, ast
::Path { segments, .. }
),
666 TokenKind
::Ident(kw
::For
| kw
::Loop
| kw
::While
, false),
667 ) if segments
.len() == 1 => {
668 let snapshot
= self.clone();
670 ident
: Ident
::from_str_and_span(
671 &format
!("'{}", segments
[0].ident
),
672 segments
[0].ident
.span
,
675 match self.parse_labeled_expr(label
, AttrVec
::new(), false) {
678 self.struct_span_err(label
.ident
.span
, "malformed loop label")
681 "use the correct loop label format",
682 label
.ident
.to_string(),
683 Applicability
::MachineApplicable
,
697 match self.parse_path(PathStyle
::Expr
) {
699 let (op_noun
, op_verb
) = match self.token
.kind
{
700 token
::Lt
=> ("comparison", "comparing"),
701 token
::BinOp(token
::Shl
) => ("shift", "shifting"),
703 // We can end up here even without `<` being the next token, for
704 // example because `parse_ty_no_plus` returns `Err` on keywords,
705 // but `parse_path` returns `Ok` on them due to error recovery.
706 // Return original error and parser state.
707 *self = parser_snapshot_after_type
;
708 return Err(type_err
);
712 // Successfully parsed the type path leaving a `<` yet to parse.
715 // Report non-fatal diagnostics, keep `x as usize` as an expression
716 // in AST and continue parsing.
718 "`<` is interpreted as a start of generic arguments for `{}`, not a {}",
719 pprust
::path_to_string(&path
),
722 let span_after_type
= parser_snapshot_after_type
.token
.span
;
724 mk_expr(self, lhs
, self.mk_ty(path
.span
, TyKind
::Path(None
, path
)));
726 self.struct_span_err(self.token
.span
, &msg
)
728 self.look_ahead(1, |t
| t
.span
).to(span_after_type
),
729 "interpreted as generic arguments",
731 .span_label(self.token
.span
, format
!("not interpreted as {}", op_noun
))
732 .multipart_suggestion(
733 &format
!("try {} the cast value", op_verb
),
735 (expr
.span
.shrink_to_lo(), "(".to_string()),
736 (expr
.span
.shrink_to_hi(), ")".to_string()),
738 Applicability
::MachineApplicable
,
744 Err(mut path_err
) => {
745 // Couldn't parse as a path, return original error and parser state.
747 *self = parser_snapshot_after_type
;
748 return Err(type_err
);
754 self.parse_and_disallow_postfix_after_cast(cast_expr
)
757 /// Parses a postfix operators such as `.`, `?`, or index (`[]`) after a cast,
758 /// then emits an error and returns the newly parsed tree.
759 /// The resulting parse tree for `&x as T[0]` has a precedence of `((&x) as T)[0]`.
760 fn parse_and_disallow_postfix_after_cast(
763 ) -> PResult
<'a
, P
<Expr
>> {
764 // Save the memory location of expr before parsing any following postfix operators.
765 // This will be compared with the memory location of the output expression.
766 // If they different we can assume we parsed another expression because the existing expression is not reallocated.
767 let addr_before
= &*cast_expr
as *const _
as usize;
768 let span
= cast_expr
.span
;
769 let with_postfix
= self.parse_dot_or_call_expr_with_(cast_expr
, span
)?
;
770 let changed
= addr_before
!= &*with_postfix
as *const _
as usize;
772 // Check if an illegal postfix operator has been added after the cast.
773 // If the resulting expression is not a cast, or has a different memory location, it is an illegal postfix operator.
774 if !matches
!(with_postfix
.kind
, ExprKind
::Cast(_
, _
) | ExprKind
::Type(_
, _
)) || changed
{
776 "casts cannot be followed by {}",
777 match with_postfix
.kind
{
778 ExprKind
::Index(_
, _
) => "indexing",
779 ExprKind
::Try(_
) => "?",
780 ExprKind
::Field(_
, _
) => "a field access",
781 ExprKind
::MethodCall(_
, _
, _
) => "a method call",
782 ExprKind
::Call(_
, _
) => "a function call",
783 ExprKind
::Await(_
) => "`.await`",
784 ExprKind
::Err
=> return Ok(with_postfix
),
785 _
=> unreachable
!("parse_dot_or_call_expr_with_ shouldn't produce this"),
788 let mut err
= self.struct_span_err(span
, &msg
);
789 // If type ascription is "likely an error", the user will already be getting a useful
790 // help message, and doesn't need a second.
791 if self.last_type_ascription
.map_or(false, |last_ascription
| last_ascription
.1) {
792 self.maybe_annotate_with_ascription(&mut err
, false);
794 let suggestions
= vec
![
795 (span
.shrink_to_lo(), "(".to_string()),
796 (span
.shrink_to_hi(), ")".to_string()),
798 err
.multipart_suggestion(
799 "try surrounding the expression in parentheses",
801 Applicability
::MachineApplicable
,
809 fn parse_assoc_op_ascribe(&mut self, lhs
: P
<Expr
>, lhs_span
: Span
) -> PResult
<'a
, P
<Expr
>> {
810 let maybe_path
= self.could_ascription_be_path(&lhs
.kind
);
811 self.last_type_ascription
= Some((self.prev_token
.span
, maybe_path
));
812 let lhs
= self.parse_assoc_op_cast(lhs
, lhs_span
, ExprKind
::Type
)?
;
813 self.sess
.gated_spans
.gate(sym
::type_ascription
, lhs
.span
);
817 /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
818 fn parse_borrow_expr(&mut self, lo
: Span
) -> PResult
<'a
, (Span
, ExprKind
)> {
820 let has_lifetime
= self.token
.is_lifetime() && self.look_ahead(1, |t
| t
!= &token
::Colon
);
821 let lifetime
= has_lifetime
.then(|| self.expect_lifetime()); // For recovery, see below.
822 let (borrow_kind
, mutbl
) = self.parse_borrow_modifiers(lo
);
823 let expr
= self.parse_prefix_expr(None
);
824 let (hi
, expr
) = self.interpolated_or_expr_span(expr
)?
;
825 let span
= lo
.to(hi
);
826 if let Some(lt
) = lifetime
{
827 self.error_remove_borrow_lifetime(span
, lt
.ident
.span
);
829 Ok((span
, ExprKind
::AddrOf(borrow_kind
, mutbl
, expr
)))
832 fn error_remove_borrow_lifetime(&self, span
: Span
, lt_span
: Span
) {
833 self.struct_span_err(span
, "borrow expressions cannot be annotated with lifetimes")
834 .span_label(lt_span
, "annotated with lifetime here")
837 "remove the lifetime annotation",
839 Applicability
::MachineApplicable
,
844 /// Parse `mut?` or `raw [ const | mut ]`.
845 fn parse_borrow_modifiers(&mut self, lo
: Span
) -> (ast
::BorrowKind
, ast
::Mutability
) {
846 if self.check_keyword(kw
::Raw
) && self.look_ahead(1, Token
::is_mutability
) {
847 // `raw [ const | mut ]`.
848 let found_raw
= self.eat_keyword(kw
::Raw
);
850 let mutability
= self.parse_const_or_mut().unwrap();
851 self.sess
.gated_spans
.gate(sym
::raw_ref_op
, lo
.to(self.prev_token
.span
));
852 (ast
::BorrowKind
::Raw
, mutability
)
855 (ast
::BorrowKind
::Ref
, self.parse_mutability())
859 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
860 fn parse_dot_or_call_expr(&mut self, attrs
: Option
<AttrWrapper
>) -> PResult
<'a
, P
<Expr
>> {
861 let attrs
= self.parse_or_use_outer_attributes(attrs
)?
;
862 self.collect_tokens_for_expr(attrs
, |this
, attrs
| {
863 let base
= this
.parse_bottom_expr();
864 let (span
, base
) = this
.interpolated_or_expr_span(base
)?
;
865 this
.parse_dot_or_call_expr_with(base
, span
, attrs
)
869 pub(super) fn parse_dot_or_call_expr_with(
873 mut attrs
: Vec
<ast
::Attribute
>,
874 ) -> PResult
<'a
, P
<Expr
>> {
875 // Stitch the list of outer attributes onto the return value.
876 // A little bit ugly, but the best way given the current code
878 self.parse_dot_or_call_expr_with_(e0
, lo
).map(|expr
| {
879 expr
.map(|mut expr
| {
880 attrs
.extend
::<Vec
<_
>>(expr
.attrs
.into());
881 expr
.attrs
= attrs
.into();
887 fn parse_dot_or_call_expr_with_(&mut self, mut e
: P
<Expr
>, lo
: Span
) -> PResult
<'a
, P
<Expr
>> {
889 if self.eat(&token
::Question
) {
891 e
= self.mk_expr(lo
.to(self.prev_token
.span
), ExprKind
::Try(e
), AttrVec
::new());
894 if self.eat(&token
::Dot
) {
896 e
= self.parse_dot_suffix_expr(lo
, e
)?
;
899 if self.expr_is_complete(&e
) {
902 e
= match self.token
.kind
{
903 token
::OpenDelim(token
::Paren
) => self.parse_fn_call_expr(lo
, e
),
904 token
::OpenDelim(token
::Bracket
) => self.parse_index_expr(lo
, e
)?
,
910 fn look_ahead_type_ascription_as_field(&mut self) -> bool
{
911 self.look_ahead(1, |t
| t
.is_ident())
912 && self.look_ahead(2, |t
| t
== &token
::Colon
)
913 && self.look_ahead(3, |t
| t
.can_begin_expr())
916 fn parse_dot_suffix_expr(&mut self, lo
: Span
, base
: P
<Expr
>) -> PResult
<'a
, P
<Expr
>> {
917 match self.token
.uninterpolate().kind
{
918 token
::Ident(..) => self.parse_dot_suffix(base
, lo
),
919 token
::Literal(token
::Lit { kind: token::Integer, symbol, suffix }
) => {
920 Ok(self.parse_tuple_field_access_expr(lo
, base
, symbol
, suffix
, None
))
922 token
::Literal(token
::Lit { kind: token::Float, symbol, suffix }
) => {
923 Ok(self.parse_tuple_field_access_expr_float(lo
, base
, symbol
, suffix
))
926 self.error_unexpected_after_dot();
932 fn error_unexpected_after_dot(&self) {
933 // FIXME Could factor this out into non_fatal_unexpected or something.
934 let actual
= pprust
::token_to_string(&self.token
);
935 self.struct_span_err(self.token
.span
, &format
!("unexpected token: `{}`", actual
)).emit();
938 // We need an identifier or integer, but the next token is a float.
939 // Break the float into components to extract the identifier or integer.
940 // FIXME: With current `TokenCursor` it's hard to break tokens into more than 2
941 // parts unless those parts are processed immediately. `TokenCursor` should either
942 // support pushing "future tokens" (would be also helpful to `break_and_eat`), or
943 // we should break everything including floats into more basic proc-macro style
944 // tokens in the lexer (probably preferable).
945 fn parse_tuple_field_access_expr_float(
950 suffix
: Option
<Symbol
>,
953 enum FloatComponent
{
957 use FloatComponent
::*;
959 let float_str
= float
.as_str();
960 let mut components
= Vec
::new();
961 let mut ident_like
= String
::new();
962 for c
in float_str
.chars() {
963 if c
== '_'
|| c
.is_ascii_alphanumeric() {
965 } else if matches
!(c
, '
.'
| '
+'
| '
-'
) {
966 if !ident_like
.is_empty() {
967 components
.push(IdentLike(mem
::take(&mut ident_like
)));
969 components
.push(Punct(c
));
971 panic
!("unexpected character in a float token: {:?}", c
)
974 if !ident_like
.is_empty() {
975 components
.push(IdentLike(ident_like
));
978 // With proc macros the span can refer to anything, the source may be too short,
979 // or too long, or non-ASCII. It only makes sense to break our span into components
980 // if its underlying text is identical to our float literal.
981 let span
= self.token
.span
;
982 let can_take_span_apart
=
983 || self.span_to_snippet(span
).as_deref() == Ok(float_str
).as_deref();
988 self.parse_tuple_field_access_expr(lo
, base
, Symbol
::intern(&i
), suffix
, None
)
991 [IdentLike(i
), Punct('
.'
)] => {
992 let (ident_span
, dot_span
) = if can_take_span_apart() {
993 let (span
, ident_len
) = (span
.data(), BytePos
::from_usize(i
.len()));
994 let ident_span
= span
.with_hi(span
.lo
+ ident_len
);
995 let dot_span
= span
.with_lo(span
.lo
+ ident_len
);
996 (ident_span
, dot_span
)
1000 assert
!(suffix
.is_none());
1001 let symbol
= Symbol
::intern(&i
);
1002 self.token
= Token
::new(token
::Ident(symbol
, false), ident_span
);
1003 let next_token
= (Token
::new(token
::Dot
, dot_span
), self.token_spacing
);
1004 self.parse_tuple_field_access_expr(lo
, base
, symbol
, None
, Some(next_token
))
1007 [IdentLike(i1
), Punct('
.'
), IdentLike(i2
)] => {
1008 let (ident1_span
, dot_span
, ident2_span
) = if can_take_span_apart() {
1009 let (span
, ident1_len
) = (span
.data(), BytePos
::from_usize(i1
.len()));
1010 let ident1_span
= span
.with_hi(span
.lo
+ ident1_len
);
1012 .with_lo(span
.lo
+ ident1_len
)
1013 .with_hi(span
.lo
+ ident1_len
+ BytePos(1));
1014 let ident2_span
= self.token
.span
.with_lo(span
.lo
+ ident1_len
+ BytePos(1));
1015 (ident1_span
, dot_span
, ident2_span
)
1019 let symbol1
= Symbol
::intern(&i1
);
1020 self.token
= Token
::new(token
::Ident(symbol1
, false), ident1_span
);
1021 // This needs to be `Spacing::Alone` to prevent regressions.
1022 // See issue #76399 and PR #76285 for more details
1023 let next_token1
= (Token
::new(token
::Dot
, dot_span
), Spacing
::Alone
);
1025 self.parse_tuple_field_access_expr(lo
, base
, symbol1
, None
, Some(next_token1
));
1026 let symbol2
= Symbol
::intern(&i2
);
1027 let next_token2
= Token
::new(token
::Ident(symbol2
, false), ident2_span
);
1028 self.bump_with((next_token2
, self.token_spacing
)); // `.`
1029 self.parse_tuple_field_access_expr(lo
, base1
, symbol2
, suffix
, None
)
1031 // 1e+ | 1e- (recovered)
1032 [IdentLike(_
), Punct('
+'
| '
-'
)] |
1034 [IdentLike(_
), Punct('
+'
| '
-'
), IdentLike(_
)] |
1036 [IdentLike(_
), Punct('
.'
), IdentLike(_
), Punct('
+'
| '
-'
), IdentLike(_
)] => {
1037 // See the FIXME about `TokenCursor` above.
1038 self.error_unexpected_after_dot();
1041 _
=> panic
!("unexpected components in a float token: {:?}", components
),
1045 fn parse_tuple_field_access_expr(
1050 suffix
: Option
<Symbol
>,
1051 next_token
: Option
<(Token
, Spacing
)>,
1054 Some(next_token
) => self.bump_with(next_token
),
1055 None
=> self.bump(),
1057 let span
= self.prev_token
.span
;
1058 let field
= ExprKind
::Field(base
, Ident
::new(field
, span
));
1059 self.expect_no_suffix(span
, "a tuple index", suffix
);
1060 self.mk_expr(lo
.to(span
), field
, AttrVec
::new())
1063 /// Parse a function call expression, `expr(...)`.
1064 fn parse_fn_call_expr(&mut self, lo
: Span
, fun
: P
<Expr
>) -> P
<Expr
> {
1065 let snapshot
= if self.token
.kind
== token
::OpenDelim(token
::Paren
)
1066 && self.look_ahead_type_ascription_as_field()
1068 Some((self.clone(), fun
.kind
.clone()))
1072 let open_paren
= self.token
.span
;
1074 let mut seq
= self.parse_paren_expr_seq().map(|args
| {
1075 self.mk_expr(lo
.to(self.prev_token
.span
), self.mk_call(fun
, args
), AttrVec
::new())
1078 self.maybe_recover_struct_lit_bad_delims(lo
, open_paren
, &mut seq
, snapshot
)
1082 self.recover_seq_parse_error(token
::Paren
, lo
, seq
)
1085 /// If we encounter a parser state that looks like the user has written a `struct` literal with
1086 /// parentheses instead of braces, recover the parser state and provide suggestions.
1087 #[instrument(skip(self, seq, snapshot), level = "trace")]
1088 fn maybe_recover_struct_lit_bad_delims(
1092 seq
: &mut PResult
<'a
, P
<Expr
>>,
1093 snapshot
: Option
<(Self, ExprKind
)>,
1094 ) -> Option
<P
<Expr
>> {
1095 match (seq
.as_mut(), snapshot
) {
1096 (Err(ref mut err
), Some((mut snapshot
, ExprKind
::Path(None
, path
)))) => {
1097 let name
= pprust
::path_to_string(&path
);
1098 snapshot
.bump(); // `(`
1099 match snapshot
.parse_struct_fields(path
, false, token
::Paren
) {
1100 Ok((fields
, ..)) if snapshot
.eat(&token
::CloseDelim(token
::Paren
)) => {
1101 // We have are certain we have `Enum::Foo(a: 3, b: 4)`, suggest
1102 // `Enum::Foo { a: 3, b: 4 }` or `Enum::Foo(3, 4)`.
1104 let close_paren
= self.prev_token
.span
;
1105 let span
= lo
.to(self.prev_token
.span
);
1107 self.struct_span_err(
1109 "invalid `struct` delimiters or `fn` call arguments",
1111 .multipart_suggestion(
1112 &format
!("if `{}` is a struct, use braces as delimiters", name
),
1113 vec
![(open_paren
, " { ".to_string()), (close_paren, " }".to_string())],
1114 Applicability
::MaybeIncorrect
,
1116 .multipart_suggestion(
1117 &format
!("if `{}` is a function, use the arguments directly", name
),
1120 .map(|field
| (field
.span
.until(field
.expr
.span
), String
::new()))
1122 Applicability
::MaybeIncorrect
,
1125 return Some(self.mk_expr_err(span
));
1128 Err(mut err
) => err
.emit(),
1136 /// Parse an indexing expression `expr[...]`.
1137 fn parse_index_expr(&mut self, lo
: Span
, base
: P
<Expr
>) -> PResult
<'a
, P
<Expr
>> {
1139 let index
= self.parse_expr()?
;
1140 self.expect(&token
::CloseDelim(token
::Bracket
))?
;
1141 Ok(self.mk_expr(lo
.to(self.prev_token
.span
), self.mk_index(base
, index
), AttrVec
::new()))
1144 /// Assuming we have just parsed `.`, continue parsing into an expression.
1145 fn parse_dot_suffix(&mut self, self_arg
: P
<Expr
>, lo
: Span
) -> PResult
<'a
, P
<Expr
>> {
1146 if self.token
.uninterpolated_span().rust_2018() && self.eat_keyword(kw
::Await
) {
1147 return Ok(self.mk_await_expr(self_arg
, lo
));
1150 let fn_span_lo
= self.token
.span
;
1151 let mut segment
= self.parse_path_segment(PathStyle
::Expr
)?
;
1152 self.check_trailing_angle_brackets(&segment
, &[&token
::OpenDelim(token
::Paren
)]);
1153 self.check_turbofish_missing_angle_brackets(&mut segment
);
1155 if self.check(&token
::OpenDelim(token
::Paren
)) {
1156 // Method call `expr.f()`
1157 let mut args
= self.parse_paren_expr_seq()?
;
1158 args
.insert(0, self_arg
);
1160 let fn_span
= fn_span_lo
.to(self.prev_token
.span
);
1161 let span
= lo
.to(self.prev_token
.span
);
1162 Ok(self.mk_expr(span
, ExprKind
::MethodCall(segment
, args
, fn_span
), AttrVec
::new()))
1164 // Field access `expr.f`
1165 if let Some(args
) = segment
.args
{
1166 self.struct_span_err(
1168 "field expressions cannot have generic arguments",
1173 let span
= lo
.to(self.prev_token
.span
);
1174 Ok(self.mk_expr(span
, ExprKind
::Field(self_arg
, segment
.ident
), AttrVec
::new()))
1178 /// At the bottom (top?) of the precedence hierarchy,
1179 /// Parses things like parenthesized exprs, macros, `return`, etc.
1181 /// N.B., this does not parse outer attributes, and is private because it only works
1182 /// correctly if called from `parse_dot_or_call_expr()`.
1183 fn parse_bottom_expr(&mut self) -> PResult
<'a
, P
<Expr
>> {
1184 maybe_recover_from_interpolated_ty_qpath
!(self, true);
1185 maybe_whole_expr
!(self);
1187 // Outer attributes are already parsed and will be
1188 // added to the return value after the fact.
1190 // Therefore, prevent sub-parser from parsing
1191 // attributes by giving them an empty "already-parsed" list.
1192 let attrs
= AttrVec
::new();
1194 // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
1195 let lo
= self.token
.span
;
1196 if let token
::Literal(_
) = self.token
.kind
{
1197 // This match arm is a special-case of the `_` match arm below and
1198 // could be removed without changing functionality, but it's faster
1199 // to have it here, especially for programs with large constants.
1200 self.parse_lit_expr(attrs
)
1201 } else if self.check(&token
::OpenDelim(token
::Paren
)) {
1202 self.parse_tuple_parens_expr(attrs
)
1203 } else if self.check(&token
::OpenDelim(token
::Brace
)) {
1204 self.parse_block_expr(None
, lo
, BlockCheckMode
::Default
, attrs
)
1205 } else if self.check(&token
::BinOp(token
::Or
)) || self.check(&token
::OrOr
) {
1206 self.parse_closure_expr(attrs
)
1207 } else if self.check(&token
::OpenDelim(token
::Bracket
)) {
1208 self.parse_array_or_repeat_expr(attrs
, token
::Bracket
)
1209 } else if self.check_path() {
1210 self.parse_path_start_expr(attrs
)
1211 } else if self.check_keyword(kw
::Move
) || self.check_keyword(kw
::Static
) {
1212 self.parse_closure_expr(attrs
)
1213 } else if self.eat_keyword(kw
::If
) {
1214 self.parse_if_expr(attrs
)
1215 } else if self.check_keyword(kw
::For
) {
1216 if self.choose_generics_over_qpath(1) {
1217 // NOTE(Centril, eddyb): DO NOT REMOVE! Beyond providing parser recovery,
1218 // this is an insurance policy in case we allow qpaths in (tuple-)struct patterns.
1219 // When `for <Foo as Bar>::Proj in $expr $block` is wanted,
1220 // you can disambiguate in favor of a pattern with `(...)`.
1221 self.recover_quantified_closure_expr(attrs
)
1223 assert
!(self.eat_keyword(kw
::For
));
1224 self.parse_for_expr(None
, self.prev_token
.span
, attrs
)
1226 } else if self.eat_keyword(kw
::While
) {
1227 self.parse_while_expr(None
, self.prev_token
.span
, attrs
)
1228 } else if let Some(label
) = self.eat_label() {
1229 self.parse_labeled_expr(label
, attrs
, true)
1230 } else if self.eat_keyword(kw
::Loop
) {
1231 self.parse_loop_expr(None
, self.prev_token
.span
, attrs
)
1232 } else if self.eat_keyword(kw
::Continue
) {
1233 let kind
= ExprKind
::Continue(self.eat_label());
1234 Ok(self.mk_expr(lo
.to(self.prev_token
.span
), kind
, attrs
))
1235 } else if self.eat_keyword(kw
::Match
) {
1236 let match_sp
= self.prev_token
.span
;
1237 self.parse_match_expr(attrs
).map_err(|mut err
| {
1238 err
.span_label(match_sp
, "while parsing this match expression");
1241 } else if self.eat_keyword(kw
::Unsafe
) {
1242 self.parse_block_expr(None
, lo
, BlockCheckMode
::Unsafe(ast
::UserProvided
), attrs
)
1243 } else if self.check_inline_const(0) {
1244 self.parse_const_block(lo
.to(self.token
.span
))
1245 } else if self.is_do_catch_block() {
1246 self.recover_do_catch(attrs
)
1247 } else if self.is_try_block() {
1248 self.expect_keyword(kw
::Try
)?
;
1249 self.parse_try_block(lo
, attrs
)
1250 } else if self.eat_keyword(kw
::Return
) {
1251 self.parse_return_expr(attrs
)
1252 } else if self.eat_keyword(kw
::Break
) {
1253 self.parse_break_expr(attrs
)
1254 } else if self.eat_keyword(kw
::Yield
) {
1255 self.parse_yield_expr(attrs
)
1256 } else if self.eat_keyword(kw
::Let
) {
1257 self.parse_let_expr(attrs
)
1258 } else if self.eat_keyword(kw
::Underscore
) {
1259 self.sess
.gated_spans
.gate(sym
::destructuring_assignment
, self.prev_token
.span
);
1260 Ok(self.mk_expr(self.prev_token
.span
, ExprKind
::Underscore
, attrs
))
1261 } else if !self.unclosed_delims
.is_empty() && self.check(&token
::Semi
) {
1262 // Don't complain about bare semicolons after unclosed braces
1263 // recovery in order to keep the error count down. Fixing the
1264 // delimiters will possibly also fix the bare semicolon found in
1265 // expression context. For example, silence the following error:
1267 // error: expected expression, found `;`
1271 // | ^ expected expression
1273 Ok(self.mk_expr_err(self.token
.span
))
1274 } else if self.token
.uninterpolated_span().rust_2018() {
1275 // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
1276 if self.check_keyword(kw
::Async
) {
1277 if self.is_async_block() {
1278 // Check for `async {` and `async move {`.
1279 self.parse_async_block(attrs
)
1281 self.parse_closure_expr(attrs
)
1283 } else if self.eat_keyword(kw
::Await
) {
1284 self.recover_incorrect_await_syntax(lo
, self.prev_token
.span
, attrs
)
1286 self.parse_lit_expr(attrs
)
1289 self.parse_lit_expr(attrs
)
1293 fn parse_lit_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1294 let lo
= self.token
.span
;
1295 match self.parse_opt_lit() {
1297 let expr
= self.mk_expr(lo
.to(self.prev_token
.span
), ExprKind
::Lit(literal
), attrs
);
1298 self.maybe_recover_from_bad_qpath(expr
, true)
1300 None
=> self.try_macro_suggestion(),
1304 fn parse_tuple_parens_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1305 let lo
= self.token
.span
;
1306 self.expect(&token
::OpenDelim(token
::Paren
))?
;
1307 let (es
, trailing_comma
) = match self.parse_seq_to_end(
1308 &token
::CloseDelim(token
::Paren
),
1309 SeqSep
::trailing_allowed(token
::Comma
),
1310 |p
| p
.parse_expr_catch_underscore(),
1313 Err(err
) => return Ok(self.recover_seq_parse_error(token
::Paren
, lo
, Err(err
))),
1315 let kind
= if es
.len() == 1 && !trailing_comma
{
1316 // `(e)` is parenthesized `e`.
1317 ExprKind
::Paren(es
.into_iter().next().unwrap())
1319 // `(e,)` is a tuple with only one field, `e`.
1322 let expr
= self.mk_expr(lo
.to(self.prev_token
.span
), kind
, attrs
);
1323 self.maybe_recover_from_bad_qpath(expr
, true)
1326 fn parse_array_or_repeat_expr(
1329 close_delim
: token
::DelimToken
,
1330 ) -> PResult
<'a
, P
<Expr
>> {
1331 let lo
= self.token
.span
;
1332 self.bump(); // `[` or other open delim
1334 let close
= &token
::CloseDelim(close_delim
);
1335 let kind
= if self.eat(close
) {
1337 ExprKind
::Array(Vec
::new())
1340 let first_expr
= self.parse_expr()?
;
1341 if self.eat(&token
::Semi
) {
1342 // Repeating array syntax: `[ 0; 512 ]`
1343 let count
= self.parse_anon_const_expr()?
;
1344 self.expect(close
)?
;
1345 ExprKind
::Repeat(first_expr
, count
)
1346 } else if self.eat(&token
::Comma
) {
1347 // Vector with two or more elements.
1348 let sep
= SeqSep
::trailing_allowed(token
::Comma
);
1349 let (remaining_exprs
, _
) = self.parse_seq_to_end(close
, sep
, |p
| p
.parse_expr())?
;
1350 let mut exprs
= vec
![first_expr
];
1351 exprs
.extend(remaining_exprs
);
1352 ExprKind
::Array(exprs
)
1354 // Vector with one element
1355 self.expect(close
)?
;
1356 ExprKind
::Array(vec
![first_expr
])
1359 let expr
= self.mk_expr(lo
.to(self.prev_token
.span
), kind
, attrs
);
1360 self.maybe_recover_from_bad_qpath(expr
, true)
1363 fn parse_path_start_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1364 let (qself
, path
) = if self.eat_lt() {
1365 let (qself
, path
) = self.parse_qpath(PathStyle
::Expr
)?
;
1368 (None
, self.parse_path(PathStyle
::Expr
)?
)
1372 // `!`, as an operator, is prefix, so we know this isn't that.
1373 let (hi
, kind
) = if self.eat(&token
::Not
) {
1374 // MACRO INVOCATION expression
1375 if qself
.is_some() {
1376 self.struct_span_err(path
.span
, "macros cannot use qualified paths").emit();
1380 args
: self.parse_mac_args()?
,
1381 prior_type_ascription
: self.last_type_ascription
,
1383 (self.prev_token
.span
, ExprKind
::MacCall(mac
))
1384 } else if self.check(&token
::OpenDelim(token
::Brace
)) {
1385 if let Some(expr
) = self.maybe_parse_struct_expr(qself
.as_ref(), &path
, &attrs
) {
1386 if qself
.is_some() {
1387 self.sess
.gated_spans
.gate(sym
::more_qualified_paths
, path
.span
);
1391 (path
.span
, ExprKind
::Path(qself
, path
))
1394 (path
.span
, ExprKind
::Path(qself
, path
))
1397 let expr
= self.mk_expr(lo
.to(hi
), kind
, attrs
);
1398 self.maybe_recover_from_bad_qpath(expr
, true)
1401 /// Parse `'label: $expr`. The label is already parsed.
1402 fn parse_labeled_expr(
1406 consume_colon
: bool
,
1407 ) -> PResult
<'a
, P
<Expr
>> {
1408 let lo
= label
.ident
.span
;
1409 let label
= Some(label
);
1410 let ate_colon
= self.eat(&token
::Colon
);
1411 let expr
= if self.eat_keyword(kw
::While
) {
1412 self.parse_while_expr(label
, lo
, attrs
)
1413 } else if self.eat_keyword(kw
::For
) {
1414 self.parse_for_expr(label
, lo
, attrs
)
1415 } else if self.eat_keyword(kw
::Loop
) {
1416 self.parse_loop_expr(label
, lo
, attrs
)
1417 } else if self.check(&token
::OpenDelim(token
::Brace
)) || self.token
.is_whole_block() {
1418 self.parse_block_expr(label
, lo
, BlockCheckMode
::Default
, attrs
)
1420 let msg
= "expected `while`, `for`, `loop` or `{` after a label";
1421 self.struct_span_err(self.token
.span
, msg
).span_label(self.token
.span
, msg
).emit();
1422 // Continue as an expression in an effort to recover on `'label: non_block_expr`.
1426 if !ate_colon
&& consume_colon
{
1427 self.error_labeled_expr_must_be_followed_by_colon(lo
, expr
.span
);
1433 fn error_labeled_expr_must_be_followed_by_colon(&self, lo
: Span
, span
: Span
) {
1434 self.struct_span_err(span
, "labeled expression must be followed by `:`")
1435 .span_label(lo
, "the label")
1436 .span_suggestion_short(
1438 "add `:` after the label",
1440 Applicability
::MachineApplicable
,
1442 .note("labels are used before loops and blocks, allowing e.g., `break 'label` to them")
1446 /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
1447 fn recover_do_catch(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1448 let lo
= self.token
.span
;
1450 self.bump(); // `do`
1451 self.bump(); // `catch`
1453 let span_dc
= lo
.to(self.prev_token
.span
);
1454 self.struct_span_err(span_dc
, "found removed `do catch` syntax")
1457 "replace with the new syntax",
1459 Applicability
::MachineApplicable
,
1461 .note("following RFC #2388, the new non-placeholder syntax is `try`")
1464 self.parse_try_block(lo
, attrs
)
1467 /// Parse an expression if the token can begin one.
1468 fn parse_expr_opt(&mut self) -> PResult
<'a
, Option
<P
<Expr
>>> {
1469 Ok(if self.token
.can_begin_expr() { Some(self.parse_expr()?) }
else { None }
)
1472 /// Parse `"return" expr?`.
1473 fn parse_return_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1474 let lo
= self.prev_token
.span
;
1475 let kind
= ExprKind
::Ret(self.parse_expr_opt()?
);
1476 let expr
= self.mk_expr(lo
.to(self.prev_token
.span
), kind
, attrs
);
1477 self.maybe_recover_from_bad_qpath(expr
, true)
1480 /// Parse `"break" (('label (:? expr)?) | expr?)` with `"break"` token already eaten.
1481 /// If the label is followed immediately by a `:` token, the label and `:` are
1482 /// parsed as part of the expression (i.e. a labeled loop). The language team has
1483 /// decided in #87026 to require parentheses as a visual aid to avoid confusion if
1484 /// the break expression of an unlabeled break is a labeled loop (as in
1485 /// `break 'lbl: loop {}`); a labeled break with an unlabeled loop as its value
1486 /// expression only gets a warning for compatibility reasons; and a labeled break
1487 /// with a labeled loop does not even get a warning because there is no ambiguity.
1488 fn parse_break_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1489 let lo
= self.prev_token
.span
;
1490 let mut label
= self.eat_label();
1491 let kind
= if label
.is_some() && self.token
== token
::Colon
{
1492 // The value expression can be a labeled loop, see issue #86948, e.g.:
1493 // `loop { break 'label: loop { break 'label 42; }; }`
1494 let lexpr
= self.parse_labeled_expr(label
.take().unwrap(), AttrVec
::new(), true)?
;
1495 self.struct_span_err(
1497 "parentheses are required around this expression to avoid confusion with a labeled break expression",
1499 .multipart_suggestion(
1500 "wrap the expression in parentheses",
1502 (lexpr
.span
.shrink_to_lo(), "(".to_string()),
1503 (lexpr
.span
.shrink_to_hi(), ")".to_string()),
1505 Applicability
::MachineApplicable
,
1509 } else if self.token
!= token
::OpenDelim(token
::Brace
)
1510 || !self.restrictions
.contains(Restrictions
::NO_STRUCT_LITERAL
)
1512 let expr
= self.parse_expr_opt()?
;
1513 if let Some(ref expr
) = expr
{
1517 ExprKind
::While(_
, _
, None
)
1518 | ExprKind
::ForLoop(_
, _
, _
, None
)
1519 | ExprKind
::Loop(_
, None
)
1520 | ExprKind
::Block(_
, None
)
1523 self.sess
.buffer_lint_with_diagnostic(
1524 BREAK_WITH_LABEL_AND_LOOP
,
1527 "this labeled break expression is easy to confuse with an unlabeled break with a labeled value expression",
1528 BuiltinLintDiagnostics
::BreakWithLabelAndLoop(expr
.span
),
1536 let expr
= self.mk_expr(lo
.to(self.prev_token
.span
), ExprKind
::Break(label
, kind
), attrs
);
1537 self.maybe_recover_from_bad_qpath(expr
, true)
1540 /// Parse `"yield" expr?`.
1541 fn parse_yield_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1542 let lo
= self.prev_token
.span
;
1543 let kind
= ExprKind
::Yield(self.parse_expr_opt()?
);
1544 let span
= lo
.to(self.prev_token
.span
);
1545 self.sess
.gated_spans
.gate(sym
::generators
, span
);
1546 let expr
= self.mk_expr(span
, kind
, attrs
);
1547 self.maybe_recover_from_bad_qpath(expr
, true)
1550 /// Returns a string literal if the next token is a string literal.
1551 /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
1552 /// and returns `None` if the next token is not literal at all.
1553 pub fn parse_str_lit(&mut self) -> Result
<ast
::StrLit
, Option
<Lit
>> {
1554 match self.parse_opt_lit() {
1555 Some(lit
) => match lit
.kind
{
1556 ast
::LitKind
::Str(symbol_unescaped
, style
) => Ok(ast
::StrLit
{
1558 symbol
: lit
.token
.symbol
,
1559 suffix
: lit
.token
.suffix
,
1563 _
=> Err(Some(lit
)),
1569 pub(super) fn parse_lit(&mut self) -> PResult
<'a
, Lit
> {
1570 self.parse_opt_lit().ok_or_else(|| {
1571 if let token
::Interpolated(inner
) = &self.token
.kind
{
1572 let expr
= match inner
.as_ref() {
1573 token
::NtExpr(expr
) => Some(expr
),
1574 token
::NtLiteral(expr
) => Some(expr
),
1577 if let Some(expr
) = expr
{
1578 if matches
!(expr
.kind
, ExprKind
::Err
) {
1580 .delay_span_bug(self.token
.span
, &"invalid interpolated expression");
1581 return self.diagnostic().struct_dummy();
1585 let msg
= format
!("unexpected token: {}", super::token_descr(&self.token
));
1586 self.struct_span_err(self.token
.span
, &msg
)
1590 /// Matches `lit = true | false | token_lit`.
1591 /// Returns `None` if the next token is not a literal.
1592 pub(super) fn parse_opt_lit(&mut self) -> Option
<Lit
> {
1593 let mut recovered
= None
;
1594 if self.token
== token
::Dot
{
1595 // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
1596 // dot would follow an optional literal, so we do this unconditionally.
1597 recovered
= self.look_ahead(1, |next_token
| {
1598 if let token
::Literal(token
::Lit { kind: token::Integer, symbol, suffix }
) =
1601 if self.token
.span
.hi() == next_token
.span
.lo() {
1602 let s
= String
::from("0.") + &symbol
.as_str();
1603 let kind
= TokenKind
::lit(token
::Float
, Symbol
::intern(&s
), suffix
);
1604 return Some(Token
::new(kind
, self.token
.span
.to(next_token
.span
)));
1609 if let Some(token
) = &recovered
{
1611 self.error_float_lits_must_have_int_part(&token
);
1615 let token
= recovered
.as_ref().unwrap_or(&self.token
);
1616 match Lit
::from_token(token
) {
1621 Err(LitError
::NotLiteral
) => None
,
1623 let span
= token
.span
;
1624 let lit
= match token
.kind
{
1625 token
::Literal(lit
) => lit
,
1626 _
=> unreachable
!(),
1629 self.report_lit_error(err
, lit
, span
);
1630 // Pack possible quotes and prefixes from the original literal into
1631 // the error literal's symbol so they can be pretty-printed faithfully.
1632 let suffixless_lit
= token
::Lit
::new(lit
.kind
, lit
.symbol
, None
);
1633 let symbol
= Symbol
::intern(&suffixless_lit
.to_string());
1634 let lit
= token
::Lit
::new(token
::Err
, symbol
, lit
.suffix
);
1635 Some(Lit
::from_lit_token(lit
, span
).unwrap_or_else(|_
| unreachable
!()))
1640 fn error_float_lits_must_have_int_part(&self, token
: &Token
) {
1641 self.struct_span_err(token
.span
, "float literals must have an integer part")
1644 "must have an integer part",
1645 pprust
::token_to_string(token
).into(),
1646 Applicability
::MachineApplicable
,
1651 fn report_lit_error(&self, err
: LitError
, lit
: token
::Lit
, span
: Span
) {
1652 // Checks if `s` looks like i32 or u1234 etc.
1653 fn looks_like_width_suffix(first_chars
: &[char], s
: &str) -> bool
{
1654 s
.len() > 1 && s
.starts_with(first_chars
) && s
[1..].chars().all(|c
| c
.is_ascii_digit())
1657 let token
::Lit { kind, suffix, .. }
= lit
;
1659 // `NotLiteral` is not an error by itself, so we don't report
1660 // it and give the parser opportunity to try something else.
1661 LitError
::NotLiteral
=> {}
1662 // `LexerError` *is* an error, but it was already reported
1663 // by lexer, so here we don't report it the second time.
1664 LitError
::LexerError
=> {}
1665 LitError
::InvalidSuffix
=> {
1666 self.expect_no_suffix(
1668 &format
!("{} {} literal", kind
.article(), kind
.descr()),
1672 LitError
::InvalidIntSuffix
=> {
1673 let suf
= suffix
.expect("suffix error with no suffix").as_str();
1674 if looks_like_width_suffix(&['i'
, 'u'
], &suf
) {
1675 // If it looks like a width, try to be helpful.
1676 let msg
= format
!("invalid width `{}` for integer literal", &suf
[1..]);
1677 self.struct_span_err(span
, &msg
)
1678 .help("valid widths are 8, 16, 32, 64 and 128")
1681 let msg
= format
!("invalid suffix `{}` for number literal", suf
);
1682 self.struct_span_err(span
, &msg
)
1683 .span_label(span
, format
!("invalid suffix `{}`", suf
))
1684 .help("the suffix must be one of the numeric types (`u32`, `isize`, `f32`, etc.)")
1688 LitError
::InvalidFloatSuffix
=> {
1689 let suf
= suffix
.expect("suffix error with no suffix").as_str();
1690 if looks_like_width_suffix(&['f'
], &suf
) {
1691 // If it looks like a width, try to be helpful.
1692 let msg
= format
!("invalid width `{}` for float literal", &suf
[1..]);
1693 self.struct_span_err(span
, &msg
).help("valid widths are 32 and 64").emit();
1695 let msg
= format
!("invalid suffix `{}` for float literal", suf
);
1696 self.struct_span_err(span
, &msg
)
1697 .span_label(span
, format
!("invalid suffix `{}`", suf
))
1698 .help("valid suffixes are `f32` and `f64`")
1702 LitError
::NonDecimalFloat(base
) => {
1703 let descr
= match base
{
1704 16 => "hexadecimal",
1707 _
=> unreachable
!(),
1709 self.struct_span_err(span
, &format
!("{} float literal is not supported", descr
))
1710 .span_label(span
, "not supported")
1713 LitError
::IntTooLarge
=> {
1714 self.struct_span_err(span
, "integer literal is too large").emit();
1719 pub(super) fn expect_no_suffix(&self, sp
: Span
, kind
: &str, suffix
: Option
<Symbol
>) {
1720 if let Some(suf
) = suffix
{
1721 let mut err
= if kind
== "a tuple index"
1722 && [sym
::i32, sym
::u32, sym
::isize, sym
::usize].contains(&suf
)
1724 // #59553: warn instead of reject out of hand to allow the fix to percolate
1725 // through the ecosystem when people fix their macros
1729 .struct_span_warn(sp
, &format
!("suffixes on {} are invalid", kind
));
1731 "`{}` is *temporarily* accepted on tuple index fields as it was \
1732 incorrectly accepted on stable for a few releases",
1736 "on proc macros, you'll want to use `syn::Index::from` or \
1737 `proc_macro::Literal::*_unsuffixed` for code that will desugar \
1738 to tuple field access",
1741 "see issue #60210 <https://github.com/rust-lang/rust/issues/60210> \
1742 for more information",
1746 self.struct_span_err(sp
, &format
!("suffixes on {} are invalid", kind
))
1748 err
.span_label(sp
, format
!("invalid suffix `{}`", suf
));
1753 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1754 /// Keep this in sync with `Token::can_begin_literal_maybe_minus`.
1755 pub fn parse_literal_maybe_minus(&mut self) -> PResult
<'a
, P
<Expr
>> {
1756 maybe_whole_expr
!(self);
1758 let lo
= self.token
.span
;
1759 let minus_present
= self.eat(&token
::BinOp(token
::Minus
));
1760 let lit
= self.parse_lit()?
;
1761 let expr
= self.mk_expr(lit
.span
, ExprKind
::Lit(lit
), AttrVec
::new());
1765 lo
.to(self.prev_token
.span
),
1766 self.mk_unary(UnOp
::Neg
, expr
),
1774 fn is_array_like_block(&mut self) -> bool
{
1775 self.look_ahead(1, |t
| matches
!(t
.kind
, TokenKind
::Ident(..) | TokenKind
::Literal(_
)))
1776 && self.look_ahead(2, |t
| t
== &token
::Comma
)
1777 && self.look_ahead(3, |t
| t
.can_begin_expr())
1780 /// Emits a suggestion if it looks like the user meant an array but
1781 /// accidentally used braces, causing the code to be interpreted as a block
1783 fn maybe_suggest_brackets_instead_of_braces(
1787 ) -> Option
<P
<Expr
>> {
1788 let mut snapshot
= self.clone();
1789 match snapshot
.parse_array_or_repeat_expr(attrs
, token
::Brace
) {
1791 let hi
= snapshot
.prev_token
.span
;
1792 self.struct_span_err(
1794 "this code is interpreted as a block expression, not an array",
1796 .multipart_suggestion(
1797 "try using [] instead of {}",
1798 vec
![(lo
, "[".to_owned()), (hi
, "]".to_owned())],
1799 Applicability
::MaybeIncorrect
,
1801 .note("to define an array, one would use square brackets instead of curly braces")
1805 Some(self.mk_expr_err(arr
.span
))
1814 /// Parses a block or unsafe block.
1815 pub(super) fn parse_block_expr(
1817 opt_label
: Option
<Label
>,
1819 blk_mode
: BlockCheckMode
,
1821 ) -> PResult
<'a
, P
<Expr
>> {
1822 if self.is_array_like_block() {
1823 if let Some(arr
) = self.maybe_suggest_brackets_instead_of_braces(lo
, attrs
.clone()) {
1828 if let Some(label
) = opt_label
{
1829 self.sess
.gated_spans
.gate(sym
::label_break_value
, label
.ident
.span
);
1832 if self.token
.is_whole_block() {
1833 self.struct_span_err(self.token
.span
, "cannot use a `block` macro fragment here")
1834 .span_label(lo
.to(self.token
.span
), "the `block` fragment is within this context")
1838 let (inner_attrs
, blk
) = self.parse_block_common(lo
, blk_mode
)?
;
1839 attrs
.extend(inner_attrs
);
1840 Ok(self.mk_expr(blk
.span
, ExprKind
::Block(blk
, opt_label
), attrs
))
1843 /// Recover on an explicitly quantified closure expression, e.g., `for<'a> |x: &'a u8| *x + 1`.
1844 fn recover_quantified_closure_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1845 let lo
= self.token
.span
;
1846 let _
= self.parse_late_bound_lifetime_defs()?
;
1847 let span_for
= lo
.to(self.prev_token
.span
);
1848 let closure
= self.parse_closure_expr(attrs
)?
;
1850 self.struct_span_err(span_for
, "cannot introduce explicit parameters for a closure")
1851 .span_label(closure
.span
, "the parameters are attached to this closure")
1854 "remove the parameters",
1856 Applicability
::MachineApplicable
,
1860 Ok(self.mk_expr_err(lo
.to(closure
.span
)))
1863 /// Parses a closure expression (e.g., `move |args| expr`).
1864 fn parse_closure_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1865 let lo
= self.token
.span
;
1868 if self.eat_keyword(kw
::Static
) { Movability::Static }
else { Movability::Movable }
;
1870 let asyncness
= if self.token
.uninterpolated_span().rust_2018() {
1871 self.parse_asyncness()
1876 let capture_clause
= self.parse_capture_clause()?
;
1877 let decl
= self.parse_fn_block_decl()?
;
1878 let decl_hi
= self.prev_token
.span
;
1879 let mut body
= match decl
.output
{
1880 FnRetTy
::Default(_
) => {
1881 let restrictions
= self.restrictions
- Restrictions
::STMT_EXPR
;
1882 self.parse_expr_res(restrictions
, None
)?
1885 // If an explicit return type is given, require a block to appear (RFC 968).
1886 let body_lo
= self.token
.span
;
1887 self.parse_block_expr(None
, body_lo
, BlockCheckMode
::Default
, AttrVec
::new())?
1891 if let Async
::Yes { span, .. }
= asyncness
{
1892 // Feature-gate `async ||` closures.
1893 self.sess
.gated_spans
.gate(sym
::async_closure
, span
);
1896 if self.token
.kind
== TokenKind
::Semi
&& self.token_cursor
.frame
.delim
== DelimToken
::Paren
1898 // It is likely that the closure body is a block but where the
1899 // braces have been removed. We will recover and eat the next
1900 // statements later in the parsing process.
1901 body
= self.mk_expr_err(body
.span
);
1904 let body_span
= body
.span
;
1906 let closure
= self.mk_expr(
1908 ExprKind
::Closure(capture_clause
, asyncness
, movability
, decl
, body
, lo
.to(decl_hi
)),
1912 // Disable recovery for closure body
1914 ClosureSpans { whole_closure: closure.span, closing_pipe: decl_hi, body: body_span }
;
1915 self.current_closure
= Some(spans
);
1920 /// Parses an optional `move` prefix to a closure-like construct.
1921 fn parse_capture_clause(&mut self) -> PResult
<'a
, CaptureBy
> {
1922 if self.eat_keyword(kw
::Move
) {
1923 // Check for `move async` and recover
1924 if self.check_keyword(kw
::Async
) {
1925 let move_async_span
= self.token
.span
.with_lo(self.prev_token
.span
.data().lo
);
1926 Err(self.incorrect_move_async_order_found(move_async_span
))
1928 Ok(CaptureBy
::Value
)
1935 /// Parses the `|arg, arg|` header of a closure.
1936 fn parse_fn_block_decl(&mut self) -> PResult
<'a
, P
<FnDecl
>> {
1937 let inputs
= if self.eat(&token
::OrOr
) {
1940 self.expect(&token
::BinOp(token
::Or
))?
;
1942 .parse_seq_to_before_tokens(
1943 &[&token
::BinOp(token
::Or
), &token
::OrOr
],
1944 SeqSep
::trailing_allowed(token
::Comma
),
1945 TokenExpectType
::NoExpect
,
1946 |p
| p
.parse_fn_block_param(),
1953 self.parse_ret_ty(AllowPlus
::Yes
, RecoverQPath
::Yes
, RecoverReturnSign
::Yes
)?
;
1955 Ok(P(FnDecl { inputs, output }
))
1958 /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
1959 fn parse_fn_block_param(&mut self) -> PResult
<'a
, Param
> {
1960 let lo
= self.token
.span
;
1961 let attrs
= self.parse_outer_attributes()?
;
1962 self.collect_tokens_trailing_token(attrs
, ForceCollect
::No
, |this
, attrs
| {
1963 let pat
= this
.parse_pat_no_top_alt(PARAM_EXPECTED
)?
;
1964 let ty
= if this
.eat(&token
::Colon
) {
1967 this
.mk_ty(this
.prev_token
.span
, TyKind
::Infer
)
1972 attrs
: attrs
.into(),
1975 span
: lo
.to(this
.token
.span
),
1977 is_placeholder
: false,
1979 TrailingToken
::MaybeComma
,
1984 /// Parses an `if` expression (`if` token already eaten).
1985 fn parse_if_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
1986 let lo
= self.prev_token
.span
;
1987 let cond
= self.parse_cond_expr()?
;
1989 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
1990 // verify that the last statement is either an implicit return (no `;`) or an explicit
1991 // return. This won't catch blocks with an explicit `return`, but that would be caught by
1992 // the dead code lint.
1993 let thn
= if self.eat_keyword(kw
::Else
) || !cond
.returns() {
1994 self.error_missing_if_cond(lo
, cond
.span
)
1996 let attrs
= self.parse_outer_attributes()?
.take_for_recovery(); // For recovery.
1997 let not_block
= self.token
!= token
::OpenDelim(token
::Brace
);
1998 let block
= self.parse_block().map_err(|mut err
| {
2000 err
.span_label(lo
, "this `if` expression has a condition, but no block");
2001 if let ExprKind
::Binary(_
, _
, ref right
) = cond
.kind
{
2002 if let ExprKind
::Block(_
, _
) = right
.kind
{
2003 err
.help("maybe you forgot the right operand of the condition?");
2009 self.error_on_if_block_attrs(lo
, false, block
.span
, &attrs
);
2012 let els
= if self.eat_keyword(kw
::Else
) { Some(self.parse_else_expr()?) }
else { None }
;
2013 Ok(self.mk_expr(lo
.to(self.prev_token
.span
), ExprKind
::If(cond
, thn
, els
), attrs
))
2016 fn error_missing_if_cond(&self, lo
: Span
, span
: Span
) -> P
<ast
::Block
> {
2017 let sp
= self.sess
.source_map().next_point(lo
);
2018 self.struct_span_err(sp
, "missing condition for `if` expression")
2019 .span_label(sp
, "expected if condition here")
2021 self.mk_block_err(span
)
2024 /// Parses the condition of a `if` or `while` expression.
2025 fn parse_cond_expr(&mut self) -> PResult
<'a
, P
<Expr
>> {
2026 let cond
= self.parse_expr_res(Restrictions
::NO_STRUCT_LITERAL
, None
)?
;
2028 if let ExprKind
::Let(..) = cond
.kind
{
2029 // Remove the last feature gating of a `let` expression since it's stable.
2030 self.sess
.gated_spans
.ungate_last(sym
::let_chains
, cond
.span
);
2036 /// Parses a `let $pat = $expr` pseudo-expression.
2037 /// The `let` token has already been eaten.
2038 fn parse_let_expr(&mut self, attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
2039 let lo
= self.prev_token
.span
;
2040 let pat
= self.parse_pat_allow_top_alt(None
, RecoverComma
::Yes
, RecoverColon
::Yes
)?
;
2041 self.expect(&token
::Eq
)?
;
2042 let expr
= self.with_res(self.restrictions
| Restrictions
::NO_STRUCT_LITERAL
, |this
| {
2043 this
.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None
.into())
2045 let span
= lo
.to(expr
.span
);
2046 self.sess
.gated_spans
.gate(sym
::let_chains
, span
);
2047 Ok(self.mk_expr(span
, ExprKind
::Let(pat
, expr
, span
), attrs
))
2050 /// Parses an `else { ... }` expression (`else` token already eaten).
2051 fn parse_else_expr(&mut self) -> PResult
<'a
, P
<Expr
>> {
2052 let ctx_span
= self.prev_token
.span
; // `else`
2053 let attrs
= self.parse_outer_attributes()?
.take_for_recovery(); // For recovery.
2054 let expr
= if self.eat_keyword(kw
::If
) {
2055 self.parse_if_expr(AttrVec
::new())?
2057 let blk
= self.parse_block()?
;
2058 self.mk_expr(blk
.span
, ExprKind
::Block(blk
, None
), AttrVec
::new())
2060 self.error_on_if_block_attrs(ctx_span
, true, expr
.span
, &attrs
);
2064 fn error_on_if_block_attrs(
2069 attrs
: &[ast
::Attribute
],
2071 let (span
, last
) = match attrs
{
2073 [x0 @ xn
] | [x0
, .., xn
] => (x0
.span
.to(xn
.span
), xn
.span
),
2075 let ctx
= if is_ctx_else { "else" }
else { "if" }
;
2076 self.struct_span_err(last
, "outer attributes are not allowed on `if` and `else` branches")
2077 .span_label(branch_span
, "the attributes are attached to this branch")
2078 .span_label(ctx_span
, format
!("the branch belongs to this `{}`", ctx
))
2081 "remove the attributes",
2083 Applicability
::MachineApplicable
,
2088 /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
2091 opt_label
: Option
<Label
>,
2094 ) -> PResult
<'a
, P
<Expr
>> {
2095 // Record whether we are about to parse `for (`.
2096 // This is used below for recovery in case of `for ( $stuff ) $block`
2097 // in which case we will suggest `for $stuff $block`.
2098 let begin_paren
= match self.token
.kind
{
2099 token
::OpenDelim(token
::Paren
) => Some(self.token
.span
),
2103 let pat
= self.parse_pat_allow_top_alt(None
, RecoverComma
::Yes
, RecoverColon
::Yes
)?
;
2104 if !self.eat_keyword(kw
::In
) {
2105 self.error_missing_in_for_loop();
2107 self.check_for_for_in_in_typo(self.prev_token
.span
);
2108 let expr
= self.parse_expr_res(Restrictions
::NO_STRUCT_LITERAL
, None
)?
;
2110 let pat
= self.recover_parens_around_for_head(pat
, begin_paren
);
2112 let (iattrs
, loop_block
) = self.parse_inner_attrs_and_block()?
;
2113 attrs
.extend(iattrs
);
2115 let kind
= ExprKind
::ForLoop(pat
, expr
, loop_block
, opt_label
);
2116 Ok(self.mk_expr(lo
.to(self.prev_token
.span
), kind
, attrs
))
2119 fn error_missing_in_for_loop(&mut self) {
2120 let (span
, msg
, sugg
) = if self.token
.is_ident_named(sym
::of
) {
2121 // Possibly using JS syntax (#75311).
2122 let span
= self.token
.span
;
2124 (span
, "try using `in` here instead", "in")
2126 (self.prev_token
.span
.between(self.token
.span
), "try adding `in` here", " in ")
2128 self.struct_span_err(span
, "missing `in` in `for` loop")
2129 .span_suggestion_short(
2133 // Has been misleading, at least in the past (closed Issue #48492).
2134 Applicability
::MaybeIncorrect
,
2139 /// Parses a `while` or `while let` expression (`while` token already eaten).
2140 fn parse_while_expr(
2142 opt_label
: Option
<Label
>,
2145 ) -> PResult
<'a
, P
<Expr
>> {
2146 let cond
= self.parse_cond_expr()?
;
2147 let (iattrs
, body
) = self.parse_inner_attrs_and_block()?
;
2148 attrs
.extend(iattrs
);
2149 Ok(self.mk_expr(lo
.to(self.prev_token
.span
), ExprKind
::While(cond
, body
, opt_label
), attrs
))
2152 /// Parses `loop { ... }` (`loop` token already eaten).
2155 opt_label
: Option
<Label
>,
2158 ) -> PResult
<'a
, P
<Expr
>> {
2159 let (iattrs
, body
) = self.parse_inner_attrs_and_block()?
;
2160 attrs
.extend(iattrs
);
2161 Ok(self.mk_expr(lo
.to(self.prev_token
.span
), ExprKind
::Loop(body
, opt_label
), attrs
))
2164 fn eat_label(&mut self) -> Option
<Label
> {
2165 self.token
.lifetime().map(|ident
| {
2171 /// Parses a `match ... { ... }` expression (`match` token already eaten).
2172 fn parse_match_expr(&mut self, mut attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
2173 let match_span
= self.prev_token
.span
;
2174 let lo
= self.prev_token
.span
;
2175 let scrutinee
= self.parse_expr_res(Restrictions
::NO_STRUCT_LITERAL
, None
)?
;
2176 if let Err(mut e
) = self.expect(&token
::OpenDelim(token
::Brace
)) {
2177 if self.token
== token
::Semi
{
2178 e
.span_suggestion_short(
2180 "try removing this `match`",
2182 Applicability
::MaybeIncorrect
, // speculative
2187 attrs
.extend(self.parse_inner_attributes()?
);
2189 let mut arms
: Vec
<Arm
> = Vec
::new();
2190 while self.token
!= token
::CloseDelim(token
::Brace
) {
2191 match self.parse_arm() {
2192 Ok(arm
) => arms
.push(arm
),
2194 // Recover by skipping to the end of the block.
2196 self.recover_stmt();
2197 let span
= lo
.to(self.token
.span
);
2198 if self.token
== token
::CloseDelim(token
::Brace
) {
2201 return Ok(self.mk_expr(span
, ExprKind
::Match(scrutinee
, arms
), attrs
));
2205 let hi
= self.token
.span
;
2207 Ok(self.mk_expr(lo
.to(hi
), ExprKind
::Match(scrutinee
, arms
), attrs
))
2210 /// Attempt to recover from match arm body with statements and no surrounding braces.
2211 fn parse_arm_body_missing_braces(
2213 first_expr
: &P
<Expr
>,
2215 ) -> Option
<P
<Expr
>> {
2216 if self.token
.kind
!= token
::Semi
{
2219 let start_snapshot
= self.clone();
2220 let semi_sp
= self.token
.span
;
2223 vec
![self.mk_stmt(first_expr
.span
, ast
::StmtKind
::Expr(first_expr
.clone()))];
2224 let err
= |this
: &mut Parser
<'_
>, stmts
: Vec
<ast
::Stmt
>| {
2225 let span
= stmts
[0].span
.to(stmts
[stmts
.len() - 1].span
);
2226 let mut err
= this
.struct_span_err(span
, "`match` arm body without braces");
2227 let (these
, s
, are
) =
2228 if stmts
.len() > 1 { ("these", "s", "are") }
else { ("this", "", "is") }
;
2232 "{these} statement{s} {are} not surrounded by a body",
2238 err
.span_label(arrow_span
, "while parsing the `match` arm starting here");
2239 if stmts
.len() > 1 {
2240 err
.multipart_suggestion(
2241 &format
!("surround the statement{} with a body", s
),
2243 (span
.shrink_to_lo(), "{ ".to_string()),
2244 (span
.shrink_to_hi(), " }".to_string()),
2246 Applicability
::MachineApplicable
,
2249 err
.span_suggestion(
2251 "use a comma to end a `match` arm expression",
2253 Applicability
::MachineApplicable
,
2257 this
.mk_expr_err(span
)
2259 // We might have either a `,` -> `;` typo, or a block without braces. We need
2260 // a more subtle parsing strategy.
2262 if self.token
.kind
== token
::CloseDelim(token
::Brace
) {
2263 // We have reached the closing brace of the `match` expression.
2264 return Some(err(self, stmts
));
2266 if self.token
.kind
== token
::Comma
{
2267 *self = start_snapshot
;
2270 let pre_pat_snapshot
= self.clone();
2271 match self.parse_pat_no_top_alt(None
) {
2273 if self.token
.kind
== token
::FatArrow
{
2275 *self = pre_pat_snapshot
;
2276 return Some(err(self, stmts
));
2284 *self = pre_pat_snapshot
;
2285 match self.parse_stmt_without_recovery(true, ForceCollect
::No
) {
2286 // Consume statements for as long as possible.
2291 *self = start_snapshot
;
2294 // We couldn't parse either yet another statement missing it's
2295 // enclosing block nor the next arm's pattern or closing brace.
2296 Err(mut stmt_err
) => {
2298 *self = start_snapshot
;
2306 pub(super) fn parse_arm(&mut self) -> PResult
<'a
, Arm
> {
2307 let attrs
= self.parse_outer_attributes()?
;
2308 self.collect_tokens_trailing_token(attrs
, ForceCollect
::No
, |this
, attrs
| {
2309 let lo
= this
.token
.span
;
2310 let pat
= this
.parse_pat_allow_top_alt(None
, RecoverComma
::Yes
, RecoverColon
::Yes
)?
;
2311 let guard
= if this
.eat_keyword(kw
::If
) {
2312 let if_span
= this
.prev_token
.span
;
2313 let cond
= this
.parse_expr()?
;
2314 if let ExprKind
::Let(..) = cond
.kind
{
2315 // Remove the last feature gating of a `let` expression since it's stable.
2316 this
.sess
.gated_spans
.ungate_last(sym
::let_chains
, cond
.span
);
2317 let span
= if_span
.to(cond
.span
);
2318 this
.sess
.gated_spans
.gate(sym
::if_let_guard
, span
);
2324 let arrow_span
= this
.token
.span
;
2325 if let Err(mut err
) = this
.expect(&token
::FatArrow
) {
2326 // We might have a `=>` -> `=` or `->` typo (issue #89396).
2327 if TokenKind
::FatArrow
2329 .map_or(false, |similar_tokens
| similar_tokens
.contains(&this
.token
.kind
))
2331 err
.span_suggestion(
2333 "try using a fat arrow here",
2335 Applicability
::MaybeIncorrect
,
2343 let arm_start_span
= this
.token
.span
;
2345 let expr
= this
.parse_expr_res(Restrictions
::STMT_EXPR
, None
).map_err(|mut err
| {
2346 err
.span_label(arrow_span
, "while parsing the `match` arm starting here");
2350 let require_comma
= classify
::expr_requires_semi_to_be_stmt(&expr
)
2351 && this
.token
!= token
::CloseDelim(token
::Brace
);
2353 let hi
= this
.prev_token
.span
;
2356 let sm
= this
.sess
.source_map();
2357 if let Some(body
) = this
.parse_arm_body_missing_braces(&expr
, arrow_span
) {
2358 let span
= body
.span
;
2361 attrs
: attrs
.into(),
2367 is_placeholder
: false,
2369 TrailingToken
::None
,
2372 this
.expect_one_of(&[token
::Comma
], &[token
::CloseDelim(token
::Brace
)]).map_err(
2374 match (sm
.span_to_lines(expr
.span
), sm
.span_to_lines(arm_start_span
)) {
2375 (Ok(ref expr_lines
), Ok(ref arm_start_lines
))
2376 if arm_start_lines
.lines
[0].end_col
2377 == expr_lines
.lines
[0].end_col
2378 && expr_lines
.lines
.len() == 2
2379 && this
.token
== token
::FatArrow
=>
2381 // We check whether there's any trailing code in the parse span,
2382 // if there isn't, we very likely have the following:
2385 // | -- - missing comma
2389 // | - ^^ self.token.span
2391 // | parsed until here as `"y" & X`
2392 err
.span_suggestion_short(
2393 arm_start_span
.shrink_to_hi(),
2394 "missing a comma here to end this `match` arm",
2396 Applicability
::MachineApplicable
,
2402 "while parsing the `match` arm starting here",
2410 this
.eat(&token
::Comma
);
2415 attrs
: attrs
.into(),
2421 is_placeholder
: false,
2423 TrailingToken
::None
,
2428 /// Parses a `try {...}` expression (`try` token already eaten).
2429 fn parse_try_block(&mut self, span_lo
: Span
, mut attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
2430 let (iattrs
, body
) = self.parse_inner_attrs_and_block()?
;
2431 attrs
.extend(iattrs
);
2432 if self.eat_keyword(kw
::Catch
) {
2433 let mut error
= self.struct_span_err(
2434 self.prev_token
.span
,
2435 "keyword `catch` cannot follow a `try` block",
2437 error
.help("try using `match` on the result of the `try` block instead");
2441 let span
= span_lo
.to(body
.span
);
2442 self.sess
.gated_spans
.gate(sym
::try_blocks
, span
);
2443 Ok(self.mk_expr(span
, ExprKind
::TryBlock(body
), attrs
))
2447 fn is_do_catch_block(&self) -> bool
{
2448 self.token
.is_keyword(kw
::Do
)
2449 && self.is_keyword_ahead(1, &[kw
::Catch
])
2450 && self.look_ahead(2, |t
| *t
== token
::OpenDelim(token
::Brace
))
2451 && !self.restrictions
.contains(Restrictions
::NO_STRUCT_LITERAL
)
2454 fn is_try_block(&self) -> bool
{
2455 self.token
.is_keyword(kw
::Try
)
2456 && self.look_ahead(1, |t
| *t
== token
::OpenDelim(token
::Brace
))
2457 && self.token
.uninterpolated_span().rust_2018()
2460 /// Parses an `async move? {...}` expression.
2461 fn parse_async_block(&mut self, mut attrs
: AttrVec
) -> PResult
<'a
, P
<Expr
>> {
2462 let lo
= self.token
.span
;
2463 self.expect_keyword(kw
::Async
)?
;
2464 let capture_clause
= self.parse_capture_clause()?
;
2465 let (iattrs
, body
) = self.parse_inner_attrs_and_block()?
;
2466 attrs
.extend(iattrs
);
2467 let kind
= ExprKind
::Async(capture_clause
, DUMMY_NODE_ID
, body
);
2468 Ok(self.mk_expr(lo
.to(self.prev_token
.span
), kind
, attrs
))
2471 fn is_async_block(&self) -> bool
{
2472 self.token
.is_keyword(kw
::Async
)
2475 self.is_keyword_ahead(1, &[kw
::Move
])
2476 && self.look_ahead(2, |t
| *t
== token
::OpenDelim(token
::Brace
))
2479 self.look_ahead(1, |t
| *t
== token
::OpenDelim(token
::Brace
))
2483 fn is_certainly_not_a_block(&self) -> bool
{
2484 self.look_ahead(1, |t
| t
.is_ident())
2486 // `{ ident, ` cannot start a block.
2487 self.look_ahead(2, |t
| t
== &token
::Comma
)
2488 || self.look_ahead(2, |t
| t
== &token
::Colon
)
2490 // `{ ident: token, ` cannot start a block.
2491 self.look_ahead(4, |t
| t
== &token
::Comma
) ||
2492 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
2493 self.look_ahead(3, |t
| !t
.can_begin_type())
2498 fn maybe_parse_struct_expr(
2500 qself
: Option
<&ast
::QSelf
>,
2503 ) -> Option
<PResult
<'a
, P
<Expr
>>> {
2504 let struct_allowed
= !self.restrictions
.contains(Restrictions
::NO_STRUCT_LITERAL
);
2505 if struct_allowed
|| self.is_certainly_not_a_block() {
2506 if let Err(err
) = self.expect(&token
::OpenDelim(token
::Brace
)) {
2507 return Some(Err(err
));
2509 let expr
= self.parse_struct_expr(qself
.cloned(), path
.clone(), attrs
.clone(), true);
2510 if let (Ok(expr
), false) = (&expr
, struct_allowed
) {
2511 // This is a struct literal, but we don't can't accept them here.
2512 self.error_struct_lit_not_allowed_here(path
.span
, expr
.span
);
2519 fn error_struct_lit_not_allowed_here(&self, lo
: Span
, sp
: Span
) {
2520 self.struct_span_err(sp
, "struct literals are not allowed here")
2521 .multipart_suggestion(
2522 "surround the struct literal with parentheses",
2523 vec
![(lo
.shrink_to_lo(), "(".to_string()), (sp
.shrink_to_hi(), ")".to_string())],
2524 Applicability
::MachineApplicable
,
2529 pub(super) fn parse_struct_fields(
2533 close_delim
: token
::DelimToken
,
2534 ) -> PResult
<'a
, (Vec
<ExprField
>, ast
::StructRest
, bool
)> {
2535 let mut fields
= Vec
::new();
2536 let mut base
= ast
::StructRest
::None
;
2537 let mut recover_async
= false;
2539 let mut async_block_err
= |e
: &mut DiagnosticBuilder
<'_
>, span
: Span
| {
2540 recover_async
= true;
2541 e
.span_label(span
, "`async` blocks are only allowed in Rust 2018 or later");
2542 e
.help(&format
!("set `edition = \"{}\"` in `Cargo.toml`", LATEST_STABLE_EDITION
));
2543 e
.note("for more on editions, read https://doc.rust-lang.org/edition-guide");
2546 while self.token
!= token
::CloseDelim(close_delim
) {
2547 if self.eat(&token
::DotDot
) {
2548 let exp_span
= self.prev_token
.span
;
2549 // We permit `.. }` on the left-hand side of a destructuring assignment.
2550 if self.check(&token
::CloseDelim(close_delim
)) {
2551 self.sess
.gated_spans
.gate(sym
::destructuring_assignment
, self.prev_token
.span
);
2552 base
= ast
::StructRest
::Rest(self.prev_token
.span
.shrink_to_hi());
2555 match self.parse_expr() {
2556 Ok(e
) => base
= ast
::StructRest
::Base(e
),
2557 Err(mut e
) if recover
=> {
2559 self.recover_stmt();
2561 Err(e
) => return Err(e
),
2563 self.recover_struct_comma_after_dotdot(exp_span
);
2567 let recovery_field
= self.find_struct_error_after_field_looking_code();
2568 let parsed_field
= match self.parse_expr_field() {
2571 if pth
== kw
::Async
{
2572 async_block_err(&mut e
, pth
.span
);
2574 e
.span_label(pth
.span
, "while parsing this struct");
2578 // If the next token is a comma, then try to parse
2579 // what comes next as additional fields, rather than
2580 // bailing out until next `}`.
2581 if self.token
!= token
::Comma
{
2582 self.recover_stmt_(SemiColonMode
::Comma
, BlockMode
::Ignore
);
2583 if self.token
!= token
::Comma
{
2591 match self.expect_one_of(&[token
::Comma
], &[token
::CloseDelim(close_delim
)]) {
2593 if let Some(f
) = parsed_field
.or(recovery_field
) {
2594 // Only include the field if there's no parse error for the field name.
2599 if pth
== kw
::Async
{
2600 async_block_err(&mut e
, pth
.span
);
2602 e
.span_label(pth
.span
, "while parsing this struct");
2603 if let Some(f
) = recovery_field
{
2606 self.prev_token
.span
.shrink_to_hi(),
2607 "try adding a comma",
2609 Applicability
::MachineApplicable
,
2617 self.recover_stmt_(SemiColonMode
::Comma
, BlockMode
::Ignore
);
2618 self.eat(&token
::Comma
);
2622 Ok((fields
, base
, recover_async
))
2625 /// Precondition: already parsed the '{'.
2626 pub(super) fn parse_struct_expr(
2628 qself
: Option
<ast
::QSelf
>,
2632 ) -> PResult
<'a
, P
<Expr
>> {
2634 let (fields
, base
, recover_async
) =
2635 self.parse_struct_fields(pth
.clone(), recover
, token
::Brace
)?
;
2636 let span
= lo
.to(self.token
.span
);
2637 self.expect(&token
::CloseDelim(token
::Brace
))?
;
2638 let expr
= if recover_async
{
2641 ExprKind
::Struct(P(ast
::StructExpr { qself, path: pth, fields, rest: base }
))
2643 Ok(self.mk_expr(span
, expr
, attrs
))
2646 /// Use in case of error after field-looking code: `S { foo: () with a }`.
2647 fn find_struct_error_after_field_looking_code(&self) -> Option
<ExprField
> {
2648 match self.token
.ident() {
2649 Some((ident
, is_raw
))
2650 if (is_raw
|| !ident
.is_reserved())
2651 && self.look_ahead(1, |t
| *t
== token
::Colon
) =>
2653 Some(ast
::ExprField
{
2655 span
: self.token
.span
,
2656 expr
: self.mk_expr_err(self.token
.span
),
2657 is_shorthand
: false,
2658 attrs
: AttrVec
::new(),
2660 is_placeholder
: false,
2667 fn recover_struct_comma_after_dotdot(&mut self, span
: Span
) {
2668 if self.token
!= token
::Comma
{
2671 self.struct_span_err(
2672 span
.to(self.prev_token
.span
),
2673 "cannot use a comma after the base struct",
2675 .span_suggestion_short(
2677 "remove this comma",
2679 Applicability
::MachineApplicable
,
2681 .note("the base struct must always be the last field")
2683 self.recover_stmt();
2686 /// Parses `ident (COLON expr)?`.
2687 fn parse_expr_field(&mut self) -> PResult
<'a
, ExprField
> {
2688 let attrs
= self.parse_outer_attributes()?
;
2689 self.collect_tokens_trailing_token(attrs
, ForceCollect
::No
, |this
, attrs
| {
2690 let lo
= this
.token
.span
;
2692 // Check if a colon exists one ahead. This means we're parsing a fieldname.
2693 let is_shorthand
= !this
.look_ahead(1, |t
| t
== &token
::Colon
|| t
== &token
::Eq
);
2694 let (ident
, expr
) = if is_shorthand
{
2695 // Mimic `x: x` for the `x` field shorthand.
2696 let ident
= this
.parse_ident_common(false)?
;
2697 let path
= ast
::Path
::from_ident(ident
);
2698 (ident
, this
.mk_expr(ident
.span
, ExprKind
::Path(None
, path
), AttrVec
::new()))
2700 let ident
= this
.parse_field_name()?
;
2701 this
.error_on_eq_field_init(ident
);
2703 (ident
, this
.parse_expr()?
)
2709 span
: lo
.to(expr
.span
),
2712 attrs
: attrs
.into(),
2714 is_placeholder
: false,
2716 TrailingToken
::MaybeComma
,
2721 /// Check for `=`. This means the source incorrectly attempts to
2722 /// initialize a field with an eq rather than a colon.
2723 fn error_on_eq_field_init(&self, field_name
: Ident
) {
2724 if self.token
!= token
::Eq
{
2728 self.struct_span_err(self.token
.span
, "expected `:`, found `=`")
2730 field_name
.span
.shrink_to_hi().to(self.token
.span
),
2731 "replace equals symbol with a colon",
2733 Applicability
::MachineApplicable
,
2738 fn err_dotdotdot_syntax(&self, span
: Span
) {
2739 self.struct_span_err(span
, "unexpected token: `...`")
2742 "use `..` for an exclusive range",
2744 Applicability
::MaybeIncorrect
,
2748 "or `..=` for an inclusive range",
2750 Applicability
::MaybeIncorrect
,
2755 fn err_larrow_operator(&self, span
: Span
) {
2756 self.struct_span_err(span
, "unexpected token: `<-`")
2759 "if you meant to write a comparison against a negative value, add a \
2760 space in between `<` and `-`",
2762 Applicability
::MaybeIncorrect
,
2767 fn mk_assign_op(&self, binop
: BinOp
, lhs
: P
<Expr
>, rhs
: P
<Expr
>) -> ExprKind
{
2768 ExprKind
::AssignOp(binop
, lhs
, rhs
)
2773 start
: Option
<P
<Expr
>>,
2774 end
: Option
<P
<Expr
>>,
2775 limits
: RangeLimits
,
2777 if end
.is_none() && limits
== RangeLimits
::Closed
{
2778 self.inclusive_range_with_incorrect_end(self.prev_token
.span
);
2781 ExprKind
::Range(start
, end
, limits
)
2785 fn mk_unary(&self, unop
: UnOp
, expr
: P
<Expr
>) -> ExprKind
{
2786 ExprKind
::Unary(unop
, expr
)
2789 fn mk_binary(&self, binop
: BinOp
, lhs
: P
<Expr
>, rhs
: P
<Expr
>) -> ExprKind
{
2790 ExprKind
::Binary(binop
, lhs
, rhs
)
2793 fn mk_index(&self, expr
: P
<Expr
>, idx
: P
<Expr
>) -> ExprKind
{
2794 ExprKind
::Index(expr
, idx
)
2797 fn mk_call(&self, f
: P
<Expr
>, args
: Vec
<P
<Expr
>>) -> ExprKind
{
2798 ExprKind
::Call(f
, args
)
2801 fn mk_await_expr(&mut self, self_arg
: P
<Expr
>, lo
: Span
) -> P
<Expr
> {
2802 let span
= lo
.to(self.prev_token
.span
);
2803 let await_expr
= self.mk_expr(span
, ExprKind
::Await(self_arg
), AttrVec
::new());
2804 self.recover_from_await_method_call();
2808 crate fn mk_expr(&self, span
: Span
, kind
: ExprKind
, attrs
: AttrVec
) -> P
<Expr
> {
2809 P(Expr { kind, span, attrs, id: DUMMY_NODE_ID, tokens: None }
)
2812 pub(super) fn mk_expr_err(&self, span
: Span
) -> P
<Expr
> {
2813 self.mk_expr(span
, ExprKind
::Err
, AttrVec
::new())
2816 /// Create expression span ensuring the span of the parent node
2817 /// is larger than the span of lhs and rhs, including the attributes.
2818 fn mk_expr_sp(&self, lhs
: &P
<Expr
>, lhs_span
: Span
, rhs_span
: Span
) -> Span
{
2821 .find(|a
| a
.style
== AttrStyle
::Outer
)
2822 .map_or(lhs_span
, |a
| a
.span
)
2826 fn collect_tokens_for_expr(
2829 f
: impl FnOnce(&mut Self, Vec
<ast
::Attribute
>) -> PResult
<'a
, P
<Expr
>>,
2830 ) -> PResult
<'a
, P
<Expr
>> {
2831 self.collect_tokens_trailing_token(attrs
, ForceCollect
::No
, |this
, attrs
| {
2832 let res
= f(this
, attrs
)?
;
2833 let trailing
= if this
.restrictions
.contains(Restrictions
::STMT_EXPR
)
2834 && this
.token
.kind
== token
::Semi
2838 // FIXME - pass this through from the place where we know
2839 // we need a comma, rather than assuming that `#[attr] expr,`
2840 // always captures a trailing comma
2841 TrailingToken
::MaybeComma