2 Parser, PResult, Restrictions, PrevTokenKind, TokenType, PathStyle, BlockMode, SemiColonMode,
3 SeqSep, TokenExpectType,
5 use super::pat::{GateOr, PARAM_EXPECTED};
8 self, DUMMY_NODE_ID, Attribute, AttrStyle, Ident, CaptureBy, BlockCheckMode,
9 Expr, ExprKind, RangeLimits, Label, Movability, IsAsync, Arm, Ty, TyKind,
10 FunctionRetTy, Param, FnDecl, BinOpKind, BinOp, UnOp, Mac, AnonConst, Field,
12 use crate::maybe_recover_from_interpolated_ty_qpath;
13 use crate::parse::classify;
14 use crate::parse::token::{self, Token};
15 use crate::parse::diagnostics::Error;
16 use crate::print::pprust;
18 use crate::source_map::{self, Span};
19 use crate::symbol::{kw, sym};
20 use crate::util::parser::{AssocOp, Fixity, prec_let_scrutinee_needs_par};
22 use errors::Applicability;
24 use rustc_data_structures::thin_vec::ThinVec;
26 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
27 /// dropped into the token stream, which happens while parsing the result of
28 /// macro expansion). Placement of these is not as complex as I feared it would
29 /// be. The important thing is to make sure that lookahead doesn't balk at
30 /// `token::Interpolated` tokens.
31 macro_rules! maybe_whole_expr {
33 if let token::Interpolated(nt) = &$p.token.kind {
35 token::NtExpr(e) | token::NtLiteral(e) => {
40 token::NtPath(path) => {
41 let path = path.clone();
44 $p.token.span, ExprKind::Path(None, path), ThinVec::new()
47 token::NtBlock(block) => {
48 let block = block.clone();
51 $p.token.span, ExprKind::Block(block, None), ThinVec::new()
54 // N.B., `NtIdent(ident)` is normalized to `Ident` in `fn bump`.
62 pub(super) enum LhsExpr {
64 AttributesParsed(ThinVec<Attribute>),
65 AlreadyParsed(P<Expr>),
68 impl From<Option<ThinVec<Attribute>>> for LhsExpr {
69 /// Converts `Some(attrs)` into `LhsExpr::AttributesParsed(attrs)`
70 /// and `None` into `LhsExpr::NotYetParsed`.
72 /// This conversion does not allocate.
73 fn from(o: Option<ThinVec<Attribute>>) -> Self {
74 if let Some(attrs) = o {
75 LhsExpr::AttributesParsed(attrs)
82 impl From<P<Expr>> for LhsExpr {
83 /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed(expr)`.
85 /// This conversion does not allocate.
86 fn from(expr: P<Expr>) -> Self {
87 LhsExpr::AlreadyParsed(expr)
92 /// Parses an expression.
94 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
95 self.parse_expr_res(Restrictions::empty(), None)
98 fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
99 self.parse_paren_comma_seq(|p| {
100 match p.parse_expr() {
101 Ok(expr) => Ok(expr),
102 Err(mut err) => match p.token.kind {
103 token::Ident(name, false)
104 if name == kw::Underscore && p.look_ahead(1, |t| {
107 // Special-case handling of `foo(_, _, _)`
109 let sp = p.token.span;
111 Ok(p.mk_expr(sp, ExprKind::Err, ThinVec::new()))
119 /// Parses an expression, subject to the given restrictions.
121 pub(super) fn parse_expr_res(
124 already_parsed_attrs: Option<ThinVec<Attribute>>
125 ) -> PResult<'a, P<Expr>> {
126 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
129 /// Parses an associative expression.
131 /// This parses an expression accounting for associativity and precedence of the operators in
136 already_parsed_attrs: Option<ThinVec<Attribute>>,
137 ) -> PResult<'a, P<Expr>> {
138 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
141 /// Parses an associative expression with operators of at least `min_prec` precedence.
142 pub(super) fn parse_assoc_expr_with(
146 ) -> PResult<'a, P<Expr>> {
147 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
150 let attrs = match lhs {
151 LhsExpr::AttributesParsed(attrs) => Some(attrs),
154 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind) {
155 return self.parse_prefix_range_expr(attrs);
157 self.parse_prefix_expr(attrs)?
160 let last_type_ascription_set = self.last_type_ascription.is_some();
162 match (self.expr_is_complete(&lhs), AssocOp::from_token(&self.token)) {
164 self.last_type_ascription = None;
165 // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
168 (false, _) => {} // continue parsing the expression
169 // An exhaustive check is done in the following block, but these are checked first
170 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
171 // want to keep their span info to improve diagnostics in these cases in a later stage.
172 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
173 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
174 (true, Some(AssocOp::LAnd)) | // `{ 42 } &&x` (#61475)
175 (true, Some(AssocOp::Add)) // `{ 42 } + 42
176 // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
177 // `if x { a } else { b } && if y { c } else { d }`
178 if !self.look_ahead(1, |t| t.is_reserved_ident()) => {
179 self.last_type_ascription = None;
180 // These cases are ambiguous and can't be identified in the parser alone
181 let sp = self.sess.source_map().start_point(self.token.span);
182 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
185 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => {
186 self.last_type_ascription = None;
190 // We've found an expression that would be parsed as a statement, but the next
191 // token implies this should be parsed as an expression.
192 // For example: `if let Some(x) = x { x } else { 0 } / 2`
193 let mut err = self.struct_span_err(self.token.span, &format!(
194 "expected expression, found `{}`",
195 pprust::token_to_string(&self.token),
197 err.span_label(self.token.span, "expected expression");
198 self.sess.expr_parentheses_needed(
201 Some(pprust::expr_to_string(&lhs),
206 self.expected_tokens.push(TokenType::Operator);
207 while let Some(op) = AssocOp::from_token(&self.token) {
209 // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
210 // it refers to. Interpolated identifiers are unwrapped early and never show up here
211 // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
212 // it as "interpolated", it doesn't change the answer for non-interpolated idents.
213 let lhs_span = match (self.prev_token_kind, &lhs.kind) {
214 (PrevTokenKind::Interpolated, _) => self.prev_span,
215 (PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
216 if path.segments.len() == 1 => self.prev_span,
220 let cur_op_span = self.token.span;
221 let restrictions = if op.is_assign_like() {
222 self.restrictions & Restrictions::NO_STRUCT_LITERAL
226 let prec = op.precedence();
230 // Check for deprecated `...` syntax
231 if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
232 self.err_dotdotdot_syntax(self.token.span);
235 if self.token == token::LArrow {
236 self.err_larrow_operator(self.token.span);
240 if op.is_comparison() {
241 if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
246 if op == AssocOp::As {
247 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
249 } else if op == AssocOp::Colon {
250 let maybe_path = self.could_ascription_be_path(&lhs.kind);
251 self.last_type_ascription = Some((self.prev_span, maybe_path));
253 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
255 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
256 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
257 // generalise it to the Fixity::None code.
259 // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
260 // two variants are handled with `parse_prefix_range_expr` call above.
261 let rhs = if self.is_at_start_of_range_notation_rhs() {
262 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
266 let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
271 let limits = if op == AssocOp::DotDot {
272 RangeLimits::HalfOpen
277 let r = self.mk_range(Some(lhs), rhs, limits)?;
278 lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
282 let fixity = op.fixity();
283 let prec_adjustment = match fixity {
286 // We currently have no non-associative operators that are not handled above by
287 // the special cases. The code is here only for future convenience.
290 let rhs = self.with_res(
291 restrictions - Restrictions::STMT_EXPR,
292 |this| this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
295 // Make sure that the span of the parent node is larger than the span of lhs and rhs,
296 // including the attributes.
300 .filter(|a| a.style == AttrStyle::Outer)
302 .map_or(lhs_span, |a| a.span);
303 let span = lhs_span.to(rhs.span);
305 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
306 AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
307 AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
308 AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
309 AssocOp::Greater | AssocOp::GreaterEqual => {
310 let ast_op = op.to_ast_binop().unwrap();
311 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
312 self.mk_expr(span, binary, ThinVec::new())
314 AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
315 AssocOp::AssignOp(k) => {
317 token::Plus => BinOpKind::Add,
318 token::Minus => BinOpKind::Sub,
319 token::Star => BinOpKind::Mul,
320 token::Slash => BinOpKind::Div,
321 token::Percent => BinOpKind::Rem,
322 token::Caret => BinOpKind::BitXor,
323 token::And => BinOpKind::BitAnd,
324 token::Or => BinOpKind::BitOr,
325 token::Shl => BinOpKind::Shl,
326 token::Shr => BinOpKind::Shr,
328 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
329 self.mk_expr(span, aopexpr, ThinVec::new())
331 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
332 self.bug("AssocOp should have been handled by special case")
336 if let Fixity::None = fixity { break }
338 if last_type_ascription_set {
339 self.last_type_ascription = None;
344 /// Checks if this expression is a successfully parsed statement.
345 fn expr_is_complete(&self, e: &Expr) -> bool {
346 self.restrictions.contains(Restrictions::STMT_EXPR) &&
347 !classify::expr_requires_semi_to_be_stmt(e)
350 fn is_at_start_of_range_notation_rhs(&self) -> bool {
351 if self.token.can_begin_expr() {
352 // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
353 if self.token == token::OpenDelim(token::Brace) {
354 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
362 /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
363 fn parse_prefix_range_expr(
365 already_parsed_attrs: Option<ThinVec<Attribute>>
366 ) -> PResult<'a, P<Expr>> {
367 // Check for deprecated `...` syntax.
368 if self.token == token::DotDotDot {
369 self.err_dotdotdot_syntax(self.token.span);
372 debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind),
373 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
375 let tok = self.token.clone();
376 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
377 let lo = self.token.span;
378 let mut hi = self.token.span;
380 let opt_end = if self.is_at_start_of_range_notation_rhs() {
381 // RHS must be parsed with more associativity than the dots.
382 let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
383 Some(self.parse_assoc_expr_with(next_prec, LhsExpr::NotYetParsed)
391 let limits = if tok == token::DotDot {
392 RangeLimits::HalfOpen
397 let r = self.mk_range(None, opt_end, limits)?;
398 Ok(self.mk_expr(lo.to(hi), r, attrs))
401 /// Parses a prefix-unary-operator expr.
402 fn parse_prefix_expr(
404 already_parsed_attrs: Option<ThinVec<Attribute>>
405 ) -> PResult<'a, P<Expr>> {
406 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
407 let lo = self.token.span;
408 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
409 let (hi, ex) = match self.token.kind {
412 let e = self.parse_prefix_expr(None);
413 let (span, e) = self.interpolated_or_expr_span(e)?;
414 (lo.to(span), self.mk_unary(UnOp::Not, e))
416 // Suggest `!` for bitwise negation when encountering a `~`
419 let e = self.parse_prefix_expr(None);
420 let (span, e) = self.interpolated_or_expr_span(e)?;
421 let span_of_tilde = lo;
422 self.struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator")
423 .span_suggestion_short(
425 "use `!` to perform bitwise negation",
427 Applicability::MachineApplicable
430 (lo.to(span), self.mk_unary(UnOp::Not, e))
432 token::BinOp(token::Minus) => {
434 let e = self.parse_prefix_expr(None);
435 let (span, e) = self.interpolated_or_expr_span(e)?;
436 (lo.to(span), self.mk_unary(UnOp::Neg, e))
438 token::BinOp(token::Star) => {
440 let e = self.parse_prefix_expr(None);
441 let (span, e) = self.interpolated_or_expr_span(e)?;
442 (lo.to(span), self.mk_unary(UnOp::Deref, e))
444 token::BinOp(token::And) | token::AndAnd => {
446 let m = self.parse_mutability();
447 let e = self.parse_prefix_expr(None);
448 let (span, e) = self.interpolated_or_expr_span(e)?;
449 (lo.to(span), ExprKind::AddrOf(m, e))
451 token::Ident(..) if self.token.is_keyword(kw::Box) => {
453 let e = self.parse_prefix_expr(None);
454 let (span, e) = self.interpolated_or_expr_span(e)?;
455 (lo.to(span), ExprKind::Box(e))
457 token::Ident(..) if self.token.is_ident_named(sym::not) => {
458 // `not` is just an ordinary identifier in Rust-the-language,
459 // but as `rustc`-the-compiler, we can issue clever diagnostics
460 // for confused users who really want to say `!`
461 let token_cannot_continue_expr = |t: &Token| match t.kind {
462 // These tokens can start an expression after `!`, but
463 // can't continue an expression after an ident
464 token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
465 token::Literal(..) | token::Pound => true,
466 _ => t.is_whole_expr(),
468 let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr);
469 if cannot_continue_expr {
471 // Emit the error ...
472 self.struct_span_err(
474 &format!("unexpected {} after identifier",self.this_token_descr())
476 .span_suggestion_short(
477 // Span the `not` plus trailing whitespace to avoid
478 // trailing whitespace after the `!` in our suggestion
479 self.sess.source_map()
480 .span_until_non_whitespace(lo.to(self.token.span)),
481 "use `!` to perform logical negation",
483 Applicability::MachineApplicable
486 // —and recover! (just as if we were in the block
487 // for the `token::Not` arm)
488 let e = self.parse_prefix_expr(None);
489 let (span, e) = self.interpolated_or_expr_span(e)?;
490 (lo.to(span), self.mk_unary(UnOp::Not, e))
492 return self.parse_dot_or_call_expr(Some(attrs));
495 _ => { return self.parse_dot_or_call_expr(Some(attrs)); }
497 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
500 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
501 fn interpolated_or_expr_span(
503 expr: PResult<'a, P<Expr>>,
504 ) -> PResult<'a, (Span, P<Expr>)> {
506 if self.prev_token_kind == PrevTokenKind::Interpolated {
514 fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
515 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
516 -> PResult<'a, P<Expr>> {
517 let mk_expr = |this: &mut Self, rhs: P<Ty>| {
518 this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
521 // Save the state of the parser before parsing type normally, in case there is a
522 // LessThan comparison after this cast.
523 let parser_snapshot_before_type = self.clone();
524 match self.parse_ty_no_plus() {
526 Ok(mk_expr(self, rhs))
528 Err(mut type_err) => {
529 // Rewind to before attempting to parse the type with generics, to recover
530 // from situations like `x as usize < y` in which we first tried to parse
531 // `usize < y` as a type with generic arguments.
532 let parser_snapshot_after_type = self.clone();
533 mem::replace(self, parser_snapshot_before_type);
535 match self.parse_path(PathStyle::Expr) {
537 let (op_noun, op_verb) = match self.token.kind {
538 token::Lt => ("comparison", "comparing"),
539 token::BinOp(token::Shl) => ("shift", "shifting"),
541 // We can end up here even without `<` being the next token, for
542 // example because `parse_ty_no_plus` returns `Err` on keywords,
543 // but `parse_path` returns `Ok` on them due to error recovery.
544 // Return original error and parser state.
545 mem::replace(self, parser_snapshot_after_type);
546 return Err(type_err);
550 // Successfully parsed the type path leaving a `<` yet to parse.
553 // Report non-fatal diagnostics, keep `x as usize` as an expression
554 // in AST and continue parsing.
556 "`<` is interpreted as a start of generic arguments for `{}`, not a {}",
557 pprust::path_to_string(&path),
560 let span_after_type = parser_snapshot_after_type.token.span;
561 let expr = mk_expr(self, P(Ty {
563 kind: TyKind::Path(None, path),
567 let expr_str = self.span_to_snippet(expr.span)
568 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
570 self.struct_span_err(self.token.span, &msg)
572 self.look_ahead(1, |t| t.span).to(span_after_type),
573 "interpreted as generic arguments"
575 .span_label(self.token.span, format!("not interpreted as {}", op_noun))
578 &format!("try {} the cast value", op_verb),
579 format!("({})", expr_str),
580 Applicability::MachineApplicable,
586 Err(mut path_err) => {
587 // Couldn't parse as a path, return original error and parser state.
589 mem::replace(self, parser_snapshot_after_type);
597 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
598 fn parse_dot_or_call_expr(
600 already_parsed_attrs: Option<ThinVec<Attribute>>,
601 ) -> PResult<'a, P<Expr>> {
602 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
604 let b = self.parse_bottom_expr();
605 let (span, b) = self.interpolated_or_expr_span(b)?;
606 self.parse_dot_or_call_expr_with(b, span, attrs)
609 pub(super) fn parse_dot_or_call_expr_with(
613 mut attrs: ThinVec<Attribute>,
614 ) -> PResult<'a, P<Expr>> {
615 // Stitch the list of outer attributes onto the return value.
616 // A little bit ugly, but the best way given the current code
618 self.parse_dot_or_call_expr_with_(e0, lo).map(|expr|
619 expr.map(|mut expr| {
620 attrs.extend::<Vec<_>>(expr.attrs.into());
623 ExprKind::If(..) if !expr.attrs.is_empty() => {
624 // Just point to the first attribute in there...
625 let span = expr.attrs[0].span;
626 self.span_err(span, "attributes are not yet allowed on `if` expressions");
635 fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
640 while self.eat(&token::Question) {
641 let hi = self.prev_span;
642 e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new());
646 if self.eat(&token::Dot) {
647 match self.token.kind {
648 token::Ident(..) => {
649 e = self.parse_dot_suffix(e, lo)?;
651 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
652 let span = self.token.span;
654 let field = ExprKind::Field(e, Ident::new(symbol, span));
655 e = self.mk_expr(lo.to(span), field, ThinVec::new());
657 self.expect_no_suffix(span, "a tuple index", suffix);
659 token::Literal(token::Lit { kind: token::Float, symbol, .. }) => {
661 let fstr = symbol.as_str();
662 let msg = format!("unexpected token: `{}`", symbol);
663 let mut err = self.diagnostic().struct_span_err(self.prev_span, &msg);
664 err.span_label(self.prev_span, "unexpected token");
665 if fstr.chars().all(|x| "0123456789.".contains(x)) {
666 let float = match fstr.parse::<f64>().ok() {
670 let sugg = pprust::to_string(|s| {
674 s.print_usize(float.trunc() as usize);
677 s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
680 lo.to(self.prev_span),
681 "try parenthesizing the first index",
683 Applicability::MachineApplicable
690 // FIXME Could factor this out into non_fatal_unexpected or something.
691 let actual = self.this_token_to_string();
692 self.span_err(self.token.span, &format!("unexpected token: `{}`", actual));
697 if self.expr_is_complete(&e) { break; }
698 match self.token.kind {
700 token::OpenDelim(token::Paren) => {
701 let seq = self.parse_paren_expr_seq().map(|es| {
702 let nd = self.mk_call(e, es);
703 let hi = self.prev_span;
704 self.mk_expr(lo.to(hi), nd, ThinVec::new())
706 e = self.recover_seq_parse_error(token::Paren, lo, seq);
710 // Could be either an index expression or a slicing expression.
711 token::OpenDelim(token::Bracket) => {
713 let ix = self.parse_expr()?;
714 hi = self.token.span;
715 self.expect(&token::CloseDelim(token::Bracket))?;
716 let index = self.mk_index(e, ix);
717 e = self.mk_expr(lo.to(hi), index, ThinVec::new())
725 /// Assuming we have just parsed `.`, continue parsing into an expression.
726 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
727 if self.token.span.rust_2018() && self.eat_keyword(kw::Await) {
728 return self.mk_await_expr(self_arg, lo);
731 let segment = self.parse_path_segment(PathStyle::Expr)?;
732 self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
734 Ok(match self.token.kind {
735 token::OpenDelim(token::Paren) => {
736 // Method call `expr.f()`
737 let mut args = self.parse_paren_expr_seq()?;
738 args.insert(0, self_arg);
740 let span = lo.to(self.prev_span);
741 self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new())
744 // Field access `expr.f`
745 if let Some(args) = segment.args {
746 self.span_err(args.span(),
747 "field expressions may not have generic arguments");
750 let span = lo.to(self.prev_span);
751 self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::new())
756 /// At the bottom (top?) of the precedence hierarchy,
757 /// Parses things like parenthesized exprs, macros, `return`, etc.
759 /// N.B., this does not parse outer attributes, and is private because it only works
760 /// correctly if called from `parse_dot_or_call_expr()`.
761 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
762 maybe_recover_from_interpolated_ty_qpath!(self, true);
763 maybe_whole_expr!(self);
765 // Outer attributes are already parsed and will be
766 // added to the return value after the fact.
768 // Therefore, prevent sub-parser from parsing
769 // attributes by giving them a empty "already-parsed" list.
770 let mut attrs = ThinVec::new();
772 let lo = self.token.span;
773 let mut hi = self.token.span;
777 macro_rules! parse_lit {
779 match self.parse_lit() {
782 ex = ExprKind::Lit(literal);
786 return Err(self.expected_expression_found());
792 // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
793 match self.token.kind {
794 // This match arm is a special-case of the `_` match arm below and
795 // could be removed without changing functionality, but it's faster
796 // to have it here, especially for programs with large constants.
797 token::Literal(_) => {
800 token::OpenDelim(token::Paren) => {
803 attrs.extend(self.parse_inner_attributes()?);
805 // `(e)` is parenthesized `e`.
806 // `(e,)` is a tuple with only one field, `e`.
808 let mut trailing_comma = false;
809 let mut recovered = false;
810 while self.token != token::CloseDelim(token::Paren) {
811 es.push(match self.parse_expr() {
814 // Recover from parse error in tuple list.
815 match self.token.kind {
816 token::Ident(name, false)
817 if name == kw::Underscore && self.look_ahead(1, |t| {
820 // Special-case handling of `Foo<(_, _, _)>`
822 let sp = self.token.span;
824 self.mk_expr(sp, ExprKind::Err, ThinVec::new())
827 self.recover_seq_parse_error(token::Paren, lo, Err(err)),
832 recovered = self.expect_one_of(
834 &[token::Comma, token::CloseDelim(token::Paren)],
836 if self.eat(&token::Comma) {
837 trailing_comma = true;
839 trailing_comma = false;
848 ex = if es.len() == 1 && !trailing_comma {
849 ExprKind::Paren(es.into_iter().nth(0).unwrap())
854 token::OpenDelim(token::Brace) => {
855 return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
857 token::BinOp(token::Or) | token::OrOr => {
858 return self.parse_closure_expr(attrs);
860 token::OpenDelim(token::Bracket) => {
863 attrs.extend(self.parse_inner_attributes()?);
865 if self.eat(&token::CloseDelim(token::Bracket)) {
867 ex = ExprKind::Array(Vec::new());
870 let first_expr = self.parse_expr()?;
871 if self.eat(&token::Semi) {
872 // Repeating array syntax: `[ 0; 512 ]`
873 let count = AnonConst {
875 value: self.parse_expr()?,
877 self.expect(&token::CloseDelim(token::Bracket))?;
878 ex = ExprKind::Repeat(first_expr, count);
879 } else if self.eat(&token::Comma) {
880 // Vector with two or more elements
881 let remaining_exprs = self.parse_seq_to_end(
882 &token::CloseDelim(token::Bracket),
883 SeqSep::trailing_allowed(token::Comma),
884 |p| Ok(p.parse_expr()?)
886 let mut exprs = vec![first_expr];
887 exprs.extend(remaining_exprs);
888 ex = ExprKind::Array(exprs);
890 // Vector with one element
891 self.expect(&token::CloseDelim(token::Bracket))?;
892 ex = ExprKind::Array(vec![first_expr]);
899 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
901 return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
903 if self.token.is_path_start() {
904 let path = self.parse_path(PathStyle::Expr)?;
906 // `!`, as an operator, is prefix, so we know this isn't that.
907 if self.eat(&token::Not) {
908 // MACRO INVOCATION expression
909 let (delim, tts) = self.expect_delimited_token_tree()?;
911 ex = ExprKind::Mac(Mac {
916 prior_type_ascription: self.last_type_ascription,
918 } else if self.check(&token::OpenDelim(token::Brace)) {
919 if let Some(expr) = self.maybe_parse_struct_expr(lo, &path, &attrs) {
923 ex = ExprKind::Path(None, path);
927 ex = ExprKind::Path(None, path);
930 let expr = self.mk_expr(lo.to(hi), ex, attrs);
931 return self.maybe_recover_from_bad_qpath(expr, true);
933 if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
934 return self.parse_closure_expr(attrs);
936 if self.eat_keyword(kw::If) {
937 return self.parse_if_expr(attrs);
939 if self.eat_keyword(kw::For) {
940 let lo = self.prev_span;
941 return self.parse_for_expr(None, lo, attrs);
943 if self.eat_keyword(kw::While) {
944 let lo = self.prev_span;
945 return self.parse_while_expr(None, lo, attrs);
947 if let Some(label) = self.eat_label() {
948 let lo = label.ident.span;
949 self.expect(&token::Colon)?;
950 if self.eat_keyword(kw::While) {
951 return self.parse_while_expr(Some(label), lo, attrs)
953 if self.eat_keyword(kw::For) {
954 return self.parse_for_expr(Some(label), lo, attrs)
956 if self.eat_keyword(kw::Loop) {
957 return self.parse_loop_expr(Some(label), lo, attrs)
959 if self.token == token::OpenDelim(token::Brace) {
960 return self.parse_block_expr(Some(label),
962 BlockCheckMode::Default,
965 let msg = "expected `while`, `for`, `loop` or `{` after a label";
966 let mut err = self.fatal(msg);
967 err.span_label(self.token.span, msg);
970 if self.eat_keyword(kw::Loop) {
971 let lo = self.prev_span;
972 return self.parse_loop_expr(None, lo, attrs);
974 if self.eat_keyword(kw::Continue) {
975 let label = self.eat_label();
976 let ex = ExprKind::Continue(label);
977 let hi = self.prev_span;
978 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
980 if self.eat_keyword(kw::Match) {
981 let match_sp = self.prev_span;
982 return self.parse_match_expr(attrs).map_err(|mut err| {
983 err.span_label(match_sp, "while parsing this match expression");
987 if self.eat_keyword(kw::Unsafe) {
988 return self.parse_block_expr(
991 BlockCheckMode::Unsafe(ast::UserProvided),
994 if self.is_do_catch_block() {
995 let mut db = self.fatal("found removed `do catch` syntax");
996 db.help("following RFC #2388, the new non-placeholder syntax is `try`");
999 if self.is_try_block() {
1000 let lo = self.token.span;
1001 assert!(self.eat_keyword(kw::Try));
1002 return self.parse_try_block(lo, attrs);
1005 // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
1006 let is_span_rust_2018 = self.token.span.rust_2018();
1007 if is_span_rust_2018 && self.check_keyword(kw::Async) {
1008 return if self.is_async_block() { // Check for `async {` and `async move {`.
1009 self.parse_async_block(attrs)
1011 self.parse_closure_expr(attrs)
1014 if self.eat_keyword(kw::Return) {
1015 if self.token.can_begin_expr() {
1016 let e = self.parse_expr()?;
1018 ex = ExprKind::Ret(Some(e));
1020 ex = ExprKind::Ret(None);
1022 } else if self.eat_keyword(kw::Break) {
1023 let label = self.eat_label();
1024 let e = if self.token.can_begin_expr()
1025 && !(self.token == token::OpenDelim(token::Brace)
1026 && self.restrictions.contains(
1027 Restrictions::NO_STRUCT_LITERAL)) {
1028 Some(self.parse_expr()?)
1032 ex = ExprKind::Break(label, e);
1033 hi = self.prev_span;
1034 } else if self.eat_keyword(kw::Yield) {
1035 if self.token.can_begin_expr() {
1036 let e = self.parse_expr()?;
1038 ex = ExprKind::Yield(Some(e));
1040 ex = ExprKind::Yield(None);
1043 let span = lo.to(hi);
1044 self.sess.gated_spans.yields.borrow_mut().push(span);
1045 } else if self.eat_keyword(kw::Let) {
1046 return self.parse_let_expr(attrs);
1047 } else if is_span_rust_2018 && self.eat_keyword(kw::Await) {
1048 let (await_hi, e_kind) = self.parse_incorrect_await_syntax(lo, self.prev_span)?;
1052 if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
1053 // Don't complain about bare semicolons after unclosed braces
1054 // recovery in order to keep the error count down. Fixing the
1055 // delimiters will possibly also fix the bare semicolon found in
1056 // expression context. For example, silence the following error:
1058 // error: expected expression, found `;`
1062 // | ^ expected expression
1064 return Ok(self.mk_expr(self.token.span, ExprKind::Err, ThinVec::new()));
1071 let expr = self.mk_expr(lo.to(hi), ex, attrs);
1072 self.maybe_recover_from_bad_qpath(expr, true)
1075 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1076 crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1077 maybe_whole_expr!(self);
1079 let minus_lo = self.token.span;
1080 let minus_present = self.eat(&token::BinOp(token::Minus));
1081 let lo = self.token.span;
1082 let literal = self.parse_lit()?;
1083 let hi = self.prev_span;
1084 let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
1087 let minus_hi = self.prev_span;
1088 let unary = self.mk_unary(UnOp::Neg, expr);
1089 Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
1095 /// Parses a block or unsafe block.
1096 crate fn parse_block_expr(
1098 opt_label: Option<Label>,
1100 blk_mode: BlockCheckMode,
1101 outer_attrs: ThinVec<Attribute>,
1102 ) -> PResult<'a, P<Expr>> {
1103 self.expect(&token::OpenDelim(token::Brace))?;
1105 let mut attrs = outer_attrs;
1106 attrs.extend(self.parse_inner_attributes()?);
1108 let blk = self.parse_block_tail(lo, blk_mode)?;
1109 Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs))
1112 /// Parses a closure expression (e.g., `move |args| expr`).
1113 fn parse_closure_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
1114 let lo = self.token.span;
1116 let movability = if self.eat_keyword(kw::Static) {
1122 let asyncness = if self.token.span.rust_2018() {
1123 self.parse_asyncness()
1127 if asyncness.is_async() {
1128 // Feature-gate `async ||` closures.
1129 self.sess.gated_spans.async_closure.borrow_mut().push(self.prev_span);
1132 let capture_clause = self.parse_capture_clause();
1133 let decl = self.parse_fn_block_decl()?;
1134 let decl_hi = self.prev_span;
1135 let body = match decl.output {
1136 FunctionRetTy::Default(_) => {
1137 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
1138 self.parse_expr_res(restrictions, None)?
1141 // If an explicit return type is given, require a block to appear (RFC 968).
1142 let body_lo = self.token.span;
1143 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
1149 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
1153 /// Parses an optional `move` prefix to a closure lke construct.
1154 fn parse_capture_clause(&mut self) -> CaptureBy {
1155 if self.eat_keyword(kw::Move) {
1162 /// Parses the `|arg, arg|` header of a closure.
1163 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
1164 let inputs_captures = {
1165 if self.eat(&token::OrOr) {
1168 self.expect(&token::BinOp(token::Or))?;
1169 let args = self.parse_seq_to_before_tokens(
1170 &[&token::BinOp(token::Or), &token::OrOr],
1171 SeqSep::trailing_allowed(token::Comma),
1172 TokenExpectType::NoExpect,
1173 |p| p.parse_fn_block_param()
1179 let output = self.parse_ret_ty(true)?;
1182 inputs: inputs_captures,
1187 /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
1188 fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
1189 let lo = self.token.span;
1190 let attrs = self.parse_outer_attributes()?;
1191 let pat = self.parse_pat(PARAM_EXPECTED)?;
1192 let t = if self.eat(&token::Colon) {
1197 kind: TyKind::Infer,
1198 span: self.prev_span,
1201 let span = lo.to(self.token.span);
1203 attrs: attrs.into(),
1208 is_placeholder: false,
1212 /// Parses an `if` expression (`if` token already eaten).
1213 fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
1214 let lo = self.prev_span;
1215 let cond = self.parse_cond_expr()?;
1217 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
1218 // verify that the last statement is either an implicit return (no `;`) or an explicit
1219 // return. This won't catch blocks with an explicit `return`, but that would be caught by
1220 // the dead code lint.
1221 if self.eat_keyword(kw::Else) || !cond.returns() {
1222 let sp = self.sess.source_map().next_point(lo);
1223 let mut err = self.diagnostic()
1224 .struct_span_err(sp, "missing condition for `if` expression");
1225 err.span_label(sp, "expected if condition here");
1228 let not_block = self.token != token::OpenDelim(token::Brace);
1229 let thn = self.parse_block().map_err(|mut err| {
1231 err.span_label(lo, "this `if` statement has a condition, but no block");
1235 let mut els: Option<P<Expr>> = None;
1236 let mut hi = thn.span;
1237 if self.eat_keyword(kw::Else) {
1238 let elexpr = self.parse_else_expr()?;
1242 Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
1245 /// Parses the condition of a `if` or `while` expression.
1246 fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
1247 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
1249 if let ExprKind::Let(..) = cond.kind {
1250 // Remove the last feature gating of a `let` expression since it's stable.
1251 let last = self.sess.gated_spans.let_chains.borrow_mut().pop();
1252 debug_assert_eq!(cond.span, last.unwrap());
1258 /// Parses a `let $pat = $expr` pseudo-expression.
1259 /// The `let` token has already been eaten.
1260 fn parse_let_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
1261 let lo = self.prev_span;
1262 let pat = self.parse_top_pat(GateOr::No)?;
1263 self.expect(&token::Eq)?;
1264 let expr = self.with_res(
1265 Restrictions::NO_STRUCT_LITERAL,
1266 |this| this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
1268 let span = lo.to(expr.span);
1269 self.sess.gated_spans.let_chains.borrow_mut().push(span);
1270 Ok(self.mk_expr(span, ExprKind::Let(pat, expr), attrs))
1273 /// Parses an `else { ... }` expression (`else` token already eaten).
1274 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
1275 if self.eat_keyword(kw::If) {
1276 return self.parse_if_expr(ThinVec::new());
1278 let blk = self.parse_block()?;
1279 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new()));
1283 /// Parses a `for ... in` expression (`for` token already eaten).
1286 opt_label: Option<Label>,
1288 mut attrs: ThinVec<Attribute>
1289 ) -> PResult<'a, P<Expr>> {
1290 // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
1292 // Record whether we are about to parse `for (`.
1293 // This is used below for recovery in case of `for ( $stuff ) $block`
1294 // in which case we will suggest `for $stuff $block`.
1295 let begin_paren = match self.token.kind {
1296 token::OpenDelim(token::Paren) => Some(self.token.span),
1300 let pat = self.parse_top_pat(GateOr::Yes)?;
1301 if !self.eat_keyword(kw::In) {
1302 let in_span = self.prev_span.between(self.token.span);
1303 self.struct_span_err(in_span, "missing `in` in `for` loop")
1304 .span_suggestion_short(
1306 "try adding `in` here", " in ".into(),
1307 // has been misleading, at least in the past (closed Issue #48492)
1308 Applicability::MaybeIncorrect
1312 let in_span = self.prev_span;
1313 self.check_for_for_in_in_typo(in_span);
1314 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
1316 let pat = self.recover_parens_around_for_head(pat, &expr, begin_paren);
1318 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
1319 attrs.extend(iattrs);
1321 let hi = self.prev_span;
1322 Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs))
1325 /// Parses a `while` or `while let` expression (`while` token already eaten).
1326 fn parse_while_expr(
1328 opt_label: Option<Label>,
1330 mut attrs: ThinVec<Attribute>
1331 ) -> PResult<'a, P<Expr>> {
1332 let cond = self.parse_cond_expr()?;
1333 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1334 attrs.extend(iattrs);
1335 let span = span_lo.to(body.span);
1336 Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs))
1339 /// Parses `loop { ... }` (`loop` token already eaten).
1342 opt_label: Option<Label>,
1344 mut attrs: ThinVec<Attribute>
1345 ) -> PResult<'a, P<Expr>> {
1346 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1347 attrs.extend(iattrs);
1348 let span = span_lo.to(body.span);
1349 Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
1352 fn eat_label(&mut self) -> Option<Label> {
1353 if let Some(ident) = self.token.lifetime() {
1354 let span = self.token.span;
1356 Some(Label { ident: Ident::new(ident.name, span) })
1362 /// Parses a `match ... { ... }` expression (`match` token already eaten).
1363 fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
1364 let match_span = self.prev_span;
1365 let lo = self.prev_span;
1366 let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
1367 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
1368 if self.token == token::Semi {
1369 e.span_suggestion_short(
1371 "try removing this `match`",
1373 Applicability::MaybeIncorrect // speculative
1378 attrs.extend(self.parse_inner_attributes()?);
1380 let mut arms: Vec<Arm> = Vec::new();
1381 while self.token != token::CloseDelim(token::Brace) {
1382 match self.parse_arm() {
1383 Ok(arm) => arms.push(arm),
1385 // Recover by skipping to the end of the block.
1387 self.recover_stmt();
1388 let span = lo.to(self.token.span);
1389 if self.token == token::CloseDelim(token::Brace) {
1392 return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
1396 let hi = self.token.span;
1398 return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
1401 crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
1402 let attrs = self.parse_outer_attributes()?;
1403 let lo = self.token.span;
1404 let pat = self.parse_top_pat(GateOr::No)?;
1405 let guard = if self.eat_keyword(kw::If) {
1406 Some(self.parse_expr()?)
1410 let arrow_span = self.token.span;
1411 self.expect(&token::FatArrow)?;
1412 let arm_start_span = self.token.span;
1414 let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
1415 .map_err(|mut err| {
1416 err.span_label(arrow_span, "while parsing the `match` arm starting here");
1420 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
1421 && self.token != token::CloseDelim(token::Brace);
1423 let hi = self.token.span;
1426 let cm = self.sess.source_map();
1427 self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])
1428 .map_err(|mut err| {
1429 match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
1430 (Ok(ref expr_lines), Ok(ref arm_start_lines))
1431 if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
1432 && expr_lines.lines.len() == 2
1433 && self.token == token::FatArrow => {
1434 // We check whether there's any trailing code in the parse span,
1435 // if there isn't, we very likely have the following:
1438 // | -- - missing comma
1442 // | - ^^ self.token.span
1444 // | parsed until here as `"y" & X`
1445 err.span_suggestion_short(
1446 cm.next_point(arm_start_span),
1447 "missing a comma here to end this `match` arm",
1449 Applicability::MachineApplicable
1453 err.span_label(arrow_span,
1454 "while parsing the `match` arm starting here");
1460 self.eat(&token::Comma);
1470 is_placeholder: false,
1474 /// Parses a `try {...}` expression (`try` token already eaten).
1478 mut attrs: ThinVec<Attribute>
1479 ) -> PResult<'a, P<Expr>> {
1480 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1481 attrs.extend(iattrs);
1482 if self.eat_keyword(kw::Catch) {
1483 let mut error = self.struct_span_err(self.prev_span,
1484 "keyword `catch` cannot follow a `try` block");
1485 error.help("try using `match` on the result of the `try` block instead");
1489 Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
1493 fn is_do_catch_block(&self) -> bool {
1494 self.token.is_keyword(kw::Do) &&
1495 self.is_keyword_ahead(1, &[kw::Catch]) &&
1496 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
1497 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1500 fn is_try_block(&self) -> bool {
1501 self.token.is_keyword(kw::Try) &&
1502 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
1503 self.token.span.rust_2018() &&
1504 // Prevent `while try {} {}`, `if try {} {} else {}`, etc.
1505 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1508 /// Parses an `async move? {...}` expression.
1509 pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
1510 let span_lo = self.token.span;
1511 self.expect_keyword(kw::Async)?;
1512 let capture_clause = self.parse_capture_clause();
1513 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1514 attrs.extend(iattrs);
1516 span_lo.to(body.span),
1517 ExprKind::Async(capture_clause, DUMMY_NODE_ID, body), attrs))
1520 fn is_async_block(&self) -> bool {
1521 self.token.is_keyword(kw::Async) &&
1524 self.is_keyword_ahead(1, &[kw::Move]) &&
1525 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
1527 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
1532 fn maybe_parse_struct_expr(
1536 attrs: &ThinVec<Attribute>,
1537 ) -> Option<PResult<'a, P<Expr>>> {
1538 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
1539 let certainly_not_a_block = || self.look_ahead(1, |t| t.is_ident()) && (
1540 // `{ ident, ` cannot start a block.
1541 self.look_ahead(2, |t| t == &token::Comma) ||
1542 self.look_ahead(2, |t| t == &token::Colon) && (
1543 // `{ ident: token, ` cannot start a block.
1544 self.look_ahead(4, |t| t == &token::Comma) ||
1545 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
1546 self.look_ahead(3, |t| !t.can_begin_type())
1550 if struct_allowed || certainly_not_a_block() {
1551 // This is a struct literal, but we don't can't accept them here.
1552 let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
1553 if let (Ok(expr), false) = (&expr, struct_allowed) {
1554 self.struct_span_err(
1556 "struct literals are not allowed here",
1558 .multipart_suggestion(
1559 "surround the struct literal with parentheses",
1561 (lo.shrink_to_lo(), "(".to_string()),
1562 (expr.span.shrink_to_hi(), ")".to_string()),
1564 Applicability::MachineApplicable,
1573 pub(super) fn parse_struct_expr(
1577 mut attrs: ThinVec<Attribute>
1578 ) -> PResult<'a, P<Expr>> {
1579 let struct_sp = lo.to(self.prev_span);
1581 let mut fields = Vec::new();
1582 let mut base = None;
1584 attrs.extend(self.parse_inner_attributes()?);
1586 while self.token != token::CloseDelim(token::Brace) {
1587 if self.eat(&token::DotDot) {
1588 let exp_span = self.prev_span;
1589 match self.parse_expr() {
1595 self.recover_stmt();
1598 if self.token == token::Comma {
1599 self.struct_span_err(
1600 exp_span.to(self.prev_span),
1601 "cannot use a comma after the base struct",
1603 .span_suggestion_short(
1605 "remove this comma",
1607 Applicability::MachineApplicable
1609 .note("the base struct must always be the last field")
1611 self.recover_stmt();
1616 let mut recovery_field = None;
1617 if let token::Ident(name, _) = self.token.kind {
1618 if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
1619 // Use in case of error after field-looking code: `S { foo: () with a }`.
1620 recovery_field = Some(ast::Field {
1621 ident: Ident::new(name, self.token.span),
1622 span: self.token.span,
1623 expr: self.mk_expr(self.token.span, ExprKind::Err, ThinVec::new()),
1624 is_shorthand: false,
1625 attrs: ThinVec::new(),
1627 is_placeholder: false,
1631 let mut parsed_field = None;
1632 match self.parse_field() {
1633 Ok(f) => parsed_field = Some(f),
1635 e.span_label(struct_sp, "while parsing this struct");
1638 // If the next token is a comma, then try to parse
1639 // what comes next as additional fields, rather than
1640 // bailing out until next `}`.
1641 if self.token != token::Comma {
1642 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
1643 if self.token != token::Comma {
1650 match self.expect_one_of(&[token::Comma],
1651 &[token::CloseDelim(token::Brace)]) {
1652 Ok(_) => if let Some(f) = parsed_field.or(recovery_field) {
1653 // Only include the field if there's no parse error for the field name.
1657 if let Some(f) = recovery_field {
1660 e.span_label(struct_sp, "while parsing this struct");
1662 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
1663 self.eat(&token::Comma);
1668 let span = lo.to(self.token.span);
1669 self.expect(&token::CloseDelim(token::Brace))?;
1670 return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
1673 /// Parses `ident (COLON expr)?`.
1674 fn parse_field(&mut self) -> PResult<'a, Field> {
1675 let attrs = self.parse_outer_attributes()?;
1676 let lo = self.token.span;
1678 // Check if a colon exists one ahead. This means we're parsing a fieldname.
1679 let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| {
1680 t == &token::Colon || t == &token::Eq
1682 let fieldname = self.parse_field_name()?;
1684 // Check for an equals token. This means the source incorrectly attempts to
1685 // initialize a field with an eq rather than a colon.
1686 if self.token == token::Eq {
1688 .struct_span_err(self.token.span, "expected `:`, found `=`")
1690 fieldname.span.shrink_to_hi().to(self.token.span),
1691 "replace equals symbol with a colon",
1693 Applicability::MachineApplicable,
1698 (fieldname, self.parse_expr()?, false)
1700 let fieldname = self.parse_ident_common(false)?;
1702 // Mimic `x: x` for the `x` field shorthand.
1703 let path = ast::Path::from_ident(fieldname);
1704 let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new());
1705 (fieldname, expr, true)
1709 span: lo.to(expr.span),
1712 attrs: attrs.into(),
1714 is_placeholder: false,
1718 fn err_dotdotdot_syntax(&self, span: Span) {
1719 self.struct_span_err(span, "unexpected token: `...`")
1722 "use `..` for an exclusive range", "..".to_owned(),
1723 Applicability::MaybeIncorrect
1727 "or `..=` for an inclusive range", "..=".to_owned(),
1728 Applicability::MaybeIncorrect
1733 fn err_larrow_operator(&self, span: Span) {
1734 self.struct_span_err(
1736 "unexpected token: `<-`"
1739 "if you meant to write a comparison against a negative value, add a \
1740 space in between `<` and `-`",
1742 Applicability::MaybeIncorrect
1746 fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
1747 ExprKind::AssignOp(binop, lhs, rhs)
1752 start: Option<P<Expr>>,
1753 end: Option<P<Expr>>,
1755 ) -> PResult<'a, ExprKind> {
1756 if end.is_none() && limits == RangeLimits::Closed {
1757 Err(self.span_fatal_err(self.token.span, Error::InclusiveRangeWithNoEnd))
1759 Ok(ExprKind::Range(start, end, limits))
1763 fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
1764 ExprKind::Unary(unop, expr)
1767 fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
1768 ExprKind::Binary(binop, lhs, rhs)
1771 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
1772 ExprKind::Index(expr, idx)
1775 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
1776 ExprKind::Call(f, args)
1779 fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
1780 let span = lo.to(self.prev_span);
1781 let await_expr = self.mk_expr(span, ExprKind::Await(self_arg), ThinVec::new());
1782 self.recover_from_await_method_call();
1786 crate fn mk_expr(&self, span: Span, kind: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
1787 P(Expr { kind, span, attrs, id: DUMMY_NODE_ID })