1 use super::pat::{GateOr, PARAM_EXPECTED};
2 use super::{BlockMode, Parser, PathStyle, PrevTokenKind, Restrictions, TokenType};
3 use super::{SemiColonMode, SeqSep, TokenExpectType};
4 use crate::maybe_recover_from_interpolated_ty_qpath;
6 use rustc_errors::{Applicability, PResult};
7 use rustc_span::source_map::{self, Span, Spanned};
8 use rustc_span::symbol::{kw, sym, Symbol};
10 use syntax::ast::{self, AttrStyle, AttrVec, CaptureBy, Field, Ident, Lit, DUMMY_NODE_ID};
12 AnonConst, BinOp, BinOpKind, FnDecl, FunctionRetTy, Mac, Param, Ty, TyKind, UnOp,
14 use syntax::ast::{Arm, BlockCheckMode, Expr, ExprKind, IsAsync, Label, Movability, RangeLimits};
15 use syntax::print::pprust;
17 use syntax::token::{self, Token, TokenKind};
18 use syntax::util::classify;
19 use syntax::util::literal::LitError;
20 use syntax::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
22 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
23 /// dropped into the token stream, which happens while parsing the result of
24 /// macro expansion). Placement of these is not as complex as I feared it would
25 /// be. The important thing is to make sure that lookahead doesn't balk at
26 /// `token::Interpolated` tokens.
27 macro_rules! maybe_whole_expr {
29 if let token::Interpolated(nt) = &$p.token.kind {
31 token::NtExpr(e) | token::NtLiteral(e) => {
36 token::NtPath(path) => {
37 let path = path.clone();
41 ExprKind::Path(None, path),
45 token::NtBlock(block) => {
46 let block = block.clone();
50 ExprKind::Block(block, None),
54 // N.B., `NtIdent(ident)` is normalized to `Ident` in `fn bump`.
62 pub(super) enum LhsExpr {
64 AttributesParsed(AttrVec),
65 AlreadyParsed(P<Expr>),
68 impl From<Option<AttrVec>> 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<AttrVec>) -> Self {
74 if let Some(attrs) = o { LhsExpr::AttributesParsed(attrs) } else { LhsExpr::NotYetParsed }
78 impl From<P<Expr>> for LhsExpr {
79 /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed(expr)`.
81 /// This conversion does not allocate.
82 fn from(expr: P<Expr>) -> Self {
83 LhsExpr::AlreadyParsed(expr)
88 /// Parses an expression.
90 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
91 self.parse_expr_res(Restrictions::empty(), None)
94 pub(super) fn parse_anon_const_expr(&mut self) -> PResult<'a, AnonConst> {
95 self.parse_expr().map(|value| AnonConst { id: DUMMY_NODE_ID, value })
98 fn parse_expr_catch_underscore(&mut self) -> PResult<'a, P<Expr>> {
99 match self.parse_expr() {
100 Ok(expr) => Ok(expr),
101 Err(mut err) => match self.token.kind {
102 token::Ident(name, false)
103 if name == kw::Underscore && self.look_ahead(1, |t| t == &token::Comma) =>
105 // Special-case handling of `foo(_, _, _)`
107 let sp = self.token.span;
109 Ok(self.mk_expr(sp, ExprKind::Err, AttrVec::new()))
116 /// Parses a sequence of expressions delimited by parentheses.
117 fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
118 self.parse_paren_comma_seq(|p| p.parse_expr_catch_underscore()).map(|(r, _)| r)
121 /// Parses an expression, subject to the given restrictions.
123 pub(super) fn parse_expr_res(
126 already_parsed_attrs: Option<AttrVec>,
127 ) -> PResult<'a, P<Expr>> {
128 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
131 /// Parses an associative expression.
133 /// This parses an expression accounting for associativity and precedence of the operators in
136 fn parse_assoc_expr(&mut self, already_parsed_attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
137 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
140 /// Parses an associative expression with operators of at least `min_prec` precedence.
141 pub(super) fn parse_assoc_expr_with(
145 ) -> PResult<'a, P<Expr>> {
146 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
149 let attrs = match lhs {
150 LhsExpr::AttributesParsed(attrs) => Some(attrs),
153 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind) {
154 return self.parse_prefix_range_expr(attrs);
156 self.parse_prefix_expr(attrs)?
159 let last_type_ascription_set = self.last_type_ascription.is_some();
161 if !self.should_continue_as_assoc_expr(&lhs) {
162 self.last_type_ascription = None;
166 self.expected_tokens.push(TokenType::Operator);
167 while let Some(op) = self.check_assoc_op() {
168 // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
169 // it refers to. Interpolated identifiers are unwrapped early and never show up here
170 // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
171 // it as "interpolated", it doesn't change the answer for non-interpolated idents.
172 let lhs_span = match (self.prev_token_kind, &lhs.kind) {
173 (PrevTokenKind::Interpolated, _) => self.prev_span,
174 (PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
175 if path.segments.len() == 1 =>
182 let cur_op_span = self.token.span;
183 let restrictions = if op.node.is_assign_like() {
184 self.restrictions & Restrictions::NO_STRUCT_LITERAL
188 let prec = op.node.precedence();
192 // Check for deprecated `...` syntax
193 if self.token == token::DotDotDot && op.node == AssocOp::DotDotEq {
194 self.err_dotdotdot_syntax(self.token.span);
197 if self.token == token::LArrow {
198 self.err_larrow_operator(self.token.span);
202 if op.node.is_comparison() {
203 if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
209 if op == AssocOp::As {
210 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
212 } else if op == AssocOp::Colon {
213 lhs = self.parse_assoc_op_ascribe(lhs, lhs_span)?;
215 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
216 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
217 // generalise it to the Fixity::None code.
218 lhs = self.parse_range_expr(prec, lhs, op, cur_op_span)?;
222 let fixity = op.fixity();
223 let prec_adjustment = match fixity {
226 // We currently have no non-associative operators that are not handled above by
227 // the special cases. The code is here only for future convenience.
230 let rhs = self.with_res(restrictions - Restrictions::STMT_EXPR, |this| {
231 this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
234 // Make sure that the span of the parent node is larger than the span of lhs and rhs,
235 // including the attributes.
239 .filter(|a| a.style == AttrStyle::Outer)
241 .map_or(lhs_span, |a| a.span);
242 let span = lhs_span.to(rhs.span);
255 | AssocOp::ShiftRight
261 | AssocOp::GreaterEqual => {
262 let ast_op = op.to_ast_binop().unwrap();
263 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
264 self.mk_expr(span, binary, AttrVec::new())
267 self.mk_expr(span, ExprKind::Assign(lhs, rhs, cur_op_span), AttrVec::new())
269 AssocOp::AssignOp(k) => {
271 token::Plus => BinOpKind::Add,
272 token::Minus => BinOpKind::Sub,
273 token::Star => BinOpKind::Mul,
274 token::Slash => BinOpKind::Div,
275 token::Percent => BinOpKind::Rem,
276 token::Caret => BinOpKind::BitXor,
277 token::And => BinOpKind::BitAnd,
278 token::Or => BinOpKind::BitOr,
279 token::Shl => BinOpKind::Shl,
280 token::Shr => BinOpKind::Shr,
282 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
283 self.mk_expr(span, aopexpr, AttrVec::new())
285 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
286 self.span_bug(span, "AssocOp should have been handled by special case")
290 if let Fixity::None = fixity {
294 if last_type_ascription_set {
295 self.last_type_ascription = None;
300 fn should_continue_as_assoc_expr(&mut self, lhs: &Expr) -> bool {
301 match (self.expr_is_complete(lhs), self.check_assoc_op().map(|op| op.node)) {
302 // Semi-statement forms are odd:
303 // See https://github.com/rust-lang/rust/issues/29071
304 (true, None) => false,
305 (false, _) => true, // Continue parsing the expression.
306 // An exhaustive check is done in the following block, but these are checked first
307 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
308 // want to keep their span info to improve diagnostics in these cases in a later stage.
309 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
310 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
311 (true, Some(AssocOp::LAnd)) | // `{ 42 } &&x` (#61475)
312 (true, Some(AssocOp::Add)) // `{ 42 } + 42
313 // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
314 // `if x { a } else { b } && if y { c } else { d }`
315 if !self.look_ahead(1, |t| t.is_reserved_ident()) => {
316 // These cases are ambiguous and can't be identified in the parser alone.
317 let sp = self.sess.source_map().start_point(self.token.span);
318 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
321 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => false,
323 self.error_found_expr_would_be_stmt(lhs);
329 /// We've found an expression that would be parsed as a statement,
330 /// but the next token implies this should be parsed as an expression.
331 /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
332 fn error_found_expr_would_be_stmt(&self, lhs: &Expr) {
333 let mut err = self.struct_span_err(
335 &format!("expected expression, found `{}`", pprust::token_to_string(&self.token),),
337 err.span_label(self.token.span, "expected expression");
338 self.sess.expr_parentheses_needed(&mut err, lhs.span, Some(pprust::expr_to_string(&lhs)));
342 /// Possibly translate the current token to an associative operator.
343 /// The method does not advance the current token.
345 /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
346 fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
348 node: match (AssocOp::from_token(&self.token), &self.token.kind) {
350 (None, token::Ident(sym::and, false)) => {
351 self.error_bad_logical_op("and", "&&", "conjunction");
354 (None, token::Ident(sym::or, false)) => {
355 self.error_bad_logical_op("or", "||", "disjunction");
360 span: self.token.span,
364 /// Error on `and` and `or` suggesting `&&` and `||` respectively.
365 fn error_bad_logical_op(&self, bad: &str, good: &str, english: &str) {
366 self.struct_span_err(self.token.span, &format!("`{}` is not a logical operator", bad))
367 .span_suggestion_short(
369 &format!("use `{}` to perform logical {}", good, english),
371 Applicability::MachineApplicable,
373 .note("unlike in e.g., python and PHP, `&&` and `||` are used for logical operators")
377 /// Checks if this expression is a successfully parsed statement.
378 fn expr_is_complete(&self, e: &Expr) -> bool {
379 self.restrictions.contains(Restrictions::STMT_EXPR)
380 && !classify::expr_requires_semi_to_be_stmt(e)
383 /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
384 /// The other two variants are handled in `parse_prefix_range_expr` below.
391 ) -> PResult<'a, P<Expr>> {
392 let rhs = if self.is_at_start_of_range_notation_rhs() {
393 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
397 let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
398 let span = lhs.span.to(rhs_span);
400 if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
401 Ok(self.mk_expr(span, self.mk_range(Some(lhs), rhs, limits)?, AttrVec::new()))
404 fn is_at_start_of_range_notation_rhs(&self) -> bool {
405 if self.token.can_begin_expr() {
406 // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
407 if self.token == token::OpenDelim(token::Brace) {
408 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
416 /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
417 fn parse_prefix_range_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
418 // Check for deprecated `...` syntax.
419 if self.token == token::DotDotDot {
420 self.err_dotdotdot_syntax(self.token.span);
424 [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind),
425 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
429 let limits = match self.token.kind {
430 token::DotDot => RangeLimits::HalfOpen,
431 _ => RangeLimits::Closed,
433 let op = AssocOp::from_token(&self.token);
434 let attrs = self.parse_or_use_outer_attributes(attrs)?;
435 let lo = self.token.span;
437 let (span, opt_end) = if self.is_at_start_of_range_notation_rhs() {
438 // RHS must be parsed with more associativity than the dots.
439 self.parse_assoc_expr_with(op.unwrap().precedence() + 1, LhsExpr::NotYetParsed)
440 .map(|x| (lo.to(x.span), Some(x)))?
444 Ok(self.mk_expr(span, self.mk_range(None, opt_end, limits)?, attrs))
447 /// Parses a prefix-unary-operator expr.
448 fn parse_prefix_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
449 let attrs = self.parse_or_use_outer_attributes(attrs)?;
450 let lo = self.token.span;
451 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
452 let (hi, ex) = match self.token.kind {
453 token::Not => self.parse_unary_expr(lo, UnOp::Not), // `!expr`
454 token::Tilde => self.recover_tilde_expr(lo), // `~expr`
455 token::BinOp(token::Minus) => self.parse_unary_expr(lo, UnOp::Neg), // `-expr`
456 token::BinOp(token::Star) => self.parse_unary_expr(lo, UnOp::Deref), // `*expr`
457 token::BinOp(token::And) | token::AndAnd => self.parse_borrow_expr(lo),
458 token::Ident(..) if self.token.is_keyword(kw::Box) => self.parse_box_expr(lo),
459 token::Ident(..) if self.is_mistaken_not_ident_negation() => self.recover_not_expr(lo),
460 _ => return self.parse_dot_or_call_expr(Some(attrs)),
462 Ok(self.mk_expr(lo.to(hi), ex, attrs))
465 fn parse_prefix_expr_common(&mut self, lo: Span) -> PResult<'a, (Span, P<Expr>)> {
467 let expr = self.parse_prefix_expr(None);
468 let (span, expr) = self.interpolated_or_expr_span(expr)?;
469 Ok((lo.to(span), expr))
472 fn parse_unary_expr(&mut self, lo: Span, op: UnOp) -> PResult<'a, (Span, ExprKind)> {
473 let (span, expr) = self.parse_prefix_expr_common(lo)?;
474 Ok((span, self.mk_unary(op, expr)))
477 // Recover on `!` suggesting for bitwise negation instead.
478 fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
479 self.struct_span_err(lo, "`~` cannot be used as a unary operator")
480 .span_suggestion_short(
482 "use `!` to perform bitwise not",
484 Applicability::MachineApplicable,
488 self.parse_unary_expr(lo, UnOp::Not)
491 /// Parse `box expr`.
492 fn parse_box_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
493 let (span, expr) = self.parse_prefix_expr_common(lo)?;
494 self.sess.gated_spans.gate(sym::box_syntax, span);
495 Ok((span, ExprKind::Box(expr)))
498 fn is_mistaken_not_ident_negation(&self) -> bool {
499 let token_cannot_continue_expr = |t: &Token| match t.kind {
500 // These tokens can start an expression after `!`, but
501 // can't continue an expression after an ident
502 token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
503 token::Literal(..) | token::Pound => true,
504 _ => t.is_whole_expr(),
506 self.token.is_ident_named(sym::not) && self.look_ahead(1, token_cannot_continue_expr)
509 /// Recover on `not expr` in favor of `!expr`.
510 fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
512 let not_token = self.look_ahead(1, |t| t.clone());
513 self.struct_span_err(
515 &format!("unexpected {} after identifier", super::token_descr(¬_token)),
517 .span_suggestion_short(
518 // Span the `not` plus trailing whitespace to avoid
519 // trailing whitespace after the `!` in our suggestion
520 self.sess.source_map().span_until_non_whitespace(lo.to(not_token.span)),
521 "use `!` to perform logical negation",
523 Applicability::MachineApplicable,
528 self.parse_unary_expr(lo, UnOp::Not)
531 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
532 fn interpolated_or_expr_span(
534 expr: PResult<'a, P<Expr>>,
535 ) -> PResult<'a, (Span, P<Expr>)> {
537 if self.prev_token_kind == PrevTokenKind::Interpolated {
545 fn parse_assoc_op_cast(
549 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
550 ) -> PResult<'a, P<Expr>> {
551 let mk_expr = |this: &mut Self, rhs: P<Ty>| {
552 this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), AttrVec::new())
555 // Save the state of the parser before parsing type normally, in case there is a
556 // LessThan comparison after this cast.
557 let parser_snapshot_before_type = self.clone();
558 match self.parse_ty_no_plus() {
559 Ok(rhs) => Ok(mk_expr(self, rhs)),
560 Err(mut type_err) => {
561 // Rewind to before attempting to parse the type with generics, to recover
562 // from situations like `x as usize < y` in which we first tried to parse
563 // `usize < y` as a type with generic arguments.
564 let parser_snapshot_after_type = self.clone();
565 mem::replace(self, parser_snapshot_before_type);
567 match self.parse_path(PathStyle::Expr) {
569 let (op_noun, op_verb) = match self.token.kind {
570 token::Lt => ("comparison", "comparing"),
571 token::BinOp(token::Shl) => ("shift", "shifting"),
573 // We can end up here even without `<` being the next token, for
574 // example because `parse_ty_no_plus` returns `Err` on keywords,
575 // but `parse_path` returns `Ok` on them due to error recovery.
576 // Return original error and parser state.
577 mem::replace(self, parser_snapshot_after_type);
578 return Err(type_err);
582 // Successfully parsed the type path leaving a `<` yet to parse.
585 // Report non-fatal diagnostics, keep `x as usize` as an expression
586 // in AST and continue parsing.
588 "`<` is interpreted as a start of generic arguments for `{}`, not a {}",
589 pprust::path_to_string(&path),
592 let span_after_type = parser_snapshot_after_type.token.span;
593 let expr = mk_expr(self, self.mk_ty(path.span, TyKind::Path(None, path)));
596 .span_to_snippet(expr.span)
597 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
599 self.struct_span_err(self.token.span, &msg)
601 self.look_ahead(1, |t| t.span).to(span_after_type),
602 "interpreted as generic arguments",
604 .span_label(self.token.span, format!("not interpreted as {}", op_noun))
607 &format!("try {} the cast value", op_verb),
608 format!("({})", expr_str),
609 Applicability::MachineApplicable,
615 Err(mut path_err) => {
616 // Couldn't parse as a path, return original error and parser state.
618 mem::replace(self, parser_snapshot_after_type);
626 fn parse_assoc_op_ascribe(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
627 let maybe_path = self.could_ascription_be_path(&lhs.kind);
628 self.last_type_ascription = Some((self.prev_span, maybe_path));
629 let lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
630 self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
634 /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
635 fn parse_borrow_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
637 let (borrow_kind, mutbl) = self.parse_borrow_modifiers(lo);
638 let expr = self.parse_prefix_expr(None);
639 let (span, expr) = self.interpolated_or_expr_span(expr)?;
640 Ok((lo.to(span), ExprKind::AddrOf(borrow_kind, mutbl, expr)))
643 /// Parse `mut?` or `raw [ const | mut ]`.
644 fn parse_borrow_modifiers(&mut self, lo: Span) -> (ast::BorrowKind, ast::Mutability) {
645 if self.check_keyword(kw::Raw) && self.look_ahead(1, Token::is_mutability) {
646 // `raw [ const | mut ]`.
647 let found_raw = self.eat_keyword(kw::Raw);
649 let mutability = self.parse_const_or_mut().unwrap();
650 self.sess.gated_spans.gate(sym::raw_ref_op, lo.to(self.prev_span));
651 (ast::BorrowKind::Raw, mutability)
654 (ast::BorrowKind::Ref, self.parse_mutability())
658 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
659 fn parse_dot_or_call_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
660 let attrs = self.parse_or_use_outer_attributes(attrs)?;
661 let base = self.parse_bottom_expr();
662 let (span, base) = self.interpolated_or_expr_span(base)?;
663 self.parse_dot_or_call_expr_with(base, span, attrs)
666 pub(super) fn parse_dot_or_call_expr_with(
671 ) -> PResult<'a, P<Expr>> {
672 // Stitch the list of outer attributes onto the return value.
673 // A little bit ugly, but the best way given the current code
675 self.parse_dot_or_call_expr_with_(e0, lo).map(|expr| {
676 expr.map(|mut expr| {
677 attrs.extend::<Vec<_>>(expr.attrs.into());
679 self.error_attr_on_if_expr(&expr);
685 fn error_attr_on_if_expr(&self, expr: &Expr) {
686 if let (ExprKind::If(..), [a0, ..]) = (&expr.kind, &*expr.attrs) {
687 // Just point to the first attribute in there...
688 self.struct_span_err(a0.span, "attributes are not yet allowed on `if` expressions")
693 fn parse_dot_or_call_expr_with_(&mut self, mut e: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
695 if self.eat(&token::Question) {
697 e = self.mk_expr(lo.to(self.prev_span), ExprKind::Try(e), AttrVec::new());
700 if self.eat(&token::Dot) {
702 e = self.parse_dot_suffix_expr(lo, e)?;
705 if self.expr_is_complete(&e) {
708 e = match self.token.kind {
709 token::OpenDelim(token::Paren) => self.parse_fn_call_expr(lo, e),
710 token::OpenDelim(token::Bracket) => self.parse_index_expr(lo, e)?,
716 fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
717 match self.token.kind {
718 token::Ident(..) => self.parse_dot_suffix(base, lo),
719 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
720 Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix))
722 token::Literal(token::Lit { kind: token::Float, symbol, .. }) => {
723 self.recover_field_access_by_float_lit(lo, base, symbol)
726 self.error_unexpected_after_dot();
732 fn error_unexpected_after_dot(&self) {
733 // FIXME Could factor this out into non_fatal_unexpected or something.
734 let actual = pprust::token_to_string(&self.token);
735 self.struct_span_err(self.token.span, &format!("unexpected token: `{}`", actual)).emit();
738 fn recover_field_access_by_float_lit(
743 ) -> PResult<'a, P<Expr>> {
746 let fstr = sym.as_str();
747 let msg = format!("unexpected token: `{}`", sym);
749 let mut err = self.struct_span_err(self.prev_span, &msg);
750 err.span_label(self.prev_span, "unexpected token");
752 if fstr.chars().all(|x| "0123456789.".contains(x)) {
753 let float = match fstr.parse::<f64>() {
760 let sugg = pprust::to_string(|s| {
764 s.print_usize(float.trunc() as usize);
767 s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
770 lo.to(self.prev_span),
771 "try parenthesizing the first index",
773 Applicability::MachineApplicable,
779 fn parse_tuple_field_access_expr(
784 suffix: Option<Symbol>,
786 let span = self.token.span;
788 let field = ExprKind::Field(base, Ident::new(field, span));
789 self.expect_no_suffix(span, "a tuple index", suffix);
790 self.mk_expr(lo.to(span), field, AttrVec::new())
793 /// Parse a function call expression, `expr(...)`.
794 fn parse_fn_call_expr(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
795 let seq = self.parse_paren_expr_seq().map(|args| {
796 self.mk_expr(lo.to(self.prev_span), self.mk_call(fun, args), AttrVec::new())
798 self.recover_seq_parse_error(token::Paren, lo, seq)
801 /// Parse an indexing expression `expr[...]`.
802 fn parse_index_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
804 let index = self.parse_expr()?;
805 self.expect(&token::CloseDelim(token::Bracket))?;
806 Ok(self.mk_expr(lo.to(self.prev_span), self.mk_index(base, index), AttrVec::new()))
809 /// Assuming we have just parsed `.`, continue parsing into an expression.
810 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
811 if self.token.span.rust_2018() && self.eat_keyword(kw::Await) {
812 return self.mk_await_expr(self_arg, lo);
815 let segment = self.parse_path_segment(PathStyle::Expr)?;
816 self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
818 if self.check(&token::OpenDelim(token::Paren)) {
819 // Method call `expr.f()`
820 let mut args = self.parse_paren_expr_seq()?;
821 args.insert(0, self_arg);
823 let span = lo.to(self.prev_span);
824 Ok(self.mk_expr(span, ExprKind::MethodCall(segment, args), AttrVec::new()))
826 // Field access `expr.f`
827 if let Some(args) = segment.args {
828 self.struct_span_err(
830 "field expressions may not have generic arguments",
835 let span = lo.to(self.prev_span);
836 Ok(self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), AttrVec::new()))
840 /// At the bottom (top?) of the precedence hierarchy,
841 /// Parses things like parenthesized exprs, macros, `return`, etc.
843 /// N.B., this does not parse outer attributes, and is private because it only works
844 /// correctly if called from `parse_dot_or_call_expr()`.
845 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
846 maybe_recover_from_interpolated_ty_qpath!(self, true);
847 maybe_whole_expr!(self);
849 // Outer attributes are already parsed and will be
850 // added to the return value after the fact.
852 // Therefore, prevent sub-parser from parsing
853 // attributes by giving them a empty "already-parsed" list.
854 let attrs = AttrVec::new();
856 // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
857 let lo = self.token.span;
858 if let token::Literal(_) = self.token.kind {
859 // This match arm is a special-case of the `_` match arm below and
860 // could be removed without changing functionality, but it's faster
861 // to have it here, especially for programs with large constants.
862 self.parse_lit_expr(attrs)
863 } else if self.check(&token::OpenDelim(token::Paren)) {
864 self.parse_tuple_parens_expr(attrs)
865 } else if self.check(&token::OpenDelim(token::Brace)) {
866 self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs)
867 } else if self.check(&token::BinOp(token::Or)) || self.check(&token::OrOr) {
868 self.parse_closure_expr(attrs)
869 } else if self.check(&token::OpenDelim(token::Bracket)) {
870 self.parse_array_or_repeat_expr(attrs)
871 } else if self.eat_lt() {
872 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
873 Ok(self.mk_expr(lo.to(path.span), ExprKind::Path(Some(qself), path), attrs))
874 } else if self.token.is_path_start() {
875 self.parse_path_start_expr(attrs)
876 } else if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
877 self.parse_closure_expr(attrs)
878 } else if self.eat_keyword(kw::If) {
879 self.parse_if_expr(attrs)
880 } else if self.eat_keyword(kw::For) {
881 self.parse_for_expr(None, self.prev_span, attrs)
882 } else if self.eat_keyword(kw::While) {
883 self.parse_while_expr(None, self.prev_span, attrs)
884 } else if let Some(label) = self.eat_label() {
885 self.parse_labeled_expr(label, attrs)
886 } else if self.eat_keyword(kw::Loop) {
887 self.parse_loop_expr(None, self.prev_span, attrs)
888 } else if self.eat_keyword(kw::Continue) {
889 let kind = ExprKind::Continue(self.eat_label());
890 Ok(self.mk_expr(lo.to(self.prev_span), kind, attrs))
891 } else if self.eat_keyword(kw::Match) {
892 let match_sp = self.prev_span;
893 self.parse_match_expr(attrs).map_err(|mut err| {
894 err.span_label(match_sp, "while parsing this match expression");
897 } else if self.eat_keyword(kw::Unsafe) {
898 self.parse_block_expr(None, lo, BlockCheckMode::Unsafe(ast::UserProvided), attrs)
899 } else if self.is_do_catch_block() {
900 self.recover_do_catch(attrs)
901 } else if self.is_try_block() {
902 self.expect_keyword(kw::Try)?;
903 self.parse_try_block(lo, attrs)
904 } else if self.eat_keyword(kw::Return) {
905 self.parse_return_expr(attrs)
906 } else if self.eat_keyword(kw::Break) {
907 self.parse_break_expr(attrs)
908 } else if self.eat_keyword(kw::Yield) {
909 self.parse_yield_expr(attrs)
910 } else if self.eat_keyword(kw::Let) {
911 self.parse_let_expr(attrs)
912 } else if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
913 // Don't complain about bare semicolons after unclosed braces
914 // recovery in order to keep the error count down. Fixing the
915 // delimiters will possibly also fix the bare semicolon found in
916 // expression context. For example, silence the following error:
918 // error: expected expression, found `;`
922 // | ^ expected expression
924 Ok(self.mk_expr_err(self.token.span))
925 } else if self.token.span.rust_2018() {
926 // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
927 if self.check_keyword(kw::Async) {
928 if self.is_async_block() {
929 // Check for `async {` and `async move {`.
930 self.parse_async_block(attrs)
932 self.parse_closure_expr(attrs)
934 } else if self.eat_keyword(kw::Await) {
935 self.recover_incorrect_await_syntax(lo, self.prev_span, attrs)
937 self.parse_lit_expr(attrs)
940 self.parse_lit_expr(attrs)
944 fn parse_lit_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
945 let lo = self.token.span;
946 match self.parse_opt_lit() {
948 let expr = self.mk_expr(lo.to(self.prev_span), ExprKind::Lit(literal), attrs);
949 self.maybe_recover_from_bad_qpath(expr, true)
951 None => return Err(self.expected_expression_found()),
955 fn parse_tuple_parens_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
956 let lo = self.token.span;
957 self.expect(&token::OpenDelim(token::Paren))?;
958 attrs.extend(self.parse_inner_attributes()?); // `(#![foo] a, b, ...)` is OK.
959 let (es, trailing_comma) = match self.parse_seq_to_end(
960 &token::CloseDelim(token::Paren),
961 SeqSep::trailing_allowed(token::Comma),
962 |p| p.parse_expr_catch_underscore(),
965 Err(err) => return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err))),
967 let kind = if es.len() == 1 && !trailing_comma {
968 // `(e)` is parenthesized `e`.
969 ExprKind::Paren(es.into_iter().nth(0).unwrap())
971 // `(e,)` is a tuple with only one field, `e`.
974 let expr = self.mk_expr(lo.to(self.prev_span), kind, attrs);
975 self.maybe_recover_from_bad_qpath(expr, true)
978 fn parse_array_or_repeat_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
979 let lo = self.token.span;
982 attrs.extend(self.parse_inner_attributes()?);
984 let close = &token::CloseDelim(token::Bracket);
985 let kind = if self.eat(close) {
987 ExprKind::Array(Vec::new())
990 let first_expr = self.parse_expr()?;
991 if self.eat(&token::Semi) {
992 // Repeating array syntax: `[ 0; 512 ]`
993 let count = self.parse_anon_const_expr()?;
995 ExprKind::Repeat(first_expr, count)
996 } else if self.eat(&token::Comma) {
997 // Vector with two or more elements.
998 let sep = SeqSep::trailing_allowed(token::Comma);
999 let (remaining_exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
1000 let mut exprs = vec![first_expr];
1001 exprs.extend(remaining_exprs);
1002 ExprKind::Array(exprs)
1004 // Vector with one element
1005 self.expect(close)?;
1006 ExprKind::Array(vec![first_expr])
1009 let expr = self.mk_expr(lo.to(self.prev_span), kind, attrs);
1010 self.maybe_recover_from_bad_qpath(expr, true)
1013 fn parse_path_start_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1014 let lo = self.token.span;
1015 let path = self.parse_path(PathStyle::Expr)?;
1017 // `!`, as an operator, is prefix, so we know this isn't that.
1018 let (hi, kind) = if self.eat(&token::Not) {
1019 // MACRO INVOCATION expression
1022 args: self.parse_mac_args()?,
1023 prior_type_ascription: self.last_type_ascription,
1025 (self.prev_span, ExprKind::Mac(mac))
1026 } else if self.check(&token::OpenDelim(token::Brace)) {
1027 if let Some(expr) = self.maybe_parse_struct_expr(lo, &path, &attrs) {
1030 (path.span, ExprKind::Path(None, path))
1033 (path.span, ExprKind::Path(None, path))
1036 let expr = self.mk_expr(lo.to(hi), kind, attrs);
1037 self.maybe_recover_from_bad_qpath(expr, true)
1040 fn parse_labeled_expr(&mut self, label: Label, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1041 let lo = label.ident.span;
1042 self.expect(&token::Colon)?;
1043 if self.eat_keyword(kw::While) {
1044 return self.parse_while_expr(Some(label), lo, attrs);
1046 if self.eat_keyword(kw::For) {
1047 return self.parse_for_expr(Some(label), lo, attrs);
1049 if self.eat_keyword(kw::Loop) {
1050 return self.parse_loop_expr(Some(label), lo, attrs);
1052 if self.token == token::OpenDelim(token::Brace) {
1053 return self.parse_block_expr(Some(label), lo, BlockCheckMode::Default, attrs);
1056 let msg = "expected `while`, `for`, `loop` or `{` after a label";
1057 self.struct_span_err(self.token.span, msg).span_label(self.token.span, msg).emit();
1058 // Continue as an expression in an effort to recover on `'label: non_block_expr`.
1062 /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
1063 fn recover_do_catch(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1064 let lo = self.token.span;
1066 self.bump(); // `do`
1067 self.bump(); // `catch`
1069 let span_dc = lo.to(self.prev_span);
1070 self.struct_span_err(span_dc, "found removed `do catch` syntax")
1073 "replace with the new syntax",
1075 Applicability::MachineApplicable,
1077 .note("following RFC #2388, the new non-placeholder syntax is `try`")
1080 self.parse_try_block(lo, attrs)
1083 /// Parse an expression if the token can begin one.
1084 fn parse_expr_opt(&mut self) -> PResult<'a, Option<P<Expr>>> {
1085 Ok(if self.token.can_begin_expr() { Some(self.parse_expr()?) } else { None })
1088 /// Parse `"return" expr?`.
1089 fn parse_return_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1090 let lo = self.prev_span;
1091 let kind = ExprKind::Ret(self.parse_expr_opt()?);
1092 let expr = self.mk_expr(lo.to(self.prev_span), kind, attrs);
1093 self.maybe_recover_from_bad_qpath(expr, true)
1096 /// Parse `"('label ":")? break expr?`.
1097 fn parse_break_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1098 let lo = self.prev_span;
1099 let label = self.eat_label();
1100 let kind = if self.token != token::OpenDelim(token::Brace)
1101 || !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1103 self.parse_expr_opt()?
1107 let expr = self.mk_expr(lo.to(self.prev_span), ExprKind::Break(label, kind), attrs);
1108 self.maybe_recover_from_bad_qpath(expr, true)
1111 /// Parse `"yield" expr?`.
1112 fn parse_yield_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1113 let lo = self.prev_span;
1114 let kind = ExprKind::Yield(self.parse_expr_opt()?);
1115 let span = lo.to(self.prev_span);
1116 self.sess.gated_spans.gate(sym::generators, span);
1117 let expr = self.mk_expr(span, kind, attrs);
1118 self.maybe_recover_from_bad_qpath(expr, true)
1121 /// Returns a string literal if the next token is a string literal.
1122 /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
1123 /// and returns `None` if the next token is not literal at all.
1124 pub fn parse_str_lit(&mut self) -> Result<ast::StrLit, Option<Lit>> {
1125 match self.parse_opt_lit() {
1126 Some(lit) => match lit.kind {
1127 ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
1129 symbol: lit.token.symbol,
1130 suffix: lit.token.suffix,
1134 _ => Err(Some(lit)),
1140 pub(super) fn parse_lit(&mut self) -> PResult<'a, Lit> {
1141 self.parse_opt_lit().ok_or_else(|| {
1142 let msg = format!("unexpected token: {}", super::token_descr(&self.token));
1143 self.struct_span_err(self.token.span, &msg)
1147 /// Matches `lit = true | false | token_lit`.
1148 /// Returns `None` if the next token is not a literal.
1149 pub(super) fn parse_opt_lit(&mut self) -> Option<Lit> {
1150 let mut recovered = None;
1151 if self.token == token::Dot {
1152 // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
1153 // dot would follow an optional literal, so we do this unconditionally.
1154 recovered = self.look_ahead(1, |next_token| {
1155 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
1158 if self.token.span.hi() == next_token.span.lo() {
1159 let s = String::from("0.") + &symbol.as_str();
1160 let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
1161 return Some(Token::new(kind, self.token.span.to(next_token.span)));
1166 if let Some(token) = &recovered {
1168 self.error_float_lits_must_have_int_part(&token);
1172 let token = recovered.as_ref().unwrap_or(&self.token);
1173 match Lit::from_token(token) {
1178 Err(LitError::NotLiteral) => None,
1180 let span = token.span;
1181 let lit = match token.kind {
1182 token::Literal(lit) => lit,
1183 _ => unreachable!(),
1186 self.report_lit_error(err, lit, span);
1187 // Pack possible quotes and prefixes from the original literal into
1188 // the error literal's symbol so they can be pretty-printed faithfully.
1189 let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
1190 let symbol = Symbol::intern(&suffixless_lit.to_string());
1191 let lit = token::Lit::new(token::Err, symbol, lit.suffix);
1192 Some(Lit::from_lit_token(lit, span).unwrap_or_else(|_| unreachable!()))
1197 fn error_float_lits_must_have_int_part(&self, token: &Token) {
1198 self.struct_span_err(token.span, "float literals must have an integer part")
1201 "must have an integer part",
1202 pprust::token_to_string(token),
1203 Applicability::MachineApplicable,
1208 fn report_lit_error(&self, err: LitError, lit: token::Lit, span: Span) {
1209 // Checks if `s` looks like i32 or u1234 etc.
1210 fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
1211 s.len() > 1 && s.starts_with(first_chars) && s[1..].chars().all(|c| c.is_ascii_digit())
1214 let token::Lit { kind, suffix, .. } = lit;
1216 // `NotLiteral` is not an error by itself, so we don't report
1217 // it and give the parser opportunity to try something else.
1218 LitError::NotLiteral => {}
1219 // `LexerError` *is* an error, but it was already reported
1220 // by lexer, so here we don't report it the second time.
1221 LitError::LexerError => {}
1222 LitError::InvalidSuffix => {
1223 self.expect_no_suffix(
1225 &format!("{} {} literal", kind.article(), kind.descr()),
1229 LitError::InvalidIntSuffix => {
1230 let suf = suffix.expect("suffix error with no suffix").as_str();
1231 if looks_like_width_suffix(&['i', 'u'], &suf) {
1232 // If it looks like a width, try to be helpful.
1233 let msg = format!("invalid width `{}` for integer literal", &suf[1..]);
1234 self.struct_span_err(span, &msg)
1235 .help("valid widths are 8, 16, 32, 64 and 128")
1238 let msg = format!("invalid suffix `{}` for integer literal", suf);
1239 self.struct_span_err(span, &msg)
1240 .span_label(span, format!("invalid suffix `{}`", suf))
1241 .help("the suffix must be one of the integral types (`u32`, `isize`, etc)")
1245 LitError::InvalidFloatSuffix => {
1246 let suf = suffix.expect("suffix error with no suffix").as_str();
1247 if looks_like_width_suffix(&['f'], &suf) {
1248 // If it looks like a width, try to be helpful.
1249 let msg = format!("invalid width `{}` for float literal", &suf[1..]);
1250 self.struct_span_err(span, &msg).help("valid widths are 32 and 64").emit();
1252 let msg = format!("invalid suffix `{}` for float literal", suf);
1253 self.struct_span_err(span, &msg)
1254 .span_label(span, format!("invalid suffix `{}`", suf))
1255 .help("valid suffixes are `f32` and `f64`")
1259 LitError::NonDecimalFloat(base) => {
1260 let descr = match base {
1261 16 => "hexadecimal",
1264 _ => unreachable!(),
1266 self.struct_span_err(span, &format!("{} float literal is not supported", descr))
1267 .span_label(span, "not supported")
1270 LitError::IntTooLarge => {
1271 self.struct_span_err(span, "integer literal is too large").emit();
1276 pub(super) fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<Symbol>) {
1277 if let Some(suf) = suffix {
1278 let mut err = if kind == "a tuple index"
1279 && [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suf)
1281 // #59553: warn instead of reject out of hand to allow the fix to percolate
1282 // through the ecosystem when people fix their macros
1286 .struct_span_warn(sp, &format!("suffixes on {} are invalid", kind));
1288 "`{}` is *temporarily* accepted on tuple index fields as it was \
1289 incorrectly accepted on stable for a few releases",
1293 "on proc macros, you'll want to use `syn::Index::from` or \
1294 `proc_macro::Literal::*_unsuffixed` for code that will desugar \
1295 to tuple field access",
1297 err.note("for more context, see https://github.com/rust-lang/rust/issues/60210");
1300 self.struct_span_err(sp, &format!("suffixes on {} are invalid", kind))
1302 err.span_label(sp, format!("invalid suffix `{}`", suf));
1307 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1308 pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1309 maybe_whole_expr!(self);
1311 let lo = self.token.span;
1312 let minus_present = self.eat(&token::BinOp(token::Minus));
1313 let lit = self.parse_lit()?;
1314 let expr = self.mk_expr(lit.span, ExprKind::Lit(lit), AttrVec::new());
1317 Ok(self.mk_expr(lo.to(self.prev_span), self.mk_unary(UnOp::Neg, expr), AttrVec::new()))
1323 /// Parses a block or unsafe block.
1324 pub(super) fn parse_block_expr(
1326 opt_label: Option<Label>,
1328 blk_mode: BlockCheckMode,
1329 outer_attrs: AttrVec,
1330 ) -> PResult<'a, P<Expr>> {
1331 if let Some(label) = opt_label {
1332 self.sess.gated_spans.gate(sym::label_break_value, label.ident.span);
1335 self.expect(&token::OpenDelim(token::Brace))?;
1337 let mut attrs = outer_attrs;
1338 attrs.extend(self.parse_inner_attributes()?);
1340 let blk = self.parse_block_tail(lo, blk_mode)?;
1341 Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs))
1344 /// Parses a closure expression (e.g., `move |args| expr`).
1345 fn parse_closure_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1346 let lo = self.token.span;
1349 if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
1352 if self.token.span.rust_2018() { self.parse_asyncness() } else { IsAsync::NotAsync };
1353 if asyncness.is_async() {
1354 // Feature-gate `async ||` closures.
1355 self.sess.gated_spans.gate(sym::async_closure, self.prev_span);
1358 let capture_clause = self.parse_capture_clause();
1359 let decl = self.parse_fn_block_decl()?;
1360 let decl_hi = self.prev_span;
1361 let body = match decl.output {
1362 FunctionRetTy::Default(_) => {
1363 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
1364 self.parse_expr_res(restrictions, None)?
1367 // If an explicit return type is given, require a block to appear (RFC 968).
1368 let body_lo = self.token.span;
1369 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, AttrVec::new())?
1375 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
1380 /// Parses an optional `move` prefix to a closure lke construct.
1381 fn parse_capture_clause(&mut self) -> CaptureBy {
1382 if self.eat_keyword(kw::Move) { CaptureBy::Value } else { CaptureBy::Ref }
1385 /// Parses the `|arg, arg|` header of a closure.
1386 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
1387 let inputs = if self.eat(&token::OrOr) {
1390 self.expect(&token::BinOp(token::Or))?;
1392 .parse_seq_to_before_tokens(
1393 &[&token::BinOp(token::Or), &token::OrOr],
1394 SeqSep::trailing_allowed(token::Comma),
1395 TokenExpectType::NoExpect,
1396 |p| p.parse_fn_block_param(),
1402 let output = self.parse_ret_ty(true, true)?;
1404 Ok(P(FnDecl { inputs, output }))
1407 /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
1408 fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
1409 let lo = self.token.span;
1410 let attrs = self.parse_outer_attributes()?;
1411 let pat = self.parse_pat(PARAM_EXPECTED)?;
1412 let ty = if self.eat(&token::Colon) {
1415 self.mk_ty(self.prev_span, TyKind::Infer)
1418 attrs: attrs.into(),
1421 span: lo.to(self.token.span),
1423 is_placeholder: false,
1427 /// Parses an `if` expression (`if` token already eaten).
1428 fn parse_if_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1429 let lo = self.prev_span;
1430 let cond = self.parse_cond_expr()?;
1432 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
1433 // verify that the last statement is either an implicit return (no `;`) or an explicit
1434 // return. This won't catch blocks with an explicit `return`, but that would be caught by
1435 // the dead code lint.
1436 let thn = if self.eat_keyword(kw::Else) || !cond.returns() {
1437 self.error_missing_if_cond(lo, cond.span)
1439 let not_block = self.token != token::OpenDelim(token::Brace);
1440 self.parse_block().map_err(|mut err| {
1442 err.span_label(lo, "this `if` expression has a condition, but no block");
1447 let els = if self.eat_keyword(kw::Else) { Some(self.parse_else_expr()?) } else { None };
1448 Ok(self.mk_expr(lo.to(self.prev_span), ExprKind::If(cond, thn, els), attrs))
1451 fn error_missing_if_cond(&self, lo: Span, span: Span) -> P<ast::Block> {
1452 let sp = self.sess.source_map().next_point(lo);
1453 self.struct_span_err(sp, "missing condition for `if` expression")
1454 .span_label(sp, "expected if condition here")
1456 self.mk_block_err(span)
1459 /// Parses the condition of a `if` or `while` expression.
1460 fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
1461 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
1463 if let ExprKind::Let(..) = cond.kind {
1464 // Remove the last feature gating of a `let` expression since it's stable.
1465 self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
1471 /// Parses a `let $pat = $expr` pseudo-expression.
1472 /// The `let` token has already been eaten.
1473 fn parse_let_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1474 let lo = self.prev_span;
1475 let pat = self.parse_top_pat(GateOr::No)?;
1476 self.expect(&token::Eq)?;
1477 let expr = self.with_res(Restrictions::NO_STRUCT_LITERAL, |this| {
1478 this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
1480 let span = lo.to(expr.span);
1481 self.sess.gated_spans.gate(sym::let_chains, span);
1482 Ok(self.mk_expr(span, ExprKind::Let(pat, expr), attrs))
1485 /// Parses an `else { ... }` expression (`else` token already eaten).
1486 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
1487 if self.eat_keyword(kw::If) {
1488 self.parse_if_expr(AttrVec::new())
1490 let blk = self.parse_block()?;
1491 Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), AttrVec::new()))
1495 /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
1498 opt_label: Option<Label>,
1501 ) -> PResult<'a, P<Expr>> {
1502 // Record whether we are about to parse `for (`.
1503 // This is used below for recovery in case of `for ( $stuff ) $block`
1504 // in which case we will suggest `for $stuff $block`.
1505 let begin_paren = match self.token.kind {
1506 token::OpenDelim(token::Paren) => Some(self.token.span),
1510 let pat = self.parse_top_pat(GateOr::Yes)?;
1511 if !self.eat_keyword(kw::In) {
1512 self.error_missing_in_for_loop();
1514 self.check_for_for_in_in_typo(self.prev_span);
1515 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
1517 let pat = self.recover_parens_around_for_head(pat, &expr, begin_paren);
1519 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
1520 attrs.extend(iattrs);
1522 let kind = ExprKind::ForLoop(pat, expr, loop_block, opt_label);
1523 Ok(self.mk_expr(lo.to(self.prev_span), kind, attrs))
1526 fn error_missing_in_for_loop(&self) {
1527 let in_span = self.prev_span.between(self.token.span);
1528 self.struct_span_err(in_span, "missing `in` in `for` loop")
1529 .span_suggestion_short(
1531 "try adding `in` here",
1533 // Has been misleading, at least in the past (closed Issue #48492).
1534 Applicability::MaybeIncorrect,
1539 /// Parses a `while` or `while let` expression (`while` token already eaten).
1540 fn parse_while_expr(
1542 opt_label: Option<Label>,
1545 ) -> PResult<'a, P<Expr>> {
1546 let cond = self.parse_cond_expr()?;
1547 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1548 attrs.extend(iattrs);
1549 Ok(self.mk_expr(lo.to(self.prev_span), ExprKind::While(cond, body, opt_label), attrs))
1552 /// Parses `loop { ... }` (`loop` token already eaten).
1555 opt_label: Option<Label>,
1558 ) -> PResult<'a, P<Expr>> {
1559 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1560 attrs.extend(iattrs);
1561 Ok(self.mk_expr(lo.to(self.prev_span), ExprKind::Loop(body, opt_label), attrs))
1564 fn eat_label(&mut self) -> Option<Label> {
1565 self.token.lifetime().map(|ident| {
1566 let span = self.token.span;
1568 Label { ident: Ident::new(ident.name, span) }
1572 /// Parses a `match ... { ... }` expression (`match` token already eaten).
1573 fn parse_match_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
1574 let match_span = self.prev_span;
1575 let lo = self.prev_span;
1576 let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
1577 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
1578 if self.token == token::Semi {
1579 e.span_suggestion_short(
1581 "try removing this `match`",
1583 Applicability::MaybeIncorrect, // speculative
1588 attrs.extend(self.parse_inner_attributes()?);
1590 let mut arms: Vec<Arm> = Vec::new();
1591 while self.token != token::CloseDelim(token::Brace) {
1592 match self.parse_arm() {
1593 Ok(arm) => arms.push(arm),
1595 // Recover by skipping to the end of the block.
1597 self.recover_stmt();
1598 let span = lo.to(self.token.span);
1599 if self.token == token::CloseDelim(token::Brace) {
1602 return Ok(self.mk_expr(span, ExprKind::Match(scrutinee, arms), attrs));
1606 let hi = self.token.span;
1608 return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(scrutinee, arms), attrs));
1611 pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
1612 let attrs = self.parse_outer_attributes()?;
1613 let lo = self.token.span;
1614 let pat = self.parse_top_pat(GateOr::No)?;
1615 let guard = if self.eat_keyword(kw::If) { Some(self.parse_expr()?) } else { None };
1616 let arrow_span = self.token.span;
1617 self.expect(&token::FatArrow)?;
1618 let arm_start_span = self.token.span;
1620 let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
1621 err.span_label(arrow_span, "while parsing the `match` arm starting here");
1625 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
1626 && self.token != token::CloseDelim(token::Brace);
1628 let hi = self.token.span;
1631 let cm = self.sess.source_map();
1632 self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)]).map_err(
1634 match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
1635 (Ok(ref expr_lines), Ok(ref arm_start_lines))
1636 if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
1637 && expr_lines.lines.len() == 2
1638 && self.token == token::FatArrow =>
1640 // We check whether there's any trailing code in the parse span,
1641 // if there isn't, we very likely have the following:
1644 // | -- - missing comma
1648 // | - ^^ self.token.span
1650 // | parsed until here as `"y" & X`
1651 err.span_suggestion_short(
1652 arm_start_span.shrink_to_hi(),
1653 "missing a comma here to end this `match` arm",
1655 Applicability::MachineApplicable,
1661 "while parsing the `match` arm starting here",
1669 self.eat(&token::Comma);
1679 is_placeholder: false,
1683 /// Parses a `try {...}` expression (`try` token already eaten).
1684 fn parse_try_block(&mut self, span_lo: Span, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
1685 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1686 attrs.extend(iattrs);
1687 if self.eat_keyword(kw::Catch) {
1689 self.struct_span_err(self.prev_span, "keyword `catch` cannot follow a `try` block");
1690 error.help("try using `match` on the result of the `try` block instead");
1694 let span = span_lo.to(body.span);
1695 self.sess.gated_spans.gate(sym::try_blocks, span);
1696 Ok(self.mk_expr(span, ExprKind::TryBlock(body), attrs))
1700 fn is_do_catch_block(&self) -> bool {
1701 self.token.is_keyword(kw::Do)
1702 && self.is_keyword_ahead(1, &[kw::Catch])
1703 && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
1704 && !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1707 fn is_try_block(&self) -> bool {
1708 self.token.is_keyword(kw::Try) &&
1709 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
1710 self.token.span.rust_2018() &&
1711 // Prevent `while try {} {}`, `if try {} {} else {}`, etc.
1712 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1715 /// Parses an `async move? {...}` expression.
1716 fn parse_async_block(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
1717 let lo = self.token.span;
1718 self.expect_keyword(kw::Async)?;
1719 let capture_clause = self.parse_capture_clause();
1720 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1721 attrs.extend(iattrs);
1722 let kind = ExprKind::Async(capture_clause, DUMMY_NODE_ID, body);
1723 Ok(self.mk_expr(lo.to(self.prev_span), kind, attrs))
1726 fn is_async_block(&self) -> bool {
1727 self.token.is_keyword(kw::Async)
1730 self.is_keyword_ahead(1, &[kw::Move])
1731 && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
1734 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
1738 fn is_certainly_not_a_block(&self) -> bool {
1739 self.look_ahead(1, |t| t.is_ident())
1741 // `{ ident, ` cannot start a block.
1742 self.look_ahead(2, |t| t == &token::Comma)
1743 || self.look_ahead(2, |t| t == &token::Colon)
1745 // `{ ident: token, ` cannot start a block.
1746 self.look_ahead(4, |t| t == &token::Comma) ||
1747 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
1748 self.look_ahead(3, |t| !t.can_begin_type())
1753 fn maybe_parse_struct_expr(
1758 ) -> Option<PResult<'a, P<Expr>>> {
1759 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
1760 if struct_allowed || self.is_certainly_not_a_block() {
1761 // This is a struct literal, but we don't can't accept them here.
1762 let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
1763 if let (Ok(expr), false) = (&expr, struct_allowed) {
1764 self.error_struct_lit_not_allowed_here(lo, expr.span);
1771 fn error_struct_lit_not_allowed_here(&self, lo: Span, sp: Span) {
1772 self.struct_span_err(sp, "struct literals are not allowed here")
1773 .multipart_suggestion(
1774 "surround the struct literal with parentheses",
1775 vec![(lo.shrink_to_lo(), "(".to_string()), (sp.shrink_to_hi(), ")".to_string())],
1776 Applicability::MachineApplicable,
1781 pub(super) fn parse_struct_expr(
1786 ) -> PResult<'a, P<Expr>> {
1787 let struct_sp = lo.to(self.prev_span);
1789 let mut fields = Vec::new();
1790 let mut base = None;
1792 attrs.extend(self.parse_inner_attributes()?);
1794 while self.token != token::CloseDelim(token::Brace) {
1795 if self.eat(&token::DotDot) {
1796 let exp_span = self.prev_span;
1797 match self.parse_expr() {
1798 Ok(e) => base = Some(e),
1801 self.recover_stmt();
1804 self.recover_struct_comma_after_dotdot(exp_span);
1808 let recovery_field = self.find_struct_error_after_field_looking_code();
1809 let parsed_field = match self.parse_field() {
1812 e.span_label(struct_sp, "while parsing this struct");
1815 // If the next token is a comma, then try to parse
1816 // what comes next as additional fields, rather than
1817 // bailing out until next `}`.
1818 if self.token != token::Comma {
1819 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
1820 if self.token != token::Comma {
1828 match self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)]) {
1830 if let Some(f) = parsed_field.or(recovery_field) {
1831 // Only include the field if there's no parse error for the field name.
1836 if let Some(f) = recovery_field {
1839 e.span_label(struct_sp, "while parsing this struct");
1841 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
1842 self.eat(&token::Comma);
1847 let span = lo.to(self.token.span);
1848 self.expect(&token::CloseDelim(token::Brace))?;
1849 Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs))
1852 /// Use in case of error after field-looking code: `S { foo: () with a }`.
1853 fn find_struct_error_after_field_looking_code(&self) -> Option<Field> {
1854 if let token::Ident(name, _) = self.token.kind {
1855 if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
1856 let span = self.token.span;
1857 return Some(ast::Field {
1858 ident: Ident::new(name, span),
1860 expr: self.mk_expr_err(span),
1861 is_shorthand: false,
1862 attrs: AttrVec::new(),
1864 is_placeholder: false,
1871 fn recover_struct_comma_after_dotdot(&mut self, span: Span) {
1872 if self.token != token::Comma {
1875 self.struct_span_err(span.to(self.prev_span), "cannot use a comma after the base struct")
1876 .span_suggestion_short(
1878 "remove this comma",
1880 Applicability::MachineApplicable,
1882 .note("the base struct must always be the last field")
1884 self.recover_stmt();
1887 /// Parses `ident (COLON expr)?`.
1888 fn parse_field(&mut self) -> PResult<'a, Field> {
1889 let attrs = self.parse_outer_attributes()?.into();
1890 let lo = self.token.span;
1892 // Check if a colon exists one ahead. This means we're parsing a fieldname.
1893 let is_shorthand = !self.look_ahead(1, |t| t == &token::Colon || t == &token::Eq);
1894 let (ident, expr) = if is_shorthand {
1895 // Mimic `x: x` for the `x` field shorthand.
1896 let ident = self.parse_ident_common(false)?;
1897 let path = ast::Path::from_ident(ident);
1898 (ident, self.mk_expr(ident.span, ExprKind::Path(None, path), AttrVec::new()))
1900 let ident = self.parse_field_name()?;
1901 self.error_on_eq_field_init(ident);
1903 (ident, self.parse_expr()?)
1907 span: lo.to(expr.span),
1912 is_placeholder: false,
1916 /// Check for `=`. This means the source incorrectly attempts to
1917 /// initialize a field with an eq rather than a colon.
1918 fn error_on_eq_field_init(&self, field_name: Ident) {
1919 if self.token != token::Eq {
1923 self.struct_span_err(self.token.span, "expected `:`, found `=`")
1925 field_name.span.shrink_to_hi().to(self.token.span),
1926 "replace equals symbol with a colon",
1928 Applicability::MachineApplicable,
1933 fn err_dotdotdot_syntax(&self, span: Span) {
1934 self.struct_span_err(span, "unexpected token: `...`")
1937 "use `..` for an exclusive range",
1939 Applicability::MaybeIncorrect,
1943 "or `..=` for an inclusive range",
1945 Applicability::MaybeIncorrect,
1950 fn err_larrow_operator(&self, span: Span) {
1951 self.struct_span_err(span, "unexpected token: `<-`")
1954 "if you meant to write a comparison against a negative value, add a \
1955 space in between `<` and `-`",
1957 Applicability::MaybeIncorrect,
1962 fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
1963 ExprKind::AssignOp(binop, lhs, rhs)
1968 start: Option<P<Expr>>,
1969 end: Option<P<Expr>>,
1970 limits: RangeLimits,
1971 ) -> PResult<'a, ExprKind> {
1972 if end.is_none() && limits == RangeLimits::Closed {
1973 self.error_inclusive_range_with_no_end(self.prev_span);
1976 Ok(ExprKind::Range(start, end, limits))
1980 fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
1981 ExprKind::Unary(unop, expr)
1984 fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
1985 ExprKind::Binary(binop, lhs, rhs)
1988 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
1989 ExprKind::Index(expr, idx)
1992 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
1993 ExprKind::Call(f, args)
1996 fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
1997 let span = lo.to(self.prev_span);
1998 let await_expr = self.mk_expr(span, ExprKind::Await(self_arg), AttrVec::new());
1999 self.recover_from_await_method_call();
2003 crate fn mk_expr(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
2004 P(Expr { kind, span, attrs, id: DUMMY_NODE_ID })
2007 pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> {
2008 self.mk_expr(span, ExprKind::Err, AttrVec::new())