1 use super::pat::{GateOr, PARAM_EXPECTED};
2 use super::ty::{AllowPlus, RecoverQPath};
3 use super::{BlockMode, Parser, PathStyle, Restrictions, TokenType};
4 use super::{SemiColonMode, SeqSep, TokenExpectType};
5 use crate::maybe_recover_from_interpolated_ty_qpath;
7 use rustc_ast::ast::{self, AttrStyle, AttrVec, CaptureBy, Field, Ident, Lit, DUMMY_NODE_ID};
8 use rustc_ast::ast::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, Mac, Param, Ty, TyKind, UnOp};
9 use rustc_ast::ast::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits};
10 use rustc_ast::ptr::P;
11 use rustc_ast::token::{self, Token, TokenKind};
12 use rustc_ast::util::classify;
13 use rustc_ast::util::literal::LitError;
14 use rustc_ast::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
15 use rustc_ast_pretty::pprust;
16 use rustc_errors::{Applicability, PResult};
17 use rustc_span::source_map::{self, Span, Spanned};
18 use rustc_span::symbol::{kw, sym, Symbol};
21 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
22 /// dropped into the token stream, which happens while parsing the result of
23 /// macro expansion). Placement of these is not as complex as I feared it would
24 /// be. The important thing is to make sure that lookahead doesn't balk at
25 /// `token::Interpolated` tokens.
26 macro_rules! maybe_whole_expr {
28 if let token::Interpolated(nt) = &$p.token.kind {
30 token::NtExpr(e) | token::NtLiteral(e) => {
35 token::NtPath(path) => {
36 let path = path.clone();
40 ExprKind::Path(None, path),
44 token::NtBlock(block) => {
45 let block = block.clone();
49 ExprKind::Block(block, None),
53 // N.B., `NtIdent(ident)` is normalized to `Ident` in `fn bump`.
61 pub(super) enum LhsExpr {
63 AttributesParsed(AttrVec),
64 AlreadyParsed(P<Expr>),
67 impl From<Option<AttrVec>> for LhsExpr {
68 /// Converts `Some(attrs)` into `LhsExpr::AttributesParsed(attrs)`
69 /// and `None` into `LhsExpr::NotYetParsed`.
71 /// This conversion does not allocate.
72 fn from(o: Option<AttrVec>) -> Self {
73 if let Some(attrs) = o { LhsExpr::AttributesParsed(attrs) } else { LhsExpr::NotYetParsed }
77 impl From<P<Expr>> for LhsExpr {
78 /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed(expr)`.
80 /// This conversion does not allocate.
81 fn from(expr: P<Expr>) -> Self {
82 LhsExpr::AlreadyParsed(expr)
87 /// Parses an expression.
89 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
90 self.parse_expr_res(Restrictions::empty(), None)
93 pub(super) fn parse_anon_const_expr(&mut self) -> PResult<'a, AnonConst> {
94 self.parse_expr().map(|value| AnonConst { id: DUMMY_NODE_ID, value })
97 fn parse_expr_catch_underscore(&mut self) -> PResult<'a, P<Expr>> {
98 match self.parse_expr() {
100 Err(mut err) => match self.normalized_token.kind {
101 token::Ident(name, false)
102 if name == kw::Underscore && self.look_ahead(1, |t| t == &token::Comma) =>
104 // Special-case handling of `foo(_, _, _)`
107 Ok(self.mk_expr(self.prev_token.span, ExprKind::Err, AttrVec::new()))
114 /// Parses a sequence of expressions delimited by parentheses.
115 fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
116 self.parse_paren_comma_seq(|p| p.parse_expr_catch_underscore()).map(|(r, _)| r)
119 /// Parses an expression, subject to the given restrictions.
121 pub(super) fn parse_expr_res(
124 already_parsed_attrs: Option<AttrVec>,
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
134 fn parse_assoc_expr(&mut self, already_parsed_attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
135 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
138 /// Parses an associative expression with operators of at least `min_prec` precedence.
139 pub(super) fn parse_assoc_expr_with(
143 ) -> PResult<'a, P<Expr>> {
144 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
147 let attrs = match lhs {
148 LhsExpr::AttributesParsed(attrs) => Some(attrs),
151 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind) {
152 return self.parse_prefix_range_expr(attrs);
154 self.parse_prefix_expr(attrs)?
157 let last_type_ascription_set = self.last_type_ascription.is_some();
159 if !self.should_continue_as_assoc_expr(&lhs) {
160 self.last_type_ascription = None;
164 self.expected_tokens.push(TokenType::Operator);
165 while let Some(op) = self.check_assoc_op() {
166 // Adjust the span for interpolated LHS to point to the `$lhs` token
167 // and not to what it refers to.
168 let lhs_span = match self.prev_token.kind {
169 TokenKind::Interpolated(..) => self.prev_token.span,
173 let cur_op_span = self.token.span;
174 let restrictions = if op.node.is_assign_like() {
175 self.restrictions & Restrictions::NO_STRUCT_LITERAL
179 let prec = op.node.precedence();
183 // Check for deprecated `...` syntax
184 if self.token == token::DotDotDot && op.node == AssocOp::DotDotEq {
185 self.err_dotdotdot_syntax(self.token.span);
188 if self.token == token::LArrow {
189 self.err_larrow_operator(self.token.span);
193 if op.node.is_comparison() {
194 if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
200 if op == AssocOp::As {
201 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
203 } else if op == AssocOp::Colon {
204 lhs = self.parse_assoc_op_ascribe(lhs, lhs_span)?;
206 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
207 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
208 // generalise it to the Fixity::None code.
209 lhs = self.parse_range_expr(prec, lhs, op, cur_op_span)?;
213 let fixity = op.fixity();
214 let prec_adjustment = match fixity {
217 // We currently have no non-associative operators that are not handled above by
218 // the special cases. The code is here only for future convenience.
221 let rhs = self.with_res(restrictions - Restrictions::STMT_EXPR, |this| {
222 this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
225 // Make sure that the span of the parent node is larger than the span of lhs and rhs,
226 // including the attributes.
228 lhs.attrs.iter().find(|a| a.style == AttrStyle::Outer).map_or(lhs_span, |a| a.span);
229 let span = lhs_span.to(rhs.span);
242 | AssocOp::ShiftRight
248 | AssocOp::GreaterEqual => {
249 let ast_op = op.to_ast_binop().unwrap();
250 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
251 self.mk_expr(span, binary, AttrVec::new())
254 self.mk_expr(span, ExprKind::Assign(lhs, rhs, cur_op_span), AttrVec::new())
256 AssocOp::AssignOp(k) => {
258 token::Plus => BinOpKind::Add,
259 token::Minus => BinOpKind::Sub,
260 token::Star => BinOpKind::Mul,
261 token::Slash => BinOpKind::Div,
262 token::Percent => BinOpKind::Rem,
263 token::Caret => BinOpKind::BitXor,
264 token::And => BinOpKind::BitAnd,
265 token::Or => BinOpKind::BitOr,
266 token::Shl => BinOpKind::Shl,
267 token::Shr => BinOpKind::Shr,
269 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
270 self.mk_expr(span, aopexpr, AttrVec::new())
272 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
273 self.span_bug(span, "AssocOp should have been handled by special case")
277 if let Fixity::None = fixity {
281 if last_type_ascription_set {
282 self.last_type_ascription = None;
287 fn should_continue_as_assoc_expr(&mut self, lhs: &Expr) -> bool {
288 match (self.expr_is_complete(lhs), self.check_assoc_op().map(|op| op.node)) {
289 // Semi-statement forms are odd:
290 // See https://github.com/rust-lang/rust/issues/29071
291 (true, None) => false,
292 (false, _) => true, // Continue parsing the expression.
293 // An exhaustive check is done in the following block, but these are checked first
294 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
295 // want to keep their span info to improve diagnostics in these cases in a later stage.
296 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
297 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
298 (true, Some(AssocOp::LAnd)) | // `{ 42 } &&x` (#61475)
299 (true, Some(AssocOp::Add)) // `{ 42 } + 42
300 // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
301 // `if x { a } else { b } && if y { c } else { d }`
302 if !self.look_ahead(1, |t| t.is_reserved_ident()) => {
303 // These cases are ambiguous and can't be identified in the parser alone.
304 let sp = self.sess.source_map().start_point(self.token.span);
305 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
308 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => false,
310 self.error_found_expr_would_be_stmt(lhs);
316 /// We've found an expression that would be parsed as a statement,
317 /// but the next token implies this should be parsed as an expression.
318 /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
319 fn error_found_expr_would_be_stmt(&self, lhs: &Expr) {
320 let mut err = self.struct_span_err(
322 &format!("expected expression, found `{}`", pprust::token_to_string(&self.token),),
324 err.span_label(self.token.span, "expected expression");
325 self.sess.expr_parentheses_needed(&mut err, lhs.span, Some(pprust::expr_to_string(&lhs)));
329 /// Possibly translate the current token to an associative operator.
330 /// The method does not advance the current token.
332 /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
333 fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
335 node: match (AssocOp::from_token(&self.token), &self.normalized_token.kind) {
337 (None, token::Ident(sym::and, false)) => {
338 self.error_bad_logical_op("and", "&&", "conjunction");
341 (None, token::Ident(sym::or, false)) => {
342 self.error_bad_logical_op("or", "||", "disjunction");
347 span: self.normalized_token.span,
351 /// Error on `and` and `or` suggesting `&&` and `||` respectively.
352 fn error_bad_logical_op(&self, bad: &str, good: &str, english: &str) {
353 self.struct_span_err(self.token.span, &format!("`{}` is not a logical operator", bad))
354 .span_suggestion_short(
356 &format!("use `{}` to perform logical {}", good, english),
358 Applicability::MachineApplicable,
360 .note("unlike in e.g., python and PHP, `&&` and `||` are used for logical operators")
364 /// Checks if this expression is a successfully parsed statement.
365 fn expr_is_complete(&self, e: &Expr) -> bool {
366 self.restrictions.contains(Restrictions::STMT_EXPR)
367 && !classify::expr_requires_semi_to_be_stmt(e)
370 /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
371 /// The other two variants are handled in `parse_prefix_range_expr` below.
378 ) -> PResult<'a, P<Expr>> {
379 let rhs = if self.is_at_start_of_range_notation_rhs() {
380 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
384 let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
385 let span = lhs.span.to(rhs_span);
387 if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
388 Ok(self.mk_expr(span, self.mk_range(Some(lhs), rhs, limits)?, AttrVec::new()))
391 fn is_at_start_of_range_notation_rhs(&self) -> bool {
392 if self.token.can_begin_expr() {
393 // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
394 if self.token == token::OpenDelim(token::Brace) {
395 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
403 /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
404 fn parse_prefix_range_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
405 // Check for deprecated `...` syntax.
406 if self.token == token::DotDotDot {
407 self.err_dotdotdot_syntax(self.token.span);
411 [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind),
412 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
416 let limits = match self.token.kind {
417 token::DotDot => RangeLimits::HalfOpen,
418 _ => RangeLimits::Closed,
420 let op = AssocOp::from_token(&self.token);
421 let attrs = self.parse_or_use_outer_attributes(attrs)?;
422 let lo = self.token.span;
424 let (span, opt_end) = if self.is_at_start_of_range_notation_rhs() {
425 // RHS must be parsed with more associativity than the dots.
426 self.parse_assoc_expr_with(op.unwrap().precedence() + 1, LhsExpr::NotYetParsed)
427 .map(|x| (lo.to(x.span), Some(x)))?
431 Ok(self.mk_expr(span, self.mk_range(None, opt_end, limits)?, attrs))
434 /// Parses a prefix-unary-operator expr.
435 fn parse_prefix_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
436 let attrs = self.parse_or_use_outer_attributes(attrs)?;
437 let lo = self.token.span;
438 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
439 let (hi, ex) = match self.normalized_token.kind {
440 token::Not => self.parse_unary_expr(lo, UnOp::Not), // `!expr`
441 token::Tilde => self.recover_tilde_expr(lo), // `~expr`
442 token::BinOp(token::Minus) => self.parse_unary_expr(lo, UnOp::Neg), // `-expr`
443 token::BinOp(token::Star) => self.parse_unary_expr(lo, UnOp::Deref), // `*expr`
444 token::BinOp(token::And) | token::AndAnd => self.parse_borrow_expr(lo),
445 token::Ident(..) if self.token.is_keyword(kw::Box) => self.parse_box_expr(lo),
446 token::Ident(..) if self.is_mistaken_not_ident_negation() => self.recover_not_expr(lo),
447 _ => return self.parse_dot_or_call_expr(Some(attrs)),
449 Ok(self.mk_expr(lo.to(hi), ex, attrs))
452 fn parse_prefix_expr_common(&mut self, lo: Span) -> PResult<'a, (Span, P<Expr>)> {
454 let expr = self.parse_prefix_expr(None);
455 let (span, expr) = self.interpolated_or_expr_span(expr)?;
456 Ok((lo.to(span), expr))
459 fn parse_unary_expr(&mut self, lo: Span, op: UnOp) -> PResult<'a, (Span, ExprKind)> {
460 let (span, expr) = self.parse_prefix_expr_common(lo)?;
461 Ok((span, self.mk_unary(op, expr)))
464 // Recover on `!` suggesting for bitwise negation instead.
465 fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
466 self.struct_span_err(lo, "`~` cannot be used as a unary operator")
467 .span_suggestion_short(
469 "use `!` to perform bitwise not",
471 Applicability::MachineApplicable,
475 self.parse_unary_expr(lo, UnOp::Not)
478 /// Parse `box expr`.
479 fn parse_box_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
480 let (span, expr) = self.parse_prefix_expr_common(lo)?;
481 self.sess.gated_spans.gate(sym::box_syntax, span);
482 Ok((span, ExprKind::Box(expr)))
485 fn is_mistaken_not_ident_negation(&self) -> bool {
486 let token_cannot_continue_expr = |t: &Token| match t.kind {
487 // These tokens can start an expression after `!`, but
488 // can't continue an expression after an ident
489 token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
490 token::Literal(..) | token::Pound => true,
491 _ => t.is_whole_expr(),
493 self.token.is_ident_named(sym::not) && self.look_ahead(1, token_cannot_continue_expr)
496 /// Recover on `not expr` in favor of `!expr`.
497 fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
499 let not_token = self.look_ahead(1, |t| t.clone());
500 self.struct_span_err(
502 &format!("unexpected {} after identifier", super::token_descr(¬_token)),
504 .span_suggestion_short(
505 // Span the `not` plus trailing whitespace to avoid
506 // trailing whitespace after the `!` in our suggestion
507 self.sess.source_map().span_until_non_whitespace(lo.to(not_token.span)),
508 "use `!` to perform logical negation",
510 Applicability::MachineApplicable,
515 self.parse_unary_expr(lo, UnOp::Not)
518 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
519 fn interpolated_or_expr_span(
521 expr: PResult<'a, P<Expr>>,
522 ) -> PResult<'a, (Span, P<Expr>)> {
525 match self.prev_token.kind {
526 TokenKind::Interpolated(..) => self.prev_token.span,
534 fn parse_assoc_op_cast(
538 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
539 ) -> PResult<'a, P<Expr>> {
540 let mk_expr = |this: &mut Self, rhs: P<Ty>| {
541 this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), AttrVec::new())
544 // Save the state of the parser before parsing type normally, in case there is a
545 // LessThan comparison after this cast.
546 let parser_snapshot_before_type = self.clone();
547 match self.parse_ty_no_plus() {
548 Ok(rhs) => Ok(mk_expr(self, rhs)),
549 Err(mut type_err) => {
550 // Rewind to before attempting to parse the type with generics, to recover
551 // from situations like `x as usize < y` in which we first tried to parse
552 // `usize < y` as a type with generic arguments.
553 let parser_snapshot_after_type = self.clone();
554 mem::replace(self, parser_snapshot_before_type);
556 match self.parse_path(PathStyle::Expr) {
558 let (op_noun, op_verb) = match self.token.kind {
559 token::Lt => ("comparison", "comparing"),
560 token::BinOp(token::Shl) => ("shift", "shifting"),
562 // We can end up here even without `<` being the next token, for
563 // example because `parse_ty_no_plus` returns `Err` on keywords,
564 // but `parse_path` returns `Ok` on them due to error recovery.
565 // Return original error and parser state.
566 mem::replace(self, parser_snapshot_after_type);
567 return Err(type_err);
571 // Successfully parsed the type path leaving a `<` yet to parse.
574 // Report non-fatal diagnostics, keep `x as usize` as an expression
575 // in AST and continue parsing.
577 "`<` is interpreted as a start of generic arguments for `{}`, not a {}",
578 pprust::path_to_string(&path),
581 let span_after_type = parser_snapshot_after_type.token.span;
582 let expr = mk_expr(self, self.mk_ty(path.span, TyKind::Path(None, path)));
585 .span_to_snippet(expr.span)
586 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
588 self.struct_span_err(self.token.span, &msg)
590 self.look_ahead(1, |t| t.span).to(span_after_type),
591 "interpreted as generic arguments",
593 .span_label(self.token.span, format!("not interpreted as {}", op_noun))
596 &format!("try {} the cast value", op_verb),
597 format!("({})", expr_str),
598 Applicability::MachineApplicable,
604 Err(mut path_err) => {
605 // Couldn't parse as a path, return original error and parser state.
607 mem::replace(self, parser_snapshot_after_type);
615 fn parse_assoc_op_ascribe(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
616 let maybe_path = self.could_ascription_be_path(&lhs.kind);
617 self.last_type_ascription = Some((self.prev_token.span, maybe_path));
618 let lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
619 self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
623 /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
624 fn parse_borrow_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
626 let (borrow_kind, mutbl) = self.parse_borrow_modifiers(lo);
627 let expr = self.parse_prefix_expr(None);
628 let (span, expr) = self.interpolated_or_expr_span(expr)?;
629 Ok((lo.to(span), ExprKind::AddrOf(borrow_kind, mutbl, expr)))
632 /// Parse `mut?` or `raw [ const | mut ]`.
633 fn parse_borrow_modifiers(&mut self, lo: Span) -> (ast::BorrowKind, ast::Mutability) {
634 if self.check_keyword(kw::Raw) && self.look_ahead(1, Token::is_mutability) {
635 // `raw [ const | mut ]`.
636 let found_raw = self.eat_keyword(kw::Raw);
638 let mutability = self.parse_const_or_mut().unwrap();
639 self.sess.gated_spans.gate(sym::raw_ref_op, lo.to(self.prev_token.span));
640 (ast::BorrowKind::Raw, mutability)
643 (ast::BorrowKind::Ref, self.parse_mutability())
647 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
648 fn parse_dot_or_call_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
649 let attrs = self.parse_or_use_outer_attributes(attrs)?;
650 let base = self.parse_bottom_expr();
651 let (span, base) = self.interpolated_or_expr_span(base)?;
652 self.parse_dot_or_call_expr_with(base, span, attrs)
655 pub(super) fn parse_dot_or_call_expr_with(
660 ) -> PResult<'a, P<Expr>> {
661 // Stitch the list of outer attributes onto the return value.
662 // A little bit ugly, but the best way given the current code
664 self.parse_dot_or_call_expr_with_(e0, lo).map(|expr| {
665 expr.map(|mut expr| {
666 attrs.extend::<Vec<_>>(expr.attrs.into());
668 self.error_attr_on_if_expr(&expr);
674 fn error_attr_on_if_expr(&self, expr: &Expr) {
675 if let (ExprKind::If(..), [a0, ..]) = (&expr.kind, &*expr.attrs) {
676 // Just point to the first attribute in there...
677 self.struct_span_err(a0.span, "attributes are not yet allowed on `if` expressions")
682 fn parse_dot_or_call_expr_with_(&mut self, mut e: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
684 if self.eat(&token::Question) {
686 e = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Try(e), AttrVec::new());
689 if self.eat(&token::Dot) {
691 e = self.parse_dot_suffix_expr(lo, e)?;
694 if self.expr_is_complete(&e) {
697 e = match self.token.kind {
698 token::OpenDelim(token::Paren) => self.parse_fn_call_expr(lo, e),
699 token::OpenDelim(token::Bracket) => self.parse_index_expr(lo, e)?,
705 fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
706 match self.normalized_token.kind {
707 token::Ident(..) => self.parse_dot_suffix(base, lo),
708 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
709 Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix))
711 token::Literal(token::Lit { kind: token::Float, symbol, .. }) => {
712 self.recover_field_access_by_float_lit(lo, base, symbol)
715 self.error_unexpected_after_dot();
721 fn error_unexpected_after_dot(&self) {
722 // FIXME Could factor this out into non_fatal_unexpected or something.
723 let actual = pprust::token_to_string(&self.token);
724 self.struct_span_err(self.token.span, &format!("unexpected token: `{}`", actual)).emit();
727 fn recover_field_access_by_float_lit(
732 ) -> PResult<'a, P<Expr>> {
735 let fstr = sym.as_str();
736 let msg = format!("unexpected token: `{}`", sym);
738 let mut err = self.struct_span_err(self.prev_token.span, &msg);
739 err.span_label(self.prev_token.span, "unexpected token");
741 if fstr.chars().all(|x| "0123456789.".contains(x)) {
742 let float = match fstr.parse::<f64>() {
749 let sugg = pprust::to_string(|s| {
753 s.print_usize(float.trunc() as usize);
756 s.s.word(fstr.splitn(2, '.').last().unwrap().to_string())
759 lo.to(self.prev_token.span),
760 "try parenthesizing the first index",
762 Applicability::MachineApplicable,
768 fn parse_tuple_field_access_expr(
773 suffix: Option<Symbol>,
776 let span = self.prev_token.span;
777 let field = ExprKind::Field(base, Ident::new(field, span));
778 self.expect_no_suffix(span, "a tuple index", suffix);
779 self.mk_expr(lo.to(span), field, AttrVec::new())
782 /// Parse a function call expression, `expr(...)`.
783 fn parse_fn_call_expr(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
784 let seq = self.parse_paren_expr_seq().map(|args| {
785 self.mk_expr(lo.to(self.prev_token.span), self.mk_call(fun, args), AttrVec::new())
787 self.recover_seq_parse_error(token::Paren, lo, seq)
790 /// Parse an indexing expression `expr[...]`.
791 fn parse_index_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
793 let index = self.parse_expr()?;
794 self.expect(&token::CloseDelim(token::Bracket))?;
795 Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_index(base, index), AttrVec::new()))
798 /// Assuming we have just parsed `.`, continue parsing into an expression.
799 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
800 if self.normalized_token.span.rust_2018() && self.eat_keyword(kw::Await) {
801 return self.mk_await_expr(self_arg, lo);
804 let segment = self.parse_path_segment(PathStyle::Expr)?;
805 self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
807 if self.check(&token::OpenDelim(token::Paren)) {
808 // Method call `expr.f()`
809 let mut args = self.parse_paren_expr_seq()?;
810 args.insert(0, self_arg);
812 let span = lo.to(self.prev_token.span);
813 Ok(self.mk_expr(span, ExprKind::MethodCall(segment, args), AttrVec::new()))
815 // Field access `expr.f`
816 if let Some(args) = segment.args {
817 self.struct_span_err(
819 "field expressions cannot have generic arguments",
824 let span = lo.to(self.prev_token.span);
825 Ok(self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), AttrVec::new()))
829 /// At the bottom (top?) of the precedence hierarchy,
830 /// Parses things like parenthesized exprs, macros, `return`, etc.
832 /// N.B., this does not parse outer attributes, and is private because it only works
833 /// correctly if called from `parse_dot_or_call_expr()`.
834 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
835 maybe_recover_from_interpolated_ty_qpath!(self, true);
836 maybe_whole_expr!(self);
838 // Outer attributes are already parsed and will be
839 // added to the return value after the fact.
841 // Therefore, prevent sub-parser from parsing
842 // attributes by giving them a empty "already-parsed" list.
843 let attrs = AttrVec::new();
845 // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
846 let lo = self.token.span;
847 if let token::Literal(_) = self.token.kind {
848 // This match arm is a special-case of the `_` match arm below and
849 // could be removed without changing functionality, but it's faster
850 // to have it here, especially for programs with large constants.
851 self.parse_lit_expr(attrs)
852 } else if self.check(&token::OpenDelim(token::Paren)) {
853 self.parse_tuple_parens_expr(attrs)
854 } else if self.check(&token::OpenDelim(token::Brace)) {
855 self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs)
856 } else if self.check(&token::BinOp(token::Or)) || self.check(&token::OrOr) {
857 self.parse_closure_expr(attrs)
858 } else if self.check(&token::OpenDelim(token::Bracket)) {
859 self.parse_array_or_repeat_expr(attrs)
860 } else if self.eat_lt() {
861 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
862 Ok(self.mk_expr(lo.to(path.span), ExprKind::Path(Some(qself), path), attrs))
863 } else if self.token.is_path_start() {
864 self.parse_path_start_expr(attrs)
865 } else if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
866 self.parse_closure_expr(attrs)
867 } else if self.eat_keyword(kw::If) {
868 self.parse_if_expr(attrs)
869 } else if self.eat_keyword(kw::For) {
870 self.parse_for_expr(None, self.prev_token.span, attrs)
871 } else if self.eat_keyword(kw::While) {
872 self.parse_while_expr(None, self.prev_token.span, attrs)
873 } else if let Some(label) = self.eat_label() {
874 self.parse_labeled_expr(label, attrs)
875 } else if self.eat_keyword(kw::Loop) {
876 self.parse_loop_expr(None, self.prev_token.span, attrs)
877 } else if self.eat_keyword(kw::Continue) {
878 let kind = ExprKind::Continue(self.eat_label());
879 Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
880 } else if self.eat_keyword(kw::Match) {
881 let match_sp = self.prev_token.span;
882 self.parse_match_expr(attrs).map_err(|mut err| {
883 err.span_label(match_sp, "while parsing this match expression");
886 } else if self.eat_keyword(kw::Unsafe) {
887 self.parse_block_expr(None, lo, BlockCheckMode::Unsafe(ast::UserProvided), attrs)
888 } else if self.is_do_catch_block() {
889 self.recover_do_catch(attrs)
890 } else if self.is_try_block() {
891 self.expect_keyword(kw::Try)?;
892 self.parse_try_block(lo, attrs)
893 } else if self.eat_keyword(kw::Return) {
894 self.parse_return_expr(attrs)
895 } else if self.eat_keyword(kw::Break) {
896 self.parse_break_expr(attrs)
897 } else if self.eat_keyword(kw::Yield) {
898 self.parse_yield_expr(attrs)
899 } else if self.eat_keyword(kw::Let) {
900 self.parse_let_expr(attrs)
901 } else if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
902 // Don't complain about bare semicolons after unclosed braces
903 // recovery in order to keep the error count down. Fixing the
904 // delimiters will possibly also fix the bare semicolon found in
905 // expression context. For example, silence the following error:
907 // error: expected expression, found `;`
911 // | ^ expected expression
913 Ok(self.mk_expr_err(self.token.span))
914 } else if self.normalized_token.span.rust_2018() {
915 // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
916 if self.check_keyword(kw::Async) {
917 if self.is_async_block() {
918 // Check for `async {` and `async move {`.
919 self.parse_async_block(attrs)
921 self.parse_closure_expr(attrs)
923 } else if self.eat_keyword(kw::Await) {
924 self.recover_incorrect_await_syntax(lo, self.prev_token.span, attrs)
926 self.parse_lit_expr(attrs)
929 self.parse_lit_expr(attrs)
933 fn parse_lit_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
934 let lo = self.token.span;
935 match self.parse_opt_lit() {
937 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Lit(literal), attrs);
938 self.maybe_recover_from_bad_qpath(expr, true)
940 None => return Err(self.expected_expression_found()),
944 fn parse_tuple_parens_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
945 let lo = self.token.span;
946 self.expect(&token::OpenDelim(token::Paren))?;
947 attrs.extend(self.parse_inner_attributes()?); // `(#![foo] a, b, ...)` is OK.
948 let (es, trailing_comma) = match self.parse_seq_to_end(
949 &token::CloseDelim(token::Paren),
950 SeqSep::trailing_allowed(token::Comma),
951 |p| p.parse_expr_catch_underscore(),
954 Err(err) => return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err))),
956 let kind = if es.len() == 1 && !trailing_comma {
957 // `(e)` is parenthesized `e`.
958 ExprKind::Paren(es.into_iter().nth(0).unwrap())
960 // `(e,)` is a tuple with only one field, `e`.
963 let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
964 self.maybe_recover_from_bad_qpath(expr, true)
967 fn parse_array_or_repeat_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
968 let lo = self.token.span;
971 attrs.extend(self.parse_inner_attributes()?);
973 let close = &token::CloseDelim(token::Bracket);
974 let kind = if self.eat(close) {
976 ExprKind::Array(Vec::new())
979 let first_expr = self.parse_expr()?;
980 if self.eat(&token::Semi) {
981 // Repeating array syntax: `[ 0; 512 ]`
982 let count = self.parse_anon_const_expr()?;
984 ExprKind::Repeat(first_expr, count)
985 } else if self.eat(&token::Comma) {
986 // Vector with two or more elements.
987 let sep = SeqSep::trailing_allowed(token::Comma);
988 let (remaining_exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
989 let mut exprs = vec![first_expr];
990 exprs.extend(remaining_exprs);
991 ExprKind::Array(exprs)
993 // Vector with one element
995 ExprKind::Array(vec![first_expr])
998 let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
999 self.maybe_recover_from_bad_qpath(expr, true)
1002 fn parse_path_start_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1003 let lo = self.token.span;
1004 let path = self.parse_path(PathStyle::Expr)?;
1006 // `!`, as an operator, is prefix, so we know this isn't that.
1007 let (hi, kind) = if self.eat(&token::Not) {
1008 // MACRO INVOCATION expression
1011 args: self.parse_mac_args()?,
1012 prior_type_ascription: self.last_type_ascription,
1014 (self.prev_token.span, ExprKind::Mac(mac))
1015 } else if self.check(&token::OpenDelim(token::Brace)) {
1016 if let Some(expr) = self.maybe_parse_struct_expr(lo, &path, &attrs) {
1019 (path.span, ExprKind::Path(None, path))
1022 (path.span, ExprKind::Path(None, path))
1025 let expr = self.mk_expr(lo.to(hi), kind, attrs);
1026 self.maybe_recover_from_bad_qpath(expr, true)
1029 fn parse_labeled_expr(&mut self, label: Label, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1030 let lo = label.ident.span;
1031 self.expect(&token::Colon)?;
1032 if self.eat_keyword(kw::While) {
1033 return self.parse_while_expr(Some(label), lo, attrs);
1035 if self.eat_keyword(kw::For) {
1036 return self.parse_for_expr(Some(label), lo, attrs);
1038 if self.eat_keyword(kw::Loop) {
1039 return self.parse_loop_expr(Some(label), lo, attrs);
1041 if self.token == token::OpenDelim(token::Brace) {
1042 return self.parse_block_expr(Some(label), lo, BlockCheckMode::Default, attrs);
1045 let msg = "expected `while`, `for`, `loop` or `{` after a label";
1046 self.struct_span_err(self.token.span, msg).span_label(self.token.span, msg).emit();
1047 // Continue as an expression in an effort to recover on `'label: non_block_expr`.
1051 /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
1052 fn recover_do_catch(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1053 let lo = self.token.span;
1055 self.bump(); // `do`
1056 self.bump(); // `catch`
1058 let span_dc = lo.to(self.prev_token.span);
1059 self.struct_span_err(span_dc, "found removed `do catch` syntax")
1062 "replace with the new syntax",
1064 Applicability::MachineApplicable,
1066 .note("following RFC #2388, the new non-placeholder syntax is `try`")
1069 self.parse_try_block(lo, attrs)
1072 /// Parse an expression if the token can begin one.
1073 fn parse_expr_opt(&mut self) -> PResult<'a, Option<P<Expr>>> {
1074 Ok(if self.token.can_begin_expr() { Some(self.parse_expr()?) } else { None })
1077 /// Parse `"return" expr?`.
1078 fn parse_return_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1079 let lo = self.prev_token.span;
1080 let kind = ExprKind::Ret(self.parse_expr_opt()?);
1081 let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
1082 self.maybe_recover_from_bad_qpath(expr, true)
1085 /// Parse `"('label ":")? break expr?`.
1086 fn parse_break_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1087 let lo = self.prev_token.span;
1088 let label = self.eat_label();
1089 let kind = if self.token != token::OpenDelim(token::Brace)
1090 || !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1092 self.parse_expr_opt()?
1096 let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Break(label, kind), attrs);
1097 self.maybe_recover_from_bad_qpath(expr, true)
1100 /// Parse `"yield" expr?`.
1101 fn parse_yield_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1102 let lo = self.prev_token.span;
1103 let kind = ExprKind::Yield(self.parse_expr_opt()?);
1104 let span = lo.to(self.prev_token.span);
1105 self.sess.gated_spans.gate(sym::generators, span);
1106 let expr = self.mk_expr(span, kind, attrs);
1107 self.maybe_recover_from_bad_qpath(expr, true)
1110 /// Returns a string literal if the next token is a string literal.
1111 /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
1112 /// and returns `None` if the next token is not literal at all.
1113 pub fn parse_str_lit(&mut self) -> Result<ast::StrLit, Option<Lit>> {
1114 match self.parse_opt_lit() {
1115 Some(lit) => match lit.kind {
1116 ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
1118 symbol: lit.token.symbol,
1119 suffix: lit.token.suffix,
1123 _ => Err(Some(lit)),
1129 pub(super) fn parse_lit(&mut self) -> PResult<'a, Lit> {
1130 self.parse_opt_lit().ok_or_else(|| {
1131 let msg = format!("unexpected token: {}", super::token_descr(&self.token));
1132 self.struct_span_err(self.token.span, &msg)
1136 /// Matches `lit = true | false | token_lit`.
1137 /// Returns `None` if the next token is not a literal.
1138 pub(super) fn parse_opt_lit(&mut self) -> Option<Lit> {
1139 let mut recovered = None;
1140 if self.token == token::Dot {
1141 // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
1142 // dot would follow an optional literal, so we do this unconditionally.
1143 recovered = self.look_ahead(1, |next_token| {
1144 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
1147 if self.token.span.hi() == next_token.span.lo() {
1148 let s = String::from("0.") + &symbol.as_str();
1149 let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
1150 return Some(Token::new(kind, self.token.span.to(next_token.span)));
1155 if let Some(token) = &recovered {
1157 self.error_float_lits_must_have_int_part(&token);
1161 let token = recovered.as_ref().unwrap_or(&self.token);
1162 match Lit::from_token(token) {
1167 Err(LitError::NotLiteral) => None,
1169 let span = token.span;
1170 let lit = match token.kind {
1171 token::Literal(lit) => lit,
1172 _ => unreachable!(),
1175 self.report_lit_error(err, lit, span);
1176 // Pack possible quotes and prefixes from the original literal into
1177 // the error literal's symbol so they can be pretty-printed faithfully.
1178 let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
1179 let symbol = Symbol::intern(&suffixless_lit.to_string());
1180 let lit = token::Lit::new(token::Err, symbol, lit.suffix);
1181 Some(Lit::from_lit_token(lit, span).unwrap_or_else(|_| unreachable!()))
1186 fn error_float_lits_must_have_int_part(&self, token: &Token) {
1187 self.struct_span_err(token.span, "float literals must have an integer part")
1190 "must have an integer part",
1191 pprust::token_to_string(token),
1192 Applicability::MachineApplicable,
1197 fn report_lit_error(&self, err: LitError, lit: token::Lit, span: Span) {
1198 // Checks if `s` looks like i32 or u1234 etc.
1199 fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
1200 s.len() > 1 && s.starts_with(first_chars) && s[1..].chars().all(|c| c.is_ascii_digit())
1203 let token::Lit { kind, suffix, .. } = lit;
1205 // `NotLiteral` is not an error by itself, so we don't report
1206 // it and give the parser opportunity to try something else.
1207 LitError::NotLiteral => {}
1208 // `LexerError` *is* an error, but it was already reported
1209 // by lexer, so here we don't report it the second time.
1210 LitError::LexerError => {}
1211 LitError::InvalidSuffix => {
1212 self.expect_no_suffix(
1214 &format!("{} {} literal", kind.article(), kind.descr()),
1218 LitError::InvalidIntSuffix => {
1219 let suf = suffix.expect("suffix error with no suffix").as_str();
1220 if looks_like_width_suffix(&['i', 'u'], &suf) {
1221 // If it looks like a width, try to be helpful.
1222 let msg = format!("invalid width `{}` for integer literal", &suf[1..]);
1223 self.struct_span_err(span, &msg)
1224 .help("valid widths are 8, 16, 32, 64 and 128")
1227 let msg = format!("invalid suffix `{}` for integer literal", suf);
1228 self.struct_span_err(span, &msg)
1229 .span_label(span, format!("invalid suffix `{}`", suf))
1230 .help("the suffix must be one of the integral types (`u32`, `isize`, etc)")
1234 LitError::InvalidFloatSuffix => {
1235 let suf = suffix.expect("suffix error with no suffix").as_str();
1236 if looks_like_width_suffix(&['f'], &suf) {
1237 // If it looks like a width, try to be helpful.
1238 let msg = format!("invalid width `{}` for float literal", &suf[1..]);
1239 self.struct_span_err(span, &msg).help("valid widths are 32 and 64").emit();
1241 let msg = format!("invalid suffix `{}` for float literal", suf);
1242 self.struct_span_err(span, &msg)
1243 .span_label(span, format!("invalid suffix `{}`", suf))
1244 .help("valid suffixes are `f32` and `f64`")
1248 LitError::NonDecimalFloat(base) => {
1249 let descr = match base {
1250 16 => "hexadecimal",
1253 _ => unreachable!(),
1255 self.struct_span_err(span, &format!("{} float literal is not supported", descr))
1256 .span_label(span, "not supported")
1259 LitError::IntTooLarge => {
1260 self.struct_span_err(span, "integer literal is too large").emit();
1265 pub(super) fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<Symbol>) {
1266 if let Some(suf) = suffix {
1267 let mut err = if kind == "a tuple index"
1268 && [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suf)
1270 // #59553: warn instead of reject out of hand to allow the fix to percolate
1271 // through the ecosystem when people fix their macros
1275 .struct_span_warn(sp, &format!("suffixes on {} are invalid", kind));
1277 "`{}` is *temporarily* accepted on tuple index fields as it was \
1278 incorrectly accepted on stable for a few releases",
1282 "on proc macros, you'll want to use `syn::Index::from` or \
1283 `proc_macro::Literal::*_unsuffixed` for code that will desugar \
1284 to tuple field access",
1287 "see issue #60210 <https://github.com/rust-lang/rust/issues/60210> \
1288 for more information",
1292 self.struct_span_err(sp, &format!("suffixes on {} are invalid", kind))
1294 err.span_label(sp, format!("invalid suffix `{}`", suf));
1299 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1300 pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1301 maybe_whole_expr!(self);
1303 let lo = self.token.span;
1304 let minus_present = self.eat(&token::BinOp(token::Minus));
1305 let lit = self.parse_lit()?;
1306 let expr = self.mk_expr(lit.span, ExprKind::Lit(lit), AttrVec::new());
1310 lo.to(self.prev_token.span),
1311 self.mk_unary(UnOp::Neg, expr),
1319 /// Parses a block or unsafe block.
1320 pub(super) fn parse_block_expr(
1322 opt_label: Option<Label>,
1324 blk_mode: BlockCheckMode,
1325 outer_attrs: AttrVec,
1326 ) -> PResult<'a, P<Expr>> {
1327 if let Some(label) = opt_label {
1328 self.sess.gated_spans.gate(sym::label_break_value, label.ident.span);
1331 self.expect(&token::OpenDelim(token::Brace))?;
1333 let mut attrs = outer_attrs;
1334 attrs.extend(self.parse_inner_attributes()?);
1336 let blk = self.parse_block_tail(lo, blk_mode)?;
1337 Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs))
1340 /// Parses a closure expression (e.g., `move |args| expr`).
1341 fn parse_closure_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1342 let lo = self.token.span;
1345 if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
1348 if self.normalized_token.span.rust_2018() { self.parse_asyncness() } else { Async::No };
1349 if asyncness.is_async() {
1350 // Feature-gate `async ||` closures.
1351 self.sess.gated_spans.gate(sym::async_closure, self.normalized_prev_token.span);
1354 let capture_clause = self.parse_capture_clause();
1355 let decl = self.parse_fn_block_decl()?;
1356 let decl_hi = self.prev_token.span;
1357 let body = match decl.output {
1358 FnRetTy::Default(_) => {
1359 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
1360 self.parse_expr_res(restrictions, None)?
1363 // If an explicit return type is given, require a block to appear (RFC 968).
1364 let body_lo = self.token.span;
1365 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, AttrVec::new())?
1371 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
1376 /// Parses an optional `move` prefix to a closure lke construct.
1377 fn parse_capture_clause(&mut self) -> CaptureBy {
1378 if self.eat_keyword(kw::Move) { CaptureBy::Value } else { CaptureBy::Ref }
1381 /// Parses the `|arg, arg|` header of a closure.
1382 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
1383 let inputs = if self.eat(&token::OrOr) {
1386 self.expect(&token::BinOp(token::Or))?;
1388 .parse_seq_to_before_tokens(
1389 &[&token::BinOp(token::Or), &token::OrOr],
1390 SeqSep::trailing_allowed(token::Comma),
1391 TokenExpectType::NoExpect,
1392 |p| p.parse_fn_block_param(),
1398 let output = self.parse_ret_ty(AllowPlus::Yes, RecoverQPath::Yes)?;
1400 Ok(P(FnDecl { inputs, output }))
1403 /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
1404 fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
1405 let lo = self.token.span;
1406 let attrs = self.parse_outer_attributes()?;
1407 let pat = self.parse_pat(PARAM_EXPECTED)?;
1408 let ty = if self.eat(&token::Colon) {
1411 self.mk_ty(self.prev_token.span, TyKind::Infer)
1414 attrs: attrs.into(),
1417 span: lo.to(self.token.span),
1419 is_placeholder: false,
1423 /// Parses an `if` expression (`if` token already eaten).
1424 fn parse_if_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1425 let lo = self.prev_token.span;
1426 let cond = self.parse_cond_expr()?;
1428 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
1429 // verify that the last statement is either an implicit return (no `;`) or an explicit
1430 // return. This won't catch blocks with an explicit `return`, but that would be caught by
1431 // the dead code lint.
1432 let thn = if self.eat_keyword(kw::Else) || !cond.returns() {
1433 self.error_missing_if_cond(lo, cond.span)
1435 let not_block = self.token != token::OpenDelim(token::Brace);
1436 self.parse_block().map_err(|mut err| {
1438 err.span_label(lo, "this `if` expression has a condition, but no block");
1443 let els = if self.eat_keyword(kw::Else) { Some(self.parse_else_expr()?) } else { None };
1444 Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::If(cond, thn, els), attrs))
1447 fn error_missing_if_cond(&self, lo: Span, span: Span) -> P<ast::Block> {
1448 let sp = self.sess.source_map().next_point(lo);
1449 self.struct_span_err(sp, "missing condition for `if` expression")
1450 .span_label(sp, "expected if condition here")
1452 self.mk_block_err(span)
1455 /// Parses the condition of a `if` or `while` expression.
1456 fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
1457 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
1459 if let ExprKind::Let(..) = cond.kind {
1460 // Remove the last feature gating of a `let` expression since it's stable.
1461 self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
1467 /// Parses a `let $pat = $expr` pseudo-expression.
1468 /// The `let` token has already been eaten.
1469 fn parse_let_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1470 let lo = self.prev_token.span;
1471 let pat = self.parse_top_pat(GateOr::No)?;
1472 self.expect(&token::Eq)?;
1473 let expr = self.with_res(Restrictions::NO_STRUCT_LITERAL, |this| {
1474 this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
1476 let span = lo.to(expr.span);
1477 self.sess.gated_spans.gate(sym::let_chains, span);
1478 Ok(self.mk_expr(span, ExprKind::Let(pat, expr), attrs))
1481 /// Parses an `else { ... }` expression (`else` token already eaten).
1482 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
1483 if self.eat_keyword(kw::If) {
1484 self.parse_if_expr(AttrVec::new())
1486 let blk = self.parse_block()?;
1487 Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), AttrVec::new()))
1491 /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
1494 opt_label: Option<Label>,
1497 ) -> PResult<'a, P<Expr>> {
1498 // Record whether we are about to parse `for (`.
1499 // This is used below for recovery in case of `for ( $stuff ) $block`
1500 // in which case we will suggest `for $stuff $block`.
1501 let begin_paren = match self.token.kind {
1502 token::OpenDelim(token::Paren) => Some(self.token.span),
1506 let pat = self.parse_top_pat(GateOr::Yes)?;
1507 if !self.eat_keyword(kw::In) {
1508 self.error_missing_in_for_loop();
1510 self.check_for_for_in_in_typo(self.prev_token.span);
1511 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
1513 let pat = self.recover_parens_around_for_head(pat, &expr, begin_paren);
1515 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
1516 attrs.extend(iattrs);
1518 let kind = ExprKind::ForLoop(pat, expr, loop_block, opt_label);
1519 Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
1522 fn error_missing_in_for_loop(&self) {
1523 let in_span = self.prev_token.span.between(self.token.span);
1524 self.struct_span_err(in_span, "missing `in` in `for` loop")
1525 .span_suggestion_short(
1527 "try adding `in` here",
1529 // Has been misleading, at least in the past (closed Issue #48492).
1530 Applicability::MaybeIncorrect,
1535 /// Parses a `while` or `while let` expression (`while` token already eaten).
1536 fn parse_while_expr(
1538 opt_label: Option<Label>,
1541 ) -> PResult<'a, P<Expr>> {
1542 let cond = self.parse_cond_expr()?;
1543 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1544 attrs.extend(iattrs);
1545 Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::While(cond, body, opt_label), attrs))
1548 /// Parses `loop { ... }` (`loop` token already eaten).
1551 opt_label: Option<Label>,
1554 ) -> PResult<'a, P<Expr>> {
1555 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1556 attrs.extend(iattrs);
1557 Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::Loop(body, opt_label), attrs))
1560 fn eat_label(&mut self) -> Option<Label> {
1561 self.token.lifetime().map(|ident| {
1567 /// Parses a `match ... { ... }` expression (`match` token already eaten).
1568 fn parse_match_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
1569 let match_span = self.prev_token.span;
1570 let lo = self.prev_token.span;
1571 let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
1572 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
1573 if self.token == token::Semi {
1574 e.span_suggestion_short(
1576 "try removing this `match`",
1578 Applicability::MaybeIncorrect, // speculative
1583 attrs.extend(self.parse_inner_attributes()?);
1585 let mut arms: Vec<Arm> = Vec::new();
1586 while self.token != token::CloseDelim(token::Brace) {
1587 match self.parse_arm() {
1588 Ok(arm) => arms.push(arm),
1590 // Recover by skipping to the end of the block.
1592 self.recover_stmt();
1593 let span = lo.to(self.token.span);
1594 if self.token == token::CloseDelim(token::Brace) {
1597 return Ok(self.mk_expr(span, ExprKind::Match(scrutinee, arms), attrs));
1601 let hi = self.token.span;
1603 return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(scrutinee, arms), attrs));
1606 pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
1607 let attrs = self.parse_outer_attributes()?;
1608 let lo = self.token.span;
1609 let pat = self.parse_top_pat(GateOr::No)?;
1610 let guard = if self.eat_keyword(kw::If) { Some(self.parse_expr()?) } else { None };
1611 let arrow_span = self.token.span;
1612 self.expect(&token::FatArrow)?;
1613 let arm_start_span = self.token.span;
1615 let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
1616 err.span_label(arrow_span, "while parsing the `match` arm starting here");
1620 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
1621 && self.token != token::CloseDelim(token::Brace);
1623 let hi = self.token.span;
1626 let sm = self.sess.source_map();
1627 self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)]).map_err(
1629 match (sm.span_to_lines(expr.span), sm.span_to_lines(arm_start_span)) {
1630 (Ok(ref expr_lines), Ok(ref arm_start_lines))
1631 if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
1632 && expr_lines.lines.len() == 2
1633 && self.token == token::FatArrow =>
1635 // We check whether there's any trailing code in the parse span,
1636 // if there isn't, we very likely have the following:
1639 // | -- - missing comma
1643 // | - ^^ self.token.span
1645 // | parsed until here as `"y" & X`
1646 err.span_suggestion_short(
1647 arm_start_span.shrink_to_hi(),
1648 "missing a comma here to end this `match` arm",
1650 Applicability::MachineApplicable,
1656 "while parsing the `match` arm starting here",
1664 self.eat(&token::Comma);
1674 is_placeholder: false,
1678 /// Parses a `try {...}` expression (`try` token already eaten).
1679 fn parse_try_block(&mut self, span_lo: Span, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
1680 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1681 attrs.extend(iattrs);
1682 if self.eat_keyword(kw::Catch) {
1683 let mut error = self.struct_span_err(
1684 self.prev_token.span,
1685 "keyword `catch` cannot follow a `try` block",
1687 error.help("try using `match` on the result of the `try` block instead");
1691 let span = span_lo.to(body.span);
1692 self.sess.gated_spans.gate(sym::try_blocks, span);
1693 Ok(self.mk_expr(span, ExprKind::TryBlock(body), attrs))
1697 fn is_do_catch_block(&self) -> bool {
1698 self.token.is_keyword(kw::Do)
1699 && self.is_keyword_ahead(1, &[kw::Catch])
1700 && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
1701 && !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1704 fn is_try_block(&self) -> bool {
1705 self.token.is_keyword(kw::Try) &&
1706 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
1707 self.normalized_token.span.rust_2018() &&
1708 // Prevent `while try {} {}`, `if try {} {} else {}`, etc.
1709 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1712 /// Parses an `async move? {...}` expression.
1713 fn parse_async_block(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
1714 let lo = self.token.span;
1715 self.expect_keyword(kw::Async)?;
1716 let capture_clause = self.parse_capture_clause();
1717 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1718 attrs.extend(iattrs);
1719 let kind = ExprKind::Async(capture_clause, DUMMY_NODE_ID, body);
1720 Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
1723 fn is_async_block(&self) -> bool {
1724 self.token.is_keyword(kw::Async)
1727 self.is_keyword_ahead(1, &[kw::Move])
1728 && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
1731 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
1735 fn is_certainly_not_a_block(&self) -> bool {
1736 self.look_ahead(1, |t| t.is_ident())
1738 // `{ ident, ` cannot start a block.
1739 self.look_ahead(2, |t| t == &token::Comma)
1740 || self.look_ahead(2, |t| t == &token::Colon)
1742 // `{ ident: token, ` cannot start a block.
1743 self.look_ahead(4, |t| t == &token::Comma) ||
1744 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
1745 self.look_ahead(3, |t| !t.can_begin_type())
1750 fn maybe_parse_struct_expr(
1755 ) -> Option<PResult<'a, P<Expr>>> {
1756 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
1757 if struct_allowed || self.is_certainly_not_a_block() {
1758 // This is a struct literal, but we don't can't accept them here.
1759 let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
1760 if let (Ok(expr), false) = (&expr, struct_allowed) {
1761 self.error_struct_lit_not_allowed_here(lo, expr.span);
1768 fn error_struct_lit_not_allowed_here(&self, lo: Span, sp: Span) {
1769 self.struct_span_err(sp, "struct literals are not allowed here")
1770 .multipart_suggestion(
1771 "surround the struct literal with parentheses",
1772 vec![(lo.shrink_to_lo(), "(".to_string()), (sp.shrink_to_hi(), ")".to_string())],
1773 Applicability::MachineApplicable,
1778 pub(super) fn parse_struct_expr(
1783 ) -> PResult<'a, P<Expr>> {
1784 let struct_sp = lo.to(self.prev_token.span);
1786 let mut fields = Vec::new();
1787 let mut base = None;
1789 attrs.extend(self.parse_inner_attributes()?);
1791 while self.token != token::CloseDelim(token::Brace) {
1792 if self.eat(&token::DotDot) {
1793 let exp_span = self.prev_token.span;
1794 match self.parse_expr() {
1795 Ok(e) => base = Some(e),
1798 self.recover_stmt();
1801 self.recover_struct_comma_after_dotdot(exp_span);
1805 let recovery_field = self.find_struct_error_after_field_looking_code();
1806 let parsed_field = match self.parse_field() {
1809 e.span_label(struct_sp, "while parsing this struct");
1812 // If the next token is a comma, then try to parse
1813 // what comes next as additional fields, rather than
1814 // bailing out until next `}`.
1815 if self.token != token::Comma {
1816 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
1817 if self.token != token::Comma {
1825 match self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)]) {
1827 if let Some(f) = parsed_field.or(recovery_field) {
1828 // Only include the field if there's no parse error for the field name.
1833 e.span_label(struct_sp, "while parsing this struct");
1834 if let Some(f) = recovery_field {
1837 self.prev_token.span.shrink_to_hi(),
1838 "try adding a comma",
1840 Applicability::MachineApplicable,
1844 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
1845 self.eat(&token::Comma);
1850 let span = lo.to(self.token.span);
1851 self.expect(&token::CloseDelim(token::Brace))?;
1852 Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs))
1855 /// Use in case of error after field-looking code: `S { foo: () with a }`.
1856 fn find_struct_error_after_field_looking_code(&self) -> Option<Field> {
1857 if let token::Ident(name, _) = self.normalized_token.kind {
1858 if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
1859 return Some(ast::Field {
1860 ident: Ident::new(name, self.normalized_token.span),
1861 span: self.token.span,
1862 expr: self.mk_expr_err(self.token.span),
1863 is_shorthand: false,
1864 attrs: AttrVec::new(),
1866 is_placeholder: false,
1873 fn recover_struct_comma_after_dotdot(&mut self, span: Span) {
1874 if self.token != token::Comma {
1877 self.struct_span_err(
1878 span.to(self.prev_token.span),
1879 "cannot use a comma after the base struct",
1881 .span_suggestion_short(
1883 "remove this comma",
1885 Applicability::MachineApplicable,
1887 .note("the base struct must always be the last field")
1889 self.recover_stmt();
1892 /// Parses `ident (COLON expr)?`.
1893 fn parse_field(&mut self) -> PResult<'a, Field> {
1894 let attrs = self.parse_outer_attributes()?.into();
1895 let lo = self.token.span;
1897 // Check if a colon exists one ahead. This means we're parsing a fieldname.
1898 let is_shorthand = !self.look_ahead(1, |t| t == &token::Colon || t == &token::Eq);
1899 let (ident, expr) = if is_shorthand {
1900 // Mimic `x: x` for the `x` field shorthand.
1901 let ident = self.parse_ident_common(false)?;
1902 let path = ast::Path::from_ident(ident);
1903 (ident, self.mk_expr(ident.span, ExprKind::Path(None, path), AttrVec::new()))
1905 let ident = self.parse_field_name()?;
1906 self.error_on_eq_field_init(ident);
1908 (ident, self.parse_expr()?)
1912 span: lo.to(expr.span),
1917 is_placeholder: false,
1921 /// Check for `=`. This means the source incorrectly attempts to
1922 /// initialize a field with an eq rather than a colon.
1923 fn error_on_eq_field_init(&self, field_name: Ident) {
1924 if self.token != token::Eq {
1928 self.struct_span_err(self.token.span, "expected `:`, found `=`")
1930 field_name.span.shrink_to_hi().to(self.token.span),
1931 "replace equals symbol with a colon",
1933 Applicability::MachineApplicable,
1938 fn err_dotdotdot_syntax(&self, span: Span) {
1939 self.struct_span_err(span, "unexpected token: `...`")
1942 "use `..` for an exclusive range",
1944 Applicability::MaybeIncorrect,
1948 "or `..=` for an inclusive range",
1950 Applicability::MaybeIncorrect,
1955 fn err_larrow_operator(&self, span: Span) {
1956 self.struct_span_err(span, "unexpected token: `<-`")
1959 "if you meant to write a comparison against a negative value, add a \
1960 space in between `<` and `-`",
1962 Applicability::MaybeIncorrect,
1967 fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
1968 ExprKind::AssignOp(binop, lhs, rhs)
1973 start: Option<P<Expr>>,
1974 end: Option<P<Expr>>,
1975 limits: RangeLimits,
1976 ) -> PResult<'a, ExprKind> {
1977 if end.is_none() && limits == RangeLimits::Closed {
1978 self.error_inclusive_range_with_no_end(self.prev_token.span);
1981 Ok(ExprKind::Range(start, end, limits))
1985 fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
1986 ExprKind::Unary(unop, expr)
1989 fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
1990 ExprKind::Binary(binop, lhs, rhs)
1993 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
1994 ExprKind::Index(expr, idx)
1997 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
1998 ExprKind::Call(f, args)
2001 fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
2002 let span = lo.to(self.prev_token.span);
2003 let await_expr = self.mk_expr(span, ExprKind::Await(self_arg), AttrVec::new());
2004 self.recover_from_await_method_call();
2008 crate fn mk_expr(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
2009 P(Expr { kind, span, attrs, id: DUMMY_NODE_ID })
2012 pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> {
2013 self.mk_expr(span, ExprKind::Err, AttrVec::new())