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_pretty::pprust;
8 use rustc_errors::{Applicability, PResult};
9 use rustc_span::source_map::{self, Span, Spanned};
10 use rustc_span::symbol::{kw, sym, Symbol};
12 use syntax::ast::{self, AttrStyle, AttrVec, CaptureBy, Field, Ident, Lit, DUMMY_NODE_ID};
13 use syntax::ast::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, Mac, Param, Ty, TyKind, UnOp};
14 use syntax::ast::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits};
16 use syntax::token::{self, Token, TokenKind};
17 use syntax::util::classify;
18 use syntax::util::literal::LitError;
19 use syntax::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
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.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(_, _, _)`
106 let sp = self.token.span;
108 Ok(self.mk_expr(sp, ExprKind::Err, AttrVec::new()))
115 /// Parses a sequence of expressions delimited by parentheses.
116 fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
117 self.parse_paren_comma_seq(|p| p.parse_expr_catch_underscore()).map(|(r, _)| r)
120 /// Parses an expression, subject to the given restrictions.
122 pub(super) fn parse_expr_res(
125 already_parsed_attrs: Option<AttrVec>,
126 ) -> PResult<'a, P<Expr>> {
127 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
130 /// Parses an associative expression.
132 /// This parses an expression accounting for associativity and precedence of the operators in
135 fn parse_assoc_expr(&mut self, already_parsed_attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
136 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
139 /// Parses an associative expression with operators of at least `min_prec` precedence.
140 pub(super) fn parse_assoc_expr_with(
144 ) -> PResult<'a, P<Expr>> {
145 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
148 let attrs = match lhs {
149 LhsExpr::AttributesParsed(attrs) => Some(attrs),
152 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind) {
153 return self.parse_prefix_range_expr(attrs);
155 self.parse_prefix_expr(attrs)?
158 let last_type_ascription_set = self.last_type_ascription.is_some();
160 if !self.should_continue_as_assoc_expr(&lhs) {
161 self.last_type_ascription = None;
165 self.expected_tokens.push(TokenType::Operator);
166 while let Some(op) = self.check_assoc_op() {
167 // Adjust the span for interpolated LHS to point to the `$lhs` token
168 // and not to what it refers to.
169 let lhs_span = match self.unnormalized_prev_token.kind {
170 TokenKind::Interpolated(..) => self.prev_span,
174 let cur_op_span = self.token.span;
175 let restrictions = if op.node.is_assign_like() {
176 self.restrictions & Restrictions::NO_STRUCT_LITERAL
180 let prec = op.node.precedence();
184 // Check for deprecated `...` syntax
185 if self.token == token::DotDotDot && op.node == AssocOp::DotDotEq {
186 self.err_dotdotdot_syntax(self.token.span);
189 if self.token == token::LArrow {
190 self.err_larrow_operator(self.token.span);
194 if op.node.is_comparison() {
195 if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
201 if op == AssocOp::As {
202 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
204 } else if op == AssocOp::Colon {
205 lhs = self.parse_assoc_op_ascribe(lhs, lhs_span)?;
207 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
208 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
209 // generalise it to the Fixity::None code.
210 lhs = self.parse_range_expr(prec, lhs, op, cur_op_span)?;
214 let fixity = op.fixity();
215 let prec_adjustment = match fixity {
218 // We currently have no non-associative operators that are not handled above by
219 // the special cases. The code is here only for future convenience.
222 let rhs = self.with_res(restrictions - Restrictions::STMT_EXPR, |this| {
223 this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
226 // Make sure that the span of the parent node is larger than the span of lhs and rhs,
227 // including the attributes.
229 lhs.attrs.iter().find(|a| a.style == AttrStyle::Outer).map_or(lhs_span, |a| a.span);
230 let span = lhs_span.to(rhs.span);
243 | AssocOp::ShiftRight
249 | AssocOp::GreaterEqual => {
250 let ast_op = op.to_ast_binop().unwrap();
251 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
252 self.mk_expr(span, binary, AttrVec::new())
255 self.mk_expr(span, ExprKind::Assign(lhs, rhs, cur_op_span), AttrVec::new())
257 AssocOp::AssignOp(k) => {
259 token::Plus => BinOpKind::Add,
260 token::Minus => BinOpKind::Sub,
261 token::Star => BinOpKind::Mul,
262 token::Slash => BinOpKind::Div,
263 token::Percent => BinOpKind::Rem,
264 token::Caret => BinOpKind::BitXor,
265 token::And => BinOpKind::BitAnd,
266 token::Or => BinOpKind::BitOr,
267 token::Shl => BinOpKind::Shl,
268 token::Shr => BinOpKind::Shr,
270 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
271 self.mk_expr(span, aopexpr, AttrVec::new())
273 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
274 self.span_bug(span, "AssocOp should have been handled by special case")
278 if let Fixity::None = fixity {
282 if last_type_ascription_set {
283 self.last_type_ascription = None;
288 fn should_continue_as_assoc_expr(&mut self, lhs: &Expr) -> bool {
289 match (self.expr_is_complete(lhs), self.check_assoc_op().map(|op| op.node)) {
290 // Semi-statement forms are odd:
291 // See https://github.com/rust-lang/rust/issues/29071
292 (true, None) => false,
293 (false, _) => true, // Continue parsing the expression.
294 // An exhaustive check is done in the following block, but these are checked first
295 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
296 // want to keep their span info to improve diagnostics in these cases in a later stage.
297 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
298 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
299 (true, Some(AssocOp::LAnd)) | // `{ 42 } &&x` (#61475)
300 (true, Some(AssocOp::Add)) // `{ 42 } + 42
301 // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
302 // `if x { a } else { b } && if y { c } else { d }`
303 if !self.look_ahead(1, |t| t.is_reserved_ident()) => {
304 // These cases are ambiguous and can't be identified in the parser alone.
305 let sp = self.sess.source_map().start_point(self.token.span);
306 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
309 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => false,
311 self.error_found_expr_would_be_stmt(lhs);
317 /// We've found an expression that would be parsed as a statement,
318 /// but the next token implies this should be parsed as an expression.
319 /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
320 fn error_found_expr_would_be_stmt(&self, lhs: &Expr) {
321 let mut err = self.struct_span_err(
323 &format!("expected expression, found `{}`", pprust::token_to_string(&self.token),),
325 err.span_label(self.token.span, "expected expression");
326 self.sess.expr_parentheses_needed(&mut err, lhs.span, Some(pprust::expr_to_string(&lhs)));
330 /// Possibly translate the current token to an associative operator.
331 /// The method does not advance the current token.
333 /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
334 fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
336 node: match (AssocOp::from_token(&self.token), &self.token.kind) {
338 (None, token::Ident(sym::and, false)) => {
339 self.error_bad_logical_op("and", "&&", "conjunction");
342 (None, token::Ident(sym::or, false)) => {
343 self.error_bad_logical_op("or", "||", "disjunction");
348 span: self.token.span,
352 /// Error on `and` and `or` suggesting `&&` and `||` respectively.
353 fn error_bad_logical_op(&self, bad: &str, good: &str, english: &str) {
354 self.struct_span_err(self.token.span, &format!("`{}` is not a logical operator", bad))
355 .span_suggestion_short(
357 &format!("use `{}` to perform logical {}", good, english),
359 Applicability::MachineApplicable,
361 .note("unlike in e.g., python and PHP, `&&` and `||` are used for logical operators")
365 /// Checks if this expression is a successfully parsed statement.
366 fn expr_is_complete(&self, e: &Expr) -> bool {
367 self.restrictions.contains(Restrictions::STMT_EXPR)
368 && !classify::expr_requires_semi_to_be_stmt(e)
371 /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
372 /// The other two variants are handled in `parse_prefix_range_expr` below.
379 ) -> PResult<'a, P<Expr>> {
380 let rhs = if self.is_at_start_of_range_notation_rhs() {
381 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
385 let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
386 let span = lhs.span.to(rhs_span);
388 if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
389 Ok(self.mk_expr(span, self.mk_range(Some(lhs), rhs, limits)?, AttrVec::new()))
392 fn is_at_start_of_range_notation_rhs(&self) -> bool {
393 if self.token.can_begin_expr() {
394 // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
395 if self.token == token::OpenDelim(token::Brace) {
396 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
404 /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
405 fn parse_prefix_range_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
406 // Check for deprecated `...` syntax.
407 if self.token == token::DotDotDot {
408 self.err_dotdotdot_syntax(self.token.span);
412 [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind),
413 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
417 let limits = match self.token.kind {
418 token::DotDot => RangeLimits::HalfOpen,
419 _ => RangeLimits::Closed,
421 let op = AssocOp::from_token(&self.token);
422 let attrs = self.parse_or_use_outer_attributes(attrs)?;
423 let lo = self.token.span;
425 let (span, opt_end) = if self.is_at_start_of_range_notation_rhs() {
426 // RHS must be parsed with more associativity than the dots.
427 self.parse_assoc_expr_with(op.unwrap().precedence() + 1, LhsExpr::NotYetParsed)
428 .map(|x| (lo.to(x.span), Some(x)))?
432 Ok(self.mk_expr(span, self.mk_range(None, opt_end, limits)?, attrs))
435 /// Parses a prefix-unary-operator expr.
436 fn parse_prefix_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
437 let attrs = self.parse_or_use_outer_attributes(attrs)?;
438 let lo = self.token.span;
439 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
440 let (hi, ex) = match self.token.kind {
441 token::Not => self.parse_unary_expr(lo, UnOp::Not), // `!expr`
442 token::Tilde => self.recover_tilde_expr(lo), // `~expr`
443 token::BinOp(token::Minus) => self.parse_unary_expr(lo, UnOp::Neg), // `-expr`
444 token::BinOp(token::Star) => self.parse_unary_expr(lo, UnOp::Deref), // `*expr`
445 token::BinOp(token::And) | token::AndAnd => self.parse_borrow_expr(lo),
446 token::Ident(..) if self.token.is_keyword(kw::Box) => self.parse_box_expr(lo),
447 token::Ident(..) if self.is_mistaken_not_ident_negation() => self.recover_not_expr(lo),
448 _ => return self.parse_dot_or_call_expr(Some(attrs)),
450 Ok(self.mk_expr(lo.to(hi), ex, attrs))
453 fn parse_prefix_expr_common(&mut self, lo: Span) -> PResult<'a, (Span, P<Expr>)> {
455 let expr = self.parse_prefix_expr(None);
456 let (span, expr) = self.interpolated_or_expr_span(expr)?;
457 Ok((lo.to(span), expr))
460 fn parse_unary_expr(&mut self, lo: Span, op: UnOp) -> PResult<'a, (Span, ExprKind)> {
461 let (span, expr) = self.parse_prefix_expr_common(lo)?;
462 Ok((span, self.mk_unary(op, expr)))
465 // Recover on `!` suggesting for bitwise negation instead.
466 fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
467 self.struct_span_err(lo, "`~` cannot be used as a unary operator")
468 .span_suggestion_short(
470 "use `!` to perform bitwise not",
472 Applicability::MachineApplicable,
476 self.parse_unary_expr(lo, UnOp::Not)
479 /// Parse `box expr`.
480 fn parse_box_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
481 let (span, expr) = self.parse_prefix_expr_common(lo)?;
482 self.sess.gated_spans.gate(sym::box_syntax, span);
483 Ok((span, ExprKind::Box(expr)))
486 fn is_mistaken_not_ident_negation(&self) -> bool {
487 let token_cannot_continue_expr = |t: &Token| match t.kind {
488 // These tokens can start an expression after `!`, but
489 // can't continue an expression after an ident
490 token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
491 token::Literal(..) | token::Pound => true,
492 _ => t.is_whole_expr(),
494 self.token.is_ident_named(sym::not) && self.look_ahead(1, token_cannot_continue_expr)
497 /// Recover on `not expr` in favor of `!expr`.
498 fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
500 let not_token = self.look_ahead(1, |t| t.clone());
501 self.struct_span_err(
503 &format!("unexpected {} after identifier", super::token_descr(¬_token)),
505 .span_suggestion_short(
506 // Span the `not` plus trailing whitespace to avoid
507 // trailing whitespace after the `!` in our suggestion
508 self.sess.source_map().span_until_non_whitespace(lo.to(not_token.span)),
509 "use `!` to perform logical negation",
511 Applicability::MachineApplicable,
516 self.parse_unary_expr(lo, UnOp::Not)
519 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
520 fn interpolated_or_expr_span(
522 expr: PResult<'a, P<Expr>>,
523 ) -> PResult<'a, (Span, P<Expr>)> {
526 match self.unnormalized_prev_token.kind {
527 TokenKind::Interpolated(..) => self.prev_span,
535 fn parse_assoc_op_cast(
539 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
540 ) -> PResult<'a, P<Expr>> {
541 let mk_expr = |this: &mut Self, rhs: P<Ty>| {
542 this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), AttrVec::new())
545 // Save the state of the parser before parsing type normally, in case there is a
546 // LessThan comparison after this cast.
547 let parser_snapshot_before_type = self.clone();
548 match self.parse_ty_no_plus() {
549 Ok(rhs) => Ok(mk_expr(self, rhs)),
550 Err(mut type_err) => {
551 // Rewind to before attempting to parse the type with generics, to recover
552 // from situations like `x as usize < y` in which we first tried to parse
553 // `usize < y` as a type with generic arguments.
554 let parser_snapshot_after_type = self.clone();
555 mem::replace(self, parser_snapshot_before_type);
557 match self.parse_path(PathStyle::Expr) {
559 let (op_noun, op_verb) = match self.token.kind {
560 token::Lt => ("comparison", "comparing"),
561 token::BinOp(token::Shl) => ("shift", "shifting"),
563 // We can end up here even without `<` being the next token, for
564 // example because `parse_ty_no_plus` returns `Err` on keywords,
565 // but `parse_path` returns `Ok` on them due to error recovery.
566 // Return original error and parser state.
567 mem::replace(self, parser_snapshot_after_type);
568 return Err(type_err);
572 // Successfully parsed the type path leaving a `<` yet to parse.
575 // Report non-fatal diagnostics, keep `x as usize` as an expression
576 // in AST and continue parsing.
578 "`<` is interpreted as a start of generic arguments for `{}`, not a {}",
579 pprust::path_to_string(&path),
582 let span_after_type = parser_snapshot_after_type.token.span;
583 let expr = mk_expr(self, self.mk_ty(path.span, TyKind::Path(None, path)));
586 .span_to_snippet(expr.span)
587 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
589 self.struct_span_err(self.token.span, &msg)
591 self.look_ahead(1, |t| t.span).to(span_after_type),
592 "interpreted as generic arguments",
594 .span_label(self.token.span, format!("not interpreted as {}", op_noun))
597 &format!("try {} the cast value", op_verb),
598 format!("({})", expr_str),
599 Applicability::MachineApplicable,
605 Err(mut path_err) => {
606 // Couldn't parse as a path, return original error and parser state.
608 mem::replace(self, parser_snapshot_after_type);
616 fn parse_assoc_op_ascribe(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
617 let maybe_path = self.could_ascription_be_path(&lhs.kind);
618 self.last_type_ascription = Some((self.prev_span, maybe_path));
619 let lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
620 self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
624 /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
625 fn parse_borrow_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
627 let (borrow_kind, mutbl) = self.parse_borrow_modifiers(lo);
628 let expr = self.parse_prefix_expr(None);
629 let (span, expr) = self.interpolated_or_expr_span(expr)?;
630 Ok((lo.to(span), ExprKind::AddrOf(borrow_kind, mutbl, expr)))
633 /// Parse `mut?` or `raw [ const | mut ]`.
634 fn parse_borrow_modifiers(&mut self, lo: Span) -> (ast::BorrowKind, ast::Mutability) {
635 if self.check_keyword(kw::Raw) && self.look_ahead(1, Token::is_mutability) {
636 // `raw [ const | mut ]`.
637 let found_raw = self.eat_keyword(kw::Raw);
639 let mutability = self.parse_const_or_mut().unwrap();
640 self.sess.gated_spans.gate(sym::raw_ref_op, lo.to(self.prev_span));
641 (ast::BorrowKind::Raw, mutability)
644 (ast::BorrowKind::Ref, self.parse_mutability())
648 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
649 fn parse_dot_or_call_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
650 let attrs = self.parse_or_use_outer_attributes(attrs)?;
651 let base = self.parse_bottom_expr();
652 let (span, base) = self.interpolated_or_expr_span(base)?;
653 self.parse_dot_or_call_expr_with(base, span, attrs)
656 pub(super) fn parse_dot_or_call_expr_with(
661 ) -> PResult<'a, P<Expr>> {
662 // Stitch the list of outer attributes onto the return value.
663 // A little bit ugly, but the best way given the current code
665 self.parse_dot_or_call_expr_with_(e0, lo).map(|expr| {
666 expr.map(|mut expr| {
667 attrs.extend::<Vec<_>>(expr.attrs.into());
669 self.error_attr_on_if_expr(&expr);
675 fn error_attr_on_if_expr(&self, expr: &Expr) {
676 if let (ExprKind::If(..), [a0, ..]) = (&expr.kind, &*expr.attrs) {
677 // Just point to the first attribute in there...
678 self.struct_span_err(a0.span, "attributes are not yet allowed on `if` expressions")
683 fn parse_dot_or_call_expr_with_(&mut self, mut e: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
685 if self.eat(&token::Question) {
687 e = self.mk_expr(lo.to(self.prev_span), ExprKind::Try(e), AttrVec::new());
690 if self.eat(&token::Dot) {
692 e = self.parse_dot_suffix_expr(lo, e)?;
695 if self.expr_is_complete(&e) {
698 e = match self.token.kind {
699 token::OpenDelim(token::Paren) => self.parse_fn_call_expr(lo, e),
700 token::OpenDelim(token::Bracket) => self.parse_index_expr(lo, e)?,
706 fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
707 match self.token.kind {
708 token::Ident(..) => self.parse_dot_suffix(base, lo),
709 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
710 Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix))
712 token::Literal(token::Lit { kind: token::Float, symbol, .. }) => {
713 self.recover_field_access_by_float_lit(lo, base, symbol)
716 self.error_unexpected_after_dot();
722 fn error_unexpected_after_dot(&self) {
723 // FIXME Could factor this out into non_fatal_unexpected or something.
724 let actual = pprust::token_to_string(&self.token);
725 self.struct_span_err(self.token.span, &format!("unexpected token: `{}`", actual)).emit();
728 fn recover_field_access_by_float_lit(
733 ) -> PResult<'a, P<Expr>> {
736 let fstr = sym.as_str();
737 let msg = format!("unexpected token: `{}`", sym);
739 let mut err = self.struct_span_err(self.prev_span, &msg);
740 err.span_label(self.prev_span, "unexpected token");
742 if fstr.chars().all(|x| "0123456789.".contains(x)) {
743 let float = match fstr.parse::<f64>() {
750 let sugg = pprust::to_string(|s| {
754 s.print_usize(float.trunc() as usize);
757 s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
760 lo.to(self.prev_span),
761 "try parenthesizing the first index",
763 Applicability::MachineApplicable,
769 fn parse_tuple_field_access_expr(
774 suffix: Option<Symbol>,
776 let span = self.token.span;
778 let field = ExprKind::Field(base, Ident::new(field, span));
779 self.expect_no_suffix(span, "a tuple index", suffix);
780 self.mk_expr(lo.to(span), field, AttrVec::new())
783 /// Parse a function call expression, `expr(...)`.
784 fn parse_fn_call_expr(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
785 let seq = self.parse_paren_expr_seq().map(|args| {
786 self.mk_expr(lo.to(self.prev_span), self.mk_call(fun, args), AttrVec::new())
788 self.recover_seq_parse_error(token::Paren, lo, seq)
791 /// Parse an indexing expression `expr[...]`.
792 fn parse_index_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
794 let index = self.parse_expr()?;
795 self.expect(&token::CloseDelim(token::Bracket))?;
796 Ok(self.mk_expr(lo.to(self.prev_span), self.mk_index(base, index), AttrVec::new()))
799 /// Assuming we have just parsed `.`, continue parsing into an expression.
800 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
801 if self.token.span.rust_2018() && self.eat_keyword(kw::Await) {
802 return self.mk_await_expr(self_arg, lo);
805 let segment = self.parse_path_segment(PathStyle::Expr)?;
806 self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
808 if self.check(&token::OpenDelim(token::Paren)) {
809 // Method call `expr.f()`
810 let mut args = self.parse_paren_expr_seq()?;
811 args.insert(0, self_arg);
813 let span = lo.to(self.prev_span);
814 Ok(self.mk_expr(span, ExprKind::MethodCall(segment, args), AttrVec::new()))
816 // Field access `expr.f`
817 if let Some(args) = segment.args {
818 self.struct_span_err(
820 "field expressions cannot have generic arguments",
825 let span = lo.to(self.prev_span);
826 Ok(self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), AttrVec::new()))
830 /// At the bottom (top?) of the precedence hierarchy,
831 /// Parses things like parenthesized exprs, macros, `return`, etc.
833 /// N.B., this does not parse outer attributes, and is private because it only works
834 /// correctly if called from `parse_dot_or_call_expr()`.
835 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
836 maybe_recover_from_interpolated_ty_qpath!(self, true);
837 maybe_whole_expr!(self);
839 // Outer attributes are already parsed and will be
840 // added to the return value after the fact.
842 // Therefore, prevent sub-parser from parsing
843 // attributes by giving them a empty "already-parsed" list.
844 let attrs = AttrVec::new();
846 // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
847 let lo = self.token.span;
848 if let token::Literal(_) = self.token.kind {
849 // This match arm is a special-case of the `_` match arm below and
850 // could be removed without changing functionality, but it's faster
851 // to have it here, especially for programs with large constants.
852 self.parse_lit_expr(attrs)
853 } else if self.check(&token::OpenDelim(token::Paren)) {
854 self.parse_tuple_parens_expr(attrs)
855 } else if self.check(&token::OpenDelim(token::Brace)) {
856 self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs)
857 } else if self.check(&token::BinOp(token::Or)) || self.check(&token::OrOr) {
858 self.parse_closure_expr(attrs)
859 } else if self.check(&token::OpenDelim(token::Bracket)) {
860 self.parse_array_or_repeat_expr(attrs)
861 } else if self.eat_lt() {
862 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
863 Ok(self.mk_expr(lo.to(path.span), ExprKind::Path(Some(qself), path), attrs))
864 } else if self.token.is_path_start() {
865 self.parse_path_start_expr(attrs)
866 } else if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
867 self.parse_closure_expr(attrs)
868 } else if self.eat_keyword(kw::If) {
869 self.parse_if_expr(attrs)
870 } else if self.eat_keyword(kw::For) {
871 self.parse_for_expr(None, self.prev_span, attrs)
872 } else if self.eat_keyword(kw::While) {
873 self.parse_while_expr(None, self.prev_span, attrs)
874 } else if let Some(label) = self.eat_label() {
875 self.parse_labeled_expr(label, attrs)
876 } else if self.eat_keyword(kw::Loop) {
877 self.parse_loop_expr(None, self.prev_span, attrs)
878 } else if self.eat_keyword(kw::Continue) {
879 let kind = ExprKind::Continue(self.eat_label());
880 Ok(self.mk_expr(lo.to(self.prev_span), kind, attrs))
881 } else if self.eat_keyword(kw::Match) {
882 let match_sp = self.prev_span;
883 self.parse_match_expr(attrs).map_err(|mut err| {
884 err.span_label(match_sp, "while parsing this match expression");
887 } else if self.eat_keyword(kw::Unsafe) {
888 self.parse_block_expr(None, lo, BlockCheckMode::Unsafe(ast::UserProvided), attrs)
889 } else if self.is_do_catch_block() {
890 self.recover_do_catch(attrs)
891 } else if self.is_try_block() {
892 self.expect_keyword(kw::Try)?;
893 self.parse_try_block(lo, attrs)
894 } else if self.eat_keyword(kw::Return) {
895 self.parse_return_expr(attrs)
896 } else if self.eat_keyword(kw::Break) {
897 self.parse_break_expr(attrs)
898 } else if self.eat_keyword(kw::Yield) {
899 self.parse_yield_expr(attrs)
900 } else if self.eat_keyword(kw::Let) {
901 self.parse_let_expr(attrs)
902 } else if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
903 // Don't complain about bare semicolons after unclosed braces
904 // recovery in order to keep the error count down. Fixing the
905 // delimiters will possibly also fix the bare semicolon found in
906 // expression context. For example, silence the following error:
908 // error: expected expression, found `;`
912 // | ^ expected expression
914 Ok(self.mk_expr_err(self.token.span))
915 } else if self.token.span.rust_2018() {
916 // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
917 if self.check_keyword(kw::Async) {
918 if self.is_async_block() {
919 // Check for `async {` and `async move {`.
920 self.parse_async_block(attrs)
922 self.parse_closure_expr(attrs)
924 } else if self.eat_keyword(kw::Await) {
925 self.recover_incorrect_await_syntax(lo, self.prev_span, attrs)
927 self.parse_lit_expr(attrs)
930 self.parse_lit_expr(attrs)
934 fn parse_lit_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
935 let lo = self.token.span;
936 match self.parse_opt_lit() {
938 let expr = self.mk_expr(lo.to(self.prev_span), ExprKind::Lit(literal), attrs);
939 self.maybe_recover_from_bad_qpath(expr, true)
941 None => return Err(self.expected_expression_found()),
945 fn parse_tuple_parens_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
946 let lo = self.token.span;
947 self.expect(&token::OpenDelim(token::Paren))?;
948 attrs.extend(self.parse_inner_attributes()?); // `(#![foo] a, b, ...)` is OK.
949 let (es, trailing_comma) = match self.parse_seq_to_end(
950 &token::CloseDelim(token::Paren),
951 SeqSep::trailing_allowed(token::Comma),
952 |p| p.parse_expr_catch_underscore(),
955 Err(err) => return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err))),
957 let kind = if es.len() == 1 && !trailing_comma {
958 // `(e)` is parenthesized `e`.
959 ExprKind::Paren(es.into_iter().nth(0).unwrap())
961 // `(e,)` is a tuple with only one field, `e`.
964 let expr = self.mk_expr(lo.to(self.prev_span), kind, attrs);
965 self.maybe_recover_from_bad_qpath(expr, true)
968 fn parse_array_or_repeat_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
969 let lo = self.token.span;
972 attrs.extend(self.parse_inner_attributes()?);
974 let close = &token::CloseDelim(token::Bracket);
975 let kind = if self.eat(close) {
977 ExprKind::Array(Vec::new())
980 let first_expr = self.parse_expr()?;
981 if self.eat(&token::Semi) {
982 // Repeating array syntax: `[ 0; 512 ]`
983 let count = self.parse_anon_const_expr()?;
985 ExprKind::Repeat(first_expr, count)
986 } else if self.eat(&token::Comma) {
987 // Vector with two or more elements.
988 let sep = SeqSep::trailing_allowed(token::Comma);
989 let (remaining_exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
990 let mut exprs = vec![first_expr];
991 exprs.extend(remaining_exprs);
992 ExprKind::Array(exprs)
994 // Vector with one element
996 ExprKind::Array(vec![first_expr])
999 let expr = self.mk_expr(lo.to(self.prev_span), kind, attrs);
1000 self.maybe_recover_from_bad_qpath(expr, true)
1003 fn parse_path_start_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1004 let lo = self.token.span;
1005 let path = self.parse_path(PathStyle::Expr)?;
1007 // `!`, as an operator, is prefix, so we know this isn't that.
1008 let (hi, kind) = if self.eat(&token::Not) {
1009 // MACRO INVOCATION expression
1012 args: self.parse_mac_args()?,
1013 prior_type_ascription: self.last_type_ascription,
1015 (self.prev_span, ExprKind::Mac(mac))
1016 } else if self.check(&token::OpenDelim(token::Brace)) {
1017 if let Some(expr) = self.maybe_parse_struct_expr(lo, &path, &attrs) {
1020 (path.span, ExprKind::Path(None, path))
1023 (path.span, ExprKind::Path(None, path))
1026 let expr = self.mk_expr(lo.to(hi), kind, attrs);
1027 self.maybe_recover_from_bad_qpath(expr, true)
1030 fn parse_labeled_expr(&mut self, label: Label, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1031 let lo = label.ident.span;
1032 self.expect(&token::Colon)?;
1033 if self.eat_keyword(kw::While) {
1034 return self.parse_while_expr(Some(label), lo, attrs);
1036 if self.eat_keyword(kw::For) {
1037 return self.parse_for_expr(Some(label), lo, attrs);
1039 if self.eat_keyword(kw::Loop) {
1040 return self.parse_loop_expr(Some(label), lo, attrs);
1042 if self.token == token::OpenDelim(token::Brace) {
1043 return self.parse_block_expr(Some(label), lo, BlockCheckMode::Default, attrs);
1046 let msg = "expected `while`, `for`, `loop` or `{` after a label";
1047 self.struct_span_err(self.token.span, msg).span_label(self.token.span, msg).emit();
1048 // Continue as an expression in an effort to recover on `'label: non_block_expr`.
1052 /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
1053 fn recover_do_catch(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1054 let lo = self.token.span;
1056 self.bump(); // `do`
1057 self.bump(); // `catch`
1059 let span_dc = lo.to(self.prev_span);
1060 self.struct_span_err(span_dc, "found removed `do catch` syntax")
1063 "replace with the new syntax",
1065 Applicability::MachineApplicable,
1067 .note("following RFC #2388, the new non-placeholder syntax is `try`")
1070 self.parse_try_block(lo, attrs)
1073 /// Parse an expression if the token can begin one.
1074 fn parse_expr_opt(&mut self) -> PResult<'a, Option<P<Expr>>> {
1075 Ok(if self.token.can_begin_expr() { Some(self.parse_expr()?) } else { None })
1078 /// Parse `"return" expr?`.
1079 fn parse_return_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1080 let lo = self.prev_span;
1081 let kind = ExprKind::Ret(self.parse_expr_opt()?);
1082 let expr = self.mk_expr(lo.to(self.prev_span), kind, attrs);
1083 self.maybe_recover_from_bad_qpath(expr, true)
1086 /// Parse `"('label ":")? break expr?`.
1087 fn parse_break_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1088 let lo = self.prev_span;
1089 let label = self.eat_label();
1090 let kind = if self.token != token::OpenDelim(token::Brace)
1091 || !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1093 self.parse_expr_opt()?
1097 let expr = self.mk_expr(lo.to(self.prev_span), ExprKind::Break(label, kind), attrs);
1098 self.maybe_recover_from_bad_qpath(expr, true)
1101 /// Parse `"yield" expr?`.
1102 fn parse_yield_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1103 let lo = self.prev_span;
1104 let kind = ExprKind::Yield(self.parse_expr_opt()?);
1105 let span = lo.to(self.prev_span);
1106 self.sess.gated_spans.gate(sym::generators, span);
1107 let expr = self.mk_expr(span, kind, attrs);
1108 self.maybe_recover_from_bad_qpath(expr, true)
1111 /// Returns a string literal if the next token is a string literal.
1112 /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
1113 /// and returns `None` if the next token is not literal at all.
1114 pub fn parse_str_lit(&mut self) -> Result<ast::StrLit, Option<Lit>> {
1115 match self.parse_opt_lit() {
1116 Some(lit) => match lit.kind {
1117 ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
1119 symbol: lit.token.symbol,
1120 suffix: lit.token.suffix,
1124 _ => Err(Some(lit)),
1130 pub(super) fn parse_lit(&mut self) -> PResult<'a, Lit> {
1131 self.parse_opt_lit().ok_or_else(|| {
1132 let msg = format!("unexpected token: {}", super::token_descr(&self.token));
1133 self.struct_span_err(self.token.span, &msg)
1137 /// Matches `lit = true | false | token_lit`.
1138 /// Returns `None` if the next token is not a literal.
1139 pub(super) fn parse_opt_lit(&mut self) -> Option<Lit> {
1140 let mut recovered = None;
1141 if self.token == token::Dot {
1142 // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
1143 // dot would follow an optional literal, so we do this unconditionally.
1144 recovered = self.look_ahead(1, |next_token| {
1145 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
1148 if self.token.span.hi() == next_token.span.lo() {
1149 let s = String::from("0.") + &symbol.as_str();
1150 let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
1151 return Some(Token::new(kind, self.token.span.to(next_token.span)));
1156 if let Some(token) = &recovered {
1158 self.error_float_lits_must_have_int_part(&token);
1162 let token = recovered.as_ref().unwrap_or(&self.token);
1163 match Lit::from_token(token) {
1168 Err(LitError::NotLiteral) => None,
1170 let span = token.span;
1171 let lit = match token.kind {
1172 token::Literal(lit) => lit,
1173 _ => unreachable!(),
1176 self.report_lit_error(err, lit, span);
1177 // Pack possible quotes and prefixes from the original literal into
1178 // the error literal's symbol so they can be pretty-printed faithfully.
1179 let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
1180 let symbol = Symbol::intern(&suffixless_lit.to_string());
1181 let lit = token::Lit::new(token::Err, symbol, lit.suffix);
1182 Some(Lit::from_lit_token(lit, span).unwrap_or_else(|_| unreachable!()))
1187 fn error_float_lits_must_have_int_part(&self, token: &Token) {
1188 self.struct_span_err(token.span, "float literals must have an integer part")
1191 "must have an integer part",
1192 pprust::token_to_string(token),
1193 Applicability::MachineApplicable,
1198 fn report_lit_error(&self, err: LitError, lit: token::Lit, span: Span) {
1199 // Checks if `s` looks like i32 or u1234 etc.
1200 fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
1201 s.len() > 1 && s.starts_with(first_chars) && s[1..].chars().all(|c| c.is_ascii_digit())
1204 let token::Lit { kind, suffix, .. } = lit;
1206 // `NotLiteral` is not an error by itself, so we don't report
1207 // it and give the parser opportunity to try something else.
1208 LitError::NotLiteral => {}
1209 // `LexerError` *is* an error, but it was already reported
1210 // by lexer, so here we don't report it the second time.
1211 LitError::LexerError => {}
1212 LitError::InvalidSuffix => {
1213 self.expect_no_suffix(
1215 &format!("{} {} literal", kind.article(), kind.descr()),
1219 LitError::InvalidIntSuffix => {
1220 let suf = suffix.expect("suffix error with no suffix").as_str();
1221 if looks_like_width_suffix(&['i', 'u'], &suf) {
1222 // If it looks like a width, try to be helpful.
1223 let msg = format!("invalid width `{}` for integer literal", &suf[1..]);
1224 self.struct_span_err(span, &msg)
1225 .help("valid widths are 8, 16, 32, 64 and 128")
1228 let msg = format!("invalid suffix `{}` for integer literal", suf);
1229 self.struct_span_err(span, &msg)
1230 .span_label(span, format!("invalid suffix `{}`", suf))
1231 .help("the suffix must be one of the integral types (`u32`, `isize`, etc)")
1235 LitError::InvalidFloatSuffix => {
1236 let suf = suffix.expect("suffix error with no suffix").as_str();
1237 if looks_like_width_suffix(&['f'], &suf) {
1238 // If it looks like a width, try to be helpful.
1239 let msg = format!("invalid width `{}` for float literal", &suf[1..]);
1240 self.struct_span_err(span, &msg).help("valid widths are 32 and 64").emit();
1242 let msg = format!("invalid suffix `{}` for float literal", suf);
1243 self.struct_span_err(span, &msg)
1244 .span_label(span, format!("invalid suffix `{}`", suf))
1245 .help("valid suffixes are `f32` and `f64`")
1249 LitError::NonDecimalFloat(base) => {
1250 let descr = match base {
1251 16 => "hexadecimal",
1254 _ => unreachable!(),
1256 self.struct_span_err(span, &format!("{} float literal is not supported", descr))
1257 .span_label(span, "not supported")
1260 LitError::IntTooLarge => {
1261 self.struct_span_err(span, "integer literal is too large").emit();
1266 pub(super) fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<Symbol>) {
1267 if let Some(suf) = suffix {
1268 let mut err = if kind == "a tuple index"
1269 && [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suf)
1271 // #59553: warn instead of reject out of hand to allow the fix to percolate
1272 // through the ecosystem when people fix their macros
1276 .struct_span_warn(sp, &format!("suffixes on {} are invalid", kind));
1278 "`{}` is *temporarily* accepted on tuple index fields as it was \
1279 incorrectly accepted on stable for a few releases",
1283 "on proc macros, you'll want to use `syn::Index::from` or \
1284 `proc_macro::Literal::*_unsuffixed` for code that will desugar \
1285 to tuple field access",
1288 "see issue #60210 <https://github.com/rust-lang/rust/issues/60210> \
1289 for more information",
1293 self.struct_span_err(sp, &format!("suffixes on {} are invalid", kind))
1295 err.span_label(sp, format!("invalid suffix `{}`", suf));
1300 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1301 pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1302 maybe_whole_expr!(self);
1304 let lo = self.token.span;
1305 let minus_present = self.eat(&token::BinOp(token::Minus));
1306 let lit = self.parse_lit()?;
1307 let expr = self.mk_expr(lit.span, ExprKind::Lit(lit), AttrVec::new());
1310 Ok(self.mk_expr(lo.to(self.prev_span), self.mk_unary(UnOp::Neg, expr), AttrVec::new()))
1316 /// Parses a block or unsafe block.
1317 pub(super) fn parse_block_expr(
1319 opt_label: Option<Label>,
1321 blk_mode: BlockCheckMode,
1322 outer_attrs: AttrVec,
1323 ) -> PResult<'a, P<Expr>> {
1324 if let Some(label) = opt_label {
1325 self.sess.gated_spans.gate(sym::label_break_value, label.ident.span);
1328 self.expect(&token::OpenDelim(token::Brace))?;
1330 let mut attrs = outer_attrs;
1331 attrs.extend(self.parse_inner_attributes()?);
1333 let blk = self.parse_block_tail(lo, blk_mode)?;
1334 Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs))
1337 /// Parses a closure expression (e.g., `move |args| expr`).
1338 fn parse_closure_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1339 let lo = self.token.span;
1342 if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
1345 if self.token.span.rust_2018() { self.parse_asyncness() } else { Async::No };
1346 if asyncness.is_async() {
1347 // Feature-gate `async ||` closures.
1348 self.sess.gated_spans.gate(sym::async_closure, self.prev_span);
1351 let capture_clause = self.parse_capture_clause();
1352 let decl = self.parse_fn_block_decl()?;
1353 let decl_hi = self.prev_span;
1354 let body = match decl.output {
1355 FnRetTy::Default(_) => {
1356 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
1357 self.parse_expr_res(restrictions, None)?
1360 // If an explicit return type is given, require a block to appear (RFC 968).
1361 let body_lo = self.token.span;
1362 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, AttrVec::new())?
1368 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
1373 /// Parses an optional `move` prefix to a closure lke construct.
1374 fn parse_capture_clause(&mut self) -> CaptureBy {
1375 if self.eat_keyword(kw::Move) { CaptureBy::Value } else { CaptureBy::Ref }
1378 /// Parses the `|arg, arg|` header of a closure.
1379 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
1380 let inputs = if self.eat(&token::OrOr) {
1383 self.expect(&token::BinOp(token::Or))?;
1385 .parse_seq_to_before_tokens(
1386 &[&token::BinOp(token::Or), &token::OrOr],
1387 SeqSep::trailing_allowed(token::Comma),
1388 TokenExpectType::NoExpect,
1389 |p| p.parse_fn_block_param(),
1395 let output = self.parse_ret_ty(AllowPlus::Yes, RecoverQPath::Yes)?;
1397 Ok(P(FnDecl { inputs, output }))
1400 /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
1401 fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
1402 let lo = self.token.span;
1403 let attrs = self.parse_outer_attributes()?;
1404 let pat = self.parse_pat(PARAM_EXPECTED)?;
1405 let ty = if self.eat(&token::Colon) {
1408 self.mk_ty(self.prev_span, TyKind::Infer)
1411 attrs: attrs.into(),
1414 span: lo.to(self.token.span),
1416 is_placeholder: false,
1420 /// Parses an `if` expression (`if` token already eaten).
1421 fn parse_if_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1422 let lo = self.prev_span;
1423 let cond = self.parse_cond_expr()?;
1425 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
1426 // verify that the last statement is either an implicit return (no `;`) or an explicit
1427 // return. This won't catch blocks with an explicit `return`, but that would be caught by
1428 // the dead code lint.
1429 let thn = if self.eat_keyword(kw::Else) || !cond.returns() {
1430 self.error_missing_if_cond(lo, cond.span)
1432 let not_block = self.token != token::OpenDelim(token::Brace);
1433 self.parse_block().map_err(|mut err| {
1435 err.span_label(lo, "this `if` expression has a condition, but no block");
1440 let els = if self.eat_keyword(kw::Else) { Some(self.parse_else_expr()?) } else { None };
1441 Ok(self.mk_expr(lo.to(self.prev_span), ExprKind::If(cond, thn, els), attrs))
1444 fn error_missing_if_cond(&self, lo: Span, span: Span) -> P<ast::Block> {
1445 let sp = self.sess.source_map().next_point(lo);
1446 self.struct_span_err(sp, "missing condition for `if` expression")
1447 .span_label(sp, "expected if condition here")
1449 self.mk_block_err(span)
1452 /// Parses the condition of a `if` or `while` expression.
1453 fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
1454 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
1456 if let ExprKind::Let(..) = cond.kind {
1457 // Remove the last feature gating of a `let` expression since it's stable.
1458 self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
1464 /// Parses a `let $pat = $expr` pseudo-expression.
1465 /// The `let` token has already been eaten.
1466 fn parse_let_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1467 let lo = self.prev_span;
1468 let pat = self.parse_top_pat(GateOr::No)?;
1469 self.expect(&token::Eq)?;
1470 let expr = self.with_res(Restrictions::NO_STRUCT_LITERAL, |this| {
1471 this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
1473 let span = lo.to(expr.span);
1474 self.sess.gated_spans.gate(sym::let_chains, span);
1475 Ok(self.mk_expr(span, ExprKind::Let(pat, expr), attrs))
1478 /// Parses an `else { ... }` expression (`else` token already eaten).
1479 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
1480 if self.eat_keyword(kw::If) {
1481 self.parse_if_expr(AttrVec::new())
1483 let blk = self.parse_block()?;
1484 Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), AttrVec::new()))
1488 /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
1491 opt_label: Option<Label>,
1494 ) -> PResult<'a, P<Expr>> {
1495 // Record whether we are about to parse `for (`.
1496 // This is used below for recovery in case of `for ( $stuff ) $block`
1497 // in which case we will suggest `for $stuff $block`.
1498 let begin_paren = match self.token.kind {
1499 token::OpenDelim(token::Paren) => Some(self.token.span),
1503 let pat = self.parse_top_pat(GateOr::Yes)?;
1504 if !self.eat_keyword(kw::In) {
1505 self.error_missing_in_for_loop();
1507 self.check_for_for_in_in_typo(self.prev_span);
1508 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
1510 let pat = self.recover_parens_around_for_head(pat, &expr, begin_paren);
1512 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
1513 attrs.extend(iattrs);
1515 let kind = ExprKind::ForLoop(pat, expr, loop_block, opt_label);
1516 Ok(self.mk_expr(lo.to(self.prev_span), kind, attrs))
1519 fn error_missing_in_for_loop(&self) {
1520 let in_span = self.prev_span.between(self.token.span);
1521 self.struct_span_err(in_span, "missing `in` in `for` loop")
1522 .span_suggestion_short(
1524 "try adding `in` here",
1526 // Has been misleading, at least in the past (closed Issue #48492).
1527 Applicability::MaybeIncorrect,
1532 /// Parses a `while` or `while let` expression (`while` token already eaten).
1533 fn parse_while_expr(
1535 opt_label: Option<Label>,
1538 ) -> PResult<'a, P<Expr>> {
1539 let cond = self.parse_cond_expr()?;
1540 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1541 attrs.extend(iattrs);
1542 Ok(self.mk_expr(lo.to(self.prev_span), ExprKind::While(cond, body, opt_label), attrs))
1545 /// Parses `loop { ... }` (`loop` token already eaten).
1548 opt_label: Option<Label>,
1551 ) -> PResult<'a, P<Expr>> {
1552 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1553 attrs.extend(iattrs);
1554 Ok(self.mk_expr(lo.to(self.prev_span), ExprKind::Loop(body, opt_label), attrs))
1557 fn eat_label(&mut self) -> Option<Label> {
1558 self.token.lifetime().map(|ident| {
1559 let span = self.token.span;
1561 Label { ident: Ident::new(ident.name, span) }
1565 /// Parses a `match ... { ... }` expression (`match` token already eaten).
1566 fn parse_match_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
1567 let match_span = self.prev_span;
1568 let lo = self.prev_span;
1569 let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
1570 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
1571 if self.token == token::Semi {
1572 e.span_suggestion_short(
1574 "try removing this `match`",
1576 Applicability::MaybeIncorrect, // speculative
1581 attrs.extend(self.parse_inner_attributes()?);
1583 let mut arms: Vec<Arm> = Vec::new();
1584 while self.token != token::CloseDelim(token::Brace) {
1585 match self.parse_arm() {
1586 Ok(arm) => arms.push(arm),
1588 // Recover by skipping to the end of the block.
1590 self.recover_stmt();
1591 let span = lo.to(self.token.span);
1592 if self.token == token::CloseDelim(token::Brace) {
1595 return Ok(self.mk_expr(span, ExprKind::Match(scrutinee, arms), attrs));
1599 let hi = self.token.span;
1601 return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(scrutinee, arms), attrs));
1604 pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
1605 let attrs = self.parse_outer_attributes()?;
1606 let lo = self.token.span;
1607 let pat = self.parse_top_pat(GateOr::No)?;
1608 let guard = if self.eat_keyword(kw::If) { Some(self.parse_expr()?) } else { None };
1609 let arrow_span = self.token.span;
1610 self.expect(&token::FatArrow)?;
1611 let arm_start_span = self.token.span;
1613 let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
1614 err.span_label(arrow_span, "while parsing the `match` arm starting here");
1618 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
1619 && self.token != token::CloseDelim(token::Brace);
1621 let hi = self.token.span;
1624 let sm = self.sess.source_map();
1625 self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)]).map_err(
1627 match (sm.span_to_lines(expr.span), sm.span_to_lines(arm_start_span)) {
1628 (Ok(ref expr_lines), Ok(ref arm_start_lines))
1629 if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
1630 && expr_lines.lines.len() == 2
1631 && self.token == token::FatArrow =>
1633 // We check whether there's any trailing code in the parse span,
1634 // if there isn't, we very likely have the following:
1637 // | -- - missing comma
1641 // | - ^^ self.token.span
1643 // | parsed until here as `"y" & X`
1644 err.span_suggestion_short(
1645 arm_start_span.shrink_to_hi(),
1646 "missing a comma here to end this `match` arm",
1648 Applicability::MachineApplicable,
1654 "while parsing the `match` arm starting here",
1662 self.eat(&token::Comma);
1672 is_placeholder: false,
1676 /// Parses a `try {...}` expression (`try` token already eaten).
1677 fn parse_try_block(&mut self, span_lo: Span, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
1678 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1679 attrs.extend(iattrs);
1680 if self.eat_keyword(kw::Catch) {
1682 self.struct_span_err(self.prev_span, "keyword `catch` cannot follow a `try` block");
1683 error.help("try using `match` on the result of the `try` block instead");
1687 let span = span_lo.to(body.span);
1688 self.sess.gated_spans.gate(sym::try_blocks, span);
1689 Ok(self.mk_expr(span, ExprKind::TryBlock(body), attrs))
1693 fn is_do_catch_block(&self) -> bool {
1694 self.token.is_keyword(kw::Do)
1695 && self.is_keyword_ahead(1, &[kw::Catch])
1696 && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
1697 && !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1700 fn is_try_block(&self) -> bool {
1701 self.token.is_keyword(kw::Try) &&
1702 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
1703 self.token.span.rust_2018() &&
1704 // Prevent `while try {} {}`, `if try {} {} else {}`, etc.
1705 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1708 /// Parses an `async move? {...}` expression.
1709 fn parse_async_block(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
1710 let lo = self.token.span;
1711 self.expect_keyword(kw::Async)?;
1712 let capture_clause = self.parse_capture_clause();
1713 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1714 attrs.extend(iattrs);
1715 let kind = ExprKind::Async(capture_clause, DUMMY_NODE_ID, body);
1716 Ok(self.mk_expr(lo.to(self.prev_span), kind, attrs))
1719 fn is_async_block(&self) -> bool {
1720 self.token.is_keyword(kw::Async)
1723 self.is_keyword_ahead(1, &[kw::Move])
1724 && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
1727 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
1731 fn is_certainly_not_a_block(&self) -> bool {
1732 self.look_ahead(1, |t| t.is_ident())
1734 // `{ ident, ` cannot start a block.
1735 self.look_ahead(2, |t| t == &token::Comma)
1736 || self.look_ahead(2, |t| t == &token::Colon)
1738 // `{ ident: token, ` cannot start a block.
1739 self.look_ahead(4, |t| t == &token::Comma) ||
1740 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
1741 self.look_ahead(3, |t| !t.can_begin_type())
1746 fn maybe_parse_struct_expr(
1751 ) -> Option<PResult<'a, P<Expr>>> {
1752 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
1753 if struct_allowed || self.is_certainly_not_a_block() {
1754 // This is a struct literal, but we don't can't accept them here.
1755 let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
1756 if let (Ok(expr), false) = (&expr, struct_allowed) {
1757 self.error_struct_lit_not_allowed_here(lo, expr.span);
1764 fn error_struct_lit_not_allowed_here(&self, lo: Span, sp: Span) {
1765 self.struct_span_err(sp, "struct literals are not allowed here")
1766 .multipart_suggestion(
1767 "surround the struct literal with parentheses",
1768 vec![(lo.shrink_to_lo(), "(".to_string()), (sp.shrink_to_hi(), ")".to_string())],
1769 Applicability::MachineApplicable,
1774 pub(super) fn parse_struct_expr(
1779 ) -> PResult<'a, P<Expr>> {
1780 let struct_sp = lo.to(self.prev_span);
1782 let mut fields = Vec::new();
1783 let mut base = None;
1785 attrs.extend(self.parse_inner_attributes()?);
1787 while self.token != token::CloseDelim(token::Brace) {
1788 if self.eat(&token::DotDot) {
1789 let exp_span = self.prev_span;
1790 match self.parse_expr() {
1791 Ok(e) => base = Some(e),
1794 self.recover_stmt();
1797 self.recover_struct_comma_after_dotdot(exp_span);
1801 let recovery_field = self.find_struct_error_after_field_looking_code();
1802 let parsed_field = match self.parse_field() {
1805 e.span_label(struct_sp, "while parsing this struct");
1808 // If the next token is a comma, then try to parse
1809 // what comes next as additional fields, rather than
1810 // bailing out until next `}`.
1811 if self.token != token::Comma {
1812 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
1813 if self.token != token::Comma {
1821 match self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)]) {
1823 if let Some(f) = parsed_field.or(recovery_field) {
1824 // Only include the field if there's no parse error for the field name.
1829 e.span_label(struct_sp, "while parsing this struct");
1830 if let Some(f) = recovery_field {
1833 self.prev_span.shrink_to_hi(),
1834 "try adding a comma",
1836 Applicability::MachineApplicable,
1840 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
1841 self.eat(&token::Comma);
1846 let span = lo.to(self.token.span);
1847 self.expect(&token::CloseDelim(token::Brace))?;
1848 Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs))
1851 /// Use in case of error after field-looking code: `S { foo: () with a }`.
1852 fn find_struct_error_after_field_looking_code(&self) -> Option<Field> {
1853 if let token::Ident(name, _) = self.token.kind {
1854 if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
1855 let span = self.token.span;
1856 return Some(ast::Field {
1857 ident: Ident::new(name, span),
1859 expr: self.mk_expr_err(span),
1860 is_shorthand: false,
1861 attrs: AttrVec::new(),
1863 is_placeholder: false,
1870 fn recover_struct_comma_after_dotdot(&mut self, span: Span) {
1871 if self.token != token::Comma {
1874 self.struct_span_err(span.to(self.prev_span), "cannot use a comma after the base struct")
1875 .span_suggestion_short(
1877 "remove this comma",
1879 Applicability::MachineApplicable,
1881 .note("the base struct must always be the last field")
1883 self.recover_stmt();
1886 /// Parses `ident (COLON expr)?`.
1887 fn parse_field(&mut self) -> PResult<'a, Field> {
1888 let attrs = self.parse_outer_attributes()?.into();
1889 let lo = self.token.span;
1891 // Check if a colon exists one ahead. This means we're parsing a fieldname.
1892 let is_shorthand = !self.look_ahead(1, |t| t == &token::Colon || t == &token::Eq);
1893 let (ident, expr) = if is_shorthand {
1894 // Mimic `x: x` for the `x` field shorthand.
1895 let ident = self.parse_ident_common(false)?;
1896 let path = ast::Path::from_ident(ident);
1897 (ident, self.mk_expr(ident.span, ExprKind::Path(None, path), AttrVec::new()))
1899 let ident = self.parse_field_name()?;
1900 self.error_on_eq_field_init(ident);
1902 (ident, self.parse_expr()?)
1906 span: lo.to(expr.span),
1911 is_placeholder: false,
1915 /// Check for `=`. This means the source incorrectly attempts to
1916 /// initialize a field with an eq rather than a colon.
1917 fn error_on_eq_field_init(&self, field_name: Ident) {
1918 if self.token != token::Eq {
1922 self.struct_span_err(self.token.span, "expected `:`, found `=`")
1924 field_name.span.shrink_to_hi().to(self.token.span),
1925 "replace equals symbol with a colon",
1927 Applicability::MachineApplicable,
1932 fn err_dotdotdot_syntax(&self, span: Span) {
1933 self.struct_span_err(span, "unexpected token: `...`")
1936 "use `..` for an exclusive range",
1938 Applicability::MaybeIncorrect,
1942 "or `..=` for an inclusive range",
1944 Applicability::MaybeIncorrect,
1949 fn err_larrow_operator(&self, span: Span) {
1950 self.struct_span_err(span, "unexpected token: `<-`")
1953 "if you meant to write a comparison against a negative value, add a \
1954 space in between `<` and `-`",
1956 Applicability::MaybeIncorrect,
1961 fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
1962 ExprKind::AssignOp(binop, lhs, rhs)
1967 start: Option<P<Expr>>,
1968 end: Option<P<Expr>>,
1969 limits: RangeLimits,
1970 ) -> PResult<'a, ExprKind> {
1971 if end.is_none() && limits == RangeLimits::Closed {
1972 self.error_inclusive_range_with_no_end(self.prev_span);
1975 Ok(ExprKind::Range(start, end, limits))
1979 fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
1980 ExprKind::Unary(unop, expr)
1983 fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
1984 ExprKind::Binary(binop, lhs, rhs)
1987 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
1988 ExprKind::Index(expr, idx)
1991 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
1992 ExprKind::Call(f, args)
1995 fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
1996 let span = lo.to(self.prev_span);
1997 let await_expr = self.mk_expr(span, ExprKind::Await(self_arg), AttrVec::new());
1998 self.recover_from_await_method_call();
2002 crate fn mk_expr(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
2003 P(Expr { kind, span, attrs, id: DUMMY_NODE_ID })
2006 pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> {
2007 self.mk_expr(span, ExprKind::Err, AttrVec::new())