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.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_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.
230 .filter(|a| a.style == AttrStyle::Outer)
232 .map_or(lhs_span, |a| a.span);
233 let span = lhs_span.to(rhs.span);
246 | AssocOp::ShiftRight
252 | AssocOp::GreaterEqual => {
253 let ast_op = op.to_ast_binop().unwrap();
254 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
255 self.mk_expr(span, binary, AttrVec::new())
258 self.mk_expr(span, ExprKind::Assign(lhs, rhs, cur_op_span), AttrVec::new())
260 AssocOp::AssignOp(k) => {
262 token::Plus => BinOpKind::Add,
263 token::Minus => BinOpKind::Sub,
264 token::Star => BinOpKind::Mul,
265 token::Slash => BinOpKind::Div,
266 token::Percent => BinOpKind::Rem,
267 token::Caret => BinOpKind::BitXor,
268 token::And => BinOpKind::BitAnd,
269 token::Or => BinOpKind::BitOr,
270 token::Shl => BinOpKind::Shl,
271 token::Shr => BinOpKind::Shr,
273 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
274 self.mk_expr(span, aopexpr, AttrVec::new())
276 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
277 self.span_bug(span, "AssocOp should have been handled by special case")
281 if let Fixity::None = fixity {
285 if last_type_ascription_set {
286 self.last_type_ascription = None;
291 fn should_continue_as_assoc_expr(&mut self, lhs: &Expr) -> bool {
292 match (self.expr_is_complete(lhs), self.check_assoc_op().map(|op| op.node)) {
293 // Semi-statement forms are odd:
294 // See https://github.com/rust-lang/rust/issues/29071
295 (true, None) => false,
296 (false, _) => true, // Continue parsing the expression.
297 // An exhaustive check is done in the following block, but these are checked first
298 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
299 // want to keep their span info to improve diagnostics in these cases in a later stage.
300 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
301 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
302 (true, Some(AssocOp::LAnd)) | // `{ 42 } &&x` (#61475)
303 (true, Some(AssocOp::Add)) // `{ 42 } + 42
304 // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
305 // `if x { a } else { b } && if y { c } else { d }`
306 if !self.look_ahead(1, |t| t.is_reserved_ident()) => {
307 // These cases are ambiguous and can't be identified in the parser alone.
308 let sp = self.sess.source_map().start_point(self.token.span);
309 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
312 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => false,
314 self.error_found_expr_would_be_stmt(lhs);
320 /// We've found an expression that would be parsed as a statement,
321 /// but the next token implies this should be parsed as an expression.
322 /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
323 fn error_found_expr_would_be_stmt(&self, lhs: &Expr) {
324 let mut err = self.struct_span_err(
326 &format!("expected expression, found `{}`", pprust::token_to_string(&self.token),),
328 err.span_label(self.token.span, "expected expression");
329 self.sess.expr_parentheses_needed(&mut err, lhs.span, Some(pprust::expr_to_string(&lhs)));
333 /// Possibly translate the current token to an associative operator.
334 /// The method does not advance the current token.
336 /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
337 fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
339 node: match (AssocOp::from_token(&self.token), &self.normalized_token.kind) {
341 (None, token::Ident(sym::and, false)) => {
342 self.error_bad_logical_op("and", "&&", "conjunction");
345 (None, token::Ident(sym::or, false)) => {
346 self.error_bad_logical_op("or", "||", "disjunction");
351 span: self.normalized_token.span,
355 /// Error on `and` and `or` suggesting `&&` and `||` respectively.
356 fn error_bad_logical_op(&self, bad: &str, good: &str, english: &str) {
357 self.struct_span_err(self.token.span, &format!("`{}` is not a logical operator", bad))
358 .span_suggestion_short(
360 &format!("use `{}` to perform logical {}", good, english),
362 Applicability::MachineApplicable,
364 .note("unlike in e.g., python and PHP, `&&` and `||` are used for logical operators")
368 /// Checks if this expression is a successfully parsed statement.
369 fn expr_is_complete(&self, e: &Expr) -> bool {
370 self.restrictions.contains(Restrictions::STMT_EXPR)
371 && !classify::expr_requires_semi_to_be_stmt(e)
374 /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
375 /// The other two variants are handled in `parse_prefix_range_expr` below.
382 ) -> PResult<'a, P<Expr>> {
383 let rhs = if self.is_at_start_of_range_notation_rhs() {
384 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
388 let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
389 let span = lhs.span.to(rhs_span);
391 if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
392 Ok(self.mk_expr(span, self.mk_range(Some(lhs), rhs, limits)?, AttrVec::new()))
395 fn is_at_start_of_range_notation_rhs(&self) -> bool {
396 if self.token.can_begin_expr() {
397 // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
398 if self.token == token::OpenDelim(token::Brace) {
399 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
407 /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
408 fn parse_prefix_range_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
409 // Check for deprecated `...` syntax.
410 if self.token == token::DotDotDot {
411 self.err_dotdotdot_syntax(self.token.span);
415 [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind),
416 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
420 let limits = match self.token.kind {
421 token::DotDot => RangeLimits::HalfOpen,
422 _ => RangeLimits::Closed,
424 let op = AssocOp::from_token(&self.token);
425 let attrs = self.parse_or_use_outer_attributes(attrs)?;
426 let lo = self.token.span;
428 let (span, opt_end) = if self.is_at_start_of_range_notation_rhs() {
429 // RHS must be parsed with more associativity than the dots.
430 self.parse_assoc_expr_with(op.unwrap().precedence() + 1, LhsExpr::NotYetParsed)
431 .map(|x| (lo.to(x.span), Some(x)))?
435 Ok(self.mk_expr(span, self.mk_range(None, opt_end, limits)?, attrs))
438 /// Parses a prefix-unary-operator expr.
439 fn parse_prefix_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
440 let attrs = self.parse_or_use_outer_attributes(attrs)?;
441 let lo = self.token.span;
442 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
443 let (hi, ex) = match self.normalized_token.kind {
444 token::Not => self.parse_unary_expr(lo, UnOp::Not), // `!expr`
445 token::Tilde => self.recover_tilde_expr(lo), // `~expr`
446 token::BinOp(token::Minus) => self.parse_unary_expr(lo, UnOp::Neg), // `-expr`
447 token::BinOp(token::Star) => self.parse_unary_expr(lo, UnOp::Deref), // `*expr`
448 token::BinOp(token::And) | token::AndAnd => self.parse_borrow_expr(lo),
449 token::Ident(..) if self.token.is_keyword(kw::Box) => self.parse_box_expr(lo),
450 token::Ident(..) if self.is_mistaken_not_ident_negation() => self.recover_not_expr(lo),
451 _ => return self.parse_dot_or_call_expr(Some(attrs)),
453 Ok(self.mk_expr(lo.to(hi), ex, attrs))
456 fn parse_prefix_expr_common(&mut self, lo: Span) -> PResult<'a, (Span, P<Expr>)> {
458 let expr = self.parse_prefix_expr(None);
459 let (span, expr) = self.interpolated_or_expr_span(expr)?;
460 Ok((lo.to(span), expr))
463 fn parse_unary_expr(&mut self, lo: Span, op: UnOp) -> PResult<'a, (Span, ExprKind)> {
464 let (span, expr) = self.parse_prefix_expr_common(lo)?;
465 Ok((span, self.mk_unary(op, expr)))
468 // Recover on `!` suggesting for bitwise negation instead.
469 fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
470 self.struct_span_err(lo, "`~` cannot be used as a unary operator")
471 .span_suggestion_short(
473 "use `!` to perform bitwise not",
475 Applicability::MachineApplicable,
479 self.parse_unary_expr(lo, UnOp::Not)
482 /// Parse `box expr`.
483 fn parse_box_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
484 let (span, expr) = self.parse_prefix_expr_common(lo)?;
485 self.sess.gated_spans.gate(sym::box_syntax, span);
486 Ok((span, ExprKind::Box(expr)))
489 fn is_mistaken_not_ident_negation(&self) -> bool {
490 let token_cannot_continue_expr = |t: &Token| match t.kind {
491 // These tokens can start an expression after `!`, but
492 // can't continue an expression after an ident
493 token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
494 token::Literal(..) | token::Pound => true,
495 _ => t.is_whole_expr(),
497 self.token.is_ident_named(sym::not) && self.look_ahead(1, token_cannot_continue_expr)
500 /// Recover on `not expr` in favor of `!expr`.
501 fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
503 let not_token = self.look_ahead(1, |t| t.clone());
504 self.struct_span_err(
506 &format!("unexpected {} after identifier", super::token_descr(¬_token)),
508 .span_suggestion_short(
509 // Span the `not` plus trailing whitespace to avoid
510 // trailing whitespace after the `!` in our suggestion
511 self.sess.source_map().span_until_non_whitespace(lo.to(not_token.span)),
512 "use `!` to perform logical negation",
514 Applicability::MachineApplicable,
519 self.parse_unary_expr(lo, UnOp::Not)
522 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
523 fn interpolated_or_expr_span(
525 expr: PResult<'a, P<Expr>>,
526 ) -> PResult<'a, (Span, P<Expr>)> {
529 match self.prev_token.kind {
530 TokenKind::Interpolated(..) => self.prev_span,
538 fn parse_assoc_op_cast(
542 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
543 ) -> PResult<'a, P<Expr>> {
544 let mk_expr = |this: &mut Self, rhs: P<Ty>| {
545 this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), AttrVec::new())
548 // Save the state of the parser before parsing type normally, in case there is a
549 // LessThan comparison after this cast.
550 let parser_snapshot_before_type = self.clone();
551 match self.parse_ty_no_plus() {
552 Ok(rhs) => Ok(mk_expr(self, rhs)),
553 Err(mut type_err) => {
554 // Rewind to before attempting to parse the type with generics, to recover
555 // from situations like `x as usize < y` in which we first tried to parse
556 // `usize < y` as a type with generic arguments.
557 let parser_snapshot_after_type = self.clone();
558 mem::replace(self, parser_snapshot_before_type);
560 match self.parse_path(PathStyle::Expr) {
562 let (op_noun, op_verb) = match self.token.kind {
563 token::Lt => ("comparison", "comparing"),
564 token::BinOp(token::Shl) => ("shift", "shifting"),
566 // We can end up here even without `<` being the next token, for
567 // example because `parse_ty_no_plus` returns `Err` on keywords,
568 // but `parse_path` returns `Ok` on them due to error recovery.
569 // Return original error and parser state.
570 mem::replace(self, parser_snapshot_after_type);
571 return Err(type_err);
575 // Successfully parsed the type path leaving a `<` yet to parse.
578 // Report non-fatal diagnostics, keep `x as usize` as an expression
579 // in AST and continue parsing.
581 "`<` is interpreted as a start of generic arguments for `{}`, not a {}",
582 pprust::path_to_string(&path),
585 let span_after_type = parser_snapshot_after_type.token.span;
586 let expr = mk_expr(self, self.mk_ty(path.span, TyKind::Path(None, path)));
589 .span_to_snippet(expr.span)
590 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
592 self.struct_span_err(self.token.span, &msg)
594 self.look_ahead(1, |t| t.span).to(span_after_type),
595 "interpreted as generic arguments",
597 .span_label(self.token.span, format!("not interpreted as {}", op_noun))
600 &format!("try {} the cast value", op_verb),
601 format!("({})", expr_str),
602 Applicability::MachineApplicable,
608 Err(mut path_err) => {
609 // Couldn't parse as a path, return original error and parser state.
611 mem::replace(self, parser_snapshot_after_type);
619 fn parse_assoc_op_ascribe(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
620 let maybe_path = self.could_ascription_be_path(&lhs.kind);
621 self.last_type_ascription = Some((self.prev_span, maybe_path));
622 let lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
623 self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
627 /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
628 fn parse_borrow_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
630 let (borrow_kind, mutbl) = self.parse_borrow_modifiers(lo);
631 let expr = self.parse_prefix_expr(None);
632 let (span, expr) = self.interpolated_or_expr_span(expr)?;
633 Ok((lo.to(span), ExprKind::AddrOf(borrow_kind, mutbl, expr)))
636 /// Parse `mut?` or `raw [ const | mut ]`.
637 fn parse_borrow_modifiers(&mut self, lo: Span) -> (ast::BorrowKind, ast::Mutability) {
638 if self.check_keyword(kw::Raw) && self.look_ahead(1, Token::is_mutability) {
639 // `raw [ const | mut ]`.
640 let found_raw = self.eat_keyword(kw::Raw);
642 let mutability = self.parse_const_or_mut().unwrap();
643 self.sess.gated_spans.gate(sym::raw_ref_op, lo.to(self.prev_span));
644 (ast::BorrowKind::Raw, mutability)
647 (ast::BorrowKind::Ref, self.parse_mutability())
651 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
652 fn parse_dot_or_call_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
653 let attrs = self.parse_or_use_outer_attributes(attrs)?;
654 let base = self.parse_bottom_expr();
655 let (span, base) = self.interpolated_or_expr_span(base)?;
656 self.parse_dot_or_call_expr_with(base, span, attrs)
659 pub(super) fn parse_dot_or_call_expr_with(
664 ) -> PResult<'a, P<Expr>> {
665 // Stitch the list of outer attributes onto the return value.
666 // A little bit ugly, but the best way given the current code
668 self.parse_dot_or_call_expr_with_(e0, lo).map(|expr| {
669 expr.map(|mut expr| {
670 attrs.extend::<Vec<_>>(expr.attrs.into());
672 self.error_attr_on_if_expr(&expr);
678 fn error_attr_on_if_expr(&self, expr: &Expr) {
679 if let (ExprKind::If(..), [a0, ..]) = (&expr.kind, &*expr.attrs) {
680 // Just point to the first attribute in there...
681 self.struct_span_err(a0.span, "attributes are not yet allowed on `if` expressions")
686 fn parse_dot_or_call_expr_with_(&mut self, mut e: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
688 if self.eat(&token::Question) {
690 e = self.mk_expr(lo.to(self.prev_span), ExprKind::Try(e), AttrVec::new());
693 if self.eat(&token::Dot) {
695 e = self.parse_dot_suffix_expr(lo, e)?;
698 if self.expr_is_complete(&e) {
701 e = match self.token.kind {
702 token::OpenDelim(token::Paren) => self.parse_fn_call_expr(lo, e),
703 token::OpenDelim(token::Bracket) => self.parse_index_expr(lo, e)?,
709 fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
710 match self.normalized_token.kind {
711 token::Ident(..) => self.parse_dot_suffix(base, lo),
712 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
713 Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix))
715 token::Literal(token::Lit { kind: token::Float, symbol, .. }) => {
716 self.recover_field_access_by_float_lit(lo, base, symbol)
719 self.error_unexpected_after_dot();
725 fn error_unexpected_after_dot(&self) {
726 // FIXME Could factor this out into non_fatal_unexpected or something.
727 let actual = pprust::token_to_string(&self.token);
728 self.struct_span_err(self.token.span, &format!("unexpected token: `{}`", actual)).emit();
731 fn recover_field_access_by_float_lit(
736 ) -> PResult<'a, P<Expr>> {
739 let fstr = sym.as_str();
740 let msg = format!("unexpected token: `{}`", sym);
742 let mut err = self.struct_span_err(self.prev_span, &msg);
743 err.span_label(self.prev_span, "unexpected token");
745 if fstr.chars().all(|x| "0123456789.".contains(x)) {
746 let float = match fstr.parse::<f64>() {
753 let sugg = pprust::to_string(|s| {
757 s.print_usize(float.trunc() as usize);
760 s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
763 lo.to(self.prev_span),
764 "try parenthesizing the first index",
766 Applicability::MachineApplicable,
772 fn parse_tuple_field_access_expr(
777 suffix: Option<Symbol>,
780 let span = self.prev_token.span;
781 let field = ExprKind::Field(base, Ident::new(field, span));
782 self.expect_no_suffix(span, "a tuple index", suffix);
783 self.mk_expr(lo.to(span), field, AttrVec::new())
786 /// Parse a function call expression, `expr(...)`.
787 fn parse_fn_call_expr(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
788 let seq = self.parse_paren_expr_seq().map(|args| {
789 self.mk_expr(lo.to(self.prev_span), self.mk_call(fun, args), AttrVec::new())
791 self.recover_seq_parse_error(token::Paren, lo, seq)
794 /// Parse an indexing expression `expr[...]`.
795 fn parse_index_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
797 let index = self.parse_expr()?;
798 self.expect(&token::CloseDelim(token::Bracket))?;
799 Ok(self.mk_expr(lo.to(self.prev_span), self.mk_index(base, index), AttrVec::new()))
802 /// Assuming we have just parsed `.`, continue parsing into an expression.
803 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
804 if self.normalized_token.span.rust_2018() && self.eat_keyword(kw::Await) {
805 return self.mk_await_expr(self_arg, lo);
808 let segment = self.parse_path_segment(PathStyle::Expr)?;
809 self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
811 if self.check(&token::OpenDelim(token::Paren)) {
812 // Method call `expr.f()`
813 let mut args = self.parse_paren_expr_seq()?;
814 args.insert(0, self_arg);
816 let span = lo.to(self.prev_span);
817 Ok(self.mk_expr(span, ExprKind::MethodCall(segment, args), AttrVec::new()))
819 // Field access `expr.f`
820 if let Some(args) = segment.args {
821 self.struct_span_err(
823 "field expressions cannot have generic arguments",
828 let span = lo.to(self.prev_span);
829 Ok(self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), AttrVec::new()))
833 /// At the bottom (top?) of the precedence hierarchy,
834 /// Parses things like parenthesized exprs, macros, `return`, etc.
836 /// N.B., this does not parse outer attributes, and is private because it only works
837 /// correctly if called from `parse_dot_or_call_expr()`.
838 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
839 maybe_recover_from_interpolated_ty_qpath!(self, true);
840 maybe_whole_expr!(self);
842 // Outer attributes are already parsed and will be
843 // added to the return value after the fact.
845 // Therefore, prevent sub-parser from parsing
846 // attributes by giving them a empty "already-parsed" list.
847 let attrs = AttrVec::new();
849 // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
850 let lo = self.token.span;
851 if let token::Literal(_) = self.token.kind {
852 // This match arm is a special-case of the `_` match arm below and
853 // could be removed without changing functionality, but it's faster
854 // to have it here, especially for programs with large constants.
855 self.parse_lit_expr(attrs)
856 } else if self.check(&token::OpenDelim(token::Paren)) {
857 self.parse_tuple_parens_expr(attrs)
858 } else if self.check(&token::OpenDelim(token::Brace)) {
859 self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs)
860 } else if self.check(&token::BinOp(token::Or)) || self.check(&token::OrOr) {
861 self.parse_closure_expr(attrs)
862 } else if self.check(&token::OpenDelim(token::Bracket)) {
863 self.parse_array_or_repeat_expr(attrs)
864 } else if self.eat_lt() {
865 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
866 Ok(self.mk_expr(lo.to(path.span), ExprKind::Path(Some(qself), path), attrs))
867 } else if self.token.is_path_start() {
868 self.parse_path_start_expr(attrs)
869 } else if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
870 self.parse_closure_expr(attrs)
871 } else if self.eat_keyword(kw::If) {
872 self.parse_if_expr(attrs)
873 } else if self.eat_keyword(kw::For) {
874 self.parse_for_expr(None, self.prev_span, attrs)
875 } else if self.eat_keyword(kw::While) {
876 self.parse_while_expr(None, self.prev_span, attrs)
877 } else if let Some(label) = self.eat_label() {
878 self.parse_labeled_expr(label, attrs)
879 } else if self.eat_keyword(kw::Loop) {
880 self.parse_loop_expr(None, self.prev_span, attrs)
881 } else if self.eat_keyword(kw::Continue) {
882 let kind = ExprKind::Continue(self.eat_label());
883 Ok(self.mk_expr(lo.to(self.prev_span), kind, attrs))
884 } else if self.eat_keyword(kw::Match) {
885 let match_sp = self.prev_span;
886 self.parse_match_expr(attrs).map_err(|mut err| {
887 err.span_label(match_sp, "while parsing this match expression");
890 } else if self.eat_keyword(kw::Unsafe) {
891 self.parse_block_expr(None, lo, BlockCheckMode::Unsafe(ast::UserProvided), attrs)
892 } else if self.is_do_catch_block() {
893 self.recover_do_catch(attrs)
894 } else if self.is_try_block() {
895 self.expect_keyword(kw::Try)?;
896 self.parse_try_block(lo, attrs)
897 } else if self.eat_keyword(kw::Return) {
898 self.parse_return_expr(attrs)
899 } else if self.eat_keyword(kw::Break) {
900 self.parse_break_expr(attrs)
901 } else if self.eat_keyword(kw::Yield) {
902 self.parse_yield_expr(attrs)
903 } else if self.eat_keyword(kw::Let) {
904 self.parse_let_expr(attrs)
905 } else if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
906 // Don't complain about bare semicolons after unclosed braces
907 // recovery in order to keep the error count down. Fixing the
908 // delimiters will possibly also fix the bare semicolon found in
909 // expression context. For example, silence the following error:
911 // error: expected expression, found `;`
915 // | ^ expected expression
917 Ok(self.mk_expr_err(self.token.span))
918 } else if self.normalized_token.span.rust_2018() {
919 // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
920 if self.check_keyword(kw::Async) {
921 if self.is_async_block() {
922 // Check for `async {` and `async move {`.
923 self.parse_async_block(attrs)
925 self.parse_closure_expr(attrs)
927 } else if self.eat_keyword(kw::Await) {
928 self.recover_incorrect_await_syntax(lo, self.prev_span, attrs)
930 self.parse_lit_expr(attrs)
933 self.parse_lit_expr(attrs)
937 fn parse_lit_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
938 let lo = self.token.span;
939 match self.parse_opt_lit() {
941 let expr = self.mk_expr(lo.to(self.prev_span), ExprKind::Lit(literal), attrs);
942 self.maybe_recover_from_bad_qpath(expr, true)
944 None => return Err(self.expected_expression_found()),
948 fn parse_tuple_parens_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
949 let lo = self.token.span;
950 self.expect(&token::OpenDelim(token::Paren))?;
951 attrs.extend(self.parse_inner_attributes()?); // `(#![foo] a, b, ...)` is OK.
952 let (es, trailing_comma) = match self.parse_seq_to_end(
953 &token::CloseDelim(token::Paren),
954 SeqSep::trailing_allowed(token::Comma),
955 |p| p.parse_expr_catch_underscore(),
958 Err(err) => return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err))),
960 let kind = if es.len() == 1 && !trailing_comma {
961 // `(e)` is parenthesized `e`.
962 ExprKind::Paren(es.into_iter().nth(0).unwrap())
964 // `(e,)` is a tuple with only one field, `e`.
967 let expr = self.mk_expr(lo.to(self.prev_span), kind, attrs);
968 self.maybe_recover_from_bad_qpath(expr, true)
971 fn parse_array_or_repeat_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
972 let lo = self.token.span;
975 attrs.extend(self.parse_inner_attributes()?);
977 let close = &token::CloseDelim(token::Bracket);
978 let kind = if self.eat(close) {
980 ExprKind::Array(Vec::new())
983 let first_expr = self.parse_expr()?;
984 if self.eat(&token::Semi) {
985 // Repeating array syntax: `[ 0; 512 ]`
986 let count = self.parse_anon_const_expr()?;
988 ExprKind::Repeat(first_expr, count)
989 } else if self.eat(&token::Comma) {
990 // Vector with two or more elements.
991 let sep = SeqSep::trailing_allowed(token::Comma);
992 let (remaining_exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
993 let mut exprs = vec![first_expr];
994 exprs.extend(remaining_exprs);
995 ExprKind::Array(exprs)
997 // Vector with one element
999 ExprKind::Array(vec![first_expr])
1002 let expr = self.mk_expr(lo.to(self.prev_span), kind, attrs);
1003 self.maybe_recover_from_bad_qpath(expr, true)
1006 fn parse_path_start_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1007 let lo = self.token.span;
1008 let path = self.parse_path(PathStyle::Expr)?;
1010 // `!`, as an operator, is prefix, so we know this isn't that.
1011 let (hi, kind) = if self.eat(&token::Not) {
1012 // MACRO INVOCATION expression
1015 args: self.parse_mac_args()?,
1016 prior_type_ascription: self.last_type_ascription,
1018 (self.prev_span, ExprKind::Mac(mac))
1019 } else if self.check(&token::OpenDelim(token::Brace)) {
1020 if let Some(expr) = self.maybe_parse_struct_expr(lo, &path, &attrs) {
1023 (path.span, ExprKind::Path(None, path))
1026 (path.span, ExprKind::Path(None, path))
1029 let expr = self.mk_expr(lo.to(hi), kind, attrs);
1030 self.maybe_recover_from_bad_qpath(expr, true)
1033 fn parse_labeled_expr(&mut self, label: Label, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1034 let lo = label.ident.span;
1035 self.expect(&token::Colon)?;
1036 if self.eat_keyword(kw::While) {
1037 return self.parse_while_expr(Some(label), lo, attrs);
1039 if self.eat_keyword(kw::For) {
1040 return self.parse_for_expr(Some(label), lo, attrs);
1042 if self.eat_keyword(kw::Loop) {
1043 return self.parse_loop_expr(Some(label), lo, attrs);
1045 if self.token == token::OpenDelim(token::Brace) {
1046 return self.parse_block_expr(Some(label), lo, BlockCheckMode::Default, attrs);
1049 let msg = "expected `while`, `for`, `loop` or `{` after a label";
1050 self.struct_span_err(self.token.span, msg).span_label(self.token.span, msg).emit();
1051 // Continue as an expression in an effort to recover on `'label: non_block_expr`.
1055 /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
1056 fn recover_do_catch(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1057 let lo = self.token.span;
1059 self.bump(); // `do`
1060 self.bump(); // `catch`
1062 let span_dc = lo.to(self.prev_span);
1063 self.struct_span_err(span_dc, "found removed `do catch` syntax")
1066 "replace with the new syntax",
1068 Applicability::MachineApplicable,
1070 .note("following RFC #2388, the new non-placeholder syntax is `try`")
1073 self.parse_try_block(lo, attrs)
1076 /// Parse an expression if the token can begin one.
1077 fn parse_expr_opt(&mut self) -> PResult<'a, Option<P<Expr>>> {
1078 Ok(if self.token.can_begin_expr() { Some(self.parse_expr()?) } else { None })
1081 /// Parse `"return" expr?`.
1082 fn parse_return_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1083 let lo = self.prev_span;
1084 let kind = ExprKind::Ret(self.parse_expr_opt()?);
1085 let expr = self.mk_expr(lo.to(self.prev_span), kind, attrs);
1086 self.maybe_recover_from_bad_qpath(expr, true)
1089 /// Parse `"('label ":")? break expr?`.
1090 fn parse_break_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1091 let lo = self.prev_span;
1092 let label = self.eat_label();
1093 let kind = if self.token != token::OpenDelim(token::Brace)
1094 || !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1096 self.parse_expr_opt()?
1100 let expr = self.mk_expr(lo.to(self.prev_span), ExprKind::Break(label, kind), attrs);
1101 self.maybe_recover_from_bad_qpath(expr, true)
1104 /// Parse `"yield" expr?`.
1105 fn parse_yield_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
1106 let lo = self.prev_span;
1107 let kind = ExprKind::Yield(self.parse_expr_opt()?);
1108 let span = lo.to(self.prev_span);
1109 self.sess.gated_spans.gate(sym::generators, span);
1110 let expr = self.mk_expr(span, kind, attrs);
1111 self.maybe_recover_from_bad_qpath(expr, true)
1114 /// Returns a string literal if the next token is a string literal.
1115 /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
1116 /// and returns `None` if the next token is not literal at all.
1117 pub fn parse_str_lit(&mut self) -> Result<ast::StrLit, Option<Lit>> {
1118 match self.parse_opt_lit() {
1119 Some(lit) => match lit.kind {
1120 ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
1122 symbol: lit.token.symbol,
1123 suffix: lit.token.suffix,
1127 _ => Err(Some(lit)),
1133 pub(super) fn parse_lit(&mut self) -> PResult<'a, Lit> {
1134 self.parse_opt_lit().ok_or_else(|| {
1135 let msg = format!("unexpected token: {}", super::token_descr(&self.token));
1136 self.struct_span_err(self.token.span, &msg)
1140 /// Matches `lit = true | false | token_lit`.
1141 /// Returns `None` if the next token is not a literal.
1142 pub(super) fn parse_opt_lit(&mut self) -> Option<Lit> {
1143 let mut recovered = None;
1144 if self.token == token::Dot {
1145 // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
1146 // dot would follow an optional literal, so we do this unconditionally.
1147 recovered = self.look_ahead(1, |next_token| {
1148 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
1151 if self.token.span.hi() == next_token.span.lo() {
1152 let s = String::from("0.") + &symbol.as_str();
1153 let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
1154 return Some(Token::new(kind, self.token.span.to(next_token.span)));
1159 if let Some(token) = &recovered {
1161 self.error_float_lits_must_have_int_part(&token);
1165 let token = recovered.as_ref().unwrap_or(&self.token);
1166 match Lit::from_token(token) {
1171 Err(LitError::NotLiteral) => None,
1173 let span = token.span;
1174 let lit = match token.kind {
1175 token::Literal(lit) => lit,
1176 _ => unreachable!(),
1179 self.report_lit_error(err, lit, span);
1180 // Pack possible quotes and prefixes from the original literal into
1181 // the error literal's symbol so they can be pretty-printed faithfully.
1182 let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
1183 let symbol = Symbol::intern(&suffixless_lit.to_string());
1184 let lit = token::Lit::new(token::Err, symbol, lit.suffix);
1185 Some(Lit::from_lit_token(lit, span).unwrap_or_else(|_| unreachable!()))
1190 fn error_float_lits_must_have_int_part(&self, token: &Token) {
1191 self.struct_span_err(token.span, "float literals must have an integer part")
1194 "must have an integer part",
1195 pprust::token_to_string(token),
1196 Applicability::MachineApplicable,
1201 fn report_lit_error(&self, err: LitError, lit: token::Lit, span: Span) {
1202 // Checks if `s` looks like i32 or u1234 etc.
1203 fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
1204 s.len() > 1 && s.starts_with(first_chars) && s[1..].chars().all(|c| c.is_ascii_digit())
1207 let token::Lit { kind, suffix, .. } = lit;
1209 // `NotLiteral` is not an error by itself, so we don't report
1210 // it and give the parser opportunity to try something else.
1211 LitError::NotLiteral => {}
1212 // `LexerError` *is* an error, but it was already reported
1213 // by lexer, so here we don't report it the second time.
1214 LitError::LexerError => {}
1215 LitError::InvalidSuffix => {
1216 self.expect_no_suffix(
1218 &format!("{} {} literal", kind.article(), kind.descr()),
1222 LitError::InvalidIntSuffix => {
1223 let suf = suffix.expect("suffix error with no suffix").as_str();
1224 if looks_like_width_suffix(&['i', 'u'], &suf) {
1225 // If it looks like a width, try to be helpful.
1226 let msg = format!("invalid width `{}` for integer literal", &suf[1..]);
1227 self.struct_span_err(span, &msg)
1228 .help("valid widths are 8, 16, 32, 64 and 128")
1231 let msg = format!("invalid suffix `{}` for integer literal", suf);
1232 self.struct_span_err(span, &msg)
1233 .span_label(span, format!("invalid suffix `{}`", suf))
1234 .help("the suffix must be one of the integral types (`u32`, `isize`, etc)")
1238 LitError::InvalidFloatSuffix => {
1239 let suf = suffix.expect("suffix error with no suffix").as_str();
1240 if looks_like_width_suffix(&['f'], &suf) {
1241 // If it looks like a width, try to be helpful.
1242 let msg = format!("invalid width `{}` for float literal", &suf[1..]);
1243 self.struct_span_err(span, &msg).help("valid widths are 32 and 64").emit();
1245 let msg = format!("invalid suffix `{}` for float literal", suf);
1246 self.struct_span_err(span, &msg)
1247 .span_label(span, format!("invalid suffix `{}`", suf))
1248 .help("valid suffixes are `f32` and `f64`")
1252 LitError::NonDecimalFloat(base) => {
1253 let descr = match base {
1254 16 => "hexadecimal",
1257 _ => unreachable!(),
1259 self.struct_span_err(span, &format!("{} float literal is not supported", descr))
1260 .span_label(span, "not supported")
1263 LitError::IntTooLarge => {
1264 self.struct_span_err(span, "integer literal is too large").emit();
1269 pub(super) fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<Symbol>) {
1270 if let Some(suf) = suffix {
1271 let mut err = if kind == "a tuple index"
1272 && [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suf)
1274 // #59553: warn instead of reject out of hand to allow the fix to percolate
1275 // through the ecosystem when people fix their macros
1279 .struct_span_warn(sp, &format!("suffixes on {} are invalid", kind));
1281 "`{}` is *temporarily* accepted on tuple index fields as it was \
1282 incorrectly accepted on stable for a few releases",
1286 "on proc macros, you'll want to use `syn::Index::from` or \
1287 `proc_macro::Literal::*_unsuffixed` for code that will desugar \
1288 to tuple field access",
1291 "see issue #60210 <https://github.com/rust-lang/rust/issues/60210> \
1292 for more information",
1296 self.struct_span_err(sp, &format!("suffixes on {} are invalid", kind))
1298 err.span_label(sp, format!("invalid suffix `{}`", suf));
1303 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1304 pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1305 maybe_whole_expr!(self);
1307 let lo = self.token.span;
1308 let minus_present = self.eat(&token::BinOp(token::Minus));
1309 let lit = self.parse_lit()?;
1310 let expr = self.mk_expr(lit.span, ExprKind::Lit(lit), AttrVec::new());
1313 Ok(self.mk_expr(lo.to(self.prev_span), self.mk_unary(UnOp::Neg, expr), AttrVec::new()))
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.prev_span);
1354 let capture_clause = self.parse_capture_clause();
1355 let decl = self.parse_fn_block_decl()?;
1356 let decl_hi = self.prev_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_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_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_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_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_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_span), kind, attrs))
1522 fn error_missing_in_for_loop(&self) {
1523 let in_span = self.prev_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_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_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_span;
1570 let lo = self.prev_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) {
1684 self.struct_span_err(self.prev_span, "keyword `catch` cannot follow a `try` block");
1685 error.help("try using `match` on the result of the `try` block instead");
1689 let span = span_lo.to(body.span);
1690 self.sess.gated_spans.gate(sym::try_blocks, span);
1691 Ok(self.mk_expr(span, ExprKind::TryBlock(body), attrs))
1695 fn is_do_catch_block(&self) -> bool {
1696 self.token.is_keyword(kw::Do)
1697 && self.is_keyword_ahead(1, &[kw::Catch])
1698 && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
1699 && !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1702 fn is_try_block(&self) -> bool {
1703 self.token.is_keyword(kw::Try) &&
1704 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
1705 self.normalized_token.span.rust_2018() &&
1706 // Prevent `while try {} {}`, `if try {} {} else {}`, etc.
1707 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
1710 /// Parses an `async move? {...}` expression.
1711 fn parse_async_block(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
1712 let lo = self.token.span;
1713 self.expect_keyword(kw::Async)?;
1714 let capture_clause = self.parse_capture_clause();
1715 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
1716 attrs.extend(iattrs);
1717 let kind = ExprKind::Async(capture_clause, DUMMY_NODE_ID, body);
1718 Ok(self.mk_expr(lo.to(self.prev_span), kind, attrs))
1721 fn is_async_block(&self) -> bool {
1722 self.token.is_keyword(kw::Async)
1725 self.is_keyword_ahead(1, &[kw::Move])
1726 && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
1729 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
1733 fn is_certainly_not_a_block(&self) -> bool {
1734 self.look_ahead(1, |t| t.is_ident())
1736 // `{ ident, ` cannot start a block.
1737 self.look_ahead(2, |t| t == &token::Comma)
1738 || self.look_ahead(2, |t| t == &token::Colon)
1740 // `{ ident: token, ` cannot start a block.
1741 self.look_ahead(4, |t| t == &token::Comma) ||
1742 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
1743 self.look_ahead(3, |t| !t.can_begin_type())
1748 fn maybe_parse_struct_expr(
1753 ) -> Option<PResult<'a, P<Expr>>> {
1754 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
1755 if struct_allowed || self.is_certainly_not_a_block() {
1756 // This is a struct literal, but we don't can't accept them here.
1757 let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
1758 if let (Ok(expr), false) = (&expr, struct_allowed) {
1759 self.error_struct_lit_not_allowed_here(lo, expr.span);
1766 fn error_struct_lit_not_allowed_here(&self, lo: Span, sp: Span) {
1767 self.struct_span_err(sp, "struct literals are not allowed here")
1768 .multipart_suggestion(
1769 "surround the struct literal with parentheses",
1770 vec![(lo.shrink_to_lo(), "(".to_string()), (sp.shrink_to_hi(), ")".to_string())],
1771 Applicability::MachineApplicable,
1776 pub(super) fn parse_struct_expr(
1781 ) -> PResult<'a, P<Expr>> {
1782 let struct_sp = lo.to(self.prev_span);
1784 let mut fields = Vec::new();
1785 let mut base = None;
1787 attrs.extend(self.parse_inner_attributes()?);
1789 while self.token != token::CloseDelim(token::Brace) {
1790 if self.eat(&token::DotDot) {
1791 let exp_span = self.prev_span;
1792 match self.parse_expr() {
1793 Ok(e) => base = Some(e),
1796 self.recover_stmt();
1799 self.recover_struct_comma_after_dotdot(exp_span);
1803 let recovery_field = self.find_struct_error_after_field_looking_code();
1804 let parsed_field = match self.parse_field() {
1807 e.span_label(struct_sp, "while parsing this struct");
1810 // If the next token is a comma, then try to parse
1811 // what comes next as additional fields, rather than
1812 // bailing out until next `}`.
1813 if self.token != token::Comma {
1814 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
1815 if self.token != token::Comma {
1823 match self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)]) {
1825 if let Some(f) = parsed_field.or(recovery_field) {
1826 // Only include the field if there's no parse error for the field name.
1831 e.span_label(struct_sp, "while parsing this struct");
1832 if let Some(f) = recovery_field {
1835 self.prev_span.shrink_to_hi(),
1836 "try adding a comma",
1838 Applicability::MachineApplicable,
1842 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
1843 self.eat(&token::Comma);
1848 let span = lo.to(self.token.span);
1849 self.expect(&token::CloseDelim(token::Brace))?;
1850 Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs))
1853 /// Use in case of error after field-looking code: `S { foo: () with a }`.
1854 fn find_struct_error_after_field_looking_code(&self) -> Option<Field> {
1855 if let token::Ident(name, _) = self.normalized_token.kind {
1856 if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
1857 return Some(ast::Field {
1858 ident: Ident::new(name, self.normalized_token.span),
1859 span: self.token.span,
1860 expr: self.mk_expr_err(self.token.span),
1861 is_shorthand: false,
1862 attrs: AttrVec::new(),
1864 is_placeholder: false,
1871 fn recover_struct_comma_after_dotdot(&mut self, span: Span) {
1872 if self.token != token::Comma {
1875 self.struct_span_err(span.to(self.prev_span), "cannot use a comma after the base struct")
1876 .span_suggestion_short(
1878 "remove this comma",
1880 Applicability::MachineApplicable,
1882 .note("the base struct must always be the last field")
1884 self.recover_stmt();
1887 /// Parses `ident (COLON expr)?`.
1888 fn parse_field(&mut self) -> PResult<'a, Field> {
1889 let attrs = self.parse_outer_attributes()?.into();
1890 let lo = self.token.span;
1892 // Check if a colon exists one ahead. This means we're parsing a fieldname.
1893 let is_shorthand = !self.look_ahead(1, |t| t == &token::Colon || t == &token::Eq);
1894 let (ident, expr) = if is_shorthand {
1895 // Mimic `x: x` for the `x` field shorthand.
1896 let ident = self.parse_ident_common(false)?;
1897 let path = ast::Path::from_ident(ident);
1898 (ident, self.mk_expr(ident.span, ExprKind::Path(None, path), AttrVec::new()))
1900 let ident = self.parse_field_name()?;
1901 self.error_on_eq_field_init(ident);
1903 (ident, self.parse_expr()?)
1907 span: lo.to(expr.span),
1912 is_placeholder: false,
1916 /// Check for `=`. This means the source incorrectly attempts to
1917 /// initialize a field with an eq rather than a colon.
1918 fn error_on_eq_field_init(&self, field_name: Ident) {
1919 if self.token != token::Eq {
1923 self.struct_span_err(self.token.span, "expected `:`, found `=`")
1925 field_name.span.shrink_to_hi().to(self.token.span),
1926 "replace equals symbol with a colon",
1928 Applicability::MachineApplicable,
1933 fn err_dotdotdot_syntax(&self, span: Span) {
1934 self.struct_span_err(span, "unexpected token: `...`")
1937 "use `..` for an exclusive range",
1939 Applicability::MaybeIncorrect,
1943 "or `..=` for an inclusive range",
1945 Applicability::MaybeIncorrect,
1950 fn err_larrow_operator(&self, span: Span) {
1951 self.struct_span_err(span, "unexpected token: `<-`")
1954 "if you meant to write a comparison against a negative value, add a \
1955 space in between `<` and `-`",
1957 Applicability::MaybeIncorrect,
1962 fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
1963 ExprKind::AssignOp(binop, lhs, rhs)
1968 start: Option<P<Expr>>,
1969 end: Option<P<Expr>>,
1970 limits: RangeLimits,
1971 ) -> PResult<'a, ExprKind> {
1972 if end.is_none() && limits == RangeLimits::Closed {
1973 self.error_inclusive_range_with_no_end(self.prev_span);
1976 Ok(ExprKind::Range(start, end, limits))
1980 fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
1981 ExprKind::Unary(unop, expr)
1984 fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
1985 ExprKind::Binary(binop, lhs, rhs)
1988 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
1989 ExprKind::Index(expr, idx)
1992 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
1993 ExprKind::Call(f, args)
1996 fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
1997 let span = lo.to(self.prev_span);
1998 let await_expr = self.mk_expr(span, ExprKind::Await(self_arg), AttrVec::new());
1999 self.recover_from_await_method_call();
2003 crate fn mk_expr(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
2004 P(Expr { kind, span, attrs, id: DUMMY_NODE_ID })
2007 pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> {
2008 self.mk_expr(span, ExprKind::Err, AttrVec::new())