--- /dev/null
+use super::pat::{GateOr, RecoverComma, PARAM_EXPECTED};
+use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
+use super::{BlockMode, Parser, PathStyle, Restrictions, TokenType};
+use super::{SemiColonMode, SeqSep, TokenExpectType};
+use crate::maybe_recover_from_interpolated_ty_qpath;
+
+use rustc_ast::ptr::P;
+use rustc_ast::token::{self, Token, TokenKind};
+use rustc_ast::tokenstream::Spacing;
+use rustc_ast::util::classify;
+use rustc_ast::util::literal::LitError;
+use rustc_ast::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
+use rustc_ast::{self as ast, AttrStyle, AttrVec, CaptureBy, Field, Lit, UnOp, DUMMY_NODE_ID};
+use rustc_ast::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, MacCall, Param, Ty, TyKind};
+use rustc_ast::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits};
+use rustc_ast_pretty::pprust;
+use rustc_errors::{Applicability, DiagnosticBuilder, PResult};
+use rustc_span::edition::LATEST_STABLE_EDITION;
+use rustc_span::source_map::{self, Span, Spanned};
+use rustc_span::symbol::{kw, sym, Ident, Symbol};
+use rustc_span::{BytePos, Pos};
+use std::mem;
+
+/// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
+/// dropped into the token stream, which happens while parsing the result of
+/// macro expansion). Placement of these is not as complex as I feared it would
+/// be. The important thing is to make sure that lookahead doesn't balk at
+/// `token::Interpolated` tokens.
+macro_rules! maybe_whole_expr {
+ ($p:expr) => {
+ if let token::Interpolated(nt) = &$p.token.kind {
+ match &**nt {
+ token::NtExpr(e) | token::NtLiteral(e) => {
+ let e = e.clone();
+ $p.bump();
+ return Ok(e);
+ }
+ token::NtPath(path) => {
+ let path = path.clone();
+ $p.bump();
+ return Ok($p.mk_expr(
+ $p.token.span,
+ ExprKind::Path(None, path),
+ AttrVec::new(),
+ ));
+ }
+ token::NtBlock(block) => {
+ let block = block.clone();
+ $p.bump();
+ return Ok($p.mk_expr(
+ $p.token.span,
+ ExprKind::Block(block, None),
+ AttrVec::new(),
+ ));
+ }
+ _ => {}
+ };
+ }
+ };
+}
+
+#[derive(Debug)]
+pub(super) enum LhsExpr {
+ NotYetParsed,
+ AttributesParsed(AttrVec),
+ AlreadyParsed(P<Expr>),
+}
+
+impl From<Option<AttrVec>> for LhsExpr {
+ /// Converts `Some(attrs)` into `LhsExpr::AttributesParsed(attrs)`
+ /// and `None` into `LhsExpr::NotYetParsed`.
+ ///
+ /// This conversion does not allocate.
+ fn from(o: Option<AttrVec>) -> Self {
+ if let Some(attrs) = o { LhsExpr::AttributesParsed(attrs) } else { LhsExpr::NotYetParsed }
+ }
+}
+
+impl From<P<Expr>> for LhsExpr {
+ /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed(expr)`.
+ ///
+ /// This conversion does not allocate.
+ fn from(expr: P<Expr>) -> Self {
+ LhsExpr::AlreadyParsed(expr)
+ }
+}
+
+impl<'a> Parser<'a> {
+ /// Parses an expression.
+ #[inline]
+ pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
+ self.parse_expr_res(Restrictions::empty(), None)
+ }
+
+ pub(super) fn parse_anon_const_expr(&mut self) -> PResult<'a, AnonConst> {
+ self.parse_expr().map(|value| AnonConst { id: DUMMY_NODE_ID, value })
+ }
+
+ fn parse_expr_catch_underscore(&mut self) -> PResult<'a, P<Expr>> {
+ match self.parse_expr() {
+ Ok(expr) => Ok(expr),
+ Err(mut err) => match self.token.ident() {
+ Some((Ident { name: kw::Underscore, .. }, false))
+ if self.look_ahead(1, |t| t == &token::Comma) =>
+ {
+ // Special-case handling of `foo(_, _, _)`
+ err.emit();
+ self.bump();
+ Ok(self.mk_expr(self.prev_token.span, ExprKind::Err, AttrVec::new()))
+ }
+ _ => Err(err),
+ },
+ }
+ }
+
+ /// Parses a sequence of expressions delimited by parentheses.
+ fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
+ self.parse_paren_comma_seq(|p| p.parse_expr_catch_underscore()).map(|(r, _)| r)
+ }
+
+ /// Parses an expression, subject to the given restrictions.
+ #[inline]
+ pub(super) fn parse_expr_res(
+ &mut self,
+ r: Restrictions,
+ already_parsed_attrs: Option<AttrVec>,
+ ) -> PResult<'a, P<Expr>> {
+ self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
+ }
+
+ /// Parses an associative expression.
+ ///
+ /// This parses an expression accounting for associativity and precedence of the operators in
+ /// the expression.
+ #[inline]
+ fn parse_assoc_expr(&mut self, already_parsed_attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
+ self.parse_assoc_expr_with(0, already_parsed_attrs.into())
+ }
+
+ /// Parses an associative expression with operators of at least `min_prec` precedence.
+ pub(super) fn parse_assoc_expr_with(
+ &mut self,
+ min_prec: usize,
+ lhs: LhsExpr,
+ ) -> PResult<'a, P<Expr>> {
+ let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
+ expr
+ } else {
+ let attrs = match lhs {
+ LhsExpr::AttributesParsed(attrs) => Some(attrs),
+ _ => None,
+ };
+ if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind) {
+ return self.parse_prefix_range_expr(attrs);
+ } else {
+ self.parse_prefix_expr(attrs)?
+ }
+ };
+ let last_type_ascription_set = self.last_type_ascription.is_some();
+
+ if !self.should_continue_as_assoc_expr(&lhs) {
+ self.last_type_ascription = None;
+ return Ok(lhs);
+ }
+
+ self.expected_tokens.push(TokenType::Operator);
+ while let Some(op) = self.check_assoc_op() {
+ // Adjust the span for interpolated LHS to point to the `$lhs` token
+ // and not to what it refers to.
+ let lhs_span = match self.prev_token.kind {
+ TokenKind::Interpolated(..) => self.prev_token.span,
+ _ => lhs.span,
+ };
+
+ let cur_op_span = self.token.span;
+ let restrictions = if op.node.is_assign_like() {
+ self.restrictions & Restrictions::NO_STRUCT_LITERAL
+ } else {
+ self.restrictions
+ };
+ let prec = op.node.precedence();
+ if prec < min_prec {
+ break;
+ }
+ // Check for deprecated `...` syntax
+ if self.token == token::DotDotDot && op.node == AssocOp::DotDotEq {
+ self.err_dotdotdot_syntax(self.token.span);
+ }
+
+ if self.token == token::LArrow {
+ self.err_larrow_operator(self.token.span);
+ }
+
+ self.bump();
+ if op.node.is_comparison() {
+ if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
+ return Ok(expr);
+ }
+ }
+
+ if (op.node == AssocOp::Equal || op.node == AssocOp::NotEqual)
+ && self.token.kind == token::Eq
+ && self.prev_token.span.hi() == self.token.span.lo()
+ {
+ // Look for JS' `===` and `!==` and recover 😇
+ let sp = op.span.to(self.token.span);
+ let sugg = match op.node {
+ AssocOp::Equal => "==",
+ AssocOp::NotEqual => "!=",
+ _ => unreachable!(),
+ };
+ self.struct_span_err(sp, &format!("invalid comparison operator `{}=`", sugg))
+ .span_suggestion_short(
+ sp,
+ &format!("`{s}=` is not a valid comparison operator, use `{s}`", s = sugg),
+ sugg.to_string(),
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ self.bump();
+ }
+
+ let op = op.node;
+ // Special cases:
+ if op == AssocOp::As {
+ lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
+ continue;
+ } else if op == AssocOp::Colon {
+ lhs = self.parse_assoc_op_ascribe(lhs, lhs_span)?;
+ continue;
+ } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
+ // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
+ // generalise it to the Fixity::None code.
+ lhs = self.parse_range_expr(prec, lhs, op, cur_op_span)?;
+ break;
+ }
+
+ let fixity = op.fixity();
+ let prec_adjustment = match fixity {
+ Fixity::Right => 0,
+ Fixity::Left => 1,
+ // We currently have no non-associative operators that are not handled above by
+ // the special cases. The code is here only for future convenience.
+ Fixity::None => 1,
+ };
+ let rhs = self.with_res(restrictions - Restrictions::STMT_EXPR, |this| {
+ this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
+ })?;
+
+ let span = self.mk_expr_sp(&lhs, lhs_span, rhs.span);
+ lhs = match op {
+ AssocOp::Add
+ | AssocOp::Subtract
+ | AssocOp::Multiply
+ | AssocOp::Divide
+ | AssocOp::Modulus
+ | AssocOp::LAnd
+ | AssocOp::LOr
+ | AssocOp::BitXor
+ | AssocOp::BitAnd
+ | AssocOp::BitOr
+ | AssocOp::ShiftLeft
+ | AssocOp::ShiftRight
+ | AssocOp::Equal
+ | AssocOp::Less
+ | AssocOp::LessEqual
+ | AssocOp::NotEqual
+ | AssocOp::Greater
+ | AssocOp::GreaterEqual => {
+ let ast_op = op.to_ast_binop().unwrap();
+ let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
+ self.mk_expr(span, binary, AttrVec::new())
+ }
+ AssocOp::Assign => {
+ self.mk_expr(span, ExprKind::Assign(lhs, rhs, cur_op_span), AttrVec::new())
+ }
+ AssocOp::AssignOp(k) => {
+ let aop = match k {
+ token::Plus => BinOpKind::Add,
+ token::Minus => BinOpKind::Sub,
+ token::Star => BinOpKind::Mul,
+ token::Slash => BinOpKind::Div,
+ token::Percent => BinOpKind::Rem,
+ token::Caret => BinOpKind::BitXor,
+ token::And => BinOpKind::BitAnd,
+ token::Or => BinOpKind::BitOr,
+ token::Shl => BinOpKind::Shl,
+ token::Shr => BinOpKind::Shr,
+ };
+ let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
+ self.mk_expr(span, aopexpr, AttrVec::new())
+ }
+ AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
+ self.span_bug(span, "AssocOp should have been handled by special case")
+ }
+ };
+
+ if let Fixity::None = fixity {
+ break;
+ }
+ }
+ if last_type_ascription_set {
+ self.last_type_ascription = None;
+ }
+ Ok(lhs)
+ }
+
+ fn should_continue_as_assoc_expr(&mut self, lhs: &Expr) -> bool {
+ match (self.expr_is_complete(lhs), AssocOp::from_token(&self.token)) {
+ // Semi-statement forms are odd:
+ // See https://github.com/rust-lang/rust/issues/29071
+ (true, None) => false,
+ (false, _) => true, // Continue parsing the expression.
+ // An exhaustive check is done in the following block, but these are checked first
+ // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
+ // want to keep their span info to improve diagnostics in these cases in a later stage.
+ (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
+ (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
+ (true, Some(AssocOp::Add)) // `{ 42 } + 42
+ // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
+ // `if x { a } else { b } && if y { c } else { d }`
+ if !self.look_ahead(1, |t| t.is_used_keyword()) => {
+ // These cases are ambiguous and can't be identified in the parser alone.
+ let sp = self.sess.source_map().start_point(self.token.span);
+ self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
+ false
+ }
+ (true, Some(AssocOp::LAnd)) => {
+ // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }`. Separated from the
+ // above due to #74233.
+ // These cases are ambiguous and can't be identified in the parser alone.
+ let sp = self.sess.source_map().start_point(self.token.span);
+ self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
+ false
+ }
+ (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => false,
+ (true, Some(_)) => {
+ self.error_found_expr_would_be_stmt(lhs);
+ true
+ }
+ }
+ }
+
+ /// We've found an expression that would be parsed as a statement,
+ /// but the next token implies this should be parsed as an expression.
+ /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
+ fn error_found_expr_would_be_stmt(&self, lhs: &Expr) {
+ let mut err = self.struct_span_err(
+ self.token.span,
+ &format!("expected expression, found `{}`", pprust::token_to_string(&self.token),),
+ );
+ err.span_label(self.token.span, "expected expression");
+ self.sess.expr_parentheses_needed(&mut err, lhs.span, Some(pprust::expr_to_string(&lhs)));
+ err.emit();
+ }
+
+ /// Possibly translate the current token to an associative operator.
+ /// The method does not advance the current token.
+ ///
+ /// Also performs recovery for `and` / `or` which are mistaken for `&&` and `||` respectively.
+ fn check_assoc_op(&self) -> Option<Spanned<AssocOp>> {
+ let (op, span) = match (AssocOp::from_token(&self.token), self.token.ident()) {
+ // When parsing const expressions, stop parsing when encountering `>`.
+ (
+ Some(
+ AssocOp::ShiftRight
+ | AssocOp::Greater
+ | AssocOp::GreaterEqual
+ | AssocOp::AssignOp(token::BinOpToken::Shr),
+ ),
+ _,
+ ) if self.restrictions.contains(Restrictions::CONST_EXPR) => {
+ return None;
+ }
+ (Some(op), _) => (op, self.token.span),
+ (None, Some((Ident { name: sym::and, span }, false))) => {
+ self.error_bad_logical_op("and", "&&", "conjunction");
+ (AssocOp::LAnd, span)
+ }
+ (None, Some((Ident { name: sym::or, span }, false))) => {
+ self.error_bad_logical_op("or", "||", "disjunction");
+ (AssocOp::LOr, span)
+ }
+ _ => return None,
+ };
+ Some(source_map::respan(span, op))
+ }
+
+ /// Error on `and` and `or` suggesting `&&` and `||` respectively.
+ fn error_bad_logical_op(&self, bad: &str, good: &str, english: &str) {
+ self.struct_span_err(self.token.span, &format!("`{}` is not a logical operator", bad))
+ .span_suggestion_short(
+ self.token.span,
+ &format!("use `{}` to perform logical {}", good, english),
+ good.to_string(),
+ Applicability::MachineApplicable,
+ )
+ .note("unlike in e.g., python and PHP, `&&` and `||` are used for logical operators")
+ .emit();
+ }
+
+ /// Checks if this expression is a successfully parsed statement.
+ fn expr_is_complete(&self, e: &Expr) -> bool {
+ self.restrictions.contains(Restrictions::STMT_EXPR)
+ && !classify::expr_requires_semi_to_be_stmt(e)
+ }
+
+ /// Parses `x..y`, `x..=y`, and `x..`/`x..=`.
+ /// The other two variants are handled in `parse_prefix_range_expr` below.
+ fn parse_range_expr(
+ &mut self,
+ prec: usize,
+ lhs: P<Expr>,
+ op: AssocOp,
+ cur_op_span: Span,
+ ) -> PResult<'a, P<Expr>> {
+ let rhs = if self.is_at_start_of_range_notation_rhs() {
+ Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
+ } else {
+ None
+ };
+ let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
+ let span = self.mk_expr_sp(&lhs, lhs.span, rhs_span);
+ let limits =
+ if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
+ Ok(self.mk_expr(span, self.mk_range(Some(lhs), rhs, limits)?, AttrVec::new()))
+ }
+
+ fn is_at_start_of_range_notation_rhs(&self) -> bool {
+ if self.token.can_begin_expr() {
+ // Parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
+ if self.token == token::OpenDelim(token::Brace) {
+ return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
+ }
+ true
+ } else {
+ false
+ }
+ }
+
+ /// Parses prefix-forms of range notation: `..expr`, `..`, `..=expr`.
+ fn parse_prefix_range_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
+ // Check for deprecated `...` syntax.
+ if self.token == token::DotDotDot {
+ self.err_dotdotdot_syntax(self.token.span);
+ }
+
+ debug_assert!(
+ [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind),
+ "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
+ self.token
+ );
+
+ let limits = match self.token.kind {
+ token::DotDot => RangeLimits::HalfOpen,
+ _ => RangeLimits::Closed,
+ };
+ let op = AssocOp::from_token(&self.token);
+ let attrs = self.parse_or_use_outer_attributes(attrs)?;
+ let lo = self.token.span;
+ self.bump();
+ let (span, opt_end) = if self.is_at_start_of_range_notation_rhs() {
+ // RHS must be parsed with more associativity than the dots.
+ self.parse_assoc_expr_with(op.unwrap().precedence() + 1, LhsExpr::NotYetParsed)
+ .map(|x| (lo.to(x.span), Some(x)))?
+ } else {
+ (lo, None)
+ };
+ Ok(self.mk_expr(span, self.mk_range(None, opt_end, limits)?, attrs))
+ }
+
+ /// Parses a prefix-unary-operator expr.
+ fn parse_prefix_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
+ let attrs = self.parse_or_use_outer_attributes(attrs)?;
+ // FIXME: Use super::attr::maybe_needs_tokens(&attrs) once we come up
+ // with a good way of passing `force_tokens` through from `parse_nonterminal`.
+ // Checking !attrs.is_empty() is correct, but will cause us to unnecessarily
+ // capture tokens in some circumstances.
+ let needs_tokens = !attrs.is_empty();
+ let do_parse = |this: &mut Parser<'a>| {
+ let lo = this.token.span;
+ // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
+ let (hi, ex) = match this.token.uninterpolate().kind {
+ token::Not => this.parse_unary_expr(lo, UnOp::Not), // `!expr`
+ token::Tilde => this.recover_tilde_expr(lo), // `~expr`
+ token::BinOp(token::Minus) => this.parse_unary_expr(lo, UnOp::Neg), // `-expr`
+ token::BinOp(token::Star) => this.parse_unary_expr(lo, UnOp::Deref), // `*expr`
+ token::BinOp(token::And) | token::AndAnd => this.parse_borrow_expr(lo),
+ token::Ident(..) if this.token.is_keyword(kw::Box) => this.parse_box_expr(lo),
+ token::Ident(..) if this.is_mistaken_not_ident_negation() => {
+ this.recover_not_expr(lo)
+ }
+ _ => return this.parse_dot_or_call_expr(Some(attrs)),
+ }?;
+ Ok(this.mk_expr(lo.to(hi), ex, attrs))
+ };
+ if needs_tokens { self.collect_tokens(do_parse) } else { do_parse(self) }
+ }
+
+ fn parse_prefix_expr_common(&mut self, lo: Span) -> PResult<'a, (Span, P<Expr>)> {
+ self.bump();
+ let expr = self.parse_prefix_expr(None);
+ let (span, expr) = self.interpolated_or_expr_span(expr)?;
+ Ok((lo.to(span), expr))
+ }
+
+ fn parse_unary_expr(&mut self, lo: Span, op: UnOp) -> PResult<'a, (Span, ExprKind)> {
+ let (span, expr) = self.parse_prefix_expr_common(lo)?;
+ Ok((span, self.mk_unary(op, expr)))
+ }
+
+ // Recover on `!` suggesting for bitwise negation instead.
+ fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
+ self.struct_span_err(lo, "`~` cannot be used as a unary operator")
+ .span_suggestion_short(
+ lo,
+ "use `!` to perform bitwise not",
+ "!".to_owned(),
+ Applicability::MachineApplicable,
+ )
+ .emit();
+
+ self.parse_unary_expr(lo, UnOp::Not)
+ }
+
+ /// Parse `box expr`.
+ fn parse_box_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
+ let (span, expr) = self.parse_prefix_expr_common(lo)?;
+ self.sess.gated_spans.gate(sym::box_syntax, span);
+ Ok((span, ExprKind::Box(expr)))
+ }
+
+ fn is_mistaken_not_ident_negation(&self) -> bool {
+ let token_cannot_continue_expr = |t: &Token| match t.uninterpolate().kind {
+ // These tokens can start an expression after `!`, but
+ // can't continue an expression after an ident
+ token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
+ token::Literal(..) | token::Pound => true,
+ _ => t.is_whole_expr(),
+ };
+ self.token.is_ident_named(sym::not) && self.look_ahead(1, token_cannot_continue_expr)
+ }
+
+ /// Recover on `not expr` in favor of `!expr`.
+ fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
+ // Emit the error...
+ let not_token = self.look_ahead(1, |t| t.clone());
+ self.struct_span_err(
+ not_token.span,
+ &format!("unexpected {} after identifier", super::token_descr(¬_token)),
+ )
+ .span_suggestion_short(
+ // Span the `not` plus trailing whitespace to avoid
+ // trailing whitespace after the `!` in our suggestion
+ self.sess.source_map().span_until_non_whitespace(lo.to(not_token.span)),
+ "use `!` to perform logical negation",
+ "!".to_owned(),
+ Applicability::MachineApplicable,
+ )
+ .emit();
+
+ // ...and recover!
+ self.parse_unary_expr(lo, UnOp::Not)
+ }
+
+ /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
+ fn interpolated_or_expr_span(
+ &self,
+ expr: PResult<'a, P<Expr>>,
+ ) -> PResult<'a, (Span, P<Expr>)> {
+ expr.map(|e| {
+ (
+ match self.prev_token.kind {
+ TokenKind::Interpolated(..) => self.prev_token.span,
+ _ => e.span,
+ },
+ e,
+ )
+ })
+ }
+
+ fn parse_assoc_op_cast(
+ &mut self,
+ lhs: P<Expr>,
+ lhs_span: Span,
+ expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
+ ) -> PResult<'a, P<Expr>> {
+ let mk_expr = |this: &mut Self, lhs: P<Expr>, rhs: P<Ty>| {
+ this.mk_expr(
+ this.mk_expr_sp(&lhs, lhs_span, rhs.span),
+ expr_kind(lhs, rhs),
+ AttrVec::new(),
+ )
+ };
+
+ // Save the state of the parser before parsing type normally, in case there is a
+ // LessThan comparison after this cast.
+ let parser_snapshot_before_type = self.clone();
+ let cast_expr = match self.parse_ty_no_plus() {
+ Ok(rhs) => mk_expr(self, lhs, rhs),
+ Err(mut type_err) => {
+ // Rewind to before attempting to parse the type with generics, to recover
+ // from situations like `x as usize < y` in which we first tried to parse
+ // `usize < y` as a type with generic arguments.
+ let parser_snapshot_after_type = mem::replace(self, parser_snapshot_before_type);
+
+ // Check for typo of `'a: loop { break 'a }` with a missing `'`.
+ match (&lhs.kind, &self.token.kind) {
+ (
+ // `foo: `
+ ExprKind::Path(None, ast::Path { segments, .. }),
+ TokenKind::Ident(kw::For | kw::Loop | kw::While, false),
+ ) if segments.len() == 1 => {
+ let snapshot = self.clone();
+ let label = Label {
+ ident: Ident::from_str_and_span(
+ &format!("'{}", segments[0].ident),
+ segments[0].ident.span,
+ ),
+ };
+ match self.parse_labeled_expr(label, AttrVec::new(), false) {
+ Ok(expr) => {
+ type_err.cancel();
+ self.struct_span_err(label.ident.span, "malformed loop label")
+ .span_suggestion(
+ label.ident.span,
+ "use the correct loop label format",
+ label.ident.to_string(),
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ return Ok(expr);
+ }
+ Err(mut err) => {
+ err.cancel();
+ *self = snapshot;
+ }
+ }
+ }
+ _ => {}
+ }
+
+ match self.parse_path(PathStyle::Expr) {
+ Ok(path) => {
+ let (op_noun, op_verb) = match self.token.kind {
+ token::Lt => ("comparison", "comparing"),
+ token::BinOp(token::Shl) => ("shift", "shifting"),
+ _ => {
+ // We can end up here even without `<` being the next token, for
+ // example because `parse_ty_no_plus` returns `Err` on keywords,
+ // but `parse_path` returns `Ok` on them due to error recovery.
+ // Return original error and parser state.
+ *self = parser_snapshot_after_type;
+ return Err(type_err);
+ }
+ };
+
+ // Successfully parsed the type path leaving a `<` yet to parse.
+ type_err.cancel();
+
+ // Report non-fatal diagnostics, keep `x as usize` as an expression
+ // in AST and continue parsing.
+ let msg = format!(
+ "`<` is interpreted as a start of generic arguments for `{}`, not a {}",
+ pprust::path_to_string(&path),
+ op_noun,
+ );
+ let span_after_type = parser_snapshot_after_type.token.span;
+ let expr =
+ mk_expr(self, lhs, self.mk_ty(path.span, TyKind::Path(None, path)));
+
+ let expr_str = self
+ .span_to_snippet(expr.span)
+ .unwrap_or_else(|_| pprust::expr_to_string(&expr));
+
+ self.struct_span_err(self.token.span, &msg)
+ .span_label(
+ self.look_ahead(1, |t| t.span).to(span_after_type),
+ "interpreted as generic arguments",
+ )
+ .span_label(self.token.span, format!("not interpreted as {}", op_noun))
+ .span_suggestion(
+ expr.span,
+ &format!("try {} the cast value", op_verb),
+ format!("({})", expr_str),
+ Applicability::MachineApplicable,
+ )
+ .emit();
+
+ expr
+ }
+ Err(mut path_err) => {
+ // Couldn't parse as a path, return original error and parser state.
+ path_err.cancel();
+ *self = parser_snapshot_after_type;
+ return Err(type_err);
+ }
+ }
+ }
+ };
+
+ self.parse_and_disallow_postfix_after_cast(cast_expr)
+ }
+
+ /// Parses a postfix operators such as `.`, `?`, or index (`[]`) after a cast,
+ /// then emits an error and returns the newly parsed tree.
+ /// The resulting parse tree for `&x as T[0]` has a precedence of `((&x) as T)[0]`.
+ fn parse_and_disallow_postfix_after_cast(
+ &mut self,
+ cast_expr: P<Expr>,
+ ) -> PResult<'a, P<Expr>> {
+ // Save the memory location of expr before parsing any following postfix operators.
+ // This will be compared with the memory location of the output expression.
+ // If they different we can assume we parsed another expression because the existing expression is not reallocated.
+ let addr_before = &*cast_expr as *const _ as usize;
+ let span = cast_expr.span;
+ let with_postfix = self.parse_dot_or_call_expr_with_(cast_expr, span)?;
+ let changed = addr_before != &*with_postfix as *const _ as usize;
+
+ // Check if an illegal postfix operator has been added after the cast.
+ // If the resulting expression is not a cast, or has a different memory location, it is an illegal postfix operator.
+ if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) || changed {
+ let msg = format!(
+ "casts cannot be followed by {}",
+ match with_postfix.kind {
+ ExprKind::Index(_, _) => "indexing",
+ ExprKind::Try(_) => "?",
+ ExprKind::Field(_, _) => "a field access",
+ ExprKind::MethodCall(_, _, _) => "a method call",
+ ExprKind::Call(_, _) => "a function call",
+ ExprKind::Await(_) => "`.await`",
+ ExprKind::Err => return Ok(with_postfix),
+ _ => unreachable!("parse_dot_or_call_expr_with_ shouldn't produce this"),
+ }
+ );
+ let mut err = self.struct_span_err(span, &msg);
+ // If type ascription is "likely an error", the user will already be getting a useful
+ // help message, and doesn't need a second.
+ if self.last_type_ascription.map_or(false, |last_ascription| last_ascription.1) {
+ self.maybe_annotate_with_ascription(&mut err, false);
+ } else {
+ let suggestions = vec![
+ (span.shrink_to_lo(), "(".to_string()),
+ (span.shrink_to_hi(), ")".to_string()),
+ ];
+ err.multipart_suggestion(
+ "try surrounding the expression in parentheses",
+ suggestions,
+ Applicability::MachineApplicable,
+ );
+ }
+ err.emit();
+ };
+ Ok(with_postfix)
+ }
+
+ fn parse_assoc_op_ascribe(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
+ let maybe_path = self.could_ascription_be_path(&lhs.kind);
+ self.last_type_ascription = Some((self.prev_token.span, maybe_path));
+ let lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
+ self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
+ Ok(lhs)
+ }
+
+ /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
+ fn parse_borrow_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
+ self.expect_and()?;
+ let has_lifetime = self.token.is_lifetime() && self.look_ahead(1, |t| t != &token::Colon);
+ let lifetime = has_lifetime.then(|| self.expect_lifetime()); // For recovery, see below.
+ let (borrow_kind, mutbl) = self.parse_borrow_modifiers(lo);
+ let expr = self.parse_prefix_expr(None);
+ let (hi, expr) = self.interpolated_or_expr_span(expr)?;
+ let span = lo.to(hi);
+ if let Some(lt) = lifetime {
+ self.error_remove_borrow_lifetime(span, lt.ident.span);
+ }
+ Ok((span, ExprKind::AddrOf(borrow_kind, mutbl, expr)))
+ }
+
+ fn error_remove_borrow_lifetime(&self, span: Span, lt_span: Span) {
+ self.struct_span_err(span, "borrow expressions cannot be annotated with lifetimes")
+ .span_label(lt_span, "annotated with lifetime here")
+ .span_suggestion(
+ lt_span,
+ "remove the lifetime annotation",
+ String::new(),
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+
+ /// Parse `mut?` or `raw [ const | mut ]`.
+ fn parse_borrow_modifiers(&mut self, lo: Span) -> (ast::BorrowKind, ast::Mutability) {
+ if self.check_keyword(kw::Raw) && self.look_ahead(1, Token::is_mutability) {
+ // `raw [ const | mut ]`.
+ let found_raw = self.eat_keyword(kw::Raw);
+ assert!(found_raw);
+ let mutability = self.parse_const_or_mut().unwrap();
+ self.sess.gated_spans.gate(sym::raw_ref_op, lo.to(self.prev_token.span));
+ (ast::BorrowKind::Raw, mutability)
+ } else {
+ // `mut?`
+ (ast::BorrowKind::Ref, self.parse_mutability())
+ }
+ }
+
+ /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
+ fn parse_dot_or_call_expr(&mut self, attrs: Option<AttrVec>) -> PResult<'a, P<Expr>> {
+ let attrs = self.parse_or_use_outer_attributes(attrs)?;
+ let base = self.parse_bottom_expr();
+ let (span, base) = self.interpolated_or_expr_span(base)?;
+ self.parse_dot_or_call_expr_with(base, span, attrs)
+ }
+
+ pub(super) fn parse_dot_or_call_expr_with(
+ &mut self,
+ e0: P<Expr>,
+ lo: Span,
+ mut attrs: AttrVec,
+ ) -> PResult<'a, P<Expr>> {
+ // Stitch the list of outer attributes onto the return value.
+ // A little bit ugly, but the best way given the current code
+ // structure
+ self.parse_dot_or_call_expr_with_(e0, lo).map(|expr| {
+ expr.map(|mut expr| {
+ attrs.extend::<Vec<_>>(expr.attrs.into());
+ expr.attrs = attrs;
+ expr
+ })
+ })
+ }
+
+ fn parse_dot_or_call_expr_with_(&mut self, mut e: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
+ loop {
+ if self.eat(&token::Question) {
+ // `expr?`
+ e = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Try(e), AttrVec::new());
+ continue;
+ }
+ if self.eat(&token::Dot) {
+ // expr.f
+ e = self.parse_dot_suffix_expr(lo, e)?;
+ continue;
+ }
+ if self.expr_is_complete(&e) {
+ return Ok(e);
+ }
+ e = match self.token.kind {
+ token::OpenDelim(token::Paren) => self.parse_fn_call_expr(lo, e),
+ token::OpenDelim(token::Bracket) => self.parse_index_expr(lo, e)?,
+ _ => return Ok(e),
+ }
+ }
+ }
+
+ fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
+ match self.token.uninterpolate().kind {
+ token::Ident(..) => self.parse_dot_suffix(base, lo),
+ token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
+ Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix, None))
+ }
+ token::Literal(token::Lit { kind: token::Float, symbol, suffix }) => {
+ Ok(self.parse_tuple_field_access_expr_float(lo, base, symbol, suffix))
+ }
+ _ => {
+ self.error_unexpected_after_dot();
+ Ok(base)
+ }
+ }
+ }
+
+ fn error_unexpected_after_dot(&self) {
+ // FIXME Could factor this out into non_fatal_unexpected or something.
+ let actual = pprust::token_to_string(&self.token);
+ self.struct_span_err(self.token.span, &format!("unexpected token: `{}`", actual)).emit();
+ }
+
+ // We need an identifier or integer, but the next token is a float.
+ // Break the float into components to extract the identifier or integer.
+ // FIXME: With current `TokenCursor` it's hard to break tokens into more than 2
+ // parts unless those parts are processed immediately. `TokenCursor` should either
+ // support pushing "future tokens" (would be also helpful to `break_and_eat`), or
+ // we should break everything including floats into more basic proc-macro style
+ // tokens in the lexer (probably preferable).
+ fn parse_tuple_field_access_expr_float(
+ &mut self,
+ lo: Span,
+ base: P<Expr>,
+ float: Symbol,
+ suffix: Option<Symbol>,
+ ) -> P<Expr> {
+ #[derive(Debug)]
+ enum FloatComponent {
+ IdentLike(String),
+ Punct(char),
+ }
+ use FloatComponent::*;
+
+ let float_str = float.as_str();
+ let mut components = Vec::new();
+ let mut ident_like = String::new();
+ for c in float_str.chars() {
+ if c == '_' || c.is_ascii_alphanumeric() {
+ ident_like.push(c);
+ } else if matches!(c, '.' | '+' | '-') {
+ if !ident_like.is_empty() {
+ components.push(IdentLike(mem::take(&mut ident_like)));
+ }
+ components.push(Punct(c));
+ } else {
+ panic!("unexpected character in a float token: {:?}", c)
+ }
+ }
+ if !ident_like.is_empty() {
+ components.push(IdentLike(ident_like));
+ }
+
+ // With proc macros the span can refer to anything, the source may be too short,
+ // or too long, or non-ASCII. It only makes sense to break our span into components
+ // if its underlying text is identical to our float literal.
+ let span = self.token.span;
+ let can_take_span_apart =
+ || self.span_to_snippet(span).as_deref() == Ok(float_str).as_deref();
+
+ match &*components {
+ // 1e2
+ [IdentLike(i)] => {
+ self.parse_tuple_field_access_expr(lo, base, Symbol::intern(&i), suffix, None)
+ }
+ // 1.
+ [IdentLike(i), Punct('.')] => {
+ let (ident_span, dot_span) = if can_take_span_apart() {
+ let (span, ident_len) = (span.data(), BytePos::from_usize(i.len()));
+ let ident_span = span.with_hi(span.lo + ident_len);
+ let dot_span = span.with_lo(span.lo + ident_len);
+ (ident_span, dot_span)
+ } else {
+ (span, span)
+ };
+ assert!(suffix.is_none());
+ let symbol = Symbol::intern(&i);
+ self.token = Token::new(token::Ident(symbol, false), ident_span);
+ let next_token = (Token::new(token::Dot, dot_span), self.token_spacing);
+ self.parse_tuple_field_access_expr(lo, base, symbol, None, Some(next_token))
+ }
+ // 1.2 | 1.2e3
+ [IdentLike(i1), Punct('.'), IdentLike(i2)] => {
+ let (ident1_span, dot_span, ident2_span) = if can_take_span_apart() {
+ let (span, ident1_len) = (span.data(), BytePos::from_usize(i1.len()));
+ let ident1_span = span.with_hi(span.lo + ident1_len);
+ let dot_span = span
+ .with_lo(span.lo + ident1_len)
+ .with_hi(span.lo + ident1_len + BytePos(1));
+ let ident2_span = self.token.span.with_lo(span.lo + ident1_len + BytePos(1));
+ (ident1_span, dot_span, ident2_span)
+ } else {
+ (span, span, span)
+ };
+ let symbol1 = Symbol::intern(&i1);
+ self.token = Token::new(token::Ident(symbol1, false), ident1_span);
+ // This needs to be `Spacing::Alone` to prevent regressions.
+ // See issue #76399 and PR #76285 for more details
+ let next_token1 = (Token::new(token::Dot, dot_span), Spacing::Alone);
+ let base1 =
+ self.parse_tuple_field_access_expr(lo, base, symbol1, None, Some(next_token1));
+ let symbol2 = Symbol::intern(&i2);
+ let next_token2 = Token::new(token::Ident(symbol2, false), ident2_span);
+ self.bump_with((next_token2, self.token_spacing)); // `.`
+ self.parse_tuple_field_access_expr(lo, base1, symbol2, suffix, None)
+ }
+ // 1e+ | 1e- (recovered)
+ [IdentLike(_), Punct('+' | '-')] |
+ // 1e+2 | 1e-2
+ [IdentLike(_), Punct('+' | '-'), IdentLike(_)] |
+ // 1.2e+3 | 1.2e-3
+ [IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-'), IdentLike(_)] => {
+ // See the FIXME about `TokenCursor` above.
+ self.error_unexpected_after_dot();
+ base
+ }
+ _ => panic!("unexpected components in a float token: {:?}", components),
+ }
+ }
+
+ fn parse_tuple_field_access_expr(
+ &mut self,
+ lo: Span,
+ base: P<Expr>,
+ field: Symbol,
+ suffix: Option<Symbol>,
+ next_token: Option<(Token, Spacing)>,
+ ) -> P<Expr> {
+ match next_token {
+ Some(next_token) => self.bump_with(next_token),
+ None => self.bump(),
+ }
+ let span = self.prev_token.span;
+ let field = ExprKind::Field(base, Ident::new(field, span));
+ self.expect_no_suffix(span, "a tuple index", suffix);
+ self.mk_expr(lo.to(span), field, AttrVec::new())
+ }
+
+ /// Parse a function call expression, `expr(...)`.
+ fn parse_fn_call_expr(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
+ let seq = self.parse_paren_expr_seq().map(|args| {
+ self.mk_expr(lo.to(self.prev_token.span), self.mk_call(fun, args), AttrVec::new())
+ });
+ self.recover_seq_parse_error(token::Paren, lo, seq)
+ }
+
+ /// Parse an indexing expression `expr[...]`.
+ fn parse_index_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
+ self.bump(); // `[`
+ let index = self.parse_expr()?;
+ self.expect(&token::CloseDelim(token::Bracket))?;
+ Ok(self.mk_expr(lo.to(self.prev_token.span), self.mk_index(base, index), AttrVec::new()))
+ }
+
+ /// Assuming we have just parsed `.`, continue parsing into an expression.
+ fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
+ if self.token.uninterpolated_span().rust_2018() && self.eat_keyword(kw::Await) {
+ return self.mk_await_expr(self_arg, lo);
+ }
+
+ let fn_span_lo = self.token.span;
+ let mut segment = self.parse_path_segment(PathStyle::Expr)?;
+ self.check_trailing_angle_brackets(&segment, &[&token::OpenDelim(token::Paren)]);
+ self.check_turbofish_missing_angle_brackets(&mut segment);
+
+ if self.check(&token::OpenDelim(token::Paren)) {
+ // Method call `expr.f()`
+ let mut args = self.parse_paren_expr_seq()?;
+ args.insert(0, self_arg);
+
+ let fn_span = fn_span_lo.to(self.prev_token.span);
+ let span = lo.to(self.prev_token.span);
+ Ok(self.mk_expr(span, ExprKind::MethodCall(segment, args, fn_span), AttrVec::new()))
+ } else {
+ // Field access `expr.f`
+ if let Some(args) = segment.args {
+ self.struct_span_err(
+ args.span(),
+ "field expressions cannot have generic arguments",
+ )
+ .emit();
+ }
+
+ let span = lo.to(self.prev_token.span);
+ Ok(self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), AttrVec::new()))
+ }
+ }
+
+ /// At the bottom (top?) of the precedence hierarchy,
+ /// Parses things like parenthesized exprs, macros, `return`, etc.
+ ///
+ /// N.B., this does not parse outer attributes, and is private because it only works
+ /// correctly if called from `parse_dot_or_call_expr()`.
+ fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
+ maybe_recover_from_interpolated_ty_qpath!(self, true);
+ maybe_whole_expr!(self);
+
+ // Outer attributes are already parsed and will be
+ // added to the return value after the fact.
+ //
+ // Therefore, prevent sub-parser from parsing
+ // attributes by giving them a empty "already-parsed" list.
+ let attrs = AttrVec::new();
+
+ // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
+ let lo = self.token.span;
+ if let token::Literal(_) = self.token.kind {
+ // This match arm is a special-case of the `_` match arm below and
+ // could be removed without changing functionality, but it's faster
+ // to have it here, especially for programs with large constants.
+ self.parse_lit_expr(attrs)
+ } else if self.check(&token::OpenDelim(token::Paren)) {
+ self.parse_tuple_parens_expr(attrs)
+ } else if self.check(&token::OpenDelim(token::Brace)) {
+ self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs)
+ } else if self.check(&token::BinOp(token::Or)) || self.check(&token::OrOr) {
+ self.parse_closure_expr(attrs)
+ } else if self.check(&token::OpenDelim(token::Bracket)) {
+ self.parse_array_or_repeat_expr(attrs)
+ } else if self.eat_lt() {
+ let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
+ Ok(self.mk_expr(lo.to(path.span), ExprKind::Path(Some(qself), path), attrs))
+ } else if self.check_path() {
+ self.parse_path_start_expr(attrs)
+ } else if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
+ self.parse_closure_expr(attrs)
+ } else if self.eat_keyword(kw::If) {
+ self.parse_if_expr(attrs)
+ } else if self.check_keyword(kw::For) {
+ if self.choose_generics_over_qpath(1) {
+ // NOTE(Centril, eddyb): DO NOT REMOVE! Beyond providing parser recovery,
+ // this is an insurance policy in case we allow qpaths in (tuple-)struct patterns.
+ // When `for <Foo as Bar>::Proj in $expr $block` is wanted,
+ // you can disambiguate in favor of a pattern with `(...)`.
+ self.recover_quantified_closure_expr(attrs)
+ } else {
+ assert!(self.eat_keyword(kw::For));
+ self.parse_for_expr(None, self.prev_token.span, attrs)
+ }
+ } else if self.eat_keyword(kw::While) {
+ self.parse_while_expr(None, self.prev_token.span, attrs)
+ } else if let Some(label) = self.eat_label() {
+ self.parse_labeled_expr(label, attrs, true)
+ } else if self.eat_keyword(kw::Loop) {
+ self.parse_loop_expr(None, self.prev_token.span, attrs)
+ } else if self.eat_keyword(kw::Continue) {
+ let kind = ExprKind::Continue(self.eat_label());
+ Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
+ } else if self.eat_keyword(kw::Match) {
+ let match_sp = self.prev_token.span;
+ self.parse_match_expr(attrs).map_err(|mut err| {
+ err.span_label(match_sp, "while parsing this match expression");
+ err
+ })
+ } else if self.eat_keyword(kw::Unsafe) {
+ self.parse_block_expr(None, lo, BlockCheckMode::Unsafe(ast::UserProvided), attrs)
+ } else if self.check_inline_const(0) {
+ self.parse_const_block(lo.to(self.token.span))
+ } else if self.is_do_catch_block() {
+ self.recover_do_catch(attrs)
+ } else if self.is_try_block() {
+ self.expect_keyword(kw::Try)?;
+ self.parse_try_block(lo, attrs)
+ } else if self.eat_keyword(kw::Return) {
+ self.parse_return_expr(attrs)
+ } else if self.eat_keyword(kw::Break) {
+ self.parse_break_expr(attrs)
+ } else if self.eat_keyword(kw::Yield) {
+ self.parse_yield_expr(attrs)
+ } else if self.eat_keyword(kw::Let) {
+ self.parse_let_expr(attrs)
+ } else if self.eat_keyword(kw::Underscore) {
+ self.sess.gated_spans.gate(sym::destructuring_assignment, self.prev_token.span);
+ Ok(self.mk_expr(self.prev_token.span, ExprKind::Underscore, attrs))
+ } else if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
+ // Don't complain about bare semicolons after unclosed braces
+ // recovery in order to keep the error count down. Fixing the
+ // delimiters will possibly also fix the bare semicolon found in
+ // expression context. For example, silence the following error:
+ //
+ // error: expected expression, found `;`
+ // --> file.rs:2:13
+ // |
+ // 2 | foo(bar(;
+ // | ^ expected expression
+ self.bump();
+ Ok(self.mk_expr_err(self.token.span))
+ } else if self.token.uninterpolated_span().rust_2018() {
+ // `Span::rust_2018()` is somewhat expensive; don't get it repeatedly.
+ if self.check_keyword(kw::Async) {
+ if self.is_async_block() {
+ // Check for `async {` and `async move {`.
+ self.parse_async_block(attrs)
+ } else {
+ self.parse_closure_expr(attrs)
+ }
+ } else if self.eat_keyword(kw::Await) {
+ self.recover_incorrect_await_syntax(lo, self.prev_token.span, attrs)
+ } else {
+ self.parse_lit_expr(attrs)
+ }
+ } else {
+ self.parse_lit_expr(attrs)
+ }
+ }
+
+ fn parse_lit_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.token.span;
+ match self.parse_opt_lit() {
+ Some(literal) => {
+ let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Lit(literal), attrs);
+ self.maybe_recover_from_bad_qpath(expr, true)
+ }
+ None => self.try_macro_suggestion(),
+ }
+ }
+
+ fn parse_tuple_parens_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.token.span;
+ self.expect(&token::OpenDelim(token::Paren))?;
+ attrs.extend(self.parse_inner_attributes()?); // `(#![foo] a, b, ...)` is OK.
+ let (es, trailing_comma) = match self.parse_seq_to_end(
+ &token::CloseDelim(token::Paren),
+ SeqSep::trailing_allowed(token::Comma),
+ |p| p.parse_expr_catch_underscore(),
+ ) {
+ Ok(x) => x,
+ Err(err) => return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err))),
+ };
+ let kind = if es.len() == 1 && !trailing_comma {
+ // `(e)` is parenthesized `e`.
+ ExprKind::Paren(es.into_iter().next().unwrap())
+ } else {
+ // `(e,)` is a tuple with only one field, `e`.
+ ExprKind::Tup(es)
+ };
+ let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
+ self.maybe_recover_from_bad_qpath(expr, true)
+ }
+
+ fn parse_array_or_repeat_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.token.span;
+ self.bump(); // `[`
+
+ attrs.extend(self.parse_inner_attributes()?);
+
+ let close = &token::CloseDelim(token::Bracket);
+ let kind = if self.eat(close) {
+ // Empty vector
+ ExprKind::Array(Vec::new())
+ } else {
+ // Non-empty vector
+ let first_expr = self.parse_expr()?;
+ if self.eat(&token::Semi) {
+ // Repeating array syntax: `[ 0; 512 ]`
+ let count = self.parse_anon_const_expr()?;
+ self.expect(close)?;
+ ExprKind::Repeat(first_expr, count)
+ } else if self.eat(&token::Comma) {
+ // Vector with two or more elements.
+ let sep = SeqSep::trailing_allowed(token::Comma);
+ let (remaining_exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
+ let mut exprs = vec![first_expr];
+ exprs.extend(remaining_exprs);
+ ExprKind::Array(exprs)
+ } else {
+ // Vector with one element
+ self.expect(close)?;
+ ExprKind::Array(vec![first_expr])
+ }
+ };
+ let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
+ self.maybe_recover_from_bad_qpath(expr, true)
+ }
+
+ fn parse_path_start_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let path = self.parse_path(PathStyle::Expr)?;
+ let lo = path.span;
+
+ // `!`, as an operator, is prefix, so we know this isn't that.
+ let (hi, kind) = if self.eat(&token::Not) {
+ // MACRO INVOCATION expression
+ let mac = MacCall {
+ path,
+ args: self.parse_mac_args()?,
+ prior_type_ascription: self.last_type_ascription,
+ };
+ (self.prev_token.span, ExprKind::MacCall(mac))
+ } else if self.check(&token::OpenDelim(token::Brace)) {
+ if let Some(expr) = self.maybe_parse_struct_expr(&path, &attrs) {
+ return expr;
+ } else {
+ (path.span, ExprKind::Path(None, path))
+ }
+ } else {
+ (path.span, ExprKind::Path(None, path))
+ };
+
+ let expr = self.mk_expr(lo.to(hi), kind, attrs);
+ self.maybe_recover_from_bad_qpath(expr, true)
+ }
+
+ /// Parse `'label: $expr`. The label is already parsed.
+ fn parse_labeled_expr(
+ &mut self,
+ label: Label,
+ attrs: AttrVec,
+ consume_colon: bool,
+ ) -> PResult<'a, P<Expr>> {
+ let lo = label.ident.span;
+ let label = Some(label);
+ let ate_colon = self.eat(&token::Colon);
+ let expr = if self.eat_keyword(kw::While) {
+ self.parse_while_expr(label, lo, attrs)
+ } else if self.eat_keyword(kw::For) {
+ self.parse_for_expr(label, lo, attrs)
+ } else if self.eat_keyword(kw::Loop) {
+ self.parse_loop_expr(label, lo, attrs)
+ } else if self.check(&token::OpenDelim(token::Brace)) || self.token.is_whole_block() {
+ self.parse_block_expr(label, lo, BlockCheckMode::Default, attrs)
+ } else {
+ let msg = "expected `while`, `for`, `loop` or `{` after a label";
+ self.struct_span_err(self.token.span, msg).span_label(self.token.span, msg).emit();
+ // Continue as an expression in an effort to recover on `'label: non_block_expr`.
+ self.parse_expr()
+ }?;
+
+ if !ate_colon && consume_colon {
+ self.error_labeled_expr_must_be_followed_by_colon(lo, expr.span);
+ }
+
+ Ok(expr)
+ }
+
+ fn error_labeled_expr_must_be_followed_by_colon(&self, lo: Span, span: Span) {
+ self.struct_span_err(span, "labeled expression must be followed by `:`")
+ .span_label(lo, "the label")
+ .span_suggestion_short(
+ lo.shrink_to_hi(),
+ "add `:` after the label",
+ ": ".to_string(),
+ Applicability::MachineApplicable,
+ )
+ .note("labels are used before loops and blocks, allowing e.g., `break 'label` to them")
+ .emit();
+ }
+
+ /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
+ fn recover_do_catch(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.token.span;
+
+ self.bump(); // `do`
+ self.bump(); // `catch`
+
+ let span_dc = lo.to(self.prev_token.span);
+ self.struct_span_err(span_dc, "found removed `do catch` syntax")
+ .span_suggestion(
+ span_dc,
+ "replace with the new syntax",
+ "try".to_string(),
+ Applicability::MachineApplicable,
+ )
+ .note("following RFC #2388, the new non-placeholder syntax is `try`")
+ .emit();
+
+ self.parse_try_block(lo, attrs)
+ }
+
+ /// Parse an expression if the token can begin one.
+ fn parse_expr_opt(&mut self) -> PResult<'a, Option<P<Expr>>> {
+ Ok(if self.token.can_begin_expr() { Some(self.parse_expr()?) } else { None })
+ }
+
+ /// Parse `"return" expr?`.
+ fn parse_return_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.prev_token.span;
+ let kind = ExprKind::Ret(self.parse_expr_opt()?);
+ let expr = self.mk_expr(lo.to(self.prev_token.span), kind, attrs);
+ self.maybe_recover_from_bad_qpath(expr, true)
+ }
+
+ /// Parse `"('label ":")? break expr?`.
+ fn parse_break_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.prev_token.span;
+ let label = self.eat_label();
+ let kind = if self.token != token::OpenDelim(token::Brace)
+ || !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
+ {
+ self.parse_expr_opt()?
+ } else {
+ None
+ };
+ let expr = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Break(label, kind), attrs);
+ self.maybe_recover_from_bad_qpath(expr, true)
+ }
+
+ /// Parse `"yield" expr?`.
+ fn parse_yield_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.prev_token.span;
+ let kind = ExprKind::Yield(self.parse_expr_opt()?);
+ let span = lo.to(self.prev_token.span);
+ self.sess.gated_spans.gate(sym::generators, span);
+ let expr = self.mk_expr(span, kind, attrs);
+ self.maybe_recover_from_bad_qpath(expr, true)
+ }
+
+ /// Returns a string literal if the next token is a string literal.
+ /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
+ /// and returns `None` if the next token is not literal at all.
+ pub fn parse_str_lit(&mut self) -> Result<ast::StrLit, Option<Lit>> {
+ match self.parse_opt_lit() {
+ Some(lit) => match lit.kind {
+ ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
+ style,
+ symbol: lit.token.symbol,
+ suffix: lit.token.suffix,
+ span: lit.span,
+ symbol_unescaped,
+ }),
+ _ => Err(Some(lit)),
+ },
+ None => Err(None),
+ }
+ }
+
+ pub(super) fn parse_lit(&mut self) -> PResult<'a, Lit> {
+ self.parse_opt_lit().ok_or_else(|| {
+ let msg = format!("unexpected token: {}", super::token_descr(&self.token));
+ self.struct_span_err(self.token.span, &msg)
+ })
+ }
+
+ /// Matches `lit = true | false | token_lit`.
+ /// Returns `None` if the next token is not a literal.
+ pub(super) fn parse_opt_lit(&mut self) -> Option<Lit> {
+ let mut recovered = None;
+ if self.token == token::Dot {
+ // Attempt to recover `.4` as `0.4`. We don't currently have any syntax where
+ // dot would follow an optional literal, so we do this unconditionally.
+ recovered = self.look_ahead(1, |next_token| {
+ if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
+ next_token.kind
+ {
+ if self.token.span.hi() == next_token.span.lo() {
+ let s = String::from("0.") + &symbol.as_str();
+ let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
+ return Some(Token::new(kind, self.token.span.to(next_token.span)));
+ }
+ }
+ None
+ });
+ if let Some(token) = &recovered {
+ self.bump();
+ self.error_float_lits_must_have_int_part(&token);
+ }
+ }
+
+ let token = recovered.as_ref().unwrap_or(&self.token);
+ match Lit::from_token(token) {
+ Ok(lit) => {
+ self.bump();
+ Some(lit)
+ }
+ Err(LitError::NotLiteral) => None,
+ Err(err) => {
+ let span = token.span;
+ let lit = match token.kind {
+ token::Literal(lit) => lit,
+ _ => unreachable!(),
+ };
+ self.bump();
+ self.report_lit_error(err, lit, span);
+ // Pack possible quotes and prefixes from the original literal into
+ // the error literal's symbol so they can be pretty-printed faithfully.
+ let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
+ let symbol = Symbol::intern(&suffixless_lit.to_string());
+ let lit = token::Lit::new(token::Err, symbol, lit.suffix);
+ Some(Lit::from_lit_token(lit, span).unwrap_or_else(|_| unreachable!()))
+ }
+ }
+ }
+
+ fn error_float_lits_must_have_int_part(&self, token: &Token) {
+ self.struct_span_err(token.span, "float literals must have an integer part")
+ .span_suggestion(
+ token.span,
+ "must have an integer part",
+ pprust::token_to_string(token),
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+
+ fn report_lit_error(&self, err: LitError, lit: token::Lit, span: Span) {
+ // Checks if `s` looks like i32 or u1234 etc.
+ fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
+ s.len() > 1 && s.starts_with(first_chars) && s[1..].chars().all(|c| c.is_ascii_digit())
+ }
+
+ let token::Lit { kind, suffix, .. } = lit;
+ match err {
+ // `NotLiteral` is not an error by itself, so we don't report
+ // it and give the parser opportunity to try something else.
+ LitError::NotLiteral => {}
+ // `LexerError` *is* an error, but it was already reported
+ // by lexer, so here we don't report it the second time.
+ LitError::LexerError => {}
+ LitError::InvalidSuffix => {
+ self.expect_no_suffix(
+ span,
+ &format!("{} {} literal", kind.article(), kind.descr()),
+ suffix,
+ );
+ }
+ LitError::InvalidIntSuffix => {
+ let suf = suffix.expect("suffix error with no suffix").as_str();
+ if looks_like_width_suffix(&['i', 'u'], &suf) {
+ // If it looks like a width, try to be helpful.
+ let msg = format!("invalid width `{}` for integer literal", &suf[1..]);
+ self.struct_span_err(span, &msg)
+ .help("valid widths are 8, 16, 32, 64 and 128")
+ .emit();
+ } else {
+ let msg = format!("invalid suffix `{}` for number literal", suf);
+ self.struct_span_err(span, &msg)
+ .span_label(span, format!("invalid suffix `{}`", suf))
+ .help("the suffix must be one of the numeric types (`u32`, `isize`, `f32`, etc.)")
+ .emit();
+ }
+ }
+ LitError::InvalidFloatSuffix => {
+ let suf = suffix.expect("suffix error with no suffix").as_str();
+ if looks_like_width_suffix(&['f'], &suf) {
+ // If it looks like a width, try to be helpful.
+ let msg = format!("invalid width `{}` for float literal", &suf[1..]);
+ self.struct_span_err(span, &msg).help("valid widths are 32 and 64").emit();
+ } else {
+ let msg = format!("invalid suffix `{}` for float literal", suf);
+ self.struct_span_err(span, &msg)
+ .span_label(span, format!("invalid suffix `{}`", suf))
+ .help("valid suffixes are `f32` and `f64`")
+ .emit();
+ }
+ }
+ LitError::NonDecimalFloat(base) => {
+ let descr = match base {
+ 16 => "hexadecimal",
+ 8 => "octal",
+ 2 => "binary",
+ _ => unreachable!(),
+ };
+ self.struct_span_err(span, &format!("{} float literal is not supported", descr))
+ .span_label(span, "not supported")
+ .emit();
+ }
+ LitError::IntTooLarge => {
+ self.struct_span_err(span, "integer literal is too large").emit();
+ }
+ }
+ }
+
+ pub(super) fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<Symbol>) {
+ if let Some(suf) = suffix {
+ let mut err = if kind == "a tuple index"
+ && [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suf)
+ {
+ // #59553: warn instead of reject out of hand to allow the fix to percolate
+ // through the ecosystem when people fix their macros
+ let mut err = self
+ .sess
+ .span_diagnostic
+ .struct_span_warn(sp, &format!("suffixes on {} are invalid", kind));
+ err.note(&format!(
+ "`{}` is *temporarily* accepted on tuple index fields as it was \
+ incorrectly accepted on stable for a few releases",
+ suf,
+ ));
+ err.help(
+ "on proc macros, you'll want to use `syn::Index::from` or \
+ `proc_macro::Literal::*_unsuffixed` for code that will desugar \
+ to tuple field access",
+ );
+ err.note(
+ "see issue #60210 <https://github.com/rust-lang/rust/issues/60210> \
+ for more information",
+ );
+ err
+ } else {
+ self.struct_span_err(sp, &format!("suffixes on {} are invalid", kind))
+ };
+ err.span_label(sp, format!("invalid suffix `{}`", suf));
+ err.emit();
+ }
+ }
+
+ /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
+ /// Keep this in sync with `Token::can_begin_literal_maybe_minus`.
+ pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
+ maybe_whole_expr!(self);
+
+ let lo = self.token.span;
+ let minus_present = self.eat(&token::BinOp(token::Minus));
+ let lit = self.parse_lit()?;
+ let expr = self.mk_expr(lit.span, ExprKind::Lit(lit), AttrVec::new());
+
+ if minus_present {
+ Ok(self.mk_expr(
+ lo.to(self.prev_token.span),
+ self.mk_unary(UnOp::Neg, expr),
+ AttrVec::new(),
+ ))
+ } else {
+ Ok(expr)
+ }
+ }
+
+ /// Parses a block or unsafe block.
+ pub(super) fn parse_block_expr(
+ &mut self,
+ opt_label: Option<Label>,
+ lo: Span,
+ blk_mode: BlockCheckMode,
+ mut attrs: AttrVec,
+ ) -> PResult<'a, P<Expr>> {
+ if let Some(label) = opt_label {
+ self.sess.gated_spans.gate(sym::label_break_value, label.ident.span);
+ }
+
+ if self.token.is_whole_block() {
+ self.struct_span_err(self.token.span, "cannot use a `block` macro fragment here")
+ .span_label(lo.to(self.token.span), "the `block` fragment is within this context")
+ .emit();
+ }
+
+ let (inner_attrs, blk) = self.parse_block_common(lo, blk_mode)?;
+ attrs.extend(inner_attrs);
+ Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs))
+ }
+
+ /// Recover on an explicitly quantified closure expression, e.g., `for<'a> |x: &'a u8| *x + 1`.
+ fn recover_quantified_closure_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.token.span;
+ let _ = self.parse_late_bound_lifetime_defs()?;
+ let span_for = lo.to(self.prev_token.span);
+ let closure = self.parse_closure_expr(attrs)?;
+
+ self.struct_span_err(span_for, "cannot introduce explicit parameters for a closure")
+ .span_label(closure.span, "the parameters are attached to this closure")
+ .span_suggestion(
+ span_for,
+ "remove the parameters",
+ String::new(),
+ Applicability::MachineApplicable,
+ )
+ .emit();
+
+ Ok(self.mk_expr_err(lo.to(closure.span)))
+ }
+
+ /// Parses a closure expression (e.g., `move |args| expr`).
+ fn parse_closure_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.token.span;
+
+ let movability =
+ if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
+
+ let asyncness = if self.token.uninterpolated_span().rust_2018() {
+ self.parse_asyncness()
+ } else {
+ Async::No
+ };
+
+ let capture_clause = self.parse_capture_clause()?;
+ let decl = self.parse_fn_block_decl()?;
+ let decl_hi = self.prev_token.span;
+ let body = match decl.output {
+ FnRetTy::Default(_) => {
+ let restrictions = self.restrictions - Restrictions::STMT_EXPR;
+ self.parse_expr_res(restrictions, None)?
+ }
+ _ => {
+ // If an explicit return type is given, require a block to appear (RFC 968).
+ let body_lo = self.token.span;
+ self.parse_block_expr(None, body_lo, BlockCheckMode::Default, AttrVec::new())?
+ }
+ };
+
+ if let Async::Yes { span, .. } = asyncness {
+ // Feature-gate `async ||` closures.
+ self.sess.gated_spans.gate(sym::async_closure, span);
+ }
+
+ Ok(self.mk_expr(
+ lo.to(body.span),
+ ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
+ attrs,
+ ))
+ }
+
+ /// Parses an optional `move` prefix to a closure-like construct.
+ fn parse_capture_clause(&mut self) -> PResult<'a, CaptureBy> {
+ if self.eat_keyword(kw::Move) {
+ // Check for `move async` and recover
+ if self.check_keyword(kw::Async) {
+ let move_async_span = self.token.span.with_lo(self.prev_token.span.data().lo);
+ Err(self.incorrect_move_async_order_found(move_async_span))
+ } else {
+ Ok(CaptureBy::Value)
+ }
+ } else {
+ Ok(CaptureBy::Ref)
+ }
+ }
+
+ /// Parses the `|arg, arg|` header of a closure.
+ fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
+ let inputs = if self.eat(&token::OrOr) {
+ Vec::new()
+ } else {
+ self.expect(&token::BinOp(token::Or))?;
+ let args = self
+ .parse_seq_to_before_tokens(
+ &[&token::BinOp(token::Or), &token::OrOr],
+ SeqSep::trailing_allowed(token::Comma),
+ TokenExpectType::NoExpect,
+ |p| p.parse_fn_block_param(),
+ )?
+ .0;
+ self.expect_or()?;
+ args
+ };
+ let output =
+ self.parse_ret_ty(AllowPlus::Yes, RecoverQPath::Yes, RecoverReturnSign::Yes)?;
+
+ Ok(P(FnDecl { inputs, output }))
+ }
+
+ /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
+ fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
+ let lo = self.token.span;
+ let attrs = self.parse_outer_attributes()?;
+ let pat = self.parse_pat(PARAM_EXPECTED)?;
+ let ty = if self.eat(&token::Colon) {
+ self.parse_ty()?
+ } else {
+ self.mk_ty(self.prev_token.span, TyKind::Infer)
+ };
+ Ok(Param {
+ attrs: attrs.into(),
+ ty,
+ pat,
+ span: lo.to(self.token.span),
+ id: DUMMY_NODE_ID,
+ is_placeholder: false,
+ })
+ }
+
+ /// Parses an `if` expression (`if` token already eaten).
+ fn parse_if_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.prev_token.span;
+ let cond = self.parse_cond_expr()?;
+
+ // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
+ // verify that the last statement is either an implicit return (no `;`) or an explicit
+ // return. This won't catch blocks with an explicit `return`, but that would be caught by
+ // the dead code lint.
+ let thn = if self.eat_keyword(kw::Else) || !cond.returns() {
+ self.error_missing_if_cond(lo, cond.span)
+ } else {
+ let attrs = self.parse_outer_attributes()?; // For recovery.
+ let not_block = self.token != token::OpenDelim(token::Brace);
+ let block = self.parse_block().map_err(|mut err| {
+ if not_block {
+ err.span_label(lo, "this `if` expression has a condition, but no block");
+ if let ExprKind::Binary(_, _, ref right) = cond.kind {
+ if let ExprKind::Block(_, _) = right.kind {
+ err.help("maybe you forgot the right operand of the condition?");
+ }
+ }
+ }
+ err
+ })?;
+ self.error_on_if_block_attrs(lo, false, block.span, &attrs);
+ block
+ };
+ let els = if self.eat_keyword(kw::Else) { Some(self.parse_else_expr()?) } else { None };
+ Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::If(cond, thn, els), attrs))
+ }
+
+ fn error_missing_if_cond(&self, lo: Span, span: Span) -> P<ast::Block> {
+ let sp = self.sess.source_map().next_point(lo);
+ self.struct_span_err(sp, "missing condition for `if` expression")
+ .span_label(sp, "expected if condition here")
+ .emit();
+ self.mk_block_err(span)
+ }
+
+ /// Parses the condition of a `if` or `while` expression.
+ fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
+ let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
+
+ if let ExprKind::Let(..) = cond.kind {
+ // Remove the last feature gating of a `let` expression since it's stable.
+ self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
+ }
+
+ Ok(cond)
+ }
+
+ /// Parses a `let $pat = $expr` pseudo-expression.
+ /// The `let` token has already been eaten.
+ fn parse_let_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.prev_token.span;
+ let pat = self.parse_top_pat(GateOr::No, RecoverComma::Yes)?;
+ self.expect(&token::Eq)?;
+ let expr = self.with_res(self.restrictions | Restrictions::NO_STRUCT_LITERAL, |this| {
+ this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
+ })?;
+ let span = lo.to(expr.span);
+ self.sess.gated_spans.gate(sym::let_chains, span);
+ Ok(self.mk_expr(span, ExprKind::Let(pat, expr), attrs))
+ }
+
+ /// Parses an `else { ... }` expression (`else` token already eaten).
+ fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
+ let ctx_span = self.prev_token.span; // `else`
+ let attrs = self.parse_outer_attributes()?; // For recovery.
+ let expr = if self.eat_keyword(kw::If) {
+ self.parse_if_expr(AttrVec::new())?
+ } else {
+ let blk = self.parse_block()?;
+ self.mk_expr(blk.span, ExprKind::Block(blk, None), AttrVec::new())
+ };
+ self.error_on_if_block_attrs(ctx_span, true, expr.span, &attrs);
+ Ok(expr)
+ }
+
+ fn error_on_if_block_attrs(
+ &self,
+ ctx_span: Span,
+ is_ctx_else: bool,
+ branch_span: Span,
+ attrs: &[ast::Attribute],
+ ) {
+ let (span, last) = match attrs {
+ [] => return,
+ [x0 @ xn] | [x0, .., xn] => (x0.span.to(xn.span), xn.span),
+ };
+ let ctx = if is_ctx_else { "else" } else { "if" };
+ self.struct_span_err(last, "outer attributes are not allowed on `if` and `else` branches")
+ .span_label(branch_span, "the attributes are attached to this branch")
+ .span_label(ctx_span, format!("the branch belongs to this `{}`", ctx))
+ .span_suggestion(
+ span,
+ "remove the attributes",
+ String::new(),
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+
+ /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
+ fn parse_for_expr(
+ &mut self,
+ opt_label: Option<Label>,
+ lo: Span,
+ mut attrs: AttrVec,
+ ) -> PResult<'a, P<Expr>> {
+ // Record whether we are about to parse `for (`.
+ // This is used below for recovery in case of `for ( $stuff ) $block`
+ // in which case we will suggest `for $stuff $block`.
+ let begin_paren = match self.token.kind {
+ token::OpenDelim(token::Paren) => Some(self.token.span),
+ _ => None,
+ };
+
+ let pat = self.parse_top_pat(GateOr::Yes, RecoverComma::Yes)?;
+ if !self.eat_keyword(kw::In) {
+ self.error_missing_in_for_loop();
+ }
+ self.check_for_for_in_in_typo(self.prev_token.span);
+ let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
+
+ let pat = self.recover_parens_around_for_head(pat, &expr, begin_paren);
+
+ let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
+ attrs.extend(iattrs);
+
+ let kind = ExprKind::ForLoop(pat, expr, loop_block, opt_label);
+ Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
+ }
+
+ fn error_missing_in_for_loop(&mut self) {
+ let (span, msg, sugg) = if self.token.is_ident_named(sym::of) {
+ // Possibly using JS syntax (#75311).
+ let span = self.token.span;
+ self.bump();
+ (span, "try using `in` here instead", "in")
+ } else {
+ (self.prev_token.span.between(self.token.span), "try adding `in` here", " in ")
+ };
+ self.struct_span_err(span, "missing `in` in `for` loop")
+ .span_suggestion_short(
+ span,
+ msg,
+ sugg.into(),
+ // Has been misleading, at least in the past (closed Issue #48492).
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ }
+
+ /// Parses a `while` or `while let` expression (`while` token already eaten).
+ fn parse_while_expr(
+ &mut self,
+ opt_label: Option<Label>,
+ lo: Span,
+ mut attrs: AttrVec,
+ ) -> PResult<'a, P<Expr>> {
+ let cond = self.parse_cond_expr()?;
+ let (iattrs, body) = self.parse_inner_attrs_and_block()?;
+ attrs.extend(iattrs);
+ Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::While(cond, body, opt_label), attrs))
+ }
+
+ /// Parses `loop { ... }` (`loop` token already eaten).
+ fn parse_loop_expr(
+ &mut self,
+ opt_label: Option<Label>,
+ lo: Span,
+ mut attrs: AttrVec,
+ ) -> PResult<'a, P<Expr>> {
+ let (iattrs, body) = self.parse_inner_attrs_and_block()?;
+ attrs.extend(iattrs);
+ Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::Loop(body, opt_label), attrs))
+ }
+
+ fn eat_label(&mut self) -> Option<Label> {
+ self.token.lifetime().map(|ident| {
+ self.bump();
+ Label { ident }
+ })
+ }
+
+ /// Parses a `match ... { ... }` expression (`match` token already eaten).
+ fn parse_match_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let match_span = self.prev_token.span;
+ let lo = self.prev_token.span;
+ let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
+ if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
+ if self.token == token::Semi {
+ e.span_suggestion_short(
+ match_span,
+ "try removing this `match`",
+ String::new(),
+ Applicability::MaybeIncorrect, // speculative
+ );
+ }
+ return Err(e);
+ }
+ attrs.extend(self.parse_inner_attributes()?);
+
+ let mut arms: Vec<Arm> = Vec::new();
+ while self.token != token::CloseDelim(token::Brace) {
+ match self.parse_arm() {
+ Ok(arm) => arms.push(arm),
+ Err(mut e) => {
+ // Recover by skipping to the end of the block.
+ e.emit();
+ self.recover_stmt();
+ let span = lo.to(self.token.span);
+ if self.token == token::CloseDelim(token::Brace) {
+ self.bump();
+ }
+ return Ok(self.mk_expr(span, ExprKind::Match(scrutinee, arms), attrs));
+ }
+ }
+ }
+ let hi = self.token.span;
+ self.bump();
+ Ok(self.mk_expr(lo.to(hi), ExprKind::Match(scrutinee, arms), attrs))
+ }
+
+ pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
+ let attrs = self.parse_outer_attributes()?;
+ let lo = self.token.span;
+ let pat = self.parse_top_pat(GateOr::No, RecoverComma::Yes)?;
+ let guard = if self.eat_keyword(kw::If) {
+ let if_span = self.prev_token.span;
+ let cond = self.parse_expr()?;
+ if let ExprKind::Let(..) = cond.kind {
+ // Remove the last feature gating of a `let` expression since it's stable.
+ self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
+ let span = if_span.to(cond.span);
+ self.sess.gated_spans.gate(sym::if_let_guard, span);
+ }
+ Some(cond)
+ } else {
+ None
+ };
+ let arrow_span = self.token.span;
+ self.expect(&token::FatArrow)?;
+ let arm_start_span = self.token.span;
+
+ let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None).map_err(|mut err| {
+ err.span_label(arrow_span, "while parsing the `match` arm starting here");
+ err
+ })?;
+
+ let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
+ && self.token != token::CloseDelim(token::Brace);
+
+ let hi = self.prev_token.span;
+
+ if require_comma {
+ let sm = self.sess.source_map();
+ self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)]).map_err(
+ |mut err| {
+ match (sm.span_to_lines(expr.span), sm.span_to_lines(arm_start_span)) {
+ (Ok(ref expr_lines), Ok(ref arm_start_lines))
+ if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
+ && expr_lines.lines.len() == 2
+ && self.token == token::FatArrow =>
+ {
+ // We check whether there's any trailing code in the parse span,
+ // if there isn't, we very likely have the following:
+ //
+ // X | &Y => "y"
+ // | -- - missing comma
+ // | |
+ // | arrow_span
+ // X | &X => "x"
+ // | - ^^ self.token.span
+ // | |
+ // | parsed until here as `"y" & X`
+ err.span_suggestion_short(
+ arm_start_span.shrink_to_hi(),
+ "missing a comma here to end this `match` arm",
+ ",".to_owned(),
+ Applicability::MachineApplicable,
+ );
+ }
+ _ => {
+ err.span_label(
+ arrow_span,
+ "while parsing the `match` arm starting here",
+ );
+ }
+ }
+ err
+ },
+ )?;
+ } else {
+ self.eat(&token::Comma);
+ }
+
+ Ok(ast::Arm {
+ attrs,
+ pat,
+ guard,
+ body: expr,
+ span: lo.to(hi),
+ id: DUMMY_NODE_ID,
+ is_placeholder: false,
+ })
+ }
+
+ /// Parses a `try {...}` expression (`try` token already eaten).
+ fn parse_try_block(&mut self, span_lo: Span, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let (iattrs, body) = self.parse_inner_attrs_and_block()?;
+ attrs.extend(iattrs);
+ if self.eat_keyword(kw::Catch) {
+ let mut error = self.struct_span_err(
+ self.prev_token.span,
+ "keyword `catch` cannot follow a `try` block",
+ );
+ error.help("try using `match` on the result of the `try` block instead");
+ error.emit();
+ Err(error)
+ } else {
+ let span = span_lo.to(body.span);
+ self.sess.gated_spans.gate(sym::try_blocks, span);
+ Ok(self.mk_expr(span, ExprKind::TryBlock(body), attrs))
+ }
+ }
+
+ fn is_do_catch_block(&self) -> bool {
+ self.token.is_keyword(kw::Do)
+ && self.is_keyword_ahead(1, &[kw::Catch])
+ && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
+ && !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
+ }
+
+ fn is_try_block(&self) -> bool {
+ self.token.is_keyword(kw::Try)
+ && self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
+ && self.token.uninterpolated_span().rust_2018()
+ }
+
+ /// Parses an `async move? {...}` expression.
+ fn parse_async_block(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
+ let lo = self.token.span;
+ self.expect_keyword(kw::Async)?;
+ let capture_clause = self.parse_capture_clause()?;
+ let (iattrs, body) = self.parse_inner_attrs_and_block()?;
+ attrs.extend(iattrs);
+ let kind = ExprKind::Async(capture_clause, DUMMY_NODE_ID, body);
+ Ok(self.mk_expr(lo.to(self.prev_token.span), kind, attrs))
+ }
+
+ fn is_async_block(&self) -> bool {
+ self.token.is_keyword(kw::Async)
+ && ((
+ // `async move {`
+ self.is_keyword_ahead(1, &[kw::Move])
+ && self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
+ ) || (
+ // `async {`
+ self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
+ ))
+ }
+
+ fn is_certainly_not_a_block(&self) -> bool {
+ self.look_ahead(1, |t| t.is_ident())
+ && (
+ // `{ ident, ` cannot start a block.
+ self.look_ahead(2, |t| t == &token::Comma)
+ || self.look_ahead(2, |t| t == &token::Colon)
+ && (
+ // `{ ident: token, ` cannot start a block.
+ self.look_ahead(4, |t| t == &token::Comma) ||
+ // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`.
+ self.look_ahead(3, |t| !t.can_begin_type())
+ )
+ )
+ }
+
+ fn maybe_parse_struct_expr(
+ &mut self,
+ path: &ast::Path,
+ attrs: &AttrVec,
+ ) -> Option<PResult<'a, P<Expr>>> {
+ let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
+ if struct_allowed || self.is_certainly_not_a_block() {
+ if let Err(err) = self.expect(&token::OpenDelim(token::Brace)) {
+ return Some(Err(err));
+ }
+ let expr = self.parse_struct_expr(path.clone(), attrs.clone(), true);
+ if let (Ok(expr), false) = (&expr, struct_allowed) {
+ // This is a struct literal, but we don't can't accept them here.
+ self.error_struct_lit_not_allowed_here(path.span, expr.span);
+ }
+ return Some(expr);
+ }
+ None
+ }
+
+ fn error_struct_lit_not_allowed_here(&self, lo: Span, sp: Span) {
+ self.struct_span_err(sp, "struct literals are not allowed here")
+ .multipart_suggestion(
+ "surround the struct literal with parentheses",
+ vec![(lo.shrink_to_lo(), "(".to_string()), (sp.shrink_to_hi(), ")".to_string())],
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+
+ /// Precondition: already parsed the '{'.
+ pub(super) fn parse_struct_expr(
+ &mut self,
+ pth: ast::Path,
+ mut attrs: AttrVec,
+ recover: bool,
+ ) -> PResult<'a, P<Expr>> {
+ let mut fields = Vec::new();
+ let mut base = ast::StructRest::None;
+ let mut recover_async = false;
+
+ attrs.extend(self.parse_inner_attributes()?);
+
+ let mut async_block_err = |e: &mut DiagnosticBuilder<'_>, span: Span| {
+ recover_async = true;
+ e.span_label(span, "`async` blocks are only allowed in Rust 2018 or later");
+ e.help(&format!("set `edition = \"{}\"` in `Cargo.toml`", LATEST_STABLE_EDITION));
+ e.note("for more on editions, read https://doc.rust-lang.org/edition-guide");
+ };
+
+ while self.token != token::CloseDelim(token::Brace) {
+ if self.eat(&token::DotDot) {
+ let exp_span = self.prev_token.span;
+ // We permit `.. }` on the left-hand side of a destructuring assignment.
+ if self.check(&token::CloseDelim(token::Brace)) {
+ self.sess.gated_spans.gate(sym::destructuring_assignment, self.prev_token.span);
+ base = ast::StructRest::Rest(self.prev_token.span.shrink_to_hi());
+ break;
+ }
+ match self.parse_expr() {
+ Ok(e) => base = ast::StructRest::Base(e),
+ Err(mut e) if recover => {
+ e.emit();
+ self.recover_stmt();
+ }
+ Err(e) => return Err(e),
+ }
+ self.recover_struct_comma_after_dotdot(exp_span);
+ break;
+ }
+
+ let recovery_field = self.find_struct_error_after_field_looking_code();
+ let parsed_field = match self.parse_field() {
+ Ok(f) => Some(f),
+ Err(mut e) => {
+ if pth == kw::Async {
+ async_block_err(&mut e, pth.span);
+ } else {
+ e.span_label(pth.span, "while parsing this struct");
+ }
+ e.emit();
+
+ // If the next token is a comma, then try to parse
+ // what comes next as additional fields, rather than
+ // bailing out until next `}`.
+ if self.token != token::Comma {
+ self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
+ if self.token != token::Comma {
+ break;
+ }
+ }
+ None
+ }
+ };
+
+ match self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)]) {
+ Ok(_) => {
+ if let Some(f) = parsed_field.or(recovery_field) {
+ // Only include the field if there's no parse error for the field name.
+ fields.push(f);
+ }
+ }
+ Err(mut e) => {
+ if pth == kw::Async {
+ async_block_err(&mut e, pth.span);
+ } else {
+ e.span_label(pth.span, "while parsing this struct");
+ if let Some(f) = recovery_field {
+ fields.push(f);
+ e.span_suggestion(
+ self.prev_token.span.shrink_to_hi(),
+ "try adding a comma",
+ ",".into(),
+ Applicability::MachineApplicable,
+ );
+ }
+ }
+ if !recover {
+ return Err(e);
+ }
+ e.emit();
+ self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
+ self.eat(&token::Comma);
+ }
+ }
+ }
+
+ let span = pth.span.to(self.token.span);
+ self.expect(&token::CloseDelim(token::Brace))?;
+ let expr = if recover_async { ExprKind::Err } else { ExprKind::Struct(pth, fields, base) };
+ Ok(self.mk_expr(span, expr, attrs))
+ }
+
+ /// Use in case of error after field-looking code: `S { foo: () with a }`.
+ fn find_struct_error_after_field_looking_code(&self) -> Option<Field> {
+ match self.token.ident() {
+ Some((ident, is_raw))
+ if (is_raw || !ident.is_reserved())
+ && self.look_ahead(1, |t| *t == token::Colon) =>
+ {
+ Some(ast::Field {
+ ident,
+ span: self.token.span,
+ expr: self.mk_expr_err(self.token.span),
+ is_shorthand: false,
+ attrs: AttrVec::new(),
+ id: DUMMY_NODE_ID,
+ is_placeholder: false,
+ })
+ }
+ _ => None,
+ }
+ }
+
+ fn recover_struct_comma_after_dotdot(&mut self, span: Span) {
+ if self.token != token::Comma {
+ return;
+ }
+ self.struct_span_err(
+ span.to(self.prev_token.span),
+ "cannot use a comma after the base struct",
+ )
+ .span_suggestion_short(
+ self.token.span,
+ "remove this comma",
+ String::new(),
+ Applicability::MachineApplicable,
+ )
+ .note("the base struct must always be the last field")
+ .emit();
+ self.recover_stmt();
+ }
+
+ /// Parses `ident (COLON expr)?`.
+ fn parse_field(&mut self) -> PResult<'a, Field> {
+ let attrs = self.parse_outer_attributes()?.into();
+ let lo = self.token.span;
+
+ // Check if a colon exists one ahead. This means we're parsing a fieldname.
+ let is_shorthand = !self.look_ahead(1, |t| t == &token::Colon || t == &token::Eq);
+ let (ident, expr) = if is_shorthand {
+ // Mimic `x: x` for the `x` field shorthand.
+ let ident = self.parse_ident_common(false)?;
+ let path = ast::Path::from_ident(ident);
+ (ident, self.mk_expr(ident.span, ExprKind::Path(None, path), AttrVec::new()))
+ } else {
+ let ident = self.parse_field_name()?;
+ self.error_on_eq_field_init(ident);
+ self.bump(); // `:`
+ (ident, self.parse_expr()?)
+ };
+ Ok(ast::Field {
+ ident,
+ span: lo.to(expr.span),
+ expr,
+ is_shorthand,
+ attrs,
+ id: DUMMY_NODE_ID,
+ is_placeholder: false,
+ })
+ }
+
+ /// Check for `=`. This means the source incorrectly attempts to
+ /// initialize a field with an eq rather than a colon.
+ fn error_on_eq_field_init(&self, field_name: Ident) {
+ if self.token != token::Eq {
+ return;
+ }
+
+ self.struct_span_err(self.token.span, "expected `:`, found `=`")
+ .span_suggestion(
+ field_name.span.shrink_to_hi().to(self.token.span),
+ "replace equals symbol with a colon",
+ ":".to_string(),
+ Applicability::MachineApplicable,
+ )
+ .emit();
+ }
+
+ fn err_dotdotdot_syntax(&self, span: Span) {
+ self.struct_span_err(span, "unexpected token: `...`")
+ .span_suggestion(
+ span,
+ "use `..` for an exclusive range",
+ "..".to_owned(),
+ Applicability::MaybeIncorrect,
+ )
+ .span_suggestion(
+ span,
+ "or `..=` for an inclusive range",
+ "..=".to_owned(),
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ }
+
+ fn err_larrow_operator(&self, span: Span) {
+ self.struct_span_err(span, "unexpected token: `<-`")
+ .span_suggestion(
+ span,
+ "if you meant to write a comparison against a negative value, add a \
+ space in between `<` and `-`",
+ "< -".to_string(),
+ Applicability::MaybeIncorrect,
+ )
+ .emit();
+ }
+
+ fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
+ ExprKind::AssignOp(binop, lhs, rhs)
+ }
+
+ fn mk_range(
+ &self,
+ start: Option<P<Expr>>,
+ end: Option<P<Expr>>,
+ limits: RangeLimits,
+ ) -> PResult<'a, ExprKind> {
+ if end.is_none() && limits == RangeLimits::Closed {
+ self.error_inclusive_range_with_no_end(self.prev_token.span);
+ Ok(ExprKind::Err)
+ } else {
+ Ok(ExprKind::Range(start, end, limits))
+ }
+ }
+
+ fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
+ ExprKind::Unary(unop, expr)
+ }
+
+ fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
+ ExprKind::Binary(binop, lhs, rhs)
+ }
+
+ fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
+ ExprKind::Index(expr, idx)
+ }
+
+ fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
+ ExprKind::Call(f, args)
+ }
+
+ fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
+ let span = lo.to(self.prev_token.span);
+ let await_expr = self.mk_expr(span, ExprKind::Await(self_arg), AttrVec::new());
+ self.recover_from_await_method_call();
+ Ok(await_expr)
+ }
+
+ crate fn mk_expr(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
+ P(Expr { kind, span, attrs, id: DUMMY_NODE_ID, tokens: None })
+ }
+
+ pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> {
+ self.mk_expr(span, ExprKind::Err, AttrVec::new())
+ }
+
+ /// Create expression span ensuring the span of the parent node
+ /// is larger than the span of lhs and rhs, including the attributes.
+ fn mk_expr_sp(&self, lhs: &P<Expr>, lhs_span: Span, rhs_span: Span) -> Span {
+ lhs.attrs
+ .iter()
+ .find(|a| a.style == AttrStyle::Outer)
+ .map_or(lhs_span, |a| a.span)
+ .to(rhs_span)
+ }
+}
projects / rustc.git / blobdiff