| use super::pat::{GateOr, PARAM_EXPECTED}; |
| use super::ty::{AllowPlus, RecoverQPath}; |
| use super::{BlockMode, Parser, PathStyle, Restrictions, TokenType}; |
| use super::{SemiColonMode, SeqSep, TokenExpectType}; |
| use crate::maybe_recover_from_interpolated_ty_qpath; |
| |
| use log::debug; |
| use rustc_ast::ast::{self, AttrStyle, AttrVec, CaptureBy, Field, Lit, UnOp, DUMMY_NODE_ID}; |
| use rustc_ast::ast::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, MacCall, Param, Ty, TyKind}; |
| use rustc_ast::ast::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits}; |
| use rustc_ast::ptr::P; |
| use rustc_ast::token::{self, Token, TokenKind}; |
| 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_pretty::pprust; |
| use rustc_errors::{Applicability, DiagnosticBuilder, PResult}; |
| use rustc_span::source_map::{self, Span, Spanned}; |
| use rustc_span::symbol::{kw, sym, Ident, Symbol}; |
| 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); |
| } |
| } |
| 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) |
| })?; |
| |
| // Make sure that the span of the parent node is larger than the span of lhs and rhs, |
| // including the attributes. |
| let lhs_span = |
| lhs.attrs.iter().find(|a| a.style == AttrStyle::Outer).map_or(lhs_span, |a| a.span); |
| let span = lhs_span.to(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), self.check_assoc_op().map(|op| op.node)) { |
| // 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::LAnd)) | // `{ 42 } &&x` (#61475) |
| (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_reserved_ident()) => { |
| // 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()) { |
| (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 = lhs.span.to(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)?; |
| self.maybe_collect_tokens(!attrs.is_empty(), |this| { |
| 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)) |
| }) |
| } |
| |
| 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, rhs: P<Ty>| { |
| this.mk_expr(lhs_span.to(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, 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); |
| |
| 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, 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)) |
| } |
| token::Literal(token::Lit { kind: token::Float, symbol, .. }) => { |
| self.recover_field_access_by_float_lit(lo, base, symbol) |
| } |
| _ => { |
| 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(); |
| } |
| |
| fn recover_field_access_by_float_lit( |
| &mut self, |
| lo: Span, |
| base: P<Expr>, |
| sym: Symbol, |
| ) -> PResult<'a, P<Expr>> { |
| self.bump(); |
| |
| let fstr = sym.as_str(); |
| let msg = format!("unexpected token: `{}`", sym); |
| |
| let mut err = self.struct_span_err(self.prev_token.span, &msg); |
| err.span_label(self.prev_token.span, "unexpected token"); |
| |
| if fstr.chars().all(|x| "0123456789.".contains(x)) { |
| let float = match fstr.parse::<f64>() { |
| Ok(f) => f, |
| Err(_) => { |
| err.emit(); |
| return Ok(base); |
| } |
| }; |
| let sugg = pprust::to_string(|s| { |
| s.popen(); |
| s.print_expr(&base); |
| s.s.word("."); |
| s.print_usize(float.trunc() as usize); |
| s.pclose(); |
| s.s.word("."); |
| s.s.word(fstr.splitn(2, '.').last().unwrap().to_string()) |
| }); |
| err.span_suggestion( |
| lo.to(self.prev_token.span), |
| "try parenthesizing the first index", |
| sugg, |
| Applicability::MachineApplicable, |
| ); |
| } |
| Err(err) |
| } |
| |
| fn parse_tuple_field_access_expr( |
| &mut self, |
| lo: Span, |
| base: P<Expr>, |
| field: Symbol, |
| suffix: Option<Symbol>, |
| ) -> P<Expr> { |
| 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 segment = self.parse_path_segment(PathStyle::Expr)?; |
| self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren)); |
| |
| 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 span = lo.to(self.prev_token.span); |
| Ok(self.mk_expr(span, ExprKind::MethodCall(segment, args), 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) |
| } 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.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.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 maybe_collect_tokens( |
| &mut self, |
| has_outer_attrs: bool, |
| f: impl FnOnce(&mut Self) -> PResult<'a, P<Expr>>, |
| ) -> PResult<'a, P<Expr>> { |
| if has_outer_attrs { |
| let (mut expr, tokens) = self.collect_tokens(f)?; |
| debug!("maybe_collect_tokens: Collected tokens for {:?} (tokens {:?}", expr, tokens); |
| expr.tokens = Some(tokens); |
| Ok(expr) |
| } else { |
| f(self) |
| } |
| } |
| |
| 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) -> 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 { |
| 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 integer literal", suf); |
| self.struct_span_err(span, &msg) |
| .span_label(span, format!("invalid suffix `{}`", suf)) |
| .help("the suffix must be one of the integral types (`u32`, `isize`, 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 |
| }; |
| if let Async::Yes { span, .. } = asyncness { |
| // Feature-gate `async ||` closures. |
| self.sess.gated_spans.gate(sym::async_closure, span); |
| } |
| |
| 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())? |
| } |
| }; |
| |
| 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) -> CaptureBy { |
| if self.eat_keyword(kw::Move) { CaptureBy::Value } else { 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)?; |
| |
| 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)?; |
| self.expect(&token::Eq)?; |
| let expr = self.with_res(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)?; |
| 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(&self) { |
| let in_span = self.prev_token.span.between(self.token.span); |
| self.struct_span_err(in_span, "missing `in` in `for` loop") |
| .span_suggestion_short( |
| in_span, |
| "try adding `in` here", |
| " in ".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)?; |
| let guard = if self.eat_keyword(kw::If) { Some(self.parse_expr()?) } 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.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() { |
| // This is a struct literal, but we don't can't accept them here. |
| let expr = self.parse_struct_expr(path.clone(), attrs.clone()); |
| if let (Ok(expr), false) = (&expr, struct_allowed) { |
| 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(); |
| } |
| |
| pub(super) fn parse_struct_expr( |
| &mut self, |
| pth: ast::Path, |
| mut attrs: AttrVec, |
| ) -> PResult<'a, P<Expr>> { |
| self.bump(); |
| let mut fields = Vec::new(); |
| let mut base = 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 the 2018 edition"); |
| e.help("set `edition = \"2018\"` in `Cargo.toml`"); |
| 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; |
| match self.parse_expr() { |
| Ok(e) => base = Some(e), |
| Err(mut e) => { |
| e.emit(); |
| self.recover_stmt(); |
| } |
| } |
| 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, |
| ); |
| } |
| } |
| 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()) |
| } |
| } |
