| use super::{Parser, PResult, Restrictions, PrevTokenKind, TokenType, PathStyle}; |
| use super::{BlockMode, SemiColonMode}; |
| use super::{SeqSep, TokenExpectType}; |
| |
| use crate::maybe_recover_from_interpolated_ty_qpath; |
| use crate::ptr::P; |
| use crate::ast::{self, Attribute, AttrStyle, Ident, CaptureBy, BlockCheckMode}; |
| use crate::ast::{Expr, ExprKind, RangeLimits, Label, Movability, IsAsync, Arm}; |
| use crate::ast::{Ty, TyKind, FunctionRetTy, Arg, FnDecl}; |
| use crate::ast::{BinOpKind, BinOp, UnOp}; |
| use crate::ast::{Mac, AnonConst, Field}; |
| |
| use crate::parse::classify; |
| use crate::parse::token::{self, Token}; |
| use crate::parse::diagnostics::{Error}; |
| use crate::print::pprust; |
| use crate::source_map::{self, Span}; |
| use crate::symbol::{kw, sym}; |
| use crate::util::parser::{AssocOp, Fixity, prec_let_scrutinee_needs_par}; |
| |
| use std::mem; |
| use errors::Applicability; |
| use rustc_data_structures::thin_vec::ThinVec; |
| |
| /// 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), ThinVec::new() |
| )); |
| } |
| token::NtBlock(block) => { |
| let block = block.clone(); |
| $p.bump(); |
| return Ok($p.mk_expr( |
| $p.token.span, ExprKind::Block(block, None), ThinVec::new() |
| )); |
| } |
| // N.B: `NtIdent(ident)` is normalized to `Ident` in `fn bump`. |
| _ => {}, |
| }; |
| } |
| } |
| } |
| |
| #[derive(Debug)] |
| pub(super) enum LhsExpr { |
| NotYetParsed, |
| AttributesParsed(ThinVec<Attribute>), |
| AlreadyParsed(P<Expr>), |
| } |
| |
| impl From<Option<ThinVec<Attribute>>> for LhsExpr { |
| fn from(o: Option<ThinVec<Attribute>>) -> Self { |
| if let Some(attrs) = o { |
| LhsExpr::AttributesParsed(attrs) |
| } else { |
| LhsExpr::NotYetParsed |
| } |
| } |
| } |
| |
| impl From<P<Expr>> for LhsExpr { |
| 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) |
| } |
| |
| fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> { |
| self.parse_paren_comma_seq(|p| { |
| match p.parse_expr() { |
| Ok(expr) => Ok(expr), |
| Err(mut err) => match p.token.kind { |
| token::Ident(name, false) |
| if name == kw::Underscore && p.look_ahead(1, |t| { |
| t == &token::Comma |
| }) => { |
| // Special-case handling of `foo(_, _, _)` |
| err.emit(); |
| let sp = p.token.span; |
| p.bump(); |
| Ok(p.mk_expr(sp, ExprKind::Err, ThinVec::new())) |
| } |
| _ => Err(err), |
| }, |
| } |
| }).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<ThinVec<Attribute>> |
| ) -> 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<ThinVec<Attribute>>, |
| ) -> 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(); |
| |
| match (self.expr_is_complete(&lhs), AssocOp::from_token(&self.token)) { |
| (true, None) => { |
| self.last_type_ascription = None; |
| // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071 |
| return Ok(lhs); |
| } |
| (false, _) => {} // 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()) => { |
| self.last_type_ascription = None; |
| // 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); |
| return Ok(lhs); |
| } |
| (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => { |
| self.last_type_ascription = None; |
| return Ok(lhs); |
| } |
| (true, Some(_)) => { |
| // 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` |
| 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(); |
| } |
| } |
| self.expected_tokens.push(TokenType::Operator); |
| while let Some(op) = AssocOp::from_token(&self.token) { |
| |
| // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what |
| // it refers to. Interpolated identifiers are unwrapped early and never show up here |
| // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process |
| // it as "interpolated", it doesn't change the answer for non-interpolated idents. |
| let lhs_span = match (self.prev_token_kind, &lhs.node) { |
| (PrevTokenKind::Interpolated, _) => self.prev_span, |
| (PrevTokenKind::Ident, &ExprKind::Path(None, ref path)) |
| if path.segments.len() == 1 => self.prev_span, |
| _ => lhs.span, |
| }; |
| |
| let cur_op_span = self.token.span; |
| let restrictions = if op.is_assign_like() { |
| self.restrictions & Restrictions::NO_STRUCT_LITERAL |
| } else { |
| self.restrictions |
| }; |
| let prec = op.precedence(); |
| if prec < min_prec { |
| break; |
| } |
| // Check for deprecated `...` syntax |
| if self.token == token::DotDotDot && op == 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.is_comparison() { |
| self.check_no_chained_comparison(&lhs, &op); |
| } |
| // Special cases: |
| if op == AssocOp::As { |
| lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?; |
| continue |
| } else if op == AssocOp::Colon { |
| let maybe_path = self.could_ascription_be_path(&lhs.node); |
| self.last_type_ascription = Some((self.prev_span, maybe_path)); |
| |
| lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?; |
| 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. |
| // |
| // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other |
| // two variants are handled with `parse_prefix_range_expr` call above. |
| let rhs = if self.is_at_start_of_range_notation_rhs() { |
| Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?) |
| } else { |
| None |
| }; |
| let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs { |
| x.span |
| } else { |
| cur_op_span |
| }); |
| let limits = if op == AssocOp::DotDot { |
| RangeLimits::HalfOpen |
| } else { |
| RangeLimits::Closed |
| }; |
| |
| let r = self.mk_range(Some(lhs), rhs, limits)?; |
| lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new()); |
| 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() |
| .filter(|a| a.style == AttrStyle::Outer) |
| .next() |
| .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, ThinVec::new()) |
| } |
| AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::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, ThinVec::new()) |
| } |
| AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => { |
| self.bug("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) |
| } |
| |
| /// 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) |
| } |
| |
| 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 |
| } |
| } |
| |
| /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr` |
| fn parse_prefix_range_expr( |
| &mut self, |
| already_parsed_attrs: Option<ThinVec<Attribute>> |
| ) -> 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 tok = self.token.clone(); |
| let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?; |
| let lo = self.token.span; |
| let mut hi = self.token.span; |
| self.bump(); |
| let opt_end = if self.is_at_start_of_range_notation_rhs() { |
| // RHS must be parsed with more associativity than the dots. |
| let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1; |
| Some(self.parse_assoc_expr_with(next_prec, LhsExpr::NotYetParsed) |
| .map(|x| { |
| hi = x.span; |
| x |
| })?) |
| } else { |
| None |
| }; |
| let limits = if tok == token::DotDot { |
| RangeLimits::HalfOpen |
| } else { |
| RangeLimits::Closed |
| }; |
| |
| let r = self.mk_range(None, opt_end, limits)?; |
| Ok(self.mk_expr(lo.to(hi), r, attrs)) |
| } |
| |
| /// Parse a prefix-unary-operator expr |
| fn parse_prefix_expr( |
| &mut self, |
| already_parsed_attrs: Option<ThinVec<Attribute>> |
| ) -> PResult<'a, P<Expr>> { |
| let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?; |
| let lo = self.token.span; |
| // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr() |
| let (hi, ex) = match self.token.kind { |
| token::Not => { |
| self.bump(); |
| let e = self.parse_prefix_expr(None); |
| let (span, e) = self.interpolated_or_expr_span(e)?; |
| (lo.to(span), self.mk_unary(UnOp::Not, e)) |
| } |
| // Suggest `!` for bitwise negation when encountering a `~` |
| token::Tilde => { |
| self.bump(); |
| let e = self.parse_prefix_expr(None); |
| let (span, e) = self.interpolated_or_expr_span(e)?; |
| let span_of_tilde = lo; |
| self.struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator") |
| .span_suggestion_short( |
| span_of_tilde, |
| "use `!` to perform bitwise negation", |
| "!".to_owned(), |
| Applicability::MachineApplicable |
| ) |
| .emit(); |
| (lo.to(span), self.mk_unary(UnOp::Not, e)) |
| } |
| token::BinOp(token::Minus) => { |
| self.bump(); |
| let e = self.parse_prefix_expr(None); |
| let (span, e) = self.interpolated_or_expr_span(e)?; |
| (lo.to(span), self.mk_unary(UnOp::Neg, e)) |
| } |
| token::BinOp(token::Star) => { |
| self.bump(); |
| let e = self.parse_prefix_expr(None); |
| let (span, e) = self.interpolated_or_expr_span(e)?; |
| (lo.to(span), self.mk_unary(UnOp::Deref, e)) |
| } |
| token::BinOp(token::And) | token::AndAnd => { |
| self.expect_and()?; |
| let m = self.parse_mutability(); |
| let e = self.parse_prefix_expr(None); |
| let (span, e) = self.interpolated_or_expr_span(e)?; |
| (lo.to(span), ExprKind::AddrOf(m, e)) |
| } |
| token::Ident(..) if self.token.is_keyword(kw::Box) => { |
| self.bump(); |
| let e = self.parse_prefix_expr(None); |
| let (span, e) = self.interpolated_or_expr_span(e)?; |
| (lo.to(span), ExprKind::Box(e)) |
| } |
| token::Ident(..) if self.token.is_ident_named(sym::not) => { |
| // `not` is just an ordinary identifier in Rust-the-language, |
| // but as `rustc`-the-compiler, we can issue clever diagnostics |
| // for confused users who really want to say `!` |
| let token_cannot_continue_expr = |t: &Token| match t.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(), |
| }; |
| let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr); |
| if cannot_continue_expr { |
| self.bump(); |
| // Emit the error ... |
| self.struct_span_err( |
| self.token.span, |
| &format!("unexpected {} after identifier",self.this_token_descr()) |
| ) |
| .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(self.token.span)), |
| "use `!` to perform logical negation", |
| "!".to_owned(), |
| Applicability::MachineApplicable |
| ) |
| .emit(); |
| // —and recover! (just as if we were in the block |
| // for the `token::Not` arm) |
| let e = self.parse_prefix_expr(None); |
| let (span, e) = self.interpolated_or_expr_span(e)?; |
| (lo.to(span), self.mk_unary(UnOp::Not, e)) |
| } else { |
| return self.parse_dot_or_call_expr(Some(attrs)); |
| } |
| } |
| _ => { return self.parse_dot_or_call_expr(Some(attrs)); } |
| }; |
| return Ok(self.mk_expr(lo.to(hi), ex, attrs)); |
| } |
| |
| /// 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| { |
| if self.prev_token_kind == PrevTokenKind::Interpolated { |
| (self.prev_span, e) |
| } else { |
| (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), ThinVec::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(); |
| match self.parse_ty_no_plus() { |
| Ok(rhs) => { |
| Ok(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 = self.clone(); |
| 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. |
| mem::replace(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 {}", path, op_noun); |
| let span_after_type = parser_snapshot_after_type.token.span; |
| let expr = mk_expr(self, P(Ty { |
| span: path.span, |
| node: TyKind::Path(None, path), |
| id: ast::DUMMY_NODE_ID |
| })); |
| |
| 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(); |
| |
| Ok(expr) |
| } |
| Err(mut path_err) => { |
| // Couldn't parse as a path, return original error and parser state. |
| path_err.cancel(); |
| mem::replace(self, parser_snapshot_after_type); |
| Err(type_err) |
| } |
| } |
| } |
| } |
| } |
| |
| /// Parses `a.b` or `a(13)` or `a[4]` or just `a`. |
| fn parse_dot_or_call_expr( |
| &mut self, |
| already_parsed_attrs: Option<ThinVec<Attribute>>, |
| ) -> PResult<'a, P<Expr>> { |
| let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?; |
| |
| let b = self.parse_bottom_expr(); |
| let (span, b) = self.interpolated_or_expr_span(b)?; |
| self.parse_dot_or_call_expr_with(b, span, attrs) |
| } |
| |
| pub(super) fn parse_dot_or_call_expr_with( |
| &mut self, |
| e0: P<Expr>, |
| lo: Span, |
| mut attrs: ThinVec<Attribute>, |
| ) -> 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; |
| match expr.node { |
| ExprKind::If(..) if !expr.attrs.is_empty() => { |
| // Just point to the first attribute in there... |
| let span = expr.attrs[0].span; |
| self.span_err(span, "attributes are not yet allowed on `if` expressions"); |
| } |
| _ => {} |
| } |
| expr |
| }) |
| ) |
| } |
| |
| fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> { |
| let mut e = e0; |
| let mut hi; |
| loop { |
| // expr? |
| while self.eat(&token::Question) { |
| let hi = self.prev_span; |
| e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new()); |
| } |
| |
| // expr.f |
| if self.eat(&token::Dot) { |
| match self.token.kind { |
| token::Ident(..) => { |
| e = self.parse_dot_suffix(e, lo)?; |
| } |
| token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => { |
| let span = self.token.span; |
| self.bump(); |
| let field = ExprKind::Field(e, Ident::new(symbol, span)); |
| e = self.mk_expr(lo.to(span), field, ThinVec::new()); |
| |
| self.expect_no_suffix(span, "a tuple index", suffix); |
| } |
| token::Literal(token::Lit { kind: token::Float, symbol, .. }) => { |
| self.bump(); |
| let fstr = symbol.as_str(); |
| let msg = format!("unexpected token: `{}`", symbol); |
| let mut err = self.diagnostic().struct_span_err(self.prev_span, &msg); |
| err.span_label(self.prev_span, "unexpected token"); |
| if fstr.chars().all(|x| "0123456789.".contains(x)) { |
| let float = match fstr.parse::<f64>().ok() { |
| Some(f) => f, |
| None => continue, |
| }; |
| let sugg = pprust::to_string(|s| { |
| s.popen(); |
| s.print_expr(&e); |
| 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_span), |
| "try parenthesizing the first index", |
| sugg, |
| Applicability::MachineApplicable |
| ); |
| } |
| return Err(err); |
| |
| } |
| _ => { |
| // FIXME Could factor this out into non_fatal_unexpected or something. |
| let actual = self.this_token_to_string(); |
| self.span_err(self.token.span, &format!("unexpected token: `{}`", actual)); |
| } |
| } |
| continue; |
| } |
| if self.expr_is_complete(&e) { break; } |
| match self.token.kind { |
| // expr(...) |
| token::OpenDelim(token::Paren) => { |
| let seq = self.parse_paren_expr_seq().map(|es| { |
| let nd = self.mk_call(e, es); |
| let hi = self.prev_span; |
| self.mk_expr(lo.to(hi), nd, ThinVec::new()) |
| }); |
| e = self.recover_seq_parse_error(token::Paren, lo, seq); |
| } |
| |
| // expr[...] |
| // Could be either an index expression or a slicing expression. |
| token::OpenDelim(token::Bracket) => { |
| self.bump(); |
| let ix = self.parse_expr()?; |
| hi = self.token.span; |
| self.expect(&token::CloseDelim(token::Bracket))?; |
| let index = self.mk_index(e, ix); |
| e = self.mk_expr(lo.to(hi), index, ThinVec::new()) |
| } |
| _ => return Ok(e) |
| } |
| } |
| return Ok(e); |
| } |
| |
| /// 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.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)); |
| |
| Ok(match self.token.kind { |
| 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_span); |
| self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new()) |
| } |
| _ => { |
| // Field access `expr.f` |
| if let Some(args) = segment.args { |
| self.span_err(args.span(), |
| "field expressions may not have generic arguments"); |
| } |
| |
| let span = lo.to(self.prev_span); |
| self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::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 mut attrs = ThinVec::new(); |
| |
| let lo = self.token.span; |
| let mut hi = self.token.span; |
| |
| let ex: ExprKind; |
| |
| macro_rules! parse_lit { |
| () => { |
| match self.parse_lit() { |
| Ok(literal) => { |
| hi = self.prev_span; |
| ex = ExprKind::Lit(literal); |
| } |
| Err(mut err) => { |
| self.cancel(&mut err); |
| return Err(self.expected_expression_found()); |
| } |
| } |
| } |
| } |
| |
| // Note: when adding new syntax here, don't forget to adjust TokenKind::can_begin_expr(). |
| match 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. |
| token::Literal(_) => { |
| parse_lit!() |
| } |
| token::OpenDelim(token::Paren) => { |
| self.bump(); |
| |
| attrs.extend(self.parse_inner_attributes()?); |
| |
| // (e) is parenthesized e |
| // (e,) is a tuple with only one field, e |
| let mut es = vec![]; |
| let mut trailing_comma = false; |
| let mut recovered = false; |
| while self.token != token::CloseDelim(token::Paren) { |
| es.push(match self.parse_expr() { |
| Ok(es) => es, |
| Err(mut err) => { |
| // recover from parse error in tuple list |
| match self.token.kind { |
| token::Ident(name, false) |
| if name == kw::Underscore && self.look_ahead(1, |t| { |
| t == &token::Comma |
| }) => { |
| // Special-case handling of `Foo<(_, _, _)>` |
| err.emit(); |
| let sp = self.token.span; |
| self.bump(); |
| self.mk_expr(sp, ExprKind::Err, ThinVec::new()) |
| } |
| _ => return Ok( |
| self.recover_seq_parse_error(token::Paren, lo, Err(err)), |
| ), |
| } |
| } |
| }); |
| recovered = self.expect_one_of( |
| &[], |
| &[token::Comma, token::CloseDelim(token::Paren)], |
| )?; |
| if self.eat(&token::Comma) { |
| trailing_comma = true; |
| } else { |
| trailing_comma = false; |
| break; |
| } |
| } |
| if !recovered { |
| self.bump(); |
| } |
| |
| hi = self.prev_span; |
| ex = if es.len() == 1 && !trailing_comma { |
| ExprKind::Paren(es.into_iter().nth(0).unwrap()) |
| } else { |
| ExprKind::Tup(es) |
| }; |
| } |
| token::OpenDelim(token::Brace) => { |
| return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs); |
| } |
| token::BinOp(token::Or) | token::OrOr => { |
| return self.parse_lambda_expr(attrs); |
| } |
| token::OpenDelim(token::Bracket) => { |
| self.bump(); |
| |
| attrs.extend(self.parse_inner_attributes()?); |
| |
| if self.eat(&token::CloseDelim(token::Bracket)) { |
| // Empty vector. |
| ex = ExprKind::Array(Vec::new()); |
| } else { |
| // Nonempty vector. |
| let first_expr = self.parse_expr()?; |
| if self.eat(&token::Semi) { |
| // Repeating array syntax: [ 0; 512 ] |
| let count = AnonConst { |
| id: ast::DUMMY_NODE_ID, |
| value: self.parse_expr()?, |
| }; |
| self.expect(&token::CloseDelim(token::Bracket))?; |
| ex = ExprKind::Repeat(first_expr, count); |
| } else if self.eat(&token::Comma) { |
| // Vector with two or more elements. |
| let remaining_exprs = self.parse_seq_to_end( |
| &token::CloseDelim(token::Bracket), |
| SeqSep::trailing_allowed(token::Comma), |
| |p| Ok(p.parse_expr()?) |
| )?; |
| let mut exprs = vec![first_expr]; |
| exprs.extend(remaining_exprs); |
| ex = ExprKind::Array(exprs); |
| } else { |
| // Vector with one element. |
| self.expect(&token::CloseDelim(token::Bracket))?; |
| ex = ExprKind::Array(vec![first_expr]); |
| } |
| } |
| hi = self.prev_span; |
| } |
| _ => { |
| if self.eat_lt() { |
| let (qself, path) = self.parse_qpath(PathStyle::Expr)?; |
| hi = path.span; |
| return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs)); |
| } |
| if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) { |
| return self.parse_lambda_expr(attrs); |
| } |
| if self.eat_keyword(kw::If) { |
| return self.parse_if_expr(attrs); |
| } |
| if self.eat_keyword(kw::For) { |
| let lo = self.prev_span; |
| return self.parse_for_expr(None, lo, attrs); |
| } |
| if self.eat_keyword(kw::While) { |
| let lo = self.prev_span; |
| return self.parse_while_expr(None, lo, attrs); |
| } |
| if let Some(label) = self.eat_label() { |
| let lo = label.ident.span; |
| self.expect(&token::Colon)?; |
| if self.eat_keyword(kw::While) { |
| return self.parse_while_expr(Some(label), lo, attrs) |
| } |
| if self.eat_keyword(kw::For) { |
| return self.parse_for_expr(Some(label), lo, attrs) |
| } |
| if self.eat_keyword(kw::Loop) { |
| return self.parse_loop_expr(Some(label), lo, attrs) |
| } |
| if self.token == token::OpenDelim(token::Brace) { |
| return self.parse_block_expr(Some(label), |
| lo, |
| BlockCheckMode::Default, |
| attrs); |
| } |
| let msg = "expected `while`, `for`, `loop` or `{` after a label"; |
| let mut err = self.fatal(msg); |
| err.span_label(self.token.span, msg); |
| return Err(err); |
| } |
| if self.eat_keyword(kw::Loop) { |
| let lo = self.prev_span; |
| return self.parse_loop_expr(None, lo, attrs); |
| } |
| if self.eat_keyword(kw::Continue) { |
| let label = self.eat_label(); |
| let ex = ExprKind::Continue(label); |
| let hi = self.prev_span; |
| return Ok(self.mk_expr(lo.to(hi), ex, attrs)); |
| } |
| if self.eat_keyword(kw::Match) { |
| let match_sp = self.prev_span; |
| return self.parse_match_expr(attrs).map_err(|mut err| { |
| err.span_label(match_sp, "while parsing this match expression"); |
| err |
| }); |
| } |
| if self.eat_keyword(kw::Unsafe) { |
| return self.parse_block_expr( |
| None, |
| lo, |
| BlockCheckMode::Unsafe(ast::UserProvided), |
| attrs); |
| } |
| if self.is_do_catch_block() { |
| let mut db = self.fatal("found removed `do catch` syntax"); |
| db.help("Following RFC #2388, the new non-placeholder syntax is `try`"); |
| return Err(db); |
| } |
| if self.is_try_block() { |
| let lo = self.token.span; |
| assert!(self.eat_keyword(kw::Try)); |
| return self.parse_try_block(lo, attrs); |
| } |
| |
| // Span::rust_2018() is somewhat expensive; don't get it repeatedly. |
| let is_span_rust_2018 = self.token.span.rust_2018(); |
| if is_span_rust_2018 && self.check_keyword(kw::Async) { |
| return if self.is_async_block() { // check for `async {` and `async move {` |
| self.parse_async_block(attrs) |
| } else { |
| self.parse_lambda_expr(attrs) |
| }; |
| } |
| if self.eat_keyword(kw::Return) { |
| if self.token.can_begin_expr() { |
| let e = self.parse_expr()?; |
| hi = e.span; |
| ex = ExprKind::Ret(Some(e)); |
| } else { |
| ex = ExprKind::Ret(None); |
| } |
| } else if self.eat_keyword(kw::Break) { |
| let label = self.eat_label(); |
| let e = if self.token.can_begin_expr() |
| && !(self.token == token::OpenDelim(token::Brace) |
| && self.restrictions.contains( |
| Restrictions::NO_STRUCT_LITERAL)) { |
| Some(self.parse_expr()?) |
| } else { |
| None |
| }; |
| ex = ExprKind::Break(label, e); |
| hi = self.prev_span; |
| } else if self.eat_keyword(kw::Yield) { |
| if self.token.can_begin_expr() { |
| let e = self.parse_expr()?; |
| hi = e.span; |
| ex = ExprKind::Yield(Some(e)); |
| } else { |
| ex = ExprKind::Yield(None); |
| } |
| |
| let span = lo.to(hi); |
| self.sess.yield_spans.borrow_mut().push(span); |
| } else if self.eat_keyword(kw::Let) { |
| return self.parse_let_expr(attrs); |
| } else if is_span_rust_2018 && self.eat_keyword(kw::Await) { |
| let (await_hi, e_kind) = self.parse_incorrect_await_syntax(lo, self.prev_span)?; |
| hi = await_hi; |
| ex = e_kind; |
| } else if self.token.is_path_start() { |
| let path = self.parse_path(PathStyle::Expr)?; |
| |
| // `!`, as an operator, is prefix, so we know this isn't that |
| if self.eat(&token::Not) { |
| // MACRO INVOCATION expression |
| let (delim, tts) = self.expect_delimited_token_tree()?; |
| hi = self.prev_span; |
| ex = ExprKind::Mac(Mac { |
| path, |
| tts, |
| delim, |
| span: lo.to(hi), |
| prior_type_ascription: self.last_type_ascription, |
| }); |
| } else if self.check(&token::OpenDelim(token::Brace)) { |
| if let Some(expr) = self.maybe_parse_struct_expr(lo, &path, &attrs) { |
| return expr; |
| } else { |
| hi = path.span; |
| ex = ExprKind::Path(None, path); |
| } |
| } else { |
| hi = path.span; |
| ex = ExprKind::Path(None, path); |
| } |
| } 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(); |
| return Ok(self.mk_expr(self.token.span, ExprKind::Err, ThinVec::new())); |
| } |
| parse_lit!() |
| } |
| } |
| } |
| |
| let expr = self.mk_expr(lo.to(hi), ex, attrs); |
| self.maybe_recover_from_bad_qpath(expr, true) |
| } |
| |
| /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`). |
| crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> { |
| maybe_whole_expr!(self); |
| |
| let minus_lo = self.token.span; |
| let minus_present = self.eat(&token::BinOp(token::Minus)); |
| let lo = self.token.span; |
| let literal = self.parse_lit()?; |
| let hi = self.prev_span; |
| let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new()); |
| |
| if minus_present { |
| let minus_hi = self.prev_span; |
| let unary = self.mk_unary(UnOp::Neg, expr); |
| Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new())) |
| } else { |
| Ok(expr) |
| } |
| } |
| |
| /// Parses a block or unsafe block. |
| crate fn parse_block_expr( |
| &mut self, |
| opt_label: Option<Label>, |
| lo: Span, |
| blk_mode: BlockCheckMode, |
| outer_attrs: ThinVec<Attribute>, |
| ) -> PResult<'a, P<Expr>> { |
| self.expect(&token::OpenDelim(token::Brace))?; |
| |
| let mut attrs = outer_attrs; |
| attrs.extend(self.parse_inner_attributes()?); |
| |
| let blk = self.parse_block_tail(lo, blk_mode)?; |
| return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs)); |
| } |
| |
| /// Parses `move |args| expr`. |
| fn parse_lambda_expr(&mut self, attrs: ThinVec<Attribute>) -> 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.span.rust_2018() { |
| self.parse_asyncness() |
| } else { |
| IsAsync::NotAsync |
| }; |
| if asyncness.is_async() { |
| // Feature gate `async ||` closures. |
| self.sess.async_closure_spans.borrow_mut().push(self.prev_span); |
| } |
| |
| let capture_clause = self.parse_capture_clause(); |
| let decl = self.parse_fn_block_decl()?; |
| let decl_hi = self.prev_span; |
| let body = match decl.output { |
| FunctionRetTy::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, ThinVec::new())? |
| } |
| }; |
| |
| Ok(self.mk_expr( |
| lo.to(body.span), |
| ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)), |
| attrs)) |
| } |
| |
| /// Parse an optional `move` prefix to a closure lke 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_captures = { |
| 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_arg() |
| )?.0; |
| self.expect_or()?; |
| args |
| } |
| }; |
| let output = self.parse_ret_ty(true)?; |
| |
| Ok(P(FnDecl { |
| inputs: inputs_captures, |
| output, |
| c_variadic: false |
| })) |
| } |
| |
| /// Parses an argument in a lambda header (e.g., `|arg, arg|`). |
| fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> { |
| let lo = self.token.span; |
| let attrs = self.parse_arg_attributes()?; |
| let pat = self.parse_pat(Some("argument name"))?; |
| let t = if self.eat(&token::Colon) { |
| self.parse_ty()? |
| } else { |
| P(Ty { |
| id: ast::DUMMY_NODE_ID, |
| node: TyKind::Infer, |
| span: self.prev_span, |
| }) |
| }; |
| let span = lo.to(self.token.span); |
| Ok(Arg { |
| attrs: attrs.into(), |
| ty: t, |
| pat, |
| span, |
| id: ast::DUMMY_NODE_ID |
| }) |
| } |
| |
| /// Parses an `if` expression (`if` token already eaten). |
| fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { |
| let lo = self.prev_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. |
| if self.eat_keyword(kw::Else) || !cond.returns() { |
| let sp = self.sess.source_map().next_point(lo); |
| let mut err = self.diagnostic() |
| .struct_span_err(sp, "missing condition for `if` expression"); |
| err.span_label(sp, "expected if condition here"); |
| return Err(err) |
| } |
| let not_block = self.token != token::OpenDelim(token::Brace); |
| let thn = self.parse_block().map_err(|mut err| { |
| if not_block { |
| err.span_label(lo, "this `if` statement has a condition, but no block"); |
| } |
| err |
| })?; |
| let mut els: Option<P<Expr>> = None; |
| let mut hi = thn.span; |
| if self.eat_keyword(kw::Else) { |
| let elexpr = self.parse_else_expr()?; |
| hi = elexpr.span; |
| els = Some(elexpr); |
| } |
| Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs)) |
| } |
| |
| /// Parse 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.node { |
| // Remove the last feature gating of a `let` expression since it's stable. |
| let last = self.sess.let_chains_spans.borrow_mut().pop(); |
| debug_assert_eq!(cond.span, last.unwrap()); |
| } |
| |
| Ok(cond) |
| } |
| |
| /// Parses a `let $pats = $expr` pseudo-expression. |
| /// The `let` token has already been eaten. |
| fn parse_let_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { |
| let lo = self.prev_span; |
| let pats = self.parse_pats()?; |
| 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.let_chains_spans.borrow_mut().push(span); |
| Ok(self.mk_expr(span, ExprKind::Let(pats, expr), attrs)) |
| } |
| |
| /// `else` token already eaten |
| fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> { |
| if self.eat_keyword(kw::If) { |
| return self.parse_if_expr(ThinVec::new()); |
| } else { |
| let blk = self.parse_block()?; |
| return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new())); |
| } |
| } |
| |
| /// Parse a 'for' .. 'in' expression ('for' token already eaten) |
| fn parse_for_expr( |
| &mut self, |
| opt_label: Option<Label>, |
| span_lo: Span, |
| mut attrs: ThinVec<Attribute> |
| ) -> PResult<'a, P<Expr>> { |
| // Parse: `for <src_pat> in <src_expr> <src_loop_block>` |
| |
| // 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_level_pat()?; |
| if !self.eat_keyword(kw::In) { |
| let in_span = self.prev_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(); |
| } |
| let in_span = self.prev_span; |
| self.check_for_for_in_in_typo(in_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 hi = self.prev_span; |
| Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs)) |
| } |
| |
| /// Parses a `while` or `while let` expression (`while` token already eaten). |
| fn parse_while_expr( |
| &mut self, |
| opt_label: Option<Label>, |
| span_lo: Span, |
| mut attrs: ThinVec<Attribute> |
| ) -> PResult<'a, P<Expr>> { |
| let cond = self.parse_cond_expr()?; |
| let (iattrs, body) = self.parse_inner_attrs_and_block()?; |
| attrs.extend(iattrs); |
| let span = span_lo.to(body.span); |
| Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs)) |
| } |
| |
| /// Parse `loop {...}`, `loop` token already eaten. |
| fn parse_loop_expr( |
| &mut self, |
| opt_label: Option<Label>, |
| span_lo: Span, |
| mut attrs: ThinVec<Attribute> |
| ) -> PResult<'a, P<Expr>> { |
| let (iattrs, body) = self.parse_inner_attrs_and_block()?; |
| attrs.extend(iattrs); |
| let span = span_lo.to(body.span); |
| Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs)) |
| } |
| |
| fn eat_label(&mut self) -> Option<Label> { |
| if let Some(ident) = self.token.lifetime() { |
| let span = self.token.span; |
| self.bump(); |
| Some(Label { ident: Ident::new(ident.name, span) }) |
| } else { |
| None |
| } |
| } |
| |
| // `match` token already eaten |
| fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { |
| let match_span = self.prev_span; |
| let lo = self.prev_span; |
| let discriminant = 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(discriminant, arms), attrs)); |
| } |
| } |
| } |
| let hi = self.token.span; |
| self.bump(); |
| return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs)); |
| } |
| |
| crate fn parse_arm(&mut self) -> PResult<'a, Arm> { |
| let attrs = self.parse_outer_attributes()?; |
| let lo = self.token.span; |
| let pats = self.parse_pats()?; |
| 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 cm = self.sess.source_map(); |
| self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)]) |
| .map_err(|mut err| { |
| match (cm.span_to_lines(expr.span), cm.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( |
| cm.next_point(arm_start_span), |
| "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, |
| pats, |
| guard, |
| body: expr, |
| span: lo.to(hi), |
| id: ast::DUMMY_NODE_ID, |
| }) |
| } |
| |
| /// Parses a `try {...}` expression (`try` token already eaten). |
| fn parse_try_block( |
| &mut self, |
| span_lo: Span, |
| mut attrs: ThinVec<Attribute> |
| ) -> 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_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 { |
| Ok(self.mk_expr(span_lo.to(body.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.span.rust_2018() && |
| // prevent `while try {} {}`, `if try {} {} else {}`, etc. |
| !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL) |
| } |
| |
| /// Parses an `async move? {...}` expression. |
| pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { |
| let span_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); |
| Ok(self.mk_expr( |
| span_lo.to(body.span), |
| ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), 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 maybe_parse_struct_expr( |
| &mut self, |
| lo: Span, |
| path: &ast::Path, |
| attrs: &ThinVec<Attribute>, |
| ) -> Option<PResult<'a, P<Expr>>> { |
| let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL); |
| let certainly_not_a_block = || 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()) |
| ) |
| ); |
| |
| if struct_allowed || certainly_not_a_block() { |
| // This is a struct literal, but we don't can't accept them here |
| let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone()); |
| if let (Ok(expr), false) = (&expr, struct_allowed) { |
| self.struct_span_err( |
| expr.span, |
| "struct literals are not allowed here", |
| ) |
| .multipart_suggestion( |
| "surround the struct literal with parentheses", |
| vec![ |
| (lo.shrink_to_lo(), "(".to_string()), |
| (expr.span.shrink_to_hi(), ")".to_string()), |
| ], |
| Applicability::MachineApplicable, |
| ) |
| .emit(); |
| } |
| return Some(expr); |
| } |
| None |
| } |
| |
| pub(super) fn parse_struct_expr( |
| &mut self, |
| lo: Span, |
| pth: ast::Path, |
| mut attrs: ThinVec<Attribute> |
| ) -> PResult<'a, P<Expr>> { |
| let struct_sp = lo.to(self.prev_span); |
| self.bump(); |
| let mut fields = Vec::new(); |
| let mut base = None; |
| |
| attrs.extend(self.parse_inner_attributes()?); |
| |
| while self.token != token::CloseDelim(token::Brace) { |
| if self.eat(&token::DotDot) { |
| let exp_span = self.prev_span; |
| match self.parse_expr() { |
| Ok(e) => { |
| base = Some(e); |
| } |
| Err(mut e) => { |
| e.emit(); |
| self.recover_stmt(); |
| } |
| } |
| if self.token == token::Comma { |
| self.struct_span_err( |
| exp_span.to(self.prev_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(); |
| } |
| break; |
| } |
| |
| let mut recovery_field = None; |
| if let token::Ident(name, _) = self.token.kind { |
| if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) { |
| // Use in case of error after field-looking code: `S { foo: () with a }` |
| recovery_field = Some(ast::Field { |
| ident: Ident::new(name, self.token.span), |
| span: self.token.span, |
| expr: self.mk_expr(self.token.span, ExprKind::Err, ThinVec::new()), |
| is_shorthand: false, |
| attrs: ThinVec::new(), |
| id: ast::DUMMY_NODE_ID, |
| }); |
| } |
| } |
| let mut parsed_field = None; |
| match self.parse_field() { |
| Ok(f) => parsed_field = Some(f), |
| Err(mut e) => { |
| e.span_label(struct_sp, "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; |
| } |
| } |
| } |
| } |
| |
| 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 let Some(f) = recovery_field { |
| fields.push(f); |
| } |
| e.span_label(struct_sp, "while parsing this struct"); |
| e.emit(); |
| self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore); |
| self.eat(&token::Comma); |
| } |
| } |
| } |
| |
| let span = lo.to(self.token.span); |
| self.expect(&token::CloseDelim(token::Brace))?; |
| return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs)); |
| } |
| |
| /// Parse ident (COLON expr)? |
| fn parse_field(&mut self) -> PResult<'a, Field> { |
| let attrs = self.parse_outer_attributes()?; |
| let lo = self.token.span; |
| |
| // Check if a colon exists one ahead. This means we're parsing a fieldname. |
| let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| { |
| t == &token::Colon || t == &token::Eq |
| }) { |
| let fieldname = self.parse_field_name()?; |
| |
| // Check for an equals token. This means the source incorrectly attempts to |
| // initialize a field with an eq rather than a colon. |
| if self.token == token::Eq { |
| self.diagnostic() |
| .struct_span_err(self.token.span, "expected `:`, found `=`") |
| .span_suggestion( |
| fieldname.span.shrink_to_hi().to(self.token.span), |
| "replace equals symbol with a colon", |
| ":".to_string(), |
| Applicability::MachineApplicable, |
| ) |
| .emit(); |
| } |
| self.bump(); // `:` |
| (fieldname, self.parse_expr()?, false) |
| } else { |
| let fieldname = self.parse_ident_common(false)?; |
| |
| // Mimic `x: x` for the `x` field shorthand. |
| let path = ast::Path::from_ident(fieldname); |
| let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new()); |
| (fieldname, expr, true) |
| }; |
| Ok(ast::Field { |
| ident: fieldname, |
| span: lo.to(expr.span), |
| expr, |
| is_shorthand, |
| attrs: attrs.into(), |
| id: ast::DUMMY_NODE_ID, |
| }) |
| } |
| |
| 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 { |
| Err(self.span_fatal_err(self.token.span, Error::InclusiveRangeWithNoEnd)) |
| } 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_span); |
| let await_expr = self.mk_expr(span, ExprKind::Await(self_arg), ThinVec::new()); |
| self.recover_from_await_method_call(); |
| Ok(await_expr) |
| } |
| |
| crate fn mk_expr(&self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> { |
| P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID }) |
| } |
| } |
