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Diffstat (limited to 'src/librustc_parse/parser/expr.rs')
| -rw-r--r-- | src/librustc_parse/parser/expr.rs | 1963 |
1 files changed, 1963 insertions, 0 deletions
diff --git a/src/librustc_parse/parser/expr.rs b/src/librustc_parse/parser/expr.rs new file mode 100644 index 00000000000..dadb91f8b3c --- /dev/null +++ b/src/librustc_parse/parser/expr.rs @@ -0,0 +1,1963 @@ +use super::{Parser, Restrictions, PrevTokenKind, TokenType, PathStyle, BlockMode}; +use super::{SemiColonMode, SeqSep, TokenExpectType}; +use super::pat::{GateOr, PARAM_EXPECTED}; +use super::diagnostics::Error; +use crate::maybe_recover_from_interpolated_ty_qpath; + +use syntax::ast::{ + self, DUMMY_NODE_ID, Attribute, AttrStyle, Ident, CaptureBy, BlockCheckMode, + Expr, ExprKind, RangeLimits, Label, Movability, IsAsync, Arm, Ty, TyKind, + FunctionRetTy, Param, FnDecl, BinOpKind, BinOp, UnOp, Mac, AnonConst, Field, Lit, +}; +use syntax::token::{self, Token, TokenKind}; +use syntax::print::pprust; +use syntax::ptr::P; +use syntax::source_map::{self, Span}; +use syntax::util::classify; +use syntax::util::literal::LitError; +use syntax::util::parser::{AssocOp, Fixity, prec_let_scrutinee_needs_par}; +use syntax_pos::symbol::{kw, sym}; +use syntax_pos::Symbol; +use errors::{PResult, Applicability}; +use std::mem; +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 { + /// Converts `Some(attrs)` into `LhsExpr::AttributesParsed(attrs)` + /// and `None` into `LhsExpr::NotYetParsed`. + /// + /// This conversion does not allocate. + fn from(o: Option<ThinVec<Attribute>>) -> 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) + } + + 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.kind) { + (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() { + if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? { + return Ok(expr); + } + } + // 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.kind); + self.last_type_ascription = Some((self.prev_span, maybe_path)); + + lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?; + self.sess.gated_spans.gate(sym::type_ascription, 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. + // + // 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 + } + } + + /// Parses 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)) + } + + /// Parses 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 not", + "!".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)?; + let span = lo.to(span); + self.sess.gated_spans.gate(sym::box_syntax, span); + (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 {}", + pprust::path_to_string(&path), + op_noun, + ); + let span_after_type = parser_snapshot_after_type.token.span; + let expr = mk_expr(self, P(Ty { + span: path.span, + kind: TyKind::Path(None, path), + id: 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.kind { + 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) => { + err.cancel(); + 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_closure_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 { + // Non-empty vector + let first_expr = self.parse_expr()?; + if self.eat(&token::Semi) { + // Repeating array syntax: `[ 0; 512 ]` + let count = AnonConst { + id: 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.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); + } + + let expr = self.mk_expr(lo.to(hi), ex, attrs); + return self.maybe_recover_from_bad_qpath(expr, true); + } + if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) { + return self.parse_closure_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_closure_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.gated_spans.gate(sym::generators, 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.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 = true | false | token_lit`. + pub(super) fn parse_lit(&mut self) -> PResult<'a, Lit> { + let mut recovered = None; + if self.token == token::Dot { + // Attempt to recover `.4` as `0.4`. + 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.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(); + } + } + + let token = recovered.as_ref().unwrap_or(&self.token); + match Lit::from_token(token) { + Ok(lit) => { + self.bump(); + Ok(lit) + } + Err(LitError::NotLiteral) => { + let msg = format!("unexpected token: {}", self.this_token_descr()); + Err(self.span_fatal(token.span, &msg)) + } + Err(err) => { + let span = token.span; + let lit = match token.kind { + token::Literal(lit) => lit, + _ => unreachable!(), + }; + self.bump(); + self.error_literal_from_token(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); + Lit::from_lit_token(lit, span).map_err(|_| unreachable!()) + } + } + } + + fn error_literal_from_token(&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( + "for more context, see https://github.com/rust-lang/rust/issues/60210", + ); + 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`). + pub 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. + pub(super) fn parse_block_expr( + &mut self, + opt_label: Option<Label>, + lo: Span, + blk_mode: BlockCheckMode, + outer_attrs: ThinVec<Attribute>, + ) -> PResult<'a, P<Expr>> { + if let Some(label) = opt_label { + self.sess.gated_spans.gate(sym::label_break_value, label.ident.span); + } + + 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)?; + Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs)) + } + + /// Parses a closure expression (e.g., `move |args| expr`). + fn parse_closure_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.gated_spans.gate(sym::async_closure, 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)) + } + + /// Parses 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_param() + )?.0; + self.expect_or()?; + args + } + }; + let output = self.parse_ret_ty(true)?; + + Ok(P(FnDecl { + inputs: inputs_captures, + 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 t = if self.eat(&token::Colon) { + self.parse_ty()? + } else { + P(Ty { + id: DUMMY_NODE_ID, + kind: TyKind::Infer, + span: self.prev_span, + }) + }; + let span = lo.to(self.token.span); + Ok(Param { + attrs: attrs.into(), + ty: t, + pat, + span, + id: DUMMY_NODE_ID, + is_placeholder: false, + }) + } + + /// 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)) + } + + /// 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: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { + let lo = self.prev_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>> { + 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())); + } + } + + /// Parses 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_pat(GateOr::Yes)?; + 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)) + } + + /// Parses `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 + } + } + + /// Parses a `match ... { ... }` expression (`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)); + } + + 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 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, + 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: 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 { + 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.span.rust_2018() && + // Prevent `while try {} {}`, `if try {} {} else {}`, etc. + !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL) + } + + /// Parses an `async move? {...}` expression. + 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, 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: DUMMY_NODE_ID, + is_placeholder: false, + }); + } + } + 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)); + } + + /// Parses `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: DUMMY_NODE_ID, + is_placeholder: false, + }) + } + + 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, kind: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> { + P(Expr { kind, span, attrs, id: DUMMY_NODE_ID }) + } + + pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> { + self.mk_expr(span, ExprKind::Err, ThinVec::new()) + } +} |