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use super::{
Parser, PResult, Restrictions, PrevTokenKind, TokenType, PathStyle, BlockMode, SemiColonMode,
SeqSep, TokenExpectType,
};
use super::pat::{GateOr, PARAM_EXPECTED};
use crate::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,
};
use crate::maybe_recover_from_interpolated_ty_qpath;
use crate::parse::classify;
use crate::parse::token::{self, Token};
use crate::parse::diagnostics::Error;
use crate::print::pprust;
use crate::ptr::P;
use crate::source_map::{self, Span};
use crate::symbol::{kw, sym};
use crate::util::parser::{AssocOp, Fixity, prec_let_scrutinee_needs_par};
use errors::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.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
}
}
/// 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 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: 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_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.yields.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.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)?;
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.async_closure.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))
}
/// 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,
c_variadic: false
}))
}
/// 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,
node: 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.node {
// Remove the last feature gating of a `let` expression since it's stable.
let last = self.sess.gated_spans.let_chains.borrow_mut().pop();
debug_assert_eq!(cond.span, last.unwrap());
}
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.let_chains.borrow_mut().push(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));
}
crate 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 {
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, 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, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
P(Expr { node, span, attrs, id: DUMMY_NODE_ID })
}
}
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