rustc_parse/parser/mod.rs
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pub mod attr;
mod attr_wrapper;
mod diagnostics;
mod expr;
mod generics;
mod item;
mod nonterminal;
mod pat;
mod path;
mod stmt;
mod ty;
use std::assert_matches::debug_assert_matches;
use std::ops::Range;
use std::{fmt, mem, slice};
use attr_wrapper::{AttrWrapper, UsePreAttrPos};
pub use diagnostics::AttemptLocalParseRecovery;
pub(crate) use expr::ForbiddenLetReason;
pub(crate) use item::FnParseMode;
pub use pat::{CommaRecoveryMode, RecoverColon, RecoverComma};
use path::PathStyle;
use rustc_ast::ptr::P;
use rustc_ast::token::{self, Delimiter, IdentIsRaw, Nonterminal, Token, TokenKind};
use rustc_ast::tokenstream::{
AttrsTarget, DelimSpacing, DelimSpan, Spacing, TokenStream, TokenTree, TokenTreeCursor,
};
use rustc_ast::util::case::Case;
use rustc_ast::{
self as ast, AnonConst, AttrArgs, AttrArgsEq, AttrId, ByRef, Const, CoroutineKind,
DUMMY_NODE_ID, DelimArgs, Expr, ExprKind, Extern, HasAttrs, HasTokens, Mutability, Recovered,
Safety, StrLit, Visibility, VisibilityKind,
};
use rustc_ast_pretty::pprust;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::sync::Lrc;
use rustc_errors::{Applicability, Diag, FatalError, MultiSpan, PResult};
use rustc_index::interval::IntervalSet;
use rustc_session::parse::ParseSess;
use rustc_span::symbol::{Ident, Symbol, kw, sym};
use rustc_span::{DUMMY_SP, Span};
use thin_vec::ThinVec;
use tracing::debug;
use crate::errors::{
self, IncorrectVisibilityRestriction, MismatchedClosingDelimiter, NonStringAbiLiteral,
};
use crate::lexer::UnmatchedDelim;
#[cfg(test)]
mod tests;
// Ideally, these tests would be in `rustc_ast`. But they depend on having a
// parser, so they are here.
#[cfg(test)]
mod tokenstream {
mod tests;
}
#[cfg(test)]
mod mut_visit {
mod tests;
}
bitflags::bitflags! {
#[derive(Clone, Copy, Debug)]
struct Restrictions: u8 {
const STMT_EXPR = 1 << 0;
const NO_STRUCT_LITERAL = 1 << 1;
const CONST_EXPR = 1 << 2;
const ALLOW_LET = 1 << 3;
const IN_IF_GUARD = 1 << 4;
const IS_PAT = 1 << 5;
}
}
#[derive(Clone, Copy, PartialEq, Debug)]
enum SemiColonMode {
Break,
Ignore,
Comma,
}
#[derive(Clone, Copy, PartialEq, Debug)]
enum BlockMode {
Break,
Ignore,
}
/// Whether or not we should force collection of tokens for an AST node,
/// regardless of whether or not it has attributes
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum ForceCollect {
Yes,
No,
}
#[macro_export]
macro_rules! maybe_whole {
($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
if let token::Interpolated(nt) = &$p.token.kind
&& let token::$constructor(x) = &**nt
{
#[allow(unused_mut)]
let mut $x = x.clone();
$p.bump();
return Ok($e);
}
};
}
/// If the next tokens are ill-formed `$ty::` recover them as `<$ty>::`.
#[macro_export]
macro_rules! maybe_recover_from_interpolated_ty_qpath {
($self: expr, $allow_qpath_recovery: expr) => {
if $allow_qpath_recovery
&& $self.may_recover()
&& $self.look_ahead(1, |t| t == &token::PathSep)
&& let token::Interpolated(nt) = &$self.token.kind
&& let token::NtTy(ty) = &**nt
{
let ty = ty.clone();
$self.bump();
return $self.maybe_recover_from_bad_qpath_stage_2($self.prev_token.span, ty);
}
};
}
#[derive(Clone, Copy, Debug)]
pub enum Recovery {
Allowed,
Forbidden,
}
#[derive(Clone)]
pub struct Parser<'a> {
pub psess: &'a ParseSess,
/// The current token.
pub token: Token,
/// The spacing for the current token.
token_spacing: Spacing,
/// The previous token.
pub prev_token: Token,
pub capture_cfg: bool,
restrictions: Restrictions,
expected_tokens: Vec<TokenType>,
token_cursor: TokenCursor,
// The number of calls to `bump`, i.e. the position in the token stream.
num_bump_calls: u32,
// During parsing we may sometimes need to "unglue" a glued token into two
// or three component tokens (e.g. `>>` into `>` and `>`, or `>>=` into `>`
// and `>` and `=`), so the parser can consume them one at a time. This
// process bypasses the normal capturing mechanism (e.g. `num_bump_calls`
// will not be incremented), since the "unglued" tokens due not exist in
// the original `TokenStream`.
//
// If we end up consuming all the component tokens, this is not an issue,
// because we'll end up capturing the single "glued" token.
//
// However, sometimes we may want to capture not all of the original
// token. For example, capturing the `Vec<u8>` in `Option<Vec<u8>>`
// requires us to unglue the trailing `>>` token. The `break_last_token`
// field is used to track these tokens. They get appended to the captured
// stream when we evaluate a `LazyAttrTokenStream`.
//
// This value is always 0, 1, or 2. It can only reach 2 when splitting
// `>>=` or `<<=`.
break_last_token: u32,
/// This field is used to keep track of how many left angle brackets we have seen. This is
/// required in order to detect extra leading left angle brackets (`<` characters) and error
/// appropriately.
///
/// See the comments in the `parse_path_segment` function for more details.
unmatched_angle_bracket_count: u16,
angle_bracket_nesting: u16,
last_unexpected_token_span: Option<Span>,
/// If present, this `Parser` is not parsing Rust code but rather a macro call.
subparser_name: Option<&'static str>,
capture_state: CaptureState,
/// This allows us to recover when the user forget to add braces around
/// multiple statements in the closure body.
current_closure: Option<ClosureSpans>,
/// Whether the parser is allowed to do recovery.
/// This is disabled when parsing macro arguments, see #103534
recovery: Recovery,
}
// This type is used a lot, e.g. it's cloned when matching many declarative macro rules with nonterminals. Make sure
// it doesn't unintentionally get bigger.
#[cfg(target_pointer_width = "64")]
rustc_data_structures::static_assert_size!(Parser<'_>, 288);
/// Stores span information about a closure.
#[derive(Clone, Debug)]
struct ClosureSpans {
whole_closure: Span,
closing_pipe: Span,
body: Span,
}
/// A token range within a `Parser`'s full token stream.
#[derive(Clone, Debug)]
struct ParserRange(Range<u32>);
/// A token range within an individual AST node's (lazy) token stream, i.e.
/// relative to that node's first token. Distinct from `ParserRange` so the two
/// kinds of range can't be mixed up.
#[derive(Clone, Debug)]
struct NodeRange(Range<u32>);
/// Indicates a range of tokens that should be replaced by an `AttrsTarget`
/// (replacement) or be replaced by nothing (deletion). This is used in two
/// places during token collection.
///
/// 1. Replacement. During the parsing of an AST node that may have a
/// `#[derive]` attribute, when we parse a nested AST node that has `#[cfg]`
/// or `#[cfg_attr]`, we replace the entire inner AST node with
/// `FlatToken::AttrsTarget`. This lets us perform eager cfg-expansion on an
/// `AttrTokenStream`.
///
/// 2. Deletion. We delete inner attributes from all collected token streams,
/// and instead track them through the `attrs` field on the AST node. This
/// lets us manipulate them similarly to outer attributes. When we create a
/// `TokenStream`, the inner attributes are inserted into the proper place
/// in the token stream.
///
/// Each replacement starts off in `ParserReplacement` form but is converted to
/// `NodeReplacement` form when it is attached to a single AST node, via
/// `LazyAttrTokenStreamImpl`.
type ParserReplacement = (ParserRange, Option<AttrsTarget>);
/// See the comment on `ParserReplacement`.
type NodeReplacement = (NodeRange, Option<AttrsTarget>);
impl NodeRange {
// Converts a range within a parser's tokens to a range within a
// node's tokens beginning at `start_pos`.
//
// For example, imagine a parser with 50 tokens in its token stream, a
// function that spans `ParserRange(20..40)` and an inner attribute within
// that function that spans `ParserRange(30..35)`. We would find the inner
// attribute's range within the function's tokens by subtracting 20, which
// is the position of the function's start token. This gives
// `NodeRange(10..15)`.
fn new(ParserRange(parser_range): ParserRange, start_pos: u32) -> NodeRange {
assert!(!parser_range.is_empty());
assert!(parser_range.start >= start_pos);
NodeRange((parser_range.start - start_pos)..(parser_range.end - start_pos))
}
}
/// Controls how we capture tokens. Capturing can be expensive,
/// so we try to avoid performing capturing in cases where
/// we will never need an `AttrTokenStream`.
#[derive(Copy, Clone, Debug)]
enum Capturing {
/// We aren't performing any capturing - this is the default mode.
No,
/// We are capturing tokens
Yes,
}
// This state is used by `Parser::collect_tokens`.
#[derive(Clone, Debug)]
struct CaptureState {
capturing: Capturing,
parser_replacements: Vec<ParserReplacement>,
inner_attr_parser_ranges: FxHashMap<AttrId, ParserRange>,
// `IntervalSet` is good for perf because attrs are mostly added to this
// set in contiguous ranges.
seen_attrs: IntervalSet<AttrId>,
}
/// Iterator over a `TokenStream` that produces `Token`s. It's a bit odd that
/// we (a) lex tokens into a nice tree structure (`TokenStream`), and then (b)
/// use this type to emit them as a linear sequence. But a linear sequence is
/// what the parser expects, for the most part.
#[derive(Clone, Debug)]
struct TokenCursor {
// Cursor for the current (innermost) token stream. The delimiters for this
// token stream are found in `self.stack.last()`; when that is `None` then
// we are in the outermost token stream which never has delimiters.
tree_cursor: TokenTreeCursor,
// Token streams surrounding the current one. The delimiters for stack[n]'s
// tokens are in `stack[n-1]`. `stack[0]` (when present) has no delimiters
// because it's the outermost token stream which never has delimiters.
stack: Vec<(TokenTreeCursor, DelimSpan, DelimSpacing, Delimiter)>,
}
impl TokenCursor {
fn next(&mut self) -> (Token, Spacing) {
self.inlined_next()
}
/// This always-inlined version should only be used on hot code paths.
#[inline(always)]
fn inlined_next(&mut self) -> (Token, Spacing) {
loop {
// FIXME: we currently don't return `Delimiter::Invisible` open/close delims. To fix
// #67062 we will need to, whereupon the `delim != Delimiter::Invisible` conditions
// below can be removed.
if let Some(tree) = self.tree_cursor.next_ref() {
match tree {
&TokenTree::Token(ref token, spacing) => {
debug_assert!(!matches!(
token.kind,
token::OpenDelim(_) | token::CloseDelim(_)
));
return (token.clone(), spacing);
}
&TokenTree::Delimited(sp, spacing, delim, ref tts) => {
let trees = tts.clone().into_trees();
self.stack.push((
mem::replace(&mut self.tree_cursor, trees),
sp,
spacing,
delim,
));
if delim != Delimiter::Invisible {
return (Token::new(token::OpenDelim(delim), sp.open), spacing.open);
}
// No open delimiter to return; continue on to the next iteration.
}
};
} else if let Some((tree_cursor, span, spacing, delim)) = self.stack.pop() {
// We have exhausted this token stream. Move back to its parent token stream.
self.tree_cursor = tree_cursor;
if delim != Delimiter::Invisible {
return (Token::new(token::CloseDelim(delim), span.close), spacing.close);
}
// No close delimiter to return; continue on to the next iteration.
} else {
// We have exhausted the outermost token stream. The use of
// `Spacing::Alone` is arbitrary and immaterial, because the
// `Eof` token's spacing is never used.
return (Token::new(token::Eof, DUMMY_SP), Spacing::Alone);
}
}
}
}
#[derive(Debug, Clone, PartialEq)]
enum TokenType {
Token(TokenKind),
Keyword(Symbol),
Operator,
Lifetime,
Ident,
Path,
Type,
Const,
}
impl TokenType {
fn to_string(&self) -> String {
match self {
TokenType::Token(t) => format!("`{}`", pprust::token_kind_to_string(t)),
TokenType::Keyword(kw) => format!("`{kw}`"),
TokenType::Operator => "an operator".to_string(),
TokenType::Lifetime => "lifetime".to_string(),
TokenType::Ident => "identifier".to_string(),
TokenType::Path => "path".to_string(),
TokenType::Type => "type".to_string(),
TokenType::Const => "a const expression".to_string(),
}
}
}
/// A sequence separator.
#[derive(Debug)]
struct SeqSep {
/// The separator token.
sep: Option<TokenKind>,
/// `true` if a trailing separator is allowed.
trailing_sep_allowed: bool,
}
impl SeqSep {
fn trailing_allowed(t: TokenKind) -> SeqSep {
SeqSep { sep: Some(t), trailing_sep_allowed: true }
}
fn none() -> SeqSep {
SeqSep { sep: None, trailing_sep_allowed: false }
}
}
#[derive(Debug)]
pub enum FollowedByType {
Yes,
No,
}
#[derive(Copy, Clone, Debug)]
enum Trailing {
No,
Yes,
}
impl From<bool> for Trailing {
fn from(b: bool) -> Trailing {
if b { Trailing::Yes } else { Trailing::No }
}
}
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub(super) enum TokenDescription {
ReservedIdentifier,
Keyword,
ReservedKeyword,
DocComment,
}
impl TokenDescription {
pub(super) fn from_token(token: &Token) -> Option<Self> {
match token.kind {
_ if token.is_special_ident() => Some(TokenDescription::ReservedIdentifier),
_ if token.is_used_keyword() => Some(TokenDescription::Keyword),
_ if token.is_unused_keyword() => Some(TokenDescription::ReservedKeyword),
token::DocComment(..) => Some(TokenDescription::DocComment),
_ => None,
}
}
}
pub fn token_descr(token: &Token) -> String {
let name = pprust::token_to_string(token).to_string();
let kind = match (TokenDescription::from_token(token), &token.kind) {
(Some(TokenDescription::ReservedIdentifier), _) => Some("reserved identifier"),
(Some(TokenDescription::Keyword), _) => Some("keyword"),
(Some(TokenDescription::ReservedKeyword), _) => Some("reserved keyword"),
(Some(TokenDescription::DocComment), _) => Some("doc comment"),
(None, TokenKind::NtIdent(..)) => Some("identifier"),
(None, TokenKind::NtLifetime(..)) => Some("lifetime"),
(None, TokenKind::Interpolated(node)) => Some(node.descr()),
(None, _) => None,
};
if let Some(kind) = kind { format!("{kind} `{name}`") } else { format!("`{name}`") }
}
impl<'a> Parser<'a> {
pub fn new(
psess: &'a ParseSess,
stream: TokenStream,
subparser_name: Option<&'static str>,
) -> Self {
let mut parser = Parser {
psess,
token: Token::dummy(),
token_spacing: Spacing::Alone,
prev_token: Token::dummy(),
capture_cfg: false,
restrictions: Restrictions::empty(),
expected_tokens: Vec::new(),
token_cursor: TokenCursor { tree_cursor: stream.into_trees(), stack: Vec::new() },
num_bump_calls: 0,
break_last_token: 0,
unmatched_angle_bracket_count: 0,
angle_bracket_nesting: 0,
last_unexpected_token_span: None,
subparser_name,
capture_state: CaptureState {
capturing: Capturing::No,
parser_replacements: Vec::new(),
inner_attr_parser_ranges: Default::default(),
seen_attrs: IntervalSet::new(u32::MAX as usize),
},
current_closure: None,
recovery: Recovery::Allowed,
};
// Make parser point to the first token.
parser.bump();
// Change this from 1 back to 0 after the bump. This eases debugging of
// `Parser::collect_tokens` because 0-indexed token positions are nicer
// than 1-indexed token positions.
parser.num_bump_calls = 0;
parser
}
#[inline]
pub fn recovery(mut self, recovery: Recovery) -> Self {
self.recovery = recovery;
self
}
/// Whether the parser is allowed to recover from broken code.
///
/// If this returns false, recovering broken code into valid code (especially if this recovery does lookahead)
/// is not allowed. All recovery done by the parser must be gated behind this check.
///
/// Technically, this only needs to restrict eager recovery by doing lookahead at more tokens.
/// But making the distinction is very subtle, and simply forbidding all recovery is a lot simpler to uphold.
#[inline]
fn may_recover(&self) -> bool {
matches!(self.recovery, Recovery::Allowed)
}
/// Version of [`unexpected`](Parser::unexpected) that "returns" any type in the `Ok`
/// (both those functions never return "Ok", and so can lie like that in the type).
pub fn unexpected_any<T>(&mut self) -> PResult<'a, T> {
match self.expect_one_of(&[], &[]) {
Err(e) => Err(e),
// We can get `Ok(true)` from `recover_closing_delimiter`
// which is called in `expected_one_of_not_found`.
Ok(_) => FatalError.raise(),
}
}
pub fn unexpected(&mut self) -> PResult<'a, ()> {
self.unexpected_any()
}
/// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
pub fn expect(&mut self, t: &TokenKind) -> PResult<'a, Recovered> {
if self.expected_tokens.is_empty() {
if self.token == *t {
self.bump();
Ok(Recovered::No)
} else {
self.unexpected_try_recover(t)
}
} else {
self.expect_one_of(slice::from_ref(t), &[])
}
}
/// Expect next token to be edible or inedible token. If edible,
/// then consume it; if inedible, then return without consuming
/// anything. Signal a fatal error if next token is unexpected.
fn expect_one_of(
&mut self,
edible: &[TokenKind],
inedible: &[TokenKind],
) -> PResult<'a, Recovered> {
if edible.contains(&self.token.kind) {
self.bump();
Ok(Recovered::No)
} else if inedible.contains(&self.token.kind) {
// leave it in the input
Ok(Recovered::No)
} else if self.token != token::Eof
&& self.last_unexpected_token_span == Some(self.token.span)
{
FatalError.raise();
} else {
self.expected_one_of_not_found(edible, inedible)
.map(|error_guaranteed| Recovered::Yes(error_guaranteed))
}
}
// Public for rustfmt usage.
pub fn parse_ident(&mut self) -> PResult<'a, Ident> {
self.parse_ident_common(true)
}
fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, Ident> {
let (ident, is_raw) = self.ident_or_err(recover)?;
if matches!(is_raw, IdentIsRaw::No) && ident.is_reserved() {
let err = self.expected_ident_found_err();
if recover {
err.emit();
} else {
return Err(err);
}
}
self.bump();
Ok(ident)
}
fn ident_or_err(&mut self, recover: bool) -> PResult<'a, (Ident, IdentIsRaw)> {
match self.token.ident() {
Some(ident) => Ok(ident),
None => self.expected_ident_found(recover),
}
}
/// Checks if the next token is `tok`, and returns `true` if so.
///
/// This method will automatically add `tok` to `expected_tokens` if `tok` is not
/// encountered.
#[inline]
fn check(&mut self, tok: &TokenKind) -> bool {
let is_present = self.token == *tok;
if !is_present {
self.expected_tokens.push(TokenType::Token(tok.clone()));
}
is_present
}
#[inline]
#[must_use]
fn check_noexpect(&self, tok: &TokenKind) -> bool {
self.token == *tok
}
/// Consumes a token 'tok' if it exists. Returns whether the given token was present.
///
/// the main purpose of this function is to reduce the cluttering of the suggestions list
/// which using the normal eat method could introduce in some cases.
#[inline]
#[must_use]
fn eat_noexpect(&mut self, tok: &TokenKind) -> bool {
let is_present = self.check_noexpect(tok);
if is_present {
self.bump()
}
is_present
}
/// Consumes a token 'tok' if it exists. Returns whether the given token was present.
#[inline]
#[must_use]
pub fn eat(&mut self, tok: &TokenKind) -> bool {
let is_present = self.check(tok);
if is_present {
self.bump()
}
is_present
}
/// If the next token is the given keyword, returns `true` without eating it.
/// An expectation is also added for diagnostics purposes.
#[inline]
#[must_use]
fn check_keyword(&mut self, kw: Symbol) -> bool {
self.expected_tokens.push(TokenType::Keyword(kw));
self.token.is_keyword(kw)
}
#[inline]
#[must_use]
fn check_keyword_case(&mut self, kw: Symbol, case: Case) -> bool {
if self.check_keyword(kw) {
return true;
}
if case == Case::Insensitive
&& let Some((ident, IdentIsRaw::No)) = self.token.ident()
&& ident.as_str().to_lowercase() == kw.as_str().to_lowercase()
{
true
} else {
false
}
}
/// If the next token is the given keyword, eats it and returns `true`.
/// Otherwise, returns `false`. An expectation is also added for diagnostics purposes.
// Public for rustc_builtin_macros and rustfmt usage.
#[inline]
#[must_use]
pub fn eat_keyword(&mut self, kw: Symbol) -> bool {
if self.check_keyword(kw) {
self.bump();
true
} else {
false
}
}
/// Eats a keyword, optionally ignoring the case.
/// If the case differs (and is ignored) an error is issued.
/// This is useful for recovery.
#[inline]
#[must_use]
fn eat_keyword_case(&mut self, kw: Symbol, case: Case) -> bool {
if self.eat_keyword(kw) {
return true;
}
if case == Case::Insensitive
&& let Some((ident, IdentIsRaw::No)) = self.token.ident()
&& ident.as_str().to_lowercase() == kw.as_str().to_lowercase()
{
self.dcx().emit_err(errors::KwBadCase { span: ident.span, kw: kw.as_str() });
self.bump();
return true;
}
false
}
/// If the next token is the given keyword, eats it and returns `true`.
/// Otherwise, returns `false`. No expectation is added.
// Public for rustc_builtin_macros usage.
#[inline]
#[must_use]
pub fn eat_keyword_noexpect(&mut self, kw: Symbol) -> bool {
if self.token.is_keyword(kw) {
self.bump();
true
} else {
false
}
}
/// If the given word is not a keyword, signals an error.
/// If the next token is not the given word, signals an error.
/// Otherwise, eats it.
pub fn expect_keyword(&mut self, kw: Symbol) -> PResult<'a, ()> {
if !self.eat_keyword(kw) { self.unexpected() } else { Ok(()) }
}
/// Is the given keyword `kw` followed by a non-reserved identifier?
fn is_kw_followed_by_ident(&self, kw: Symbol) -> bool {
self.token.is_keyword(kw) && self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
}
#[inline]
fn check_or_expected(&mut self, ok: bool, typ: TokenType) -> bool {
if ok {
true
} else {
self.expected_tokens.push(typ);
false
}
}
fn check_ident(&mut self) -> bool {
self.check_or_expected(self.token.is_ident(), TokenType::Ident)
}
fn check_path(&mut self) -> bool {
self.check_or_expected(self.token.is_path_start(), TokenType::Path)
}
fn check_type(&mut self) -> bool {
self.check_or_expected(self.token.can_begin_type(), TokenType::Type)
}
fn check_const_arg(&mut self) -> bool {
self.check_or_expected(self.token.can_begin_const_arg(), TokenType::Const)
}
fn check_const_closure(&self) -> bool {
self.is_keyword_ahead(0, &[kw::Const])
&& self.look_ahead(1, |t| match &t.kind {
// async closures do not work with const closures, so we do not parse that here.
token::Ident(kw::Move | kw::Static, _) | token::OrOr | token::BinOp(token::Or) => {
true
}
_ => false,
})
}
fn check_inline_const(&self, dist: usize) -> bool {
self.is_keyword_ahead(dist, &[kw::Const])
&& self.look_ahead(dist + 1, |t| match &t.kind {
token::Interpolated(nt) => matches!(&**nt, token::NtBlock(..)),
token::OpenDelim(Delimiter::Brace) => true,
_ => false,
})
}
/// Checks to see if the next token is either `+` or `+=`.
/// Otherwise returns `false`.
#[inline]
fn check_plus(&mut self) -> bool {
self.check_or_expected(
self.token.is_like_plus(),
TokenType::Token(token::BinOp(token::Plus)),
)
}
/// Eats the expected token if it's present possibly breaking
/// compound tokens like multi-character operators in process.
/// Returns `true` if the token was eaten.
fn break_and_eat(&mut self, expected: TokenKind) -> bool {
if self.token == expected {
self.bump();
return true;
}
match self.token.kind.break_two_token_op(1) {
Some((first, second)) if first == expected => {
let first_span = self.psess.source_map().start_point(self.token.span);
let second_span = self.token.span.with_lo(first_span.hi());
self.token = Token::new(first, first_span);
// Keep track of this token - if we end token capturing now,
// we'll want to append this token to the captured stream.
//
// If we consume any additional tokens, then this token
// is not needed (we'll capture the entire 'glued' token),
// and `bump` will set this field to 0.
self.break_last_token += 1;
// Use the spacing of the glued token as the spacing of the
// unglued second token.
self.bump_with((Token::new(second, second_span), self.token_spacing));
true
}
_ => {
self.expected_tokens.push(TokenType::Token(expected));
false
}
}
}
/// Eats `+` possibly breaking tokens like `+=` in process.
fn eat_plus(&mut self) -> bool {
self.break_and_eat(token::BinOp(token::Plus))
}
/// Eats `&` possibly breaking tokens like `&&` in process.
/// Signals an error if `&` is not eaten.
fn expect_and(&mut self) -> PResult<'a, ()> {
if self.break_and_eat(token::BinOp(token::And)) { Ok(()) } else { self.unexpected() }
}
/// Eats `|` possibly breaking tokens like `||` in process.
/// Signals an error if `|` was not eaten.
fn expect_or(&mut self) -> PResult<'a, ()> {
if self.break_and_eat(token::BinOp(token::Or)) { Ok(()) } else { self.unexpected() }
}
/// Eats `<` possibly breaking tokens like `<<` in process.
fn eat_lt(&mut self) -> bool {
let ate = self.break_and_eat(token::Lt);
if ate {
// See doc comment for `unmatched_angle_bracket_count`.
self.unmatched_angle_bracket_count += 1;
debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count);
}
ate
}
/// Eats `<` possibly breaking tokens like `<<` in process.
/// Signals an error if `<` was not eaten.
fn expect_lt(&mut self) -> PResult<'a, ()> {
if self.eat_lt() { Ok(()) } else { self.unexpected() }
}
/// Eats `>` possibly breaking tokens like `>>` in process.
/// Signals an error if `>` was not eaten.
fn expect_gt(&mut self) -> PResult<'a, ()> {
if self.break_and_eat(token::Gt) {
// See doc comment for `unmatched_angle_bracket_count`.
if self.unmatched_angle_bracket_count > 0 {
self.unmatched_angle_bracket_count -= 1;
debug!("expect_gt: (decrement) count={:?}", self.unmatched_angle_bracket_count);
}
Ok(())
} else {
self.unexpected()
}
}
/// Checks if the next token is contained within `kets`, and returns `true` if so.
fn expect_any_with_type(
&mut self,
kets_expected: &[&TokenKind],
kets_not_expected: &[&TokenKind],
) -> bool {
kets_expected.iter().any(|k| self.check(k))
|| kets_not_expected.iter().any(|k| self.check_noexpect(k))
}
/// Parses a sequence until the specified delimiters. The function
/// `f` must consume tokens until reaching the next separator or
/// closing bracket.
fn parse_seq_to_before_tokens<T>(
&mut self,
kets_expected: &[&TokenKind],
kets_not_expected: &[&TokenKind],
sep: SeqSep,
mut f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
) -> PResult<'a, (ThinVec<T>, Trailing, Recovered)> {
let mut first = true;
let mut recovered = Recovered::No;
let mut trailing = Trailing::No;
let mut v = ThinVec::new();
while !self.expect_any_with_type(kets_expected, kets_not_expected) {
if let token::CloseDelim(..) | token::Eof = self.token.kind {
break;
}
if let Some(t) = &sep.sep {
if first {
// no separator for the first element
first = false;
} else {
// check for separator
match self.expect(t) {
Ok(Recovered::No) => {
self.current_closure.take();
}
Ok(Recovered::Yes(guar)) => {
self.current_closure.take();
recovered = Recovered::Yes(guar);
break;
}
Err(mut expect_err) => {
let sp = self.prev_token.span.shrink_to_hi();
let token_str = pprust::token_kind_to_string(t);
match self.current_closure.take() {
Some(closure_spans) if self.token == TokenKind::Semi => {
// Finding a semicolon instead of a comma
// after a closure body indicates that the
// closure body may be a block but the user
// forgot to put braces around its
// statements.
self.recover_missing_braces_around_closure_body(
closure_spans,
expect_err,
)?;
continue;
}
_ => {
// Attempt to keep parsing if it was a similar separator.
if let Some(tokens) = t.similar_tokens() {
if tokens.contains(&self.token.kind) {
self.bump();
}
}
}
}
// If this was a missing `@` in a binding pattern
// bail with a suggestion
// https://github.com/rust-lang/rust/issues/72373
if self.prev_token.is_ident() && self.token == token::DotDot {
let msg = format!(
"if you meant to bind the contents of the rest of the array \
pattern into `{}`, use `@`",
pprust::token_to_string(&self.prev_token)
);
expect_err
.with_span_suggestion_verbose(
self.prev_token.span.shrink_to_hi().until(self.token.span),
msg,
" @ ",
Applicability::MaybeIncorrect,
)
.emit();
break;
}
// Attempt to keep parsing if it was an omitted separator.
self.last_unexpected_token_span = None;
match f(self) {
Ok(t) => {
// Parsed successfully, therefore most probably the code only
// misses a separator.
expect_err
.with_span_suggestion_short(
sp,
format!("missing `{token_str}`"),
token_str,
Applicability::MaybeIncorrect,
)
.emit();
v.push(t);
continue;
}
Err(e) => {
// Parsing failed, therefore it must be something more serious
// than just a missing separator.
for xx in &e.children {
// propagate the help message from sub error 'e' to main error 'expect_err;
expect_err.children.push(xx.clone());
}
e.cancel();
if self.token == token::Colon {
// we will try to recover in `maybe_recover_struct_lit_bad_delims`
return Err(expect_err);
} else if let [token::CloseDelim(Delimiter::Parenthesis)] =
kets_expected
{
return Err(expect_err);
} else {
expect_err.emit();
break;
}
}
}
}
}
}
}
if sep.trailing_sep_allowed
&& self.expect_any_with_type(kets_expected, kets_not_expected)
{
trailing = Trailing::Yes;
break;
}
let t = f(self)?;
v.push(t);
}
Ok((v, trailing, recovered))
}
fn recover_missing_braces_around_closure_body(
&mut self,
closure_spans: ClosureSpans,
mut expect_err: Diag<'_>,
) -> PResult<'a, ()> {
let initial_semicolon = self.token.span;
while self.eat(&TokenKind::Semi) {
let _ = self.parse_stmt_without_recovery(false, ForceCollect::No).unwrap_or_else(|e| {
e.cancel();
None
});
}
expect_err
.primary_message("closure bodies that contain statements must be surrounded by braces");
let preceding_pipe_span = closure_spans.closing_pipe;
let following_token_span = self.token.span;
let mut first_note = MultiSpan::from(vec![initial_semicolon]);
first_note.push_span_label(
initial_semicolon,
"this `;` turns the preceding closure into a statement",
);
first_note.push_span_label(
closure_spans.body,
"this expression is a statement because of the trailing semicolon",
);
expect_err.span_note(first_note, "statement found outside of a block");
let mut second_note = MultiSpan::from(vec![closure_spans.whole_closure]);
second_note.push_span_label(closure_spans.whole_closure, "this is the parsed closure...");
second_note.push_span_label(
following_token_span,
"...but likely you meant the closure to end here",
);
expect_err.span_note(second_note, "the closure body may be incorrectly delimited");
expect_err.span(vec![preceding_pipe_span, following_token_span]);
let opening_suggestion_str = " {".to_string();
let closing_suggestion_str = "}".to_string();
expect_err.multipart_suggestion(
"try adding braces",
vec![
(preceding_pipe_span.shrink_to_hi(), opening_suggestion_str),
(following_token_span.shrink_to_lo(), closing_suggestion_str),
],
Applicability::MaybeIncorrect,
);
expect_err.emit();
Ok(())
}
/// Parses a sequence, not including the delimiters. The function
/// `f` must consume tokens until reaching the next separator or
/// closing bracket.
fn parse_seq_to_before_end<T>(
&mut self,
ket: &TokenKind,
sep: SeqSep,
f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
) -> PResult<'a, (ThinVec<T>, Trailing, Recovered)> {
self.parse_seq_to_before_tokens(&[ket], &[], sep, f)
}
/// Parses a sequence, including only the closing delimiter. The function
/// `f` must consume tokens until reaching the next separator or
/// closing bracket.
fn parse_seq_to_end<T>(
&mut self,
ket: &TokenKind,
sep: SeqSep,
f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
) -> PResult<'a, (ThinVec<T>, Trailing)> {
let (val, trailing, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
if matches!(recovered, Recovered::No) && !self.eat(ket) {
self.dcx().span_delayed_bug(
self.token.span,
"recovered but `parse_seq_to_before_end` did not give us the ket token",
);
}
Ok((val, trailing))
}
/// Parses a sequence, including both delimiters. The function
/// `f` must consume tokens until reaching the next separator or
/// closing bracket.
fn parse_unspanned_seq<T>(
&mut self,
bra: &TokenKind,
ket: &TokenKind,
sep: SeqSep,
f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
) -> PResult<'a, (ThinVec<T>, Trailing)> {
self.expect(bra)?;
self.parse_seq_to_end(ket, sep, f)
}
/// Parses a comma-separated sequence, including both delimiters.
/// The function `f` must consume tokens until reaching the next separator or
/// closing bracket.
fn parse_delim_comma_seq<T>(
&mut self,
delim: Delimiter,
f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
) -> PResult<'a, (ThinVec<T>, Trailing)> {
self.parse_unspanned_seq(
&token::OpenDelim(delim),
&token::CloseDelim(delim),
SeqSep::trailing_allowed(token::Comma),
f,
)
}
/// Parses a comma-separated sequence delimited by parentheses (e.g. `(x, y)`).
/// The function `f` must consume tokens until reaching the next separator or
/// closing bracket.
fn parse_paren_comma_seq<T>(
&mut self,
f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
) -> PResult<'a, (ThinVec<T>, Trailing)> {
self.parse_delim_comma_seq(Delimiter::Parenthesis, f)
}
/// Advance the parser by one token using provided token as the next one.
fn bump_with(&mut self, next: (Token, Spacing)) {
self.inlined_bump_with(next)
}
/// This always-inlined version should only be used on hot code paths.
#[inline(always)]
fn inlined_bump_with(&mut self, (next_token, next_spacing): (Token, Spacing)) {
// Update the current and previous tokens.
self.prev_token = mem::replace(&mut self.token, next_token);
self.token_spacing = next_spacing;
// Diagnostics.
self.expected_tokens.clear();
}
/// Advance the parser by one token.
pub fn bump(&mut self) {
// Note: destructuring here would give nicer code, but it was found in #96210 to be slower
// than `.0`/`.1` access.
let mut next = self.token_cursor.inlined_next();
self.num_bump_calls += 1;
// We got a token from the underlying cursor and no longer need to
// worry about an unglued token. See `break_and_eat` for more details.
self.break_last_token = 0;
if next.0.span.is_dummy() {
// Tweak the location for better diagnostics, but keep syntactic context intact.
let fallback_span = self.token.span;
next.0.span = fallback_span.with_ctxt(next.0.span.ctxt());
}
debug_assert!(!matches!(
next.0.kind,
token::OpenDelim(Delimiter::Invisible) | token::CloseDelim(Delimiter::Invisible)
));
self.inlined_bump_with(next)
}
/// Look-ahead `dist` tokens of `self.token` and get access to that token there.
/// When `dist == 0` then the current token is looked at. `Eof` will be
/// returned if the look-ahead is any distance past the end of the tokens.
pub fn look_ahead<R>(&self, dist: usize, looker: impl FnOnce(&Token) -> R) -> R {
if dist == 0 {
return looker(&self.token);
}
// Typically around 98% of the `dist > 0` cases have `dist == 1`, so we
// have a fast special case for that.
if dist == 1 {
// The index is zero because the tree cursor's index always points
// to the next token to be gotten.
match self.token_cursor.tree_cursor.look_ahead(0) {
Some(tree) => {
// Indexing stayed within the current token tree.
match tree {
TokenTree::Token(token, _) => return looker(token),
&TokenTree::Delimited(dspan, _, delim, _) => {
if delim != Delimiter::Invisible {
return looker(&Token::new(token::OpenDelim(delim), dspan.open));
}
}
};
}
None => {
// The tree cursor lookahead went (one) past the end of the
// current token tree. Try to return a close delimiter.
if let Some(&(_, span, _, delim)) = self.token_cursor.stack.last()
&& delim != Delimiter::Invisible
{
// We are not in the outermost token stream, so we have
// delimiters. Also, those delimiters are not skipped.
return looker(&Token::new(token::CloseDelim(delim), span.close));
}
}
}
}
// Just clone the token cursor and use `next`, skipping delimiters as
// necessary. Slow but simple.
let mut cursor = self.token_cursor.clone();
let mut i = 0;
let mut token = Token::dummy();
while i < dist {
token = cursor.next().0;
if matches!(
token.kind,
token::OpenDelim(Delimiter::Invisible) | token::CloseDelim(Delimiter::Invisible)
) {
continue;
}
i += 1;
}
looker(&token)
}
/// Returns whether any of the given keywords are `dist` tokens ahead of the current one.
pub(crate) fn is_keyword_ahead(&self, dist: usize, kws: &[Symbol]) -> bool {
self.look_ahead(dist, |t| kws.iter().any(|&kw| t.is_keyword(kw)))
}
/// Parses asyncness: `async` or nothing.
fn parse_coroutine_kind(&mut self, case: Case) -> Option<CoroutineKind> {
let span = self.token.uninterpolated_span();
if self.eat_keyword_case(kw::Async, case) {
// FIXME(gen_blocks): Do we want to unconditionally parse `gen` and then
// error if edition <= 2024, like we do with async and edition <= 2018?
if self.token.uninterpolated_span().at_least_rust_2024()
&& self.eat_keyword_case(kw::Gen, case)
{
let gen_span = self.prev_token.uninterpolated_span();
Some(CoroutineKind::AsyncGen {
span: span.to(gen_span),
closure_id: DUMMY_NODE_ID,
return_impl_trait_id: DUMMY_NODE_ID,
})
} else {
Some(CoroutineKind::Async {
span,
closure_id: DUMMY_NODE_ID,
return_impl_trait_id: DUMMY_NODE_ID,
})
}
} else if self.token.uninterpolated_span().at_least_rust_2024()
&& self.eat_keyword_case(kw::Gen, case)
{
Some(CoroutineKind::Gen {
span,
closure_id: DUMMY_NODE_ID,
return_impl_trait_id: DUMMY_NODE_ID,
})
} else {
None
}
}
/// Parses fn unsafety: `unsafe`, `safe` or nothing.
fn parse_safety(&mut self, case: Case) -> Safety {
if self.eat_keyword_case(kw::Unsafe, case) {
Safety::Unsafe(self.prev_token.uninterpolated_span())
} else if self.eat_keyword_case(kw::Safe, case) {
Safety::Safe(self.prev_token.uninterpolated_span())
} else {
Safety::Default
}
}
/// Parses constness: `const` or nothing.
fn parse_constness(&mut self, case: Case) -> Const {
self.parse_constness_(case, false)
}
/// Parses constness for closures (case sensitive, feature-gated)
fn parse_closure_constness(&mut self) -> Const {
let constness = self.parse_constness_(Case::Sensitive, true);
if let Const::Yes(span) = constness {
self.psess.gated_spans.gate(sym::const_closures, span);
}
constness
}
fn parse_constness_(&mut self, case: Case, is_closure: bool) -> Const {
// Avoid const blocks and const closures to be parsed as const items
if (self.check_const_closure() == is_closure)
&& !self
.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace) || t.is_whole_block())
&& self.eat_keyword_case(kw::Const, case)
{
Const::Yes(self.prev_token.uninterpolated_span())
} else {
Const::No
}
}
/// Parses inline const expressions.
fn parse_const_block(&mut self, span: Span, pat: bool) -> PResult<'a, P<Expr>> {
if pat {
self.psess.gated_spans.gate(sym::inline_const_pat, span);
}
self.expect_keyword(kw::Const)?;
let (attrs, blk) = self.parse_inner_attrs_and_block()?;
let anon_const = AnonConst {
id: DUMMY_NODE_ID,
value: self.mk_expr(blk.span, ExprKind::Block(blk, None)),
};
let blk_span = anon_const.value.span;
Ok(self.mk_expr_with_attrs(span.to(blk_span), ExprKind::ConstBlock(anon_const), attrs))
}
/// Parses mutability (`mut` or nothing).
fn parse_mutability(&mut self) -> Mutability {
if self.eat_keyword(kw::Mut) { Mutability::Mut } else { Mutability::Not }
}
/// Parses reference binding mode (`ref`, `ref mut`, or nothing).
fn parse_byref(&mut self) -> ByRef {
if self.eat_keyword(kw::Ref) { ByRef::Yes(self.parse_mutability()) } else { ByRef::No }
}
/// Possibly parses mutability (`const` or `mut`).
fn parse_const_or_mut(&mut self) -> Option<Mutability> {
if self.eat_keyword(kw::Mut) {
Some(Mutability::Mut)
} else if self.eat_keyword(kw::Const) {
Some(Mutability::Not)
} else {
None
}
}
fn parse_field_name(&mut self) -> PResult<'a, Ident> {
if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) = self.token.kind
{
if let Some(suffix) = suffix {
self.expect_no_tuple_index_suffix(self.token.span, suffix);
}
self.bump();
Ok(Ident::new(symbol, self.prev_token.span))
} else {
self.parse_ident_common(true)
}
}
fn parse_delim_args(&mut self) -> PResult<'a, P<DelimArgs>> {
if let Some(args) = self.parse_delim_args_inner() {
Ok(P(args))
} else {
self.unexpected_any()
}
}
fn parse_attr_args(&mut self) -> PResult<'a, AttrArgs> {
Ok(if let Some(args) = self.parse_delim_args_inner() {
AttrArgs::Delimited(args)
} else if self.eat(&token::Eq) {
let eq_span = self.prev_token.span;
AttrArgs::Eq(eq_span, AttrArgsEq::Ast(self.parse_expr_force_collect()?))
} else {
AttrArgs::Empty
})
}
fn parse_delim_args_inner(&mut self) -> Option<DelimArgs> {
let delimited = self.check(&token::OpenDelim(Delimiter::Parenthesis))
|| self.check(&token::OpenDelim(Delimiter::Bracket))
|| self.check(&token::OpenDelim(Delimiter::Brace));
delimited.then(|| {
let TokenTree::Delimited(dspan, _, delim, tokens) = self.parse_token_tree() else {
unreachable!()
};
DelimArgs { dspan, delim, tokens }
})
}
/// Parses a single token tree from the input.
pub fn parse_token_tree(&mut self) -> TokenTree {
match self.token.kind {
token::OpenDelim(..) => {
// Grab the tokens within the delimiters.
let stream = self.token_cursor.tree_cursor.stream.clone();
let (_, span, spacing, delim) = *self.token_cursor.stack.last().unwrap();
// Advance the token cursor through the entire delimited
// sequence. After getting the `OpenDelim` we are *within* the
// delimited sequence, i.e. at depth `d`. After getting the
// matching `CloseDelim` we are *after* the delimited sequence,
// i.e. at depth `d - 1`.
let target_depth = self.token_cursor.stack.len() - 1;
loop {
// Advance one token at a time, so `TokenCursor::next()`
// can capture these tokens if necessary.
self.bump();
if self.token_cursor.stack.len() == target_depth {
debug_assert_matches!(self.token.kind, token::CloseDelim(_));
break;
}
}
// Consume close delimiter
self.bump();
TokenTree::Delimited(span, spacing, delim, stream)
}
token::CloseDelim(_) | token::Eof => unreachable!(),
_ => {
let prev_spacing = self.token_spacing;
self.bump();
TokenTree::Token(self.prev_token.clone(), prev_spacing)
}
}
}
pub fn parse_tokens(&mut self) -> TokenStream {
let mut result = Vec::new();
loop {
match self.token.kind {
token::Eof | token::CloseDelim(..) => break,
_ => result.push(self.parse_token_tree()),
}
}
TokenStream::new(result)
}
/// Evaluates the closure with restrictions in place.
///
/// Afters the closure is evaluated, restrictions are reset.
fn with_res<T>(&mut self, res: Restrictions, f: impl FnOnce(&mut Self) -> T) -> T {
let old = self.restrictions;
self.restrictions = res;
let res = f(self);
self.restrictions = old;
res
}
/// Parses `pub` and `pub(in path)` plus shortcuts `pub(crate)` for `pub(in crate)`, `pub(self)`
/// for `pub(in self)` and `pub(super)` for `pub(in super)`.
/// If the following element can't be a tuple (i.e., it's a function definition), then
/// it's not a tuple struct field), and the contents within the parentheses aren't valid,
/// so emit a proper diagnostic.
// Public for rustfmt usage.
pub fn parse_visibility(&mut self, fbt: FollowedByType) -> PResult<'a, Visibility> {
maybe_whole!(self, NtVis, |vis| vis.into_inner());
if !self.eat_keyword(kw::Pub) {
// We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
// keyword to grab a span from for inherited visibility; an empty span at the
// beginning of the current token would seem to be the "Schelling span".
return Ok(Visibility {
span: self.token.span.shrink_to_lo(),
kind: VisibilityKind::Inherited,
tokens: None,
});
}
let lo = self.prev_token.span;
if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
// We don't `self.bump()` the `(` yet because this might be a struct definition where
// `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
// Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
// by the following tokens.
if self.is_keyword_ahead(1, &[kw::In]) {
// Parse `pub(in path)`.
self.bump(); // `(`
self.bump(); // `in`
let path = self.parse_path(PathStyle::Mod)?; // `path`
self.expect(&token::CloseDelim(Delimiter::Parenthesis))?; // `)`
let vis = VisibilityKind::Restricted {
path: P(path),
id: ast::DUMMY_NODE_ID,
shorthand: false,
};
return Ok(Visibility {
span: lo.to(self.prev_token.span),
kind: vis,
tokens: None,
});
} else if self.look_ahead(2, |t| t == &token::CloseDelim(Delimiter::Parenthesis))
&& self.is_keyword_ahead(1, &[kw::Crate, kw::Super, kw::SelfLower])
{
// Parse `pub(crate)`, `pub(self)`, or `pub(super)`.
self.bump(); // `(`
let path = self.parse_path(PathStyle::Mod)?; // `crate`/`super`/`self`
self.expect(&token::CloseDelim(Delimiter::Parenthesis))?; // `)`
let vis = VisibilityKind::Restricted {
path: P(path),
id: ast::DUMMY_NODE_ID,
shorthand: true,
};
return Ok(Visibility {
span: lo.to(self.prev_token.span),
kind: vis,
tokens: None,
});
} else if let FollowedByType::No = fbt {
// Provide this diagnostic if a type cannot follow;
// in particular, if this is not a tuple struct.
self.recover_incorrect_vis_restriction()?;
// Emit diagnostic, but continue with public visibility.
}
}
Ok(Visibility { span: lo, kind: VisibilityKind::Public, tokens: None })
}
/// Recovery for e.g. `pub(something) fn ...` or `struct X { pub(something) y: Z }`
fn recover_incorrect_vis_restriction(&mut self) -> PResult<'a, ()> {
self.bump(); // `(`
let path = self.parse_path(PathStyle::Mod)?;
self.expect(&token::CloseDelim(Delimiter::Parenthesis))?; // `)`
let path_str = pprust::path_to_string(&path);
self.dcx()
.emit_err(IncorrectVisibilityRestriction { span: path.span, inner_str: path_str });
Ok(())
}
/// Parses `extern string_literal?`.
fn parse_extern(&mut self, case: Case) -> Extern {
if self.eat_keyword_case(kw::Extern, case) {
let mut extern_span = self.prev_token.span;
let abi = self.parse_abi();
if let Some(abi) = abi {
extern_span = extern_span.to(abi.span);
}
Extern::from_abi(abi, extern_span)
} else {
Extern::None
}
}
/// Parses a string literal as an ABI spec.
fn parse_abi(&mut self) -> Option<StrLit> {
match self.parse_str_lit() {
Ok(str_lit) => Some(str_lit),
Err(Some(lit)) => match lit.kind {
ast::LitKind::Err(_) => None,
_ => {
self.dcx().emit_err(NonStringAbiLiteral { span: lit.span });
None
}
},
Err(None) => None,
}
}
fn collect_tokens_no_attrs<R: HasAttrs + HasTokens>(
&mut self,
f: impl FnOnce(&mut Self) -> PResult<'a, R>,
) -> PResult<'a, R> {
// The only reason to call `collect_tokens_no_attrs` is if you want tokens, so use
// `ForceCollect::Yes`
self.collect_tokens(None, AttrWrapper::empty(), ForceCollect::Yes, |this, _attrs| {
Ok((f(this)?, Trailing::No, UsePreAttrPos::No))
})
}
/// Checks for `::` or, potentially, `:::` and then look ahead after it.
fn check_path_sep_and_look_ahead(&mut self, looker: impl Fn(&Token) -> bool) -> bool {
if self.check(&token::PathSep) {
if self.may_recover() && self.look_ahead(1, |t| t.kind == token::Colon) {
debug_assert!(!self.look_ahead(1, &looker), "Looker must not match on colon");
self.look_ahead(2, looker)
} else {
self.look_ahead(1, looker)
}
} else {
false
}
}
/// `::{` or `::*`
fn is_import_coupler(&mut self) -> bool {
self.check_path_sep_and_look_ahead(|t| {
matches!(t.kind, token::OpenDelim(Delimiter::Brace) | token::BinOp(token::Star))
})
}
// Debug view of the parser's token stream, up to `{lookahead}` tokens.
// Only used when debugging.
#[allow(unused)]
pub(crate) fn debug_lookahead(&self, lookahead: usize) -> impl fmt::Debug + '_ {
struct DebugParser<'dbg> {
parser: &'dbg Parser<'dbg>,
lookahead: usize,
}
impl fmt::Debug for DebugParser<'_> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let Self { parser, lookahead } = self;
let mut dbg_fmt = f.debug_struct("Parser"); // or at least, one view of
// we don't need N spans, but we want at least one, so print all of prev_token
dbg_fmt.field("prev_token", &parser.prev_token);
let mut tokens = vec![];
for i in 0..*lookahead {
let tok = parser.look_ahead(i, |tok| tok.kind.clone());
let is_eof = tok == TokenKind::Eof;
tokens.push(tok);
if is_eof {
// Don't look ahead past EOF.
break;
}
}
dbg_fmt.field_with("tokens", |field| field.debug_list().entries(tokens).finish());
dbg_fmt.field("approx_token_stream_pos", &parser.num_bump_calls);
// some fields are interesting for certain values, as they relate to macro parsing
if let Some(subparser) = parser.subparser_name {
dbg_fmt.field("subparser_name", &subparser);
}
if let Recovery::Forbidden = parser.recovery {
dbg_fmt.field("recovery", &parser.recovery);
}
// imply there's "more to know" than this view
dbg_fmt.finish_non_exhaustive()
}
}
DebugParser { parser: self, lookahead }
}
pub fn clear_expected_tokens(&mut self) {
self.expected_tokens.clear();
}
pub fn approx_token_stream_pos(&self) -> u32 {
self.num_bump_calls
}
}
pub(crate) fn make_unclosed_delims_error(
unmatched: UnmatchedDelim,
psess: &ParseSess,
) -> Option<Diag<'_>> {
// `None` here means an `Eof` was found. We already emit those errors elsewhere, we add them to
// `unmatched_delims` only for error recovery in the `Parser`.
let found_delim = unmatched.found_delim?;
let mut spans = vec![unmatched.found_span];
if let Some(sp) = unmatched.unclosed_span {
spans.push(sp);
};
let err = psess.dcx().create_err(MismatchedClosingDelimiter {
spans,
delimiter: pprust::token_kind_to_string(&token::CloseDelim(found_delim)).to_string(),
unmatched: unmatched.found_span,
opening_candidate: unmatched.candidate_span,
unclosed: unmatched.unclosed_span,
});
Some(err)
}
/// A helper struct used when building an `AttrTokenStream` from
/// a `LazyAttrTokenStream`. Both delimiter and non-delimited tokens
/// are stored as `FlatToken::Token`. A vector of `FlatToken`s
/// is then 'parsed' to build up an `AttrTokenStream` with nested
/// `AttrTokenTree::Delimited` tokens.
#[derive(Debug, Clone)]
enum FlatToken {
/// A token - this holds both delimiter (e.g. '{' and '}')
/// and non-delimiter tokens
Token((Token, Spacing)),
/// Holds the `AttrsTarget` for an AST node. The `AttrsTarget` is inserted
/// directly into the constructed `AttrTokenStream` as an
/// `AttrTokenTree::AttrsTarget`.
AttrsTarget(AttrsTarget),
/// A special 'empty' token that is ignored during the conversion
/// to an `AttrTokenStream`. This is used to simplify the
/// handling of replace ranges.
Empty,
}
// Metavar captures of various kinds.
#[derive(Clone, Debug)]
pub enum ParseNtResult {
Tt(TokenTree),
Ident(Ident, IdentIsRaw),
Lifetime(Ident, IdentIsRaw),
/// This case will eventually be removed, along with `Token::Interpolate`.
Nt(Lrc<Nonterminal>),
}