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Diffstat (limited to 'compiler/rustc_parse/src/parser/mod.rs')
| -rw-r--r-- | compiler/rustc_parse/src/parser/mod.rs | 1270 |
1 files changed, 1270 insertions, 0 deletions
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs new file mode 100644 index 00000000000..d67ed74bc99 --- /dev/null +++ b/compiler/rustc_parse/src/parser/mod.rs @@ -0,0 +1,1270 @@ +pub mod attr; +mod diagnostics; +mod expr; +mod generics; +mod item; +mod nonterminal; +mod pat; +mod path; +mod stmt; +mod ty; + +use crate::lexer::UnmatchedBrace; +use diagnostics::Error; +pub use path::PathStyle; + +use rustc_ast::ptr::P; +use rustc_ast::token::{self, DelimToken, Token, TokenKind}; +use rustc_ast::tokenstream::{self, DelimSpan, TokenStream, TokenTree, TreeAndJoint}; +use rustc_ast::DUMMY_NODE_ID; +use rustc_ast::{self as ast, AttrStyle, AttrVec, Const, CrateSugar, Extern, Unsafe}; +use rustc_ast::{Async, MacArgs, MacDelimiter, Mutability, StrLit, Visibility, VisibilityKind}; +use rustc_ast_pretty::pprust; +use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, FatalError, PResult}; +use rustc_session::parse::ParseSess; +use rustc_span::source_map::{respan, Span, DUMMY_SP}; +use rustc_span::symbol::{kw, sym, Ident, Symbol}; +use tracing::debug; + +use std::{cmp, mem, slice}; + +bitflags::bitflags! { + struct Restrictions: u8 { + const STMT_EXPR = 1 << 0; + const NO_STRUCT_LITERAL = 1 << 1; + } +} + +#[derive(Clone, Copy, PartialEq, Debug)] +enum SemiColonMode { + Break, + Ignore, + Comma, +} + +#[derive(Clone, Copy, PartialEq, Debug)] +enum BlockMode { + Break, + Ignore, +} + +/// Like `maybe_whole_expr`, but for things other than expressions. +#[macro_export] +macro_rules! maybe_whole { + ($p:expr, $constructor:ident, |$x:ident| $e:expr) => { + if let token::Interpolated(nt) = &$p.token.kind { + if let token::$constructor(x) = &**nt { + let $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 && $self.look_ahead(1, |t| t == &token::ModSep) { + if let token::Interpolated(nt) = &$self.token.kind { + if 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)] +pub struct Parser<'a> { + pub sess: &'a ParseSess, + /// The current token. + pub token: Token, + /// The previous token. + pub prev_token: Token, + restrictions: Restrictions, + expected_tokens: Vec<TokenType>, + token_cursor: TokenCursor, + desugar_doc_comments: bool, + /// 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: u32, + max_angle_bracket_count: u32, + /// A list of all unclosed delimiters found by the lexer. If an entry is used for error recovery + /// it gets removed from here. Every entry left at the end gets emitted as an independent + /// error. + pub(super) unclosed_delims: Vec<UnmatchedBrace>, + last_unexpected_token_span: Option<Span>, + /// Span pointing at the `:` for the last type ascription the parser has seen, and whether it + /// looked like it could have been a mistyped path or literal `Option:Some(42)`). + pub last_type_ascription: Option<(Span, bool /* likely path typo */)>, + /// If present, this `Parser` is not parsing Rust code but rather a macro call. + subparser_name: Option<&'static str>, +} + +impl<'a> Drop for Parser<'a> { + fn drop(&mut self) { + emit_unclosed_delims(&mut self.unclosed_delims, &self.sess); + } +} + +#[derive(Clone)] +struct TokenCursor { + frame: TokenCursorFrame, + stack: Vec<TokenCursorFrame>, + cur_token: Option<TreeAndJoint>, + collecting: Option<Collecting>, +} + +#[derive(Clone)] +struct TokenCursorFrame { + delim: token::DelimToken, + span: DelimSpan, + open_delim: bool, + tree_cursor: tokenstream::Cursor, + close_delim: bool, +} + +/// Used to track additional state needed by `collect_tokens` +#[derive(Clone, Debug)] +struct Collecting { + /// Holds the current tokens captured during the most + /// recent call to `collect_tokens` + buf: Vec<TreeAndJoint>, + /// The depth of the `TokenCursor` stack at the time + /// collection was started. When we encounter a `TokenTree::Delimited`, + /// we want to record the `TokenTree::Delimited` itself, + /// but *not* any of the inner tokens while we are inside + /// the new frame (this would cause us to record duplicate tokens). + /// + /// This `depth` fields tracks stack depth we are recording tokens. + /// Only tokens encountered at this depth will be recorded. See + /// `TokenCursor::next` for more details. + depth: usize, +} + +impl TokenCursorFrame { + fn new(span: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self { + TokenCursorFrame { + delim, + span, + open_delim: delim == token::NoDelim, + tree_cursor: tts.clone().into_trees(), + close_delim: delim == token::NoDelim, + } + } +} + +impl TokenCursor { + fn next(&mut self) -> Token { + loop { + let tree = if !self.frame.open_delim { + self.frame.open_delim = true; + TokenTree::open_tt(self.frame.span, self.frame.delim).into() + } else if let Some(tree) = self.frame.tree_cursor.next_with_joint() { + tree + } else if !self.frame.close_delim { + self.frame.close_delim = true; + TokenTree::close_tt(self.frame.span, self.frame.delim).into() + } else if let Some(frame) = self.stack.pop() { + self.frame = frame; + continue; + } else { + return Token::new(token::Eof, DUMMY_SP); + }; + + // Don't set an open delimiter as our current token - we want + // to leave it as the full `TokenTree::Delimited` from the previous + // iteration of this loop + if !matches!(tree.0, TokenTree::Token(Token { kind: TokenKind::OpenDelim(_), .. })) { + self.cur_token = Some(tree.clone()); + } + + if let Some(collecting) = &mut self.collecting { + if collecting.depth == self.stack.len() { + debug!( + "TokenCursor::next(): collected {:?} at depth {:?}", + tree, + self.stack.len() + ); + collecting.buf.push(tree.clone()) + } + } + + match tree.0 { + TokenTree::Token(token) => return token, + TokenTree::Delimited(sp, delim, tts) => { + let frame = TokenCursorFrame::new(sp, delim, &tts); + self.stack.push(mem::replace(&mut self.frame, frame)); + } + } + } + } + + fn next_desugared(&mut self) -> Token { + let (data, attr_style, sp) = match self.next() { + Token { kind: token::DocComment(_, attr_style, data), span } => { + (data, attr_style, span) + } + tok => return tok, + }; + + // Searches for the occurrences of `"#*` and returns the minimum number of `#`s + // required to wrap the text. + let mut num_of_hashes = 0; + let mut count = 0; + for ch in data.as_str().chars() { + count = match ch { + '"' => 1, + '#' if count > 0 => count + 1, + _ => 0, + }; + num_of_hashes = cmp::max(num_of_hashes, count); + } + + let delim_span = DelimSpan::from_single(sp); + let body = TokenTree::Delimited( + delim_span, + token::Bracket, + [ + TokenTree::token(token::Ident(sym::doc, false), sp), + TokenTree::token(token::Eq, sp), + TokenTree::token(TokenKind::lit(token::StrRaw(num_of_hashes), data, None), sp), + ] + .iter() + .cloned() + .collect::<TokenStream>(), + ); + + self.stack.push(mem::replace( + &mut self.frame, + TokenCursorFrame::new( + delim_span, + token::NoDelim, + &if attr_style == AttrStyle::Inner { + [TokenTree::token(token::Pound, sp), TokenTree::token(token::Not, sp), body] + .iter() + .cloned() + .collect::<TokenStream>() + } else { + [TokenTree::token(token::Pound, sp), body] + .iter() + .cloned() + .collect::<TokenStream>() + }, + ), + )); + + self.next() + } +} + +#[derive(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(ref 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 => "const".to_string(), + } + } +} + +#[derive(Copy, Clone, Debug)] +enum TokenExpectType { + Expect, + NoExpect, +} + +/// A sequence separator. +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 } + } +} + +pub enum FollowedByType { + Yes, + No, +} + +fn token_descr_opt(token: &Token) -> Option<&'static str> { + Some(match token.kind { + _ if token.is_special_ident() => "reserved identifier", + _ if token.is_used_keyword() => "keyword", + _ if token.is_unused_keyword() => "reserved keyword", + token::DocComment(..) => "doc comment", + _ => return None, + }) +} + +pub(super) fn token_descr(token: &Token) -> String { + let token_str = pprust::token_to_string(token); + match token_descr_opt(token) { + Some(prefix) => format!("{} `{}`", prefix, token_str), + _ => format!("`{}`", token_str), + } +} + +impl<'a> Parser<'a> { + pub fn new( + sess: &'a ParseSess, + tokens: TokenStream, + desugar_doc_comments: bool, + subparser_name: Option<&'static str>, + ) -> Self { + let mut parser = Parser { + sess, + token: Token::dummy(), + prev_token: Token::dummy(), + restrictions: Restrictions::empty(), + expected_tokens: Vec::new(), + token_cursor: TokenCursor { + frame: TokenCursorFrame::new(DelimSpan::dummy(), token::NoDelim, &tokens), + stack: Vec::new(), + cur_token: None, + collecting: None, + }, + desugar_doc_comments, + unmatched_angle_bracket_count: 0, + max_angle_bracket_count: 0, + unclosed_delims: Vec::new(), + last_unexpected_token_span: None, + last_type_ascription: None, + subparser_name, + }; + + // Make parser point to the first token. + parser.bump(); + + parser + } + + fn next_tok(&mut self, fallback_span: Span) -> Token { + let mut next = if self.desugar_doc_comments { + self.token_cursor.next_desugared() + } else { + self.token_cursor.next() + }; + if next.span.is_dummy() { + // Tweak the location for better diagnostics, but keep syntactic context intact. + next.span = fallback_span.with_ctxt(next.span.ctxt()); + } + next + } + + crate fn unexpected<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(), + } + } + + /// 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, bool /* recovered */> { + if self.expected_tokens.is_empty() { + if self.token == *t { + self.bump(); + Ok(false) + } 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. + pub fn expect_one_of( + &mut self, + edible: &[TokenKind], + inedible: &[TokenKind], + ) -> PResult<'a, bool /* recovered */> { + if edible.contains(&self.token.kind) { + self.bump(); + Ok(false) + } else if inedible.contains(&self.token.kind) { + // leave it in the input + Ok(false) + } else if self.last_unexpected_token_span == Some(self.token.span) { + FatalError.raise(); + } else { + self.expected_one_of_not_found(edible, inedible) + } + } + + // 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> { + match self.token.ident() { + Some((ident, is_raw)) => { + if !is_raw && ident.is_reserved() { + let mut err = self.expected_ident_found(); + if recover { + err.emit(); + } else { + return Err(err); + } + } + self.bump(); + Ok(ident) + } + _ => Err(match self.prev_token.kind { + TokenKind::DocComment(..) => { + self.span_fatal_err(self.prev_token.span, Error::UselessDocComment) + } + _ => self.expected_ident_found(), + }), + } + } + + /// 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. + 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 + } + + /// Consumes a token 'tok' if it exists. Returns whether the given token was present. + 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. + fn check_keyword(&mut self, kw: Symbol) -> bool { + self.expected_tokens.push(TokenType::Keyword(kw)); + self.token.is_keyword(kw) + } + + /// 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 rustfmt usage. + pub fn eat_keyword(&mut self, kw: Symbol) -> bool { + if self.check_keyword(kw) { + self.bump(); + true + } else { + false + } + } + + 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. + 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()) + } + + 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) + } + + /// Checks to see if the next token is either `+` or `+=`. + /// Otherwise returns `false`. + 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.kind == expected { + self.bump(); + return true; + } + match self.token.kind.break_two_token_op() { + Some((first, second)) if first == expected => { + let first_span = self.sess.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); + self.bump_with(Token::new(second, second_span)); + 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; + self.max_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() + } + } + + fn expect_any_with_type(&mut self, kets: &[&TokenKind], expect: TokenExpectType) -> bool { + kets.iter().any(|k| match expect { + TokenExpectType::Expect => self.check(k), + TokenExpectType::NoExpect => self.token == **k, + }) + } + + fn parse_seq_to_before_tokens<T>( + &mut self, + kets: &[&TokenKind], + sep: SeqSep, + expect: TokenExpectType, + mut f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>, + ) -> PResult<'a, (Vec<T>, bool /* trailing */, bool /* recovered */)> { + let mut first = true; + let mut recovered = false; + let mut trailing = false; + let mut v = vec![]; + while !self.expect_any_with_type(kets, expect) { + if let token::CloseDelim(..) | token::Eof = self.token.kind { + break; + } + if let Some(ref t) = sep.sep { + if first { + first = false; + } else { + match self.expect(t) { + Ok(false) => {} + Ok(true) => { + recovered = true; + break; + } + Err(mut expect_err) => { + let sp = self.prev_token.span.shrink_to_hi(); + let token_str = pprust::token_kind_to_string(t); + + // Attempt to keep parsing if it was a similar separator. + if let Some(ref 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.kind == 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 + .span_suggestion_verbose( + self.prev_token.span.shrink_to_hi().until(self.token.span), + &msg, + " @ ".to_string(), + Applicability::MaybeIncorrect, + ) + .emit(); + break; + } + + // Attempt to keep parsing if it was an omitted separator. + match f(self) { + Ok(t) => { + // Parsed successfully, therefore most probably the code only + // misses a separator. + expect_err + .span_suggestion_short( + self.sess.source_map().next_point(sp), + &format!("missing `{}`", token_str), + token_str, + Applicability::MaybeIncorrect, + ) + .emit(); + + v.push(t); + continue; + } + Err(mut e) => { + // Parsing failed, therefore it must be something more serious + // than just a missing separator. + expect_err.emit(); + + e.cancel(); + break; + } + } + } + } + } + } + if sep.trailing_sep_allowed && self.expect_any_with_type(kets, expect) { + trailing = true; + break; + } + + let t = f(self)?; + v.push(t); + } + + Ok((v, trailing, recovered)) + } + + /// Parses a sequence, not including the closing delimiter. 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, (Vec<T>, bool, bool)> { + self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f) + } + + /// Parses a sequence, including 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, (Vec<T>, bool /* trailing */)> { + let (val, trailing, recovered) = self.parse_seq_to_before_end(ket, sep, f)?; + if !recovered { + self.eat(ket); + } + Ok((val, trailing)) + } + + /// Parses a sequence, including the closing delimiter. 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, (Vec<T>, bool)> { + self.expect(bra)?; + self.parse_seq_to_end(ket, sep, f) + } + + fn parse_delim_comma_seq<T>( + &mut self, + delim: DelimToken, + f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>, + ) -> PResult<'a, (Vec<T>, bool)> { + self.parse_unspanned_seq( + &token::OpenDelim(delim), + &token::CloseDelim(delim), + SeqSep::trailing_allowed(token::Comma), + f, + ) + } + + fn parse_paren_comma_seq<T>( + &mut self, + f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>, + ) -> PResult<'a, (Vec<T>, bool)> { + self.parse_delim_comma_seq(token::Paren, f) + } + + /// Advance the parser by one token using provided token as the next one. + fn bump_with(&mut self, next_token: Token) { + // Bumping after EOF is a bad sign, usually an infinite loop. + if self.prev_token.kind == TokenKind::Eof { + let msg = "attempted to bump the parser past EOF (may be stuck in a loop)"; + self.span_bug(self.token.span, msg); + } + + // Update the current and previous tokens. + self.prev_token = mem::replace(&mut self.token, next_token); + + // Diagnostics. + self.expected_tokens.clear(); + } + + /// Advance the parser by one token. + pub fn bump(&mut self) { + let next_token = self.next_tok(self.token.span); + self.bump_with(next_token); + } + + /// Look-ahead `dist` tokens of `self.token` and get access to that token there. + /// When `dist == 0` then the current token is looked at. + pub fn look_ahead<R>(&self, dist: usize, looker: impl FnOnce(&Token) -> R) -> R { + if dist == 0 { + return looker(&self.token); + } + + let frame = &self.token_cursor.frame; + looker(&match frame.tree_cursor.look_ahead(dist - 1) { + Some(tree) => match tree { + TokenTree::Token(token) => token, + TokenTree::Delimited(dspan, delim, _) => { + Token::new(token::OpenDelim(delim), dspan.open) + } + }, + None => Token::new(token::CloseDelim(frame.delim), frame.span.close), + }) + } + + /// Returns whether any of the given keywords are `dist` tokens ahead of the current one. + 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_asyncness(&mut self) -> Async { + if self.eat_keyword(kw::Async) { + let span = self.prev_token.uninterpolated_span(); + Async::Yes { span, closure_id: DUMMY_NODE_ID, return_impl_trait_id: DUMMY_NODE_ID } + } else { + Async::No + } + } + + /// Parses unsafety: `unsafe` or nothing. + fn parse_unsafety(&mut self) -> Unsafe { + if self.eat_keyword(kw::Unsafe) { + Unsafe::Yes(self.prev_token.uninterpolated_span()) + } else { + Unsafe::No + } + } + + /// Parses constness: `const` or nothing. + fn parse_constness(&mut self) -> Const { + if self.eat_keyword(kw::Const) { + Const::Yes(self.prev_token.uninterpolated_span()) + } else { + Const::No + } + } + + /// Parses mutability (`mut` or nothing). + fn parse_mutability(&mut self) -> Mutability { + if self.eat_keyword(kw::Mut) { Mutability::Mut } else { Mutability::Not } + } + + /// 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 + { + self.expect_no_suffix(self.token.span, "a tuple index", suffix); + self.bump(); + Ok(Ident::new(symbol, self.prev_token.span)) + } else { + self.parse_ident_common(false) + } + } + + fn parse_mac_args(&mut self) -> PResult<'a, P<MacArgs>> { + self.parse_mac_args_common(true).map(P) + } + + fn parse_attr_args(&mut self) -> PResult<'a, MacArgs> { + self.parse_mac_args_common(false) + } + + fn parse_mac_args_common(&mut self, delimited_only: bool) -> PResult<'a, MacArgs> { + Ok( + if self.check(&token::OpenDelim(DelimToken::Paren)) + || self.check(&token::OpenDelim(DelimToken::Bracket)) + || self.check(&token::OpenDelim(DelimToken::Brace)) + { + match self.parse_token_tree() { + TokenTree::Delimited(dspan, delim, tokens) => + // We've confirmed above that there is a delimiter so unwrapping is OK. + { + MacArgs::Delimited(dspan, MacDelimiter::from_token(delim).unwrap(), tokens) + } + _ => unreachable!(), + } + } else if !delimited_only { + if self.eat(&token::Eq) { + let eq_span = self.prev_token.span; + let mut is_interpolated_expr = false; + if let token::Interpolated(nt) = &self.token.kind { + if let token::NtExpr(..) = **nt { + is_interpolated_expr = true; + } + } + let token_tree = if is_interpolated_expr { + // We need to accept arbitrary interpolated expressions to continue + // supporting things like `doc = $expr` that work on stable. + // Non-literal interpolated expressions are rejected after expansion. + self.parse_token_tree() + } else { + self.parse_unsuffixed_lit()?.token_tree() + }; + + MacArgs::Eq(eq_span, token_tree.into()) + } else { + MacArgs::Empty + } + } else { + return self.unexpected(); + }, + ) + } + + fn parse_or_use_outer_attributes( + &mut self, + already_parsed_attrs: Option<AttrVec>, + ) -> PResult<'a, AttrVec> { + if let Some(attrs) = already_parsed_attrs { + Ok(attrs) + } else { + self.parse_outer_attributes().map(|a| a.into()) + } + } + + /// Parses a single token tree from the input. + pub(crate) fn parse_token_tree(&mut self) -> TokenTree { + match self.token.kind { + token::OpenDelim(..) => { + let frame = mem::replace( + &mut self.token_cursor.frame, + self.token_cursor.stack.pop().unwrap(), + ); + self.token = Token::new(TokenKind::CloseDelim(frame.delim), frame.span.close); + self.bump(); + TokenTree::Delimited(frame.span, frame.delim, frame.tree_cursor.stream) + } + token::CloseDelim(_) | token::Eof => unreachable!(), + _ => { + self.bump(); + TokenTree::Token(self.prev_token.clone()) + } + } + } + + /// Parses a stream of tokens into a list of `TokenTree`s, up to EOF. + pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> { + let mut tts = Vec::new(); + while self.token != token::Eof { + tts.push(self.parse_token_tree()); + } + Ok(tts) + } + + 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().into()), + } + } + 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 + } + + fn is_crate_vis(&self) -> bool { + self.token.is_keyword(kw::Crate) && self.look_ahead(1, |t| t != &token::ModSep) + } + + /// Parses `pub`, `pub(crate)` and `pub(in path)` plus shortcuts `crate` for `pub(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 isn't valid, + /// so emit a proper diagnostic. + pub(crate) fn parse_visibility(&mut self, fbt: FollowedByType) -> PResult<'a, Visibility> { + maybe_whole!(self, NtVis, |x| x); + + self.expected_tokens.push(TokenType::Keyword(kw::Crate)); + if self.is_crate_vis() { + self.bump(); // `crate` + self.sess.gated_spans.gate(sym::crate_visibility_modifier, self.prev_token.span); + return Ok(respan(self.prev_token.span, VisibilityKind::Crate(CrateSugar::JustCrate))); + } + + 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(respan(self.token.span.shrink_to_lo(), VisibilityKind::Inherited)); + } + let lo = self.prev_token.span; + + if self.check(&token::OpenDelim(token::Paren)) { + // 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::Crate]) && self.look_ahead(2, |t| t != &token::ModSep) + // account for `pub(crate::foo)` + { + // Parse `pub(crate)`. + self.bump(); // `(` + self.bump(); // `crate` + self.expect(&token::CloseDelim(token::Paren))?; // `)` + let vis = VisibilityKind::Crate(CrateSugar::PubCrate); + return Ok(respan(lo.to(self.prev_token.span), vis)); + } else 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(token::Paren))?; // `)` + let vis = VisibilityKind::Restricted { path: P(path), id: ast::DUMMY_NODE_ID }; + return Ok(respan(lo.to(self.prev_token.span), vis)); + } else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) + && self.is_keyword_ahead(1, &[kw::Super, kw::SelfLower]) + { + // Parse `pub(self)` or `pub(super)`. + self.bump(); // `(` + let path = self.parse_path(PathStyle::Mod)?; // `super`/`self` + self.expect(&token::CloseDelim(token::Paren))?; // `)` + let vis = VisibilityKind::Restricted { path: P(path), id: ast::DUMMY_NODE_ID }; + return Ok(respan(lo.to(self.prev_token.span), vis)); + } 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(respan(lo, VisibilityKind::Public)) + } + + /// 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(token::Paren))?; // `)` + + let msg = "incorrect visibility restriction"; + let suggestion = r##"some possible visibility restrictions are: +`pub(crate)`: visible only on the current crate +`pub(super)`: visible only in the current module's parent +`pub(in path::to::module)`: visible only on the specified path"##; + + let path_str = pprust::path_to_string(&path); + + struct_span_err!(self.sess.span_diagnostic, path.span, E0704, "{}", msg) + .help(suggestion) + .span_suggestion( + path.span, + &format!("make this visible only to module `{}` with `in`", path_str), + format!("in {}", path_str), + Applicability::MachineApplicable, + ) + .emit(); + + Ok(()) + } + + /// Parses `extern string_literal?`. + fn parse_extern(&mut self) -> PResult<'a, Extern> { + Ok(if self.eat_keyword(kw::Extern) { + Extern::from_abi(self.parse_abi()) + } 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.struct_span_err(lit.span, "non-string ABI literal") + .span_suggestion( + lit.span, + "specify the ABI with a string literal", + "\"C\"".to_string(), + Applicability::MaybeIncorrect, + ) + .emit(); + None + } + }, + Err(None) => None, + } + } + + /// Records all tokens consumed by the provided callback, + /// including the current token. These tokens are collected + /// into a `TokenStream`, and returned along with the result + /// of the callback. + /// + /// Note: If your callback consumes an opening delimiter + /// (including the case where you call `collect_tokens` + /// when the current token is an opening delimeter), + /// you must also consume the corresponding closing delimiter. + /// + /// That is, you can consume + /// `something ([{ }])` or `([{}])`, but not `([{}]` + /// + /// This restriction shouldn't be an issue in practice, + /// since this function is used to record the tokens for + /// a parsed AST item, which always has matching delimiters. + pub fn collect_tokens<R>( + &mut self, + f: impl FnOnce(&mut Self) -> PResult<'a, R>, + ) -> PResult<'a, (R, TokenStream)> { + // Record all tokens we parse when parsing this item. + let tokens: Vec<TreeAndJoint> = self.token_cursor.cur_token.clone().into_iter().collect(); + debug!("collect_tokens: starting with {:?}", tokens); + + // We need special handling for the case where `collect_tokens` is called + // on an opening delimeter (e.g. '('). At this point, we have already pushed + // a new frame - however, we want to record the original `TokenTree::Delimited`, + // for consistency with the case where we start recording one token earlier. + // See `TokenCursor::next` to see how `cur_token` is set up. + let prev_depth = + if matches!(self.token_cursor.cur_token, Some((TokenTree::Delimited(..), _))) { + if self.token_cursor.stack.is_empty() { + // There is nothing below us in the stack that + // the function could consume, so the only thing it can legally + // capture is the entire contents of the current frame. + return Ok((f(self)?, TokenStream::new(tokens))); + } + // We have already recorded the full `TokenTree::Delimited` when we created + // our `tokens` vector at the start of this function. We are now inside + // a new frame corresponding to the `TokenTree::Delimited` we already recoreded. + // We don't want to record any of the tokens inside this frame, since they + // will be duplicates of the tokens nested inside the `TokenTree::Delimited`. + // Therefore, we set our recording depth to the *previous* frame. This allows + // us to record a sequence like: `(foo).bar()`: the `(foo)` will be recored + // as our initial `cur_token`, while the `.bar()` will be recored after we + // pop the `(foo)` frame. + self.token_cursor.stack.len() - 1 + } else { + self.token_cursor.stack.len() + }; + let prev_collecting = + self.token_cursor.collecting.replace(Collecting { buf: tokens, depth: prev_depth }); + + let ret = f(self); + + let mut collected_tokens = if let Some(collecting) = self.token_cursor.collecting.take() { + collecting.buf + } else { + let msg = "our vector went away?"; + debug!("collect_tokens: {}", msg); + self.sess.span_diagnostic.delay_span_bug(self.token.span, &msg); + // This can happen due to a bad interaction of two unrelated recovery mechanisms + // with mismatched delimiters *and* recovery lookahead on the likely typo + // `pub ident(` (#62895, different but similar to the case above). + return Ok((ret?, TokenStream::default())); + }; + + debug!("collect_tokens: got raw tokens {:?}", collected_tokens); + + // If we're not at EOF our current token wasn't actually consumed by + // `f`, but it'll still be in our list that we pulled out. In that case + // put it back. + let extra_token = if self.token != token::Eof { collected_tokens.pop() } else { None }; + + if let Some(mut collecting) = prev_collecting { + // If we were previously collecting at the same depth, + // then the previous call to `collect_tokens` needs to see + // the tokens we just recorded. + // + // If we were previously recording at an lower `depth`, + // then the previous `collect_tokens` call already recorded + // this entire frame in the form of a `TokenTree::Delimited`, + // so there is nothing else for us to do. + if collecting.depth == prev_depth { + collecting.buf.extend(collected_tokens.iter().cloned()); + collecting.buf.extend(extra_token); + debug!("collect_tokens: updating previous buf to {:?}", collecting); + } + self.token_cursor.collecting = Some(collecting) + } + + Ok((ret?, TokenStream::new(collected_tokens))) + } + + /// `::{` or `::*` + fn is_import_coupler(&mut self) -> bool { + self.check(&token::ModSep) + && self.look_ahead(1, |t| { + *t == token::OpenDelim(token::Brace) || *t == token::BinOp(token::Star) + }) + } +} + +crate fn make_unclosed_delims_error( + unmatched: UnmatchedBrace, + sess: &ParseSess, +) -> Option<DiagnosticBuilder<'_>> { + // `None` here means an `Eof` was found. We already emit those errors elsewhere, we add them to + // `unmatched_braces` only for error recovery in the `Parser`. + let found_delim = unmatched.found_delim?; + let mut err = sess.span_diagnostic.struct_span_err( + unmatched.found_span, + &format!( + "mismatched closing delimiter: `{}`", + pprust::token_kind_to_string(&token::CloseDelim(found_delim)), + ), + ); + err.span_label(unmatched.found_span, "mismatched closing delimiter"); + if let Some(sp) = unmatched.candidate_span { + err.span_label(sp, "closing delimiter possibly meant for this"); + } + if let Some(sp) = unmatched.unclosed_span { + err.span_label(sp, "unclosed delimiter"); + } + Some(err) +} + +pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, sess: &ParseSess) { + *sess.reached_eof.borrow_mut() |= + unclosed_delims.iter().any(|unmatched_delim| unmatched_delim.found_delim.is_none()); + for unmatched in unclosed_delims.drain(..) { + if let Some(mut e) = make_unclosed_delims_error(unmatched, sess) { + e.emit(); + } + } +} |