diff options
Diffstat (limited to 'src/libsyntax/parse/parser.rs')
| -rw-r--r-- | src/libsyntax/parse/parser.rs | 111 |
1 files changed, 58 insertions, 53 deletions
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs index eac78f5e6c6..463ec334cc5 100644 --- a/src/libsyntax/parse/parser.rs +++ b/src/libsyntax/parse/parser.rs @@ -245,6 +245,22 @@ enum PrevTokenKind { Other, } +// Simple circular buffer used for keeping few next tokens. +#[derive(Default)] +struct LookaheadBuffer { + buffer: [TokenAndSpan; LOOKAHEAD_BUFFER_CAPACITY], + start: usize, + end: usize, +} + +const LOOKAHEAD_BUFFER_CAPACITY: usize = 8; + +impl LookaheadBuffer { + fn len(&self) -> usize { + (LOOKAHEAD_BUFFER_CAPACITY + self.end - self.start) % LOOKAHEAD_BUFFER_CAPACITY + } +} + /* ident is handled by common.rs */ pub struct Parser<'a> { @@ -258,9 +274,7 @@ pub struct Parser<'a> { pub cfg: CrateConfig, /// the previous token kind prev_token_kind: PrevTokenKind, - pub buffer: [TokenAndSpan; 4], - pub buffer_start: isize, - pub buffer_end: isize, + lookahead_buffer: LookaheadBuffer, pub tokens_consumed: usize, pub restrictions: Restrictions, pub quote_depth: usize, // not (yet) related to the quasiquoter @@ -356,10 +370,6 @@ impl<'a> Parser<'a> { _ => PathBuf::from(sess.codemap().span_to_filename(span)), }; directory.pop(); - let placeholder = TokenAndSpan { - tok: token::Underscore, - sp: span, - }; Parser { reader: rdr, @@ -369,14 +379,7 @@ impl<'a> Parser<'a> { span: span, prev_span: span, prev_token_kind: PrevTokenKind::Other, - buffer: [ - placeholder.clone(), - placeholder.clone(), - placeholder.clone(), - placeholder.clone(), - ], - buffer_start: 0, - buffer_end: 0, + lookahead_buffer: Default::default(), tokens_consumed: 0, restrictions: Restrictions::empty(), quote_depth: 0, @@ -937,19 +940,13 @@ impl<'a> Parser<'a> { _ => PrevTokenKind::Other, }; - let next = if self.buffer_start == self.buffer_end { + let next = if self.lookahead_buffer.start == self.lookahead_buffer.end { self.reader.real_token() } else { // Avoid token copies with `replace`. - let buffer_start = self.buffer_start as usize; - let next_index = (buffer_start + 1) & 3; - self.buffer_start = next_index as isize; - - let placeholder = TokenAndSpan { - tok: token::Underscore, - sp: self.span, - }; - mem::replace(&mut self.buffer[buffer_start], placeholder) + let old_start = self.lookahead_buffer.start; + self.lookahead_buffer.start = (old_start + 1) % LOOKAHEAD_BUFFER_CAPACITY; + mem::replace(&mut self.lookahead_buffer.buffer[old_start], Default::default()) }; self.span = next.sp; self.token = next.tok; @@ -982,21 +979,22 @@ impl<'a> Parser<'a> { self.expected_tokens.clear(); } - pub fn buffer_length(&mut self) -> isize { - if self.buffer_start <= self.buffer_end { - return self.buffer_end - self.buffer_start; - } - return (4 - self.buffer_start) + self.buffer_end; - } - pub fn look_ahead<R, F>(&mut self, distance: usize, f: F) -> R where + pub fn look_ahead<R, F>(&mut self, dist: usize, f: F) -> R where F: FnOnce(&token::Token) -> R, { - let dist = distance as isize; - while self.buffer_length() < dist { - self.buffer[self.buffer_end as usize] = self.reader.real_token(); - self.buffer_end = (self.buffer_end + 1) & 3; + if dist == 0 { + f(&self.token) + } else if dist < LOOKAHEAD_BUFFER_CAPACITY { + while self.lookahead_buffer.len() < dist { + self.lookahead_buffer.buffer[self.lookahead_buffer.end] = self.reader.real_token(); + self.lookahead_buffer.end = + (self.lookahead_buffer.end + 1) % LOOKAHEAD_BUFFER_CAPACITY; + } + let index = (self.lookahead_buffer.start + dist - 1) % LOOKAHEAD_BUFFER_CAPACITY; + f(&self.lookahead_buffer.buffer[index].tok) + } else { + self.bug("lookahead distance is too large"); } - f(&self.buffer[((self.buffer_start + dist - 1) & 3) as usize].tok) } pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> { self.sess.span_diagnostic.struct_span_fatal(self.span, m) @@ -1118,7 +1116,6 @@ impl<'a> Parser<'a> { Ok(ast::TyKind::ImplTrait(bounds)) } - pub fn parse_ty_path(&mut self) -> PResult<'a, TyKind> { Ok(TyKind::Path(None, self.parse_path(PathStyle::Type)?)) } @@ -3623,7 +3620,7 @@ impl<'a> Parser<'a> { // Parse box pat let subpat = self.parse_pat()?; pat = PatKind::Box(subpat); - } else if self.token.is_ident() && self.token.is_path_start() && + } else if self.token.is_ident() && !self.token.is_any_keyword() && self.look_ahead(1, |t| match *t { token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) | token::DotDotDot | token::ModSep | token::Not => false, @@ -3874,6 +3871,11 @@ impl<'a> Parser<'a> { }) } + fn is_union_item(&mut self) -> bool { + self.token.is_keyword(keywords::Union) && + self.look_ahead(1, |t| t.is_ident() && !t.is_any_keyword()) + } + fn parse_stmt_without_recovery(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> { @@ -3888,10 +3890,10 @@ impl<'a> Parser<'a> { node: StmtKind::Local(self.parse_local(attrs.into())?), span: mk_sp(lo, self.prev_span.hi), } - } else if self.token.is_path_start() && self.token != token::Lt && { - !self.check_keyword(keywords::Union) || - self.look_ahead(1, |t| *t == token::Not || *t == token::ModSep) - } { + // Starts like a simple path, but not a union item. + } else if self.token.is_path_start() && + !self.token.is_qpath_start() && + !self.is_union_item() { let pth = self.parse_path(PathStyle::Expr)?; if !self.eat(&token::Not) { @@ -4602,6 +4604,10 @@ impl<'a> Parser<'a> { token::Ident(ident) => { this.bump(); codemap::respan(this.prev_span, ident) } _ => unreachable!() }; + let isolated_self = |this: &mut Self, n| { + this.look_ahead(n, |t| t.is_keyword(keywords::SelfValue)) && + this.look_ahead(n + 1, |t| t != &token::ModSep) + }; // Parse optional self parameter of a method. // Only a limited set of initial token sequences is considered self parameters, anything @@ -4614,22 +4620,22 @@ impl<'a> Parser<'a> { // &'lt self // &'lt mut self // ¬_self - if self.look_ahead(1, |t| t.is_keyword(keywords::SelfValue)) { + if isolated_self(self, 1) { self.bump(); (SelfKind::Region(None, Mutability::Immutable), expect_ident(self)) } else if self.look_ahead(1, |t| t.is_keyword(keywords::Mut)) && - self.look_ahead(2, |t| t.is_keyword(keywords::SelfValue)) { + isolated_self(self, 2) { self.bump(); self.bump(); (SelfKind::Region(None, Mutability::Mutable), expect_ident(self)) } else if self.look_ahead(1, |t| t.is_lifetime()) && - self.look_ahead(2, |t| t.is_keyword(keywords::SelfValue)) { + isolated_self(self, 2) { self.bump(); let lt = self.parse_lifetime()?; (SelfKind::Region(Some(lt), Mutability::Immutable), expect_ident(self)) } else if self.look_ahead(1, |t| t.is_lifetime()) && self.look_ahead(2, |t| t.is_keyword(keywords::Mut)) && - self.look_ahead(3, |t| t.is_keyword(keywords::SelfValue)) { + isolated_self(self, 3) { self.bump(); let lt = self.parse_lifetime()?; self.bump(); @@ -4644,12 +4650,12 @@ impl<'a> Parser<'a> { // *mut self // *not_self // Emit special error for `self` cases. - if self.look_ahead(1, |t| t.is_keyword(keywords::SelfValue)) { + if isolated_self(self, 1) { self.bump(); self.span_err(self.span, "cannot pass `self` by raw pointer"); (SelfKind::Value(Mutability::Immutable), expect_ident(self)) } else if self.look_ahead(1, |t| t.is_mutability()) && - self.look_ahead(2, |t| t.is_keyword(keywords::SelfValue)) { + isolated_self(self, 2) { self.bump(); self.bump(); self.span_err(self.span, "cannot pass `self` by raw pointer"); @@ -4659,7 +4665,7 @@ impl<'a> Parser<'a> { } } token::Ident(..) => { - if self.token.is_keyword(keywords::SelfValue) { + if isolated_self(self, 0) { // self // self: TYPE let eself_ident = expect_ident(self); @@ -4670,7 +4676,7 @@ impl<'a> Parser<'a> { (SelfKind::Value(Mutability::Immutable), eself_ident) } } else if self.token.is_keyword(keywords::Mut) && - self.look_ahead(1, |t| t.is_keyword(keywords::SelfValue)) { + isolated_self(self, 1) { // mut self // mut self: TYPE self.bump(); @@ -5961,8 +5967,7 @@ impl<'a> Parser<'a> { maybe_append(attrs, extra_attrs)); return Ok(Some(item)); } - if self.check_keyword(keywords::Union) && - self.look_ahead(1, |t| t.is_ident() && !t.is_any_keyword()) { + if self.is_union_item() { // UNION ITEM self.bump(); let (ident, item_, extra_attrs) = self.parse_item_union()?; |