From 61f15b72ac52c23148038b3867198597b345e2f6 Mon Sep 17 00:00:00 2001 From: Aleksey Kladov Date: Tue, 9 Feb 2021 21:52:34 +0300 Subject: [PATCH] Add parsing benchmark --- bench_data/glorious_old_parser | 8562 +++++++++++++++++++ crates/ide/src/syntax_highlighting/tests.rs | 37 +- crates/syntax/src/tests.rs | 28 +- crates/test_utils/src/bench_fixture.rs | 9 + 4 files changed, 8628 insertions(+), 8 deletions(-) create mode 100644 bench_data/glorious_old_parser diff --git a/bench_data/glorious_old_parser b/bench_data/glorious_old_parser new file mode 100644 index 0000000000..7e900dfeb1 --- /dev/null +++ b/bench_data/glorious_old_parser @@ -0,0 +1,8562 @@ +use crate::ast::{AngleBracketedArgs, ParenthesizedArgs, AttrStyle, BareFnTy}; +use crate::ast::{GenericBound, TraitBoundModifier}; +use crate::ast::Unsafety; +use crate::ast::{Mod, AnonConst, Arg, Arm, Guard, Attribute, BindingMode, TraitItemKind}; +use crate::ast::Block; +use crate::ast::{BlockCheckMode, CaptureBy, Movability}; +use crate::ast::{Constness, Crate}; +use crate::ast::Defaultness; +use crate::ast::EnumDef; +use crate::ast::{Expr, ExprKind, RangeLimits}; +use crate::ast::{Field, FnDecl, FnHeader}; +use crate::ast::{ForeignItem, ForeignItemKind, FunctionRetTy}; +use crate::ast::{GenericParam, GenericParamKind}; +use crate::ast::GenericArg; +use crate::ast::{Ident, ImplItem, IsAsync, IsAuto, Item, ItemKind}; +use crate::ast::{Label, Lifetime, Lit, LitKind}; +use crate::ast::Local; +use crate::ast::MacStmtStyle; +use crate::ast::{Mac, Mac_, MacDelimiter}; +use crate::ast::{MutTy, Mutability}; +use crate::ast::{Pat, PatKind, PathSegment}; +use crate::ast::{PolyTraitRef, QSelf}; +use crate::ast::{Stmt, StmtKind}; +use crate::ast::{VariantData, StructField}; +use crate::ast::StrStyle; +use crate::ast::SelfKind; +use crate::ast::{TraitItem, TraitRef, TraitObjectSyntax}; +use crate::ast::{Ty, TyKind, TypeBinding, GenericBounds}; +use crate::ast::{Visibility, VisibilityKind, WhereClause, CrateSugar}; +use crate::ast::{UseTree, UseTreeKind}; +use crate::ast::{BinOpKind, UnOp}; +use crate::ast::{RangeEnd, RangeSyntax}; +use crate::{ast, attr}; +use crate::ext::base::DummyResult; +use crate::source_map::{self, SourceMap, Spanned, respan}; +use crate::parse::{self, SeqSep, classify, token}; +use crate::parse::lexer::{TokenAndSpan, UnmatchedBrace}; +use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration}; +use crate::parse::token::DelimToken; +use crate::parse::{new_sub_parser_from_file, ParseSess, Directory, DirectoryOwnership}; +use crate::util::parser::{AssocOp, Fixity}; +use crate::print::pprust; +use crate::ptr::P; +use crate::parse::PResult; +use crate::ThinVec; +use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint}; +use crate::symbol::{Symbol, keywords}; + +use errors::{Applicability, DiagnosticBuilder, DiagnosticId}; +use rustc_target::spec::abi::{self, Abi}; +use syntax_pos::{Span, MultiSpan, BytePos, FileName}; +use log::{debug, trace}; + +use std::borrow::Cow; +use std::cmp; +use std::mem; +use std::path::{self, Path, PathBuf}; +use std::slice; + +#[derive(Debug)] +/// Whether the type alias or associated type is a concrete type or an existential type +pub enum AliasKind { + /// Just a new name for the same type + Weak(P), + /// Only trait impls of the type will be usable, not the actual type itself + Existential(GenericBounds), +} + +bitflags::bitflags! { + struct Restrictions: u8 { + const STMT_EXPR = 1 << 0; + const NO_STRUCT_LITERAL = 1 << 1; + } +} + +type ItemInfo = (Ident, ItemKind, Option>); + +/// Specifies how to parse a path. +#[derive(Copy, Clone, PartialEq)] +pub enum PathStyle { + /// In some contexts, notably in expressions, paths with generic arguments are ambiguous + /// with something else. For example, in expressions `segment < ....` can be interpreted + /// as a comparison and `segment ( ....` can be interpreted as a function call. + /// In all such contexts the non-path interpretation is preferred by default for practical + /// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g. + /// `x` - comparisons, `x::` - unambiguously a path. + Expr, + /// In other contexts, notably in types, no ambiguity exists and paths can be written + /// without the disambiguator, e.g., `x` - unambiguously a path. + /// Paths with disambiguators are still accepted, `x::` - unambiguously a path too. + Type, + /// A path with generic arguments disallowed, e.g., `foo::bar::Baz`, used in imports, + /// visibilities or attributes. + /// Technically, this variant is unnecessary and e.g., `Expr` can be used instead + /// (paths in "mod" contexts have to be checked later for absence of generic arguments + /// anyway, due to macros), but it is used to avoid weird suggestions about expected + /// tokens when something goes wrong. + Mod, +} + +#[derive(Clone, Copy, PartialEq, Debug)] +enum SemiColonMode { + Break, + Ignore, + Comma, +} + +#[derive(Clone, Copy, PartialEq, Debug)] +enum BlockMode { + Break, + Ignore, +} + +/// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression +/// dropped into the token stream, which happens while parsing the result of +/// macro expansion). Placement of these is not as complex as I feared it would +/// be. The important thing is to make sure that lookahead doesn't balk at +/// `token::Interpolated` tokens. +macro_rules! maybe_whole_expr { + ($p:expr) => { + if let token::Interpolated(nt) = $p.token.clone() { + match *nt { + token::NtExpr(ref e) | token::NtLiteral(ref e) => { + $p.bump(); + return Ok((*e).clone()); + } + token::NtPath(ref path) => { + $p.bump(); + let span = $p.span; + let kind = ExprKind::Path(None, (*path).clone()); + return Ok($p.mk_expr(span, kind, ThinVec::new())); + } + token::NtBlock(ref block) => { + $p.bump(); + let span = $p.span; + let kind = ExprKind::Block((*block).clone(), None); + return Ok($p.mk_expr(span, kind, ThinVec::new())); + } + _ => {}, + }; + } + } +} + +/// As maybe_whole_expr, but for things other than expressions +macro_rules! maybe_whole { + ($p:expr, $constructor:ident, |$x:ident| $e:expr) => { + if let token::Interpolated(nt) = $p.token.clone() { + if let token::$constructor($x) = (*nt).clone() { + $p.bump(); + return Ok($e); + } + } + }; +} + +fn maybe_append(mut lhs: Vec, mut rhs: Option>) -> Vec { + if let Some(ref mut rhs) = rhs { + lhs.append(rhs); + } + lhs +} + +#[derive(Debug, Clone, Copy, PartialEq)] +enum PrevTokenKind { + DocComment, + Comma, + Plus, + Interpolated, + Eof, + Ident, + Other, +} + +trait RecoverQPath: Sized { + const PATH_STYLE: PathStyle = PathStyle::Expr; + fn to_ty(&self) -> Option>; + fn to_recovered(&self, qself: Option, path: ast::Path) -> Self; + fn to_string(&self) -> String; +} + +impl RecoverQPath for Ty { + const PATH_STYLE: PathStyle = PathStyle::Type; + fn to_ty(&self) -> Option> { + Some(P(self.clone())) + } + fn to_recovered(&self, qself: Option, path: ast::Path) -> Self { + Self { span: path.span, node: TyKind::Path(qself, path), id: self.id } + } + fn to_string(&self) -> String { + pprust::ty_to_string(self) + } +} + +impl RecoverQPath for Pat { + fn to_ty(&self) -> Option> { + self.to_ty() + } + fn to_recovered(&self, qself: Option, path: ast::Path) -> Self { + Self { span: path.span, node: PatKind::Path(qself, path), id: self.id } + } + fn to_string(&self) -> String { + pprust::pat_to_string(self) + } +} + +impl RecoverQPath for Expr { + fn to_ty(&self) -> Option> { + self.to_ty() + } + fn to_recovered(&self, qself: Option, path: ast::Path) -> Self { + Self { span: path.span, node: ExprKind::Path(qself, path), + id: self.id, attrs: self.attrs.clone() } + } + fn to_string(&self) -> String { + pprust::expr_to_string(self) + } +} + +/* ident is handled by common.rs */ + +#[derive(Clone)] +pub struct Parser<'a> { + pub sess: &'a ParseSess, + /// the current token: + pub token: token::Token, + /// the span of the current token: + pub span: Span, + /// the span of the previous token: + meta_var_span: Option, + pub prev_span: Span, + /// the previous token kind + prev_token_kind: PrevTokenKind, + restrictions: Restrictions, + /// Used to determine the path to externally loaded source files + crate directory: Directory<'a>, + /// Whether to parse sub-modules in other files. + pub recurse_into_file_modules: bool, + /// Name of the root module this parser originated from. If `None`, then the + /// name is not known. This does not change while the parser is descending + /// into modules, and sub-parsers have new values for this name. + pub root_module_name: Option, + crate expected_tokens: Vec, + token_cursor: TokenCursor, + desugar_doc_comments: bool, + /// Whether we should configure out of line modules as we parse. + pub cfg_mods: 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. + crate unmatched_angle_bracket_count: u32, + crate max_angle_bracket_count: u32, + /// 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. + crate unclosed_delims: Vec, +} + + +#[derive(Clone)] +struct TokenCursor { + frame: TokenCursorFrame, + stack: Vec, +} + +#[derive(Clone)] +struct TokenCursorFrame { + delim: token::DelimToken, + span: DelimSpan, + open_delim: bool, + tree_cursor: tokenstream::Cursor, + close_delim: bool, + last_token: LastToken, +} + +/// This is used in `TokenCursorFrame` above to track tokens that are consumed +/// by the parser, and then that's transitively used to record the tokens that +/// each parse AST item is created with. +/// +/// Right now this has two states, either collecting tokens or not collecting +/// tokens. If we're collecting tokens we just save everything off into a local +/// `Vec`. This should eventually though likely save tokens from the original +/// token stream and just use slicing of token streams to avoid creation of a +/// whole new vector. +/// +/// The second state is where we're passively not recording tokens, but the last +/// token is still tracked for when we want to start recording tokens. This +/// "last token" means that when we start recording tokens we'll want to ensure +/// that this, the first token, is included in the output. +/// +/// You can find some more example usage of this in the `collect_tokens` method +/// on the parser. +#[derive(Clone)] +enum LastToken { + Collecting(Vec), + Was(Option), +} + +impl TokenCursorFrame { + fn new(sp: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self { + TokenCursorFrame { + delim: delim, + span: sp, + open_delim: delim == token::NoDelim, + tree_cursor: tts.clone().into_trees(), + close_delim: delim == token::NoDelim, + last_token: LastToken::Was(None), + } + } +} + +impl TokenCursor { + fn next(&mut self) -> TokenAndSpan { + loop { + let tree = if !self.frame.open_delim { + self.frame.open_delim = true; + TokenTree::open_tt(self.frame.span.open, self.frame.delim) + } else if let Some(tree) = self.frame.tree_cursor.next() { + tree + } else if !self.frame.close_delim { + self.frame.close_delim = true; + TokenTree::close_tt(self.frame.span.close, self.frame.delim) + } else if let Some(frame) = self.stack.pop() { + self.frame = frame; + continue + } else { + return TokenAndSpan { tok: token::Eof, sp: syntax_pos::DUMMY_SP } + }; + + match self.frame.last_token { + LastToken::Collecting(ref mut v) => v.push(tree.clone().into()), + LastToken::Was(ref mut t) => *t = Some(tree.clone().into()), + } + + match tree { + TokenTree::Token(sp, tok) => return TokenAndSpan { tok: tok, sp: sp }, + 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) -> TokenAndSpan { + let (sp, name) = match self.next() { + TokenAndSpan { sp, tok: token::DocComment(name) } => (sp, name), + tok => return tok, + }; + + let stripped = strip_doc_comment_decoration(&name.as_str()); + + // 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 stripped.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(sp, token::Ident(ast::Ident::from_str("doc"), false)), + TokenTree::Token(sp, token::Eq), + TokenTree::Token(sp, token::Literal( + token::StrRaw(Symbol::intern(&stripped), num_of_hashes), None)) + ] + .iter().cloned().collect::().into(), + ); + + self.stack.push(mem::replace(&mut self.frame, TokenCursorFrame::new( + delim_span, + token::NoDelim, + &if doc_comment_style(&name.as_str()) == AttrStyle::Inner { + [TokenTree::Token(sp, token::Pound), TokenTree::Token(sp, token::Not), body] + .iter().cloned().collect::().into() + } else { + [TokenTree::Token(sp, token::Pound), body] + .iter().cloned().collect::().into() + }, + ))); + + self.next() + } +} + +#[derive(Clone, PartialEq)] +crate enum TokenType { + Token(token::Token), + Keyword(keywords::Keyword), + Operator, + Lifetime, + Ident, + Path, + Type, + Const, +} + +impl TokenType { + fn to_string(&self) -> String { + match *self { + TokenType::Token(ref t) => format!("`{}`", pprust::token_to_string(t)), + TokenType::Keyword(kw) => format!("`{}`", kw.name()), + 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(), + } + } +} + +/// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT`, +/// `IDENT<::AssocTy>`. +/// +/// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes +/// that `IDENT` is not the ident of a fn trait. +fn can_continue_type_after_non_fn_ident(t: &token::Token) -> bool { + t == &token::ModSep || t == &token::Lt || + t == &token::BinOp(token::Shl) +} + +/// Information about the path to a module. +pub struct ModulePath { + name: String, + path_exists: bool, + pub result: Result, +} + +pub struct ModulePathSuccess { + pub path: PathBuf, + pub directory_ownership: DirectoryOwnership, + warn: bool, +} + +pub enum Error { + FileNotFoundForModule { + mod_name: String, + default_path: String, + secondary_path: String, + dir_path: String, + }, + DuplicatePaths { + mod_name: String, + default_path: String, + secondary_path: String, + }, + UselessDocComment, + InclusiveRangeWithNoEnd, +} + +impl Error { + fn span_err>(self, + sp: S, + handler: &errors::Handler) -> DiagnosticBuilder<'_> { + match self { + Error::FileNotFoundForModule { ref mod_name, + ref default_path, + ref secondary_path, + ref dir_path } => { + let mut err = struct_span_err!(handler, sp, E0583, + "file not found for module `{}`", mod_name); + err.help(&format!("name the file either {} or {} inside the directory \"{}\"", + default_path, + secondary_path, + dir_path)); + err + } + Error::DuplicatePaths { ref mod_name, ref default_path, ref secondary_path } => { + let mut err = struct_span_err!(handler, sp, E0584, + "file for module `{}` found at both {} and {}", + mod_name, + default_path, + secondary_path); + err.help("delete or rename one of them to remove the ambiguity"); + err + } + Error::UselessDocComment => { + let mut err = struct_span_err!(handler, sp, E0585, + "found a documentation comment that doesn't document anything"); + err.help("doc comments must come before what they document, maybe a comment was \ + intended with `//`?"); + err + } + Error::InclusiveRangeWithNoEnd => { + let mut err = struct_span_err!(handler, sp, E0586, + "inclusive range with no end"); + err.help("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)"); + err + } + } + } +} + +#[derive(Debug)] +enum LhsExpr { + NotYetParsed, + AttributesParsed(ThinVec), + AlreadyParsed(P), +} + +impl From>> for LhsExpr { + fn from(o: Option>) -> Self { + if let Some(attrs) = o { + LhsExpr::AttributesParsed(attrs) + } else { + LhsExpr::NotYetParsed + } + } +} + +impl From> for LhsExpr { + fn from(expr: P) -> Self { + LhsExpr::AlreadyParsed(expr) + } +} + +/// Creates a placeholder argument. +fn dummy_arg(span: Span) -> Arg { + let ident = Ident::new(keywords::Invalid.name(), span); + let pat = P(Pat { + id: ast::DUMMY_NODE_ID, + node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None), + span, + }); + let ty = Ty { + node: TyKind::Err, + span, + id: ast::DUMMY_NODE_ID + }; + Arg { ty: P(ty), pat: pat, id: ast::DUMMY_NODE_ID } +} + +#[derive(Copy, Clone, Debug)] +enum TokenExpectType { + Expect, + NoExpect, +} + +impl<'a> Parser<'a> { + pub fn new(sess: &'a ParseSess, + tokens: TokenStream, + directory: Option>, + recurse_into_file_modules: bool, + desugar_doc_comments: bool) + -> Self { + let mut parser = Parser { + sess, + token: token::Whitespace, + span: syntax_pos::DUMMY_SP, + prev_span: syntax_pos::DUMMY_SP, + meta_var_span: None, + prev_token_kind: PrevTokenKind::Other, + restrictions: Restrictions::empty(), + recurse_into_file_modules, + directory: Directory { + path: Cow::from(PathBuf::new()), + ownership: DirectoryOwnership::Owned { relative: None } + }, + root_module_name: None, + expected_tokens: Vec::new(), + token_cursor: TokenCursor { + frame: TokenCursorFrame::new( + DelimSpan::dummy(), + token::NoDelim, + &tokens.into(), + ), + stack: Vec::new(), + }, + desugar_doc_comments, + cfg_mods: true, + unmatched_angle_bracket_count: 0, + max_angle_bracket_count: 0, + unclosed_delims: Vec::new(), + }; + + let tok = parser.next_tok(); + parser.token = tok.tok; + parser.span = tok.sp; + + if let Some(directory) = directory { + parser.directory = directory; + } else if !parser.span.is_dummy() { + if let FileName::Real(mut path) = sess.source_map().span_to_unmapped_path(parser.span) { + path.pop(); + parser.directory.path = Cow::from(path); + } + } + + parser.process_potential_macro_variable(); + parser + } + + fn next_tok(&mut self) -> TokenAndSpan { + let mut next = if self.desugar_doc_comments { + self.token_cursor.next_desugared() + } else { + self.token_cursor.next() + }; + if next.sp.is_dummy() { + // Tweak the location for better diagnostics, but keep syntactic context intact. + next.sp = self.prev_span.with_ctxt(next.sp.ctxt()); + } + next + } + + /// Converts the current token to a string using `self`'s reader. + pub fn this_token_to_string(&self) -> String { + pprust::token_to_string(&self.token) + } + + fn token_descr(&self) -> Option<&'static str> { + Some(match &self.token { + t if t.is_special_ident() => "reserved identifier", + t if t.is_used_keyword() => "keyword", + t if t.is_unused_keyword() => "reserved keyword", + token::DocComment(..) => "doc comment", + _ => return None, + }) + } + + fn this_token_descr(&self) -> String { + if let Some(prefix) = self.token_descr() { + format!("{} `{}`", prefix, self.this_token_to_string()) + } else { + format!("`{}`", self.this_token_to_string()) + } + } + + fn unexpected_last(&self, t: &token::Token) -> PResult<'a, T> { + let token_str = pprust::token_to_string(t); + Err(self.span_fatal(self.prev_span, &format!("unexpected token: `{}`", token_str))) + } + + crate fn unexpected(&mut self) -> PResult<'a, T> { + match self.expect_one_of(&[], &[]) { + Err(e) => Err(e), + Ok(_) => unreachable!(), + } + } + + /// Expects and consumes the token `t`. Signals an error if the next token is not `t`. + pub fn expect(&mut self, t: &token::Token) -> PResult<'a, bool /* recovered */> { + if self.expected_tokens.is_empty() { + if self.token == *t { + self.bump(); + Ok(false) + } else { + let token_str = pprust::token_to_string(t); + let this_token_str = self.this_token_descr(); + let mut err = self.fatal(&format!("expected `{}`, found {}", + token_str, + this_token_str)); + + let sp = if self.token == token::Token::Eof { + // EOF, don't want to point at the following char, but rather the last token + self.prev_span + } else { + self.sess.source_map().next_point(self.prev_span) + }; + let label_exp = format!("expected `{}`", token_str); + match self.recover_closing_delimiter(&[t.clone()], err) { + Err(e) => err = e, + Ok(recovered) => { + return Ok(recovered); + } + } + let cm = self.sess.source_map(); + match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) { + (Ok(ref a), Ok(ref b)) if a.line == b.line => { + // When the spans are in the same line, it means that the only content + // between them is whitespace, point only at the found token. + err.span_label(self.span, label_exp); + } + _ => { + err.span_label(sp, label_exp); + err.span_label(self.span, "unexpected token"); + } + } + Err(err) + } + } else { + self.expect_one_of(slice::from_ref(t), &[]) + } + } + + fn recover_closing_delimiter( + &mut self, + tokens: &[token::Token], + mut err: DiagnosticBuilder<'a>, + ) -> PResult<'a, bool> { + let mut pos = None; + // we want to use the last closing delim that would apply + for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() { + if tokens.contains(&token::CloseDelim(unmatched.expected_delim)) + && Some(self.span) > unmatched.unclosed_span + { + pos = Some(i); + } + } + match pos { + Some(pos) => { + // Recover and assume that the detected unclosed delimiter was meant for + // this location. Emit the diagnostic and act as if the delimiter was + // present for the parser's sake. + + // Don't attempt to recover from this unclosed delimiter more than once. + let unmatched = self.unclosed_delims.remove(pos); + let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim)); + + // We want to suggest the inclusion of the closing delimiter where it makes + // the most sense, which is immediately after the last token: + // + // {foo(bar {}} + // - ^ + // | | + // | help: `)` may belong here (FIXME: #58270) + // | + // unclosed delimiter + if let Some(sp) = unmatched.unclosed_span { + err.span_label(sp, "unclosed delimiter"); + } + err.span_suggestion_short( + self.sess.source_map().next_point(self.prev_span), + &format!("{} may belong here", delim.to_string()), + delim.to_string(), + Applicability::MaybeIncorrect, + ); + err.emit(); + self.expected_tokens.clear(); // reduce errors + Ok(true) + } + _ => Err(err), + } + } + + /// 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: &[token::Token], + inedible: &[token::Token], + ) -> PResult<'a, bool /* recovered */> { + fn tokens_to_string(tokens: &[TokenType]) -> String { + let mut i = tokens.iter(); + // This might be a sign we need a connect method on Iterator. + let b = i.next() + .map_or(String::new(), |t| t.to_string()); + i.enumerate().fold(b, |mut b, (i, a)| { + if tokens.len() > 2 && i == tokens.len() - 2 { + b.push_str(", or "); + } else if tokens.len() == 2 && i == tokens.len() - 2 { + b.push_str(" or "); + } else { + b.push_str(", "); + } + b.push_str(&a.to_string()); + b + }) + } + if edible.contains(&self.token) { + self.bump(); + Ok(false) + } else if inedible.contains(&self.token) { + // leave it in the input + Ok(false) + } else { + let mut expected = edible.iter() + .map(|x| TokenType::Token(x.clone())) + .chain(inedible.iter().map(|x| TokenType::Token(x.clone()))) + .chain(self.expected_tokens.iter().cloned()) + .collect::>(); + expected.sort_by_cached_key(|x| x.to_string()); + expected.dedup(); + let expect = tokens_to_string(&expected[..]); + let actual = self.this_token_to_string(); + let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 { + let short_expect = if expected.len() > 6 { + format!("{} possible tokens", expected.len()) + } else { + expect.clone() + }; + (format!("expected one of {}, found `{}`", expect, actual), + (self.sess.source_map().next_point(self.prev_span), + format!("expected one of {} here", short_expect))) + } else if expected.is_empty() { + (format!("unexpected token: `{}`", actual), + (self.prev_span, "unexpected token after this".to_string())) + } else { + (format!("expected {}, found `{}`", expect, actual), + (self.sess.source_map().next_point(self.prev_span), + format!("expected {} here", expect))) + }; + let mut err = self.fatal(&msg_exp); + if self.token.is_ident_named("and") { + err.span_suggestion_short( + self.span, + "use `&&` instead of `and` for the boolean operator", + "&&".to_string(), + Applicability::MaybeIncorrect, + ); + } + if self.token.is_ident_named("or") { + err.span_suggestion_short( + self.span, + "use `||` instead of `or` for the boolean operator", + "||".to_string(), + Applicability::MaybeIncorrect, + ); + } + let sp = if self.token == token::Token::Eof { + // This is EOF, don't want to point at the following char, but rather the last token + self.prev_span + } else { + label_sp + }; + match self.recover_closing_delimiter(&expected.iter().filter_map(|tt| match tt { + TokenType::Token(t) => Some(t.clone()), + _ => None, + }).collect::>(), err) { + Err(e) => err = e, + Ok(recovered) => { + return Ok(recovered); + } + } + + let cm = self.sess.source_map(); + match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) { + (Ok(ref a), Ok(ref b)) if a.line == b.line => { + // When the spans are in the same line, it means that the only content between + // them is whitespace, point at the found token in that case: + // + // X | () => { syntax error }; + // | ^^^^^ expected one of 8 possible tokens here + // + // instead of having: + // + // X | () => { syntax error }; + // | -^^^^^ unexpected token + // | | + // | expected one of 8 possible tokens here + err.span_label(self.span, label_exp); + } + _ if self.prev_span == syntax_pos::DUMMY_SP => { + // Account for macro context where the previous span might not be + // available to avoid incorrect output (#54841). + err.span_label(self.span, "unexpected token"); + } + _ => { + err.span_label(sp, label_exp); + err.span_label(self.span, "unexpected token"); + } + } + Err(err) + } + } + + /// Returns the span of expr, if it was not interpolated or the span of the interpolated token. + fn interpolated_or_expr_span(&self, + expr: PResult<'a, P>) + -> PResult<'a, (Span, P)> { + expr.map(|e| { + if self.prev_token_kind == PrevTokenKind::Interpolated { + (self.prev_span, e) + } else { + (e.span, e) + } + }) + } + + fn expected_ident_found(&self) -> DiagnosticBuilder<'a> { + let mut err = self.struct_span_err(self.span, + &format!("expected identifier, found {}", + self.this_token_descr())); + if let token::Ident(ident, false) = &self.token { + if ident.is_reserved() && !ident.is_path_segment_keyword() && + ident.name != keywords::Underscore.name() + { + err.span_suggestion( + self.span, + "you can escape reserved keywords to use them as identifiers", + format!("r#{}", ident), + Applicability::MaybeIncorrect, + ); + } + } + if let Some(token_descr) = self.token_descr() { + err.span_label(self.span, format!("expected identifier, found {}", token_descr)); + } else { + err.span_label(self.span, "expected identifier"); + if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) { + err.span_suggestion( + self.span, + "remove this comma", + String::new(), + Applicability::MachineApplicable, + ); + } + } + err + } + + pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> { + self.parse_ident_common(true) + } + + fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> { + match self.token { + token::Ident(ident, _) => { + if self.token.is_reserved_ident() { + let mut err = self.expected_ident_found(); + if recover { + err.emit(); + } else { + return Err(err); + } + } + let span = self.span; + self.bump(); + Ok(Ident::new(ident.name, span)) + } + _ => { + Err(if self.prev_token_kind == PrevTokenKind::DocComment { + self.span_fatal_err(self.prev_span, Error::UselessDocComment) + } else { + 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. + crate fn check(&mut self, tok: &token::Token) -> 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: &token::Token) -> bool { + let is_present = self.check(tok); + if is_present { self.bump() } + is_present + } + + fn check_keyword(&mut self, kw: keywords::Keyword) -> 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`. + pub fn eat_keyword(&mut self, kw: keywords::Keyword) -> bool { + if self.check_keyword(kw) { + self.bump(); + true + } else { + false + } + } + + fn eat_keyword_noexpect(&mut self, kw: keywords::Keyword) -> 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: keywords::Keyword) -> PResult<'a, ()> { + if !self.eat_keyword(kw) { + self.unexpected() + } else { + Ok(()) + } + } + + fn check_ident(&mut self) -> bool { + if self.token.is_ident() { + true + } else { + self.expected_tokens.push(TokenType::Ident); + false + } + } + + fn check_path(&mut self) -> bool { + if self.token.is_path_start() { + true + } else { + self.expected_tokens.push(TokenType::Path); + false + } + } + + fn check_type(&mut self) -> bool { + if self.token.can_begin_type() { + true + } else { + self.expected_tokens.push(TokenType::Type); + false + } + } + + fn check_const_arg(&mut self) -> bool { + if self.token.can_begin_const_arg() { + true + } else { + self.expected_tokens.push(TokenType::Const); + false + } + } + + /// Expects and consumes a `+`. if `+=` is seen, replaces it with a `=` + /// and continues. If a `+` is not seen, returns `false`. + /// + /// This is used when token-splitting `+=` into `+`. + /// See issue #47856 for an example of when this may occur. + fn eat_plus(&mut self) -> bool { + self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus))); + match self.token { + token::BinOp(token::Plus) => { + self.bump(); + true + } + token::BinOpEq(token::Plus) => { + let span = self.span.with_lo(self.span.lo() + BytePos(1)); + self.bump_with(token::Eq, span); + true + } + _ => false, + } + } + + + /// Checks to see if the next token is either `+` or `+=`. + /// Otherwise returns `false`. + fn check_plus(&mut self) -> bool { + if self.token.is_like_plus() { + true + } + else { + self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus))); + false + } + } + + /// Expects and consumes an `&`. If `&&` is seen, replaces it with a single + /// `&` and continues. If an `&` is not seen, signals an error. + fn expect_and(&mut self) -> PResult<'a, ()> { + self.expected_tokens.push(TokenType::Token(token::BinOp(token::And))); + match self.token { + token::BinOp(token::And) => { + self.bump(); + Ok(()) + } + token::AndAnd => { + let span = self.span.with_lo(self.span.lo() + BytePos(1)); + Ok(self.bump_with(token::BinOp(token::And), span)) + } + _ => self.unexpected() + } + } + + /// Expects and consumes an `|`. If `||` is seen, replaces it with a single + /// `|` and continues. If an `|` is not seen, signals an error. + fn expect_or(&mut self) -> PResult<'a, ()> { + self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or))); + match self.token { + token::BinOp(token::Or) => { + self.bump(); + Ok(()) + } + token::OrOr => { + let span = self.span.with_lo(self.span.lo() + BytePos(1)); + Ok(self.bump_with(token::BinOp(token::Or), span)) + } + _ => self.unexpected() + } + } + + fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option) { + match suffix { + None => {/* everything ok */} + Some(suf) => { + let text = suf.as_str(); + if text.is_empty() { + self.span_bug(sp, "found empty literal suffix in Some") + } + let msg = format!("{} with a suffix is invalid", kind); + self.struct_span_err(sp, &msg) + .span_label(sp, msg) + .emit(); + } + } + } + + /// Attempts to consume a `<`. If `<<` is seen, replaces it with a single + /// `<` and continue. If `<-` is seen, replaces it with a single `<` + /// and continue. If a `<` is not seen, returns false. + /// + /// This is meant to be used when parsing generics on a path to get the + /// starting token. + fn eat_lt(&mut self) -> bool { + self.expected_tokens.push(TokenType::Token(token::Lt)); + let ate = match self.token { + token::Lt => { + self.bump(); + true + } + token::BinOp(token::Shl) => { + let span = self.span.with_lo(self.span.lo() + BytePos(1)); + self.bump_with(token::Lt, span); + true + } + token::LArrow => { + let span = self.span.with_lo(self.span.lo() + BytePos(1)); + self.bump_with(token::BinOp(token::Minus), span); + true + } + _ => false, + }; + + 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 + } + + fn expect_lt(&mut self) -> PResult<'a, ()> { + if !self.eat_lt() { + self.unexpected() + } else { + Ok(()) + } + } + + /// Expects and consumes a single `>` token. if a `>>` is seen, replaces it + /// with a single `>` and continues. If a `>` is not seen, signals an error. + fn expect_gt(&mut self) -> PResult<'a, ()> { + self.expected_tokens.push(TokenType::Token(token::Gt)); + let ate = match self.token { + token::Gt => { + self.bump(); + Some(()) + } + token::BinOp(token::Shr) => { + let span = self.span.with_lo(self.span.lo() + BytePos(1)); + Some(self.bump_with(token::Gt, span)) + } + token::BinOpEq(token::Shr) => { + let span = self.span.with_lo(self.span.lo() + BytePos(1)); + Some(self.bump_with(token::Ge, span)) + } + token::Ge => { + let span = self.span.with_lo(self.span.lo() + BytePos(1)); + Some(self.bump_with(token::Eq, span)) + } + _ => None, + }; + + match ate { + Some(_) => { + // 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(()) + }, + None => self.unexpected(), + } + } + + /// Eats and discards tokens until one of `kets` is encountered. Respects token trees, + /// passes through any errors encountered. Used for error recovery. + fn eat_to_tokens(&mut self, kets: &[&token::Token]) { + let handler = self.diagnostic(); + + if let Err(ref mut err) = self.parse_seq_to_before_tokens(kets, + SeqSep::none(), + TokenExpectType::Expect, + |p| Ok(p.parse_token_tree())) { + handler.cancel(err); + } + } + + /// Parses a sequence, including the closing delimiter. The function + /// `f` must consume tokens until reaching the next separator or + /// closing bracket. + pub fn parse_seq_to_end(&mut self, + ket: &token::Token, + sep: SeqSep, + f: F) + -> PResult<'a, Vec> where + F: FnMut(&mut Parser<'a>) -> PResult<'a, T>, + { + let (val, recovered) = self.parse_seq_to_before_end(ket, sep, f)?; + if !recovered { + self.bump(); + } + Ok(val) + } + + /// Parses a sequence, not including the closing delimiter. The function + /// `f` must consume tokens until reaching the next separator or + /// closing bracket. + pub fn parse_seq_to_before_end( + &mut self, + ket: &token::Token, + sep: SeqSep, + f: F, + ) -> PResult<'a, (Vec, bool)> + where F: FnMut(&mut Parser<'a>) -> PResult<'a, T> + { + self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f) + } + + fn parse_seq_to_before_tokens( + &mut self, + kets: &[&token::Token], + sep: SeqSep, + expect: TokenExpectType, + mut f: F, + ) -> PResult<'a, (Vec, bool /* recovered */)> + where F: FnMut(&mut Parser<'a>) -> PResult<'a, T> + { + let mut first = true; + let mut recovered = false; + let mut v = vec![]; + while !kets.iter().any(|k| { + match expect { + TokenExpectType::Expect => self.check(k), + TokenExpectType::NoExpect => self.token == **k, + } + }) { + match self.token { + token::CloseDelim(..) | token::Eof => 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 e) => { + // Attempt to keep parsing if it was a similar separator + if let Some(ref tokens) = t.similar_tokens() { + if tokens.contains(&self.token) { + self.bump(); + } + } + e.emit(); + // Attempt to keep parsing if it was an omitted separator + match f(self) { + Ok(t) => { + v.push(t); + continue; + }, + Err(mut e) => { + e.cancel(); + break; + } + } + } + } + } + } + if sep.trailing_sep_allowed && kets.iter().any(|k| { + match expect { + TokenExpectType::Expect => self.check(k), + TokenExpectType::NoExpect => self.token == **k, + } + }) { + break; + } + + let t = f(self)?; + v.push(t); + } + + Ok((v, recovered)) + } + + /// 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( + &mut self, + bra: &token::Token, + ket: &token::Token, + sep: SeqSep, + f: F, + ) -> PResult<'a, Vec> where + F: FnMut(&mut Parser<'a>) -> PResult<'a, T>, + { + self.expect(bra)?; + let (result, recovered) = self.parse_seq_to_before_end(ket, sep, f)?; + if !recovered { + self.eat(ket); + } + Ok(result) + } + + /// Advance the parser by one token + pub fn bump(&mut self) { + if self.prev_token_kind == PrevTokenKind::Eof { + // Bumping after EOF is a bad sign, usually an infinite loop. + self.bug("attempted to bump the parser past EOF (may be stuck in a loop)"); + } + + self.prev_span = self.meta_var_span.take().unwrap_or(self.span); + + // Record last token kind for possible error recovery. + self.prev_token_kind = match self.token { + token::DocComment(..) => PrevTokenKind::DocComment, + token::Comma => PrevTokenKind::Comma, + token::BinOp(token::Plus) => PrevTokenKind::Plus, + token::Interpolated(..) => PrevTokenKind::Interpolated, + token::Eof => PrevTokenKind::Eof, + token::Ident(..) => PrevTokenKind::Ident, + _ => PrevTokenKind::Other, + }; + + let next = self.next_tok(); + self.span = next.sp; + self.token = next.tok; + self.expected_tokens.clear(); + // check after each token + self.process_potential_macro_variable(); + } + + /// Advance the parser using provided token as a next one. Use this when + /// consuming a part of a token. For example a single `<` from `<<`. + fn bump_with(&mut self, next: token::Token, span: Span) { + self.prev_span = self.span.with_hi(span.lo()); + // It would be incorrect to record the kind of the current token, but + // fortunately for tokens currently using `bump_with`, the + // prev_token_kind will be of no use anyway. + self.prev_token_kind = PrevTokenKind::Other; + self.span = span; + self.token = next; + self.expected_tokens.clear(); + } + + pub fn look_ahead(&self, dist: usize, f: F) -> R where + F: FnOnce(&token::Token) -> R, + { + if dist == 0 { + return f(&self.token) + } + + f(&match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) { + Some(tree) => match tree { + TokenTree::Token(_, tok) => tok, + TokenTree::Delimited(_, delim, _) => token::OpenDelim(delim), + }, + None => token::CloseDelim(self.token_cursor.frame.delim), + }) + } + + fn look_ahead_span(&self, dist: usize) -> Span { + if dist == 0 { + return self.span + } + + match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) { + Some(TokenTree::Token(span, _)) => span, + Some(TokenTree::Delimited(span, ..)) => span.entire(), + None => self.look_ahead_span(dist - 1), + } + } + pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> { + self.sess.span_diagnostic.struct_span_fatal(self.span, m) + } + pub fn span_fatal>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> { + self.sess.span_diagnostic.struct_span_fatal(sp, m) + } + fn span_fatal_err>(&self, sp: S, err: Error) -> DiagnosticBuilder<'a> { + err.span_err(sp, self.diagnostic()) + } + fn bug(&self, m: &str) -> ! { + self.sess.span_diagnostic.span_bug(self.span, m) + } + fn span_err>(&self, sp: S, m: &str) { + self.sess.span_diagnostic.span_err(sp, m) + } + fn struct_span_err>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> { + self.sess.span_diagnostic.struct_span_err(sp, m) + } + crate fn span_bug>(&self, sp: S, m: &str) -> ! { + self.sess.span_diagnostic.span_bug(sp, m) + } + + fn cancel(&self, err: &mut DiagnosticBuilder<'_>) { + self.sess.span_diagnostic.cancel(err) + } + + crate fn diagnostic(&self) -> &'a errors::Handler { + &self.sess.span_diagnostic + } + + /// Is the current token one of the keywords that signals a bare function type? + fn token_is_bare_fn_keyword(&mut self) -> bool { + self.check_keyword(keywords::Fn) || + self.check_keyword(keywords::Unsafe) || + self.check_keyword(keywords::Extern) + } + + /// Parses a `TyKind::BareFn` type. + fn parse_ty_bare_fn(&mut self, generic_params: Vec) -> PResult<'a, TyKind> { + /* + + [unsafe] [extern "ABI"] fn (S) -> T + ^~~~^ ^~~~^ ^~^ ^ + | | | | + | | | Return type + | | Argument types + | | + | ABI + Function Style + */ + + let unsafety = self.parse_unsafety(); + let abi = if self.eat_keyword(keywords::Extern) { + self.parse_opt_abi()?.unwrap_or(Abi::C) + } else { + Abi::Rust + }; + + self.expect_keyword(keywords::Fn)?; + let (inputs, variadic) = self.parse_fn_args(false, true)?; + let ret_ty = self.parse_ret_ty(false)?; + let decl = P(FnDecl { + inputs, + output: ret_ty, + variadic, + }); + Ok(TyKind::BareFn(P(BareFnTy { + abi, + unsafety, + generic_params, + decl, + }))) + } + + /// Parses asyncness: `async` or nothing. + fn parse_asyncness(&mut self) -> IsAsync { + if self.eat_keyword(keywords::Async) { + IsAsync::Async { + closure_id: ast::DUMMY_NODE_ID, + return_impl_trait_id: ast::DUMMY_NODE_ID, + } + } else { + IsAsync::NotAsync + } + } + + /// Parses unsafety: `unsafe` or nothing. + fn parse_unsafety(&mut self) -> Unsafety { + if self.eat_keyword(keywords::Unsafe) { + Unsafety::Unsafe + } else { + Unsafety::Normal + } + } + + /// Parses the items in a trait declaration. + pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> { + maybe_whole!(self, NtTraitItem, |x| x); + let attrs = self.parse_outer_attributes()?; + let (mut item, tokens) = self.collect_tokens(|this| { + this.parse_trait_item_(at_end, attrs) + })?; + // See `parse_item` for why this clause is here. + if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) { + item.tokens = Some(tokens); + } + Ok(item) + } + + fn parse_trait_item_(&mut self, + at_end: &mut bool, + mut attrs: Vec) -> PResult<'a, TraitItem> { + let lo = self.span; + + let (name, node, generics) = if self.eat_keyword(keywords::Type) { + self.parse_trait_item_assoc_ty()? + } else if self.is_const_item() { + self.expect_keyword(keywords::Const)?; + let ident = self.parse_ident()?; + self.expect(&token::Colon)?; + let ty = self.parse_ty()?; + let default = if self.eat(&token::Eq) { + let expr = self.parse_expr()?; + self.expect(&token::Semi)?; + Some(expr) + } else { + self.expect(&token::Semi)?; + None + }; + (ident, TraitItemKind::Const(ty, default), ast::Generics::default()) + } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? { + // trait item macro. + (keywords::Invalid.ident(), ast::TraitItemKind::Macro(mac), ast::Generics::default()) + } else { + let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?; + + let ident = self.parse_ident()?; + let mut generics = self.parse_generics()?; + + let d = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| { + // This is somewhat dubious; We don't want to allow + // argument names to be left off if there is a + // definition... + + // We don't allow argument names to be left off in edition 2018. + p.parse_arg_general(p.span.rust_2018(), true) + })?; + generics.where_clause = self.parse_where_clause()?; + + let sig = ast::MethodSig { + header: FnHeader { + unsafety, + constness, + abi, + asyncness, + }, + decl: d, + }; + + let body = match self.token { + token::Semi => { + self.bump(); + *at_end = true; + debug!("parse_trait_methods(): parsing required method"); + None + } + token::OpenDelim(token::Brace) => { + debug!("parse_trait_methods(): parsing provided method"); + *at_end = true; + let (inner_attrs, body) = self.parse_inner_attrs_and_block()?; + attrs.extend(inner_attrs.iter().cloned()); + Some(body) + } + token::Interpolated(ref nt) => { + match **nt { + token::NtBlock(..) => { + *at_end = true; + let (inner_attrs, body) = self.parse_inner_attrs_and_block()?; + attrs.extend(inner_attrs.iter().cloned()); + Some(body) + } + _ => { + let token_str = self.this_token_descr(); + let mut err = self.fatal(&format!("expected `;` or `{{`, found {}", + token_str)); + err.span_label(self.span, "expected `;` or `{`"); + return Err(err); + } + } + } + _ => { + let token_str = self.this_token_descr(); + let mut err = self.fatal(&format!("expected `;` or `{{`, found {}", + token_str)); + err.span_label(self.span, "expected `;` or `{`"); + return Err(err); + } + }; + (ident, ast::TraitItemKind::Method(sig, body), generics) + }; + + Ok(TraitItem { + id: ast::DUMMY_NODE_ID, + ident: name, + attrs, + generics, + node, + span: lo.to(self.prev_span), + tokens: None, + }) + } + + /// Parses an optional return type `[ -> TY ]` in a function declaration. + fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> { + if self.eat(&token::RArrow) { + Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true)?)) + } else { + Ok(FunctionRetTy::Default(self.span.shrink_to_lo())) + } + } + + /// Parses a type. + pub fn parse_ty(&mut self) -> PResult<'a, P> { + self.parse_ty_common(true, true) + } + + /// Parses a type in restricted contexts where `+` is not permitted. + /// + /// Example 1: `&'a TYPE` + /// `+` is prohibited to maintain operator priority (P(+) < P(&)). + /// Example 2: `value1 as TYPE + value2` + /// `+` is prohibited to avoid interactions with expression grammar. + fn parse_ty_no_plus(&mut self) -> PResult<'a, P> { + self.parse_ty_common(false, true) + } + + fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool) + -> PResult<'a, P> { + maybe_whole!(self, NtTy, |x| x); + + let lo = self.span; + let mut impl_dyn_multi = false; + let node = if self.eat(&token::OpenDelim(token::Paren)) { + // `(TYPE)` is a parenthesized type. + // `(TYPE,)` is a tuple with a single field of type TYPE. + let mut ts = vec![]; + let mut last_comma = false; + while self.token != token::CloseDelim(token::Paren) { + ts.push(self.parse_ty()?); + if self.eat(&token::Comma) { + last_comma = true; + } else { + last_comma = false; + break; + } + } + let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus; + self.expect(&token::CloseDelim(token::Paren))?; + + if ts.len() == 1 && !last_comma { + let ty = ts.into_iter().nth(0).unwrap().into_inner(); + let maybe_bounds = allow_plus && self.token.is_like_plus(); + match ty.node { + // `(TY_BOUND_NOPAREN) + BOUND + ...`. + TyKind::Path(None, ref path) if maybe_bounds => { + self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)? + } + TyKind::TraitObject(ref bounds, TraitObjectSyntax::None) + if maybe_bounds && bounds.len() == 1 && !trailing_plus => { + let path = match bounds[0] { + GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(), + GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"), + }; + self.parse_remaining_bounds(Vec::new(), path, lo, true)? + } + // `(TYPE)` + _ => TyKind::Paren(P(ty)) + } + } else { + TyKind::Tup(ts) + } + } else if self.eat(&token::Not) { + // Never type `!` + TyKind::Never + } else if self.eat(&token::BinOp(token::Star)) { + // Raw pointer + TyKind::Ptr(self.parse_ptr()?) + } else if self.eat(&token::OpenDelim(token::Bracket)) { + // Array or slice + let t = self.parse_ty()?; + // Parse optional `; EXPR` in `[TYPE; EXPR]` + let t = match self.maybe_parse_fixed_length_of_vec()? { + None => TyKind::Slice(t), + Some(length) => TyKind::Array(t, AnonConst { + id: ast::DUMMY_NODE_ID, + value: length, + }), + }; + self.expect(&token::CloseDelim(token::Bracket))?; + t + } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) { + // Reference + self.expect_and()?; + self.parse_borrowed_pointee()? + } else if self.eat_keyword_noexpect(keywords::Typeof) { + // `typeof(EXPR)` + // In order to not be ambiguous, the type must be surrounded by parens. + self.expect(&token::OpenDelim(token::Paren))?; + let e = AnonConst { + id: ast::DUMMY_NODE_ID, + value: self.parse_expr()?, + }; + self.expect(&token::CloseDelim(token::Paren))?; + TyKind::Typeof(e) + } else if self.eat_keyword(keywords::Underscore) { + // A type to be inferred `_` + TyKind::Infer + } else if self.token_is_bare_fn_keyword() { + // Function pointer type + self.parse_ty_bare_fn(Vec::new())? + } else if self.check_keyword(keywords::For) { + // Function pointer type or bound list (trait object type) starting with a poly-trait. + // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T` + // `for<'lt> Trait1<'lt> + Trait2 + 'a` + let lo = self.span; + let lifetime_defs = self.parse_late_bound_lifetime_defs()?; + if self.token_is_bare_fn_keyword() { + self.parse_ty_bare_fn(lifetime_defs)? + } else { + let path = self.parse_path(PathStyle::Type)?; + let parse_plus = allow_plus && self.check_plus(); + self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)? + } + } else if self.eat_keyword(keywords::Impl) { + // Always parse bounds greedily for better error recovery. + let bounds = self.parse_generic_bounds(None)?; + impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus; + TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds) + } else if self.check_keyword(keywords::Dyn) && + (self.span.rust_2018() || + self.look_ahead(1, |t| t.can_begin_bound() && + !can_continue_type_after_non_fn_ident(t))) { + self.bump(); // `dyn` + // Always parse bounds greedily for better error recovery. + let bounds = self.parse_generic_bounds(None)?; + impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus; + TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn) + } else if self.check(&token::Question) || + self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) { + // Bound list (trait object type) + TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?, + TraitObjectSyntax::None) + } else if self.eat_lt() { + // Qualified path + let (qself, path) = self.parse_qpath(PathStyle::Type)?; + TyKind::Path(Some(qself), path) + } else if self.token.is_path_start() { + // Simple path + let path = self.parse_path(PathStyle::Type)?; + if self.eat(&token::Not) { + // Macro invocation in type position + let (delim, tts) = self.expect_delimited_token_tree()?; + let node = Mac_ { path, tts, delim }; + TyKind::Mac(respan(lo.to(self.prev_span), node)) + } else { + // Just a type path or bound list (trait object type) starting with a trait. + // `Type` + // `Trait1 + Trait2 + 'a` + if allow_plus && self.check_plus() { + self.parse_remaining_bounds(Vec::new(), path, lo, true)? + } else { + TyKind::Path(None, path) + } + } + } else { + let msg = format!("expected type, found {}", self.this_token_descr()); + return Err(self.fatal(&msg)); + }; + + let span = lo.to(self.prev_span); + let ty = Ty { node, span, id: ast::DUMMY_NODE_ID }; + + // Try to recover from use of `+` with incorrect priority. + self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty); + self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?; + let ty = self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)?; + + Ok(P(ty)) + } + + fn parse_remaining_bounds(&mut self, generic_params: Vec, path: ast::Path, + lo: Span, parse_plus: bool) -> PResult<'a, TyKind> { + let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span)); + let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)]; + if parse_plus { + self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded + bounds.append(&mut self.parse_generic_bounds(None)?); + } + Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None)) + } + + fn maybe_report_ambiguous_plus(&mut self, allow_plus: bool, impl_dyn_multi: bool, ty: &Ty) { + if !allow_plus && impl_dyn_multi { + let sum_with_parens = format!("({})", pprust::ty_to_string(&ty)); + self.struct_span_err(ty.span, "ambiguous `+` in a type") + .span_suggestion( + ty.span, + "use parentheses to disambiguate", + sum_with_parens, + Applicability::MachineApplicable + ).emit(); + } + } + + fn maybe_recover_from_bad_type_plus(&mut self, allow_plus: bool, ty: &Ty) -> PResult<'a, ()> { + // Do not add `+` to expected tokens. + if !allow_plus || !self.token.is_like_plus() { + return Ok(()) + } + + self.bump(); // `+` + let bounds = self.parse_generic_bounds(None)?; + let sum_span = ty.span.to(self.prev_span); + + let mut err = struct_span_err!(self.sess.span_diagnostic, sum_span, E0178, + "expected a path on the left-hand side of `+`, not `{}`", pprust::ty_to_string(ty)); + + match ty.node { + TyKind::Rptr(ref lifetime, ref mut_ty) => { + let sum_with_parens = pprust::to_string(|s| { + use crate::print::pprust::PrintState; + + s.s.word("&")?; + s.print_opt_lifetime(lifetime)?; + s.print_mutability(mut_ty.mutbl)?; + s.popen()?; + s.print_type(&mut_ty.ty)?; + s.print_type_bounds(" +", &bounds)?; + s.pclose() + }); + err.span_suggestion( + sum_span, + "try adding parentheses", + sum_with_parens, + Applicability::MachineApplicable + ); + } + TyKind::Ptr(..) | TyKind::BareFn(..) => { + err.span_label(sum_span, "perhaps you forgot parentheses?"); + } + _ => { + err.span_label(sum_span, "expected a path"); + }, + } + err.emit(); + Ok(()) + } + + // Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`. + fn maybe_recover_from_bad_qpath(&mut self, base: T, allow_recovery: bool) + -> PResult<'a, T> { + // Do not add `::` to expected tokens. + if !allow_recovery || self.token != token::ModSep { + return Ok(base); + } + let ty = match base.to_ty() { + Some(ty) => ty, + None => return Ok(base), + }; + + self.bump(); // `::` + let mut segments = Vec::new(); + self.parse_path_segments(&mut segments, T::PATH_STYLE, true)?; + + let span = ty.span.to(self.prev_span); + let path_span = span.to(span); // use an empty path since `position` == 0 + let recovered = base.to_recovered( + Some(QSelf { ty, path_span, position: 0 }), + ast::Path { segments, span }, + ); + + self.diagnostic() + .struct_span_err(span, "missing angle brackets in associated item path") + .span_suggestion( // this is a best-effort recovery + span, "try", recovered.to_string(), Applicability::MaybeIncorrect + ).emit(); + + Ok(recovered) + } + + fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> { + let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None }; + let mutbl = self.parse_mutability(); + let ty = self.parse_ty_no_plus()?; + return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl })); + } + + fn parse_ptr(&mut self) -> PResult<'a, MutTy> { + let mutbl = if self.eat_keyword(keywords::Mut) { + Mutability::Mutable + } else if self.eat_keyword(keywords::Const) { + Mutability::Immutable + } else { + let span = self.prev_span; + let msg = "expected mut or const in raw pointer type"; + self.struct_span_err(span, msg) + .span_label(span, msg) + .help("use `*mut T` or `*const T` as appropriate") + .emit(); + Mutability::Immutable + }; + let t = self.parse_ty_no_plus()?; + Ok(MutTy { ty: t, mutbl: mutbl }) + } + + fn is_named_argument(&mut self) -> bool { + let offset = match self.token { + token::Interpolated(ref nt) => match **nt { + token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon), + _ => 0, + } + token::BinOp(token::And) | token::AndAnd => 1, + _ if self.token.is_keyword(keywords::Mut) => 1, + _ => 0, + }; + + self.look_ahead(offset, |t| t.is_ident()) && + self.look_ahead(offset + 1, |t| t == &token::Colon) + } + + /// Skips unexpected attributes and doc comments in this position and emits an appropriate + /// error. + fn eat_incorrect_doc_comment(&mut self, applied_to: &str) { + if let token::DocComment(_) = self.token { + let mut err = self.diagnostic().struct_span_err( + self.span, + &format!("documentation comments cannot be applied to {}", applied_to), + ); + err.span_label(self.span, "doc comments are not allowed here"); + err.emit(); + self.bump(); + } else if self.token == token::Pound && self.look_ahead(1, |t| { + *t == token::OpenDelim(token::Bracket) + }) { + let lo = self.span; + // Skip every token until next possible arg. + while self.token != token::CloseDelim(token::Bracket) { + self.bump(); + } + let sp = lo.to(self.span); + self.bump(); + let mut err = self.diagnostic().struct_span_err( + sp, + &format!("attributes cannot be applied to {}", applied_to), + ); + err.span_label(sp, "attributes are not allowed here"); + err.emit(); + } + } + + /// This version of parse arg doesn't necessarily require identifier names. + fn parse_arg_general(&mut self, require_name: bool, is_trait_item: bool) -> PResult<'a, Arg> { + maybe_whole!(self, NtArg, |x| x); + + if let Ok(Some(_)) = self.parse_self_arg() { + let mut err = self.struct_span_err(self.prev_span, + "unexpected `self` argument in function"); + err.span_label(self.prev_span, + "`self` is only valid as the first argument of an associated function"); + return Err(err); + } + + let (pat, ty) = if require_name || self.is_named_argument() { + debug!("parse_arg_general parse_pat (require_name:{})", + require_name); + self.eat_incorrect_doc_comment("method arguments"); + let pat = self.parse_pat(Some("argument name"))?; + + if let Err(mut err) = self.expect(&token::Colon) { + // If we find a pattern followed by an identifier, it could be an (incorrect) + // C-style parameter declaration. + if self.check_ident() && self.look_ahead(1, |t| { + *t == token::Comma || *t == token::CloseDelim(token::Paren) + }) { + let ident = self.parse_ident().unwrap(); + let span = pat.span.with_hi(ident.span.hi()); + + err.span_suggestion( + span, + "declare the type after the parameter binding", + String::from(": "), + Applicability::HasPlaceholders, + ); + } else if require_name && is_trait_item { + if let PatKind::Ident(_, ident, _) = pat.node { + err.span_suggestion( + pat.span, + "explicitly ignore parameter", + format!("_: {}", ident), + Applicability::MachineApplicable, + ); + } + + err.note("anonymous parameters are removed in the 2018 edition (see RFC 1685)"); + } + + return Err(err); + } + + self.eat_incorrect_doc_comment("a method argument's type"); + (pat, self.parse_ty()?) + } else { + debug!("parse_arg_general ident_to_pat"); + let parser_snapshot_before_ty = self.clone(); + self.eat_incorrect_doc_comment("a method argument's type"); + let mut ty = self.parse_ty(); + if ty.is_ok() && self.token != token::Comma && + self.token != token::CloseDelim(token::Paren) { + // This wasn't actually a type, but a pattern looking like a type, + // so we are going to rollback and re-parse for recovery. + ty = self.unexpected(); + } + match ty { + Ok(ty) => { + let ident = Ident::new(keywords::Invalid.name(), self.prev_span); + let pat = P(Pat { + id: ast::DUMMY_NODE_ID, + node: PatKind::Ident( + BindingMode::ByValue(Mutability::Immutable), ident, None), + span: ty.span, + }); + (pat, ty) + } + Err(mut err) => { + // Recover from attempting to parse the argument as a type without pattern. + err.cancel(); + mem::replace(self, parser_snapshot_before_ty); + let pat = self.parse_pat(Some("argument name"))?; + self.expect(&token::Colon)?; + let ty = self.parse_ty()?; + + let mut err = self.diagnostic().struct_span_err_with_code( + pat.span, + "patterns aren't allowed in methods without bodies", + DiagnosticId::Error("E0642".into()), + ); + err.span_suggestion_short( + pat.span, + "give this argument a name or use an underscore to ignore it", + "_".to_owned(), + Applicability::MachineApplicable, + ); + err.emit(); + + // Pretend the pattern is `_`, to avoid duplicate errors from AST validation. + let pat = P(Pat { + node: PatKind::Wild, + span: pat.span, + id: ast::DUMMY_NODE_ID + }); + (pat, ty) + } + } + }; + + Ok(Arg { ty, pat, id: ast::DUMMY_NODE_ID }) + } + + /// Parses a single function argument. + crate fn parse_arg(&mut self) -> PResult<'a, Arg> { + self.parse_arg_general(true, false) + } + + /// Parses an argument in a lambda header (e.g., `|arg, arg|`). + fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> { + let pat = self.parse_pat(Some("argument name"))?; + let t = if self.eat(&token::Colon) { + self.parse_ty()? + } else { + P(Ty { + id: ast::DUMMY_NODE_ID, + node: TyKind::Infer, + span: self.prev_span, + }) + }; + Ok(Arg { + ty: t, + pat, + id: ast::DUMMY_NODE_ID + }) + } + + fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option>> { + if self.eat(&token::Semi) { + Ok(Some(self.parse_expr()?)) + } else { + Ok(None) + } + } + + /// Matches `token_lit = LIT_INTEGER | ...`. + fn parse_lit_token(&mut self) -> PResult<'a, LitKind> { + let out = match self.token { + token::Interpolated(ref nt) => match **nt { + token::NtExpr(ref v) | token::NtLiteral(ref v) => match v.node { + ExprKind::Lit(ref lit) => { lit.node.clone() } + _ => { return self.unexpected_last(&self.token); } + }, + _ => { return self.unexpected_last(&self.token); } + }, + token::Literal(lit, suf) => { + let diag = Some((self.span, &self.sess.span_diagnostic)); + let (suffix_illegal, result) = parse::lit_token(lit, suf, diag); + + if suffix_illegal { + let sp = self.span; + self.expect_no_suffix(sp, lit.literal_name(), suf) + } + + result.unwrap() + } + token::Dot if self.look_ahead(1, |t| match t { + token::Literal(parse::token::Lit::Integer(_) , _) => true, + _ => false, + }) => { // recover from `let x = .4;` + let lo = self.span; + self.bump(); + if let token::Literal( + parse::token::Lit::Integer(val), + suffix, + ) = self.token { + let suffix = suffix.and_then(|s| { + let s = s.as_str().get(); + if ["f32", "f64"].contains(&s) { + Some(s) + } else { + None + } + }).unwrap_or(""); + self.bump(); + let sp = lo.to(self.prev_span); + let mut err = self.diagnostic() + .struct_span_err(sp, "float literals must have an integer part"); + err.span_suggestion( + sp, + "must have an integer part", + format!("0.{}{}", val, suffix), + Applicability::MachineApplicable, + ); + err.emit(); + return Ok(match suffix { + "f32" => ast::LitKind::Float(val, ast::FloatTy::F32), + "f64" => ast::LitKind::Float(val, ast::FloatTy::F64), + _ => ast::LitKind::FloatUnsuffixed(val), + }); + } else { + unreachable!(); + }; + } + _ => { return self.unexpected_last(&self.token); } + }; + + self.bump(); + Ok(out) + } + + /// Matches `lit = true | false | token_lit`. + crate fn parse_lit(&mut self) -> PResult<'a, Lit> { + let lo = self.span; + let lit = if self.eat_keyword(keywords::True) { + LitKind::Bool(true) + } else if self.eat_keyword(keywords::False) { + LitKind::Bool(false) + } else { + let lit = self.parse_lit_token()?; + lit + }; + Ok(source_map::Spanned { node: lit, span: lo.to(self.prev_span) }) + } + + /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`). + crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P> { + maybe_whole_expr!(self); + + let minus_lo = self.span; + let minus_present = self.eat(&token::BinOp(token::Minus)); + let lo = self.span; + let literal = self.parse_lit()?; + let hi = self.prev_span; + let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new()); + + if minus_present { + let minus_hi = self.prev_span; + let unary = self.mk_unary(UnOp::Neg, expr); + Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new())) + } else { + Ok(expr) + } + } + + fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> { + match self.token { + token::Ident(ident, _) if self.token.is_path_segment_keyword() => { + let span = self.span; + self.bump(); + Ok(Ident::new(ident.name, span)) + } + _ => self.parse_ident(), + } + } + + fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> { + match self.token { + token::Ident(ident, false) if ident.name == keywords::Underscore.name() => { + let span = self.span; + self.bump(); + Ok(Ident::new(ident.name, span)) + } + _ => self.parse_ident(), + } + } + + /// Parses a qualified path. + /// Assumes that the leading `<` has been parsed already. + /// + /// `qualified_path = ::path` + /// + /// # Examples + /// `::default` + /// `::a` + /// `::F::a` (without disambiguator) + /// `::F::a::` (with disambiguator) + fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> { + let lo = self.prev_span; + let ty = self.parse_ty()?; + + // `path` will contain the prefix of the path up to the `>`, + // if any (e.g., `U` in the `::*` examples + // above). `path_span` has the span of that path, or an empty + // span in the case of something like `::Bar`. + let (mut path, path_span); + if self.eat_keyword(keywords::As) { + let path_lo = self.span; + path = self.parse_path(PathStyle::Type)?; + path_span = path_lo.to(self.prev_span); + } else { + path = ast::Path { segments: Vec::new(), span: syntax_pos::DUMMY_SP }; + path_span = self.span.to(self.span); + } + + // See doc comment for `unmatched_angle_bracket_count`. + self.expect(&token::Gt)?; + if self.unmatched_angle_bracket_count > 0 { + self.unmatched_angle_bracket_count -= 1; + debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count); + } + + self.expect(&token::ModSep)?; + + let qself = QSelf { ty, path_span, position: path.segments.len() }; + self.parse_path_segments(&mut path.segments, style, true)?; + + Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) })) + } + + /// Parses simple paths. + /// + /// `path = [::] segment+` + /// `segment = ident | ident[::] | ident[::](args) [-> type]` + /// + /// # Examples + /// `a::b::C` (without disambiguator) + /// `a::b::C::` (with disambiguator) + /// `Fn(Args)` (without disambiguator) + /// `Fn::(Args)` (with disambiguator) + pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> { + self.parse_path_common(style, true) + } + + crate fn parse_path_common(&mut self, style: PathStyle, enable_warning: bool) + -> PResult<'a, ast::Path> { + maybe_whole!(self, NtPath, |path| { + if style == PathStyle::Mod && + path.segments.iter().any(|segment| segment.args.is_some()) { + self.diagnostic().span_err(path.span, "unexpected generic arguments in path"); + } + path + }); + + let lo = self.meta_var_span.unwrap_or(self.span); + let mut segments = Vec::new(); + let mod_sep_ctxt = self.span.ctxt(); + if self.eat(&token::ModSep) { + segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt))); + } + self.parse_path_segments(&mut segments, style, enable_warning)?; + + Ok(ast::Path { segments, span: lo.to(self.prev_span) }) + } + + /// Like `parse_path`, but also supports parsing `Word` meta items into paths for + /// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]` + /// attributes. + pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> { + let meta_ident = match self.token { + token::Interpolated(ref nt) => match **nt { + token::NtMeta(ref meta) => match meta.node { + ast::MetaItemKind::Word => Some(meta.ident.clone()), + _ => None, + }, + _ => None, + }, + _ => None, + }; + if let Some(path) = meta_ident { + self.bump(); + return Ok(path); + } + self.parse_path(style) + } + + fn parse_path_segments(&mut self, + segments: &mut Vec, + style: PathStyle, + enable_warning: bool) + -> PResult<'a, ()> { + loop { + let segment = self.parse_path_segment(style, enable_warning)?; + if style == PathStyle::Expr { + // In order to check for trailing angle brackets, we must have finished + // recursing (`parse_path_segment` can indirectly call this function), + // that is, the next token must be the highlighted part of the below example: + // + // `Foo::>::Qux` + // ^ here + // + // As opposed to the below highlight (if we had only finished the first + // recursion): + // + // `Foo::>::Qux` + // ^ here + // + // `PathStyle::Expr` is only provided at the root invocation and never in + // `parse_path_segment` to recurse and therefore can be checked to maintain + // this invariant. + self.check_trailing_angle_brackets(&segment, token::ModSep); + } + segments.push(segment); + + if self.is_import_coupler() || !self.eat(&token::ModSep) { + return Ok(()); + } + } + } + + fn parse_path_segment(&mut self, style: PathStyle, enable_warning: bool) + -> PResult<'a, PathSegment> { + let ident = self.parse_path_segment_ident()?; + + let is_args_start = |token: &token::Token| match *token { + token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren) => true, + _ => false, + }; + let check_args_start = |this: &mut Self| { + this.expected_tokens.extend_from_slice( + &[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))] + ); + is_args_start(&this.token) + }; + + Ok(if style == PathStyle::Type && check_args_start(self) || + style != PathStyle::Mod && self.check(&token::ModSep) + && self.look_ahead(1, |t| is_args_start(t)) { + // Generic arguments are found - `<`, `(`, `::<` or `::(`. + if self.eat(&token::ModSep) && style == PathStyle::Type && enable_warning { + self.diagnostic().struct_span_warn(self.prev_span, "unnecessary path disambiguator") + .span_label(self.prev_span, "try removing `::`").emit(); + } + let lo = self.span; + + // We use `style == PathStyle::Expr` to check if this is in a recursion or not. If + // it isn't, then we reset the unmatched angle bracket count as we're about to start + // parsing a new path. + if style == PathStyle::Expr { + self.unmatched_angle_bracket_count = 0; + self.max_angle_bracket_count = 0; + } + + let args = if self.eat_lt() { + // `<'a, T, A = U>` + let (args, bindings) = + self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?; + self.expect_gt()?; + let span = lo.to(self.prev_span); + AngleBracketedArgs { args, bindings, span }.into() + } else { + // `(T, U) -> R` + self.bump(); // `(` + let (inputs, recovered) = self.parse_seq_to_before_tokens( + &[&token::CloseDelim(token::Paren)], + SeqSep::trailing_allowed(token::Comma), + TokenExpectType::Expect, + |p| p.parse_ty())?; + if !recovered { + self.bump(); // `)` + } + let span = lo.to(self.prev_span); + let output = if self.eat(&token::RArrow) { + Some(self.parse_ty_common(false, false)?) + } else { + None + }; + ParenthesizedArgs { inputs, output, span }.into() + }; + + PathSegment { ident, args, id: ast::DUMMY_NODE_ID } + } else { + // Generic arguments are not found. + PathSegment::from_ident(ident) + }) + } + + crate fn check_lifetime(&mut self) -> bool { + self.expected_tokens.push(TokenType::Lifetime); + self.token.is_lifetime() + } + + /// Parses a single lifetime `'a` or panics. + crate fn expect_lifetime(&mut self) -> Lifetime { + if let Some(ident) = self.token.lifetime() { + let span = self.span; + self.bump(); + Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID } + } else { + self.span_bug(self.span, "not a lifetime") + } + } + + fn eat_label(&mut self) -> Option