src/libsyntax/parse/parser.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 pub use self::PathParsingMode::*;
  12
  13 use abi;
  14 use ast::BareFnTy;
  15 use ast::{RegionTyParamBound, TraitTyParamBound, TraitBoundModifier};
  16 use ast::{Public, Unsafety};
  17 use ast::{Mod, BiAdd, Arg, Arm, Attribute, BindByRef, BindByValue};
  18 use ast::{BiBitAnd, BiBitOr, BiBitXor, BiRem, BiLt, BiGt, Block};
  19 use ast::{BlockCheckMode, CaptureByRef, CaptureByValue, CaptureClause};
  20 use ast::{Constness, ConstImplItem, ConstTraitItem, Crate, CrateConfig};
  21 use ast::{Decl, DeclItem, DeclLocal, DefaultBlock, DefaultReturn};
  22 use ast::{UnDeref, BiDiv, EMPTY_CTXT, EnumDef, ExplicitSelf};
  23 use ast::{Expr, Expr_, ExprAddrOf, ExprMatch, ExprAgain};
  24 use ast::{ExprAssign, ExprAssignOp, ExprBinary, ExprBlock, ExprBox};
  25 use ast::{ExprBreak, ExprCall, ExprCast, ExprInPlace};
  26 use ast::{ExprField, ExprTupField, ExprClosure, ExprIf, ExprIfLet, ExprIndex};
  27 use ast::{ExprLit, ExprLoop, ExprMac, ExprRange};
  28 use ast::{ExprMethodCall, ExprParen, ExprPath};
  29 use ast::{ExprRepeat, ExprRet, ExprStruct, ExprTup, ExprUnary};
  30 use ast::{ExprVec, ExprWhile, ExprWhileLet, ExprForLoop, Field, FnDecl};
  31 use ast::{ForeignItem, ForeignItemStatic, ForeignItemFn, ForeignMod, FunctionRetTy};
  32 use ast::{Ident, Inherited, ImplItem, Item, Item_, ItemStatic};
  33 use ast::{ItemEnum, ItemFn, ItemForeignMod, ItemImpl, ItemConst};
  34 use ast::{ItemMac, ItemMod, ItemStruct, ItemTrait, ItemTy, ItemDefaultImpl};
  35 use ast::{ItemExternCrate, ItemUse};
  36 use ast::{LifetimeDef, Lit, Lit_};
  37 use ast::{LitBool, LitChar, LitByte, LitByteStr};
  38 use ast::{LitStr, LitInt, Local};
  39 use ast::{MacStmtWithBraces, MacStmtWithSemicolon, MacStmtWithoutBraces};
  40 use ast::{MutImmutable, MutMutable, Mac_, MatchSource};
  41 use ast::{MutTy, BiMul, Mutability};
  42 use ast::{MethodImplItem, NamedField, UnNeg, NoReturn, UnNot};
  43 use ast::{Pat, PatBox, PatEnum, PatIdent, PatLit, PatQPath, PatMac, PatRange};
  44 use ast::{PatRegion, PatStruct, PatTup, PatVec, PatWild, PatWildMulti};
  45 use ast::PatWildSingle;
  46 use ast::{PolyTraitRef, QSelf};
  47 use ast::{Return, BiShl, BiShr, Stmt, StmtDecl};
  48 use ast::{StmtExpr, StmtSemi, StmtMac, StructDef, StructField};
  49 use ast::{StructVariantKind, BiSub, StrStyle};
  50 use ast::{SelfExplicit, SelfRegion, SelfStatic, SelfValue};
  51 use ast::{Delimited, SequenceRepetition, TokenTree, TraitItem, TraitRef};
  52 use ast::{TtDelimited, TtSequence, TtToken};
  53 use ast::{TupleVariantKind, Ty, Ty_, TypeBinding};
  54 use ast::{TyMac};
  55 use ast::{TyFixedLengthVec, TyBareFn, TyTypeof, TyInfer};
  56 use ast::{TyParam, TyParamBound, TyParen, TyPath, TyPolyTraitRef, TyPtr};
  57 use ast::{TyRptr, TyTup, TyU32, TyVec};
  58 use ast::{TypeImplItem, TypeTraitItem};
  59 use ast::{UnnamedField, UnsafeBlock};
  60 use ast::{ViewPath, ViewPathGlob, ViewPathList, ViewPathSimple};
  61 use ast::{Visibility, WhereClause};
  62 use ast;
  63 use ast_util::{self, AS_PREC, ident_to_path, operator_prec};
  64 use codemap::{self, Span, BytePos, Spanned, spanned, mk_sp, CodeMap};
  65 use diagnostic;
  66 use ext::tt::macro_parser;
  67 use parse;
  68 use parse::attr::ParserAttr;
  69 use parse::classify;
  70 use parse::common::{SeqSep, seq_sep_none, seq_sep_trailing_allowed};
  71 use parse::lexer::{Reader, TokenAndSpan};
  72 use parse::obsolete::{ParserObsoleteMethods, ObsoleteSyntax};
  73 use parse::token::{self, MatchNt, SubstNt, SpecialVarNt, InternedString};
  74 use parse::token::{keywords, special_idents, SpecialMacroVar};
  75 use parse::{new_sub_parser_from_file, ParseSess};
  76 use print::pprust;
  77 use ptr::P;
  78 use owned_slice::OwnedSlice;
  79 use parse::PResult;
  80 use diagnostic::FatalError;
  81
  82 use std::collections::HashSet;
  83 use std::io::prelude::*;
  84 use std::mem;
  85 use std::path::{Path, PathBuf};
  86 use std::rc::Rc;
  87 use std::slice;
  88
  89 bitflags! {
  90     flags Restrictions: u8 {
  91         const RESTRICTION_STMT_EXPR         = 1 << 0,
  92         const RESTRICTION_NO_STRUCT_LITERAL = 1 << 1,
  93     }
  94 }
  95
  96 type ItemInfo = (Ident, Item_, Option<Vec<Attribute> >);
  97
  98 /// How to parse a path. There are four different kinds of paths, all of which
  99 /// are parsed somewhat differently.
 100 #[derive(Copy, Clone, PartialEq)]
 101 pub enum PathParsingMode {
 102     /// A path with no type parameters; e.g. `foo::bar::Baz`
 103     NoTypesAllowed,
 104     /// A path with a lifetime and type parameters, with no double colons
 105     /// before the type parameters; e.g. `foo::bar<'a>::Baz<T>`
 106     LifetimeAndTypesWithoutColons,
 107     /// A path with a lifetime and type parameters with double colons before
 108     /// the type parameters; e.g. `foo::bar::<'a>::Baz::<T>`
 109     LifetimeAndTypesWithColons,
 110 }
 111
 112 /// How to parse a bound, whether to allow bound modifiers such as `?`.
 113 #[derive(Copy, Clone, PartialEq)]
 114 pub enum BoundParsingMode {
 115     Bare,
 116     Modified,
 117 }
 118
 119 /// Possibly accept an `token::Interpolated` expression (a pre-parsed expression
 120 /// dropped into the token stream, which happens while parsing the result of
 121 /// macro expansion). Placement of these is not as complex as I feared it would
 122 /// be. The important thing is to make sure that lookahead doesn't balk at
 123 /// `token::Interpolated` tokens.
 124 macro_rules! maybe_whole_expr {
 125     ($p:expr) => (
 126         {
 127             let found = match $p.token {
 128                 token::Interpolated(token::NtExpr(ref e)) => {
 129                     Some((*e).clone())
 130                 }
 131                 token::Interpolated(token::NtPath(_)) => {
 132                     // FIXME: The following avoids an issue with lexical borrowck scopes,
 133                     // but the clone is unfortunate.
 134                     let pt = match $p.token {
 135                         token::Interpolated(token::NtPath(ref pt)) => (**pt).clone(),
 136                         _ => unreachable!()
 137                     };
 138                     let span = $p.span;
 139                     Some($p.mk_expr(span.lo, span.hi, ExprPath(None, pt)))
 140                 }
 141                 token::Interpolated(token::NtBlock(_)) => {
 142                     // FIXME: The following avoids an issue with lexical borrowck scopes,
 143                     // but the clone is unfortunate.
 144                     let b = match $p.token {
 145                         token::Interpolated(token::NtBlock(ref b)) => (*b).clone(),
 146                         _ => unreachable!()
 147                     };
 148                     let span = $p.span;
 149                     Some($p.mk_expr(span.lo, span.hi, ExprBlock(b)))
 150                 }
 151                 _ => None
 152             };
 153             match found {
 154                 Some(e) => {
 155                     try!($p.bump());
 156                     return Ok(e);
 157                 }
 158                 None => ()
 159             }
 160         }
 161     )
 162 }
 163
 164 /// As maybe_whole_expr, but for things other than expressions
 165 macro_rules! maybe_whole {
 166     ($p:expr, $constructor:ident) => (
 167         {
 168             let found = match ($p).token {
 169                 token::Interpolated(token::$constructor(_)) => {
 170                     Some(try!(($p).bump_and_get()))
 171                 }
 172                 _ => None
 173             };
 174             if let Some(token::Interpolated(token::$constructor(x))) = found {
 175                 return Ok(x.clone());
 176             }
 177         }
 178     );
 179     (no_clone $p:expr, $constructor:ident) => (
 180         {
 181             let found = match ($p).token {
 182                 token::Interpolated(token::$constructor(_)) => {
 183                     Some(try!(($p).bump_and_get()))
 184                 }
 185                 _ => None
 186             };
 187             if let Some(token::Interpolated(token::$constructor(x))) = found {
 188                 return Ok(x);
 189             }
 190         }
 191     );
 192     (deref $p:expr, $constructor:ident) => (
 193         {
 194             let found = match ($p).token {
 195                 token::Interpolated(token::$constructor(_)) => {
 196                     Some(try!(($p).bump_and_get()))
 197                 }
 198                 _ => None
 199             };
 200             if let Some(token::Interpolated(token::$constructor(x))) = found {
 201                 return Ok((*x).clone());
 202             }
 203         }
 204     );
 205     (Some deref $p:expr, $constructor:ident) => (
 206         {
 207             let found = match ($p).token {
 208                 token::Interpolated(token::$constructor(_)) => {
 209                     Some(try!(($p).bump_and_get()))
 210                 }
 211                 _ => None
 212             };
 213             if let Some(token::Interpolated(token::$constructor(x))) = found {
 214                 return Ok(Some((*x).clone()));
 215             }
 216         }
 217     );
 218     (pair_empty $p:expr, $constructor:ident) => (
 219         {
 220             let found = match ($p).token {
 221                 token::Interpolated(token::$constructor(_)) => {
 222                     Some(try!(($p).bump_and_get()))
 223                 }
 224                 _ => None
 225             };
 226             if let Some(token::Interpolated(token::$constructor(x))) = found {
 227                 return Ok((Vec::new(), x));
 228             }
 229         }
 230     )
 231 }
 232
 233
 234 fn maybe_append(mut lhs: Vec<Attribute>, rhs: Option<Vec<Attribute>>)
 235                 -> Vec<Attribute> {
 236     if let Some(ref attrs) = rhs {
 237         lhs.extend(attrs.iter().cloned())
 238     }
 239     lhs
 240 }
 241
 242 /* ident is handled by common.rs */
 243
 244 pub struct Parser<'a> {
 245     pub sess: &'a ParseSess,
 246     /// the current token:
 247     pub token: token::Token,
 248     /// the span of the current token:
 249     pub span: Span,
 250     /// the span of the prior token:
 251     pub last_span: Span,
 252     pub cfg: CrateConfig,
 253     /// the previous token or None (only stashed sometimes).
 254     pub last_token: Option<Box<token::Token>>,
 255     pub buffer: [TokenAndSpan; 4],
 256     pub buffer_start: isize,
 257     pub buffer_end: isize,
 258     pub tokens_consumed: usize,
 259     pub restrictions: Restrictions,
 260     pub quote_depth: usize, // not (yet) related to the quasiquoter
 261     pub reader: Box<Reader+'a>,
 262     pub interner: Rc<token::IdentInterner>,
 263     /// The set of seen errors about obsolete syntax. Used to suppress
 264     /// extra detail when the same error is seen twice
 265     pub obsolete_set: HashSet<ObsoleteSyntax>,
 266     /// Used to determine the path to externally loaded source files
 267     pub mod_path_stack: Vec<InternedString>,
 268     /// Stack of spans of open delimiters. Used for error message.
 269     pub open_braces: Vec<Span>,
 270     /// Flag if this parser "owns" the directory that it is currently parsing
 271     /// in. This will affect how nested files are looked up.
 272     pub owns_directory: bool,
 273     /// Name of the root module this parser originated from. If `None`, then the
 274     /// name is not known. This does not change while the parser is descending
 275     /// into modules, and sub-parsers have new values for this name.
 276     pub root_module_name: Option<String>,
 277     pub expected_tokens: Vec<TokenType>,
 278 }
 279
 280 #[derive(PartialEq, Eq, Clone)]
 281 pub enum TokenType {
 282     Token(token::Token),
 283     Keyword(keywords::Keyword),
 284     Operator,
 285 }
 286
 287 impl TokenType {
 288     fn to_string(&self) -> String {
 289         match *self {
 290             TokenType::Token(ref t) => format!("`{}`", Parser::token_to_string(t)),
 291             TokenType::Operator => "an operator".to_string(),
 292             TokenType::Keyword(kw) => format!("`{}`", kw.to_name()),
 293         }
 294     }
 295 }
 296
 297 fn is_plain_ident_or_underscore(t: &token::Token) -> bool {
 298     t.is_plain_ident() || *t == token::Underscore
 299 }
 300
 301 /// Information about the path to a module.
 302 pub struct ModulePath {
 303     pub name: String,
 304     pub path_exists: bool,
 305     pub result: Result<ModulePathSuccess, ModulePathError>,
 306 }
 307
 308 pub struct ModulePathSuccess {
 309     pub path: ::std::path::PathBuf,
 310     pub owns_directory: bool,
 311 }
 312
 313 pub struct ModulePathError {
 314     pub err_msg: String,
 315     pub help_msg: String,
 316 }
 317
 318
 319 impl<'a> Parser<'a> {
 320     pub fn new(sess: &'a ParseSess,
 321                cfg: ast::CrateConfig,
 322                mut rdr: Box<Reader+'a>)
 323                -> Parser<'a>
 324     {
 325         let tok0 = rdr.real_token();
 326         let span = tok0.sp;
 327         let placeholder = TokenAndSpan {
 328             tok: token::Underscore,
 329             sp: span,
 330         };
 331
 332         Parser {
 333             reader: rdr,
 334             interner: token::get_ident_interner(),
 335             sess: sess,
 336             cfg: cfg,
 337             token: tok0.tok,
 338             span: span,
 339             last_span: span,
 340             last_token: None,
 341             buffer: [
 342                 placeholder.clone(),
 343                 placeholder.clone(),
 344                 placeholder.clone(),
 345                 placeholder.clone(),
 346             ],
 347             buffer_start: 0,
 348             buffer_end: 0,
 349             tokens_consumed: 0,
 350             restrictions: Restrictions::empty(),
 351             quote_depth: 0,
 352             obsolete_set: HashSet::new(),
 353             mod_path_stack: Vec::new(),
 354             open_braces: Vec::new(),
 355             owns_directory: true,
 356             root_module_name: None,
 357             expected_tokens: Vec::new(),
 358         }
 359     }
 360
 361     // Panicing fns (for now!)
 362     // This is so that the quote_*!() syntax extensions
 363     pub fn parse_expr(&mut self) -> P<Expr> {
 364         panictry!(self.parse_expr_nopanic())
 365     }
 366
 367     pub fn parse_item(&mut self) -> Option<P<Item>> {
 368         panictry!(self.parse_item_nopanic())
 369     }
 370
 371     pub fn parse_pat(&mut self) -> P<Pat> {
 372         panictry!(self.parse_pat_nopanic())
 373     }
 374
 375     pub fn parse_arm(&mut self) -> Arm {
 376         panictry!(self.parse_arm_nopanic())
 377     }
 378
 379     pub fn parse_ty(&mut self) -> P<Ty> {
 380         panictry!(self.parse_ty_nopanic())
 381     }
 382
 383     pub fn parse_stmt(&mut self) -> Option<P<Stmt>> {
 384         panictry!(self.parse_stmt_nopanic())
 385     }
 386
 387     /// Convert a token to a string using self's reader
 388     pub fn token_to_string(token: &token::Token) -> String {
 389         pprust::token_to_string(token)
 390     }
 391
 392     /// Convert the current token to a string using self's reader
 393     pub fn this_token_to_string(&self) -> String {
 394         Parser::token_to_string(&self.token)
 395     }
 396
 397     pub fn unexpected_last(&self, t: &token::Token) -> FatalError {
 398         let token_str = Parser::token_to_string(t);
 399         let last_span = self.last_span;
 400         self.span_fatal(last_span, &format!("unexpected token: `{}`",
 401                                                 token_str))
 402     }
 403
 404     pub fn unexpected(&mut self) -> FatalError {
 405         match self.expect_one_of(&[], &[]) {
 406             Err(e) => e,
 407             Ok(_) => unreachable!()
 408         }
 409     }
 410
 411     /// Expect and consume the token t. Signal an error if
 412     /// the next token is not t.
 413     pub fn expect(&mut self, t: &token::Token) -> PResult<()> {
 414         if self.expected_tokens.is_empty() {
 415             if self.token == *t {
 416                 self.bump()
 417             } else {
 418                 let token_str = Parser::token_to_string(t);
 419                 let this_token_str = self.this_token_to_string();
 420                 Err(self.fatal(&format!("expected `{}`, found `{}`",
 421                                    token_str,
 422                                    this_token_str)))
 423             }
 424         } else {
 425             self.expect_one_of(slice::ref_slice(t), &[])
 426         }
 427     }
 428
 429     /// Expect next token to be edible or inedible token.  If edible,
 430     /// then consume it; if inedible, then return without consuming
 431     /// anything.  Signal a fatal error if next token is unexpected.
 432     pub fn expect_one_of(&mut self,
 433                          edible: &[token::Token],
 434                          inedible: &[token::Token]) -> PResult<()>{
 435         fn tokens_to_string(tokens: &[TokenType]) -> String {
 436             let mut i = tokens.iter();
 437             // This might be a sign we need a connect method on Iterator.
 438             let b = i.next()
 439                      .map_or("".to_string(), |t| t.to_string());
 440             i.enumerate().fold(b, |mut b, (i, ref a)| {
 441                 if tokens.len() > 2 && i == tokens.len() - 2 {
 442                     b.push_str(", or ");
 443                 } else if tokens.len() == 2 && i == tokens.len() - 2 {
 444                     b.push_str(" or ");
 445                 } else {
 446                     b.push_str(", ");
 447                 }
 448                 b.push_str(&*a.to_string());
 449                 b
 450             })
 451         }
 452         if edible.contains(&self.token) {
 453             self.bump()
 454         } else if inedible.contains(&self.token) {
 455             // leave it in the input
 456             Ok(())
 457         } else {
 458             let mut expected = edible.iter()
 459                 .map(|x| TokenType::Token(x.clone()))
 460                 .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
 461                 .chain(self.expected_tokens.iter().cloned())
 462                 .collect::<Vec<_>>();
 463             expected.sort_by(|a, b| a.to_string().cmp(&b.to_string()));
 464             expected.dedup();
 465             let expect = tokens_to_string(&expected[..]);
 466             let actual = self.this_token_to_string();
 467             Err(self.fatal(
 468                 &(if expected.len() > 1 {
 469                     (format!("expected one of {}, found `{}`",
 470                              expect,
 471                              actual))
 472                 } else if expected.is_empty() {
 473                     (format!("unexpected token: `{}`",
 474                              actual))
 475                 } else {
 476                     (format!("expected {}, found `{}`",
 477                              expect,
 478                              actual))
 479                 })[..]
 480             ))
 481         }
 482     }
 483
 484     /// Check for erroneous `ident { }`; if matches, signal error and
 485     /// recover (without consuming any expected input token).  Returns
 486     /// true if and only if input was consumed for recovery.
 487     pub fn check_for_erroneous_unit_struct_expecting(&mut self,
 488                                                      expected: &[token::Token])
 489                                                      -> PResult<bool> {
 490         if self.token == token::OpenDelim(token::Brace)
 491             && expected.iter().all(|t| *t != token::OpenDelim(token::Brace))
 492             && self.look_ahead(1, |t| *t == token::CloseDelim(token::Brace)) {
 493             // matched; signal non-fatal error and recover.
 494             let span = self.span;
 495             self.span_err(span,
 496                           "unit-like struct construction is written with no trailing `{ }`");
 497             try!(self.eat(&token::OpenDelim(token::Brace)));
 498             try!(self.eat(&token::CloseDelim(token::Brace)));
 499             Ok(true)
 500         } else {
 501             Ok(false)
 502         }
 503     }
 504
 505     /// Commit to parsing a complete expression `e` expected to be
 506     /// followed by some token from the set edible + inedible.  Recover
 507     /// from anticipated input errors, discarding erroneous characters.
 508     pub fn commit_expr(&mut self, e: &Expr, edible: &[token::Token],
 509                        inedible: &[token::Token]) -> PResult<()> {
 510         debug!("commit_expr {:?}", e);
 511         if let ExprPath(..) = e.node {
 512             // might be unit-struct construction; check for recoverableinput error.
 513             let expected = edible.iter()
 514                 .cloned()
 515                 .chain(inedible.iter().cloned())
 516                 .collect::<Vec<_>>();
 517             try!(self.check_for_erroneous_unit_struct_expecting(&expected[..]));
 518         }
 519         self.expect_one_of(edible, inedible)
 520     }
 521
 522     pub fn commit_expr_expecting(&mut self, e: &Expr, edible: token::Token) -> PResult<()> {
 523         self.commit_expr(e, &[edible], &[])
 524     }
 525
 526     /// Commit to parsing a complete statement `s`, which expects to be
 527     /// followed by some token from the set edible + inedible.  Check
 528     /// for recoverable input errors, discarding erroneous characters.
 529     pub fn commit_stmt(&mut self, edible: &[token::Token],
 530                        inedible: &[token::Token]) -> PResult<()> {
 531         if self.last_token
 532                .as_ref()
 533                .map_or(false, |t| t.is_ident() || t.is_path()) {
 534             let expected = edible.iter()
 535                 .cloned()
 536                 .chain(inedible.iter().cloned())
 537                 .collect::<Vec<_>>();
 538             try!(self.check_for_erroneous_unit_struct_expecting(&expected));
 539         }
 540         self.expect_one_of(edible, inedible)
 541     }
 542
 543     pub fn commit_stmt_expecting(&mut self, edible: token::Token) -> PResult<()> {
 544         self.commit_stmt(&[edible], &[])
 545     }
 546
 547     pub fn parse_ident(&mut self) -> PResult<ast::Ident> {
 548         self.check_strict_keywords();
 549         try!(self.check_reserved_keywords());
 550         match self.token {
 551             token::Ident(i, _) => {
 552                 try!(self.bump());
 553                 Ok(i)
 554             }
 555             token::Interpolated(token::NtIdent(..)) => {
 556                 self.bug("ident interpolation not converted to real token");
 557             }
 558             _ => {
 559                 let token_str = self.this_token_to_string();
 560                 Err(self.fatal(&format!("expected ident, found `{}`",
 561                                     token_str)))
 562             }
 563         }
 564     }
 565
 566     pub fn parse_ident_or_self_type(&mut self) -> PResult<ast::Ident> {
 567         if self.is_self_type_ident() {
 568             self.expect_self_type_ident()
 569         } else {
 570             self.parse_ident()
 571         }
 572     }
 573
 574     pub fn parse_path_list_item(&mut self) -> PResult<ast::PathListItem> {
 575         let lo = self.span.lo;
 576         let node = if try!(self.eat_keyword(keywords::SelfValue)) {
 577             let rename = try!(self.parse_rename());
 578             ast::PathListMod { id: ast::DUMMY_NODE_ID, rename: rename }
 579         } else {
 580             let ident = try!(self.parse_ident());
 581             let rename = try!(self.parse_rename());
 582             ast::PathListIdent { name: ident, rename: rename, id: ast::DUMMY_NODE_ID }
 583         };
 584         let hi = self.last_span.hi;
 585         Ok(spanned(lo, hi, node))
 586     }
 587
 588     /// Check if the next token is `tok`, and return `true` if so.
 589     ///
 590     /// This method is will automatically add `tok` to `expected_tokens` if `tok` is not
 591     /// encountered.
 592     pub fn check(&mut self, tok: &token::Token) -> bool {
 593         let is_present = self.token == *tok;
 594         if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
 595         is_present
 596     }
 597
 598     /// Consume token 'tok' if it exists. Returns true if the given
 599     /// token was present, false otherwise.
 600     pub fn eat(&mut self, tok: &token::Token) -> PResult<bool> {
 601         let is_present = self.check(tok);
 602         if is_present { try!(self.bump())}
 603         Ok(is_present)
 604     }
 605
 606     pub fn check_keyword(&mut self, kw: keywords::Keyword) -> bool {
 607         self.expected_tokens.push(TokenType::Keyword(kw));
 608         self.token.is_keyword(kw)
 609     }
 610
 611     /// If the next token is the given keyword, eat it and return
 612     /// true. Otherwise, return false.
 613     pub fn eat_keyword(&mut self, kw: keywords::Keyword) -> PResult<bool> {
 614         if self.check_keyword(kw) {
 615             try!(self.bump());
 616             Ok(true)
 617         } else {
 618             Ok(false)
 619         }
 620     }
 621
 622     pub fn eat_keyword_noexpect(&mut self, kw: keywords::Keyword) -> PResult<bool> {
 623         if self.token.is_keyword(kw) {
 624             try!(self.bump());
 625             Ok(true)
 626         } else {
 627             Ok(false)
 628         }
 629     }
 630
 631     /// If the given word is not a keyword, signal an error.
 632     /// If the next token is not the given word, signal an error.
 633     /// Otherwise, eat it.
 634     pub fn expect_keyword(&mut self, kw: keywords::Keyword) -> PResult<()> {
 635         if !try!(self.eat_keyword(kw) ){
 636             self.expect_one_of(&[], &[])
 637         } else {
 638             Ok(())
 639         }
 640     }
 641
 642     /// Signal an error if the given string is a strict keyword
 643     pub fn check_strict_keywords(&mut self) {
 644         if self.token.is_strict_keyword() {
 645             let token_str = self.this_token_to_string();
 646             let span = self.span;
 647             self.span_err(span,
 648                           &format!("expected identifier, found keyword `{}`",
 649                                   token_str));
 650         }
 651     }
 652
 653     /// Signal an error if the current token is a reserved keyword
 654     pub fn check_reserved_keywords(&mut self) -> PResult<()>{
 655         if self.token.is_reserved_keyword() {
 656             let token_str = self.this_token_to_string();
 657             Err(self.fatal(&format!("`{}` is a reserved keyword",
 658                                token_str)))
 659         } else {
 660             Ok(())
 661         }
 662     }
 663
 664     /// Expect and consume an `&`. If `&&` is seen, replace it with a single
 665     /// `&` and continue. If an `&` is not seen, signal an error.
 666     fn expect_and(&mut self) -> PResult<()> {
 667         self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
 668         match self.token {
 669             token::BinOp(token::And) => self.bump(),
 670             token::AndAnd => {
 671                 let span = self.span;
 672                 let lo = span.lo + BytePos(1);
 673                 Ok(self.replace_token(token::BinOp(token::And), lo, span.hi))
 674             }
 675             _ => self.expect_one_of(&[], &[])
 676         }
 677     }
 678
 679     pub fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
 680         match suffix {
 681             None => {/* everything ok */}
 682             Some(suf) => {
 683                 let text = suf.as_str();
 684                 if text.is_empty() {
 685                     self.span_bug(sp, "found empty literal suffix in Some")
 686                 }
 687                 self.span_err(sp, &*format!("{} with a suffix is invalid", kind));
 688             }
 689         }
 690     }
 691
 692
 693     /// Attempt to consume a `<`. If `<<` is seen, replace it with a single
 694     /// `<` and continue. If a `<` is not seen, return false.
 695     ///
 696     /// This is meant to be used when parsing generics on a path to get the
 697     /// starting token.
 698     fn eat_lt(&mut self) -> PResult<bool> {
 699         self.expected_tokens.push(TokenType::Token(token::Lt));
 700         match self.token {
 701             token::Lt => { try!(self.bump()); Ok(true)}
 702             token::BinOp(token::Shl) => {
 703                 let span = self.span;
 704                 let lo = span.lo + BytePos(1);
 705                 self.replace_token(token::Lt, lo, span.hi);
 706                 Ok(true)
 707             }
 708             _ => Ok(false),
 709         }
 710     }
 711
 712     fn expect_lt(&mut self) -> PResult<()> {
 713         if !try!(self.eat_lt()) {
 714             self.expect_one_of(&[], &[])
 715         } else {
 716             Ok(())
 717         }
 718     }
 719
 720     /// Expect and consume a GT. if a >> is seen, replace it
 721     /// with a single > and continue. If a GT is not seen,
 722     /// signal an error.
 723     pub fn expect_gt(&mut self) -> PResult<()> {
 724         self.expected_tokens.push(TokenType::Token(token::Gt));
 725         match self.token {
 726             token::Gt => self.bump(),
 727             token::BinOp(token::Shr) => {
 728                 let span = self.span;
 729                 let lo = span.lo + BytePos(1);
 730                 Ok(self.replace_token(token::Gt, lo, span.hi))
 731             }
 732             token::BinOpEq(token::Shr) => {
 733                 let span = self.span;
 734                 let lo = span.lo + BytePos(1);
 735                 Ok(self.replace_token(token::Ge, lo, span.hi))
 736             }
 737             token::Ge => {
 738                 let span = self.span;
 739                 let lo = span.lo + BytePos(1);
 740                 Ok(self.replace_token(token::Eq, lo, span.hi))
 741             }
 742             _ => {
 743                 let gt_str = Parser::token_to_string(&token::Gt);
 744                 let this_token_str = self.this_token_to_string();
 745                 Err(self.fatal(&format!("expected `{}`, found `{}`",
 746                                    gt_str,
 747                                    this_token_str)))
 748             }
 749         }
 750     }
 751
 752     pub fn parse_seq_to_before_gt_or_return<T, F>(&mut self,
 753                                                   sep: Option<token::Token>,
 754                                                   mut f: F)
 755                                                   -> PResult<(OwnedSlice<T>, bool)> where
 756         F: FnMut(&mut Parser) -> PResult<Option<T>>,
 757     {
 758         let mut v = Vec::new();
 759         // This loop works by alternating back and forth between parsing types
 760         // and commas.  For example, given a string `A, B,>`, the parser would
 761         // first parse `A`, then a comma, then `B`, then a comma. After that it
 762         // would encounter a `>` and stop. This lets the parser handle trailing
 763         // commas in generic parameters, because it can stop either after
 764         // parsing a type or after parsing a comma.
 765         for i in 0.. {
 766             if self.check(&token::Gt)
 767                 || self.token == token::BinOp(token::Shr)
 768                 || self.token == token::Ge
 769                 || self.token == token::BinOpEq(token::Shr) {
 770                 break;
 771             }
 772
 773             if i % 2 == 0 {
 774                 match try!(f(self)) {
 775                     Some(result) => v.push(result),
 776                     None => return Ok((OwnedSlice::from_vec(v), true))
 777                 }
 778             } else {
 779                 if let Some(t) = sep.as_ref() {
 780                     try!(self.expect(t));
 781                 }
 782
 783             }
 784         }
 785         return Ok((OwnedSlice::from_vec(v), false));
 786     }
 787
 788     /// Parse a sequence bracketed by '<' and '>', stopping
 789     /// before the '>'.
 790     pub fn parse_seq_to_before_gt<T, F>(&mut self,
 791                                         sep: Option<token::Token>,
 792                                         mut f: F)
 793                                         -> PResult<OwnedSlice<T>> where
 794         F: FnMut(&mut Parser) -> PResult<T>,
 795     {
 796         let (result, returned) = try!(self.parse_seq_to_before_gt_or_return(sep,
 797                                                     |p| Ok(Some(try!(f(p))))));
 798         assert!(!returned);
 799         return Ok(result);
 800     }
 801
 802     pub fn parse_seq_to_gt<T, F>(&mut self,
 803                                  sep: Option<token::Token>,
 804                                  f: F)
 805                                  -> PResult<OwnedSlice<T>> where
 806         F: FnMut(&mut Parser) -> PResult<T>,
 807     {
 808         let v = try!(self.parse_seq_to_before_gt(sep, f));
 809         try!(self.expect_gt());
 810         return Ok(v);
 811     }
 812
 813     pub fn parse_seq_to_gt_or_return<T, F>(&mut self,
 814                                            sep: Option<token::Token>,
 815                                            f: F)
 816                                            -> PResult<(OwnedSlice<T>, bool)> where
 817         F: FnMut(&mut Parser) -> PResult<Option<T>>,
 818     {
 819         let (v, returned) = try!(self.parse_seq_to_before_gt_or_return(sep, f));
 820         if !returned {
 821             try!(self.expect_gt());
 822         }
 823         return Ok((v, returned));
 824     }
 825
 826     /// Parse a sequence, including the closing delimiter. The function
 827     /// f must consume tokens until reaching the next separator or
 828     /// closing bracket.
 829     pub fn parse_seq_to_end<T, F>(&mut self,
 830                                   ket: &token::Token,
 831                                   sep: SeqSep,
 832                                   f: F)
 833                                   -> PResult<Vec<T>> where
 834         F: FnMut(&mut Parser) -> PResult<T>,
 835     {
 836         let val = try!(self.parse_seq_to_before_end(ket, sep, f));
 837         try!(self.bump());
 838         Ok(val)
 839     }
 840
 841     /// Parse a sequence, not including the closing delimiter. The function
 842     /// f must consume tokens until reaching the next separator or
 843     /// closing bracket.
 844     pub fn parse_seq_to_before_end<T, F>(&mut self,
 845                                          ket: &token::Token,
 846                                          sep: SeqSep,
 847                                          mut f: F)
 848                                          -> PResult<Vec<T>> where
 849         F: FnMut(&mut Parser) -> PResult<T>,
 850     {
 851         let mut first: bool = true;
 852         let mut v = vec!();
 853         while self.token != *ket {
 854             match sep.sep {
 855               Some(ref t) => {
 856                 if first { first = false; }
 857                 else { try!(self.expect(t)); }
 858               }
 859               _ => ()
 860             }
 861             if sep.trailing_sep_allowed && self.check(ket) { break; }
 862             v.push(try!(f(self)));
 863         }
 864         return Ok(v);
 865     }
 866
 867     /// Parse a sequence, including the closing delimiter. The function
 868     /// f must consume tokens until reaching the next separator or
 869     /// closing bracket.
 870     pub fn parse_unspanned_seq<T, F>(&mut self,
 871                                      bra: &token::Token,
 872                                      ket: &token::Token,
 873                                      sep: SeqSep,
 874                                      f: F)
 875                                      -> PResult<Vec<T>> where
 876         F: FnMut(&mut Parser) -> PResult<T>,
 877     {
 878         try!(self.expect(bra));
 879         let result = try!(self.parse_seq_to_before_end(ket, sep, f));
 880         try!(self.bump());
 881         Ok(result)
 882     }
 883
 884     /// Parse a sequence parameter of enum variant. For consistency purposes,
 885     /// these should not be empty.
 886     pub fn parse_enum_variant_seq<T, F>(&mut self,
 887                                         bra: &token::Token,
 888                                         ket: &token::Token,
 889                                         sep: SeqSep,
 890                                         f: F)
 891                                         -> PResult<Vec<T>> where
 892         F: FnMut(&mut Parser) -> PResult<T>,
 893     {
 894         let result = try!(self.parse_unspanned_seq(bra, ket, sep, f));
 895         if result.is_empty() {
 896             let last_span = self.last_span;
 897             self.span_err(last_span,
 898             "nullary enum variants are written with no trailing `( )`");
 899         }
 900         Ok(result)
 901     }
 902
 903     // NB: Do not use this function unless you actually plan to place the
 904     // spanned list in the AST.
 905     pub fn parse_seq<T, F>(&mut self,
 906                            bra: &token::Token,
 907                            ket: &token::Token,
 908                            sep: SeqSep,
 909                            f: F)
 910                            -> PResult<Spanned<Vec<T>>> where
 911         F: FnMut(&mut Parser) -> PResult<T>,
 912     {
 913         let lo = self.span.lo;
 914         try!(self.expect(bra));
 915         let result = try!(self.parse_seq_to_before_end(ket, sep, f));
 916         let hi = self.span.hi;
 917         try!(self.bump());
 918         Ok(spanned(lo, hi, result))
 919     }
 920
 921     /// Advance the parser by one token
 922     pub fn bump(&mut self) -> PResult<()> {
 923         self.last_span = self.span;
 924         // Stash token for error recovery (sometimes; clone is not necessarily cheap).
 925         self.last_token = if self.token.is_ident() ||
 926                           self.token.is_path() ||
 927                           self.token == token::Comma {
 928             Some(Box::new(self.token.clone()))
 929         } else {
 930             None
 931         };
 932         let next = if self.buffer_start == self.buffer_end {
 933             self.reader.real_token()
 934         } else {
 935             // Avoid token copies with `replace`.
 936             let buffer_start = self.buffer_start as usize;
 937             let next_index = (buffer_start + 1) & 3;
 938             self.buffer_start = next_index as isize;
 939
 940             let placeholder = TokenAndSpan {
 941                 tok: token::Underscore,
 942                 sp: self.span,
 943             };
 944             mem::replace(&mut self.buffer[buffer_start], placeholder)
 945         };
 946         self.span = next.sp;
 947         self.token = next.tok;
 948         self.tokens_consumed += 1;
 949         self.expected_tokens.clear();
 950         // check after each token
 951         self.check_unknown_macro_variable()
 952     }
 953
 954     /// Advance the parser by one token and return the bumped token.
 955     pub fn bump_and_get(&mut self) -> PResult<token::Token> {
 956         let old_token = mem::replace(&mut self.token, token::Underscore);
 957         try!(self.bump());
 958         Ok(old_token)
 959     }
 960
 961     /// EFFECT: replace the current token and span with the given one
 962     pub fn replace_token(&mut self,
 963                          next: token::Token,
 964                          lo: BytePos,
 965                          hi: BytePos) {
 966         self.last_span = mk_sp(self.span.lo, lo);
 967         self.token = next;
 968         self.span = mk_sp(lo, hi);
 969     }
 970     pub fn buffer_length(&mut self) -> isize {
 971         if self.buffer_start <= self.buffer_end {
 972             return self.buffer_end - self.buffer_start;
 973         }
 974         return (4 - self.buffer_start) + self.buffer_end;
 975     }
 976     pub fn look_ahead<R, F>(&mut self, distance: usize, f: F) -> R where
 977         F: FnOnce(&token::Token) -> R,
 978     {
 979         let dist = distance as isize;
 980         while self.buffer_length() < dist {
 981             self.buffer[self.buffer_end as usize] = self.reader.real_token();
 982             self.buffer_end = (self.buffer_end + 1) & 3;
 983         }
 984         f(&self.buffer[((self.buffer_start + dist - 1) & 3) as usize].tok)
 985     }
 986     pub fn fatal(&self, m: &str) -> diagnostic::FatalError {
 987         self.sess.span_diagnostic.span_fatal(self.span, m)
 988     }
 989     pub fn span_fatal(&self, sp: Span, m: &str) -> diagnostic::FatalError {
 990         self.sess.span_diagnostic.span_fatal(sp, m)
 991     }
 992     pub fn span_fatal_help(&self, sp: Span, m: &str, help: &str) -> diagnostic::FatalError {
 993         self.span_err(sp, m);
 994         self.fileline_help(sp, help);
 995         diagnostic::FatalError
 996     }
 997     pub fn span_note(&self, sp: Span, m: &str) {
 998         self.sess.span_diagnostic.span_note(sp, m)
 999     }
1000     pub fn span_help(&self, sp: Span, m: &str) {
1001         self.sess.span_diagnostic.span_help(sp, m)
1002     }
1003     pub fn span_suggestion(&self, sp: Span, m: &str, n: String) {
1004         self.sess.span_diagnostic.span_suggestion(sp, m, n)
1005     }
1006     pub fn fileline_help(&self, sp: Span, m: &str) {
1007         self.sess.span_diagnostic.fileline_help(sp, m)
1008     }
1009     pub fn bug(&self, m: &str) -> ! {
1010         self.sess.span_diagnostic.span_bug(self.span, m)
1011     }
1012     pub fn warn(&self, m: &str) {
1013         self.sess.span_diagnostic.span_warn(self.span, m)
1014     }
1015     pub fn span_warn(&self, sp: Span, m: &str) {
1016         self.sess.span_diagnostic.span_warn(sp, m)
1017     }
1018     pub fn span_err(&self, sp: Span, m: &str) {
1019         self.sess.span_diagnostic.span_err(sp, m)
1020     }
1021     pub fn span_bug(&self, sp: Span, m: &str) -> ! {
1022         self.sess.span_diagnostic.span_bug(sp, m)
1023     }
1024     pub fn abort_if_errors(&self) {
1025         self.sess.span_diagnostic.handler().abort_if_errors();
1026     }
1027
1028     pub fn id_to_interned_str(&mut self, id: Ident) -> InternedString {
1029         id.name.as_str()
1030     }
1031
1032     /// Is the current token one of the keywords that signals a bare function
1033     /// type?
1034     pub fn token_is_bare_fn_keyword(&mut self) -> bool {
1035         self.check_keyword(keywords::Fn) ||
1036             self.check_keyword(keywords::Unsafe) ||
1037             self.check_keyword(keywords::Extern)
1038     }
1039
1040     pub fn get_lifetime(&mut self) -> ast::Ident {
1041         match self.token {
1042             token::Lifetime(ref ident) => *ident,
1043             _ => self.bug("not a lifetime"),
1044         }
1045     }
1046
1047     pub fn parse_for_in_type(&mut self) -> PResult<Ty_> {
1048         /*
1049         Parses whatever can come after a `for` keyword in a type.
1050         The `for` has already been consumed.
1051
1052         Deprecated:
1053
1054         - for <'lt> |S| -> T
1055
1056         Eventually:
1057
1058         - for <'lt> [unsafe] [extern "ABI"] fn (S) -> T
1059         - for <'lt> path::foo(a, b)
1060
1061         */
1062
1063         // parse <'lt>
1064         let lo = self.span.lo;
1065
1066         let lifetime_defs = try!(self.parse_late_bound_lifetime_defs());
1067
1068         // examine next token to decide to do
1069         if self.token_is_bare_fn_keyword() {
1070             self.parse_ty_bare_fn(lifetime_defs)
1071         } else {
1072             let hi = self.span.hi;
1073             let trait_ref = try!(self.parse_trait_ref());
1074             let poly_trait_ref = ast::PolyTraitRef { bound_lifetimes: lifetime_defs,
1075                                                      trait_ref: trait_ref,
1076                                                      span: mk_sp(lo, hi)};
1077             let other_bounds = if try!(self.eat(&token::BinOp(token::Plus)) ){
1078                 try!(self.parse_ty_param_bounds(BoundParsingMode::Bare))
1079             } else {
1080                 OwnedSlice::empty()
1081             };
1082             let all_bounds =
1083                 Some(TraitTyParamBound(poly_trait_ref, TraitBoundModifier::None)).into_iter()
1084                 .chain(other_bounds.into_vec())
1085                 .collect();
1086             Ok(ast::TyPolyTraitRef(all_bounds))
1087         }
1088     }
1089
1090     pub fn parse_ty_path(&mut self) -> PResult<Ty_> {
1091         Ok(TyPath(None, try!(self.parse_path(LifetimeAndTypesWithoutColons))))
1092     }
1093
1094     /// parse a TyBareFn type:
1095     pub fn parse_ty_bare_fn(&mut self, lifetime_defs: Vec<ast::LifetimeDef>) -> PResult<Ty_> {
1096         /*
1097
1098         [unsafe] [extern "ABI"] fn <'lt> (S) -> T
1099          ^~~~^           ^~~~^     ^~~~^ ^~^    ^
1100            |               |         |    |     |
1101            |               |         |    |   Return type
1102            |               |         |  Argument types
1103            |               |     Lifetimes
1104            |              ABI
1105         Function Style
1106         */
1107
1108         let unsafety = try!(self.parse_unsafety());
1109         let abi = if try!(self.eat_keyword(keywords::Extern) ){
1110             try!(self.parse_opt_abi()).unwrap_or(abi::C)
1111         } else {
1112             abi::Rust
1113         };
1114
1115         try!(self.expect_keyword(keywords::Fn));
1116         let (inputs, variadic) = try!(self.parse_fn_args(false, true));
1117         let ret_ty = try!(self.parse_ret_ty());
1118         let decl = P(FnDecl {
1119             inputs: inputs,
1120             output: ret_ty,
1121             variadic: variadic
1122         });
1123         Ok(TyBareFn(P(BareFnTy {
1124             abi: abi,
1125             unsafety: unsafety,
1126             lifetimes: lifetime_defs,
1127             decl: decl
1128         })))
1129     }
1130
1131     /// Parses an obsolete closure kind (`&:`, `&mut:`, or `:`).
1132     pub fn parse_obsolete_closure_kind(&mut self) -> PResult<()> {
1133          let lo = self.span.lo;
1134         if
1135             self.check(&token::BinOp(token::And)) &&
1136             self.look_ahead(1, |t| t.is_keyword(keywords::Mut)) &&
1137             self.look_ahead(2, |t| *t == token::Colon)
1138         {
1139             try!(self.bump());
1140             try!(self.bump());
1141             try!(self.bump());
1142         } else if
1143             self.token == token::BinOp(token::And) &&
1144             self.look_ahead(1, |t| *t == token::Colon)
1145         {
1146             try!(self.bump());
1147             try!(self.bump());
1148         } else if
1149             try!(self.eat(&token::Colon))
1150         {
1151             /* nothing */
1152         } else {
1153             return Ok(());
1154         }
1155
1156         let span = mk_sp(lo, self.span.hi);
1157         self.obsolete(span, ObsoleteSyntax::ClosureKind);
1158         Ok(())
1159     }
1160
1161     pub fn parse_unsafety(&mut self) -> PResult<Unsafety> {
1162         if try!(self.eat_keyword(keywords::Unsafe)) {
1163             return Ok(Unsafety::Unsafe);
1164         } else {
1165             return Ok(Unsafety::Normal);
1166         }
1167     }
1168
1169     /// Parse the items in a trait declaration
1170     pub fn parse_trait_items(&mut self) -> PResult<Vec<P<TraitItem>>> {
1171         self.parse_unspanned_seq(
1172             &token::OpenDelim(token::Brace),
1173             &token::CloseDelim(token::Brace),
1174             seq_sep_none(),
1175             |p| -> PResult<P<TraitItem>> {
1176             maybe_whole!(no_clone p, NtTraitItem);
1177             let mut attrs = p.parse_outer_attributes();
1178             let lo = p.span.lo;
1179
1180             let (name, node) = if try!(p.eat_keyword(keywords::Type)) {
1181                 let TyParam {ident, bounds, default, ..} = try!(p.parse_ty_param());
1182                 try!(p.expect(&token::Semi));
1183                 (ident, TypeTraitItem(bounds, default))
1184             } else if p.is_const_item() {
1185                 try!(p.expect_keyword(keywords::Const));
1186                 let ident = try!(p.parse_ident());
1187                 try!(p.expect(&token::Colon));
1188                 let ty = try!(p.parse_ty_sum());
1189                 let default = if p.check(&token::Eq) {
1190                     try!(p.bump());
1191                     let expr = try!(p.parse_expr_nopanic());
1192                     try!(p.commit_expr_expecting(&expr, token::Semi));
1193                     Some(expr)
1194                 } else {
1195                     try!(p.expect(&token::Semi));
1196                     None
1197                 };
1198                 (ident, ConstTraitItem(ty, default))
1199             } else {
1200                 let (constness, unsafety, abi) = try!(p.parse_fn_front_matter());
1201
1202                 let ident = try!(p.parse_ident());
1203                 let mut generics = try!(p.parse_generics());
1204
1205                 let (explicit_self, d) = try!(p.parse_fn_decl_with_self(|p|{
1206                     // This is somewhat dubious; We don't want to allow
1207                     // argument names to be left off if there is a
1208                     // definition...
1209                     p.parse_arg_general(false)
1210                 }));
1211
1212                 generics.where_clause = try!(p.parse_where_clause());
1213                 let sig = ast::MethodSig {
1214                     unsafety: unsafety,
1215                     constness: constness,
1216                     decl: d,
1217                     generics: generics,
1218                     abi: abi,
1219                     explicit_self: explicit_self,
1220                 };
1221
1222                 let body = match p.token {
1223                   token::Semi => {
1224                     try!(p.bump());
1225                     debug!("parse_trait_methods(): parsing required method");
1226                     None
1227                   }
1228                   token::OpenDelim(token::Brace) => {
1229                     debug!("parse_trait_methods(): parsing provided method");
1230                     let (inner_attrs, body) =
1231                         try!(p.parse_inner_attrs_and_block());
1232                     attrs.extend(inner_attrs.iter().cloned());
1233                     Some(body)
1234                   }
1235
1236                   _ => {
1237                       let token_str = p.this_token_to_string();
1238                       return Err(p.fatal(&format!("expected `;` or `{{`, found `{}`",
1239                                        token_str)[..]))
1240                   }
1241                 };
1242                 (ident, ast::MethodTraitItem(sig, body))
1243             };
1244
1245             Ok(P(TraitItem {
1246                 id: ast::DUMMY_NODE_ID,
1247                 ident: name,
1248                 attrs: attrs,
1249                 node: node,
1250                 span: mk_sp(lo, p.last_span.hi),
1251             }))
1252         })
1253     }
1254
1255     /// Parse a possibly mutable type
1256     pub fn parse_mt(&mut self) -> PResult<MutTy> {
1257         let mutbl = try!(self.parse_mutability());
1258         let t = try!(self.parse_ty_nopanic());
1259         Ok(MutTy { ty: t, mutbl: mutbl })
1260     }
1261
1262     /// Parse optional return type [ -> TY ] in function decl
1263     pub fn parse_ret_ty(&mut self) -> PResult<FunctionRetTy> {
1264         if try!(self.eat(&token::RArrow) ){
1265             if try!(self.eat(&token::Not) ){
1266                 Ok(NoReturn(self.last_span))
1267             } else {
1268                 Ok(Return(try!(self.parse_ty_nopanic())))
1269             }
1270         } else {
1271             let pos = self.span.lo;
1272             Ok(DefaultReturn(mk_sp(pos, pos)))
1273         }
1274     }
1275
1276     /// Parse a type in a context where `T1+T2` is allowed.
1277     pub fn parse_ty_sum(&mut self) -> PResult<P<Ty>> {
1278         let lo = self.span.lo;
1279         let lhs = try!(self.parse_ty_nopanic());
1280
1281         if !try!(self.eat(&token::BinOp(token::Plus)) ){
1282             return Ok(lhs);
1283         }
1284
1285         let bounds = try!(self.parse_ty_param_bounds(BoundParsingMode::Bare));
1286
1287         // In type grammar, `+` is treated like a binary operator,
1288         // and hence both L and R side are required.
1289         if bounds.is_empty() {
1290             let last_span = self.last_span;
1291             self.span_err(last_span,
1292                           "at least one type parameter bound \
1293                           must be specified");
1294         }
1295
1296         let sp = mk_sp(lo, self.last_span.hi);
1297         let sum = ast::TyObjectSum(lhs, bounds);
1298         Ok(P(Ty {id: ast::DUMMY_NODE_ID, node: sum, span: sp}))
1299     }
1300
1301     /// Parse a type.
1302     pub fn parse_ty_nopanic(&mut self) -> PResult<P<Ty>> {
1303         maybe_whole!(no_clone self, NtTy);
1304
1305         let lo = self.span.lo;
1306
1307         let t = if self.check(&token::OpenDelim(token::Paren)) {
1308             try!(self.bump());
1309
1310             // (t) is a parenthesized ty
1311             // (t,) is the type of a tuple with only one field,
1312             // of type t
1313             let mut ts = vec![];
1314             let mut last_comma = false;
1315             while self.token != token::CloseDelim(token::Paren) {
1316                 ts.push(try!(self.parse_ty_sum()));
1317                 if self.check(&token::Comma) {
1318                     last_comma = true;
1319                     try!(self.bump());
1320                 } else {
1321                     last_comma = false;
1322                     break;
1323                 }
1324             }
1325
1326             try!(self.expect(&token::CloseDelim(token::Paren)));
1327             if ts.len() == 1 && !last_comma {
1328                 TyParen(ts.into_iter().nth(0).unwrap())
1329             } else {
1330                 TyTup(ts)
1331             }
1332         } else if self.check(&token::BinOp(token::Star)) {
1333             // STAR POINTER (bare pointer?)
1334             try!(self.bump());
1335             TyPtr(try!(self.parse_ptr()))
1336         } else if self.check(&token::OpenDelim(token::Bracket)) {
1337             // VECTOR
1338             try!(self.expect(&token::OpenDelim(token::Bracket)));
1339             let t = try!(self.parse_ty_sum());
1340
1341             // Parse the `; e` in `[ i32; e ]`
1342             // where `e` is a const expression
1343             let t = match try!(self.maybe_parse_fixed_length_of_vec()) {
1344                 None => TyVec(t),
1345                 Some(suffix) => TyFixedLengthVec(t, suffix)
1346             };
1347             try!(self.expect(&token::CloseDelim(token::Bracket)));
1348             t
1349         } else if self.check(&token::BinOp(token::And)) ||
1350                   self.token == token::AndAnd {
1351             // BORROWED POINTER
1352             try!(self.expect_and());
1353             try!(self.parse_borrowed_pointee())
1354         } else if self.check_keyword(keywords::For) {
1355             try!(self.parse_for_in_type())
1356         } else if self.token_is_bare_fn_keyword() {
1357             // BARE FUNCTION
1358             try!(self.parse_ty_bare_fn(Vec::new()))
1359         } else if try!(self.eat_keyword_noexpect(keywords::Typeof)) {
1360             // TYPEOF
1361             // In order to not be ambiguous, the type must be surrounded by parens.
1362             try!(self.expect(&token::OpenDelim(token::Paren)));
1363             let e = try!(self.parse_expr_nopanic());
1364             try!(self.expect(&token::CloseDelim(token::Paren)));
1365             TyTypeof(e)
1366         } else if try!(self.eat_lt()) {
1367
1368             let (qself, path) =
1369                  try!(self.parse_qualified_path(NoTypesAllowed));
1370
1371             TyPath(Some(qself), path)
1372         } else if self.check(&token::ModSep) ||
1373                   self.token.is_ident() ||
1374                   self.token.is_path() {
1375             let path = try!(self.parse_path(LifetimeAndTypesWithoutColons));
1376             if self.check(&token::Not) {
1377                 // MACRO INVOCATION
1378                 try!(self.bump());
1379                 let delim = try!(self.expect_open_delim());
1380                 let tts = try!(self.parse_seq_to_end(&token::CloseDelim(delim),
1381                                                      seq_sep_none(),
1382                                                      |p| p.parse_token_tree()));
1383                 let hi = self.span.hi;
1384                 TyMac(spanned(lo, hi, Mac_ { path: path, tts: tts, ctxt: EMPTY_CTXT }))
1385             } else {
1386                 // NAMED TYPE
1387                 TyPath(None, path)
1388             }
1389         } else if try!(self.eat(&token::Underscore) ){
1390             // TYPE TO BE INFERRED
1391             TyInfer
1392         } else {
1393             let this_token_str = self.this_token_to_string();
1394             let msg = format!("expected type, found `{}`", this_token_str);
1395             return Err(self.fatal(&msg[..]));
1396         };
1397
1398         let sp = mk_sp(lo, self.last_span.hi);
1399         Ok(P(Ty {id: ast::DUMMY_NODE_ID, node: t, span: sp}))
1400     }
1401
1402     pub fn parse_borrowed_pointee(&mut self) -> PResult<Ty_> {
1403         // look for `&'lt` or `&'foo ` and interpret `foo` as the region name:
1404         let opt_lifetime = try!(self.parse_opt_lifetime());
1405
1406         let mt = try!(self.parse_mt());
1407         return Ok(TyRptr(opt_lifetime, mt));
1408     }
1409
1410     pub fn parse_ptr(&mut self) -> PResult<MutTy> {
1411         let mutbl = if try!(self.eat_keyword(keywords::Mut) ){
1412             MutMutable
1413         } else if try!(self.eat_keyword(keywords::Const) ){
1414             MutImmutable
1415         } else {
1416             let span = self.last_span;
1417             self.span_err(span,
1418                           "bare raw pointers are no longer allowed, you should \
1419                            likely use `*mut T`, but otherwise `*T` is now \
1420                            known as `*const T`");
1421             MutImmutable
1422         };
1423         let t = try!(self.parse_ty_nopanic());
1424         Ok(MutTy { ty: t, mutbl: mutbl })
1425     }
1426
1427     pub fn is_named_argument(&mut self) -> bool {
1428         let offset = match self.token {
1429             token::BinOp(token::And) => 1,
1430             token::AndAnd => 1,
1431             _ if self.token.is_keyword(keywords::Mut) => 1,
1432             _ => 0
1433         };
1434
1435         debug!("parser is_named_argument offset:{}", offset);
1436
1437         if offset == 0 {
1438             is_plain_ident_or_underscore(&self.token)
1439                 && self.look_ahead(1, |t| *t == token::Colon)
1440         } else {
1441             self.look_ahead(offset, |t| is_plain_ident_or_underscore(t))
1442                 && self.look_ahead(offset + 1, |t| *t == token::Colon)
1443         }
1444     }
1445
1446     /// This version of parse arg doesn't necessarily require
1447     /// identifier names.
1448     pub fn parse_arg_general(&mut self, require_name: bool) -> PResult<Arg> {
1449         let pat = if require_name || self.is_named_argument() {
1450             debug!("parse_arg_general parse_pat (require_name:{})",
1451                    require_name);
1452             let pat = try!(self.parse_pat_nopanic());
1453
1454             try!(self.expect(&token::Colon));
1455             pat
1456         } else {
1457             debug!("parse_arg_general ident_to_pat");
1458             ast_util::ident_to_pat(ast::DUMMY_NODE_ID,
1459                                    self.last_span,
1460                                    special_idents::invalid)
1461         };
1462
1463         let t = try!(self.parse_ty_sum());
1464
1465         Ok(Arg {
1466             ty: t,
1467             pat: pat,
1468             id: ast::DUMMY_NODE_ID,
1469         })
1470     }
1471
1472     /// Parse a single function argument
1473     pub fn parse_arg(&mut self) -> PResult<Arg> {
1474         self.parse_arg_general(true)
1475     }
1476
1477     /// Parse an argument in a lambda header e.g. |arg, arg|
1478     pub fn parse_fn_block_arg(&mut self) -> PResult<Arg> {
1479         let pat = try!(self.parse_pat_nopanic());
1480         let t = if try!(self.eat(&token::Colon) ){
1481             try!(self.parse_ty_sum())
1482         } else {
1483             P(Ty {
1484                 id: ast::DUMMY_NODE_ID,
1485                 node: TyInfer,
1486                 span: mk_sp(self.span.lo, self.span.hi),
1487             })
1488         };
1489         Ok(Arg {
1490             ty: t,
1491             pat: pat,
1492             id: ast::DUMMY_NODE_ID
1493         })
1494     }
1495
1496     pub fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<Option<P<ast::Expr>>> {
1497         if self.check(&token::Semi) {
1498             try!(self.bump());
1499             Ok(Some(try!(self.parse_expr_nopanic())))
1500         } else {
1501             Ok(None)
1502         }
1503     }
1504
1505     /// Matches token_lit = LIT_INTEGER | ...
1506     pub fn lit_from_token(&self, tok: &token::Token) -> PResult<Lit_> {
1507         match *tok {
1508             token::Interpolated(token::NtExpr(ref v)) => {
1509                 match v.node {
1510                     ExprLit(ref lit) => { Ok(lit.node.clone()) }
1511                     _ => { return Err(self.unexpected_last(tok)); }
1512                 }
1513             }
1514             token::Literal(lit, suf) => {
1515                 let (suffix_illegal, out) = match lit {
1516                     token::Byte(i) => (true, LitByte(parse::byte_lit(&i.as_str()).0)),
1517                     token::Char(i) => (true, LitChar(parse::char_lit(&i.as_str()).0)),
1518
1519                     // there are some valid suffixes for integer and
1520                     // float literals, so all the handling is done
1521                     // internally.
1522                     token::Integer(s) => {
1523                         (false, parse::integer_lit(&s.as_str(),
1524                                                    suf.as_ref().map(|s| s.as_str()),
1525                                                    &self.sess.span_diagnostic,
1526                                                    self.last_span))
1527                     }
1528                     token::Float(s) => {
1529                         (false, parse::float_lit(&s.as_str(),
1530                                                  suf.as_ref().map(|s| s.as_str()),
1531                                                   &self.sess.span_diagnostic,
1532                                                  self.last_span))
1533                     }
1534
1535                     token::Str_(s) => {
1536                         (true,
1537                          LitStr(token::intern_and_get_ident(&parse::str_lit(&s.as_str())),
1538                                 ast::CookedStr))
1539                     }
1540                     token::StrRaw(s, n) => {
1541                         (true,
1542                          LitStr(
1543                             token::intern_and_get_ident(&parse::raw_str_lit(&s.as_str())),
1544                             ast::RawStr(n)))
1545                     }
1546                     token::ByteStr(i) =>
1547                         (true, LitByteStr(parse::byte_str_lit(&i.as_str()))),
1548                     token::ByteStrRaw(i, _) =>
1549                         (true,
1550                          LitByteStr(Rc::new(i.to_string().into_bytes()))),
1551                 };
1552
1553                 if suffix_illegal {
1554                     let sp = self.last_span;
1555                     self.expect_no_suffix(sp, &*format!("{} literal", lit.short_name()), suf)
1556                 }
1557
1558                 Ok(out)
1559             }
1560             _ => { return Err(self.unexpected_last(tok)); }
1561         }
1562     }
1563
1564     /// Matches lit = true | false | token_lit
1565     pub fn parse_lit(&mut self) -> PResult<Lit> {
1566         let lo = self.span.lo;
1567         let lit = if try!(self.eat_keyword(keywords::True) ){
1568             LitBool(true)
1569         } else if try!(self.eat_keyword(keywords::False) ){
1570             LitBool(false)
1571         } else {
1572             let token = try!(self.bump_and_get());
1573             let lit = try!(self.lit_from_token(&token));
1574             lit
1575         };
1576         Ok(codemap::Spanned { node: lit, span: mk_sp(lo, self.last_span.hi) })
1577     }
1578
1579     /// matches '-' lit | lit
1580     pub fn parse_literal_maybe_minus(&mut self) -> PResult<P<Expr>> {
1581         let minus_lo = self.span.lo;
1582         let minus_present = try!(self.eat(&token::BinOp(token::Minus)));
1583
1584         let lo = self.span.lo;
1585         let literal = P(try!(self.parse_lit()));
1586         let hi = self.span.hi;
1587         let expr = self.mk_expr(lo, hi, ExprLit(literal));
1588
1589         if minus_present {
1590             let minus_hi = self.span.hi;
1591             let unary = self.mk_unary(UnNeg, expr);
1592             Ok(self.mk_expr(minus_lo, minus_hi, unary))
1593         } else {
1594             Ok(expr)
1595         }
1596     }
1597
1598     // QUALIFIED PATH `<TYPE [as TRAIT_REF]>::IDENT[::<PARAMS>]`
1599     // Assumes that the leading `<` has been parsed already.
1600     pub fn parse_qualified_path(&mut self, mode: PathParsingMode)
1601                                 -> PResult<(QSelf, ast::Path)> {
1602         let span = self.last_span;
1603         let self_type = try!(self.parse_ty_sum());
1604         let mut path = if try!(self.eat_keyword(keywords::As)) {
1605             try!(self.parse_path(LifetimeAndTypesWithoutColons))
1606         } else {
1607             ast::Path {
1608                 span: span,
1609                 global: false,
1610                 segments: vec![]
1611             }
1612         };
1613
1614         let qself = QSelf {
1615             ty: self_type,
1616             position: path.segments.len()
1617         };
1618
1619         try!(self.expect(&token::Gt));
1620         try!(self.expect(&token::ModSep));
1621
1622         let segments = match mode {
1623             LifetimeAndTypesWithoutColons => {
1624                 try!(self.parse_path_segments_without_colons())
1625             }
1626             LifetimeAndTypesWithColons => {
1627                 try!(self.parse_path_segments_with_colons())
1628             }
1629             NoTypesAllowed => {
1630                 try!(self.parse_path_segments_without_types())
1631             }
1632         };
1633         path.segments.extend(segments);
1634
1635         path.span.hi = self.last_span.hi;
1636
1637         Ok((qself, path))
1638     }
1639
1640     /// Parses a path and optional type parameter bounds, depending on the
1641     /// mode. The `mode` parameter determines whether lifetimes, types, and/or
1642     /// bounds are permitted and whether `::` must precede type parameter
1643     /// groups.
1644     pub fn parse_path(&mut self, mode: PathParsingMode) -> PResult<ast::Path> {
1645         // Check for a whole path...
1646         let found = match self.token {
1647             token::Interpolated(token::NtPath(_)) => Some(try!(self.bump_and_get())),
1648             _ => None,
1649         };
1650         if let Some(token::Interpolated(token::NtPath(path))) = found {
1651             return Ok(*path);
1652         }
1653
1654         let lo = self.span.lo;
1655         let is_global = try!(self.eat(&token::ModSep));
1656
1657         // Parse any number of segments and bound sets. A segment is an
1658         // identifier followed by an optional lifetime and a set of types.
1659         // A bound set is a set of type parameter bounds.
1660         let segments = match mode {
1661             LifetimeAndTypesWithoutColons => {
1662                 try!(self.parse_path_segments_without_colons())
1663             }
1664             LifetimeAndTypesWithColons => {
1665                 try!(self.parse_path_segments_with_colons())
1666             }
1667             NoTypesAllowed => {
1668                 try!(self.parse_path_segments_without_types())
1669             }
1670         };
1671
1672         // Assemble the span.
1673         let span = mk_sp(lo, self.last_span.hi);
1674
1675         // Assemble the result.
1676         Ok(ast::Path {
1677             span: span,
1678             global: is_global,
1679             segments: segments,
1680         })
1681     }
1682
1683     /// Examples:
1684     /// - `a::b<T,U>::c<V,W>`
1685     /// - `a::b<T,U>::c(V) -> W`
1686     /// - `a::b<T,U>::c(V)`
1687     pub fn parse_path_segments_without_colons(&mut self) -> PResult<Vec<ast::PathSegment>> {
1688         let mut segments = Vec::new();
1689         loop {
1690             // First, parse an identifier.
1691             let identifier = try!(self.parse_ident_or_self_type());
1692
1693             // Parse types, optionally.
1694             let parameters = if try!(self.eat_lt() ){
1695                 let (lifetimes, types, bindings) = try!(self.parse_generic_values_after_lt());
1696
1697                 ast::AngleBracketedParameters(ast::AngleBracketedParameterData {
1698                     lifetimes: lifetimes,
1699                     types: OwnedSlice::from_vec(types),
1700                     bindings: OwnedSlice::from_vec(bindings),
1701                 })
1702             } else if try!(self.eat(&token::OpenDelim(token::Paren)) ){
1703                 let lo = self.last_span.lo;
1704
1705                 let inputs = try!(self.parse_seq_to_end(
1706                     &token::CloseDelim(token::Paren),
1707                     seq_sep_trailing_allowed(token::Comma),
1708                     |p| p.parse_ty_sum()));
1709
1710                 let output_ty = if try!(self.eat(&token::RArrow) ){
1711                     Some(try!(self.parse_ty_nopanic()))
1712                 } else {
1713                     None
1714                 };
1715
1716                 let hi = self.last_span.hi;
1717
1718                 ast::ParenthesizedParameters(ast::ParenthesizedParameterData {
1719                     span: mk_sp(lo, hi),
1720                     inputs: inputs,
1721                     output: output_ty,
1722                 })
1723             } else {
1724                 ast::PathParameters::none()
1725             };
1726
1727             // Assemble and push the result.
1728             segments.push(ast::PathSegment { identifier: identifier,
1729                                              parameters: parameters });
1730
1731             // Continue only if we see a `::`
1732             if !try!(self.eat(&token::ModSep) ){
1733                 return Ok(segments);
1734             }
1735         }
1736     }
1737
1738     /// Examples:
1739     /// - `a::b::<T,U>::c`
1740     pub fn parse_path_segments_with_colons(&mut self) -> PResult<Vec<ast::PathSegment>> {
1741         let mut segments = Vec::new();
1742         loop {
1743             // First, parse an identifier.
1744             let identifier = try!(self.parse_ident_or_self_type());
1745
1746             // If we do not see a `::`, stop.
1747             if !try!(self.eat(&token::ModSep) ){
1748                 segments.push(ast::PathSegment {
1749                     identifier: identifier,
1750                     parameters: ast::PathParameters::none()
1751                 });
1752                 return Ok(segments);
1753             }
1754
1755             // Check for a type segment.
1756             if try!(self.eat_lt() ){
1757                 // Consumed `a::b::<`, go look for types
1758                 let (lifetimes, types, bindings) = try!(self.parse_generic_values_after_lt());
1759                 segments.push(ast::PathSegment {
1760                     identifier: identifier,
1761                     parameters: ast::AngleBracketedParameters(ast::AngleBracketedParameterData {
1762                         lifetimes: lifetimes,
1763                         types: OwnedSlice::from_vec(types),
1764                         bindings: OwnedSlice::from_vec(bindings),
1765                     }),
1766                 });
1767
1768                 // Consumed `a::b::<T,U>`, check for `::` before proceeding
1769                 if !try!(self.eat(&token::ModSep) ){
1770                     return Ok(segments);
1771                 }
1772             } else {
1773                 // Consumed `a::`, go look for `b`
1774                 segments.push(ast::PathSegment {
1775                     identifier: identifier,
1776                     parameters: ast::PathParameters::none(),
1777                 });
1778             }
1779         }
1780     }
1781
1782
1783     /// Examples:
1784     /// - `a::b::c`
1785     pub fn parse_path_segments_without_types(&mut self) -> PResult<Vec<ast::PathSegment>> {
1786         let mut segments = Vec::new();
1787         loop {
1788             // First, parse an identifier.
1789             let identifier = try!(self.parse_ident_or_self_type());
1790
1791             // Assemble and push the result.
1792             segments.push(ast::PathSegment {
1793                 identifier: identifier,
1794                 parameters: ast::PathParameters::none()
1795             });
1796
1797             // If we do not see a `::`, stop.
1798             if !try!(self.eat(&token::ModSep) ){
1799                 return Ok(segments);
1800             }
1801         }
1802     }
1803
1804     /// parses 0 or 1 lifetime
1805     pub fn parse_opt_lifetime(&mut self) -> PResult<Option<ast::Lifetime>> {
1806         match self.token {
1807             token::Lifetime(..) => {
1808                 Ok(Some(try!(self.parse_lifetime())))
1809             }
1810             _ => {
1811                 Ok(None)
1812             }
1813         }
1814     }
1815
1816     /// Parses a single lifetime
1817     /// Matches lifetime = LIFETIME
1818     pub fn parse_lifetime(&mut self) -> PResult<ast::Lifetime> {
1819         match self.token {
1820             token::Lifetime(i) => {
1821                 let span = self.span;
1822                 try!(self.bump());
1823                 return Ok(ast::Lifetime {
1824                     id: ast::DUMMY_NODE_ID,
1825                     span: span,
1826                     name: i.name
1827                 });
1828             }
1829             _ => {
1830                 return Err(self.fatal(&format!("expected a lifetime name")));
1831             }
1832         }
1833     }
1834
1835     /// Parses `lifetime_defs = [ lifetime_defs { ',' lifetime_defs } ]` where `lifetime_def  =
1836     /// lifetime [':' lifetimes]`
1837     pub fn parse_lifetime_defs(&mut self) -> PResult<Vec<ast::LifetimeDef>> {
1838
1839         let mut res = Vec::new();
1840         loop {
1841             match self.token {
1842                 token::Lifetime(_) => {
1843                     let lifetime = try!(self.parse_lifetime());
1844                     let bounds =
1845                         if try!(self.eat(&token::Colon) ){
1846                             try!(self.parse_lifetimes(token::BinOp(token::Plus)))
1847                         } else {
1848                             Vec::new()
1849                         };
1850                     res.push(ast::LifetimeDef { lifetime: lifetime,
1851                                                 bounds: bounds });
1852                 }
1853
1854                 _ => {
1855                     return Ok(res);
1856                 }
1857             }
1858
1859             match self.token {
1860                 token::Comma => { try!(self.bump());}
1861                 token::Gt => { return Ok(res); }
1862                 token::BinOp(token::Shr) => { return Ok(res); }
1863                 _ => {
1864                     let this_token_str = self.this_token_to_string();
1865                     let msg = format!("expected `,` or `>` after lifetime \
1866                                       name, found `{}`",
1867                                       this_token_str);
1868                     return Err(self.fatal(&msg[..]));
1869                 }
1870             }
1871         }
1872     }
1873
1874     /// matches lifetimes = ( lifetime ) | ( lifetime , lifetimes ) actually, it matches the empty
1875     /// one too, but putting that in there messes up the grammar....
1876     ///
1877     /// Parses zero or more comma separated lifetimes. Expects each lifetime to be followed by
1878     /// either a comma or `>`.  Used when parsing type parameter lists, where we expect something
1879     /// like `<'a, 'b, T>`.
1880     pub fn parse_lifetimes(&mut self, sep: token::Token) -> PResult<Vec<ast::Lifetime>> {
1881
1882         let mut res = Vec::new();
1883         loop {
1884             match self.token {
1885                 token::Lifetime(_) => {
1886                     res.push(try!(self.parse_lifetime()));
1887                 }
1888                 _ => {
1889                     return Ok(res);
1890                 }
1891             }
1892
1893             if self.token != sep {
1894                 return Ok(res);
1895             }
1896
1897             try!(self.bump());
1898         }
1899     }
1900
1901     /// Parse mutability declaration (mut/const/imm)
1902     pub fn parse_mutability(&mut self) -> PResult<Mutability> {
1903         if try!(self.eat_keyword(keywords::Mut) ){
1904             Ok(MutMutable)
1905         } else {
1906             Ok(MutImmutable)
1907         }
1908     }
1909
1910     /// Parse ident COLON expr
1911     pub fn parse_field(&mut self) -> PResult<Field> {
1912         let lo = self.span.lo;
1913         let i = try!(self.parse_ident());
1914         let hi = self.last_span.hi;
1915         try!(self.expect(&token::Colon));
1916         let e = try!(self.parse_expr_nopanic());
1917         Ok(ast::Field {
1918             ident: spanned(lo, hi, i),
1919             span: mk_sp(lo, e.span.hi),
1920             expr: e,
1921         })
1922     }
1923
1924     pub fn mk_expr(&mut self, lo: BytePos, hi: BytePos, node: Expr_) -> P<Expr> {
1925         P(Expr {
1926             id: ast::DUMMY_NODE_ID,
1927             node: node,
1928             span: mk_sp(lo, hi),
1929         })
1930     }
1931
1932     pub fn mk_unary(&mut self, unop: ast::UnOp, expr: P<Expr>) -> ast::Expr_ {
1933         ExprUnary(unop, expr)
1934     }
1935
1936     pub fn mk_binary(&mut self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::Expr_ {
1937         ExprBinary(binop, lhs, rhs)
1938     }
1939
1940     pub fn mk_call(&mut self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::Expr_ {
1941         ExprCall(f, args)
1942     }
1943
1944     fn mk_method_call(&mut self,
1945                       ident: ast::SpannedIdent,
1946                       tps: Vec<P<Ty>>,
1947                       args: Vec<P<Expr>>)
1948                       -> ast::Expr_ {
1949         ExprMethodCall(ident, tps, args)
1950     }
1951
1952     pub fn mk_index(&mut self, expr: P<Expr>, idx: P<Expr>) -> ast::Expr_ {
1953         ExprIndex(expr, idx)
1954     }
1955
1956     pub fn mk_range(&mut self,
1957                     start: Option<P<Expr>>,
1958                     end: Option<P<Expr>>)
1959                     -> ast::Expr_ {
1960         ExprRange(start, end)
1961     }
1962
1963     pub fn mk_field(&mut self, expr: P<Expr>, ident: ast::SpannedIdent) -> ast::Expr_ {
1964         ExprField(expr, ident)
1965     }
1966
1967     pub fn mk_tup_field(&mut self, expr: P<Expr>, idx: codemap::Spanned<usize>) -> ast::Expr_ {
1968         ExprTupField(expr, idx)
1969     }
1970
1971     pub fn mk_assign_op(&mut self, binop: ast::BinOp,
1972                         lhs: P<Expr>, rhs: P<Expr>) -> ast::Expr_ {
1973         ExprAssignOp(binop, lhs, rhs)
1974     }
1975
1976     pub fn mk_mac_expr(&mut self, lo: BytePos, hi: BytePos, m: Mac_) -> P<Expr> {
1977         P(Expr {
1978             id: ast::DUMMY_NODE_ID,
1979             node: ExprMac(codemap::Spanned {node: m, span: mk_sp(lo, hi)}),
1980             span: mk_sp(lo, hi),
1981         })
1982     }
1983
1984     pub fn mk_lit_u32(&mut self, i: u32) -> P<Expr> {
1985         let span = &self.span;
1986         let lv_lit = P(codemap::Spanned {
1987             node: LitInt(i as u64, ast::UnsignedIntLit(TyU32)),
1988             span: *span
1989         });
1990
1991         P(Expr {
1992             id: ast::DUMMY_NODE_ID,
1993             node: ExprLit(lv_lit),
1994             span: *span,
1995         })
1996     }
1997
1998     fn expect_open_delim(&mut self) -> PResult<token::DelimToken> {
1999         self.expected_tokens.push(TokenType::Token(token::Gt));
2000         match self.token {
2001             token::OpenDelim(delim) => {
2002                 try!(self.bump());
2003                 Ok(delim)
2004             },
2005             _ => Err(self.fatal("expected open delimiter")),
2006         }
2007     }
2008
2009     /// At the bottom (top?) of the precedence hierarchy,
2010     /// parse things like parenthesized exprs,
2011     /// macros, return, etc.
2012     pub fn parse_bottom_expr(&mut self) -> PResult<P<Expr>> {
2013         maybe_whole_expr!(self);
2014
2015         let lo = self.span.lo;
2016         let mut hi = self.span.hi;
2017
2018         let ex: Expr_;
2019
2020         // Note: when adding new syntax here, don't forget to adjust Token::can_begin_expr().
2021         match self.token {
2022             token::OpenDelim(token::Paren) => {
2023                 try!(self.bump());
2024
2025                 // (e) is parenthesized e
2026                 // (e,) is a tuple with only one field, e
2027                 let mut es = vec![];
2028                 let mut trailing_comma = false;
2029                 while self.token != token::CloseDelim(token::Paren) {
2030                     es.push(try!(self.parse_expr_nopanic()));
2031                     try!(self.commit_expr(&**es.last().unwrap(), &[],
2032                                      &[token::Comma, token::CloseDelim(token::Paren)]));
2033                     if self.check(&token::Comma) {
2034                         trailing_comma = true;
2035
2036                         try!(self.bump());
2037                     } else {
2038                         trailing_comma = false;
2039                         break;
2040                     }
2041                 }
2042                 try!(self.bump());
2043
2044                 hi = self.last_span.hi;
2045                 return if es.len() == 1 && !trailing_comma {
2046                     Ok(self.mk_expr(lo, hi, ExprParen(es.into_iter().nth(0).unwrap())))
2047                 } else {
2048                     Ok(self.mk_expr(lo, hi, ExprTup(es)))
2049                 }
2050             },
2051             token::OpenDelim(token::Brace) => {
2052                 return self.parse_block_expr(lo, DefaultBlock);
2053             },
2054             token::BinOp(token::Or) |  token::OrOr => {
2055                 let lo = self.span.lo;
2056                 return self.parse_lambda_expr(lo, CaptureByRef);
2057             },
2058             token::Ident(id @ ast::Ident {
2059                             name: token::SELF_KEYWORD_NAME,
2060                             ctxt: _
2061                          }, token::Plain) => {
2062                 try!(self.bump());
2063                 let path = ast_util::ident_to_path(mk_sp(lo, hi), id);
2064                 ex = ExprPath(None, path);
2065                 hi = self.last_span.hi;
2066             }
2067             token::OpenDelim(token::Bracket) => {
2068                 try!(self.bump());
2069
2070                 if self.check(&token::CloseDelim(token::Bracket)) {
2071                     // Empty vector.
2072                     try!(self.bump());
2073                     ex = ExprVec(Vec::new());
2074                 } else {
2075                     // Nonempty vector.
2076                     let first_expr = try!(self.parse_expr_nopanic());
2077                     if self.check(&token::Semi) {
2078                         // Repeating array syntax: [ 0; 512 ]
2079                         try!(self.bump());
2080                         let count = try!(self.parse_expr_nopanic());
2081                         try!(self.expect(&token::CloseDelim(token::Bracket)));
2082                         ex = ExprRepeat(first_expr, count);
2083                     } else if self.check(&token::Comma) {
2084                         // Vector with two or more elements.
2085                         try!(self.bump());
2086                         let remaining_exprs = try!(self.parse_seq_to_end(
2087                             &token::CloseDelim(token::Bracket),
2088                             seq_sep_trailing_allowed(token::Comma),
2089                             |p| Ok(try!(p.parse_expr_nopanic()))
2090                                 ));
2091                         let mut exprs = vec!(first_expr);
2092                         exprs.extend(remaining_exprs);
2093                         ex = ExprVec(exprs);
2094                     } else {
2095                         // Vector with one element.
2096                         try!(self.expect(&token::CloseDelim(token::Bracket)));
2097                         ex = ExprVec(vec!(first_expr));
2098                     }
2099                 }
2100                 hi = self.last_span.hi;
2101             }
2102             _ => {
2103                 if try!(self.eat_lt()){
2104                     let (qself, path) =
2105                         try!(self.parse_qualified_path(LifetimeAndTypesWithColons));
2106                     hi = path.span.hi;
2107                     return Ok(self.mk_expr(lo, hi, ExprPath(Some(qself), path)));
2108                 }
2109                 if try!(self.eat_keyword(keywords::Move) ){
2110                     let lo = self.last_span.lo;
2111                     return self.parse_lambda_expr(lo, CaptureByValue);
2112                 }
2113                 if try!(self.eat_keyword(keywords::If)) {
2114                     return self.parse_if_expr();
2115                 }
2116                 if try!(self.eat_keyword(keywords::For) ){
2117                     let lo = self.last_span.lo;
2118                     return self.parse_for_expr(None, lo);
2119                 }
2120                 if try!(self.eat_keyword(keywords::While) ){
2121                     let lo = self.last_span.lo;
2122                     return self.parse_while_expr(None, lo);
2123                 }
2124                 if self.token.is_lifetime() {
2125                     let lifetime = self.get_lifetime();
2126                     let lo = self.span.lo;
2127                     try!(self.bump());
2128                     try!(self.expect(&token::Colon));
2129                     if try!(self.eat_keyword(keywords::While) ){
2130                         return self.parse_while_expr(Some(lifetime), lo)
2131                     }
2132                     if try!(self.eat_keyword(keywords::For) ){
2133                         return self.parse_for_expr(Some(lifetime), lo)
2134                     }
2135                     if try!(self.eat_keyword(keywords::Loop) ){
2136                         return self.parse_loop_expr(Some(lifetime), lo)
2137                     }
2138                     return Err(self.fatal("expected `while`, `for`, or `loop` after a label"))
2139                 }
2140                 if try!(self.eat_keyword(keywords::Loop) ){
2141                     let lo = self.last_span.lo;
2142                     return self.parse_loop_expr(None, lo);
2143                 }
2144                 if try!(self.eat_keyword(keywords::Continue) ){
2145                     let ex = if self.token.is_lifetime() {
2146                         let ex = ExprAgain(Some(Spanned{
2147                             node: self.get_lifetime(),
2148                             span: self.span
2149                         }));
2150                         try!(self.bump());
2151                         ex
2152                     } else {
2153                         ExprAgain(None)
2154                     };
2155                     let hi = self.last_span.hi;
2156                     return Ok(self.mk_expr(lo, hi, ex));
2157                 }
2158                 if try!(self.eat_keyword(keywords::Match) ){
2159                     return self.parse_match_expr();
2160                 }
2161                 if try!(self.eat_keyword(keywords::Unsafe) ){
2162                     return self.parse_block_expr(
2163                         lo,
2164                         UnsafeBlock(ast::UserProvided));
2165                 }
2166                 if try!(self.eat_keyword(keywords::Return) ){
2167                     if self.token.can_begin_expr() {
2168                         let e = try!(self.parse_expr_nopanic());
2169                         hi = e.span.hi;
2170                         ex = ExprRet(Some(e));
2171                     } else {
2172                         ex = ExprRet(None);
2173                     }
2174                 } else if try!(self.eat_keyword(keywords::Break) ){
2175                     if self.token.is_lifetime() {
2176                         ex = ExprBreak(Some(Spanned {
2177                             node: self.get_lifetime(),
2178                             span: self.span
2179                         }));
2180                         try!(self.bump());
2181                     } else {
2182                         ex = ExprBreak(None);
2183                     }
2184                     hi = self.last_span.hi;
2185                 } else if self.check(&token::ModSep) ||
2186                         self.token.is_ident() &&
2187                         !self.check_keyword(keywords::True) &&
2188                         !self.check_keyword(keywords::False) {
2189                     let pth =
2190                         try!(self.parse_path(LifetimeAndTypesWithColons));
2191
2192                     // `!`, as an operator, is prefix, so we know this isn't that
2193                     if self.check(&token::Not) {
2194                         // MACRO INVOCATION expression
2195                         try!(self.bump());
2196
2197                         let delim = try!(self.expect_open_delim());
2198                         let tts = try!(self.parse_seq_to_end(
2199                             &token::CloseDelim(delim),
2200                             seq_sep_none(),
2201                             |p| p.parse_token_tree()));
2202                         let hi = self.last_span.hi;
2203
2204                         return Ok(self.mk_mac_expr(lo,
2205                                                    hi,
2206                                                    Mac_ { path: pth, tts: tts, ctxt: EMPTY_CTXT }));
2207                     }
2208                     if self.check(&token::OpenDelim(token::Brace)) {
2209                         // This is a struct literal, unless we're prohibited
2210                         // from parsing struct literals here.
2211                         let prohibited = self.restrictions.contains(
2212                             Restrictions::RESTRICTION_NO_STRUCT_LITERAL
2213                         );
2214                         if !prohibited {
2215                             // It's a struct literal.
2216                             try!(self.bump());
2217                             let mut fields = Vec::new();
2218                             let mut base = None;
2219
2220                             while self.token != token::CloseDelim(token::Brace) {
2221                                 if try!(self.eat(&token::DotDot) ){
2222                                     base = Some(try!(self.parse_expr_nopanic()));
2223                                     break;
2224                                 }
2225
2226                                 fields.push(try!(self.parse_field()));
2227                                 try!(self.commit_expr(&*fields.last().unwrap().expr,
2228                                                  &[token::Comma],
2229                                                  &[token::CloseDelim(token::Brace)]));
2230                             }
2231
2232                             hi = self.span.hi;
2233                             try!(self.expect(&token::CloseDelim(token::Brace)));
2234                             ex = ExprStruct(pth, fields, base);
2235                             return Ok(self.mk_expr(lo, hi, ex));
2236                         }
2237                     }
2238
2239                     hi = pth.span.hi;
2240                     ex = ExprPath(None, pth);
2241                 } else {
2242                     // other literal expression
2243                     let lit = try!(self.parse_lit());
2244                     hi = lit.span.hi;
2245                     ex = ExprLit(P(lit));
2246                 }
2247             }
2248         }
2249
2250         return Ok(self.mk_expr(lo, hi, ex));
2251     }
2252
2253     /// Parse a block or unsafe block
2254     pub fn parse_block_expr(&mut self, lo: BytePos, blk_mode: BlockCheckMode)
2255                             -> PResult<P<Expr>> {
2256         try!(self.expect(&token::OpenDelim(token::Brace)));
2257         let blk = try!(self.parse_block_tail(lo, blk_mode));
2258         return Ok(self.mk_expr(blk.span.lo, blk.span.hi, ExprBlock(blk)));
2259     }
2260
2261     /// parse a.b or a(13) or a[4] or just a
2262     pub fn parse_dot_or_call_expr(&mut self) -> PResult<P<Expr>> {
2263         let b = try!(self.parse_bottom_expr());
2264         self.parse_dot_or_call_expr_with(b)
2265     }
2266
2267     pub fn parse_dot_or_call_expr_with(&mut self, e0: P<Expr>) -> PResult<P<Expr>> {
2268         let mut e = e0;
2269         let lo = e.span.lo;
2270         let mut hi;
2271         loop {
2272             // expr.f
2273             if try!(self.eat(&token::Dot) ){
2274                 match self.token {
2275                   token::Ident(i, _) => {
2276                     let dot = self.last_span.hi;
2277                     hi = self.span.hi;
2278                     try!(self.bump());
2279                     let (_, tys, bindings) = if try!(self.eat(&token::ModSep) ){
2280                         try!(self.expect_lt());
2281                         try!(self.parse_generic_values_after_lt())
2282                     } else {
2283                         (Vec::new(), Vec::new(), Vec::new())
2284                     };
2285
2286                     if !bindings.is_empty() {
2287                         let last_span = self.last_span;
2288                         self.span_err(last_span, "type bindings are only permitted on trait paths");
2289                     }
2290
2291                     // expr.f() method call
2292                     match self.token {
2293                         token::OpenDelim(token::Paren) => {
2294                             let mut es = try!(self.parse_unspanned_seq(
2295                                 &token::OpenDelim(token::Paren),
2296                                 &token::CloseDelim(token::Paren),
2297                                 seq_sep_trailing_allowed(token::Comma),
2298                                 |p| Ok(try!(p.parse_expr_nopanic()))
2299                             ));
2300                             hi = self.last_span.hi;
2301
2302                             es.insert(0, e);
2303                             let id = spanned(dot, hi, i);
2304                             let nd = self.mk_method_call(id, tys, es);
2305                             e = self.mk_expr(lo, hi, nd);
2306                         }
2307                         _ => {
2308                             if !tys.is_empty() {
2309                                 let last_span = self.last_span;
2310                                 self.span_err(last_span,
2311                                               "field expressions may not \
2312                                                have type parameters");
2313                             }
2314
2315                             let id = spanned(dot, hi, i);
2316                             let field = self.mk_field(e, id);
2317                             e = self.mk_expr(lo, hi, field);
2318                         }
2319                     }
2320                   }
2321                   token::Literal(token::Integer(n), suf) => {
2322                     let sp = self.span;
2323
2324                     // A tuple index may not have a suffix
2325                     self.expect_no_suffix(sp, "tuple index", suf);
2326
2327                     let dot = self.last_span.hi;
2328                     hi = self.span.hi;
2329                     try!(self.bump());
2330
2331                     let index = n.as_str().parse::<usize>().ok();
2332                     match index {
2333                         Some(n) => {
2334                             let id = spanned(dot, hi, n);
2335                             let field = self.mk_tup_field(e, id);
2336                             e = self.mk_expr(lo, hi, field);
2337                         }
2338                         None => {
2339                             let last_span = self.last_span;
2340                             self.span_err(last_span, "invalid tuple or tuple struct index");
2341                         }
2342                     }
2343                   }
2344                   token::Literal(token::Float(n), _suf) => {
2345                     try!(self.bump());
2346                     let last_span = self.last_span;
2347                     let fstr = n.as_str();
2348                     self.span_err(last_span,
2349                                   &format!("unexpected token: `{}`", n.as_str()));
2350                     if fstr.chars().all(|x| "0123456789.".contains(x)) {
2351                         let float = match fstr.parse::<f64>().ok() {
2352                             Some(f) => f,
2353                             None => continue,
2354                         };
2355                         self.fileline_help(last_span,
2356                             &format!("try parenthesizing the first index; e.g., `(foo.{}){}`",
2357                                     float.trunc() as usize,
2358                                     format!(".{}", fstr.splitn(2, ".").last().unwrap())));
2359                     }
2360                     self.abort_if_errors();
2361
2362                   }
2363                   _ => return Err(self.unexpected())
2364                 }
2365                 continue;
2366             }
2367             if self.expr_is_complete(&*e) { break; }
2368             match self.token {
2369               // expr(...)
2370               token::OpenDelim(token::Paren) => {
2371                 let es = try!(self.parse_unspanned_seq(
2372                     &token::OpenDelim(token::Paren),
2373                     &token::CloseDelim(token::Paren),
2374                     seq_sep_trailing_allowed(token::Comma),
2375                     |p| Ok(try!(p.parse_expr_nopanic()))
2376                 ));
2377                 hi = self.last_span.hi;
2378
2379                 let nd = self.mk_call(e, es);
2380                 e = self.mk_expr(lo, hi, nd);
2381               }
2382
2383               // expr[...]
2384               // Could be either an index expression or a slicing expression.
2385               token::OpenDelim(token::Bracket) => {
2386                 try!(self.bump());
2387                 let ix = try!(self.parse_expr_nopanic());
2388                 hi = self.span.hi;
2389                 try!(self.commit_expr_expecting(&*ix, token::CloseDelim(token::Bracket)));
2390                 let index = self.mk_index(e, ix);
2391                 e = self.mk_expr(lo, hi, index)
2392               }
2393               _ => return Ok(e)
2394             }
2395         }
2396         return Ok(e);
2397     }
2398
2399     // Parse unquoted tokens after a `$` in a token tree
2400     fn parse_unquoted(&mut self) -> PResult<TokenTree> {
2401         let mut sp = self.span;
2402         let (name, namep) = match self.token {
2403             token::Dollar => {
2404                 try!(self.bump());
2405
2406                 if self.token == token::OpenDelim(token::Paren) {
2407                     let Spanned { node: seq, span: seq_span } = try!(self.parse_seq(
2408                         &token::OpenDelim(token::Paren),
2409                         &token::CloseDelim(token::Paren),
2410                         seq_sep_none(),
2411                         |p| p.parse_token_tree()
2412                     ));
2413                     let (sep, repeat) = try!(self.parse_sep_and_kleene_op());
2414                     let name_num = macro_parser::count_names(&seq);
2415                     return Ok(TtSequence(mk_sp(sp.lo, seq_span.hi),
2416                                       Rc::new(SequenceRepetition {
2417                                           tts: seq,
2418                                           separator: sep,
2419                                           op: repeat,
2420                                           num_captures: name_num
2421                                       })));
2422                 } else if self.token.is_keyword_allow_following_colon(keywords::Crate) {
2423                     try!(self.bump());
2424                     return Ok(TtToken(sp, SpecialVarNt(SpecialMacroVar::CrateMacroVar)));
2425                 } else {
2426                     sp = mk_sp(sp.lo, self.span.hi);
2427                     let namep = match self.token { token::Ident(_, p) => p, _ => token::Plain };
2428                     let name = try!(self.parse_ident());
2429                     (name, namep)
2430                 }
2431             }
2432             token::SubstNt(name, namep) => {
2433                 try!(self.bump());
2434                 (name, namep)
2435             }
2436             _ => unreachable!()
2437         };
2438         // continue by trying to parse the `:ident` after `$name`
2439         if self.token == token::Colon && self.look_ahead(1, |t| t.is_ident() &&
2440                                                                 !t.is_strict_keyword() &&
2441                                                                 !t.is_reserved_keyword()) {
2442             try!(self.bump());
2443             sp = mk_sp(sp.lo, self.span.hi);
2444             let kindp = match self.token { token::Ident(_, p) => p, _ => token::Plain };
2445             let nt_kind = try!(self.parse_ident());
2446             Ok(TtToken(sp, MatchNt(name, nt_kind, namep, kindp)))
2447         } else {
2448             Ok(TtToken(sp, SubstNt(name, namep)))
2449         }
2450     }
2451
2452     pub fn check_unknown_macro_variable(&mut self) -> PResult<()> {
2453         if self.quote_depth == 0 {
2454             match self.token {
2455                 token::SubstNt(name, _) =>
2456                     return Err(self.fatal(&format!("unknown macro variable `{}`",
2457                                        name))),
2458                 _ => {}
2459             }
2460         }
2461         Ok(())
2462     }
2463
2464     /// Parse an optional separator followed by a Kleene-style
2465     /// repetition token (+ or *).
2466     pub fn parse_sep_and_kleene_op(&mut self) -> PResult<(Option<token::Token>, ast::KleeneOp)> {
2467         fn parse_kleene_op(parser: &mut Parser) -> PResult<Option<ast::KleeneOp>> {
2468             match parser.token {
2469                 token::BinOp(token::Star) => {
2470                     try!(parser.bump());
2471                     Ok(Some(ast::ZeroOrMore))
2472                 },
2473                 token::BinOp(token::Plus) => {
2474                     try!(parser.bump());
2475                     Ok(Some(ast::OneOrMore))
2476                 },
2477                 _ => Ok(None)
2478             }
2479         };
2480
2481         match try!(parse_kleene_op(self)) {
2482             Some(kleene_op) => return Ok((None, kleene_op)),
2483             None => {}
2484         }
2485
2486         let separator = try!(self.bump_and_get());
2487         match try!(parse_kleene_op(self)) {
2488             Some(zerok) => Ok((Some(separator), zerok)),
2489             None => return Err(self.fatal("expected `*` or `+`"))
2490         }
2491     }
2492
2493     /// parse a single token tree from the input.
2494     pub fn parse_token_tree(&mut self) -> PResult<TokenTree> {
2495         // FIXME #6994: currently, this is too eager. It
2496         // parses token trees but also identifies TtSequence's
2497         // and token::SubstNt's; it's too early to know yet
2498         // whether something will be a nonterminal or a seq
2499         // yet.
2500         maybe_whole!(deref self, NtTT);
2501
2502         // this is the fall-through for the 'match' below.
2503         // invariants: the current token is not a left-delimiter,
2504         // not an EOF, and not the desired right-delimiter (if
2505         // it were, parse_seq_to_before_end would have prevented
2506         // reaching this point.
2507         fn parse_non_delim_tt_tok(p: &mut Parser) -> PResult<TokenTree> {
2508             maybe_whole!(deref p, NtTT);
2509             match p.token {
2510                 token::CloseDelim(_) => {
2511                     // This is a conservative error: only report the last unclosed delimiter. The
2512                     // previous unclosed delimiters could actually be closed! The parser just hasn't
2513                     // gotten to them yet.
2514                     match p.open_braces.last() {
2515                         None => {}
2516                         Some(&sp) => p.span_note(sp, "unclosed delimiter"),
2517                     };
2518                     let token_str = p.this_token_to_string();
2519                     Err(p.fatal(&format!("incorrect close delimiter: `{}`",
2520                                     token_str)))
2521                 },
2522                 /* we ought to allow different depths of unquotation */
2523                 token::Dollar | token::SubstNt(..) if p.quote_depth > 0 => {
2524                     p.parse_unquoted()
2525                 }
2526                 _ => {
2527                     Ok(TtToken(p.span, try!(p.bump_and_get())))
2528                 }
2529             }
2530         }
2531
2532         match self.token {
2533             token::Eof => {
2534                 let open_braces = self.open_braces.clone();
2535                 for sp in &open_braces {
2536                     self.span_help(*sp, "did you mean to close this delimiter?");
2537                 }
2538                 // There shouldn't really be a span, but it's easier for the test runner
2539                 // if we give it one
2540                 return Err(self.fatal("this file contains an un-closed delimiter "));
2541             },
2542             token::OpenDelim(delim) => {
2543                 // The span for beginning of the delimited section
2544                 let pre_span = self.span;
2545
2546                 // Parse the open delimiter.
2547                 self.open_braces.push(self.span);
2548                 let open_span = self.span;
2549                 try!(self.bump());
2550
2551                 // Parse the token trees within the delimiters
2552                 let tts = try!(self.parse_seq_to_before_end(
2553                     &token::CloseDelim(delim),
2554                     seq_sep_none(),
2555                     |p| p.parse_token_tree()
2556                 ));
2557
2558                 // Parse the close delimiter.
2559                 let close_span = self.span;
2560                 try!(self.bump());
2561                 self.open_braces.pop().unwrap();
2562
2563                 // Expand to cover the entire delimited token tree
2564                 let span = Span { hi: close_span.hi, ..pre_span };
2565
2566                 Ok(TtDelimited(span, Rc::new(Delimited {
2567                     delim: delim,
2568                     open_span: open_span,
2569                     tts: tts,
2570                     close_span: close_span,
2571                 })))
2572             },
2573             _ => parse_non_delim_tt_tok(self),
2574         }
2575     }
2576
2577     // parse a stream of tokens into a list of TokenTree's,
2578     // up to EOF.
2579     pub fn parse_all_token_trees(&mut self) -> PResult<Vec<TokenTree>> {
2580         let mut tts = Vec::new();
2581         while self.token != token::Eof {
2582             tts.push(try!(self.parse_token_tree()));
2583         }
2584         Ok(tts)
2585     }
2586
2587     /// Parse a prefix-operator expr
2588     pub fn parse_prefix_expr(&mut self) -> PResult<P<Expr>> {
2589         let lo = self.span.lo;
2590         let hi;
2591
2592         // Note: when adding new unary operators, don't forget to adjust Token::can_begin_expr()
2593         let ex;
2594         match self.token {
2595           token::Not => {
2596             try!(self.bump());
2597             let e = try!(self.parse_prefix_expr());
2598             hi = e.span.hi;
2599             ex = self.mk_unary(UnNot, e);
2600           }
2601           token::BinOp(token::Minus) => {
2602             try!(self.bump());
2603             let e = try!(self.parse_prefix_expr());
2604             hi = e.span.hi;
2605             ex = self.mk_unary(UnNeg, e);
2606           }
2607           token::BinOp(token::Star) => {
2608             try!(self.bump());
2609             let e = try!(self.parse_prefix_expr());
2610             hi = e.span.hi;
2611             ex = self.mk_unary(UnDeref, e);
2612           }
2613           token::BinOp(token::And) | token::AndAnd => {
2614             try!(self.expect_and());
2615             let m = try!(self.parse_mutability());
2616             let e = try!(self.parse_prefix_expr());
2617             hi = e.span.hi;
2618             ex = ExprAddrOf(m, e);
2619           }
2620           token::Ident(..) if self.token.is_keyword(keywords::In) => {
2621               try!(self.bump());
2622               let place = try!(self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL));
2623               let blk = try!(self.parse_block());
2624               hi = blk.span.hi;
2625               let blk_expr = self.mk_expr(blk.span.lo, blk.span.hi, ExprBlock(blk));
2626               ex = ExprInPlace(place, blk_expr);
2627           }
2628           token::Ident(..) if self.token.is_keyword(keywords::Box) => {
2629               try!(self.bump());
2630               let subexpression = try!(self.parse_prefix_expr());
2631               hi = subexpression.span.hi;
2632               ex = ExprBox(subexpression);
2633           }
2634           _ => return self.parse_dot_or_call_expr()
2635         }
2636         return Ok(self.mk_expr(lo, hi, ex));
2637     }
2638
2639     /// Parse an expression of binops
2640     pub fn parse_binops(&mut self) -> PResult<P<Expr>> {
2641         let prefix_expr = try!(self.parse_prefix_expr());
2642         self.parse_more_binops(prefix_expr, 0)
2643     }
2644
2645     /// Parse an expression of binops of at least min_prec precedence
2646     pub fn parse_more_binops(&mut self, lhs: P<Expr>, min_prec: usize) -> PResult<P<Expr>> {
2647         if self.expr_is_complete(&*lhs) { return Ok(lhs); }
2648
2649         self.expected_tokens.push(TokenType::Operator);
2650
2651         let cur_op_span = self.span;
2652         let cur_opt = self.token.to_binop();
2653         match cur_opt {
2654             Some(cur_op) => {
2655                 if ast_util::is_comparison_binop(cur_op) {
2656                     self.check_no_chained_comparison(&*lhs, cur_op)
2657                 }
2658                 let cur_prec = operator_prec(cur_op);
2659                 if cur_prec >= min_prec {
2660                     try!(self.bump());
2661                     let expr = try!(self.parse_prefix_expr());
2662                     let rhs = try!(self.parse_more_binops(expr, cur_prec + 1));
2663                     let lhs_span = lhs.span;
2664                     let rhs_span = rhs.span;
2665                     let binary = self.mk_binary(codemap::respan(cur_op_span, cur_op), lhs, rhs);
2666                     let bin = self.mk_expr(lhs_span.lo, rhs_span.hi, binary);
2667                     self.parse_more_binops(bin, min_prec)
2668                 } else {
2669                     Ok(lhs)
2670                 }
2671             }
2672             None => {
2673                 if AS_PREC >= min_prec && try!(self.eat_keyword_noexpect(keywords::As) ){
2674                     let rhs = try!(self.parse_ty_nopanic());
2675                     let _as = self.mk_expr(lhs.span.lo,
2676                                            rhs.span.hi,
2677                                            ExprCast(lhs, rhs));
2678                     self.parse_more_binops(_as, min_prec)
2679                 } else {
2680                     Ok(lhs)
2681                 }
2682             }
2683         }
2684     }
2685
2686     /// Produce an error if comparison operators are chained (RFC #558).
2687     /// We only need to check lhs, not rhs, because all comparison ops
2688     /// have same precedence and are left-associative
2689     fn check_no_chained_comparison(&mut self, lhs: &Expr, outer_op: ast::BinOp_) {
2690         debug_assert!(ast_util::is_comparison_binop(outer_op));
2691         match lhs.node {
2692             ExprBinary(op, _, _) if ast_util::is_comparison_binop(op.node) => {
2693                 // respan to include both operators
2694                 let op_span = mk_sp(op.span.lo, self.span.hi);
2695                 self.span_err(op_span,
2696                     "chained comparison operators require parentheses");
2697                 if op.node == BiLt && outer_op == BiGt {
2698                     self.fileline_help(op_span,
2699                         "use `::<...>` instead of `<...>` if you meant to specify type arguments");
2700                 }
2701             }
2702             _ => {}
2703         }
2704     }
2705
2706     /// Parse an assignment expression....
2707     /// actually, this seems to be the main entry point for
2708     /// parsing an arbitrary expression.
2709     pub fn parse_assign_expr(&mut self) -> PResult<P<Expr>> {
2710         match self.token {
2711           token::DotDot => {
2712             // prefix-form of range notation '..expr'
2713             // This has the same precedence as assignment expressions
2714             // (much lower than other prefix expressions) to be consistent
2715             // with the postfix-form 'expr..'
2716             let lo = self.span.lo;
2717             let mut hi = self.span.hi;
2718             try!(self.bump());
2719             let opt_end = if self.is_at_start_of_range_notation_rhs() {
2720                 let end = try!(self.parse_binops());
2721                 hi = end.span.hi;
2722                 Some(end)
2723             } else {
2724                 None
2725             };
2726             let ex = self.mk_range(None, opt_end);
2727             Ok(self.mk_expr(lo, hi, ex))
2728           }
2729           _ => {
2730             let lhs = try!(self.parse_binops());
2731             self.parse_assign_expr_with(lhs)
2732           }
2733         }
2734     }
2735
2736     pub fn parse_assign_expr_with(&mut self, lhs: P<Expr>) -> PResult<P<Expr>> {
2737         let restrictions = self.restrictions & Restrictions::RESTRICTION_NO_STRUCT_LITERAL;
2738         let op_span = self.span;
2739         match self.token {
2740           token::Eq => {
2741               try!(self.bump());
2742               let rhs = try!(self.parse_expr_res(restrictions));
2743               Ok(self.mk_expr(lhs.span.lo, rhs.span.hi, ExprAssign(lhs, rhs)))
2744           }
2745           token::BinOpEq(op) => {
2746               try!(self.bump());
2747               let rhs = try!(self.parse_expr_res(restrictions));
2748               let aop = match op {
2749                   token::Plus =>    BiAdd,
2750                   token::Minus =>   BiSub,
2751                   token::Star =>    BiMul,
2752                   token::Slash =>   BiDiv,
2753                   token::Percent => BiRem,
2754                   token::Caret =>   BiBitXor,
2755                   token::And =>     BiBitAnd,
2756                   token::Or =>      BiBitOr,
2757                   token::Shl =>     BiShl,
2758                   token::Shr =>     BiShr
2759               };
2760               let rhs_span = rhs.span;
2761               let span = lhs.span;
2762               let assign_op = self.mk_assign_op(codemap::respan(op_span, aop), lhs, rhs);
2763               Ok(self.mk_expr(span.lo, rhs_span.hi, assign_op))
2764           }
2765           // A range expression, either `expr..expr` or `expr..`.
2766           token::DotDot => {
2767             let lo = lhs.span.lo;
2768             let mut hi = self.span.hi;
2769             try!(self.bump());
2770
2771             let opt_end = if self.is_at_start_of_range_notation_rhs() {
2772                 let end = try!(self.parse_binops());
2773                 hi = end.span.hi;
2774                 Some(end)
2775             } else {
2776                 None
2777             };
2778             let range = self.mk_range(Some(lhs), opt_end);
2779             return Ok(self.mk_expr(lo, hi, range));
2780           }
2781
2782           _ => {
2783               Ok(lhs)
2784           }
2785         }
2786     }
2787
2788     fn is_at_start_of_range_notation_rhs(&self) -> bool {
2789         if self.token.can_begin_expr() {
2790             // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
2791             if self.token == token::OpenDelim(token::Brace) {
2792                 return !self.restrictions.contains(Restrictions::RESTRICTION_NO_STRUCT_LITERAL);
2793             }
2794             true
2795         } else {
2796             false
2797         }
2798     }
2799
2800     /// Parse an 'if' or 'if let' expression ('if' token already eaten)
2801     pub fn parse_if_expr(&mut self) -> PResult<P<Expr>> {
2802         if self.check_keyword(keywords::Let) {
2803             return self.parse_if_let_expr();
2804         }
2805         let lo = self.last_span.lo;
2806         let cond = try!(self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL));
2807         let thn = try!(self.parse_block());
2808         let mut els: Option<P<Expr>> = None;
2809         let mut hi = thn.span.hi;
2810         if try!(self.eat_keyword(keywords::Else) ){
2811             let elexpr = try!(self.parse_else_expr());
2812             hi = elexpr.span.hi;
2813             els = Some(elexpr);
2814         }
2815         Ok(self.mk_expr(lo, hi, ExprIf(cond, thn, els)))
2816     }
2817
2818     /// Parse an 'if let' expression ('if' token already eaten)
2819     pub fn parse_if_let_expr(&mut self) -> PResult<P<Expr>> {
2820         let lo = self.last_span.lo;
2821         try!(self.expect_keyword(keywords::Let));
2822         let pat = try!(self.parse_pat_nopanic());
2823         try!(self.expect(&token::Eq));
2824         let expr = try!(self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL));
2825         let thn = try!(self.parse_block());
2826         let (hi, els) = if try!(self.eat_keyword(keywords::Else) ){
2827             let expr = try!(self.parse_else_expr());
2828             (expr.span.hi, Some(expr))
2829         } else {
2830             (thn.span.hi, None)
2831         };
2832         Ok(self.mk_expr(lo, hi, ExprIfLet(pat, expr, thn, els)))
2833     }
2834
2835     // `|args| expr`
2836     pub fn parse_lambda_expr(&mut self, lo: BytePos, capture_clause: CaptureClause)
2837                              -> PResult<P<Expr>>
2838     {
2839         let decl = try!(self.parse_fn_block_decl());
2840         let body = match decl.output {
2841             DefaultReturn(_) => {
2842                 // If no explicit return type is given, parse any
2843                 // expr and wrap it up in a dummy block:
2844                 let body_expr = try!(self.parse_expr_nopanic());
2845                 P(ast::Block {
2846                     id: ast::DUMMY_NODE_ID,
2847                     stmts: vec![],
2848                     span: body_expr.span,
2849                     expr: Some(body_expr),
2850                     rules: DefaultBlock,
2851                 })
2852             }
2853             _ => {
2854                 // If an explicit return type is given, require a
2855                 // block to appear (RFC 968).
2856                 try!(self.parse_block())
2857             }
2858         };
2859
2860         Ok(self.mk_expr(
2861             lo,
2862             body.span.hi,
2863             ExprClosure(capture_clause, decl, body)))
2864     }
2865
2866     pub fn parse_else_expr(&mut self) -> PResult<P<Expr>> {
2867         if try!(self.eat_keyword(keywords::If) ){
2868             return self.parse_if_expr();
2869         } else {
2870             let blk = try!(self.parse_block());
2871             return Ok(self.mk_expr(blk.span.lo, blk.span.hi, ExprBlock(blk)));
2872         }
2873     }
2874
2875     /// Parse a 'for' .. 'in' expression ('for' token already eaten)
2876     pub fn parse_for_expr(&mut self, opt_ident: Option<ast::Ident>,
2877                           span_lo: BytePos) -> PResult<P<Expr>> {
2878         // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
2879
2880         let pat = try!(self.parse_pat_nopanic());
2881         try!(self.expect_keyword(keywords::In));
2882         let expr = try!(self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL));
2883         let loop_block = try!(self.parse_block());
2884         let hi = self.last_span.hi;
2885
2886         Ok(self.mk_expr(span_lo, hi, ExprForLoop(pat, expr, loop_block, opt_ident)))
2887     }
2888
2889     /// Parse a 'while' or 'while let' expression ('while' token already eaten)
2890     pub fn parse_while_expr(&mut self, opt_ident: Option<ast::Ident>,
2891                             span_lo: BytePos) -> PResult<P<Expr>> {
2892         if self.token.is_keyword(keywords::Let) {
2893             return self.parse_while_let_expr(opt_ident, span_lo);
2894         }
2895         let cond = try!(self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL));
2896         let body = try!(self.parse_block());
2897         let hi = body.span.hi;
2898         return Ok(self.mk_expr(span_lo, hi, ExprWhile(cond, body, opt_ident)));
2899     }
2900
2901     /// Parse a 'while let' expression ('while' token already eaten)
2902     pub fn parse_while_let_expr(&mut self, opt_ident: Option<ast::Ident>,
2903                                 span_lo: BytePos) -> PResult<P<Expr>> {
2904         try!(self.expect_keyword(keywords::Let));
2905         let pat = try!(self.parse_pat_nopanic());
2906         try!(self.expect(&token::Eq));
2907         let expr = try!(self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL));
2908         let body = try!(self.parse_block());
2909         let hi = body.span.hi;
2910         return Ok(self.mk_expr(span_lo, hi, ExprWhileLet(pat, expr, body, opt_ident)));
2911     }
2912
2913     pub fn parse_loop_expr(&mut self, opt_ident: Option<ast::Ident>,
2914                            span_lo: BytePos) -> PResult<P<Expr>> {
2915         let body = try!(self.parse_block());
2916         let hi = body.span.hi;
2917         Ok(self.mk_expr(span_lo, hi, ExprLoop(body, opt_ident)))
2918     }
2919
2920     fn parse_match_expr(&mut self) -> PResult<P<Expr>> {
2921         let lo = self.last_span.lo;
2922         let discriminant = try!(self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL));
2923         try!(self.commit_expr_expecting(&*discriminant, token::OpenDelim(token::Brace)));
2924         let mut arms: Vec<Arm> = Vec::new();
2925         while self.token != token::CloseDelim(token::Brace) {
2926             arms.push(try!(self.parse_arm_nopanic()));
2927         }
2928         let hi = self.span.hi;
2929         try!(self.bump());
2930         return Ok(self.mk_expr(lo, hi, ExprMatch(discriminant, arms, MatchSource::Normal)));
2931     }
2932
2933     pub fn parse_arm_nopanic(&mut self) -> PResult<Arm> {
2934         maybe_whole!(no_clone self, NtArm);
2935
2936         let attrs = self.parse_outer_attributes();
2937         let pats = try!(self.parse_pats());
2938         let mut guard = None;
2939         if try!(self.eat_keyword(keywords::If) ){
2940             guard = Some(try!(self.parse_expr_nopanic()));
2941         }
2942         try!(self.expect(&token::FatArrow));
2943         let expr = try!(self.parse_expr_res(Restrictions::RESTRICTION_STMT_EXPR));
2944
2945         let require_comma =
2946             !classify::expr_is_simple_block(&*expr)
2947             && self.token != token::CloseDelim(token::Brace);
2948
2949         if require_comma {
2950             try!(self.commit_expr(&*expr, &[token::Comma], &[token::CloseDelim(token::Brace)]));
2951         } else {
2952             try!(self.eat(&token::Comma));
2953         }
2954
2955         Ok(ast::Arm {
2956             attrs: attrs,
2957             pats: pats,
2958             guard: guard,
2959             body: expr,
2960         })
2961     }
2962
2963     /// Parse an expression
2964     pub fn parse_expr_nopanic(&mut self) -> PResult<P<Expr>> {
2965         self.parse_expr_res(Restrictions::empty())
2966     }
2967
2968     /// Parse an expression, subject to the given restrictions
2969     pub fn parse_expr_res(&mut self, r: Restrictions) -> PResult<P<Expr>> {
2970         let old = self.restrictions;
2971         self.restrictions = r;
2972         let e = try!(self.parse_assign_expr());
2973         self.restrictions = old;
2974         return Ok(e);
2975     }
2976
2977     /// Parse the RHS of a local variable declaration (e.g. '= 14;')
2978     fn parse_initializer(&mut self) -> PResult<Option<P<Expr>>> {
2979         if self.check(&token::Eq) {
2980             try!(self.bump());
2981             Ok(Some(try!(self.parse_expr_nopanic())))
2982         } else {
2983             Ok(None)
2984         }
2985     }
2986
2987     /// Parse patterns, separated by '|' s
2988     fn parse_pats(&mut self) -> PResult<Vec<P<Pat>>> {
2989         let mut pats = Vec::new();
2990         loop {
2991             pats.push(try!(self.parse_pat_nopanic()));
2992             if self.check(&token::BinOp(token::Or)) { try!(self.bump());}
2993             else { return Ok(pats); }
2994         };
2995     }
2996
2997     fn parse_pat_tuple_elements(&mut self) -> PResult<Vec<P<Pat>>> {
2998         let mut fields = vec![];
2999         if !self.check(&token::CloseDelim(token::Paren)) {
3000             fields.push(try!(self.parse_pat_nopanic()));
3001             if self.look_ahead(1, |t| *t != token::CloseDelim(token::Paren)) {
3002                 while try!(self.eat(&token::Comma)) &&
3003                       !self.check(&token::CloseDelim(token::Paren)) {
3004                     fields.push(try!(self.parse_pat_nopanic()));
3005                 }
3006             }
3007             if fields.len() == 1 {
3008                 try!(self.expect(&token::Comma));
3009             }
3010         }
3011         Ok(fields)
3012     }
3013
3014     fn parse_pat_vec_elements(
3015         &mut self,
3016     ) -> PResult<(Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
3017         let mut before = Vec::new();
3018         let mut slice = None;
3019         let mut after = Vec::new();
3020         let mut first = true;
3021         let mut before_slice = true;
3022
3023         while self.token != token::CloseDelim(token::Bracket) {
3024             if first {
3025                 first = false;
3026             } else {
3027                 try!(self.expect(&token::Comma));
3028
3029                 if self.token == token::CloseDelim(token::Bracket)
3030                         && (before_slice || !after.is_empty()) {
3031                     break
3032                 }
3033             }
3034
3035             if before_slice {
3036                 if self.check(&token::DotDot) {
3037                     try!(self.bump());
3038
3039                     if self.check(&token::Comma) ||
3040                             self.check(&token::CloseDelim(token::Bracket)) {
3041                         slice = Some(P(ast::Pat {
3042                             id: ast::DUMMY_NODE_ID,
3043                             node: PatWild(PatWildMulti),
3044                             span: self.span,
3045                         }));
3046                         before_slice = false;
3047                     }
3048                     continue
3049                 }
3050             }
3051
3052             let subpat = try!(self.parse_pat_nopanic());
3053             if before_slice && self.check(&token::DotDot) {
3054                 try!(self.bump());
3055                 slice = Some(subpat);
3056                 before_slice = false;
3057             } else if before_slice {
3058                 before.push(subpat);
3059             } else {
3060                 after.push(subpat);
3061             }
3062         }
3063
3064         Ok((before, slice, after))
3065     }
3066
3067     /// Parse the fields of a struct-like pattern
3068     fn parse_pat_fields(&mut self) -> PResult<(Vec<codemap::Spanned<ast::FieldPat>> , bool)> {
3069         let mut fields = Vec::new();
3070         let mut etc = false;
3071         let mut first = true;
3072         while self.token != token::CloseDelim(token::Brace) {
3073             if first {
3074                 first = false;
3075             } else {
3076                 try!(self.expect(&token::Comma));
3077                 // accept trailing commas
3078                 if self.check(&token::CloseDelim(token::Brace)) { break }
3079             }
3080
3081             let lo = self.span.lo;
3082             let hi;
3083
3084             if self.check(&token::DotDot) {
3085                 try!(self.bump());
3086                 if self.token != token::CloseDelim(token::Brace) {
3087                     let token_str = self.this_token_to_string();
3088                     return Err(self.fatal(&format!("expected `{}`, found `{}`", "}",
3089                                        token_str)))
3090                 }
3091                 etc = true;
3092                 break;
3093             }
3094
3095             // Check if a colon exists one ahead. This means we're parsing a fieldname.
3096             let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
3097                 // Parsing a pattern of the form "fieldname: pat"
3098                 let fieldname = try!(self.parse_ident());
3099                 try!(self.bump());
3100                 let pat = try!(self.parse_pat_nopanic());
3101                 hi = pat.span.hi;
3102                 (pat, fieldname, false)
3103             } else {
3104                 // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
3105                 let is_box = try!(self.eat_keyword(keywords::Box));
3106                 let boxed_span_lo = self.span.lo;
3107                 let is_ref = try!(self.eat_keyword(keywords::Ref));
3108                 let is_mut = try!(self.eat_keyword(keywords::Mut));
3109                 let fieldname = try!(self.parse_ident());
3110                 hi = self.last_span.hi;
3111
3112                 let bind_type = match (is_ref, is_mut) {
3113                     (true, true) => BindByRef(MutMutable),
3114                     (true, false) => BindByRef(MutImmutable),
3115                     (false, true) => BindByValue(MutMutable),
3116                     (false, false) => BindByValue(MutImmutable),
3117                 };
3118                 let fieldpath = codemap::Spanned{span:self.last_span, node:fieldname};
3119                 let fieldpat = P(ast::Pat{
3120                     id: ast::DUMMY_NODE_ID,
3121                     node: PatIdent(bind_type, fieldpath, None),
3122                     span: mk_sp(boxed_span_lo, hi),
3123                 });
3124
3125                 let subpat = if is_box {
3126                     P(ast::Pat{
3127                         id: ast::DUMMY_NODE_ID,
3128                         node: PatBox(fieldpat),
3129                         span: mk_sp(lo, hi),
3130                     })
3131                 } else {
3132                     fieldpat
3133                 };
3134                 (subpat, fieldname, true)
3135             };
3136
3137             fields.push(codemap::Spanned { span: mk_sp(lo, hi),
3138                                            node: ast::FieldPat { ident: fieldname,
3139                                                                  pat: subpat,
3140                                                                  is_shorthand: is_shorthand }});
3141         }
3142         return Ok((fields, etc));
3143     }
3144
3145     fn parse_pat_range_end(&mut self) -> PResult<P<Expr>> {
3146         if self.is_path_start() {
3147             let lo = self.span.lo;
3148             let (qself, path) = if try!(self.eat_lt()) {
3149                 // Parse a qualified path
3150                 let (qself, path) =
3151                     try!(self.parse_qualified_path(NoTypesAllowed));
3152                 (Some(qself), path)
3153             } else {
3154                 // Parse an unqualified path
3155                 (None, try!(self.parse_path(LifetimeAndTypesWithColons)))
3156             };
3157             let hi = self.last_span.hi;
3158             Ok(self.mk_expr(lo, hi, ExprPath(qself, path)))
3159         } else {
3160             self.parse_literal_maybe_minus()
3161         }
3162     }
3163
3164     fn is_path_start(&self) -> bool {
3165         (self.token == token::Lt || self.token == token::ModSep
3166             || self.token.is_ident() || self.token.is_path())
3167             && !self.token.is_keyword(keywords::True) && !self.token.is_keyword(keywords::False)
3168     }
3169
3170     /// Parse a pattern.
3171     pub fn parse_pat_nopanic(&mut self) -> PResult<P<Pat>> {
3172         maybe_whole!(self, NtPat);
3173
3174         let lo = self.span.lo;
3175         let pat;
3176         match self.token {
3177           token::Underscore => {
3178             // Parse _
3179             try!(self.bump());
3180             pat = PatWild(PatWildSingle);
3181           }
3182           token::BinOp(token::And) | token::AndAnd => {
3183             // Parse &pat / &mut pat
3184             try!(self.expect_and());
3185             let mutbl = try!(self.parse_mutability());
3186             let subpat = try!(self.parse_pat_nopanic());
3187             pat = PatRegion(subpat, mutbl);
3188           }
3189           token::OpenDelim(token::Paren) => {
3190             // Parse (pat,pat,pat,...) as tuple pattern
3191             try!(self.bump());
3192             let fields = try!(self.parse_pat_tuple_elements());
3193             try!(self.expect(&token::CloseDelim(token::Paren)));
3194             pat = PatTup(fields);
3195           }
3196           token::OpenDelim(token::Bracket) => {
3197             // Parse [pat,pat,...] as slice pattern
3198             try!(self.bump());
3199             let (before, slice, after) = try!(self.parse_pat_vec_elements());
3200             try!(self.expect(&token::CloseDelim(token::Bracket)));
3201             pat = PatVec(before, slice, after);
3202           }
3203           _ => {
3204             // At this point, token != _, &, &&, (, [
3205             if try!(self.eat_keyword(keywords::Mut)) {
3206                 // Parse mut ident @ pat
3207                 pat = try!(self.parse_pat_ident(BindByValue(MutMutable)));
3208             } else if try!(self.eat_keyword(keywords::Ref)) {
3209                 // Parse ref ident @ pat / ref mut ident @ pat
3210                 let mutbl = try!(self.parse_mutability());
3211                 pat = try!(self.parse_pat_ident(BindByRef(mutbl)));
3212             } else if try!(self.eat_keyword(keywords::Box)) {
3213                 // Parse box pat
3214                 let subpat = try!(self.parse_pat_nopanic());
3215                 pat = PatBox(subpat);
3216             } else if self.is_path_start() {
3217                 // Parse pattern starting with a path
3218                 if self.token.is_plain_ident() && self.look_ahead(1, |t| *t != token::DotDotDot &&
3219                         *t != token::OpenDelim(token::Brace) &&
3220                         *t != token::OpenDelim(token::Paren) &&
3221                         // Contrary to its definition, a plain ident can be followed by :: in macros
3222                         *t != token::ModSep) {
3223                     // Plain idents have some extra abilities here compared to general paths
3224                     if self.look_ahead(1, |t| *t == token::Not) {
3225                         // Parse macro invocation
3226                         let ident = try!(self.parse_ident());
3227                         let ident_span = self.last_span;
3228                         let path = ident_to_path(ident_span, ident);
3229                         try!(self.bump());
3230                         let delim = try!(self.expect_open_delim());
3231                         let tts = try!(self.parse_seq_to_end(&token::CloseDelim(delim),
3232                                 seq_sep_none(), |p| p.parse_token_tree()));
3233                         let mac = Mac_ { path: path, tts: tts, ctxt: EMPTY_CTXT };
3234                         pat = PatMac(codemap::Spanned {node: mac, span: self.span});
3235                     } else {
3236                         // Parse ident @ pat
3237                         // This can give false positives and parse nullary enums,
3238                         // they are dealt with later in resolve
3239                         pat = try!(self.parse_pat_ident(BindByValue(MutImmutable)));
3240                     }
3241                 } else {
3242                     let (qself, path) = if try!(self.eat_lt()) {
3243                         // Parse a qualified path
3244                         let (qself, path) =
3245                             try!(self.parse_qualified_path(NoTypesAllowed));
3246                         (Some(qself), path)
3247                     } else {
3248                         // Parse an unqualified path
3249                         (None, try!(self.parse_path(LifetimeAndTypesWithColons)))
3250                     };
3251                     match self.token {
3252                       token::DotDotDot => {
3253                         // Parse range
3254                         let hi = self.last_span.hi;
3255                         let begin = self.mk_expr(lo, hi, ExprPath(qself, path));
3256                         try!(self.bump());
3257                         let end = try!(self.parse_pat_range_end());
3258                         pat = PatRange(begin, end);
3259                       }
3260                       token::OpenDelim(token::Brace) => {
3261                          if qself.is_some() {
3262                             let span = self.span;
3263                             self.span_err(span,
3264                                           "unexpected `{` after qualified path");
3265                             self.abort_if_errors();
3266                         }
3267                        // Parse struct pattern
3268                         try!(self.bump());
3269                         let (fields, etc) = try!(self.parse_pat_fields());
3270                         try!(self.bump());
3271                         pat = PatStruct(path, fields, etc);
3272                       }
3273                       token::OpenDelim(token::Paren) => {
3274                         if qself.is_some() {
3275                             let span = self.span;
3276                             self.span_err(span,
3277                                           "unexpected `(` after qualified path");
3278                             self.abort_if_errors();
3279                         }
3280                         // Parse tuple struct or enum pattern
3281                         if self.look_ahead(1, |t| *t == token::DotDot) {
3282                             // This is a "top constructor only" pat
3283                             try!(self.bump());
3284                             try!(self.bump());
3285                             try!(self.expect(&token::CloseDelim(token::Paren)));
3286                             pat = PatEnum(path, None);
3287                         } else {
3288                             let args = try!(self.parse_enum_variant_seq(
3289                                     &token::OpenDelim(token::Paren),
3290                                     &token::CloseDelim(token::Paren),
3291                                     seq_sep_trailing_allowed(token::Comma),
3292                                     |p| p.parse_pat_nopanic()));
3293                             pat = PatEnum(path, Some(args));
3294                         }
3295                       }
3296                       _ if qself.is_some() => {
3297                         // Parse qualified path
3298                         pat = PatQPath(qself.unwrap(), path);
3299                       }
3300                       _ => {
3301                         // Parse nullary enum
3302                         pat = PatEnum(path, Some(vec![]));
3303                       }
3304                     }
3305                 }
3306             } else {
3307                 // Try to parse everything else as literal with optional minus
3308                 let begin = try!(self.parse_literal_maybe_minus());
3309                 if try!(self.eat(&token::DotDotDot)) {
3310                     let end = try!(self.parse_pat_range_end());
3311                     pat = PatRange(begin, end);
3312                 } else {
3313                     pat = PatLit(begin);
3314                 }
3315             }
3316           }
3317         }
3318
3319         let hi = self.last_span.hi;
3320         Ok(P(ast::Pat {
3321             id: ast::DUMMY_NODE_ID,
3322             node: pat,
3323             span: mk_sp(lo, hi),
3324         }))
3325     }
3326
3327     /// Parse ident or ident @ pat
3328     /// used by the copy foo and ref foo patterns to give a good
3329     /// error message when parsing mistakes like ref foo(a,b)
3330     fn parse_pat_ident(&mut self,
3331                        binding_mode: ast::BindingMode)
3332                        -> PResult<ast::Pat_> {
3333         if !self.token.is_plain_ident() {
3334             let span = self.span;
3335             let tok_str = self.this_token_to_string();
3336             return Err(self.span_fatal(span,
3337                             &format!("expected identifier, found `{}`", tok_str)))
3338         }
3339         let ident = try!(self.parse_ident());
3340         let last_span = self.last_span;
3341         let name = codemap::Spanned{span: last_span, node: ident};
3342         let sub = if try!(self.eat(&token::At) ){
3343             Some(try!(self.parse_pat_nopanic()))
3344         } else {
3345             None
3346         };
3347
3348         // just to be friendly, if they write something like
3349         //   ref Some(i)
3350         // we end up here with ( as the current token.  This shortly
3351         // leads to a parse error.  Note that if there is no explicit
3352         // binding mode then we do not end up here, because the lookahead
3353         // will direct us over to parse_enum_variant()
3354         if self.token == token::OpenDelim(token::Paren) {
3355             let last_span = self.last_span;
3356             return Err(self.span_fatal(
3357                 last_span,
3358                 "expected identifier, found enum pattern"))
3359         }
3360
3361         Ok(PatIdent(binding_mode, name, sub))
3362     }
3363
3364     /// Parse a local variable declaration
3365     fn parse_local(&mut self) -> PResult<P<Local>> {
3366         let lo = self.span.lo;
3367         let pat = try!(self.parse_pat_nopanic());
3368
3369         let mut ty = None;
3370         if try!(self.eat(&token::Colon) ){
3371             ty = Some(try!(self.parse_ty_sum()));
3372         }
3373         let init = try!(self.parse_initializer());
3374         Ok(P(ast::Local {
3375             ty: ty,
3376             pat: pat,
3377             init: init,
3378             id: ast::DUMMY_NODE_ID,
3379             span: mk_sp(lo, self.last_span.hi),
3380         }))
3381     }
3382
3383     /// Parse a "let" stmt
3384     fn parse_let(&mut self) -> PResult<P<Decl>> {
3385         let lo = self.span.lo;
3386         let local = try!(self.parse_local());
3387         Ok(P(spanned(lo, self.last_span.hi, DeclLocal(local))))
3388     }
3389
3390     /// Parse a structure field
3391     fn parse_name_and_ty(&mut self, pr: Visibility,
3392                          attrs: Vec<Attribute> ) -> PResult<StructField> {
3393         let lo = match pr {
3394             Inherited => self.span.lo,
3395             Public => self.last_span.lo,
3396         };
3397         if !self.token.is_plain_ident() {
3398             return Err(self.fatal("expected ident"));
3399         }
3400         let name = try!(self.parse_ident());
3401         try!(self.expect(&token::Colon));
3402         let ty = try!(self.parse_ty_sum());
3403         Ok(spanned(lo, self.last_span.hi, ast::StructField_ {
3404             kind: NamedField(name, pr),
3405             id: ast::DUMMY_NODE_ID,
3406             ty: ty,
3407             attrs: attrs,
3408         }))
3409     }
3410
3411     /// Emit an expected item after attributes error.
3412     fn expected_item_err(&self, attrs: &[Attribute]) {
3413         let message = match attrs.last() {
3414             Some(&Attribute { node: ast::Attribute_ { is_sugared_doc: true, .. }, .. }) => {
3415                 "expected item after doc comment"
3416             }
3417             _ => "expected item after attributes",
3418         };
3419
3420         self.span_err(self.last_span, message);
3421     }
3422
3423     /// Parse a statement. may include decl.
3424     pub fn parse_stmt_nopanic(&mut self) -> PResult<Option<P<Stmt>>> {
3425         Ok(try!(self.parse_stmt_()).map(P))
3426     }
3427
3428     fn parse_stmt_(&mut self) -> PResult<Option<Stmt>> {
3429         maybe_whole!(Some deref self, NtStmt);
3430
3431         fn check_expected_item(p: &mut Parser, attrs: &[Attribute]) {
3432             // If we have attributes then we should have an item
3433             if !attrs.is_empty() {
3434                 p.expected_item_err(attrs);
3435             }
3436         }
3437
3438         let attrs = self.parse_outer_attributes();
3439         let lo = self.span.lo;
3440
3441         Ok(Some(if self.check_keyword(keywords::Let) {
3442             check_expected_item(self, &attrs);
3443             try!(self.expect_keyword(keywords::Let));
3444             let decl = try!(self.parse_let());
3445             spanned(lo, decl.span.hi, StmtDecl(decl, ast::DUMMY_NODE_ID))
3446         } else if self.token.is_ident()
3447             && !self.token.is_any_keyword()
3448             && self.look_ahead(1, |t| *t == token::Not) {
3449             // it's a macro invocation:
3450
3451             check_expected_item(self, &attrs);
3452
3453             // Potential trouble: if we allow macros with paths instead of
3454             // idents, we'd need to look ahead past the whole path here...
3455             let pth = try!(self.parse_path(NoTypesAllowed));
3456             try!(self.bump());
3457
3458             let id = match self.token {
3459                 token::OpenDelim(_) => token::special_idents::invalid, // no special identifier
3460                 _ => try!(self.parse_ident()),
3461             };
3462
3463             // check that we're pointing at delimiters (need to check
3464             // again after the `if`, because of `parse_ident`
3465             // consuming more tokens).
3466             let delim = match self.token {
3467                 token::OpenDelim(delim) => delim,
3468                 _ => {
3469                     // we only expect an ident if we didn't parse one
3470                     // above.
3471                     let ident_str = if id.name == token::special_idents::invalid.name {
3472                         "identifier, "
3473                     } else {
3474                         ""
3475                     };
3476                     let tok_str = self.this_token_to_string();
3477                     return Err(self.fatal(&format!("expected {}`(` or `{{`, found `{}`",
3478                                        ident_str,
3479                                        tok_str)))
3480                 },
3481             };
3482
3483             let tts = try!(self.parse_unspanned_seq(
3484                 &token::OpenDelim(delim),
3485                 &token::CloseDelim(delim),
3486                 seq_sep_none(),
3487                 |p| p.parse_token_tree()
3488             ));
3489             let hi = self.last_span.hi;
3490
3491             let style = if delim == token::Brace {
3492                 MacStmtWithBraces
3493             } else {
3494                 MacStmtWithoutBraces
3495             };
3496
3497             if id.name == token::special_idents::invalid.name {
3498                 spanned(lo, hi,
3499                         StmtMac(P(spanned(lo,
3500                                           hi,
3501                                           Mac_ { path: pth, tts: tts, ctxt: EMPTY_CTXT })),
3502                                   style))
3503             } else {
3504                 // if it has a special ident, it's definitely an item
3505                 //
3506                 // Require a semicolon or braces.
3507                 if style != MacStmtWithBraces {
3508                     if !try!(self.eat(&token::Semi) ){
3509                         let last_span = self.last_span;
3510                         self.span_err(last_span,
3511                                       "macros that expand to items must \
3512                                        either be surrounded with braces or \
3513                                        followed by a semicolon");
3514                     }
3515                 }
3516                 spanned(lo, hi, StmtDecl(
3517                     P(spanned(lo, hi, DeclItem(
3518                         self.mk_item(
3519                             lo, hi, id /*id is good here*/,
3520                             ItemMac(spanned(lo, hi,
3521                                             Mac_ { path: pth, tts: tts, ctxt: EMPTY_CTXT })),
3522                             Inherited, Vec::new(/*no attrs*/))))),
3523                     ast::DUMMY_NODE_ID))
3524             }
3525         } else {
3526             match try!(self.parse_item_(attrs, false)) {
3527                 Some(i) => {
3528                     let hi = i.span.hi;
3529                     let decl = P(spanned(lo, hi, DeclItem(i)));
3530                     spanned(lo, hi, StmtDecl(decl, ast::DUMMY_NODE_ID))
3531                 }
3532                 None => {
3533                     // Do not attempt to parse an expression if we're done here.
3534                     if self.token == token::Semi {
3535                         try!(self.bump());
3536                         return Ok(None);
3537                     }
3538
3539                     if self.token == token::CloseDelim(token::Brace) {
3540                         return Ok(None);
3541                     }
3542
3543                     // Remainder are line-expr stmts.
3544                     let e = try!(self.parse_expr_res(Restrictions::RESTRICTION_STMT_EXPR));
3545                     spanned(lo, e.span.hi, StmtExpr(e, ast::DUMMY_NODE_ID))
3546                 }
3547             }
3548         }))
3549     }
3550
3551     /// Is this expression a successfully-parsed statement?
3552     fn expr_is_complete(&mut self, e: &Expr) -> bool {
3553         self.restrictions.contains(Restrictions::RESTRICTION_STMT_EXPR) &&
3554             !classify::expr_requires_semi_to_be_stmt(e)
3555     }
3556
3557     /// Parse a block. No inner attrs are allowed.
3558     pub fn parse_block(&mut self) -> PResult<P<Block>> {
3559         maybe_whole!(no_clone self, NtBlock);
3560
3561         let lo = self.span.lo;
3562
3563         if !try!(self.eat(&token::OpenDelim(token::Brace)) ){
3564             let sp = self.span;
3565             let tok = self.this_token_to_string();
3566             return Err(self.span_fatal_help(sp,
3567                                  &format!("expected `{{`, found `{}`", tok),
3568                                  "place this code inside a block"));
3569         }
3570
3571         self.parse_block_tail(lo, DefaultBlock)
3572     }
3573
3574     /// Parse a block. Inner attrs are allowed.
3575     fn parse_inner_attrs_and_block(&mut self) -> PResult<(Vec<Attribute>, P<Block>)> {
3576         maybe_whole!(pair_empty self, NtBlock);
3577
3578         let lo = self.span.lo;
3579         try!(self.expect(&token::OpenDelim(token::Brace)));
3580         Ok((self.parse_inner_attributes(),
3581          try!(self.parse_block_tail(lo, DefaultBlock))))
3582     }
3583
3584     /// Parse the rest of a block expression or function body
3585     /// Precondition: already parsed the '{'.
3586     fn parse_block_tail(&mut self, lo: BytePos, s: BlockCheckMode) -> PResult<P<Block>> {
3587         let mut stmts = vec![];
3588         let mut expr = None;
3589
3590         while !try!(self.eat(&token::CloseDelim(token::Brace))) {
3591             let Spanned {node, span} = if let Some(s) = try!(self.parse_stmt_()) {
3592                 s
3593             } else {
3594                 // Found only `;` or `}`.
3595                 continue;
3596             };
3597             match node {
3598                 StmtExpr(e, _) => {
3599                     try!(self.handle_expression_like_statement(e, span, &mut stmts, &mut expr));
3600                 }
3601                 StmtMac(mac, MacStmtWithoutBraces) => {
3602                     // statement macro without braces; might be an
3603                     // expr depending on whether a semicolon follows
3604                     match self.token {
3605                         token::Semi => {
3606                             stmts.push(P(Spanned {
3607                                 node: StmtMac(mac, MacStmtWithSemicolon),
3608                                 span: mk_sp(span.lo, self.span.hi),
3609                             }));
3610                             try!(self.bump());
3611                         }
3612                         _ => {
3613                             let e = self.mk_mac_expr(span.lo, span.hi,
3614                                                      mac.and_then(|m| m.node));
3615                             let e = try!(self.parse_dot_or_call_expr_with(e));
3616                             let e = try!(self.parse_more_binops(e, 0));
3617                             let e = try!(self.parse_assign_expr_with(e));
3618                             try!(self.handle_expression_like_statement(
3619                                 e,
3620                                 span,
3621                                 &mut stmts,
3622                                 &mut expr));
3623                         }
3624                     }
3625                 }
3626                 StmtMac(m, style) => {
3627                     // statement macro; might be an expr
3628                     match self.token {
3629                         token::Semi => {
3630                             stmts.push(P(Spanned {
3631                                 node: StmtMac(m, MacStmtWithSemicolon),
3632                                 span: mk_sp(span.lo, self.span.hi),
3633                             }));
3634                             try!(self.bump());
3635                         }
3636                         token::CloseDelim(token::Brace) => {
3637                             // if a block ends in `m!(arg)` without
3638                             // a `;`, it must be an expr
3639                             expr = Some(self.mk_mac_expr(span.lo, span.hi,
3640                                                          m.and_then(|x| x.node)));
3641                         }
3642                         _ => {
3643                             stmts.push(P(Spanned {
3644                                 node: StmtMac(m, style),
3645                                 span: span
3646                             }));
3647                         }
3648                     }
3649                 }
3650                 _ => { // all other kinds of statements:
3651                     let mut hi = span.hi;
3652                     if classify::stmt_ends_with_semi(&node) {
3653                         try!(self.commit_stmt_expecting(token::Semi));
3654                         hi = self.last_span.hi;
3655                     }
3656
3657                     stmts.push(P(Spanned {
3658                         node: node,
3659                         span: mk_sp(span.lo, hi)
3660                     }));
3661                 }
3662             }
3663         }
3664
3665         Ok(P(ast::Block {
3666             stmts: stmts,
3667             expr: expr,
3668             id: ast::DUMMY_NODE_ID,
3669             rules: s,
3670             span: mk_sp(lo, self.last_span.hi),
3671         }))
3672     }
3673
3674     fn handle_expression_like_statement(
3675             &mut self,
3676             e: P<Expr>,
3677             span: Span,
3678             stmts: &mut Vec<P<Stmt>>,
3679             last_block_expr: &mut Option<P<Expr>>) -> PResult<()> {
3680         // expression without semicolon
3681         if classify::expr_requires_semi_to_be_stmt(&*e) {
3682             // Just check for errors and recover; do not eat semicolon yet.
3683             try!(self.commit_stmt(&[],
3684                              &[token::Semi, token::CloseDelim(token::Brace)]));
3685         }
3686
3687         match self.token {
3688             token::Semi => {
3689                 try!(self.bump());
3690                 let span_with_semi = Span {
3691                     lo: span.lo,
3692                     hi: self.last_span.hi,
3693                     expn_id: span.expn_id,
3694                 };
3695                 stmts.push(P(Spanned {
3696                     node: StmtSemi(e, ast::DUMMY_NODE_ID),
3697                     span: span_with_semi,
3698                 }));
3699             }
3700             token::CloseDelim(token::Brace) => *last_block_expr = Some(e),
3701             _ => {
3702                 stmts.push(P(Spanned {
3703                     node: StmtExpr(e, ast::DUMMY_NODE_ID),
3704                     span: span
3705                 }));
3706             }
3707         }
3708         Ok(())
3709     }
3710
3711     // Parses a sequence of bounds if a `:` is found,
3712     // otherwise returns empty list.
3713     fn parse_colon_then_ty_param_bounds(&mut self,
3714                                         mode: BoundParsingMode)
3715                                         -> PResult<OwnedSlice<TyParamBound>>
3716     {
3717         if !try!(self.eat(&token::Colon) ){
3718             Ok(OwnedSlice::empty())
3719         } else {
3720             self.parse_ty_param_bounds(mode)
3721         }
3722     }
3723
3724     // matches bounds    = ( boundseq )?
3725     // where   boundseq  = ( polybound + boundseq ) | polybound
3726     // and     polybound = ( 'for' '<' 'region '>' )? bound
3727     // and     bound     = 'region | trait_ref
3728     fn parse_ty_param_bounds(&mut self,
3729                              mode: BoundParsingMode)
3730                              -> PResult<OwnedSlice<TyParamBound>>
3731     {
3732         let mut result = vec!();
3733         loop {
3734             let question_span = self.span;
3735             let ate_question = try!(self.eat(&token::Question));
3736             match self.token {
3737                 token::Lifetime(lifetime) => {
3738                     if ate_question {
3739                         self.span_err(question_span,
3740                                       "`?` may only modify trait bounds, not lifetime bounds");
3741                     }
3742                     result.push(RegionTyParamBound(ast::Lifetime {
3743                         id: ast::DUMMY_NODE_ID,
3744                         span: self.span,
3745                         name: lifetime.name
3746                     }));
3747                     try!(self.bump());
3748                 }
3749                 token::ModSep | token::Ident(..) => {
3750                     let poly_trait_ref = try!(self.parse_poly_trait_ref());
3751                     let modifier = if ate_question {
3752                         if mode == BoundParsingMode::Modified {
3753                             TraitBoundModifier::Maybe
3754                         } else {
3755                             self.span_err(question_span,
3756                                           "unexpected `?`");
3757                             TraitBoundModifier::None
3758                         }
3759                     } else {
3760                         TraitBoundModifier::None
3761                     };
3762                     result.push(TraitTyParamBound(poly_trait_ref, modifier))
3763                 }
3764                 _ => break,
3765             }
3766
3767             if !try!(self.eat(&token::BinOp(token::Plus)) ){
3768                 break;
3769             }
3770         }
3771
3772         return Ok(OwnedSlice::from_vec(result));
3773     }
3774
3775     /// Matches typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?
3776     fn parse_ty_param(&mut self) -> PResult<TyParam> {
3777         let span = self.span;
3778         let ident = try!(self.parse_ident());
3779
3780         let bounds = try!(self.parse_colon_then_ty_param_bounds(BoundParsingMode::Modified));
3781
3782         let default = if self.check(&token::Eq) {
3783             try!(self.bump());
3784             Some(try!(self.parse_ty_sum()))
3785         } else {
3786             None
3787         };
3788
3789         Ok(TyParam {
3790             ident: ident,
3791             id: ast::DUMMY_NODE_ID,
3792             bounds: bounds,
3793             default: default,
3794             span: span,
3795         })
3796     }
3797
3798     /// Parse a set of optional generic type parameter declarations. Where
3799     /// clauses are not parsed here, and must be added later via
3800     /// `parse_where_clause()`.
3801     ///
3802     /// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
3803     ///                  | ( < lifetimes , typaramseq ( , )? > )
3804     /// where   typaramseq = ( typaram ) | ( typaram , typaramseq )
3805     pub fn parse_generics(&mut self) -> PResult<ast::Generics> {
3806         maybe_whole!(self, NtGenerics);
3807
3808         if try!(self.eat(&token::Lt) ){
3809             let lifetime_defs = try!(self.parse_lifetime_defs());
3810             let mut seen_default = false;
3811             let ty_params = try!(self.parse_seq_to_gt(Some(token::Comma), |p| {
3812                 try!(p.forbid_lifetime());
3813                 let ty_param = try!(p.parse_ty_param());
3814                 if ty_param.default.is_some() {
3815                     seen_default = true;
3816                 } else if seen_default {
3817                     let last_span = p.last_span;
3818                     p.span_err(last_span,
3819                                "type parameters with a default must be trailing");
3820                 }
3821                 Ok(ty_param)
3822             }));
3823             Ok(ast::Generics {
3824                 lifetimes: lifetime_defs,
3825                 ty_params: ty_params,
3826                 where_clause: WhereClause {
3827                     id: ast::DUMMY_NODE_ID,
3828                     predicates: Vec::new(),
3829                 }
3830             })
3831         } else {
3832             Ok(ast_util::empty_generics())
3833         }
3834     }
3835
3836     fn parse_generic_values_after_lt(&mut self) -> PResult<(Vec<ast::Lifetime>,
3837                                                             Vec<P<Ty>>,
3838                                                             Vec<P<TypeBinding>>)> {
3839         let span_lo = self.span.lo;
3840         let lifetimes = try!(self.parse_lifetimes(token::Comma));
3841
3842         let missing_comma = !lifetimes.is_empty() &&
3843                             !self.token.is_like_gt() &&
3844                             self.last_token
3845                                 .as_ref().map_or(true,
3846                                                  |x| &**x != &token::Comma);
3847
3848         if missing_comma {
3849
3850             let msg = format!("expected `,` or `>` after lifetime \
3851                               name, found `{}`",
3852                               self.this_token_to_string());
3853             self.span_err(self.span, &msg);
3854
3855             let span_hi = self.span.hi;
3856             let span_hi = if self.parse_ty_nopanic().is_ok() {
3857                 self.span.hi
3858             } else {
3859                 span_hi
3860             };
3861
3862             let msg = format!("did you mean a single argument type &'a Type, \
3863                               or did you mean the comma-separated arguments \
3864                               'a, Type?");
3865             self.span_note(mk_sp(span_lo, span_hi), &msg);
3866
3867             self.abort_if_errors()
3868         }
3869
3870         // First parse types.
3871         let (types, returned) = try!(self.parse_seq_to_gt_or_return(
3872             Some(token::Comma),
3873             |p| {
3874                 try!(p.forbid_lifetime());
3875                 if p.look_ahead(1, |t| t == &token::Eq) {
3876                     Ok(None)
3877                 } else {
3878                     Ok(Some(try!(p.parse_ty_sum())))
3879                 }
3880             }
3881         ));
3882
3883         // If we found the `>`, don't continue.
3884         if !returned {
3885             return Ok((lifetimes, types.into_vec(), Vec::new()));
3886         }
3887
3888         // Then parse type bindings.
3889         let bindings = try!(self.parse_seq_to_gt(
3890             Some(token::Comma),
3891             |p| {
3892                 try!(p.forbid_lifetime());
3893                 let lo = p.span.lo;
3894                 let ident = try!(p.parse_ident());
3895                 let found_eq = try!(p.eat(&token::Eq));
3896                 if !found_eq {
3897                     let span = p.span;
3898                     p.span_warn(span, "whoops, no =?");
3899                 }
3900                 let ty = try!(p.parse_ty_nopanic());
3901                 let hi = ty.span.hi;
3902                 let span = mk_sp(lo, hi);
3903                 return Ok(P(TypeBinding{id: ast::DUMMY_NODE_ID,
3904                     ident: ident,
3905                     ty: ty,
3906                     span: span,
3907                 }));
3908             }
3909         ));
3910         Ok((lifetimes, types.into_vec(), bindings.into_vec()))
3911     }
3912
3913     fn forbid_lifetime(&mut self) -> PResult<()> {
3914         if self.token.is_lifetime() {
3915             let span = self.span;
3916             return Err(self.span_fatal(span, "lifetime parameters must be declared \
3917                                         prior to type parameters"))
3918         }
3919         Ok(())
3920     }
3921
3922     /// Parses an optional `where` clause and places it in `generics`.
3923     ///
3924     /// ```
3925     /// where T : Trait<U, V> + 'b, 'a : 'b
3926     /// ```
3927     pub fn parse_where_clause(&mut self) -> PResult<ast::WhereClause> {
3928         maybe_whole!(self, NtWhereClause);
3929
3930         let mut where_clause = WhereClause {
3931             id: ast::DUMMY_NODE_ID,
3932             predicates: Vec::new(),
3933         };
3934
3935         if !try!(self.eat_keyword(keywords::Where)) {
3936             return Ok(where_clause);
3937         }
3938
3939         let mut parsed_something = false;
3940         loop {
3941             let lo = self.span.lo;
3942             match self.token {
3943                 token::OpenDelim(token::Brace) => {
3944                     break
3945                 }
3946
3947                 token::Lifetime(..) => {
3948                     let bounded_lifetime =
3949                         try!(self.parse_lifetime());
3950
3951                     try!(self.eat(&token::Colon));
3952
3953                     let bounds =
3954                         try!(self.parse_lifetimes(token::BinOp(token::Plus)));
3955
3956                     let hi = self.last_span.hi;
3957                     let span = mk_sp(lo, hi);
3958
3959                     where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
3960                         ast::WhereRegionPredicate {
3961                             span: span,
3962                             lifetime: bounded_lifetime,
3963                             bounds: bounds
3964                         }
3965                     ));
3966
3967                     parsed_something = true;
3968                 }
3969
3970                 _ => {
3971                     let bound_lifetimes = if try!(self.eat_keyword(keywords::For) ){
3972                         // Higher ranked constraint.
3973                         try!(self.expect(&token::Lt));
3974                         let lifetime_defs = try!(self.parse_lifetime_defs());
3975                         try!(self.expect_gt());
3976                         lifetime_defs
3977                     } else {
3978                         vec![]
3979                     };
3980
3981                     let bounded_ty = try!(self.parse_ty_nopanic());
3982
3983                     if try!(self.eat(&token::Colon) ){
3984                         let bounds = try!(self.parse_ty_param_bounds(BoundParsingMode::Bare));
3985                         let hi = self.last_span.hi;
3986                         let span = mk_sp(lo, hi);
3987
3988                         if bounds.is_empty() {
3989                             self.span_err(span,
3990                                           "each predicate in a `where` clause must have \
3991                                            at least one bound in it");
3992                         }
3993
3994                         where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
3995                                 ast::WhereBoundPredicate {
3996                                     span: span,
3997                                     bound_lifetimes: bound_lifetimes,
3998                                     bounded_ty: bounded_ty,
3999                                     bounds: bounds,
4000                         }));
4001
4002                         parsed_something = true;
4003                     } else if try!(self.eat(&token::Eq) ){
4004                         // let ty = try!(self.parse_ty_nopanic());
4005                         let hi = self.last_span.hi;
4006                         let span = mk_sp(lo, hi);
4007                         // where_clause.predicates.push(
4008                         //     ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
4009                         //         id: ast::DUMMY_NODE_ID,
4010                         //         span: span,
4011                         //         path: panic!("NYI"), //bounded_ty,
4012                         //         ty: ty,
4013                         // }));
4014                         // parsed_something = true;
4015                         // // FIXME(#18433)
4016                         self.span_err(span,
4017                                      "equality constraints are not yet supported \
4018                                      in where clauses (#20041)");
4019                     } else {
4020                         let last_span = self.last_span;
4021                         self.span_err(last_span,
4022                               "unexpected token in `where` clause");
4023                     }
4024                 }
4025             };
4026
4027             if !try!(self.eat(&token::Comma) ){
4028                 break
4029             }
4030         }
4031
4032         if !parsed_something {
4033             let last_span = self.last_span;
4034             self.span_err(last_span,
4035                           "a `where` clause must have at least one predicate \
4036                            in it");
4037         }
4038
4039         Ok(where_clause)
4040     }
4041
4042     fn parse_fn_args(&mut self, named_args: bool, allow_variadic: bool)
4043                      -> PResult<(Vec<Arg> , bool)> {
4044         let sp = self.span;
4045         let mut args: Vec<Option<Arg>> =
4046             try!(self.parse_unspanned_seq(
4047                 &token::OpenDelim(token::Paren),
4048                 &token::CloseDelim(token::Paren),
4049                 seq_sep_trailing_allowed(token::Comma),
4050                 |p| {
4051                     if p.token == token::DotDotDot {
4052                         try!(p.bump());
4053                         if allow_variadic {
4054                             if p.token != token::CloseDelim(token::Paren) {
4055                                 let span = p.span;
4056                                 return Err(p.span_fatal(span,
4057                                     "`...` must be last in argument list for variadic function"))
4058                             }
4059                         } else {
4060                             let span = p.span;
4061                             return Err(p.span_fatal(span,
4062                                          "only foreign functions are allowed to be variadic"))
4063                         }
4064                         Ok(None)
4065                     } else {
4066                         Ok(Some(try!(p.parse_arg_general(named_args))))
4067                     }
4068                 }
4069             ));
4070
4071         let variadic = match args.pop() {
4072             Some(None) => true,
4073             Some(x) => {
4074                 // Need to put back that last arg
4075                 args.push(x);
4076                 false
4077             }
4078             None => false
4079         };
4080
4081         if variadic && args.is_empty() {
4082             self.span_err(sp,
4083                           "variadic function must be declared with at least one named argument");
4084         }
4085
4086         let args = args.into_iter().map(|x| x.unwrap()).collect();
4087
4088         Ok((args, variadic))
4089     }
4090
4091     /// Parse the argument list and result type of a function declaration
4092     pub fn parse_fn_decl(&mut self, allow_variadic: bool) -> PResult<P<FnDecl>> {
4093
4094         let (args, variadic) = try!(self.parse_fn_args(true, allow_variadic));
4095         let ret_ty = try!(self.parse_ret_ty());
4096
4097         Ok(P(FnDecl {
4098             inputs: args,
4099             output: ret_ty,
4100             variadic: variadic
4101         }))
4102     }
4103
4104     fn is_self_ident(&mut self) -> bool {
4105         match self.token {
4106           token::Ident(id, token::Plain) => id.name == special_idents::self_.name,
4107           _ => false
4108         }
4109     }
4110
4111     fn expect_self_ident(&mut self) -> PResult<ast::Ident> {
4112         match self.token {
4113             token::Ident(id, token::Plain) if id.name == special_idents::self_.name => {
4114                 try!(self.bump());
4115                 Ok(id)
4116             },
4117             _ => {
4118                 let token_str = self.this_token_to_string();
4119                 return Err(self.fatal(&format!("expected `self`, found `{}`",
4120                                    token_str)))
4121             }
4122         }
4123     }
4124
4125     fn is_self_type_ident(&mut self) -> bool {
4126         match self.token {
4127           token::Ident(id, token::Plain) => id.name == special_idents::type_self.name,
4128           _ => false
4129         }
4130     }
4131
4132     fn expect_self_type_ident(&mut self) -> PResult<ast::Ident> {
4133         match self.token {
4134             token::Ident(id, token::Plain) if id.name == special_idents::type_self.name => {
4135                 try!(self.bump());
4136                 Ok(id)
4137             },
4138             _ => {
4139                 let token_str = self.this_token_to_string();
4140                 Err(self.fatal(&format!("expected `Self`, found `{}`",
4141                                    token_str)))
4142             }
4143         }
4144     }
4145
4146     /// Parse the argument list and result type of a function
4147     /// that may have a self type.
4148     fn parse_fn_decl_with_self<F>(&mut self,
4149                                   parse_arg_fn: F) -> PResult<(ExplicitSelf, P<FnDecl>)> where
4150         F: FnMut(&mut Parser) -> PResult<Arg>,
4151     {
4152         fn maybe_parse_borrowed_explicit_self(this: &mut Parser)
4153                                               -> PResult<ast::ExplicitSelf_> {
4154             // The following things are possible to see here:
4155             //
4156             //     fn(&mut self)
4157             //     fn(&mut self)
4158             //     fn(&'lt self)
4159             //     fn(&'lt mut self)
4160             //
4161             // We already know that the current token is `&`.
4162
4163             if this.look_ahead(1, |t| t.is_keyword(keywords::SelfValue)) {
4164                 try!(this.bump());
4165                 Ok(SelfRegion(None, MutImmutable, try!(this.expect_self_ident())))
4166             } else if this.look_ahead(1, |t| t.is_mutability()) &&
4167                       this.look_ahead(2, |t| t.is_keyword(keywords::SelfValue)) {
4168                 try!(this.bump());
4169                 let mutability = try!(this.parse_mutability());
4170                 Ok(SelfRegion(None, mutability, try!(this.expect_self_ident())))
4171             } else if this.look_ahead(1, |t| t.is_lifetime()) &&
4172                       this.look_ahead(2, |t| t.is_keyword(keywords::SelfValue)) {
4173                 try!(this.bump());
4174                 let lifetime = try!(this.parse_lifetime());
4175                 Ok(SelfRegion(Some(lifetime), MutImmutable, try!(this.expect_self_ident())))
4176             } else if this.look_ahead(1, |t| t.is_lifetime()) &&
4177                       this.look_ahead(2, |t| t.is_mutability()) &&
4178                       this.look_ahead(3, |t| t.is_keyword(keywords::SelfValue)) {
4179                 try!(this.bump());
4180                 let lifetime = try!(this.parse_lifetime());
4181                 let mutability = try!(this.parse_mutability());
4182                 Ok(SelfRegion(Some(lifetime), mutability, try!(this.expect_self_ident())))
4183             } else {
4184                 Ok(SelfStatic)
4185             }
4186         }
4187
4188         try!(self.expect(&token::OpenDelim(token::Paren)));
4189
4190         // A bit of complexity and lookahead is needed here in order to be
4191         // backwards compatible.
4192         let lo = self.span.lo;
4193         let mut self_ident_lo = self.span.lo;
4194         let mut self_ident_hi = self.span.hi;
4195
4196         let mut mutbl_self = MutImmutable;
4197         let explicit_self = match self.token {
4198             token::BinOp(token::And) => {
4199                 let eself = try!(maybe_parse_borrowed_explicit_self(self));
4200                 self_ident_lo = self.last_span.lo;
4201                 self_ident_hi = self.last_span.hi;
4202                 eself
4203             }
4204             token::BinOp(token::Star) => {
4205                 // Possibly "*self" or "*mut self" -- not supported. Try to avoid
4206                 // emitting cryptic "unexpected token" errors.
4207                 try!(self.bump());
4208                 let _mutability = if self.token.is_mutability() {
4209                     try!(self.parse_mutability())
4210                 } else {
4211                     MutImmutable
4212                 };
4213                 if self.is_self_ident() {
4214                     let span = self.span;
4215                     self.span_err(span, "cannot pass self by raw pointer");
4216                     try!(self.bump());
4217                 }
4218                 // error case, making bogus self ident:
4219                 SelfValue(special_idents::self_)
4220             }
4221             token::Ident(..) => {
4222                 if self.is_self_ident() {
4223                     let self_ident = try!(self.expect_self_ident());
4224
4225                     // Determine whether this is the fully explicit form, `self:
4226                     // TYPE`.
4227                     if try!(self.eat(&token::Colon) ){
4228                         SelfExplicit(try!(self.parse_ty_sum()), self_ident)
4229                     } else {
4230                         SelfValue(self_ident)
4231                     }
4232                 } else if self.token.is_mutability() &&
4233                         self.look_ahead(1, |t| t.is_keyword(keywords::SelfValue)) {
4234                     mutbl_self = try!(self.parse_mutability());
4235                     let self_ident = try!(self.expect_self_ident());
4236
4237                     // Determine whether this is the fully explicit form,
4238                     // `self: TYPE`.
4239                     if try!(self.eat(&token::Colon) ){
4240                         SelfExplicit(try!(self.parse_ty_sum()), self_ident)
4241                     } else {
4242                         SelfValue(self_ident)
4243                     }
4244                 } else {
4245                     SelfStatic
4246                 }
4247             }
4248             _ => SelfStatic,
4249         };
4250
4251         let explicit_self_sp = mk_sp(self_ident_lo, self_ident_hi);
4252
4253         // shared fall-through for the three cases below. borrowing prevents simply
4254         // writing this as a closure
4255         macro_rules! parse_remaining_arguments {
4256             ($self_id:ident) =>
4257             {
4258             // If we parsed a self type, expect a comma before the argument list.
4259             match self.token {
4260                 token::Comma => {
4261                     try!(self.bump());
4262                     let sep = seq_sep_trailing_allowed(token::Comma);
4263                     let mut fn_inputs = try!(self.parse_seq_to_before_end(
4264                         &token::CloseDelim(token::Paren),
4265                         sep,
4266                         parse_arg_fn
4267                     ));
4268                     fn_inputs.insert(0, Arg::new_self(explicit_self_sp, mutbl_self, $self_id));
4269                     fn_inputs
4270                 }
4271                 token::CloseDelim(token::Paren) => {
4272                     vec!(Arg::new_self(explicit_self_sp, mutbl_self, $self_id))
4273                 }
4274                 _ => {
4275                     let token_str = self.this_token_to_string();
4276                     return Err(self.fatal(&format!("expected `,` or `)`, found `{}`",
4277                                        token_str)))
4278                 }
4279             }
4280             }
4281         }
4282
4283         let fn_inputs = match explicit_self {
4284             SelfStatic =>  {
4285                 let sep = seq_sep_trailing_allowed(token::Comma);
4286                 try!(self.parse_seq_to_before_end(&token::CloseDelim(token::Paren),
4287                                                   sep, parse_arg_fn))
4288             }
4289             SelfValue(id) => parse_remaining_arguments!(id),
4290             SelfRegion(_,_,id) => parse_remaining_arguments!(id),
4291             SelfExplicit(_,id) => parse_remaining_arguments!(id),
4292         };
4293
4294
4295         try!(self.expect(&token::CloseDelim(token::Paren)));
4296
4297         let hi = self.span.hi;
4298
4299         let ret_ty = try!(self.parse_ret_ty());
4300
4301         let fn_decl = P(FnDecl {
4302             inputs: fn_inputs,
4303             output: ret_ty,
4304             variadic: false
4305         });
4306
4307         Ok((spanned(lo, hi, explicit_self), fn_decl))
4308     }
4309
4310     // parse the |arg, arg| header on a lambda
4311     fn parse_fn_block_decl(&mut self) -> PResult<P<FnDecl>> {
4312         let inputs_captures = {
4313             if try!(self.eat(&token::OrOr) ){
4314                 Vec::new()
4315             } else {
4316                 try!(self.expect(&token::BinOp(token::Or)));
4317                 try!(self.parse_obsolete_closure_kind());
4318                 let args = try!(self.parse_seq_to_before_end(
4319                     &token::BinOp(token::Or),
4320                     seq_sep_trailing_allowed(token::Comma),
4321                     |p| p.parse_fn_block_arg()
4322                 ));
4323                 try!(self.bump());
4324                 args
4325             }
4326         };
4327         let output = try!(self.parse_ret_ty());
4328
4329         Ok(P(FnDecl {
4330             inputs: inputs_captures,
4331             output: output,
4332             variadic: false
4333         }))
4334     }
4335
4336     /// Parse the name and optional generic types of a function header.
4337     fn parse_fn_header(&mut self) -> PResult<(Ident, ast::Generics)> {
4338         let id = try!(self.parse_ident());
4339         let generics = try!(self.parse_generics());
4340         Ok((id, generics))
4341     }
4342
4343     fn mk_item(&mut self, lo: BytePos, hi: BytePos, ident: Ident,
4344                node: Item_, vis: Visibility,
4345                attrs: Vec<Attribute>) -> P<Item> {
4346         P(Item {
4347             ident: ident,
4348             attrs: attrs,
4349             id: ast::DUMMY_NODE_ID,
4350             node: node,
4351             vis: vis,
4352             span: mk_sp(lo, hi)
4353         })
4354     }
4355
4356     /// Parse an item-position function declaration.
4357     fn parse_item_fn(&mut self,
4358                      unsafety: Unsafety,
4359                      constness: Constness,
4360                      abi: abi::Abi)
4361                      -> PResult<ItemInfo> {
4362         let (ident, mut generics) = try!(self.parse_fn_header());
4363         let decl = try!(self.parse_fn_decl(false));
4364         generics.where_clause = try!(self.parse_where_clause());
4365         let (inner_attrs, body) = try!(self.parse_inner_attrs_and_block());
4366         Ok((ident, ItemFn(decl, unsafety, constness, abi, generics, body), Some(inner_attrs)))
4367     }
4368
4369     /// true if we are looking at `const ID`, false for things like `const fn` etc
4370     pub fn is_const_item(&mut self) -> bool {
4371         self.token.is_keyword(keywords::Const) &&
4372             !self.look_ahead(1, |t| t.is_keyword(keywords::Fn))
4373     }
4374
4375     /// parses all the "front matter" for a `fn` declaration, up to
4376     /// and including the `fn` keyword:
4377     ///
4378     /// - `const fn`
4379     /// - `unsafe fn`
4380     /// - `extern fn`
4381     /// - etc
4382     pub fn parse_fn_front_matter(&mut self) -> PResult<(ast::Constness, ast::Unsafety, abi::Abi)> {
4383         let is_const_fn = try!(self.eat_keyword(keywords::Const));
4384         let (constness, unsafety, abi) = if is_const_fn {
4385             (Constness::Const, Unsafety::Normal, abi::Rust)
4386         } else {
4387             let unsafety = try!(self.parse_unsafety());
4388             let abi = if try!(self.eat_keyword(keywords::Extern)) {
4389                 try!(self.parse_opt_abi()).unwrap_or(abi::C)
4390             } else {
4391                 abi::Rust
4392             };
4393             (Constness::NotConst, unsafety, abi)
4394         };
4395         try!(self.expect_keyword(keywords::Fn));
4396         Ok((constness, unsafety, abi))
4397     }
4398
4399     /// Parse an impl item.
4400     pub fn parse_impl_item(&mut self) -> PResult<P<ImplItem>> {
4401         maybe_whole!(no_clone self, NtImplItem);
4402
4403         let mut attrs = self.parse_outer_attributes();
4404         let lo = self.span.lo;
4405         let vis = try!(self.parse_visibility());
4406         let (name, node) = if try!(self.eat_keyword(keywords::Type)) {
4407             let name = try!(self.parse_ident());
4408             try!(self.expect(&token::Eq));
4409             let typ = try!(self.parse_ty_sum());
4410             try!(self.expect(&token::Semi));
4411             (name, TypeImplItem(typ))
4412         } else if self.is_const_item() {
4413             try!(self.expect_keyword(keywords::Const));
4414             let name = try!(self.parse_ident());
4415             try!(self.expect(&token::Colon));
4416             let typ = try!(self.parse_ty_sum());
4417             try!(self.expect(&token::Eq));
4418             let expr = try!(self.parse_expr_nopanic());
4419             try!(self.commit_expr_expecting(&expr, token::Semi));
4420             (name, ConstImplItem(typ, expr))
4421         } else {
4422             let (name, inner_attrs, node) = try!(self.parse_impl_method(vis));
4423             attrs.extend(inner_attrs);
4424             (name, node)
4425         };
4426
4427         Ok(P(ImplItem {
4428             id: ast::DUMMY_NODE_ID,
4429             span: mk_sp(lo, self.last_span.hi),
4430             ident: name,
4431             vis: vis,
4432             attrs: attrs,
4433             node: node
4434         }))
4435     }
4436
4437     fn complain_if_pub_macro(&mut self, visa: Visibility, span: Span) {
4438         match visa {
4439             Public => {
4440                 self.span_err(span, "can't qualify macro invocation with `pub`");
4441                 self.fileline_help(span, "try adjusting the macro to put `pub` inside \
4442                                       the invocation");
4443             }
4444             Inherited => (),
4445         }
4446     }
4447
4448     /// Parse a method or a macro invocation in a trait impl.
4449     fn parse_impl_method(&mut self, vis: Visibility)
4450                          -> PResult<(Ident, Vec<ast::Attribute>, ast::ImplItem_)> {
4451         // code copied from parse_macro_use_or_failure... abstraction!
4452         if !self.token.is_any_keyword()
4453             && self.look_ahead(1, |t| *t == token::Not)
4454             && (self.look_ahead(2, |t| *t == token::OpenDelim(token::Paren))
4455                 || self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))) {
4456             // method macro.
4457
4458             let last_span = self.last_span;
4459             self.complain_if_pub_macro(vis, last_span);
4460
4461             let pth = try!(self.parse_path(NoTypesAllowed));
4462             try!(self.expect(&token::Not));
4463
4464             // eat a matched-delimiter token tree:
4465             let delim = try!(self.expect_open_delim());
4466             let tts = try!(self.parse_seq_to_end(&token::CloseDelim(delim),
4467                                             seq_sep_none(),
4468                                             |p| p.parse_token_tree()));
4469             let m_ = Mac_ { path: pth, tts: tts, ctxt: EMPTY_CTXT };
4470             let m: ast::Mac = codemap::Spanned { node: m_,
4471                                                 span: mk_sp(self.span.lo,
4472                                                             self.span.hi) };
4473             if delim != token::Brace {
4474                 try!(self.expect(&token::Semi))
4475             }
4476             Ok((token::special_idents::invalid, vec![], ast::MacImplItem(m)))
4477         } else {
4478             let (constness, unsafety, abi) = try!(self.parse_fn_front_matter());
4479             let ident = try!(self.parse_ident());
4480             let mut generics = try!(self.parse_generics());
4481             let (explicit_self, decl) = try!(self.parse_fn_decl_with_self(|p| {
4482                     p.parse_arg()
4483                 }));
4484             generics.where_clause = try!(self.parse_where_clause());
4485             let (inner_attrs, body) = try!(self.parse_inner_attrs_and_block());
4486             Ok((ident, inner_attrs, MethodImplItem(ast::MethodSig {
4487                 generics: generics,
4488                 abi: abi,
4489                 explicit_self: explicit_self,
4490                 unsafety: unsafety,
4491                 constness: constness,
4492                 decl: decl
4493              }, body)))
4494         }
4495     }
4496
4497     /// Parse trait Foo { ... }
4498     fn parse_item_trait(&mut self, unsafety: Unsafety) -> PResult<ItemInfo> {
4499
4500         let ident = try!(self.parse_ident());
4501         let mut tps = try!(self.parse_generics());
4502
4503         // Parse supertrait bounds.
4504         let bounds = try!(self.parse_colon_then_ty_param_bounds(BoundParsingMode::Bare));
4505
4506         tps.where_clause = try!(self.parse_where_clause());
4507
4508         let meths = try!(self.parse_trait_items());
4509         Ok((ident, ItemTrait(unsafety, tps, bounds, meths), None))
4510     }
4511
4512     /// Parses items implementations variants
4513     ///    impl<T> Foo { ... }
4514     ///    impl<T> ToString for &'static T { ... }
4515     ///    impl Send for .. {}
4516     fn parse_item_impl(&mut self, unsafety: ast::Unsafety) -> PResult<ItemInfo> {
4517         let impl_span = self.span;
4518
4519         // First, parse type parameters if necessary.
4520         let mut generics = try!(self.parse_generics());
4521
4522         // Special case: if the next identifier that follows is '(', don't
4523         // allow this to be parsed as a trait.
4524         let could_be_trait = self.token != token::OpenDelim(token::Paren);
4525
4526         let neg_span = self.span;
4527         let polarity = if try!(self.eat(&token::Not) ){
4528             ast::ImplPolarity::Negative
4529         } else {
4530             ast::ImplPolarity::Positive
4531         };
4532
4533         // Parse the trait.
4534         let mut ty = try!(self.parse_ty_sum());
4535
4536         // Parse traits, if necessary.
4537         let opt_trait = if could_be_trait && try!(self.eat_keyword(keywords::For) ){
4538             // New-style trait. Reinterpret the type as a trait.
4539             match ty.node {
4540                 TyPath(None, ref path) => {
4541                     Some(TraitRef {
4542                         path: (*path).clone(),
4543                         ref_id: ty.id,
4544                     })
4545                 }
4546                 _ => {
4547                     self.span_err(ty.span, "not a trait");
4548                     None
4549                 }
4550             }
4551         } else {
4552             match polarity {
4553                 ast::ImplPolarity::Negative => {
4554                     // This is a negated type implementation
4555                     // `impl !MyType {}`, which is not allowed.
4556                     self.span_err(neg_span, "inherent implementation can't be negated");
4557                 },
4558                 _ => {}
4559             }
4560             None
4561         };
4562
4563         if opt_trait.is_some() && try!(self.eat(&token::DotDot) ){
4564             if generics.is_parameterized() {
4565                 self.span_err(impl_span, "default trait implementations are not \
4566                                           allowed to have generics");
4567             }
4568
4569             try!(self.expect(&token::OpenDelim(token::Brace)));
4570             try!(self.expect(&token::CloseDelim(token::Brace)));
4571             Ok((ast_util::impl_pretty_name(&opt_trait, None),
4572              ItemDefaultImpl(unsafety, opt_trait.unwrap()), None))
4573         } else {
4574             if opt_trait.is_some() {
4575                 ty = try!(self.parse_ty_sum());
4576             }
4577             generics.where_clause = try!(self.parse_where_clause());
4578
4579             try!(self.expect(&token::OpenDelim(token::Brace)));
4580             let attrs = self.parse_inner_attributes();
4581
4582             let mut impl_items = vec![];
4583             while !try!(self.eat(&token::CloseDelim(token::Brace))) {
4584                 impl_items.push(try!(self.parse_impl_item()));
4585             }
4586
4587             Ok((ast_util::impl_pretty_name(&opt_trait, Some(&*ty)),
4588              ItemImpl(unsafety, polarity, generics, opt_trait, ty, impl_items),
4589              Some(attrs)))
4590         }
4591     }
4592
4593     /// Parse a::B<String,i32>
4594     fn parse_trait_ref(&mut self) -> PResult<TraitRef> {
4595         Ok(ast::TraitRef {
4596             path: try!(self.parse_path(LifetimeAndTypesWithoutColons)),
4597             ref_id: ast::DUMMY_NODE_ID,
4598         })
4599     }
4600
4601     fn parse_late_bound_lifetime_defs(&mut self) -> PResult<Vec<ast::LifetimeDef>> {
4602         if try!(self.eat_keyword(keywords::For) ){
4603             try!(self.expect(&token::Lt));
4604             let lifetime_defs = try!(self.parse_lifetime_defs());
4605             try!(self.expect_gt());
4606             Ok(lifetime_defs)
4607         } else {
4608             Ok(Vec::new())
4609         }
4610     }
4611
4612     /// Parse for<'l> a::B<String,i32>
4613     fn parse_poly_trait_ref(&mut self) -> PResult<PolyTraitRef> {
4614         let lo = self.span.lo;
4615         let lifetime_defs = try!(self.parse_late_bound_lifetime_defs());
4616
4617         Ok(ast::PolyTraitRef {
4618             bound_lifetimes: lifetime_defs,
4619             trait_ref: try!(self.parse_trait_ref()),
4620             span: mk_sp(lo, self.last_span.hi),
4621         })
4622     }
4623
4624     /// Parse struct Foo { ... }
4625     fn parse_item_struct(&mut self) -> PResult<ItemInfo> {
4626         let class_name = try!(self.parse_ident());
4627         let mut generics = try!(self.parse_generics());
4628
4629         // There is a special case worth noting here, as reported in issue #17904.
4630         // If we are parsing a tuple struct it is the case that the where clause
4631         // should follow the field list. Like so:
4632         //
4633         // struct Foo<T>(T) where T: Copy;
4634         //
4635         // If we are parsing a normal record-style struct it is the case
4636         // that the where clause comes before the body, and after the generics.
4637         // So if we look ahead and see a brace or a where-clause we begin
4638         // parsing a record style struct.
4639         //
4640         // Otherwise if we look ahead and see a paren we parse a tuple-style
4641         // struct.
4642
4643         let (fields, ctor_id) = if self.token.is_keyword(keywords::Where) {
4644             generics.where_clause = try!(self.parse_where_clause());
4645             if try!(self.eat(&token::Semi)) {
4646                 // If we see a: `struct Foo<T> where T: Copy;` style decl.
4647                 (Vec::new(), Some(ast::DUMMY_NODE_ID))
4648             } else {
4649                 // If we see: `struct Foo<T> where T: Copy { ... }`
4650                 (try!(self.parse_record_struct_body()), None)
4651             }
4652         // No `where` so: `struct Foo<T>;`
4653         } else if try!(self.eat(&token::Semi) ){
4654             (Vec::new(), Some(ast::DUMMY_NODE_ID))
4655         // Record-style struct definition
4656         } else if self.token == token::OpenDelim(token::Brace) {
4657             let fields = try!(self.parse_record_struct_body());
4658             (fields, None)
4659         // Tuple-style struct definition with optional where-clause.
4660         } else if self.token == token::OpenDelim(token::Paren) {
4661             let fields = try!(self.parse_tuple_struct_body(class_name, &mut generics));
4662             (fields, Some(ast::DUMMY_NODE_ID))
4663         } else {
4664             let token_str = self.this_token_to_string();
4665             return Err(self.fatal(&format!("expected `where`, `{{`, `(`, or `;` after struct \
4666                                             name, found `{}`", token_str)))
4667         };
4668
4669         Ok((class_name,
4670          ItemStruct(P(ast::StructDef {
4671              fields: fields,
4672              ctor_id: ctor_id,
4673          }), generics),
4674          None))
4675     }
4676
4677     pub fn parse_record_struct_body(&mut self) -> PResult<Vec<StructField>> {
4678         let mut fields = Vec::new();
4679         if try!(self.eat(&token::OpenDelim(token::Brace)) ){
4680             while self.token != token::CloseDelim(token::Brace) {
4681                 fields.push(try!(self.parse_struct_decl_field(true)));
4682             }
4683
4684             try!(self.bump());
4685         } else {
4686             let token_str = self.this_token_to_string();
4687             return Err(self.fatal(&format!("expected `where`, or `{{` after struct \
4688                                 name, found `{}`",
4689                                 token_str)));
4690         }
4691
4692         Ok(fields)
4693     }
4694
4695     pub fn parse_tuple_struct_body(&mut self,
4696                                    class_name: ast::Ident,
4697                                    generics: &mut ast::Generics)
4698                                    -> PResult<Vec<StructField>> {
4699         // This is the case where we find `struct Foo<T>(T) where T: Copy;`
4700         // Unit like structs are handled in parse_item_struct function
4701         let fields = try!(self.parse_unspanned_seq(
4702             &token::OpenDelim(token::Paren),
4703             &token::CloseDelim(token::Paren),
4704             seq_sep_trailing_allowed(token::Comma),
4705             |p| {
4706                 let attrs = p.parse_outer_attributes();
4707                 let lo = p.span.lo;
4708                 let struct_field_ = ast::StructField_ {
4709                     kind: UnnamedField(try!(p.parse_visibility())),
4710                     id: ast::DUMMY_NODE_ID,
4711                     ty: try!(p.parse_ty_sum()),
4712                     attrs: attrs,
4713                 };
4714                 Ok(spanned(lo, p.span.hi, struct_field_))
4715             }));
4716
4717         if fields.is_empty() {
4718             return Err(self.fatal(&format!("unit-like struct definition should be \
4719                                             written as `struct {};`",
4720                                            class_name)));
4721         }
4722
4723         generics.where_clause = try!(self.parse_where_clause());
4724         try!(self.expect(&token::Semi));
4725         Ok(fields)
4726     }
4727
4728     /// Parse a structure field declaration
4729     pub fn parse_single_struct_field(&mut self,
4730                                      vis: Visibility,
4731                                      attrs: Vec<Attribute> )
4732                                      -> PResult<StructField> {
4733         let a_var = try!(self.parse_name_and_ty(vis, attrs));
4734         match self.token {
4735             token::Comma => {
4736                 try!(self.bump());
4737             }
4738             token::CloseDelim(token::Brace) => {}
4739             _ => {
4740                 let span = self.span;
4741                 let token_str = self.this_token_to_string();
4742                 return Err(self.span_fatal_help(span,
4743                                      &format!("expected `,`, or `}}`, found `{}`",
4744                                              token_str),
4745                                      "struct fields should be separated by commas"))
4746             }
4747         }
4748         Ok(a_var)
4749     }
4750
4751     /// Parse an element of a struct definition
4752     fn parse_struct_decl_field(&mut self, allow_pub: bool) -> PResult<StructField> {
4753
4754         let attrs = self.parse_outer_attributes();
4755
4756         if try!(self.eat_keyword(keywords::Pub) ){
4757             if !allow_pub {
4758                 let span = self.last_span;
4759                 self.span_err(span, "`pub` is not allowed here");
4760             }
4761             return self.parse_single_struct_field(Public, attrs);
4762         }
4763
4764         return self.parse_single_struct_field(Inherited, attrs);
4765     }
4766
4767     /// Parse visibility: PUB or nothing
4768     fn parse_visibility(&mut self) -> PResult<Visibility> {
4769         if try!(self.eat_keyword(keywords::Pub)) { Ok(Public) }
4770         else { Ok(Inherited) }
4771     }
4772
4773     /// Given a termination token, parse all of the items in a module
4774     fn parse_mod_items(&mut self, term: &token::Token, inner_lo: BytePos) -> PResult<Mod> {
4775         let mut items = vec![];
4776         while let Some(item) = try!(self.parse_item_nopanic()) {
4777             items.push(item);
4778         }
4779
4780         if !try!(self.eat(term)) {
4781             let token_str = self.this_token_to_string();
4782             return Err(self.fatal(&format!("expected item, found `{}`", token_str)));
4783         }
4784
4785         let hi = if self.span == codemap::DUMMY_SP {
4786             inner_lo
4787         } else {
4788             self.last_span.hi
4789         };
4790
4791         Ok(ast::Mod {
4792             inner: mk_sp(inner_lo, hi),
4793             items: items
4794         })
4795     }
4796
4797     fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<ItemInfo> {
4798         let id = try!(self.parse_ident());
4799         try!(self.expect(&token::Colon));
4800         let ty = try!(self.parse_ty_sum());
4801         try!(self.expect(&token::Eq));
4802         let e = try!(self.parse_expr_nopanic());
4803         try!(self.commit_expr_expecting(&*e, token::Semi));
4804         let item = match m {
4805             Some(m) => ItemStatic(ty, m, e),
4806             None => ItemConst(ty, e),
4807         };
4808         Ok((id, item, None))
4809     }
4810
4811     /// Parse a `mod <foo> { ... }` or `mod <foo>;` item
4812     fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<ItemInfo> {
4813         let id_span = self.span;
4814         let id = try!(self.parse_ident());
4815         if self.check(&token::Semi) {
4816             try!(self.bump());
4817             // This mod is in an external file. Let's go get it!
4818             let (m, attrs) = try!(self.eval_src_mod(id, outer_attrs, id_span));
4819             Ok((id, m, Some(attrs)))
4820         } else {
4821             self.push_mod_path(id, outer_attrs);
4822             try!(self.expect(&token::OpenDelim(token::Brace)));
4823             let mod_inner_lo = self.span.lo;
4824             let old_owns_directory = self.owns_directory;
4825             self.owns_directory = true;
4826             let attrs = self.parse_inner_attributes();
4827             let m = try!(self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo));
4828             self.owns_directory = old_owns_directory;
4829             self.pop_mod_path();
4830             Ok((id, ItemMod(m), Some(attrs)))
4831         }
4832     }
4833
4834     fn push_mod_path(&mut self, id: Ident, attrs: &[Attribute]) {
4835         let default_path = self.id_to_interned_str(id);
4836         let file_path = match ::attr::first_attr_value_str_by_name(attrs, "path") {
4837             Some(d) => d,
4838             None => default_path,
4839         };
4840         self.mod_path_stack.push(file_path)
4841     }
4842
4843     fn pop_mod_path(&mut self) {
4844         self.mod_path_stack.pop().unwrap();
4845     }
4846
4847     pub fn submod_path_from_attr(attrs: &[ast::Attribute], dir_path: &Path) -> Option<PathBuf> {
4848         ::attr::first_attr_value_str_by_name(attrs, "path").map(|d| dir_path.join(&*d))
4849     }
4850
4851     /// Returns either a path to a module, or .
4852     pub fn default_submod_path(id: ast::Ident, dir_path: &Path, codemap: &CodeMap) -> ModulePath
4853     {
4854         let mod_name = id.to_string();
4855         let default_path_str = format!("{}.rs", mod_name);
4856         let secondary_path_str = format!("{}/mod.rs", mod_name);
4857         let default_path = dir_path.join(&default_path_str);
4858         let secondary_path = dir_path.join(&secondary_path_str);
4859         let default_exists = codemap.file_exists(&default_path);
4860         let secondary_exists = codemap.file_exists(&secondary_path);
4861
4862         let result = match (default_exists, secondary_exists) {
4863             (true, false) => Ok(ModulePathSuccess { path: default_path, owns_directory: false }),
4864             (false, true) => Ok(ModulePathSuccess { path: secondary_path, owns_directory: true }),
4865             (false, false) => Err(ModulePathError {
4866                 err_msg: format!("file not found for module `{}`", mod_name),
4867                 help_msg: format!("name the file either {} or {} inside the directory {:?}",
4868                                   default_path_str,
4869                                   secondary_path_str,
4870                                   dir_path.display()),
4871             }),
4872             (true, true) => Err(ModulePathError {
4873                 err_msg: format!("file for module `{}` found at both {} and {}",
4874                                  mod_name,
4875                                  default_path_str,
4876                                  secondary_path_str),
4877                 help_msg: "delete or rename one of them to remove the ambiguity".to_owned(),
4878             }),
4879         };
4880
4881         ModulePath {
4882             name: mod_name,
4883             path_exists: default_exists || secondary_exists,
4884             result: result,
4885         }
4886     }
4887
4888     fn submod_path(&mut self,
4889                    id: ast::Ident,
4890                    outer_attrs: &[ast::Attribute],
4891                    id_sp: Span) -> PResult<ModulePathSuccess> {
4892         let mut prefix = PathBuf::from(&self.sess.codemap().span_to_filename(self.span));
4893         prefix.pop();
4894         let mut dir_path = prefix;
4895         for part in &self.mod_path_stack {
4896             dir_path.push(&**part);
4897         }
4898
4899         if let Some(p) = Parser::submod_path_from_attr(outer_attrs, &dir_path) {
4900             return Ok(ModulePathSuccess { path: p, owns_directory: true });
4901         }
4902
4903         let paths = Parser::default_submod_path(id, &dir_path, self.sess.codemap());
4904
4905         if !self.owns_directory {
4906             self.span_err(id_sp, "cannot declare a new module at this location");
4907             let this_module = match self.mod_path_stack.last() {
4908                 Some(name) => name.to_string(),
4909                 None => self.root_module_name.as_ref().unwrap().clone(),
4910             };
4911             self.span_note(id_sp,
4912                            &format!("maybe move this module `{0}` to its own directory \
4913                                      via `{0}/mod.rs`",
4914                                     this_module));
4915             if paths.path_exists {
4916                 self.span_note(id_sp,
4917                                &format!("... or maybe `use` the module `{}` instead \
4918                                          of possibly redeclaring it",
4919                                         paths.name));
4920             }
4921             self.abort_if_errors();
4922         }
4923
4924         match paths.result {
4925             Ok(succ) => Ok(succ),
4926             Err(err) => Err(self.span_fatal_help(id_sp, &err.err_msg, &err.help_msg)),
4927         }
4928     }
4929
4930     /// Read a module from a source file.
4931     fn eval_src_mod(&mut self,
4932                     id: ast::Ident,
4933                     outer_attrs: &[ast::Attribute],
4934                     id_sp: Span)
4935                     -> PResult<(ast::Item_, Vec<ast::Attribute> )> {
4936         let ModulePathSuccess { path, owns_directory } = try!(self.submod_path(id,
4937                                                                                outer_attrs,
4938                                                                                id_sp));
4939
4940         self.eval_src_mod_from_path(path,
4941                                     owns_directory,
4942                                     id.to_string(),
4943                                     id_sp)
4944     }
4945
4946     fn eval_src_mod_from_path(&mut self,
4947                               path: PathBuf,
4948                               owns_directory: bool,
4949                               name: String,
4950                               id_sp: Span) -> PResult<(ast::Item_, Vec<ast::Attribute> )> {
4951         let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
4952         match included_mod_stack.iter().position(|p| *p == path) {
4953             Some(i) => {
4954                 let mut err = String::from("circular modules: ");
4955                 let len = included_mod_stack.len();
4956                 for p in &included_mod_stack[i.. len] {
4957                     err.push_str(&p.to_string_lossy());
4958                     err.push_str(" -> ");
4959                 }
4960                 err.push_str(&path.to_string_lossy());
4961                 return Err(self.span_fatal(id_sp, &err[..]));
4962             }
4963             None => ()
4964         }
4965         included_mod_stack.push(path.clone());
4966         drop(included_mod_stack);
4967
4968         let mut p0 = new_sub_parser_from_file(self.sess,
4969                                               self.cfg.clone(),
4970                                               &path,
4971                                               owns_directory,
4972                                               Some(name),
4973                                               id_sp);
4974         let mod_inner_lo = p0.span.lo;
4975         let mod_attrs = p0.parse_inner_attributes();
4976         let m0 = try!(p0.parse_mod_items(&token::Eof, mod_inner_lo));
4977         self.sess.included_mod_stack.borrow_mut().pop();
4978         Ok((ast::ItemMod(m0), mod_attrs))
4979     }
4980
4981     /// Parse a function declaration from a foreign module
4982     fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: BytePos,
4983                              attrs: Vec<Attribute>) -> PResult<P<ForeignItem>> {
4984         try!(self.expect_keyword(keywords::Fn));
4985
4986         let (ident, mut generics) = try!(self.parse_fn_header());
4987         let decl = try!(self.parse_fn_decl(true));
4988         generics.where_clause = try!(self.parse_where_clause());
4989         let hi = self.span.hi;
4990         try!(self.expect(&token::Semi));
4991         Ok(P(ast::ForeignItem {
4992             ident: ident,
4993             attrs: attrs,
4994             node: ForeignItemFn(decl, generics),
4995             id: ast::DUMMY_NODE_ID,
4996             span: mk_sp(lo, hi),
4997             vis: vis
4998         }))
4999     }
5000
5001     /// Parse a static item from a foreign module
5002     fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: BytePos,
5003                                  attrs: Vec<Attribute>) -> PResult<P<ForeignItem>> {
5004         try!(self.expect_keyword(keywords::Static));
5005         let mutbl = try!(self.eat_keyword(keywords::Mut));
5006
5007         let ident = try!(self.parse_ident());
5008         try!(self.expect(&token::Colon));
5009         let ty = try!(self.parse_ty_sum());
5010         let hi = self.span.hi;
5011         try!(self.expect(&token::Semi));
5012         Ok(P(ForeignItem {
5013             ident: ident,
5014             attrs: attrs,
5015             node: ForeignItemStatic(ty, mutbl),
5016             id: ast::DUMMY_NODE_ID,
5017             span: mk_sp(lo, hi),
5018             vis: vis
5019         }))
5020     }
5021
5022     /// Parse extern crate links
5023     ///
5024     /// # Examples
5025     ///
5026     /// extern crate foo;
5027     /// extern crate bar as foo;
5028     fn parse_item_extern_crate(&mut self,
5029                                lo: BytePos,
5030                                visibility: Visibility,
5031                                attrs: Vec<Attribute>)
5032                                 -> PResult<P<Item>> {
5033
5034         let crate_name = try!(self.parse_ident());
5035         let (maybe_path, ident) = if let Some(ident) = try!(self.parse_rename()) {
5036             (Some(crate_name.name), ident)
5037         } else {
5038             (None, crate_name)
5039         };
5040         try!(self.expect(&token::Semi));
5041
5042         let last_span = self.last_span;
5043
5044         if visibility == ast::Public {
5045             self.span_warn(mk_sp(lo, last_span.hi),
5046                            "`pub extern crate` does not work as expected and should not be used. \
5047                             Likely to become an error. Prefer `extern crate` and `pub use`.");
5048         }
5049
5050         Ok(self.mk_item(lo,
5051                         last_span.hi,
5052                         ident,
5053                         ItemExternCrate(maybe_path),
5054                         visibility,
5055                         attrs))
5056     }
5057
5058     /// Parse `extern` for foreign ABIs
5059     /// modules.
5060     ///
5061     /// `extern` is expected to have been
5062     /// consumed before calling this method
5063     ///
5064     /// # Examples:
5065     ///
5066     /// extern "C" {}
5067     /// extern {}
5068     fn parse_item_foreign_mod(&mut self,
5069                               lo: BytePos,
5070                               opt_abi: Option<abi::Abi>,
5071                               visibility: Visibility,
5072                               mut attrs: Vec<Attribute>)
5073                               -> PResult<P<Item>> {
5074         try!(self.expect(&token::OpenDelim(token::Brace)));
5075
5076         let abi = opt_abi.unwrap_or(abi::C);
5077
5078         attrs.extend(self.parse_inner_attributes());
5079
5080         let mut foreign_items = vec![];
5081         while let Some(item) = try!(self.parse_foreign_item()) {
5082             foreign_items.push(item);
5083         }
5084         try!(self.expect(&token::CloseDelim(token::Brace)));
5085
5086         let last_span = self.last_span;
5087         let m = ast::ForeignMod {
5088             abi: abi,
5089             items: foreign_items
5090         };
5091         Ok(self.mk_item(lo,
5092                      last_span.hi,
5093                      special_idents::invalid,
5094                      ItemForeignMod(m),
5095                      visibility,
5096                      attrs))
5097     }
5098
5099     /// Parse type Foo = Bar;
5100     fn parse_item_type(&mut self) -> PResult<ItemInfo> {
5101         let ident = try!(self.parse_ident());
5102         let mut tps = try!(self.parse_generics());
5103         tps.where_clause = try!(self.parse_where_clause());
5104         try!(self.expect(&token::Eq));
5105         let ty = try!(self.parse_ty_sum());
5106         try!(self.expect(&token::Semi));
5107         Ok((ident, ItemTy(ty, tps), None))
5108     }
5109
5110     /// Parse a structure-like enum variant definition
5111     /// this should probably be renamed or refactored...
5112     fn parse_struct_def(&mut self) -> PResult<P<StructDef>> {
5113         let mut fields: Vec<StructField> = Vec::new();
5114         while self.token != token::CloseDelim(token::Brace) {
5115             fields.push(try!(self.parse_struct_decl_field(false)));
5116         }
5117         try!(self.bump());
5118
5119         Ok(P(StructDef {
5120             fields: fields,
5121             ctor_id: None,
5122         }))
5123     }
5124
5125     /// Parse the part of an "enum" decl following the '{'
5126     fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<EnumDef> {
5127         let mut variants = Vec::new();
5128         let mut all_nullary = true;
5129         let mut any_disr = None;
5130         while self.token != token::CloseDelim(token::Brace) {
5131             let variant_attrs = self.parse_outer_attributes();
5132             let vlo = self.span.lo;
5133
5134             let kind;
5135             let mut args = Vec::new();
5136             let mut disr_expr = None;
5137             let ident = try!(self.parse_ident());
5138             if try!(self.eat(&token::OpenDelim(token::Brace)) ){
5139                 // Parse a struct variant.
5140                 all_nullary = false;
5141                 let start_span = self.span;
5142                 let struct_def = try!(self.parse_struct_def());
5143                 if struct_def.fields.is_empty() {
5144                     self.span_err(start_span,
5145                         &format!("unit-like struct variant should be written \
5146                                  without braces, as `{},`",
5147                                 ident));
5148                 }
5149                 kind = StructVariantKind(struct_def);
5150             } else if self.check(&token::OpenDelim(token::Paren)) {
5151                 all_nullary = false;
5152                 let arg_tys = try!(self.parse_enum_variant_seq(
5153                     &token::OpenDelim(token::Paren),
5154                     &token::CloseDelim(token::Paren),
5155                     seq_sep_trailing_allowed(token::Comma),
5156                     |p| p.parse_ty_sum()
5157                 ));
5158                 for ty in arg_tys {
5159                     args.push(ast::VariantArg {
5160                         ty: ty,
5161                         id: ast::DUMMY_NODE_ID,
5162                     });
5163                 }
5164                 kind = TupleVariantKind(args);
5165             } else if try!(self.eat(&token::Eq) ){
5166                 disr_expr = Some(try!(self.parse_expr_nopanic()));
5167                 any_disr = disr_expr.as_ref().map(|expr| expr.span);
5168                 kind = TupleVariantKind(args);
5169             } else {
5170                 kind = TupleVariantKind(Vec::new());
5171             }
5172
5173             let vr = ast::Variant_ {
5174                 name: ident,
5175                 attrs: variant_attrs,
5176                 kind: kind,
5177                 id: ast::DUMMY_NODE_ID,
5178                 disr_expr: disr_expr,
5179             };
5180             variants.push(P(spanned(vlo, self.last_span.hi, vr)));
5181
5182             if !try!(self.eat(&token::Comma)) { break; }
5183         }
5184         try!(self.expect(&token::CloseDelim(token::Brace)));
5185         match any_disr {
5186             Some(disr_span) if !all_nullary =>
5187                 self.span_err(disr_span,
5188                     "discriminator values can only be used with a c-like enum"),
5189             _ => ()
5190         }
5191
5192         Ok(ast::EnumDef { variants: variants })
5193     }
5194
5195     /// Parse an "enum" declaration
5196     fn parse_item_enum(&mut self) -> PResult<ItemInfo> {
5197         let id = try!(self.parse_ident());
5198         let mut generics = try!(self.parse_generics());
5199         generics.where_clause = try!(self.parse_where_clause());
5200         try!(self.expect(&token::OpenDelim(token::Brace)));
5201
5202         let enum_definition = try!(self.parse_enum_def(&generics));
5203         Ok((id, ItemEnum(enum_definition, generics), None))
5204     }
5205
5206     /// Parses a string as an ABI spec on an extern type or module. Consumes
5207     /// the `extern` keyword, if one is found.
5208     fn parse_opt_abi(&mut self) -> PResult<Option<abi::Abi>> {
5209         match self.token {
5210             token::Literal(token::Str_(s), suf) | token::Literal(token::StrRaw(s, _), suf) => {
5211                 let sp = self.span;
5212                 self.expect_no_suffix(sp, "ABI spec", suf);
5213                 try!(self.bump());
5214                 match abi::lookup(&s.as_str()) {
5215                     Some(abi) => Ok(Some(abi)),
5216                     None => {
5217                         let last_span = self.last_span;
5218                         self.span_err(
5219                             last_span,
5220                             &format!("invalid ABI: expected one of [{}], \
5221                                      found `{}`",
5222                                     abi::all_names().join(", "),
5223                                     s));
5224                         Ok(None)
5225                     }
5226                 }
5227             }
5228
5229             _ => Ok(None),
5230         }
5231     }
5232
5233     /// Parse one of the items allowed by the flags.
5234     /// NB: this function no longer parses the items inside an
5235     /// extern crate.
5236     fn parse_item_(&mut self, attrs: Vec<Attribute>,
5237                    macros_allowed: bool) -> PResult<Option<P<Item>>> {
5238         let nt_item = match self.token {
5239             token::Interpolated(token::NtItem(ref item)) => {
5240                 Some((**item).clone())
5241             }
5242             _ => None
5243         };
5244         match nt_item {
5245             Some(mut item) => {
5246                 try!(self.bump());
5247                 let mut attrs = attrs;
5248                 mem::swap(&mut item.attrs, &mut attrs);
5249                 item.attrs.extend(attrs);
5250                 return Ok(Some(P(item)));
5251             }
5252             None => {}
5253         }
5254
5255         let lo = self.span.lo;
5256
5257         let visibility = try!(self.parse_visibility());
5258
5259         if try!(self.eat_keyword(keywords::Use) ){
5260             // USE ITEM
5261             let item_ = ItemUse(try!(self.parse_view_path()));
5262             try!(self.expect(&token::Semi));
5263
5264             let last_span = self.last_span;
5265             let item = self.mk_item(lo,
5266                                     last_span.hi,
5267                                     token::special_idents::invalid,
5268                                     item_,
5269                                     visibility,
5270                                     attrs);
5271             return Ok(Some(item));
5272         }
5273
5274         if try!(self.eat_keyword(keywords::Extern)) {
5275             if try!(self.eat_keyword(keywords::Crate)) {
5276                 return Ok(Some(try!(self.parse_item_extern_crate(lo, visibility, attrs))));
5277             }
5278
5279             let opt_abi = try!(self.parse_opt_abi());
5280
5281             if try!(self.eat_keyword(keywords::Fn) ){
5282                 // EXTERN FUNCTION ITEM
5283                 let abi = opt_abi.unwrap_or(abi::C);
5284                 let (ident, item_, extra_attrs) =
5285                     try!(self.parse_item_fn(Unsafety::Normal, Constness::NotConst, abi));
5286                 let last_span = self.last_span;
5287                 let item = self.mk_item(lo,
5288                                         last_span.hi,
5289                                         ident,
5290                                         item_,
5291                                         visibility,
5292                                         maybe_append(attrs, extra_attrs));
5293                 return Ok(Some(item));
5294             } else if self.check(&token::OpenDelim(token::Brace)) {
5295                 return Ok(Some(try!(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs))));
5296             }
5297
5298             try!(self.expect_one_of(&[], &[]));
5299         }
5300
5301         if try!(self.eat_keyword(keywords::Static) ){
5302             // STATIC ITEM
5303             let m = if try!(self.eat_keyword(keywords::Mut)) {MutMutable} else {MutImmutable};
5304             let (ident, item_, extra_attrs) = try!(self.parse_item_const(Some(m)));
5305             let last_span = self.last_span;
5306             let item = self.mk_item(lo,
5307                                     last_span.hi,
5308                                     ident,
5309                                     item_,
5310                                     visibility,
5311                                     maybe_append(attrs, extra_attrs));
5312             return Ok(Some(item));
5313         }
5314         if try!(self.eat_keyword(keywords::Const) ){
5315             if self.check_keyword(keywords::Fn) {
5316                 // CONST FUNCTION ITEM
5317                 try!(self.bump());
5318                 let (ident, item_, extra_attrs) =
5319                     try!(self.parse_item_fn(Unsafety::Normal, Constness::Const, abi::Rust));
5320                 let last_span = self.last_span;
5321                 let item = self.mk_item(lo,
5322                                         last_span.hi,
5323                                         ident,
5324                                         item_,
5325                                         visibility,
5326                                         maybe_append(attrs, extra_attrs));
5327                 return Ok(Some(item));
5328             }
5329
5330             // CONST ITEM
5331             if try!(self.eat_keyword(keywords::Mut) ){
5332                 let last_span = self.last_span;
5333                 self.span_err(last_span, "const globals cannot be mutable");
5334                 self.fileline_help(last_span, "did you mean to declare a static?");
5335             }
5336             let (ident, item_, extra_attrs) = try!(self.parse_item_const(None));
5337             let last_span = self.last_span;
5338             let item = self.mk_item(lo,
5339                                     last_span.hi,
5340                                     ident,
5341                                     item_,
5342                                     visibility,
5343                                     maybe_append(attrs, extra_attrs));
5344             return Ok(Some(item));
5345         }
5346         if self.check_keyword(keywords::Unsafe) &&
5347             self.look_ahead(1, |t| t.is_keyword(keywords::Trait))
5348         {
5349             // UNSAFE TRAIT ITEM
5350             try!(self.expect_keyword(keywords::Unsafe));
5351             try!(self.expect_keyword(keywords::Trait));
5352             let (ident, item_, extra_attrs) =
5353                 try!(self.parse_item_trait(ast::Unsafety::Unsafe));
5354             let last_span = self.last_span;
5355             let item = self.mk_item(lo,
5356                                     last_span.hi,
5357                                     ident,
5358                                     item_,
5359                                     visibility,
5360                                     maybe_append(attrs, extra_attrs));
5361             return Ok(Some(item));
5362         }
5363         if self.check_keyword(keywords::Unsafe) &&
5364             self.look_ahead(1, |t| t.is_keyword(keywords::Impl))
5365         {
5366             // IMPL ITEM
5367             try!(self.expect_keyword(keywords::Unsafe));
5368             try!(self.expect_keyword(keywords::Impl));
5369             let (ident, item_, extra_attrs) = try!(self.parse_item_impl(ast::Unsafety::Unsafe));
5370             let last_span = self.last_span;
5371             let item = self.mk_item(lo,
5372                                     last_span.hi,
5373                                     ident,
5374                                     item_,
5375                                     visibility,
5376                                     maybe_append(attrs, extra_attrs));
5377             return Ok(Some(item));
5378         }
5379         if self.check_keyword(keywords::Fn) {
5380             // FUNCTION ITEM
5381             try!(self.bump());
5382             let (ident, item_, extra_attrs) =
5383                 try!(self.parse_item_fn(Unsafety::Normal, Constness::NotConst, abi::Rust));
5384             let last_span = self.last_span;
5385             let item = self.mk_item(lo,
5386                                     last_span.hi,
5387                                     ident,
5388                                     item_,
5389                                     visibility,
5390                                     maybe_append(attrs, extra_attrs));
5391             return Ok(Some(item));
5392         }
5393         if self.check_keyword(keywords::Unsafe)
5394             && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
5395             // UNSAFE FUNCTION ITEM
5396             try!(self.bump());
5397             let abi = if try!(self.eat_keyword(keywords::Extern) ){
5398                 try!(self.parse_opt_abi()).unwrap_or(abi::C)
5399             } else {
5400                 abi::Rust
5401             };
5402             try!(self.expect_keyword(keywords::Fn));
5403             let (ident, item_, extra_attrs) =
5404                 try!(self.parse_item_fn(Unsafety::Unsafe, Constness::NotConst, abi));
5405             let last_span = self.last_span;
5406             let item = self.mk_item(lo,
5407                                     last_span.hi,
5408                                     ident,
5409                                     item_,
5410                                     visibility,
5411                                     maybe_append(attrs, extra_attrs));
5412             return Ok(Some(item));
5413         }
5414         if try!(self.eat_keyword(keywords::Mod) ){
5415             // MODULE ITEM
5416             let (ident, item_, extra_attrs) =
5417                 try!(self.parse_item_mod(&attrs[..]));
5418             let last_span = self.last_span;
5419             let item = self.mk_item(lo,
5420                                     last_span.hi,
5421                                     ident,
5422                                     item_,
5423                                     visibility,
5424                                     maybe_append(attrs, extra_attrs));
5425             return Ok(Some(item));
5426         }
5427         if try!(self.eat_keyword(keywords::Type) ){
5428             // TYPE ITEM
5429             let (ident, item_, extra_attrs) = try!(self.parse_item_type());
5430             let last_span = self.last_span;
5431             let item = self.mk_item(lo,
5432                                     last_span.hi,
5433                                     ident,
5434                                     item_,
5435                                     visibility,
5436                                     maybe_append(attrs, extra_attrs));
5437             return Ok(Some(item));
5438         }
5439         if try!(self.eat_keyword(keywords::Enum) ){
5440             // ENUM ITEM
5441             let (ident, item_, extra_attrs) = try!(self.parse_item_enum());
5442             let last_span = self.last_span;
5443             let item = self.mk_item(lo,
5444                                     last_span.hi,
5445                                     ident,
5446                                     item_,
5447                                     visibility,
5448                                     maybe_append(attrs, extra_attrs));
5449             return Ok(Some(item));
5450         }
5451         if try!(self.eat_keyword(keywords::Trait) ){
5452             // TRAIT ITEM
5453             let (ident, item_, extra_attrs) =
5454                 try!(self.parse_item_trait(ast::Unsafety::Normal));
5455             let last_span = self.last_span;
5456             let item = self.mk_item(lo,
5457                                     last_span.hi,
5458                                     ident,
5459                                     item_,
5460                                     visibility,
5461                                     maybe_append(attrs, extra_attrs));
5462             return Ok(Some(item));
5463         }
5464         if try!(self.eat_keyword(keywords::Impl) ){
5465             // IMPL ITEM
5466             let (ident, item_, extra_attrs) = try!(self.parse_item_impl(ast::Unsafety::Normal));
5467             let last_span = self.last_span;
5468             let item = self.mk_item(lo,
5469                                     last_span.hi,
5470                                     ident,
5471                                     item_,
5472                                     visibility,
5473                                     maybe_append(attrs, extra_attrs));
5474             return Ok(Some(item));
5475         }
5476         if try!(self.eat_keyword(keywords::Struct) ){
5477             // STRUCT ITEM
5478             let (ident, item_, extra_attrs) = try!(self.parse_item_struct());
5479             let last_span = self.last_span;
5480             let item = self.mk_item(lo,
5481                                     last_span.hi,
5482                                     ident,
5483                                     item_,
5484                                     visibility,
5485                                     maybe_append(attrs, extra_attrs));
5486             return Ok(Some(item));
5487         }
5488         self.parse_macro_use_or_failure(attrs,macros_allowed,lo,visibility)
5489     }
5490
5491     /// Parse a foreign item.
5492     fn parse_foreign_item(&mut self) -> PResult<Option<P<ForeignItem>>> {
5493         let attrs = self.parse_outer_attributes();
5494         let lo = self.span.lo;
5495         let visibility = try!(self.parse_visibility());
5496
5497         if self.check_keyword(keywords::Static) {
5498             // FOREIGN STATIC ITEM
5499             return Ok(Some(try!(self.parse_item_foreign_static(visibility, lo, attrs))));
5500         }
5501         if self.check_keyword(keywords::Fn) || self.check_keyword(keywords::Unsafe) {
5502             // FOREIGN FUNCTION ITEM
5503             return Ok(Some(try!(self.parse_item_foreign_fn(visibility, lo, attrs))));
5504         }
5505
5506         // FIXME #5668: this will occur for a macro invocation:
5507         match try!(self.parse_macro_use_or_failure(attrs, true, lo, visibility)) {
5508             Some(item) => {
5509                 return Err(self.span_fatal(item.span, "macros cannot expand to foreign items"));
5510             }
5511             None => Ok(None)
5512         }
5513     }
5514
5515     /// This is the fall-through for parsing items.
5516     fn parse_macro_use_or_failure(
5517         &mut self,
5518         attrs: Vec<Attribute> ,
5519         macros_allowed: bool,
5520         lo: BytePos,
5521         visibility: Visibility
5522     ) -> PResult<Option<P<Item>>> {
5523         if macros_allowed && !self.token.is_any_keyword()
5524                 && self.look_ahead(1, |t| *t == token::Not)
5525                 && (self.look_ahead(2, |t| t.is_plain_ident())
5526                     || self.look_ahead(2, |t| *t == token::OpenDelim(token::Paren))
5527                     || self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))) {
5528             // MACRO INVOCATION ITEM
5529
5530             let last_span = self.last_span;
5531             self.complain_if_pub_macro(visibility, last_span);
5532
5533             // item macro.
5534             let pth = try!(self.parse_path(NoTypesAllowed));
5535             try!(self.expect(&token::Not));
5536
5537             // a 'special' identifier (like what `macro_rules!` uses)
5538             // is optional. We should eventually unify invoc syntax
5539             // and remove this.
5540             let id = if self.token.is_plain_ident() {
5541                 try!(self.parse_ident())
5542             } else {
5543                 token::special_idents::invalid // no special identifier
5544             };
5545             // eat a matched-delimiter token tree:
5546             let delim = try!(self.expect_open_delim());
5547             let tts = try!(self.parse_seq_to_end(&token::CloseDelim(delim),
5548                                             seq_sep_none(),
5549                                             |p| p.parse_token_tree()));
5550             // single-variant-enum... :
5551             let m = Mac_ { path: pth, tts: tts, ctxt: EMPTY_CTXT };
5552             let m: ast::Mac = codemap::Spanned { node: m,
5553                                              span: mk_sp(self.span.lo,
5554                                                          self.span.hi) };
5555
5556             if delim != token::Brace {
5557                 if !try!(self.eat(&token::Semi) ){
5558                     let last_span = self.last_span;
5559                     self.span_err(last_span,
5560                                   "macros that expand to items must either \
5561                                    be surrounded with braces or followed by \
5562                                    a semicolon");
5563                 }
5564             }
5565
5566             let item_ = ItemMac(m);
5567             let last_span = self.last_span;
5568             let item = self.mk_item(lo,
5569                                     last_span.hi,
5570                                     id,
5571                                     item_,
5572                                     visibility,
5573                                     attrs);
5574             return Ok(Some(item));
5575         }
5576
5577         // FAILURE TO PARSE ITEM
5578         match visibility {
5579             Inherited => {}
5580             Public => {
5581                 let last_span = self.last_span;
5582                 return Err(self.span_fatal(last_span, "unmatched visibility `pub`"));
5583             }
5584         }
5585
5586         if !attrs.is_empty() {
5587             self.expected_item_err(&attrs);
5588         }
5589         Ok(None)
5590     }
5591
5592     pub fn parse_item_nopanic(&mut self) -> PResult<Option<P<Item>>> {
5593         let attrs = self.parse_outer_attributes();
5594         self.parse_item_(attrs, true)
5595     }
5596
5597
5598     /// Matches view_path : MOD? non_global_path as IDENT
5599     /// | MOD? non_global_path MOD_SEP LBRACE RBRACE
5600     /// | MOD? non_global_path MOD_SEP LBRACE ident_seq RBRACE
5601     /// | MOD? non_global_path MOD_SEP STAR
5602     /// | MOD? non_global_path
5603     fn parse_view_path(&mut self) -> PResult<P<ViewPath>> {
5604         let lo = self.span.lo;
5605
5606         // Allow a leading :: because the paths are absolute either way.
5607         // This occurs with "use $crate::..." in macros.
5608         try!(self.eat(&token::ModSep));
5609
5610         if self.check(&token::OpenDelim(token::Brace)) {
5611             // use {foo,bar}
5612             let idents = try!(self.parse_unspanned_seq(
5613                 &token::OpenDelim(token::Brace),
5614                 &token::CloseDelim(token::Brace),
5615                 seq_sep_trailing_allowed(token::Comma),
5616                 |p| p.parse_path_list_item()));
5617             let path = ast::Path {
5618                 span: mk_sp(lo, self.span.hi),
5619                 global: false,
5620                 segments: Vec::new()
5621             };
5622             return Ok(P(spanned(lo, self.span.hi, ViewPathList(path, idents))));
5623         }
5624
5625         let first_ident = try!(self.parse_ident());
5626         let mut path = vec!(first_ident);
5627         if let token::ModSep = self.token {
5628             // foo::bar or foo::{a,b,c} or foo::*
5629             while self.check(&token::ModSep) {
5630                 try!(self.bump());
5631
5632                 match self.token {
5633                   token::Ident(..) => {
5634                     let ident = try!(self.parse_ident());
5635                     path.push(ident);
5636                   }
5637
5638                   // foo::bar::{a,b,c}
5639                   token::OpenDelim(token::Brace) => {
5640                     let idents = try!(self.parse_unspanned_seq(
5641                         &token::OpenDelim(token::Brace),
5642                         &token::CloseDelim(token::Brace),
5643                         seq_sep_trailing_allowed(token::Comma),
5644                         |p| p.parse_path_list_item()
5645                     ));
5646                     let path = ast::Path {
5647                         span: mk_sp(lo, self.span.hi),
5648                         global: false,
5649                         segments: path.into_iter().map(|identifier| {
5650                             ast::PathSegment {
5651                                 identifier: identifier,
5652                                 parameters: ast::PathParameters::none(),
5653                             }
5654                         }).collect()
5655                     };
5656                     return Ok(P(spanned(lo, self.span.hi, ViewPathList(path, idents))));
5657                   }
5658
5659                   // foo::bar::*
5660                   token::BinOp(token::Star) => {
5661                     try!(self.bump());
5662                     let path = ast::Path {
5663                         span: mk_sp(lo, self.span.hi),
5664                         global: false,
5665                         segments: path.into_iter().map(|identifier| {
5666                             ast::PathSegment {
5667                                 identifier: identifier,
5668                                 parameters: ast::PathParameters::none(),
5669                             }
5670                         }).collect()
5671                     };
5672                     return Ok(P(spanned(lo, self.span.hi, ViewPathGlob(path))));
5673                   }
5674
5675                   // fall-through for case foo::bar::;
5676                   token::Semi => {
5677                     self.span_err(self.span, "expected identifier or `{` or `*`, found `;`");
5678                   }
5679
5680                   _ => break
5681                 }
5682             }
5683         }
5684         let mut rename_to = path[path.len() - 1];
5685         let path = ast::Path {
5686             span: mk_sp(lo, self.last_span.hi),
5687             global: false,
5688             segments: path.into_iter().map(|identifier| {
5689                 ast::PathSegment {
5690                     identifier: identifier,
5691                     parameters: ast::PathParameters::none(),
5692                 }
5693             }).collect()
5694         };
5695         rename_to = try!(self.parse_rename()).unwrap_or(rename_to);
5696         Ok(P(spanned(lo, self.last_span.hi, ViewPathSimple(rename_to, path))))
5697     }
5698
5699     fn parse_rename(&mut self) -> PResult<Option<Ident>> {
5700         if try!(self.eat_keyword(keywords::As)) {
5701             self.parse_ident().map(Some)
5702         } else {
5703             Ok(None)
5704         }
5705     }
5706
5707     /// Parses a source module as a crate. This is the main
5708     /// entry point for the parser.
5709     pub fn parse_crate_mod(&mut self) -> PResult<Crate> {
5710         let lo = self.span.lo;
5711         Ok(ast::Crate {
5712             attrs: self.parse_inner_attributes(),
5713             module: try!(self.parse_mod_items(&token::Eof, lo)),
5714             config: self.cfg.clone(),
5715             span: mk_sp(lo, self.span.lo),
5716             exported_macros: Vec::new(),
5717         })
5718     }
5719
5720     pub fn parse_optional_str(&mut self)
5721                               -> PResult<Option<(InternedString,
5722                                                  ast::StrStyle,
5723                                                  Option<ast::Name>)>> {
5724         let ret = match self.token {
5725             token::Literal(token::Str_(s), suf) => {
5726                 (self.id_to_interned_str(ast::Ident::with_empty_ctxt(s)), ast::CookedStr, suf)
5727             }
5728             token::Literal(token::StrRaw(s, n), suf) => {
5729                 (self.id_to_interned_str(ast::Ident::with_empty_ctxt(s)), ast::RawStr(n), suf)
5730             }
5731             _ => return Ok(None)
5732         };
5733         try!(self.bump());
5734         Ok(Some(ret))
5735     }
5736
5737     pub fn parse_str(&mut self) -> PResult<(InternedString, StrStyle)> {
5738         match try!(self.parse_optional_str()) {
5739             Some((s, style, suf)) => {
5740                 let sp = self.last_span;
5741                 self.expect_no_suffix(sp, "string literal", suf);
5742                 Ok((s, style))
5743             }
5744             _ =>  Err(self.fatal("expected string literal"))
5745         }
5746     }
5747 }