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Cut out a bunch of Result and panictry! boilerplate from libsyntax.
[rust.git] / 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, BindingMode};
18 use ast::{BiBitAnd, BiBitOr, BiBitXor, BiRem, BiLt, Block};
19 use ast::{BlockCheckMode, CaptureByRef, CaptureByValue, CaptureClause};
20 use ast::{Constness, 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, ExprType, ExprUnary};
30 use ast::{ExprVec, ExprWhile, ExprWhileLet, ExprForLoop, Field, FnDecl};
31 use ast::{ForeignItem, ForeignItemStatic, ForeignItemFn, 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::{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_};
41 use ast::{MutTy, BiMul, Mutability};
42 use ast::{NamedField, UnNeg, NoReturn, UnNot};
43 use ast::{Pat, PatBox, PatEnum, PatIdent, PatLit, PatQPath, PatMac, PatRange};
44 use ast::{PatRegion, PatStruct, PatTup, PatVec, PatWild};
45 use ast::{PolyTraitRef, QSelf};
46 use ast::{Return, BiShl, BiShr, Stmt, StmtDecl};
47 use ast::{StmtExpr, StmtSemi, StmtMac, VariantData, StructField};
48 use ast::{BiSub, StrStyle};
49 use ast::{SelfExplicit, SelfRegion, SelfStatic, SelfValue};
50 use ast::{Delimited, SequenceRepetition, TokenTree, TraitItem, TraitRef};
51 use ast::{Ty, Ty_, TypeBinding, TyMac};
52 use ast::{TyFixedLengthVec, TyBareFn, TyTypeof, TyInfer};
53 use ast::{TyParam, TyParamBounds, TyParen, TyPath, TyPtr};
54 use ast::{TyRptr, TyTup, TyU32, TyVec};
55 use ast::TypeTraitItem;
56 use ast::{UnnamedField, UnsafeBlock};
57 use ast::{ViewPath, ViewPathGlob, ViewPathList, ViewPathSimple};
58 use ast::{Visibility, WhereClause};
59 use attr::{ThinAttributes, ThinAttributesExt, AttributesExt};
60 use ast;
61 use ast_util::{self, ident_to_path};
62 use codemap::{self, Span, BytePos, Spanned, spanned, mk_sp, CodeMap};
63 use errors::{self, DiagnosticBuilder};
64 use ext::tt::macro_parser;
65 use parse;
66 use parse::classify;
67 use parse::common::{SeqSep, seq_sep_none, seq_sep_trailing_allowed};
68 use parse::lexer::{Reader, TokenAndSpan};
69 use parse::obsolete::{ParserObsoleteMethods, ObsoleteSyntax};
70 use parse::token::{self, MatchNt, SubstNt, SpecialVarNt, InternedString};
71 use parse::token::{keywords, special_idents, SpecialMacroVar};
72 use parse::{new_sub_parser_from_file, ParseSess};
73 use util::parser::{AssocOp, Fixity};
74 use print::pprust;
75 use ptr::P;
76 use parse::PResult;
77
78 use std::collections::HashSet;
79 use std::io::prelude::*;
80 use std::mem;
81 use std::path::{Path, PathBuf};
82 use std::rc::Rc;
83 use std::slice;
84
85 bitflags! {
86     flags Restrictions: u8 {
87         const RESTRICTION_STMT_EXPR         = 1 << 0,
88         const RESTRICTION_NO_STRUCT_LITERAL = 1 << 1,
89     }
90 }
91
92 type ItemInfo = (Ident, Item_, Option<Vec<Attribute> >);
93
94 /// How to parse a path. There are four different kinds of paths, all of which
95 /// are parsed somewhat differently.
96 #[derive(Copy, Clone, PartialEq)]
97 pub enum PathParsingMode {
98     /// A path with no type parameters; e.g. `foo::bar::Baz`
99     NoTypesAllowed,
100     /// A path with a lifetime and type parameters, with no double colons
101     /// before the type parameters; e.g. `foo::bar<'a>::Baz<T>`
102     LifetimeAndTypesWithoutColons,
103     /// A path with a lifetime and type parameters with double colons before
104     /// the type parameters; e.g. `foo::bar::<'a>::Baz::<T>`
105     LifetimeAndTypesWithColons,
106 }
107
108 /// How to parse a bound, whether to allow bound modifiers such as `?`.
109 #[derive(Copy, Clone, PartialEq)]
110 pub enum BoundParsingMode {
111     Bare,
112     Modified,
113 }
114
115 /// `pub` should be parsed in struct fields and not parsed in variant fields
116 #[derive(Clone, Copy, PartialEq)]
117 pub enum ParsePub {
118     Yes,
119     No,
120 }
121
122 /// Possibly accept an `token::Interpolated` expression (a pre-parsed expression
123 /// dropped into the token stream, which happens while parsing the result of
124 /// macro expansion). Placement of these is not as complex as I feared it would
125 /// be. The important thing is to make sure that lookahead doesn't balk at
126 /// `token::Interpolated` tokens.
127 macro_rules! maybe_whole_expr {
128     ($p:expr) => (
129         {
130             let found = match $p.token {
131                 token::Interpolated(token::NtExpr(ref e)) => {
132                     Some((*e).clone())
133                 }
134                 token::Interpolated(token::NtPath(_)) => {
135                     // FIXME: The following avoids an issue with lexical borrowck scopes,
136                     // but the clone is unfortunate.
137                     let pt = match $p.token {
138                         token::Interpolated(token::NtPath(ref pt)) => (**pt).clone(),
139                         _ => unreachable!()
140                     };
141                     let span = $p.span;
142                     Some($p.mk_expr(span.lo, span.hi, ExprPath(None, pt), None))
143                 }
144                 token::Interpolated(token::NtBlock(_)) => {
145                     // FIXME: The following avoids an issue with lexical borrowck scopes,
146                     // but the clone is unfortunate.
147                     let b = match $p.token {
148                         token::Interpolated(token::NtBlock(ref b)) => (*b).clone(),
149                         _ => unreachable!()
150                     };
151                     let span = $p.span;
152                     Some($p.mk_expr(span.lo, span.hi, ExprBlock(b), None))
153                 }
154                 _ => None
155             };
156             match found {
157                 Some(e) => {
158                     $p.bump();
159                     return Ok(e);
160                 }
161                 None => ()
162             }
163         }
164     )
165 }
166
167 /// As maybe_whole_expr, but for things other than expressions
168 macro_rules! maybe_whole {
169     ($p:expr, $constructor:ident) => (
170         {
171             let found = match ($p).token {
172                 token::Interpolated(token::$constructor(_)) => {
173                     Some(($p).bump_and_get())
174                 }
175                 _ => None
176             };
177             if let Some(token::Interpolated(token::$constructor(x))) = found {
178                 return Ok(x.clone());
179             }
180         }
181     );
182     (no_clone $p:expr, $constructor:ident) => (
183         {
184             let found = match ($p).token {
185                 token::Interpolated(token::$constructor(_)) => {
186                     Some(($p).bump_and_get())
187                 }
188                 _ => None
189             };
190             if let Some(token::Interpolated(token::$constructor(x))) = found {
191                 return Ok(x);
192             }
193         }
194     );
195     (deref $p:expr, $constructor:ident) => (
196         {
197             let found = match ($p).token {
198                 token::Interpolated(token::$constructor(_)) => {
199                     Some(($p).bump_and_get())
200                 }
201                 _ => None
202             };
203             if let Some(token::Interpolated(token::$constructor(x))) = found {
204                 return Ok((*x).clone());
205             }
206         }
207     );
208     (Some deref $p:expr, $constructor:ident) => (
209         {
210             let found = match ($p).token {
211                 token::Interpolated(token::$constructor(_)) => {
212                     Some(($p).bump_and_get())
213                 }
214                 _ => None
215             };
216             if let Some(token::Interpolated(token::$constructor(x))) = found {
217                 return Ok(Some((*x).clone()));
218             }
219         }
220     );
221     (pair_empty $p:expr, $constructor:ident) => (
222         {
223             let found = match ($p).token {
224                 token::Interpolated(token::$constructor(_)) => {
225                     Some(($p).bump_and_get())
226                 }
227                 _ => None
228             };
229             if let Some(token::Interpolated(token::$constructor(x))) = found {
230                 return Ok((Vec::new(), x));
231             }
232         }
233     )
234 }
235
236
237 fn maybe_append(mut lhs: Vec<Attribute>, rhs: Option<Vec<Attribute>>)
238                 -> Vec<Attribute> {
239     if let Some(ref attrs) = rhs {
240         lhs.extend(attrs.iter().cloned())
241     }
242     lhs
243 }
244
245 /* ident is handled by common.rs */
246
247 pub struct Parser<'a> {
248     pub sess: &'a ParseSess,
249     /// the current token:
250     pub token: token::Token,
251     /// the span of the current token:
252     pub span: Span,
253     /// the span of the prior token:
254     pub last_span: Span,
255     pub cfg: CrateConfig,
256     /// the previous token or None (only stashed sometimes).
257     pub last_token: Option<Box<token::Token>>,
258     pub buffer: [TokenAndSpan; 4],
259     pub buffer_start: isize,
260     pub buffer_end: isize,
261     pub tokens_consumed: usize,
262     pub restrictions: Restrictions,
263     pub quote_depth: usize, // not (yet) related to the quasiquoter
264     pub reader: Box<Reader+'a>,
265     pub interner: Rc<token::IdentInterner>,
266     /// The set of seen errors about obsolete syntax. Used to suppress
267     /// extra detail when the same error is seen twice
268     pub obsolete_set: HashSet<ObsoleteSyntax>,
269     /// Used to determine the path to externally loaded source files
270     pub mod_path_stack: Vec<InternedString>,
271     /// Stack of spans of open delimiters. Used for error message.
272     pub open_braces: Vec<Span>,
273     /// Flag if this parser "owns" the directory that it is currently parsing
274     /// in. This will affect how nested files are looked up.
275     pub owns_directory: bool,
276     /// Name of the root module this parser originated from. If `None`, then the
277     /// name is not known. This does not change while the parser is descending
278     /// into modules, and sub-parsers have new values for this name.
279     pub root_module_name: Option<String>,
280     pub expected_tokens: Vec<TokenType>,
281 }
282
283 #[derive(PartialEq, Eq, Clone)]
284 pub enum TokenType {
285     Token(token::Token),
286     Keyword(keywords::Keyword),
287     Operator,
288 }
289
290 impl TokenType {
291     fn to_string(&self) -> String {
292         match *self {
293             TokenType::Token(ref t) => format!("`{}`", Parser::token_to_string(t)),
294             TokenType::Operator => "an operator".to_string(),
295             TokenType::Keyword(kw) => format!("`{}`", kw.to_name()),
296         }
297     }
298 }
299
300 fn is_plain_ident_or_underscore(t: &token::Token) -> bool {
301     t.is_plain_ident() || *t == token::Underscore
302 }
303
304 /// Information about the path to a module.
305 pub struct ModulePath {
306     pub name: String,
307     pub path_exists: bool,
308     pub result: Result<ModulePathSuccess, ModulePathError>,
309 }
310
311 pub struct ModulePathSuccess {
312     pub path: ::std::path::PathBuf,
313     pub owns_directory: bool,
314 }
315
316 pub struct ModulePathError {
317     pub err_msg: String,
318     pub help_msg: String,
319 }
320
321 pub enum LhsExpr {
322     NotYetParsed,
323     AttributesParsed(ThinAttributes),
324     AlreadyParsed(P<Expr>),
325 }
326
327 impl From<Option<ThinAttributes>> for LhsExpr {
328     fn from(o: Option<ThinAttributes>) -> Self {
329         if let Some(attrs) = o {
330             LhsExpr::AttributesParsed(attrs)
331         } else {
332             LhsExpr::NotYetParsed
333         }
334     }
335 }
336
337 impl From<P<Expr>> for LhsExpr {
338     fn from(expr: P<Expr>) -> Self {
339         LhsExpr::AlreadyParsed(expr)
340     }
341 }
342
343 impl<'a> Parser<'a> {
344     pub fn new(sess: &'a ParseSess,
345                cfg: ast::CrateConfig,
346                mut rdr: Box<Reader+'a>)
347                -> Parser<'a>
348     {
349         let tok0 = rdr.real_token();
350         let span = tok0.sp;
351         let placeholder = TokenAndSpan {
352             tok: token::Underscore,
353             sp: span,
354         };
355
356         Parser {
357             reader: rdr,
358             interner: token::get_ident_interner(),
359             sess: sess,
360             cfg: cfg,
361             token: tok0.tok,
362             span: span,
363             last_span: span,
364             last_token: None,
365             buffer: [
366                 placeholder.clone(),
367                 placeholder.clone(),
368                 placeholder.clone(),
369                 placeholder.clone(),
370             ],
371             buffer_start: 0,
372             buffer_end: 0,
373             tokens_consumed: 0,
374             restrictions: Restrictions::empty(),
375             quote_depth: 0,
376             obsolete_set: HashSet::new(),
377             mod_path_stack: Vec::new(),
378             open_braces: Vec::new(),
379             owns_directory: true,
380             root_module_name: None,
381             expected_tokens: Vec::new(),
382         }
383     }
384
385     /// Convert a token to a string using self's reader
386     pub fn token_to_string(token: &token::Token) -> String {
387         pprust::token_to_string(token)
388     }
389
390     /// Convert the current token to a string using self's reader
391     pub fn this_token_to_string(&self) -> String {
392         Parser::token_to_string(&self.token)
393     }
394
395     pub fn unexpected_last<T>(&self, t: &token::Token) -> PResult<'a, T> {
396         let token_str = Parser::token_to_string(t);
397         let last_span = self.last_span;
398         Err(self.span_fatal(last_span, &format!("unexpected token: `{}`", token_str)))
399     }
400
401     pub fn unexpected<T>(&mut self) -> PResult<'a, T> {
402         match self.expect_one_of(&[], &[]) {
403             Err(e) => Err(e),
404             Ok(_) => unreachable!(),
405         }
406     }
407
408     /// Expect and consume the token t. Signal an error if
409     /// the next token is not t.
410     pub fn expect(&mut self, t: &token::Token) -> PResult<'a,  ()> {
411         if self.expected_tokens.is_empty() {
412             if self.token == *t {
413                 self.bump();
414                 Ok(())
415             } else {
416                 let token_str = Parser::token_to_string(t);
417                 let this_token_str = self.this_token_to_string();
418                 Err(self.fatal(&format!("expected `{}`, found `{}`",
419                                    token_str,
420                                    this_token_str)))
421             }
422         } else {
423             self.expect_one_of(unsafe { slice::from_raw_parts(t, 1) }, &[])
424         }
425     }
426
427     /// Expect next token to be edible or inedible token.  If edible,
428     /// then consume it; if inedible, then return without consuming
429     /// anything.  Signal a fatal error if next token is unexpected.
430     pub fn expect_one_of(&mut self,
431                          edible: &[token::Token],
432                          inedible: &[token::Token]) -> PResult<'a,  ()>{
433         fn tokens_to_string(tokens: &[TokenType]) -> String {
434             let mut i = tokens.iter();
435             // This might be a sign we need a connect method on Iterator.
436             let b = i.next()
437                      .map_or("".to_string(), |t| t.to_string());
438             i.enumerate().fold(b, |mut b, (i, ref a)| {
439                 if tokens.len() > 2 && i == tokens.len() - 2 {
440                     b.push_str(", or ");
441                 } else if tokens.len() == 2 && i == tokens.len() - 2 {
442                     b.push_str(" or ");
443                 } else {
444                     b.push_str(", ");
445                 }
446                 b.push_str(&*a.to_string());
447                 b
448             })
449         }
450         if edible.contains(&self.token) {
451             self.bump();
452             Ok(())
453         } else if inedible.contains(&self.token) {
454             // leave it in the input
455             Ok(())
456         } else {
457             let mut expected = edible.iter()
458                 .map(|x| TokenType::Token(x.clone()))
459                 .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
460                 .chain(self.expected_tokens.iter().cloned())
461                 .collect::<Vec<_>>();
462             expected.sort_by(|a, b| a.to_string().cmp(&b.to_string()));
463             expected.dedup();
464             let expect = tokens_to_string(&expected[..]);
465             let actual = self.this_token_to_string();
466             Err(self.fatal(
467                 &(if expected.len() > 1 {
468                     (format!("expected one of {}, found `{}`",
469                              expect,
470                              actual))
471                 } else if expected.is_empty() {
472                     (format!("unexpected token: `{}`",
473                              actual))
474                 } else {
475                     (format!("expected {}, found `{}`",
476                              expect,
477                              actual))
478                 })[..]
479             ))
480         }
481     }
482
483     /// Check for erroneous `ident { }`; if matches, signal error and
484     /// recover (without consuming any expected input token).  Returns
485     /// true if and only if input was consumed for recovery.
486     pub fn check_for_erroneous_unit_struct_expecting(&mut self,
487                                                      expected: &[token::Token])
488                                                      -> bool {
489         if self.token == token::OpenDelim(token::Brace)
490             && expected.iter().all(|t| *t != token::OpenDelim(token::Brace))
491             && self.look_ahead(1, |t| *t == token::CloseDelim(token::Brace)) {
492             // matched; signal non-fatal error and recover.
493             let span = self.span;
494             self.span_err(span, "unit-like struct construction is written with no trailing `{ }`");
495             self.eat(&token::OpenDelim(token::Brace));
496             self.eat(&token::CloseDelim(token::Brace));
497             true
498         } else {
499             false
500         }
501     }
502
503     /// Commit to parsing a complete expression `e` expected to be
504     /// followed by some token from the set edible + inedible.  Recover
505     /// from anticipated input errors, discarding erroneous characters.
506     pub fn commit_expr(&mut self, e: &Expr, edible: &[token::Token],
507                        inedible: &[token::Token]) -> PResult<'a, ()> {
508         debug!("commit_expr {:?}", e);
509         if let ExprPath(..) = e.node {
510             // might be unit-struct construction; check for recoverableinput error.
511             let expected = edible.iter()
512                 .cloned()
513                 .chain(inedible.iter().cloned())
514                 .collect::<Vec<_>>();
515             self.check_for_erroneous_unit_struct_expecting(&expected[..]);
516         }
517         self.expect_one_of(edible, inedible)
518     }
519
520     pub fn commit_expr_expecting(&mut self, e: &Expr, edible: token::Token) -> PResult<'a, ()> {
521         self.commit_expr(e, &[edible], &[])
522     }
523
524     /// Commit to parsing a complete statement `s`, which expects to be
525     /// followed by some token from the set edible + inedible.  Check
526     /// for recoverable input errors, discarding erroneous characters.
527     pub fn commit_stmt(&mut self, edible: &[token::Token],
528                        inedible: &[token::Token]) -> PResult<'a, ()> {
529         if self.last_token
530                .as_ref()
531                .map_or(false, |t| t.is_ident() || t.is_path()) {
532             let expected = edible.iter()
533                 .cloned()
534                 .chain(inedible.iter().cloned())
535                 .collect::<Vec<_>>();
536             self.check_for_erroneous_unit_struct_expecting(&expected);
537         }
538         self.expect_one_of(edible, inedible)
539     }
540
541     pub fn commit_stmt_expecting(&mut self, edible: token::Token) -> PResult<'a, ()> {
542         self.commit_stmt(&[edible], &[])
543     }
544
545     pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
546         self.check_strict_keywords();
547         self.check_reserved_keywords();
548         match self.token {
549             token::Ident(i, _) => {
550                 self.bump();
551                 Ok(i)
552             }
553             token::Interpolated(token::NtIdent(..)) => {
554                 self.bug("ident interpolation not converted to real token");
555             }
556             _ => {
557                 let token_str = self.this_token_to_string();
558                 Err(self.fatal(&format!("expected ident, found `{}`",
559                                     token_str)))
560             }
561         }
562     }
563
564     pub fn parse_ident_or_self_type(&mut self) -> PResult<'a, ast::Ident> {
565         if self.is_self_type_ident() {
566             self.expect_self_type_ident()
567         } else {
568             self.parse_ident()
569         }
570     }
571
572     pub fn parse_path_list_item(&mut self) -> PResult<'a, ast::PathListItem> {
573         let lo = self.span.lo;
574         let node = if self.eat_keyword(keywords::SelfValue) {
575             let rename = try!(self.parse_rename());
576             ast::PathListMod { id: ast::DUMMY_NODE_ID, rename: rename }
577         } else {
578             let ident = try!(self.parse_ident());
579             let rename = try!(self.parse_rename());
580             ast::PathListIdent { name: ident, rename: rename, id: ast::DUMMY_NODE_ID }
581         };
582         let hi = self.last_span.hi;
583         Ok(spanned(lo, hi, node))
584     }
585
586     /// Check if the next token is `tok`, and return `true` if so.
587     ///
588     /// This method is will automatically add `tok` to `expected_tokens` if `tok` is not
589     /// encountered.
590     pub fn check(&mut self, tok: &token::Token) -> bool {
591         let is_present = self.token == *tok;
592         if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
593         is_present
594     }
595
596     /// Consume token 'tok' if it exists. Returns true if the given
597     /// token was present, false otherwise.
598     pub fn eat(&mut self, tok: &token::Token) -> bool {
599         let is_present = self.check(tok);
600         if is_present { self.bump() }
601         is_present
602     }
603
604     pub fn check_keyword(&mut self, kw: keywords::Keyword) -> bool {
605         self.expected_tokens.push(TokenType::Keyword(kw));
606         self.token.is_keyword(kw)
607     }
608
609     /// If the next token is the given keyword, eat it and return
610     /// true. Otherwise, return false.
611     pub fn eat_keyword(&mut self, kw: keywords::Keyword) -> bool {
612         if self.check_keyword(kw) {
613             self.bump();
614             true
615         } else {
616             false
617         }
618     }
619
620     pub fn eat_keyword_noexpect(&mut self, kw: keywords::Keyword) -> bool {
621         if self.token.is_keyword(kw) {
622             self.bump();
623             true
624         } else {
625             false
626         }
627     }
628
629     /// If the given word is not a keyword, signal an error.
630     /// If the next token is not the given word, signal an error.
631     /// Otherwise, eat it.
632     pub fn expect_keyword(&mut self, kw: keywords::Keyword) -> PResult<'a, ()> {
633         if !self.eat_keyword(kw) {
634             self.unexpected()
635         } else {
636             Ok(())
637         }
638     }
639
640     /// Signal an error if the given string is a strict keyword
641     pub fn check_strict_keywords(&mut self) {
642         if self.token.is_strict_keyword() {
643             let token_str = self.this_token_to_string();
644             let span = self.span;
645             self.span_err(span,
646                           &format!("expected identifier, found keyword `{}`",
647                                   token_str));
648         }
649     }
650
651     /// Signal an error if the current token is a reserved keyword
652     pub fn check_reserved_keywords(&mut self) {
653         if self.token.is_reserved_keyword() {
654             let token_str = self.this_token_to_string();
655             self.fatal(&format!("`{}` is a reserved keyword", token_str)).emit()
656         }
657     }
658
659     /// Expect and consume an `&`. If `&&` is seen, replace it with a single
660     /// `&` and continue. If an `&` is not seen, signal an error.
661     fn expect_and(&mut self) -> PResult<'a, ()> {
662         self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
663         match self.token {
664             token::BinOp(token::And) => {
665                 self.bump();
666                 Ok(())
667             }
668             token::AndAnd => {
669                 let span = self.span;
670                 let lo = span.lo + BytePos(1);
671                 Ok(self.replace_token(token::BinOp(token::And), lo, span.hi))
672             }
673             _ => self.unexpected()
674         }
675     }
676
677     pub fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
678         match suffix {
679             None => {/* everything ok */}
680             Some(suf) => {
681                 let text = suf.as_str();
682                 if text.is_empty() {
683                     self.span_bug(sp, "found empty literal suffix in Some")
684                 }
685                 self.span_err(sp, &*format!("{} with a suffix is invalid", kind));
686             }
687         }
688     }
689
690
691     /// Attempt to consume a `<`. If `<<` is seen, replace it with a single
692     /// `<` and continue. If a `<` is not seen, return false.
693     ///
694     /// This is meant to be used when parsing generics on a path to get the
695     /// starting token.
696     fn eat_lt(&mut self) -> bool {
697         self.expected_tokens.push(TokenType::Token(token::Lt));
698         match self.token {
699             token::Lt => {
700                 self.bump();
701                 true
702             }
703             token::BinOp(token::Shl) => {
704                 let span = self.span;
705                 let lo = span.lo + BytePos(1);
706                 self.replace_token(token::Lt, lo, span.hi);
707                 true
708             }
709             _ => false,
710         }
711     }
712
713     fn expect_lt(&mut self) -> PResult<'a, ()> {
714         if !self.eat_lt() {
715             self.unexpected()
716         } else {
717             Ok(())
718         }
719     }
720
721     /// Expect and consume a GT. if a >> is seen, replace it
722     /// with a single > and continue. If a GT is not seen,
723     /// signal an error.
724     pub fn expect_gt(&mut self) -> PResult<'a, ()> {
725         self.expected_tokens.push(TokenType::Token(token::Gt));
726         match self.token {
727             token::Gt => {
728                 self.bump();
729                 Ok(())
730             }
731             token::BinOp(token::Shr) => {
732                 let span = self.span;
733                 let lo = span.lo + BytePos(1);
734                 Ok(self.replace_token(token::Gt, lo, span.hi))
735             }
736             token::BinOpEq(token::Shr) => {
737                 let span = self.span;
738                 let lo = span.lo + BytePos(1);
739                 Ok(self.replace_token(token::Ge, lo, span.hi))
740             }
741             token::Ge => {
742                 let span = self.span;
743                 let lo = span.lo + BytePos(1);
744                 Ok(self.replace_token(token::Eq, lo, span.hi))
745             }
746             _ => {
747                 let gt_str = Parser::token_to_string(&token::Gt);
748                 let this_token_str = self.this_token_to_string();
749                 Err(self.fatal(&format!("expected `{}`, found `{}`",
750                                    gt_str,
751                                    this_token_str)))
752             }
753         }
754     }
755
756     pub fn parse_seq_to_before_gt_or_return<T, F>(&mut self,
757                                                   sep: Option<token::Token>,
758                                                   mut f: F)
759                                                   -> PResult<'a, (P<[T]>, bool)>
760         where F: FnMut(&mut Parser<'a>) -> PResult<'a, Option<T>>,
761     {
762         let mut v = Vec::new();
763         // This loop works by alternating back and forth between parsing types
764         // and commas.  For example, given a string `A, B,>`, the parser would
765         // first parse `A`, then a comma, then `B`, then a comma. After that it
766         // would encounter a `>` and stop. This lets the parser handle trailing
767         // commas in generic parameters, because it can stop either after
768         // parsing a type or after parsing a comma.
769         for i in 0.. {
770             if self.check(&token::Gt)
771                 || self.token == token::BinOp(token::Shr)
772                 || self.token == token::Ge
773                 || self.token == token::BinOpEq(token::Shr) {
774                 break;
775             }
776
777             if i % 2 == 0 {
778                 match try!(f(self)) {
779                     Some(result) => v.push(result),
780                     None => return Ok((P::from_vec(v), true))
781                 }
782             } else {
783                 if let Some(t) = sep.as_ref() {
784                     try!(self.expect(t));
785                 }
786
787             }
788         }
789         return Ok((P::from_vec(v), false));
790     }
791
792     /// Parse a sequence bracketed by '<' and '>', stopping
793     /// before the '>'.
794     pub fn parse_seq_to_before_gt<T, F>(&mut self,
795                                         sep: Option<token::Token>,
796                                         mut f: F)
797                                         -> PResult<'a, P<[T]>> where
798         F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
799     {
800         let (result, returned) = try!(self.parse_seq_to_before_gt_or_return(sep,
801                                                     |p| Ok(Some(try!(f(p))))));
802         assert!(!returned);
803         return Ok(result);
804     }
805
806     pub fn parse_seq_to_gt<T, F>(&mut self,
807                                  sep: Option<token::Token>,
808                                  f: F)
809                                  -> PResult<'a, P<[T]>> where
810         F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
811     {
812         let v = try!(self.parse_seq_to_before_gt(sep, f));
813         try!(self.expect_gt());
814         return Ok(v);
815     }
816
817     pub fn parse_seq_to_gt_or_return<T, F>(&mut self,
818                                            sep: Option<token::Token>,
819                                            f: F)
820                                            -> PResult<'a, (P<[T]>, bool)> where
821         F: FnMut(&mut Parser<'a>) -> PResult<'a, Option<T>>,
822     {
823         let (v, returned) = try!(self.parse_seq_to_before_gt_or_return(sep, f));
824         if !returned {
825             try!(self.expect_gt());
826         }
827         return Ok((v, returned));
828     }
829
830     /// Parse a sequence, including the closing delimiter. The function
831     /// f must consume tokens until reaching the next separator or
832     /// closing bracket.
833     pub fn parse_seq_to_end<T, F>(&mut self,
834                                   ket: &token::Token,
835                                   sep: SeqSep,
836                                   f: F)
837                                   -> PResult<'a, Vec<T>> where
838         F: FnMut(&mut Parser<'a>) -> PResult<'a,  T>,
839     {
840         let val = try!(self.parse_seq_to_before_end(ket, sep, f));
841         self.bump();
842         Ok(val)
843     }
844
845     /// Parse a sequence, not including the closing delimiter. The function
846     /// f must consume tokens until reaching the next separator or
847     /// closing bracket.
848     pub fn parse_seq_to_before_end<T, F>(&mut self,
849                                          ket: &token::Token,
850                                          sep: SeqSep,
851                                          mut f: F)
852                                          -> PResult<'a, Vec<T>> where
853         F: FnMut(&mut Parser<'a>) -> PResult<'a,  T>,
854     {
855         let mut first: bool = true;
856         let mut v = vec!();
857         while self.token != *ket {
858             match sep.sep {
859               Some(ref t) => {
860                 if first { first = false; }
861                 else { try!(self.expect(t)); }
862               }
863               _ => ()
864             }
865             if sep.trailing_sep_allowed && self.check(ket) { break; }
866             v.push(try!(f(self)));
867         }
868         return Ok(v);
869     }
870
871     /// Parse a sequence, including the closing delimiter. The function
872     /// f must consume tokens until reaching the next separator or
873     /// closing bracket.
874     pub fn parse_unspanned_seq<T, F>(&mut self,
875                                      bra: &token::Token,
876                                      ket: &token::Token,
877                                      sep: SeqSep,
878                                      f: F)
879                                      -> PResult<'a, Vec<T>> where
880         F: FnMut(&mut Parser<'a>) -> PResult<'a,  T>,
881     {
882         try!(self.expect(bra));
883         let result = try!(self.parse_seq_to_before_end(ket, sep, f));
884         self.bump();
885         Ok(result)
886     }
887
888     /// Parse a sequence parameter of enum variant. For consistency purposes,
889     /// these should not be empty.
890     pub fn parse_enum_variant_seq<T, F>(&mut self,
891                                         bra: &token::Token,
892                                         ket: &token::Token,
893                                         sep: SeqSep,
894                                         f: F)
895                                         -> PResult<'a, Vec<T>> where
896         F: FnMut(&mut Parser<'a>) -> PResult<'a,  T>,
897     {
898         let result = try!(self.parse_unspanned_seq(bra, ket, sep, f));
899         if result.is_empty() {
900             let last_span = self.last_span;
901             self.span_err(last_span,
902             "nullary enum variants are written with no trailing `( )`");
903         }
904         Ok(result)
905     }
906
907     // NB: Do not use this function unless you actually plan to place the
908     // spanned list in the AST.
909     pub fn parse_seq<T, F>(&mut self,
910                            bra: &token::Token,
911                            ket: &token::Token,
912                            sep: SeqSep,
913                            f: F)
914                            -> PResult<'a, Spanned<Vec<T>>> where
915         F: FnMut(&mut Parser<'a>) -> PResult<'a,  T>,
916     {
917         let lo = self.span.lo;
918         try!(self.expect(bra));
919         let result = try!(self.parse_seq_to_before_end(ket, sep, f));
920         let hi = self.span.hi;
921         self.bump();
922         Ok(spanned(lo, hi, result))
923     }
924
925     /// Advance the parser by one token
926     pub fn bump(&mut self) {
927         self.last_span = self.span;
928         // Stash token for error recovery (sometimes; clone is not necessarily cheap).
929         self.last_token = if self.token.is_ident() ||
930                           self.token.is_path() ||
931                           self.token == token::Comma {
932             Some(Box::new(self.token.clone()))
933         } else {
934             None
935         };
936         let next = if self.buffer_start == self.buffer_end {
937             self.reader.real_token()
938         } else {
939             // Avoid token copies with `replace`.
940             let buffer_start = self.buffer_start as usize;
941             let next_index = (buffer_start + 1) & 3;
942             self.buffer_start = next_index as isize;
943
944             let placeholder = TokenAndSpan {
945                 tok: token::Underscore,
946                 sp: self.span,
947             };
948             mem::replace(&mut self.buffer[buffer_start], placeholder)
949         };
950         self.span = next.sp;
951         self.token = next.tok;
952         self.tokens_consumed += 1;
953         self.expected_tokens.clear();
954         // check after each token
955         self.check_unknown_macro_variable();
956     }
957
958     /// Advance the parser by one token and return the bumped token.
959     pub fn bump_and_get(&mut self) -> token::Token {
960         let old_token = mem::replace(&mut self.token, token::Underscore);
961         self.bump();
962         old_token
963     }
964
965     /// EFFECT: replace the current token and span with the given one
966     pub fn replace_token(&mut self,
967                          next: token::Token,
968                          lo: BytePos,
969                          hi: BytePos) {
970         self.last_span = mk_sp(self.span.lo, lo);
971         self.token = next;
972         self.span = mk_sp(lo, hi);
973     }
974     pub fn buffer_length(&mut self) -> isize {
975         if self.buffer_start <= self.buffer_end {
976             return self.buffer_end - self.buffer_start;
977         }
978         return (4 - self.buffer_start) + self.buffer_end;
979     }
980     pub fn look_ahead<R, F>(&mut self, distance: usize, f: F) -> R where
981         F: FnOnce(&token::Token) -> R,
982     {
983         let dist = distance as isize;
984         while self.buffer_length() < dist {
985             self.buffer[self.buffer_end as usize] = self.reader.real_token();
986             self.buffer_end = (self.buffer_end + 1) & 3;
987         }
988         f(&self.buffer[((self.buffer_start + dist - 1) & 3) as usize].tok)
989     }
990     pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
991         self.sess.span_diagnostic.struct_span_fatal(self.span, m)
992     }
993     pub fn span_fatal(&self, sp: Span, m: &str) -> DiagnosticBuilder<'a> {
994         self.sess.span_diagnostic.struct_span_fatal(sp, m)
995     }
996     pub fn span_fatal_help(&self, sp: Span, m: &str, help: &str) -> DiagnosticBuilder<'a> {
997         let mut err = self.sess.span_diagnostic.struct_span_fatal(sp, m);
998         err.fileline_help(sp, help);
999         err
1000     }
1001     pub fn bug(&self, m: &str) -> ! {
1002         self.sess.span_diagnostic.span_bug(self.span, m)
1003     }
1004     pub fn warn(&self, m: &str) {
1005         self.sess.span_diagnostic.span_warn(self.span, m)
1006     }
1007     pub fn span_warn(&self, sp: Span, m: &str) {
1008         self.sess.span_diagnostic.span_warn(sp, m)
1009     }
1010     pub fn span_err(&self, sp: Span, m: &str) {
1011         self.sess.span_diagnostic.span_err(sp, m)
1012     }
1013     pub fn span_bug(&self, sp: Span, m: &str) -> ! {
1014         self.sess.span_diagnostic.span_bug(sp, m)
1015     }
1016     pub fn abort_if_errors(&self) {
1017         self.sess.span_diagnostic.abort_if_errors();
1018     }
1019
1020     pub fn diagnostic(&self) -> &'a errors::Handler {
1021         &self.sess.span_diagnostic
1022     }
1023
1024     pub fn id_to_interned_str(&mut self, id: Ident) -> InternedString {
1025         id.name.as_str()
1026     }
1027
1028     /// Is the current token one of the keywords that signals a bare function
1029     /// type?
1030     pub fn token_is_bare_fn_keyword(&mut self) -> bool {
1031         self.check_keyword(keywords::Fn) ||
1032             self.check_keyword(keywords::Unsafe) ||
1033             self.check_keyword(keywords::Extern)
1034     }
1035
1036     pub fn get_lifetime(&mut self) -> ast::Ident {
1037         match self.token {
1038             token::Lifetime(ref ident) => *ident,
1039             _ => self.bug("not a lifetime"),
1040         }
1041     }
1042
1043     pub fn parse_for_in_type(&mut self) -> PResult<'a, Ty_> {
1044         /*
1045         Parses whatever can come after a `for` keyword in a type.
1046         The `for` has already been consumed.
1047
1048         Deprecated:
1049
1050         - for <'lt> |S| -> T
1051
1052         Eventually:
1053
1054         - for <'lt> [unsafe] [extern "ABI"] fn (S) -> T
1055         - for <'lt> path::foo(a, b)
1056
1057         */
1058
1059         // parse <'lt>
1060         let lo = self.span.lo;
1061
1062         let lifetime_defs = try!(self.parse_late_bound_lifetime_defs());
1063
1064         // examine next token to decide to do
1065         if self.token_is_bare_fn_keyword() {
1066             self.parse_ty_bare_fn(lifetime_defs)
1067         } else {
1068             let hi = self.span.hi;
1069             let trait_ref = try!(self.parse_trait_ref());
1070             let poly_trait_ref = ast::PolyTraitRef { bound_lifetimes: lifetime_defs,
1071                                                      trait_ref: trait_ref,
1072                                                      span: mk_sp(lo, hi)};
1073             let other_bounds = if self.eat(&token::BinOp(token::Plus)) {
1074                 try!(self.parse_ty_param_bounds(BoundParsingMode::Bare))
1075             } else {
1076                 P::empty()
1077             };
1078             let all_bounds =
1079                 Some(TraitTyParamBound(poly_trait_ref, TraitBoundModifier::None)).into_iter()
1080                 .chain(other_bounds.into_vec())
1081                 .collect();
1082             Ok(ast::TyPolyTraitRef(all_bounds))
1083         }
1084     }
1085
1086     pub fn parse_ty_path(&mut self) -> PResult<'a, Ty_> {
1087         Ok(TyPath(None, try!(self.parse_path(LifetimeAndTypesWithoutColons))))
1088     }
1089
1090     /// parse a TyBareFn type:
1091     pub fn parse_ty_bare_fn(&mut self, lifetime_defs: Vec<ast::LifetimeDef>) -> PResult<'a, Ty_> {
1092         /*
1093
1094         [unsafe] [extern "ABI"] fn <'lt> (S) -> T
1095          ^~~~^           ^~~~^     ^~~~^ ^~^    ^
1096            |               |         |    |     |
1097            |               |         |    |   Return type
1098            |               |         |  Argument types
1099            |               |     Lifetimes
1100            |              ABI
1101         Function Style
1102         */
1103
1104         let unsafety = try!(self.parse_unsafety());
1105         let abi = if self.eat_keyword(keywords::Extern) {
1106             try!(self.parse_opt_abi()).unwrap_or(abi::C)
1107         } else {
1108             abi::Rust
1109         };
1110
1111         try!(self.expect_keyword(keywords::Fn));
1112         let (inputs, variadic) = try!(self.parse_fn_args(false, true));
1113         let ret_ty = try!(self.parse_ret_ty());
1114         let decl = P(FnDecl {
1115             inputs: inputs,
1116             output: ret_ty,
1117             variadic: variadic
1118         });
1119         Ok(TyBareFn(P(BareFnTy {
1120             abi: abi,
1121             unsafety: unsafety,
1122             lifetimes: lifetime_defs,
1123             decl: decl
1124         })))
1125     }
1126
1127     /// Parses an obsolete closure kind (`&:`, `&mut:`, or `:`).
1128     pub fn parse_obsolete_closure_kind(&mut self) -> PResult<'a, ()> {
1129          let lo = self.span.lo;
1130         if
1131             self.check(&token::BinOp(token::And)) &&
1132             self.look_ahead(1, |t| t.is_keyword(keywords::Mut)) &&
1133             self.look_ahead(2, |t| *t == token::Colon)
1134         {
1135             self.bump();
1136             self.bump();
1137             self.bump();
1138         } else if
1139             self.token == token::BinOp(token::And) &&
1140             self.look_ahead(1, |t| *t == token::Colon)
1141         {
1142             self.bump();
1143             self.bump();
1144         } else if
1145             self.eat(&token::Colon)
1146         {
1147             /* nothing */
1148         } else {
1149             return Ok(());
1150         }
1151
1152         let span = mk_sp(lo, self.span.hi);
1153         self.obsolete(span, ObsoleteSyntax::ClosureKind);
1154         Ok(())
1155     }
1156
1157     pub fn parse_unsafety(&mut self) -> PResult<'a, Unsafety> {
1158         if self.eat_keyword(keywords::Unsafe) {
1159             return Ok(Unsafety::Unsafe);
1160         } else {
1161             return Ok(Unsafety::Normal);
1162         }
1163     }
1164
1165     /// Parse the items in a trait declaration
1166     pub fn parse_trait_items(&mut self) -> PResult<'a,  Vec<P<TraitItem>>> {
1167         self.parse_unspanned_seq(
1168             &token::OpenDelim(token::Brace),
1169             &token::CloseDelim(token::Brace),
1170             seq_sep_none(),
1171             |p| -> PResult<'a, P<TraitItem>> {
1172             maybe_whole!(no_clone p, NtTraitItem);
1173             let mut attrs = try!(p.parse_outer_attributes());
1174             let lo = p.span.lo;
1175
1176             let (name, node) = if p.eat_keyword(keywords::Type) {
1177                 let TyParam {ident, bounds, default, ..} = try!(p.parse_ty_param());
1178                 try!(p.expect(&token::Semi));
1179                 (ident, TypeTraitItem(bounds, default))
1180             } else if p.is_const_item() {
1181                 try!(p.expect_keyword(keywords::Const));
1182                 let ident = try!(p.parse_ident());
1183                 try!(p.expect(&token::Colon));
1184                 let ty = try!(p.parse_ty_sum());
1185                 let default = if p.check(&token::Eq) {
1186                     p.bump();
1187                     let expr = try!(p.parse_expr());
1188                     try!(p.commit_expr_expecting(&expr, token::Semi));
1189                     Some(expr)
1190                 } else {
1191                     try!(p.expect(&token::Semi));
1192                     None
1193                 };
1194                 (ident, ConstTraitItem(ty, default))
1195             } else {
1196                 let (constness, unsafety, abi) = try!(p.parse_fn_front_matter());
1197
1198                 let ident = try!(p.parse_ident());
1199                 let mut generics = try!(p.parse_generics());
1200
1201                 let (explicit_self, d) = try!(p.parse_fn_decl_with_self(|p: &mut Parser<'a>|{
1202                     // This is somewhat dubious; We don't want to allow
1203                     // argument names to be left off if there is a
1204                     // definition...
1205                     p.parse_arg_general(false)
1206                 }));
1207
1208                 generics.where_clause = try!(p.parse_where_clause());
1209                 let sig = ast::MethodSig {
1210                     unsafety: unsafety,
1211                     constness: constness,
1212                     decl: d,
1213                     generics: generics,
1214                     abi: abi,
1215                     explicit_self: explicit_self,
1216                 };
1217
1218                 let body = match p.token {
1219                   token::Semi => {
1220                     p.bump();
1221                     debug!("parse_trait_methods(): parsing required method");
1222                     None
1223                   }
1224                   token::OpenDelim(token::Brace) => {
1225                     debug!("parse_trait_methods(): parsing provided method");
1226                     let (inner_attrs, body) =
1227                         try!(p.parse_inner_attrs_and_block());
1228                     attrs.extend(inner_attrs.iter().cloned());
1229                     Some(body)
1230                   }
1231
1232                   _ => {
1233                       let token_str = p.this_token_to_string();
1234                       return Err(p.fatal(&format!("expected `;` or `{{`, found `{}`",
1235                                        token_str)[..]))
1236                   }
1237                 };
1238                 (ident, ast::MethodTraitItem(sig, body))
1239             };
1240
1241             Ok(P(TraitItem {
1242                 id: ast::DUMMY_NODE_ID,
1243                 ident: name,
1244                 attrs: attrs,
1245                 node: node,
1246                 span: mk_sp(lo, p.last_span.hi),
1247             }))
1248         })
1249     }
1250
1251     /// Parse a possibly mutable type
1252     pub fn parse_mt(&mut self) -> PResult<'a, MutTy> {
1253         let mutbl = try!(self.parse_mutability());
1254         let t = try!(self.parse_ty());
1255         Ok(MutTy { ty: t, mutbl: mutbl })
1256     }
1257
1258     /// Parse optional return type [ -> TY ] in function decl
1259     pub fn parse_ret_ty(&mut self) -> PResult<'a, FunctionRetTy> {
1260         if self.eat(&token::RArrow) {
1261             if self.eat(&token::Not) {
1262                 Ok(NoReturn(self.last_span))
1263             } else {
1264                 Ok(Return(try!(self.parse_ty())))
1265             }
1266         } else {
1267             let pos = self.span.lo;
1268             Ok(DefaultReturn(mk_sp(pos, pos)))
1269         }
1270     }
1271
1272     /// Parse a type in a context where `T1+T2` is allowed.
1273     pub fn parse_ty_sum(&mut self) -> PResult<'a, P<Ty>> {
1274         let lo = self.span.lo;
1275         let lhs = try!(self.parse_ty());
1276
1277         if !self.eat(&token::BinOp(token::Plus)) {
1278             return Ok(lhs);
1279         }
1280
1281         let bounds = try!(self.parse_ty_param_bounds(BoundParsingMode::Bare));
1282
1283         // In type grammar, `+` is treated like a binary operator,
1284         // and hence both L and R side are required.
1285         if bounds.is_empty() {
1286             let last_span = self.last_span;
1287             self.span_err(last_span,
1288                           "at least one type parameter bound \
1289                           must be specified");
1290         }
1291
1292         let sp = mk_sp(lo, self.last_span.hi);
1293         let sum = ast::TyObjectSum(lhs, bounds);
1294         Ok(P(Ty {id: ast::DUMMY_NODE_ID, node: sum, span: sp}))
1295     }
1296
1297     /// Parse a type.
1298     pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
1299         maybe_whole!(no_clone self, NtTy);
1300
1301         let lo = self.span.lo;
1302
1303         let t = if self.check(&token::OpenDelim(token::Paren)) {
1304             self.bump();
1305
1306             // (t) is a parenthesized ty
1307             // (t,) is the type of a tuple with only one field,
1308             // of type t
1309             let mut ts = vec![];
1310             let mut last_comma = false;
1311             while self.token != token::CloseDelim(token::Paren) {
1312                 ts.push(try!(self.parse_ty_sum()));
1313                 if self.check(&token::Comma) {
1314                     last_comma = true;
1315                     self.bump();
1316                 } else {
1317                     last_comma = false;
1318                     break;
1319                 }
1320             }
1321
1322             try!(self.expect(&token::CloseDelim(token::Paren)));
1323             if ts.len() == 1 && !last_comma {
1324                 TyParen(ts.into_iter().nth(0).unwrap())
1325             } else {
1326                 TyTup(ts)
1327             }
1328         } else if self.check(&token::BinOp(token::Star)) {
1329             // STAR POINTER (bare pointer?)
1330             self.bump();
1331             TyPtr(try!(self.parse_ptr()))
1332         } else if self.check(&token::OpenDelim(token::Bracket)) {
1333             // VECTOR
1334             try!(self.expect(&token::OpenDelim(token::Bracket)));
1335             let t = try!(self.parse_ty_sum());
1336
1337             // Parse the `; e` in `[ i32; e ]`
1338             // where `e` is a const expression
1339             let t = match try!(self.maybe_parse_fixed_length_of_vec()) {
1340                 None => TyVec(t),
1341                 Some(suffix) => TyFixedLengthVec(t, suffix)
1342             };
1343             try!(self.expect(&token::CloseDelim(token::Bracket)));
1344             t
1345         } else if self.check(&token::BinOp(token::And)) ||
1346                   self.token == token::AndAnd {
1347             // BORROWED POINTER
1348             try!(self.expect_and());
1349             try!(self.parse_borrowed_pointee())
1350         } else if self.check_keyword(keywords::For) {
1351             try!(self.parse_for_in_type())
1352         } else if self.token_is_bare_fn_keyword() {
1353             // BARE FUNCTION
1354             try!(self.parse_ty_bare_fn(Vec::new()))
1355         } else if self.eat_keyword_noexpect(keywords::Typeof) {
1356             // TYPEOF
1357             // In order to not be ambiguous, the type must be surrounded by parens.
1358             try!(self.expect(&token::OpenDelim(token::Paren)));
1359             let e = try!(self.parse_expr());
1360             try!(self.expect(&token::CloseDelim(token::Paren)));
1361             TyTypeof(e)
1362         } else if self.eat_lt() {
1363
1364             let (qself, path) =
1365                  try!(self.parse_qualified_path(NoTypesAllowed));
1366
1367             TyPath(Some(qself), path)
1368         } else if self.check(&token::ModSep) ||
1369                   self.token.is_ident() ||
1370                   self.token.is_path() {
1371             let path = try!(self.parse_path(LifetimeAndTypesWithoutColons));
1372             if self.check(&token::Not) {
1373                 // MACRO INVOCATION
1374                 self.bump();
1375                 let delim = try!(self.expect_open_delim());
1376                 let tts = try!(self.parse_seq_to_end(&token::CloseDelim(delim),
1377                                                      seq_sep_none(),
1378                                                      |p| p.parse_token_tree()));
1379                 let hi = self.span.hi;
1380                 TyMac(spanned(lo, hi, Mac_ { path: path, tts: tts, ctxt: EMPTY_CTXT }))
1381             } else {
1382                 // NAMED TYPE
1383                 TyPath(None, path)
1384             }
1385         } else if self.eat(&token::Underscore) {
1386             // TYPE TO BE INFERRED
1387             TyInfer
1388         } else {
1389             let this_token_str = self.this_token_to_string();
1390             let msg = format!("expected type, found `{}`", this_token_str);
1391             return Err(self.fatal(&msg[..]));
1392         };
1393
1394         let sp = mk_sp(lo, self.last_span.hi);
1395         Ok(P(Ty {id: ast::DUMMY_NODE_ID, node: t, span: sp}))
1396     }
1397
1398     pub fn parse_borrowed_pointee(&mut self) -> PResult<'a, Ty_> {
1399         // look for `&'lt` or `&'foo ` and interpret `foo` as the region name:
1400         let opt_lifetime = try!(self.parse_opt_lifetime());
1401
1402         let mt = try!(self.parse_mt());
1403         return Ok(TyRptr(opt_lifetime, mt));
1404     }
1405
1406     pub fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
1407         let mutbl = if self.eat_keyword(keywords::Mut) {
1408             MutMutable
1409         } else if self.eat_keyword(keywords::Const) {
1410             MutImmutable
1411         } else {
1412             let span = self.last_span;
1413             self.span_err(span,
1414                           "bare raw pointers are no longer allowed, you should \
1415                            likely use `*mut T`, but otherwise `*T` is now \
1416                            known as `*const T`");
1417             MutImmutable
1418         };
1419         let t = try!(self.parse_ty());
1420         Ok(MutTy { ty: t, mutbl: mutbl })
1421     }
1422
1423     pub fn is_named_argument(&mut self) -> bool {
1424         let offset = match self.token {
1425             token::BinOp(token::And) => 1,
1426             token::AndAnd => 1,
1427             _ if self.token.is_keyword(keywords::Mut) => 1,
1428             _ => 0
1429         };
1430
1431         debug!("parser is_named_argument offset:{}", offset);
1432
1433         if offset == 0 {
1434             is_plain_ident_or_underscore(&self.token)
1435                 && self.look_ahead(1, |t| *t == token::Colon)
1436         } else {
1437             self.look_ahead(offset, |t| is_plain_ident_or_underscore(t))
1438                 && self.look_ahead(offset + 1, |t| *t == token::Colon)
1439         }
1440     }
1441
1442     /// This version of parse arg doesn't necessarily require
1443     /// identifier names.
1444     pub fn parse_arg_general(&mut self, require_name: bool) -> PResult<'a, Arg> {
1445         maybe_whole!(no_clone self, NtArg);
1446
1447         let pat = if require_name || self.is_named_argument() {
1448             debug!("parse_arg_general parse_pat (require_name:{})",
1449                    require_name);
1450             let pat = try!(self.parse_pat());
1451
1452             try!(self.expect(&token::Colon));
1453             pat
1454         } else {
1455             debug!("parse_arg_general ident_to_pat");
1456             ast_util::ident_to_pat(ast::DUMMY_NODE_ID,
1457                                    self.last_span,
1458                                    special_idents::invalid)
1459         };
1460
1461         let t = try!(self.parse_ty_sum());
1462
1463         Ok(Arg {
1464             ty: t,
1465             pat: pat,
1466             id: ast::DUMMY_NODE_ID,
1467         })
1468     }
1469
1470     /// Parse a single function argument
1471     pub fn parse_arg(&mut self) -> PResult<'a, Arg> {
1472         self.parse_arg_general(true)
1473     }
1474
1475     /// Parse an argument in a lambda header e.g. |arg, arg|
1476     pub fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
1477         let pat = try!(self.parse_pat());
1478         let t = if self.eat(&token::Colon) {
1479             try!(self.parse_ty_sum())
1480         } else {
1481             P(Ty {
1482                 id: ast::DUMMY_NODE_ID,
1483                 node: TyInfer,
1484                 span: mk_sp(self.span.lo, self.span.hi),
1485             })
1486         };
1487         Ok(Arg {
1488             ty: t,
1489             pat: pat,
1490             id: ast::DUMMY_NODE_ID
1491         })
1492     }
1493
1494     pub fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
1495         if self.check(&token::Semi) {
1496             self.bump();
1497             Ok(Some(try!(self.parse_expr())))
1498         } else {
1499             Ok(None)
1500         }
1501     }
1502
1503     /// Matches token_lit = LIT_INTEGER | ...
1504     pub fn lit_from_token(&self, tok: &token::Token) -> PResult<'a, Lit_> {
1505         match *tok {
1506             token::Interpolated(token::NtExpr(ref v)) => {
1507                 match v.node {
1508                     ExprLit(ref lit) => { Ok(lit.node.clone()) }
1509                     _ => { return self.unexpected_last(tok); }
1510                 }
1511             }
1512             token::Literal(lit, suf) => {
1513                 let (suffix_illegal, out) = match lit {
1514                     token::Byte(i) => (true, LitByte(parse::byte_lit(&i.as_str()).0)),
1515                     token::Char(i) => (true, LitChar(parse::char_lit(&i.as_str()).0)),
1516
1517                     // there are some valid suffixes for integer and
1518                     // float literals, so all the handling is done
1519                     // internally.
1520                     token::Integer(s) => {
1521                         (false, parse::integer_lit(&s.as_str(),
1522                                                    suf.as_ref().map(|s| s.as_str()),
1523                                                    &self.sess.span_diagnostic,
1524                                                    self.last_span))
1525                     }
1526                     token::Float(s) => {
1527                         (false, parse::float_lit(&s.as_str(),
1528                                                  suf.as_ref().map(|s| s.as_str()),
1529                                                   &self.sess.span_diagnostic,
1530                                                  self.last_span))
1531                     }
1532
1533                     token::Str_(s) => {
1534                         (true,
1535                          LitStr(token::intern_and_get_ident(&parse::str_lit(&s.as_str())),
1536                                 ast::CookedStr))
1537                     }
1538                     token::StrRaw(s, n) => {
1539                         (true,
1540                          LitStr(
1541                             token::intern_and_get_ident(&parse::raw_str_lit(&s.as_str())),
1542                             ast::RawStr(n)))
1543                     }
1544                     token::ByteStr(i) =>
1545                         (true, LitByteStr(parse::byte_str_lit(&i.as_str()))),
1546                     token::ByteStrRaw(i, _) =>
1547                         (true,
1548                          LitByteStr(Rc::new(i.to_string().into_bytes()))),
1549                 };
1550
1551                 if suffix_illegal {
1552                     let sp = self.last_span;
1553                     self.expect_no_suffix(sp, &*format!("{} literal", lit.short_name()), suf)
1554                 }
1555
1556                 Ok(out)
1557             }
1558             _ => { return self.unexpected_last(tok); }
1559         }
1560     }
1561
1562     /// Matches lit = true | false | token_lit
1563     pub fn parse_lit(&mut self) -> PResult<'a, Lit> {
1564         let lo = self.span.lo;
1565         let lit = if self.eat_keyword(keywords::True) {
1566             LitBool(true)
1567         } else if self.eat_keyword(keywords::False) {
1568             LitBool(false)
1569         } else {
1570             let token = self.bump_and_get();
1571             let lit = try!(self.lit_from_token(&token));
1572             lit
1573         };
1574         Ok(codemap::Spanned { node: lit, span: mk_sp(lo, self.last_span.hi) })
1575     }
1576
1577     /// matches '-' lit | lit
1578     pub fn parse_pat_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1579         let minus_lo = self.span.lo;
1580         let minus_present = self.eat(&token::BinOp(token::Minus));
1581         let lo = self.span.lo;
1582         let literal = P(try!(self.parse_lit()));
1583         let hi = self.last_span.hi;
1584         let expr = self.mk_expr(lo, hi, ExprLit(literal), None);
1585
1586         if minus_present {
1587             let minus_hi = self.last_span.hi;
1588             let unary = self.mk_unary(UnNeg, expr);
1589             Ok(self.mk_expr(minus_lo, minus_hi, unary, None))
1590         } else {
1591             Ok(expr)
1592         }
1593     }
1594
1595     /// Parses qualified path.
1596     ///
1597     /// Assumes that the leading `<` has been parsed already.
1598     ///
1599     /// Qualifed paths are a part of the universal function call
1600     /// syntax (UFCS).
1601     ///
1602     /// `qualified_path = <type [as trait_ref]>::path`
1603     ///
1604     /// See `parse_path` for `mode` meaning.
1605     ///
1606     /// # Examples:
1607     ///
1608     /// `<T as U>::a`
1609     /// `<T as U>::F::a::<S>`
1610     pub fn parse_qualified_path(&mut self, mode: PathParsingMode)
1611                                 -> PResult<'a, (QSelf, ast::Path)> {
1612         let span = self.last_span;
1613         let self_type = try!(self.parse_ty_sum());
1614         let mut path = if self.eat_keyword(keywords::As) {
1615             try!(self.parse_path(LifetimeAndTypesWithoutColons))
1616         } else {
1617             ast::Path {
1618                 span: span,
1619                 global: false,
1620                 segments: vec![]
1621             }
1622         };
1623
1624         let qself = QSelf {
1625             ty: self_type,
1626             position: path.segments.len()
1627         };
1628
1629         try!(self.expect(&token::Gt));
1630         try!(self.expect(&token::ModSep));
1631
1632         let segments = match mode {
1633             LifetimeAndTypesWithoutColons => {
1634                 try!(self.parse_path_segments_without_colons())
1635             }
1636             LifetimeAndTypesWithColons => {
1637                 try!(self.parse_path_segments_with_colons())
1638             }
1639             NoTypesAllowed => {
1640                 try!(self.parse_path_segments_without_types())
1641             }
1642         };
1643         path.segments.extend(segments);
1644
1645         path.span.hi = self.last_span.hi;
1646
1647         Ok((qself, path))
1648     }
1649
1650     /// Parses a path and optional type parameter bounds, depending on the
1651     /// mode. The `mode` parameter determines whether lifetimes, types, and/or
1652     /// bounds are permitted and whether `::` must precede type parameter
1653     /// groups.
1654     pub fn parse_path(&mut self, mode: PathParsingMode) -> PResult<'a, ast::Path> {
1655         // Check for a whole path...
1656         let found = match self.token {
1657             token::Interpolated(token::NtPath(_)) => Some(self.bump_and_get()),
1658             _ => None,
1659         };
1660         if let Some(token::Interpolated(token::NtPath(path))) = found {
1661             return Ok(*path);
1662         }
1663
1664         let lo = self.span.lo;
1665         let is_global = self.eat(&token::ModSep);
1666
1667         // Parse any number of segments and bound sets. A segment is an
1668         // identifier followed by an optional lifetime and a set of types.
1669         // A bound set is a set of type parameter bounds.
1670         let segments = match mode {
1671             LifetimeAndTypesWithoutColons => {
1672                 try!(self.parse_path_segments_without_colons())
1673             }
1674             LifetimeAndTypesWithColons => {
1675                 try!(self.parse_path_segments_with_colons())
1676             }
1677             NoTypesAllowed => {
1678                 try!(self.parse_path_segments_without_types())
1679             }
1680         };
1681
1682         // Assemble the span.
1683         let span = mk_sp(lo, self.last_span.hi);
1684
1685         // Assemble the result.
1686         Ok(ast::Path {
1687             span: span,
1688             global: is_global,
1689             segments: segments,
1690         })
1691     }
1692
1693     /// Examples:
1694     /// - `a::b<T,U>::c<V,W>`
1695     /// - `a::b<T,U>::c(V) -> W`
1696     /// - `a::b<T,U>::c(V)`
1697     pub fn parse_path_segments_without_colons(&mut self) -> PResult<'a, Vec<ast::PathSegment>> {
1698         let mut segments = Vec::new();
1699         loop {
1700             // First, parse an identifier.
1701             let identifier = try!(self.parse_ident_or_self_type());
1702
1703             // Parse types, optionally.
1704             let parameters = if self.eat_lt() {
1705                 let (lifetimes, types, bindings) = try!(self.parse_generic_values_after_lt());
1706
1707                 ast::PathParameters::AngleBracketed(ast::AngleBracketedParameterData {
1708                     lifetimes: lifetimes,
1709                     types: P::from_vec(types),
1710                     bindings: P::from_vec(bindings),
1711                 })
1712             } else if self.eat(&token::OpenDelim(token::Paren)) {
1713                 let lo = self.last_span.lo;
1714
1715                 let inputs = try!(self.parse_seq_to_end(
1716                     &token::CloseDelim(token::Paren),
1717                     seq_sep_trailing_allowed(token::Comma),
1718                     |p| p.parse_ty_sum()));
1719
1720                 let output_ty = if self.eat(&token::RArrow) {
1721                     Some(try!(self.parse_ty()))
1722                 } else {
1723                     None
1724                 };
1725
1726                 let hi = self.last_span.hi;
1727
1728                 ast::PathParameters::Parenthesized(ast::ParenthesizedParameterData {
1729                     span: mk_sp(lo, hi),
1730                     inputs: inputs,
1731                     output: output_ty,
1732                 })
1733             } else {
1734                 ast::PathParameters::none()
1735             };
1736
1737             // Assemble and push the result.
1738             segments.push(ast::PathSegment { identifier: identifier,
1739                                              parameters: parameters });
1740
1741             // Continue only if we see a `::`
1742             if !self.eat(&token::ModSep) {
1743                 return Ok(segments);
1744             }
1745         }
1746     }
1747
1748     /// Examples:
1749     /// - `a::b::<T,U>::c`
1750     pub fn parse_path_segments_with_colons(&mut self) -> PResult<'a, Vec<ast::PathSegment>> {
1751         let mut segments = Vec::new();
1752         loop {
1753             // First, parse an identifier.
1754             let identifier = try!(self.parse_ident_or_self_type());
1755
1756             // If we do not see a `::`, stop.
1757             if !self.eat(&token::ModSep) {
1758                 segments.push(ast::PathSegment {
1759                     identifier: identifier,
1760                     parameters: ast::PathParameters::none()
1761                 });
1762                 return Ok(segments);
1763             }
1764
1765             // Check for a type segment.
1766             if self.eat_lt() {
1767                 // Consumed `a::b::<`, go look for types
1768                 let (lifetimes, types, bindings) = try!(self.parse_generic_values_after_lt());
1769                 let parameters = ast::AngleBracketedParameterData {
1770                     lifetimes: lifetimes,
1771                     types: P::from_vec(types),
1772                     bindings: P::from_vec(bindings),
1773                 };
1774                 segments.push(ast::PathSegment {
1775                     identifier: identifier,
1776                     parameters: ast::PathParameters::AngleBracketed(parameters),
1777                 });
1778
1779                 // Consumed `a::b::<T,U>`, check for `::` before proceeding
1780                 if !self.eat(&token::ModSep) {
1781                     return Ok(segments);
1782                 }
1783             } else {
1784                 // Consumed `a::`, go look for `b`
1785                 segments.push(ast::PathSegment {
1786                     identifier: identifier,
1787                     parameters: ast::PathParameters::none(),
1788                 });
1789             }
1790         }
1791     }
1792
1793
1794     /// Examples:
1795     /// - `a::b::c`
1796     pub fn parse_path_segments_without_types(&mut self) -> PResult<'a, Vec<ast::PathSegment>> {
1797         let mut segments = Vec::new();
1798         loop {
1799             // First, parse an identifier.
1800             let identifier = try!(self.parse_ident_or_self_type());
1801
1802             // Assemble and push the result.
1803             segments.push(ast::PathSegment {
1804                 identifier: identifier,
1805                 parameters: ast::PathParameters::none()
1806             });
1807
1808             // If we do not see a `::`, stop.
1809             if !self.eat(&token::ModSep) {
1810                 return Ok(segments);
1811             }
1812         }
1813     }
1814
1815     /// parses 0 or 1 lifetime
1816     pub fn parse_opt_lifetime(&mut self) -> PResult<'a, Option<ast::Lifetime>> {
1817         match self.token {
1818             token::Lifetime(..) => {
1819                 Ok(Some(try!(self.parse_lifetime())))
1820             }
1821             _ => {
1822                 Ok(None)
1823             }
1824         }
1825     }
1826
1827     /// Parses a single lifetime
1828     /// Matches lifetime = LIFETIME
1829     pub fn parse_lifetime(&mut self) -> PResult<'a, ast::Lifetime> {
1830         match self.token {
1831             token::Lifetime(i) => {
1832                 let span = self.span;
1833                 self.bump();
1834                 return Ok(ast::Lifetime {
1835                     id: ast::DUMMY_NODE_ID,
1836                     span: span,
1837                     name: i.name
1838                 });
1839             }
1840             _ => {
1841                 return Err(self.fatal("expected a lifetime name"));
1842             }
1843         }
1844     }
1845
1846     /// Parses `lifetime_defs = [ lifetime_defs { ',' lifetime_defs } ]` where `lifetime_def  =
1847     /// lifetime [':' lifetimes]`
1848     pub fn parse_lifetime_defs(&mut self) -> PResult<'a, Vec<ast::LifetimeDef>> {
1849
1850         let mut res = Vec::new();
1851         loop {
1852             match self.token {
1853                 token::Lifetime(_) => {
1854                     let lifetime = try!(self.parse_lifetime());
1855                     let bounds =
1856                         if self.eat(&token::Colon) {
1857                             try!(self.parse_lifetimes(token::BinOp(token::Plus)))
1858                         } else {
1859                             Vec::new()
1860                         };
1861                     res.push(ast::LifetimeDef { lifetime: lifetime,
1862                                                 bounds: bounds });
1863                 }
1864
1865                 _ => {
1866                     return Ok(res);
1867                 }
1868             }
1869
1870             match self.token {
1871                 token::Comma => { self.bump();}
1872                 token::Gt => { return Ok(res); }
1873                 token::BinOp(token::Shr) => { return Ok(res); }
1874                 _ => {
1875                     let this_token_str = self.this_token_to_string();
1876                     let msg = format!("expected `,` or `>` after lifetime \
1877                                       name, found `{}`",
1878                                       this_token_str);
1879                     return Err(self.fatal(&msg[..]));
1880                 }
1881             }
1882         }
1883     }
1884
1885     /// matches lifetimes = ( lifetime ) | ( lifetime , lifetimes ) actually, it matches the empty
1886     /// one too, but putting that in there messes up the grammar....
1887     ///
1888     /// Parses zero or more comma separated lifetimes. Expects each lifetime to be followed by
1889     /// either a comma or `>`.  Used when parsing type parameter lists, where we expect something
1890     /// like `<'a, 'b, T>`.
1891     pub fn parse_lifetimes(&mut self, sep: token::Token) -> PResult<'a, Vec<ast::Lifetime>> {
1892
1893         let mut res = Vec::new();
1894         loop {
1895             match self.token {
1896                 token::Lifetime(_) => {
1897                     res.push(try!(self.parse_lifetime()));
1898                 }
1899                 _ => {
1900                     return Ok(res);
1901                 }
1902             }
1903
1904             if self.token != sep {
1905                 return Ok(res);
1906             }
1907
1908             self.bump();
1909         }
1910     }
1911
1912     /// Parse mutability declaration (mut/const/imm)
1913     pub fn parse_mutability(&mut self) -> PResult<'a, Mutability> {
1914         if self.eat_keyword(keywords::Mut) {
1915             Ok(MutMutable)
1916         } else {
1917             Ok(MutImmutable)
1918         }
1919     }
1920
1921     /// Parse ident COLON expr
1922     pub fn parse_field(&mut self) -> PResult<'a, Field> {
1923         let lo = self.span.lo;
1924         let i = try!(self.parse_ident());
1925         let hi = self.last_span.hi;
1926         try!(self.expect(&token::Colon));
1927         let e = try!(self.parse_expr());
1928         Ok(ast::Field {
1929             ident: spanned(lo, hi, i),
1930             span: mk_sp(lo, e.span.hi),
1931             expr: e,
1932         })
1933     }
1934
1935     pub fn mk_expr(&mut self, lo: BytePos, hi: BytePos,
1936                    node: Expr_, attrs: ThinAttributes) -> P<Expr> {
1937         P(Expr {
1938             id: ast::DUMMY_NODE_ID,
1939             node: node,
1940             span: mk_sp(lo, hi),
1941             attrs: attrs,
1942         })
1943     }
1944
1945     pub fn mk_unary(&mut self, unop: ast::UnOp, expr: P<Expr>) -> ast::Expr_ {
1946         ExprUnary(unop, expr)
1947     }
1948
1949     pub fn mk_binary(&mut self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::Expr_ {
1950         ExprBinary(binop, lhs, rhs)
1951     }
1952
1953     pub fn mk_call(&mut self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::Expr_ {
1954         ExprCall(f, args)
1955     }
1956
1957     fn mk_method_call(&mut self,
1958                       ident: ast::SpannedIdent,
1959                       tps: Vec<P<Ty>>,
1960                       args: Vec<P<Expr>>)
1961                       -> ast::Expr_ {
1962         ExprMethodCall(ident, tps, args)
1963     }
1964
1965     pub fn mk_index(&mut self, expr: P<Expr>, idx: P<Expr>) -> ast::Expr_ {
1966         ExprIndex(expr, idx)
1967     }
1968
1969     pub fn mk_range(&mut self,
1970                     start: Option<P<Expr>>,
1971                     end: Option<P<Expr>>)
1972                     -> ast::Expr_ {
1973         ExprRange(start, end)
1974     }
1975
1976     pub fn mk_field(&mut self, expr: P<Expr>, ident: ast::SpannedIdent) -> ast::Expr_ {
1977         ExprField(expr, ident)
1978     }
1979
1980     pub fn mk_tup_field(&mut self, expr: P<Expr>, idx: codemap::Spanned<usize>) -> ast::Expr_ {
1981         ExprTupField(expr, idx)
1982     }
1983
1984     pub fn mk_assign_op(&mut self, binop: ast::BinOp,
1985                         lhs: P<Expr>, rhs: P<Expr>) -> ast::Expr_ {
1986         ExprAssignOp(binop, lhs, rhs)
1987     }
1988
1989     pub fn mk_mac_expr(&mut self, lo: BytePos, hi: BytePos,
1990                        m: Mac_, attrs: ThinAttributes) -> P<Expr> {
1991         P(Expr {
1992             id: ast::DUMMY_NODE_ID,
1993             node: ExprMac(codemap::Spanned {node: m, span: mk_sp(lo, hi)}),
1994             span: mk_sp(lo, hi),
1995             attrs: attrs,
1996         })
1997     }
1998
1999     pub fn mk_lit_u32(&mut self, i: u32, attrs: ThinAttributes) -> P<Expr> {
2000         let span = &self.span;
2001         let lv_lit = P(codemap::Spanned {
2002             node: LitInt(i as u64, ast::UnsignedIntLit(TyU32)),
2003             span: *span
2004         });
2005
2006         P(Expr {
2007             id: ast::DUMMY_NODE_ID,
2008             node: ExprLit(lv_lit),
2009             span: *span,
2010             attrs: attrs,
2011         })
2012     }
2013
2014     fn expect_open_delim(&mut self) -> PResult<'a, token::DelimToken> {
2015         self.expected_tokens.push(TokenType::Token(token::Gt));
2016         match self.token {
2017             token::OpenDelim(delim) => {
2018                 self.bump();
2019                 Ok(delim)
2020             },
2021             _ => Err(self.fatal("expected open delimiter")),
2022         }
2023     }
2024
2025     /// At the bottom (top?) of the precedence hierarchy,
2026     /// parse things like parenthesized exprs,
2027     /// macros, return, etc.
2028     ///
2029     /// NB: This does not parse outer attributes,
2030     ///     and is private because it only works
2031     ///     correctly if called from parse_dot_or_call_expr().
2032     fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
2033         maybe_whole_expr!(self);
2034
2035         // Outer attributes are already parsed and will be
2036         // added to the return value after the fact.
2037         //
2038         // Therefore, prevent sub-parser from parsing
2039         // attributes by giving them a empty "already parsed" list.
2040         let mut attrs = None;
2041
2042         let lo = self.span.lo;
2043         let mut hi = self.span.hi;
2044
2045         let ex: Expr_;
2046
2047         // Note: when adding new syntax here, don't forget to adjust Token::can_begin_expr().
2048         match self.token {
2049             token::OpenDelim(token::Paren) => {
2050                 self.bump();
2051
2052                 let attrs = try!(self.parse_inner_attributes())
2053                     .into_thin_attrs()
2054                     .prepend(attrs);
2055
2056                 // (e) is parenthesized e
2057                 // (e,) is a tuple with only one field, e
2058                 let mut es = vec![];
2059                 let mut trailing_comma = false;
2060                 while self.token != token::CloseDelim(token::Paren) {
2061                     es.push(try!(self.parse_expr()));
2062                     try!(self.commit_expr(&**es.last().unwrap(), &[],
2063                                      &[token::Comma, token::CloseDelim(token::Paren)]));
2064                     if self.check(&token::Comma) {
2065                         trailing_comma = true;
2066
2067                         self.bump();
2068                     } else {
2069                         trailing_comma = false;
2070                         break;
2071                     }
2072                 }
2073                 self.bump();
2074
2075                 hi = self.last_span.hi;
2076                 return if es.len() == 1 && !trailing_comma {
2077                     Ok(self.mk_expr(lo, hi, ExprParen(es.into_iter().nth(0).unwrap()), attrs))
2078                 } else {
2079                     Ok(self.mk_expr(lo, hi, ExprTup(es), attrs))
2080                 }
2081             },
2082             token::OpenDelim(token::Brace) => {
2083                 return self.parse_block_expr(lo, DefaultBlock, attrs);
2084             },
2085             token::BinOp(token::Or) |  token::OrOr => {
2086                 let lo = self.span.lo;
2087                 return self.parse_lambda_expr(lo, CaptureByRef, attrs);
2088             },
2089             token::Ident(id @ ast::Ident {
2090                             name: token::SELF_KEYWORD_NAME,
2091                             ctxt: _
2092                          }, token::Plain) => {
2093                 self.bump();
2094                 let path = ast_util::ident_to_path(mk_sp(lo, hi), id);
2095                 ex = ExprPath(None, path);
2096                 hi = self.last_span.hi;
2097             }
2098             token::OpenDelim(token::Bracket) => {
2099                 self.bump();
2100
2101                 let inner_attrs = try!(self.parse_inner_attributes())
2102                     .into_thin_attrs();
2103                 attrs.update(|attrs| attrs.append(inner_attrs));
2104
2105                 if self.check(&token::CloseDelim(token::Bracket)) {
2106                     // Empty vector.
2107                     self.bump();
2108                     ex = ExprVec(Vec::new());
2109                 } else {
2110                     // Nonempty vector.
2111                     let first_expr = try!(self.parse_expr());
2112                     if self.check(&token::Semi) {
2113                         // Repeating array syntax: [ 0; 512 ]
2114                         self.bump();
2115                         let count = try!(self.parse_expr());
2116                         try!(self.expect(&token::CloseDelim(token::Bracket)));
2117                         ex = ExprRepeat(first_expr, count);
2118                     } else if self.check(&token::Comma) {
2119                         // Vector with two or more elements.
2120                         self.bump();
2121                         let remaining_exprs = try!(self.parse_seq_to_end(
2122                             &token::CloseDelim(token::Bracket),
2123                             seq_sep_trailing_allowed(token::Comma),
2124                             |p| Ok(try!(p.parse_expr()))
2125                                 ));
2126                         let mut exprs = vec!(first_expr);
2127                         exprs.extend(remaining_exprs);
2128                         ex = ExprVec(exprs);
2129                     } else {
2130                         // Vector with one element.
2131                         try!(self.expect(&token::CloseDelim(token::Bracket)));
2132                         ex = ExprVec(vec!(first_expr));
2133                     }
2134                 }
2135                 hi = self.last_span.hi;
2136             }
2137             _ => {
2138                 if self.eat_lt() {
2139                     let (qself, path) =
2140                         try!(self.parse_qualified_path(LifetimeAndTypesWithColons));
2141                     hi = path.span.hi;
2142                     return Ok(self.mk_expr(lo, hi, ExprPath(Some(qself), path), attrs));
2143                 }
2144                 if self.eat_keyword(keywords::Move) {
2145                     let lo = self.last_span.lo;
2146                     return self.parse_lambda_expr(lo, CaptureByValue, attrs);
2147                 }
2148                 if self.eat_keyword(keywords::If) {
2149                     return self.parse_if_expr(attrs);
2150                 }
2151                 if self.eat_keyword(keywords::For) {
2152                     let lo = self.last_span.lo;
2153                     return self.parse_for_expr(None, lo, attrs);
2154                 }
2155                 if self.eat_keyword(keywords::While) {
2156                     let lo = self.last_span.lo;
2157                     return self.parse_while_expr(None, lo, attrs);
2158                 }
2159                 if self.token.is_lifetime() {
2160                     let lifetime = self.get_lifetime();
2161                     let lo = self.span.lo;
2162                     self.bump();
2163                     try!(self.expect(&token::Colon));
2164                     if self.eat_keyword(keywords::While) {
2165                         return self.parse_while_expr(Some(lifetime), lo, attrs)
2166                     }
2167                     if self.eat_keyword(keywords::For) {
2168                         return self.parse_for_expr(Some(lifetime), lo, attrs)
2169                     }
2170                     if self.eat_keyword(keywords::Loop) {
2171                         return self.parse_loop_expr(Some(lifetime), lo, attrs)
2172                     }
2173                     return Err(self.fatal("expected `while`, `for`, or `loop` after a label"))
2174                 }
2175                 if self.eat_keyword(keywords::Loop) {
2176                     let lo = self.last_span.lo;
2177                     return self.parse_loop_expr(None, lo, attrs);
2178                 }
2179                 if self.eat_keyword(keywords::Continue) {
2180                     let ex = if self.token.is_lifetime() {
2181                         let ex = ExprAgain(Some(Spanned{
2182                             node: self.get_lifetime(),
2183                             span: self.span
2184                         }));
2185                         self.bump();
2186                         ex
2187                     } else {
2188                         ExprAgain(None)
2189                     };
2190                     let hi = self.last_span.hi;
2191                     return Ok(self.mk_expr(lo, hi, ex, attrs));
2192                 }
2193                 if self.eat_keyword(keywords::Match) {
2194                     return self.parse_match_expr(attrs);
2195                 }
2196                 if self.eat_keyword(keywords::Unsafe) {
2197                     return self.parse_block_expr(
2198                         lo,
2199                         UnsafeBlock(ast::UserProvided),
2200                         attrs);
2201                 }
2202                 if self.eat_keyword(keywords::Return) {
2203                     if self.token.can_begin_expr() {
2204                         let e = try!(self.parse_expr());
2205                         hi = e.span.hi;
2206                         ex = ExprRet(Some(e));
2207                     } else {
2208                         ex = ExprRet(None);
2209                     }
2210                 } else if self.eat_keyword(keywords::Break) {
2211                     if self.token.is_lifetime() {
2212                         ex = ExprBreak(Some(Spanned {
2213                             node: self.get_lifetime(),
2214                             span: self.span
2215                         }));
2216                         self.bump();
2217                     } else {
2218                         ex = ExprBreak(None);
2219                     }
2220                     hi = self.last_span.hi;
2221                 } else if self.check(&token::ModSep) ||
2222                         self.token.is_ident() &&
2223                         !self.check_keyword(keywords::True) &&
2224                         !self.check_keyword(keywords::False) {
2225                     let pth =
2226                         try!(self.parse_path(LifetimeAndTypesWithColons));
2227
2228                     // `!`, as an operator, is prefix, so we know this isn't that
2229                     if self.check(&token::Not) {
2230                         // MACRO INVOCATION expression
2231                         self.bump();
2232
2233                         let delim = try!(self.expect_open_delim());
2234                         let tts = try!(self.parse_seq_to_end(
2235                             &token::CloseDelim(delim),
2236                             seq_sep_none(),
2237                             |p| p.parse_token_tree()));
2238                         let hi = self.last_span.hi;
2239
2240                         return Ok(self.mk_mac_expr(lo,
2241                                                    hi,
2242                                                    Mac_ { path: pth, tts: tts, ctxt: EMPTY_CTXT },
2243                                                    attrs));
2244                     }
2245                     if self.check(&token::OpenDelim(token::Brace)) {
2246                         // This is a struct literal, unless we're prohibited
2247                         // from parsing struct literals here.
2248                         let prohibited = self.restrictions.contains(
2249                             Restrictions::RESTRICTION_NO_STRUCT_LITERAL
2250                         );
2251                         if !prohibited {
2252                             // It's a struct literal.
2253                             self.bump();
2254                             let mut fields = Vec::new();
2255                             let mut base = None;
2256
2257                             let attrs = attrs.append(
2258                                 try!(self.parse_inner_attributes())
2259                                     .into_thin_attrs());
2260
2261                             while self.token != token::CloseDelim(token::Brace) {
2262                                 if self.eat(&token::DotDot) {
2263                                     base = Some(try!(self.parse_expr()));
2264                                     break;
2265                                 }
2266
2267                                 fields.push(try!(self.parse_field()));
2268                                 try!(self.commit_expr(&*fields.last().unwrap().expr,
2269                                                  &[token::Comma],
2270                                                  &[token::CloseDelim(token::Brace)]));
2271                             }
2272
2273                             hi = self.span.hi;
2274                             try!(self.expect(&token::CloseDelim(token::Brace)));
2275                             ex = ExprStruct(pth, fields, base);
2276                             return Ok(self.mk_expr(lo, hi, ex, attrs));
2277                         }
2278                     }
2279
2280                     hi = pth.span.hi;
2281                     ex = ExprPath(None, pth);
2282                 } else {
2283                     // other literal expression
2284                     let lit = try!(self.parse_lit());
2285                     hi = lit.span.hi;
2286                     ex = ExprLit(P(lit));
2287                 }
2288             }
2289         }
2290
2291         return Ok(self.mk_expr(lo, hi, ex, attrs));
2292     }
2293
2294     fn parse_or_use_outer_attributes(&mut self,
2295                                      already_parsed_attrs: Option<ThinAttributes>)
2296                                      -> PResult<'a, ThinAttributes> {
2297         if let Some(attrs) = already_parsed_attrs {
2298             Ok(attrs)
2299         } else {
2300             self.parse_outer_attributes().map(|a| a.into_thin_attrs())
2301         }
2302     }
2303
2304     /// Parse a block or unsafe block
2305     pub fn parse_block_expr(&mut self, lo: BytePos, blk_mode: BlockCheckMode,
2306                             attrs: ThinAttributes)
2307                             -> PResult<'a, P<Expr>> {
2308
2309         let outer_attrs = attrs;
2310         try!(self.expect(&token::OpenDelim(token::Brace)));
2311
2312         let inner_attrs = try!(self.parse_inner_attributes()).into_thin_attrs();
2313         let attrs = outer_attrs.append(inner_attrs);
2314
2315         let blk = try!(self.parse_block_tail(lo, blk_mode));
2316         return Ok(self.mk_expr(blk.span.lo, blk.span.hi, ExprBlock(blk), attrs));
2317     }
2318
2319     /// parse a.b or a(13) or a[4] or just a
2320     pub fn parse_dot_or_call_expr(&mut self,
2321                                   already_parsed_attrs: Option<ThinAttributes>)
2322                                   -> PResult<'a, P<Expr>> {
2323         let attrs = try!(self.parse_or_use_outer_attributes(already_parsed_attrs));
2324
2325         let b = try!(self.parse_bottom_expr());
2326         self.parse_dot_or_call_expr_with(b, attrs)
2327     }
2328
2329     pub fn parse_dot_or_call_expr_with(&mut self,
2330                                        e0: P<Expr>,
2331                                        attrs: ThinAttributes)
2332                                        -> PResult<'a, P<Expr>> {
2333         // Stitch the list of outer attributes onto the return value.
2334         // A little bit ugly, but the best way given the current code
2335         // structure
2336         self.parse_dot_or_call_expr_with_(e0)
2337         .map(|expr|
2338             expr.map(|mut expr| {
2339                 expr.attrs.update(|a| a.prepend(attrs));
2340                 match expr.node {
2341                     ExprIf(..) | ExprIfLet(..) => {
2342                         if !expr.attrs.as_attr_slice().is_empty() {
2343                             // Just point to the first attribute in there...
2344                             let span = expr.attrs.as_attr_slice()[0].span;
2345
2346                             self.span_err(span,
2347                                 "attributes are not yet allowed on `if` \
2348                                 expressions");
2349                         }
2350                     }
2351                     _ => {}
2352                 }
2353                 expr
2354             })
2355         )
2356     }
2357
2358     fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>) -> PResult<'a, P<Expr>> {
2359         let mut e = e0;
2360         let lo = e.span.lo;
2361         let mut hi;
2362         loop {
2363             // expr.f
2364             if self.eat(&token::Dot) {
2365                 match self.token {
2366                   token::Ident(i, _) => {
2367                     let dot = self.last_span.hi;
2368                     hi = self.span.hi;
2369                     self.bump();
2370                     let (_, tys, bindings) = if self.eat(&token::ModSep) {
2371                         try!(self.expect_lt());
2372                         try!(self.parse_generic_values_after_lt())
2373                     } else {
2374                         (Vec::new(), Vec::new(), Vec::new())
2375                     };
2376
2377                     if !bindings.is_empty() {
2378                         let last_span = self.last_span;
2379                         self.span_err(last_span, "type bindings are only permitted on trait paths");
2380                     }
2381
2382                     // expr.f() method call
2383                     match self.token {
2384                         token::OpenDelim(token::Paren) => {
2385                             let mut es = try!(self.parse_unspanned_seq(
2386                                 &token::OpenDelim(token::Paren),
2387                                 &token::CloseDelim(token::Paren),
2388                                 seq_sep_trailing_allowed(token::Comma),
2389                                 |p| Ok(try!(p.parse_expr()))
2390                             ));
2391                             hi = self.last_span.hi;
2392
2393                             es.insert(0, e);
2394                             let id = spanned(dot, hi, i);
2395                             let nd = self.mk_method_call(id, tys, es);
2396                             e = self.mk_expr(lo, hi, nd, None);
2397                         }
2398                         _ => {
2399                             if !tys.is_empty() {
2400                                 let last_span = self.last_span;
2401                                 self.span_err(last_span,
2402                                               "field expressions may not \
2403                                                have type parameters");
2404                             }
2405
2406                             let id = spanned(dot, hi, i);
2407                             let field = self.mk_field(e, id);
2408                             e = self.mk_expr(lo, hi, field, None);
2409                         }
2410                     }
2411                   }
2412                   token::Literal(token::Integer(n), suf) => {
2413                     let sp = self.span;
2414
2415                     // A tuple index may not have a suffix
2416                     self.expect_no_suffix(sp, "tuple index", suf);
2417
2418                     let dot = self.last_span.hi;
2419                     hi = self.span.hi;
2420                     self.bump();
2421
2422                     let index = n.as_str().parse::<usize>().ok();
2423                     match index {
2424                         Some(n) => {
2425                             let id = spanned(dot, hi, n);
2426                             let field = self.mk_tup_field(e, id);
2427                             e = self.mk_expr(lo, hi, field, None);
2428                         }
2429                         None => {
2430                             let last_span = self.last_span;
2431                             self.span_err(last_span, "invalid tuple or tuple struct index");
2432                         }
2433                     }
2434                   }
2435                   token::Literal(token::Float(n), _suf) => {
2436                     self.bump();
2437                     let last_span = self.last_span;
2438                     let fstr = n.as_str();
2439                     let mut err = self.diagnostic().struct_span_err(last_span,
2440                         &format!("unexpected token: `{}`", n.as_str()));
2441                     if fstr.chars().all(|x| "0123456789.".contains(x)) {
2442                         let float = match fstr.parse::<f64>().ok() {
2443                             Some(f) => f,
2444                             None => continue,
2445                         };
2446                         err.fileline_help(last_span,
2447                             &format!("try parenthesizing the first index; e.g., `(foo.{}){}`",
2448                                     float.trunc() as usize,
2449                                     format!(".{}", fstr.splitn(2, ".").last().unwrap())));
2450                     }
2451                     err.emit();
2452                     self.abort_if_errors();
2453
2454                   }
2455                   _ => return self.unexpected()
2456                 }
2457                 continue;
2458             }
2459             if self.expr_is_complete(&*e) { break; }
2460             match self.token {
2461               // expr(...)
2462               token::OpenDelim(token::Paren) => {
2463                 let es = try!(self.parse_unspanned_seq(
2464                     &token::OpenDelim(token::Paren),
2465                     &token::CloseDelim(token::Paren),
2466                     seq_sep_trailing_allowed(token::Comma),
2467                     |p| Ok(try!(p.parse_expr()))
2468                 ));
2469                 hi = self.last_span.hi;
2470
2471                 let nd = self.mk_call(e, es);
2472                 e = self.mk_expr(lo, hi, nd, None);
2473               }
2474
2475               // expr[...]
2476               // Could be either an index expression or a slicing expression.
2477               token::OpenDelim(token::Bracket) => {
2478                 self.bump();
2479                 let ix = try!(self.parse_expr());
2480                 hi = self.span.hi;
2481                 try!(self.commit_expr_expecting(&*ix, token::CloseDelim(token::Bracket)));
2482                 let index = self.mk_index(e, ix);
2483                 e = self.mk_expr(lo, hi, index, None)
2484               }
2485               _ => return Ok(e)
2486             }
2487         }
2488         return Ok(e);
2489     }
2490
2491     // Parse unquoted tokens after a `$` in a token tree
2492     fn parse_unquoted(&mut self) -> PResult<'a, TokenTree> {
2493         let mut sp = self.span;
2494         let (name, namep) = match self.token {
2495             token::Dollar => {
2496                 self.bump();
2497
2498                 if self.token == token::OpenDelim(token::Paren) {
2499                     let Spanned { node: seq, span: seq_span } = try!(self.parse_seq(
2500                         &token::OpenDelim(token::Paren),
2501                         &token::CloseDelim(token::Paren),
2502                         seq_sep_none(),
2503                         |p| p.parse_token_tree()
2504                     ));
2505                     let (sep, repeat) = try!(self.parse_sep_and_kleene_op());
2506                     let name_num = macro_parser::count_names(&seq);
2507                     return Ok(TokenTree::Sequence(mk_sp(sp.lo, seq_span.hi),
2508                                       Rc::new(SequenceRepetition {
2509                                           tts: seq,
2510                                           separator: sep,
2511                                           op: repeat,
2512                                           num_captures: name_num
2513                                       })));
2514                 } else if self.token.is_keyword_allow_following_colon(keywords::Crate) {
2515                     self.bump();
2516                     return Ok(TokenTree::Token(sp, SpecialVarNt(SpecialMacroVar::CrateMacroVar)));
2517                 } else {
2518                     sp = mk_sp(sp.lo, self.span.hi);
2519                     let namep = match self.token { token::Ident(_, p) => p, _ => token::Plain };
2520                     let name = try!(self.parse_ident());
2521                     (name, namep)
2522                 }
2523             }
2524             token::SubstNt(name, namep) => {
2525                 self.bump();
2526                 (name, namep)
2527             }
2528             _ => unreachable!()
2529         };
2530         // continue by trying to parse the `:ident` after `$name`
2531         if self.token == token::Colon && self.look_ahead(1, |t| t.is_ident() &&
2532                                                                 !t.is_strict_keyword() &&
2533                                                                 !t.is_reserved_keyword()) {
2534             self.bump();
2535             sp = mk_sp(sp.lo, self.span.hi);
2536             let kindp = match self.token { token::Ident(_, p) => p, _ => token::Plain };
2537             let nt_kind = try!(self.parse_ident());
2538             Ok(TokenTree::Token(sp, MatchNt(name, nt_kind, namep, kindp)))
2539         } else {
2540             Ok(TokenTree::Token(sp, SubstNt(name, namep)))
2541         }
2542     }
2543
2544     pub fn check_unknown_macro_variable(&mut self) {
2545         if self.quote_depth == 0 {
2546             match self.token {
2547                 token::SubstNt(name, _) =>
2548                     self.fatal(&format!("unknown macro variable `{}`", name)).emit(),
2549                 _ => {}
2550             }
2551         }
2552     }
2553
2554     /// Parse an optional separator followed by a Kleene-style
2555     /// repetition token (+ or *).
2556     pub fn parse_sep_and_kleene_op(&mut self)
2557                                    -> PResult<'a, (Option<token::Token>, ast::KleeneOp)> {
2558         fn parse_kleene_op<'a>(parser: &mut Parser<'a>) -> PResult<'a,  Option<ast::KleeneOp>> {
2559             match parser.token {
2560                 token::BinOp(token::Star) => {
2561                     parser.bump();
2562                     Ok(Some(ast::ZeroOrMore))
2563                 },
2564                 token::BinOp(token::Plus) => {
2565                     parser.bump();
2566                     Ok(Some(ast::OneOrMore))
2567                 },
2568                 _ => Ok(None)
2569             }
2570         };
2571
2572         match try!(parse_kleene_op(self)) {
2573             Some(kleene_op) => return Ok((None, kleene_op)),
2574             None => {}
2575         }
2576
2577         let separator = self.bump_and_get();
2578         match try!(parse_kleene_op(self)) {
2579             Some(zerok) => Ok((Some(separator), zerok)),
2580             None => return Err(self.fatal("expected `*` or `+`"))
2581         }
2582     }
2583
2584     /// parse a single token tree from the input.
2585     pub fn parse_token_tree(&mut self) -> PResult<'a, TokenTree> {
2586         // FIXME #6994: currently, this is too eager. It
2587         // parses token trees but also identifies TokenType::Sequence's
2588         // and token::SubstNt's; it's too early to know yet
2589         // whether something will be a nonterminal or a seq
2590         // yet.
2591         maybe_whole!(deref self, NtTT);
2592
2593         // this is the fall-through for the 'match' below.
2594         // invariants: the current token is not a left-delimiter,
2595         // not an EOF, and not the desired right-delimiter (if
2596         // it were, parse_seq_to_before_end would have prevented
2597         // reaching this point.
2598         fn parse_non_delim_tt_tok<'b>(p: &mut Parser<'b>) -> PResult<'b,  TokenTree> {
2599             maybe_whole!(deref p, NtTT);
2600             match p.token {
2601                 token::CloseDelim(_) => {
2602                     let token_str = p.this_token_to_string();
2603                     let mut err = p.fatal(
2604                         &format!("incorrect close delimiter: `{}`", token_str));
2605                     // This is a conservative error: only report the last unclosed delimiter. The
2606                     // previous unclosed delimiters could actually be closed! The parser just hasn't
2607                     // gotten to them yet.
2608                     if let Some(&sp) = p.open_braces.last() {
2609                         err.span_note(sp, "unclosed delimiter");
2610                     };
2611                     Err(err)
2612                 },
2613                 /* we ought to allow different depths of unquotation */
2614                 token::Dollar | token::SubstNt(..) if p.quote_depth > 0 => {
2615                     p.parse_unquoted()
2616                 }
2617                 _ => {
2618                     Ok(TokenTree::Token(p.span, p.bump_and_get()))
2619                 }
2620             }
2621         }
2622
2623         match self.token {
2624             token::Eof => {
2625                 let open_braces = self.open_braces.clone();
2626                 let mut err: DiagnosticBuilder<'a> =
2627                     self.fatal("this file contains an un-closed delimiter");
2628                 for sp in &open_braces {
2629                     err.span_help(*sp, "did you mean to close this delimiter?");
2630                 }
2631                 return Err(err);
2632             },
2633             token::OpenDelim(delim) => {
2634                 // The span for beginning of the delimited section
2635                 let pre_span = self.span;
2636
2637                 // Parse the open delimiter.
2638                 self.open_braces.push(self.span);
2639                 let open_span = self.span;
2640                 self.bump();
2641
2642                 // Parse the token trees within the delimiters
2643                 let tts = try!(self.parse_seq_to_before_end(
2644                     &token::CloseDelim(delim),
2645                     seq_sep_none(),
2646                     |p| p.parse_token_tree()
2647                 ));
2648
2649                 // Parse the close delimiter.
2650                 let close_span = self.span;
2651                 self.bump();
2652                 self.open_braces.pop().unwrap();
2653
2654                 // Expand to cover the entire delimited token tree
2655                 let span = Span { hi: close_span.hi, ..pre_span };
2656
2657                 Ok(TokenTree::Delimited(span, Rc::new(Delimited {
2658                     delim: delim,
2659                     open_span: open_span,
2660                     tts: tts,
2661                     close_span: close_span,
2662                 })))
2663             },
2664             _ => parse_non_delim_tt_tok(self),
2665         }
2666     }
2667
2668     // parse a stream of tokens into a list of TokenTree's,
2669     // up to EOF.
2670     pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
2671         let mut tts = Vec::new();
2672         while self.token != token::Eof {
2673             tts.push(try!(self.parse_token_tree()));
2674         }
2675         Ok(tts)
2676     }
2677
2678     /// Parse a prefix-unary-operator expr
2679     pub fn parse_prefix_expr(&mut self,
2680                              already_parsed_attrs: Option<ThinAttributes>)
2681                              -> PResult<'a, P<Expr>> {
2682         let attrs = try!(self.parse_or_use_outer_attributes(already_parsed_attrs));
2683         let lo = self.span.lo;
2684         let hi;
2685         // Note: when adding new unary operators, don't forget to adjust Token::can_begin_expr()
2686         let ex = match self.token {
2687             token::Not => {
2688                 self.bump();
2689                 let e = try!(self.parse_prefix_expr(None));
2690                 hi = e.span.hi;
2691                 self.mk_unary(UnNot, e)
2692             }
2693             token::BinOp(token::Minus) => {
2694                 self.bump();
2695                 let e = try!(self.parse_prefix_expr(None));
2696                 hi = e.span.hi;
2697                 self.mk_unary(UnNeg, e)
2698             }
2699             token::BinOp(token::Star) => {
2700                 self.bump();
2701                 let e = try!(self.parse_prefix_expr(None));
2702                 hi = e.span.hi;
2703                 self.mk_unary(UnDeref, e)
2704             }
2705             token::BinOp(token::And) | token::AndAnd => {
2706                 try!(self.expect_and());
2707                 let m = try!(self.parse_mutability());
2708                 let e = try!(self.parse_prefix_expr(None));
2709                 hi = e.span.hi;
2710                 ExprAddrOf(m, e)
2711             }
2712             token::Ident(..) if self.token.is_keyword(keywords::In) => {
2713                 self.bump();
2714                 let place = try!(self.parse_expr_res(
2715                     Restrictions::RESTRICTION_NO_STRUCT_LITERAL,
2716                     None,
2717                 ));
2718                 let blk = try!(self.parse_block());
2719                 let span = blk.span;
2720                 hi = span.hi;
2721                 let blk_expr = self.mk_expr(span.lo, span.hi, ExprBlock(blk),
2722                                             None);
2723                 ExprInPlace(place, blk_expr)
2724             }
2725             token::Ident(..) if self.token.is_keyword(keywords::Box) => {
2726                 self.bump();
2727                 let subexpression = try!(self.parse_prefix_expr(None));
2728                 hi = subexpression.span.hi;
2729                 ExprBox(subexpression)
2730             }
2731             _ => return self.parse_dot_or_call_expr(Some(attrs))
2732         };
2733         return Ok(self.mk_expr(lo, hi, ex, attrs));
2734     }
2735
2736     /// Parse an associative expression
2737     ///
2738     /// This parses an expression accounting for associativity and precedence of the operators in
2739     /// the expression.
2740     pub fn parse_assoc_expr(&mut self,
2741                             already_parsed_attrs: Option<ThinAttributes>)
2742                             -> PResult<'a, P<Expr>> {
2743         self.parse_assoc_expr_with(0, already_parsed_attrs.into())
2744     }
2745
2746     /// Parse an associative expression with operators of at least `min_prec` precedence
2747     pub fn parse_assoc_expr_with(&mut self,
2748                                  min_prec: usize,
2749                                  lhs: LhsExpr)
2750                                  -> PResult<'a, P<Expr>> {
2751         let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
2752             expr
2753         } else {
2754             let attrs = match lhs {
2755                 LhsExpr::AttributesParsed(attrs) => Some(attrs),
2756                 _ => None,
2757             };
2758             if self.token == token::DotDot {
2759                 return self.parse_prefix_range_expr(attrs);
2760             } else {
2761                 try!(self.parse_prefix_expr(attrs))
2762             }
2763         };
2764         if self.expr_is_complete(&*lhs) {
2765             // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
2766             return Ok(lhs);
2767         }
2768         self.expected_tokens.push(TokenType::Operator);
2769         while let Some(op) = AssocOp::from_token(&self.token) {
2770             let cur_op_span = self.span;
2771             let restrictions = if op.is_assign_like() {
2772                 self.restrictions & Restrictions::RESTRICTION_NO_STRUCT_LITERAL
2773             } else {
2774                 self.restrictions
2775             };
2776             if op.precedence() < min_prec {
2777                 break;
2778             }
2779             self.bump();
2780             if op.is_comparison() {
2781                 self.check_no_chained_comparison(&*lhs, &op);
2782             }
2783             // Special cases:
2784             if op == AssocOp::As {
2785                 let rhs = try!(self.parse_ty());
2786                 lhs = self.mk_expr(lhs.span.lo, rhs.span.hi,
2787                                    ExprCast(lhs, rhs), None);
2788                 continue
2789             } else if op == AssocOp::Colon {
2790                 let rhs = try!(self.parse_ty());
2791                 lhs = self.mk_expr(lhs.span.lo, rhs.span.hi,
2792                                    ExprType(lhs, rhs), None);
2793                 continue
2794             } else if op == AssocOp::DotDot {
2795                     // If we didn’t have to handle `x..`, it would be pretty easy to generalise
2796                     // it to the Fixity::None code.
2797                     //
2798                     // We have 2 alternatives here: `x..y` and `x..` The other two variants are
2799                     // handled with `parse_prefix_range_expr` call above.
2800                     let rhs = if self.is_at_start_of_range_notation_rhs() {
2801                         self.parse_assoc_expr_with(op.precedence() + 1,
2802                                                    LhsExpr::NotYetParsed).ok()
2803                     } else {
2804                         None
2805                     };
2806                     let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
2807                         x.span
2808                     } else {
2809                         cur_op_span
2810                     });
2811                     let r = self.mk_range(Some(lhs), rhs);
2812                     lhs = self.mk_expr(lhs_span.lo, rhs_span.hi, r, None);
2813                     break
2814             }
2815
2816             let rhs = try!(match op.fixity() {
2817                 Fixity::Right => self.with_res(restrictions, |this|{
2818                     this.parse_assoc_expr_with(op.precedence(), LhsExpr::NotYetParsed)
2819                 }),
2820                 Fixity::Left => self.with_res(restrictions, |this|{
2821                     this.parse_assoc_expr_with(op.precedence() + 1, LhsExpr::NotYetParsed)
2822                 }),
2823                 // We currently have no non-associative operators that are not handled above by
2824                 // the special cases. The code is here only for future convenience.
2825                 Fixity::None => self.with_res(restrictions, |this|{
2826                     this.parse_assoc_expr_with(op.precedence() + 1, LhsExpr::NotYetParsed)
2827                 }),
2828             });
2829
2830             lhs = match op {
2831                 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
2832                 AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
2833                 AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
2834                 AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
2835                 AssocOp::Greater | AssocOp::GreaterEqual => {
2836                     let ast_op = op.to_ast_binop().unwrap();
2837                     let (lhs_span, rhs_span) = (lhs.span, rhs.span);
2838                     let binary = self.mk_binary(codemap::respan(cur_op_span, ast_op), lhs, rhs);
2839                     self.mk_expr(lhs_span.lo, rhs_span.hi, binary, None)
2840                 }
2841                 AssocOp::Assign =>
2842                     self.mk_expr(lhs.span.lo, rhs.span.hi, ExprAssign(lhs, rhs), None),
2843                 AssocOp::Inplace =>
2844                     self.mk_expr(lhs.span.lo, rhs.span.hi, ExprInPlace(lhs, rhs), None),
2845                 AssocOp::AssignOp(k) => {
2846                     let aop = match k {
2847                         token::Plus =>    BiAdd,
2848                         token::Minus =>   BiSub,
2849                         token::Star =>    BiMul,
2850                         token::Slash =>   BiDiv,
2851                         token::Percent => BiRem,
2852                         token::Caret =>   BiBitXor,
2853                         token::And =>     BiBitAnd,
2854                         token::Or =>      BiBitOr,
2855                         token::Shl =>     BiShl,
2856                         token::Shr =>     BiShr
2857                     };
2858                     let (lhs_span, rhs_span) = (lhs.span, rhs.span);
2859                     let aopexpr = self.mk_assign_op(codemap::respan(cur_op_span, aop), lhs, rhs);
2860                     self.mk_expr(lhs_span.lo, rhs_span.hi, aopexpr, None)
2861                 }
2862                 AssocOp::As | AssocOp::Colon | AssocOp::DotDot => {
2863                     self.bug("As, Colon or DotDot branch reached")
2864                 }
2865             };
2866
2867             if op.fixity() == Fixity::None { break }
2868         }
2869         Ok(lhs)
2870     }
2871
2872     /// Produce an error if comparison operators are chained (RFC #558).
2873     /// We only need to check lhs, not rhs, because all comparison ops
2874     /// have same precedence and are left-associative
2875     fn check_no_chained_comparison(&mut self, lhs: &Expr, outer_op: &AssocOp) {
2876         debug_assert!(outer_op.is_comparison());
2877         match lhs.node {
2878             ExprBinary(op, _, _) if op.node.is_comparison() => {
2879                 // respan to include both operators
2880                 let op_span = mk_sp(op.span.lo, self.span.hi);
2881                 let mut err = self.diagnostic().struct_span_err(op_span,
2882                     "chained comparison operators require parentheses");
2883                 if op.node == BiLt && *outer_op == AssocOp::Greater {
2884                     err.fileline_help(op_span,
2885                         "use `::<...>` instead of `<...>` if you meant to specify type arguments");
2886                 }
2887                 err.emit();
2888             }
2889             _ => {}
2890         }
2891     }
2892
2893     /// Parse prefix-forms of range notation: `..expr` and `..`
2894     fn parse_prefix_range_expr(&mut self,
2895                                already_parsed_attrs: Option<ThinAttributes>)
2896                                -> PResult<'a, P<Expr>> {
2897         debug_assert!(self.token == token::DotDot);
2898         let attrs = try!(self.parse_or_use_outer_attributes(already_parsed_attrs));
2899         let lo = self.span.lo;
2900         let mut hi = self.span.hi;
2901         self.bump();
2902         let opt_end = if self.is_at_start_of_range_notation_rhs() {
2903             // RHS must be parsed with more associativity than DotDot.
2904             let next_prec = AssocOp::from_token(&token::DotDot).unwrap().precedence() + 1;
2905             Some(try!(self.parse_assoc_expr_with(next_prec,
2906                                                  LhsExpr::NotYetParsed)
2907             .map(|x|{
2908                 hi = x.span.hi;
2909                 x
2910             })))
2911          } else {
2912             None
2913         };
2914         let r = self.mk_range(None, opt_end);
2915         Ok(self.mk_expr(lo, hi, r, attrs))
2916     }
2917
2918     fn is_at_start_of_range_notation_rhs(&self) -> bool {
2919         if self.token.can_begin_expr() {
2920             // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
2921             if self.token == token::OpenDelim(token::Brace) {
2922                 return !self.restrictions.contains(Restrictions::RESTRICTION_NO_STRUCT_LITERAL);
2923             }
2924             true
2925         } else {
2926             false
2927         }
2928     }
2929
2930     /// Parse an 'if' or 'if let' expression ('if' token already eaten)
2931     pub fn parse_if_expr(&mut self, attrs: ThinAttributes) -> PResult<'a, P<Expr>> {
2932         if self.check_keyword(keywords::Let) {
2933             return self.parse_if_let_expr(attrs);
2934         }
2935         let lo = self.last_span.lo;
2936         let cond = try!(self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL, None));
2937         let thn = try!(self.parse_block());
2938         let mut els: Option<P<Expr>> = None;
2939         let mut hi = thn.span.hi;
2940         if self.eat_keyword(keywords::Else) {
2941             let elexpr = try!(self.parse_else_expr());
2942             hi = elexpr.span.hi;
2943             els = Some(elexpr);
2944         }
2945         Ok(self.mk_expr(lo, hi, ExprIf(cond, thn, els), attrs))
2946     }
2947
2948     /// Parse an 'if let' expression ('if' token already eaten)
2949     pub fn parse_if_let_expr(&mut self, attrs: ThinAttributes)
2950                              -> PResult<'a, P<Expr>> {
2951         let lo = self.last_span.lo;
2952         try!(self.expect_keyword(keywords::Let));
2953         let pat = try!(self.parse_pat());
2954         try!(self.expect(&token::Eq));
2955         let expr = try!(self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL, None));
2956         let thn = try!(self.parse_block());
2957         let (hi, els) = if self.eat_keyword(keywords::Else) {
2958             let expr = try!(self.parse_else_expr());
2959             (expr.span.hi, Some(expr))
2960         } else {
2961             (thn.span.hi, None)
2962         };
2963         Ok(self.mk_expr(lo, hi, ExprIfLet(pat, expr, thn, els), attrs))
2964     }
2965
2966     // `|args| expr`
2967     pub fn parse_lambda_expr(&mut self, lo: BytePos,
2968                              capture_clause: CaptureClause,
2969                              attrs: ThinAttributes)
2970                              -> PResult<'a, P<Expr>>
2971     {
2972         let decl = try!(self.parse_fn_block_decl());
2973         let body = match decl.output {
2974             DefaultReturn(_) => {
2975                 // If no explicit return type is given, parse any
2976                 // expr and wrap it up in a dummy block:
2977                 let body_expr = try!(self.parse_expr());
2978                 P(ast::Block {
2979                     id: ast::DUMMY_NODE_ID,
2980                     stmts: vec![],
2981                     span: body_expr.span,
2982                     expr: Some(body_expr),
2983                     rules: DefaultBlock,
2984                 })
2985             }
2986             _ => {
2987                 // If an explicit return type is given, require a
2988                 // block to appear (RFC 968).
2989                 try!(self.parse_block())
2990             }
2991         };
2992
2993         Ok(self.mk_expr(
2994             lo,
2995             body.span.hi,
2996             ExprClosure(capture_clause, decl, body), attrs))
2997     }
2998
2999     // `else` token already eaten
3000     pub fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
3001         if self.eat_keyword(keywords::If) {
3002             return self.parse_if_expr(None);
3003         } else {
3004             let blk = try!(self.parse_block());
3005             return Ok(self.mk_expr(blk.span.lo, blk.span.hi, ExprBlock(blk), None));
3006         }
3007     }
3008
3009     /// Parse a 'for' .. 'in' expression ('for' token already eaten)
3010     pub fn parse_for_expr(&mut self, opt_ident: Option<ast::Ident>,
3011                           span_lo: BytePos,
3012                           attrs: ThinAttributes) -> PResult<'a, P<Expr>> {
3013         // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
3014
3015         let pat = try!(self.parse_pat());
3016         try!(self.expect_keyword(keywords::In));
3017         let expr = try!(self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL, None));
3018         let (iattrs, loop_block) = try!(self.parse_inner_attrs_and_block());
3019         let attrs = attrs.append(iattrs.into_thin_attrs());
3020
3021         let hi = self.last_span.hi;
3022
3023         Ok(self.mk_expr(span_lo, hi,
3024                         ExprForLoop(pat, expr, loop_block, opt_ident),
3025                         attrs))
3026     }
3027
3028     /// Parse a 'while' or 'while let' expression ('while' token already eaten)
3029     pub fn parse_while_expr(&mut self, opt_ident: Option<ast::Ident>,
3030                             span_lo: BytePos,
3031                             attrs: ThinAttributes) -> PResult<'a, P<Expr>> {
3032         if self.token.is_keyword(keywords::Let) {
3033             return self.parse_while_let_expr(opt_ident, span_lo, attrs);
3034         }
3035         let cond = try!(self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL, None));
3036         let (iattrs, body) = try!(self.parse_inner_attrs_and_block());
3037         let attrs = attrs.append(iattrs.into_thin_attrs());
3038         let hi = body.span.hi;
3039         return Ok(self.mk_expr(span_lo, hi, ExprWhile(cond, body, opt_ident),
3040                                attrs));
3041     }
3042
3043     /// Parse a 'while let' expression ('while' token already eaten)
3044     pub fn parse_while_let_expr(&mut self, opt_ident: Option<ast::Ident>,
3045                                 span_lo: BytePos,
3046                                 attrs: ThinAttributes) -> PResult<'a, P<Expr>> {
3047         try!(self.expect_keyword(keywords::Let));
3048         let pat = try!(self.parse_pat());
3049         try!(self.expect(&token::Eq));
3050         let expr = try!(self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL, None));
3051         let (iattrs, body) = try!(self.parse_inner_attrs_and_block());
3052         let attrs = attrs.append(iattrs.into_thin_attrs());
3053         let hi = body.span.hi;
3054         return Ok(self.mk_expr(span_lo, hi, ExprWhileLet(pat, expr, body, opt_ident), attrs));
3055     }
3056
3057     // parse `loop {...}`, `loop` token already eaten
3058     pub fn parse_loop_expr(&mut self, opt_ident: Option<ast::Ident>,
3059                            span_lo: BytePos,
3060                            attrs: ThinAttributes) -> PResult<'a, P<Expr>> {
3061         let (iattrs, body) = try!(self.parse_inner_attrs_and_block());
3062         let attrs = attrs.append(iattrs.into_thin_attrs());
3063         let hi = body.span.hi;
3064         Ok(self.mk_expr(span_lo, hi, ExprLoop(body, opt_ident), attrs))
3065     }
3066
3067     // `match` token already eaten
3068     fn parse_match_expr(&mut self, attrs: ThinAttributes) -> PResult<'a, P<Expr>> {
3069         let match_span = self.last_span;
3070         let lo = self.last_span.lo;
3071         let discriminant = try!(self.parse_expr_res(
3072             Restrictions::RESTRICTION_NO_STRUCT_LITERAL, None));
3073         if let Err(mut e) = self.commit_expr_expecting(&*discriminant,
3074                                                        token::OpenDelim(token::Brace)) {
3075             if self.token == token::Token::Semi {
3076                 e.span_note(match_span, "did you mean to remove this `match` keyword?");
3077             }
3078             return Err(e)
3079         }
3080         let attrs = attrs.append(
3081             try!(self.parse_inner_attributes()).into_thin_attrs());
3082         let mut arms: Vec<Arm> = Vec::new();
3083         while self.token != token::CloseDelim(token::Brace) {
3084             arms.push(try!(self.parse_arm()));
3085         }
3086         let hi = self.span.hi;
3087         self.bump();
3088         return Ok(self.mk_expr(lo, hi, ExprMatch(discriminant, arms), attrs));
3089     }
3090
3091     pub fn parse_arm(&mut self) -> PResult<'a, Arm> {
3092         maybe_whole!(no_clone self, NtArm);
3093
3094         let attrs = try!(self.parse_outer_attributes());
3095         let pats = try!(self.parse_pats());
3096         let mut guard = None;
3097         if self.eat_keyword(keywords::If) {
3098             guard = Some(try!(self.parse_expr()));
3099         }
3100         try!(self.expect(&token::FatArrow));
3101         let expr = try!(self.parse_expr_res(Restrictions::RESTRICTION_STMT_EXPR, None));
3102
3103         let require_comma =
3104             !classify::expr_is_simple_block(&*expr)
3105             && self.token != token::CloseDelim(token::Brace);
3106
3107         if require_comma {
3108             try!(self.commit_expr(&*expr, &[token::Comma], &[token::CloseDelim(token::Brace)]));
3109         } else {
3110             self.eat(&token::Comma);
3111         }
3112
3113         Ok(ast::Arm {
3114             attrs: attrs,
3115             pats: pats,
3116             guard: guard,
3117             body: expr,
3118         })
3119     }
3120
3121     /// Parse an expression
3122     pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
3123         self.parse_expr_res(Restrictions::empty(), None)
3124     }
3125
3126     /// Evaluate the closure with restrictions in place.
3127     ///
3128     /// After the closure is evaluated, restrictions are reset.
3129     pub fn with_res<F>(&mut self, r: Restrictions, f: F) -> PResult<'a, P<Expr>>
3130         where F: FnOnce(&mut Self) -> PResult<'a,  P<Expr>>
3131     {
3132         let old = self.restrictions;
3133         self.restrictions = r;
3134         let r = f(self);
3135         self.restrictions = old;
3136         return r;
3137
3138     }
3139
3140     /// Parse an expression, subject to the given restrictions
3141     pub fn parse_expr_res(&mut self, r: Restrictions,
3142                           already_parsed_attrs: Option<ThinAttributes>)
3143                           -> PResult<'a, P<Expr>> {
3144         self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
3145     }
3146
3147     /// Parse the RHS of a local variable declaration (e.g. '= 14;')
3148     fn parse_initializer(&mut self) -> PResult<'a, Option<P<Expr>>> {
3149         if self.check(&token::Eq) {
3150             self.bump();
3151             Ok(Some(try!(self.parse_expr())))
3152         } else {
3153             Ok(None)
3154         }
3155     }
3156
3157     /// Parse patterns, separated by '|' s
3158     fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
3159         let mut pats = Vec::new();
3160         loop {
3161             pats.push(try!(self.parse_pat()));
3162             if self.check(&token::BinOp(token::Or)) { self.bump();}
3163             else { return Ok(pats); }
3164         };
3165     }
3166
3167     fn parse_pat_tuple_elements(&mut self) -> PResult<'a, Vec<P<Pat>>> {
3168         let mut fields = vec![];
3169         if !self.check(&token::CloseDelim(token::Paren)) {
3170             fields.push(try!(self.parse_pat()));
3171             if self.look_ahead(1, |t| *t != token::CloseDelim(token::Paren)) {
3172                 while self.eat(&token::Comma) &&
3173                       !self.check(&token::CloseDelim(token::Paren)) {
3174                     fields.push(try!(self.parse_pat()));
3175                 }
3176             }
3177             if fields.len() == 1 {
3178                 try!(self.expect(&token::Comma));
3179             }
3180         }
3181         Ok(fields)
3182     }
3183
3184     fn parse_pat_vec_elements(
3185         &mut self,
3186     ) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
3187         let mut before = Vec::new();
3188         let mut slice = None;
3189         let mut after = Vec::new();
3190         let mut first = true;
3191         let mut before_slice = true;
3192
3193         while self.token != token::CloseDelim(token::Bracket) {
3194             if first {
3195                 first = false;
3196             } else {
3197                 try!(self.expect(&token::Comma));
3198
3199                 if self.token == token::CloseDelim(token::Bracket)
3200                         && (before_slice || !after.is_empty()) {
3201                     break
3202                 }
3203             }
3204
3205             if before_slice {
3206                 if self.check(&token::DotDot) {
3207                     self.bump();
3208
3209                     if self.check(&token::Comma) ||
3210                             self.check(&token::CloseDelim(token::Bracket)) {
3211                         slice = Some(P(ast::Pat {
3212                             id: ast::DUMMY_NODE_ID,
3213                             node: PatWild,
3214                             span: self.span,
3215                         }));
3216                         before_slice = false;
3217                     }
3218                     continue
3219                 }
3220             }
3221
3222             let subpat = try!(self.parse_pat());
3223             if before_slice && self.check(&token::DotDot) {
3224                 self.bump();
3225                 slice = Some(subpat);
3226                 before_slice = false;
3227             } else if before_slice {
3228                 before.push(subpat);
3229             } else {
3230                 after.push(subpat);
3231             }
3232         }
3233
3234         Ok((before, slice, after))
3235     }
3236
3237     /// Parse the fields of a struct-like pattern
3238     fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<codemap::Spanned<ast::FieldPat>> , bool)> {
3239         let mut fields = Vec::new();
3240         let mut etc = false;
3241         let mut first = true;
3242         while self.token != token::CloseDelim(token::Brace) {
3243             if first {
3244                 first = false;
3245             } else {
3246                 try!(self.expect(&token::Comma));
3247                 // accept trailing commas
3248                 if self.check(&token::CloseDelim(token::Brace)) { break }
3249             }
3250
3251             let lo = self.span.lo;
3252             let hi;
3253
3254             if self.check(&token::DotDot) {
3255                 self.bump();
3256                 if self.token != token::CloseDelim(token::Brace) {
3257                     let token_str = self.this_token_to_string();
3258                     return Err(self.fatal(&format!("expected `{}`, found `{}`", "}",
3259                                        token_str)))
3260                 }
3261                 etc = true;
3262                 break;
3263             }
3264
3265             // Check if a colon exists one ahead. This means we're parsing a fieldname.
3266             let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
3267                 // Parsing a pattern of the form "fieldname: pat"
3268                 let fieldname = try!(self.parse_ident());
3269                 self.bump();
3270                 let pat = try!(self.parse_pat());
3271                 hi = pat.span.hi;
3272                 (pat, fieldname, false)
3273             } else {
3274                 // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
3275                 let is_box = self.eat_keyword(keywords::Box);
3276                 let boxed_span_lo = self.span.lo;
3277                 let is_ref = self.eat_keyword(keywords::Ref);
3278                 let is_mut = self.eat_keyword(keywords::Mut);
3279                 let fieldname = try!(self.parse_ident());
3280                 hi = self.last_span.hi;
3281
3282                 let bind_type = match (is_ref, is_mut) {
3283                     (true, true) => BindingMode::ByRef(MutMutable),
3284                     (true, false) => BindingMode::ByRef(MutImmutable),
3285                     (false, true) => BindingMode::ByValue(MutMutable),
3286                     (false, false) => BindingMode::ByValue(MutImmutable),
3287                 };
3288                 let fieldpath = codemap::Spanned{span:self.last_span, node:fieldname};
3289                 let fieldpat = P(ast::Pat{
3290                     id: ast::DUMMY_NODE_ID,
3291                     node: PatIdent(bind_type, fieldpath, None),
3292                     span: mk_sp(boxed_span_lo, hi),
3293                 });
3294
3295                 let subpat = if is_box {
3296                     P(ast::Pat{
3297                         id: ast::DUMMY_NODE_ID,
3298                         node: PatBox(fieldpat),
3299                         span: mk_sp(lo, hi),
3300                     })
3301                 } else {
3302                     fieldpat
3303                 };
3304                 (subpat, fieldname, true)
3305             };
3306
3307             fields.push(codemap::Spanned { span: mk_sp(lo, hi),
3308                                            node: ast::FieldPat { ident: fieldname,
3309                                                                  pat: subpat,
3310                                                                  is_shorthand: is_shorthand }});
3311         }
3312         return Ok((fields, etc));
3313     }
3314
3315     fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
3316         if self.is_path_start() {
3317             let lo = self.span.lo;
3318             let (qself, path) = if self.eat_lt() {
3319                 // Parse a qualified path
3320                 let (qself, path) =
3321                     try!(self.parse_qualified_path(NoTypesAllowed));
3322                 (Some(qself), path)
3323             } else {
3324                 // Parse an unqualified path
3325                 (None, try!(self.parse_path(LifetimeAndTypesWithColons)))
3326             };
3327             let hi = self.last_span.hi;
3328             Ok(self.mk_expr(lo, hi, ExprPath(qself, path), None))
3329         } else {
3330             self.parse_pat_literal_maybe_minus()
3331         }
3332     }
3333
3334     fn is_path_start(&self) -> bool {
3335         (self.token == token::Lt || self.token == token::ModSep
3336             || self.token.is_ident() || self.token.is_path())
3337             && !self.token.is_keyword(keywords::True) && !self.token.is_keyword(keywords::False)
3338     }
3339
3340     /// Parse a pattern.
3341     pub fn parse_pat(&mut self) -> PResult<'a, P<Pat>> {
3342         maybe_whole!(self, NtPat);
3343
3344         let lo = self.span.lo;
3345         let pat;
3346         match self.token {
3347           token::Underscore => {
3348             // Parse _
3349             self.bump();
3350             pat = PatWild;
3351           }
3352           token::BinOp(token::And) | token::AndAnd => {
3353             // Parse &pat / &mut pat
3354             try!(self.expect_and());
3355             let mutbl = try!(self.parse_mutability());
3356             if let token::Lifetime(ident) = self.token {
3357                 return Err(self.fatal(&format!("unexpected lifetime `{}` in pattern", ident)));
3358             }
3359
3360             let subpat = try!(self.parse_pat());
3361             pat = PatRegion(subpat, mutbl);
3362           }
3363           token::OpenDelim(token::Paren) => {
3364             // Parse (pat,pat,pat,...) as tuple pattern
3365             self.bump();
3366             let fields = try!(self.parse_pat_tuple_elements());
3367             try!(self.expect(&token::CloseDelim(token::Paren)));
3368             pat = PatTup(fields);
3369           }
3370           token::OpenDelim(token::Bracket) => {
3371             // Parse [pat,pat,...] as slice pattern
3372             self.bump();
3373             let (before, slice, after) = try!(self.parse_pat_vec_elements());
3374             try!(self.expect(&token::CloseDelim(token::Bracket)));
3375             pat = PatVec(before, slice, after);
3376           }
3377           _ => {
3378             // At this point, token != _, &, &&, (, [
3379             if self.eat_keyword(keywords::Mut) {
3380                 // Parse mut ident @ pat
3381                 pat = try!(self.parse_pat_ident(BindingMode::ByValue(MutMutable)));
3382             } else if self.eat_keyword(keywords::Ref) {
3383                 // Parse ref ident @ pat / ref mut ident @ pat
3384                 let mutbl = try!(self.parse_mutability());
3385                 pat = try!(self.parse_pat_ident(BindingMode::ByRef(mutbl)));
3386             } else if self.eat_keyword(keywords::Box) {
3387                 // Parse box pat
3388                 let subpat = try!(self.parse_pat());
3389                 pat = PatBox(subpat);
3390             } else if self.is_path_start() {
3391                 // Parse pattern starting with a path
3392                 if self.token.is_plain_ident() && self.look_ahead(1, |t| *t != token::DotDotDot &&
3393                         *t != token::OpenDelim(token::Brace) &&
3394                         *t != token::OpenDelim(token::Paren) &&
3395                         // Contrary to its definition, a plain ident can be followed by :: in macros
3396                         *t != token::ModSep) {
3397                     // Plain idents have some extra abilities here compared to general paths
3398                     if self.look_ahead(1, |t| *t == token::Not) {
3399                         // Parse macro invocation
3400                         let ident = try!(self.parse_ident());
3401                         let ident_span = self.last_span;
3402                         let path = ident_to_path(ident_span, ident);
3403                         self.bump();
3404                         let delim = try!(self.expect_open_delim());
3405                         let tts = try!(self.parse_seq_to_end(&token::CloseDelim(delim),
3406                                 seq_sep_none(), |p| p.parse_token_tree()));
3407                         let mac = Mac_ { path: path, tts: tts, ctxt: EMPTY_CTXT };
3408                         pat = PatMac(codemap::Spanned {node: mac,
3409                                                        span: mk_sp(lo, self.last_span.hi)});
3410                     } else {
3411                         // Parse ident @ pat
3412                         // This can give false positives and parse nullary enums,
3413                         // they are dealt with later in resolve
3414                         pat = try!(self.parse_pat_ident(BindingMode::ByValue(MutImmutable)));
3415                     }
3416                 } else {
3417                     let (qself, path) = if self.eat_lt() {
3418                         // Parse a qualified path
3419                         let (qself, path) =
3420                             try!(self.parse_qualified_path(NoTypesAllowed));
3421                         (Some(qself), path)
3422                     } else {
3423                         // Parse an unqualified path
3424                         (None, try!(self.parse_path(LifetimeAndTypesWithColons)))
3425                     };
3426                     match self.token {
3427                       token::DotDotDot => {
3428                         // Parse range
3429                         let hi = self.last_span.hi;
3430                         let begin = self.mk_expr(lo, hi, ExprPath(qself, path), None);
3431                         self.bump();
3432                         let end = try!(self.parse_pat_range_end());
3433                         pat = PatRange(begin, end);
3434                       }
3435                       token::OpenDelim(token::Brace) => {
3436                          if qself.is_some() {
3437                             return Err(self.fatal("unexpected `{` after qualified path"));
3438                         }
3439                         // Parse struct pattern
3440                         self.bump();
3441                         let (fields, etc) = try!(self.parse_pat_fields());
3442                         self.bump();
3443                         pat = PatStruct(path, fields, etc);
3444                       }
3445                       token::OpenDelim(token::Paren) => {
3446                         if qself.is_some() {
3447                             return Err(self.fatal("unexpected `(` after qualified path"));
3448                         }
3449                         // Parse tuple struct or enum pattern
3450                         if self.look_ahead(1, |t| *t == token::DotDot) {
3451                             // This is a "top constructor only" pat
3452                             self.bump();
3453                             self.bump();
3454                             try!(self.expect(&token::CloseDelim(token::Paren)));
3455                             pat = PatEnum(path, None);
3456                         } else {
3457                             let args = try!(self.parse_enum_variant_seq(
3458                                     &token::OpenDelim(token::Paren),
3459                                     &token::CloseDelim(token::Paren),
3460                                     seq_sep_trailing_allowed(token::Comma),
3461                                     |p| p.parse_pat()));
3462                             pat = PatEnum(path, Some(args));
3463                         }
3464                       }
3465                       _ => {
3466                         pat = match qself {
3467                             // Parse qualified path
3468                             Some(qself) => PatQPath(qself, path),
3469                             // Parse nullary enum
3470                             None => PatEnum(path, Some(vec![]))
3471                         };
3472                       }
3473                     }
3474                 }
3475             } else {
3476                 // Try to parse everything else as literal with optional minus
3477                 let begin = try!(self.parse_pat_literal_maybe_minus());
3478                 if self.eat(&token::DotDotDot) {
3479                     let end = try!(self.parse_pat_range_end());
3480                     pat = PatRange(begin, end);
3481                 } else {
3482                     pat = PatLit(begin);
3483                 }
3484             }
3485           }
3486         }
3487
3488         let hi = self.last_span.hi;
3489         Ok(P(ast::Pat {
3490             id: ast::DUMMY_NODE_ID,
3491             node: pat,
3492             span: mk_sp(lo, hi),
3493         }))
3494     }
3495
3496     /// Parse ident or ident @ pat
3497     /// used by the copy foo and ref foo patterns to give a good
3498     /// error message when parsing mistakes like ref foo(a,b)
3499     fn parse_pat_ident(&mut self,
3500                        binding_mode: ast::BindingMode)
3501                        -> PResult<'a, ast::Pat_> {
3502         if !self.token.is_plain_ident() {
3503             let span = self.span;
3504             let tok_str = self.this_token_to_string();
3505             return Err(self.span_fatal(span,
3506                             &format!("expected identifier, found `{}`", tok_str)))
3507         }
3508         let ident = try!(self.parse_ident());
3509         let last_span = self.last_span;
3510         let name = codemap::Spanned{span: last_span, node: ident};
3511         let sub = if self.eat(&token::At) {
3512             Some(try!(self.parse_pat()))
3513         } else {
3514             None
3515         };
3516
3517         // just to be friendly, if they write something like
3518         //   ref Some(i)
3519         // we end up here with ( as the current token.  This shortly
3520         // leads to a parse error.  Note that if there is no explicit
3521         // binding mode then we do not end up here, because the lookahead
3522         // will direct us over to parse_enum_variant()
3523         if self.token == token::OpenDelim(token::Paren) {
3524             let last_span = self.last_span;
3525             return Err(self.span_fatal(
3526                 last_span,
3527                 "expected identifier, found enum pattern"))
3528         }
3529
3530         Ok(PatIdent(binding_mode, name, sub))
3531     }
3532
3533     /// Parse a local variable declaration
3534     fn parse_local(&mut self, attrs: ThinAttributes) -> PResult<'a, P<Local>> {
3535         let lo = self.span.lo;
3536         let pat = try!(self.parse_pat());
3537
3538         let mut ty = None;
3539         if self.eat(&token::Colon) {
3540             ty = Some(try!(self.parse_ty_sum()));
3541         }
3542         let init = try!(self.parse_initializer());
3543         Ok(P(ast::Local {
3544             ty: ty,
3545             pat: pat,
3546             init: init,
3547             id: ast::DUMMY_NODE_ID,
3548             span: mk_sp(lo, self.last_span.hi),
3549             attrs: attrs,
3550         }))
3551     }
3552
3553     /// Parse a "let" stmt
3554     fn parse_let(&mut self, attrs: ThinAttributes) -> PResult<'a, P<Decl>> {
3555         let lo = self.span.lo;
3556         let local = try!(self.parse_local(attrs));
3557         Ok(P(spanned(lo, self.last_span.hi, DeclLocal(local))))
3558     }
3559
3560     /// Parse a structure field
3561     fn parse_name_and_ty(&mut self, pr: Visibility,
3562                          attrs: Vec<Attribute> ) -> PResult<'a, StructField> {
3563         let lo = match pr {
3564             Inherited => self.span.lo,
3565             Public => self.last_span.lo,
3566         };
3567         if !self.token.is_plain_ident() {
3568             return Err(self.fatal("expected ident"));
3569         }
3570         let name = try!(self.parse_ident());
3571         try!(self.expect(&token::Colon));
3572         let ty = try!(self.parse_ty_sum());
3573         Ok(spanned(lo, self.last_span.hi, ast::StructField_ {
3574             kind: NamedField(name, pr),
3575             id: ast::DUMMY_NODE_ID,
3576             ty: ty,
3577             attrs: attrs,
3578         }))
3579     }
3580
3581     /// Emit an expected item after attributes error.
3582     fn expected_item_err(&self, attrs: &[Attribute]) {
3583         let message = match attrs.last() {
3584             Some(&Attribute { node: ast::Attribute_ { is_sugared_doc: true, .. }, .. }) => {
3585                 "expected item after doc comment"
3586             }
3587             _ => "expected item after attributes",
3588         };
3589
3590         self.span_err(self.last_span, message);
3591     }
3592
3593     /// Parse a statement. may include decl.
3594     pub fn parse_stmt(&mut self) -> PResult<'a, Option<P<Stmt>>> {
3595         Ok(try!(self.parse_stmt_()).map(P))
3596     }
3597
3598     fn parse_stmt_(&mut self) -> PResult<'a, Option<Stmt>> {
3599         maybe_whole!(Some deref self, NtStmt);
3600
3601         let attrs = try!(self.parse_outer_attributes());
3602         let lo = self.span.lo;
3603
3604         Ok(Some(if self.check_keyword(keywords::Let) {
3605             try!(self.expect_keyword(keywords::Let));
3606             let decl = try!(self.parse_let(attrs.into_thin_attrs()));
3607             let hi = decl.span.hi;
3608             let stmt = StmtDecl(decl, ast::DUMMY_NODE_ID);
3609             spanned(lo, hi, stmt)
3610         } else if self.token.is_ident()
3611             && !self.token.is_any_keyword()
3612             && self.look_ahead(1, |t| *t == token::Not) {
3613             // it's a macro invocation:
3614
3615             // Potential trouble: if we allow macros with paths instead of
3616             // idents, we'd need to look ahead past the whole path here...
3617             let pth = try!(self.parse_path(NoTypesAllowed));
3618             self.bump();
3619
3620             let id = match self.token {
3621                 token::OpenDelim(_) => token::special_idents::invalid, // no special identifier
3622                 _ => try!(self.parse_ident()),
3623             };
3624
3625             // check that we're pointing at delimiters (need to check
3626             // again after the `if`, because of `parse_ident`
3627             // consuming more tokens).
3628             let delim = match self.token {
3629                 token::OpenDelim(delim) => delim,
3630                 _ => {
3631                     // we only expect an ident if we didn't parse one
3632                     // above.
3633                     let ident_str = if id.name == token::special_idents::invalid.name {
3634                         "identifier, "
3635                     } else {
3636                         ""
3637                     };
3638                     let tok_str = self.this_token_to_string();
3639                     return Err(self.fatal(&format!("expected {}`(` or `{{`, found `{}`",
3640                                        ident_str,
3641                                        tok_str)))
3642                 },
3643             };
3644
3645             let tts = try!(self.parse_unspanned_seq(
3646                 &token::OpenDelim(delim),
3647                 &token::CloseDelim(delim),
3648                 seq_sep_none(),
3649                 |p| p.parse_token_tree()
3650             ));
3651             let hi = self.last_span.hi;
3652
3653             let style = if delim == token::Brace {
3654                 MacStmtWithBraces
3655             } else {
3656                 MacStmtWithoutBraces
3657             };
3658
3659             if id.name == token::special_idents::invalid.name {
3660                 let stmt = StmtMac(P(spanned(lo,
3661                                              hi,
3662                                              Mac_ { path: pth, tts: tts, ctxt: EMPTY_CTXT })),
3663                                    style,
3664                                    attrs.into_thin_attrs());
3665                 spanned(lo, hi, stmt)
3666             } else {
3667                 // if it has a special ident, it's definitely an item
3668                 //
3669                 // Require a semicolon or braces.
3670                 if style != MacStmtWithBraces {
3671                     if !self.eat(&token::Semi) {
3672                         let last_span = self.last_span;
3673                         self.span_err(last_span,
3674                                       "macros that expand to items must \
3675                                        either be surrounded with braces or \
3676                                        followed by a semicolon");
3677                     }
3678                 }
3679                 spanned(lo, hi, StmtDecl(
3680                     P(spanned(lo, hi, DeclItem(
3681                         self.mk_item(
3682                             lo, hi, id /*id is good here*/,
3683                             ItemMac(spanned(lo, hi,
3684                                             Mac_ { path: pth, tts: tts, ctxt: EMPTY_CTXT })),
3685                             Inherited, attrs)))),
3686                     ast::DUMMY_NODE_ID))
3687             }
3688         } else {
3689             // FIXME: Bad copy of attrs
3690             match try!(self.parse_item_(attrs.clone(), false, true)) {
3691                 Some(i) => {
3692                     let hi = i.span.hi;
3693                     let decl = P(spanned(lo, hi, DeclItem(i)));
3694                     spanned(lo, hi, StmtDecl(decl, ast::DUMMY_NODE_ID))
3695                 }
3696                 None => {
3697                     let unused_attrs = |attrs: &[_], s: &mut Self| {
3698                         if attrs.len() > 0 {
3699                             s.span_err(s.span,
3700                                 "expected statement after outer attribute");
3701                         }
3702                     };
3703
3704                     // Do not attempt to parse an expression if we're done here.
3705                     if self.token == token::Semi {
3706                         unused_attrs(&attrs, self);
3707                         self.bump();
3708                         return Ok(None);
3709                     }
3710
3711                     if self.token == token::CloseDelim(token::Brace) {
3712                         unused_attrs(&attrs, self);
3713                         return Ok(None);
3714                     }
3715
3716                     // Remainder are line-expr stmts.
3717                     let e = try!(self.parse_expr_res(
3718                         Restrictions::RESTRICTION_STMT_EXPR, Some(attrs.into_thin_attrs())));
3719                     let hi = e.span.hi;
3720                     let stmt = StmtExpr(e, ast::DUMMY_NODE_ID);
3721                     spanned(lo, hi, stmt)
3722                 }
3723             }
3724         }))
3725     }
3726
3727     /// Is this expression a successfully-parsed statement?
3728     fn expr_is_complete(&mut self, e: &Expr) -> bool {
3729         self.restrictions.contains(Restrictions::RESTRICTION_STMT_EXPR) &&
3730             !classify::expr_requires_semi_to_be_stmt(e)
3731     }
3732
3733     /// Parse a block. No inner attrs are allowed.
3734     pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
3735         maybe_whole!(no_clone self, NtBlock);
3736
3737         let lo = self.span.lo;
3738
3739         if !self.eat(&token::OpenDelim(token::Brace)) {
3740             let sp = self.span;
3741             let tok = self.this_token_to_string();
3742             return Err(self.span_fatal_help(sp,
3743                                  &format!("expected `{{`, found `{}`", tok),
3744                                  "place this code inside a block"));
3745         }
3746
3747         self.parse_block_tail(lo, DefaultBlock)
3748     }
3749
3750     /// Parse a block. Inner attrs are allowed.
3751     fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
3752         maybe_whole!(pair_empty self, NtBlock);
3753
3754         let lo = self.span.lo;
3755         try!(self.expect(&token::OpenDelim(token::Brace)));
3756         Ok((try!(self.parse_inner_attributes()),
3757          try!(self.parse_block_tail(lo, DefaultBlock))))
3758     }
3759
3760     /// Parse the rest of a block expression or function body
3761     /// Precondition: already parsed the '{'.
3762     fn parse_block_tail(&mut self, lo: BytePos, s: BlockCheckMode) -> PResult<'a, P<Block>> {
3763         let mut stmts = vec![];
3764         let mut expr = None;
3765
3766         while !self.eat(&token::CloseDelim(token::Brace)) {
3767             let Spanned {node, span} = if let Some(s) = try!(self.parse_stmt_()) {
3768                 s
3769             } else {
3770                 // Found only `;` or `}`.
3771                 continue;
3772             };
3773             match node {
3774                 StmtExpr(e, _) => {
3775                     try!(self.handle_expression_like_statement(e, span, &mut stmts, &mut expr));
3776                 }
3777                 StmtMac(mac, MacStmtWithoutBraces, attrs) => {
3778                     // statement macro without braces; might be an
3779                     // expr depending on whether a semicolon follows
3780                     match self.token {
3781                         token::Semi => {
3782                             stmts.push(P(Spanned {
3783                                 node: StmtMac(mac, MacStmtWithSemicolon, attrs),
3784                                 span: mk_sp(span.lo, self.span.hi),
3785                             }));
3786                             self.bump();
3787                         }
3788                         _ => {
3789                             let e = self.mk_mac_expr(span.lo, span.hi,
3790                                                      mac.and_then(|m| m.node),
3791                                                      None);
3792                             let e = try!(self.parse_dot_or_call_expr_with(e, attrs));
3793                             let e = try!(self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e)));
3794                             try!(self.handle_expression_like_statement(
3795                                 e,
3796                                 span,
3797                                 &mut stmts,
3798                                 &mut expr));
3799                         }
3800                     }
3801                 }
3802                 StmtMac(m, style, attrs) => {
3803                     // statement macro; might be an expr
3804                     match self.token {
3805                         token::Semi => {
3806                             stmts.push(P(Spanned {
3807                                 node: StmtMac(m, MacStmtWithSemicolon, attrs),
3808                                 span: mk_sp(span.lo, self.span.hi),
3809                             }));
3810                             self.bump();
3811                         }
3812                         token::CloseDelim(token::Brace) => {
3813                             // if a block ends in `m!(arg)` without
3814                             // a `;`, it must be an expr
3815                             expr = Some(self.mk_mac_expr(span.lo, span.hi,
3816                                                          m.and_then(|x| x.node),
3817                                                          attrs));
3818                         }
3819                         _ => {
3820                             stmts.push(P(Spanned {
3821                                 node: StmtMac(m, style, attrs),
3822                                 span: span
3823                             }));
3824                         }
3825                     }
3826                 }
3827                 _ => { // all other kinds of statements:
3828                     let mut hi = span.hi;
3829                     if classify::stmt_ends_with_semi(&node) {
3830                         try!(self.commit_stmt_expecting(token::Semi));
3831                         hi = self.last_span.hi;
3832                     }
3833
3834                     stmts.push(P(Spanned {
3835                         node: node,
3836                         span: mk_sp(span.lo, hi)
3837                     }));
3838                 }
3839             }
3840         }
3841
3842         Ok(P(ast::Block {
3843             stmts: stmts,
3844             expr: expr,
3845             id: ast::DUMMY_NODE_ID,
3846             rules: s,
3847             span: mk_sp(lo, self.last_span.hi),
3848         }))
3849     }
3850
3851     fn handle_expression_like_statement(
3852             &mut self,
3853             e: P<Expr>,
3854             span: Span,
3855             stmts: &mut Vec<P<Stmt>>,
3856             last_block_expr: &mut Option<P<Expr>>) -> PResult<'a, ()> {
3857         // expression without semicolon
3858         if classify::expr_requires_semi_to_be_stmt(&*e) {
3859             // Just check for errors and recover; do not eat semicolon yet.
3860             try!(self.commit_stmt(&[],
3861                              &[token::Semi, token::CloseDelim(token::Brace)]));
3862         }
3863
3864         match self.token {
3865             token::Semi => {
3866                 self.bump();
3867                 let span_with_semi = Span {
3868                     lo: span.lo,
3869                     hi: self.last_span.hi,
3870                     expn_id: span.expn_id,
3871                 };
3872                 stmts.push(P(Spanned {
3873                     node: StmtSemi(e, ast::DUMMY_NODE_ID),
3874                     span: span_with_semi,
3875                 }));
3876             }
3877             token::CloseDelim(token::Brace) => *last_block_expr = Some(e),
3878             _ => {
3879                 stmts.push(P(Spanned {
3880                     node: StmtExpr(e, ast::DUMMY_NODE_ID),
3881                     span: span
3882                 }));
3883             }
3884         }
3885         Ok(())
3886     }
3887
3888     // Parses a sequence of bounds if a `:` is found,
3889     // otherwise returns empty list.
3890     fn parse_colon_then_ty_param_bounds(&mut self,
3891                                         mode: BoundParsingMode)
3892                                         -> PResult<'a, TyParamBounds>
3893     {
3894         if !self.eat(&token::Colon) {
3895             Ok(P::empty())
3896         } else {
3897             self.parse_ty_param_bounds(mode)
3898         }
3899     }
3900
3901     // matches bounds    = ( boundseq )?
3902     // where   boundseq  = ( polybound + boundseq ) | polybound
3903     // and     polybound = ( 'for' '<' 'region '>' )? bound
3904     // and     bound     = 'region | trait_ref
3905     fn parse_ty_param_bounds(&mut self,
3906                              mode: BoundParsingMode)
3907                              -> PResult<'a, TyParamBounds>
3908     {
3909         let mut result = vec!();
3910         loop {
3911             let question_span = self.span;
3912             let ate_question = self.eat(&token::Question);
3913             match self.token {
3914                 token::Lifetime(lifetime) => {
3915                     if ate_question {
3916                         self.span_err(question_span,
3917                                       "`?` may only modify trait bounds, not lifetime bounds");
3918                     }
3919                     result.push(RegionTyParamBound(ast::Lifetime {
3920                         id: ast::DUMMY_NODE_ID,
3921                         span: self.span,
3922                         name: lifetime.name
3923                     }));
3924                     self.bump();
3925                 }
3926                 token::ModSep | token::Ident(..) => {
3927                     let poly_trait_ref = try!(self.parse_poly_trait_ref());
3928                     let modifier = if ate_question {
3929                         if mode == BoundParsingMode::Modified {
3930                             TraitBoundModifier::Maybe
3931                         } else {
3932                             self.span_err(question_span,
3933                                           "unexpected `?`");
3934                             TraitBoundModifier::None
3935                         }
3936                     } else {
3937                         TraitBoundModifier::None
3938                     };
3939                     result.push(TraitTyParamBound(poly_trait_ref, modifier))
3940                 }
3941                 _ => break,
3942             }
3943
3944             if !self.eat(&token::BinOp(token::Plus)) {
3945                 break;
3946             }
3947         }
3948
3949         return Ok(P::from_vec(result));
3950     }
3951
3952     /// Matches typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?
3953     fn parse_ty_param(&mut self) -> PResult<'a, TyParam> {
3954         let span = self.span;
3955         let ident = try!(self.parse_ident());
3956
3957         let bounds = try!(self.parse_colon_then_ty_param_bounds(BoundParsingMode::Modified));
3958
3959         let default = if self.check(&token::Eq) {
3960             self.bump();
3961             Some(try!(self.parse_ty_sum()))
3962         } else {
3963             None
3964         };
3965
3966         Ok(TyParam {
3967             ident: ident,
3968             id: ast::DUMMY_NODE_ID,
3969             bounds: bounds,
3970             default: default,
3971             span: span,
3972         })
3973     }
3974
3975     /// Parse a set of optional generic type parameter declarations. Where
3976     /// clauses are not parsed here, and must be added later via
3977     /// `parse_where_clause()`.
3978     ///
3979     /// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
3980     ///                  | ( < lifetimes , typaramseq ( , )? > )
3981     /// where   typaramseq = ( typaram ) | ( typaram , typaramseq )
3982     pub fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
3983         maybe_whole!(self, NtGenerics);
3984
3985         if self.eat(&token::Lt) {
3986             let lifetime_defs = try!(self.parse_lifetime_defs());
3987             let mut seen_default = false;
3988             let ty_params = try!(self.parse_seq_to_gt(Some(token::Comma), |p| {
3989                 try!(p.forbid_lifetime());
3990                 let ty_param = try!(p.parse_ty_param());
3991                 if ty_param.default.is_some() {
3992                     seen_default = true;
3993                 } else if seen_default {
3994                     let last_span = p.last_span;
3995                     p.span_err(last_span,
3996                                "type parameters with a default must be trailing");
3997                 }
3998                 Ok(ty_param)
3999             }));
4000             Ok(ast::Generics {
4001                 lifetimes: lifetime_defs,
4002                 ty_params: ty_params,
4003                 where_clause: WhereClause {
4004                     id: ast::DUMMY_NODE_ID,
4005                     predicates: Vec::new(),
4006                 }
4007             })
4008         } else {
4009             Ok(ast::Generics::default())
4010         }
4011     }
4012
4013     fn parse_generic_values_after_lt(&mut self) -> PResult<'a, (Vec<ast::Lifetime>,
4014                                                             Vec<P<Ty>>,
4015                                                             Vec<P<TypeBinding>>)> {
4016         let span_lo = self.span.lo;
4017         let lifetimes = try!(self.parse_lifetimes(token::Comma));
4018
4019         let missing_comma = !lifetimes.is_empty() &&
4020                             !self.token.is_like_gt() &&
4021                             self.last_token
4022                                 .as_ref().map_or(true,
4023                                                  |x| &**x != &token::Comma);
4024
4025         if missing_comma {
4026
4027             let msg = format!("expected `,` or `>` after lifetime \
4028                               name, found `{}`",
4029                               self.this_token_to_string());
4030             let mut err = self.diagnostic().struct_span_err(self.span, &msg);
4031
4032             let span_hi = self.span.hi;
4033             let span_hi = if self.parse_ty().is_ok() {
4034                 self.span.hi
4035             } else {
4036                 span_hi
4037             };
4038
4039             let msg = format!("did you mean a single argument type &'a Type, \
4040                               or did you mean the comma-separated arguments \
4041                               'a, Type?");
4042             err.span_note(mk_sp(span_lo, span_hi), &msg);
4043             err.emit();
4044
4045             self.abort_if_errors()
4046         }
4047
4048         // First parse types.
4049         let (types, returned) = try!(self.parse_seq_to_gt_or_return(
4050             Some(token::Comma),
4051             |p| {
4052                 try!(p.forbid_lifetime());
4053                 if p.look_ahead(1, |t| t == &token::Eq) {
4054                     Ok(None)
4055                 } else {
4056                     Ok(Some(try!(p.parse_ty_sum())))
4057                 }
4058             }
4059         ));
4060
4061         // If we found the `>`, don't continue.
4062         if !returned {
4063             return Ok((lifetimes, types.into_vec(), Vec::new()));
4064         }
4065
4066         // Then parse type bindings.
4067         let bindings = try!(self.parse_seq_to_gt(
4068             Some(token::Comma),
4069             |p| {
4070                 try!(p.forbid_lifetime());
4071                 let lo = p.span.lo;
4072                 let ident = try!(p.parse_ident());
4073                 let found_eq = p.eat(&token::Eq);
4074                 if !found_eq {
4075                     let span = p.span;
4076                     p.span_warn(span, "whoops, no =?");
4077                 }
4078                 let ty = try!(p.parse_ty());
4079                 let hi = ty.span.hi;
4080                 let span = mk_sp(lo, hi);
4081                 return Ok(P(TypeBinding{id: ast::DUMMY_NODE_ID,
4082                     ident: ident,
4083                     ty: ty,
4084                     span: span,
4085                 }));
4086             }
4087         ));
4088         Ok((lifetimes, types.into_vec(), bindings.into_vec()))
4089     }
4090
4091     fn forbid_lifetime(&mut self) -> PResult<'a, ()> {
4092         if self.token.is_lifetime() {
4093             let span = self.span;
4094             return Err(self.span_fatal(span, "lifetime parameters must be declared \
4095                                         prior to type parameters"))
4096         }
4097         Ok(())
4098     }
4099
4100     /// Parses an optional `where` clause and places it in `generics`.
4101     ///
4102     /// ```ignore
4103     /// where T : Trait<U, V> + 'b, 'a : 'b
4104     /// ```
4105     pub fn parse_where_clause(&mut self) -> PResult<'a, ast::WhereClause> {
4106         maybe_whole!(self, NtWhereClause);
4107
4108         let mut where_clause = WhereClause {
4109             id: ast::DUMMY_NODE_ID,
4110             predicates: Vec::new(),
4111         };
4112
4113         if !self.eat_keyword(keywords::Where) {
4114             return Ok(where_clause);
4115         }
4116
4117         let mut parsed_something = false;
4118         loop {
4119             let lo = self.span.lo;
4120             match self.token {
4121                 token::OpenDelim(token::Brace) => {
4122                     break
4123                 }
4124
4125                 token::Lifetime(..) => {
4126                     let bounded_lifetime =
4127                         try!(self.parse_lifetime());
4128
4129                     self.eat(&token::Colon);
4130
4131                     let bounds =
4132                         try!(self.parse_lifetimes(token::BinOp(token::Plus)));
4133
4134                     let hi = self.last_span.hi;
4135                     let span = mk_sp(lo, hi);
4136
4137                     where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
4138                         ast::WhereRegionPredicate {
4139                             span: span,
4140                             lifetime: bounded_lifetime,
4141                             bounds: bounds
4142                         }
4143                     ));
4144
4145                     parsed_something = true;
4146                 }
4147
4148                 _ => {
4149                     let bound_lifetimes = if self.eat_keyword(keywords::For) {
4150                         // Higher ranked constraint.
4151                         try!(self.expect(&token::Lt));
4152                         let lifetime_defs = try!(self.parse_lifetime_defs());
4153                         try!(self.expect_gt());
4154                         lifetime_defs
4155                     } else {
4156                         vec![]
4157                     };
4158
4159                     let bounded_ty = try!(self.parse_ty());
4160
4161                     if self.eat(&token::Colon) {
4162                         let bounds = try!(self.parse_ty_param_bounds(BoundParsingMode::Bare));
4163                         let hi = self.last_span.hi;
4164                         let span = mk_sp(lo, hi);
4165
4166                         if bounds.is_empty() {
4167                             self.span_err(span,
4168                                           "each predicate in a `where` clause must have \
4169                                            at least one bound in it");
4170                         }
4171
4172                         where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
4173                                 ast::WhereBoundPredicate {
4174                                     span: span,
4175                                     bound_lifetimes: bound_lifetimes,
4176                                     bounded_ty: bounded_ty,
4177                                     bounds: bounds,
4178                         }));
4179
4180                         parsed_something = true;
4181                     } else if self.eat(&token::Eq) {
4182                         // let ty = try!(self.parse_ty());
4183                         let hi = self.last_span.hi;
4184                         let span = mk_sp(lo, hi);
4185                         // where_clause.predicates.push(
4186                         //     ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
4187                         //         id: ast::DUMMY_NODE_ID,
4188                         //         span: span,
4189                         //         path: panic!("NYI"), //bounded_ty,
4190                         //         ty: ty,
4191                         // }));
4192                         // parsed_something = true;
4193                         // // FIXME(#18433)
4194                         self.span_err(span,
4195                                      "equality constraints are not yet supported \
4196                                      in where clauses (#20041)");
4197                     } else {
4198                         let last_span = self.last_span;
4199                         self.span_err(last_span,
4200                               "unexpected token in `where` clause");
4201                     }
4202                 }
4203             };
4204
4205             if !self.eat(&token::Comma) {
4206                 break
4207             }
4208         }
4209
4210         if !parsed_something {
4211             let last_span = self.last_span;
4212             self.span_err(last_span,
4213                           "a `where` clause must have at least one predicate \
4214                            in it");
4215         }
4216
4217         Ok(where_clause)
4218     }
4219
4220     fn parse_fn_args(&mut self, named_args: bool, allow_variadic: bool)
4221                      -> PResult<'a, (Vec<Arg> , bool)> {
4222         let sp = self.span;
4223         let mut args: Vec<Option<Arg>> =
4224             try!(self.parse_unspanned_seq(
4225                 &token::OpenDelim(token::Paren),
4226                 &token::CloseDelim(token::Paren),
4227                 seq_sep_trailing_allowed(token::Comma),
4228                 |p| {
4229                     if p.token == token::DotDotDot {
4230                         p.bump();
4231                         if allow_variadic {
4232                             if p.token != token::CloseDelim(token::Paren) {
4233                                 let span = p.span;
4234                                 return Err(p.span_fatal(span,
4235                                     "`...` must be last in argument list for variadic function"))
4236                             }
4237                         } else {
4238                             let span = p.span;
4239                             return Err(p.span_fatal(span,
4240                                          "only foreign functions are allowed to be variadic"))
4241                         }
4242                         Ok(None)
4243                     } else {
4244                         Ok(Some(try!(p.parse_arg_general(named_args))))
4245                     }
4246                 }
4247             ));
4248
4249         let variadic = match args.pop() {
4250             Some(None) => true,
4251             Some(x) => {
4252                 // Need to put back that last arg
4253                 args.push(x);
4254                 false
4255             }
4256             None => false
4257         };
4258
4259         if variadic && args.is_empty() {
4260             self.span_err(sp,
4261                           "variadic function must be declared with at least one named argument");
4262         }
4263
4264         let args = args.into_iter().map(|x| x.unwrap()).collect();
4265
4266         Ok((args, variadic))
4267     }
4268
4269     /// Parse the argument list and result type of a function declaration
4270     pub fn parse_fn_decl(&mut self, allow_variadic: bool) -> PResult<'a, P<FnDecl>> {
4271
4272         let (args, variadic) = try!(self.parse_fn_args(true, allow_variadic));
4273         let ret_ty = try!(self.parse_ret_ty());
4274
4275         Ok(P(FnDecl {
4276             inputs: args,
4277             output: ret_ty,
4278             variadic: variadic
4279         }))
4280     }
4281
4282     fn is_self_ident(&mut self) -> bool {
4283         match self.token {
4284           token::Ident(id, token::Plain) => id.name == special_idents::self_.name,
4285           _ => false
4286         }
4287     }
4288
4289     fn expect_self_ident(&mut self) -> PResult<'a, ast::Ident> {
4290         match self.token {
4291             token::Ident(id, token::Plain) if id.name == special_idents::self_.name => {
4292                 self.bump();
4293                 Ok(id)
4294             },
4295             _ => {
4296                 let token_str = self.this_token_to_string();
4297                 return Err(self.fatal(&format!("expected `self`, found `{}`",
4298                                    token_str)))
4299             }
4300         }
4301     }
4302
4303     fn is_self_type_ident(&mut self) -> bool {
4304         match self.token {
4305           token::Ident(id, token::Plain) => id.name == special_idents::type_self.name,
4306           _ => false
4307         }
4308     }
4309
4310     fn expect_self_type_ident(&mut self) -> PResult<'a, ast::Ident> {
4311         match self.token {
4312             token::Ident(id, token::Plain) if id.name == special_idents::type_self.name => {
4313                 self.bump();
4314                 Ok(id)
4315             },
4316             _ => {
4317                 let token_str = self.this_token_to_string();
4318                 Err(self.fatal(&format!("expected `Self`, found `{}`",
4319                                    token_str)))
4320             }
4321         }
4322     }
4323
4324     /// Parse the argument list and result type of a function
4325     /// that may have a self type.
4326     fn parse_fn_decl_with_self<F>(&mut self,
4327                                   parse_arg_fn: F) -> PResult<'a, (ExplicitSelf, P<FnDecl>)> where
4328         F: FnMut(&mut Parser<'a>) -> PResult<'a,  Arg>,
4329     {
4330         fn maybe_parse_borrowed_explicit_self<'b>(this: &mut Parser<'b>)
4331                                                   -> PResult<'b,  ast::ExplicitSelf_> {
4332             // The following things are possible to see here:
4333             //
4334             //     fn(&mut self)
4335             //     fn(&mut self)
4336             //     fn(&'lt self)
4337             //     fn(&'lt mut self)
4338             //
4339             // We already know that the current token is `&`.
4340
4341             if this.look_ahead(1, |t| t.is_keyword(keywords::SelfValue)) {
4342                 this.bump();
4343                 Ok(SelfRegion(None, MutImmutable, try!(this.expect_self_ident())))
4344             } else if this.look_ahead(1, |t| t.is_mutability()) &&
4345                       this.look_ahead(2, |t| t.is_keyword(keywords::SelfValue)) {
4346                 this.bump();
4347                 let mutability = try!(this.parse_mutability());
4348                 Ok(SelfRegion(None, mutability, try!(this.expect_self_ident())))
4349             } else if this.look_ahead(1, |t| t.is_lifetime()) &&
4350                       this.look_ahead(2, |t| t.is_keyword(keywords::SelfValue)) {
4351                 this.bump();
4352                 let lifetime = try!(this.parse_lifetime());
4353                 Ok(SelfRegion(Some(lifetime), MutImmutable, try!(this.expect_self_ident())))
4354             } else if this.look_ahead(1, |t| t.is_lifetime()) &&
4355                       this.look_ahead(2, |t| t.is_mutability()) &&
4356                       this.look_ahead(3, |t| t.is_keyword(keywords::SelfValue)) {
4357                 this.bump();
4358                 let lifetime = try!(this.parse_lifetime());
4359                 let mutability = try!(this.parse_mutability());
4360                 Ok(SelfRegion(Some(lifetime), mutability, try!(this.expect_self_ident())))
4361             } else {
4362                 Ok(SelfStatic)
4363             }
4364         }
4365
4366         try!(self.expect(&token::OpenDelim(token::Paren)));
4367
4368         // A bit of complexity and lookahead is needed here in order to be
4369         // backwards compatible.
4370         let lo = self.span.lo;
4371         let mut self_ident_lo = self.span.lo;
4372         let mut self_ident_hi = self.span.hi;
4373
4374         let mut mutbl_self = MutImmutable;
4375         let explicit_self = match self.token {
4376             token::BinOp(token::And) => {
4377                 let eself = try!(maybe_parse_borrowed_explicit_self(self));
4378                 self_ident_lo = self.last_span.lo;
4379                 self_ident_hi = self.last_span.hi;
4380                 eself
4381             }
4382             token::BinOp(token::Star) => {
4383                 // Possibly "*self" or "*mut self" -- not supported. Try to avoid
4384                 // emitting cryptic "unexpected token" errors.
4385                 self.bump();
4386                 let _mutability = if self.token.is_mutability() {
4387                     try!(self.parse_mutability())
4388                 } else {
4389                     MutImmutable
4390                 };
4391                 if self.is_self_ident() {
4392                     let span = self.span;
4393                     self.span_err(span, "cannot pass self by raw pointer");
4394                     self.bump();
4395                 }
4396                 // error case, making bogus self ident:
4397                 SelfValue(special_idents::self_)
4398             }
4399             token::Ident(..) => {
4400                 if self.is_self_ident() {
4401                     let self_ident = try!(self.expect_self_ident());
4402
4403                     // Determine whether this is the fully explicit form, `self:
4404                     // TYPE`.
4405                     if self.eat(&token::Colon) {
4406                         SelfExplicit(try!(self.parse_ty_sum()), self_ident)
4407                     } else {
4408                         SelfValue(self_ident)
4409                     }
4410                 } else if self.token.is_mutability() &&
4411                         self.look_ahead(1, |t| t.is_keyword(keywords::SelfValue)) {
4412                     mutbl_self = try!(self.parse_mutability());
4413                     let self_ident = try!(self.expect_self_ident());
4414
4415                     // Determine whether this is the fully explicit form,
4416                     // `self: TYPE`.
4417                     if self.eat(&token::Colon) {
4418                         SelfExplicit(try!(self.parse_ty_sum()), self_ident)
4419                     } else {
4420                         SelfValue(self_ident)
4421                     }
4422                 } else {
4423                     SelfStatic
4424                 }
4425             }
4426             _ => SelfStatic,
4427         };
4428
4429         let explicit_self_sp = mk_sp(self_ident_lo, self_ident_hi);
4430
4431         // shared fall-through for the three cases below. borrowing prevents simply
4432         // writing this as a closure
4433         macro_rules! parse_remaining_arguments {
4434             ($self_id:ident) =>
4435             {
4436             // If we parsed a self type, expect a comma before the argument list.
4437             match self.token {
4438                 token::Comma => {
4439                     self.bump();
4440                     let sep = seq_sep_trailing_allowed(token::Comma);
4441                     let mut fn_inputs = try!(self.parse_seq_to_before_end(
4442                         &token::CloseDelim(token::Paren),
4443                         sep,
4444                         parse_arg_fn
4445                     ));
4446                     fn_inputs.insert(0, Arg::new_self(explicit_self_sp, mutbl_self, $self_id));
4447                     fn_inputs
4448                 }
4449                 token::CloseDelim(token::Paren) => {
4450                     vec!(Arg::new_self(explicit_self_sp, mutbl_self, $self_id))
4451                 }
4452                 _ => {
4453                     let token_str = self.this_token_to_string();
4454                     return Err(self.fatal(&format!("expected `,` or `)`, found `{}`",
4455                                        token_str)))
4456                 }
4457             }
4458             }
4459         }
4460
4461         let fn_inputs = match explicit_self {
4462             SelfStatic =>  {
4463                 let sep = seq_sep_trailing_allowed(token::Comma);
4464                 try!(self.parse_seq_to_before_end(&token::CloseDelim(token::Paren),
4465                                                   sep, parse_arg_fn))
4466             }
4467             SelfValue(id) => parse_remaining_arguments!(id),
4468             SelfRegion(_,_,id) => parse_remaining_arguments!(id),
4469             SelfExplicit(_,id) => parse_remaining_arguments!(id),
4470         };
4471
4472
4473         try!(self.expect(&token::CloseDelim(token::Paren)));
4474
4475         let hi = self.span.hi;
4476
4477         let ret_ty = try!(self.parse_ret_ty());
4478
4479         let fn_decl = P(FnDecl {
4480             inputs: fn_inputs,
4481             output: ret_ty,
4482             variadic: false
4483         });
4484
4485         Ok((spanned(lo, hi, explicit_self), fn_decl))
4486     }
4487
4488     // parse the |arg, arg| header on a lambda
4489     fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
4490         let inputs_captures = {
4491             if self.eat(&token::OrOr) {
4492                 Vec::new()
4493             } else {
4494                 try!(self.expect(&token::BinOp(token::Or)));
4495                 try!(self.parse_obsolete_closure_kind());
4496                 let args = try!(self.parse_seq_to_before_end(
4497                     &token::BinOp(token::Or),
4498                     seq_sep_trailing_allowed(token::Comma),
4499                     |p| p.parse_fn_block_arg()
4500                 ));
4501                 self.bump();
4502                 args
4503             }
4504         };
4505         let output = try!(self.parse_ret_ty());
4506
4507         Ok(P(FnDecl {
4508             inputs: inputs_captures,
4509             output: output,
4510             variadic: false
4511         }))
4512     }
4513
4514     /// Parse the name and optional generic types of a function header.
4515     fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> {
4516         let id = try!(self.parse_ident());
4517         let generics = try!(self.parse_generics());
4518         Ok((id, generics))
4519     }
4520
4521     fn mk_item(&mut self, lo: BytePos, hi: BytePos, ident: Ident,
4522                node: Item_, vis: Visibility,
4523                attrs: Vec<Attribute>) -> P<Item> {
4524         P(Item {
4525             ident: ident,
4526             attrs: attrs,
4527             id: ast::DUMMY_NODE_ID,
4528             node: node,
4529             vis: vis,
4530             span: mk_sp(lo, hi)
4531         })
4532     }
4533
4534     /// Parse an item-position function declaration.
4535     fn parse_item_fn(&mut self,
4536                      unsafety: Unsafety,
4537                      constness: Constness,
4538                      abi: abi::Abi)
4539                      -> PResult<'a, ItemInfo> {
4540         let (ident, mut generics) = try!(self.parse_fn_header());
4541         let decl = try!(self.parse_fn_decl(false));
4542         generics.where_clause = try!(self.parse_where_clause());
4543         let (inner_attrs, body) = try!(self.parse_inner_attrs_and_block());
4544         Ok((ident, ItemFn(decl, unsafety, constness, abi, generics, body), Some(inner_attrs)))
4545     }
4546
4547     /// true if we are looking at `const ID`, false for things like `const fn` etc
4548     pub fn is_const_item(&mut self) -> bool {
4549         self.token.is_keyword(keywords::Const) &&
4550             !self.look_ahead(1, |t| t.is_keyword(keywords::Fn)) &&
4551             !self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe))
4552     }
4553
4554     /// parses all the "front matter" for a `fn` declaration, up to
4555     /// and including the `fn` keyword:
4556     ///
4557     /// - `const fn`
4558     /// - `unsafe fn`
4559     /// - `const unsafe fn`
4560     /// - `extern fn`
4561     /// - etc
4562     pub fn parse_fn_front_matter(&mut self)
4563                                  -> PResult<'a, (ast::Constness, ast::Unsafety, abi::Abi)> {
4564         let is_const_fn = self.eat_keyword(keywords::Const);
4565         let unsafety = try!(self.parse_unsafety());
4566         let (constness, unsafety, abi) = if is_const_fn {
4567             (Constness::Const, unsafety, abi::Rust)
4568         } else {
4569             let abi = if self.eat_keyword(keywords::Extern) {
4570                 try!(self.parse_opt_abi()).unwrap_or(abi::C)
4571             } else {
4572                 abi::Rust
4573             };
4574             (Constness::NotConst, unsafety, abi)
4575         };
4576         try!(self.expect_keyword(keywords::Fn));
4577         Ok((constness, unsafety, abi))
4578     }
4579
4580     /// Parse an impl item.
4581     pub fn parse_impl_item(&mut self) -> PResult<'a, P<ImplItem>> {
4582         maybe_whole!(no_clone self, NtImplItem);
4583
4584         let mut attrs = try!(self.parse_outer_attributes());
4585         let lo = self.span.lo;
4586         let vis = try!(self.parse_visibility());
4587         let (name, node) = if self.eat_keyword(keywords::Type) {
4588             let name = try!(self.parse_ident());
4589             try!(self.expect(&token::Eq));
4590             let typ = try!(self.parse_ty_sum());
4591             try!(self.expect(&token::Semi));
4592             (name, ast::ImplItemKind::Type(typ))
4593         } else if self.is_const_item() {
4594             try!(self.expect_keyword(keywords::Const));
4595             let name = try!(self.parse_ident());
4596             try!(self.expect(&token::Colon));
4597             let typ = try!(self.parse_ty_sum());
4598             try!(self.expect(&token::Eq));
4599             let expr = try!(self.parse_expr());
4600             try!(self.commit_expr_expecting(&expr, token::Semi));
4601             (name, ast::ImplItemKind::Const(typ, expr))
4602         } else {
4603             let (name, inner_attrs, node) = try!(self.parse_impl_method(vis));
4604             attrs.extend(inner_attrs);
4605             (name, node)
4606         };
4607
4608         Ok(P(ImplItem {
4609             id: ast::DUMMY_NODE_ID,
4610             span: mk_sp(lo, self.last_span.hi),
4611             ident: name,
4612             vis: vis,
4613             attrs: attrs,
4614             node: node
4615         }))
4616     }
4617
4618     fn complain_if_pub_macro(&mut self, visa: Visibility, span: Span) {
4619         match visa {
4620             Public => {
4621                 self.diagnostic().struct_span_err(span, "can't qualify macro invocation with `pub`")
4622                                  .fileline_help(span, "try adjusting the macro to put `pub` inside \
4623                                                        the invocation")
4624                                  .emit();
4625             }
4626             Inherited => (),
4627         }
4628     }
4629
4630     /// Parse a method or a macro invocation in a trait impl.
4631     fn parse_impl_method(&mut self, vis: Visibility)
4632                          -> PResult<'a, (Ident, Vec<ast::Attribute>, ast::ImplItemKind)> {
4633         // code copied from parse_macro_use_or_failure... abstraction!
4634         if !self.token.is_any_keyword()
4635             && self.look_ahead(1, |t| *t == token::Not)
4636             && (self.look_ahead(2, |t| *t == token::OpenDelim(token::Paren))
4637                 || self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))) {
4638             // method macro.
4639
4640             let last_span = self.last_span;
4641             self.complain_if_pub_macro(vis, last_span);
4642
4643             let lo = self.span.lo;
4644             let pth = try!(self.parse_path(NoTypesAllowed));
4645             try!(self.expect(&token::Not));
4646
4647             // eat a matched-delimiter token tree:
4648             let delim = try!(self.expect_open_delim());
4649             let tts = try!(self.parse_seq_to_end(&token::CloseDelim(delim),
4650                                             seq_sep_none(),
4651                                             |p| p.parse_token_tree()));
4652             let m_ = Mac_ { path: pth, tts: tts, ctxt: EMPTY_CTXT };
4653             let m: ast::Mac = codemap::Spanned { node: m_,
4654                                                 span: mk_sp(lo,
4655                                                             self.last_span.hi) };
4656             if delim != token::Brace {
4657                 try!(self.expect(&token::Semi))
4658             }
4659             Ok((token::special_idents::invalid, vec![], ast::ImplItemKind::Macro(m)))
4660         } else {
4661             let (constness, unsafety, abi) = try!(self.parse_fn_front_matter());
4662             let ident = try!(self.parse_ident());
4663             let mut generics = try!(self.parse_generics());
4664             let (explicit_self, decl) = try!(self.parse_fn_decl_with_self(|p| {
4665                     p.parse_arg()
4666                 }));
4667             generics.where_clause = try!(self.parse_where_clause());
4668             let (inner_attrs, body) = try!(self.parse_inner_attrs_and_block());
4669             Ok((ident, inner_attrs, ast::ImplItemKind::Method(ast::MethodSig {
4670                 generics: generics,
4671                 abi: abi,
4672                 explicit_self: explicit_self,
4673                 unsafety: unsafety,
4674                 constness: constness,
4675                 decl: decl
4676              }, body)))
4677         }
4678     }
4679
4680     /// Parse trait Foo { ... }
4681     fn parse_item_trait(&mut self, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
4682
4683         let ident = try!(self.parse_ident());
4684         let mut tps = try!(self.parse_generics());
4685
4686         // Parse supertrait bounds.
4687         let bounds = try!(self.parse_colon_then_ty_param_bounds(BoundParsingMode::Bare));
4688
4689         tps.where_clause = try!(self.parse_where_clause());
4690
4691         let meths = try!(self.parse_trait_items());
4692         Ok((ident, ItemTrait(unsafety, tps, bounds, meths), None))
4693     }
4694
4695     /// Parses items implementations variants
4696     ///    impl<T> Foo { ... }
4697     ///    impl<T> ToString for &'static T { ... }
4698     ///    impl Send for .. {}
4699     fn parse_item_impl(&mut self, unsafety: ast::Unsafety) -> PResult<'a, ItemInfo> {
4700         let impl_span = self.span;
4701
4702         // First, parse type parameters if necessary.
4703         let mut generics = try!(self.parse_generics());
4704
4705         // Special case: if the next identifier that follows is '(', don't
4706         // allow this to be parsed as a trait.
4707         let could_be_trait = self.token != token::OpenDelim(token::Paren);
4708
4709         let neg_span = self.span;
4710         let polarity = if self.eat(&token::Not) {
4711             ast::ImplPolarity::Negative
4712         } else {
4713             ast::ImplPolarity::Positive
4714         };
4715
4716         // Parse the trait.
4717         let mut ty = try!(self.parse_ty_sum());
4718
4719         // Parse traits, if necessary.
4720         let opt_trait = if could_be_trait && self.eat_keyword(keywords::For) {
4721             // New-style trait. Reinterpret the type as a trait.
4722             match ty.node {
4723                 TyPath(None, ref path) => {
4724                     Some(TraitRef {
4725                         path: (*path).clone(),
4726                         ref_id: ty.id,
4727                     })
4728                 }
4729                 _ => {
4730                     self.span_err(ty.span, "not a trait");
4731                     None
4732                 }
4733             }
4734         } else {
4735             match polarity {
4736                 ast::ImplPolarity::Negative => {
4737                     // This is a negated type implementation
4738                     // `impl !MyType {}`, which is not allowed.
4739                     self.span_err(neg_span, "inherent implementation can't be negated");
4740                 },
4741                 _ => {}
4742             }
4743             None
4744         };
4745
4746         if opt_trait.is_some() && self.eat(&token::DotDot) {
4747             if generics.is_parameterized() {
4748                 self.span_err(impl_span, "default trait implementations are not \
4749                                           allowed to have generics");
4750             }
4751
4752             try!(self.expect(&token::OpenDelim(token::Brace)));
4753             try!(self.expect(&token::CloseDelim(token::Brace)));
4754             Ok((ast_util::impl_pretty_name(&opt_trait, None),
4755              ItemDefaultImpl(unsafety, opt_trait.unwrap()), None))
4756         } else {
4757             if opt_trait.is_some() {
4758                 ty = try!(self.parse_ty_sum());
4759             }
4760             generics.where_clause = try!(self.parse_where_clause());
4761
4762             try!(self.expect(&token::OpenDelim(token::Brace)));
4763             let attrs = try!(self.parse_inner_attributes());
4764
4765             let mut impl_items = vec![];
4766             while !self.eat(&token::CloseDelim(token::Brace)) {
4767                 impl_items.push(try!(self.parse_impl_item()));
4768             }
4769
4770             Ok((ast_util::impl_pretty_name(&opt_trait, Some(&*ty)),
4771              ItemImpl(unsafety, polarity, generics, opt_trait, ty, impl_items),
4772              Some(attrs)))
4773         }
4774     }
4775
4776     /// Parse a::B<String,i32>
4777     fn parse_trait_ref(&mut self) -> PResult<'a, TraitRef> {
4778         Ok(ast::TraitRef {
4779             path: try!(self.parse_path(LifetimeAndTypesWithoutColons)),
4780             ref_id: ast::DUMMY_NODE_ID,
4781         })
4782     }
4783
4784     fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<ast::LifetimeDef>> {
4785         if self.eat_keyword(keywords::For) {
4786             try!(self.expect(&token::Lt));
4787             let lifetime_defs = try!(self.parse_lifetime_defs());
4788             try!(self.expect_gt());
4789             Ok(lifetime_defs)
4790         } else {
4791             Ok(Vec::new())
4792         }
4793     }
4794
4795     /// Parse for<'l> a::B<String,i32>
4796     fn parse_poly_trait_ref(&mut self) -> PResult<'a, PolyTraitRef> {
4797         let lo = self.span.lo;
4798         let lifetime_defs = try!(self.parse_late_bound_lifetime_defs());
4799
4800         Ok(ast::PolyTraitRef {
4801             bound_lifetimes: lifetime_defs,
4802             trait_ref: try!(self.parse_trait_ref()),
4803             span: mk_sp(lo, self.last_span.hi),
4804         })
4805     }
4806
4807     /// Parse struct Foo { ... }
4808     fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
4809         let class_name = try!(self.parse_ident());
4810         let mut generics = try!(self.parse_generics());
4811
4812         // There is a special case worth noting here, as reported in issue #17904.
4813         // If we are parsing a tuple struct it is the case that the where clause
4814         // should follow the field list. Like so:
4815         //
4816         // struct Foo<T>(T) where T: Copy;
4817         //
4818         // If we are parsing a normal record-style struct it is the case
4819         // that the where clause comes before the body, and after the generics.
4820         // So if we look ahead and see a brace or a where-clause we begin
4821         // parsing a record style struct.
4822         //
4823         // Otherwise if we look ahead and see a paren we parse a tuple-style
4824         // struct.
4825
4826         let vdata = if self.token.is_keyword(keywords::Where) {
4827             generics.where_clause = try!(self.parse_where_clause());
4828             if self.eat(&token::Semi) {
4829                 // If we see a: `struct Foo<T> where T: Copy;` style decl.
4830                 VariantData::Unit(ast::DUMMY_NODE_ID)
4831             } else {
4832                 // If we see: `struct Foo<T> where T: Copy { ... }`
4833                 VariantData::Struct(try!(self.parse_record_struct_body(ParsePub::Yes)),
4834                                     ast::DUMMY_NODE_ID)
4835             }
4836         // No `where` so: `struct Foo<T>;`
4837         } else if self.eat(&token::Semi) {
4838             VariantData::Unit(ast::DUMMY_NODE_ID)
4839         // Record-style struct definition
4840         } else if self.token == token::OpenDelim(token::Brace) {
4841             VariantData::Struct(try!(self.parse_record_struct_body(ParsePub::Yes)),
4842                                 ast::DUMMY_NODE_ID)
4843         // Tuple-style struct definition with optional where-clause.
4844         } else if self.token == token::OpenDelim(token::Paren) {
4845             let body = VariantData::Tuple(try!(self.parse_tuple_struct_body(ParsePub::Yes)),
4846                                           ast::DUMMY_NODE_ID);
4847             generics.where_clause = try!(self.parse_where_clause());
4848             try!(self.expect(&token::Semi));
4849             body
4850         } else {
4851             let token_str = self.this_token_to_string();
4852             return Err(self.fatal(&format!("expected `where`, `{{`, `(`, or `;` after struct \
4853                                             name, found `{}`", token_str)))
4854         };
4855
4856         Ok((class_name, ItemStruct(vdata, generics), None))
4857     }
4858
4859     pub fn parse_record_struct_body(&mut self,
4860                                     parse_pub: ParsePub)
4861                                     -> PResult<'a, Vec<StructField>> {
4862         let mut fields = Vec::new();
4863         if self.eat(&token::OpenDelim(token::Brace)) {
4864             while self.token != token::CloseDelim(token::Brace) {
4865                 fields.push(try!(self.parse_struct_decl_field(parse_pub)));
4866             }
4867
4868             self.bump();
4869         } else {
4870             let token_str = self.this_token_to_string();
4871             return Err(self.fatal(&format!("expected `where`, or `{{` after struct \
4872                                 name, found `{}`",
4873                                 token_str)));
4874         }
4875
4876         Ok(fields)
4877     }
4878
4879     pub fn parse_tuple_struct_body(&mut self,
4880                                    parse_pub: ParsePub)
4881                                    -> PResult<'a, Vec<StructField>> {
4882         // This is the case where we find `struct Foo<T>(T) where T: Copy;`
4883         // Unit like structs are handled in parse_item_struct function
4884         let fields = try!(self.parse_unspanned_seq(
4885             &token::OpenDelim(token::Paren),
4886             &token::CloseDelim(token::Paren),
4887             seq_sep_trailing_allowed(token::Comma),
4888             |p| {
4889                 let attrs = try!(p.parse_outer_attributes());
4890                 let lo = p.span.lo;
4891                 let struct_field_ = ast::StructField_ {
4892                     kind: UnnamedField (
4893                         if parse_pub == ParsePub::Yes {
4894                             try!(p.parse_visibility())
4895                         } else {
4896                             Inherited
4897                         }
4898                     ),
4899                     id: ast::DUMMY_NODE_ID,
4900                     ty: try!(p.parse_ty_sum()),
4901                     attrs: attrs,
4902                 };
4903                 Ok(spanned(lo, p.span.hi, struct_field_))
4904             }));
4905
4906         Ok(fields)
4907     }
4908
4909     /// Parse a structure field declaration
4910     pub fn parse_single_struct_field(&mut self,
4911                                      vis: Visibility,
4912                                      attrs: Vec<Attribute> )
4913                                      -> PResult<'a, StructField> {
4914         let a_var = try!(self.parse_name_and_ty(vis, attrs));
4915         match self.token {
4916             token::Comma => {
4917                 self.bump();
4918             }
4919             token::CloseDelim(token::Brace) => {}
4920             _ => {
4921                 let span = self.span;
4922                 let token_str = self.this_token_to_string();
4923                 return Err(self.span_fatal_help(span,
4924                                      &format!("expected `,`, or `}}`, found `{}`",
4925                                              token_str),
4926                                      "struct fields should be separated by commas"))
4927             }
4928         }
4929         Ok(a_var)
4930     }
4931
4932     /// Parse an element of a struct definition
4933     fn parse_struct_decl_field(&mut self, parse_pub: ParsePub) -> PResult<'a, StructField> {
4934
4935         let attrs = try!(self.parse_outer_attributes());
4936
4937         if self.eat_keyword(keywords::Pub) {
4938             if parse_pub == ParsePub::No {
4939                 let span = self.last_span;
4940                 self.span_err(span, "`pub` is not allowed here");
4941             }
4942             return self.parse_single_struct_field(Public, attrs);
4943         }
4944
4945         return self.parse_single_struct_field(Inherited, attrs);
4946     }
4947
4948     /// Parse visibility: PUB or nothing
4949     fn parse_visibility(&mut self) -> PResult<'a, Visibility> {
4950         if self.eat_keyword(keywords::Pub) { Ok(Public) }
4951         else { Ok(Inherited) }
4952     }
4953
4954     /// Given a termination token, parse all of the items in a module
4955     fn parse_mod_items(&mut self, term: &token::Token, inner_lo: BytePos) -> PResult<'a, Mod> {
4956         let mut items = vec![];
4957         while let Some(item) = try!(self.parse_item()) {
4958             items.push(item);
4959         }
4960
4961         if !self.eat(term) {
4962             let token_str = self.this_token_to_string();
4963             return Err(self.fatal(&format!("expected item, found `{}`", token_str)));
4964         }
4965
4966         let hi = if self.span == codemap::DUMMY_SP {
4967             inner_lo
4968         } else {
4969             self.last_span.hi
4970         };
4971
4972         Ok(ast::Mod {
4973             inner: mk_sp(inner_lo, hi),
4974             items: items
4975         })
4976     }
4977
4978     fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
4979         let id = try!(self.parse_ident());
4980         try!(self.expect(&token::Colon));
4981         let ty = try!(self.parse_ty_sum());
4982         try!(self.expect(&token::Eq));
4983         let e = try!(self.parse_expr());
4984         try!(self.commit_expr_expecting(&*e, token::Semi));
4985         let item = match m {
4986             Some(m) => ItemStatic(ty, m, e),
4987             None => ItemConst(ty, e),
4988         };
4989         Ok((id, item, None))
4990     }
4991
4992     /// Parse a `mod <foo> { ... }` or `mod <foo>;` item
4993     fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
4994         let id_span = self.span;
4995         let id = try!(self.parse_ident());
4996         if self.check(&token::Semi) {
4997             self.bump();
4998             // This mod is in an external file. Let's go get it!
4999             let (m, attrs) = try!(self.eval_src_mod(id, outer_attrs, id_span));
5000             Ok((id, m, Some(attrs)))
5001         } else {
5002             self.push_mod_path(id, outer_attrs);
5003             try!(self.expect(&token::OpenDelim(token::Brace)));
5004             let mod_inner_lo = self.span.lo;
5005             let old_owns_directory = self.owns_directory;
5006             self.owns_directory = true;
5007             let attrs = try!(self.parse_inner_attributes());
5008             let m = try!(self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo));
5009             self.owns_directory = old_owns_directory;
5010             self.pop_mod_path();
5011             Ok((id, ItemMod(m), Some(attrs)))
5012         }
5013     }
5014
5015     fn push_mod_path(&mut self, id: Ident, attrs: &[Attribute]) {
5016         let default_path = self.id_to_interned_str(id);
5017         let file_path = match ::attr::first_attr_value_str_by_name(attrs, "path") {
5018             Some(d) => d,
5019             None => default_path,
5020         };
5021         self.mod_path_stack.push(file_path)
5022     }
5023
5024     fn pop_mod_path(&mut self) {
5025         self.mod_path_stack.pop().unwrap();
5026     }
5027
5028     pub fn submod_path_from_attr(attrs: &[ast::Attribute], dir_path: &Path) -> Option<PathBuf> {
5029         ::attr::first_attr_value_str_by_name(attrs, "path").map(|d| dir_path.join(&*d))
5030     }
5031
5032     /// Returns either a path to a module, or .
5033     pub fn default_submod_path(id: ast::Ident, dir_path: &Path, codemap: &CodeMap) -> ModulePath
5034     {
5035         let mod_name = id.to_string();
5036         let default_path_str = format!("{}.rs", mod_name);
5037         let secondary_path_str = format!("{}/mod.rs", mod_name);
5038         let default_path = dir_path.join(&default_path_str);
5039         let secondary_path = dir_path.join(&secondary_path_str);
5040         let default_exists = codemap.file_exists(&default_path);
5041         let secondary_exists = codemap.file_exists(&secondary_path);
5042
5043         let result = match (default_exists, secondary_exists) {
5044             (true, false) => Ok(ModulePathSuccess { path: default_path, owns_directory: false }),
5045             (false, true) => Ok(ModulePathSuccess { path: secondary_path, owns_directory: true }),
5046             (false, false) => Err(ModulePathError {
5047                 err_msg: format!("file not found for module `{}`", mod_name),
5048                 help_msg: format!("name the file either {} or {} inside the directory {:?}",
5049                                   default_path_str,
5050                                   secondary_path_str,
5051                                   dir_path.display()),
5052             }),
5053             (true, true) => Err(ModulePathError {
5054                 err_msg: format!("file for module `{}` found at both {} and {}",
5055                                  mod_name,
5056                                  default_path_str,
5057                                  secondary_path_str),
5058                 help_msg: "delete or rename one of them to remove the ambiguity".to_owned(),
5059             }),
5060         };
5061
5062         ModulePath {
5063             name: mod_name,
5064             path_exists: default_exists || secondary_exists,
5065             result: result,
5066         }
5067     }
5068
5069     fn submod_path(&mut self,
5070                    id: ast::Ident,
5071                    outer_attrs: &[ast::Attribute],
5072                    id_sp: Span) -> PResult<'a, ModulePathSuccess> {
5073         let mut prefix = PathBuf::from(&self.sess.codemap().span_to_filename(self.span));
5074         prefix.pop();
5075         let mut dir_path = prefix;
5076         for part in &self.mod_path_stack {
5077             dir_path.push(&**part);
5078         }
5079
5080         if let Some(p) = Parser::submod_path_from_attr(outer_attrs, &dir_path) {
5081             return Ok(ModulePathSuccess { path: p, owns_directory: true });
5082         }
5083
5084         let paths = Parser::default_submod_path(id, &dir_path, self.sess.codemap());
5085
5086         if !self.owns_directory {
5087             let mut err = self.diagnostic().struct_span_err(id_sp,
5088                 "cannot declare a new module at this location");
5089             let this_module = match self.mod_path_stack.last() {
5090                 Some(name) => name.to_string(),
5091                 None => self.root_module_name.as_ref().unwrap().clone(),
5092             };
5093             err.span_note(id_sp,
5094                           &format!("maybe move this module `{0}` to its own directory \
5095                                      via `{0}/mod.rs`",
5096                                     this_module));
5097             if paths.path_exists {
5098                 err.span_note(id_sp,
5099                               &format!("... or maybe `use` the module `{}` instead \
5100                                         of possibly redeclaring it",
5101                                        paths.name));
5102             }
5103             err.emit();
5104             self.abort_if_errors();
5105         }
5106
5107         match paths.result {
5108             Ok(succ) => Ok(succ),
5109             Err(err) => Err(self.span_fatal_help(id_sp, &err.err_msg, &err.help_msg)),
5110         }
5111     }
5112
5113     /// Read a module from a source file.
5114     fn eval_src_mod(&mut self,
5115                     id: ast::Ident,
5116                     outer_attrs: &[ast::Attribute],
5117                     id_sp: Span)
5118                     -> PResult<'a, (ast::Item_, Vec<ast::Attribute> )> {
5119         let ModulePathSuccess { path, owns_directory } = try!(self.submod_path(id,
5120                                                                                outer_attrs,
5121                                                                                id_sp));
5122
5123         self.eval_src_mod_from_path(path,
5124                                     owns_directory,
5125                                     id.to_string(),
5126                                     id_sp)
5127     }
5128
5129     fn eval_src_mod_from_path(&mut self,
5130                               path: PathBuf,
5131                               owns_directory: bool,
5132                               name: String,
5133                               id_sp: Span) -> PResult<'a, (ast::Item_, Vec<ast::Attribute> )> {
5134         let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
5135         match included_mod_stack.iter().position(|p| *p == path) {
5136             Some(i) => {
5137                 let mut err = String::from("circular modules: ");
5138                 let len = included_mod_stack.len();
5139                 for p in &included_mod_stack[i.. len] {
5140                     err.push_str(&p.to_string_lossy());
5141                     err.push_str(" -> ");
5142                 }
5143                 err.push_str(&path.to_string_lossy());
5144                 return Err(self.span_fatal(id_sp, &err[..]));
5145             }
5146             None => ()
5147         }
5148         included_mod_stack.push(path.clone());
5149         drop(included_mod_stack);
5150
5151         let mut p0 = new_sub_parser_from_file(self.sess,
5152                                               self.cfg.clone(),
5153                                               &path,
5154                                               owns_directory,
5155                                               Some(name),
5156                                               id_sp);
5157         let mod_inner_lo = p0.span.lo;
5158         let mod_attrs = try!(p0.parse_inner_attributes());
5159         let m0 = try!(p0.parse_mod_items(&token::Eof, mod_inner_lo));
5160         self.sess.included_mod_stack.borrow_mut().pop();
5161         Ok((ast::ItemMod(m0), mod_attrs))
5162     }
5163
5164     /// Parse a function declaration from a foreign module
5165     fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: BytePos,
5166                              attrs: Vec<Attribute>) -> PResult<'a, P<ForeignItem>> {
5167         try!(self.expect_keyword(keywords::Fn));
5168
5169         let (ident, mut generics) = try!(self.parse_fn_header());
5170         let decl = try!(self.parse_fn_decl(true));
5171         generics.where_clause = try!(self.parse_where_clause());
5172         let hi = self.span.hi;
5173         try!(self.expect(&token::Semi));
5174         Ok(P(ast::ForeignItem {
5175             ident: ident,
5176             attrs: attrs,
5177             node: ForeignItemFn(decl, generics),
5178             id: ast::DUMMY_NODE_ID,
5179             span: mk_sp(lo, hi),
5180             vis: vis
5181         }))
5182     }
5183
5184     /// Parse a static item from a foreign module
5185     fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: BytePos,
5186                                  attrs: Vec<Attribute>) -> PResult<'a, P<ForeignItem>> {
5187         try!(self.expect_keyword(keywords::Static));
5188         let mutbl = self.eat_keyword(keywords::Mut);
5189
5190         let ident = try!(self.parse_ident());
5191         try!(self.expect(&token::Colon));
5192         let ty = try!(self.parse_ty_sum());
5193         let hi = self.span.hi;
5194         try!(self.expect(&token::Semi));
5195         Ok(P(ForeignItem {
5196             ident: ident,
5197             attrs: attrs,
5198             node: ForeignItemStatic(ty, mutbl),
5199             id: ast::DUMMY_NODE_ID,
5200             span: mk_sp(lo, hi),
5201             vis: vis
5202         }))
5203     }
5204
5205     /// Parse extern crate links
5206     ///
5207     /// # Examples
5208     ///
5209     /// extern crate foo;
5210     /// extern crate bar as foo;
5211     fn parse_item_extern_crate(&mut self,
5212                                lo: BytePos,
5213                                visibility: Visibility,
5214                                attrs: Vec<Attribute>)
5215                                 -> PResult<'a, P<Item>> {
5216
5217         let crate_name = try!(self.parse_ident());
5218         let (maybe_path, ident) = if let Some(ident) = try!(self.parse_rename()) {
5219             (Some(crate_name.name), ident)
5220         } else {
5221             (None, crate_name)
5222         };
5223         try!(self.expect(&token::Semi));
5224
5225         let last_span = self.last_span;
5226
5227         if visibility == ast::Public {
5228             self.span_warn(mk_sp(lo, last_span.hi),
5229                            "`pub extern crate` does not work as expected and should not be used. \
5230                             Likely to become an error. Prefer `extern crate` and `pub use`.");
5231         }
5232
5233         Ok(self.mk_item(lo,
5234                         last_span.hi,
5235                         ident,
5236                         ItemExternCrate(maybe_path),
5237                         visibility,
5238                         attrs))
5239     }
5240
5241     /// Parse `extern` for foreign ABIs
5242     /// modules.
5243     ///
5244     /// `extern` is expected to have been
5245     /// consumed before calling this method
5246     ///
5247     /// # Examples:
5248     ///
5249     /// extern "C" {}
5250     /// extern {}
5251     fn parse_item_foreign_mod(&mut self,
5252                               lo: BytePos,
5253                               opt_abi: Option<abi::Abi>,
5254                               visibility: Visibility,
5255                               mut attrs: Vec<Attribute>)
5256                               -> PResult<'a, P<Item>> {
5257         try!(self.expect(&token::OpenDelim(token::Brace)));
5258
5259         let abi = opt_abi.unwrap_or(abi::C);
5260
5261         attrs.extend(try!(self.parse_inner_attributes()));
5262
5263         let mut foreign_items = vec![];
5264         while let Some(item) = try!(self.parse_foreign_item()) {
5265             foreign_items.push(item);
5266         }
5267         try!(self.expect(&token::CloseDelim(token::Brace)));
5268
5269         let last_span = self.last_span;
5270         let m = ast::ForeignMod {
5271             abi: abi,
5272             items: foreign_items
5273         };
5274         Ok(self.mk_item(lo,
5275                      last_span.hi,
5276                      special_idents::invalid,
5277                      ItemForeignMod(m),
5278                      visibility,
5279                      attrs))
5280     }
5281
5282     /// Parse type Foo = Bar;
5283     fn parse_item_type(&mut self) -> PResult<'a, ItemInfo> {
5284         let ident = try!(self.parse_ident());
5285         let mut tps = try!(self.parse_generics());
5286         tps.where_clause = try!(self.parse_where_clause());
5287         try!(self.expect(&token::Eq));
5288         let ty = try!(self.parse_ty_sum());
5289         try!(self.expect(&token::Semi));
5290         Ok((ident, ItemTy(ty, tps), None))
5291     }
5292
5293     /// Parse the part of an "enum" decl following the '{'
5294     fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
5295         let mut variants = Vec::new();
5296         let mut all_nullary = true;
5297         let mut any_disr = None;
5298         while self.token != token::CloseDelim(token::Brace) {
5299             let variant_attrs = try!(self.parse_outer_attributes());
5300             let vlo = self.span.lo;
5301
5302             let struct_def;
5303             let mut disr_expr = None;
5304             let ident = try!(self.parse_ident());
5305             if self.check(&token::OpenDelim(token::Brace)) {
5306                 // Parse a struct variant.
5307                 all_nullary = false;
5308                 struct_def = VariantData::Struct(try!(self.parse_record_struct_body(ParsePub::No)),
5309                                                  ast::DUMMY_NODE_ID);
5310             } else if self.check(&token::OpenDelim(token::Paren)) {
5311                 all_nullary = false;
5312                 struct_def = VariantData::Tuple(try!(self.parse_tuple_struct_body(ParsePub::No)),
5313                                                 ast::DUMMY_NODE_ID);
5314             } else if self.eat(&token::Eq) {
5315                 disr_expr = Some(try!(self.parse_expr()));
5316                 any_disr = disr_expr.as_ref().map(|expr| expr.span);
5317                 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
5318             } else {
5319                 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
5320             }
5321
5322             let vr = ast::Variant_ {
5323                 name: ident,
5324                 attrs: variant_attrs,
5325                 data: struct_def,
5326                 disr_expr: disr_expr,
5327             };
5328             variants.push(P(spanned(vlo, self.last_span.hi, vr)));
5329
5330             if !self.eat(&token::Comma) { break; }
5331         }
5332         try!(self.expect(&token::CloseDelim(token::Brace)));
5333         match any_disr {
5334             Some(disr_span) if !all_nullary =>
5335                 self.span_err(disr_span,
5336                     "discriminator values can only be used with a c-like enum"),
5337             _ => ()
5338         }
5339
5340         Ok(ast::EnumDef { variants: variants })
5341     }
5342
5343     /// Parse an "enum" declaration
5344     fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
5345         let id = try!(self.parse_ident());
5346         let mut generics = try!(self.parse_generics());
5347         generics.where_clause = try!(self.parse_where_clause());
5348         try!(self.expect(&token::OpenDelim(token::Brace)));
5349
5350         let enum_definition = try!(self.parse_enum_def(&generics));
5351         Ok((id, ItemEnum(enum_definition, generics), None))
5352     }
5353
5354     /// Parses a string as an ABI spec on an extern type or module. Consumes
5355     /// the `extern` keyword, if one is found.
5356     fn parse_opt_abi(&mut self) -> PResult<'a, Option<abi::Abi>> {
5357         match self.token {
5358             token::Literal(token::Str_(s), suf) | token::Literal(token::StrRaw(s, _), suf) => {
5359                 let sp = self.span;
5360                 self.expect_no_suffix(sp, "ABI spec", suf);
5361                 self.bump();
5362                 match abi::lookup(&s.as_str()) {
5363                     Some(abi) => Ok(Some(abi)),
5364                     None => {
5365                         let last_span = self.last_span;
5366                         self.span_err(
5367                             last_span,
5368                             &format!("invalid ABI: expected one of [{}], \
5369                                      found `{}`",
5370                                     abi::all_names().join(", "),
5371                                     s));
5372                         Ok(None)
5373                     }
5374                 }
5375             }
5376
5377             _ => Ok(None),
5378         }
5379     }
5380
5381     /// Parse one of the items allowed by the flags.
5382     /// NB: this function no longer parses the items inside an
5383     /// extern crate.
5384     fn parse_item_(&mut self, attrs: Vec<Attribute>,
5385                    macros_allowed: bool, attributes_allowed: bool) -> PResult<'a, Option<P<Item>>> {
5386         let nt_item = match self.token {
5387             token::Interpolated(token::NtItem(ref item)) => {
5388                 Some((**item).clone())
5389             }
5390             _ => None
5391         };
5392         match nt_item {
5393             Some(mut item) => {
5394                 self.bump();
5395                 let mut attrs = attrs;
5396                 mem::swap(&mut item.attrs, &mut attrs);
5397                 item.attrs.extend(attrs);
5398                 return Ok(Some(P(item)));
5399             }
5400             None => {}
5401         }
5402
5403         let lo = self.span.lo;
5404
5405         let visibility = try!(self.parse_visibility());
5406
5407         if self.eat_keyword(keywords::Use) {
5408             // USE ITEM
5409             let item_ = ItemUse(try!(self.parse_view_path()));
5410             try!(self.expect(&token::Semi));
5411
5412             let last_span = self.last_span;
5413             let item = self.mk_item(lo,
5414                                     last_span.hi,
5415                                     token::special_idents::invalid,
5416                                     item_,
5417                                     visibility,
5418                                     attrs);
5419             return Ok(Some(item));
5420         }
5421
5422         if self.eat_keyword(keywords::Extern) {
5423             if self.eat_keyword(keywords::Crate) {
5424                 return Ok(Some(try!(self.parse_item_extern_crate(lo, visibility, attrs))));
5425             }
5426
5427             let opt_abi = try!(self.parse_opt_abi());
5428
5429             if self.eat_keyword(keywords::Fn) {
5430                 // EXTERN FUNCTION ITEM
5431                 let abi = opt_abi.unwrap_or(abi::C);
5432                 let (ident, item_, extra_attrs) =
5433                     try!(self.parse_item_fn(Unsafety::Normal, Constness::NotConst, abi));
5434                 let last_span = self.last_span;
5435                 let item = self.mk_item(lo,
5436                                         last_span.hi,
5437                                         ident,
5438                                         item_,
5439                                         visibility,
5440                                         maybe_append(attrs, extra_attrs));
5441                 return Ok(Some(item));
5442             } else if self.check(&token::OpenDelim(token::Brace)) {
5443                 return Ok(Some(try!(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs))));
5444             }
5445
5446             try!(self.unexpected());
5447         }
5448
5449         if self.eat_keyword(keywords::Static) {
5450             // STATIC ITEM
5451             let m = if self.eat_keyword(keywords::Mut) {MutMutable} else {MutImmutable};
5452             let (ident, item_, extra_attrs) = try!(self.parse_item_const(Some(m)));
5453             let last_span = self.last_span;
5454             let item = self.mk_item(lo,
5455                                     last_span.hi,
5456                                     ident,
5457                                     item_,
5458                                     visibility,
5459                                     maybe_append(attrs, extra_attrs));
5460             return Ok(Some(item));
5461         }
5462         if self.eat_keyword(keywords::Const) {
5463             if self.check_keyword(keywords::Fn)
5464                 || (self.check_keyword(keywords::Unsafe)
5465                     && self.look_ahead(1, |t| t.is_keyword(keywords::Fn))) {
5466                 // CONST FUNCTION ITEM
5467                 let unsafety = if self.eat_keyword(keywords::Unsafe) {
5468                     Unsafety::Unsafe
5469                 } else {
5470                     Unsafety::Normal
5471                 };
5472                 self.bump();
5473                 let (ident, item_, extra_attrs) =
5474                     try!(self.parse_item_fn(unsafety, Constness::Const, abi::Rust));
5475                 let last_span = self.last_span;
5476                 let item = self.mk_item(lo,
5477                                         last_span.hi,
5478                                         ident,
5479                                         item_,
5480                                         visibility,
5481                                         maybe_append(attrs, extra_attrs));
5482                 return Ok(Some(item));
5483             }
5484
5485             // CONST ITEM
5486             if self.eat_keyword(keywords::Mut) {
5487                 let last_span = self.last_span;
5488                 self.diagnostic().struct_span_err(last_span, "const globals cannot be mutable")
5489                                  .fileline_help(last_span, "did you mean to declare a static?")
5490                                  .emit();
5491             }
5492             let (ident, item_, extra_attrs) = try!(self.parse_item_const(None));
5493             let last_span = self.last_span;
5494             let item = self.mk_item(lo,
5495                                     last_span.hi,
5496                                     ident,
5497                                     item_,
5498                                     visibility,
5499                                     maybe_append(attrs, extra_attrs));
5500             return Ok(Some(item));
5501         }
5502         if self.check_keyword(keywords::Unsafe) &&
5503             self.look_ahead(1, |t| t.is_keyword(keywords::Trait))
5504         {
5505             // UNSAFE TRAIT ITEM
5506             try!(self.expect_keyword(keywords::Unsafe));
5507             try!(self.expect_keyword(keywords::Trait));
5508             let (ident, item_, extra_attrs) =
5509                 try!(self.parse_item_trait(ast::Unsafety::Unsafe));
5510             let last_span = self.last_span;
5511             let item = self.mk_item(lo,
5512                                     last_span.hi,
5513                                     ident,
5514                                     item_,
5515                                     visibility,
5516                                     maybe_append(attrs, extra_attrs));
5517             return Ok(Some(item));
5518         }
5519         if self.check_keyword(keywords::Unsafe) &&
5520             self.look_ahead(1, |t| t.is_keyword(keywords::Impl))
5521         {
5522             // IMPL ITEM
5523             try!(self.expect_keyword(keywords::Unsafe));
5524             try!(self.expect_keyword(keywords::Impl));
5525             let (ident, item_, extra_attrs) = try!(self.parse_item_impl(ast::Unsafety::Unsafe));
5526             let last_span = self.last_span;
5527             let item = self.mk_item(lo,
5528                                     last_span.hi,
5529                                     ident,
5530                                     item_,
5531                                     visibility,
5532                                     maybe_append(attrs, extra_attrs));
5533             return Ok(Some(item));
5534         }
5535         if self.check_keyword(keywords::Fn) {
5536             // FUNCTION ITEM
5537             self.bump();
5538             let (ident, item_, extra_attrs) =
5539                 try!(self.parse_item_fn(Unsafety::Normal, Constness::NotConst, abi::Rust));
5540             let last_span = self.last_span;
5541             let item = self.mk_item(lo,
5542                                     last_span.hi,
5543                                     ident,
5544                                     item_,
5545                                     visibility,
5546                                     maybe_append(attrs, extra_attrs));
5547             return Ok(Some(item));
5548         }
5549         if self.check_keyword(keywords::Unsafe)
5550             && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
5551             // UNSAFE FUNCTION ITEM
5552             self.bump();
5553             let abi = if self.eat_keyword(keywords::Extern) {
5554                 try!(self.parse_opt_abi()).unwrap_or(abi::C)
5555             } else {
5556                 abi::Rust
5557             };
5558             try!(self.expect_keyword(keywords::Fn));
5559             let (ident, item_, extra_attrs) =
5560                 try!(self.parse_item_fn(Unsafety::Unsafe, Constness::NotConst, abi));
5561             let last_span = self.last_span;
5562             let item = self.mk_item(lo,
5563                                     last_span.hi,
5564                                     ident,
5565                                     item_,
5566                                     visibility,
5567                                     maybe_append(attrs, extra_attrs));
5568             return Ok(Some(item));
5569         }
5570         if self.eat_keyword(keywords::Mod) {
5571             // MODULE ITEM
5572             let (ident, item_, extra_attrs) =
5573                 try!(self.parse_item_mod(&attrs[..]));
5574             let last_span = self.last_span;
5575             let item = self.mk_item(lo,
5576                                     last_span.hi,
5577                                     ident,
5578                                     item_,
5579                                     visibility,
5580                                     maybe_append(attrs, extra_attrs));
5581             return Ok(Some(item));
5582         }
5583         if self.eat_keyword(keywords::Type) {
5584             // TYPE ITEM
5585             let (ident, item_, extra_attrs) = try!(self.parse_item_type());
5586             let last_span = self.last_span;
5587             let item = self.mk_item(lo,
5588                                     last_span.hi,
5589                                     ident,
5590                                     item_,
5591                                     visibility,
5592                                     maybe_append(attrs, extra_attrs));
5593             return Ok(Some(item));
5594         }
5595         if self.eat_keyword(keywords::Enum) {
5596             // ENUM ITEM
5597             let (ident, item_, extra_attrs) = try!(self.parse_item_enum());
5598             let last_span = self.last_span;
5599             let item = self.mk_item(lo,
5600                                     last_span.hi,
5601                                     ident,
5602                                     item_,
5603                                     visibility,
5604                                     maybe_append(attrs, extra_attrs));
5605             return Ok(Some(item));
5606         }
5607         if self.eat_keyword(keywords::Trait) {
5608             // TRAIT ITEM
5609             let (ident, item_, extra_attrs) =
5610                 try!(self.parse_item_trait(ast::Unsafety::Normal));
5611             let last_span = self.last_span;
5612             let item = self.mk_item(lo,
5613                                     last_span.hi,
5614                                     ident,
5615                                     item_,
5616                                     visibility,
5617                                     maybe_append(attrs, extra_attrs));
5618             return Ok(Some(item));
5619         }
5620         if self.eat_keyword(keywords::Impl) {
5621             // IMPL ITEM
5622             let (ident, item_, extra_attrs) = try!(self.parse_item_impl(ast::Unsafety::Normal));
5623             let last_span = self.last_span;
5624             let item = self.mk_item(lo,
5625                                     last_span.hi,
5626                                     ident,
5627                                     item_,
5628                                     visibility,
5629                                     maybe_append(attrs, extra_attrs));
5630             return Ok(Some(item));
5631         }
5632         if self.eat_keyword(keywords::Struct) {
5633             // STRUCT ITEM
5634             let (ident, item_, extra_attrs) = try!(self.parse_item_struct());
5635             let last_span = self.last_span;
5636             let item = self.mk_item(lo,
5637                                     last_span.hi,
5638                                     ident,
5639                                     item_,
5640                                     visibility,
5641                                     maybe_append(attrs, extra_attrs));
5642             return Ok(Some(item));
5643         }
5644         self.parse_macro_use_or_failure(attrs,macros_allowed,attributes_allowed,lo,visibility)
5645     }
5646
5647     /// Parse a foreign item.
5648     fn parse_foreign_item(&mut self) -> PResult<'a, Option<P<ForeignItem>>> {
5649         let attrs = try!(self.parse_outer_attributes());
5650         let lo = self.span.lo;
5651         let visibility = try!(self.parse_visibility());
5652
5653         if self.check_keyword(keywords::Static) {
5654             // FOREIGN STATIC ITEM
5655             return Ok(Some(try!(self.parse_item_foreign_static(visibility, lo, attrs))));
5656         }
5657         if self.check_keyword(keywords::Fn) || self.check_keyword(keywords::Unsafe) {
5658             // FOREIGN FUNCTION ITEM
5659             return Ok(Some(try!(self.parse_item_foreign_fn(visibility, lo, attrs))));
5660         }
5661
5662         // FIXME #5668: this will occur for a macro invocation:
5663         match try!(self.parse_macro_use_or_failure(attrs, true, false, lo, visibility)) {
5664             Some(item) => {
5665                 return Err(self.span_fatal(item.span, "macros cannot expand to foreign items"));
5666             }
5667             None => Ok(None)
5668         }
5669     }
5670
5671     /// This is the fall-through for parsing items.
5672     fn parse_macro_use_or_failure(
5673         &mut self,
5674         attrs: Vec<Attribute> ,
5675         macros_allowed: bool,
5676         attributes_allowed: bool,
5677         lo: BytePos,
5678         visibility: Visibility
5679     ) -> PResult<'a, Option<P<Item>>> {
5680         if macros_allowed && !self.token.is_any_keyword()
5681                 && self.look_ahead(1, |t| *t == token::Not)
5682                 && (self.look_ahead(2, |t| t.is_plain_ident())
5683                     || self.look_ahead(2, |t| *t == token::OpenDelim(token::Paren))
5684                     || self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))) {
5685             // MACRO INVOCATION ITEM
5686
5687             let last_span = self.last_span;
5688             self.complain_if_pub_macro(visibility, last_span);
5689
5690             let mac_lo = self.span.lo;
5691
5692             // item macro.
5693             let pth = try!(self.parse_path(NoTypesAllowed));
5694             try!(self.expect(&token::Not));
5695
5696             // a 'special' identifier (like what `macro_rules!` uses)
5697             // is optional. We should eventually unify invoc syntax
5698             // and remove this.
5699             let id = if self.token.is_plain_ident() {
5700                 try!(self.parse_ident())
5701             } else {
5702                 token::special_idents::invalid // no special identifier
5703             };
5704             // eat a matched-delimiter token tree:
5705             let delim = try!(self.expect_open_delim());
5706             let tts = try!(self.parse_seq_to_end(&token::CloseDelim(delim),
5707                                             seq_sep_none(),
5708                                             |p| p.parse_token_tree()));
5709             // single-variant-enum... :
5710             let m = Mac_ { path: pth, tts: tts, ctxt: EMPTY_CTXT };
5711             let m: ast::Mac = codemap::Spanned { node: m,
5712                                              span: mk_sp(mac_lo,
5713                                                          self.last_span.hi) };
5714
5715             if delim != token::Brace {
5716                 if !self.eat(&token::Semi) {
5717                     let last_span = self.last_span;
5718                     self.span_err(last_span,
5719                                   "macros that expand to items must either \
5720                                    be surrounded with braces or followed by \
5721                                    a semicolon");
5722                 }
5723             }
5724
5725             let item_ = ItemMac(m);
5726             let last_span = self.last_span;
5727             let item = self.mk_item(lo,
5728                                     last_span.hi,
5729                                     id,
5730                                     item_,
5731                                     visibility,
5732                                     attrs);
5733             return Ok(Some(item));
5734         }
5735
5736         // FAILURE TO PARSE ITEM
5737         match visibility {
5738             Inherited => {}
5739             Public => {
5740                 let last_span = self.last_span;
5741                 return Err(self.span_fatal(last_span, "unmatched visibility `pub`"));
5742             }
5743         }
5744
5745         if !attributes_allowed && !attrs.is_empty() {
5746             self.expected_item_err(&attrs);
5747         }
5748         Ok(None)
5749     }
5750
5751     pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
5752         let attrs = try!(self.parse_outer_attributes());
5753         self.parse_item_(attrs, true, false)
5754     }
5755
5756
5757     /// Matches view_path : MOD? non_global_path as IDENT
5758     /// | MOD? non_global_path MOD_SEP LBRACE RBRACE
5759     /// | MOD? non_global_path MOD_SEP LBRACE ident_seq RBRACE
5760     /// | MOD? non_global_path MOD_SEP STAR
5761     /// | MOD? non_global_path
5762     fn parse_view_path(&mut self) -> PResult<'a, P<ViewPath>> {
5763         let lo = self.span.lo;
5764
5765         // Allow a leading :: because the paths are absolute either way.
5766         // This occurs with "use $crate::..." in macros.
5767         self.eat(&token::ModSep);
5768
5769         if self.check(&token::OpenDelim(token::Brace)) {
5770             // use {foo,bar}
5771             let idents = try!(self.parse_unspanned_seq(
5772                 &token::OpenDelim(token::Brace),
5773                 &token::CloseDelim(token::Brace),
5774                 seq_sep_trailing_allowed(token::Comma),
5775                 |p| p.parse_path_list_item()));
5776             let path = ast::Path {
5777                 span: mk_sp(lo, self.span.hi),
5778                 global: false,
5779                 segments: Vec::new()
5780             };
5781             return Ok(P(spanned(lo, self.span.hi, ViewPathList(path, idents))));
5782         }
5783
5784         let first_ident = try!(self.parse_ident());
5785         let mut path = vec!(first_ident);
5786         if let token::ModSep = self.token {
5787             // foo::bar or foo::{a,b,c} or foo::*
5788             while self.check(&token::ModSep) {
5789                 self.bump();
5790
5791                 match self.token {
5792                   token::Ident(..) => {
5793                     let ident = try!(self.parse_ident());
5794                     path.push(ident);
5795                   }
5796
5797                   // foo::bar::{a,b,c}
5798                   token::OpenDelim(token::Brace) => {
5799                     let idents = try!(self.parse_unspanned_seq(
5800                         &token::OpenDelim(token::Brace),
5801                         &token::CloseDelim(token::Brace),
5802                         seq_sep_trailing_allowed(token::Comma),
5803                         |p| p.parse_path_list_item()
5804                     ));
5805                     let path = ast::Path {
5806                         span: mk_sp(lo, self.span.hi),
5807                         global: false,
5808                         segments: path.into_iter().map(|identifier| {
5809                             ast::PathSegment {
5810                                 identifier: identifier,
5811                                 parameters: ast::PathParameters::none(),
5812                             }
5813                         }).collect()
5814                     };
5815                     return Ok(P(spanned(lo, self.span.hi, ViewPathList(path, idents))));
5816                   }
5817
5818                   // foo::bar::*
5819                   token::BinOp(token::Star) => {
5820                     self.bump();
5821                     let path = ast::Path {
5822                         span: mk_sp(lo, self.span.hi),
5823                         global: false,
5824                         segments: path.into_iter().map(|identifier| {
5825                             ast::PathSegment {
5826                                 identifier: identifier,
5827                                 parameters: ast::PathParameters::none(),
5828                             }
5829                         }).collect()
5830                     };
5831                     return Ok(P(spanned(lo, self.span.hi, ViewPathGlob(path))));
5832                   }
5833
5834                   // fall-through for case foo::bar::;
5835                   token::Semi => {
5836                     self.span_err(self.span, "expected identifier or `{` or `*`, found `;`");
5837                   }
5838
5839                   _ => break
5840                 }
5841             }
5842         }
5843         let mut rename_to = path[path.len() - 1];
5844         let path = ast::Path {
5845             span: mk_sp(lo, self.last_span.hi),
5846             global: false,
5847             segments: path.into_iter().map(|identifier| {
5848                 ast::PathSegment {
5849                     identifier: identifier,
5850                     parameters: ast::PathParameters::none(),
5851                 }
5852             }).collect()
5853         };
5854         rename_to = try!(self.parse_rename()).unwrap_or(rename_to);
5855         Ok(P(spanned(lo, self.last_span.hi, ViewPathSimple(rename_to, path))))
5856     }
5857
5858     fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
5859         if self.eat_keyword(keywords::As) {
5860             self.parse_ident().map(Some)
5861         } else {
5862             Ok(None)
5863         }
5864     }
5865
5866     /// Parses a source module as a crate. This is the main
5867     /// entry point for the parser.
5868     pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> {
5869         let lo = self.span.lo;
5870         Ok(ast::Crate {
5871             attrs: try!(self.parse_inner_attributes()),
5872             module: try!(self.parse_mod_items(&token::Eof, lo)),
5873             config: self.cfg.clone(),
5874             span: mk_sp(lo, self.span.lo),
5875             exported_macros: Vec::new(),
5876         })
5877     }
5878
5879     pub fn parse_optional_str(&mut self)
5880                               -> Option<(InternedString,
5881                                          ast::StrStyle,
5882                                          Option<ast::Name>)> {
5883         let ret = match self.token {
5884             token::Literal(token::Str_(s), suf) => {
5885                 (self.id_to_interned_str(ast::Ident::with_empty_ctxt(s)), ast::CookedStr, suf)
5886             }
5887             token::Literal(token::StrRaw(s, n), suf) => {
5888                 (self.id_to_interned_str(ast::Ident::with_empty_ctxt(s)), ast::RawStr(n), suf)
5889             }
5890             _ => return None
5891         };
5892         self.bump();
5893         Some(ret)
5894     }
5895
5896     pub fn parse_str(&mut self) -> PResult<'a, (InternedString, StrStyle)> {
5897         match self.parse_optional_str() {
5898             Some((s, style, suf)) => {
5899                 let sp = self.last_span;
5900                 self.expect_no_suffix(sp, "string literal", suf);
5901                 Ok((s, style))
5902             }
5903             _ =>  Err(self.fatal("expected string literal"))
5904         }
5905     }
5906 }