src/libsyntax/parse/token.rs

   1 // Copyright 2012-2013 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::BinOpToken::*;
  12 pub use self::Nonterminal::*;
  13 pub use self::DelimToken::*;
  14 pub use self::IdentStyle::*;
  15 pub use self::Lit::*;
  16 pub use self::Token::*;
  17
  18 use ast;
  19 use ext::mtwt;
  20 use ptr::P;
  21 use util::interner::{RcStr, StrInterner};
  22 use util::interner;
  23
  24 use serialize::{Decodable, Decoder, Encodable, Encoder};
  25 use std::fmt;
  26 use std::ops::Deref;
  27 use std::rc::Rc;
  28
  29 #[allow(non_camel_case_types)]
  30 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug, Copy)]
  31 pub enum BinOpToken {
  32     Plus,
  33     Minus,
  34     Star,
  35     Slash,
  36     Percent,
  37     Caret,
  38     And,
  39     Or,
  40     Shl,
  41     Shr,
  42 }
  43
  44 /// A delimiter token
  45 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug, Copy)]
  46 pub enum DelimToken {
  47     /// A round parenthesis: `(` or `)`
  48     Paren,
  49     /// A square bracket: `[` or `]`
  50     Bracket,
  51     /// A curly brace: `{` or `}`
  52     Brace,
  53 }
  54
  55 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug, Copy)]
  56 pub enum IdentStyle {
  57     /// `::` follows the identifier with no whitespace in-between.
  58     ModName,
  59     Plain,
  60 }
  61
  62 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug, Copy)]
  63 pub enum SpecialMacroVar {
  64     /// `$crate` will be filled in with the name of the crate a macro was
  65     /// imported from, if any.
  66     CrateMacroVar,
  67 }
  68
  69 impl SpecialMacroVar {
  70     pub fn as_str(self) -> &'static str {
  71         match self {
  72             SpecialMacroVar::CrateMacroVar => "crate",
  73         }
  74     }
  75 }
  76
  77 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug, Copy)]
  78 pub enum Lit {
  79     Byte(ast::Name),
  80     Char(ast::Name),
  81     Integer(ast::Name),
  82     Float(ast::Name),
  83     Str_(ast::Name),
  84     StrRaw(ast::Name, usize), /* raw str delimited by n hash symbols */
  85     Binary(ast::Name),
  86     BinaryRaw(ast::Name, usize), /* raw binary str delimited by n hash symbols */
  87 }
  88
  89 impl Lit {
  90     pub fn short_name(&self) -> &'static str {
  91         match *self {
  92             Byte(_) => "byte",
  93             Char(_) => "char",
  94             Integer(_) => "integer",
  95             Float(_) => "float",
  96             Str_(_) | StrRaw(..) => "str",
  97             Binary(_) | BinaryRaw(..) => "binary str"
  98         }
  99     }
 100 }
 101
 102 #[allow(non_camel_case_types)]
 103 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug)]
 104 pub enum Token {
 105     /* Expression-operator symbols. */
 106     Eq,
 107     Lt,
 108     Le,
 109     EqEq,
 110     Ne,
 111     Ge,
 112     Gt,
 113     AndAnd,
 114     OrOr,
 115     Not,
 116     Tilde,
 117     BinOp(BinOpToken),
 118     BinOpEq(BinOpToken),
 119
 120     /* Structural symbols */
 121     At,
 122     Dot,
 123     DotDot,
 124     DotDotDot,
 125     Comma,
 126     Semi,
 127     Colon,
 128     ModSep,
 129     RArrow,
 130     LArrow,
 131     FatArrow,
 132     Pound,
 133     Dollar,
 134     Question,
 135     /// An opening delimiter, eg. `{`
 136     OpenDelim(DelimToken),
 137     /// A closing delimiter, eg. `}`
 138     CloseDelim(DelimToken),
 139
 140     /* Literals */
 141     Literal(Lit, Option<ast::Name>),
 142
 143     /* Name components */
 144     Ident(ast::Ident, IdentStyle),
 145     Underscore,
 146     Lifetime(ast::Ident),
 147
 148     /* For interpolation */
 149     Interpolated(Nonterminal),
 150     // Can be expanded into several tokens.
 151     /// Doc comment
 152     DocComment(ast::Name),
 153     // In left-hand-sides of MBE macros:
 154     /// Parse a nonterminal (name to bind, name of NT, styles of their idents)
 155     MatchNt(ast::Ident, ast::Ident, IdentStyle, IdentStyle),
 156     // In right-hand-sides of MBE macros:
 157     /// A syntactic variable that will be filled in by macro expansion.
 158     SubstNt(ast::Ident, IdentStyle),
 159     /// A macro variable with special meaning.
 160     SpecialVarNt(SpecialMacroVar),
 161
 162     // Junk. These carry no data because we don't really care about the data
 163     // they *would* carry, and don't really want to allocate a new ident for
 164     // them. Instead, users could extract that from the associated span.
 165
 166     /// Whitespace
 167     Whitespace,
 168     /// Comment
 169     Comment,
 170     Shebang(ast::Name),
 171
 172     Eof,
 173 }
 174
 175 impl Token {
 176     /// Returns `true` if the token starts with '>'.
 177     pub fn is_like_gt(&self) -> bool {
 178         match *self {
 179             BinOp(Shr) | BinOpEq(Shr) | Gt | Ge => true,
 180             _ => false,
 181         }
 182     }
 183
 184     /// Returns `true` if the token can appear at the start of an expression.
 185     pub fn can_begin_expr(&self) -> bool {
 186         match *self {
 187             OpenDelim(_)                => true,
 188             Ident(_, _)                 => true,
 189             Underscore                  => true,
 190             Tilde                       => true,
 191             Literal(_, _)               => true,
 192             Not                         => true,
 193             BinOp(Minus)                => true,
 194             BinOp(Star)                 => true,
 195             BinOp(And)                  => true,
 196             BinOp(Or)                   => true, // in lambda syntax
 197             OrOr                        => true, // in lambda syntax
 198             AndAnd                      => true, // double borrow
 199             DotDot                      => true, // range notation
 200             ModSep                      => true,
 201             Interpolated(NtExpr(..))    => true,
 202             Interpolated(NtIdent(..))   => true,
 203             Interpolated(NtBlock(..))   => true,
 204             Interpolated(NtPath(..))    => true,
 205             _                           => false,
 206         }
 207     }
 208
 209     /// Returns `true` if the token is any literal
 210     pub fn is_lit(&self) -> bool {
 211         match *self {
 212             Literal(_, _) => true,
 213             _          => false,
 214         }
 215     }
 216
 217     /// Returns `true` if the token is an identifier.
 218     pub fn is_ident(&self) -> bool {
 219         match *self {
 220             Ident(_, _) => true,
 221             _           => false,
 222         }
 223     }
 224
 225     /// Returns `true` if the token is an interpolated path.
 226     pub fn is_path(&self) -> bool {
 227         match *self {
 228             Interpolated(NtPath(..))    => true,
 229             _                           => false,
 230         }
 231     }
 232
 233     /// Returns `true` if the token is a path that is not followed by a `::`
 234     /// token.
 235     #[allow(non_upper_case_globals)]
 236     pub fn is_plain_ident(&self) -> bool {
 237         match *self {
 238             Ident(_, Plain) => true,
 239             _               => false,
 240         }
 241     }
 242
 243     /// Returns `true` if the token is a lifetime.
 244     pub fn is_lifetime(&self) -> bool {
 245         match *self {
 246             Lifetime(..) => true,
 247             _            => false,
 248         }
 249     }
 250
 251     /// Returns `true` if the token is either the `mut` or `const` keyword.
 252     pub fn is_mutability(&self) -> bool {
 253         self.is_keyword(keywords::Mut) ||
 254         self.is_keyword(keywords::Const)
 255     }
 256
 257     /// Maps a token to its corresponding binary operator.
 258     pub fn to_binop(&self) -> Option<ast::BinOp_> {
 259         match *self {
 260             BinOp(Star)     => Some(ast::BiMul),
 261             BinOp(Slash)    => Some(ast::BiDiv),
 262             BinOp(Percent)  => Some(ast::BiRem),
 263             BinOp(Plus)     => Some(ast::BiAdd),
 264             BinOp(Minus)    => Some(ast::BiSub),
 265             BinOp(Shl)      => Some(ast::BiShl),
 266             BinOp(Shr)      => Some(ast::BiShr),
 267             BinOp(And)      => Some(ast::BiBitAnd),
 268             BinOp(Caret)    => Some(ast::BiBitXor),
 269             BinOp(Or)       => Some(ast::BiBitOr),
 270             Lt              => Some(ast::BiLt),
 271             Le              => Some(ast::BiLe),
 272             Ge              => Some(ast::BiGe),
 273             Gt              => Some(ast::BiGt),
 274             EqEq            => Some(ast::BiEq),
 275             Ne              => Some(ast::BiNe),
 276             AndAnd          => Some(ast::BiAnd),
 277             OrOr            => Some(ast::BiOr),
 278             _               => None,
 279         }
 280     }
 281
 282     /// Returns `true` if the token is a given keyword, `kw`.
 283     #[allow(non_upper_case_globals)]
 284     pub fn is_keyword(&self, kw: keywords::Keyword) -> bool {
 285         match *self {
 286             Ident(sid, Plain) => kw.to_name() == sid.name,
 287             _                      => false,
 288         }
 289     }
 290
 291     pub fn is_keyword_allow_following_colon(&self, kw: keywords::Keyword) -> bool {
 292         match *self {
 293             Ident(sid, _) => { kw.to_name() == sid.name }
 294             _ => { false }
 295         }
 296     }
 297
 298     /// Returns `true` if the token is either a special identifier, or a strict
 299     /// or reserved keyword.
 300     #[allow(non_upper_case_globals)]
 301     pub fn is_any_keyword(&self) -> bool {
 302         match *self {
 303             Ident(sid, Plain) => {
 304                 let n = sid.name;
 305
 306                    n == SELF_KEYWORD_NAME
 307                 || n == STATIC_KEYWORD_NAME
 308                 || n == SUPER_KEYWORD_NAME
 309                 || n == SELF_TYPE_KEYWORD_NAME
 310                 || STRICT_KEYWORD_START <= n
 311                 && n <= RESERVED_KEYWORD_FINAL
 312             },
 313             _ => false
 314         }
 315     }
 316
 317     /// Returns `true` if the token may not appear as an identifier.
 318     #[allow(non_upper_case_globals)]
 319     pub fn is_strict_keyword(&self) -> bool {
 320         match *self {
 321             Ident(sid, Plain) => {
 322                 let n = sid.name;
 323
 324                    n == SELF_KEYWORD_NAME
 325                 || n == STATIC_KEYWORD_NAME
 326                 || n == SUPER_KEYWORD_NAME
 327                 || n == SELF_TYPE_KEYWORD_NAME
 328                 || STRICT_KEYWORD_START <= n
 329                 && n <= STRICT_KEYWORD_FINAL
 330             },
 331             Ident(sid, ModName) => {
 332                 let n = sid.name;
 333
 334                    n != SELF_KEYWORD_NAME
 335                 && n != SUPER_KEYWORD_NAME
 336                 && STRICT_KEYWORD_START <= n
 337                 && n <= STRICT_KEYWORD_FINAL
 338             }
 339             _ => false,
 340         }
 341     }
 342
 343     /// Returns `true` if the token is a keyword that has been reserved for
 344     /// possible future use.
 345     #[allow(non_upper_case_globals)]
 346     pub fn is_reserved_keyword(&self) -> bool {
 347         match *self {
 348             Ident(sid, Plain) => {
 349                 let n = sid.name;
 350
 351                    RESERVED_KEYWORD_START <= n
 352                 && n <= RESERVED_KEYWORD_FINAL
 353             },
 354             _ => false,
 355         }
 356     }
 357
 358     /// Hygienic identifier equality comparison.
 359     ///
 360     /// See `styntax::ext::mtwt`.
 361     pub fn mtwt_eq(&self, other : &Token) -> bool {
 362         match (self, other) {
 363             (&Ident(id1,_), &Ident(id2,_)) | (&Lifetime(id1), &Lifetime(id2)) =>
 364                 mtwt::resolve(id1) == mtwt::resolve(id2),
 365             _ => *self == *other
 366         }
 367     }
 368 }
 369
 370 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash)]
 371 /// For interpolation during macro expansion.
 372 pub enum Nonterminal {
 373     NtItem(P<ast::Item>),
 374     NtBlock(P<ast::Block>),
 375     NtStmt(P<ast::Stmt>),
 376     NtPat(P<ast::Pat>),
 377     NtExpr(P<ast::Expr>),
 378     NtTy(P<ast::Ty>),
 379     NtIdent(Box<ast::Ident>, IdentStyle),
 380     /// Stuff inside brackets for attributes
 381     NtMeta(P<ast::MetaItem>),
 382     NtPath(Box<ast::Path>),
 383     NtTT(P<ast::TokenTree>), // needs P'ed to break a circularity
 384 }
 385
 386 impl fmt::Debug for Nonterminal {
 387     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 388         match *self {
 389             NtItem(..) => f.pad("NtItem(..)"),
 390             NtBlock(..) => f.pad("NtBlock(..)"),
 391             NtStmt(..) => f.pad("NtStmt(..)"),
 392             NtPat(..) => f.pad("NtPat(..)"),
 393             NtExpr(..) => f.pad("NtExpr(..)"),
 394             NtTy(..) => f.pad("NtTy(..)"),
 395             NtIdent(..) => f.pad("NtIdent(..)"),
 396             NtMeta(..) => f.pad("NtMeta(..)"),
 397             NtPath(..) => f.pad("NtPath(..)"),
 398             NtTT(..) => f.pad("NtTT(..)"),
 399         }
 400     }
 401 }
 402
 403
 404 // Get the first "argument"
 405 macro_rules! first {
 406     ( $first:expr, $( $remainder:expr, )* ) => ( $first )
 407 }
 408
 409 // Get the last "argument" (has to be done recursively to avoid phoney local ambiguity error)
 410 macro_rules! last {
 411     ( $first:expr, $( $remainder:expr, )+ ) => ( last!( $( $remainder, )+ ) );
 412     ( $first:expr, ) => ( $first )
 413 }
 414
 415 // In this macro, there is the requirement that the name (the number) must be monotonically
 416 // increasing by one in the special identifiers, starting at 0; the same holds for the keywords,
 417 // except starting from the next number instead of zero, and with the additional exception that
 418 // special identifiers are *also* allowed (they are deduplicated in the important place, the
 419 // interner), an exception which is demonstrated by "static" and "self".
 420 macro_rules! declare_special_idents_and_keywords {(
 421     // So now, in these rules, why is each definition parenthesised?
 422     // Answer: otherwise we get a spurious local ambiguity bug on the "}"
 423     pub mod special_idents {
 424         $( ($si_name:expr, $si_static:ident, $si_str:expr); )*
 425     }
 426
 427     pub mod keywords {
 428         'strict:
 429         $( ($sk_name:expr, $sk_variant:ident, $sk_str:expr); )*
 430         'reserved:
 431         $( ($rk_name:expr, $rk_variant:ident, $rk_str:expr); )*
 432     }
 433 ) => {
 434     const STRICT_KEYWORD_START: ast::Name = first!($( ast::Name($sk_name), )*);
 435     const STRICT_KEYWORD_FINAL: ast::Name = last!($( ast::Name($sk_name), )*);
 436     const RESERVED_KEYWORD_START: ast::Name = first!($( ast::Name($rk_name), )*);
 437     const RESERVED_KEYWORD_FINAL: ast::Name = last!($( ast::Name($rk_name), )*);
 438
 439     pub mod special_idents {
 440         use ast;
 441         $(
 442             #[allow(non_upper_case_globals)]
 443             pub const $si_static: ast::Ident = ast::Ident {
 444                 name: ast::Name($si_name),
 445                 ctxt: 0,
 446             };
 447          )*
 448     }
 449
 450     pub mod special_names {
 451         use ast;
 452         $(
 453             #[allow(non_upper_case_globals)]
 454             pub const $si_static: ast::Name =  ast::Name($si_name);
 455         )*
 456     }
 457
 458     /// All the valid words that have meaning in the Rust language.
 459     ///
 460     /// Rust keywords are either 'strict' or 'reserved'.  Strict keywords may not
 461     /// appear as identifiers at all. Reserved keywords are not used anywhere in
 462     /// the language and may not appear as identifiers.
 463     pub mod keywords {
 464         pub use self::Keyword::*;
 465         use ast;
 466
 467         #[derive(Copy, Clone, PartialEq, Eq)]
 468         pub enum Keyword {
 469             $( $sk_variant, )*
 470             $( $rk_variant, )*
 471         }
 472
 473         impl Keyword {
 474             pub fn to_name(&self) -> ast::Name {
 475                 match *self {
 476                     $( $sk_variant => ast::Name($sk_name), )*
 477                     $( $rk_variant => ast::Name($rk_name), )*
 478                 }
 479             }
 480         }
 481     }
 482
 483     fn mk_fresh_ident_interner() -> IdentInterner {
 484         // The indices here must correspond to the numbers in
 485         // special_idents, in Keyword to_name(), and in static
 486         // constants below.
 487         let mut init_vec = Vec::new();
 488         $(init_vec.push($si_str);)*
 489         $(init_vec.push($sk_str);)*
 490         $(init_vec.push($rk_str);)*
 491         interner::StrInterner::prefill(&init_vec[..])
 492     }
 493 }}
 494
 495 // If the special idents get renumbered, remember to modify these two as appropriate
 496 pub const SELF_KEYWORD_NAME: ast::Name = ast::Name(SELF_KEYWORD_NAME_NUM);
 497 const STATIC_KEYWORD_NAME: ast::Name = ast::Name(STATIC_KEYWORD_NAME_NUM);
 498 const SUPER_KEYWORD_NAME: ast::Name = ast::Name(SUPER_KEYWORD_NAME_NUM);
 499 const SELF_TYPE_KEYWORD_NAME: ast::Name = ast::Name(SELF_TYPE_KEYWORD_NAME_NUM);
 500
 501 pub const SELF_KEYWORD_NAME_NUM: u32 = 1;
 502 const STATIC_KEYWORD_NAME_NUM: u32 = 2;
 503 const SUPER_KEYWORD_NAME_NUM: u32 = 3;
 504 const SELF_TYPE_KEYWORD_NAME_NUM: u32 = 10;
 505
 506 // NB: leaving holes in the ident table is bad! a different ident will get
 507 // interned with the id from the hole, but it will be between the min and max
 508 // of the reserved words, and thus tagged as "reserved".
 509
 510 declare_special_idents_and_keywords! {
 511     pub mod special_idents {
 512         // These ones are statics
 513         (0,                          invalid,                "");
 514         (super::SELF_KEYWORD_NAME_NUM,   self_,              "self");
 515         (super::STATIC_KEYWORD_NAME_NUM, statik,             "static");
 516         (super::SUPER_KEYWORD_NAME_NUM, super_,              "super");
 517         (4,                          static_lifetime,        "'static");
 518
 519         // for matcher NTs
 520         (5,                          tt,                     "tt");
 521         (6,                          matchers,               "matchers");
 522
 523         // outside of libsyntax
 524         (7,                          clownshoe_abi,          "__rust_abi");
 525         (8,                          opaque,                 "<opaque>");
 526         (9,                          unnamed_field,          "<unnamed_field>");
 527         (super::SELF_TYPE_KEYWORD_NAME_NUM, type_self,       "Self");
 528         (11,                         prelude_import,         "prelude_import");
 529     }
 530
 531     pub mod keywords {
 532         // These ones are variants of the Keyword enum
 533
 534         'strict:
 535         (12,                         As,         "as");
 536         (13,                         Break,      "break");
 537         (14,                         Crate,      "crate");
 538         (15,                         Else,       "else");
 539         (16,                         Enum,       "enum");
 540         (17,                         Extern,     "extern");
 541         (18,                         False,      "false");
 542         (19,                         Fn,         "fn");
 543         (20,                         For,        "for");
 544         (21,                         If,         "if");
 545         (22,                         Impl,       "impl");
 546         (23,                         In,         "in");
 547         (24,                         Let,        "let");
 548         (25,                         Loop,       "loop");
 549         (26,                         Match,      "match");
 550         (27,                         Mod,        "mod");
 551         (28,                         Move,       "move");
 552         (29,                         Mut,        "mut");
 553         (30,                         Pub,        "pub");
 554         (31,                         Ref,        "ref");
 555         (32,                         Return,     "return");
 556         // Static and Self are also special idents (prefill de-dupes)
 557         (super::STATIC_KEYWORD_NAME_NUM, Static, "static");
 558         (super::SELF_KEYWORD_NAME_NUM, SelfValue, "self");
 559         (super::SELF_TYPE_KEYWORD_NAME_NUM, SelfType, "Self");
 560         (33,                         Struct,     "struct");
 561         (super::SUPER_KEYWORD_NAME_NUM, Super,   "super");
 562         (34,                         True,       "true");
 563         (35,                         Trait,      "trait");
 564         (36,                         Type,       "type");
 565         (37,                         Unsafe,     "unsafe");
 566         (38,                         Use,        "use");
 567         (39,                         Virtual,    "virtual");
 568         (40,                         While,      "while");
 569         (41,                         Continue,   "continue");
 570         (42,                         Box,        "box");
 571         (43,                         Const,      "const");
 572         (44,                         Where,      "where");
 573         'reserved:
 574         (45,                         Proc,       "proc");
 575         (46,                         Alignof,    "alignof");
 576         (47,                         Become,     "become");
 577         (48,                         Offsetof,   "offsetof");
 578         (49,                         Priv,       "priv");
 579         (50,                         Pure,       "pure");
 580         (51,                         Sizeof,     "sizeof");
 581         (52,                         Typeof,     "typeof");
 582         (53,                         Unsized,    "unsized");
 583         (54,                         Yield,      "yield");
 584         (55,                         Do,         "do");
 585         (56,                         Abstract,   "abstract");
 586         (57,                         Final,      "final");
 587         (58,                         Override,   "override");
 588         (59,                         Macro,      "macro");
 589     }
 590 }
 591
 592 // looks like we can get rid of this completely...
 593 pub type IdentInterner = StrInterner;
 594
 595 // if an interner exists in TLS, return it. Otherwise, prepare a
 596 // fresh one.
 597 // FIXME(eddyb) #8726 This should probably use a thread-local reference.
 598 pub fn get_ident_interner() -> Rc<IdentInterner> {
 599     thread_local!(static KEY: Rc<::parse::token::IdentInterner> = {
 600         Rc::new(mk_fresh_ident_interner())
 601     });
 602     KEY.with(|k| k.clone())
 603 }
 604
 605 /// Reset the ident interner to its initial state.
 606 pub fn reset_ident_interner() {
 607     let interner = get_ident_interner();
 608     interner.reset(mk_fresh_ident_interner());
 609 }
 610
 611 /// Represents a string stored in the thread-local interner. Because the
 612 /// interner lives for the life of the thread, this can be safely treated as an
 613 /// immortal string, as long as it never crosses between threads.
 614 ///
 615 /// FIXME(pcwalton): You must be careful about what you do in the destructors
 616 /// of objects stored in TLS, because they may run after the interner is
 617 /// destroyed. In particular, they must not access string contents. This can
 618 /// be fixed in the future by just leaking all strings until thread death
 619 /// somehow.
 620 #[derive(Clone, PartialEq, Hash, PartialOrd, Eq, Ord)]
 621 pub struct InternedString {
 622     string: RcStr,
 623 }
 624
 625 impl InternedString {
 626     #[inline]
 627     pub fn new(string: &'static str) -> InternedString {
 628         InternedString {
 629             string: RcStr::new(string),
 630         }
 631     }
 632
 633     #[inline]
 634     fn new_from_rc_str(string: RcStr) -> InternedString {
 635         InternedString {
 636             string: string,
 637         }
 638     }
 639 }
 640
 641 impl Deref for InternedString {
 642     type Target = str;
 643
 644     fn deref(&self) -> &str { &*self.string }
 645 }
 646
 647 impl fmt::Debug for InternedString {
 648     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 649         fmt::Debug::fmt(&self.string, f)
 650     }
 651 }
 652
 653 impl fmt::Display for InternedString {
 654     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 655         fmt::Display::fmt(&self.string, f)
 656     }
 657 }
 658
 659 impl<'a> PartialEq<&'a str> for InternedString {
 660     #[inline(always)]
 661     fn eq(&self, other: & &'a str) -> bool {
 662         PartialEq::eq(&self.string[..], *other)
 663     }
 664     #[inline(always)]
 665     fn ne(&self, other: & &'a str) -> bool {
 666         PartialEq::ne(&self.string[..], *other)
 667     }
 668 }
 669
 670 impl<'a> PartialEq<InternedString > for &'a str {
 671     #[inline(always)]
 672     fn eq(&self, other: &InternedString) -> bool {
 673         PartialEq::eq(*self, &other.string[..])
 674     }
 675     #[inline(always)]
 676     fn ne(&self, other: &InternedString) -> bool {
 677         PartialEq::ne(*self, &other.string[..])
 678     }
 679 }
 680
 681 impl Decodable for InternedString {
 682     fn decode<D: Decoder>(d: &mut D) -> Result<InternedString, D::Error> {
 683         Ok(get_name(get_ident_interner().intern(&try!(d.read_str())[..])))
 684     }
 685 }
 686
 687 impl Encodable for InternedString {
 688     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 689         s.emit_str(&self.string)
 690     }
 691 }
 692
 693 /// Returns the string contents of a name, using the thread-local interner.
 694 #[inline]
 695 pub fn get_name(name: ast::Name) -> InternedString {
 696     let interner = get_ident_interner();
 697     InternedString::new_from_rc_str(interner.get(name))
 698 }
 699
 700 /// Returns the string contents of an identifier, using the thread-local
 701 /// interner.
 702 #[inline]
 703 pub fn get_ident(ident: ast::Ident) -> InternedString {
 704     get_name(ident.name)
 705 }
 706
 707 /// Interns and returns the string contents of an identifier, using the
 708 /// thread-local interner.
 709 #[inline]
 710 pub fn intern_and_get_ident(s: &str) -> InternedString {
 711     get_name(intern(s))
 712 }
 713
 714 /// Maps a string to its interned representation.
 715 #[inline]
 716 pub fn intern(s: &str) -> ast::Name {
 717     get_ident_interner().intern(s)
 718 }
 719
 720 /// gensym's a new usize, using the current interner.
 721 #[inline]
 722 pub fn gensym(s: &str) -> ast::Name {
 723     get_ident_interner().gensym(s)
 724 }
 725
 726 /// Maps a string to an identifier with an empty syntax context.
 727 #[inline]
 728 pub fn str_to_ident(s: &str) -> ast::Ident {
 729     ast::Ident::new(intern(s))
 730 }
 731
 732 /// Maps a string to a gensym'ed identifier.
 733 #[inline]
 734 pub fn gensym_ident(s: &str) -> ast::Ident {
 735     ast::Ident::new(gensym(s))
 736 }
 737
 738 // create a fresh name that maps to the same string as the old one.
 739 // note that this guarantees that str_ptr_eq(ident_to_string(src),interner_get(fresh_name(src)));
 740 // that is, that the new name and the old one are connected to ptr_eq strings.
 741 pub fn fresh_name(src: &ast::Ident) -> ast::Name {
 742     let interner = get_ident_interner();
 743     interner.gensym_copy(src.name)
 744     // following: debug version. Could work in final except that it's incompatible with
 745     // good error messages and uses of struct names in ambiguous could-be-binding
 746     // locations. Also definitely destroys the guarantee given above about ptr_eq.
 747     /*let num = rand::thread_rng().gen_uint_range(0,0xffff);
 748     gensym(format!("{}_{}",ident_to_string(src),num))*/
 749 }
 750
 751 // create a fresh mark.
 752 pub fn fresh_mark() -> ast::Mrk {
 753     gensym("mark").usize() as u32
 754 }
 755
 756 #[cfg(test)]
 757 mod test {
 758     use super::*;
 759     use ast;
 760     use ext::mtwt;
 761
 762     fn mark_ident(id : ast::Ident, m : ast::Mrk) -> ast::Ident {
 763         ast::Ident { name: id.name, ctxt:mtwt::apply_mark(m, id.ctxt) }
 764     }
 765
 766     #[test] fn mtwt_token_eq_test() {
 767         assert!(Gt.mtwt_eq(&Gt));
 768         let a = str_to_ident("bac");
 769         let a1 = mark_ident(a,92);
 770         assert!(Ident(a, ModName).mtwt_eq(&Ident(a1, Plain)));
 771     }
 772 }