src/libsyntax/ast.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 // The Rust abstract syntax tree.
  12
  13 pub use self::TyParamBound::*;
  14 pub use self::UnsafeSource::*;
  15 pub use self::ViewPath_::*;
  16 pub use self::PathParameters::*;
  17 pub use symbol::Symbol as Name;
  18 pub use util::ThinVec;
  19
  20 use syntax_pos::{mk_sp, Span, DUMMY_SP, ExpnId};
  21 use codemap::{respan, Spanned};
  22 use abi::Abi;
  23 use ext::hygiene::SyntaxContext;
  24 use print::pprust;
  25 use ptr::P;
  26 use symbol::{Symbol, keywords};
  27 use tokenstream::{ThinTokenStream, TokenStream};
  28
  29 use std::collections::HashSet;
  30 use std::fmt;
  31 use std::rc::Rc;
  32 use std::u32;
  33
  34 use serialize::{self, Encodable, Decodable, Encoder, Decoder};
  35
  36 /// An identifier contains a Name (index into the interner
  37 /// table) and a SyntaxContext to track renaming and
  38 /// macro expansion per Flatt et al., "Macros That Work Together"
  39 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
  40 pub struct Ident {
  41     pub name: Symbol,
  42     pub ctxt: SyntaxContext
  43 }
  44
  45 impl Ident {
  46     pub const fn with_empty_ctxt(name: Name) -> Ident {
  47         Ident { name: name, ctxt: SyntaxContext::empty() }
  48     }
  49
  50     /// Maps a string to an identifier with an empty syntax context.
  51     pub fn from_str(s: &str) -> Ident {
  52         Ident::with_empty_ctxt(Symbol::intern(s))
  53     }
  54
  55     pub fn unhygienize(&self) -> Ident {
  56         Ident { name: self.name, ctxt: SyntaxContext::empty() }
  57     }
  58 }
  59
  60 impl fmt::Debug for Ident {
  61     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
  62         write!(f, "{}{:?}", self.name, self.ctxt)
  63     }
  64 }
  65
  66 impl fmt::Display for Ident {
  67     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
  68         fmt::Display::fmt(&self.name, f)
  69     }
  70 }
  71
  72 impl Encodable for Ident {
  73     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
  74         self.name.encode(s)
  75     }
  76 }
  77
  78 impl Decodable for Ident {
  79     fn decode<D: Decoder>(d: &mut D) -> Result<Ident, D::Error> {
  80         Ok(Ident::with_empty_ctxt(Name::decode(d)?))
  81     }
  82 }
  83
  84 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Copy)]
  85 pub struct Lifetime {
  86     pub id: NodeId,
  87     pub span: Span,
  88     pub name: Name
  89 }
  90
  91 impl fmt::Debug for Lifetime {
  92     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
  93         write!(f, "lifetime({}: {})", self.id, pprust::lifetime_to_string(self))
  94     }
  95 }
  96
  97 /// A lifetime definition, e.g. `'a: 'b+'c+'d`
  98 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
  99 pub struct LifetimeDef {
 100     pub attrs: ThinVec<Attribute>,
 101     pub lifetime: Lifetime,
 102     pub bounds: Vec<Lifetime>
 103 }
 104
 105 /// A "Path" is essentially Rust's notion of a name.
 106 ///
 107 /// It's represented as a sequence of identifiers,
 108 /// along with a bunch of supporting information.
 109 ///
 110 /// E.g. `std::cmp::PartialEq`
 111 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash)]
 112 pub struct Path {
 113     pub span: Span,
 114     /// The segments in the path: the things separated by `::`.
 115     /// Global paths begin with `keywords::CrateRoot`.
 116     pub segments: Vec<PathSegment>,
 117 }
 118
 119 impl fmt::Debug for Path {
 120     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 121         write!(f, "path({})", pprust::path_to_string(self))
 122     }
 123 }
 124
 125 impl fmt::Display for Path {
 126     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 127         write!(f, "{}", pprust::path_to_string(self))
 128     }
 129 }
 130
 131 impl Path {
 132     // convert a span and an identifier to the corresponding
 133     // 1-segment path
 134     pub fn from_ident(s: Span, identifier: Ident) -> Path {
 135         Path {
 136             span: s,
 137             segments: vec![PathSegment::from_ident(identifier, s)],
 138         }
 139     }
 140
 141     pub fn default_to_global(mut self) -> Path {
 142         let name = self.segments[0].identifier.name;
 143         if !self.is_global() && name != "$crate" &&
 144            name != keywords::SelfValue.name() && name != keywords::Super.name() {
 145             self.segments.insert(0, PathSegment::crate_root());
 146         }
 147         self
 148     }
 149
 150     pub fn is_global(&self) -> bool {
 151         !self.segments.is_empty() && self.segments[0].identifier.name == keywords::CrateRoot.name()
 152     }
 153 }
 154
 155 /// A segment of a path: an identifier, an optional lifetime, and a set of types.
 156 ///
 157 /// E.g. `std`, `String` or `Box<T>`
 158 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 159 pub struct PathSegment {
 160     /// The identifier portion of this path segment.
 161     pub identifier: Ident,
 162     /// Span of the segment identifier.
 163     pub span: Span,
 164
 165     /// Type/lifetime parameters attached to this path. They come in
 166     /// two flavors: `Path<A,B,C>` and `Path(A,B) -> C`. Note that
 167     /// this is more than just simple syntactic sugar; the use of
 168     /// parens affects the region binding rules, so we preserve the
 169     /// distinction.
 170     /// The `Option<P<..>>` wrapper is purely a size optimization;
 171     /// `None` is used to represent both `Path` and `Path<>`.
 172     pub parameters: Option<P<PathParameters>>,
 173 }
 174
 175 impl PathSegment {
 176     pub fn from_ident(ident: Ident, span: Span) -> Self {
 177         PathSegment { identifier: ident, span: span, parameters: None }
 178     }
 179     pub fn crate_root() -> Self {
 180         PathSegment {
 181             identifier: keywords::CrateRoot.ident(),
 182             span: DUMMY_SP,
 183             parameters: None,
 184         }
 185     }
 186 }
 187
 188 /// Parameters of a path segment.
 189 ///
 190 /// E.g. `<A, B>` as in `Foo<A, B>` or `(A, B)` as in `Foo(A, B)`
 191 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 192 pub enum PathParameters {
 193     /// The `<'a, A,B,C>` in `foo::bar::baz::<'a, A,B,C>`
 194     AngleBracketed(AngleBracketedParameterData),
 195     /// The `(A,B)` and `C` in `Foo(A,B) -> C`
 196     Parenthesized(ParenthesizedParameterData),
 197 }
 198
 199 /// A path like `Foo<'a, T>`
 200 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Default)]
 201 pub struct AngleBracketedParameterData {
 202     /// The lifetime parameters for this path segment.
 203     pub lifetimes: Vec<Lifetime>,
 204     /// The type parameters for this path segment, if present.
 205     pub types: Vec<P<Ty>>,
 206     /// Bindings (equality constraints) on associated types, if present.
 207     ///
 208     /// E.g., `Foo<A=Bar>`.
 209     pub bindings: Vec<TypeBinding>,
 210 }
 211
 212 impl Into<Option<P<PathParameters>>> for AngleBracketedParameterData {
 213     fn into(self) -> Option<P<PathParameters>> {
 214         let empty = self.lifetimes.is_empty() && self.types.is_empty() && self.bindings.is_empty();
 215         if empty { None } else { Some(P(PathParameters::AngleBracketed(self))) }
 216     }
 217 }
 218
 219 /// A path like `Foo(A,B) -> C`
 220 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 221 pub struct ParenthesizedParameterData {
 222     /// Overall span
 223     pub span: Span,
 224
 225     /// `(A,B)`
 226     pub inputs: Vec<P<Ty>>,
 227
 228     /// `C`
 229     pub output: Option<P<Ty>>,
 230 }
 231
 232 #[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Hash, Debug)]
 233 pub struct NodeId(u32);
 234
 235 impl NodeId {
 236     pub fn new(x: usize) -> NodeId {
 237         assert!(x < (u32::MAX as usize));
 238         NodeId(x as u32)
 239     }
 240
 241     pub fn from_u32(x: u32) -> NodeId {
 242         NodeId(x)
 243     }
 244
 245     pub fn as_usize(&self) -> usize {
 246         self.0 as usize
 247     }
 248
 249     pub fn as_u32(&self) -> u32 {
 250         self.0
 251     }
 252 }
 253
 254 impl fmt::Display for NodeId {
 255     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 256         fmt::Display::fmt(&self.0, f)
 257     }
 258 }
 259
 260 impl serialize::UseSpecializedEncodable for NodeId {
 261     fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
 262         s.emit_u32(self.0)
 263     }
 264 }
 265
 266 impl serialize::UseSpecializedDecodable for NodeId {
 267     fn default_decode<D: Decoder>(d: &mut D) -> Result<NodeId, D::Error> {
 268         d.read_u32().map(NodeId)
 269     }
 270 }
 271
 272 /// Node id used to represent the root of the crate.
 273 pub const CRATE_NODE_ID: NodeId = NodeId(0);
 274
 275 /// When parsing and doing expansions, we initially give all AST nodes this AST
 276 /// node value. Then later, in the renumber pass, we renumber them to have
 277 /// small, positive ids.
 278 pub const DUMMY_NODE_ID: NodeId = NodeId(!0);
 279
 280 /// The AST represents all type param bounds as types.
 281 /// typeck::collect::compute_bounds matches these against
 282 /// the "special" built-in traits (see middle::lang_items) and
 283 /// detects Copy, Send and Sync.
 284 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 285 pub enum TyParamBound {
 286     TraitTyParamBound(PolyTraitRef, TraitBoundModifier),
 287     RegionTyParamBound(Lifetime)
 288 }
 289
 290 /// A modifier on a bound, currently this is only used for `?Sized`, where the
 291 /// modifier is `Maybe`. Negative bounds should also be handled here.
 292 #[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 293 pub enum TraitBoundModifier {
 294     None,
 295     Maybe,
 296 }
 297
 298 pub type TyParamBounds = Vec<TyParamBound>;
 299
 300 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 301 pub struct TyParam {
 302     pub attrs: ThinVec<Attribute>,
 303     pub ident: Ident,
 304     pub id: NodeId,
 305     pub bounds: TyParamBounds,
 306     pub default: Option<P<Ty>>,
 307     pub span: Span,
 308 }
 309
 310 /// Represents lifetimes and type parameters attached to a declaration
 311 /// of a function, enum, trait, etc.
 312 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 313 pub struct Generics {
 314     pub lifetimes: Vec<LifetimeDef>,
 315     pub ty_params: Vec<TyParam>,
 316     pub where_clause: WhereClause,
 317     pub span: Span,
 318 }
 319
 320 impl Generics {
 321     pub fn is_lt_parameterized(&self) -> bool {
 322         !self.lifetimes.is_empty()
 323     }
 324     pub fn is_type_parameterized(&self) -> bool {
 325         !self.ty_params.is_empty()
 326     }
 327     pub fn is_parameterized(&self) -> bool {
 328         self.is_lt_parameterized() || self.is_type_parameterized()
 329     }
 330     pub fn span_for_name(&self, name: &str) -> Option<Span> {
 331         for t in &self.ty_params {
 332             if t.ident.name == name {
 333                 return Some(t.span);
 334             }
 335         }
 336         None
 337     }
 338 }
 339
 340 impl Default for Generics {
 341     /// Creates an instance of `Generics`.
 342     fn default() ->  Generics {
 343         Generics {
 344             lifetimes: Vec::new(),
 345             ty_params: Vec::new(),
 346             where_clause: WhereClause {
 347                 id: DUMMY_NODE_ID,
 348                 predicates: Vec::new(),
 349             },
 350             span: DUMMY_SP,
 351         }
 352     }
 353 }
 354
 355 /// A `where` clause in a definition
 356 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 357 pub struct WhereClause {
 358     pub id: NodeId,
 359     pub predicates: Vec<WherePredicate>,
 360 }
 361
 362 /// A single predicate in a `where` clause
 363 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 364 pub enum WherePredicate {
 365     /// A type binding, e.g. `for<'c> Foo: Send+Clone+'c`
 366     BoundPredicate(WhereBoundPredicate),
 367     /// A lifetime predicate, e.g. `'a: 'b+'c`
 368     RegionPredicate(WhereRegionPredicate),
 369     /// An equality predicate (unsupported)
 370     EqPredicate(WhereEqPredicate),
 371 }
 372
 373 /// A type bound.
 374 ///
 375 /// E.g. `for<'c> Foo: Send+Clone+'c`
 376 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 377 pub struct WhereBoundPredicate {
 378     pub span: Span,
 379     /// Any lifetimes from a `for` binding
 380     pub bound_lifetimes: Vec<LifetimeDef>,
 381     /// The type being bounded
 382     pub bounded_ty: P<Ty>,
 383     /// Trait and lifetime bounds (`Clone+Send+'static`)
 384     pub bounds: TyParamBounds,
 385 }
 386
 387 /// A lifetime predicate.
 388 ///
 389 /// E.g. `'a: 'b+'c`
 390 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 391 pub struct WhereRegionPredicate {
 392     pub span: Span,
 393     pub lifetime: Lifetime,
 394     pub bounds: Vec<Lifetime>,
 395 }
 396
 397 /// An equality predicate (unsupported).
 398 ///
 399 /// E.g. `T=int`
 400 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 401 pub struct WhereEqPredicate {
 402     pub id: NodeId,
 403     pub span: Span,
 404     pub lhs_ty: P<Ty>,
 405     pub rhs_ty: P<Ty>,
 406 }
 407
 408 /// The set of MetaItems that define the compilation environment of the crate,
 409 /// used to drive conditional compilation
 410 pub type CrateConfig = HashSet<(Name, Option<Symbol>)>;
 411
 412 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 413 pub struct Crate {
 414     pub module: Mod,
 415     pub attrs: Vec<Attribute>,
 416     pub span: Span,
 417 }
 418
 419 /// A spanned compile-time attribute list item.
 420 pub type NestedMetaItem = Spanned<NestedMetaItemKind>;
 421
 422 /// Possible values inside of compile-time attribute lists.
 423 ///
 424 /// E.g. the '..' in `#[name(..)]`.
 425 #[derive(Clone, Eq, RustcEncodable, RustcDecodable, Hash, Debug, PartialEq)]
 426 pub enum NestedMetaItemKind {
 427     /// A full MetaItem, for recursive meta items.
 428     MetaItem(MetaItem),
 429     /// A literal.
 430     ///
 431     /// E.g. "foo", 64, true
 432     Literal(Lit),
 433 }
 434
 435 /// A spanned compile-time attribute item.
 436 ///
 437 /// E.g. `#[test]`, `#[derive(..)]` or `#[feature = "foo"]`
 438 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 439 pub struct MetaItem {
 440     pub name: Name,
 441     pub node: MetaItemKind,
 442     pub span: Span,
 443 }
 444
 445 /// A compile-time attribute item.
 446 ///
 447 /// E.g. `#[test]`, `#[derive(..)]` or `#[feature = "foo"]`
 448 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 449 pub enum MetaItemKind {
 450     /// Word meta item.
 451     ///
 452     /// E.g. `test` as in `#[test]`
 453     Word,
 454     /// List meta item.
 455     ///
 456     /// E.g. `derive(..)` as in `#[derive(..)]`
 457     List(Vec<NestedMetaItem>),
 458     /// Name value meta item.
 459     ///
 460     /// E.g. `feature = "foo"` as in `#[feature = "foo"]`
 461     NameValue(Lit)
 462 }
 463
 464 /// A Block (`{ .. }`).
 465 ///
 466 /// E.g. `{ .. }` as in `fn foo() { .. }`
 467 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 468 pub struct Block {
 469     /// Statements in a block
 470     pub stmts: Vec<Stmt>,
 471     pub id: NodeId,
 472     /// Distinguishes between `unsafe { ... }` and `{ ... }`
 473     pub rules: BlockCheckMode,
 474     pub span: Span,
 475 }
 476
 477 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash)]
 478 pub struct Pat {
 479     pub id: NodeId,
 480     pub node: PatKind,
 481     pub span: Span,
 482 }
 483
 484 impl fmt::Debug for Pat {
 485     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 486         write!(f, "pat({}: {})", self.id, pprust::pat_to_string(self))
 487     }
 488 }
 489
 490 impl Pat {
 491     pub fn walk<F>(&self, it: &mut F) -> bool
 492         where F: FnMut(&Pat) -> bool
 493     {
 494         if !it(self) {
 495             return false;
 496         }
 497
 498         match self.node {
 499             PatKind::Ident(_, _, Some(ref p)) => p.walk(it),
 500             PatKind::Struct(_, ref fields, _) => {
 501                 fields.iter().all(|field| field.node.pat.walk(it))
 502             }
 503             PatKind::TupleStruct(_, ref s, _) | PatKind::Tuple(ref s, _) => {
 504                 s.iter().all(|p| p.walk(it))
 505             }
 506             PatKind::Box(ref s) | PatKind::Ref(ref s, _) => {
 507                 s.walk(it)
 508             }
 509             PatKind::Slice(ref before, ref slice, ref after) => {
 510                 before.iter().all(|p| p.walk(it)) &&
 511                 slice.iter().all(|p| p.walk(it)) &&
 512                 after.iter().all(|p| p.walk(it))
 513             }
 514             PatKind::Wild |
 515             PatKind::Lit(_) |
 516             PatKind::Range(..) |
 517             PatKind::Ident(..) |
 518             PatKind::Path(..) |
 519             PatKind::Mac(_) => {
 520                 true
 521             }
 522         }
 523     }
 524 }
 525
 526 /// A single field in a struct pattern
 527 ///
 528 /// Patterns like the fields of Foo `{ x, ref y, ref mut z }`
 529 /// are treated the same as` x: x, y: ref y, z: ref mut z`,
 530 /// except is_shorthand is true
 531 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 532 pub struct FieldPat {
 533     /// The identifier for the field
 534     pub ident: Ident,
 535     /// The pattern the field is destructured to
 536     pub pat: P<Pat>,
 537     pub is_shorthand: bool,
 538     pub attrs: ThinVec<Attribute>,
 539 }
 540
 541 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
 542 pub enum BindingMode {
 543     ByRef(Mutability),
 544     ByValue(Mutability),
 545 }
 546
 547 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 548 pub enum RangeEnd {
 549     Included,
 550     Excluded,
 551 }
 552
 553 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 554 pub enum PatKind {
 555     /// Represents a wildcard pattern (`_`)
 556     Wild,
 557
 558     /// A `PatKind::Ident` may either be a new bound variable (`ref mut binding @ OPT_SUBPATTERN`),
 559     /// or a unit struct/variant pattern, or a const pattern (in the last two cases the third
 560     /// field must be `None`). Disambiguation cannot be done with parser alone, so it happens
 561     /// during name resolution.
 562     Ident(BindingMode, SpannedIdent, Option<P<Pat>>),
 563
 564     /// A struct or struct variant pattern, e.g. `Variant {x, y, ..}`.
 565     /// The `bool` is `true` in the presence of a `..`.
 566     Struct(Path, Vec<Spanned<FieldPat>>, bool),
 567
 568     /// A tuple struct/variant pattern `Variant(x, y, .., z)`.
 569     /// If the `..` pattern fragment is present, then `Option<usize>` denotes its position.
 570     /// 0 <= position <= subpats.len()
 571     TupleStruct(Path, Vec<P<Pat>>, Option<usize>),
 572
 573     /// A possibly qualified path pattern.
 574     /// Unquailfied path patterns `A::B::C` can legally refer to variants, structs, constants
 575     /// or associated constants. Quailfied path patterns `<A>::B::C`/`<A as Trait>::B::C` can
 576     /// only legally refer to associated constants.
 577     Path(Option<QSelf>, Path),
 578
 579     /// A tuple pattern `(a, b)`.
 580     /// If the `..` pattern fragment is present, then `Option<usize>` denotes its position.
 581     /// 0 <= position <= subpats.len()
 582     Tuple(Vec<P<Pat>>, Option<usize>),
 583     /// A `box` pattern
 584     Box(P<Pat>),
 585     /// A reference pattern, e.g. `&mut (a, b)`
 586     Ref(P<Pat>, Mutability),
 587     /// A literal
 588     Lit(P<Expr>),
 589     /// A range pattern, e.g. `1...2` or `1..2`
 590     Range(P<Expr>, P<Expr>, RangeEnd),
 591     /// `[a, b, ..i, y, z]` is represented as:
 592     ///     `PatKind::Slice(box [a, b], Some(i), box [y, z])`
 593     Slice(Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>),
 594     /// A macro pattern; pre-expansion
 595     Mac(Mac),
 596 }
 597
 598 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
 599 pub enum Mutability {
 600     Mutable,
 601     Immutable,
 602 }
 603
 604 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
 605 pub enum BinOpKind {
 606     /// The `+` operator (addition)
 607     Add,
 608     /// The `-` operator (subtraction)
 609     Sub,
 610     /// The `*` operator (multiplication)
 611     Mul,
 612     /// The `/` operator (division)
 613     Div,
 614     /// The `%` operator (modulus)
 615     Rem,
 616     /// The `&&` operator (logical and)
 617     And,
 618     /// The `||` operator (logical or)
 619     Or,
 620     /// The `^` operator (bitwise xor)
 621     BitXor,
 622     /// The `&` operator (bitwise and)
 623     BitAnd,
 624     /// The `|` operator (bitwise or)
 625     BitOr,
 626     /// The `<<` operator (shift left)
 627     Shl,
 628     /// The `>>` operator (shift right)
 629     Shr,
 630     /// The `==` operator (equality)
 631     Eq,
 632     /// The `<` operator (less than)
 633     Lt,
 634     /// The `<=` operator (less than or equal to)
 635     Le,
 636     /// The `!=` operator (not equal to)
 637     Ne,
 638     /// The `>=` operator (greater than or equal to)
 639     Ge,
 640     /// The `>` operator (greater than)
 641     Gt,
 642 }
 643
 644 impl BinOpKind {
 645     pub fn to_string(&self) -> &'static str {
 646         use self::BinOpKind::*;
 647         match *self {
 648             Add => "+",
 649             Sub => "-",
 650             Mul => "*",
 651             Div => "/",
 652             Rem => "%",
 653             And => "&&",
 654             Or => "||",
 655             BitXor => "^",
 656             BitAnd => "&",
 657             BitOr => "|",
 658             Shl => "<<",
 659             Shr => ">>",
 660             Eq => "==",
 661             Lt => "<",
 662             Le => "<=",
 663             Ne => "!=",
 664             Ge => ">=",
 665             Gt => ">",
 666         }
 667     }
 668     pub fn lazy(&self) -> bool {
 669         match *self {
 670             BinOpKind::And | BinOpKind::Or => true,
 671             _ => false
 672         }
 673     }
 674
 675     pub fn is_shift(&self) -> bool {
 676         match *self {
 677             BinOpKind::Shl | BinOpKind::Shr => true,
 678             _ => false
 679         }
 680     }
 681     pub fn is_comparison(&self) -> bool {
 682         use self::BinOpKind::*;
 683         match *self {
 684             Eq | Lt | Le | Ne | Gt | Ge =>
 685             true,
 686             And | Or | Add | Sub | Mul | Div | Rem |
 687             BitXor | BitAnd | BitOr | Shl | Shr =>
 688             false,
 689         }
 690     }
 691     /// Returns `true` if the binary operator takes its arguments by value
 692     pub fn is_by_value(&self) -> bool {
 693         !self.is_comparison()
 694     }
 695 }
 696
 697 pub type BinOp = Spanned<BinOpKind>;
 698
 699 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
 700 pub enum UnOp {
 701     /// The `*` operator for dereferencing
 702     Deref,
 703     /// The `!` operator for logical inversion
 704     Not,
 705     /// The `-` operator for negation
 706     Neg,
 707 }
 708
 709 impl UnOp {
 710     /// Returns `true` if the unary operator takes its argument by value
 711     pub fn is_by_value(u: UnOp) -> bool {
 712         match u {
 713             UnOp::Neg | UnOp::Not => true,
 714             _ => false,
 715         }
 716     }
 717
 718     pub fn to_string(op: UnOp) -> &'static str {
 719         match op {
 720             UnOp::Deref => "*",
 721             UnOp::Not => "!",
 722             UnOp::Neg => "-",
 723         }
 724     }
 725 }
 726
 727 /// A statement
 728 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash)]
 729 pub struct Stmt {
 730     pub id: NodeId,
 731     pub node: StmtKind,
 732     pub span: Span,
 733 }
 734
 735 impl Stmt {
 736     pub fn add_trailing_semicolon(mut self) -> Self {
 737         self.node = match self.node {
 738             StmtKind::Expr(expr) => StmtKind::Semi(expr),
 739             StmtKind::Mac(mac) => StmtKind::Mac(mac.map(|(mac, _style, attrs)| {
 740                 (mac, MacStmtStyle::Semicolon, attrs)
 741             })),
 742             node @ _ => node,
 743         };
 744         self
 745     }
 746 }
 747
 748 impl fmt::Debug for Stmt {
 749     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 750         write!(f, "stmt({}: {})", self.id.to_string(), pprust::stmt_to_string(self))
 751     }
 752 }
 753
 754
 755 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash)]
 756 pub enum StmtKind {
 757     /// A local (let) binding.
 758     Local(P<Local>),
 759
 760     /// An item definition.
 761     Item(P<Item>),
 762
 763     /// Expr without trailing semi-colon.
 764     Expr(P<Expr>),
 765
 766     Semi(P<Expr>),
 767
 768     Mac(P<(Mac, MacStmtStyle, ThinVec<Attribute>)>),
 769 }
 770
 771 #[derive(Clone, Copy, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 772 pub enum MacStmtStyle {
 773     /// The macro statement had a trailing semicolon, e.g. `foo! { ... };`
 774     /// `foo!(...);`, `foo![...];`
 775     Semicolon,
 776     /// The macro statement had braces; e.g. foo! { ... }
 777     Braces,
 778     /// The macro statement had parentheses or brackets and no semicolon; e.g.
 779     /// `foo!(...)`. All of these will end up being converted into macro
 780     /// expressions.
 781     NoBraces,
 782 }
 783
 784 // FIXME (pending discussion of #1697, #2178...): local should really be
 785 // a refinement on pat.
 786 /// Local represents a `let` statement, e.g., `let <pat>:<ty> = <expr>;`
 787 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 788 pub struct Local {
 789     pub pat: P<Pat>,
 790     pub ty: Option<P<Ty>>,
 791     /// Initializer expression to set the value, if any
 792     pub init: Option<P<Expr>>,
 793     pub id: NodeId,
 794     pub span: Span,
 795     pub attrs: ThinVec<Attribute>,
 796 }
 797
 798 /// An arm of a 'match'.
 799 ///
 800 /// E.g. `0...10 => { println!("match!") }` as in
 801 ///
 802 /// ```rust,ignore
 803 /// match n {
 804 ///     0...10 => { println!("match!") },
 805 ///     // ..
 806 /// }
 807 /// ```
 808 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 809 pub struct Arm {
 810     pub attrs: Vec<Attribute>,
 811     pub pats: Vec<P<Pat>>,
 812     pub guard: Option<P<Expr>>,
 813     pub body: P<Expr>,
 814 }
 815
 816 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 817 pub struct Field {
 818     pub ident: SpannedIdent,
 819     pub expr: P<Expr>,
 820     pub span: Span,
 821     pub is_shorthand: bool,
 822     pub attrs: ThinVec<Attribute>,
 823 }
 824
 825 pub type SpannedIdent = Spanned<Ident>;
 826
 827 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
 828 pub enum BlockCheckMode {
 829     Default,
 830     Unsafe(UnsafeSource),
 831 }
 832
 833 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
 834 pub enum UnsafeSource {
 835     CompilerGenerated,
 836     UserProvided,
 837 }
 838
 839 /// An expression
 840 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash,)]
 841 pub struct Expr {
 842     pub id: NodeId,
 843     pub node: ExprKind,
 844     pub span: Span,
 845     pub attrs: ThinVec<Attribute>
 846 }
 847
 848 impl fmt::Debug for Expr {
 849     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 850         write!(f, "expr({}: {})", self.id, pprust::expr_to_string(self))
 851     }
 852 }
 853
 854 /// Limit types of a range (inclusive or exclusive)
 855 #[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 856 pub enum RangeLimits {
 857     /// Inclusive at the beginning, exclusive at the end
 858     HalfOpen,
 859     /// Inclusive at the beginning and end
 860     Closed,
 861 }
 862
 863 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 864 pub enum ExprKind {
 865     /// A `box x` expression.
 866     Box(P<Expr>),
 867     /// First expr is the place; second expr is the value.
 868     InPlace(P<Expr>, P<Expr>),
 869     /// An array (`[a, b, c, d]`)
 870     Array(Vec<P<Expr>>),
 871     /// A function call
 872     ///
 873     /// The first field resolves to the function itself,
 874     /// and the second field is the list of arguments
 875     Call(P<Expr>, Vec<P<Expr>>),
 876     /// A method call (`x.foo::<Bar, Baz>(a, b, c, d)`)
 877     ///
 878     /// The `SpannedIdent` is the identifier for the method name.
 879     /// The vector of `Ty`s are the ascripted type parameters for the method
 880     /// (within the angle brackets).
 881     ///
 882     /// The first element of the vector of `Expr`s is the expression that evaluates
 883     /// to the object on which the method is being called on (the receiver),
 884     /// and the remaining elements are the rest of the arguments.
 885     ///
 886     /// Thus, `x.foo::<Bar, Baz>(a, b, c, d)` is represented as
 887     /// `ExprKind::MethodCall(foo, [Bar, Baz], [x, a, b, c, d])`.
 888     MethodCall(SpannedIdent, Vec<P<Ty>>, Vec<P<Expr>>),
 889     /// A tuple (`(a, b, c ,d)`)
 890     Tup(Vec<P<Expr>>),
 891     /// A binary operation (For example: `a + b`, `a * b`)
 892     Binary(BinOp, P<Expr>, P<Expr>),
 893     /// A unary operation (For example: `!x`, `*x`)
 894     Unary(UnOp, P<Expr>),
 895     /// A literal (For example: `1`, `"foo"`)
 896     Lit(P<Lit>),
 897     /// A cast (`foo as f64`)
 898     Cast(P<Expr>, P<Ty>),
 899     Type(P<Expr>, P<Ty>),
 900     /// An `if` block, with an optional else block
 901     ///
 902     /// `if expr { block } else { expr }`
 903     If(P<Expr>, P<Block>, Option<P<Expr>>),
 904     /// An `if let` expression with an optional else block
 905     ///
 906     /// `if let pat = expr { block } else { expr }`
 907     ///
 908     /// This is desugared to a `match` expression.
 909     IfLet(P<Pat>, P<Expr>, P<Block>, Option<P<Expr>>),
 910     /// A while loop, with an optional label
 911     ///
 912     /// `'label: while expr { block }`
 913     While(P<Expr>, P<Block>, Option<SpannedIdent>),
 914     /// A while-let loop, with an optional label
 915     ///
 916     /// `'label: while let pat = expr { block }`
 917     ///
 918     /// This is desugared to a combination of `loop` and `match` expressions.
 919     WhileLet(P<Pat>, P<Expr>, P<Block>, Option<SpannedIdent>),
 920     /// A for loop, with an optional label
 921     ///
 922     /// `'label: for pat in expr { block }`
 923     ///
 924     /// This is desugared to a combination of `loop` and `match` expressions.
 925     ForLoop(P<Pat>, P<Expr>, P<Block>, Option<SpannedIdent>),
 926     /// Conditionless loop (can be exited with break, continue, or return)
 927     ///
 928     /// `'label: loop { block }`
 929     Loop(P<Block>, Option<SpannedIdent>),
 930     /// A `match` block.
 931     Match(P<Expr>, Vec<Arm>),
 932     /// A closure (for example, `move |a, b, c| a + b + c`)
 933     ///
 934     /// The final span is the span of the argument block `|...|`
 935     Closure(CaptureBy, P<FnDecl>, P<Expr>, Span),
 936     /// A block (`{ ... }`)
 937     Block(P<Block>),
 938
 939     /// An assignment (`a = foo()`)
 940     Assign(P<Expr>, P<Expr>),
 941     /// An assignment with an operator
 942     ///
 943     /// For example, `a += 1`.
 944     AssignOp(BinOp, P<Expr>, P<Expr>),
 945     /// Access of a named struct field (`obj.foo`)
 946     Field(P<Expr>, SpannedIdent),
 947     /// Access of an unnamed field of a struct or tuple-struct
 948     ///
 949     /// For example, `foo.0`.
 950     TupField(P<Expr>, Spanned<usize>),
 951     /// An indexing operation (`foo[2]`)
 952     Index(P<Expr>, P<Expr>),
 953     /// A range (`1..2`, `1..`, `..2`, `1...2`, `1...`, `...2`)
 954     Range(Option<P<Expr>>, Option<P<Expr>>, RangeLimits),
 955
 956     /// Variable reference, possibly containing `::` and/or type
 957     /// parameters, e.g. foo::bar::<baz>.
 958     ///
 959     /// Optionally "qualified",
 960     /// E.g. `<Vec<T> as SomeTrait>::SomeType`.
 961     Path(Option<QSelf>, Path),
 962
 963     /// A referencing operation (`&a` or `&mut a`)
 964     AddrOf(Mutability, P<Expr>),
 965     /// A `break`, with an optional label to break, and an optional expression
 966     Break(Option<SpannedIdent>, Option<P<Expr>>),
 967     /// A `continue`, with an optional label
 968     Continue(Option<SpannedIdent>),
 969     /// A `return`, with an optional value to be returned
 970     Ret(Option<P<Expr>>),
 971
 972     /// Output of the `asm!()` macro
 973     InlineAsm(P<InlineAsm>),
 974
 975     /// A macro invocation; pre-expansion
 976     Mac(Mac),
 977
 978     /// A struct literal expression.
 979     ///
 980     /// For example, `Foo {x: 1, y: 2}`, or
 981     /// `Foo {x: 1, .. base}`, where `base` is the `Option<Expr>`.
 982     Struct(Path, Vec<Field>, Option<P<Expr>>),
 983
 984     /// An array literal constructed from one repeated element.
 985     ///
 986     /// For example, `[1; 5]`. The first expression is the element
 987     /// to be repeated; the second is the number of times to repeat it.
 988     Repeat(P<Expr>, P<Expr>),
 989
 990     /// No-op: used solely so we can pretty-print faithfully
 991     Paren(P<Expr>),
 992
 993     /// `expr?`
 994     Try(P<Expr>),
 995 }
 996
 997 /// The explicit Self type in a "qualified path". The actual
 998 /// path, including the trait and the associated item, is stored
 999 /// separately. `position` represents the index of the associated
1000 /// item qualified with this Self type.
1001 ///
1002 /// ```rust,ignore
1003 /// <Vec<T> as a::b::Trait>::AssociatedItem
1004 ///  ^~~~~     ~~~~~~~~~~~~~~^
1005 ///  ty        position = 3
1006 ///
1007 /// <Vec<T>>::AssociatedItem
1008 ///  ^~~~~    ^
1009 ///  ty       position = 0
1010 /// ```
1011 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1012 pub struct QSelf {
1013     pub ty: P<Ty>,
1014     pub position: usize
1015 }
1016
1017 /// A capture clause
1018 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
1019 pub enum CaptureBy {
1020     Value,
1021     Ref,
1022 }
1023
1024 pub type Mac = Spanned<Mac_>;
1025
1026 /// Represents a macro invocation. The Path indicates which macro
1027 /// is being invoked, and the vector of token-trees contains the source
1028 /// of the macro invocation.
1029 ///
1030 /// NB: the additional ident for a macro_rules-style macro is actually
1031 /// stored in the enclosing item. Oog.
1032 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1033 pub struct Mac_ {
1034     pub path: Path,
1035     pub tts: ThinTokenStream,
1036 }
1037
1038 impl Mac_ {
1039     pub fn stream(&self) -> TokenStream {
1040         self.tts.clone().into()
1041     }
1042 }
1043
1044 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
1045 pub enum StrStyle {
1046     /// A regular string, like `"foo"`
1047     Cooked,
1048     /// A raw string, like `r##"foo"##`
1049     ///
1050     /// The uint is the number of `#` symbols used
1051     Raw(usize)
1052 }
1053
1054 /// A literal
1055 pub type Lit = Spanned<LitKind>;
1056
1057 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
1058 pub enum LitIntType {
1059     Signed(IntTy),
1060     Unsigned(UintTy),
1061     Unsuffixed,
1062 }
1063
1064 /// Literal kind.
1065 ///
1066 /// E.g. `"foo"`, `42`, `12.34` or `bool`
1067 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1068 pub enum LitKind {
1069     /// A string literal (`"foo"`)
1070     Str(Symbol, StrStyle),
1071     /// A byte string (`b"foo"`)
1072     ByteStr(Rc<Vec<u8>>),
1073     /// A byte char (`b'f'`)
1074     Byte(u8),
1075     /// A character literal (`'a'`)
1076     Char(char),
1077     /// An integer literal (`1`)
1078     Int(u128, LitIntType),
1079     /// A float literal (`1f64` or `1E10f64`)
1080     Float(Symbol, FloatTy),
1081     /// A float literal without a suffix (`1.0 or 1.0E10`)
1082     FloatUnsuffixed(Symbol),
1083     /// A boolean literal
1084     Bool(bool),
1085 }
1086
1087 impl LitKind {
1088     /// Returns true if this literal is a string and false otherwise.
1089     pub fn is_str(&self) -> bool {
1090         match *self {
1091             LitKind::Str(..) => true,
1092             _ => false,
1093         }
1094     }
1095
1096     /// Returns true if this literal has no suffix. Note: this will return true
1097     /// for literals with prefixes such as raw strings and byte strings.
1098     pub fn is_unsuffixed(&self) -> bool {
1099         match *self {
1100             // unsuffixed variants
1101             LitKind::Str(..) => true,
1102             LitKind::ByteStr(..) => true,
1103             LitKind::Byte(..) => true,
1104             LitKind::Char(..) => true,
1105             LitKind::Int(_, LitIntType::Unsuffixed) => true,
1106             LitKind::FloatUnsuffixed(..) => true,
1107             LitKind::Bool(..) => true,
1108             // suffixed variants
1109             LitKind::Int(_, LitIntType::Signed(..)) => false,
1110             LitKind::Int(_, LitIntType::Unsigned(..)) => false,
1111             LitKind::Float(..) => false,
1112         }
1113     }
1114
1115     /// Returns true if this literal has a suffix.
1116     pub fn is_suffixed(&self) -> bool {
1117         !self.is_unsuffixed()
1118     }
1119 }
1120
1121 // NB: If you change this, you'll probably want to change the corresponding
1122 // type structure in middle/ty.rs as well.
1123 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1124 pub struct MutTy {
1125     pub ty: P<Ty>,
1126     pub mutbl: Mutability,
1127 }
1128
1129 /// Represents a method's signature in a trait declaration,
1130 /// or in an implementation.
1131 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1132 pub struct MethodSig {
1133     pub unsafety: Unsafety,
1134     pub constness: Spanned<Constness>,
1135     pub abi: Abi,
1136     pub decl: P<FnDecl>,
1137     pub generics: Generics,
1138 }
1139
1140 /// Represents an item declaration within a trait declaration,
1141 /// possibly including a default implementation. A trait item is
1142 /// either required (meaning it doesn't have an implementation, just a
1143 /// signature) or provided (meaning it has a default implementation).
1144 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1145 pub struct TraitItem {
1146     pub id: NodeId,
1147     pub ident: Ident,
1148     pub attrs: Vec<Attribute>,
1149     pub node: TraitItemKind,
1150     pub span: Span,
1151 }
1152
1153 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1154 pub enum TraitItemKind {
1155     Const(P<Ty>, Option<P<Expr>>),
1156     Method(MethodSig, Option<P<Block>>),
1157     Type(TyParamBounds, Option<P<Ty>>),
1158     Macro(Mac),
1159 }
1160
1161 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1162 pub struct ImplItem {
1163     pub id: NodeId,
1164     pub ident: Ident,
1165     pub vis: Visibility,
1166     pub defaultness: Defaultness,
1167     pub attrs: Vec<Attribute>,
1168     pub node: ImplItemKind,
1169     pub span: Span,
1170 }
1171
1172 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1173 pub enum ImplItemKind {
1174     Const(P<Ty>, P<Expr>),
1175     Method(MethodSig, P<Block>),
1176     Type(P<Ty>),
1177     Macro(Mac),
1178 }
1179
1180 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Copy)]
1181 pub enum IntTy {
1182     Is,
1183     I8,
1184     I16,
1185     I32,
1186     I64,
1187     I128,
1188 }
1189
1190 impl fmt::Debug for IntTy {
1191     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1192         fmt::Display::fmt(self, f)
1193     }
1194 }
1195
1196 impl fmt::Display for IntTy {
1197     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1198         write!(f, "{}", self.ty_to_string())
1199     }
1200 }
1201
1202 impl IntTy {
1203     pub fn ty_to_string(&self) -> &'static str {
1204         match *self {
1205             IntTy::Is => "isize",
1206             IntTy::I8 => "i8",
1207             IntTy::I16 => "i16",
1208             IntTy::I32 => "i32",
1209             IntTy::I64 => "i64",
1210             IntTy::I128 => "i128",
1211         }
1212     }
1213
1214     pub fn val_to_string(&self, val: i128) -> String {
1215         // cast to a u128 so we can correctly print INT128_MIN. All integral types
1216         // are parsed as u128, so we wouldn't want to print an extra negative
1217         // sign.
1218         format!("{}{}", val as u128, self.ty_to_string())
1219     }
1220
1221     pub fn bit_width(&self) -> Option<usize> {
1222         Some(match *self {
1223             IntTy::Is => return None,
1224             IntTy::I8 => 8,
1225             IntTy::I16 => 16,
1226             IntTy::I32 => 32,
1227             IntTy::I64 => 64,
1228             IntTy::I128 => 128,
1229         })
1230     }
1231 }
1232
1233 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Copy)]
1234 pub enum UintTy {
1235     Us,
1236     U8,
1237     U16,
1238     U32,
1239     U64,
1240     U128,
1241 }
1242
1243 impl UintTy {
1244     pub fn ty_to_string(&self) -> &'static str {
1245         match *self {
1246             UintTy::Us => "usize",
1247             UintTy::U8 => "u8",
1248             UintTy::U16 => "u16",
1249             UintTy::U32 => "u32",
1250             UintTy::U64 => "u64",
1251             UintTy::U128 => "u128",
1252         }
1253     }
1254
1255     pub fn val_to_string(&self, val: u128) -> String {
1256         format!("{}{}", val, self.ty_to_string())
1257     }
1258
1259     pub fn bit_width(&self) -> Option<usize> {
1260         Some(match *self {
1261             UintTy::Us => return None,
1262             UintTy::U8 => 8,
1263             UintTy::U16 => 16,
1264             UintTy::U32 => 32,
1265             UintTy::U64 => 64,
1266             UintTy::U128 => 128,
1267         })
1268     }
1269 }
1270
1271 impl fmt::Debug for UintTy {
1272     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1273         fmt::Display::fmt(self, f)
1274     }
1275 }
1276
1277 impl fmt::Display for UintTy {
1278     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1279         write!(f, "{}", self.ty_to_string())
1280     }
1281 }
1282
1283 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Copy)]
1284 pub enum FloatTy {
1285     F32,
1286     F64,
1287 }
1288
1289 impl fmt::Debug for FloatTy {
1290     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1291         fmt::Display::fmt(self, f)
1292     }
1293 }
1294
1295 impl fmt::Display for FloatTy {
1296     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1297         write!(f, "{}", self.ty_to_string())
1298     }
1299 }
1300
1301 impl FloatTy {
1302     pub fn ty_to_string(&self) -> &'static str {
1303         match *self {
1304             FloatTy::F32 => "f32",
1305             FloatTy::F64 => "f64",
1306         }
1307     }
1308
1309     pub fn bit_width(&self) -> usize {
1310         match *self {
1311             FloatTy::F32 => 32,
1312             FloatTy::F64 => 64,
1313         }
1314     }
1315 }
1316
1317 // Bind a type to an associated type: `A=Foo`.
1318 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1319 pub struct TypeBinding {
1320     pub id: NodeId,
1321     pub ident: Ident,
1322     pub ty: P<Ty>,
1323     pub span: Span,
1324 }
1325
1326 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash)]
1327 pub struct Ty {
1328     pub id: NodeId,
1329     pub node: TyKind,
1330     pub span: Span,
1331 }
1332
1333 impl fmt::Debug for Ty {
1334     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1335         write!(f, "type({})", pprust::ty_to_string(self))
1336     }
1337 }
1338
1339 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1340 pub struct BareFnTy {
1341     pub unsafety: Unsafety,
1342     pub abi: Abi,
1343     pub lifetimes: Vec<LifetimeDef>,
1344     pub decl: P<FnDecl>
1345 }
1346
1347 /// The different kinds of types recognized by the compiler
1348 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1349 pub enum TyKind {
1350     /// A variable-length slice (`[T]`)
1351     Slice(P<Ty>),
1352     /// A fixed length array (`[T; n]`)
1353     Array(P<Ty>, P<Expr>),
1354     /// A raw pointer (`*const T` or `*mut T`)
1355     Ptr(MutTy),
1356     /// A reference (`&'a T` or `&'a mut T`)
1357     Rptr(Option<Lifetime>, MutTy),
1358     /// A bare function (e.g. `fn(usize) -> bool`)
1359     BareFn(P<BareFnTy>),
1360     /// The never type (`!`)
1361     Never,
1362     /// A tuple (`(A, B, C, D,...)`)
1363     Tup(Vec<P<Ty>> ),
1364     /// A path (`module::module::...::Type`), optionally
1365     /// "qualified", e.g. `<Vec<T> as SomeTrait>::SomeType`.
1366     ///
1367     /// Type parameters are stored in the Path itself
1368     Path(Option<QSelf>, Path),
1369     /// A trait object type `Bound1 + Bound2 + Bound3`
1370     /// where `Bound` is a trait or a lifetime.
1371     TraitObject(TyParamBounds),
1372     /// An `impl Bound1 + Bound2 + Bound3` type
1373     /// where `Bound` is a trait or a lifetime.
1374     ImplTrait(TyParamBounds),
1375     /// No-op; kept solely so that we can pretty-print faithfully
1376     Paren(P<Ty>),
1377     /// Unused for now
1378     Typeof(P<Expr>),
1379     /// TyKind::Infer means the type should be inferred instead of it having been
1380     /// specified. This can appear anywhere in a type.
1381     Infer,
1382     /// Inferred type of a `self` or `&self` argument in a method.
1383     ImplicitSelf,
1384     // A macro in the type position.
1385     Mac(Mac),
1386 }
1387
1388 /// Inline assembly dialect.
1389 ///
1390 /// E.g. `"intel"` as in `asm!("mov eax, 2" : "={eax}"(result) : : : "intel")``
1391 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
1392 pub enum AsmDialect {
1393     Att,
1394     Intel,
1395 }
1396
1397 /// Inline assembly.
1398 ///
1399 /// E.g. `"={eax}"(result)` as in `asm!("mov eax, 2" : "={eax}"(result) : : : "intel")``
1400 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1401 pub struct InlineAsmOutput {
1402     pub constraint: Symbol,
1403     pub expr: P<Expr>,
1404     pub is_rw: bool,
1405     pub is_indirect: bool,
1406 }
1407
1408 /// Inline assembly.
1409 ///
1410 /// E.g. `asm!("NOP");`
1411 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1412 pub struct InlineAsm {
1413     pub asm: Symbol,
1414     pub asm_str_style: StrStyle,
1415     pub outputs: Vec<InlineAsmOutput>,
1416     pub inputs: Vec<(Symbol, P<Expr>)>,
1417     pub clobbers: Vec<Symbol>,
1418     pub volatile: bool,
1419     pub alignstack: bool,
1420     pub dialect: AsmDialect,
1421     pub expn_id: ExpnId,
1422 }
1423
1424 /// An argument in a function header.
1425 ///
1426 /// E.g. `bar: usize` as in `fn foo(bar: usize)`
1427 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1428 pub struct Arg {
1429     pub ty: P<Ty>,
1430     pub pat: P<Pat>,
1431     pub id: NodeId,
1432 }
1433
1434 /// Alternative representation for `Arg`s describing `self` parameter of methods.
1435 ///
1436 /// E.g. `&mut self` as in `fn foo(&mut self)`
1437 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1438 pub enum SelfKind {
1439     /// `self`, `mut self`
1440     Value(Mutability),
1441     /// `&'lt self`, `&'lt mut self`
1442     Region(Option<Lifetime>, Mutability),
1443     /// `self: TYPE`, `mut self: TYPE`
1444     Explicit(P<Ty>, Mutability),
1445 }
1446
1447 pub type ExplicitSelf = Spanned<SelfKind>;
1448
1449 impl Arg {
1450     pub fn to_self(&self) -> Option<ExplicitSelf> {
1451         if let PatKind::Ident(BindingMode::ByValue(mutbl), ident, _) = self.pat.node {
1452             if ident.node.name == keywords::SelfValue.name() {
1453                 return match self.ty.node {
1454                     TyKind::ImplicitSelf => Some(respan(self.pat.span, SelfKind::Value(mutbl))),
1455                     TyKind::Rptr(lt, MutTy{ref ty, mutbl}) if ty.node == TyKind::ImplicitSelf => {
1456                         Some(respan(self.pat.span, SelfKind::Region(lt, mutbl)))
1457                     }
1458                     _ => Some(respan(mk_sp(self.pat.span.lo, self.ty.span.hi),
1459                                      SelfKind::Explicit(self.ty.clone(), mutbl))),
1460                 }
1461             }
1462         }
1463         None
1464     }
1465
1466     pub fn is_self(&self) -> bool {
1467         if let PatKind::Ident(_, ident, _) = self.pat.node {
1468             ident.node.name == keywords::SelfValue.name()
1469         } else {
1470             false
1471         }
1472     }
1473
1474     pub fn from_self(eself: ExplicitSelf, eself_ident: SpannedIdent) -> Arg {
1475         let span = mk_sp(eself.span.lo, eself_ident.span.hi);
1476         let infer_ty = P(Ty {
1477             id: DUMMY_NODE_ID,
1478             node: TyKind::ImplicitSelf,
1479             span: span,
1480         });
1481         let arg = |mutbl, ty| Arg {
1482             pat: P(Pat {
1483                 id: DUMMY_NODE_ID,
1484                 node: PatKind::Ident(BindingMode::ByValue(mutbl), eself_ident, None),
1485                 span: span,
1486             }),
1487             ty: ty,
1488             id: DUMMY_NODE_ID,
1489         };
1490         match eself.node {
1491             SelfKind::Explicit(ty, mutbl) => arg(mutbl, ty),
1492             SelfKind::Value(mutbl) => arg(mutbl, infer_ty),
1493             SelfKind::Region(lt, mutbl) => arg(Mutability::Immutable, P(Ty {
1494                 id: DUMMY_NODE_ID,
1495                 node: TyKind::Rptr(lt, MutTy { ty: infer_ty, mutbl: mutbl }),
1496                 span: span,
1497             })),
1498         }
1499     }
1500 }
1501
1502 /// Header (not the body) of a function declaration.
1503 ///
1504 /// E.g. `fn foo(bar: baz)`
1505 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1506 pub struct FnDecl {
1507     pub inputs: Vec<Arg>,
1508     pub output: FunctionRetTy,
1509     pub variadic: bool
1510 }
1511
1512 impl FnDecl {
1513     pub fn get_self(&self) -> Option<ExplicitSelf> {
1514         self.inputs.get(0).and_then(Arg::to_self)
1515     }
1516     pub fn has_self(&self) -> bool {
1517         self.inputs.get(0).map(Arg::is_self).unwrap_or(false)
1518     }
1519 }
1520
1521 #[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1522 pub enum Unsafety {
1523     Unsafe,
1524     Normal,
1525 }
1526
1527 #[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1528 pub enum Constness {
1529     Const,
1530     NotConst,
1531 }
1532
1533 #[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1534 pub enum Defaultness {
1535     Default,
1536     Final,
1537 }
1538
1539 impl fmt::Display for Unsafety {
1540     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1541         fmt::Display::fmt(match *self {
1542             Unsafety::Normal => "normal",
1543             Unsafety::Unsafe => "unsafe",
1544         }, f)
1545     }
1546 }
1547
1548 #[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash)]
1549 pub enum ImplPolarity {
1550     /// `impl Trait for Type`
1551     Positive,
1552     /// `impl !Trait for Type`
1553     Negative,
1554 }
1555
1556 impl fmt::Debug for ImplPolarity {
1557     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1558         match *self {
1559             ImplPolarity::Positive => "positive".fmt(f),
1560             ImplPolarity::Negative => "negative".fmt(f),
1561         }
1562     }
1563 }
1564
1565
1566 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1567 pub enum FunctionRetTy {
1568     /// Return type is not specified.
1569     ///
1570     /// Functions default to `()` and
1571     /// closures default to inference. Span points to where return
1572     /// type would be inserted.
1573     Default(Span),
1574     /// Everything else
1575     Ty(P<Ty>),
1576 }
1577
1578 impl FunctionRetTy {
1579     pub fn span(&self) -> Span {
1580         match *self {
1581             FunctionRetTy::Default(span) => span,
1582             FunctionRetTy::Ty(ref ty) => ty.span,
1583         }
1584     }
1585 }
1586
1587 /// Module declaration.
1588 ///
1589 /// E.g. `mod foo;` or `mod foo { .. }`
1590 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1591 pub struct Mod {
1592     /// A span from the first token past `{` to the last token until `}`.
1593     /// For `mod foo;`, the inner span ranges from the first token
1594     /// to the last token in the external file.
1595     pub inner: Span,
1596     pub items: Vec<P<Item>>,
1597 }
1598
1599 /// Foreign module declaration.
1600 ///
1601 /// E.g. `extern { .. }` or `extern C { .. }`
1602 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1603 pub struct ForeignMod {
1604     pub abi: Abi,
1605     pub items: Vec<ForeignItem>,
1606 }
1607
1608 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1609 pub struct EnumDef {
1610     pub variants: Vec<Variant>,
1611 }
1612
1613 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1614 pub struct Variant_ {
1615     pub name: Ident,
1616     pub attrs: Vec<Attribute>,
1617     pub data: VariantData,
1618     /// Explicit discriminant, e.g. `Foo = 1`
1619     pub disr_expr: Option<P<Expr>>,
1620 }
1621
1622 pub type Variant = Spanned<Variant_>;
1623
1624 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
1625 pub struct PathListItem_ {
1626     pub name: Ident,
1627     /// renamed in list, e.g. `use foo::{bar as baz};`
1628     pub rename: Option<Ident>,
1629     pub id: NodeId,
1630 }
1631
1632 pub type PathListItem = Spanned<PathListItem_>;
1633
1634 pub type ViewPath = Spanned<ViewPath_>;
1635
1636 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1637 pub enum ViewPath_ {
1638
1639     /// `foo::bar::baz as quux`
1640     ///
1641     /// or just
1642     ///
1643     /// `foo::bar::baz` (with `as baz` implicitly on the right)
1644     ViewPathSimple(Ident, Path),
1645
1646     /// `foo::bar::*`
1647     ViewPathGlob(Path),
1648
1649     /// `foo::bar::{a,b,c}`
1650     ViewPathList(Path, Vec<PathListItem>)
1651 }
1652
1653 impl ViewPath_ {
1654     pub fn path(&self) -> &Path {
1655         match *self {
1656             ViewPathSimple(_, ref path) |
1657             ViewPathGlob (ref path) |
1658             ViewPathList(ref path, _) => path
1659         }
1660     }
1661 }
1662
1663
1664 /// Distinguishes between Attributes that decorate items and Attributes that
1665 /// are contained as statements within items. These two cases need to be
1666 /// distinguished for pretty-printing.
1667 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
1668 pub enum AttrStyle {
1669     Outer,
1670     Inner,
1671 }
1672
1673 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
1674 pub struct AttrId(pub usize);
1675
1676 /// Meta-data associated with an item
1677 /// Doc-comments are promoted to attributes that have is_sugared_doc = true
1678 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1679 pub struct Attribute {
1680     pub id: AttrId,
1681     pub style: AttrStyle,
1682     pub value: MetaItem,
1683     pub is_sugared_doc: bool,
1684     pub span: Span,
1685 }
1686
1687 /// TraitRef's appear in impls.
1688 ///
1689 /// resolve maps each TraitRef's ref_id to its defining trait; that's all
1690 /// that the ref_id is for. The impl_id maps to the "self type" of this impl.
1691 /// If this impl is an ItemKind::Impl, the impl_id is redundant (it could be the
1692 /// same as the impl's node id).
1693 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1694 pub struct TraitRef {
1695     pub path: Path,
1696     pub ref_id: NodeId,
1697 }
1698
1699 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1700 pub struct PolyTraitRef {
1701     /// The `'a` in `<'a> Foo<&'a T>`
1702     pub bound_lifetimes: Vec<LifetimeDef>,
1703
1704     /// The `Foo<&'a T>` in `<'a> Foo<&'a T>`
1705     pub trait_ref: TraitRef,
1706
1707     pub span: Span,
1708 }
1709
1710 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1711 pub enum Visibility {
1712     Public,
1713     Crate(Span),
1714     Restricted { path: P<Path>, id: NodeId },
1715     Inherited,
1716 }
1717
1718 /// Field of a struct.
1719 ///
1720 /// E.g. `bar: usize` as in `struct Foo { bar: usize }`
1721 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1722 pub struct StructField {
1723     pub span: Span,
1724     pub ident: Option<Ident>,
1725     pub vis: Visibility,
1726     pub id: NodeId,
1727     pub ty: P<Ty>,
1728     pub attrs: Vec<Attribute>,
1729 }
1730
1731 /// Fields and Ids of enum variants and structs
1732 ///
1733 /// For enum variants: `NodeId` represents both an Id of the variant itself (relevant for all
1734 /// variant kinds) and an Id of the variant's constructor (not relevant for `Struct`-variants).
1735 /// One shared Id can be successfully used for these two purposes.
1736 /// Id of the whole enum lives in `Item`.
1737 ///
1738 /// For structs: `NodeId` represents an Id of the structure's constructor, so it is not actually
1739 /// used for `Struct`-structs (but still presents). Structures don't have an analogue of "Id of
1740 /// the variant itself" from enum variants.
1741 /// Id of the whole struct lives in `Item`.
1742 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1743 pub enum VariantData {
1744     /// Struct variant.
1745     ///
1746     /// E.g. `Bar { .. }` as in `enum Foo { Bar { .. } }`
1747     Struct(Vec<StructField>, NodeId),
1748     /// Tuple variant.
1749     ///
1750     /// E.g. `Bar(..)` as in `enum Foo { Bar(..) }`
1751     Tuple(Vec<StructField>, NodeId),
1752     /// Unit variant.
1753     ///
1754     /// E.g. `Bar = ..` as in `enum Foo { Bar = .. }`
1755     Unit(NodeId),
1756 }
1757
1758 impl VariantData {
1759     pub fn fields(&self) -> &[StructField] {
1760         match *self {
1761             VariantData::Struct(ref fields, _) | VariantData::Tuple(ref fields, _) => fields,
1762             _ => &[],
1763         }
1764     }
1765     pub fn id(&self) -> NodeId {
1766         match *self {
1767             VariantData::Struct(_, id) | VariantData::Tuple(_, id) | VariantData::Unit(id) => id
1768         }
1769     }
1770     pub fn is_struct(&self) -> bool {
1771         if let VariantData::Struct(..) = *self { true } else { false }
1772     }
1773     pub fn is_tuple(&self) -> bool {
1774         if let VariantData::Tuple(..) = *self { true } else { false }
1775     }
1776     pub fn is_unit(&self) -> bool {
1777         if let VariantData::Unit(..) = *self { true } else { false }
1778     }
1779 }
1780
1781 /// An item
1782 ///
1783 /// The name might be a dummy name in case of anonymous items
1784 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1785 pub struct Item {
1786     pub ident: Ident,
1787     pub attrs: Vec<Attribute>,
1788     pub id: NodeId,
1789     pub node: ItemKind,
1790     pub vis: Visibility,
1791     pub span: Span,
1792 }
1793
1794 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1795 pub enum ItemKind {
1796     /// An`extern crate` item, with optional original crate name.
1797     ///
1798     /// E.g. `extern crate foo` or `extern crate foo_bar as foo`
1799     ExternCrate(Option<Name>),
1800     /// A use declaration (`use` or `pub use`) item.
1801     ///
1802     /// E.g. `use foo;`, `use foo::bar;` or `use foo::bar as FooBar;`
1803     Use(P<ViewPath>),
1804     /// A static item (`static` or `pub static`).
1805     ///
1806     /// E.g. `static FOO: i32 = 42;` or `static FOO: &'static str = "bar";`
1807     Static(P<Ty>, Mutability, P<Expr>),
1808     /// A constant item (`const` or `pub const`).
1809     ///
1810     /// E.g. `const FOO: i32 = 42;`
1811     Const(P<Ty>, P<Expr>),
1812     /// A function declaration (`fn` or `pub fn`).
1813     ///
1814     /// E.g. `fn foo(bar: usize) -> usize { .. }`
1815     Fn(P<FnDecl>, Unsafety, Spanned<Constness>, Abi, Generics, P<Block>),
1816     /// A module declaration (`mod` or `pub mod`).
1817     ///
1818     /// E.g. `mod foo;` or `mod foo { .. }`
1819     Mod(Mod),
1820     /// An external module (`extern` or `pub extern`).
1821     ///
1822     /// E.g. `extern {}` or `extern "C" {}`
1823     ForeignMod(ForeignMod),
1824     /// A type alias (`type` or `pub type`).
1825     ///
1826     /// E.g. `type Foo = Bar<u8>;`
1827     Ty(P<Ty>, Generics),
1828     /// An enum definition (`enum` or `pub enum`).
1829     ///
1830     /// E.g. `enum Foo<A, B> { C<A>, D<B> }`
1831     Enum(EnumDef, Generics),
1832     /// A struct definition (`struct` or `pub struct`).
1833     ///
1834     /// E.g. `struct Foo<A> { x: A }`
1835     Struct(VariantData, Generics),
1836     /// A union definition (`union` or `pub union`).
1837     ///
1838     /// E.g. `union Foo<A, B> { x: A, y: B }`
1839     Union(VariantData, Generics),
1840     /// A Trait declaration (`trait` or `pub trait`).
1841     ///
1842     /// E.g. `trait Foo { .. }` or `trait Foo<T> { .. }`
1843     Trait(Unsafety, Generics, TyParamBounds, Vec<TraitItem>),
1844     // Default trait implementation.
1845     ///
1846     /// E.g. `impl Trait for .. {}` or `impl<T> Trait<T> for .. {}`
1847     DefaultImpl(Unsafety, TraitRef),
1848     /// An implementation.
1849     ///
1850     /// E.g. `impl<A> Foo<A> { .. }` or `impl<A> Trait for Foo<A> { .. }`
1851     Impl(Unsafety,
1852              ImplPolarity,
1853              Generics,
1854              Option<TraitRef>, // (optional) trait this impl implements
1855              P<Ty>, // self
1856              Vec<ImplItem>),
1857     /// A macro invocation.
1858     ///
1859     /// E.g. `macro_rules! foo { .. }` or `foo!(..)`
1860     Mac(Mac),
1861
1862     /// A macro definition.
1863     MacroDef(ThinTokenStream),
1864 }
1865
1866 impl ItemKind {
1867     pub fn descriptive_variant(&self) -> &str {
1868         match *self {
1869             ItemKind::ExternCrate(..) => "extern crate",
1870             ItemKind::Use(..) => "use",
1871             ItemKind::Static(..) => "static item",
1872             ItemKind::Const(..) => "constant item",
1873             ItemKind::Fn(..) => "function",
1874             ItemKind::Mod(..) => "module",
1875             ItemKind::ForeignMod(..) => "foreign module",
1876             ItemKind::Ty(..) => "type alias",
1877             ItemKind::Enum(..) => "enum",
1878             ItemKind::Struct(..) => "struct",
1879             ItemKind::Union(..) => "union",
1880             ItemKind::Trait(..) => "trait",
1881             ItemKind::Mac(..) |
1882             ItemKind::MacroDef(..) |
1883             ItemKind::Impl(..) |
1884             ItemKind::DefaultImpl(..) => "item"
1885         }
1886     }
1887 }
1888
1889 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1890 pub struct ForeignItem {
1891     pub ident: Ident,
1892     pub attrs: Vec<Attribute>,
1893     pub node: ForeignItemKind,
1894     pub id: NodeId,
1895     pub span: Span,
1896     pub vis: Visibility,
1897 }
1898
1899 /// An item within an `extern` block
1900 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
1901 pub enum ForeignItemKind {
1902     /// A foreign function
1903     Fn(P<FnDecl>, Generics),
1904     /// A foreign static item (`static ext: u8`), with optional mutability
1905     /// (the boolean is true when mutable)
1906     Static(P<Ty>, bool),
1907 }
1908
1909 impl ForeignItemKind {
1910     pub fn descriptive_variant(&self) -> &str {
1911         match *self {
1912             ForeignItemKind::Fn(..) => "foreign function",
1913             ForeignItemKind::Static(..) => "foreign static item"
1914         }
1915     }
1916 }
1917
1918 #[cfg(test)]
1919 mod tests {
1920     use serialize;
1921     use super::*;
1922
1923     // are ASTs encodable?
1924     #[test]
1925     fn check_asts_encodable() {
1926         fn assert_encodable<T: serialize::Encodable>() {}
1927         assert_encodable::<Crate>();
1928     }
1929 }