src/libsyntax/visit.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 //! AST walker. Each overridden visit method has full control over what
  12 //! happens with its node, it can do its own traversal of the node's children,
  13 //! call `visit::walk_*` to apply the default traversal algorithm, or prevent
  14 //! deeper traversal by doing nothing.
  15 //!
  16 //! Note: it is an important invariant that the default visitor walks the body
  17 //! of a function in "execution order" (more concretely, reverse post-order
  18 //! with respect to the CFG implied by the AST), meaning that if AST node A may
  19 //! execute before AST node B, then A is visited first.  The borrow checker in
  20 //! particular relies on this property.
  21 //!
  22 //! Note: walking an AST before macro expansion is probably a bad idea. For
  23 //! instance, a walker looking for item names in a module will miss all of
  24 //! those that are created by the expansion of a macro.
  25
  26 use abi::Abi;
  27 use ast::*;
  28 use ast;
  29 use codemap::Span;
  30 use ptr::P;
  31 use owned_slice::OwnedSlice;
  32
  33 #[derive(Copy, Clone, PartialEq, Eq)]
  34 pub enum FnKind<'a> {
  35     /// fn foo() or extern "Abi" fn foo()
  36     ItemFn(Ident, &'a Generics, Unsafety, Constness, Abi, Visibility),
  37
  38     /// fn foo(&self)
  39     Method(Ident, &'a MethodSig, Option<Visibility>),
  40
  41     /// |x, y| {}
  42     Closure,
  43 }
  44
  45 /// Each method of the Visitor trait is a hook to be potentially
  46 /// overridden.  Each method's default implementation recursively visits
  47 /// the substructure of the input via the corresponding `walk` method;
  48 /// e.g. the `visit_mod` method by default calls `visit::walk_mod`.
  49 ///
  50 /// If you want to ensure that your code handles every variant
  51 /// explicitly, you need to override each method.  (And you also need
  52 /// to monitor future changes to `Visitor` in case a new method with a
  53 /// new default implementation gets introduced.)
  54 pub trait Visitor<'v> : Sized {
  55     fn visit_name(&mut self, _span: Span, _name: Name) {
  56         // Nothing to do.
  57     }
  58     fn visit_ident(&mut self, span: Span, ident: Ident) {
  59         self.visit_name(span, ident.name);
  60     }
  61     fn visit_mod(&mut self, m: &'v Mod, _s: Span, _n: NodeId) { walk_mod(self, m) }
  62     fn visit_foreign_item(&mut self, i: &'v ForeignItem) { walk_foreign_item(self, i) }
  63     fn visit_item(&mut self, i: &'v Item) { walk_item(self, i) }
  64     fn visit_local(&mut self, l: &'v Local) { walk_local(self, l) }
  65     fn visit_block(&mut self, b: &'v Block) { walk_block(self, b) }
  66     fn visit_stmt(&mut self, s: &'v Stmt) { walk_stmt(self, s) }
  67     fn visit_arm(&mut self, a: &'v Arm) { walk_arm(self, a) }
  68     fn visit_pat(&mut self, p: &'v Pat) { walk_pat(self, p) }
  69     fn visit_decl(&mut self, d: &'v Decl) { walk_decl(self, d) }
  70     fn visit_expr(&mut self, ex: &'v Expr) { walk_expr(self, ex) }
  71     fn visit_expr_post(&mut self, _ex: &'v Expr) { }
  72     fn visit_ty(&mut self, t: &'v Ty) { walk_ty(self, t) }
  73     fn visit_generics(&mut self, g: &'v Generics) { walk_generics(self, g) }
  74     fn visit_fn(&mut self, fk: FnKind<'v>, fd: &'v FnDecl, b: &'v Block, s: Span, _: NodeId) {
  75         walk_fn(self, fk, fd, b, s)
  76     }
  77     fn visit_trait_item(&mut self, ti: &'v TraitItem) { walk_trait_item(self, ti) }
  78     fn visit_impl_item(&mut self, ii: &'v ImplItem) { walk_impl_item(self, ii) }
  79     fn visit_trait_ref(&mut self, t: &'v TraitRef) { walk_trait_ref(self, t) }
  80     fn visit_ty_param_bound(&mut self, bounds: &'v TyParamBound) {
  81         walk_ty_param_bound(self, bounds)
  82     }
  83     fn visit_poly_trait_ref(&mut self, t: &'v PolyTraitRef, m: &'v TraitBoundModifier) {
  84         walk_poly_trait_ref(self, t, m)
  85     }
  86     fn visit_struct_def(&mut self, s: &'v StructDef, _: Ident, _: &'v Generics, _: NodeId) {
  87         walk_struct_def(self, s)
  88     }
  89     fn visit_struct_field(&mut self, s: &'v StructField) { walk_struct_field(self, s) }
  90     fn visit_enum_def(&mut self, enum_definition: &'v EnumDef,
  91                       generics: &'v Generics) {
  92         walk_enum_def(self, enum_definition, generics)
  93     }
  94
  95     fn visit_variant(&mut self, v: &'v Variant, g: &'v Generics) { walk_variant(self, v, g) }
  96
  97     /// Visits an optional reference to a lifetime. The `span` is the span of some surrounding
  98     /// reference should opt_lifetime be None.
  99     fn visit_opt_lifetime_ref(&mut self,
 100                               _span: Span,
 101                               opt_lifetime: &'v Option<Lifetime>) {
 102         match *opt_lifetime {
 103             Some(ref l) => self.visit_lifetime_ref(l),
 104             None => ()
 105         }
 106     }
 107     fn visit_lifetime_bound(&mut self, lifetime: &'v Lifetime) {
 108         walk_lifetime_bound(self, lifetime)
 109     }
 110     fn visit_lifetime_ref(&mut self, lifetime: &'v Lifetime) {
 111         walk_lifetime_ref(self, lifetime)
 112     }
 113     fn visit_lifetime_def(&mut self, lifetime: &'v LifetimeDef) {
 114         walk_lifetime_def(self, lifetime)
 115     }
 116     fn visit_explicit_self(&mut self, es: &'v ExplicitSelf) {
 117         walk_explicit_self(self, es)
 118     }
 119     fn visit_mac(&mut self, _mac: &'v Mac) {
 120         panic!("visit_mac disabled by default");
 121         // NB: see note about macros above.
 122         // if you really want a visitor that
 123         // works on macros, use this
 124         // definition in your trait impl:
 125         // visit::walk_mac(self, _mac)
 126     }
 127     fn visit_path(&mut self, path: &'v Path, _id: ast::NodeId) {
 128         walk_path(self, path)
 129     }
 130     fn visit_path_segment(&mut self, path_span: Span, path_segment: &'v PathSegment) {
 131         walk_path_segment(self, path_span, path_segment)
 132     }
 133     fn visit_path_parameters(&mut self, path_span: Span, path_parameters: &'v PathParameters) {
 134         walk_path_parameters(self, path_span, path_parameters)
 135     }
 136     fn visit_assoc_type_binding(&mut self, type_binding: &'v TypeBinding) {
 137         walk_assoc_type_binding(self, type_binding)
 138     }
 139     fn visit_attribute(&mut self, _attr: &'v Attribute) {}
 140 }
 141
 142 pub fn walk_crate<'v, V: Visitor<'v>>(visitor: &mut V, krate: &'v Crate) {
 143     visitor.visit_mod(&krate.module, krate.span, CRATE_NODE_ID);
 144     for attr in &krate.attrs {
 145         visitor.visit_attribute(attr);
 146     }
 147 }
 148
 149 pub fn walk_mod<'v, V: Visitor<'v>>(visitor: &mut V, module: &'v Mod) {
 150     for item in &module.items {
 151         visitor.visit_item(&**item)
 152     }
 153 }
 154
 155 pub fn walk_local<'v, V: Visitor<'v>>(visitor: &mut V, local: &'v Local) {
 156     visitor.visit_pat(&*local.pat);
 157     walk_ty_opt(visitor, &local.ty);
 158     walk_expr_opt(visitor, &local.init);
 159 }
 160
 161 pub fn walk_lifetime_def<'v, V: Visitor<'v>>(visitor: &mut V,
 162                                               lifetime_def: &'v LifetimeDef) {
 163     visitor.visit_name(lifetime_def.lifetime.span, lifetime_def.lifetime.name);
 164     for bound in &lifetime_def.bounds {
 165         visitor.visit_lifetime_bound(bound);
 166     }
 167 }
 168
 169 pub fn walk_lifetime_bound<'v, V: Visitor<'v>>(visitor: &mut V,
 170                                                lifetime_ref: &'v Lifetime) {
 171     visitor.visit_lifetime_ref(lifetime_ref)
 172 }
 173
 174 pub fn walk_lifetime_ref<'v, V: Visitor<'v>>(visitor: &mut V,
 175                                              lifetime_ref: &'v Lifetime) {
 176     visitor.visit_name(lifetime_ref.span, lifetime_ref.name)
 177 }
 178
 179 pub fn walk_explicit_self<'v, V: Visitor<'v>>(visitor: &mut V,
 180                                               explicit_self: &'v ExplicitSelf) {
 181     match explicit_self.node {
 182         SelfStatic | SelfValue(_) => {},
 183         SelfRegion(ref lifetime, _, _) => {
 184             visitor.visit_opt_lifetime_ref(explicit_self.span, lifetime)
 185         }
 186         SelfExplicit(ref typ, _) => visitor.visit_ty(&**typ),
 187     }
 188 }
 189
 190 pub fn walk_poly_trait_ref<'v, V>(visitor: &mut V,
 191                                   trait_ref: &'v PolyTraitRef,
 192                                   _modifier: &'v TraitBoundModifier)
 193     where V: Visitor<'v>
 194 {
 195     walk_lifetime_decls_helper(visitor, &trait_ref.bound_lifetimes);
 196     visitor.visit_trait_ref(&trait_ref.trait_ref);
 197 }
 198
 199 pub fn walk_trait_ref<'v,V>(visitor: &mut V,
 200                                    trait_ref: &'v TraitRef)
 201     where V: Visitor<'v>
 202 {
 203     visitor.visit_path(&trait_ref.path, trait_ref.ref_id)
 204 }
 205
 206 pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item) {
 207     visitor.visit_ident(item.span, item.ident);
 208     match item.node {
 209         ItemExternCrate(..) => {}
 210         ItemUse(ref vp) => {
 211             match vp.node {
 212                 ViewPathSimple(ident, ref path) => {
 213                     visitor.visit_ident(vp.span, ident);
 214                     visitor.visit_path(path, item.id);
 215                 }
 216                 ViewPathGlob(ref path) => {
 217                     visitor.visit_path(path, item.id);
 218                 }
 219                 ViewPathList(ref prefix, ref list) => {
 220                     for id in list {
 221                         match id.node {
 222                             PathListIdent { name, rename, .. } => {
 223                                 visitor.visit_ident(id.span, name);
 224                                 if let Some(ident) = rename {
 225                                     visitor.visit_ident(id.span, ident);
 226                                 }
 227                             }
 228                             PathListMod { rename, .. } => {
 229                                 if let Some(ident) = rename {
 230                                     visitor.visit_ident(id.span, ident);
 231                                 }
 232                             }
 233                         }
 234                     }
 235
 236                     // Note that the `prefix` here is not a complete
 237                     // path, so we don't use `visit_path`.
 238                     walk_path(visitor, prefix);
 239                 }
 240             }
 241         }
 242         ItemStatic(ref typ, _, ref expr) |
 243         ItemConst(ref typ, ref expr) => {
 244             visitor.visit_ty(&**typ);
 245             visitor.visit_expr(&**expr);
 246         }
 247         ItemFn(ref declaration, unsafety, constness, abi, ref generics, ref body) => {
 248             visitor.visit_fn(FnKind::ItemFn(item.ident, generics, unsafety,
 249                                             constness, abi, item.vis),
 250                              &**declaration,
 251                              &**body,
 252                              item.span,
 253                              item.id)
 254         }
 255         ItemMod(ref module) => {
 256             visitor.visit_mod(module, item.span, item.id)
 257         }
 258         ItemForeignMod(ref foreign_module) => {
 259             for foreign_item in &foreign_module.items {
 260                 visitor.visit_foreign_item(&**foreign_item)
 261             }
 262         }
 263         ItemTy(ref typ, ref type_parameters) => {
 264             visitor.visit_ty(&**typ);
 265             visitor.visit_generics(type_parameters)
 266         }
 267         ItemEnum(ref enum_definition, ref type_parameters) => {
 268             visitor.visit_generics(type_parameters);
 269             visitor.visit_enum_def(enum_definition, type_parameters)
 270         }
 271         ItemDefaultImpl(_, ref trait_ref) => {
 272             visitor.visit_trait_ref(trait_ref)
 273         }
 274         ItemImpl(_, _,
 275                  ref type_parameters,
 276                  ref trait_reference,
 277                  ref typ,
 278                  ref impl_items) => {
 279             visitor.visit_generics(type_parameters);
 280             match *trait_reference {
 281                 Some(ref trait_reference) => visitor.visit_trait_ref(trait_reference),
 282                 None => ()
 283             }
 284             visitor.visit_ty(&**typ);
 285             for impl_item in impl_items {
 286                 visitor.visit_impl_item(impl_item);
 287             }
 288         }
 289         ItemStruct(ref struct_definition, ref generics) => {
 290             visitor.visit_generics(generics);
 291             visitor.visit_struct_def(&**struct_definition,
 292                                      item.ident,
 293                                      generics,
 294                                      item.id)
 295         }
 296         ItemTrait(_, ref generics, ref bounds, ref methods) => {
 297             visitor.visit_generics(generics);
 298             walk_ty_param_bounds_helper(visitor, bounds);
 299             for method in methods {
 300                 visitor.visit_trait_item(method)
 301             }
 302         }
 303         ItemMac(ref mac) => visitor.visit_mac(mac),
 304     }
 305     for attr in &item.attrs {
 306         visitor.visit_attribute(attr);
 307     }
 308 }
 309
 310 pub fn walk_enum_def<'v, V: Visitor<'v>>(visitor: &mut V,
 311                                          enum_definition: &'v EnumDef,
 312                                          generics: &'v Generics) {
 313     for variant in &enum_definition.variants {
 314         visitor.visit_variant(&**variant, generics);
 315     }
 316 }
 317
 318 pub fn walk_variant<'v, V: Visitor<'v>>(visitor: &mut V,
 319                                         variant: &'v Variant,
 320                                         generics: &'v Generics) {
 321     visitor.visit_ident(variant.span, variant.node.name);
 322
 323     match variant.node.kind {
 324         TupleVariantKind(ref variant_arguments) => {
 325             for variant_argument in variant_arguments {
 326                 visitor.visit_ty(&*variant_argument.ty)
 327             }
 328         }
 329         StructVariantKind(ref struct_definition) => {
 330             visitor.visit_struct_def(&**struct_definition,
 331                                      variant.node.name,
 332                                      generics,
 333                                      variant.node.id)
 334         }
 335     }
 336     match variant.node.disr_expr {
 337         Some(ref expr) => visitor.visit_expr(&**expr),
 338         None => ()
 339     }
 340     for attr in &variant.node.attrs {
 341         visitor.visit_attribute(attr);
 342     }
 343 }
 344
 345 pub fn skip_ty<'v, V: Visitor<'v>>(_: &mut V, _: &'v Ty) {
 346     // Empty!
 347 }
 348
 349 pub fn walk_ty_opt<'v, V: Visitor<'v>>(visitor: &mut V, optional_type: &'v Option<P<Ty>>) {
 350     match *optional_type {
 351         Some(ref ty) => visitor.visit_ty(&**ty),
 352         None => ()
 353     }
 354 }
 355
 356 pub fn walk_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty) {
 357     match typ.node {
 358         TyVec(ref ty) | TyParen(ref ty) => {
 359             visitor.visit_ty(&**ty)
 360         }
 361         TyPtr(ref mutable_type) => {
 362             visitor.visit_ty(&*mutable_type.ty)
 363         }
 364         TyRptr(ref lifetime, ref mutable_type) => {
 365             visitor.visit_opt_lifetime_ref(typ.span, lifetime);
 366             visitor.visit_ty(&*mutable_type.ty)
 367         }
 368         TyTup(ref tuple_element_types) => {
 369             for tuple_element_type in tuple_element_types {
 370                 visitor.visit_ty(&**tuple_element_type)
 371             }
 372         }
 373         TyBareFn(ref function_declaration) => {
 374             for argument in &function_declaration.decl.inputs {
 375                 visitor.visit_ty(&*argument.ty)
 376             }
 377             walk_fn_ret_ty(visitor, &function_declaration.decl.output);
 378             walk_lifetime_decls_helper(visitor, &function_declaration.lifetimes);
 379         }
 380         TyPath(ref maybe_qself, ref path) => {
 381             if let Some(ref qself) = *maybe_qself {
 382                 visitor.visit_ty(&qself.ty);
 383             }
 384             visitor.visit_path(path, typ.id);
 385         }
 386         TyObjectSum(ref ty, ref bounds) => {
 387             visitor.visit_ty(&**ty);
 388             walk_ty_param_bounds_helper(visitor, bounds);
 389         }
 390         TyFixedLengthVec(ref ty, ref expression) => {
 391             visitor.visit_ty(&**ty);
 392             visitor.visit_expr(&**expression)
 393         }
 394         TyPolyTraitRef(ref bounds) => {
 395             walk_ty_param_bounds_helper(visitor, bounds)
 396         }
 397         TyTypeof(ref expression) => {
 398             visitor.visit_expr(&**expression)
 399         }
 400         TyInfer => {}
 401         TyMac(ref mac) => {
 402             visitor.visit_mac(mac)
 403         }
 404     }
 405 }
 406
 407 pub fn walk_lifetime_decls_helper<'v, V: Visitor<'v>>(visitor: &mut V,
 408                                                       lifetimes: &'v Vec<LifetimeDef>) {
 409     for l in lifetimes {
 410         visitor.visit_lifetime_def(l);
 411     }
 412 }
 413
 414 pub fn walk_path<'v, V: Visitor<'v>>(visitor: &mut V, path: &'v Path) {
 415     for segment in &path.segments {
 416         visitor.visit_path_segment(path.span, segment);
 417     }
 418 }
 419
 420 pub fn walk_path_segment<'v, V: Visitor<'v>>(visitor: &mut V,
 421                                              path_span: Span,
 422                                              segment: &'v PathSegment) {
 423     visitor.visit_ident(path_span, segment.identifier);
 424     visitor.visit_path_parameters(path_span, &segment.parameters);
 425 }
 426
 427 pub fn walk_path_parameters<'v, V: Visitor<'v>>(visitor: &mut V,
 428                                                 _path_span: Span,
 429                                                 path_parameters: &'v PathParameters) {
 430     match *path_parameters {
 431         ast::AngleBracketedParameters(ref data) => {
 432             for typ in data.types.iter() {
 433                 visitor.visit_ty(&**typ);
 434             }
 435             for lifetime in &data.lifetimes {
 436                 visitor.visit_lifetime_ref(lifetime);
 437             }
 438             for binding in data.bindings.iter() {
 439                 visitor.visit_assoc_type_binding(&**binding);
 440             }
 441         }
 442         ast::ParenthesizedParameters(ref data) => {
 443             for typ in &data.inputs {
 444                 visitor.visit_ty(&**typ);
 445             }
 446             if let Some(ref typ) = data.output {
 447                 visitor.visit_ty(&**typ);
 448             }
 449         }
 450     }
 451 }
 452
 453 pub fn walk_assoc_type_binding<'v, V: Visitor<'v>>(visitor: &mut V,
 454                                                    type_binding: &'v TypeBinding) {
 455     visitor.visit_ident(type_binding.span, type_binding.ident);
 456     visitor.visit_ty(&*type_binding.ty);
 457 }
 458
 459 pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat) {
 460     match pattern.node {
 461         PatEnum(ref path, ref children) => {
 462             visitor.visit_path(path, pattern.id);
 463             if let Some(ref children) = *children {
 464                 for child in children {
 465                     visitor.visit_pat(&*child)
 466                 }
 467             }
 468         }
 469         PatQPath(ref qself, ref path) => {
 470             visitor.visit_ty(&qself.ty);
 471             visitor.visit_path(path, pattern.id)
 472         }
 473         PatStruct(ref path, ref fields, _) => {
 474             visitor.visit_path(path, pattern.id);
 475             for field in fields {
 476                 visitor.visit_pat(&*field.node.pat)
 477             }
 478         }
 479         PatTup(ref tuple_elements) => {
 480             for tuple_element in tuple_elements {
 481                 visitor.visit_pat(&**tuple_element)
 482             }
 483         }
 484         PatBox(ref subpattern) |
 485         PatRegion(ref subpattern, _) => {
 486             visitor.visit_pat(&**subpattern)
 487         }
 488         PatIdent(_, ref pth1, ref optional_subpattern) => {
 489             visitor.visit_ident(pth1.span, pth1.node);
 490             match *optional_subpattern {
 491                 None => {}
 492                 Some(ref subpattern) => visitor.visit_pat(&**subpattern),
 493             }
 494         }
 495         PatLit(ref expression) => visitor.visit_expr(&**expression),
 496         PatRange(ref lower_bound, ref upper_bound) => {
 497             visitor.visit_expr(&**lower_bound);
 498             visitor.visit_expr(&**upper_bound)
 499         }
 500         PatWild(_) => (),
 501         PatVec(ref prepattern, ref slice_pattern, ref postpatterns) => {
 502             for prepattern in prepattern {
 503                 visitor.visit_pat(&**prepattern)
 504             }
 505             if let Some(ref slice_pattern) = *slice_pattern {
 506                 visitor.visit_pat(&**slice_pattern)
 507             }
 508             for postpattern in postpatterns {
 509                 visitor.visit_pat(&**postpattern)
 510             }
 511         }
 512         PatMac(ref mac) => visitor.visit_mac(mac),
 513     }
 514 }
 515
 516 pub fn walk_foreign_item<'v, V: Visitor<'v>>(visitor: &mut V,
 517                                              foreign_item: &'v ForeignItem) {
 518     visitor.visit_ident(foreign_item.span, foreign_item.ident);
 519
 520     match foreign_item.node {
 521         ForeignItemFn(ref function_declaration, ref generics) => {
 522             walk_fn_decl(visitor, &**function_declaration);
 523             visitor.visit_generics(generics)
 524         }
 525         ForeignItemStatic(ref typ, _) => visitor.visit_ty(&**typ),
 526     }
 527
 528     for attr in &foreign_item.attrs {
 529         visitor.visit_attribute(attr);
 530     }
 531 }
 532
 533 pub fn walk_ty_param_bounds_helper<'v, V: Visitor<'v>>(visitor: &mut V,
 534                                                        bounds: &'v OwnedSlice<TyParamBound>) {
 535     for bound in bounds.iter() {
 536         visitor.visit_ty_param_bound(bound)
 537     }
 538 }
 539
 540 pub fn walk_ty_param_bound<'v, V: Visitor<'v>>(visitor: &mut V,
 541                                                bound: &'v TyParamBound) {
 542     match *bound {
 543         TraitTyParamBound(ref typ, ref modifier) => {
 544             visitor.visit_poly_trait_ref(typ, modifier);
 545         }
 546         RegionTyParamBound(ref lifetime) => {
 547             visitor.visit_lifetime_bound(lifetime);
 548         }
 549     }
 550 }
 551
 552 pub fn walk_generics<'v, V: Visitor<'v>>(visitor: &mut V, generics: &'v Generics) {
 553     for param in generics.ty_params.iter() {
 554         visitor.visit_ident(param.span, param.ident);
 555         walk_ty_param_bounds_helper(visitor, &param.bounds);
 556         walk_ty_opt(visitor, &param.default);
 557     }
 558     walk_lifetime_decls_helper(visitor, &generics.lifetimes);
 559     for predicate in &generics.where_clause.predicates {
 560         match predicate {
 561             &ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate{ref bounded_ty,
 562                                                                           ref bounds,
 563                                                                           ..}) => {
 564                 visitor.visit_ty(&**bounded_ty);
 565                 walk_ty_param_bounds_helper(visitor, bounds);
 566             }
 567             &ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate{ref lifetime,
 568                                                                             ref bounds,
 569                                                                             ..}) => {
 570                 visitor.visit_lifetime_ref(lifetime);
 571
 572                 for bound in bounds {
 573                     visitor.visit_lifetime_ref(bound);
 574                 }
 575             }
 576             &ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{id,
 577                                                                     ref path,
 578                                                                     ref ty,
 579                                                                     ..}) => {
 580                 visitor.visit_path(path, id);
 581                 visitor.visit_ty(&**ty);
 582             }
 583         }
 584     }
 585 }
 586
 587 pub fn walk_fn_ret_ty<'v, V: Visitor<'v>>(visitor: &mut V, ret_ty: &'v FunctionRetTy) {
 588     if let Return(ref output_ty) = *ret_ty {
 589         visitor.visit_ty(&**output_ty)
 590     }
 591 }
 592
 593 pub fn walk_fn_decl<'v, V: Visitor<'v>>(visitor: &mut V, function_declaration: &'v FnDecl) {
 594     for argument in &function_declaration.inputs {
 595         visitor.visit_pat(&*argument.pat);
 596         visitor.visit_ty(&*argument.ty)
 597     }
 598     walk_fn_ret_ty(visitor, &function_declaration.output)
 599 }
 600
 601 pub fn walk_fn<'v, V: Visitor<'v>>(visitor: &mut V,
 602                                    function_kind: FnKind<'v>,
 603                                    function_declaration: &'v FnDecl,
 604                                    function_body: &'v Block,
 605                                    _span: Span) {
 606     walk_fn_decl(visitor, function_declaration);
 607
 608     match function_kind {
 609         FnKind::ItemFn(_, generics, _, _, _, _) => {
 610             visitor.visit_generics(generics);
 611         }
 612         FnKind::Method(_, sig, _) => {
 613             visitor.visit_generics(&sig.generics);
 614             visitor.visit_explicit_self(&sig.explicit_self);
 615         }
 616         FnKind::Closure(..) => {}
 617     }
 618
 619     visitor.visit_block(function_body)
 620 }
 621
 622 pub fn walk_trait_item<'v, V: Visitor<'v>>(visitor: &mut V, trait_item: &'v TraitItem) {
 623     visitor.visit_ident(trait_item.span, trait_item.ident);
 624     for attr in &trait_item.attrs {
 625         visitor.visit_attribute(attr);
 626     }
 627     match trait_item.node {
 628         ConstTraitItem(ref ty, ref default) => {
 629             visitor.visit_ty(ty);
 630             if let Some(ref expr) = *default {
 631                 visitor.visit_expr(expr);
 632             }
 633         }
 634         MethodTraitItem(ref sig, None) => {
 635             visitor.visit_explicit_self(&sig.explicit_self);
 636             visitor.visit_generics(&sig.generics);
 637             walk_fn_decl(visitor, &sig.decl);
 638         }
 639         MethodTraitItem(ref sig, Some(ref body)) => {
 640             visitor.visit_fn(FnKind::Method(trait_item.ident, sig, None), &sig.decl,
 641                              body, trait_item.span, trait_item.id);
 642         }
 643         TypeTraitItem(ref bounds, ref default) => {
 644             walk_ty_param_bounds_helper(visitor, bounds);
 645             walk_ty_opt(visitor, default);
 646         }
 647     }
 648 }
 649
 650 pub fn walk_impl_item<'v, V: Visitor<'v>>(visitor: &mut V, impl_item: &'v ImplItem) {
 651     visitor.visit_ident(impl_item.span, impl_item.ident);
 652     for attr in &impl_item.attrs {
 653         visitor.visit_attribute(attr);
 654     }
 655     match impl_item.node {
 656         ConstImplItem(ref ty, ref expr) => {
 657             visitor.visit_ty(ty);
 658             visitor.visit_expr(expr);
 659         }
 660         MethodImplItem(ref sig, ref body) => {
 661             visitor.visit_fn(FnKind::Method(impl_item.ident, sig, Some(impl_item.vis)), &sig.decl,
 662                              body, impl_item.span, impl_item.id);
 663         }
 664         TypeImplItem(ref ty) => {
 665             visitor.visit_ty(ty);
 666         }
 667         MacImplItem(ref mac) => {
 668             visitor.visit_mac(mac);
 669         }
 670     }
 671 }
 672
 673 pub fn walk_struct_def<'v, V: Visitor<'v>>(visitor: &mut V,
 674                                            struct_definition: &'v StructDef) {
 675     for field in &struct_definition.fields {
 676         visitor.visit_struct_field(field)
 677     }
 678 }
 679
 680 pub fn walk_struct_field<'v, V: Visitor<'v>>(visitor: &mut V,
 681                                              struct_field: &'v StructField) {
 682     if let NamedField(name, _) = struct_field.node.kind {
 683         visitor.visit_ident(struct_field.span, name);
 684     }
 685
 686     visitor.visit_ty(&*struct_field.node.ty);
 687
 688     for attr in &struct_field.node.attrs {
 689         visitor.visit_attribute(attr);
 690     }
 691 }
 692
 693 pub fn walk_block<'v, V: Visitor<'v>>(visitor: &mut V, block: &'v Block) {
 694     for statement in &block.stmts {
 695         visitor.visit_stmt(&**statement)
 696     }
 697     walk_expr_opt(visitor, &block.expr)
 698 }
 699
 700 pub fn walk_stmt<'v, V: Visitor<'v>>(visitor: &mut V, statement: &'v Stmt) {
 701     match statement.node {
 702         StmtDecl(ref declaration, _) => visitor.visit_decl(&**declaration),
 703         StmtExpr(ref expression, _) | StmtSemi(ref expression, _) => {
 704             visitor.visit_expr(&**expression)
 705         }
 706         StmtMac(ref mac, _) => visitor.visit_mac(&**mac),
 707     }
 708 }
 709
 710 pub fn walk_decl<'v, V: Visitor<'v>>(visitor: &mut V, declaration: &'v Decl) {
 711     match declaration.node {
 712         DeclLocal(ref local) => visitor.visit_local(&**local),
 713         DeclItem(ref item) => visitor.visit_item(&**item),
 714     }
 715 }
 716
 717 pub fn walk_expr_opt<'v, V: Visitor<'v>>(visitor: &mut V,
 718                                          optional_expression: &'v Option<P<Expr>>) {
 719     match *optional_expression {
 720         None => {}
 721         Some(ref expression) => visitor.visit_expr(&**expression),
 722     }
 723 }
 724
 725 pub fn walk_exprs<'v, V: Visitor<'v>>(visitor: &mut V, expressions: &'v [P<Expr>]) {
 726     for expression in expressions {
 727         visitor.visit_expr(&**expression)
 728     }
 729 }
 730
 731 pub fn walk_mac<'v, V: Visitor<'v>>(_: &mut V, _: &'v Mac) {
 732     // Empty!
 733 }
 734
 735 pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr) {
 736     match expression.node {
 737         ExprBox(ref place, ref subexpression) => {
 738             place.as_ref().map(|e|visitor.visit_expr(&**e));
 739             visitor.visit_expr(&**subexpression)
 740         }
 741         ExprVec(ref subexpressions) => {
 742             walk_exprs(visitor, subexpressions)
 743         }
 744         ExprRepeat(ref element, ref count) => {
 745             visitor.visit_expr(&**element);
 746             visitor.visit_expr(&**count)
 747         }
 748         ExprStruct(ref path, ref fields, ref optional_base) => {
 749             visitor.visit_path(path, expression.id);
 750             for field in fields {
 751                 visitor.visit_expr(&*field.expr)
 752             }
 753             walk_expr_opt(visitor, optional_base)
 754         }
 755         ExprTup(ref subexpressions) => {
 756             for subexpression in subexpressions {
 757                 visitor.visit_expr(&**subexpression)
 758             }
 759         }
 760         ExprCall(ref callee_expression, ref arguments) => {
 761             for argument in arguments {
 762                 visitor.visit_expr(&**argument)
 763             }
 764             visitor.visit_expr(&**callee_expression)
 765         }
 766         ExprMethodCall(_, ref types, ref arguments) => {
 767             walk_exprs(visitor, arguments);
 768             for typ in types {
 769                 visitor.visit_ty(&**typ)
 770             }
 771         }
 772         ExprBinary(_, ref left_expression, ref right_expression) => {
 773             visitor.visit_expr(&**left_expression);
 774             visitor.visit_expr(&**right_expression)
 775         }
 776         ExprAddrOf(_, ref subexpression) | ExprUnary(_, ref subexpression) => {
 777             visitor.visit_expr(&**subexpression)
 778         }
 779         ExprLit(_) => {}
 780         ExprCast(ref subexpression, ref typ) => {
 781             visitor.visit_expr(&**subexpression);
 782             visitor.visit_ty(&**typ)
 783         }
 784         ExprIf(ref head_expression, ref if_block, ref optional_else) => {
 785             visitor.visit_expr(&**head_expression);
 786             visitor.visit_block(&**if_block);
 787             walk_expr_opt(visitor, optional_else)
 788         }
 789         ExprWhile(ref subexpression, ref block, _) => {
 790             visitor.visit_expr(&**subexpression);
 791             visitor.visit_block(&**block)
 792         }
 793         ExprIfLet(ref pattern, ref subexpression, ref if_block, ref optional_else) => {
 794             visitor.visit_pat(&**pattern);
 795             visitor.visit_expr(&**subexpression);
 796             visitor.visit_block(&**if_block);
 797             walk_expr_opt(visitor, optional_else);
 798         }
 799         ExprWhileLet(ref pattern, ref subexpression, ref block, _) => {
 800             visitor.visit_pat(&**pattern);
 801             visitor.visit_expr(&**subexpression);
 802             visitor.visit_block(&**block);
 803         }
 804         ExprForLoop(ref pattern, ref subexpression, ref block, _) => {
 805             visitor.visit_pat(&**pattern);
 806             visitor.visit_expr(&**subexpression);
 807             visitor.visit_block(&**block)
 808         }
 809         ExprLoop(ref block, _) => visitor.visit_block(&**block),
 810         ExprMatch(ref subexpression, ref arms, _) => {
 811             visitor.visit_expr(&**subexpression);
 812             for arm in arms {
 813                 visitor.visit_arm(arm)
 814             }
 815         }
 816         ExprClosure(_, ref function_declaration, ref body) => {
 817             visitor.visit_fn(FnKind::Closure,
 818                              &**function_declaration,
 819                              &**body,
 820                              expression.span,
 821                              expression.id)
 822         }
 823         ExprBlock(ref block) => visitor.visit_block(&**block),
 824         ExprAssign(ref left_hand_expression, ref right_hand_expression) => {
 825             visitor.visit_expr(&**right_hand_expression);
 826             visitor.visit_expr(&**left_hand_expression)
 827         }
 828         ExprAssignOp(_, ref left_expression, ref right_expression) => {
 829             visitor.visit_expr(&**right_expression);
 830             visitor.visit_expr(&**left_expression)
 831         }
 832         ExprField(ref subexpression, _) => {
 833             visitor.visit_expr(&**subexpression);
 834         }
 835         ExprTupField(ref subexpression, _) => {
 836             visitor.visit_expr(&**subexpression);
 837         }
 838         ExprIndex(ref main_expression, ref index_expression) => {
 839             visitor.visit_expr(&**main_expression);
 840             visitor.visit_expr(&**index_expression)
 841         }
 842         ExprRange(ref start, ref end) => {
 843             walk_expr_opt(visitor, start);
 844             walk_expr_opt(visitor, end)
 845         }
 846         ExprPath(ref maybe_qself, ref path) => {
 847             if let Some(ref qself) = *maybe_qself {
 848                 visitor.visit_ty(&qself.ty);
 849             }
 850             visitor.visit_path(path, expression.id)
 851         }
 852         ExprBreak(_) | ExprAgain(_) => {}
 853         ExprRet(ref optional_expression) => {
 854             walk_expr_opt(visitor, optional_expression)
 855         }
 856         ExprMac(ref mac) => visitor.visit_mac(mac),
 857         ExprParen(ref subexpression) => {
 858             visitor.visit_expr(&**subexpression)
 859         }
 860         ExprInlineAsm(ref ia) => {
 861             for input in &ia.inputs {
 862                 let (_, ref input) = *input;
 863                 visitor.visit_expr(&**input)
 864             }
 865             for output in &ia.outputs {
 866                 let (_, ref output, _) = *output;
 867                 visitor.visit_expr(&**output)
 868             }
 869         }
 870     }
 871
 872     visitor.visit_expr_post(expression)
 873 }
 874
 875 pub fn walk_arm<'v, V: Visitor<'v>>(visitor: &mut V, arm: &'v Arm) {
 876     for pattern in &arm.pats {
 877         visitor.visit_pat(&**pattern)
 878     }
 879     walk_expr_opt(visitor, &arm.guard);
 880     visitor.visit_expr(&*arm.body);
 881     for attr in &arm.attrs {
 882         visitor.visit_attribute(attr);
 883     }
 884 }