src/libsyntax/visit.rs

   1 // Copyright 2012-2015 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 codemap::Span;
  29
  30 #[derive(Copy, Clone, PartialEq, Eq)]
  31 pub enum FnKind<'a> {
  32     /// fn foo() or extern "Abi" fn foo()
  33     ItemFn(Ident, &'a Generics, Unsafety, Constness, Abi, Visibility),
  34
  35     /// fn foo(&self)
  36     Method(Ident, &'a MethodSig, Option<Visibility>),
  37
  38     /// |x, y| {}
  39     Closure,
  40 }
  41
  42 /// Each method of the Visitor trait is a hook to be potentially
  43 /// overridden.  Each method's default implementation recursively visits
  44 /// the substructure of the input via the corresponding `walk` method;
  45 /// e.g. the `visit_mod` method by default calls `visit::walk_mod`.
  46 ///
  47 /// If you want to ensure that your code handles every variant
  48 /// explicitly, you need to override each method.  (And you also need
  49 /// to monitor future changes to `Visitor` in case a new method with a
  50 /// new default implementation gets introduced.)
  51 pub trait Visitor<'v> : Sized {
  52     fn visit_name(&mut self, _span: Span, _name: Name) {
  53         // Nothing to do.
  54     }
  55     fn visit_ident(&mut self, span: Span, ident: Ident) {
  56         walk_ident(self, span, ident);
  57     }
  58     fn visit_mod(&mut self, m: &'v Mod, _s: Span, _n: NodeId) { walk_mod(self, m) }
  59     fn visit_foreign_item(&mut self, i: &'v ForeignItem) { walk_foreign_item(self, i) }
  60     fn visit_item(&mut self, i: &'v Item) { walk_item(self, i) }
  61     fn visit_local(&mut self, l: &'v Local) { walk_local(self, l) }
  62     fn visit_block(&mut self, b: &'v Block) { walk_block(self, b) }
  63     fn visit_stmt(&mut self, s: &'v Stmt) { walk_stmt(self, s) }
  64     fn visit_arm(&mut self, a: &'v Arm) { walk_arm(self, a) }
  65     fn visit_pat(&mut self, p: &'v Pat) { walk_pat(self, p) }
  66     fn visit_decl(&mut self, d: &'v Decl) { walk_decl(self, d) }
  67     fn visit_expr(&mut self, ex: &'v Expr) { walk_expr(self, ex) }
  68     fn visit_expr_post(&mut self, _ex: &'v Expr) { }
  69     fn visit_ty(&mut self, t: &'v Ty) { walk_ty(self, t) }
  70     fn visit_generics(&mut self, g: &'v Generics) { walk_generics(self, g) }
  71     fn visit_fn(&mut self, fk: FnKind<'v>, fd: &'v FnDecl, b: &'v Block, s: Span, _: NodeId) {
  72         walk_fn(self, fk, fd, b, s)
  73     }
  74     fn visit_trait_item(&mut self, ti: &'v TraitItem) { walk_trait_item(self, ti) }
  75     fn visit_impl_item(&mut self, ii: &'v ImplItem) { walk_impl_item(self, ii) }
  76     fn visit_trait_ref(&mut self, t: &'v TraitRef) { walk_trait_ref(self, t) }
  77     fn visit_ty_param_bound(&mut self, bounds: &'v TyParamBound) {
  78         walk_ty_param_bound(self, bounds)
  79     }
  80     fn visit_poly_trait_ref(&mut self, t: &'v PolyTraitRef, m: &'v TraitBoundModifier) {
  81         walk_poly_trait_ref(self, t, m)
  82     }
  83     fn visit_variant_data(&mut self, s: &'v VariantData, _: Ident,
  84                         _: &'v Generics, _: NodeId, _: Span) {
  85         walk_struct_def(self, s)
  86     }
  87     fn visit_struct_field(&mut self, s: &'v StructField) { walk_struct_field(self, s) }
  88     fn visit_enum_def(&mut self, enum_definition: &'v EnumDef,
  89                       generics: &'v Generics, item_id: NodeId) {
  90         walk_enum_def(self, enum_definition, generics, item_id)
  91     }
  92     fn visit_variant(&mut self, v: &'v Variant, g: &'v Generics, item_id: NodeId) {
  93         walk_variant(self, v, g, item_id)
  94     }
  95     fn visit_lifetime(&mut self, lifetime: &'v Lifetime) {
  96         walk_lifetime(self, lifetime)
  97     }
  98     fn visit_lifetime_def(&mut self, lifetime: &'v LifetimeDef) {
  99         walk_lifetime_def(self, lifetime)
 100     }
 101     fn visit_explicit_self(&mut self, es: &'v ExplicitSelf) {
 102         walk_explicit_self(self, es)
 103     }
 104     fn visit_mac(&mut self, _mac: &'v Mac) {
 105         panic!("visit_mac disabled by default");
 106         // NB: see note about macros above.
 107         // if you really want a visitor that
 108         // works on macros, use this
 109         // definition in your trait impl:
 110         // visit::walk_mac(self, _mac)
 111     }
 112     fn visit_path(&mut self, path: &'v Path, _id: NodeId) {
 113         walk_path(self, path)
 114     }
 115     fn visit_path_list_item(&mut self, prefix: &'v Path, item: &'v PathListItem) {
 116         walk_path_list_item(self, prefix, item)
 117     }
 118     fn visit_path_segment(&mut self, path_span: Span, path_segment: &'v PathSegment) {
 119         walk_path_segment(self, path_span, path_segment)
 120     }
 121     fn visit_path_parameters(&mut self, path_span: Span, path_parameters: &'v PathParameters) {
 122         walk_path_parameters(self, path_span, path_parameters)
 123     }
 124     fn visit_assoc_type_binding(&mut self, type_binding: &'v TypeBinding) {
 125         walk_assoc_type_binding(self, type_binding)
 126     }
 127     fn visit_attribute(&mut self, _attr: &'v Attribute) {}
 128     fn visit_macro_def(&mut self, macro_def: &'v MacroDef) {
 129         walk_macro_def(self, macro_def)
 130     }
 131 }
 132
 133 #[macro_export]
 134 macro_rules! walk_list {
 135     ($visitor: expr, $method: ident, $list: expr) => {
 136         for elem in $list {
 137             $visitor.$method(elem)
 138         }
 139     }
 140 }
 141
 142 pub fn walk_opt_name<'v, V: Visitor<'v>>(visitor: &mut V, span: Span, opt_name: Option<Name>) {
 143     for name in opt_name {
 144         visitor.visit_name(span, name);
 145     }
 146 }
 147
 148 pub fn walk_opt_ident<'v, V: Visitor<'v>>(visitor: &mut V, span: Span, opt_ident: Option<Ident>) {
 149     for ident in opt_ident {
 150         visitor.visit_ident(span, ident);
 151     }
 152 }
 153
 154 pub fn walk_ident<'v, V: Visitor<'v>>(visitor: &mut V, span: Span, ident: Ident) {
 155     visitor.visit_name(span, ident.name);
 156 }
 157
 158 pub fn walk_crate<'v, V: Visitor<'v>>(visitor: &mut V, krate: &'v Crate) {
 159     visitor.visit_mod(&krate.module, krate.span, CRATE_NODE_ID);
 160     walk_list!(visitor, visit_attribute, &krate.attrs);
 161     walk_list!(visitor, visit_macro_def, &krate.exported_macros);
 162 }
 163
 164 pub fn walk_macro_def<'v, V: Visitor<'v>>(visitor: &mut V, macro_def: &'v MacroDef) {
 165     visitor.visit_ident(macro_def.span, macro_def.ident);
 166     walk_opt_ident(visitor, macro_def.span, macro_def.imported_from);
 167     walk_list!(visitor, visit_attribute, &macro_def.attrs);
 168 }
 169
 170 pub fn walk_mod<'v, V: Visitor<'v>>(visitor: &mut V, module: &'v Mod) {
 171     walk_list!(visitor, visit_item, &module.items);
 172 }
 173
 174 pub fn walk_local<'v, V: Visitor<'v>>(visitor: &mut V, local: &'v Local) {
 175     visitor.visit_pat(&local.pat);
 176     walk_list!(visitor, visit_ty, &local.ty);
 177     walk_list!(visitor, visit_expr, &local.init);
 178 }
 179
 180 pub fn walk_lifetime<'v, V: Visitor<'v>>(visitor: &mut V, lifetime: &'v Lifetime) {
 181     visitor.visit_name(lifetime.span, lifetime.name);
 182 }
 183
 184 pub fn walk_lifetime_def<'v, V: Visitor<'v>>(visitor: &mut V,
 185                                               lifetime_def: &'v LifetimeDef) {
 186     visitor.visit_lifetime(&lifetime_def.lifetime);
 187     walk_list!(visitor, visit_lifetime, &lifetime_def.bounds);
 188 }
 189
 190 pub fn walk_explicit_self<'v, V: Visitor<'v>>(visitor: &mut V,
 191                                               explicit_self: &'v ExplicitSelf) {
 192     match explicit_self.node {
 193         SelfStatic => {},
 194         SelfValue(ident) => {
 195             visitor.visit_ident(explicit_self.span, ident)
 196         }
 197         SelfRegion(ref opt_lifetime, _, ident) => {
 198             visitor.visit_ident(explicit_self.span, ident);
 199             walk_list!(visitor, visit_lifetime, opt_lifetime);
 200         }
 201         SelfExplicit(ref typ, ident) => {
 202             visitor.visit_ident(explicit_self.span, ident);
 203             visitor.visit_ty(typ)
 204         }
 205     }
 206 }
 207
 208 pub fn walk_poly_trait_ref<'v, V>(visitor: &mut V,
 209                                   trait_ref: &'v PolyTraitRef,
 210                                   _modifier: &'v TraitBoundModifier)
 211     where V: Visitor<'v>
 212 {
 213     walk_list!(visitor, visit_lifetime_def, &trait_ref.bound_lifetimes);
 214     visitor.visit_trait_ref(&trait_ref.trait_ref);
 215 }
 216
 217 pub fn walk_trait_ref<'v,V>(visitor: &mut V,
 218                                    trait_ref: &'v TraitRef)
 219     where V: Visitor<'v>
 220 {
 221     visitor.visit_path(&trait_ref.path, trait_ref.ref_id)
 222 }
 223
 224 pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item) {
 225     visitor.visit_ident(item.span, item.ident);
 226     match item.node {
 227         ItemExternCrate(opt_name) => {
 228             walk_opt_name(visitor, item.span, opt_name)
 229         }
 230         ItemUse(ref vp) => {
 231             match vp.node {
 232                 ViewPathSimple(ident, ref path) => {
 233                     visitor.visit_ident(vp.span, ident);
 234                     visitor.visit_path(path, item.id);
 235                 }
 236                 ViewPathGlob(ref path) => {
 237                     visitor.visit_path(path, item.id);
 238                 }
 239                 ViewPathList(ref prefix, ref list) => {
 240                     if !list.is_empty() {
 241                         for item in list {
 242                             visitor.visit_path_list_item(prefix, item)
 243                         }
 244                     } else {
 245                         visitor.visit_path(prefix, item.id);
 246                     }
 247                 }
 248             }
 249         }
 250         ItemStatic(ref typ, _, ref expr) |
 251         ItemConst(ref typ, ref expr) => {
 252             visitor.visit_ty(typ);
 253             visitor.visit_expr(expr);
 254         }
 255         ItemFn(ref declaration, unsafety, constness, abi, ref generics, ref body) => {
 256             visitor.visit_fn(FnKind::ItemFn(item.ident, generics, unsafety,
 257                                             constness, abi, item.vis),
 258                              declaration,
 259                              body,
 260                              item.span,
 261                              item.id)
 262         }
 263         ItemMod(ref module) => {
 264             visitor.visit_mod(module, item.span, item.id)
 265         }
 266         ItemForeignMod(ref foreign_module) => {
 267             walk_list!(visitor, visit_foreign_item, &foreign_module.items);
 268         }
 269         ItemTy(ref typ, ref type_parameters) => {
 270             visitor.visit_ty(typ);
 271             visitor.visit_generics(type_parameters)
 272         }
 273         ItemEnum(ref enum_definition, ref type_parameters) => {
 274             visitor.visit_generics(type_parameters);
 275             visitor.visit_enum_def(enum_definition, type_parameters, item.id)
 276         }
 277         ItemDefaultImpl(_, ref trait_ref) => {
 278             visitor.visit_trait_ref(trait_ref)
 279         }
 280         ItemImpl(_, _,
 281                  ref type_parameters,
 282                  ref opt_trait_reference,
 283                  ref typ,
 284                  ref impl_items) => {
 285             visitor.visit_generics(type_parameters);
 286             walk_list!(visitor, visit_trait_ref, opt_trait_reference);
 287             visitor.visit_ty(typ);
 288             walk_list!(visitor, visit_impl_item, impl_items);
 289         }
 290         ItemStruct(ref struct_definition, ref generics) => {
 291             visitor.visit_generics(generics);
 292             visitor.visit_variant_data(struct_definition, item.ident,
 293                                      generics, item.id, item.span);
 294         }
 295         ItemTrait(_, ref generics, ref bounds, ref methods) => {
 296             visitor.visit_generics(generics);
 297             walk_list!(visitor, visit_ty_param_bound, bounds);
 298             walk_list!(visitor, visit_trait_item, methods);
 299         }
 300         ItemMac(ref mac) => visitor.visit_mac(mac),
 301     }
 302     walk_list!(visitor, visit_attribute, &item.attrs);
 303 }
 304
 305 pub fn walk_enum_def<'v, V: Visitor<'v>>(visitor: &mut V,
 306                                          enum_definition: &'v EnumDef,
 307                                          generics: &'v Generics,
 308                                          item_id: NodeId) {
 309     for variant in &enum_definition.variants {
 310         visitor.visit_variant(variant, generics, item_id);
 311     }
 312 }
 313
 314 pub fn walk_variant<'v, V: Visitor<'v>>(visitor: &mut V,
 315                                         variant: &'v Variant,
 316                                         generics: &'v Generics,
 317                                         item_id: NodeId) {
 318     visitor.visit_ident(variant.span, variant.node.name);
 319     visitor.visit_variant_data(&variant.node.data, variant.node.name,
 320                              generics, item_id, variant.span);
 321     walk_list!(visitor, visit_expr, &variant.node.disr_expr);
 322     walk_list!(visitor, visit_attribute, &variant.node.attrs);
 323 }
 324
 325 pub fn walk_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty) {
 326     match typ.node {
 327         TyVec(ref ty) | TyParen(ref ty) => {
 328             visitor.visit_ty(ty)
 329         }
 330         TyPtr(ref mutable_type) => {
 331             visitor.visit_ty(&mutable_type.ty)
 332         }
 333         TyRptr(ref opt_lifetime, ref mutable_type) => {
 334             walk_list!(visitor, visit_lifetime, opt_lifetime);
 335             visitor.visit_ty(&mutable_type.ty)
 336         }
 337         TyTup(ref tuple_element_types) => {
 338             walk_list!(visitor, visit_ty, tuple_element_types);
 339         }
 340         TyBareFn(ref function_declaration) => {
 341             walk_fn_decl(visitor, &function_declaration.decl);
 342             walk_list!(visitor, visit_lifetime_def, &function_declaration.lifetimes);
 343         }
 344         TyPath(ref maybe_qself, ref path) => {
 345             if let Some(ref qself) = *maybe_qself {
 346                 visitor.visit_ty(&qself.ty);
 347             }
 348             visitor.visit_path(path, typ.id);
 349         }
 350         TyObjectSum(ref ty, ref bounds) => {
 351             visitor.visit_ty(ty);
 352             walk_list!(visitor, visit_ty_param_bound, bounds);
 353         }
 354         TyFixedLengthVec(ref ty, ref expression) => {
 355             visitor.visit_ty(ty);
 356             visitor.visit_expr(expression)
 357         }
 358         TyPolyTraitRef(ref bounds) => {
 359             walk_list!(visitor, visit_ty_param_bound, bounds);
 360         }
 361         TyTypeof(ref expression) => {
 362             visitor.visit_expr(expression)
 363         }
 364         TyInfer => {}
 365         TyMac(ref mac) => {
 366             visitor.visit_mac(mac)
 367         }
 368     }
 369 }
 370
 371 pub fn walk_path<'v, V: Visitor<'v>>(visitor: &mut V, path: &'v Path) {
 372     for segment in &path.segments {
 373         visitor.visit_path_segment(path.span, segment);
 374     }
 375 }
 376
 377 pub fn walk_path_list_item<'v, V: Visitor<'v>>(visitor: &mut V, prefix: &'v Path,
 378                                                item: &'v PathListItem) {
 379     for segment in &prefix.segments {
 380         visitor.visit_path_segment(prefix.span, segment);
 381     }
 382
 383     walk_opt_ident(visitor, item.span, item.node.name());
 384     walk_opt_ident(visitor, item.span, item.node.rename());
 385 }
 386
 387 pub fn walk_path_segment<'v, V: Visitor<'v>>(visitor: &mut V,
 388                                              path_span: Span,
 389                                              segment: &'v PathSegment) {
 390     visitor.visit_ident(path_span, segment.identifier);
 391     visitor.visit_path_parameters(path_span, &segment.parameters);
 392 }
 393
 394 pub fn walk_path_parameters<'v, V: Visitor<'v>>(visitor: &mut V,
 395                                                 _path_span: Span,
 396                                                 path_parameters: &'v PathParameters) {
 397     match *path_parameters {
 398         AngleBracketedParameters(ref data) => {
 399             walk_list!(visitor, visit_ty, &data.types);
 400             walk_list!(visitor, visit_lifetime, &data.lifetimes);
 401             walk_list!(visitor, visit_assoc_type_binding, &data.bindings);
 402         }
 403         ParenthesizedParameters(ref data) => {
 404             walk_list!(visitor, visit_ty, &data.inputs);
 405             walk_list!(visitor, visit_ty, &data.output);
 406         }
 407     }
 408 }
 409
 410 pub fn walk_assoc_type_binding<'v, V: Visitor<'v>>(visitor: &mut V,
 411                                                    type_binding: &'v TypeBinding) {
 412     visitor.visit_ident(type_binding.span, type_binding.ident);
 413     visitor.visit_ty(&type_binding.ty);
 414 }
 415
 416 pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat) {
 417     match pattern.node {
 418         PatEnum(ref path, ref opt_children) => {
 419             visitor.visit_path(path, pattern.id);
 420             if let Some(ref children) = *opt_children {
 421                 walk_list!(visitor, visit_pat, children);
 422             }
 423         }
 424         PatQPath(ref qself, ref path) => {
 425             visitor.visit_ty(&qself.ty);
 426             visitor.visit_path(path, pattern.id)
 427         }
 428         PatStruct(ref path, ref fields, _) => {
 429             visitor.visit_path(path, pattern.id);
 430             for field in fields {
 431                 visitor.visit_ident(field.span, field.node.ident);
 432                 visitor.visit_pat(&field.node.pat)
 433             }
 434         }
 435         PatTup(ref tuple_elements) => {
 436             walk_list!(visitor, visit_pat, tuple_elements);
 437         }
 438         PatBox(ref subpattern) |
 439         PatRegion(ref subpattern, _) => {
 440             visitor.visit_pat(subpattern)
 441         }
 442         PatIdent(_, ref pth1, ref optional_subpattern) => {
 443             visitor.visit_ident(pth1.span, pth1.node);
 444             walk_list!(visitor, visit_pat, optional_subpattern);
 445         }
 446         PatLit(ref expression) => visitor.visit_expr(expression),
 447         PatRange(ref lower_bound, ref upper_bound) => {
 448             visitor.visit_expr(lower_bound);
 449             visitor.visit_expr(upper_bound)
 450         }
 451         PatWild(_) => (),
 452         PatVec(ref prepatterns, ref slice_pattern, ref postpatterns) => {
 453             walk_list!(visitor, visit_pat, prepatterns);
 454             walk_list!(visitor, visit_pat, slice_pattern);
 455             walk_list!(visitor, visit_pat, postpatterns);
 456         }
 457         PatMac(ref mac) => visitor.visit_mac(mac),
 458     }
 459 }
 460
 461 pub fn walk_foreign_item<'v, V: Visitor<'v>>(visitor: &mut V,
 462                                              foreign_item: &'v ForeignItem) {
 463     visitor.visit_ident(foreign_item.span, foreign_item.ident);
 464
 465     match foreign_item.node {
 466         ForeignItemFn(ref function_declaration, ref generics) => {
 467             walk_fn_decl(visitor, function_declaration);
 468             visitor.visit_generics(generics)
 469         }
 470         ForeignItemStatic(ref typ, _) => visitor.visit_ty(typ),
 471     }
 472
 473     walk_list!(visitor, visit_attribute, &foreign_item.attrs);
 474 }
 475
 476 pub fn walk_ty_param_bound<'v, V: Visitor<'v>>(visitor: &mut V,
 477                                                bound: &'v TyParamBound) {
 478     match *bound {
 479         TraitTyParamBound(ref typ, ref modifier) => {
 480             visitor.visit_poly_trait_ref(typ, modifier);
 481         }
 482         RegionTyParamBound(ref lifetime) => {
 483             visitor.visit_lifetime(lifetime);
 484         }
 485     }
 486 }
 487
 488 pub fn walk_generics<'v, V: Visitor<'v>>(visitor: &mut V, generics: &'v Generics) {
 489     for param in &generics.ty_params {
 490         visitor.visit_ident(param.span, param.ident);
 491         walk_list!(visitor, visit_ty_param_bound, &param.bounds);
 492         walk_list!(visitor, visit_ty, &param.default);
 493     }
 494     walk_list!(visitor, visit_lifetime_def, &generics.lifetimes);
 495     for predicate in &generics.where_clause.predicates {
 496         match predicate {
 497             &WherePredicate::BoundPredicate(WhereBoundPredicate{ref bounded_ty,
 498                                                                           ref bounds,
 499                                                                           ref bound_lifetimes,
 500                                                                           ..}) => {
 501                 visitor.visit_ty(bounded_ty);
 502                 walk_list!(visitor, visit_ty_param_bound, bounds);
 503                 walk_list!(visitor, visit_lifetime_def, bound_lifetimes);
 504             }
 505             &WherePredicate::RegionPredicate(WhereRegionPredicate{ref lifetime,
 506                                                                             ref bounds,
 507                                                                             ..}) => {
 508                 visitor.visit_lifetime(lifetime);
 509                 walk_list!(visitor, visit_lifetime, bounds);
 510             }
 511             &WherePredicate::EqPredicate(WhereEqPredicate{id,
 512                                                                     ref path,
 513                                                                     ref ty,
 514                                                                     ..}) => {
 515                 visitor.visit_path(path, id);
 516                 visitor.visit_ty(ty);
 517             }
 518         }
 519     }
 520 }
 521
 522 pub fn walk_fn_ret_ty<'v, V: Visitor<'v>>(visitor: &mut V, ret_ty: &'v FunctionRetTy) {
 523     if let Return(ref output_ty) = *ret_ty {
 524         visitor.visit_ty(output_ty)
 525     }
 526 }
 527
 528 pub fn walk_fn_decl<'v, V: Visitor<'v>>(visitor: &mut V, function_declaration: &'v FnDecl) {
 529     for argument in &function_declaration.inputs {
 530         visitor.visit_pat(&argument.pat);
 531         visitor.visit_ty(&argument.ty)
 532     }
 533     walk_fn_ret_ty(visitor, &function_declaration.output)
 534 }
 535
 536 pub fn walk_fn_kind<'v, V: Visitor<'v>>(visitor: &mut V,
 537                                         function_kind: FnKind<'v>) {
 538     match function_kind {
 539         FnKind::ItemFn(_, generics, _, _, _, _) => {
 540             visitor.visit_generics(generics);
 541         }
 542         FnKind::Method(_, sig, _) => {
 543             visitor.visit_generics(&sig.generics);
 544             visitor.visit_explicit_self(&sig.explicit_self);
 545         }
 546         FnKind::Closure => {}
 547     }
 548 }
 549
 550 pub fn walk_fn<'v, V: Visitor<'v>>(visitor: &mut V,
 551                                    function_kind: FnKind<'v>,
 552                                    function_declaration: &'v FnDecl,
 553                                    function_body: &'v Block,
 554                                    _span: Span) {
 555     walk_fn_decl(visitor, function_declaration);
 556     walk_fn_kind(visitor, function_kind);
 557     visitor.visit_block(function_body)
 558 }
 559
 560 pub fn walk_trait_item<'v, V: Visitor<'v>>(visitor: &mut V, trait_item: &'v TraitItem) {
 561     visitor.visit_ident(trait_item.span, trait_item.ident);
 562     walk_list!(visitor, visit_attribute, &trait_item.attrs);
 563     match trait_item.node {
 564         ConstTraitItem(ref ty, ref default) => {
 565             visitor.visit_ty(ty);
 566             walk_list!(visitor, visit_expr, default);
 567         }
 568         MethodTraitItem(ref sig, None) => {
 569             visitor.visit_explicit_self(&sig.explicit_self);
 570             visitor.visit_generics(&sig.generics);
 571             walk_fn_decl(visitor, &sig.decl);
 572         }
 573         MethodTraitItem(ref sig, Some(ref body)) => {
 574             visitor.visit_fn(FnKind::Method(trait_item.ident, sig, None), &sig.decl,
 575                              body, trait_item.span, trait_item.id);
 576         }
 577         TypeTraitItem(ref bounds, ref default) => {
 578             walk_list!(visitor, visit_ty_param_bound, bounds);
 579             walk_list!(visitor, visit_ty, default);
 580         }
 581     }
 582 }
 583
 584 pub fn walk_impl_item<'v, V: Visitor<'v>>(visitor: &mut V, impl_item: &'v ImplItem) {
 585     visitor.visit_ident(impl_item.span, impl_item.ident);
 586     walk_list!(visitor, visit_attribute, &impl_item.attrs);
 587     match impl_item.node {
 588         ConstImplItem(ref ty, ref expr) => {
 589             visitor.visit_ty(ty);
 590             visitor.visit_expr(expr);
 591         }
 592         MethodImplItem(ref sig, ref body) => {
 593             visitor.visit_fn(FnKind::Method(impl_item.ident, sig, Some(impl_item.vis)), &sig.decl,
 594                              body, impl_item.span, impl_item.id);
 595         }
 596         TypeImplItem(ref ty) => {
 597             visitor.visit_ty(ty);
 598         }
 599         MacImplItem(ref mac) => {
 600             visitor.visit_mac(mac);
 601         }
 602     }
 603 }
 604
 605 pub fn walk_struct_def<'v, V: Visitor<'v>>(visitor: &mut V,
 606                                            struct_definition: &'v VariantData) {
 607     walk_list!(visitor, visit_struct_field, struct_definition.fields());
 608 }
 609
 610 pub fn walk_struct_field<'v, V: Visitor<'v>>(visitor: &mut V,
 611                                              struct_field: &'v StructField) {
 612     walk_opt_ident(visitor, struct_field.span, struct_field.node.ident());
 613     visitor.visit_ty(&struct_field.node.ty);
 614     walk_list!(visitor, visit_attribute, &struct_field.node.attrs);
 615 }
 616
 617 pub fn walk_block<'v, V: Visitor<'v>>(visitor: &mut V, block: &'v Block) {
 618     walk_list!(visitor, visit_stmt, &block.stmts);
 619     walk_list!(visitor, visit_expr, &block.expr);
 620 }
 621
 622 pub fn walk_stmt<'v, V: Visitor<'v>>(visitor: &mut V, statement: &'v Stmt) {
 623     match statement.node {
 624         StmtDecl(ref declaration, _) => visitor.visit_decl(declaration),
 625         StmtExpr(ref expression, _) | StmtSemi(ref expression, _) => {
 626             visitor.visit_expr(expression)
 627         }
 628         StmtMac(ref mac, _) => visitor.visit_mac(mac),
 629     }
 630 }
 631
 632 pub fn walk_decl<'v, V: Visitor<'v>>(visitor: &mut V, declaration: &'v Decl) {
 633     match declaration.node {
 634         DeclLocal(ref local) => visitor.visit_local(local),
 635         DeclItem(ref item) => visitor.visit_item(item),
 636     }
 637 }
 638
 639 pub fn walk_mac<'v, V: Visitor<'v>>(_: &mut V, _: &'v Mac) {
 640     // Empty!
 641 }
 642
 643 pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr) {
 644     match expression.node {
 645         ExprBox(ref subexpression) => {
 646             visitor.visit_expr(subexpression)
 647         }
 648         ExprInPlace(ref place, ref subexpression) => {
 649             visitor.visit_expr(place);
 650             visitor.visit_expr(subexpression)
 651         }
 652         ExprVec(ref subexpressions) => {
 653             walk_list!(visitor, visit_expr, subexpressions);
 654         }
 655         ExprRepeat(ref element, ref count) => {
 656             visitor.visit_expr(element);
 657             visitor.visit_expr(count)
 658         }
 659         ExprStruct(ref path, ref fields, ref optional_base) => {
 660             visitor.visit_path(path, expression.id);
 661             for field in fields {
 662                 visitor.visit_ident(field.ident.span, field.ident.node);
 663                 visitor.visit_expr(&field.expr)
 664             }
 665             walk_list!(visitor, visit_expr, optional_base);
 666         }
 667         ExprTup(ref subexpressions) => {
 668             walk_list!(visitor, visit_expr, subexpressions);
 669         }
 670         ExprCall(ref callee_expression, ref arguments) => {
 671             walk_list!(visitor, visit_expr, arguments);
 672             visitor.visit_expr(callee_expression)
 673         }
 674         ExprMethodCall(ref ident, ref types, ref arguments) => {
 675             visitor.visit_ident(ident.span, ident.node);
 676             walk_list!(visitor, visit_expr, arguments);
 677             walk_list!(visitor, visit_ty, types);
 678         }
 679         ExprBinary(_, ref left_expression, ref right_expression) => {
 680             visitor.visit_expr(left_expression);
 681             visitor.visit_expr(right_expression)
 682         }
 683         ExprAddrOf(_, ref subexpression) | ExprUnary(_, ref subexpression) => {
 684             visitor.visit_expr(subexpression)
 685         }
 686         ExprLit(_) => {}
 687         ExprCast(ref subexpression, ref typ) => {
 688             visitor.visit_expr(subexpression);
 689             visitor.visit_ty(typ)
 690         }
 691         ExprIf(ref head_expression, ref if_block, ref optional_else) => {
 692             visitor.visit_expr(head_expression);
 693             visitor.visit_block(if_block);
 694             walk_list!(visitor, visit_expr, optional_else);
 695         }
 696         ExprWhile(ref subexpression, ref block, opt_ident) => {
 697             visitor.visit_expr(subexpression);
 698             visitor.visit_block(block);
 699             walk_opt_ident(visitor, expression.span, opt_ident)
 700         }
 701         ExprIfLet(ref pattern, ref subexpression, ref if_block, ref optional_else) => {
 702             visitor.visit_pat(pattern);
 703             visitor.visit_expr(subexpression);
 704             visitor.visit_block(if_block);
 705             walk_list!(visitor, visit_expr, optional_else);
 706         }
 707         ExprWhileLet(ref pattern, ref subexpression, ref block, opt_ident) => {
 708             visitor.visit_pat(pattern);
 709             visitor.visit_expr(subexpression);
 710             visitor.visit_block(block);
 711             walk_opt_ident(visitor, expression.span, opt_ident)
 712         }
 713         ExprForLoop(ref pattern, ref subexpression, ref block, opt_ident) => {
 714             visitor.visit_pat(pattern);
 715             visitor.visit_expr(subexpression);
 716             visitor.visit_block(block);
 717             walk_opt_ident(visitor, expression.span, opt_ident)
 718         }
 719         ExprLoop(ref block, opt_ident) => {
 720             visitor.visit_block(block);
 721             walk_opt_ident(visitor, expression.span, opt_ident)
 722         }
 723         ExprMatch(ref subexpression, ref arms) => {
 724             visitor.visit_expr(subexpression);
 725             walk_list!(visitor, visit_arm, arms);
 726         }
 727         ExprClosure(_, ref function_declaration, ref body) => {
 728             visitor.visit_fn(FnKind::Closure,
 729                              function_declaration,
 730                              body,
 731                              expression.span,
 732                              expression.id)
 733         }
 734         ExprBlock(ref block) => visitor.visit_block(block),
 735         ExprAssign(ref left_hand_expression, ref right_hand_expression) => {
 736             visitor.visit_expr(right_hand_expression);
 737             visitor.visit_expr(left_hand_expression)
 738         }
 739         ExprAssignOp(_, ref left_expression, ref right_expression) => {
 740             visitor.visit_expr(right_expression);
 741             visitor.visit_expr(left_expression)
 742         }
 743         ExprField(ref subexpression, ref ident) => {
 744             visitor.visit_expr(subexpression);
 745             visitor.visit_ident(ident.span, ident.node);
 746         }
 747         ExprTupField(ref subexpression, _) => {
 748             visitor.visit_expr(subexpression);
 749         }
 750         ExprIndex(ref main_expression, ref index_expression) => {
 751             visitor.visit_expr(main_expression);
 752             visitor.visit_expr(index_expression)
 753         }
 754         ExprRange(ref start, ref end) => {
 755             walk_list!(visitor, visit_expr, start);
 756             walk_list!(visitor, visit_expr, end);
 757         }
 758         ExprPath(ref maybe_qself, ref path) => {
 759             if let Some(ref qself) = *maybe_qself {
 760                 visitor.visit_ty(&qself.ty);
 761             }
 762             visitor.visit_path(path, expression.id)
 763         }
 764         ExprBreak(ref opt_sp_ident) | ExprAgain(ref opt_sp_ident) => {
 765             for sp_ident in opt_sp_ident {
 766                 visitor.visit_ident(sp_ident.span, sp_ident.node);
 767             }
 768         }
 769         ExprRet(ref optional_expression) => {
 770             walk_list!(visitor, visit_expr, optional_expression);
 771         }
 772         ExprMac(ref mac) => visitor.visit_mac(mac),
 773         ExprParen(ref subexpression) => {
 774             visitor.visit_expr(subexpression)
 775         }
 776         ExprInlineAsm(ref ia) => {
 777             for &(_, ref input) in &ia.inputs {
 778                 visitor.visit_expr(&input)
 779             }
 780             for &(_, ref output, _) in &ia.outputs {
 781                 visitor.visit_expr(&output)
 782             }
 783         }
 784     }
 785
 786     visitor.visit_expr_post(expression)
 787 }
 788
 789 pub fn walk_arm<'v, V: Visitor<'v>>(visitor: &mut V, arm: &'v Arm) {
 790     walk_list!(visitor, visit_pat, &arm.pats);
 791     walk_list!(visitor, visit_expr, &arm.guard);
 792     visitor.visit_expr(&arm.body);
 793     walk_list!(visitor, visit_attribute, &arm.attrs);
 794 }