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 syntax_pos::Span;
  29 use codemap::Spanned;
  30 use parse::token::Token;
  31 use tokenstream::{TokenTree, TokenStream};
  32
  33 #[derive(Copy, Clone, PartialEq, Eq)]
  34 pub enum FnKind<'a> {
  35     /// fn foo() or extern "Abi" fn foo()
  36     ItemFn(Ident, Unsafety, Spanned<Constness>, Abi, &'a Visibility, &'a Block),
  37
  38     /// fn foo(&self)
  39     Method(Ident, &'a MethodSig, Option<&'a Visibility>, &'a Block),
  40
  41     /// |x, y| body
  42     Closure(&'a Expr),
  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<'ast>: 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         walk_ident(self, span, ident);
  60     }
  61     fn visit_mod(&mut self, m: &'ast Mod, _s: Span, _attrs: &[Attribute], _n: NodeId) {
  62         walk_mod(self, m);
  63     }
  64     fn visit_foreign_item(&mut self, i: &'ast ForeignItem) { walk_foreign_item(self, i) }
  65     fn visit_global_asm(&mut self, ga: &'ast GlobalAsm) { walk_global_asm(self, ga) }
  66     fn visit_item(&mut self, i: &'ast Item) { walk_item(self, i) }
  67     fn visit_local(&mut self, l: &'ast Local) { walk_local(self, l) }
  68     fn visit_block(&mut self, b: &'ast Block) { walk_block(self, b) }
  69     fn visit_stmt(&mut self, s: &'ast Stmt) { walk_stmt(self, s) }
  70     fn visit_arm(&mut self, a: &'ast Arm) { walk_arm(self, a) }
  71     fn visit_pat(&mut self, p: &'ast Pat) { walk_pat(self, p) }
  72     fn visit_expr(&mut self, ex: &'ast Expr) { walk_expr(self, ex) }
  73     fn visit_expr_post(&mut self, _ex: &'ast Expr) { }
  74     fn visit_ty(&mut self, t: &'ast Ty) { walk_ty(self, t) }
  75     fn visit_generic_param(&mut self, param: &'ast GenericParam) { walk_generic_param(self, param) }
  76     fn visit_generics(&mut self, g: &'ast Generics) { walk_generics(self, g) }
  77     fn visit_where_predicate(&mut self, p: &'ast WherePredicate) {
  78         walk_where_predicate(self, p)
  79     }
  80     fn visit_fn(&mut self, fk: FnKind<'ast>, fd: &'ast FnDecl, s: Span, _: NodeId) {
  81         walk_fn(self, fk, fd, s)
  82     }
  83     fn visit_trait_item(&mut self, ti: &'ast TraitItem) { walk_trait_item(self, ti) }
  84     fn visit_impl_item(&mut self, ii: &'ast ImplItem) { walk_impl_item(self, ii) }
  85     fn visit_trait_ref(&mut self, t: &'ast TraitRef) { walk_trait_ref(self, t) }
  86     fn visit_ty_param_bound(&mut self, bounds: &'ast TyParamBound) {
  87         walk_ty_param_bound(self, bounds)
  88     }
  89     fn visit_poly_trait_ref(&mut self, t: &'ast PolyTraitRef, m: &'ast TraitBoundModifier) {
  90         walk_poly_trait_ref(self, t, m)
  91     }
  92     fn visit_variant_data(&mut self, s: &'ast VariantData, _: Ident,
  93                           _: &'ast Generics, _: NodeId, _: Span) {
  94         walk_struct_def(self, s)
  95     }
  96     fn visit_struct_field(&mut self, s: &'ast StructField) { walk_struct_field(self, s) }
  97     fn visit_enum_def(&mut self, enum_definition: &'ast EnumDef,
  98                       generics: &'ast Generics, item_id: NodeId, _: Span) {
  99         walk_enum_def(self, enum_definition, generics, item_id)
 100     }
 101     fn visit_variant(&mut self, v: &'ast Variant, g: &'ast Generics, item_id: NodeId) {
 102         walk_variant(self, v, g, item_id)
 103     }
 104     fn visit_label(&mut self, label: &'ast Label) {
 105         walk_label(self, label)
 106     }
 107     fn visit_lifetime(&mut self, lifetime: &'ast Lifetime) {
 108         walk_lifetime(self, lifetime)
 109     }
 110     fn visit_mac(&mut self, _mac: &'ast Mac) {
 111         panic!("visit_mac disabled by default");
 112         // NB: see note about macros above.
 113         // if you really want a visitor that
 114         // works on macros, use this
 115         // definition in your trait impl:
 116         // visit::walk_mac(self, _mac)
 117     }
 118     fn visit_mac_def(&mut self, _mac: &'ast MacroDef, _id: NodeId) {
 119         // Nothing to do
 120     }
 121     fn visit_path(&mut self, path: &'ast Path, _id: NodeId) {
 122         walk_path(self, path)
 123     }
 124     fn visit_use_tree(&mut self, use_tree: &'ast UseTree, id: NodeId, _nested: bool) {
 125         walk_use_tree(self, use_tree, id)
 126     }
 127     fn visit_path_segment(&mut self, path_span: Span, path_segment: &'ast PathSegment) {
 128         walk_path_segment(self, path_span, path_segment)
 129     }
 130     fn visit_path_parameters(&mut self, path_span: Span, path_parameters: &'ast PathParameters) {
 131         walk_path_parameters(self, path_span, path_parameters)
 132     }
 133     fn visit_assoc_type_binding(&mut self, type_binding: &'ast TypeBinding) {
 134         walk_assoc_type_binding(self, type_binding)
 135     }
 136     fn visit_attribute(&mut self, attr: &'ast Attribute) {
 137         walk_attribute(self, attr)
 138     }
 139     fn visit_tt(&mut self, tt: TokenTree) {
 140         walk_tt(self, tt)
 141     }
 142     fn visit_tts(&mut self, tts: TokenStream) {
 143         walk_tts(self, tts)
 144     }
 145     fn visit_token(&mut self, _t: Token) {}
 146     // FIXME: add `visit_interpolated` and `walk_interpolated`
 147     fn visit_vis(&mut self, vis: &'ast Visibility) {
 148         walk_vis(self, vis)
 149     }
 150     fn visit_fn_ret_ty(&mut self, ret_ty: &'ast FunctionRetTy) {
 151         walk_fn_ret_ty(self, ret_ty)
 152     }
 153 }
 154
 155 #[macro_export]
 156 macro_rules! walk_list {
 157     ($visitor: expr, $method: ident, $list: expr) => {
 158         for elem in $list {
 159             $visitor.$method(elem)
 160         }
 161     };
 162     ($visitor: expr, $method: ident, $list: expr, $($extra_args: expr),*) => {
 163         for elem in $list {
 164             $visitor.$method(elem, $($extra_args,)*)
 165         }
 166     }
 167 }
 168
 169 pub fn walk_ident<'a, V: Visitor<'a>>(visitor: &mut V, span: Span, ident: Ident) {
 170     visitor.visit_name(span, ident.name);
 171 }
 172
 173 pub fn walk_crate<'a, V: Visitor<'a>>(visitor: &mut V, krate: &'a Crate) {
 174     visitor.visit_mod(&krate.module, krate.span, &krate.attrs, CRATE_NODE_ID);
 175     walk_list!(visitor, visit_attribute, &krate.attrs);
 176 }
 177
 178 pub fn walk_mod<'a, V: Visitor<'a>>(visitor: &mut V, module: &'a Mod) {
 179     walk_list!(visitor, visit_item, &module.items);
 180 }
 181
 182 pub fn walk_local<'a, V: Visitor<'a>>(visitor: &mut V, local: &'a Local) {
 183     for attr in local.attrs.iter() {
 184         visitor.visit_attribute(attr);
 185     }
 186     visitor.visit_pat(&local.pat);
 187     walk_list!(visitor, visit_ty, &local.ty);
 188     walk_list!(visitor, visit_expr, &local.init);
 189 }
 190
 191 pub fn walk_label<'a, V: Visitor<'a>>(visitor: &mut V, label: &'a Label) {
 192     visitor.visit_ident(label.span, label.ident);
 193 }
 194
 195 pub fn walk_lifetime<'a, V: Visitor<'a>>(visitor: &mut V, lifetime: &'a Lifetime) {
 196     visitor.visit_ident(lifetime.span, lifetime.ident);
 197 }
 198
 199 pub fn walk_poly_trait_ref<'a, V>(visitor: &mut V,
 200                                   trait_ref: &'a PolyTraitRef,
 201                                   _: &TraitBoundModifier)
 202     where V: Visitor<'a>,
 203 {
 204     walk_list!(visitor, visit_generic_param, &trait_ref.bound_generic_params);
 205     visitor.visit_trait_ref(&trait_ref.trait_ref);
 206 }
 207
 208 pub fn walk_trait_ref<'a, V: Visitor<'a>>(visitor: &mut V, trait_ref: &'a TraitRef) {
 209     visitor.visit_path(&trait_ref.path, trait_ref.ref_id)
 210 }
 211
 212 pub fn walk_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a Item) {
 213     visitor.visit_vis(&item.vis);
 214     visitor.visit_ident(item.span, item.ident);
 215     match item.node {
 216         ItemKind::ExternCrate(orig_name) => {
 217             if let Some(orig_name) = orig_name {
 218                 visitor.visit_name(item.span, orig_name);
 219             }
 220         }
 221         ItemKind::Use(ref use_tree) => {
 222             visitor.visit_use_tree(use_tree, item.id, false)
 223         }
 224         ItemKind::Static(ref typ, _, ref expr) |
 225         ItemKind::Const(ref typ, ref expr) => {
 226             visitor.visit_ty(typ);
 227             visitor.visit_expr(expr);
 228         }
 229         ItemKind::Fn(ref declaration, unsafety, constness, abi, ref generics, ref body) => {
 230             visitor.visit_generics(generics);
 231             visitor.visit_fn(FnKind::ItemFn(item.ident, unsafety,
 232                                             constness, abi, &item.vis, body),
 233                              declaration,
 234                              item.span,
 235                              item.id)
 236         }
 237         ItemKind::Mod(ref module) => {
 238             visitor.visit_mod(module, item.span, &item.attrs, item.id)
 239         }
 240         ItemKind::ForeignMod(ref foreign_module) => {
 241             walk_list!(visitor, visit_foreign_item, &foreign_module.items);
 242         }
 243         ItemKind::GlobalAsm(ref ga) => visitor.visit_global_asm(ga),
 244         ItemKind::Ty(ref typ, ref type_parameters) => {
 245             visitor.visit_ty(typ);
 246             visitor.visit_generics(type_parameters)
 247         }
 248         ItemKind::Enum(ref enum_definition, ref type_parameters) => {
 249             visitor.visit_generics(type_parameters);
 250             visitor.visit_enum_def(enum_definition, type_parameters, item.id, item.span)
 251         }
 252         ItemKind::Impl(_, _, _,
 253                  ref type_parameters,
 254                  ref opt_trait_reference,
 255                  ref typ,
 256                  ref impl_items) => {
 257             visitor.visit_generics(type_parameters);
 258             walk_list!(visitor, visit_trait_ref, opt_trait_reference);
 259             visitor.visit_ty(typ);
 260             walk_list!(visitor, visit_impl_item, impl_items);
 261         }
 262         ItemKind::Struct(ref struct_definition, ref generics) |
 263         ItemKind::Union(ref struct_definition, ref generics) => {
 264             visitor.visit_generics(generics);
 265             visitor.visit_variant_data(struct_definition, item.ident,
 266                                      generics, item.id, item.span);
 267         }
 268         ItemKind::Trait(.., ref generics, ref bounds, ref methods) => {
 269             visitor.visit_generics(generics);
 270             walk_list!(visitor, visit_ty_param_bound, bounds);
 271             walk_list!(visitor, visit_trait_item, methods);
 272         }
 273         ItemKind::TraitAlias(ref generics, ref bounds) => {
 274             visitor.visit_generics(generics);
 275             walk_list!(visitor, visit_ty_param_bound, bounds);
 276         }
 277         ItemKind::Mac(ref mac) => visitor.visit_mac(mac),
 278         ItemKind::MacroDef(ref ts) => visitor.visit_mac_def(ts, item.id),
 279     }
 280     walk_list!(visitor, visit_attribute, &item.attrs);
 281 }
 282
 283 pub fn walk_enum_def<'a, V: Visitor<'a>>(visitor: &mut V,
 284                                  enum_definition: &'a EnumDef,
 285                                  generics: &'a Generics,
 286                                  item_id: NodeId) {
 287     walk_list!(visitor, visit_variant, &enum_definition.variants, generics, item_id);
 288 }
 289
 290 pub fn walk_variant<'a, V>(visitor: &mut V,
 291                            variant: &'a Variant,
 292                            generics: &'a Generics,
 293                            item_id: NodeId)
 294     where V: Visitor<'a>,
 295 {
 296     visitor.visit_ident(variant.span, variant.node.name);
 297     visitor.visit_variant_data(&variant.node.data, variant.node.name,
 298                              generics, item_id, variant.span);
 299     walk_list!(visitor, visit_expr, &variant.node.disr_expr);
 300     walk_list!(visitor, visit_attribute, &variant.node.attrs);
 301 }
 302
 303 pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) {
 304     match typ.node {
 305         TyKind::Slice(ref ty) | TyKind::Paren(ref ty) => {
 306             visitor.visit_ty(ty)
 307         }
 308         TyKind::Ptr(ref mutable_type) => {
 309             visitor.visit_ty(&mutable_type.ty)
 310         }
 311         TyKind::Rptr(ref opt_lifetime, ref mutable_type) => {
 312             walk_list!(visitor, visit_lifetime, opt_lifetime);
 313             visitor.visit_ty(&mutable_type.ty)
 314         }
 315         TyKind::Never => {},
 316         TyKind::Tup(ref tuple_element_types) => {
 317             walk_list!(visitor, visit_ty, tuple_element_types);
 318         }
 319         TyKind::BareFn(ref function_declaration) => {
 320             walk_fn_decl(visitor, &function_declaration.decl);
 321             walk_list!(visitor, visit_generic_param, &function_declaration.generic_params);
 322         }
 323         TyKind::Path(ref maybe_qself, ref path) => {
 324             if let Some(ref qself) = *maybe_qself {
 325                 visitor.visit_ty(&qself.ty);
 326             }
 327             visitor.visit_path(path, typ.id);
 328         }
 329         TyKind::Array(ref ty, ref expression) => {
 330             visitor.visit_ty(ty);
 331             visitor.visit_expr(expression)
 332         }
 333         TyKind::TraitObject(ref bounds, ..) |
 334         TyKind::ImplTrait(ref bounds) => {
 335             walk_list!(visitor, visit_ty_param_bound, bounds);
 336         }
 337         TyKind::Typeof(ref expression) => {
 338             visitor.visit_expr(expression)
 339         }
 340         TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => {}
 341         TyKind::Mac(ref mac) => {
 342             visitor.visit_mac(mac)
 343         }
 344     }
 345 }
 346
 347 pub fn walk_path<'a, V: Visitor<'a>>(visitor: &mut V, path: &'a Path) {
 348     for segment in &path.segments {
 349         visitor.visit_path_segment(path.span, segment);
 350     }
 351 }
 352
 353 pub fn walk_use_tree<'a, V: Visitor<'a>>(
 354     visitor: &mut V, use_tree: &'a UseTree, id: NodeId,
 355 ) {
 356     visitor.visit_path(&use_tree.prefix, id);
 357     match use_tree.kind {
 358         UseTreeKind::Simple(rename) => {
 359             if let Some(rename) = rename {
 360                 visitor.visit_ident(use_tree.span, rename);
 361             }
 362         }
 363         UseTreeKind::Glob => {},
 364         UseTreeKind::Nested(ref use_trees) => {
 365             for &(ref nested_tree, nested_id) in use_trees {
 366                 visitor.visit_use_tree(nested_tree, nested_id, true);
 367             }
 368         }
 369     }
 370 }
 371
 372 pub fn walk_path_segment<'a, V: Visitor<'a>>(visitor: &mut V,
 373                                              path_span: Span,
 374                                              segment: &'a PathSegment) {
 375     visitor.visit_ident(path_span, segment.identifier);
 376     if let Some(ref parameters) = segment.parameters {
 377         visitor.visit_path_parameters(path_span, parameters);
 378     }
 379 }
 380
 381 pub fn walk_path_parameters<'a, V>(visitor: &mut V,
 382                                    _path_span: Span,
 383                                    path_parameters: &'a PathParameters)
 384     where V: Visitor<'a>,
 385 {
 386     match *path_parameters {
 387         PathParameters::AngleBracketed(ref data) => {
 388             walk_list!(visitor, visit_ty, &data.types);
 389             walk_list!(visitor, visit_lifetime, &data.lifetimes);
 390             walk_list!(visitor, visit_assoc_type_binding, &data.bindings);
 391         }
 392         PathParameters::Parenthesized(ref data) => {
 393             walk_list!(visitor, visit_ty, &data.inputs);
 394             walk_list!(visitor, visit_ty, &data.output);
 395         }
 396     }
 397 }
 398
 399 pub fn walk_assoc_type_binding<'a, V: Visitor<'a>>(visitor: &mut V,
 400                                                    type_binding: &'a TypeBinding) {
 401     visitor.visit_ident(type_binding.span, type_binding.ident);
 402     visitor.visit_ty(&type_binding.ty);
 403 }
 404
 405 pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) {
 406     match pattern.node {
 407         PatKind::TupleStruct(ref path, ref children, _) => {
 408             visitor.visit_path(path, pattern.id);
 409             walk_list!(visitor, visit_pat, children);
 410         }
 411         PatKind::Path(ref opt_qself, ref path) => {
 412             if let Some(ref qself) = *opt_qself {
 413                 visitor.visit_ty(&qself.ty);
 414             }
 415             visitor.visit_path(path, pattern.id)
 416         }
 417         PatKind::Struct(ref path, ref fields, _) => {
 418             visitor.visit_path(path, pattern.id);
 419             for field in fields {
 420                 walk_list!(visitor, visit_attribute, field.node.attrs.iter());
 421                 visitor.visit_ident(field.span, field.node.ident);
 422                 visitor.visit_pat(&field.node.pat)
 423             }
 424         }
 425         PatKind::Tuple(ref tuple_elements, _) => {
 426             walk_list!(visitor, visit_pat, tuple_elements);
 427         }
 428         PatKind::Box(ref subpattern) |
 429         PatKind::Ref(ref subpattern, _) |
 430         PatKind::Paren(ref subpattern) => {
 431             visitor.visit_pat(subpattern)
 432         }
 433         PatKind::Ident(_, ref pth1, ref optional_subpattern) => {
 434             visitor.visit_ident(pth1.span, pth1.node);
 435             walk_list!(visitor, visit_pat, optional_subpattern);
 436         }
 437         PatKind::Lit(ref expression) => visitor.visit_expr(expression),
 438         PatKind::Range(ref lower_bound, ref upper_bound, _) => {
 439             visitor.visit_expr(lower_bound);
 440             visitor.visit_expr(upper_bound);
 441         }
 442         PatKind::Wild => (),
 443         PatKind::Slice(ref prepatterns, ref slice_pattern, ref postpatterns) => {
 444             walk_list!(visitor, visit_pat, prepatterns);
 445             walk_list!(visitor, visit_pat, slice_pattern);
 446             walk_list!(visitor, visit_pat, postpatterns);
 447         }
 448         PatKind::Mac(ref mac) => visitor.visit_mac(mac),
 449     }
 450 }
 451
 452 pub fn walk_foreign_item<'a, V: Visitor<'a>>(visitor: &mut V, foreign_item: &'a ForeignItem) {
 453     visitor.visit_vis(&foreign_item.vis);
 454     visitor.visit_ident(foreign_item.span, foreign_item.ident);
 455
 456     match foreign_item.node {
 457         ForeignItemKind::Fn(ref function_declaration, ref generics) => {
 458             walk_fn_decl(visitor, function_declaration);
 459             visitor.visit_generics(generics)
 460         }
 461         ForeignItemKind::Static(ref typ, _) => visitor.visit_ty(typ),
 462         ForeignItemKind::Ty => (),
 463     }
 464
 465     walk_list!(visitor, visit_attribute, &foreign_item.attrs);
 466 }
 467
 468 pub fn walk_global_asm<'a, V: Visitor<'a>>(_: &mut V, _: &'a GlobalAsm) {
 469     // Empty!
 470 }
 471
 472 pub fn walk_ty_param_bound<'a, V: Visitor<'a>>(visitor: &mut V, bound: &'a TyParamBound) {
 473     match *bound {
 474         TraitTyParamBound(ref typ, ref modifier) => {
 475             visitor.visit_poly_trait_ref(typ, modifier);
 476         }
 477         RegionTyParamBound(ref lifetime) => {
 478             visitor.visit_lifetime(lifetime);
 479         }
 480     }
 481 }
 482
 483 pub fn walk_generic_param<'a, V: Visitor<'a>>(visitor: &mut V, param: &'a GenericParam) {
 484     match *param {
 485         GenericParam::Lifetime(ref l) => {
 486             visitor.visit_lifetime(&l.lifetime);
 487             walk_list!(visitor, visit_lifetime, &l.bounds);
 488             walk_list!(visitor, visit_attribute, &*l.attrs);
 489         }
 490         GenericParam::Type(ref t) => {
 491             visitor.visit_ident(t.span, t.ident);
 492             walk_list!(visitor, visit_ty_param_bound, &t.bounds);
 493             walk_list!(visitor, visit_ty, &t.default);
 494             walk_list!(visitor, visit_attribute, &*t.attrs);
 495         }
 496     }
 497 }
 498
 499 pub fn walk_generics<'a, V: Visitor<'a>>(visitor: &mut V, generics: &'a Generics) {
 500     walk_list!(visitor, visit_generic_param, &generics.params);
 501     walk_list!(visitor, visit_where_predicate, &generics.where_clause.predicates);
 502 }
 503
 504 pub fn walk_where_predicate<'a, V: Visitor<'a>>(visitor: &mut V, predicate: &'a WherePredicate) {
 505     match *predicate {
 506         WherePredicate::BoundPredicate(WhereBoundPredicate{ref bounded_ty,
 507                                                            ref bounds,
 508                                                            ref bound_generic_params,
 509                                                            ..}) => {
 510             visitor.visit_ty(bounded_ty);
 511             walk_list!(visitor, visit_ty_param_bound, bounds);
 512             walk_list!(visitor, visit_generic_param, bound_generic_params);
 513         }
 514         WherePredicate::RegionPredicate(WhereRegionPredicate{ref lifetime,
 515                                                              ref bounds,
 516                                                              ..}) => {
 517             visitor.visit_lifetime(lifetime);
 518             walk_list!(visitor, visit_lifetime, bounds);
 519         }
 520         WherePredicate::EqPredicate(WhereEqPredicate{ref lhs_ty,
 521                                                      ref rhs_ty,
 522                                                      ..}) => {
 523             visitor.visit_ty(lhs_ty);
 524             visitor.visit_ty(rhs_ty);
 525         }
 526     }
 527 }
 528
 529 pub fn walk_fn_ret_ty<'a, V: Visitor<'a>>(visitor: &mut V, ret_ty: &'a FunctionRetTy) {
 530     if let FunctionRetTy::Ty(ref output_ty) = *ret_ty {
 531         visitor.visit_ty(output_ty)
 532     }
 533 }
 534
 535 pub fn walk_fn_decl<'a, V: Visitor<'a>>(visitor: &mut V, function_declaration: &'a FnDecl) {
 536     for argument in &function_declaration.inputs {
 537         visitor.visit_pat(&argument.pat);
 538         visitor.visit_ty(&argument.ty)
 539     }
 540     visitor.visit_fn_ret_ty(&function_declaration.output)
 541 }
 542
 543 pub fn walk_fn<'a, V>(visitor: &mut V, kind: FnKind<'a>, declaration: &'a FnDecl, _span: Span)
 544     where V: Visitor<'a>,
 545 {
 546     match kind {
 547         FnKind::ItemFn(_, _, _, _, _, body) => {
 548             walk_fn_decl(visitor, declaration);
 549             visitor.visit_block(body);
 550         }
 551         FnKind::Method(_, _, _, body) => {
 552             walk_fn_decl(visitor, declaration);
 553             visitor.visit_block(body);
 554         }
 555         FnKind::Closure(body) => {
 556             walk_fn_decl(visitor, declaration);
 557             visitor.visit_expr(body);
 558         }
 559     }
 560 }
 561
 562 pub fn walk_trait_item<'a, V: Visitor<'a>>(visitor: &mut V, trait_item: &'a TraitItem) {
 563     visitor.visit_ident(trait_item.span, trait_item.ident);
 564     walk_list!(visitor, visit_attribute, &trait_item.attrs);
 565     visitor.visit_generics(&trait_item.generics);
 566     match trait_item.node {
 567         TraitItemKind::Const(ref ty, ref default) => {
 568             visitor.visit_ty(ty);
 569             walk_list!(visitor, visit_expr, default);
 570         }
 571         TraitItemKind::Method(ref sig, None) => {
 572             walk_fn_decl(visitor, &sig.decl);
 573         }
 574         TraitItemKind::Method(ref sig, Some(ref body)) => {
 575             visitor.visit_fn(FnKind::Method(trait_item.ident, sig, None, body),
 576                              &sig.decl, trait_item.span, trait_item.id);
 577         }
 578         TraitItemKind::Type(ref bounds, ref default) => {
 579             walk_list!(visitor, visit_ty_param_bound, bounds);
 580             walk_list!(visitor, visit_ty, default);
 581         }
 582         TraitItemKind::Macro(ref mac) => {
 583             visitor.visit_mac(mac);
 584         }
 585     }
 586 }
 587
 588 pub fn walk_impl_item<'a, V: Visitor<'a>>(visitor: &mut V, impl_item: &'a ImplItem) {
 589     visitor.visit_vis(&impl_item.vis);
 590     visitor.visit_ident(impl_item.span, impl_item.ident);
 591     walk_list!(visitor, visit_attribute, &impl_item.attrs);
 592     visitor.visit_generics(&impl_item.generics);
 593     match impl_item.node {
 594         ImplItemKind::Const(ref ty, ref expr) => {
 595             visitor.visit_ty(ty);
 596             visitor.visit_expr(expr);
 597         }
 598         ImplItemKind::Method(ref sig, ref body) => {
 599             visitor.visit_fn(FnKind::Method(impl_item.ident, sig, Some(&impl_item.vis), body),
 600                              &sig.decl, impl_item.span, impl_item.id);
 601         }
 602         ImplItemKind::Type(ref ty) => {
 603             visitor.visit_ty(ty);
 604         }
 605         ImplItemKind::Macro(ref mac) => {
 606             visitor.visit_mac(mac);
 607         }
 608     }
 609 }
 610
 611 pub fn walk_struct_def<'a, V: Visitor<'a>>(visitor: &mut V, struct_definition: &'a VariantData) {
 612     walk_list!(visitor, visit_struct_field, struct_definition.fields());
 613 }
 614
 615 pub fn walk_struct_field<'a, V: Visitor<'a>>(visitor: &mut V, struct_field: &'a StructField) {
 616     visitor.visit_vis(&struct_field.vis);
 617     if let Some(ident) = struct_field.ident {
 618         visitor.visit_ident(struct_field.span, ident);
 619     }
 620     visitor.visit_ty(&struct_field.ty);
 621     walk_list!(visitor, visit_attribute, &struct_field.attrs);
 622 }
 623
 624 pub fn walk_block<'a, V: Visitor<'a>>(visitor: &mut V, block: &'a Block) {
 625     walk_list!(visitor, visit_stmt, &block.stmts);
 626 }
 627
 628 pub fn walk_stmt<'a, V: Visitor<'a>>(visitor: &mut V, statement: &'a Stmt) {
 629     match statement.node {
 630         StmtKind::Local(ref local) => visitor.visit_local(local),
 631         StmtKind::Item(ref item) => visitor.visit_item(item),
 632         StmtKind::Expr(ref expression) | StmtKind::Semi(ref expression) => {
 633             visitor.visit_expr(expression)
 634         }
 635         StmtKind::Mac(ref mac) => {
 636             let (ref mac, _, ref attrs) = **mac;
 637             visitor.visit_mac(mac);
 638             for attr in attrs.iter() {
 639                 visitor.visit_attribute(attr);
 640             }
 641         }
 642     }
 643 }
 644
 645 pub fn walk_mac<'a, V: Visitor<'a>>(_: &mut V, _: &Mac) {
 646     // Empty!
 647 }
 648
 649 pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
 650     for attr in expression.attrs.iter() {
 651         visitor.visit_attribute(attr);
 652     }
 653     match expression.node {
 654         ExprKind::Box(ref subexpression) => {
 655             visitor.visit_expr(subexpression)
 656         }
 657         ExprKind::InPlace(ref place, ref subexpression) => {
 658             visitor.visit_expr(place);
 659             visitor.visit_expr(subexpression)
 660         }
 661         ExprKind::Array(ref subexpressions) => {
 662             walk_list!(visitor, visit_expr, subexpressions);
 663         }
 664         ExprKind::Repeat(ref element, ref count) => {
 665             visitor.visit_expr(element);
 666             visitor.visit_expr(count)
 667         }
 668         ExprKind::Struct(ref path, ref fields, ref optional_base) => {
 669             visitor.visit_path(path, expression.id);
 670             for field in fields {
 671                 walk_list!(visitor, visit_attribute, field.attrs.iter());
 672                 visitor.visit_ident(field.ident.span, field.ident.node);
 673                 visitor.visit_expr(&field.expr)
 674             }
 675             walk_list!(visitor, visit_expr, optional_base);
 676         }
 677         ExprKind::Tup(ref subexpressions) => {
 678             walk_list!(visitor, visit_expr, subexpressions);
 679         }
 680         ExprKind::Call(ref callee_expression, ref arguments) => {
 681             visitor.visit_expr(callee_expression);
 682             walk_list!(visitor, visit_expr, arguments);
 683         }
 684         ExprKind::MethodCall(ref segment, ref arguments) => {
 685             visitor.visit_path_segment(expression.span, segment);
 686             walk_list!(visitor, visit_expr, arguments);
 687         }
 688         ExprKind::Binary(_, ref left_expression, ref right_expression) => {
 689             visitor.visit_expr(left_expression);
 690             visitor.visit_expr(right_expression)
 691         }
 692         ExprKind::AddrOf(_, ref subexpression) | ExprKind::Unary(_, ref subexpression) => {
 693             visitor.visit_expr(subexpression)
 694         }
 695         ExprKind::Lit(_) => {}
 696         ExprKind::Cast(ref subexpression, ref typ) | ExprKind::Type(ref subexpression, ref typ) => {
 697             visitor.visit_expr(subexpression);
 698             visitor.visit_ty(typ)
 699         }
 700         ExprKind::If(ref head_expression, ref if_block, ref optional_else) => {
 701             visitor.visit_expr(head_expression);
 702             visitor.visit_block(if_block);
 703             walk_list!(visitor, visit_expr, optional_else);
 704         }
 705         ExprKind::While(ref subexpression, ref block, ref opt_label) => {
 706             walk_list!(visitor, visit_label, opt_label);
 707             visitor.visit_expr(subexpression);
 708             visitor.visit_block(block);
 709         }
 710         ExprKind::IfLet(ref pats, ref subexpression, ref if_block, ref optional_else) => {
 711             walk_list!(visitor, visit_pat, pats);
 712             visitor.visit_expr(subexpression);
 713             visitor.visit_block(if_block);
 714             walk_list!(visitor, visit_expr, optional_else);
 715         }
 716         ExprKind::WhileLet(ref pats, ref subexpression, ref block, ref opt_label) => {
 717             walk_list!(visitor, visit_label, opt_label);
 718             walk_list!(visitor, visit_pat, pats);
 719             visitor.visit_expr(subexpression);
 720             visitor.visit_block(block);
 721         }
 722         ExprKind::ForLoop(ref pattern, ref subexpression, ref block, ref opt_label) => {
 723             walk_list!(visitor, visit_label, opt_label);
 724             visitor.visit_pat(pattern);
 725             visitor.visit_expr(subexpression);
 726             visitor.visit_block(block);
 727         }
 728         ExprKind::Loop(ref block, ref opt_label) => {
 729             walk_list!(visitor, visit_label, opt_label);
 730             visitor.visit_block(block);
 731         }
 732         ExprKind::Match(ref subexpression, ref arms) => {
 733             visitor.visit_expr(subexpression);
 734             walk_list!(visitor, visit_arm, arms);
 735         }
 736         ExprKind::Closure(_, _, ref function_declaration, ref body, _decl_span) => {
 737             visitor.visit_fn(FnKind::Closure(body),
 738                              function_declaration,
 739                              expression.span,
 740                              expression.id)
 741         }
 742         ExprKind::Block(ref block) => visitor.visit_block(block),
 743         ExprKind::Assign(ref left_hand_expression, ref right_hand_expression) => {
 744             visitor.visit_expr(left_hand_expression);
 745             visitor.visit_expr(right_hand_expression);
 746         }
 747         ExprKind::AssignOp(_, ref left_expression, ref right_expression) => {
 748             visitor.visit_expr(left_expression);
 749             visitor.visit_expr(right_expression);
 750         }
 751         ExprKind::Field(ref subexpression, ref ident) => {
 752             visitor.visit_expr(subexpression);
 753             visitor.visit_ident(ident.span, ident.node);
 754         }
 755         ExprKind::TupField(ref subexpression, _) => {
 756             visitor.visit_expr(subexpression);
 757         }
 758         ExprKind::Index(ref main_expression, ref index_expression) => {
 759             visitor.visit_expr(main_expression);
 760             visitor.visit_expr(index_expression)
 761         }
 762         ExprKind::Range(ref start, ref end, _) => {
 763             walk_list!(visitor, visit_expr, start);
 764             walk_list!(visitor, visit_expr, end);
 765         }
 766         ExprKind::Path(ref maybe_qself, ref path) => {
 767             if let Some(ref qself) = *maybe_qself {
 768                 visitor.visit_ty(&qself.ty);
 769             }
 770             visitor.visit_path(path, expression.id)
 771         }
 772         ExprKind::Break(ref opt_label, ref opt_expr) => {
 773             walk_list!(visitor, visit_label, opt_label);
 774             walk_list!(visitor, visit_expr, opt_expr);
 775         }
 776         ExprKind::Continue(ref opt_label) => {
 777             walk_list!(visitor, visit_label, opt_label);
 778         }
 779         ExprKind::Ret(ref optional_expression) => {
 780             walk_list!(visitor, visit_expr, optional_expression);
 781         }
 782         ExprKind::Mac(ref mac) => visitor.visit_mac(mac),
 783         ExprKind::Paren(ref subexpression) => {
 784             visitor.visit_expr(subexpression)
 785         }
 786         ExprKind::InlineAsm(ref ia) => {
 787             for &(_, ref input) in &ia.inputs {
 788                 visitor.visit_expr(input)
 789             }
 790             for output in &ia.outputs {
 791                 visitor.visit_expr(&output.expr)
 792             }
 793         }
 794         ExprKind::Yield(ref optional_expression) => {
 795             walk_list!(visitor, visit_expr, optional_expression);
 796         }
 797         ExprKind::Try(ref subexpression) => {
 798             visitor.visit_expr(subexpression)
 799         }
 800         ExprKind::Catch(ref body) => {
 801             visitor.visit_block(body)
 802         }
 803     }
 804
 805     visitor.visit_expr_post(expression)
 806 }
 807
 808 pub fn walk_arm<'a, V: Visitor<'a>>(visitor: &mut V, arm: &'a Arm) {
 809     walk_list!(visitor, visit_pat, &arm.pats);
 810     walk_list!(visitor, visit_expr, &arm.guard);
 811     visitor.visit_expr(&arm.body);
 812     walk_list!(visitor, visit_attribute, &arm.attrs);
 813 }
 814
 815 pub fn walk_vis<'a, V: Visitor<'a>>(visitor: &mut V, vis: &'a Visibility) {
 816     if let VisibilityKind::Restricted { ref path, id } = vis.node {
 817         visitor.visit_path(path, id);
 818     }
 819 }
 820
 821 pub fn walk_attribute<'a, V: Visitor<'a>>(visitor: &mut V, attr: &'a Attribute) {
 822     visitor.visit_tts(attr.tokens.clone());
 823 }
 824
 825 pub fn walk_tt<'a, V: Visitor<'a>>(visitor: &mut V, tt: TokenTree) {
 826     match tt {
 827         TokenTree::Token(_, tok) => visitor.visit_token(tok),
 828         TokenTree::Delimited(_, delimed) => visitor.visit_tts(delimed.stream()),
 829     }
 830 }
 831
 832 pub fn walk_tts<'a, V: Visitor<'a>>(visitor: &mut V, tts: TokenStream) {
 833     for tt in tts.trees() {
 834         visitor.visit_tt(tt);
 835     }
 836 }