src/libsyntax/visit.rs

   1 //! AST walker. Each overridden visit method has full control over what
   2 //! happens with its node, it can do its own traversal of the node's children,
   3 //! call `visit::walk_*` to apply the default traversal algorithm, or prevent
   4 //! deeper traversal by doing nothing.
   5 //!
   6 //! Note: it is an important invariant that the default visitor walks the body
   7 //! of a function in "execution order" (more concretely, reverse post-order
   8 //! with respect to the CFG implied by the AST), meaning that if AST node A may
   9 //! execute before AST node B, then A is visited first. The borrow checker in
  10 //! particular relies on this property.
  11 //!
  12 //! Note: walking an AST before macro expansion is probably a bad idea. For
  13 //! instance, a walker looking for item names in a module will miss all of
  14 //! those that are created by the expansion of a macro.
  15
  16 use crate::ast::*;
  17 use crate::parse::token::Token;
  18 use crate::tokenstream::{TokenTree, TokenStream};
  19
  20 use syntax_pos::Span;
  21
  22 #[derive(Copy, Clone)]
  23 pub enum FnKind<'a> {
  24     /// E.g., `fn foo()` or `extern "Abi" fn foo()`.
  25     ItemFn(Ident, &'a FnHeader, &'a Visibility, &'a Block),
  26
  27     /// E.g., `fn foo(&self)`.
  28     Method(Ident, &'a MethodSig, Option<&'a Visibility>, &'a Block),
  29
  30     /// E.g., `|x, y| body`.
  31     Closure(&'a Expr),
  32 }
  33
  34 impl<'a> FnKind<'a> {
  35     pub fn header(&self) -> Option<&'a FnHeader> {
  36         match *self {
  37             FnKind::ItemFn(_, header, _, _) => Some(header),
  38             FnKind::Method(_, sig, _, _) => Some(&sig.header),
  39             FnKind::Closure(_) => None,
  40         }
  41     }
  42 }
  43
  44 /// Each method of the `Visitor` trait is a hook to be potentially
  45 /// overridden. Each method's default implementation recursively visits
  46 /// the substructure of the input via the corresponding `walk` method;
  47 /// e.g., the `visit_mod` method by default calls `visit::walk_mod`.
  48 ///
  49 /// If you want to ensure that your code handles every variant
  50 /// explicitly, you need to override each method. (And you also need
  51 /// to monitor future changes to `Visitor` in case a new method with a
  52 /// new default implementation gets introduced.)
  53 pub trait Visitor<'ast>: Sized {
  54     fn visit_name(&mut self, _span: Span, _name: Name) {
  55         // Nothing to do.
  56     }
  57     fn visit_ident(&mut self, ident: Ident) {
  58         walk_ident(self, ident);
  59     }
  60     fn visit_mod(&mut self, m: &'ast Mod, _s: Span, _attrs: &[Attribute], _n: NodeId) {
  61         walk_mod(self, m);
  62     }
  63     fn visit_foreign_item(&mut self, i: &'ast ForeignItem) { walk_foreign_item(self, i) }
  64     fn visit_global_asm(&mut self, ga: &'ast GlobalAsm) { walk_global_asm(self, ga) }
  65     fn visit_item(&mut self, i: &'ast Item) { walk_item(self, i) }
  66     fn visit_local(&mut self, l: &'ast Local) { walk_local(self, l) }
  67     fn visit_block(&mut self, b: &'ast Block) { walk_block(self, b) }
  68     fn visit_stmt(&mut self, s: &'ast Stmt) { walk_stmt(self, s) }
  69     fn visit_param(&mut self, param: &'ast Param) { walk_param(self, param) }
  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_anon_const(&mut self, c: &'ast AnonConst) { walk_anon_const(self, c) }
  73     fn visit_expr(&mut self, ex: &'ast Expr) { walk_expr(self, ex) }
  74     fn visit_expr_post(&mut self, _ex: &'ast Expr) { }
  75     fn visit_ty(&mut self, t: &'ast Ty) { walk_ty(self, t) }
  76     fn visit_generic_param(&mut self, param: &'ast GenericParam) {
  77         walk_generic_param(self, param)
  78     }
  79     fn visit_generics(&mut self, g: &'ast Generics) { walk_generics(self, g) }
  80     fn visit_where_predicate(&mut self, p: &'ast WherePredicate) {
  81         walk_where_predicate(self, p)
  82     }
  83     fn visit_fn(&mut self, fk: FnKind<'ast>, fd: &'ast FnDecl, s: Span, _: NodeId) {
  84         walk_fn(self, fk, fd, s)
  85     }
  86     fn visit_trait_item(&mut self, ti: &'ast TraitItem) { walk_trait_item(self, ti) }
  87     fn visit_impl_item(&mut self, ii: &'ast ImplItem) { walk_impl_item(self, ii) }
  88     fn visit_trait_ref(&mut self, t: &'ast TraitRef) { walk_trait_ref(self, t) }
  89     fn visit_param_bound(&mut self, bounds: &'ast GenericBound) {
  90         walk_param_bound(self, bounds)
  91     }
  92     fn visit_poly_trait_ref(&mut self, t: &'ast PolyTraitRef, m: &'ast TraitBoundModifier) {
  93         walk_poly_trait_ref(self, t, m)
  94     }
  95     fn visit_variant_data(&mut self, s: &'ast VariantData) {
  96         walk_struct_def(self, s)
  97     }
  98     fn visit_struct_field(&mut self, s: &'ast StructField) { walk_struct_field(self, s) }
  99     fn visit_enum_def(&mut self, enum_definition: &'ast EnumDef,
 100                       generics: &'ast Generics, item_id: NodeId, _: Span) {
 101         walk_enum_def(self, enum_definition, generics, item_id)
 102     }
 103     fn visit_variant(&mut self, v: &'ast Variant) {
 104         walk_variant(self, v)
 105     }
 106     fn visit_label(&mut self, label: &'ast Label) {
 107         walk_label(self, label)
 108     }
 109     fn visit_lifetime(&mut self, lifetime: &'ast Lifetime) {
 110         walk_lifetime(self, lifetime)
 111     }
 112     fn visit_mac(&mut self, _mac: &'ast Mac) {
 113         panic!("visit_mac disabled by default");
 114         // N.B., see note about macros above.
 115         // if you really want a visitor that
 116         // works on macros, use this
 117         // definition in your trait impl:
 118         // visit::walk_mac(self, _mac)
 119     }
 120     fn visit_mac_def(&mut self, _mac: &'ast MacroDef, _id: NodeId) {
 121         // Nothing to do
 122     }
 123     fn visit_path(&mut self, path: &'ast Path, _id: NodeId) {
 124         walk_path(self, path)
 125     }
 126     fn visit_use_tree(&mut self, use_tree: &'ast UseTree, id: NodeId, _nested: bool) {
 127         walk_use_tree(self, use_tree, id)
 128     }
 129     fn visit_path_segment(&mut self, path_span: Span, path_segment: &'ast PathSegment) {
 130         walk_path_segment(self, path_span, path_segment)
 131     }
 132     fn visit_generic_args(&mut self, path_span: Span, generic_args: &'ast GenericArgs) {
 133         walk_generic_args(self, path_span, generic_args)
 134     }
 135     fn visit_generic_arg(&mut self, generic_arg: &'ast GenericArg) {
 136         match generic_arg {
 137             GenericArg::Lifetime(lt) => self.visit_lifetime(lt),
 138             GenericArg::Type(ty) => self.visit_ty(ty),
 139             GenericArg::Const(ct) => self.visit_anon_const(ct),
 140         }
 141     }
 142     fn visit_assoc_ty_constraint(&mut self, constraint: &'ast AssocTyConstraint) {
 143         walk_assoc_ty_constraint(self, constraint)
 144     }
 145     fn visit_attribute(&mut self, attr: &'ast Attribute) {
 146         walk_attribute(self, attr)
 147     }
 148     fn visit_tt(&mut self, tt: TokenTree) {
 149         walk_tt(self, tt)
 150     }
 151     fn visit_tts(&mut self, tts: TokenStream) {
 152         walk_tts(self, tts)
 153     }
 154     fn visit_token(&mut self, _t: Token) {}
 155     // FIXME: add `visit_interpolated` and `walk_interpolated`
 156     fn visit_vis(&mut self, vis: &'ast Visibility) {
 157         walk_vis(self, vis)
 158     }
 159     fn visit_fn_ret_ty(&mut self, ret_ty: &'ast FunctionRetTy) {
 160         walk_fn_ret_ty(self, ret_ty)
 161     }
 162     fn visit_fn_header(&mut self, _header: &'ast FnHeader) {
 163         // Nothing to do
 164     }
 165     fn visit_field(&mut self, f: &'ast Field) {
 166         walk_field(self, f)
 167     }
 168     fn visit_field_pattern(&mut self, fp: &'ast FieldPat) {
 169         walk_field_pattern(self, fp)
 170     }
 171 }
 172
 173 #[macro_export]
 174 macro_rules! walk_list {
 175     ($visitor: expr, $method: ident, $list: expr) => {
 176         for elem in $list {
 177             $visitor.$method(elem)
 178         }
 179     };
 180     ($visitor: expr, $method: ident, $list: expr, $($extra_args: expr),*) => {
 181         for elem in $list {
 182             $visitor.$method(elem, $($extra_args,)*)
 183         }
 184     }
 185 }
 186
 187 pub fn walk_ident<'a, V: Visitor<'a>>(visitor: &mut V, ident: Ident) {
 188     visitor.visit_name(ident.span, ident.name);
 189 }
 190
 191 pub fn walk_crate<'a, V: Visitor<'a>>(visitor: &mut V, krate: &'a Crate) {
 192     visitor.visit_mod(&krate.module, krate.span, &krate.attrs, CRATE_NODE_ID);
 193     walk_list!(visitor, visit_attribute, &krate.attrs);
 194 }
 195
 196 pub fn walk_mod<'a, V: Visitor<'a>>(visitor: &mut V, module: &'a Mod) {
 197     walk_list!(visitor, visit_item, &module.items);
 198 }
 199
 200 pub fn walk_local<'a, V: Visitor<'a>>(visitor: &mut V, local: &'a Local) {
 201     for attr in local.attrs.iter() {
 202         visitor.visit_attribute(attr);
 203     }
 204     visitor.visit_pat(&local.pat);
 205     walk_list!(visitor, visit_ty, &local.ty);
 206     walk_list!(visitor, visit_expr, &local.init);
 207 }
 208
 209 pub fn walk_label<'a, V: Visitor<'a>>(visitor: &mut V, label: &'a Label) {
 210     visitor.visit_ident(label.ident);
 211 }
 212
 213 pub fn walk_lifetime<'a, V: Visitor<'a>>(visitor: &mut V, lifetime: &'a Lifetime) {
 214     visitor.visit_ident(lifetime.ident);
 215 }
 216
 217 pub fn walk_poly_trait_ref<'a, V>(visitor: &mut V,
 218                                   trait_ref: &'a PolyTraitRef,
 219                                   _: &TraitBoundModifier)
 220     where V: Visitor<'a>,
 221 {
 222     walk_list!(visitor, visit_generic_param, &trait_ref.bound_generic_params);
 223     visitor.visit_trait_ref(&trait_ref.trait_ref);
 224 }
 225
 226 pub fn walk_trait_ref<'a, V: Visitor<'a>>(visitor: &mut V, trait_ref: &'a TraitRef) {
 227     visitor.visit_path(&trait_ref.path, trait_ref.ref_id)
 228 }
 229
 230 pub fn walk_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a Item) {
 231     visitor.visit_vis(&item.vis);
 232     visitor.visit_ident(item.ident);
 233     match item.node {
 234         ItemKind::ExternCrate(orig_name) => {
 235             if let Some(orig_name) = orig_name {
 236                 visitor.visit_name(item.span, orig_name);
 237             }
 238         }
 239         ItemKind::Use(ref use_tree) => {
 240             visitor.visit_use_tree(use_tree, item.id, false)
 241         }
 242         ItemKind::Static(ref typ, _, ref expr) |
 243         ItemKind::Const(ref typ, ref expr) => {
 244             visitor.visit_ty(typ);
 245             visitor.visit_expr(expr);
 246         }
 247         ItemKind::Fn(ref declaration, ref header, ref generics, ref body) => {
 248             visitor.visit_generics(generics);
 249             visitor.visit_fn_header(header);
 250             visitor.visit_fn(FnKind::ItemFn(item.ident, header,
 251                                             &item.vis, body),
 252                              declaration,
 253                              item.span,
 254                              item.id)
 255         }
 256         ItemKind::Mod(ref module) => {
 257             visitor.visit_mod(module, item.span, &item.attrs, item.id)
 258         }
 259         ItemKind::ForeignMod(ref foreign_module) => {
 260             walk_list!(visitor, visit_foreign_item, &foreign_module.items);
 261         }
 262         ItemKind::GlobalAsm(ref ga) => visitor.visit_global_asm(ga),
 263         ItemKind::TyAlias(ref typ, ref generics) => {
 264             visitor.visit_ty(typ);
 265             visitor.visit_generics(generics)
 266         }
 267         ItemKind::OpaqueTy(ref bounds, ref generics) => {
 268             walk_list!(visitor, visit_param_bound, bounds);
 269             visitor.visit_generics(generics)
 270         }
 271         ItemKind::Enum(ref enum_definition, ref generics) => {
 272             visitor.visit_generics(generics);
 273             visitor.visit_enum_def(enum_definition, generics, item.id, item.span)
 274         }
 275         ItemKind::Impl(_, _, _,
 276                  ref generics,
 277                  ref opt_trait_reference,
 278                  ref typ,
 279                  ref impl_items) => {
 280             visitor.visit_generics(generics);
 281             walk_list!(visitor, visit_trait_ref, opt_trait_reference);
 282             visitor.visit_ty(typ);
 283             walk_list!(visitor, visit_impl_item, impl_items);
 284         }
 285         ItemKind::Struct(ref struct_definition, ref generics) |
 286         ItemKind::Union(ref struct_definition, ref generics) => {
 287             visitor.visit_generics(generics);
 288             visitor.visit_variant_data(struct_definition);
 289         }
 290         ItemKind::Trait(.., ref generics, ref bounds, ref methods) => {
 291             visitor.visit_generics(generics);
 292             walk_list!(visitor, visit_param_bound, bounds);
 293             walk_list!(visitor, visit_trait_item, methods);
 294         }
 295         ItemKind::TraitAlias(ref generics, ref bounds) => {
 296             visitor.visit_generics(generics);
 297             walk_list!(visitor, visit_param_bound, bounds);
 298         }
 299         ItemKind::Mac(ref mac) => visitor.visit_mac(mac),
 300         ItemKind::MacroDef(ref ts) => visitor.visit_mac_def(ts, item.id),
 301     }
 302     walk_list!(visitor, visit_attribute, &item.attrs);
 303 }
 304
 305 pub fn walk_enum_def<'a, V: Visitor<'a>>(
 306     visitor: &mut V,
 307     enum_definition: &'a EnumDef,
 308     _: &'a Generics,
 309     _: NodeId,
 310 ) {
 311     walk_list!(visitor, visit_variant, &enum_definition.variants);
 312 }
 313
 314 pub fn walk_variant<'a, V: Visitor<'a>>(visitor: &mut V, variant: &'a Variant)
 315     where V: Visitor<'a>,
 316 {
 317     visitor.visit_ident(variant.ident);
 318     visitor.visit_variant_data(&variant.data);
 319     walk_list!(visitor, visit_anon_const, &variant.disr_expr);
 320     walk_list!(visitor, visit_attribute, &variant.attrs);
 321 }
 322
 323 pub fn walk_field<'a, V: Visitor<'a>>(visitor: &mut V, f: &'a Field) {
 324     visitor.visit_expr(&f.expr);
 325     visitor.visit_ident(f.ident);
 326     walk_list!(visitor, visit_attribute, f.attrs.iter());
 327 }
 328
 329 pub fn walk_field_pattern<'a, V: Visitor<'a>>(visitor: &mut V, fp: &'a FieldPat) {
 330     visitor.visit_ident(fp.ident);
 331     visitor.visit_pat(&fp.pat);
 332     walk_list!(visitor, visit_attribute, fp.attrs.iter());
 333 }
 334
 335 pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) {
 336     match typ.node {
 337         TyKind::Slice(ref ty) | TyKind::Paren(ref ty) => {
 338             visitor.visit_ty(ty)
 339         }
 340         TyKind::Ptr(ref mutable_type) => {
 341             visitor.visit_ty(&mutable_type.ty)
 342         }
 343         TyKind::Rptr(ref opt_lifetime, ref mutable_type) => {
 344             walk_list!(visitor, visit_lifetime, opt_lifetime);
 345             visitor.visit_ty(&mutable_type.ty)
 346         }
 347         TyKind::Tup(ref tuple_element_types) => {
 348             walk_list!(visitor, visit_ty, tuple_element_types);
 349         }
 350         TyKind::BareFn(ref function_declaration) => {
 351             walk_list!(visitor, visit_generic_param, &function_declaration.generic_params);
 352             walk_fn_decl(visitor, &function_declaration.decl);
 353         }
 354         TyKind::Path(ref maybe_qself, ref path) => {
 355             if let Some(ref qself) = *maybe_qself {
 356                 visitor.visit_ty(&qself.ty);
 357             }
 358             visitor.visit_path(path, typ.id);
 359         }
 360         TyKind::Array(ref ty, ref length) => {
 361             visitor.visit_ty(ty);
 362             visitor.visit_anon_const(length)
 363         }
 364         TyKind::TraitObject(ref bounds, ..) |
 365         TyKind::ImplTrait(_, ref bounds) => {
 366             walk_list!(visitor, visit_param_bound, bounds);
 367         }
 368         TyKind::Typeof(ref expression) => {
 369             visitor.visit_anon_const(expression)
 370         }
 371         TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => {}
 372         TyKind::Mac(ref mac) => {
 373             visitor.visit_mac(mac)
 374         }
 375         TyKind::Never |
 376         TyKind::CVarArgs => {}
 377     }
 378 }
 379
 380 pub fn walk_path<'a, V: Visitor<'a>>(visitor: &mut V, path: &'a Path) {
 381     for segment in &path.segments {
 382         visitor.visit_path_segment(path.span, segment);
 383     }
 384 }
 385
 386 pub fn walk_use_tree<'a, V: Visitor<'a>>(
 387     visitor: &mut V, use_tree: &'a UseTree, id: NodeId,
 388 ) {
 389     visitor.visit_path(&use_tree.prefix, id);
 390     match use_tree.kind {
 391         UseTreeKind::Simple(rename, ..) => {
 392             // The extra IDs are handled during HIR lowering.
 393             if let Some(rename) = rename {
 394                 visitor.visit_ident(rename);
 395             }
 396         }
 397         UseTreeKind::Glob => {},
 398         UseTreeKind::Nested(ref use_trees) => {
 399             for &(ref nested_tree, nested_id) in use_trees {
 400                 visitor.visit_use_tree(nested_tree, nested_id, true);
 401             }
 402         }
 403     }
 404 }
 405
 406 pub fn walk_path_segment<'a, V: Visitor<'a>>(visitor: &mut V,
 407                                              path_span: Span,
 408                                              segment: &'a PathSegment) {
 409     visitor.visit_ident(segment.ident);
 410     if let Some(ref args) = segment.args {
 411         visitor.visit_generic_args(path_span, args);
 412     }
 413 }
 414
 415 pub fn walk_generic_args<'a, V>(visitor: &mut V,
 416                                 _path_span: Span,
 417                                 generic_args: &'a GenericArgs)
 418     where V: Visitor<'a>,
 419 {
 420     match *generic_args {
 421         GenericArgs::AngleBracketed(ref data) => {
 422             walk_list!(visitor, visit_generic_arg, &data.args);
 423             walk_list!(visitor, visit_assoc_ty_constraint, &data.constraints);
 424         }
 425         GenericArgs::Parenthesized(ref data) => {
 426             walk_list!(visitor, visit_ty, &data.inputs);
 427             walk_list!(visitor, visit_ty, &data.output);
 428         }
 429     }
 430 }
 431
 432 pub fn walk_assoc_ty_constraint<'a, V: Visitor<'a>>(visitor: &mut V,
 433                                                     constraint: &'a AssocTyConstraint) {
 434     visitor.visit_ident(constraint.ident);
 435     match constraint.kind {
 436         AssocTyConstraintKind::Equality { ref ty } => {
 437             visitor.visit_ty(ty);
 438         }
 439         AssocTyConstraintKind::Bound { ref bounds } => {
 440             walk_list!(visitor, visit_param_bound, bounds);
 441         }
 442     }
 443 }
 444
 445 pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) {
 446     match pattern.node {
 447         PatKind::TupleStruct(ref path, ref elems) => {
 448             visitor.visit_path(path, pattern.id);
 449             walk_list!(visitor, visit_pat, elems);
 450         }
 451         PatKind::Path(ref opt_qself, ref path) => {
 452             if let Some(ref qself) = *opt_qself {
 453                 visitor.visit_ty(&qself.ty);
 454             }
 455             visitor.visit_path(path, pattern.id)
 456         }
 457         PatKind::Struct(ref path, ref fields, _) => {
 458             visitor.visit_path(path, pattern.id);
 459             walk_list!(visitor, visit_field_pattern, fields);
 460         }
 461         PatKind::Box(ref subpattern) |
 462         PatKind::Ref(ref subpattern, _) |
 463         PatKind::Paren(ref subpattern) => {
 464             visitor.visit_pat(subpattern)
 465         }
 466         PatKind::Ident(_, ident, ref optional_subpattern) => {
 467             visitor.visit_ident(ident);
 468             walk_list!(visitor, visit_pat, optional_subpattern);
 469         }
 470         PatKind::Lit(ref expression) => visitor.visit_expr(expression),
 471         PatKind::Range(ref lower_bound, ref upper_bound, _) => {
 472             visitor.visit_expr(lower_bound);
 473             visitor.visit_expr(upper_bound);
 474         }
 475         PatKind::Wild | PatKind::Rest => {},
 476         PatKind::Tuple(ref elems)
 477         | PatKind::Slice(ref elems)
 478         | PatKind::Or(ref elems) => {
 479             walk_list!(visitor, visit_pat, elems);
 480         }
 481         PatKind::Mac(ref mac) => visitor.visit_mac(mac),
 482     }
 483 }
 484
 485 pub fn walk_foreign_item<'a, V: Visitor<'a>>(visitor: &mut V, foreign_item: &'a ForeignItem) {
 486     visitor.visit_vis(&foreign_item.vis);
 487     visitor.visit_ident(foreign_item.ident);
 488
 489     match foreign_item.node {
 490         ForeignItemKind::Fn(ref function_declaration, ref generics) => {
 491             walk_fn_decl(visitor, function_declaration);
 492             visitor.visit_generics(generics)
 493         }
 494         ForeignItemKind::Static(ref typ, _) => visitor.visit_ty(typ),
 495         ForeignItemKind::Ty => (),
 496         ForeignItemKind::Macro(ref mac) => visitor.visit_mac(mac),
 497     }
 498
 499     walk_list!(visitor, visit_attribute, &foreign_item.attrs);
 500 }
 501
 502 pub fn walk_global_asm<'a, V: Visitor<'a>>(_: &mut V, _: &'a GlobalAsm) {
 503     // Empty!
 504 }
 505
 506 pub fn walk_param_bound<'a, V: Visitor<'a>>(visitor: &mut V, bound: &'a GenericBound) {
 507     match *bound {
 508         GenericBound::Trait(ref typ, ref modifier) => visitor.visit_poly_trait_ref(typ, modifier),
 509         GenericBound::Outlives(ref lifetime) => visitor.visit_lifetime(lifetime),
 510     }
 511 }
 512
 513 pub fn walk_generic_param<'a, V: Visitor<'a>>(visitor: &mut V, param: &'a GenericParam) {
 514     visitor.visit_ident(param.ident);
 515     walk_list!(visitor, visit_attribute, param.attrs.iter());
 516     walk_list!(visitor, visit_param_bound, &param.bounds);
 517     match param.kind {
 518         GenericParamKind::Lifetime => (),
 519         GenericParamKind::Type { ref default } => walk_list!(visitor, visit_ty, default),
 520         GenericParamKind::Const { ref ty, .. } => visitor.visit_ty(ty),
 521     }
 522 }
 523
 524 pub fn walk_generics<'a, V: Visitor<'a>>(visitor: &mut V, generics: &'a Generics) {
 525     walk_list!(visitor, visit_generic_param, &generics.params);
 526     walk_list!(visitor, visit_where_predicate, &generics.where_clause.predicates);
 527 }
 528
 529 pub fn walk_where_predicate<'a, V: Visitor<'a>>(visitor: &mut V, predicate: &'a WherePredicate) {
 530     match *predicate {
 531         WherePredicate::BoundPredicate(WhereBoundPredicate{ref bounded_ty,
 532                                                            ref bounds,
 533                                                            ref bound_generic_params,
 534                                                            ..}) => {
 535             visitor.visit_ty(bounded_ty);
 536             walk_list!(visitor, visit_param_bound, bounds);
 537             walk_list!(visitor, visit_generic_param, bound_generic_params);
 538         }
 539         WherePredicate::RegionPredicate(WhereRegionPredicate{ref lifetime,
 540                                                              ref bounds,
 541                                                              ..}) => {
 542             visitor.visit_lifetime(lifetime);
 543             walk_list!(visitor, visit_param_bound, bounds);
 544         }
 545         WherePredicate::EqPredicate(WhereEqPredicate{ref lhs_ty,
 546                                                      ref rhs_ty,
 547                                                      ..}) => {
 548             visitor.visit_ty(lhs_ty);
 549             visitor.visit_ty(rhs_ty);
 550         }
 551     }
 552 }
 553
 554 pub fn walk_fn_ret_ty<'a, V: Visitor<'a>>(visitor: &mut V, ret_ty: &'a FunctionRetTy) {
 555     if let FunctionRetTy::Ty(ref output_ty) = *ret_ty {
 556         visitor.visit_ty(output_ty)
 557     }
 558 }
 559
 560 pub fn walk_fn_decl<'a, V: Visitor<'a>>(visitor: &mut V, function_declaration: &'a FnDecl) {
 561     for param in &function_declaration.inputs {
 562         visitor.visit_param(param);
 563     }
 564     visitor.visit_fn_ret_ty(&function_declaration.output);
 565 }
 566
 567 pub fn walk_fn<'a, V>(visitor: &mut V, kind: FnKind<'a>, declaration: &'a FnDecl, _span: Span)
 568     where V: Visitor<'a>,
 569 {
 570     match kind {
 571         FnKind::ItemFn(_, header, _, body) => {
 572             visitor.visit_fn_header(header);
 573             walk_fn_decl(visitor, declaration);
 574             visitor.visit_block(body);
 575         }
 576         FnKind::Method(_, sig, _, body) => {
 577             visitor.visit_fn_header(&sig.header);
 578             walk_fn_decl(visitor, declaration);
 579             visitor.visit_block(body);
 580         }
 581         FnKind::Closure(body) => {
 582             walk_fn_decl(visitor, declaration);
 583             visitor.visit_expr(body);
 584         }
 585     }
 586 }
 587
 588 pub fn walk_trait_item<'a, V: Visitor<'a>>(visitor: &mut V, trait_item: &'a TraitItem) {
 589     visitor.visit_ident(trait_item.ident);
 590     walk_list!(visitor, visit_attribute, &trait_item.attrs);
 591     visitor.visit_generics(&trait_item.generics);
 592     match trait_item.node {
 593         TraitItemKind::Const(ref ty, ref default) => {
 594             visitor.visit_ty(ty);
 595             walk_list!(visitor, visit_expr, default);
 596         }
 597         TraitItemKind::Method(ref sig, None) => {
 598             visitor.visit_fn_header(&sig.header);
 599             walk_fn_decl(visitor, &sig.decl);
 600         }
 601         TraitItemKind::Method(ref sig, Some(ref body)) => {
 602             visitor.visit_fn(FnKind::Method(trait_item.ident, sig, None, body),
 603                              &sig.decl, trait_item.span, trait_item.id);
 604         }
 605         TraitItemKind::Type(ref bounds, ref default) => {
 606             walk_list!(visitor, visit_param_bound, bounds);
 607             walk_list!(visitor, visit_ty, default);
 608         }
 609         TraitItemKind::Macro(ref mac) => {
 610             visitor.visit_mac(mac);
 611         }
 612     }
 613 }
 614
 615 pub fn walk_impl_item<'a, V: Visitor<'a>>(visitor: &mut V, impl_item: &'a ImplItem) {
 616     visitor.visit_vis(&impl_item.vis);
 617     visitor.visit_ident(impl_item.ident);
 618     walk_list!(visitor, visit_attribute, &impl_item.attrs);
 619     visitor.visit_generics(&impl_item.generics);
 620     match impl_item.node {
 621         ImplItemKind::Const(ref ty, ref expr) => {
 622             visitor.visit_ty(ty);
 623             visitor.visit_expr(expr);
 624         }
 625         ImplItemKind::Method(ref sig, ref body) => {
 626             visitor.visit_fn(FnKind::Method(impl_item.ident, sig, Some(&impl_item.vis), body),
 627                              &sig.decl, impl_item.span, impl_item.id);
 628         }
 629         ImplItemKind::TyAlias(ref ty) => {
 630             visitor.visit_ty(ty);
 631         }
 632         ImplItemKind::OpaqueTy(ref bounds) => {
 633             walk_list!(visitor, visit_param_bound, bounds);
 634         }
 635         ImplItemKind::Macro(ref mac) => {
 636             visitor.visit_mac(mac);
 637         }
 638     }
 639 }
 640
 641 pub fn walk_struct_def<'a, V: Visitor<'a>>(visitor: &mut V, struct_definition: &'a VariantData) {
 642     walk_list!(visitor, visit_struct_field, struct_definition.fields());
 643 }
 644
 645 pub fn walk_struct_field<'a, V: Visitor<'a>>(visitor: &mut V, struct_field: &'a StructField) {
 646     visitor.visit_vis(&struct_field.vis);
 647     if let Some(ident) = struct_field.ident {
 648         visitor.visit_ident(ident);
 649     }
 650     visitor.visit_ty(&struct_field.ty);
 651     walk_list!(visitor, visit_attribute, &struct_field.attrs);
 652 }
 653
 654 pub fn walk_block<'a, V: Visitor<'a>>(visitor: &mut V, block: &'a Block) {
 655     walk_list!(visitor, visit_stmt, &block.stmts);
 656 }
 657
 658 pub fn walk_stmt<'a, V: Visitor<'a>>(visitor: &mut V, statement: &'a Stmt) {
 659     match statement.node {
 660         StmtKind::Local(ref local) => visitor.visit_local(local),
 661         StmtKind::Item(ref item) => visitor.visit_item(item),
 662         StmtKind::Expr(ref expression) | StmtKind::Semi(ref expression) => {
 663             visitor.visit_expr(expression)
 664         }
 665         StmtKind::Mac(ref mac) => {
 666             let (ref mac, _, ref attrs) = **mac;
 667             visitor.visit_mac(mac);
 668             for attr in attrs.iter() {
 669                 visitor.visit_attribute(attr);
 670             }
 671         }
 672     }
 673 }
 674
 675 pub fn walk_mac<'a, V: Visitor<'a>>(visitor: &mut V, mac: &'a Mac) {
 676     visitor.visit_path(&mac.path, DUMMY_NODE_ID);
 677 }
 678
 679 pub fn walk_anon_const<'a, V: Visitor<'a>>(visitor: &mut V, constant: &'a AnonConst) {
 680     visitor.visit_expr(&constant.value);
 681 }
 682
 683 pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
 684     walk_list!(visitor, visit_attribute, expression.attrs.iter());
 685
 686     match expression.node {
 687         ExprKind::Box(ref subexpression) => {
 688             visitor.visit_expr(subexpression)
 689         }
 690         ExprKind::Array(ref subexpressions) => {
 691             walk_list!(visitor, visit_expr, subexpressions);
 692         }
 693         ExprKind::Repeat(ref element, ref count) => {
 694             visitor.visit_expr(element);
 695             visitor.visit_anon_const(count)
 696         }
 697         ExprKind::Struct(ref path, ref fields, ref optional_base) => {
 698             visitor.visit_path(path, expression.id);
 699             walk_list!(visitor, visit_field, fields);
 700             walk_list!(visitor, visit_expr, optional_base);
 701         }
 702         ExprKind::Tup(ref subexpressions) => {
 703             walk_list!(visitor, visit_expr, subexpressions);
 704         }
 705         ExprKind::Call(ref callee_expression, ref arguments) => {
 706             visitor.visit_expr(callee_expression);
 707             walk_list!(visitor, visit_expr, arguments);
 708         }
 709         ExprKind::MethodCall(ref segment, ref arguments) => {
 710             visitor.visit_path_segment(expression.span, segment);
 711             walk_list!(visitor, visit_expr, arguments);
 712         }
 713         ExprKind::Binary(_, ref left_expression, ref right_expression) => {
 714             visitor.visit_expr(left_expression);
 715             visitor.visit_expr(right_expression)
 716         }
 717         ExprKind::AddrOf(_, ref subexpression) | ExprKind::Unary(_, ref subexpression) => {
 718             visitor.visit_expr(subexpression)
 719         }
 720         ExprKind::Cast(ref subexpression, ref typ) | ExprKind::Type(ref subexpression, ref typ) => {
 721             visitor.visit_expr(subexpression);
 722             visitor.visit_ty(typ)
 723         }
 724         ExprKind::Let(ref pat, ref scrutinee) => {
 725             visitor.visit_pat(pat);
 726             visitor.visit_expr(scrutinee);
 727         }
 728         ExprKind::If(ref head_expression, ref if_block, ref optional_else) => {
 729             visitor.visit_expr(head_expression);
 730             visitor.visit_block(if_block);
 731             walk_list!(visitor, visit_expr, optional_else);
 732         }
 733         ExprKind::While(ref subexpression, ref block, ref opt_label) => {
 734             walk_list!(visitor, visit_label, opt_label);
 735             visitor.visit_expr(subexpression);
 736             visitor.visit_block(block);
 737         }
 738         ExprKind::ForLoop(ref pattern, ref subexpression, ref block, ref opt_label) => {
 739             walk_list!(visitor, visit_label, opt_label);
 740             visitor.visit_pat(pattern);
 741             visitor.visit_expr(subexpression);
 742             visitor.visit_block(block);
 743         }
 744         ExprKind::Loop(ref block, ref opt_label) => {
 745             walk_list!(visitor, visit_label, opt_label);
 746             visitor.visit_block(block);
 747         }
 748         ExprKind::Match(ref subexpression, ref arms) => {
 749             visitor.visit_expr(subexpression);
 750             walk_list!(visitor, visit_arm, arms);
 751         }
 752         ExprKind::Closure(_, _, _, ref function_declaration, ref body, _decl_span) => {
 753             visitor.visit_fn(FnKind::Closure(body),
 754                              function_declaration,
 755                              expression.span,
 756                              expression.id)
 757         }
 758         ExprKind::Block(ref block, ref opt_label) => {
 759             walk_list!(visitor, visit_label, opt_label);
 760             visitor.visit_block(block);
 761         }
 762         ExprKind::Async(_, _, ref body) => {
 763             visitor.visit_block(body);
 764         }
 765         ExprKind::Await(ref expr) => visitor.visit_expr(expr),
 766         ExprKind::Assign(ref left_hand_expression, ref right_hand_expression) => {
 767             visitor.visit_expr(left_hand_expression);
 768             visitor.visit_expr(right_hand_expression);
 769         }
 770         ExprKind::AssignOp(_, ref left_expression, ref right_expression) => {
 771             visitor.visit_expr(left_expression);
 772             visitor.visit_expr(right_expression);
 773         }
 774         ExprKind::Field(ref subexpression, ident) => {
 775             visitor.visit_expr(subexpression);
 776             visitor.visit_ident(ident);
 777         }
 778         ExprKind::Index(ref main_expression, ref index_expression) => {
 779             visitor.visit_expr(main_expression);
 780             visitor.visit_expr(index_expression)
 781         }
 782         ExprKind::Range(ref start, ref end, _) => {
 783             walk_list!(visitor, visit_expr, start);
 784             walk_list!(visitor, visit_expr, end);
 785         }
 786         ExprKind::Path(ref maybe_qself, ref path) => {
 787             if let Some(ref qself) = *maybe_qself {
 788                 visitor.visit_ty(&qself.ty);
 789             }
 790             visitor.visit_path(path, expression.id)
 791         }
 792         ExprKind::Break(ref opt_label, ref opt_expr) => {
 793             walk_list!(visitor, visit_label, opt_label);
 794             walk_list!(visitor, visit_expr, opt_expr);
 795         }
 796         ExprKind::Continue(ref opt_label) => {
 797             walk_list!(visitor, visit_label, opt_label);
 798         }
 799         ExprKind::Ret(ref optional_expression) => {
 800             walk_list!(visitor, visit_expr, optional_expression);
 801         }
 802         ExprKind::Mac(ref mac) => visitor.visit_mac(mac),
 803         ExprKind::Paren(ref subexpression) => {
 804             visitor.visit_expr(subexpression)
 805         }
 806         ExprKind::InlineAsm(ref ia) => {
 807             for &(_, ref input) in &ia.inputs {
 808                 visitor.visit_expr(input)
 809             }
 810             for output in &ia.outputs {
 811                 visitor.visit_expr(&output.expr)
 812             }
 813         }
 814         ExprKind::Yield(ref optional_expression) => {
 815             walk_list!(visitor, visit_expr, optional_expression);
 816         }
 817         ExprKind::Try(ref subexpression) => {
 818             visitor.visit_expr(subexpression)
 819         }
 820         ExprKind::TryBlock(ref body) => {
 821             visitor.visit_block(body)
 822         }
 823         ExprKind::Lit(_) | ExprKind::Err => {}
 824     }
 825
 826     visitor.visit_expr_post(expression)
 827 }
 828
 829 pub fn walk_param<'a, V: Visitor<'a>>(visitor: &mut V, param: &'a Param) {
 830     walk_list!(visitor, visit_attribute, param.attrs.iter());
 831     visitor.visit_pat(&param.pat);
 832     visitor.visit_ty(&param.ty);
 833 }
 834
 835 pub fn walk_arm<'a, V: Visitor<'a>>(visitor: &mut V, arm: &'a Arm) {
 836     visitor.visit_pat(&arm.pat);
 837     // NOTE(or_patterns; Centril | dlrobertson):
 838     // If you change this, also change the hack in `lowering.rs`.
 839     walk_list!(visitor, visit_expr, &arm.guard);
 840     visitor.visit_expr(&arm.body);
 841     walk_list!(visitor, visit_attribute, &arm.attrs);
 842 }
 843
 844 pub fn walk_vis<'a, V: Visitor<'a>>(visitor: &mut V, vis: &'a Visibility) {
 845     if let VisibilityKind::Restricted { ref path, id } = vis.node {
 846         visitor.visit_path(path, id);
 847     }
 848 }
 849
 850 pub fn walk_attribute<'a, V: Visitor<'a>>(visitor: &mut V, attr: &'a Attribute) {
 851     visitor.visit_tts(attr.tokens.clone());
 852 }
 853
 854 pub fn walk_tt<'a, V: Visitor<'a>>(visitor: &mut V, tt: TokenTree) {
 855     match tt {
 856         TokenTree::Token(token) => visitor.visit_token(token),
 857         TokenTree::Delimited(_, _, tts) => visitor.visit_tts(tts),
 858     }
 859 }
 860
 861 pub fn walk_tts<'a, V: Visitor<'a>>(visitor: &mut V, tts: TokenStream) {
 862     for tt in tts.trees() {
 863         visitor.visit_tt(tt);
 864     }
 865 }