src/librustc_ast/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::token::Token;
  18 use crate::tokenstream::{TokenStream, TokenTree};
  19
  20 use rustc_span::symbol::{Ident, Symbol};
  21 use rustc_span::Span;
  22
  23 #[derive(Copy, Clone, PartialEq)]
  24 pub enum AssocCtxt {
  25     Trait,
  26     Impl,
  27 }
  28
  29 #[derive(Copy, Clone, PartialEq)]
  30 pub enum FnCtxt {
  31     Free,
  32     Foreign,
  33     Assoc(AssocCtxt),
  34 }
  35
  36 #[derive(Copy, Clone)]
  37 pub enum FnKind<'a> {
  38     /// E.g., `fn foo()`, `fn foo(&self)`, or `extern "Abi" fn foo()`.
  39     Fn(FnCtxt, Ident, &'a FnSig, &'a Visibility, Option<&'a Block>),
  40
  41     /// E.g., `|x, y| body`.
  42     Closure(&'a FnDecl, &'a Expr),
  43 }
  44
  45 impl<'a> FnKind<'a> {
  46     pub fn header(&self) -> Option<&'a FnHeader> {
  47         match *self {
  48             FnKind::Fn(_, _, sig, _, _) => Some(&sig.header),
  49             FnKind::Closure(_, _) => None,
  50         }
  51     }
  52
  53     pub fn decl(&self) -> &'a FnDecl {
  54         match self {
  55             FnKind::Fn(_, _, sig, _, _) => &sig.decl,
  56             FnKind::Closure(decl, _) => decl,
  57         }
  58     }
  59
  60     pub fn ctxt(&self) -> Option<FnCtxt> {
  61         match self {
  62             FnKind::Fn(ctxt, ..) => Some(*ctxt),
  63             FnKind::Closure(..) => None,
  64         }
  65     }
  66 }
  67
  68 /// Each method of the `Visitor` trait is a hook to be potentially
  69 /// overridden. Each method's default implementation recursively visits
  70 /// the substructure of the input via the corresponding `walk` method;
  71 /// e.g., the `visit_mod` method by default calls `visit::walk_mod`.
  72 ///
  73 /// If you want to ensure that your code handles every variant
  74 /// explicitly, you need to override each method. (And you also need
  75 /// to monitor future changes to `Visitor` in case a new method with a
  76 /// new default implementation gets introduced.)
  77 pub trait Visitor<'ast>: Sized {
  78     fn visit_name(&mut self, _span: Span, _name: Symbol) {
  79         // Nothing to do.
  80     }
  81     fn visit_ident(&mut self, ident: Ident) {
  82         walk_ident(self, ident);
  83     }
  84     fn visit_mod(&mut self, m: &'ast Mod, _s: Span, _attrs: &[Attribute], _n: NodeId) {
  85         walk_mod(self, m);
  86     }
  87     fn visit_foreign_item(&mut self, i: &'ast ForeignItem) {
  88         walk_foreign_item(self, i)
  89     }
  90     fn visit_global_asm(&mut self, ga: &'ast GlobalAsm) {
  91         walk_global_asm(self, ga)
  92     }
  93     fn visit_item(&mut self, i: &'ast Item) {
  94         walk_item(self, i)
  95     }
  96     fn visit_local(&mut self, l: &'ast Local) {
  97         walk_local(self, l)
  98     }
  99     fn visit_block(&mut self, b: &'ast Block) {
 100         walk_block(self, b)
 101     }
 102     fn visit_stmt(&mut self, s: &'ast Stmt) {
 103         walk_stmt(self, s)
 104     }
 105     fn visit_param(&mut self, param: &'ast Param) {
 106         walk_param(self, param)
 107     }
 108     fn visit_arm(&mut self, a: &'ast Arm) {
 109         walk_arm(self, a)
 110     }
 111     fn visit_pat(&mut self, p: &'ast Pat) {
 112         walk_pat(self, p)
 113     }
 114     fn visit_anon_const(&mut self, c: &'ast AnonConst) {
 115         walk_anon_const(self, c)
 116     }
 117     fn visit_expr(&mut self, ex: &'ast Expr) {
 118         walk_expr(self, ex)
 119     }
 120     fn visit_expr_post(&mut self, _ex: &'ast Expr) {}
 121     fn visit_ty(&mut self, t: &'ast Ty) {
 122         walk_ty(self, t)
 123     }
 124     fn visit_generic_param(&mut self, param: &'ast GenericParam) {
 125         walk_generic_param(self, param)
 126     }
 127     fn visit_generics(&mut self, g: &'ast Generics) {
 128         walk_generics(self, g)
 129     }
 130     fn visit_where_predicate(&mut self, p: &'ast WherePredicate) {
 131         walk_where_predicate(self, p)
 132     }
 133     fn visit_fn(&mut self, fk: FnKind<'ast>, s: Span, _: NodeId) {
 134         walk_fn(self, fk, s)
 135     }
 136     fn visit_assoc_item(&mut self, i: &'ast AssocItem, ctxt: AssocCtxt) {
 137         walk_assoc_item(self, i, ctxt)
 138     }
 139     fn visit_trait_ref(&mut self, t: &'ast TraitRef) {
 140         walk_trait_ref(self, t)
 141     }
 142     fn visit_param_bound(&mut self, bounds: &'ast GenericBound) {
 143         walk_param_bound(self, bounds)
 144     }
 145     fn visit_poly_trait_ref(&mut self, t: &'ast PolyTraitRef, m: &'ast TraitBoundModifier) {
 146         walk_poly_trait_ref(self, t, m)
 147     }
 148     fn visit_variant_data(&mut self, s: &'ast VariantData) {
 149         walk_struct_def(self, s)
 150     }
 151     fn visit_struct_field(&mut self, s: &'ast StructField) {
 152         walk_struct_field(self, s)
 153     }
 154     fn visit_enum_def(
 155         &mut self,
 156         enum_definition: &'ast EnumDef,
 157         generics: &'ast Generics,
 158         item_id: NodeId,
 159         _: Span,
 160     ) {
 161         walk_enum_def(self, enum_definition, generics, item_id)
 162     }
 163     fn visit_variant(&mut self, v: &'ast Variant) {
 164         walk_variant(self, v)
 165     }
 166     fn visit_label(&mut self, label: &'ast Label) {
 167         walk_label(self, label)
 168     }
 169     fn visit_lifetime(&mut self, lifetime: &'ast Lifetime) {
 170         walk_lifetime(self, lifetime)
 171     }
 172     fn visit_mac(&mut self, _mac: &'ast MacCall) {
 173         panic!("visit_mac disabled by default");
 174         // N.B., see note about macros above.
 175         // if you really want a visitor that
 176         // works on macros, use this
 177         // definition in your trait impl:
 178         // visit::walk_mac(self, _mac)
 179     }
 180     fn visit_mac_def(&mut self, _mac: &'ast MacroDef, _id: NodeId) {
 181         // Nothing to do
 182     }
 183     fn visit_path(&mut self, path: &'ast Path, _id: NodeId) {
 184         walk_path(self, path)
 185     }
 186     fn visit_use_tree(&mut self, use_tree: &'ast UseTree, id: NodeId, _nested: bool) {
 187         walk_use_tree(self, use_tree, id)
 188     }
 189     fn visit_path_segment(&mut self, path_span: Span, path_segment: &'ast PathSegment) {
 190         walk_path_segment(self, path_span, path_segment)
 191     }
 192     fn visit_generic_args(&mut self, path_span: Span, generic_args: &'ast GenericArgs) {
 193         walk_generic_args(self, path_span, generic_args)
 194     }
 195     fn visit_generic_arg(&mut self, generic_arg: &'ast GenericArg) {
 196         match generic_arg {
 197             GenericArg::Lifetime(lt) => self.visit_lifetime(lt),
 198             GenericArg::Type(ty) => self.visit_ty(ty),
 199             GenericArg::Const(ct) => self.visit_anon_const(ct),
 200         }
 201     }
 202     fn visit_assoc_ty_constraint(&mut self, constraint: &'ast AssocTyConstraint) {
 203         walk_assoc_ty_constraint(self, constraint)
 204     }
 205     fn visit_attribute(&mut self, attr: &'ast Attribute) {
 206         walk_attribute(self, attr)
 207     }
 208     fn visit_tt(&mut self, tt: TokenTree) {
 209         walk_tt(self, tt)
 210     }
 211     fn visit_tts(&mut self, tts: TokenStream) {
 212         walk_tts(self, tts)
 213     }
 214     fn visit_token(&mut self, _t: Token) {}
 215     // FIXME: add `visit_interpolated` and `walk_interpolated`
 216     fn visit_vis(&mut self, vis: &'ast Visibility) {
 217         walk_vis(self, vis)
 218     }
 219     fn visit_fn_ret_ty(&mut self, ret_ty: &'ast FnRetTy) {
 220         walk_fn_ret_ty(self, ret_ty)
 221     }
 222     fn visit_fn_header(&mut self, _header: &'ast FnHeader) {
 223         // Nothing to do
 224     }
 225     fn visit_field(&mut self, f: &'ast Field) {
 226         walk_field(self, f)
 227     }
 228     fn visit_field_pattern(&mut self, fp: &'ast FieldPat) {
 229         walk_field_pattern(self, fp)
 230     }
 231 }
 232
 233 #[macro_export]
 234 macro_rules! walk_list {
 235     ($visitor: expr, $method: ident, $list: expr) => {
 236         for elem in $list {
 237             $visitor.$method(elem)
 238         }
 239     };
 240     ($visitor: expr, $method: ident, $list: expr, $($extra_args: expr),*) => {
 241         for elem in $list {
 242             $visitor.$method(elem, $($extra_args,)*)
 243         }
 244     }
 245 }
 246
 247 pub fn walk_ident<'a, V: Visitor<'a>>(visitor: &mut V, ident: Ident) {
 248     visitor.visit_name(ident.span, ident.name);
 249 }
 250
 251 pub fn walk_crate<'a, V: Visitor<'a>>(visitor: &mut V, krate: &'a Crate) {
 252     visitor.visit_mod(&krate.module, krate.span, &krate.attrs, CRATE_NODE_ID);
 253     walk_list!(visitor, visit_attribute, &krate.attrs);
 254 }
 255
 256 pub fn walk_mod<'a, V: Visitor<'a>>(visitor: &mut V, module: &'a Mod) {
 257     walk_list!(visitor, visit_item, &module.items);
 258 }
 259
 260 pub fn walk_local<'a, V: Visitor<'a>>(visitor: &mut V, local: &'a Local) {
 261     for attr in local.attrs.iter() {
 262         visitor.visit_attribute(attr);
 263     }
 264     visitor.visit_pat(&local.pat);
 265     walk_list!(visitor, visit_ty, &local.ty);
 266     walk_list!(visitor, visit_expr, &local.init);
 267 }
 268
 269 pub fn walk_label<'a, V: Visitor<'a>>(visitor: &mut V, label: &'a Label) {
 270     visitor.visit_ident(label.ident);
 271 }
 272
 273 pub fn walk_lifetime<'a, V: Visitor<'a>>(visitor: &mut V, lifetime: &'a Lifetime) {
 274     visitor.visit_ident(lifetime.ident);
 275 }
 276
 277 pub fn walk_poly_trait_ref<'a, V>(
 278     visitor: &mut V,
 279     trait_ref: &'a PolyTraitRef,
 280     _: &TraitBoundModifier,
 281 ) where
 282     V: Visitor<'a>,
 283 {
 284     walk_list!(visitor, visit_generic_param, &trait_ref.bound_generic_params);
 285     visitor.visit_trait_ref(&trait_ref.trait_ref);
 286 }
 287
 288 pub fn walk_trait_ref<'a, V: Visitor<'a>>(visitor: &mut V, trait_ref: &'a TraitRef) {
 289     visitor.visit_path(&trait_ref.path, trait_ref.ref_id)
 290 }
 291
 292 pub fn walk_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a Item) {
 293     visitor.visit_vis(&item.vis);
 294     visitor.visit_ident(item.ident);
 295     match item.kind {
 296         ItemKind::ExternCrate(orig_name) => {
 297             if let Some(orig_name) = orig_name {
 298                 visitor.visit_name(item.span, orig_name);
 299             }
 300         }
 301         ItemKind::Use(ref use_tree) => visitor.visit_use_tree(use_tree, item.id, false),
 302         ItemKind::Static(ref typ, _, ref expr) | ItemKind::Const(_, ref typ, ref expr) => {
 303             visitor.visit_ty(typ);
 304             walk_list!(visitor, visit_expr, expr);
 305         }
 306         ItemKind::Fn(_, ref sig, ref generics, ref body) => {
 307             visitor.visit_generics(generics);
 308             let kind = FnKind::Fn(FnCtxt::Free, item.ident, sig, &item.vis, body.as_deref());
 309             visitor.visit_fn(kind, item.span, item.id)
 310         }
 311         ItemKind::Mod(ref module) => visitor.visit_mod(module, item.span, &item.attrs, item.id),
 312         ItemKind::ForeignMod(ref foreign_module) => {
 313             walk_list!(visitor, visit_foreign_item, &foreign_module.items);
 314         }
 315         ItemKind::GlobalAsm(ref ga) => visitor.visit_global_asm(ga),
 316         ItemKind::TyAlias(_, ref generics, ref bounds, ref ty) => {
 317             visitor.visit_generics(generics);
 318             walk_list!(visitor, visit_param_bound, bounds);
 319             walk_list!(visitor, visit_ty, ty);
 320         }
 321         ItemKind::Enum(ref enum_definition, ref generics) => {
 322             visitor.visit_generics(generics);
 323             visitor.visit_enum_def(enum_definition, generics, item.id, item.span)
 324         }
 325         ItemKind::Impl {
 326             unsafety: _,
 327             polarity: _,
 328             defaultness: _,
 329             constness: _,
 330             ref generics,
 331             ref of_trait,
 332             ref self_ty,
 333             ref items,
 334         } => {
 335             visitor.visit_generics(generics);
 336             walk_list!(visitor, visit_trait_ref, of_trait);
 337             visitor.visit_ty(self_ty);
 338             walk_list!(visitor, visit_assoc_item, items, AssocCtxt::Impl);
 339         }
 340         ItemKind::Struct(ref struct_definition, ref generics)
 341         | ItemKind::Union(ref struct_definition, ref generics) => {
 342             visitor.visit_generics(generics);
 343             visitor.visit_variant_data(struct_definition);
 344         }
 345         ItemKind::Trait(.., ref generics, ref bounds, ref items) => {
 346             visitor.visit_generics(generics);
 347             walk_list!(visitor, visit_param_bound, bounds);
 348             walk_list!(visitor, visit_assoc_item, items, AssocCtxt::Trait);
 349         }
 350         ItemKind::TraitAlias(ref generics, ref bounds) => {
 351             visitor.visit_generics(generics);
 352             walk_list!(visitor, visit_param_bound, bounds);
 353         }
 354         ItemKind::MacCall(ref mac) => visitor.visit_mac(mac),
 355         ItemKind::MacroDef(ref ts) => visitor.visit_mac_def(ts, item.id),
 356     }
 357     walk_list!(visitor, visit_attribute, &item.attrs);
 358 }
 359
 360 pub fn walk_enum_def<'a, V: Visitor<'a>>(
 361     visitor: &mut V,
 362     enum_definition: &'a EnumDef,
 363     _: &'a Generics,
 364     _: NodeId,
 365 ) {
 366     walk_list!(visitor, visit_variant, &enum_definition.variants);
 367 }
 368
 369 pub fn walk_variant<'a, V: Visitor<'a>>(visitor: &mut V, variant: &'a Variant)
 370 where
 371     V: Visitor<'a>,
 372 {
 373     visitor.visit_ident(variant.ident);
 374     visitor.visit_vis(&variant.vis);
 375     visitor.visit_variant_data(&variant.data);
 376     walk_list!(visitor, visit_anon_const, &variant.disr_expr);
 377     walk_list!(visitor, visit_attribute, &variant.attrs);
 378 }
 379
 380 pub fn walk_field<'a, V: Visitor<'a>>(visitor: &mut V, f: &'a Field) {
 381     visitor.visit_expr(&f.expr);
 382     visitor.visit_ident(f.ident);
 383     walk_list!(visitor, visit_attribute, f.attrs.iter());
 384 }
 385
 386 pub fn walk_field_pattern<'a, V: Visitor<'a>>(visitor: &mut V, fp: &'a FieldPat) {
 387     visitor.visit_ident(fp.ident);
 388     visitor.visit_pat(&fp.pat);
 389     walk_list!(visitor, visit_attribute, fp.attrs.iter());
 390 }
 391
 392 pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) {
 393     match typ.kind {
 394         TyKind::Slice(ref ty) | TyKind::Paren(ref ty) => visitor.visit_ty(ty),
 395         TyKind::Ptr(ref mutable_type) => visitor.visit_ty(&mutable_type.ty),
 396         TyKind::Rptr(ref opt_lifetime, ref mutable_type) => {
 397             walk_list!(visitor, visit_lifetime, opt_lifetime);
 398             visitor.visit_ty(&mutable_type.ty)
 399         }
 400         TyKind::Tup(ref tuple_element_types) => {
 401             walk_list!(visitor, visit_ty, tuple_element_types);
 402         }
 403         TyKind::BareFn(ref function_declaration) => {
 404             walk_list!(visitor, visit_generic_param, &function_declaration.generic_params);
 405             walk_fn_decl(visitor, &function_declaration.decl);
 406         }
 407         TyKind::Path(ref maybe_qself, ref path) => {
 408             if let Some(ref qself) = *maybe_qself {
 409                 visitor.visit_ty(&qself.ty);
 410             }
 411             visitor.visit_path(path, typ.id);
 412         }
 413         TyKind::Array(ref ty, ref length) => {
 414             visitor.visit_ty(ty);
 415             visitor.visit_anon_const(length)
 416         }
 417         TyKind::TraitObject(ref bounds, ..) | TyKind::ImplTrait(_, ref bounds) => {
 418             walk_list!(visitor, visit_param_bound, bounds);
 419         }
 420         TyKind::Typeof(ref expression) => visitor.visit_anon_const(expression),
 421         TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => {}
 422         TyKind::MacCall(ref mac) => visitor.visit_mac(mac),
 423         TyKind::Never | TyKind::CVarArgs => {}
 424     }
 425 }
 426
 427 pub fn walk_path<'a, V: Visitor<'a>>(visitor: &mut V, path: &'a Path) {
 428     for segment in &path.segments {
 429         visitor.visit_path_segment(path.span, segment);
 430     }
 431 }
 432
 433 pub fn walk_use_tree<'a, V: Visitor<'a>>(visitor: &mut V, use_tree: &'a UseTree, id: NodeId) {
 434     visitor.visit_path(&use_tree.prefix, id);
 435     match use_tree.kind {
 436         UseTreeKind::Simple(rename, ..) => {
 437             // The extra IDs are handled during HIR lowering.
 438             if let Some(rename) = rename {
 439                 visitor.visit_ident(rename);
 440             }
 441         }
 442         UseTreeKind::Glob => {}
 443         UseTreeKind::Nested(ref use_trees) => {
 444             for &(ref nested_tree, nested_id) in use_trees {
 445                 visitor.visit_use_tree(nested_tree, nested_id, true);
 446             }
 447         }
 448     }
 449 }
 450
 451 pub fn walk_path_segment<'a, V: Visitor<'a>>(
 452     visitor: &mut V,
 453     path_span: Span,
 454     segment: &'a PathSegment,
 455 ) {
 456     visitor.visit_ident(segment.ident);
 457     if let Some(ref args) = segment.args {
 458         visitor.visit_generic_args(path_span, args);
 459     }
 460 }
 461
 462 pub fn walk_generic_args<'a, V>(visitor: &mut V, _path_span: Span, generic_args: &'a GenericArgs)
 463 where
 464     V: Visitor<'a>,
 465 {
 466     match *generic_args {
 467         GenericArgs::AngleBracketed(ref data) => {
 468             for arg in &data.args {
 469                 match arg {
 470                     AngleBracketedArg::Arg(a) => visitor.visit_generic_arg(a),
 471                     AngleBracketedArg::Constraint(c) => visitor.visit_assoc_ty_constraint(c),
 472                 }
 473             }
 474         }
 475         GenericArgs::Parenthesized(ref data) => {
 476             walk_list!(visitor, visit_ty, &data.inputs);
 477             walk_fn_ret_ty(visitor, &data.output);
 478         }
 479     }
 480 }
 481
 482 pub fn walk_assoc_ty_constraint<'a, V: Visitor<'a>>(
 483     visitor: &mut V,
 484     constraint: &'a AssocTyConstraint,
 485 ) {
 486     visitor.visit_ident(constraint.ident);
 487     match constraint.kind {
 488         AssocTyConstraintKind::Equality { ref ty } => {
 489             visitor.visit_ty(ty);
 490         }
 491         AssocTyConstraintKind::Bound { ref bounds } => {
 492             walk_list!(visitor, visit_param_bound, bounds);
 493         }
 494     }
 495 }
 496
 497 pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) {
 498     match pattern.kind {
 499         PatKind::TupleStruct(ref path, ref elems) => {
 500             visitor.visit_path(path, pattern.id);
 501             walk_list!(visitor, visit_pat, elems);
 502         }
 503         PatKind::Path(ref opt_qself, ref path) => {
 504             if let Some(ref qself) = *opt_qself {
 505                 visitor.visit_ty(&qself.ty);
 506             }
 507             visitor.visit_path(path, pattern.id)
 508         }
 509         PatKind::Struct(ref path, ref fields, _) => {
 510             visitor.visit_path(path, pattern.id);
 511             walk_list!(visitor, visit_field_pattern, fields);
 512         }
 513         PatKind::Box(ref subpattern)
 514         | PatKind::Ref(ref subpattern, _)
 515         | PatKind::Paren(ref subpattern) => visitor.visit_pat(subpattern),
 516         PatKind::Ident(_, ident, ref optional_subpattern) => {
 517             visitor.visit_ident(ident);
 518             walk_list!(visitor, visit_pat, optional_subpattern);
 519         }
 520         PatKind::Lit(ref expression) => visitor.visit_expr(expression),
 521         PatKind::Range(ref lower_bound, ref upper_bound, _) => {
 522             walk_list!(visitor, visit_expr, lower_bound);
 523             walk_list!(visitor, visit_expr, upper_bound);
 524         }
 525         PatKind::Wild | PatKind::Rest => {}
 526         PatKind::Tuple(ref elems) | PatKind::Slice(ref elems) | PatKind::Or(ref elems) => {
 527             walk_list!(visitor, visit_pat, elems);
 528         }
 529         PatKind::MacCall(ref mac) => visitor.visit_mac(mac),
 530     }
 531 }
 532
 533 pub fn walk_foreign_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a ForeignItem) {
 534     let Item { id, span, ident, ref vis, ref attrs, ref kind, tokens: _ } = *item;
 535     visitor.visit_vis(vis);
 536     visitor.visit_ident(ident);
 537     walk_list!(visitor, visit_attribute, attrs);
 538     match kind {
 539         ForeignItemKind::Static(ty, _, expr) => {
 540             visitor.visit_ty(ty);
 541             walk_list!(visitor, visit_expr, expr);
 542         }
 543         ForeignItemKind::Fn(_, sig, generics, body) => {
 544             visitor.visit_generics(generics);
 545             let kind = FnKind::Fn(FnCtxt::Foreign, ident, sig, vis, body.as_deref());
 546             visitor.visit_fn(kind, span, id);
 547         }
 548         ForeignItemKind::TyAlias(_, generics, bounds, ty) => {
 549             visitor.visit_generics(generics);
 550             walk_list!(visitor, visit_param_bound, bounds);
 551             walk_list!(visitor, visit_ty, ty);
 552         }
 553         ForeignItemKind::MacCall(mac) => {
 554             visitor.visit_mac(mac);
 555         }
 556     }
 557 }
 558
 559 pub fn walk_global_asm<'a, V: Visitor<'a>>(_: &mut V, _: &'a GlobalAsm) {
 560     // Empty!
 561 }
 562
 563 pub fn walk_param_bound<'a, V: Visitor<'a>>(visitor: &mut V, bound: &'a GenericBound) {
 564     match *bound {
 565         GenericBound::Trait(ref typ, ref modifier) => visitor.visit_poly_trait_ref(typ, modifier),
 566         GenericBound::Outlives(ref lifetime) => visitor.visit_lifetime(lifetime),
 567     }
 568 }
 569
 570 pub fn walk_generic_param<'a, V: Visitor<'a>>(visitor: &mut V, param: &'a GenericParam) {
 571     visitor.visit_ident(param.ident);
 572     walk_list!(visitor, visit_attribute, param.attrs.iter());
 573     walk_list!(visitor, visit_param_bound, &param.bounds);
 574     match param.kind {
 575         GenericParamKind::Lifetime => (),
 576         GenericParamKind::Type { ref default } => walk_list!(visitor, visit_ty, default),
 577         GenericParamKind::Const { ref ty, .. } => visitor.visit_ty(ty),
 578     }
 579 }
 580
 581 pub fn walk_generics<'a, V: Visitor<'a>>(visitor: &mut V, generics: &'a Generics) {
 582     walk_list!(visitor, visit_generic_param, &generics.params);
 583     walk_list!(visitor, visit_where_predicate, &generics.where_clause.predicates);
 584 }
 585
 586 pub fn walk_where_predicate<'a, V: Visitor<'a>>(visitor: &mut V, predicate: &'a WherePredicate) {
 587     match *predicate {
 588         WherePredicate::BoundPredicate(WhereBoundPredicate {
 589             ref bounded_ty,
 590             ref bounds,
 591             ref bound_generic_params,
 592             ..
 593         }) => {
 594             visitor.visit_ty(bounded_ty);
 595             walk_list!(visitor, visit_param_bound, bounds);
 596             walk_list!(visitor, visit_generic_param, bound_generic_params);
 597         }
 598         WherePredicate::RegionPredicate(WhereRegionPredicate {
 599             ref lifetime, ref bounds, ..
 600         }) => {
 601             visitor.visit_lifetime(lifetime);
 602             walk_list!(visitor, visit_param_bound, bounds);
 603         }
 604         WherePredicate::EqPredicate(WhereEqPredicate { ref lhs_ty, ref rhs_ty, .. }) => {
 605             visitor.visit_ty(lhs_ty);
 606             visitor.visit_ty(rhs_ty);
 607         }
 608     }
 609 }
 610
 611 pub fn walk_fn_ret_ty<'a, V: Visitor<'a>>(visitor: &mut V, ret_ty: &'a FnRetTy) {
 612     if let FnRetTy::Ty(ref output_ty) = *ret_ty {
 613         visitor.visit_ty(output_ty)
 614     }
 615 }
 616
 617 pub fn walk_fn_decl<'a, V: Visitor<'a>>(visitor: &mut V, function_declaration: &'a FnDecl) {
 618     for param in &function_declaration.inputs {
 619         visitor.visit_param(param);
 620     }
 621     visitor.visit_fn_ret_ty(&function_declaration.output);
 622 }
 623
 624 pub fn walk_fn<'a, V: Visitor<'a>>(visitor: &mut V, kind: FnKind<'a>, _span: Span) {
 625     match kind {
 626         FnKind::Fn(_, _, sig, _, body) => {
 627             visitor.visit_fn_header(&sig.header);
 628             walk_fn_decl(visitor, &sig.decl);
 629             walk_list!(visitor, visit_block, body);
 630         }
 631         FnKind::Closure(decl, body) => {
 632             walk_fn_decl(visitor, decl);
 633             visitor.visit_expr(body);
 634         }
 635     }
 636 }
 637
 638 pub fn walk_assoc_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a AssocItem, ctxt: AssocCtxt) {
 639     let Item { id, span, ident, ref vis, ref attrs, ref kind, tokens: _ } = *item;
 640     visitor.visit_vis(vis);
 641     visitor.visit_ident(ident);
 642     walk_list!(visitor, visit_attribute, attrs);
 643     match kind {
 644         AssocItemKind::Const(_, ty, expr) => {
 645             visitor.visit_ty(ty);
 646             walk_list!(visitor, visit_expr, expr);
 647         }
 648         AssocItemKind::Fn(_, sig, generics, body) => {
 649             visitor.visit_generics(generics);
 650             let kind = FnKind::Fn(FnCtxt::Assoc(ctxt), ident, sig, vis, body.as_deref());
 651             visitor.visit_fn(kind, span, id);
 652         }
 653         AssocItemKind::TyAlias(_, generics, bounds, ty) => {
 654             visitor.visit_generics(generics);
 655             walk_list!(visitor, visit_param_bound, bounds);
 656             walk_list!(visitor, visit_ty, ty);
 657         }
 658         AssocItemKind::MacCall(mac) => {
 659             visitor.visit_mac(mac);
 660         }
 661     }
 662 }
 663
 664 pub fn walk_struct_def<'a, V: Visitor<'a>>(visitor: &mut V, struct_definition: &'a VariantData) {
 665     walk_list!(visitor, visit_struct_field, struct_definition.fields());
 666 }
 667
 668 pub fn walk_struct_field<'a, V: Visitor<'a>>(visitor: &mut V, struct_field: &'a StructField) {
 669     visitor.visit_vis(&struct_field.vis);
 670     if let Some(ident) = struct_field.ident {
 671         visitor.visit_ident(ident);
 672     }
 673     visitor.visit_ty(&struct_field.ty);
 674     walk_list!(visitor, visit_attribute, &struct_field.attrs);
 675 }
 676
 677 pub fn walk_block<'a, V: Visitor<'a>>(visitor: &mut V, block: &'a Block) {
 678     walk_list!(visitor, visit_stmt, &block.stmts);
 679 }
 680
 681 pub fn walk_stmt<'a, V: Visitor<'a>>(visitor: &mut V, statement: &'a Stmt) {
 682     match statement.kind {
 683         StmtKind::Local(ref local) => visitor.visit_local(local),
 684         StmtKind::Item(ref item) => visitor.visit_item(item),
 685         StmtKind::Expr(ref expr) | StmtKind::Semi(ref expr) => visitor.visit_expr(expr),
 686         StmtKind::Empty => {}
 687         StmtKind::MacCall(ref mac) => {
 688             let (ref mac, _, ref attrs) = **mac;
 689             visitor.visit_mac(mac);
 690             for attr in attrs.iter() {
 691                 visitor.visit_attribute(attr);
 692             }
 693         }
 694     }
 695 }
 696
 697 pub fn walk_mac<'a, V: Visitor<'a>>(visitor: &mut V, mac: &'a MacCall) {
 698     visitor.visit_path(&mac.path, DUMMY_NODE_ID);
 699 }
 700
 701 pub fn walk_anon_const<'a, V: Visitor<'a>>(visitor: &mut V, constant: &'a AnonConst) {
 702     visitor.visit_expr(&constant.value);
 703 }
 704
 705 pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
 706     walk_list!(visitor, visit_attribute, expression.attrs.iter());
 707
 708     match expression.kind {
 709         ExprKind::Box(ref subexpression) => visitor.visit_expr(subexpression),
 710         ExprKind::Array(ref subexpressions) => {
 711             walk_list!(visitor, visit_expr, subexpressions);
 712         }
 713         ExprKind::Repeat(ref element, ref count) => {
 714             visitor.visit_expr(element);
 715             visitor.visit_anon_const(count)
 716         }
 717         ExprKind::Struct(ref path, ref fields, ref optional_base) => {
 718             visitor.visit_path(path, expression.id);
 719             walk_list!(visitor, visit_field, fields);
 720             walk_list!(visitor, visit_expr, optional_base);
 721         }
 722         ExprKind::Tup(ref subexpressions) => {
 723             walk_list!(visitor, visit_expr, subexpressions);
 724         }
 725         ExprKind::Call(ref callee_expression, ref arguments) => {
 726             visitor.visit_expr(callee_expression);
 727             walk_list!(visitor, visit_expr, arguments);
 728         }
 729         ExprKind::MethodCall(ref segment, ref arguments, _span) => {
 730             visitor.visit_path_segment(expression.span, segment);
 731             walk_list!(visitor, visit_expr, arguments);
 732         }
 733         ExprKind::Binary(_, ref left_expression, ref right_expression) => {
 734             visitor.visit_expr(left_expression);
 735             visitor.visit_expr(right_expression)
 736         }
 737         ExprKind::AddrOf(_, _, ref subexpression) | ExprKind::Unary(_, ref subexpression) => {
 738             visitor.visit_expr(subexpression)
 739         }
 740         ExprKind::Cast(ref subexpression, ref typ) | ExprKind::Type(ref subexpression, ref typ) => {
 741             visitor.visit_expr(subexpression);
 742             visitor.visit_ty(typ)
 743         }
 744         ExprKind::Let(ref pat, ref scrutinee) => {
 745             visitor.visit_pat(pat);
 746             visitor.visit_expr(scrutinee);
 747         }
 748         ExprKind::If(ref head_expression, ref if_block, ref optional_else) => {
 749             visitor.visit_expr(head_expression);
 750             visitor.visit_block(if_block);
 751             walk_list!(visitor, visit_expr, optional_else);
 752         }
 753         ExprKind::While(ref subexpression, ref block, ref opt_label) => {
 754             walk_list!(visitor, visit_label, opt_label);
 755             visitor.visit_expr(subexpression);
 756             visitor.visit_block(block);
 757         }
 758         ExprKind::ForLoop(ref pattern, ref subexpression, ref block, ref opt_label) => {
 759             walk_list!(visitor, visit_label, opt_label);
 760             visitor.visit_pat(pattern);
 761             visitor.visit_expr(subexpression);
 762             visitor.visit_block(block);
 763         }
 764         ExprKind::Loop(ref block, ref opt_label) => {
 765             walk_list!(visitor, visit_label, opt_label);
 766             visitor.visit_block(block);
 767         }
 768         ExprKind::Match(ref subexpression, ref arms) => {
 769             visitor.visit_expr(subexpression);
 770             walk_list!(visitor, visit_arm, arms);
 771         }
 772         ExprKind::Closure(_, _, _, ref decl, ref body, _decl_span) => {
 773             visitor.visit_fn(FnKind::Closure(decl, body), expression.span, expression.id)
 774         }
 775         ExprKind::Block(ref block, ref opt_label) => {
 776             walk_list!(visitor, visit_label, opt_label);
 777             visitor.visit_block(block);
 778         }
 779         ExprKind::Async(_, _, ref body) => {
 780             visitor.visit_block(body);
 781         }
 782         ExprKind::Await(ref expr) => visitor.visit_expr(expr),
 783         ExprKind::Assign(ref lhs, ref rhs, _) => {
 784             visitor.visit_expr(lhs);
 785             visitor.visit_expr(rhs);
 786         }
 787         ExprKind::AssignOp(_, ref left_expression, ref right_expression) => {
 788             visitor.visit_expr(left_expression);
 789             visitor.visit_expr(right_expression);
 790         }
 791         ExprKind::Field(ref subexpression, ident) => {
 792             visitor.visit_expr(subexpression);
 793             visitor.visit_ident(ident);
 794         }
 795         ExprKind::Index(ref main_expression, ref index_expression) => {
 796             visitor.visit_expr(main_expression);
 797             visitor.visit_expr(index_expression)
 798         }
 799         ExprKind::Range(ref start, ref end, _) => {
 800             walk_list!(visitor, visit_expr, start);
 801             walk_list!(visitor, visit_expr, end);
 802         }
 803         ExprKind::Path(ref maybe_qself, ref path) => {
 804             if let Some(ref qself) = *maybe_qself {
 805                 visitor.visit_ty(&qself.ty);
 806             }
 807             visitor.visit_path(path, expression.id)
 808         }
 809         ExprKind::Break(ref opt_label, ref opt_expr) => {
 810             walk_list!(visitor, visit_label, opt_label);
 811             walk_list!(visitor, visit_expr, opt_expr);
 812         }
 813         ExprKind::Continue(ref opt_label) => {
 814             walk_list!(visitor, visit_label, opt_label);
 815         }
 816         ExprKind::Ret(ref optional_expression) => {
 817             walk_list!(visitor, visit_expr, optional_expression);
 818         }
 819         ExprKind::MacCall(ref mac) => visitor.visit_mac(mac),
 820         ExprKind::Paren(ref subexpression) => visitor.visit_expr(subexpression),
 821         ExprKind::InlineAsm(ref ia) => {
 822             for (op, _) in &ia.operands {
 823                 match op {
 824                     InlineAsmOperand::In { expr, .. }
 825                     | InlineAsmOperand::InOut { expr, .. }
 826                     | InlineAsmOperand::Const { expr, .. }
 827                     | InlineAsmOperand::Sym { expr, .. } => visitor.visit_expr(expr),
 828                     InlineAsmOperand::Out { expr, .. } => {
 829                         if let Some(expr) = expr {
 830                             visitor.visit_expr(expr);
 831                         }
 832                     }
 833                     InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
 834                         visitor.visit_expr(in_expr);
 835                         if let Some(out_expr) = out_expr {
 836                             visitor.visit_expr(out_expr);
 837                         }
 838                     }
 839                 }
 840             }
 841         }
 842         ExprKind::LlvmInlineAsm(ref ia) => {
 843             for &(_, ref input) in &ia.inputs {
 844                 visitor.visit_expr(input)
 845             }
 846             for output in &ia.outputs {
 847                 visitor.visit_expr(&output.expr)
 848             }
 849         }
 850         ExprKind::Yield(ref optional_expression) => {
 851             walk_list!(visitor, visit_expr, optional_expression);
 852         }
 853         ExprKind::Try(ref subexpression) => visitor.visit_expr(subexpression),
 854         ExprKind::TryBlock(ref body) => visitor.visit_block(body),
 855         ExprKind::Lit(_) | ExprKind::Err => {}
 856     }
 857
 858     visitor.visit_expr_post(expression)
 859 }
 860
 861 pub fn walk_param<'a, V: Visitor<'a>>(visitor: &mut V, param: &'a Param) {
 862     walk_list!(visitor, visit_attribute, param.attrs.iter());
 863     visitor.visit_pat(&param.pat);
 864     visitor.visit_ty(&param.ty);
 865 }
 866
 867 pub fn walk_arm<'a, V: Visitor<'a>>(visitor: &mut V, arm: &'a Arm) {
 868     visitor.visit_pat(&arm.pat);
 869     walk_list!(visitor, visit_expr, &arm.guard);
 870     visitor.visit_expr(&arm.body);
 871     walk_list!(visitor, visit_attribute, &arm.attrs);
 872 }
 873
 874 pub fn walk_vis<'a, V: Visitor<'a>>(visitor: &mut V, vis: &'a Visibility) {
 875     if let VisibilityKind::Restricted { ref path, id } = vis.node {
 876         visitor.visit_path(path, id);
 877     }
 878 }
 879
 880 pub fn walk_attribute<'a, V: Visitor<'a>>(visitor: &mut V, attr: &'a Attribute) {
 881     match attr.kind {
 882         AttrKind::Normal(ref item) => walk_mac_args(visitor, &item.args),
 883         AttrKind::DocComment(_) => {}
 884     }
 885 }
 886
 887 pub fn walk_mac_args<'a, V: Visitor<'a>>(visitor: &mut V, args: &'a MacArgs) {
 888     match args {
 889         MacArgs::Empty => {}
 890         MacArgs::Delimited(_dspan, _delim, tokens) => visitor.visit_tts(tokens.clone()),
 891         MacArgs::Eq(_eq_span, tokens) => visitor.visit_tts(tokens.clone()),
 892     }
 893 }
 894
 895 pub fn walk_tt<'a, V: Visitor<'a>>(visitor: &mut V, tt: TokenTree) {
 896     match tt {
 897         TokenTree::Token(token) => visitor.visit_token(token),
 898         TokenTree::Delimited(_, _, tts) => visitor.visit_tts(tts),
 899     }
 900 }
 901
 902 pub fn walk_tts<'a, V: Visitor<'a>>(visitor: &mut V, tts: TokenStream) {
 903     for tt in tts.trees() {
 904         visitor.visit_tt(tt);
 905     }
 906 }