compiler/rustc_ast/src/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;
  18
  19 use rustc_span::symbol::{Ident, Symbol};
  20 use rustc_span::Span;
  21
  22 #[derive(Copy, Clone, PartialEq)]
  23 pub enum AssocCtxt {
  24     Trait,
  25     Impl,
  26 }
  27
  28 #[derive(Copy, Clone, PartialEq)]
  29 pub enum FnCtxt {
  30     Free,
  31     Foreign,
  32     Assoc(AssocCtxt),
  33 }
  34
  35 #[derive(Copy, Clone)]
  36 pub enum FnKind<'a> {
  37     /// E.g., `fn foo()`, `fn foo(&self)`, or `extern "Abi" fn foo()`.
  38     Fn(FnCtxt, Ident, &'a FnSig, &'a Visibility, Option<&'a Block>),
  39
  40     /// E.g., `|x, y| body`.
  41     Closure(&'a FnDecl, &'a Expr),
  42 }
  43
  44 impl<'a> FnKind<'a> {
  45     pub fn header(&self) -> Option<&'a FnHeader> {
  46         match *self {
  47             FnKind::Fn(_, _, sig, _, _) => Some(&sig.header),
  48             FnKind::Closure(_, _) => None,
  49         }
  50     }
  51
  52     pub fn ident(&self) -> Option<&Ident> {
  53         match self {
  54             FnKind::Fn(_, ident, ..) => Some(ident),
  55             _ => None,
  56         }
  57     }
  58
  59     pub fn decl(&self) -> &'a FnDecl {
  60         match self {
  61             FnKind::Fn(_, _, sig, _, _) => &sig.decl,
  62             FnKind::Closure(decl, _) => decl,
  63         }
  64     }
  65
  66     pub fn ctxt(&self) -> Option<FnCtxt> {
  67         match self {
  68             FnKind::Fn(ctxt, ..) => Some(*ctxt),
  69             FnKind::Closure(..) => None,
  70         }
  71     }
  72 }
  73
  74 /// Each method of the `Visitor` trait is a hook to be potentially
  75 /// overridden. Each method's default implementation recursively visits
  76 /// the substructure of the input via the corresponding `walk` method;
  77 /// e.g., the `visit_item` method by default calls `visit::walk_item`.
  78 ///
  79 /// If you want to ensure that your code handles every variant
  80 /// explicitly, you need to override each method. (And you also need
  81 /// to monitor future changes to `Visitor` in case a new method with a
  82 /// new default implementation gets introduced.)
  83 pub trait Visitor<'ast>: Sized {
  84     fn visit_name(&mut self, _span: Span, _name: Symbol) {
  85         // Nothing to do.
  86     }
  87     fn visit_ident(&mut self, ident: Ident) {
  88         walk_ident(self, ident);
  89     }
  90     fn visit_foreign_item(&mut self, i: &'ast ForeignItem) {
  91         walk_foreign_item(self, i)
  92     }
  93     fn visit_global_asm(&mut self, ga: &'ast GlobalAsm) {
  94         walk_global_asm(self, ga)
  95     }
  96     fn visit_item(&mut self, i: &'ast Item) {
  97         walk_item(self, i)
  98     }
  99     fn visit_local(&mut self, l: &'ast Local) {
 100         walk_local(self, l)
 101     }
 102     fn visit_block(&mut self, b: &'ast Block) {
 103         walk_block(self, b)
 104     }
 105     fn visit_stmt(&mut self, s: &'ast Stmt) {
 106         walk_stmt(self, s)
 107     }
 108     fn visit_param(&mut self, param: &'ast Param) {
 109         walk_param(self, param)
 110     }
 111     fn visit_arm(&mut self, a: &'ast Arm) {
 112         walk_arm(self, a)
 113     }
 114     fn visit_pat(&mut self, p: &'ast Pat) {
 115         walk_pat(self, p)
 116     }
 117     fn visit_anon_const(&mut self, c: &'ast AnonConst) {
 118         walk_anon_const(self, c)
 119     }
 120     fn visit_expr(&mut self, ex: &'ast Expr) {
 121         walk_expr(self, ex)
 122     }
 123     fn visit_expr_post(&mut self, _ex: &'ast Expr) {}
 124     fn visit_ty(&mut self, t: &'ast Ty) {
 125         walk_ty(self, t)
 126     }
 127     fn visit_generic_param(&mut self, param: &'ast GenericParam) {
 128         walk_generic_param(self, param)
 129     }
 130     fn visit_generics(&mut self, g: &'ast Generics) {
 131         walk_generics(self, g)
 132     }
 133     fn visit_where_predicate(&mut self, p: &'ast WherePredicate) {
 134         walk_where_predicate(self, p)
 135     }
 136     fn visit_fn(&mut self, fk: FnKind<'ast>, s: Span, _: NodeId) {
 137         walk_fn(self, fk, s)
 138     }
 139     fn visit_assoc_item(&mut self, i: &'ast AssocItem, ctxt: AssocCtxt) {
 140         walk_assoc_item(self, i, ctxt)
 141     }
 142     fn visit_trait_ref(&mut self, t: &'ast TraitRef) {
 143         walk_trait_ref(self, t)
 144     }
 145     fn visit_param_bound(&mut self, bounds: &'ast GenericBound) {
 146         walk_param_bound(self, bounds)
 147     }
 148     fn visit_poly_trait_ref(&mut self, t: &'ast PolyTraitRef, m: &'ast TraitBoundModifier) {
 149         walk_poly_trait_ref(self, t, m)
 150     }
 151     fn visit_variant_data(&mut self, s: &'ast VariantData) {
 152         walk_struct_def(self, s)
 153     }
 154     fn visit_field_def(&mut self, s: &'ast FieldDef) {
 155         walk_field_def(self, s)
 156     }
 157     fn visit_enum_def(
 158         &mut self,
 159         enum_definition: &'ast EnumDef,
 160         generics: &'ast Generics,
 161         item_id: NodeId,
 162         _: Span,
 163     ) {
 164         walk_enum_def(self, enum_definition, generics, item_id)
 165     }
 166     fn visit_variant(&mut self, v: &'ast Variant) {
 167         walk_variant(self, v)
 168     }
 169     fn visit_label(&mut self, label: &'ast Label) {
 170         walk_label(self, label)
 171     }
 172     fn visit_lifetime(&mut self, lifetime: &'ast Lifetime) {
 173         walk_lifetime(self, lifetime)
 174     }
 175     fn visit_mac_call(&mut self, mac: &'ast MacCall) {
 176         walk_mac(self, mac)
 177     }
 178     fn visit_mac_def(&mut self, _mac: &'ast MacroDef, _id: NodeId) {
 179         // Nothing to do
 180     }
 181     fn visit_path(&mut self, path: &'ast Path, _id: NodeId) {
 182         walk_path(self, path)
 183     }
 184     fn visit_use_tree(&mut self, use_tree: &'ast UseTree, id: NodeId, _nested: bool) {
 185         walk_use_tree(self, use_tree, id)
 186     }
 187     fn visit_path_segment(&mut self, path_span: Span, path_segment: &'ast PathSegment) {
 188         walk_path_segment(self, path_span, path_segment)
 189     }
 190     fn visit_generic_args(&mut self, path_span: Span, generic_args: &'ast GenericArgs) {
 191         walk_generic_args(self, path_span, generic_args)
 192     }
 193     fn visit_generic_arg(&mut self, generic_arg: &'ast GenericArg) {
 194         walk_generic_arg(self, generic_arg)
 195     }
 196     fn visit_assoc_ty_constraint(&mut self, constraint: &'ast AssocTyConstraint) {
 197         walk_assoc_ty_constraint(self, constraint)
 198     }
 199     fn visit_attribute(&mut self, attr: &'ast Attribute) {
 200         walk_attribute(self, attr)
 201     }
 202     fn visit_vis(&mut self, vis: &'ast Visibility) {
 203         walk_vis(self, vis)
 204     }
 205     fn visit_fn_ret_ty(&mut self, ret_ty: &'ast FnRetTy) {
 206         walk_fn_ret_ty(self, ret_ty)
 207     }
 208     fn visit_fn_header(&mut self, _header: &'ast FnHeader) {
 209         // Nothing to do
 210     }
 211     fn visit_expr_field(&mut self, f: &'ast ExprField) {
 212         walk_expr_field(self, f)
 213     }
 214     fn visit_pat_field(&mut self, fp: &'ast PatField) {
 215         walk_pat_field(self, fp)
 216     }
 217 }
 218
 219 #[macro_export]
 220 macro_rules! walk_list {
 221     ($visitor: expr, $method: ident, $list: expr) => {
 222         for elem in $list {
 223             $visitor.$method(elem)
 224         }
 225     };
 226     ($visitor: expr, $method: ident, $list: expr, $($extra_args: expr),*) => {
 227         for elem in $list {
 228             $visitor.$method(elem, $($extra_args,)*)
 229         }
 230     }
 231 }
 232
 233 pub fn walk_ident<'a, V: Visitor<'a>>(visitor: &mut V, ident: Ident) {
 234     visitor.visit_name(ident.span, ident.name);
 235 }
 236
 237 pub fn walk_crate<'a, V: Visitor<'a>>(visitor: &mut V, krate: &'a Crate) {
 238     walk_list!(visitor, visit_item, &krate.items);
 239     walk_list!(visitor, visit_attribute, &krate.attrs);
 240 }
 241
 242 pub fn walk_local<'a, V: Visitor<'a>>(visitor: &mut V, local: &'a Local) {
 243     for attr in local.attrs.iter() {
 244         visitor.visit_attribute(attr);
 245     }
 246     visitor.visit_pat(&local.pat);
 247     walk_list!(visitor, visit_ty, &local.ty);
 248     walk_list!(visitor, visit_expr, &local.init);
 249 }
 250
 251 pub fn walk_label<'a, V: Visitor<'a>>(visitor: &mut V, label: &'a Label) {
 252     visitor.visit_ident(label.ident);
 253 }
 254
 255 pub fn walk_lifetime<'a, V: Visitor<'a>>(visitor: &mut V, lifetime: &'a Lifetime) {
 256     visitor.visit_ident(lifetime.ident);
 257 }
 258
 259 pub fn walk_poly_trait_ref<'a, V>(
 260     visitor: &mut V,
 261     trait_ref: &'a PolyTraitRef,
 262     _: &TraitBoundModifier,
 263 ) where
 264     V: Visitor<'a>,
 265 {
 266     walk_list!(visitor, visit_generic_param, &trait_ref.bound_generic_params);
 267     visitor.visit_trait_ref(&trait_ref.trait_ref);
 268 }
 269
 270 pub fn walk_trait_ref<'a, V: Visitor<'a>>(visitor: &mut V, trait_ref: &'a TraitRef) {
 271     visitor.visit_path(&trait_ref.path, trait_ref.ref_id)
 272 }
 273
 274 pub fn walk_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a Item) {
 275     visitor.visit_vis(&item.vis);
 276     visitor.visit_ident(item.ident);
 277     match item.kind {
 278         ItemKind::ExternCrate(orig_name) => {
 279             if let Some(orig_name) = orig_name {
 280                 visitor.visit_name(item.span, orig_name);
 281             }
 282         }
 283         ItemKind::Use(ref use_tree) => visitor.visit_use_tree(use_tree, item.id, false),
 284         ItemKind::Static(ref typ, _, ref expr) | ItemKind::Const(_, ref typ, ref expr) => {
 285             visitor.visit_ty(typ);
 286             walk_list!(visitor, visit_expr, expr);
 287         }
 288         ItemKind::Fn(box FnKind(_, ref sig, ref generics, ref body)) => {
 289             visitor.visit_generics(generics);
 290             let kind = FnKind::Fn(FnCtxt::Free, item.ident, sig, &item.vis, body.as_deref());
 291             visitor.visit_fn(kind, item.span, item.id)
 292         }
 293         ItemKind::Mod(_unsafety, ref mod_kind) => match mod_kind {
 294             ModKind::Loaded(items, _inline, _inner_span) => {
 295                 walk_list!(visitor, visit_item, items)
 296             }
 297             ModKind::Unloaded => {}
 298         },
 299         ItemKind::ForeignMod(ref foreign_module) => {
 300             walk_list!(visitor, visit_foreign_item, &foreign_module.items);
 301         }
 302         ItemKind::GlobalAsm(ref ga) => visitor.visit_global_asm(ga),
 303         ItemKind::TyAlias(box TyAliasKind(_, ref generics, ref bounds, ref ty)) => {
 304             visitor.visit_generics(generics);
 305             walk_list!(visitor, visit_param_bound, bounds);
 306             walk_list!(visitor, visit_ty, ty);
 307         }
 308         ItemKind::Enum(ref enum_definition, ref generics) => {
 309             visitor.visit_generics(generics);
 310             visitor.visit_enum_def(enum_definition, generics, item.id, item.span)
 311         }
 312         ItemKind::Impl(box ImplKind {
 313             unsafety: _,
 314             polarity: _,
 315             defaultness: _,
 316             constness: _,
 317             ref generics,
 318             ref of_trait,
 319             ref self_ty,
 320             ref items,
 321         }) => {
 322             visitor.visit_generics(generics);
 323             walk_list!(visitor, visit_trait_ref, of_trait);
 324             visitor.visit_ty(self_ty);
 325             walk_list!(visitor, visit_assoc_item, items, AssocCtxt::Impl);
 326         }
 327         ItemKind::Struct(ref struct_definition, ref generics)
 328         | ItemKind::Union(ref struct_definition, ref generics) => {
 329             visitor.visit_generics(generics);
 330             visitor.visit_variant_data(struct_definition);
 331         }
 332         ItemKind::Trait(box TraitKind(.., ref generics, ref bounds, ref items)) => {
 333             visitor.visit_generics(generics);
 334             walk_list!(visitor, visit_param_bound, bounds);
 335             walk_list!(visitor, visit_assoc_item, items, AssocCtxt::Trait);
 336         }
 337         ItemKind::TraitAlias(ref generics, ref bounds) => {
 338             visitor.visit_generics(generics);
 339             walk_list!(visitor, visit_param_bound, bounds);
 340         }
 341         ItemKind::MacCall(ref mac) => visitor.visit_mac_call(mac),
 342         ItemKind::MacroDef(ref ts) => visitor.visit_mac_def(ts, item.id),
 343     }
 344     walk_list!(visitor, visit_attribute, &item.attrs);
 345 }
 346
 347 pub fn walk_enum_def<'a, V: Visitor<'a>>(
 348     visitor: &mut V,
 349     enum_definition: &'a EnumDef,
 350     _: &'a Generics,
 351     _: NodeId,
 352 ) {
 353     walk_list!(visitor, visit_variant, &enum_definition.variants);
 354 }
 355
 356 pub fn walk_variant<'a, V: Visitor<'a>>(visitor: &mut V, variant: &'a Variant)
 357 where
 358     V: Visitor<'a>,
 359 {
 360     visitor.visit_ident(variant.ident);
 361     visitor.visit_vis(&variant.vis);
 362     visitor.visit_variant_data(&variant.data);
 363     walk_list!(visitor, visit_anon_const, &variant.disr_expr);
 364     walk_list!(visitor, visit_attribute, &variant.attrs);
 365 }
 366
 367 pub fn walk_expr_field<'a, V: Visitor<'a>>(visitor: &mut V, f: &'a ExprField) {
 368     visitor.visit_expr(&f.expr);
 369     visitor.visit_ident(f.ident);
 370     walk_list!(visitor, visit_attribute, f.attrs.iter());
 371 }
 372
 373 pub fn walk_pat_field<'a, V: Visitor<'a>>(visitor: &mut V, fp: &'a PatField) {
 374     visitor.visit_ident(fp.ident);
 375     visitor.visit_pat(&fp.pat);
 376     walk_list!(visitor, visit_attribute, fp.attrs.iter());
 377 }
 378
 379 pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) {
 380     match typ.kind {
 381         TyKind::Slice(ref ty) | TyKind::Paren(ref ty) => visitor.visit_ty(ty),
 382         TyKind::Ptr(ref mutable_type) => visitor.visit_ty(&mutable_type.ty),
 383         TyKind::Rptr(ref opt_lifetime, ref mutable_type) => {
 384             walk_list!(visitor, visit_lifetime, opt_lifetime);
 385             visitor.visit_ty(&mutable_type.ty)
 386         }
 387         TyKind::Tup(ref tuple_element_types) => {
 388             walk_list!(visitor, visit_ty, tuple_element_types);
 389         }
 390         TyKind::BareFn(ref function_declaration) => {
 391             walk_list!(visitor, visit_generic_param, &function_declaration.generic_params);
 392             walk_fn_decl(visitor, &function_declaration.decl);
 393         }
 394         TyKind::Path(ref maybe_qself, ref path) => {
 395             if let Some(ref qself) = *maybe_qself {
 396                 visitor.visit_ty(&qself.ty);
 397             }
 398             visitor.visit_path(path, typ.id);
 399         }
 400         TyKind::Array(ref ty, ref length) => {
 401             visitor.visit_ty(ty);
 402             visitor.visit_anon_const(length)
 403         }
 404         TyKind::TraitObject(ref bounds, ..) | TyKind::ImplTrait(_, ref bounds) => {
 405             walk_list!(visitor, visit_param_bound, bounds);
 406         }
 407         TyKind::Typeof(ref expression) => visitor.visit_anon_const(expression),
 408         TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => {}
 409         TyKind::MacCall(ref mac) => visitor.visit_mac_call(mac),
 410         TyKind::Never | TyKind::CVarArgs => {}
 411     }
 412 }
 413
 414 pub fn walk_path<'a, V: Visitor<'a>>(visitor: &mut V, path: &'a Path) {
 415     for segment in &path.segments {
 416         visitor.visit_path_segment(path.span, segment);
 417     }
 418 }
 419
 420 pub fn walk_use_tree<'a, V: Visitor<'a>>(visitor: &mut V, use_tree: &'a UseTree, id: NodeId) {
 421     visitor.visit_path(&use_tree.prefix, id);
 422     match use_tree.kind {
 423         UseTreeKind::Simple(rename, ..) => {
 424             // The extra IDs are handled during HIR lowering.
 425             if let Some(rename) = rename {
 426                 visitor.visit_ident(rename);
 427             }
 428         }
 429         UseTreeKind::Glob => {}
 430         UseTreeKind::Nested(ref use_trees) => {
 431             for &(ref nested_tree, nested_id) in use_trees {
 432                 visitor.visit_use_tree(nested_tree, nested_id, true);
 433             }
 434         }
 435     }
 436 }
 437
 438 pub fn walk_path_segment<'a, V: Visitor<'a>>(
 439     visitor: &mut V,
 440     path_span: Span,
 441     segment: &'a PathSegment,
 442 ) {
 443     visitor.visit_ident(segment.ident);
 444     if let Some(ref args) = segment.args {
 445         visitor.visit_generic_args(path_span, args);
 446     }
 447 }
 448
 449 pub fn walk_generic_args<'a, V>(visitor: &mut V, _path_span: Span, generic_args: &'a GenericArgs)
 450 where
 451     V: Visitor<'a>,
 452 {
 453     match *generic_args {
 454         GenericArgs::AngleBracketed(ref data) => {
 455             for arg in &data.args {
 456                 match arg {
 457                     AngleBracketedArg::Arg(a) => visitor.visit_generic_arg(a),
 458                     AngleBracketedArg::Constraint(c) => visitor.visit_assoc_ty_constraint(c),
 459                 }
 460             }
 461         }
 462         GenericArgs::Parenthesized(ref data) => {
 463             walk_list!(visitor, visit_ty, &data.inputs);
 464             walk_fn_ret_ty(visitor, &data.output);
 465         }
 466     }
 467 }
 468
 469 pub fn walk_generic_arg<'a, V>(visitor: &mut V, generic_arg: &'a GenericArg)
 470 where
 471     V: Visitor<'a>,
 472 {
 473     match generic_arg {
 474         GenericArg::Lifetime(lt) => visitor.visit_lifetime(lt),
 475         GenericArg::Type(ty) => visitor.visit_ty(ty),
 476         GenericArg::Const(ct) => visitor.visit_anon_const(ct),
 477     }
 478 }
 479
 480 pub fn walk_assoc_ty_constraint<'a, V: Visitor<'a>>(
 481     visitor: &mut V,
 482     constraint: &'a AssocTyConstraint,
 483 ) {
 484     visitor.visit_ident(constraint.ident);
 485     if let Some(ref gen_args) = constraint.gen_args {
 486         visitor.visit_generic_args(gen_args.span(), gen_args);
 487     }
 488     match constraint.kind {
 489         AssocTyConstraintKind::Equality { ref ty } => {
 490             visitor.visit_ty(ty);
 491         }
 492         AssocTyConstraintKind::Bound { ref bounds } => {
 493             walk_list!(visitor, visit_param_bound, bounds);
 494         }
 495     }
 496 }
 497
 498 pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) {
 499     match pattern.kind {
 500         PatKind::TupleStruct(ref path, ref elems) => {
 501             visitor.visit_path(path, pattern.id);
 502             walk_list!(visitor, visit_pat, elems);
 503         }
 504         PatKind::Path(ref opt_qself, ref path) => {
 505             if let Some(ref qself) = *opt_qself {
 506                 visitor.visit_ty(&qself.ty);
 507             }
 508             visitor.visit_path(path, pattern.id)
 509         }
 510         PatKind::Struct(ref path, ref fields, _) => {
 511             visitor.visit_path(path, pattern.id);
 512             walk_list!(visitor, visit_pat_field, fields);
 513         }
 514         PatKind::Box(ref subpattern)
 515         | PatKind::Ref(ref subpattern, _)
 516         | PatKind::Paren(ref subpattern) => visitor.visit_pat(subpattern),
 517         PatKind::Ident(_, ident, ref optional_subpattern) => {
 518             visitor.visit_ident(ident);
 519             walk_list!(visitor, visit_pat, optional_subpattern);
 520         }
 521         PatKind::Lit(ref expression) => visitor.visit_expr(expression),
 522         PatKind::Range(ref lower_bound, ref upper_bound, _) => {
 523             walk_list!(visitor, visit_expr, lower_bound);
 524             walk_list!(visitor, visit_expr, upper_bound);
 525         }
 526         PatKind::Wild | PatKind::Rest => {}
 527         PatKind::Tuple(ref elems) | PatKind::Slice(ref elems) | PatKind::Or(ref elems) => {
 528             walk_list!(visitor, visit_pat, elems);
 529         }
 530         PatKind::MacCall(ref mac) => visitor.visit_mac_call(mac),
 531     }
 532 }
 533
 534 pub fn walk_foreign_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a ForeignItem) {
 535     let Item { id, span, ident, ref vis, ref attrs, ref kind, tokens: _ } = *item;
 536     visitor.visit_vis(vis);
 537     visitor.visit_ident(ident);
 538     walk_list!(visitor, visit_attribute, attrs);
 539     match kind {
 540         ForeignItemKind::Static(ty, _, expr) => {
 541             visitor.visit_ty(ty);
 542             walk_list!(visitor, visit_expr, expr);
 543         }
 544         ForeignItemKind::Fn(box FnKind(_, sig, generics, body)) => {
 545             visitor.visit_generics(generics);
 546             let kind = FnKind::Fn(FnCtxt::Foreign, ident, sig, vis, body.as_deref());
 547             visitor.visit_fn(kind, span, id);
 548         }
 549         ForeignItemKind::TyAlias(box TyAliasKind(_, generics, bounds, ty)) => {
 550             visitor.visit_generics(generics);
 551             walk_list!(visitor, visit_param_bound, bounds);
 552             walk_list!(visitor, visit_ty, ty);
 553         }
 554         ForeignItemKind::MacCall(mac) => {
 555             visitor.visit_mac_call(mac);
 556         }
 557     }
 558 }
 559
 560 pub fn walk_global_asm<'a, V: Visitor<'a>>(_: &mut V, _: &'a GlobalAsm) {
 561     // Empty!
 562 }
 563
 564 pub fn walk_param_bound<'a, V: Visitor<'a>>(visitor: &mut V, bound: &'a GenericBound) {
 565     match *bound {
 566         GenericBound::Trait(ref typ, ref modifier) => visitor.visit_poly_trait_ref(typ, modifier),
 567         GenericBound::Outlives(ref lifetime) => visitor.visit_lifetime(lifetime),
 568     }
 569 }
 570
 571 pub fn walk_generic_param<'a, V: Visitor<'a>>(visitor: &mut V, param: &'a GenericParam) {
 572     visitor.visit_ident(param.ident);
 573     walk_list!(visitor, visit_attribute, param.attrs.iter());
 574     walk_list!(visitor, visit_param_bound, &param.bounds);
 575     match param.kind {
 576         GenericParamKind::Lifetime => (),
 577         GenericParamKind::Type { ref default } => walk_list!(visitor, visit_ty, default),
 578         GenericParamKind::Const { ref ty, ref default, .. } => {
 579             visitor.visit_ty(ty);
 580             if let Some(default) = default {
 581                 visitor.visit_anon_const(default);
 582             }
 583         }
 584     }
 585 }
 586
 587 pub fn walk_generics<'a, V: Visitor<'a>>(visitor: &mut V, generics: &'a Generics) {
 588     walk_list!(visitor, visit_generic_param, &generics.params);
 589     walk_list!(visitor, visit_where_predicate, &generics.where_clause.predicates);
 590 }
 591
 592 pub fn walk_where_predicate<'a, V: Visitor<'a>>(visitor: &mut V, predicate: &'a WherePredicate) {
 593     match *predicate {
 594         WherePredicate::BoundPredicate(WhereBoundPredicate {
 595             ref bounded_ty,
 596             ref bounds,
 597             ref bound_generic_params,
 598             ..
 599         }) => {
 600             visitor.visit_ty(bounded_ty);
 601             walk_list!(visitor, visit_param_bound, bounds);
 602             walk_list!(visitor, visit_generic_param, bound_generic_params);
 603         }
 604         WherePredicate::RegionPredicate(WhereRegionPredicate {
 605             ref lifetime, ref bounds, ..
 606         }) => {
 607             visitor.visit_lifetime(lifetime);
 608             walk_list!(visitor, visit_param_bound, bounds);
 609         }
 610         WherePredicate::EqPredicate(WhereEqPredicate { ref lhs_ty, ref rhs_ty, .. }) => {
 611             visitor.visit_ty(lhs_ty);
 612             visitor.visit_ty(rhs_ty);
 613         }
 614     }
 615 }
 616
 617 pub fn walk_fn_ret_ty<'a, V: Visitor<'a>>(visitor: &mut V, ret_ty: &'a FnRetTy) {
 618     if let FnRetTy::Ty(ref output_ty) = *ret_ty {
 619         visitor.visit_ty(output_ty)
 620     }
 621 }
 622
 623 pub fn walk_fn_decl<'a, V: Visitor<'a>>(visitor: &mut V, function_declaration: &'a FnDecl) {
 624     for param in &function_declaration.inputs {
 625         visitor.visit_param(param);
 626     }
 627     visitor.visit_fn_ret_ty(&function_declaration.output);
 628 }
 629
 630 pub fn walk_fn<'a, V: Visitor<'a>>(visitor: &mut V, kind: FnKind<'a>, _span: Span) {
 631     match kind {
 632         FnKind::Fn(_, _, sig, _, body) => {
 633             visitor.visit_fn_header(&sig.header);
 634             walk_fn_decl(visitor, &sig.decl);
 635             walk_list!(visitor, visit_block, body);
 636         }
 637         FnKind::Closure(decl, body) => {
 638             walk_fn_decl(visitor, decl);
 639             visitor.visit_expr(body);
 640         }
 641     }
 642 }
 643
 644 pub fn walk_assoc_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a AssocItem, ctxt: AssocCtxt) {
 645     let Item { id, span, ident, ref vis, ref attrs, ref kind, tokens: _ } = *item;
 646     visitor.visit_vis(vis);
 647     visitor.visit_ident(ident);
 648     walk_list!(visitor, visit_attribute, attrs);
 649     match kind {
 650         AssocItemKind::Const(_, ty, expr) => {
 651             visitor.visit_ty(ty);
 652             walk_list!(visitor, visit_expr, expr);
 653         }
 654         AssocItemKind::Fn(box FnKind(_, sig, generics, body)) => {
 655             visitor.visit_generics(generics);
 656             let kind = FnKind::Fn(FnCtxt::Assoc(ctxt), ident, sig, vis, body.as_deref());
 657             visitor.visit_fn(kind, span, id);
 658         }
 659         AssocItemKind::TyAlias(box TyAliasKind(_, generics, bounds, ty)) => {
 660             visitor.visit_generics(generics);
 661             walk_list!(visitor, visit_param_bound, bounds);
 662             walk_list!(visitor, visit_ty, ty);
 663         }
 664         AssocItemKind::MacCall(mac) => {
 665             visitor.visit_mac_call(mac);
 666         }
 667     }
 668 }
 669
 670 pub fn walk_struct_def<'a, V: Visitor<'a>>(visitor: &mut V, struct_definition: &'a VariantData) {
 671     walk_list!(visitor, visit_field_def, struct_definition.fields());
 672 }
 673
 674 pub fn walk_field_def<'a, V: Visitor<'a>>(visitor: &mut V, field: &'a FieldDef) {
 675     visitor.visit_vis(&field.vis);
 676     if let Some(ident) = field.ident {
 677         visitor.visit_ident(ident);
 678     }
 679     visitor.visit_ty(&field.ty);
 680     walk_list!(visitor, visit_attribute, &field.attrs);
 681 }
 682
 683 pub fn walk_block<'a, V: Visitor<'a>>(visitor: &mut V, block: &'a Block) {
 684     walk_list!(visitor, visit_stmt, &block.stmts);
 685 }
 686
 687 pub fn walk_stmt<'a, V: Visitor<'a>>(visitor: &mut V, statement: &'a Stmt) {
 688     match statement.kind {
 689         StmtKind::Local(ref local) => visitor.visit_local(local),
 690         StmtKind::Item(ref item) => visitor.visit_item(item),
 691         StmtKind::Expr(ref expr) | StmtKind::Semi(ref expr) => visitor.visit_expr(expr),
 692         StmtKind::Empty => {}
 693         StmtKind::MacCall(ref mac) => {
 694             let MacCallStmt { ref mac, style: _, ref attrs, tokens: _ } = **mac;
 695             visitor.visit_mac_call(mac);
 696             for attr in attrs.iter() {
 697                 visitor.visit_attribute(attr);
 698             }
 699         }
 700     }
 701 }
 702
 703 pub fn walk_mac<'a, V: Visitor<'a>>(visitor: &mut V, mac: &'a MacCall) {
 704     visitor.visit_path(&mac.path, DUMMY_NODE_ID);
 705 }
 706
 707 pub fn walk_anon_const<'a, V: Visitor<'a>>(visitor: &mut V, constant: &'a AnonConst) {
 708     visitor.visit_expr(&constant.value);
 709 }
 710
 711 pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
 712     walk_list!(visitor, visit_attribute, expression.attrs.iter());
 713
 714     match expression.kind {
 715         ExprKind::Box(ref subexpression) => visitor.visit_expr(subexpression),
 716         ExprKind::Array(ref subexpressions) => {
 717             walk_list!(visitor, visit_expr, subexpressions);
 718         }
 719         ExprKind::ConstBlock(ref anon_const) => visitor.visit_anon_const(anon_const),
 720         ExprKind::Repeat(ref element, ref count) => {
 721             visitor.visit_expr(element);
 722             visitor.visit_anon_const(count)
 723         }
 724         ExprKind::Struct(ref se) => {
 725             visitor.visit_path(&se.path, expression.id);
 726             walk_list!(visitor, visit_expr_field, &se.fields);
 727             match &se.rest {
 728                 StructRest::Base(expr) => visitor.visit_expr(expr),
 729                 StructRest::Rest(_span) => {}
 730                 StructRest::None => {}
 731             }
 732         }
 733         ExprKind::Tup(ref subexpressions) => {
 734             walk_list!(visitor, visit_expr, subexpressions);
 735         }
 736         ExprKind::Call(ref callee_expression, ref arguments) => {
 737             visitor.visit_expr(callee_expression);
 738             walk_list!(visitor, visit_expr, arguments);
 739         }
 740         ExprKind::MethodCall(ref segment, ref arguments, _span) => {
 741             visitor.visit_path_segment(expression.span, segment);
 742             walk_list!(visitor, visit_expr, arguments);
 743         }
 744         ExprKind::Binary(_, ref left_expression, ref right_expression) => {
 745             visitor.visit_expr(left_expression);
 746             visitor.visit_expr(right_expression)
 747         }
 748         ExprKind::AddrOf(_, _, ref subexpression) | ExprKind::Unary(_, ref subexpression) => {
 749             visitor.visit_expr(subexpression)
 750         }
 751         ExprKind::Cast(ref subexpression, ref typ) | ExprKind::Type(ref subexpression, ref typ) => {
 752             visitor.visit_expr(subexpression);
 753             visitor.visit_ty(typ)
 754         }
 755         ExprKind::Let(ref pat, ref scrutinee) => {
 756             visitor.visit_pat(pat);
 757             visitor.visit_expr(scrutinee);
 758         }
 759         ExprKind::If(ref head_expression, ref if_block, ref optional_else) => {
 760             visitor.visit_expr(head_expression);
 761             visitor.visit_block(if_block);
 762             walk_list!(visitor, visit_expr, optional_else);
 763         }
 764         ExprKind::While(ref subexpression, ref block, ref opt_label) => {
 765             walk_list!(visitor, visit_label, opt_label);
 766             visitor.visit_expr(subexpression);
 767             visitor.visit_block(block);
 768         }
 769         ExprKind::ForLoop(ref pattern, ref subexpression, ref block, ref opt_label) => {
 770             walk_list!(visitor, visit_label, opt_label);
 771             visitor.visit_pat(pattern);
 772             visitor.visit_expr(subexpression);
 773             visitor.visit_block(block);
 774         }
 775         ExprKind::Loop(ref block, ref opt_label) => {
 776             walk_list!(visitor, visit_label, opt_label);
 777             visitor.visit_block(block);
 778         }
 779         ExprKind::Match(ref subexpression, ref arms) => {
 780             visitor.visit_expr(subexpression);
 781             walk_list!(visitor, visit_arm, arms);
 782         }
 783         ExprKind::Closure(_, _, _, ref decl, ref body, _decl_span) => {
 784             visitor.visit_fn(FnKind::Closure(decl, body), expression.span, expression.id)
 785         }
 786         ExprKind::Block(ref block, ref opt_label) => {
 787             walk_list!(visitor, visit_label, opt_label);
 788             visitor.visit_block(block);
 789         }
 790         ExprKind::Async(_, _, ref body) => {
 791             visitor.visit_block(body);
 792         }
 793         ExprKind::Await(ref expr) => visitor.visit_expr(expr),
 794         ExprKind::Assign(ref lhs, ref rhs, _) => {
 795             visitor.visit_expr(lhs);
 796             visitor.visit_expr(rhs);
 797         }
 798         ExprKind::AssignOp(_, ref left_expression, ref right_expression) => {
 799             visitor.visit_expr(left_expression);
 800             visitor.visit_expr(right_expression);
 801         }
 802         ExprKind::Field(ref subexpression, ident) => {
 803             visitor.visit_expr(subexpression);
 804             visitor.visit_ident(ident);
 805         }
 806         ExprKind::Index(ref main_expression, ref index_expression) => {
 807             visitor.visit_expr(main_expression);
 808             visitor.visit_expr(index_expression)
 809         }
 810         ExprKind::Range(ref start, ref end, _) => {
 811             walk_list!(visitor, visit_expr, start);
 812             walk_list!(visitor, visit_expr, end);
 813         }
 814         ExprKind::Underscore => {}
 815         ExprKind::Path(ref maybe_qself, ref path) => {
 816             if let Some(ref qself) = *maybe_qself {
 817                 visitor.visit_ty(&qself.ty);
 818             }
 819             visitor.visit_path(path, expression.id)
 820         }
 821         ExprKind::Break(ref opt_label, ref opt_expr) => {
 822             walk_list!(visitor, visit_label, opt_label);
 823             walk_list!(visitor, visit_expr, opt_expr);
 824         }
 825         ExprKind::Continue(ref opt_label) => {
 826             walk_list!(visitor, visit_label, opt_label);
 827         }
 828         ExprKind::Ret(ref optional_expression) => {
 829             walk_list!(visitor, visit_expr, optional_expression);
 830         }
 831         ExprKind::MacCall(ref mac) => visitor.visit_mac_call(mac),
 832         ExprKind::Paren(ref subexpression) => visitor.visit_expr(subexpression),
 833         ExprKind::InlineAsm(ref ia) => {
 834             for (op, _) in &ia.operands {
 835                 match op {
 836                     InlineAsmOperand::In { expr, .. }
 837                     | InlineAsmOperand::InOut { expr, .. }
 838                     | InlineAsmOperand::Const { expr, .. }
 839                     | InlineAsmOperand::Sym { expr, .. } => visitor.visit_expr(expr),
 840                     InlineAsmOperand::Out { expr, .. } => {
 841                         if let Some(expr) = expr {
 842                             visitor.visit_expr(expr);
 843                         }
 844                     }
 845                     InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
 846                         visitor.visit_expr(in_expr);
 847                         if let Some(out_expr) = out_expr {
 848                             visitor.visit_expr(out_expr);
 849                         }
 850                     }
 851                 }
 852             }
 853         }
 854         ExprKind::LlvmInlineAsm(ref ia) => {
 855             for &(_, ref input) in &ia.inputs {
 856                 visitor.visit_expr(input)
 857             }
 858             for output in &ia.outputs {
 859                 visitor.visit_expr(&output.expr)
 860             }
 861         }
 862         ExprKind::Yield(ref optional_expression) => {
 863             walk_list!(visitor, visit_expr, optional_expression);
 864         }
 865         ExprKind::Try(ref subexpression) => visitor.visit_expr(subexpression),
 866         ExprKind::TryBlock(ref body) => visitor.visit_block(body),
 867         ExprKind::Lit(_) | ExprKind::Err => {}
 868     }
 869
 870     visitor.visit_expr_post(expression)
 871 }
 872
 873 pub fn walk_param<'a, V: Visitor<'a>>(visitor: &mut V, param: &'a Param) {
 874     walk_list!(visitor, visit_attribute, param.attrs.iter());
 875     visitor.visit_pat(&param.pat);
 876     visitor.visit_ty(&param.ty);
 877 }
 878
 879 pub fn walk_arm<'a, V: Visitor<'a>>(visitor: &mut V, arm: &'a Arm) {
 880     visitor.visit_pat(&arm.pat);
 881     walk_list!(visitor, visit_expr, &arm.guard);
 882     visitor.visit_expr(&arm.body);
 883     walk_list!(visitor, visit_attribute, &arm.attrs);
 884 }
 885
 886 pub fn walk_vis<'a, V: Visitor<'a>>(visitor: &mut V, vis: &'a Visibility) {
 887     if let VisibilityKind::Restricted { ref path, id } = vis.kind {
 888         visitor.visit_path(path, id);
 889     }
 890 }
 891
 892 pub fn walk_attribute<'a, V: Visitor<'a>>(visitor: &mut V, attr: &'a Attribute) {
 893     match attr.kind {
 894         AttrKind::Normal(ref item, ref _tokens) => walk_mac_args(visitor, &item.args),
 895         AttrKind::DocComment(..) => {}
 896     }
 897 }
 898
 899 pub fn walk_mac_args<'a, V: Visitor<'a>>(visitor: &mut V, args: &'a MacArgs) {
 900     match args {
 901         MacArgs::Empty => {}
 902         MacArgs::Delimited(_dspan, _delim, _tokens) => {}
 903         // The value in `#[key = VALUE]` must be visited as an expression for backward
 904         // compatibility, so that macros can be expanded in that position.
 905         MacArgs::Eq(_eq_span, token) => match &token.kind {
 906             token::Interpolated(nt) => match &**nt {
 907                 token::NtExpr(expr) => visitor.visit_expr(expr),
 908                 t => panic!("unexpected token in key-value attribute: {:?}", t),
 909             },
 910             t => panic!("unexpected token in key-value attribute: {:?}", t),
 911         },
 912     }
 913 }