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
  18 use rustc_span::symbol::{Ident, Symbol};
  19 use rustc_span::Span;
  20
  21 #[derive(Copy, Clone, Debug, PartialEq)]
  22 pub enum AssocCtxt {
  23     Trait,
  24     Impl,
  25 }
  26
  27 #[derive(Copy, Clone, Debug, PartialEq)]
  28 pub enum FnCtxt {
  29     Free,
  30     Foreign,
  31     Assoc(AssocCtxt),
  32 }
  33
  34 #[derive(Copy, Clone, Debug)]
  35 pub enum BoundKind {
  36     /// Trait bounds in generics bounds and type/trait alias.
  37     /// E.g., `<T: Bound>`, `type A: Bound`, or `where T: Bound`.
  38     Bound,
  39
  40     /// Trait bounds in `impl` type.
  41     /// E.g., `type Foo = impl Bound1 + Bound2 + Bound3`.
  42     Impl,
  43
  44     /// Trait bounds in trait object type.
  45     /// E.g., `dyn Bound1 + Bound2 + Bound3`.
  46     TraitObject,
  47
  48     /// Super traits of a trait.
  49     /// E.g., `trait A: B`
  50     SuperTraits,
  51 }
  52
  53 #[derive(Copy, Clone, Debug)]
  54 pub enum FnKind<'a> {
  55     /// E.g., `fn foo()`, `fn foo(&self)`, or `extern "Abi" fn foo()`.
  56     Fn(FnCtxt, Ident, &'a FnSig, &'a Visibility, &'a Generics, Option<&'a Block>),
  57
  58     /// E.g., `|x, y| body`.
  59     Closure(&'a FnDecl, &'a Expr),
  60 }
  61
  62 impl<'a> FnKind<'a> {
  63     pub fn header(&self) -> Option<&'a FnHeader> {
  64         match *self {
  65             FnKind::Fn(_, _, sig, _, _, _) => Some(&sig.header),
  66             FnKind::Closure(_, _) => None,
  67         }
  68     }
  69
  70     pub fn ident(&self) -> Option<&Ident> {
  71         match self {
  72             FnKind::Fn(_, ident, ..) => Some(ident),
  73             _ => None,
  74         }
  75     }
  76
  77     pub fn decl(&self) -> &'a FnDecl {
  78         match self {
  79             FnKind::Fn(_, _, sig, _, _, _) => &sig.decl,
  80             FnKind::Closure(decl, _) => decl,
  81         }
  82     }
  83
  84     pub fn ctxt(&self) -> Option<FnCtxt> {
  85         match self {
  86             FnKind::Fn(ctxt, ..) => Some(*ctxt),
  87             FnKind::Closure(..) => None,
  88         }
  89     }
  90 }
  91
  92 #[derive(Copy, Clone, Debug)]
  93 pub enum LifetimeCtxt {
  94     /// Appears in a reference type.
  95     Rptr,
  96     /// Appears as a bound on a type or another lifetime.
  97     Bound,
  98     /// Appears as a generic argument.
  99     GenericArg,
 100 }
 101
 102 /// Each method of the `Visitor` trait is a hook to be potentially
 103 /// overridden. Each method's default implementation recursively visits
 104 /// the substructure of the input via the corresponding `walk` method;
 105 /// e.g., the `visit_item` method by default calls `visit::walk_item`.
 106 ///
 107 /// If you want to ensure that your code handles every variant
 108 /// explicitly, you need to override each method. (And you also need
 109 /// to monitor future changes to `Visitor` in case a new method with a
 110 /// new default implementation gets introduced.)
 111 pub trait Visitor<'ast>: Sized {
 112     fn visit_name(&mut self, _span: Span, _name: Symbol) {
 113         // Nothing to do.
 114     }
 115     fn visit_ident(&mut self, ident: Ident) {
 116         walk_ident(self, ident);
 117     }
 118     fn visit_foreign_item(&mut self, i: &'ast ForeignItem) {
 119         walk_foreign_item(self, i)
 120     }
 121     fn visit_item(&mut self, i: &'ast Item) {
 122         walk_item(self, i)
 123     }
 124     fn visit_local(&mut self, l: &'ast Local) {
 125         walk_local(self, l)
 126     }
 127     fn visit_block(&mut self, b: &'ast Block) {
 128         walk_block(self, b)
 129     }
 130     fn visit_stmt(&mut self, s: &'ast Stmt) {
 131         walk_stmt(self, s)
 132     }
 133     fn visit_param(&mut self, param: &'ast Param) {
 134         walk_param(self, param)
 135     }
 136     fn visit_arm(&mut self, a: &'ast Arm) {
 137         walk_arm(self, a)
 138     }
 139     fn visit_pat(&mut self, p: &'ast Pat) {
 140         walk_pat(self, p)
 141     }
 142     fn visit_anon_const(&mut self, c: &'ast AnonConst) {
 143         walk_anon_const(self, c)
 144     }
 145     fn visit_expr(&mut self, ex: &'ast Expr) {
 146         walk_expr(self, ex)
 147     }
 148     fn visit_expr_post(&mut self, _ex: &'ast Expr) {}
 149     fn visit_ty(&mut self, t: &'ast Ty) {
 150         walk_ty(self, t)
 151     }
 152     fn visit_generic_param(&mut self, param: &'ast GenericParam) {
 153         walk_generic_param(self, param)
 154     }
 155     fn visit_generics(&mut self, g: &'ast Generics) {
 156         walk_generics(self, g)
 157     }
 158     fn visit_where_predicate(&mut self, p: &'ast WherePredicate) {
 159         walk_where_predicate(self, p)
 160     }
 161     fn visit_fn(&mut self, fk: FnKind<'ast>, s: Span, _: NodeId) {
 162         walk_fn(self, fk, s)
 163     }
 164     fn visit_assoc_item(&mut self, i: &'ast AssocItem, ctxt: AssocCtxt) {
 165         walk_assoc_item(self, i, ctxt)
 166     }
 167     fn visit_trait_ref(&mut self, t: &'ast TraitRef) {
 168         walk_trait_ref(self, t)
 169     }
 170     fn visit_param_bound(&mut self, bounds: &'ast GenericBound, _ctxt: BoundKind) {
 171         walk_param_bound(self, bounds)
 172     }
 173     fn visit_poly_trait_ref(&mut self, t: &'ast PolyTraitRef, m: &'ast TraitBoundModifier) {
 174         walk_poly_trait_ref(self, t, m)
 175     }
 176     fn visit_variant_data(&mut self, s: &'ast VariantData) {
 177         walk_struct_def(self, s)
 178     }
 179     fn visit_field_def(&mut self, s: &'ast FieldDef) {
 180         walk_field_def(self, s)
 181     }
 182     fn visit_enum_def(
 183         &mut self,
 184         enum_definition: &'ast EnumDef,
 185         generics: &'ast Generics,
 186         item_id: NodeId,
 187         _: Span,
 188     ) {
 189         walk_enum_def(self, enum_definition, generics, item_id)
 190     }
 191     fn visit_variant(&mut self, v: &'ast Variant) {
 192         walk_variant(self, v)
 193     }
 194     fn visit_label(&mut self, label: &'ast Label) {
 195         walk_label(self, label)
 196     }
 197     fn visit_lifetime(&mut self, lifetime: &'ast Lifetime, _: LifetimeCtxt) {
 198         walk_lifetime(self, lifetime)
 199     }
 200     fn visit_mac_call(&mut self, mac: &'ast MacCall) {
 201         walk_mac(self, mac)
 202     }
 203     fn visit_mac_def(&mut self, _mac: &'ast MacroDef, _id: NodeId) {
 204         // Nothing to do
 205     }
 206     fn visit_path(&mut self, path: &'ast Path, _id: NodeId) {
 207         walk_path(self, path)
 208     }
 209     fn visit_use_tree(&mut self, use_tree: &'ast UseTree, id: NodeId, _nested: bool) {
 210         walk_use_tree(self, use_tree, id)
 211     }
 212     fn visit_path_segment(&mut self, path_span: Span, path_segment: &'ast PathSegment) {
 213         walk_path_segment(self, path_span, path_segment)
 214     }
 215     fn visit_generic_args(&mut self, path_span: Span, generic_args: &'ast GenericArgs) {
 216         walk_generic_args(self, path_span, generic_args)
 217     }
 218     fn visit_generic_arg(&mut self, generic_arg: &'ast GenericArg) {
 219         walk_generic_arg(self, generic_arg)
 220     }
 221     fn visit_assoc_constraint(&mut self, constraint: &'ast AssocConstraint) {
 222         walk_assoc_constraint(self, constraint)
 223     }
 224     fn visit_attribute(&mut self, attr: &'ast Attribute) {
 225         walk_attribute(self, attr)
 226     }
 227     fn visit_vis(&mut self, vis: &'ast Visibility) {
 228         walk_vis(self, vis)
 229     }
 230     fn visit_fn_ret_ty(&mut self, ret_ty: &'ast FnRetTy) {
 231         walk_fn_ret_ty(self, ret_ty)
 232     }
 233     fn visit_fn_header(&mut self, _header: &'ast FnHeader) {
 234         // Nothing to do
 235     }
 236     fn visit_expr_field(&mut self, f: &'ast ExprField) {
 237         walk_expr_field(self, f)
 238     }
 239     fn visit_pat_field(&mut self, fp: &'ast PatField) {
 240         walk_pat_field(self, fp)
 241     }
 242     fn visit_crate(&mut self, krate: &'ast Crate) {
 243         walk_crate(self, krate)
 244     }
 245     fn visit_inline_asm(&mut self, asm: &'ast InlineAsm) {
 246         walk_inline_asm(self, asm)
 247     }
 248     fn visit_inline_asm_sym(&mut self, sym: &'ast InlineAsmSym) {
 249         walk_inline_asm_sym(self, sym)
 250     }
 251 }
 252
 253 #[macro_export]
 254 macro_rules! walk_list {
 255     ($visitor: expr, $method: ident, $list: expr) => {
 256         for elem in $list {
 257             $visitor.$method(elem)
 258         }
 259     };
 260     ($visitor: expr, $method: ident, $list: expr, $($extra_args: expr),*) => {
 261         for elem in $list {
 262             $visitor.$method(elem, $($extra_args,)*)
 263         }
 264     }
 265 }
 266
 267 pub fn walk_ident<'a, V: Visitor<'a>>(visitor: &mut V, ident: Ident) {
 268     visitor.visit_name(ident.span, ident.name);
 269 }
 270
 271 pub fn walk_crate<'a, V: Visitor<'a>>(visitor: &mut V, krate: &'a Crate) {
 272     walk_list!(visitor, visit_item, &krate.items);
 273     walk_list!(visitor, visit_attribute, &krate.attrs);
 274 }
 275
 276 pub fn walk_local<'a, V: Visitor<'a>>(visitor: &mut V, local: &'a Local) {
 277     for attr in local.attrs.iter() {
 278         visitor.visit_attribute(attr);
 279     }
 280     visitor.visit_pat(&local.pat);
 281     walk_list!(visitor, visit_ty, &local.ty);
 282     if let Some((init, els)) = local.kind.init_else_opt() {
 283         visitor.visit_expr(init);
 284         walk_list!(visitor, visit_block, els);
 285     }
 286 }
 287
 288 pub fn walk_label<'a, V: Visitor<'a>>(visitor: &mut V, label: &'a Label) {
 289     visitor.visit_ident(label.ident);
 290 }
 291
 292 pub fn walk_lifetime<'a, V: Visitor<'a>>(visitor: &mut V, lifetime: &'a Lifetime) {
 293     visitor.visit_ident(lifetime.ident);
 294 }
 295
 296 pub fn walk_poly_trait_ref<'a, V>(
 297     visitor: &mut V,
 298     trait_ref: &'a PolyTraitRef,
 299     _: &TraitBoundModifier,
 300 ) where
 301     V: Visitor<'a>,
 302 {
 303     walk_list!(visitor, visit_generic_param, &trait_ref.bound_generic_params);
 304     visitor.visit_trait_ref(&trait_ref.trait_ref);
 305 }
 306
 307 pub fn walk_trait_ref<'a, V: Visitor<'a>>(visitor: &mut V, trait_ref: &'a TraitRef) {
 308     visitor.visit_path(&trait_ref.path, trait_ref.ref_id)
 309 }
 310
 311 pub fn walk_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a Item) {
 312     visitor.visit_vis(&item.vis);
 313     visitor.visit_ident(item.ident);
 314     match item.kind {
 315         ItemKind::ExternCrate(orig_name) => {
 316             if let Some(orig_name) = orig_name {
 317                 visitor.visit_name(item.span, orig_name);
 318             }
 319         }
 320         ItemKind::Use(ref use_tree) => visitor.visit_use_tree(use_tree, item.id, false),
 321         ItemKind::Static(ref typ, _, ref expr) | ItemKind::Const(_, ref typ, ref expr) => {
 322             visitor.visit_ty(typ);
 323             walk_list!(visitor, visit_expr, expr);
 324         }
 325         ItemKind::Fn(box Fn { defaultness: _, ref generics, ref sig, ref body }) => {
 326             let kind =
 327                 FnKind::Fn(FnCtxt::Free, item.ident, sig, &item.vis, generics, body.as_deref());
 328             visitor.visit_fn(kind, item.span, item.id)
 329         }
 330         ItemKind::Mod(_unsafety, ref mod_kind) => match mod_kind {
 331             ModKind::Loaded(items, _inline, _inner_span) => {
 332                 walk_list!(visitor, visit_item, items)
 333             }
 334             ModKind::Unloaded => {}
 335         },
 336         ItemKind::ForeignMod(ref foreign_module) => {
 337             walk_list!(visitor, visit_foreign_item, &foreign_module.items);
 338         }
 339         ItemKind::GlobalAsm(ref asm) => visitor.visit_inline_asm(asm),
 340         ItemKind::TyAlias(box TyAlias { ref generics, ref bounds, ref ty, .. }) => {
 341             visitor.visit_generics(generics);
 342             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Bound);
 343             walk_list!(visitor, visit_ty, ty);
 344         }
 345         ItemKind::Enum(ref enum_definition, ref generics) => {
 346             visitor.visit_generics(generics);
 347             visitor.visit_enum_def(enum_definition, generics, item.id, item.span)
 348         }
 349         ItemKind::Impl(box Impl {
 350             defaultness: _,
 351             unsafety: _,
 352             ref generics,
 353             constness: _,
 354             polarity: _,
 355             ref of_trait,
 356             ref self_ty,
 357             ref items,
 358         }) => {
 359             visitor.visit_generics(generics);
 360             walk_list!(visitor, visit_trait_ref, of_trait);
 361             visitor.visit_ty(self_ty);
 362             walk_list!(visitor, visit_assoc_item, items, AssocCtxt::Impl);
 363         }
 364         ItemKind::Struct(ref struct_definition, ref generics)
 365         | ItemKind::Union(ref struct_definition, ref generics) => {
 366             visitor.visit_generics(generics);
 367             visitor.visit_variant_data(struct_definition);
 368         }
 369         ItemKind::Trait(box Trait {
 370             unsafety: _,
 371             is_auto: _,
 372             ref generics,
 373             ref bounds,
 374             ref items,
 375         }) => {
 376             visitor.visit_generics(generics);
 377             walk_list!(visitor, visit_param_bound, bounds, BoundKind::SuperTraits);
 378             walk_list!(visitor, visit_assoc_item, items, AssocCtxt::Trait);
 379         }
 380         ItemKind::TraitAlias(ref generics, ref bounds) => {
 381             visitor.visit_generics(generics);
 382             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Bound);
 383         }
 384         ItemKind::MacCall(ref mac) => visitor.visit_mac_call(mac),
 385         ItemKind::MacroDef(ref ts) => visitor.visit_mac_def(ts, item.id),
 386     }
 387     walk_list!(visitor, visit_attribute, &item.attrs);
 388 }
 389
 390 pub fn walk_enum_def<'a, V: Visitor<'a>>(
 391     visitor: &mut V,
 392     enum_definition: &'a EnumDef,
 393     _: &'a Generics,
 394     _: NodeId,
 395 ) {
 396     walk_list!(visitor, visit_variant, &enum_definition.variants);
 397 }
 398
 399 pub fn walk_variant<'a, V: Visitor<'a>>(visitor: &mut V, variant: &'a Variant)
 400 where
 401     V: Visitor<'a>,
 402 {
 403     visitor.visit_ident(variant.ident);
 404     visitor.visit_vis(&variant.vis);
 405     visitor.visit_variant_data(&variant.data);
 406     walk_list!(visitor, visit_anon_const, &variant.disr_expr);
 407     walk_list!(visitor, visit_attribute, &variant.attrs);
 408 }
 409
 410 pub fn walk_expr_field<'a, V: Visitor<'a>>(visitor: &mut V, f: &'a ExprField) {
 411     visitor.visit_expr(&f.expr);
 412     visitor.visit_ident(f.ident);
 413     walk_list!(visitor, visit_attribute, f.attrs.iter());
 414 }
 415
 416 pub fn walk_pat_field<'a, V: Visitor<'a>>(visitor: &mut V, fp: &'a PatField) {
 417     visitor.visit_ident(fp.ident);
 418     visitor.visit_pat(&fp.pat);
 419     walk_list!(visitor, visit_attribute, fp.attrs.iter());
 420 }
 421
 422 pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) {
 423     match typ.kind {
 424         TyKind::Slice(ref ty) | TyKind::Paren(ref ty) => visitor.visit_ty(ty),
 425         TyKind::Ptr(ref mutable_type) => visitor.visit_ty(&mutable_type.ty),
 426         TyKind::Rptr(ref opt_lifetime, ref mutable_type) => {
 427             walk_list!(visitor, visit_lifetime, opt_lifetime, LifetimeCtxt::Rptr);
 428             visitor.visit_ty(&mutable_type.ty)
 429         }
 430         TyKind::Tup(ref tuple_element_types) => {
 431             walk_list!(visitor, visit_ty, tuple_element_types);
 432         }
 433         TyKind::BareFn(ref function_declaration) => {
 434             walk_list!(visitor, visit_generic_param, &function_declaration.generic_params);
 435             walk_fn_decl(visitor, &function_declaration.decl);
 436         }
 437         TyKind::Path(ref maybe_qself, ref path) => {
 438             if let Some(ref qself) = *maybe_qself {
 439                 visitor.visit_ty(&qself.ty);
 440             }
 441             visitor.visit_path(path, typ.id);
 442         }
 443         TyKind::Array(ref ty, ref length) => {
 444             visitor.visit_ty(ty);
 445             visitor.visit_anon_const(length)
 446         }
 447         TyKind::TraitObject(ref bounds, ..) => {
 448             walk_list!(visitor, visit_param_bound, bounds, BoundKind::TraitObject);
 449         }
 450         TyKind::ImplTrait(_, ref bounds) => {
 451             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Impl);
 452         }
 453         TyKind::Typeof(ref expression) => visitor.visit_anon_const(expression),
 454         TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => {}
 455         TyKind::MacCall(ref mac) => visitor.visit_mac_call(mac),
 456         TyKind::Never | TyKind::CVarArgs => {}
 457     }
 458 }
 459
 460 pub fn walk_path<'a, V: Visitor<'a>>(visitor: &mut V, path: &'a Path) {
 461     for segment in &path.segments {
 462         visitor.visit_path_segment(path.span, segment);
 463     }
 464 }
 465
 466 pub fn walk_use_tree<'a, V: Visitor<'a>>(visitor: &mut V, use_tree: &'a UseTree, id: NodeId) {
 467     visitor.visit_path(&use_tree.prefix, id);
 468     match use_tree.kind {
 469         UseTreeKind::Simple(rename, ..) => {
 470             // The extra IDs are handled during HIR lowering.
 471             if let Some(rename) = rename {
 472                 visitor.visit_ident(rename);
 473             }
 474         }
 475         UseTreeKind::Glob => {}
 476         UseTreeKind::Nested(ref use_trees) => {
 477             for &(ref nested_tree, nested_id) in use_trees {
 478                 visitor.visit_use_tree(nested_tree, nested_id, true);
 479             }
 480         }
 481     }
 482 }
 483
 484 pub fn walk_path_segment<'a, V: Visitor<'a>>(
 485     visitor: &mut V,
 486     path_span: Span,
 487     segment: &'a PathSegment,
 488 ) {
 489     visitor.visit_ident(segment.ident);
 490     if let Some(ref args) = segment.args {
 491         visitor.visit_generic_args(path_span, args);
 492     }
 493 }
 494
 495 pub fn walk_generic_args<'a, V>(visitor: &mut V, _path_span: Span, generic_args: &'a GenericArgs)
 496 where
 497     V: Visitor<'a>,
 498 {
 499     match *generic_args {
 500         GenericArgs::AngleBracketed(ref data) => {
 501             for arg in &data.args {
 502                 match arg {
 503                     AngleBracketedArg::Arg(a) => visitor.visit_generic_arg(a),
 504                     AngleBracketedArg::Constraint(c) => visitor.visit_assoc_constraint(c),
 505                 }
 506             }
 507         }
 508         GenericArgs::Parenthesized(ref data) => {
 509             walk_list!(visitor, visit_ty, &data.inputs);
 510             walk_fn_ret_ty(visitor, &data.output);
 511         }
 512     }
 513 }
 514
 515 pub fn walk_generic_arg<'a, V>(visitor: &mut V, generic_arg: &'a GenericArg)
 516 where
 517     V: Visitor<'a>,
 518 {
 519     match generic_arg {
 520         GenericArg::Lifetime(lt) => visitor.visit_lifetime(lt, LifetimeCtxt::GenericArg),
 521         GenericArg::Type(ty) => visitor.visit_ty(ty),
 522         GenericArg::Const(ct) => visitor.visit_anon_const(ct),
 523     }
 524 }
 525
 526 pub fn walk_assoc_constraint<'a, V: Visitor<'a>>(visitor: &mut V, constraint: &'a AssocConstraint) {
 527     visitor.visit_ident(constraint.ident);
 528     if let Some(ref gen_args) = constraint.gen_args {
 529         visitor.visit_generic_args(gen_args.span(), gen_args);
 530     }
 531     match constraint.kind {
 532         AssocConstraintKind::Equality { ref term } => match term {
 533             Term::Ty(ty) => visitor.visit_ty(ty),
 534             Term::Const(c) => visitor.visit_anon_const(c),
 535         },
 536         AssocConstraintKind::Bound { ref bounds } => {
 537             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Bound);
 538         }
 539     }
 540 }
 541
 542 pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) {
 543     match pattern.kind {
 544         PatKind::TupleStruct(ref opt_qself, ref path, ref elems) => {
 545             if let Some(ref qself) = *opt_qself {
 546                 visitor.visit_ty(&qself.ty);
 547             }
 548             visitor.visit_path(path, pattern.id);
 549             walk_list!(visitor, visit_pat, elems);
 550         }
 551         PatKind::Path(ref opt_qself, ref path) => {
 552             if let Some(ref qself) = *opt_qself {
 553                 visitor.visit_ty(&qself.ty);
 554             }
 555             visitor.visit_path(path, pattern.id)
 556         }
 557         PatKind::Struct(ref opt_qself, ref path, ref fields, _) => {
 558             if let Some(ref qself) = *opt_qself {
 559                 visitor.visit_ty(&qself.ty);
 560             }
 561             visitor.visit_path(path, pattern.id);
 562             walk_list!(visitor, visit_pat_field, fields);
 563         }
 564         PatKind::Box(ref subpattern)
 565         | PatKind::Ref(ref subpattern, _)
 566         | PatKind::Paren(ref subpattern) => visitor.visit_pat(subpattern),
 567         PatKind::Ident(_, ident, ref optional_subpattern) => {
 568             visitor.visit_ident(ident);
 569             walk_list!(visitor, visit_pat, optional_subpattern);
 570         }
 571         PatKind::Lit(ref expression) => visitor.visit_expr(expression),
 572         PatKind::Range(ref lower_bound, ref upper_bound, _) => {
 573             walk_list!(visitor, visit_expr, lower_bound);
 574             walk_list!(visitor, visit_expr, upper_bound);
 575         }
 576         PatKind::Wild | PatKind::Rest => {}
 577         PatKind::Tuple(ref elems) | PatKind::Slice(ref elems) | PatKind::Or(ref elems) => {
 578             walk_list!(visitor, visit_pat, elems);
 579         }
 580         PatKind::MacCall(ref mac) => visitor.visit_mac_call(mac),
 581     }
 582 }
 583
 584 pub fn walk_foreign_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a ForeignItem) {
 585     let Item { id, span, ident, ref vis, ref attrs, ref kind, tokens: _ } = *item;
 586     visitor.visit_vis(vis);
 587     visitor.visit_ident(ident);
 588     walk_list!(visitor, visit_attribute, attrs);
 589     match kind {
 590         ForeignItemKind::Static(ty, _, expr) => {
 591             visitor.visit_ty(ty);
 592             walk_list!(visitor, visit_expr, expr);
 593         }
 594         ForeignItemKind::Fn(box Fn { defaultness: _, ref generics, ref sig, ref body }) => {
 595             let kind = FnKind::Fn(FnCtxt::Foreign, ident, sig, vis, generics, body.as_deref());
 596             visitor.visit_fn(kind, span, id);
 597         }
 598         ForeignItemKind::TyAlias(box TyAlias { generics, bounds, ty, .. }) => {
 599             visitor.visit_generics(generics);
 600             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Bound);
 601             walk_list!(visitor, visit_ty, ty);
 602         }
 603         ForeignItemKind::MacCall(mac) => {
 604             visitor.visit_mac_call(mac);
 605         }
 606     }
 607 }
 608
 609 pub fn walk_param_bound<'a, V: Visitor<'a>>(visitor: &mut V, bound: &'a GenericBound) {
 610     match *bound {
 611         GenericBound::Trait(ref typ, ref modifier) => visitor.visit_poly_trait_ref(typ, modifier),
 612         GenericBound::Outlives(ref lifetime) => {
 613             visitor.visit_lifetime(lifetime, LifetimeCtxt::Bound)
 614         }
 615     }
 616 }
 617
 618 pub fn walk_generic_param<'a, V: Visitor<'a>>(visitor: &mut V, param: &'a GenericParam) {
 619     visitor.visit_ident(param.ident);
 620     walk_list!(visitor, visit_attribute, param.attrs.iter());
 621     walk_list!(visitor, visit_param_bound, &param.bounds, BoundKind::Bound);
 622     match param.kind {
 623         GenericParamKind::Lifetime => (),
 624         GenericParamKind::Type { ref default } => walk_list!(visitor, visit_ty, default),
 625         GenericParamKind::Const { ref ty, ref default, .. } => {
 626             visitor.visit_ty(ty);
 627             if let Some(default) = default {
 628                 visitor.visit_anon_const(default);
 629             }
 630         }
 631     }
 632 }
 633
 634 pub fn walk_generics<'a, V: Visitor<'a>>(visitor: &mut V, generics: &'a Generics) {
 635     walk_list!(visitor, visit_generic_param, &generics.params);
 636     walk_list!(visitor, visit_where_predicate, &generics.where_clause.predicates);
 637 }
 638
 639 pub fn walk_where_predicate<'a, V: Visitor<'a>>(visitor: &mut V, predicate: &'a WherePredicate) {
 640     match *predicate {
 641         WherePredicate::BoundPredicate(WhereBoundPredicate {
 642             ref bounded_ty,
 643             ref bounds,
 644             ref bound_generic_params,
 645             ..
 646         }) => {
 647             visitor.visit_ty(bounded_ty);
 648             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Bound);
 649             walk_list!(visitor, visit_generic_param, bound_generic_params);
 650         }
 651         WherePredicate::RegionPredicate(WhereRegionPredicate {
 652             ref lifetime, ref bounds, ..
 653         }) => {
 654             visitor.visit_lifetime(lifetime, LifetimeCtxt::Bound);
 655             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Bound);
 656         }
 657         WherePredicate::EqPredicate(WhereEqPredicate { ref lhs_ty, ref rhs_ty, .. }) => {
 658             visitor.visit_ty(lhs_ty);
 659             visitor.visit_ty(rhs_ty);
 660         }
 661     }
 662 }
 663
 664 pub fn walk_fn_ret_ty<'a, V: Visitor<'a>>(visitor: &mut V, ret_ty: &'a FnRetTy) {
 665     if let FnRetTy::Ty(ref output_ty) = *ret_ty {
 666         visitor.visit_ty(output_ty)
 667     }
 668 }
 669
 670 pub fn walk_fn_decl<'a, V: Visitor<'a>>(visitor: &mut V, function_declaration: &'a FnDecl) {
 671     for param in &function_declaration.inputs {
 672         visitor.visit_param(param);
 673     }
 674     visitor.visit_fn_ret_ty(&function_declaration.output);
 675 }
 676
 677 pub fn walk_fn<'a, V: Visitor<'a>>(visitor: &mut V, kind: FnKind<'a>, _span: Span) {
 678     match kind {
 679         FnKind::Fn(_, _, sig, _, generics, body) => {
 680             visitor.visit_generics(generics);
 681             visitor.visit_fn_header(&sig.header);
 682             walk_fn_decl(visitor, &sig.decl);
 683             walk_list!(visitor, visit_block, body);
 684         }
 685         FnKind::Closure(decl, body) => {
 686             walk_fn_decl(visitor, decl);
 687             visitor.visit_expr(body);
 688         }
 689     }
 690 }
 691
 692 pub fn walk_assoc_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a AssocItem, ctxt: AssocCtxt) {
 693     let Item { id, span, ident, ref vis, ref attrs, ref kind, tokens: _ } = *item;
 694     visitor.visit_vis(vis);
 695     visitor.visit_ident(ident);
 696     walk_list!(visitor, visit_attribute, attrs);
 697     match kind {
 698         AssocItemKind::Const(_, ty, expr) => {
 699             visitor.visit_ty(ty);
 700             walk_list!(visitor, visit_expr, expr);
 701         }
 702         AssocItemKind::Fn(box Fn { defaultness: _, ref generics, ref sig, ref body }) => {
 703             let kind = FnKind::Fn(FnCtxt::Assoc(ctxt), ident, sig, vis, generics, body.as_deref());
 704             visitor.visit_fn(kind, span, id);
 705         }
 706         AssocItemKind::TyAlias(box TyAlias { generics, bounds, ty, .. }) => {
 707             visitor.visit_generics(generics);
 708             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Bound);
 709             walk_list!(visitor, visit_ty, ty);
 710         }
 711         AssocItemKind::MacCall(mac) => {
 712             visitor.visit_mac_call(mac);
 713         }
 714     }
 715 }
 716
 717 pub fn walk_struct_def<'a, V: Visitor<'a>>(visitor: &mut V, struct_definition: &'a VariantData) {
 718     walk_list!(visitor, visit_field_def, struct_definition.fields());
 719 }
 720
 721 pub fn walk_field_def<'a, V: Visitor<'a>>(visitor: &mut V, field: &'a FieldDef) {
 722     visitor.visit_vis(&field.vis);
 723     if let Some(ident) = field.ident {
 724         visitor.visit_ident(ident);
 725     }
 726     visitor.visit_ty(&field.ty);
 727     walk_list!(visitor, visit_attribute, &field.attrs);
 728 }
 729
 730 pub fn walk_block<'a, V: Visitor<'a>>(visitor: &mut V, block: &'a Block) {
 731     walk_list!(visitor, visit_stmt, &block.stmts);
 732 }
 733
 734 pub fn walk_stmt<'a, V: Visitor<'a>>(visitor: &mut V, statement: &'a Stmt) {
 735     match statement.kind {
 736         StmtKind::Local(ref local) => visitor.visit_local(local),
 737         StmtKind::Item(ref item) => visitor.visit_item(item),
 738         StmtKind::Expr(ref expr) | StmtKind::Semi(ref expr) => visitor.visit_expr(expr),
 739         StmtKind::Empty => {}
 740         StmtKind::MacCall(ref mac) => {
 741             let MacCallStmt { ref mac, style: _, ref attrs, tokens: _ } = **mac;
 742             visitor.visit_mac_call(mac);
 743             for attr in attrs.iter() {
 744                 visitor.visit_attribute(attr);
 745             }
 746         }
 747     }
 748 }
 749
 750 pub fn walk_mac<'a, V: Visitor<'a>>(visitor: &mut V, mac: &'a MacCall) {
 751     visitor.visit_path(&mac.path, DUMMY_NODE_ID);
 752 }
 753
 754 pub fn walk_anon_const<'a, V: Visitor<'a>>(visitor: &mut V, constant: &'a AnonConst) {
 755     visitor.visit_expr(&constant.value);
 756 }
 757
 758 pub fn walk_inline_asm<'a, V: Visitor<'a>>(visitor: &mut V, asm: &'a InlineAsm) {
 759     for (op, _) in &asm.operands {
 760         match op {
 761             InlineAsmOperand::In { expr, .. }
 762             | InlineAsmOperand::Out { expr: Some(expr), .. }
 763             | InlineAsmOperand::InOut { expr, .. } => visitor.visit_expr(expr),
 764             InlineAsmOperand::Out { expr: None, .. } => {}
 765             InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
 766                 visitor.visit_expr(in_expr);
 767                 if let Some(out_expr) = out_expr {
 768                     visitor.visit_expr(out_expr);
 769                 }
 770             }
 771             InlineAsmOperand::Const { anon_const, .. } => visitor.visit_anon_const(anon_const),
 772             InlineAsmOperand::Sym { sym } => visitor.visit_inline_asm_sym(sym),
 773         }
 774     }
 775 }
 776
 777 pub fn walk_inline_asm_sym<'a, V: Visitor<'a>>(visitor: &mut V, sym: &'a InlineAsmSym) {
 778     if let Some(ref qself) = sym.qself {
 779         visitor.visit_ty(&qself.ty);
 780     }
 781     visitor.visit_path(&sym.path, sym.id);
 782 }
 783
 784 pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
 785     walk_list!(visitor, visit_attribute, expression.attrs.iter());
 786
 787     match expression.kind {
 788         ExprKind::Box(ref subexpression) => visitor.visit_expr(subexpression),
 789         ExprKind::Array(ref subexpressions) => {
 790             walk_list!(visitor, visit_expr, subexpressions);
 791         }
 792         ExprKind::ConstBlock(ref anon_const) => visitor.visit_anon_const(anon_const),
 793         ExprKind::Repeat(ref element, ref count) => {
 794             visitor.visit_expr(element);
 795             visitor.visit_anon_const(count)
 796         }
 797         ExprKind::Struct(ref se) => {
 798             if let Some(ref qself) = se.qself {
 799                 visitor.visit_ty(&qself.ty);
 800             }
 801             visitor.visit_path(&se.path, expression.id);
 802             walk_list!(visitor, visit_expr_field, &se.fields);
 803             match &se.rest {
 804                 StructRest::Base(expr) => visitor.visit_expr(expr),
 805                 StructRest::Rest(_span) => {}
 806                 StructRest::None => {}
 807             }
 808         }
 809         ExprKind::Tup(ref subexpressions) => {
 810             walk_list!(visitor, visit_expr, subexpressions);
 811         }
 812         ExprKind::Call(ref callee_expression, ref arguments) => {
 813             visitor.visit_expr(callee_expression);
 814             walk_list!(visitor, visit_expr, arguments);
 815         }
 816         ExprKind::MethodCall(ref segment, ref arguments, _span) => {
 817             visitor.visit_path_segment(expression.span, segment);
 818             walk_list!(visitor, visit_expr, arguments);
 819         }
 820         ExprKind::Binary(_, ref left_expression, ref right_expression) => {
 821             visitor.visit_expr(left_expression);
 822             visitor.visit_expr(right_expression)
 823         }
 824         ExprKind::AddrOf(_, _, ref subexpression) | ExprKind::Unary(_, ref subexpression) => {
 825             visitor.visit_expr(subexpression)
 826         }
 827         ExprKind::Cast(ref subexpression, ref typ) | ExprKind::Type(ref subexpression, ref typ) => {
 828             visitor.visit_expr(subexpression);
 829             visitor.visit_ty(typ)
 830         }
 831         ExprKind::Let(ref pat, ref expr, _) => {
 832             visitor.visit_pat(pat);
 833             visitor.visit_expr(expr);
 834         }
 835         ExprKind::If(ref head_expression, ref if_block, ref optional_else) => {
 836             visitor.visit_expr(head_expression);
 837             visitor.visit_block(if_block);
 838             walk_list!(visitor, visit_expr, optional_else);
 839         }
 840         ExprKind::While(ref subexpression, ref block, ref opt_label) => {
 841             walk_list!(visitor, visit_label, opt_label);
 842             visitor.visit_expr(subexpression);
 843             visitor.visit_block(block);
 844         }
 845         ExprKind::ForLoop(ref pattern, ref subexpression, ref block, ref opt_label) => {
 846             walk_list!(visitor, visit_label, opt_label);
 847             visitor.visit_pat(pattern);
 848             visitor.visit_expr(subexpression);
 849             visitor.visit_block(block);
 850         }
 851         ExprKind::Loop(ref block, ref opt_label) => {
 852             walk_list!(visitor, visit_label, opt_label);
 853             visitor.visit_block(block);
 854         }
 855         ExprKind::Match(ref subexpression, ref arms) => {
 856             visitor.visit_expr(subexpression);
 857             walk_list!(visitor, visit_arm, arms);
 858         }
 859         ExprKind::Closure(_, _, _, ref decl, ref body, _decl_span) => {
 860             visitor.visit_fn(FnKind::Closure(decl, body), expression.span, expression.id)
 861         }
 862         ExprKind::Block(ref block, ref opt_label) => {
 863             walk_list!(visitor, visit_label, opt_label);
 864             visitor.visit_block(block);
 865         }
 866         ExprKind::Async(_, _, ref body) => {
 867             visitor.visit_block(body);
 868         }
 869         ExprKind::Await(ref expr) => visitor.visit_expr(expr),
 870         ExprKind::Assign(ref lhs, ref rhs, _) => {
 871             visitor.visit_expr(lhs);
 872             visitor.visit_expr(rhs);
 873         }
 874         ExprKind::AssignOp(_, ref left_expression, ref right_expression) => {
 875             visitor.visit_expr(left_expression);
 876             visitor.visit_expr(right_expression);
 877         }
 878         ExprKind::Field(ref subexpression, ident) => {
 879             visitor.visit_expr(subexpression);
 880             visitor.visit_ident(ident);
 881         }
 882         ExprKind::Index(ref main_expression, ref index_expression) => {
 883             visitor.visit_expr(main_expression);
 884             visitor.visit_expr(index_expression)
 885         }
 886         ExprKind::Range(ref start, ref end, _) => {
 887             walk_list!(visitor, visit_expr, start);
 888             walk_list!(visitor, visit_expr, end);
 889         }
 890         ExprKind::Underscore => {}
 891         ExprKind::Path(ref maybe_qself, ref path) => {
 892             if let Some(ref qself) = *maybe_qself {
 893                 visitor.visit_ty(&qself.ty);
 894             }
 895             visitor.visit_path(path, expression.id)
 896         }
 897         ExprKind::Break(ref opt_label, ref opt_expr) => {
 898             walk_list!(visitor, visit_label, opt_label);
 899             walk_list!(visitor, visit_expr, opt_expr);
 900         }
 901         ExprKind::Continue(ref opt_label) => {
 902             walk_list!(visitor, visit_label, opt_label);
 903         }
 904         ExprKind::Ret(ref optional_expression) => {
 905             walk_list!(visitor, visit_expr, optional_expression);
 906         }
 907         ExprKind::Yeet(ref optional_expression) => {
 908             walk_list!(visitor, visit_expr, optional_expression);
 909         }
 910         ExprKind::MacCall(ref mac) => visitor.visit_mac_call(mac),
 911         ExprKind::Paren(ref subexpression) => visitor.visit_expr(subexpression),
 912         ExprKind::InlineAsm(ref asm) => visitor.visit_inline_asm(asm),
 913         ExprKind::Yield(ref optional_expression) => {
 914             walk_list!(visitor, visit_expr, optional_expression);
 915         }
 916         ExprKind::Try(ref subexpression) => visitor.visit_expr(subexpression),
 917         ExprKind::TryBlock(ref body) => visitor.visit_block(body),
 918         ExprKind::Lit(_) | ExprKind::Err => {}
 919     }
 920
 921     visitor.visit_expr_post(expression)
 922 }
 923
 924 pub fn walk_param<'a, V: Visitor<'a>>(visitor: &mut V, param: &'a Param) {
 925     walk_list!(visitor, visit_attribute, param.attrs.iter());
 926     visitor.visit_pat(&param.pat);
 927     visitor.visit_ty(&param.ty);
 928 }
 929
 930 pub fn walk_arm<'a, V: Visitor<'a>>(visitor: &mut V, arm: &'a Arm) {
 931     visitor.visit_pat(&arm.pat);
 932     walk_list!(visitor, visit_expr, &arm.guard);
 933     visitor.visit_expr(&arm.body);
 934     walk_list!(visitor, visit_attribute, &arm.attrs);
 935 }
 936
 937 pub fn walk_vis<'a, V: Visitor<'a>>(visitor: &mut V, vis: &'a Visibility) {
 938     if let VisibilityKind::Restricted { ref path, id } = vis.kind {
 939         visitor.visit_path(path, id);
 940     }
 941 }
 942
 943 pub fn walk_attribute<'a, V: Visitor<'a>>(visitor: &mut V, attr: &'a Attribute) {
 944     match attr.kind {
 945         AttrKind::Normal(ref item, ref _tokens) => walk_mac_args(visitor, &item.args),
 946         AttrKind::DocComment(..) => {}
 947     }
 948 }
 949
 950 pub fn walk_mac_args<'a, V: Visitor<'a>>(visitor: &mut V, args: &'a MacArgs) {
 951     match args {
 952         MacArgs::Empty => {}
 953         MacArgs::Delimited(_dspan, _delim, _tokens) => {}
 954         MacArgs::Eq(_eq_span, MacArgsEq::Ast(expr)) => visitor.visit_expr(expr),
 955         MacArgs::Eq(_, MacArgsEq::Hir(lit)) => {
 956             unreachable!("in literal form when walking mac args eq: {:?}", lit)
 957         }
 958     }
 959 }