rustc_ast/
mut_visit.rs

1//! A `MutVisitor` represents an AST modification; it accepts an AST piece and
2//! mutates it in place. So, for instance, macro expansion is a `MutVisitor`
3//! that walks over an AST and modifies it.
4//!
5//! Note: using a `MutVisitor` (other than the `MacroExpander` `MutVisitor`) on
6//! an AST before macro expansion is probably a bad idea. For instance,
7//! a `MutVisitor` renaming item names in a module will miss all of those
8//! that are created by the expansion of a macro.
9
10use std::ops::DerefMut;
11use std::panic;
12
13use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
14use rustc_data_structures::stack::ensure_sufficient_stack;
15use rustc_span::{Ident, Span};
16use smallvec::{Array, SmallVec, smallvec};
17use thin_vec::ThinVec;
18
19use crate::ast::*;
20use crate::ptr::P;
21use crate::tokenstream::*;
22use crate::visit::{AssocCtxt, BoundKind, FnCtxt, try_visit, visit_opt, walk_list};
23
24pub trait ExpectOne<A: Array> {
25    fn expect_one(self, err: &'static str) -> A::Item;
26}
27
28impl<A: Array> ExpectOne<A> for SmallVec<A> {
29    fn expect_one(self, err: &'static str) -> A::Item {
30        assert!(self.len() == 1, "{}", err);
31        self.into_iter().next().unwrap()
32    }
33}
34
35pub trait MutVisitor: Sized {
36    // Methods in this trait have one of three forms:
37    //
38    //   fn visit_t(&mut self, t: &mut T);                      // common
39    //   fn flat_map_t(&mut self, t: T) -> SmallVec<[T; 1]>;    // rare
40    //   fn filter_map_t(&mut self, t: T) -> Option<T>;         // rarest
41    //
42    // When writing these methods, it is better to use destructuring like this:
43    //
44    //   fn visit_abc(&mut self, ABC { a, b, c: _ }: &mut ABC) {
45    //       visit_a(a);
46    //       visit_b(b);
47    //   }
48    //
49    // than to use field access like this:
50    //
51    //   fn visit_abc(&mut self, abc: &mut ABC) {
52    //       visit_a(&mut abc.a);
53    //       visit_b(&mut abc.b);
54    //       // ignore abc.c
55    //   }
56    //
57    // As well as being more concise, the former is explicit about which fields
58    // are skipped. Furthermore, if a new field is added, the destructuring
59    // version will cause a compile error, which is good. In comparison, the
60    // field access version will continue working and it would be easy to
61    // forget to add handling for it.
62
63    fn visit_crate(&mut self, c: &mut Crate) {
64        walk_crate(self, c)
65    }
66
67    fn visit_meta_list_item(&mut self, list_item: &mut MetaItemInner) {
68        walk_meta_list_item(self, list_item);
69    }
70
71    fn visit_meta_item(&mut self, meta_item: &mut MetaItem) {
72        walk_meta_item(self, meta_item);
73    }
74
75    fn visit_use_tree(&mut self, use_tree: &mut UseTree) {
76        walk_use_tree(self, use_tree);
77    }
78
79    fn visit_foreign_item(&mut self, ni: &mut ForeignItem) {
80        walk_item(self, ni);
81    }
82
83    fn flat_map_foreign_item(&mut self, ni: P<ForeignItem>) -> SmallVec<[P<ForeignItem>; 1]> {
84        walk_flat_map_foreign_item(self, ni)
85    }
86
87    fn visit_item(&mut self, i: &mut Item) {
88        walk_item(self, i);
89    }
90
91    fn flat_map_item(&mut self, i: P<Item>) -> SmallVec<[P<Item>; 1]> {
92        walk_flat_map_item(self, i)
93    }
94
95    fn visit_fn_header(&mut self, header: &mut FnHeader) {
96        walk_fn_header(self, header);
97    }
98
99    fn visit_field_def(&mut self, fd: &mut FieldDef) {
100        walk_field_def(self, fd);
101    }
102
103    fn flat_map_field_def(&mut self, fd: FieldDef) -> SmallVec<[FieldDef; 1]> {
104        walk_flat_map_field_def(self, fd)
105    }
106
107    fn visit_assoc_item(&mut self, i: &mut AssocItem, ctxt: AssocCtxt) {
108        walk_assoc_item(self, i, ctxt)
109    }
110
111    fn flat_map_assoc_item(
112        &mut self,
113        i: P<AssocItem>,
114        ctxt: AssocCtxt,
115    ) -> SmallVec<[P<AssocItem>; 1]> {
116        walk_flat_map_assoc_item(self, i, ctxt)
117    }
118
119    fn visit_contract(&mut self, c: &mut FnContract) {
120        walk_contract(self, c);
121    }
122
123    fn visit_fn_decl(&mut self, d: &mut FnDecl) {
124        walk_fn_decl(self, d);
125    }
126
127    /// `Span` and `NodeId` are mutated at the caller site.
128    fn visit_fn(&mut self, fk: FnKind<'_>, _: Span, _: NodeId) {
129        walk_fn(self, fk)
130    }
131
132    fn visit_coroutine_kind(&mut self, a: &mut CoroutineKind) {
133        walk_coroutine_kind(self, a);
134    }
135
136    fn visit_closure_binder(&mut self, b: &mut ClosureBinder) {
137        walk_closure_binder(self, b);
138    }
139
140    fn visit_block(&mut self, b: &mut Block) {
141        walk_block(self, b);
142    }
143
144    fn flat_map_stmt(&mut self, s: Stmt) -> SmallVec<[Stmt; 1]> {
145        walk_flat_map_stmt(self, s)
146    }
147
148    fn visit_arm(&mut self, arm: &mut Arm) {
149        walk_arm(self, arm);
150    }
151
152    fn flat_map_arm(&mut self, arm: Arm) -> SmallVec<[Arm; 1]> {
153        walk_flat_map_arm(self, arm)
154    }
155
156    fn visit_pat(&mut self, p: &mut P<Pat>) {
157        walk_pat(self, p);
158    }
159
160    fn visit_anon_const(&mut self, c: &mut AnonConst) {
161        walk_anon_const(self, c);
162    }
163
164    fn visit_expr(&mut self, e: &mut P<Expr>) {
165        walk_expr(self, e);
166    }
167
168    /// This method is a hack to workaround unstable of `stmt_expr_attributes`.
169    /// It can be removed once that feature is stabilized.
170    fn visit_method_receiver_expr(&mut self, ex: &mut P<Expr>) {
171        self.visit_expr(ex)
172    }
173
174    fn filter_map_expr(&mut self, e: P<Expr>) -> Option<P<Expr>> {
175        walk_filter_map_expr(self, e)
176    }
177
178    fn visit_generic_arg(&mut self, arg: &mut GenericArg) {
179        walk_generic_arg(self, arg);
180    }
181
182    fn visit_ty(&mut self, t: &mut P<Ty>) {
183        walk_ty(self, t);
184    }
185
186    fn visit_ty_pat(&mut self, t: &mut TyPat) {
187        walk_ty_pat(self, t);
188    }
189
190    fn visit_lifetime(&mut self, l: &mut Lifetime) {
191        walk_lifetime(self, l);
192    }
193
194    fn visit_assoc_item_constraint(&mut self, c: &mut AssocItemConstraint) {
195        walk_assoc_item_constraint(self, c);
196    }
197
198    fn visit_foreign_mod(&mut self, nm: &mut ForeignMod) {
199        walk_foreign_mod(self, nm);
200    }
201
202    fn visit_variant(&mut self, v: &mut Variant) {
203        walk_variant(self, v);
204    }
205
206    fn flat_map_variant(&mut self, v: Variant) -> SmallVec<[Variant; 1]> {
207        walk_flat_map_variant(self, v)
208    }
209
210    fn visit_ident(&mut self, i: &mut Ident) {
211        walk_ident(self, i);
212    }
213
214    fn visit_modifiers(&mut self, m: &mut TraitBoundModifiers) {
215        walk_modifiers(self, m);
216    }
217
218    fn visit_path(&mut self, p: &mut Path) {
219        walk_path(self, p);
220    }
221
222    fn visit_path_segment(&mut self, p: &mut PathSegment) {
223        walk_path_segment(self, p)
224    }
225
226    fn visit_qself(&mut self, qs: &mut Option<P<QSelf>>) {
227        walk_qself(self, qs);
228    }
229
230    fn visit_generic_args(&mut self, p: &mut GenericArgs) {
231        walk_generic_args(self, p);
232    }
233
234    fn visit_angle_bracketed_parameter_data(&mut self, p: &mut AngleBracketedArgs) {
235        walk_angle_bracketed_parameter_data(self, p);
236    }
237
238    fn visit_parenthesized_parameter_data(&mut self, p: &mut ParenthesizedArgs) {
239        walk_parenthesized_parameter_data(self, p);
240    }
241
242    fn visit_local(&mut self, l: &mut Local) {
243        walk_local(self, l);
244    }
245
246    fn visit_mac_call(&mut self, mac: &mut MacCall) {
247        walk_mac(self, mac);
248    }
249
250    fn visit_macro_def(&mut self, def: &mut MacroDef) {
251        walk_macro_def(self, def);
252    }
253
254    fn visit_label(&mut self, label: &mut Label) {
255        walk_label(self, label);
256    }
257
258    fn visit_attribute(&mut self, at: &mut Attribute) {
259        walk_attribute(self, at);
260    }
261
262    fn visit_param(&mut self, param: &mut Param) {
263        walk_param(self, param);
264    }
265
266    fn flat_map_param(&mut self, param: Param) -> SmallVec<[Param; 1]> {
267        walk_flat_map_param(self, param)
268    }
269
270    fn visit_generics(&mut self, generics: &mut Generics) {
271        walk_generics(self, generics);
272    }
273
274    fn visit_trait_ref(&mut self, tr: &mut TraitRef) {
275        walk_trait_ref(self, tr);
276    }
277
278    fn visit_poly_trait_ref(&mut self, p: &mut PolyTraitRef) {
279        walk_poly_trait_ref(self, p);
280    }
281
282    fn visit_variant_data(&mut self, vdata: &mut VariantData) {
283        walk_variant_data(self, vdata);
284    }
285
286    fn visit_generic_param(&mut self, param: &mut GenericParam) {
287        walk_generic_param(self, param)
288    }
289
290    fn flat_map_generic_param(&mut self, param: GenericParam) -> SmallVec<[GenericParam; 1]> {
291        walk_flat_map_generic_param(self, param)
292    }
293
294    fn visit_param_bound(&mut self, tpb: &mut GenericBound, _ctxt: BoundKind) {
295        walk_param_bound(self, tpb);
296    }
297
298    fn visit_precise_capturing_arg(&mut self, arg: &mut PreciseCapturingArg) {
299        walk_precise_capturing_arg(self, arg);
300    }
301
302    fn visit_expr_field(&mut self, f: &mut ExprField) {
303        walk_expr_field(self, f);
304    }
305
306    fn flat_map_expr_field(&mut self, f: ExprField) -> SmallVec<[ExprField; 1]> {
307        walk_flat_map_expr_field(self, f)
308    }
309
310    fn visit_where_clause(&mut self, where_clause: &mut WhereClause) {
311        walk_where_clause(self, where_clause);
312    }
313
314    fn flat_map_where_predicate(
315        &mut self,
316        where_predicate: WherePredicate,
317    ) -> SmallVec<[WherePredicate; 1]> {
318        walk_flat_map_where_predicate(self, where_predicate)
319    }
320
321    fn visit_where_predicate_kind(&mut self, kind: &mut WherePredicateKind) {
322        walk_where_predicate_kind(self, kind)
323    }
324
325    fn visit_vis(&mut self, vis: &mut Visibility) {
326        walk_vis(self, vis);
327    }
328
329    fn visit_id(&mut self, _id: &mut NodeId) {
330        // Do nothing.
331    }
332
333    // Span visiting is no longer used, but we keep it for now,
334    // in case it's needed for something like #127241.
335    fn visit_span(&mut self, _sp: &mut Span) {
336        // Do nothing.
337    }
338
339    fn visit_pat_field(&mut self, fp: &mut PatField) {
340        walk_pat_field(self, fp)
341    }
342
343    fn flat_map_pat_field(&mut self, fp: PatField) -> SmallVec<[PatField; 1]> {
344        walk_flat_map_pat_field(self, fp)
345    }
346
347    fn visit_inline_asm(&mut self, asm: &mut InlineAsm) {
348        walk_inline_asm(self, asm)
349    }
350
351    fn visit_inline_asm_sym(&mut self, sym: &mut InlineAsmSym) {
352        walk_inline_asm_sym(self, sym)
353    }
354
355    fn visit_format_args(&mut self, fmt: &mut FormatArgs) {
356        walk_format_args(self, fmt)
357    }
358
359    fn visit_capture_by(&mut self, capture_by: &mut CaptureBy) {
360        walk_capture_by(self, capture_by)
361    }
362
363    fn visit_fn_ret_ty(&mut self, fn_ret_ty: &mut FnRetTy) {
364        walk_fn_ret_ty(self, fn_ret_ty)
365    }
366}
367
368super::common_visitor_and_walkers!((mut) MutVisitor);
369
370#[inline]
371fn visit_vec<T, F>(elems: &mut Vec<T>, mut visit_elem: F)
372where
373    F: FnMut(&mut T),
374{
375    for elem in elems {
376        visit_elem(elem);
377    }
378}
379
380#[inline]
381fn visit_thin_vec<T, F>(elems: &mut ThinVec<T>, mut visit_elem: F)
382where
383    F: FnMut(&mut T),
384{
385    for elem in elems {
386        visit_elem(elem);
387    }
388}
389
390#[inline]
391fn visit_opt<T, F>(opt: &mut Option<T>, mut visit_elem: F)
392where
393    F: FnMut(&mut T),
394{
395    if let Some(elem) = opt {
396        visit_elem(elem);
397    }
398}
399
400fn visit_attrs<T: MutVisitor>(vis: &mut T, attrs: &mut AttrVec) {
401    for attr in attrs.iter_mut() {
402        vis.visit_attribute(attr);
403    }
404}
405
406#[allow(unused)]
407fn visit_exprs<T: MutVisitor>(vis: &mut T, exprs: &mut Vec<P<Expr>>) {
408    exprs.flat_map_in_place(|expr| vis.filter_map_expr(expr))
409}
410
411fn visit_thin_exprs<T: MutVisitor>(vis: &mut T, exprs: &mut ThinVec<P<Expr>>) {
412    exprs.flat_map_in_place(|expr| vis.filter_map_expr(expr))
413}
414
415fn visit_attr_args<T: MutVisitor>(vis: &mut T, args: &mut AttrArgs) {
416    match args {
417        AttrArgs::Empty => {}
418        AttrArgs::Delimited(args) => visit_delim_args(vis, args),
419        AttrArgs::Eq { eq_span, expr } => {
420            vis.visit_expr(expr);
421            vis.visit_span(eq_span);
422        }
423    }
424}
425
426fn visit_delim_args<T: MutVisitor>(vis: &mut T, args: &mut DelimArgs) {
427    let DelimArgs { dspan, delim: _, tokens: _ } = args;
428    let DelimSpan { open, close } = dspan;
429    vis.visit_span(open);
430    vis.visit_span(close);
431}
432
433pub fn walk_pat_field<T: MutVisitor>(vis: &mut T, fp: &mut PatField) {
434    let PatField { attrs, id, ident, is_placeholder: _, is_shorthand: _, pat, span } = fp;
435    vis.visit_id(id);
436    visit_attrs(vis, attrs);
437    vis.visit_ident(ident);
438    vis.visit_pat(pat);
439    vis.visit_span(span);
440}
441
442pub fn walk_flat_map_pat_field<T: MutVisitor>(
443    vis: &mut T,
444    mut fp: PatField,
445) -> SmallVec<[PatField; 1]> {
446    vis.visit_pat_field(&mut fp);
447    smallvec![fp]
448}
449
450fn walk_use_tree<T: MutVisitor>(vis: &mut T, use_tree: &mut UseTree) {
451    let UseTree { prefix, kind, span } = use_tree;
452    vis.visit_path(prefix);
453    match kind {
454        UseTreeKind::Simple(rename) => visit_opt(rename, |rename| vis.visit_ident(rename)),
455        UseTreeKind::Nested { items, span } => {
456            for (tree, id) in items {
457                vis.visit_id(id);
458                vis.visit_use_tree(tree);
459            }
460            vis.visit_span(span);
461        }
462        UseTreeKind::Glob => {}
463    }
464    vis.visit_span(span);
465}
466
467pub fn walk_arm<T: MutVisitor>(vis: &mut T, arm: &mut Arm) {
468    let Arm { attrs, pat, guard, body, span, id, is_placeholder: _ } = arm;
469    vis.visit_id(id);
470    visit_attrs(vis, attrs);
471    vis.visit_pat(pat);
472    visit_opt(guard, |guard| vis.visit_expr(guard));
473    visit_opt(body, |body| vis.visit_expr(body));
474    vis.visit_span(span);
475}
476
477pub fn walk_flat_map_arm<T: MutVisitor>(vis: &mut T, mut arm: Arm) -> SmallVec<[Arm; 1]> {
478    vis.visit_arm(&mut arm);
479    smallvec![arm]
480}
481
482fn walk_assoc_item_constraint<T: MutVisitor>(
483    vis: &mut T,
484    AssocItemConstraint { id, ident, gen_args, kind, span }: &mut AssocItemConstraint,
485) {
486    vis.visit_id(id);
487    vis.visit_ident(ident);
488    if let Some(gen_args) = gen_args {
489        vis.visit_generic_args(gen_args);
490    }
491    match kind {
492        AssocItemConstraintKind::Equality { term } => match term {
493            Term::Ty(ty) => vis.visit_ty(ty),
494            Term::Const(c) => vis.visit_anon_const(c),
495        },
496        AssocItemConstraintKind::Bound { bounds } => visit_bounds(vis, bounds, BoundKind::Bound),
497    }
498    vis.visit_span(span);
499}
500
501pub fn walk_ty_pat<T: MutVisitor>(vis: &mut T, ty: &mut TyPat) {
502    let TyPat { id, kind, span, tokens: _ } = ty;
503    vis.visit_id(id);
504    match kind {
505        TyPatKind::Range(start, end, _include_end) => {
506            visit_opt(start, |c| vis.visit_anon_const(c));
507            visit_opt(end, |c| vis.visit_anon_const(c));
508        }
509        TyPatKind::Or(variants) => visit_thin_vec(variants, |p| vis.visit_ty_pat(p)),
510        TyPatKind::Err(_) => {}
511    }
512    vis.visit_span(span);
513}
514
515pub fn walk_variant<T: MutVisitor>(visitor: &mut T, variant: &mut Variant) {
516    let Variant { ident, vis, attrs, id, data, disr_expr, span, is_placeholder: _ } = variant;
517    visitor.visit_id(id);
518    visit_attrs(visitor, attrs);
519    visitor.visit_vis(vis);
520    visitor.visit_ident(ident);
521    visitor.visit_variant_data(data);
522    visit_opt(disr_expr, |disr_expr| visitor.visit_anon_const(disr_expr));
523    visitor.visit_span(span);
524}
525
526pub fn walk_flat_map_variant<T: MutVisitor>(
527    vis: &mut T,
528    mut variant: Variant,
529) -> SmallVec<[Variant; 1]> {
530    vis.visit_variant(&mut variant);
531    smallvec![variant]
532}
533
534fn walk_ident<T: MutVisitor>(vis: &mut T, Ident { name: _, span }: &mut Ident) {
535    vis.visit_span(span);
536}
537
538fn walk_path<T: MutVisitor>(vis: &mut T, Path { segments, span, tokens: _ }: &mut Path) {
539    for segment in segments {
540        vis.visit_path_segment(segment);
541    }
542    vis.visit_span(span);
543}
544
545fn walk_qself<T: MutVisitor>(vis: &mut T, qself: &mut Option<P<QSelf>>) {
546    visit_opt(qself, |qself| {
547        let QSelf { ty, path_span, position: _ } = &mut **qself;
548        vis.visit_ty(ty);
549        vis.visit_span(path_span);
550    })
551}
552
553fn walk_generic_args<T: MutVisitor>(vis: &mut T, generic_args: &mut GenericArgs) {
554    match generic_args {
555        GenericArgs::AngleBracketed(data) => vis.visit_angle_bracketed_parameter_data(data),
556        GenericArgs::Parenthesized(data) => vis.visit_parenthesized_parameter_data(data),
557        GenericArgs::ParenthesizedElided(span) => vis.visit_span(span),
558    }
559}
560
561fn walk_generic_arg<T: MutVisitor>(vis: &mut T, arg: &mut GenericArg) {
562    match arg {
563        GenericArg::Lifetime(lt) => vis.visit_lifetime(lt),
564        GenericArg::Type(ty) => vis.visit_ty(ty),
565        GenericArg::Const(ct) => vis.visit_anon_const(ct),
566    }
567}
568
569fn walk_angle_bracketed_parameter_data<T: MutVisitor>(vis: &mut T, data: &mut AngleBracketedArgs) {
570    let AngleBracketedArgs { args, span } = data;
571    visit_thin_vec(args, |arg| match arg {
572        AngleBracketedArg::Arg(arg) => vis.visit_generic_arg(arg),
573        AngleBracketedArg::Constraint(constraint) => vis.visit_assoc_item_constraint(constraint),
574    });
575    vis.visit_span(span);
576}
577
578fn walk_parenthesized_parameter_data<T: MutVisitor>(vis: &mut T, args: &mut ParenthesizedArgs) {
579    let ParenthesizedArgs { inputs, output, span, inputs_span } = args;
580    visit_thin_vec(inputs, |input| vis.visit_ty(input));
581    vis.visit_fn_ret_ty(output);
582    vis.visit_span(span);
583    vis.visit_span(inputs_span);
584}
585
586fn walk_local<T: MutVisitor>(vis: &mut T, local: &mut Local) {
587    let Local { id, super_, pat, ty, kind, span, colon_sp, attrs, tokens: _ } = local;
588    visit_opt(super_, |sp| vis.visit_span(sp));
589    vis.visit_id(id);
590    visit_attrs(vis, attrs);
591    vis.visit_pat(pat);
592    visit_opt(ty, |ty| vis.visit_ty(ty));
593    match kind {
594        LocalKind::Decl => {}
595        LocalKind::Init(init) => {
596            vis.visit_expr(init);
597        }
598        LocalKind::InitElse(init, els) => {
599            vis.visit_expr(init);
600            vis.visit_block(els);
601        }
602    }
603    visit_opt(colon_sp, |sp| vis.visit_span(sp));
604    vis.visit_span(span);
605}
606
607fn walk_attribute<T: MutVisitor>(vis: &mut T, attr: &mut Attribute) {
608    let Attribute { kind, id: _, style: _, span } = attr;
609    match kind {
610        AttrKind::Normal(normal) => {
611            let NormalAttr { item: AttrItem { unsafety: _, path, args, tokens: _ }, tokens: _ } =
612                &mut **normal;
613            vis.visit_path(path);
614            visit_attr_args(vis, args);
615        }
616        AttrKind::DocComment(_kind, _sym) => {}
617    }
618    vis.visit_span(span);
619}
620
621fn walk_mac<T: MutVisitor>(vis: &mut T, mac: &mut MacCall) {
622    let MacCall { path, args } = mac;
623    vis.visit_path(path);
624    visit_delim_args(vis, args);
625}
626
627fn walk_macro_def<T: MutVisitor>(vis: &mut T, macro_def: &mut MacroDef) {
628    let MacroDef { body, macro_rules: _ } = macro_def;
629    visit_delim_args(vis, body);
630}
631
632fn walk_meta_list_item<T: MutVisitor>(vis: &mut T, li: &mut MetaItemInner) {
633    match li {
634        MetaItemInner::MetaItem(mi) => vis.visit_meta_item(mi),
635        MetaItemInner::Lit(_lit) => {}
636    }
637}
638
639fn walk_meta_item<T: MutVisitor>(vis: &mut T, mi: &mut MetaItem) {
640    let MetaItem { unsafety: _, path: _, kind, span } = mi;
641    match kind {
642        MetaItemKind::Word => {}
643        MetaItemKind::List(mis) => visit_thin_vec(mis, |mi| vis.visit_meta_list_item(mi)),
644        MetaItemKind::NameValue(_s) => {}
645    }
646    vis.visit_span(span);
647}
648
649pub fn walk_param<T: MutVisitor>(vis: &mut T, param: &mut Param) {
650    let Param { attrs, id, pat, span, ty, is_placeholder: _ } = param;
651    vis.visit_id(id);
652    visit_attrs(vis, attrs);
653    vis.visit_pat(pat);
654    vis.visit_ty(ty);
655    vis.visit_span(span);
656}
657
658pub fn walk_flat_map_param<T: MutVisitor>(vis: &mut T, mut param: Param) -> SmallVec<[Param; 1]> {
659    vis.visit_param(&mut param);
660    smallvec![param]
661}
662
663fn walk_closure_binder<T: MutVisitor>(vis: &mut T, binder: &mut ClosureBinder) {
664    match binder {
665        ClosureBinder::NotPresent => {}
666        ClosureBinder::For { span: _, generic_params } => {
667            generic_params.flat_map_in_place(|param| vis.flat_map_generic_param(param));
668        }
669    }
670}
671
672fn walk_fn<T: MutVisitor>(vis: &mut T, kind: FnKind<'_>) {
673    match kind {
674        FnKind::Fn(
675            _ctxt,
676            _vis,
677            Fn {
678                defaultness,
679                ident,
680                generics,
681                contract,
682                body,
683                sig: FnSig { header, decl, span },
684                define_opaque,
685            },
686        ) => {
687            // Visibility is visited as a part of the item.
688            visit_defaultness(vis, defaultness);
689            vis.visit_ident(ident);
690            vis.visit_fn_header(header);
691            vis.visit_generics(generics);
692            vis.visit_fn_decl(decl);
693            if let Some(contract) = contract {
694                vis.visit_contract(contract);
695            }
696            if let Some(body) = body {
697                vis.visit_block(body);
698            }
699            vis.visit_span(span);
700
701            walk_define_opaques(vis, define_opaque);
702        }
703        FnKind::Closure(binder, coroutine_kind, decl, body) => {
704            vis.visit_closure_binder(binder);
705            coroutine_kind.as_mut().map(|coroutine_kind| vis.visit_coroutine_kind(coroutine_kind));
706            vis.visit_fn_decl(decl);
707            vis.visit_expr(body);
708        }
709    }
710}
711
712fn walk_contract<T: MutVisitor>(vis: &mut T, contract: &mut FnContract) {
713    let FnContract { requires, ensures } = contract;
714    if let Some(pred) = requires {
715        vis.visit_expr(pred);
716    }
717    if let Some(pred) = ensures {
718        vis.visit_expr(pred);
719    }
720}
721
722fn walk_fn_decl<T: MutVisitor>(vis: &mut T, decl: &mut FnDecl) {
723    let FnDecl { inputs, output } = decl;
724    inputs.flat_map_in_place(|param| vis.flat_map_param(param));
725    vis.visit_fn_ret_ty(output);
726}
727
728fn walk_fn_ret_ty<T: MutVisitor>(vis: &mut T, fn_ret_ty: &mut FnRetTy) {
729    match fn_ret_ty {
730        FnRetTy::Default(span) => vis.visit_span(span),
731        FnRetTy::Ty(ty) => vis.visit_ty(ty),
732    }
733}
734
735fn walk_param_bound<T: MutVisitor>(vis: &mut T, pb: &mut GenericBound) {
736    match pb {
737        GenericBound::Trait(trait_ref) => vis.visit_poly_trait_ref(trait_ref),
738        GenericBound::Outlives(lifetime) => walk_lifetime(vis, lifetime),
739        GenericBound::Use(args, span) => {
740            for arg in args {
741                vis.visit_precise_capturing_arg(arg);
742            }
743            vis.visit_span(span);
744        }
745    }
746}
747
748fn walk_precise_capturing_arg<T: MutVisitor>(vis: &mut T, arg: &mut PreciseCapturingArg) {
749    match arg {
750        PreciseCapturingArg::Lifetime(lt) => {
751            vis.visit_lifetime(lt);
752        }
753        PreciseCapturingArg::Arg(path, id) => {
754            vis.visit_id(id);
755            vis.visit_path(path);
756        }
757    }
758}
759
760pub fn walk_generic_param<T: MutVisitor>(vis: &mut T, param: &mut GenericParam) {
761    let GenericParam { id, ident, attrs, bounds, kind, colon_span, is_placeholder: _ } = param;
762    vis.visit_id(id);
763    visit_attrs(vis, attrs);
764    vis.visit_ident(ident);
765    visit_vec(bounds, |bound| vis.visit_param_bound(bound, BoundKind::Bound));
766    match kind {
767        GenericParamKind::Lifetime => {}
768        GenericParamKind::Type { default } => {
769            visit_opt(default, |default| vis.visit_ty(default));
770        }
771        GenericParamKind::Const { ty, kw_span: _, default } => {
772            vis.visit_ty(ty);
773            visit_opt(default, |default| vis.visit_anon_const(default));
774        }
775    }
776    if let Some(colon_span) = colon_span {
777        vis.visit_span(colon_span);
778    }
779}
780
781pub fn walk_flat_map_generic_param<T: MutVisitor>(
782    vis: &mut T,
783    mut param: GenericParam,
784) -> SmallVec<[GenericParam; 1]> {
785    vis.visit_generic_param(&mut param);
786    smallvec![param]
787}
788
789fn walk_generics<T: MutVisitor>(vis: &mut T, generics: &mut Generics) {
790    let Generics { params, where_clause, span } = generics;
791    params.flat_map_in_place(|param| vis.flat_map_generic_param(param));
792    vis.visit_where_clause(where_clause);
793    vis.visit_span(span);
794}
795
796fn walk_ty_alias_where_clauses<T: MutVisitor>(vis: &mut T, tawcs: &mut TyAliasWhereClauses) {
797    let TyAliasWhereClauses { before, after, split: _ } = tawcs;
798    let TyAliasWhereClause { has_where_token: _, span: span_before } = before;
799    let TyAliasWhereClause { has_where_token: _, span: span_after } = after;
800    vis.visit_span(span_before);
801    vis.visit_span(span_after);
802}
803
804fn walk_where_clause<T: MutVisitor>(vis: &mut T, wc: &mut WhereClause) {
805    let WhereClause { has_where_token: _, predicates, span } = wc;
806    predicates.flat_map_in_place(|predicate| vis.flat_map_where_predicate(predicate));
807    vis.visit_span(span);
808}
809
810pub fn walk_flat_map_where_predicate<T: MutVisitor>(
811    vis: &mut T,
812    mut pred: WherePredicate,
813) -> SmallVec<[WherePredicate; 1]> {
814    let WherePredicate { attrs, kind, id, span, is_placeholder: _ } = &mut pred;
815    vis.visit_id(id);
816    visit_attrs(vis, attrs);
817    vis.visit_where_predicate_kind(kind);
818    vis.visit_span(span);
819    smallvec![pred]
820}
821
822pub fn walk_where_predicate_kind<T: MutVisitor>(vis: &mut T, kind: &mut WherePredicateKind) {
823    match kind {
824        WherePredicateKind::BoundPredicate(bp) => {
825            let WhereBoundPredicate { bound_generic_params, bounded_ty, bounds } = bp;
826            bound_generic_params.flat_map_in_place(|param| vis.flat_map_generic_param(param));
827            vis.visit_ty(bounded_ty);
828            visit_vec(bounds, |bound| vis.visit_param_bound(bound, BoundKind::Bound));
829        }
830        WherePredicateKind::RegionPredicate(rp) => {
831            let WhereRegionPredicate { lifetime, bounds } = rp;
832            vis.visit_lifetime(lifetime);
833            visit_vec(bounds, |bound| vis.visit_param_bound(bound, BoundKind::Bound));
834        }
835        WherePredicateKind::EqPredicate(ep) => {
836            let WhereEqPredicate { lhs_ty, rhs_ty } = ep;
837            vis.visit_ty(lhs_ty);
838            vis.visit_ty(rhs_ty);
839        }
840    }
841}
842
843fn walk_variant_data<T: MutVisitor>(vis: &mut T, vdata: &mut VariantData) {
844    match vdata {
845        VariantData::Struct { fields, recovered: _ } => {
846            fields.flat_map_in_place(|field| vis.flat_map_field_def(field));
847        }
848        VariantData::Tuple(fields, id) => {
849            vis.visit_id(id);
850            fields.flat_map_in_place(|field| vis.flat_map_field_def(field));
851        }
852        VariantData::Unit(id) => vis.visit_id(id),
853    }
854}
855
856fn walk_trait_ref<T: MutVisitor>(vis: &mut T, TraitRef { path, ref_id }: &mut TraitRef) {
857    vis.visit_id(ref_id);
858    vis.visit_path(path);
859}
860
861fn walk_poly_trait_ref<T: MutVisitor>(vis: &mut T, p: &mut PolyTraitRef) {
862    let PolyTraitRef { bound_generic_params, modifiers, trait_ref, span } = p;
863    vis.visit_modifiers(modifiers);
864    bound_generic_params.flat_map_in_place(|param| vis.flat_map_generic_param(param));
865    vis.visit_trait_ref(trait_ref);
866    vis.visit_span(span);
867}
868
869fn walk_modifiers<V: MutVisitor>(vis: &mut V, m: &mut TraitBoundModifiers) {
870    let TraitBoundModifiers { constness, asyncness, polarity } = m;
871    match constness {
872        BoundConstness::Never => {}
873        BoundConstness::Always(span) | BoundConstness::Maybe(span) => vis.visit_span(span),
874    }
875    match asyncness {
876        BoundAsyncness::Normal => {}
877        BoundAsyncness::Async(span) => vis.visit_span(span),
878    }
879    match polarity {
880        BoundPolarity::Positive => {}
881        BoundPolarity::Negative(span) | BoundPolarity::Maybe(span) => vis.visit_span(span),
882    }
883}
884
885pub fn walk_field_def<T: MutVisitor>(visitor: &mut T, fd: &mut FieldDef) {
886    let FieldDef { span, ident, vis, id, ty, attrs, is_placeholder: _, safety, default } = fd;
887    visitor.visit_id(id);
888    visit_attrs(visitor, attrs);
889    visitor.visit_vis(vis);
890    visit_safety(visitor, safety);
891    visit_opt(ident, |ident| visitor.visit_ident(ident));
892    visitor.visit_ty(ty);
893    visit_opt(default, |default| visitor.visit_anon_const(default));
894    visitor.visit_span(span);
895}
896
897pub fn walk_flat_map_field_def<T: MutVisitor>(
898    vis: &mut T,
899    mut fd: FieldDef,
900) -> SmallVec<[FieldDef; 1]> {
901    vis.visit_field_def(&mut fd);
902    smallvec![fd]
903}
904
905pub fn walk_expr_field<T: MutVisitor>(vis: &mut T, f: &mut ExprField) {
906    let ExprField { ident, expr, span, is_shorthand: _, attrs, id, is_placeholder: _ } = f;
907    vis.visit_id(id);
908    visit_attrs(vis, attrs);
909    vis.visit_ident(ident);
910    vis.visit_expr(expr);
911    vis.visit_span(span);
912}
913
914pub fn walk_flat_map_expr_field<T: MutVisitor>(
915    vis: &mut T,
916    mut f: ExprField,
917) -> SmallVec<[ExprField; 1]> {
918    vis.visit_expr_field(&mut f);
919    smallvec![f]
920}
921
922pub fn walk_item_kind<K: WalkItemKind>(
923    kind: &mut K,
924    span: Span,
925    id: NodeId,
926    visibility: &mut Visibility,
927    ctxt: K::Ctxt,
928    vis: &mut impl MutVisitor,
929) {
930    kind.walk(span, id, visibility, ctxt, vis)
931}
932
933pub fn walk_crate<T: MutVisitor>(vis: &mut T, krate: &mut Crate) {
934    let Crate { attrs, items, spans, id, is_placeholder: _ } = krate;
935    vis.visit_id(id);
936    visit_attrs(vis, attrs);
937    items.flat_map_in_place(|item| vis.flat_map_item(item));
938    let ModSpans { inner_span, inject_use_span } = spans;
939    vis.visit_span(inner_span);
940    vis.visit_span(inject_use_span);
941}
942
943pub fn walk_flat_map_item(vis: &mut impl MutVisitor, mut item: P<Item>) -> SmallVec<[P<Item>; 1]> {
944    vis.visit_item(&mut item);
945    smallvec![item]
946}
947
948pub fn walk_flat_map_foreign_item(
949    vis: &mut impl MutVisitor,
950    mut item: P<ForeignItem>,
951) -> SmallVec<[P<ForeignItem>; 1]> {
952    vis.visit_foreign_item(&mut item);
953    smallvec![item]
954}
955
956pub fn walk_flat_map_assoc_item(
957    vis: &mut impl MutVisitor,
958    mut item: P<AssocItem>,
959    ctxt: AssocCtxt,
960) -> SmallVec<[P<AssocItem>; 1]> {
961    vis.visit_assoc_item(&mut item, ctxt);
962    smallvec![item]
963}
964
965fn walk_inline_asm<T: MutVisitor>(vis: &mut T, asm: &mut InlineAsm) {
966    // FIXME: Visit spans inside all this currently ignored stuff.
967    let InlineAsm {
968        asm_macro: _,
969        template: _,
970        template_strs: _,
971        operands,
972        clobber_abis: _,
973        options: _,
974        line_spans: _,
975    } = asm;
976    for (op, span) in operands {
977        match op {
978            InlineAsmOperand::In { expr, reg: _ }
979            | InlineAsmOperand::Out { expr: Some(expr), reg: _, late: _ }
980            | InlineAsmOperand::InOut { expr, reg: _, late: _ } => vis.visit_expr(expr),
981            InlineAsmOperand::Out { expr: None, reg: _, late: _ } => {}
982            InlineAsmOperand::SplitInOut { in_expr, out_expr, reg: _, late: _ } => {
983                vis.visit_expr(in_expr);
984                if let Some(out_expr) = out_expr {
985                    vis.visit_expr(out_expr);
986                }
987            }
988            InlineAsmOperand::Const { anon_const } => vis.visit_anon_const(anon_const),
989            InlineAsmOperand::Sym { sym } => vis.visit_inline_asm_sym(sym),
990            InlineAsmOperand::Label { block } => vis.visit_block(block),
991        }
992        vis.visit_span(span);
993    }
994}
995
996fn walk_inline_asm_sym<T: MutVisitor>(
997    vis: &mut T,
998    InlineAsmSym { id, qself, path }: &mut InlineAsmSym,
999) {
1000    vis.visit_id(id);
1001    vis.visit_qself(qself);
1002    vis.visit_path(path);
1003}
1004
1005fn walk_format_args<T: MutVisitor>(vis: &mut T, fmt: &mut FormatArgs) {
1006    // FIXME: visit the template exhaustively.
1007    let FormatArgs { span, template: _, arguments, uncooked_fmt_str: _ } = fmt;
1008    for FormatArgument { kind, expr } in arguments.all_args_mut() {
1009        match kind {
1010            FormatArgumentKind::Named(ident) | FormatArgumentKind::Captured(ident) => {
1011                vis.visit_ident(ident)
1012            }
1013            FormatArgumentKind::Normal => {}
1014        }
1015        vis.visit_expr(expr);
1016    }
1017    vis.visit_span(span);
1018}
1019
1020pub fn walk_expr<T: MutVisitor>(vis: &mut T, Expr { kind, id, span, attrs, tokens: _ }: &mut Expr) {
1021    vis.visit_id(id);
1022    visit_attrs(vis, attrs);
1023    match kind {
1024        ExprKind::Array(exprs) => visit_thin_exprs(vis, exprs),
1025        ExprKind::ConstBlock(anon_const) => {
1026            vis.visit_anon_const(anon_const);
1027        }
1028        ExprKind::Repeat(expr, count) => {
1029            vis.visit_expr(expr);
1030            vis.visit_anon_const(count);
1031        }
1032        ExprKind::Tup(exprs) => visit_thin_exprs(vis, exprs),
1033        ExprKind::Call(f, args) => {
1034            vis.visit_expr(f);
1035            visit_thin_exprs(vis, args);
1036        }
1037        ExprKind::MethodCall(box MethodCall {
1038            seg: PathSegment { ident, id, args: seg_args },
1039            receiver,
1040            args: call_args,
1041            span,
1042        }) => {
1043            vis.visit_method_receiver_expr(receiver);
1044            vis.visit_id(id);
1045            vis.visit_ident(ident);
1046            visit_opt(seg_args, |args| vis.visit_generic_args(args));
1047            visit_thin_exprs(vis, call_args);
1048            vis.visit_span(span);
1049        }
1050        ExprKind::Binary(binop, lhs, rhs) => {
1051            vis.visit_expr(lhs);
1052            vis.visit_expr(rhs);
1053            vis.visit_span(&mut binop.span);
1054        }
1055        ExprKind::Unary(_unop, ohs) => vis.visit_expr(ohs),
1056        ExprKind::Cast(expr, ty) => {
1057            vis.visit_expr(expr);
1058            vis.visit_ty(ty);
1059        }
1060        ExprKind::Type(expr, ty) => {
1061            vis.visit_expr(expr);
1062            vis.visit_ty(ty);
1063        }
1064        ExprKind::AddrOf(_kind, _mut, ohs) => vis.visit_expr(ohs),
1065        ExprKind::Let(pat, scrutinee, span, _recovered) => {
1066            vis.visit_pat(pat);
1067            vis.visit_expr(scrutinee);
1068            vis.visit_span(span);
1069        }
1070        ExprKind::If(cond, tr, fl) => {
1071            vis.visit_expr(cond);
1072            vis.visit_block(tr);
1073            visit_opt(fl, |fl| ensure_sufficient_stack(|| vis.visit_expr(fl)));
1074        }
1075        ExprKind::While(cond, body, label) => {
1076            visit_opt(label, |label| vis.visit_label(label));
1077            vis.visit_expr(cond);
1078            vis.visit_block(body);
1079        }
1080        ExprKind::ForLoop { pat, iter, body, label, kind: _ } => {
1081            visit_opt(label, |label| vis.visit_label(label));
1082            vis.visit_pat(pat);
1083            vis.visit_expr(iter);
1084            vis.visit_block(body);
1085        }
1086        ExprKind::Loop(body, label, span) => {
1087            visit_opt(label, |label| vis.visit_label(label));
1088            vis.visit_block(body);
1089            vis.visit_span(span);
1090        }
1091        ExprKind::Match(expr, arms, _kind) => {
1092            vis.visit_expr(expr);
1093            arms.flat_map_in_place(|arm| vis.flat_map_arm(arm));
1094        }
1095        ExprKind::Closure(box Closure {
1096            binder,
1097            capture_clause,
1098            constness,
1099            coroutine_kind,
1100            movability: _,
1101            fn_decl,
1102            body,
1103            fn_decl_span,
1104            fn_arg_span,
1105        }) => {
1106            visit_constness(vis, constness);
1107            vis.visit_capture_by(capture_clause);
1108            vis.visit_fn(FnKind::Closure(binder, coroutine_kind, fn_decl, body), *span, *id);
1109            vis.visit_span(fn_decl_span);
1110            vis.visit_span(fn_arg_span);
1111        }
1112        ExprKind::Block(blk, label) => {
1113            visit_opt(label, |label| vis.visit_label(label));
1114            vis.visit_block(blk);
1115        }
1116        ExprKind::Gen(_capture_by, body, _kind, decl_span) => {
1117            vis.visit_block(body);
1118            vis.visit_span(decl_span);
1119        }
1120        ExprKind::Await(expr, await_kw_span) => {
1121            vis.visit_expr(expr);
1122            vis.visit_span(await_kw_span);
1123        }
1124        ExprKind::Use(expr, use_kw_span) => {
1125            vis.visit_expr(expr);
1126            vis.visit_span(use_kw_span);
1127        }
1128        ExprKind::Assign(el, er, span) => {
1129            vis.visit_expr(el);
1130            vis.visit_expr(er);
1131            vis.visit_span(span);
1132        }
1133        ExprKind::AssignOp(_op, el, er) => {
1134            vis.visit_expr(el);
1135            vis.visit_expr(er);
1136        }
1137        ExprKind::Field(el, ident) => {
1138            vis.visit_expr(el);
1139            vis.visit_ident(ident);
1140        }
1141        ExprKind::Index(el, er, brackets_span) => {
1142            vis.visit_expr(el);
1143            vis.visit_expr(er);
1144            vis.visit_span(brackets_span);
1145        }
1146        ExprKind::Range(e1, e2, _lim) => {
1147            visit_opt(e1, |e1| vis.visit_expr(e1));
1148            visit_opt(e2, |e2| vis.visit_expr(e2));
1149        }
1150        ExprKind::Underscore => {}
1151        ExprKind::Path(qself, path) => {
1152            vis.visit_qself(qself);
1153            vis.visit_path(path);
1154        }
1155        ExprKind::Break(label, expr) => {
1156            visit_opt(label, |label| vis.visit_label(label));
1157            visit_opt(expr, |expr| vis.visit_expr(expr));
1158        }
1159        ExprKind::Continue(label) => {
1160            visit_opt(label, |label| vis.visit_label(label));
1161        }
1162        ExprKind::Ret(expr) => {
1163            visit_opt(expr, |expr| vis.visit_expr(expr));
1164        }
1165        ExprKind::Yeet(expr) => {
1166            visit_opt(expr, |expr| vis.visit_expr(expr));
1167        }
1168        ExprKind::Become(expr) => vis.visit_expr(expr),
1169        ExprKind::InlineAsm(asm) => vis.visit_inline_asm(asm),
1170        ExprKind::FormatArgs(fmt) => vis.visit_format_args(fmt),
1171        ExprKind::OffsetOf(container, fields) => {
1172            vis.visit_ty(container);
1173            for field in fields.iter_mut() {
1174                vis.visit_ident(field);
1175            }
1176        }
1177        ExprKind::MacCall(mac) => vis.visit_mac_call(mac),
1178        ExprKind::Struct(se) => {
1179            let StructExpr { qself, path, fields, rest } = se.deref_mut();
1180            vis.visit_qself(qself);
1181            vis.visit_path(path);
1182            fields.flat_map_in_place(|field| vis.flat_map_expr_field(field));
1183            match rest {
1184                StructRest::Base(expr) => vis.visit_expr(expr),
1185                StructRest::Rest(_span) => {}
1186                StructRest::None => {}
1187            }
1188        }
1189        ExprKind::Paren(expr) => {
1190            vis.visit_expr(expr);
1191        }
1192        ExprKind::Yield(kind) => {
1193            let expr = kind.expr_mut();
1194            if let Some(expr) = expr {
1195                vis.visit_expr(expr);
1196            }
1197        }
1198        ExprKind::Try(expr) => vis.visit_expr(expr),
1199        ExprKind::TryBlock(body) => vis.visit_block(body),
1200        ExprKind::Lit(_token) => {}
1201        ExprKind::IncludedBytes(_bytes) => {}
1202        ExprKind::UnsafeBinderCast(_kind, expr, ty) => {
1203            vis.visit_expr(expr);
1204            if let Some(ty) = ty {
1205                vis.visit_ty(ty);
1206            }
1207        }
1208        ExprKind::Err(_guar) => {}
1209        ExprKind::Dummy => {}
1210    }
1211    vis.visit_span(span);
1212}
1213
1214pub fn walk_filter_map_expr<T: MutVisitor>(vis: &mut T, mut e: P<Expr>) -> Option<P<Expr>> {
1215    vis.visit_expr(&mut e);
1216    Some(e)
1217}
1218
1219pub fn walk_flat_map_stmt<T: MutVisitor>(
1220    vis: &mut T,
1221    Stmt { kind, span, mut id }: Stmt,
1222) -> SmallVec<[Stmt; 1]> {
1223    vis.visit_id(&mut id);
1224    let mut stmts: SmallVec<[Stmt; 1]> = walk_flat_map_stmt_kind(vis, kind)
1225        .into_iter()
1226        .map(|kind| Stmt { id, kind, span })
1227        .collect();
1228    match &mut stmts[..] {
1229        [] => {}
1230        [stmt] => vis.visit_span(&mut stmt.span),
1231        _ => panic!(
1232            "cloning statement `NodeId`s is prohibited by default, \
1233             the visitor should implement custom statement visiting"
1234        ),
1235    }
1236    stmts
1237}
1238
1239fn walk_flat_map_stmt_kind<T: MutVisitor>(vis: &mut T, kind: StmtKind) -> SmallVec<[StmtKind; 1]> {
1240    match kind {
1241        StmtKind::Let(mut local) => smallvec![StmtKind::Let({
1242            vis.visit_local(&mut local);
1243            local
1244        })],
1245        StmtKind::Item(item) => vis.flat_map_item(item).into_iter().map(StmtKind::Item).collect(),
1246        StmtKind::Expr(expr) => vis.filter_map_expr(expr).into_iter().map(StmtKind::Expr).collect(),
1247        StmtKind::Semi(expr) => vis.filter_map_expr(expr).into_iter().map(StmtKind::Semi).collect(),
1248        StmtKind::Empty => smallvec![StmtKind::Empty],
1249        StmtKind::MacCall(mut mac) => {
1250            let MacCallStmt { mac: mac_, style: _, attrs, tokens: _ } = mac.deref_mut();
1251            visit_attrs(vis, attrs);
1252            vis.visit_mac_call(mac_);
1253            smallvec![StmtKind::MacCall(mac)]
1254        }
1255    }
1256}
1257
1258fn walk_vis<T: MutVisitor>(vis: &mut T, visibility: &mut Visibility) {
1259    let Visibility { kind, span, tokens: _ } = visibility;
1260    match kind {
1261        VisibilityKind::Public | VisibilityKind::Inherited => {}
1262        VisibilityKind::Restricted { path, id, shorthand: _ } => {
1263            vis.visit_id(id);
1264            vis.visit_path(path);
1265        }
1266    }
1267    vis.visit_span(span);
1268}
1269
1270fn walk_capture_by<T: MutVisitor>(vis: &mut T, capture_by: &mut CaptureBy) {
1271    match capture_by {
1272        CaptureBy::Ref => {}
1273        CaptureBy::Value { move_kw } => {
1274            vis.visit_span(move_kw);
1275        }
1276        CaptureBy::Use { use_kw } => {
1277            vis.visit_span(use_kw);
1278        }
1279    }
1280}
1281
1282#[derive(Debug)]
1283pub enum FnKind<'a> {
1284    /// E.g., `fn foo()`, `fn foo(&self)`, or `extern "Abi" fn foo()`.
1285    Fn(FnCtxt, &'a mut Visibility, &'a mut Fn),
1286
1287    /// E.g., `|x, y| body`.
1288    Closure(
1289        &'a mut ClosureBinder,
1290        &'a mut Option<CoroutineKind>,
1291        &'a mut P<FnDecl>,
1292        &'a mut P<Expr>,
1293    ),
1294}