rustdoc/
visit_ast.rs

1//! The Rust AST Visitor. Extracts useful information and massages it into a form
2//! usable for `clean`.
3
4use std::mem;
5
6use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
7use rustc_hir as hir;
8use rustc_hir::def::{DefKind, Res};
9use rustc_hir::def_id::{DefId, DefIdMap, LocalDefId, LocalDefIdSet};
10use rustc_hir::intravisit::{Visitor, walk_body, walk_item};
11use rustc_hir::{CRATE_HIR_ID, Node};
12use rustc_middle::hir::nested_filter;
13use rustc_middle::ty::TyCtxt;
14use rustc_span::Span;
15use rustc_span::def_id::{CRATE_DEF_ID, LOCAL_CRATE};
16use rustc_span::hygiene::MacroKind;
17use rustc_span::symbol::{Symbol, kw, sym};
18use tracing::debug;
19
20use crate::clean::cfg::Cfg;
21use crate::clean::utils::{inherits_doc_hidden, should_ignore_res};
22use crate::clean::{NestedAttributesExt, hir_attr_lists, reexport_chain};
23use crate::core;
24
25/// This module is used to store stuff from Rust's AST in a more convenient
26/// manner (and with prettier names) before cleaning.
27#[derive(Debug)]
28pub(crate) struct Module<'hir> {
29    pub(crate) name: Symbol,
30    pub(crate) where_inner: Span,
31    pub(crate) mods: Vec<Module<'hir>>,
32    pub(crate) def_id: LocalDefId,
33    pub(crate) renamed: Option<Symbol>,
34    pub(crate) import_id: Option<LocalDefId>,
35    /// The key is the item `ItemId` and the value is: (item, renamed, import_id).
36    /// We use `FxIndexMap` to keep the insert order.
37    pub(crate) items: FxIndexMap<
38        (LocalDefId, Option<Symbol>),
39        (&'hir hir::Item<'hir>, Option<Symbol>, Option<LocalDefId>),
40    >,
41    /// Same as for `items`.
42    pub(crate) inlined_foreigns: FxIndexMap<(DefId, Option<Symbol>), (Res, LocalDefId)>,
43    pub(crate) foreigns: Vec<(&'hir hir::ForeignItem<'hir>, Option<Symbol>)>,
44}
45
46impl Module<'_> {
47    pub(crate) fn new(
48        name: Symbol,
49        def_id: LocalDefId,
50        where_inner: Span,
51        renamed: Option<Symbol>,
52        import_id: Option<LocalDefId>,
53    ) -> Self {
54        Module {
55            name,
56            def_id,
57            where_inner,
58            renamed,
59            import_id,
60            mods: Vec::new(),
61            items: FxIndexMap::default(),
62            inlined_foreigns: FxIndexMap::default(),
63            foreigns: Vec::new(),
64        }
65    }
66
67    pub(crate) fn where_outer(&self, tcx: TyCtxt<'_>) -> Span {
68        tcx.def_span(self.def_id)
69    }
70}
71
72// FIXME: Should this be replaced with tcx.def_path_str?
73fn def_id_to_path(tcx: TyCtxt<'_>, did: DefId) -> Vec<Symbol> {
74    let crate_name = tcx.crate_name(did.krate);
75    let relative = tcx.def_path(did).data.into_iter().filter_map(|elem| elem.data.get_opt_name());
76    std::iter::once(crate_name).chain(relative).collect()
77}
78
79pub(crate) struct RustdocVisitor<'a, 'tcx> {
80    cx: &'a mut core::DocContext<'tcx>,
81    view_item_stack: LocalDefIdSet,
82    inlining: bool,
83    /// Are the current module and all of its parents public?
84    inside_public_path: bool,
85    exact_paths: DefIdMap<Vec<Symbol>>,
86    modules: Vec<Module<'tcx>>,
87    is_importable_from_parent: bool,
88    inside_body: bool,
89}
90
91impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
92    pub(crate) fn new(cx: &'a mut core::DocContext<'tcx>) -> RustdocVisitor<'a, 'tcx> {
93        // If the root is re-exported, terminate all recursion.
94        let mut stack = LocalDefIdSet::default();
95        stack.insert(CRATE_DEF_ID);
96        let om = Module::new(
97            cx.tcx.crate_name(LOCAL_CRATE),
98            CRATE_DEF_ID,
99            cx.tcx.hir_root_module().spans.inner_span,
100            None,
101            None,
102        );
103
104        RustdocVisitor {
105            cx,
106            view_item_stack: stack,
107            inlining: false,
108            inside_public_path: true,
109            exact_paths: Default::default(),
110            modules: vec![om],
111            is_importable_from_parent: true,
112            inside_body: false,
113        }
114    }
115
116    fn store_path(&mut self, did: DefId) {
117        let tcx = self.cx.tcx;
118        self.exact_paths.entry(did).or_insert_with(|| def_id_to_path(tcx, did));
119    }
120
121    pub(crate) fn visit(mut self) -> Module<'tcx> {
122        let root_module = self.cx.tcx.hir_root_module();
123        self.visit_mod_contents(CRATE_DEF_ID, root_module);
124
125        let mut top_level_module = self.modules.pop().unwrap();
126
127        // `#[macro_export] macro_rules!` items are reexported at the top level of the
128        // crate, regardless of where they're defined. We want to document the
129        // top level re-export of the macro, not its original definition, since
130        // the re-export defines the path that a user will actually see. Accordingly,
131        // we add the re-export as an item here, and then skip over the original
132        // definition in `visit_item()` below.
133        //
134        // We also skip `#[macro_export] macro_rules!` that have already been inserted,
135        // it can happen if within the same module a `#[macro_export] macro_rules!`
136        // is declared but also a reexport of itself producing two exports of the same
137        // macro in the same module.
138        let mut inserted = FxHashSet::default();
139        for child in self.cx.tcx.module_children_local(CRATE_DEF_ID) {
140            if !child.reexport_chain.is_empty()
141                && let Res::Def(DefKind::Macro(_), def_id) = child.res
142                && let Some(local_def_id) = def_id.as_local()
143                && self.cx.tcx.has_attr(def_id, sym::macro_export)
144                && inserted.insert(def_id)
145            {
146                let item = self.cx.tcx.hir_expect_item(local_def_id);
147                let (ident, _, _) = item.expect_macro();
148                top_level_module.items.insert((local_def_id, Some(ident.name)), (item, None, None));
149            }
150        }
151
152        self.cx.cache.hidden_cfg = self
153            .cx
154            .tcx
155            .hir_attrs(CRATE_HIR_ID)
156            .iter()
157            .filter(|attr| attr.has_name(sym::doc))
158            .flat_map(|attr| attr.meta_item_list().into_iter().flatten())
159            .filter(|attr| attr.has_name(sym::cfg_hide))
160            .flat_map(|attr| {
161                attr.meta_item_list()
162                    .unwrap_or(&[])
163                    .iter()
164                    .filter_map(|attr| {
165                        Cfg::parse(attr)
166                            .map_err(|e| self.cx.sess().dcx().span_err(e.span, e.msg))
167                            .ok()
168                    })
169                    .collect::<Vec<_>>()
170            })
171            .chain([
172                Cfg::Cfg(sym::test, None),
173                Cfg::Cfg(sym::doc, None),
174                Cfg::Cfg(sym::doctest, None),
175            ])
176            .collect();
177
178        self.cx.cache.exact_paths = self.exact_paths;
179        top_level_module
180    }
181
182    /// This method will go through the given module items in two passes:
183    /// 1. The items which are not glob imports/reexports.
184    /// 2. The glob imports/reexports.
185    fn visit_mod_contents(&mut self, def_id: LocalDefId, m: &'tcx hir::Mod<'tcx>) {
186        debug!("Going through module {m:?}");
187        // Keep track of if there were any private modules in the path.
188        let orig_inside_public_path = self.inside_public_path;
189        self.inside_public_path &= self.cx.tcx.local_visibility(def_id).is_public();
190
191        // Reimplementation of `walk_mod` because we need to do it in two passes (explanations in
192        // the second loop):
193        for &i in m.item_ids {
194            let item = self.cx.tcx.hir_item(i);
195            if !matches!(item.kind, hir::ItemKind::Use(_, hir::UseKind::Glob)) {
196                self.visit_item(item);
197            }
198        }
199        for &i in m.item_ids {
200            let item = self.cx.tcx.hir_item(i);
201            // To match the way import precedence works, visit glob imports last.
202            // Later passes in rustdoc will de-duplicate by name and kind, so if glob-
203            // imported items appear last, then they'll be the ones that get discarded.
204            if matches!(item.kind, hir::ItemKind::Use(_, hir::UseKind::Glob)) {
205                self.visit_item(item);
206            }
207        }
208        self.inside_public_path = orig_inside_public_path;
209        debug!("Leaving module {m:?}");
210    }
211
212    /// Tries to resolve the target of a `pub use` statement and inlines the
213    /// target if it is defined locally and would not be documented otherwise,
214    /// or when it is specifically requested with `please_inline`.
215    /// (the latter is the case when the import is marked `doc(inline)`)
216    ///
217    /// Cross-crate inlining occurs later on during crate cleaning
218    /// and follows different rules.
219    ///
220    /// Returns `true` if the target has been inlined.
221    fn maybe_inline_local(
222        &mut self,
223        def_id: LocalDefId,
224        res: Res,
225        renamed: Option<Symbol>,
226        please_inline: bool,
227    ) -> bool {
228        debug!("maybe_inline_local (renamed: {renamed:?}) res: {res:?}");
229
230        let glob = renamed.is_none();
231        if renamed == Some(kw::Underscore) {
232            // We never inline `_` reexports.
233            return false;
234        }
235
236        if self.cx.is_json_output() {
237            return false;
238        }
239
240        let tcx = self.cx.tcx;
241        let Some(ori_res_did) = res.opt_def_id() else {
242            return false;
243        };
244
245        let document_hidden = self.cx.render_options.document_hidden;
246        let use_attrs = tcx.hir_attrs(tcx.local_def_id_to_hir_id(def_id));
247        // Don't inline `doc(hidden)` imports so they can be stripped at a later stage.
248        let is_no_inline = hir_attr_lists(use_attrs, sym::doc).has_word(sym::no_inline)
249            || (document_hidden && hir_attr_lists(use_attrs, sym::doc).has_word(sym::hidden));
250
251        if is_no_inline {
252            return false;
253        }
254
255        let is_hidden = !document_hidden && tcx.is_doc_hidden(ori_res_did);
256        let Some(res_did) = ori_res_did.as_local() else {
257            // For cross-crate impl inlining we need to know whether items are
258            // reachable in documentation -- a previously unreachable item can be
259            // made reachable by cross-crate inlining which we're checking here.
260            // (this is done here because we need to know this upfront).
261            crate::visit_lib::lib_embargo_visit_item(self.cx, ori_res_did);
262            if is_hidden || glob {
263                return false;
264            }
265            // We store inlined foreign items otherwise, it'd mean that the `use` item would be kept
266            // around. It's not a problem unless this `use` imports both a local AND a foreign item.
267            // If a local item is inlined, its `use` is not supposed to still be around in `clean`,
268            // which would make appear the `use` in the generated documentation like the local item
269            // was not inlined even though it actually was.
270            self.modules
271                .last_mut()
272                .unwrap()
273                .inlined_foreigns
274                .insert((ori_res_did, renamed), (res, def_id));
275            return true;
276        };
277
278        let is_private = !self.cx.cache.effective_visibilities.is_directly_public(tcx, ori_res_did);
279        let item = tcx.hir_node_by_def_id(res_did);
280
281        if !please_inline {
282            let inherits_hidden = !document_hidden && inherits_doc_hidden(tcx, res_did, None);
283            // Only inline if requested or if the item would otherwise be stripped.
284            if (!is_private && !inherits_hidden) || (
285                is_hidden &&
286                // If it's a doc hidden module, we need to keep it in case some of its inner items
287                // are re-exported.
288                !matches!(item, Node::Item(&hir::Item { kind: hir::ItemKind::Mod(..), .. }))
289            ) ||
290                // The imported item is public and not `doc(hidden)` so no need to inline it.
291                self.reexport_public_and_not_hidden(def_id, res_did)
292            {
293                return false;
294            }
295        }
296
297        let is_bang_macro = matches!(
298            item,
299            Node::Item(&hir::Item { kind: hir::ItemKind::Macro(_, _, MacroKind::Bang), .. })
300        );
301
302        if !self.view_item_stack.insert(res_did) && !is_bang_macro {
303            return false;
304        }
305
306        let inlined = match item {
307            // Bang macros are handled a bit on their because of how they are handled by the
308            // compiler. If they have `#[doc(hidden)]` and the re-export doesn't have
309            // `#[doc(inline)]`, then we don't inline it.
310            Node::Item(_) if is_bang_macro && !please_inline && renamed.is_some() && is_hidden => {
311                return false;
312            }
313            Node::Item(&hir::Item { kind: hir::ItemKind::Mod(_, m), .. }) if glob => {
314                let prev = mem::replace(&mut self.inlining, true);
315                for &i in m.item_ids {
316                    let i = tcx.hir_item(i);
317                    self.visit_item_inner(i, None, Some(def_id));
318                }
319                self.inlining = prev;
320                true
321            }
322            Node::Item(it) if !glob => {
323                let prev = mem::replace(&mut self.inlining, true);
324                self.visit_item_inner(it, renamed, Some(def_id));
325                self.inlining = prev;
326                true
327            }
328            Node::ForeignItem(it) if !glob => {
329                let prev = mem::replace(&mut self.inlining, true);
330                self.visit_foreign_item_inner(it, renamed);
331                self.inlining = prev;
332                true
333            }
334            _ => false,
335        };
336        self.view_item_stack.remove(&res_did);
337        if inlined {
338            self.cx.cache.inlined_items.insert(ori_res_did);
339        }
340        inlined
341    }
342
343    /// Returns `true` if the item is visible, meaning it's not `#[doc(hidden)]` or private.
344    ///
345    /// This function takes into account the entire re-export `use` chain, so it needs the
346    /// ID of the "leaf" `use` and the ID of the "root" item.
347    fn reexport_public_and_not_hidden(
348        &self,
349        import_def_id: LocalDefId,
350        target_def_id: LocalDefId,
351    ) -> bool {
352        if self.cx.render_options.document_hidden {
353            return true;
354        }
355        let tcx = self.cx.tcx;
356        let item_def_id = reexport_chain(tcx, import_def_id, target_def_id.to_def_id())
357            .iter()
358            .flat_map(|reexport| reexport.id())
359            .map(|id| id.expect_local())
360            .nth(1)
361            .unwrap_or(target_def_id);
362        item_def_id != import_def_id
363            && self.cx.cache.effective_visibilities.is_directly_public(tcx, item_def_id.to_def_id())
364            && !tcx.is_doc_hidden(item_def_id)
365            && !inherits_doc_hidden(tcx, item_def_id, None)
366    }
367
368    #[inline]
369    fn add_to_current_mod(
370        &mut self,
371        item: &'tcx hir::Item<'_>,
372        renamed: Option<Symbol>,
373        parent_id: Option<LocalDefId>,
374    ) {
375        if self.is_importable_from_parent
376            // If we're inside an item, only impl blocks and `macro_rules!` with the `macro_export`
377            // attribute can still be visible.
378            || match item.kind {
379                hir::ItemKind::Impl(..) => true,
380                hir::ItemKind::Macro(_, _, MacroKind::Bang) => {
381                    self.cx.tcx.has_attr(item.owner_id.def_id, sym::macro_export)
382                }
383                _ => false,
384            }
385        {
386            self.modules
387                .last_mut()
388                .unwrap()
389                .items
390                .insert((item.owner_id.def_id, renamed), (item, renamed, parent_id));
391        }
392    }
393
394    fn visit_item_inner(
395        &mut self,
396        item: &'tcx hir::Item<'_>,
397        renamed: Option<Symbol>,
398        import_id: Option<LocalDefId>,
399    ) {
400        debug!("visiting item {item:?}");
401        if self.inside_body {
402            // Only impls can be "seen" outside a body. For example:
403            //
404            // ```
405            // struct Bar;
406            //
407            // fn foo() {
408            //     impl Bar { fn bar() {} }
409            // }
410            // Bar::bar();
411            // ```
412            if let hir::ItemKind::Impl(impl_) = item.kind &&
413                // Don't duplicate impls when inlining or if it's implementing a trait, we'll pick
414                // them up regardless of where they're located.
415                impl_.of_trait.is_none()
416            {
417                self.add_to_current_mod(item, None, None);
418            }
419            return;
420        }
421        let get_name = || renamed.unwrap_or(item.kind.ident().unwrap().name);
422        let tcx = self.cx.tcx;
423
424        let def_id = item.owner_id.to_def_id();
425        let is_pub = tcx.visibility(def_id).is_public();
426
427        if is_pub {
428            self.store_path(item.owner_id.to_def_id());
429        }
430
431        match item.kind {
432            hir::ItemKind::ForeignMod { items, .. } => {
433                for item in items {
434                    let item = tcx.hir_foreign_item(item.id);
435                    self.visit_foreign_item_inner(item, None);
436                }
437            }
438            // If we're inlining, skip private items.
439            _ if self.inlining && !is_pub => {}
440            hir::ItemKind::GlobalAsm { .. } => {}
441            hir::ItemKind::Use(_, hir::UseKind::ListStem) => {}
442            hir::ItemKind::Use(path, kind) => {
443                for &res in &path.res {
444                    // Struct and variant constructors and proc macro stubs always show up alongside
445                    // their definitions, we've already processed them so just discard these.
446                    if should_ignore_res(res) {
447                        continue;
448                    }
449
450                    let attrs = tcx.hir_attrs(tcx.local_def_id_to_hir_id(item.owner_id.def_id));
451
452                    // If there was a private module in the current path then don't bother inlining
453                    // anything as it will probably be stripped anyway.
454                    if is_pub && self.inside_public_path {
455                        let please_inline = attrs.iter().any(|item| match item.meta_item_list() {
456                            Some(ref list) if item.has_name(sym::doc) => {
457                                list.iter().any(|i| i.has_name(sym::inline))
458                            }
459                            _ => false,
460                        });
461                        let ident = match kind {
462                            hir::UseKind::Single(ident) => Some(renamed.unwrap_or(ident.name)),
463                            hir::UseKind::Glob => None,
464                            hir::UseKind::ListStem => unreachable!(),
465                        };
466                        if self.maybe_inline_local(item.owner_id.def_id, res, ident, please_inline)
467                        {
468                            debug!("Inlining {:?}", item.owner_id.def_id);
469                            continue;
470                        }
471                    }
472                    self.add_to_current_mod(item, renamed, import_id);
473                }
474            }
475            hir::ItemKind::Macro(_, macro_def, _) => {
476                // `#[macro_export] macro_rules!` items are handled separately in `visit()`,
477                // above, since they need to be documented at the module top level. Accordingly,
478                // we only want to handle macros if one of three conditions holds:
479                //
480                // 1. This macro was defined by `macro`, and thus isn't covered by the case
481                //    above.
482                // 2. This macro isn't marked with `#[macro_export]`, and thus isn't covered
483                //    by the case above.
484                // 3. We're inlining, since a reexport where inlining has been requested
485                //    should be inlined even if it is also documented at the top level.
486
487                let def_id = item.owner_id.to_def_id();
488                let is_macro_2_0 = !macro_def.macro_rules;
489                let nonexported = !tcx.has_attr(def_id, sym::macro_export);
490
491                if is_macro_2_0 || nonexported || self.inlining {
492                    self.add_to_current_mod(item, renamed, import_id);
493                }
494            }
495            hir::ItemKind::Mod(_, m) => {
496                self.enter_mod(item.owner_id.def_id, m, get_name(), renamed, import_id);
497            }
498            hir::ItemKind::Fn { .. }
499            | hir::ItemKind::ExternCrate(..)
500            | hir::ItemKind::Enum(..)
501            | hir::ItemKind::Struct(..)
502            | hir::ItemKind::Union(..)
503            | hir::ItemKind::TyAlias(..)
504            | hir::ItemKind::Static(..)
505            | hir::ItemKind::Trait(..)
506            | hir::ItemKind::TraitAlias(..) => {
507                self.add_to_current_mod(item, renamed, import_id);
508            }
509            hir::ItemKind::Const(..) => {
510                // Underscore constants do not correspond to a nameable item and
511                // so are never useful in documentation.
512                if get_name() != kw::Underscore {
513                    self.add_to_current_mod(item, renamed, import_id);
514                }
515            }
516            hir::ItemKind::Impl(impl_) => {
517                // Don't duplicate impls when inlining or if it's implementing a trait, we'll pick
518                // them up regardless of where they're located.
519                if !self.inlining && impl_.of_trait.is_none() {
520                    self.add_to_current_mod(item, None, None);
521                }
522            }
523        }
524    }
525
526    fn visit_foreign_item_inner(
527        &mut self,
528        item: &'tcx hir::ForeignItem<'_>,
529        renamed: Option<Symbol>,
530    ) {
531        // If inlining we only want to include public functions.
532        if !self.inlining || self.cx.tcx.visibility(item.owner_id).is_public() {
533            self.modules.last_mut().unwrap().foreigns.push((item, renamed));
534        }
535    }
536
537    /// This method will create a new module and push it onto the "modules stack" then call
538    /// `visit_mod_contents`. Once done, it'll remove it from the "modules stack" and instead
539    /// add into the list of modules of the current module.
540    fn enter_mod(
541        &mut self,
542        id: LocalDefId,
543        m: &'tcx hir::Mod<'tcx>,
544        name: Symbol,
545        renamed: Option<Symbol>,
546        import_id: Option<LocalDefId>,
547    ) {
548        self.modules.push(Module::new(name, id, m.spans.inner_span, renamed, import_id));
549
550        self.visit_mod_contents(id, m);
551
552        let last = self.modules.pop().unwrap();
553        self.modules.last_mut().unwrap().mods.push(last);
554    }
555}
556
557// We need to implement this visitor so it'll go everywhere and retrieve items we're interested in
558// such as impl blocks in const blocks.
559impl<'tcx> Visitor<'tcx> for RustdocVisitor<'_, 'tcx> {
560    type NestedFilter = nested_filter::All;
561
562    fn maybe_tcx(&mut self) -> Self::MaybeTyCtxt {
563        self.cx.tcx
564    }
565
566    fn visit_item(&mut self, i: &'tcx hir::Item<'tcx>) {
567        self.visit_item_inner(i, None, None);
568        let new_value = self.is_importable_from_parent
569            && matches!(
570                i.kind,
571                hir::ItemKind::Mod(..)
572                    | hir::ItemKind::ForeignMod { .. }
573                    | hir::ItemKind::Impl(..)
574                    | hir::ItemKind::Trait(..)
575            );
576        let prev = mem::replace(&mut self.is_importable_from_parent, new_value);
577        walk_item(self, i);
578        self.is_importable_from_parent = prev;
579    }
580
581    fn visit_mod(&mut self, _: &hir::Mod<'tcx>, _: Span, _: hir::HirId) {
582        // Handled in `visit_item_inner`
583    }
584
585    fn visit_use(&mut self, _: &hir::UsePath<'tcx>, _: hir::HirId) {
586        // Handled in `visit_item_inner`
587    }
588
589    fn visit_path(&mut self, _: &hir::Path<'tcx>, _: hir::HirId) {
590        // Handled in `visit_item_inner`
591    }
592
593    fn visit_label(&mut self, _: &rustc_ast::Label) {
594        // Unneeded.
595    }
596
597    fn visit_infer(
598        &mut self,
599        _inf_id: hir::HirId,
600        _inf_span: Span,
601        _kind: hir::intravisit::InferKind<'tcx>,
602    ) -> Self::Result {
603        // Unneeded
604    }
605
606    fn visit_lifetime(&mut self, _: &hir::Lifetime) {
607        // Unneeded.
608    }
609
610    fn visit_body(&mut self, b: &hir::Body<'tcx>) {
611        let prev = mem::replace(&mut self.inside_body, true);
612        walk_body(self, b);
613        self.inside_body = prev;
614    }
615}