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                top_level_module
148                    .items
149                    .insert((local_def_id, Some(item.ident.name)), (item, None, None));
150            }
151        }
152
153        self.cx.cache.hidden_cfg = self
154            .cx
155            .tcx
156            .hir()
157            .attrs(CRATE_HIR_ID)
158            .iter()
159            .filter(|attr| attr.has_name(sym::doc))
160            .flat_map(|attr| attr.meta_item_list().into_iter().flatten())
161            .filter(|attr| attr.has_name(sym::cfg_hide))
162            .flat_map(|attr| {
163                attr.meta_item_list()
164                    .unwrap_or(&[])
165                    .iter()
166                    .filter_map(|attr| {
167                        Cfg::parse(attr)
168                            .map_err(|e| self.cx.sess().dcx().span_err(e.span, e.msg))
169                            .ok()
170                    })
171                    .collect::<Vec<_>>()
172            })
173            .chain([
174                Cfg::Cfg(sym::test, None),
175                Cfg::Cfg(sym::doc, None),
176                Cfg::Cfg(sym::doctest, None),
177            ])
178            .collect();
179
180        self.cx.cache.exact_paths = self.exact_paths;
181        top_level_module
182    }
183
184    /// This method will go through the given module items in two passes:
185    /// 1. The items which are not glob imports/reexports.
186    /// 2. The glob imports/reexports.
187    fn visit_mod_contents(&mut self, def_id: LocalDefId, m: &'tcx hir::Mod<'tcx>) {
188        debug!("Going through module {m:?}");
189        // Keep track of if there were any private modules in the path.
190        let orig_inside_public_path = self.inside_public_path;
191        self.inside_public_path &= self.cx.tcx.local_visibility(def_id).is_public();
192
193        // Reimplementation of `walk_mod` because we need to do it in two passes (explanations in
194        // the second loop):
195        for &i in m.item_ids {
196            let item = self.cx.tcx.hir_item(i);
197            if !matches!(item.kind, hir::ItemKind::Use(_, hir::UseKind::Glob)) {
198                self.visit_item(item);
199            }
200        }
201        for &i in m.item_ids {
202            let item = self.cx.tcx.hir_item(i);
203            // To match the way import precedence works, visit glob imports last.
204            // Later passes in rustdoc will de-duplicate by name and kind, so if glob-
205            // imported items appear last, then they'll be the ones that get discarded.
206            if matches!(item.kind, hir::ItemKind::Use(_, hir::UseKind::Glob)) {
207                self.visit_item(item);
208            }
209        }
210        self.inside_public_path = orig_inside_public_path;
211        debug!("Leaving module {m:?}");
212    }
213
214    /// Tries to resolve the target of a `pub use` statement and inlines the
215    /// target if it is defined locally and would not be documented otherwise,
216    /// or when it is specifically requested with `please_inline`.
217    /// (the latter is the case when the import is marked `doc(inline)`)
218    ///
219    /// Cross-crate inlining occurs later on during crate cleaning
220    /// and follows different rules.
221    ///
222    /// Returns `true` if the target has been inlined.
223    fn maybe_inline_local(
224        &mut self,
225        def_id: LocalDefId,
226        res: Res,
227        renamed: Option<Symbol>,
228        glob: bool,
229        please_inline: bool,
230    ) -> bool {
231        debug!("maybe_inline_local (renamed: {renamed:?}) res: {res:?}");
232
233        if renamed == Some(kw::Underscore) {
234            // We never inline `_` reexports.
235            return false;
236        }
237
238        if self.cx.is_json_output() {
239            return false;
240        }
241
242        let tcx = self.cx.tcx;
243        let Some(ori_res_did) = res.opt_def_id() else {
244            return false;
245        };
246
247        let document_hidden = self.cx.render_options.document_hidden;
248        let use_attrs = tcx.hir().attrs(tcx.local_def_id_to_hir_id(def_id));
249        // Don't inline `doc(hidden)` imports so they can be stripped at a later stage.
250        let is_no_inline = hir_attr_lists(use_attrs, sym::doc).has_word(sym::no_inline)
251            || (document_hidden && hir_attr_lists(use_attrs, sym::doc).has_word(sym::hidden));
252
253        if is_no_inline {
254            return false;
255        }
256
257        let is_hidden = !document_hidden && tcx.is_doc_hidden(ori_res_did);
258        let Some(res_did) = ori_res_did.as_local() else {
259            // For cross-crate impl inlining we need to know whether items are
260            // reachable in documentation -- a previously unreachable item can be
261            // made reachable by cross-crate inlining which we're checking here.
262            // (this is done here because we need to know this upfront).
263            crate::visit_lib::lib_embargo_visit_item(self.cx, ori_res_did);
264            if is_hidden || glob {
265                return false;
266            }
267            // We store inlined foreign items otherwise, it'd mean that the `use` item would be kept
268            // around. It's not a problem unless this `use` imports both a local AND a foreign item.
269            // If a local item is inlined, its `use` is not supposed to still be around in `clean`,
270            // which would make appear the `use` in the generated documentation like the local item
271            // was not inlined even though it actually was.
272            self.modules
273                .last_mut()
274                .unwrap()
275                .inlined_foreigns
276                .insert((ori_res_did, renamed), (res, def_id));
277            return true;
278        };
279
280        let is_private = !self.cx.cache.effective_visibilities.is_directly_public(tcx, ori_res_did);
281        let item = tcx.hir_node_by_def_id(res_did);
282
283        if !please_inline {
284            let inherits_hidden = !document_hidden && inherits_doc_hidden(tcx, res_did, None);
285            // Only inline if requested or if the item would otherwise be stripped.
286            if (!is_private && !inherits_hidden) || (
287                is_hidden &&
288                // If it's a doc hidden module, we need to keep it in case some of its inner items
289                // are re-exported.
290                !matches!(item, Node::Item(&hir::Item { kind: hir::ItemKind::Mod(_), .. }))
291            ) ||
292                // The imported item is public and not `doc(hidden)` so no need to inline it.
293                self.reexport_public_and_not_hidden(def_id, res_did)
294            {
295                return false;
296            }
297        }
298
299        let is_bang_macro = matches!(
300            item,
301            Node::Item(&hir::Item { kind: hir::ItemKind::Macro(_, MacroKind::Bang), .. })
302        );
303
304        if !self.view_item_stack.insert(res_did) && !is_bang_macro {
305            return false;
306        }
307
308        let inlined = match item {
309            // Bang macros are handled a bit on their because of how they are handled by the
310            // compiler. If they have `#[doc(hidden)]` and the re-export doesn't have
311            // `#[doc(inline)]`, then we don't inline it.
312            Node::Item(_) if is_bang_macro && !please_inline && renamed.is_some() && is_hidden => {
313                return false;
314            }
315            Node::Item(&hir::Item { kind: hir::ItemKind::Mod(m), .. }) if glob => {
316                let prev = mem::replace(&mut self.inlining, true);
317                for &i in m.item_ids {
318                    let i = tcx.hir_item(i);
319                    self.visit_item_inner(i, None, Some(def_id));
320                }
321                self.inlining = prev;
322                true
323            }
324            Node::Item(it) if !glob => {
325                let prev = mem::replace(&mut self.inlining, true);
326                self.visit_item_inner(it, renamed, Some(def_id));
327                self.inlining = prev;
328                true
329            }
330            Node::ForeignItem(it) if !glob => {
331                let prev = mem::replace(&mut self.inlining, true);
332                self.visit_foreign_item_inner(it, renamed);
333                self.inlining = prev;
334                true
335            }
336            _ => false,
337        };
338        self.view_item_stack.remove(&res_did);
339        if inlined {
340            self.cx.cache.inlined_items.insert(ori_res_did);
341        }
342        inlined
343    }
344
345    /// Returns `true` if the item is visible, meaning it's not `#[doc(hidden)]` or private.
346    ///
347    /// This function takes into account the entire re-export `use` chain, so it needs the
348    /// ID of the "leaf" `use` and the ID of the "root" item.
349    fn reexport_public_and_not_hidden(
350        &self,
351        import_def_id: LocalDefId,
352        target_def_id: LocalDefId,
353    ) -> bool {
354        if self.cx.render_options.document_hidden {
355            return true;
356        }
357        let tcx = self.cx.tcx;
358        let item_def_id = reexport_chain(tcx, import_def_id, target_def_id.to_def_id())
359            .iter()
360            .flat_map(|reexport| reexport.id())
361            .map(|id| id.expect_local())
362            .nth(1)
363            .unwrap_or(target_def_id);
364        item_def_id != import_def_id
365            && self.cx.cache.effective_visibilities.is_directly_public(tcx, item_def_id.to_def_id())
366            && !tcx.is_doc_hidden(item_def_id)
367            && !inherits_doc_hidden(tcx, item_def_id, None)
368    }
369
370    #[inline]
371    fn add_to_current_mod(
372        &mut self,
373        item: &'tcx hir::Item<'_>,
374        renamed: Option<Symbol>,
375        parent_id: Option<LocalDefId>,
376    ) {
377        if self.is_importable_from_parent
378            // If we're inside an item, only impl blocks and `macro_rules!` with the `macro_export`
379            // attribute can still be visible.
380            || match item.kind {
381                hir::ItemKind::Impl(..) => true,
382                hir::ItemKind::Macro(_, MacroKind::Bang) => {
383                    self.cx.tcx.has_attr(item.owner_id.def_id, sym::macro_export)
384                }
385                _ => false,
386            }
387        {
388            self.modules
389                .last_mut()
390                .unwrap()
391                .items
392                .insert((item.owner_id.def_id, renamed), (item, renamed, parent_id));
393        }
394    }
395
396    fn visit_item_inner(
397        &mut self,
398        item: &'tcx hir::Item<'_>,
399        renamed: Option<Symbol>,
400        import_id: Option<LocalDefId>,
401    ) {
402        debug!("visiting item {item:?}");
403        if self.inside_body {
404            // Only impls can be "seen" outside a body. For example:
405            //
406            // ```
407            // struct Bar;
408            //
409            // fn foo() {
410            //     impl Bar { fn bar() {} }
411            // }
412            // Bar::bar();
413            // ```
414            if let hir::ItemKind::Impl(impl_) = item.kind &&
415                // Don't duplicate impls when inlining or if it's implementing a trait, we'll pick
416                // them up regardless of where they're located.
417                impl_.of_trait.is_none()
418            {
419                self.add_to_current_mod(item, None, None);
420            }
421            return;
422        }
423        let name = renamed.unwrap_or(item.ident.name);
424        let tcx = self.cx.tcx;
425
426        let def_id = item.owner_id.to_def_id();
427        let is_pub = tcx.visibility(def_id).is_public();
428
429        if is_pub {
430            self.store_path(item.owner_id.to_def_id());
431        }
432
433        match item.kind {
434            hir::ItemKind::ForeignMod { items, .. } => {
435                for item in items {
436                    let item = tcx.hir_foreign_item(item.id);
437                    self.visit_foreign_item_inner(item, None);
438                }
439            }
440            // If we're inlining, skip private items.
441            _ if self.inlining && !is_pub => {}
442            hir::ItemKind::GlobalAsm(..) => {}
443            hir::ItemKind::Use(_, hir::UseKind::ListStem) => {}
444            hir::ItemKind::Use(path, kind) => {
445                for &res in &path.res {
446                    // Struct and variant constructors and proc macro stubs always show up alongside
447                    // their definitions, we've already processed them so just discard these.
448                    if should_ignore_res(res) {
449                        continue;
450                    }
451
452                    let attrs = tcx.hir().attrs(tcx.local_def_id_to_hir_id(item.owner_id.def_id));
453
454                    // If there was a private module in the current path then don't bother inlining
455                    // anything as it will probably be stripped anyway.
456                    if is_pub && self.inside_public_path {
457                        let please_inline = attrs.iter().any(|item| match item.meta_item_list() {
458                            Some(ref list) if item.has_name(sym::doc) => {
459                                list.iter().any(|i| i.has_name(sym::inline))
460                            }
461                            _ => false,
462                        });
463                        let is_glob = kind == hir::UseKind::Glob;
464                        let ident = if is_glob { None } else { Some(name) };
465                        if self.maybe_inline_local(
466                            item.owner_id.def_id,
467                            res,
468                            ident,
469                            is_glob,
470                            please_inline,
471                        ) {
472                            debug!("Inlining {:?}", item.owner_id.def_id);
473                            continue;
474                        }
475                    }
476                    self.add_to_current_mod(item, renamed, import_id);
477                }
478            }
479            hir::ItemKind::Macro(macro_def, _) => {
480                // `#[macro_export] macro_rules!` items are handled separately in `visit()`,
481                // above, since they need to be documented at the module top level. Accordingly,
482                // we only want to handle macros if one of three conditions holds:
483                //
484                // 1. This macro was defined by `macro`, and thus isn't covered by the case
485                //    above.
486                // 2. This macro isn't marked with `#[macro_export]`, and thus isn't covered
487                //    by the case above.
488                // 3. We're inlining, since a reexport where inlining has been requested
489                //    should be inlined even if it is also documented at the top level.
490
491                let def_id = item.owner_id.to_def_id();
492                let is_macro_2_0 = !macro_def.macro_rules;
493                let nonexported = !tcx.has_attr(def_id, sym::macro_export);
494
495                if is_macro_2_0 || nonexported || self.inlining {
496                    self.add_to_current_mod(item, renamed, import_id);
497                }
498            }
499            hir::ItemKind::Mod(m) => {
500                self.enter_mod(item.owner_id.def_id, m, name, renamed, import_id);
501            }
502            hir::ItemKind::Fn { .. }
503            | hir::ItemKind::ExternCrate(..)
504            | hir::ItemKind::Enum(..)
505            | hir::ItemKind::Struct(..)
506            | hir::ItemKind::Union(..)
507            | hir::ItemKind::TyAlias(..)
508            | hir::ItemKind::Static(..)
509            | hir::ItemKind::Trait(..)
510            | hir::ItemKind::TraitAlias(..) => {
511                self.add_to_current_mod(item, renamed, import_id);
512            }
513            hir::ItemKind::Const(..) => {
514                // Underscore constants do not correspond to a nameable item and
515                // so are never useful in documentation.
516                if name != kw::Underscore {
517                    self.add_to_current_mod(item, renamed, import_id);
518                }
519            }
520            hir::ItemKind::Impl(impl_) => {
521                // Don't duplicate impls when inlining or if it's implementing a trait, we'll pick
522                // them up regardless of where they're located.
523                if !self.inlining && impl_.of_trait.is_none() {
524                    self.add_to_current_mod(item, None, None);
525                }
526            }
527        }
528    }
529
530    fn visit_foreign_item_inner(
531        &mut self,
532        item: &'tcx hir::ForeignItem<'_>,
533        renamed: Option<Symbol>,
534    ) {
535        // If inlining we only want to include public functions.
536        if !self.inlining || self.cx.tcx.visibility(item.owner_id).is_public() {
537            self.modules.last_mut().unwrap().foreigns.push((item, renamed));
538        }
539    }
540
541    /// This method will create a new module and push it onto the "modules stack" then call
542    /// `visit_mod_contents`. Once done, it'll remove it from the "modules stack" and instead
543    /// add into the list of modules of the current module.
544    fn enter_mod(
545        &mut self,
546        id: LocalDefId,
547        m: &'tcx hir::Mod<'tcx>,
548        name: Symbol,
549        renamed: Option<Symbol>,
550        import_id: Option<LocalDefId>,
551    ) {
552        self.modules.push(Module::new(name, id, m.spans.inner_span, renamed, import_id));
553
554        self.visit_mod_contents(id, m);
555
556        let last = self.modules.pop().unwrap();
557        self.modules.last_mut().unwrap().mods.push(last);
558    }
559}
560
561// We need to implement this visitor so it'll go everywhere and retrieve items we're interested in
562// such as impl blocks in const blocks.
563impl<'tcx> Visitor<'tcx> for RustdocVisitor<'_, 'tcx> {
564    type NestedFilter = nested_filter::All;
565
566    fn maybe_tcx(&mut self) -> Self::MaybeTyCtxt {
567        self.cx.tcx
568    }
569
570    fn visit_item(&mut self, i: &'tcx hir::Item<'tcx>) {
571        self.visit_item_inner(i, None, None);
572        let new_value = self.is_importable_from_parent
573            && matches!(
574                i.kind,
575                hir::ItemKind::Mod(..)
576                    | hir::ItemKind::ForeignMod { .. }
577                    | hir::ItemKind::Impl(..)
578                    | hir::ItemKind::Trait(..)
579            );
580        let prev = mem::replace(&mut self.is_importable_from_parent, new_value);
581        walk_item(self, i);
582        self.is_importable_from_parent = prev;
583    }
584
585    fn visit_mod(&mut self, _: &hir::Mod<'tcx>, _: Span, _: hir::HirId) {
586        // Handled in `visit_item_inner`
587    }
588
589    fn visit_use(&mut self, _: &hir::UsePath<'tcx>, _: hir::HirId) {
590        // Handled in `visit_item_inner`
591    }
592
593    fn visit_path(&mut self, _: &hir::Path<'tcx>, _: hir::HirId) {
594        // Handled in `visit_item_inner`
595    }
596
597    fn visit_label(&mut self, _: &rustc_ast::Label) {
598        // Unneeded.
599    }
600
601    fn visit_infer(
602        &mut self,
603        _inf_id: hir::HirId,
604        _inf_span: Span,
605        _kind: hir::intravisit::InferKind<'tcx>,
606    ) -> Self::Result {
607        // Unneeded
608    }
609
610    fn visit_lifetime(&mut self, _: &hir::Lifetime) {
611        // Unneeded.
612    }
613
614    fn visit_body(&mut self, b: &hir::Body<'tcx>) {
615        let prev = mem::replace(&mut self.inside_body, true);
616        walk_body(self, b);
617        self.inside_body = prev;
618    }
619}
rustdoc/visit_ast.rs

rustdoc/
visit_ast.rs
