repo_description: A community fork of a language named after a plant fungus. All of the memory-safe features you love, now with 100% less bureaucracy! 
code: //! The Rust AST Visitor. Extracts useful information and massages it into a form
  //! usable for `clean`.
  
  use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
  use rustc_hir as hir;
  use rustc_hir::def::{DefKind, Res};
  use rustc_hir::def_id::{DefId, DefIdMap, LocalDefId, LocalDefIdSet};
  use rustc_hir::intravisit::{walk_body, walk_item, Visitor};
  use rustc_hir::{Node, CRATE_HIR_ID};
  use rustc_middle::hir::nested_filter;
  use rustc_middle::ty::TyCtxt;
  use rustc_span::def_id::{CRATE_DEF_ID, LOCAL_CRATE};
  use rustc_span::hygiene::MacroKind;
  use rustc_span::symbol::{kw, sym, Symbol};
  use rustc_span::Span;
  
  use std::mem;
  
  use crate::clean::{cfg::Cfg, reexport_chain, AttributesExt, NestedAttributesExt};
  use crate::core;
  
  /// This module is used to store stuff from Rust's AST in a more convenient
  /// manner (and with prettier names) before cleaning.
  #[derive(Debug)]
  pub(crate) struct Module<'hir> {
      pub(crate) name: Symbol,
      pub(crate) where_inner: Span,
      pub(crate) mods: Vec<Module<'hir>>,
      pub(crate) def_id: LocalDefId,
      pub(crate) renamed: Option<Symbol>,
      pub(crate) import_id: Option<LocalDefId>,
      /// The key is the item `ItemId` and the value is: (item, renamed, import_id).
      /// We use `FxIndexMap` to keep the insert order.
      pub(crate) items: FxIndexMap<
          (LocalDefId, Option<Symbol>),
          (&'hir hir::Item<'hir>, Option<Symbol>, Option<LocalDefId>),
      >,
      /// Same as for `items`.
      pub(crate) inlined_foreigns: FxIndexMap<(DefId, Option<Symbol>), (Res, LocalDefId)>,
      pub(crate) foreigns: Vec<(&'hir hir::ForeignItem<'hir>, Option<Symbol>)>,
  }
  
  impl Module<'_> {
      pub(crate) fn new(
          name: Symbol,
          def_id: LocalDefId,
          where_inner: Span,
          renamed: Option<Symbol>,
          import_id: Option<LocalDefId>,
      ) -> Self {
          Module {
              name,
              def_id,
              where_inner,
              renamed,
              import_id,
              mods: Vec::new(),
              items: FxIndexMap::default(),
              inlined_foreigns: FxIndexMap::default(),
              foreigns: Vec::new(),
          }
      }
  
      pub(crate) fn where_outer(&self, tcx: TyCtxt<'_>) -> Span {
          tcx.def_span(self.def_id)
      }
  }
  
  // FIXME: Should this be replaced with tcx.def_path_str?
  fn def_id_to_path(tcx: TyCtxt<'_>, did: DefId) -> Vec<Symbol> {
      let crate_name = tcx.crate_name(did.krate);
      let relative = tcx.def_path(did).data.into_iter().filter_map(|elem| elem.data.get_opt_name());
      std::iter::once(crate_name).chain(relative).collect()
  }
  
  pub(crate) fn inherits_doc_hidden(
      tcx: TyCtxt<'_>,
      mut def_id: LocalDefId,
      stop_at: Option<LocalDefId>,
  ) -> bool {
      let hir = tcx.hir();
      while let Some(id) = tcx.opt_local_parent(def_id) {
          if let Some(stop_at) = stop_at && id == stop_at {
              return false;
          }
          def_id = id;
          if tcx.is_doc_hidden(def_id.to_def_id()) {
              return true;
          } else if let Some(node) = hir.find_by_def_id(def_id) &&
              matches!(
                  node,
                  hir::Node::Item(hir::Item { kind: hir::ItemKind::Impl(_), .. }),
              )
          {
              // `impl` blocks stand a bit on their own: unless they have `#[doc(hidden)]` directly
              // on them, they don't inherit it from the parent context.
              return false;
          }
      }
      false
  }
  
  pub(crate) struct RustdocVisitor<'a, 'tcx> {
      cx: &'a mut core::DocContext<'tcx>,
      view_item_stack: LocalDefIdSet,
      inlining: bool,
      /// Are the current module and all of its parents public?
      inside_public_path: bool,
      exact_paths: DefIdMap<Vec<Symbol>>,
      modules: Vec<Module<'tcx>>,
      is_importable_from_parent: bool,
      inside_body: bool,
  }
  
  impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
      pub(crate) fn new(cx: &'a mut core::DocContext<'tcx>) -> RustdocVisitor<'a, 'tcx> {
          // If the root is re-exported, terminate all recursion.
          let mut stack = LocalDefIdSet::default();
          stack.insert(CRATE_DEF_ID);
          let om = Module::new(
              cx.tcx.crate_name(LOCAL_CRATE),
              CRATE_DEF_ID,
              cx.tcx.hir().root_module().spans.inner_span,
              None,
              None,
          );
  
          RustdocVisitor {
              cx,
              view_item_stack: stack,
              inlining: false,
              inside_public_path: true,
              exact_paths: Default::default(),
              modules: vec![om],
              is_importable_from_parent: true,
              inside_body: false,
          }
      }
  
      fn store_path(&mut self, did: DefId) {
          let tcx = self.cx.tcx;
          self.exact_paths.entry(did).or_insert_with(|| def_id_to_path(tcx, did));
      }
  
      pub(crate) fn visit(mut self) -> Module<'tcx> {
          let root_module = self.cx.tcx.hir().root_module();
          self.visit_mod_contents(CRATE_DEF_ID, root_module);
  
          let mut top_level_module = self.modules.pop().unwrap();
  
          // `#[macro_export] macro_rules!` items are reexported at the top level of the
          // crate, regardless of where they're defined. We want to document the
          // top level re-export of the macro, not its original definition, since
          // the re-export defines the path that a user will actually see. Accordingly,
          // we add the re-export as an item here, and then skip over the original
          // definition in `visit_item()` below.
          //
          // We also skip `#[macro_export] macro_rules!` that have already been inserted,
          // it can happen if within the same module a `#[macro_export] macro_rules!`
          // is declared but also a reexport of itself producing two exports of the same
          // macro in the same module.
          let mut inserted = FxHashSet::default();
          for child in self.cx.tcx.module_children_local(CRATE_DEF_ID) {
              if !child.reexport_chain.is_empty() &&
                  let Res::Def(DefKind::Macro(_), def_id) = child.res &&
                  let Some(local_def_id) = def_id.as_local() &&
                  self.cx.tcx.has_attr(def_id, sym::macro_export) &&
                  inserted.insert(def_id)
              {
                  let item = self.cx.tcx.hir().expect_item(local_def_id);
                  top_level_module.items.insert((local_def_id, Some(item.ident.name)), (item, None, None));
              }
          }
  
          self.cx.cache.hidden_cfg = self
              .cx
              .tcx
              .hir()
              .attrs(CRATE_HIR_ID)
              .iter()
              .filter(|attr| attr.has_name(sym::doc))
              .flat_map(|attr| attr.meta_item_list().into_iter().flatten())
              .filter(|attr| attr.has_name(sym::cfg_hide))
              .flat_map(|attr| {
                  attr.meta_item_list()
                      .unwrap_or(&[])
                      .iter()
                      .filter_map(|attr| {
                          Cfg::parse(attr.meta_item()?)
                              .map_err(|e| self.cx.sess().diagnostic().span_err(e.span, e.msg))
                              .ok()
                      })
                      .collect::<Vec<_>>()
              })
              .chain(
                  [Cfg::Cfg(sym::test, None), Cfg::Cfg(sym::doc, None), Cfg::Cfg(sym::doctest, None)]
                      .into_iter(),
              )
              .collect();
  
          self.cx.cache.exact_paths = self.exact_paths;
          top_level_module
      }
  
      /// This method will go through the given module items in two passes:
      /// 1. The items which are not glob imports/reexports.
      /// 2. The glob imports/reexports.
      fn visit_mod_contents(&mut self, def_id: LocalDefId, m: &'tcx hir::Mod<'tcx>) {
          debug!("Going through module {:?}", m);
          // Keep track of if there were any private modules in the path.
          let orig_inside_public_path = self.inside_public_path;
          self.inside_public_path &= self.cx.tcx.local_visibility(def_id).is_public();
  
          // Reimplementation of `walk_mod` because we need to do it in two passes (explanations in
          // the second loop):
          for &i in m.item_ids {
              let item = self.cx.tcx.hir().item(i);
              if !matches!(item.kind, hir::ItemKind::Use(_, hir::UseKind::Glob)) {
                  self.visit_item(item);
              }
          }
          for &i in m.item_ids {
              let item = self.cx.tcx.hir().item(i);
              // To match the way import precedence works, visit glob imports last.
              // Later passes in rustdoc will de-duplicate by name and kind, so if glob-
              // imported items appear last, then they'll be the ones that get discarded.
              if matches!(item.kind, hir::ItemKind::Use(_, hir::UseKind::Glob)) {
                  self.visit_item(item);
              }
          }
          self.inside_public_path = orig_inside_public_path;
          debug!("Leaving module {:?}", m);
      }
  
      /// Tries to resolve the target of a `pub use` statement and inlines the
      /// target if it is defined locally and would not be documented otherwise,
      /// or when it is specifically requested with `please_inline`.
      /// (the latter is the case when the import is marked `doc(inline)`)
      ///
      /// Cross-crate inlining occurs later on during crate cleaning
      /// and follows different rules.
      ///
      /// Returns `true` if the target has been inlined.
      fn maybe_inline_local(
          &mut self,
          def_id: LocalDefId,
          res: Res,
          renamed: Option<Symbol>,
          glob: bool,
          please_inline: bool,
      ) -> bool {
          debug!("maybe_inline_local (renamed: {renamed:?}) res: {res:?}");
  
          if renamed == Some(kw::Underscore) {
              // We never inline `_` reexports.
              return false;
          }
  
          if self.cx.output_format.is_json() {
              return false;
          }
  
          let tcx = self.cx.tcx;
          let Some(ori_res_did) = res.opt_def_id() else {
              return false;
          };
  
          let document_hidden = self.cx.render_options.document_hidden;
          let use_attrs = tcx.hir().attrs(tcx.hir().local_def_id_to_hir_id(def_id));
          // Don't inline `doc(hidden)` imports so they can be stripped at a later stage.
          let is_no_inline = use_attrs.lists(sym::doc).has_word(sym::no_inline)
              || (document_hidden && use_attrs.lists(sym::doc).has_word(sym::hidden));
  
          if is_no_inline {
              return false;
          }
  
          let is_hidden = !document_hidden && tcx.is_doc_hidden(ori_res_did);
          let Some(res_did) = ori_res_did.as_local() else {
              // For cross-crate impl inlining we need to know whether items are
              // reachable in documentation -- a previously unreachable item can be
              // made reachable by cross-crate inlining which we're checking here.
              // (this is done here because we need to know this upfront).
              crate::visit_lib::lib_embargo_visit_item(self.cx, ori_res_did);
              if is_hidden || glob {
                  return false;
              }
              // We store inlined foreign items otherwise, it'd mean that the `use` item would be kept
              // around. It's not a problem unless this `use` imports both a local AND a foreign item.
              // If a local item is inlined, its `use` is not supposed to still be around in `clean`,
              // which would make appear the `use` in the generated documentation like the local item
              // was not inlined even though it actually was.
              self.modules
                  .last_mut()
                  .unwrap()
                  .inlined_foreigns
                  .insert((ori_res_did, renamed), (res, def_id));
              return true;
          };
  
          let is_private = !self.cx.cache.effective_visibilities.is_directly_public(tcx, ori_res_did);
          let item = tcx.hir().get_by_def_id(res_did);
  
          if !please_inline {
              let inherits_hidden = !document_hidden && inherits_doc_hidden(tcx, res_did, None);
              // Only inline if requested or if the item would otherwise be stripped.
              if (!is_private && !inherits_hidden) || (
                  is_hidden &&
                  // If it's a doc hidden module, we need to keep it in case some of its inner items
                  // are re-exported.
                  !matches!(item, Node::Item(&hir::Item { kind: hir::ItemKind::Mod(_), .. }))
              ) ||
                  // The imported item is public and not `doc(hidden)` so no need to inline it.
                  self.reexport_public_and_not_hidden(def_id, res_did)
              {
                  return false;
              }
          }
  
          let is_bang_macro = matches!(
              item,
              Node::Item(&hir::Item { kind: hir::ItemKind::Macro(_, MacroKind::Bang), .. })
          );
  
          if !self.view_item_stack.insert(res_did) && !is_bang_macro {
              return false;
          }
  
          let inlined = match item {
              // Bang macros are handled a bit on their because of how they are handled by the
              // compiler. If they have `#[doc(hidden)]` and the re-export doesn't have
              // `#[doc(inline)]`, then we don't inline it.
              Node::Item(_) if is_bang_macro && !please_inline && renamed.is_some() && is_hidden => {
                  return false;
              }
              Node::Item(&hir::Item { kind: hir::ItemKind::Mod(ref m), .. }) if glob => {
                  let prev = mem::replace(&mut self.inlining, true);
                  for &i in m.item_ids {
                      let i = tcx.hir().item(i);
                      self.visit_item_inner(i, None, Some(def_id));
                  }
                  self.inlining = prev;
                  true
              }
              Node::Item(it) if !glob => {
                  let prev = mem::replace(&mut self.inlining, true);
                  self.visit_item_inner(it, renamed, Some(def_id));
                  self.inlining = prev;
                  true
              }
              Node::ForeignItem(it) if !glob => {
                  let prev = mem::replace(&mut self.inlining, true);
                  self.visit_foreign_item_inner(it, renamed);
                  self.inlining = prev;
                  true
              }
              _ => false,
          };
          self.view_item_stack.remove(&res_did);
          if inlined {
              self.cx.cache.inlined_items.insert(ori_res_did);
          }
          inlined
      }
  
      /// Returns `true` if the item is visible, meaning it's not `#[doc(hidden)]` or private.
      ///
      /// This function takes into account the entire re-export `use` chain, so it needs the
      /// ID of the "leaf" `use` and the ID of the "root" item.
      fn reexport_public_and_not_hidden(
          &self,
          import_def_id: LocalDefId,
          target_def_id: LocalDefId,
      ) -> bool {
          if self.cx.render_options.document_hidden {
              return true;
          }
          let tcx = self.cx.tcx;
          let item_def_id = reexport_chain(tcx, import_def_id, target_def_id.to_def_id())
              .iter()
              .flat_map(|reexport| reexport.id())
              .map(|id| id.expect_local())
              .nth(1)
              .unwrap_or(target_def_id);
          item_def_id != import_def_id
              && self.cx.cache.effective_visibilities.is_directly_public(tcx, item_def_id.to_def_id())
              && !tcx.is_doc_hidden(item_def_id)
              && !inherits_doc_hidden(tcx, item_def_id, None)
      }
  
      #[inline]
      fn add_to_current_mod(
          &mut self,
          item: &'tcx hir::Item<'_>,
          renamed: Option<Symbol>,
          parent_id: Option<LocalDefId>,
      ) {
          if self.is_importable_from_parent
              // If we're inside an item, only impl blocks and `macro_rules!` with the `macro_export`
              // attribute can still be visible.
              || match item.kind {
                  hir::ItemKind::Impl(..) => true,
                  hir::ItemKind::Macro(_, MacroKind::Bang) => {
                      self.cx.tcx.has_attr(item.owner_id.def_id, sym::macro_export)
                  }
                  _ => false,
              }
          {
              self.modules
                  .last_mut()
                  .unwrap()
                  .items
                  .insert((item.owner_id.def_id, renamed), (item, renamed, parent_id));
          }
      }
  
      fn visit_item_inner(
          &mut self,
          item: &'tcx hir::Item<'_>,
          renamed: Option<Symbol>,
          import_id: Option<LocalDefId>,
      ) {
          debug!("visiting item {:?}", item);
          if self.inside_body {
              // Only impls can be "seen" outside a body. For example:
              //
              // ```
              // struct Bar;
              //
              // fn foo() {
              //     impl Bar { fn bar() {} }
              // }
              // Bar::bar();
              // ```
              if let hir::ItemKind::Impl(impl_) = item.kind &&
                  // Don't duplicate impls when inlining or if it's implementing a trait, we'll pick
                  // them up regardless of where they're located.
                  impl_.of_trait.is_none()
              {
                  self.add_to_current_mod(item, None, None);
              }
              return;
          }
          let name = renamed.unwrap_or(item.ident.name);
          let tcx = self.cx.tcx;
  
          let def_id = item.owner_id.to_def_id();
          let is_pub = tcx.visibility(def_id).is_public();
  
          if is_pub {
              self.store_path(item.owner_id.to_def_id());
          }
  
          match item.kind {
              hir::ItemKind::ForeignMod { items, .. } => {
                  for item in items {
                      let item = tcx.hir().foreign_item(item.id);
                      self.visit_foreign_item_inner(item, None);
                  }
              }
              // If we're inlining, skip private items.
              _ if self.inlining && !is_pub => {}
              hir::ItemKind::GlobalAsm(..) => {}
              hir::ItemKind::Use(_, hir::UseKind::ListStem) => {}
              hir::ItemKind::Use(path, kind) => {
                  for &res in &path.res {
                      // Struct and variant constructors and proc macro stubs always show up alongside
                      // their definitions, we've already processed them so just discard these.
                      if let Res::Def(DefKind::Ctor(..), _) | Res::SelfCtor(..) = res {
                          continue;
                      }
  
                      let attrs =
                          tcx.hir().attrs(tcx.hir().local_def_id_to_hir_id(item.owner_id.def_id));
  
                      // If there was a private module in the current path then don't bother inlining
                      // anything as it will probably be stripped anyway.
                      if is_pub && self.inside_public_path {
                          let please_inline = attrs.iter().any(|item| match item.meta_item_list() {
                              Some(ref list) if item.has_name(sym::doc) => {
                                  list.iter().any(|i| i.has_name(sym::inline))
                              }
                              _ => false,
                          });
                          let is_glob = kind == hir::UseKind::Glob;
                          let ident = if is_glob { None } else { Some(name) };
                          if self.maybe_inline_local(
                              item.owner_id.def_id,
                              res,
                              ident,
                              is_glob,
                              please_inline,
                          ) {
                              debug!("Inlining {:?}", item.owner_id.def_id);
                              continue;
                          }
                      }
                      self.add_to_current_mod(item, renamed, import_id);
                  }
              }
              hir::ItemKind::Macro(ref macro_def, _) => {
                  // `#[macro_export] macro_rules!` items are handled separately in `visit()`,
                  // above, since they need to be documented at the module top level. Accordingly,
                  // we only want to handle macros if one of three conditions holds:
                  //
                  // 1. This macro was defined by `macro`, and thus isn't covered by the case
                  //    above.
                  // 2. This macro isn't marked with `#[macro_export]`, and thus isn't covered
                  //    by the case above.
                  // 3. We're inlining, since a reexport where inlining has been requested
                  //    should be inlined even if it is also documented at the top level.
  
                  let def_id = item.owner_id.to_def_id();
                  let is_macro_2_0 = !macro_def.macro_rules;
                  let nonexported = !tcx.has_attr(def_id, sym::macro_export);
  
                  if is_macro_2_0 || nonexported || self.inlining {
                      self.add_to_current_mod(item, renamed, import_id);
                  }
              }
              hir::ItemKind::Mod(ref m) => {
                  self.enter_mod(item.owner_id.def_id, m, name, renamed, import_id);
              }
              hir::ItemKind::Fn(..)
              | hir::ItemKind::ExternCrate(..)
              | hir::ItemKind::Enum(..)
              | hir::ItemKind::Struct(..)
              | hir::ItemKind::Union(..)
              | hir::ItemKind::TyAlias(..)
              | hir::ItemKind::OpaqueTy(hir::OpaqueTy {
                  origin: hir::OpaqueTyOrigin::TyAlias { .. },
                  ..
              })
              | hir::ItemKind::Static(..)
              | hir::ItemKind::Trait(..)
              | hir::ItemKind::TraitAlias(..) => {
                  self.add_to_current_mod(item, renamed, import_id);
              }
              hir::ItemKind::OpaqueTy(hir::OpaqueTy {
                  origin: hir::OpaqueTyOrigin::AsyncFn(_) | hir::OpaqueTyOrigin::FnReturn(_),
                  ..
              }) => {
                  // return-position impl traits are never nameable, and should never be documented.
              }
              hir::ItemKind::Const(..) => {
                  // Underscore constants do not correspond to a nameable item and
                  // so are never useful in documentation.
                  if name != kw::Underscore {
                      self.add_to_current_mod(item, renamed, import_id);
                  }
              }
              hir::ItemKind::Impl(impl_) => {
                  // Don't duplicate impls when inlining or if it's implementing a trait, we'll pick
                  // them up regardless of where they're located.
                  if !self.inlining && impl_.of_trait.is_none() {
                      self.add_to_current_mod(item, None, None);
                  }
              }
          }
      }
  
      fn visit_foreign_item_inner(
          &mut self,
          item: &'tcx hir::ForeignItem<'_>,
          renamed: Option<Symbol>,
      ) {
          // If inlining we only want to include public functions.
          if !self.inlining || self.cx.tcx.visibility(item.owner_id).is_public() {
              self.modules.last_mut().unwrap().foreigns.push((item, renamed));
          }
      }
  
      /// This method will create a new module and push it onto the "modules stack" then call
      /// `visit_mod_contents`. Once done, it'll remove it from the "modules stack" and instead
      /// add into the list of modules of the current module.
      fn enter_mod(
          &mut self,
          id: LocalDefId,
          m: &'tcx hir::Mod<'tcx>,
          name: Symbol,
          renamed: Option<Symbol>,
          import_id: Option<LocalDefId>,
      ) {
          self.modules.push(Module::new(name, id, m.spans.inner_span, renamed, import_id));
  
          self.visit_mod_contents(id, m);
  
          let last = self.modules.pop().unwrap();
          self.modules.last_mut().unwrap().mods.push(last);
      }
  }
  
  // We need to implement this visitor so it'll go everywhere and retrieve items we're interested in
  // such as impl blocks in const blocks.
  impl<'a, 'tcx> Visitor<'tcx> for RustdocVisitor<'a, 'tcx> {
      type NestedFilter = nested_filter::All;
  
      fn nested_visit_map(&mut self) -> Self::Map {
          self.cx.tcx.hir()
      }
  
      fn visit_item(&mut self, i: &'tcx hir::Item<'tcx>) {
          self.visit_item_inner(i, None, None);
          let new_value = self.is_importable_from_parent
              && matches!(
                  i.kind,
                  hir::ItemKind::Mod(..)
                      | hir::ItemKind::ForeignMod { .. }
                      | hir::ItemKind::Impl(..)
                      | hir::ItemKind::Trait(..)
              );
          let prev = mem::replace(&mut self.is_importable_from_parent, new_value);
          walk_item(self, i);
          self.is_importable_from_parent = prev;
      }
  
      fn visit_mod(&mut self, _: &hir::Mod<'tcx>, _: Span, _: hir::HirId) {
          // Handled in `visit_item_inner`
      }
  
      fn visit_use(&mut self, _: &hir::UsePath<'tcx>, _: hir::HirId) {
          // Handled in `visit_item_inner`
      }
  
      fn visit_path(&mut self, _: &hir::Path<'tcx>, _: hir::HirId) {
          // Handled in `visit_item_inner`
      }
  
      fn visit_label(&mut self, _: &rustc_ast::Label) {
          // Unneeded.
      }
  
      fn visit_infer(&mut self, _: &hir::InferArg) {
          // Unneeded.
      }
  
      fn visit_lifetime(&mut self, _: &hir::Lifetime) {
          // Unneeded.
      }
  
      fn visit_body(&mut self, b: &'tcx hir::Body<'tcx>) {
          let prev = mem::replace(&mut self.inside_body, true);
          walk_body(self, b);
          self.inside_body = prev;
      }
  }
  