1 //! Collects trait impls for each item in the crate. For example, if a crate
2 //! defines a struct that implements a trait, this pass will note that the
3 //! struct implements that trait.
6 use crate::core::DocContext;
7 use crate::formats::cache::Cache;
8 use crate::visit::DocVisitor;
10 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
11 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
12 use rustc_middle::ty::{self, DefIdTree};
13 use rustc_span::symbol::sym;
15 pub(crate) const COLLECT_TRAIT_IMPLS: Pass = Pass {
16 name: "collect-trait-impls",
17 run: collect_trait_impls,
18 description: "retrieves trait impls for items in the crate",
21 pub(crate) fn collect_trait_impls(mut krate: Crate, cx: &mut DocContext<'_>) -> Crate {
22 let synth_impls = cx.sess().time("collect_synthetic_impls", || {
23 let mut synth = SyntheticImplCollector { cx, impls: Vec::new() };
24 synth.visit_crate(&krate);
28 let local_crate = ExternalCrate { crate_num: LOCAL_CRATE };
29 let prims: FxHashSet<PrimitiveType> =
30 local_crate.primitives(cx.tcx).iter().map(|p| p.1).collect();
33 let mut coll = ItemCollector::new();
34 cx.sess().time("collect_items_for_trait_impls", || coll.visit_crate(&krate));
38 let mut new_items_external = Vec::new();
39 let mut new_items_local = Vec::new();
41 // External trait impls.
42 cx.with_all_trait_impls(|cx, all_trait_impls| {
43 let _prof_timer = cx.tcx.sess.prof.generic_activity("build_extern_trait_impls");
44 for &impl_def_id in all_trait_impls.iter().skip_while(|def_id| def_id.is_local()) {
45 inline::build_impl(cx, None, impl_def_id, None, &mut new_items_external);
50 cx.with_all_trait_impls(|cx, all_trait_impls| {
51 let _prof_timer = cx.tcx.sess.prof.generic_activity("build_local_trait_impls");
52 let mut attr_buf = Vec::new();
53 for &impl_def_id in all_trait_impls.iter().take_while(|def_id| def_id.is_local()) {
54 let mut parent = Some(cx.tcx.parent(impl_def_id));
55 while let Some(did) = parent {
58 .get_attrs(did, sym::doc)
60 if let Some([attr]) = attr.meta_item_list().as_deref() {
61 attr.has_name(sym::cfg)
68 parent = cx.tcx.opt_parent(did);
70 inline::build_impl(cx, None, impl_def_id, Some(&attr_buf), &mut new_items_local);
75 cx.tcx.sess.prof.generic_activity("build_primitive_trait_impls").run(|| {
76 for def_id in PrimitiveType::all_impls(cx.tcx) {
77 // Try to inline primitive impls from other crates.
78 if !def_id.is_local() {
79 inline::build_impl(cx, None, def_id, None, &mut new_items_external);
82 for (prim, did) in PrimitiveType::primitive_locations(cx.tcx) {
83 // Do not calculate blanket impl list for docs that are not going to be rendered.
84 // While the `impl` blocks themselves are only in `libcore`, the module with `doc`
85 // attached is directly included in `libstd` as well.
88 for def_id in prim.impls(tcx).filter(|def_id| {
89 // Avoid including impl blocks with filled-in generics.
90 // https://github.com/rust-lang/rust/issues/94937
92 // FIXME(notriddle): https://github.com/rust-lang/rust/issues/97129
94 // This tactic of using inherent impl blocks for getting
95 // auto traits and blanket impls is a hack. What we really
96 // want is to check if `[T]` impls `Send`, which has
97 // nothing to do with the inherent impl.
99 // Rustdoc currently uses these `impl` block as a source of
100 // the `Ty`, as well as the `ParamEnv`, `SubstsRef`, and
101 // `Generics`. To avoid relying on the `impl` block, these
102 // things would need to be created from wholecloth, in a
103 // form that is valid for use in type inference.
104 let ty = tcx.type_of(def_id);
108 | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
109 matches!(ty.kind(), ty::Param(..))
111 ty::Tuple(tys) => tys.iter().all(|ty| matches!(ty.kind(), ty::Param(..))),
115 let impls = get_auto_trait_and_blanket_impls(cx, def_id);
116 new_items_external.extend(impls.filter(|i| cx.inlined.insert(i.item_id)));
122 let mut cleaner = BadImplStripper { prims, items: crate_items, cache: &cx.cache };
123 let mut type_did_to_deref_target: FxHashMap<DefId, &Type> = FxHashMap::default();
125 // Follow all `Deref` targets of included items and recursively add them as valid
128 map: &FxHashMap<DefId, &Type>,
129 cleaner: &mut BadImplStripper<'_>,
130 targets: &mut FxHashSet<DefId>,
133 if let Some(target) = map.get(&type_did) {
134 debug!("add_deref_target: type {:?}, target {:?}", type_did, target);
135 if let Some(target_prim) = target.primitive_type() {
136 cleaner.prims.insert(target_prim);
137 } else if let Some(target_did) = target.def_id(&cx.cache) {
138 // `impl Deref<Target = S> for S`
139 if !targets.insert(target_did) {
140 // Avoid infinite cycles
143 cleaner.items.insert(target_did.into());
144 add_deref_target(cx, map, cleaner, targets, target_did);
149 // scan through included items ahead of time to splice in Deref targets to the "valid" sets
150 for it in new_items_external.iter().chain(new_items_local.iter()) {
151 if let ImplItem(box Impl { ref for_, ref trait_, ref items, .. }) = *it.kind {
152 if trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait()
153 && cleaner.keep_impl(for_, true)
157 .find_map(|item| match *item.kind {
158 AssocTypeItem(ref t, _) => Some(&t.type_),
161 .expect("Deref impl without Target type");
163 if let Some(prim) = target.primitive_type() {
164 cleaner.prims.insert(prim);
165 } else if let Some(did) = target.def_id(&cx.cache) {
166 cleaner.items.insert(did.into());
168 if let Some(for_did) = for_.def_id(&cx.cache) {
169 if type_did_to_deref_target.insert(for_did, target).is_none() {
170 // Since only the `DefId` portion of the `Type` instances is known to be same for both the
171 // `Deref` target type and the impl for type positions, this map of types is keyed by
172 // `DefId` and for convenience uses a special cleaner that accepts `DefId`s directly.
173 if cleaner.keep_impl_with_def_id(for_did.into()) {
174 let mut targets = FxHashSet::default();
175 targets.insert(for_did);
178 &type_did_to_deref_target,
190 // Filter out external items that are not needed
191 new_items_external.retain(|it| {
192 if let ImplItem(box Impl { ref for_, ref trait_, ref kind, .. }) = *it.kind {
195 trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait(),
196 ) || trait_.as_ref().map_or(false, |t| cleaner.keep_impl_with_def_id(t.def_id().into()))
203 if let ModuleItem(Module { items, .. }) = &mut *krate.module.kind {
204 items.extend(synth_impls);
205 items.extend(new_items_external);
206 items.extend(new_items_local);
208 panic!("collect-trait-impls can't run");
214 struct SyntheticImplCollector<'a, 'tcx> {
215 cx: &'a mut DocContext<'tcx>,
219 impl<'a, 'tcx> DocVisitor for SyntheticImplCollector<'a, 'tcx> {
220 fn visit_item(&mut self, i: &Item) {
221 if i.is_struct() || i.is_enum() || i.is_union() {
222 // FIXME(eddyb) is this `doc(hidden)` check needed?
223 if !self.cx.tcx.is_doc_hidden(i.item_id.expect_def_id()) {
225 .extend(get_auto_trait_and_blanket_impls(self.cx, i.item_id.expect_def_id()));
229 self.visit_item_recur(i)
234 struct ItemCollector {
235 items: FxHashSet<ItemId>,
244 impl DocVisitor for ItemCollector {
245 fn visit_item(&mut self, i: &Item) {
246 self.items.insert(i.item_id);
248 self.visit_item_recur(i)
252 struct BadImplStripper<'a> {
253 prims: FxHashSet<PrimitiveType>,
254 items: FxHashSet<ItemId>,
258 impl<'a> BadImplStripper<'a> {
259 fn keep_impl(&self, ty: &Type, is_deref: bool) -> bool {
260 if let Generic(_) = ty {
261 // keep impls made on generics
263 } else if let Some(prim) = ty.primitive_type() {
264 self.prims.contains(&prim)
265 } else if let Some(did) = ty.def_id(self.cache) {
266 is_deref || self.keep_impl_with_def_id(did.into())
272 fn keep_impl_with_def_id(&self, item_id: ItemId) -> bool {
273 self.items.contains(&item_id)