src/librustdoc/passes/collect_trait_impls.rs

   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.
   4 use super::Pass;
   5 use crate::clean::*;
   6 use crate::core::DocContext;
   7 use crate::formats::cache::Cache;
   8 use crate::visit::DocVisitor;
   9
  10 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
  11 use rustc_hir::def_id::DefId;
  12 use rustc_middle::ty::DefIdTree;
  13 use rustc_span::symbol::sym;
  14
  15 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",
  19 };
  20
  21 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);
  25         synth.impls
  26     });
  27
  28     let prims: FxHashSet<PrimitiveType> = krate.primitives.iter().map(|p| p.1).collect();
  29
  30     let crate_items = {
  31         let mut coll = ItemCollector::new();
  32         cx.sess().time("collect_items_for_trait_impls", || coll.visit_crate(&krate));
  33         coll.items
  34     };
  35
  36     let mut new_items_external = Vec::new();
  37     let mut new_items_local = Vec::new();
  38
  39     // External trait impls.
  40     cx.with_all_trait_impls(|cx, all_trait_impls| {
  41         let _prof_timer = cx.tcx.sess.prof.generic_activity("build_extern_trait_impls");
  42         for &impl_def_id in all_trait_impls.iter().skip_while(|def_id| def_id.is_local()) {
  43             inline::build_impl(cx, None, impl_def_id, None, &mut new_items_external);
  44         }
  45     });
  46
  47     // Local trait impls.
  48     cx.with_all_trait_impls(|cx, all_trait_impls| {
  49         let _prof_timer = cx.tcx.sess.prof.generic_activity("build_local_trait_impls");
  50         let mut attr_buf = Vec::new();
  51         for &impl_def_id in all_trait_impls.iter().take_while(|def_id| def_id.is_local()) {
  52             let mut parent = Some(cx.tcx.parent(impl_def_id));
  53             while let Some(did) = parent {
  54                 attr_buf.extend(
  55                     cx.tcx
  56                         .get_attrs(did)
  57                         .iter()
  58                         .filter(|attr| attr.has_name(sym::doc))
  59                         .filter(|attr| {
  60                             if let Some([attr]) = attr.meta_item_list().as_deref() {
  61                                 attr.has_name(sym::cfg)
  62                             } else {
  63                                 false
  64                             }
  65                         })
  66                         .cloned(),
  67                 );
  68                 parent = cx.tcx.opt_parent(did);
  69             }
  70             inline::build_impl(cx, None, impl_def_id, Some(&attr_buf), &mut new_items_local);
  71             attr_buf.clear();
  72         }
  73     });
  74
  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);
  80             }
  81         }
  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.
  86             if did.is_local() {
  87                 for def_id in prim.impls(cx.tcx) {
  88                     let impls = get_auto_trait_and_blanket_impls(cx, def_id);
  89                     new_items_external.extend(impls.filter(|i| cx.inlined.insert(i.item_id)));
  90                 }
  91             }
  92         }
  93     });
  94
  95     let mut cleaner = BadImplStripper { prims, items: crate_items, cache: &cx.cache };
  96     let mut type_did_to_deref_target: FxHashMap<DefId, &Type> = FxHashMap::default();
  97
  98     // Follow all `Deref` targets of included items and recursively add them as valid
  99     fn add_deref_target(
 100         cx: &DocContext<'_>,
 101         map: &FxHashMap<DefId, &Type>,
 102         cleaner: &mut BadImplStripper<'_>,
 103         targets: &mut FxHashSet<DefId>,
 104         type_did: DefId,
 105     ) {
 106         if let Some(target) = map.get(&type_did) {
 107             debug!("add_deref_target: type {:?}, target {:?}", type_did, target);
 108             if let Some(target_prim) = target.primitive_type() {
 109                 cleaner.prims.insert(target_prim);
 110             } else if let Some(target_did) = target.def_id(&cx.cache) {
 111                 // `impl Deref<Target = S> for S`
 112                 if !targets.insert(target_did) {
 113                     // Avoid infinite cycles
 114                     return;
 115                 }
 116                 cleaner.items.insert(target_did.into());
 117                 add_deref_target(cx, map, cleaner, targets, target_did);
 118             }
 119         }
 120     }
 121
 122     // scan through included items ahead of time to splice in Deref targets to the "valid" sets
 123     for it in new_items_external.iter().chain(new_items_local.iter()) {
 124         if let ImplItem(Impl { ref for_, ref trait_, ref items, .. }) = *it.kind {
 125             if trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait()
 126                 && cleaner.keep_impl(for_, true)
 127             {
 128                 let target = items
 129                     .iter()
 130                     .find_map(|item| match *item.kind {
 131                         AssocTypeItem(ref t, _) => Some(&t.type_),
 132                         _ => None,
 133                     })
 134                     .expect("Deref impl without Target type");
 135
 136                 if let Some(prim) = target.primitive_type() {
 137                     cleaner.prims.insert(prim);
 138                 } else if let Some(did) = target.def_id(&cx.cache) {
 139                     cleaner.items.insert(did.into());
 140                 }
 141                 if let Some(for_did) = for_.def_id(&cx.cache) {
 142                     if type_did_to_deref_target.insert(for_did, target).is_none() {
 143                         // Since only the `DefId` portion of the `Type` instances is known to be same for both the
 144                         // `Deref` target type and the impl for type positions, this map of types is keyed by
 145                         // `DefId` and for convenience uses a special cleaner that accepts `DefId`s directly.
 146                         if cleaner.keep_impl_with_def_id(for_did.into()) {
 147                             let mut targets = FxHashSet::default();
 148                             targets.insert(for_did);
 149                             add_deref_target(
 150                                 cx,
 151                                 &type_did_to_deref_target,
 152                                 &mut cleaner,
 153                                 &mut targets,
 154                                 for_did,
 155                             );
 156                         }
 157                     }
 158                 }
 159             }
 160         }
 161     }
 162
 163     // Filter out external items that are not needed
 164     new_items_external.retain(|it| {
 165         if let ImplItem(Impl { ref for_, ref trait_, ref kind, .. }) = *it.kind {
 166             cleaner.keep_impl(
 167                 for_,
 168                 trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait(),
 169             ) || trait_.as_ref().map_or(false, |t| cleaner.keep_impl_with_def_id(t.def_id().into()))
 170                 || kind.is_blanket()
 171         } else {
 172             true
 173         }
 174     });
 175
 176     if let ModuleItem(Module { items, .. }) = &mut *krate.module.kind {
 177         items.extend(synth_impls);
 178         items.extend(new_items_external);
 179         items.extend(new_items_local);
 180     } else {
 181         panic!("collect-trait-impls can't run");
 182     };
 183
 184     krate
 185 }
 186
 187 struct SyntheticImplCollector<'a, 'tcx> {
 188     cx: &'a mut DocContext<'tcx>,
 189     impls: Vec<Item>,
 190 }
 191
 192 impl<'a, 'tcx> DocVisitor for SyntheticImplCollector<'a, 'tcx> {
 193     fn visit_item(&mut self, i: &Item) {
 194         if i.is_struct() || i.is_enum() || i.is_union() {
 195             // FIXME(eddyb) is this `doc(hidden)` check needed?
 196             if !self.cx.tcx.is_doc_hidden(i.item_id.expect_def_id()) {
 197                 self.impls
 198                     .extend(get_auto_trait_and_blanket_impls(self.cx, i.item_id.expect_def_id()));
 199             }
 200         }
 201
 202         self.visit_item_recur(i)
 203     }
 204 }
 205
 206 #[derive(Default)]
 207 struct ItemCollector {
 208     items: FxHashSet<ItemId>,
 209 }
 210
 211 impl ItemCollector {
 212     fn new() -> Self {
 213         Self::default()
 214     }
 215 }
 216
 217 impl DocVisitor for ItemCollector {
 218     fn visit_item(&mut self, i: &Item) {
 219         self.items.insert(i.item_id);
 220
 221         self.visit_item_recur(i)
 222     }
 223 }
 224
 225 struct BadImplStripper<'a> {
 226     prims: FxHashSet<PrimitiveType>,
 227     items: FxHashSet<ItemId>,
 228     cache: &'a Cache,
 229 }
 230
 231 impl<'a> BadImplStripper<'a> {
 232     fn keep_impl(&self, ty: &Type, is_deref: bool) -> bool {
 233         if let Generic(_) = ty {
 234             // keep impls made on generics
 235             true
 236         } else if let Some(prim) = ty.primitive_type() {
 237             self.prims.contains(&prim)
 238         } else if let Some(did) = ty.def_id(self.cache) {
 239             is_deref || self.keep_impl_with_def_id(did.into())
 240         } else {
 241             false
 242         }
 243     }
 244
 245     fn keep_impl_with_def_id(&self, item_id: ItemId) -> bool {
 246         self.items.contains(&item_id)
 247     }
 248 }