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::visit::DocVisitor;
   8
   9 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
  10 use rustc_hir::def_id::DefId;
  11 use rustc_middle::ty::DefIdTree;
  12 use rustc_span::symbol::sym;
  13
  14 crate const COLLECT_TRAIT_IMPLS: Pass = Pass {
  15     name: "collect-trait-impls",
  16     run: collect_trait_impls,
  17     description: "retrieves trait impls for items in the crate",
  18 };
  19
  20 crate fn collect_trait_impls(mut krate: Crate, cx: &mut DocContext<'_>) -> Crate {
  21     let synth_impls = cx.sess().time("collect_synthetic_impls", || {
  22         let mut synth = SyntheticImplCollector { cx, impls: Vec::new() };
  23         synth.visit_crate(&krate);
  24         synth.impls
  25     });
  26
  27     let prims: FxHashSet<PrimitiveType> = krate.primitives.iter().map(|p| p.1).collect();
  28
  29     let crate_items = {
  30         let mut coll = ItemCollector::new();
  31         cx.sess().time("collect_items_for_trait_impls", || coll.visit_crate(&krate));
  32         coll.items
  33     };
  34
  35     let mut new_items = Vec::new();
  36
  37     // External trait impls.
  38     cx.with_all_trait_impls(|cx, all_trait_impls| {
  39         let _prof_timer = cx.tcx.sess.prof.generic_activity("build_extern_trait_impls");
  40         for &impl_def_id in all_trait_impls.iter().skip_while(|def_id| def_id.is_local()) {
  41             inline::build_impl(cx, None, impl_def_id, None, &mut new_items);
  42         }
  43     });
  44
  45     // Also try to inline primitive impls from other crates.
  46     cx.tcx.sess.prof.generic_activity("build_primitive_trait_impls").run(|| {
  47         for &def_id in PrimitiveType::all_impls(cx.tcx).values().flatten() {
  48             if !def_id.is_local() {
  49                 inline::build_impl(cx, None, def_id, None, &mut new_items);
  50
  51                 // FIXME(eddyb) is this `doc(hidden)` check needed?
  52                 if !cx.tcx.is_doc_hidden(def_id) {
  53                     let impls = get_auto_trait_and_blanket_impls(cx, def_id);
  54                     new_items.extend(impls.filter(|i| cx.inlined.insert(i.def_id)));
  55                 }
  56             }
  57         }
  58     });
  59
  60     let mut cleaner = BadImplStripper { prims, items: crate_items };
  61     let mut type_did_to_deref_target: FxHashMap<DefId, &Type> = FxHashMap::default();
  62
  63     // Follow all `Deref` targets of included items and recursively add them as valid
  64     fn add_deref_target(
  65         cx: &DocContext<'_>,
  66         map: &FxHashMap<DefId, &Type>,
  67         cleaner: &mut BadImplStripper,
  68         type_did: DefId,
  69     ) {
  70         if let Some(target) = map.get(&type_did) {
  71             debug!("add_deref_target: type {:?}, target {:?}", type_did, target);
  72             if let Some(target_prim) = target.primitive_type() {
  73                 cleaner.prims.insert(target_prim);
  74             } else if let Some(target_did) = target.def_id(&cx.cache) {
  75                 // `impl Deref<Target = S> for S`
  76                 if target_did == type_did {
  77                     // Avoid infinite cycles
  78                     return;
  79                 }
  80                 cleaner.items.insert(target_did.into());
  81                 add_deref_target(cx, map, cleaner, target_did);
  82             }
  83         }
  84     }
  85
  86     // scan through included items ahead of time to splice in Deref targets to the "valid" sets
  87     for it in &new_items {
  88         if let ImplItem(Impl { ref for_, ref trait_, ref items, .. }) = *it.kind {
  89             if trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait()
  90                 && cleaner.keep_impl(for_, true)
  91             {
  92                 let target = items
  93                     .iter()
  94                     .find_map(|item| match *item.kind {
  95                         TypedefItem(ref t, true) => Some(&t.type_),
  96                         _ => None,
  97                     })
  98                     .expect("Deref impl without Target type");
  99
 100                 if let Some(prim) = target.primitive_type() {
 101                     cleaner.prims.insert(prim);
 102                 } else if let Some(did) = target.def_id(&cx.cache) {
 103                     cleaner.items.insert(did.into());
 104                 }
 105                 if let Some(for_did) = for_.def_id_no_primitives() {
 106                     if type_did_to_deref_target.insert(for_did, target).is_none() {
 107                         // Since only the `DefId` portion of the `Type` instances is known to be same for both the
 108                         // `Deref` target type and the impl for type positions, this map of types is keyed by
 109                         // `DefId` and for convenience uses a special cleaner that accepts `DefId`s directly.
 110                         if cleaner.keep_impl_with_def_id(for_did.into()) {
 111                             add_deref_target(cx, &type_did_to_deref_target, &mut cleaner, for_did);
 112                         }
 113                     }
 114                 }
 115             }
 116         }
 117     }
 118
 119     new_items.retain(|it| {
 120         if let ImplItem(Impl { ref for_, ref trait_, ref kind, .. }) = *it.kind {
 121             cleaner.keep_impl(
 122                 for_,
 123                 trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait(),
 124             ) || trait_.as_ref().map_or(false, |t| cleaner.keep_impl_with_def_id(t.def_id().into()))
 125                 || kind.is_blanket()
 126         } else {
 127             true
 128         }
 129     });
 130
 131     // Local trait impls.
 132     cx.with_all_trait_impls(|cx, all_trait_impls| {
 133         let _prof_timer = cx.tcx.sess.prof.generic_activity("build_local_trait_impls");
 134         let mut attr_buf = Vec::new();
 135         for &impl_def_id in all_trait_impls.iter().take_while(|def_id| def_id.is_local()) {
 136             let mut parent = cx.tcx.parent(impl_def_id);
 137             while let Some(did) = parent {
 138                 attr_buf.extend(
 139                     cx.tcx
 140                         .get_attrs(did)
 141                         .iter()
 142                         .filter(|attr| attr.has_name(sym::doc))
 143                         .filter(|attr| {
 144                             if let Some([attr]) = attr.meta_item_list().as_deref() {
 145                                 attr.has_name(sym::cfg)
 146                             } else {
 147                                 false
 148                             }
 149                         })
 150                         .cloned(),
 151                 );
 152                 parent = cx.tcx.parent(did);
 153             }
 154             inline::build_impl(cx, None, impl_def_id, Some(&attr_buf), &mut new_items);
 155             attr_buf.clear();
 156         }
 157     });
 158
 159     if let ModuleItem(Module { items, .. }) = &mut *krate.module.kind {
 160         items.extend(synth_impls);
 161         items.extend(new_items);
 162     } else {
 163         panic!("collect-trait-impls can't run");
 164     };
 165
 166     krate
 167 }
 168
 169 struct SyntheticImplCollector<'a, 'tcx> {
 170     cx: &'a mut DocContext<'tcx>,
 171     impls: Vec<Item>,
 172 }
 173
 174 impl<'a, 'tcx> DocVisitor for SyntheticImplCollector<'a, 'tcx> {
 175     fn visit_item(&mut self, i: &Item) {
 176         if i.is_struct() || i.is_enum() || i.is_union() {
 177             // FIXME(eddyb) is this `doc(hidden)` check needed?
 178             if !self.cx.tcx.is_doc_hidden(i.def_id.expect_def_id()) {
 179                 self.impls
 180                     .extend(get_auto_trait_and_blanket_impls(self.cx, i.def_id.expect_def_id()));
 181             }
 182         }
 183
 184         self.visit_item_recur(i)
 185     }
 186 }
 187
 188 #[derive(Default)]
 189 struct ItemCollector {
 190     items: FxHashSet<ItemId>,
 191 }
 192
 193 impl ItemCollector {
 194     fn new() -> Self {
 195         Self::default()
 196     }
 197 }
 198
 199 impl DocVisitor for ItemCollector {
 200     fn visit_item(&mut self, i: &Item) {
 201         self.items.insert(i.def_id);
 202
 203         self.visit_item_recur(i)
 204     }
 205 }
 206
 207 struct BadImplStripper {
 208     prims: FxHashSet<PrimitiveType>,
 209     items: FxHashSet<ItemId>,
 210 }
 211
 212 impl BadImplStripper {
 213     fn keep_impl(&self, ty: &Type, is_deref: bool) -> bool {
 214         if let Generic(_) = ty {
 215             // keep impls made on generics
 216             true
 217         } else if let Some(prim) = ty.primitive_type() {
 218             self.prims.contains(&prim)
 219         } else if let Some(did) = ty.def_id_no_primitives() {
 220             is_deref || self.keep_impl_with_def_id(did.into())
 221         } else {
 222             false
 223         }
 224     }
 225
 226     fn keep_impl_with_def_id(&self, did: ItemId) -> bool {
 227         self.items.contains(&did)
 228     }
 229 }