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 = Vec::new();
  37
  38     // External trait impls.
  39     cx.with_all_trait_impls(|cx, all_trait_impls| {
  40         let _prof_timer = cx.tcx.sess.prof.generic_activity("build_extern_trait_impls");
  41         for &impl_def_id in all_trait_impls.iter().skip_while(|def_id| def_id.is_local()) {
  42             inline::build_impl(cx, None, impl_def_id, None, &mut new_items);
  43         }
  44     });
  45
  46     // Also try to inline primitive impls from other crates.
  47     cx.tcx.sess.prof.generic_activity("build_primitive_trait_impls").run(|| {
  48         for &def_id in PrimitiveType::all_impls(cx.tcx).values().flatten() {
  49             if !def_id.is_local() {
  50                 inline::build_impl(cx, None, def_id, None, &mut new_items);
  51
  52                 // FIXME(eddyb) is this `doc(hidden)` check needed?
  53                 if !cx.tcx.is_doc_hidden(def_id) {
  54                     let impls = get_auto_trait_and_blanket_impls(cx, def_id);
  55                     new_items.extend(impls.filter(|i| cx.inlined.insert(i.def_id)));
  56                 }
  57             }
  58         }
  59     });
  60
  61     let mut cleaner = BadImplStripper { prims, items: crate_items, cache: &cx.cache };
  62     let mut type_did_to_deref_target: FxHashMap<DefId, &Type> = FxHashMap::default();
  63
  64     // Follow all `Deref` targets of included items and recursively add them as valid
  65     fn add_deref_target(
  66         cx: &DocContext<'_>,
  67         map: &FxHashMap<DefId, &Type>,
  68         cleaner: &mut BadImplStripper<'_>,
  69         type_did: DefId,
  70     ) {
  71         if let Some(target) = map.get(&type_did) {
  72             debug!("add_deref_target: type {:?}, target {:?}", type_did, target);
  73             if let Some(target_prim) = target.primitive_type() {
  74                 cleaner.prims.insert(target_prim);
  75             } else if let Some(target_did) = target.def_id(&cx.cache) {
  76                 // `impl Deref<Target = S> for S`
  77                 if target_did == type_did {
  78                     // Avoid infinite cycles
  79                     return;
  80                 }
  81                 cleaner.items.insert(target_did.into());
  82                 add_deref_target(cx, map, cleaner, target_did);
  83             }
  84         }
  85     }
  86
  87     // scan through included items ahead of time to splice in Deref targets to the "valid" sets
  88     for it in &new_items {
  89         if let ImplItem(Impl { ref for_, ref trait_, ref items, .. }) = *it.kind {
  90             if trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait()
  91                 && cleaner.keep_impl(for_, true)
  92             {
  93                 let target = items
  94                     .iter()
  95                     .find_map(|item| match *item.kind {
  96                         TypedefItem(ref t, true) => Some(&t.type_),
  97                         _ => None,
  98                     })
  99                     .expect("Deref impl without Target type");
 100
 101                 if let Some(prim) = target.primitive_type() {
 102                     cleaner.prims.insert(prim);
 103                 } else if let Some(did) = target.def_id(&cx.cache) {
 104                     cleaner.items.insert(did.into());
 105                 }
 106                 if let Some(for_did) = for_.def_id(&cx.cache) {
 107                     if type_did_to_deref_target.insert(for_did, target).is_none() {
 108                         // Since only the `DefId` portion of the `Type` instances is known to be same for both the
 109                         // `Deref` target type and the impl for type positions, this map of types is keyed by
 110                         // `DefId` and for convenience uses a special cleaner that accepts `DefId`s directly.
 111                         if cleaner.keep_impl_with_def_id(for_did.into()) {
 112                             add_deref_target(cx, &type_did_to_deref_target, &mut cleaner, for_did);
 113                         }
 114                     }
 115                 }
 116             }
 117         }
 118     }
 119
 120     new_items.retain(|it| {
 121         if let ImplItem(Impl { ref for_, ref trait_, ref kind, .. }) = *it.kind {
 122             cleaner.keep_impl(
 123                 for_,
 124                 trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait(),
 125             ) || trait_.as_ref().map_or(false, |t| cleaner.keep_impl_with_def_id(t.def_id().into()))
 126                 || kind.is_blanket()
 127         } else {
 128             true
 129         }
 130     });
 131
 132     // Local trait impls.
 133     cx.with_all_trait_impls(|cx, all_trait_impls| {
 134         let _prof_timer = cx.tcx.sess.prof.generic_activity("build_local_trait_impls");
 135         let mut attr_buf = Vec::new();
 136         for &impl_def_id in all_trait_impls.iter().take_while(|def_id| def_id.is_local()) {
 137             let mut parent = cx.tcx.parent(impl_def_id);
 138             while let Some(did) = parent {
 139                 attr_buf.extend(
 140                     cx.tcx
 141                         .get_attrs(did)
 142                         .iter()
 143                         .filter(|attr| attr.has_name(sym::doc))
 144                         .filter(|attr| {
 145                             if let Some([attr]) = attr.meta_item_list().as_deref() {
 146                                 attr.has_name(sym::cfg)
 147                             } else {
 148                                 false
 149                             }
 150                         })
 151                         .cloned(),
 152                 );
 153                 parent = cx.tcx.parent(did);
 154             }
 155             inline::build_impl(cx, None, impl_def_id, Some(&attr_buf), &mut new_items);
 156             attr_buf.clear();
 157         }
 158     });
 159
 160     if let ModuleItem(Module { items, .. }) = &mut *krate.module.kind {
 161         items.extend(synth_impls);
 162         items.extend(new_items);
 163     } else {
 164         panic!("collect-trait-impls can't run");
 165     };
 166
 167     krate
 168 }
 169
 170 struct SyntheticImplCollector<'a, 'tcx> {
 171     cx: &'a mut DocContext<'tcx>,
 172     impls: Vec<Item>,
 173 }
 174
 175 impl<'a, 'tcx> DocVisitor for SyntheticImplCollector<'a, 'tcx> {
 176     fn visit_item(&mut self, i: &Item) {
 177         if i.is_struct() || i.is_enum() || i.is_union() {
 178             // FIXME(eddyb) is this `doc(hidden)` check needed?
 179             if !self.cx.tcx.is_doc_hidden(i.def_id.expect_def_id()) {
 180                 self.impls
 181                     .extend(get_auto_trait_and_blanket_impls(self.cx, i.def_id.expect_def_id()));
 182             }
 183         }
 184
 185         self.visit_item_recur(i)
 186     }
 187 }
 188
 189 #[derive(Default)]
 190 struct ItemCollector {
 191     items: FxHashSet<ItemId>,
 192 }
 193
 194 impl ItemCollector {
 195     fn new() -> Self {
 196         Self::default()
 197     }
 198 }
 199
 200 impl DocVisitor for ItemCollector {
 201     fn visit_item(&mut self, i: &Item) {
 202         self.items.insert(i.def_id);
 203
 204         self.visit_item_recur(i)
 205     }
 206 }
 207
 208 struct BadImplStripper<'a> {
 209     prims: FxHashSet<PrimitiveType>,
 210     items: FxHashSet<ItemId>,
 211     cache: &'a Cache,
 212 }
 213
 214 impl<'a> BadImplStripper<'a> {
 215     fn keep_impl(&self, ty: &Type, is_deref: bool) -> bool {
 216         if let Generic(_) = ty {
 217             // keep impls made on generics
 218             true
 219         } else if let Some(prim) = ty.primitive_type() {
 220             self.prims.contains(&prim)
 221         } else if let Some(did) = ty.def_id(self.cache) {
 222             is_deref || self.keep_impl_with_def_id(did.into())
 223         } else {
 224             false
 225         }
 226     }
 227
 228     fn keep_impl_with_def_id(&self, did: ItemId) -> bool {
 229         self.items.contains(&did)
 230     }
 231 }