filter collected trait impls against items in the crate

Author: QuietMisdreavus

src/librustdoc/passes/collect_trait_impls.rs

@@ -10,6 +10,9 @@
 
 use clean::*;
 
+use rustc::util::nodemap::FxHashSet;
+use rustc::hir::def_id::DefId;
+
 use super::Pass;
 use core::DocContext;
 use fold::DocFolder;
@@ -22,22 +25,20 @@ pub fn collect_trait_impls(krate: Crate, cx: &DocContext) -> Crate {
     let mut synth = SyntheticImplCollector::new(cx);
     let mut krate = synth.fold_crate(krate);
 
-    if let Some(ref mut it) = krate.module {
-        if let ModuleItem(Module { ref mut items, .. }) = it.inner {
-            items.extend(synth.impls);
+    let prims: FxHashSet<PrimitiveType> =
+        krate.primitives.iter().map(|p| p.1).collect();
+
+    let crate_items = {
+        let mut coll = ItemCollector::new();
+        krate = coll.fold_crate(krate);
+        coll.items
+    };
+
+    let mut new_items = Vec::new();
 
     for &cnum in cx.tcx.crates().iter() {
         for &did in cx.tcx.all_trait_implementations(cnum).iter() {
-                    inline::build_impl(cx, did, items);
-                }
-            }
-
-            // `tcx.crates()` doesn't include the local crate, and `tcx.all_trait_implementations`
-            // doesn't work with it anyway, so pull them from the HIR map instead
-            for &trait_did in cx.all_traits.iter() {
-                for &impl_node in cx.tcx.hir.trait_impls(trait_did) {
-                    let impl_did = cx.tcx.hir.local_def_id(impl_node);
-                    inline::build_impl(cx, impl_did, items);
+            inline::build_impl(cx, did, &mut new_items);
         }
     }
 
@@ -73,7 +74,7 @@ pub fn collect_trait_impls(krate: Crate, cx: &DocContext) -> Crate {
 
     for def_id in primitive_impls.iter().filter_map(|&def_id| def_id) {
         if !def_id.is_local() {
-                    inline::build_impl(cx, def_id, items);
+            inline::build_impl(cx, def_id, &mut new_items);
 
             let auto_impls = get_auto_traits_with_def_id(cx, def_id);
             let blanket_impls = get_blanket_impls_with_def_id(cx, def_id);
@@ -84,9 +85,58 @@ pub fn collect_trait_impls(krate: Crate, cx: &DocContext) -> Crate {
                 .filter(|i| renderinfo.inlined.insert(i.def_id))
                 .collect();
 
-                    items.extend(new_impls);
+            new_items.extend(new_impls);
         }
     }
+
+    let mut cleaner = BadImplStripper {
+        prims,
+        items: crate_items,
+    };
+
+    // scan through included items ahead of time to splice in Deref targets to the "valid" sets
+    for it in &new_items {
+        if let ImplItem(Impl { ref for_, ref trait_, ref items, .. }) = it.inner {
+            if cleaner.keep_item(for_) && trait_.def_id() == cx.tcx.lang_items().deref_trait() {
+                let target = items.iter().filter_map(|item| {
+                    match item.inner {
+                        TypedefItem(ref t, true) => Some(&t.type_),
+                        _ => None,
+                    }
+                }).next().expect("Deref impl without Target type");
+
+                if let Some(prim) = target.primitive_type() {
+                    cleaner.prims.insert(prim);
+                } else if let Some(did) = target.def_id() {
+                    cleaner.items.insert(did);
+                }
+            }
+        }
+    }
+
+    new_items.retain(|it| {
+        if let ImplItem(Impl { ref for_, ref trait_, ref blanket_impl, .. }) = it.inner {
+            cleaner.keep_item(for_) ||
+                trait_.as_ref().map_or(false, |t| cleaner.keep_item(t)) ||
+                blanket_impl.is_some()
+        } else {
+            true
+        }
+    });
+
+    // `tcx.crates()` doesn't include the local crate, and `tcx.all_trait_implementations`
+    // doesn't work with it anyway, so pull them from the HIR map instead
+    for &trait_did in cx.all_traits.iter() {
+        for &impl_node in cx.tcx.hir.trait_impls(trait_did) {
+            let impl_did = cx.tcx.hir.local_def_id(impl_node);
+            inline::build_impl(cx, impl_did, &mut new_items);
+        }
+    }
+
+    if let Some(ref mut it) = krate.module {
+        if let ModuleItem(Module { ref mut items, .. }) = it.inner {
+            items.extend(synth.impls);
+            items.extend(new_items);
         } else {
             panic!("collect-trait-impls can't run");
         }
@@ -128,3 +178,42 @@ impl<'a, 'tcx, 'rcx, 'cstore> DocFolder for SyntheticImplCollector<'a, 'tcx, 'rc
         self.fold_item_recur(i)
     }
 }
+
+#[derive(Default)]
+struct ItemCollector {
+    items: FxHashSet<DefId>,
+}
+
+impl ItemCollector {
+    fn new() -> Self {
+        Self::default()
+    }
+}
+
+impl DocFolder for ItemCollector {
+    fn fold_item(&mut self, i: Item) -> Option<Item> {
+        self.items.insert(i.def_id);
+
+        self.fold_item_recur(i)
+    }
+}
+
+struct BadImplStripper {
+    prims: FxHashSet<PrimitiveType>,
+    items: FxHashSet<DefId>,
+}
+
+impl BadImplStripper {
+    fn keep_item(&self, ty: &Type) -> bool {
+        if let Generic(_) = ty {
+            // keep impls made on generics
+            true
+        } else if let Some(prim) = ty.primitive_type() {
+            self.prims.contains(&prim)
+        } else if let Some(did) = ty.def_id() {
+            self.items.contains(&did)
+        } else {
+            false
+        }
+    }
+}