Prevent showing methods from blanket impls of not available foreign t…

…raits to show up in the search results.

src/librustdoc/formats/cache.rs

@@ -311,7 +311,20 @@ impl<'a, 'tcx> DocFolder for CacheBuilder<'a, 'tcx> {
                                 for_: clean::Type::BorrowedRef { type_, .. },
                                 ..
                             } => type_.def_id(&self.cache),
-                            ParentStackItem::Impl { for_, .. } => for_.def_id(&self.cache),
+                            ParentStackItem::Impl { for_, trait_, .. } => {
+                                if let Some(trait_) = trait_ {
+                                    let trait_did = trait_.def_id();
+                                    // If this is a foreign trait impl but the trait documentation
+                                    // is not available, we should not allow the methods to show up
+                                    // in the search results.
+                                    if !trait_did.is_local()
+                                        && !self.cache.traits.contains_key(&trait_did)
+                                    {
+                                        return None;
+                                    }
+                                }
+                                for_.def_id(&self.cache)
+                            }
                             ParentStackItem::Type(item_id) => item_id.as_def_id(),
                         };
                         let path = did