Only hash the Hir owner (including its bodies)

src/librustc/hir/map/collector.rs

@@ -203,12 +203,22 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
         let owner = HirOwner { parent: entry.parent, node: entry.node };
 
         let arena = self.arena;
+        let krate = self.krate;
 
         let items = self.owner_items_map.entry(id.owner).or_insert_with(|| {
-            arena.alloc(HirOwnerItems { items: IndexVec::new(), bodies: FxHashMap::default() })
+            arena.alloc(HirOwnerItems {
+                // Insert a dummy node which will be overwritten
+                // when we call `insert_entry` on the HIR owner.
+                owner: Node::Crate(&krate.item),
+                items: IndexVec::new(),
+                bodies: FxHashMap::default(),
+            })
         });
 
         if i == 0 {
+            // Overwrite the dummy node with the real HIR owner.
+            items.owner = entry.node;
+
             self.owner_map.insert(id.owner, self.arena.alloc(owner));
         // FIXME: feature(impl_trait_in_bindings) broken and trigger this assert
         //assert!(self.owner_map.insert(id.owner, self.arena.alloc(owner)).is_none());

src/librustc/hir/mod.rs

@@ -5,10 +5,12 @@
 pub mod exports;
 pub mod map;
 
+use crate::ich::StableHashingContext;
 use crate::ty::query::Providers;
 use crate::ty::TyCtxt;
 use rustc_data_structures::cold_path;
 use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 use rustc_hir::print;
 use rustc_hir::Body;
@@ -25,19 +27,39 @@ pub struct HirOwner<'tcx> {
     node: Node<'tcx>,
 }
 
-#[derive(HashStable, Clone)]
+#[derive(Clone)]
 pub struct HirItem<'tcx> {
     parent: ItemLocalId,
     node: Node<'tcx>,
 }
 
-#[derive(HashStable)]
+impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for HirItem<'tcx> {
+    fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
+        let HirItem { parent, node } = self;
+        hcx.while_hashing_hir_bodies(false, |hcx| {
+            parent.hash_stable(hcx, hasher);
+            node.hash_stable(hcx, hasher);
+        });
+    }
+}
+
 pub struct HirOwnerItems<'tcx> {
-    //owner: &'tcx HirOwner<'tcx>,
+    owner: Node<'tcx>,
     items: IndexVec<ItemLocalId, Option<HirItem<'tcx>>>,
     bodies: FxHashMap<ItemLocalId, &'tcx Body<'tcx>>,
 }
 
+impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for HirOwnerItems<'tcx> {
+    fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
+        // We ignore the `items` and `bodies` fields since these refer to information reachable
+        // when hashing `owner` with its bodies.
+        let HirOwnerItems { owner, items: _, bodies: _ } = *self;
+        hcx.while_hashing_hir_bodies(true, |hcx| {
+            owner.hash_stable(hcx, hasher);
+        });
+    }
+}
+
 /// A wrapper type which allows you to access HIR.
 #[derive(Clone)]
 pub struct Hir<'tcx> {