1 files changed, 143 insertions, 0 deletions
diff --git a/compiler/rustc_hir/src/stable_hash_impls.rs b/compiler/rustc_hir/src/stable_hash_impls.rs
new file mode 100644
index 000000000..8ccd59e8e
--- /dev/null
+++ b/compiler/rustc_hir/src/stable_hash_impls.rs
@@ -0,0 +1,143 @@
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher, ToStableHashKey};
+
+use crate::hir::{
+    AttributeMap, BodyId, Crate, Expr, ForeignItemId, ImplItemId, ItemId, OwnerNodes, TraitItemId,
+    Ty,
+};
+use crate::hir_id::{HirId, ItemLocalId};
+use rustc_span::def_id::DefPathHash;
+
+/// Requirements for a `StableHashingContext` to be used in this crate.
+/// This is a hack to allow using the `HashStable_Generic` derive macro
+/// instead of implementing everything in `rustc_middle`.
+pub trait HashStableContext:
+    rustc_ast::HashStableContext + rustc_target::HashStableContext
+{
+    fn hash_body_id(&mut self, _: BodyId, hasher: &mut StableHasher);
+    fn hash_hir_expr(&mut self, _: &Expr<'_>, hasher: &mut StableHasher);
+    fn hash_hir_ty(&mut self, _: &Ty<'_>, hasher: &mut StableHasher);
+}
+
+impl<HirCtx: crate::HashStableContext> ToStableHashKey<HirCtx> for HirId {
+    type KeyType = (DefPathHash, ItemLocalId);
+
+    #[inline]
+    fn to_stable_hash_key(&self, hcx: &HirCtx) -> (DefPathHash, ItemLocalId) {
+        let def_path_hash = self.owner.to_stable_hash_key(hcx);
+        (def_path_hash, self.local_id)
+    }
+}
+
+impl<HirCtx: crate::HashStableContext> ToStableHashKey<HirCtx> for ItemLocalId {
+    type KeyType = ItemLocalId;
+
+    #[inline]
+    fn to_stable_hash_key(&self, _: &HirCtx) -> ItemLocalId {
+        *self
+    }
+}
+
+impl<HirCtx: crate::HashStableContext> ToStableHashKey<HirCtx> for BodyId {
+    type KeyType = (DefPathHash, ItemLocalId);
+
+    #[inline]
+    fn to_stable_hash_key(&self, hcx: &HirCtx) -> (DefPathHash, ItemLocalId) {
+        let BodyId { hir_id } = *self;
+        hir_id.to_stable_hash_key(hcx)
+    }
+}
+
+impl<HirCtx: crate::HashStableContext> ToStableHashKey<HirCtx> for ItemId {
+    type KeyType = DefPathHash;
+
+    #[inline]
+    fn to_stable_hash_key(&self, hcx: &HirCtx) -> DefPathHash {
+        self.def_id.to_stable_hash_key(hcx)
+    }
+}
+
+impl<HirCtx: crate::HashStableContext> ToStableHashKey<HirCtx> for TraitItemId {
+    type KeyType = DefPathHash;
+
+    #[inline]
+    fn to_stable_hash_key(&self, hcx: &HirCtx) -> DefPathHash {
+        self.def_id.to_stable_hash_key(hcx)
+    }
+}
+
+impl<HirCtx: crate::HashStableContext> ToStableHashKey<HirCtx> for ImplItemId {
+    type KeyType = DefPathHash;
+
+    #[inline]
+    fn to_stable_hash_key(&self, hcx: &HirCtx) -> DefPathHash {
+        self.def_id.to_stable_hash_key(hcx)
+    }
+}
+
+impl<HirCtx: crate::HashStableContext> ToStableHashKey<HirCtx> for ForeignItemId {
+    type KeyType = DefPathHash;
+
+    #[inline]
+    fn to_stable_hash_key(&self, hcx: &HirCtx) -> DefPathHash {
+        self.def_id.to_stable_hash_key(hcx)
+    }
+}
+
+impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for BodyId {
+    fn hash_stable(&self, hcx: &mut HirCtx, hasher: &mut StableHasher) {
+        hcx.hash_body_id(*self, hasher)
+    }
+}
+
+// The following implementations of HashStable for `ItemId`, `TraitItemId`, and
+// `ImplItemId` deserve special attention. Normally we do not hash `NodeId`s within
+// the HIR, since they just signify a HIR nodes own path. But `ItemId` et al
+// are used when another item in the HIR is *referenced* and we certainly
+// want to pick up on a reference changing its target, so we hash the NodeIds
+// in "DefPath Mode".
+
+impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for Expr<'_> {
+    fn hash_stable(&self, hcx: &mut HirCtx, hasher: &mut StableHasher) {
+        hcx.hash_hir_expr(self, hasher)
+    }
+}
+
+impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for Ty<'_> {
+    fn hash_stable(&self, hcx: &mut HirCtx, hasher: &mut StableHasher) {
+        hcx.hash_hir_ty(self, hasher)
+    }
+}
+
+impl<'tcx, HirCtx: crate::HashStableContext> HashStable<HirCtx> for OwnerNodes<'tcx> {
+    fn hash_stable(&self, hcx: &mut HirCtx, hasher: &mut StableHasher) {
+        // We ignore the `nodes` and `bodies` fields since these refer to information included in
+        // `hash` which is hashed in the collector and used for the crate hash.
+        // `local_id_to_def_id` is also ignored because is dependent on the body, then just hashing
+        // the body satisfies the condition of two nodes being different have different
+        // `hash_stable` results.
+        let OwnerNodes {
+            hash_including_bodies,
+            hash_without_bodies: _,
+            nodes: _,
+            bodies: _,
+            local_id_to_def_id: _,
+        } = *self;
+        hash_including_bodies.hash_stable(hcx, hasher);
+    }
+}
+
+impl<'tcx, HirCtx: crate::HashStableContext> HashStable<HirCtx> for AttributeMap<'tcx> {
+    fn hash_stable(&self, hcx: &mut HirCtx, hasher: &mut StableHasher) {
+        // We ignore the `map` since it refers to information included in `hash` which is hashed in
+        // the collector and used for the crate hash.
+        let AttributeMap { hash, map: _ } = *self;
+        hash.hash_stable(hcx, hasher);
+    }
+}
+
+impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for Crate<'_> {
+    fn hash_stable(&self, hcx: &mut HirCtx, hasher: &mut StableHasher) {
+        let Crate { owners: _, hir_hash } = self;
+        hir_hash.hash_stable(hcx, hasher)
+    }
+}