Make hash_result an Option.

compiler/rustc_query_system/src/query/config.rs

@@ -24,7 +24,7 @@ pub(crate) struct QueryVtable<CTX: QueryContext, K, V> {
     pub dep_kind: CTX::DepKind,
     pub eval_always: bool,
 
-    pub hash_result: fn(&mut StableHashingContext<'_>, &V) -> Option<Fingerprint>,
+    pub hash_result: Option<fn(&mut StableHashingContext<'_>, &V) -> Fingerprint>,
     pub handle_cycle_error: fn(CTX, DiagnosticBuilder<'_>) -> V,
     pub cache_on_disk: fn(CTX, &K, Option<&V>) -> bool,
     pub try_load_from_disk: fn(CTX, SerializedDepNodeIndex) -> Option<V>,
@@ -38,14 +38,6 @@ impl<CTX: QueryContext, K, V> QueryVtable<CTX, K, V> {
         DepNode::construct(tcx, self.dep_kind, key)
     }
 
-    pub(crate) fn hash_result(
-        &self,
-        hcx: &mut StableHashingContext<'_>,
-        value: &V,
-    ) -> Option<Fingerprint> {
-        (self.hash_result)(hcx, value)
-    }
-
     pub(crate) fn cache_on_disk(&self, tcx: CTX, key: &K, value: Option<&V>) -> bool {
         (self.cache_on_disk)(tcx, key, value)
     }
@@ -59,6 +51,9 @@ pub trait QueryAccessors<CTX: QueryContext>: QueryConfig {
     const ANON: bool;
     const EVAL_ALWAYS: bool;
     const DEP_KIND: CTX::DepKind;
+    const HASH_RESULT: Option<
+        fn(hcx: &mut StableHashingContext<'_>, result: &Self::Value) -> Fingerprint,
+    >;
 
     type Cache: QueryCache<Key = Self::Key, Stored = Self::Stored, Value = Self::Value>;
 
@@ -75,9 +70,6 @@ pub trait QueryAccessors<CTX: QueryContext>: QueryConfig {
     // Don't use this method to compute query results, instead use the methods on TyCtxt
     fn compute_fn(tcx: CTX, key: &Self::Key) -> fn(CTX::DepContext, Self::Key) -> Self::Value;
 
-    fn hash_result(hcx: &mut StableHashingContext<'_>, result: &Self::Value)
-    -> Option<Fingerprint>;
-
     fn handle_cycle_error(tcx: CTX, diag: DiagnosticBuilder<'_>) -> Self::Value;
 }
 
@@ -107,7 +99,7 @@ where
         anon: Q::ANON,
         dep_kind: Q::DEP_KIND,
         eval_always: Q::EVAL_ALWAYS,
-        hash_result: Q::hash_result,
+        hash_result: Q::HASH_RESULT,
         handle_cycle_error: Q::handle_cycle_error,
         cache_on_disk: Q::cache_on_disk,
         try_load_from_disk: Q::try_load_from_disk,

compiler/rustc_query_system/src/query/plumbing.rs

@@ -577,12 +577,12 @@ fn incremental_verify_ich<CTX, K, V: Debug>(
     );
 
     debug!("BEGIN verify_ich({:?})", dep_node);
-    let mut hcx = tcx.create_stable_hashing_context();
-
-    let new_hash = query.hash_result(&mut hcx, result).unwrap_or(Fingerprint::ZERO);
-    debug!("END verify_ich({:?})", dep_node);
-
+    let new_hash = query.hash_result.map_or(Fingerprint::ZERO, |f| {
+        let mut hcx = tcx.create_stable_hashing_context();
+        f(&mut hcx, result)
+    });
     let old_hash = tcx.dep_graph().prev_fingerprint_of(dep_node);
+    debug!("END verify_ich({:?})", dep_node);
 
     if Some(new_hash) != old_hash {
         let run_cmd = if let Some(crate_name) = &tcx.sess().opts.crate_name {