Try using a dyn Debug trait object instead of a closure

compiler/rustc_hir/src/definitions.rs

@@ -380,14 +380,19 @@ impl Definitions {
     pub fn local_def_path_hash_to_def_id(
         &self,
         hash: DefPathHash,
-        err: &mut dyn FnMut() -> !,
+        err_msg: &dyn std::fmt::Debug,
     ) -> LocalDefId {
         debug_assert!(hash.stable_crate_id() == self.table.stable_crate_id);
+        #[cold]
+        #[inline(never)]
+        fn err(err_msg: &dyn std::fmt::Debug) -> ! {
+            panic!("{err_msg:?}")
+        }
         self.table
             .def_path_hash_to_index
             .get(&hash.local_hash())
             .map(|local_def_index| LocalDefId { local_def_index })
-            .unwrap_or_else(|| err())
+            .unwrap_or_else(|| err(err_msg))
     }
 
     pub fn def_path_hash_to_def_index_map(&self) -> &DefPathHashMap {

compiler/rustc_middle/src/dep_graph/dep_node.rs

@@ -194,9 +194,10 @@ impl DepNodeExt for DepNode {
     /// has been removed.
     fn extract_def_id(&self, tcx: TyCtxt<'_>) -> Option<DefId> {
         if tcx.fingerprint_style(self.kind) == FingerprintStyle::DefPathHash {
-            Some(tcx.def_path_hash_to_def_id(DefPathHash(self.hash.into()), &mut || {
-                panic!("Failed to extract DefId: {:?} {}", self.kind, self.hash)
-            }))
+            Some(tcx.def_path_hash_to_def_id(
+                DefPathHash(self.hash.into()),
+                &("Failed to extract DefId", self.kind, self.hash),
+            ))
         } else {
             None
         }
@@ -390,9 +391,10 @@ impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for HirId {
             let (local_hash, local_id) = Fingerprint::from(dep_node.hash).split();
             let def_path_hash = DefPathHash::new(tcx.stable_crate_id(LOCAL_CRATE), local_hash);
             let def_id = tcx
-                .def_path_hash_to_def_id(def_path_hash, &mut || {
-                    panic!("Failed to extract HirId: {:?} {}", dep_node.kind, dep_node.hash)
-                })
+                .def_path_hash_to_def_id(
+                    def_path_hash,
+                    &("Failed to extract HirId", dep_node.kind, dep_node.hash),
+                )
                 .expect_local();
             let local_id = local_id
                 .as_u64()

compiler/rustc_middle/src/query/on_disk_cache.rs

@@ -737,9 +737,10 @@ impl<'a, 'tcx> SpanDecoder for CacheDecoder<'a, 'tcx> {
         // If we get to this point, then all of the query inputs were green,
         // which means that the definition with this hash is guaranteed to
         // still exist in the current compilation session.
-        self.tcx.def_path_hash_to_def_id(def_path_hash, &mut || {
-            panic!("Failed to convert DefPathHash {def_path_hash:?}")
-        })
+        self.tcx.def_path_hash_to_def_id(
+            def_path_hash,
+            &("Failed to convert DefPathHash", def_path_hash),
+        )
     }
 
     fn decode_attr_id(&mut self) -> rustc_span::AttrId {

compiler/rustc_middle/src/ty/context.rs

@@ -1063,15 +1063,23 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Converts a `DefPathHash` to its corresponding `DefId` in the current compilation
     /// session, if it still exists. This is used during incremental compilation to
     /// turn a deserialized `DefPathHash` into its current `DefId`.
-    pub fn def_path_hash_to_def_id(self, hash: DefPathHash, err: &mut dyn FnMut() -> !) -> DefId {
+    pub fn def_path_hash_to_def_id(
+        self,
+        hash: DefPathHash,
+        err_msg: &dyn std::fmt::Debug,
+    ) -> DefId {
         debug!("def_path_hash_to_def_id({:?})", hash);
 
         let stable_crate_id = hash.stable_crate_id();
 
         // If this is a DefPathHash from the local crate, we can look up the
         // DefId in the tcx's `Definitions`.
         if stable_crate_id == self.stable_crate_id(LOCAL_CRATE) {
-            self.untracked.definitions.read().local_def_path_hash_to_def_id(hash, err).to_def_id()
+            self.untracked
+                .definitions
+                .read()
+                .local_def_path_hash_to_def_id(hash, err_msg)
+                .to_def_id()
         } else {
             // If this is a DefPathHash from an upstream crate, let the CrateStore map
             // it to a DefId.