Show a more informative panic message when DefPathHash does not exist

This should hopefully make it easier to debug incremental compilation
bugs like rust-lang#93096 without affecting performance.

compiler/rustc_hir/src/definitions.rs

@@ -449,13 +449,17 @@ impl Definitions {
     }
 
     #[inline(always)]
-    pub fn local_def_path_hash_to_def_id(&self, hash: DefPathHash) -> LocalDefId {
+    pub fn local_def_path_hash_to_def_id(
+        &self,
+        hash: DefPathHash,
+        err: &mut dyn FnMut() -> !,
+    ) -> LocalDefId {
         debug_assert!(hash.stable_crate_id() == self.stable_crate_id);
         self.table
             .def_path_hash_to_index
             .get(&hash)
             .map(|local_def_index| LocalDefId { local_def_index })
-            .unwrap()
+            .unwrap_or_else(|| err())
     }
 
     pub fn def_path_hash_to_def_index_map(&self) -> &DefPathHashMap {

compiler/rustc_middle/src/dep_graph/dep_node.rs

@@ -266,7 +266,9 @@ impl DepNodeExt for DepNode {
     /// has been removed.
     fn extract_def_id<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Option<DefId> {
         if self.kind.fingerprint_style(tcx) == FingerprintStyle::DefPathHash {
-            Some(tcx.def_path_hash_to_def_id(DefPathHash(self.hash.into())))
+            Some(tcx.def_path_hash_to_def_id(DefPathHash(self.hash.into()), &mut || {
+                panic!("Failed to extract DefId: {:?} {}", self.kind, self.hash)
+            }))
         } else {
             None
         }

compiler/rustc_middle/src/ty/context.rs

@@ -1308,15 +1308,18 @@ 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) -> DefId {
+    pub fn def_path_hash_to_def_id(self, hash: DefPathHash, err: &mut dyn FnMut() -> !) -> 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.sess.local_stable_crate_id() {
-            self.untracked_resolutions.definitions.local_def_path_hash_to_def_id(hash).to_def_id()
+            self.untracked_resolutions
+                .definitions
+                .local_def_path_hash_to_def_id(hash, err)
+                .to_def_id()
         } else {
             // If this is a DefPathHash from an upstream crate, let the CrateStore map
             // it to a DefId.

compiler/rustc_query_impl/src/on_disk_cache.rs

@@ -761,7 +761,9 @@ impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>> for DefId {
         // 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.
-        Ok(d.tcx().def_path_hash_to_def_id(def_path_hash))
+        Ok(d.tcx().def_path_hash_to_def_id(def_path_hash, &mut || {
+            panic!("Failed to convert DefPathHash {:?}", def_path_hash)
+        }))
     }
 }