Make DefPathHash->DefId panic for if the mapping fails.

We only use this mapping for cases where we know that it must succeed.
Letting it panic otherwise makes it harder to use the API in unsupported
ways.

compiler/rustc_hir/src/definitions.rs

@@ -443,12 +443,13 @@ impl Definitions {
     }
 
     #[inline(always)]
-    pub fn local_def_path_hash_to_def_id(&self, hash: DefPathHash) -> Option<LocalDefId> {
+    pub fn local_def_path_hash_to_def_id(&self, hash: DefPathHash) -> 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()
     }
 
     pub fn def_path_hash_to_def_index_map(&self) -> &DefPathHashMap {

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -1622,7 +1622,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
     }
 
     #[inline]
-    fn def_path_hash_to_def_index(&self, hash: DefPathHash) -> Option<DefIndex> {
+    fn def_path_hash_to_def_index(&self, hash: DefPathHash) -> DefIndex {
         self.def_path_hash_map.def_path_hash_to_def_index(&hash)
     }
 

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -517,10 +517,9 @@ impl CrateStore for CStore {
         self.get_crate_data(def.krate).def_path_hash(def.index)
     }
 
-    fn def_path_hash_to_def_id(&self, cnum: CrateNum, hash: DefPathHash) -> Option<DefId> {
-        self.get_crate_data(cnum)
-            .def_path_hash_to_def_index(hash)
-            .map(|index| DefId { krate: cnum, index })
+    fn def_path_hash_to_def_id(&self, cnum: CrateNum, hash: DefPathHash) -> DefId {
+        let def_index = self.get_crate_data(cnum).def_path_hash_to_def_index(hash);
+        DefId { krate: cnum, index: def_index }
     }
 
     fn expn_hash_to_expn_id(&self, cnum: CrateNum, index_guess: u32, hash: ExpnHash) -> ExpnId {

compiler/rustc_metadata/src/rmeta/def_path_hash_map.rs

@@ -15,9 +15,9 @@ crate enum DefPathHashMap<'tcx> {
 
 impl DefPathHashMap<'tcx> {
     #[inline]
-    pub fn def_path_hash_to_def_index(&self, def_path_hash: &DefPathHash) -> Option<DefIndex> {
+    pub fn def_path_hash_to_def_index(&self, def_path_hash: &DefPathHash) -> DefIndex {
         match *self {
-            DefPathHashMap::OwnedFromMetadata(ref map) => map.get(def_path_hash),
+            DefPathHashMap::OwnedFromMetadata(ref map) => map.get(def_path_hash).unwrap(),
             DefPathHashMap::BorrowedFromTcx(_) => {
                 panic!("DefPathHashMap::BorrowedFromTcx variant only exists for serialization")
             }

compiler/rustc_middle/src/dep_graph/dep_node.rs

@@ -336,7 +336,11 @@ impl DepNodeExt for DepNode {
     /// has been removed.
     fn extract_def_id(&self, tcx: TyCtxt<'tcx>) -> Option<DefId> {
         if self.kind.can_reconstruct_query_key() {
-            tcx.on_disk_cache.as_ref()?.def_path_hash_to_def_id(tcx, DefPathHash(self.hash.into()))
+            Some(
+                tcx.on_disk_cache
+                    .as_ref()?
+                    .def_path_hash_to_def_id(tcx, DefPathHash(self.hash.into())),
+            )
         } else {
             None
         }

compiler/rustc_middle/src/middle/cstore.rs

@@ -202,7 +202,7 @@ pub trait CrateStore: std::fmt::Debug {
     fn stable_crate_id_to_crate_num(&self, stable_crate_id: StableCrateId) -> CrateNum;
 
     /// Fetch a DefId from a DefPathHash for a foreign crate.
-    fn def_path_hash_to_def_id(&self, cnum: CrateNum, hash: DefPathHash) -> Option<DefId>;
+    fn def_path_hash_to_def_id(&self, cnum: CrateNum, hash: DefPathHash) -> DefId;
     fn expn_hash_to_expn_id(&self, cnum: CrateNum, index_guess: u32, hash: ExpnHash) -> ExpnId;
 
     // utility functions

compiler/rustc_middle/src/ty/context.rs

@@ -83,11 +83,7 @@ pub trait OnDiskCache<'tcx>: rustc_data_structures::sync::Sync {
     /// 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`.
-    fn def_path_hash_to_def_id(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        def_path_hash: DefPathHash,
-    ) -> Option<DefId>;
+    fn def_path_hash_to_def_id(&self, tcx: TyCtxt<'tcx>, def_path_hash: DefPathHash) -> DefId;
 
     fn drop_serialized_data(&self, tcx: TyCtxt<'tcx>);
 

compiler/rustc_query_impl/src/on_disk_cache.rs

@@ -361,7 +361,7 @@ impl<'sess> rustc_middle::ty::OnDiskCache<'sess> for OnDiskCache<'sess> {
         })
     }
 
-    fn def_path_hash_to_def_id(&self, tcx: TyCtxt<'tcx>, hash: DefPathHash) -> Option<DefId> {
+    fn def_path_hash_to_def_id(&self, tcx: TyCtxt<'tcx>, hash: DefPathHash) -> DefId {
         debug!("def_path_hash_to_def_id({:?})", hash);
 
         let stable_crate_id = hash.stable_crate_id();
@@ -369,9 +369,7 @@ impl<'sess> rustc_middle::ty::OnDiskCache<'sess> for OnDiskCache<'sess> {
         // If this is a DefPathHash from the local crate, we can look up the
         // DefId in the tcx's `Definitions`.
         if stable_crate_id == tcx.sess.local_stable_crate_id() {
-            tcx.definitions_untracked()
-                .local_def_path_hash_to_def_id(hash)
-                .map(LocalDefId::to_def_id)
+            tcx.definitions_untracked().local_def_path_hash_to_def_id(hash).to_def_id()
         } else {
             // If this is a DefPathHash from an upstream crate, let the CrateStore map
             // it to a DefId.
@@ -779,12 +777,7 @@ 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()
-            .on_disk_cache
-            .as_ref()
-            .unwrap()
-            .def_path_hash_to_def_id(d.tcx(), def_path_hash)
-            .unwrap())
+        Ok(d.tcx().on_disk_cache.as_ref().unwrap().def_path_hash_to_def_id(d.tcx(), def_path_hash))
     }
 }