Trying to address an incremental compilation issues

compiler/rustc_hir/src/definitions.rs

@@ -377,22 +377,17 @@ impl Definitions {
     }
 
     #[inline(always)]
-    pub fn local_def_path_hash_to_def_id(
-        &self,
-        hash: DefPathHash,
-        err_msg: &dyn std::fmt::Debug,
-    ) -> LocalDefId {
+    /// Returns `None` if the `DefPathHash` does not correspond to a `LocalDefId`
+    /// in the current compilation session. This can legitimately happen if the
+    /// `DefPathHash` is from a `DefId` in an upstream crate or, during incr. comp.,
+    /// if the `DefPathHash` is from a previous compilation session and
+    /// the def-path does not exist anymore.
+    pub fn local_def_path_hash_to_def_id(&self, hash: DefPathHash) -> Option<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(err_msg))
     }
 
     pub fn def_path_hash_to_def_index_map(&self) -> &DefPathHashMap {

compiler/rustc_middle/src/dep_graph/dep_node.rs

@@ -194,10 +194,7 @@ 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()),
-                &("Failed to extract DefId", self.kind, self.hash),
-            ))
+            tcx.def_path_hash_to_def_id(DefPathHash(self.hash.into()))
         } else {
             None
         }
@@ -390,12 +387,7 @@ impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for HirId {
         if tcx.fingerprint_style(dep_node.kind) == FingerprintStyle::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,
-                    &("Failed to extract HirId", dep_node.kind, dep_node.hash),
-                )
-                .expect_local();
+            let def_id = tcx.def_path_hash_to_def_id(def_path_hash)?.expect_local();
             let local_id = local_id
                 .as_u64()
                 .try_into()

compiler/rustc_middle/src/query/on_disk_cache.rs

@@ -733,10 +733,10 @@ 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,
-            &("Failed to convert DefPathHash", def_path_hash),
-        )
+        match self.tcx.def_path_hash_to_def_id(def_path_hash) {
+            Some(r) => r,
+            None => panic!("Failed to convert DefPathHash {def_path_hash:?}"),
+        }
     }
 
     fn decode_attr_id(&mut self) -> rustc_span::AttrId {

compiler/rustc_middle/src/ty/context.rs

@@ -1677,25 +1677,17 @@ 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_msg: &dyn std::fmt::Debug,
-    ) -> DefId {
+    pub fn def_path_hash_to_def_id(self, hash: DefPathHash) -> Option<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_msg)
-                .to_def_id()
+            Some(self.untracked.definitions.read().local_def_path_hash_to_def_id(hash)?.to_def_id())
         } else {
-            self.def_path_hash_to_def_id_extern(hash, stable_crate_id)
+            Some(self.def_path_hash_to_def_id_extern(hash, stable_crate_id))
         }
     }
 

compiler/rustc_query_system/src/dep_graph/mod.rs

@@ -51,20 +51,24 @@ pub trait DepContext: Copy {
     }
 
     /// Try to force a dep node to execute and see if it's green.
+    ///
+    /// Returns true if the query has actually been forced. It is valid that a query
+    /// fails to be forced, e.g. when the query key cannot be reconstructed from the
+    /// dep-node or when the query kind outright does not support it.
     #[inline]
     #[instrument(skip(self, frame), level = "debug")]
     fn try_force_from_dep_node(self, dep_node: DepNode, frame: Option<&MarkFrame<'_>>) -> bool {
         let cb = self.dep_kind_info(dep_node.kind);
         if let Some(f) = cb.force_from_dep_node {
-            if let Err(value) = panic::catch_unwind(panic::AssertUnwindSafe(|| {
-                f(self, dep_node);
-            })) {
-                if !value.is::<rustc_errors::FatalErrorMarker>() {
-                    print_markframe_trace(self.dep_graph(), frame);
+            match panic::catch_unwind(panic::AssertUnwindSafe(|| f(self, dep_node))) {
+                Err(value) => {
+                    if !value.is::<rustc_errors::FatalErrorMarker>() {
+                        print_markframe_trace(self.dep_graph(), frame);
+                    }
+                    panic::resume_unwind(value)
                 }
-                panic::resume_unwind(value)
+                Ok(query_has_been_forced) => query_has_been_forced,
             }
-            true
         } else {
             false
         }

tests/incremental/unrecoverable_query.rs

@@ -0,0 +1,40 @@
+// If it is impossible to find query arguments just from the hash
+// compiler should treat the node as red
+
+// In this test prior to fixing compiler was having problems figuring out
+// drop impl for T inside of m
+
+//@ revisions:cfail1 cfail2
+//@ compile-flags: --crate-type=lib
+//@ build-pass
+
+pub trait P {
+    type A;
+}
+
+struct S;
+
+impl P for S {
+    type A = C;
+}
+
+struct T<D: P>(D::A, Z<D>);
+
+struct Z<D: P>(D::A, String);
+
+impl<D: P> T<D> {
+    pub fn i() -> Self {
+        loop {}
+    }
+}
+
+enum C {
+    #[cfg(cfail1)]
+    Up(()),
+    #[cfg(cfail2)]
+    Lorry(()),
+}
+
+pub fn m() {
+    T::<S>::i();
+}