Don't rely on Debug impl for Erased

compiler/rustc_middle/src/query/erase.rs

@@ -1,21 +1,12 @@
 use crate::ty;
 use std::intrinsics::type_name;
-use std::{
+use std::mem::{size_of, transmute_copy, MaybeUninit};
-    fmt,
-    mem::{size_of, transmute_copy, MaybeUninit},
-};
 
 #[derive(Copy, Clone)]
 pub struct Erased<T: Copy> {
     data: MaybeUninit<T>,
 }
 
-impl<T: Copy> fmt::Debug for Erased<T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "Erased")
-    }
-}
-
 pub trait EraseType: Copy {
     type Result: Copy;
 }

compiler/rustc_middle/src/ty/query.rs

@@ -501,6 +501,7 @@ macro_rules! define_feedable {
 
                 match try_get_cached(tcx, cache, &key) {
                     Some(old) => {
+                        let old = restore::<$V>(old);
                         bug!(
                             "Trying to feed an already recorded value for query {} key={key:?}:\nold value: {old:?}\nnew value: {value:?}",
                             stringify!($name),

compiler/rustc_query_impl/src/plumbing.rs

@@ -486,6 +486,11 @@ macro_rules! define_queries {
                 stringify!($name)
             }
 
+            #[inline]
+            fn format_value(self) -> fn(&Self::Value) -> String {
+                |value| format!("{:?}", restore::<query_values::$name<'tcx>>(*value))
+            }
+
             #[inline]
             fn cache_on_disk(self, tcx: TyCtxt<'tcx>, key: &Self::Key) -> bool {
                 ::rustc_middle::query::cached::$name(tcx, key)
@@ -819,7 +824,7 @@ macro_rules! define_queries_struct {
 
             $($(#[$attr])*
             #[inline(always)]
-            #[tracing::instrument(level = "trace", skip(self, tcx), ret)]
+            #[tracing::instrument(level = "trace", skip(self, tcx))]
             fn $name(
                 &'tcx self,
                 tcx: TyCtxt<'tcx>,

compiler/rustc_query_system/src/dep_graph/graph.rs

@@ -538,7 +538,14 @@ impl<K: DepKind> DepGraph<K> {
             if let Some(prev_index) = data.previous.node_to_index_opt(&node) {
                 let dep_node_index = data.current.prev_index_to_index.lock()[prev_index];
                 if let Some(dep_node_index) = dep_node_index {
-                    crate::query::incremental_verify_ich(cx, data, result, prev_index, hash_result);
+                    crate::query::incremental_verify_ich(
+                        cx,
+                        data,
+                        result,
+                        prev_index,
+                        hash_result,
+                        |value| format!("{:?}", value),
+                    );
 
                     #[cfg(debug_assertions)]
                     if hash_result.is_some() {

compiler/rustc_query_system/src/query/caches.rs

@@ -18,7 +18,7 @@ pub trait CacheSelector<'tcx, V> {
 
 pub trait QueryCache: Sized {
     type Key: Hash + Eq + Copy + Debug;
-    type Value: Copy + Debug;
+    type Value: Copy;
 
     /// Checks if the query is already computed and in the cache.
     fn lookup(&self, key: &Self::Key) -> Option<(Self::Value, DepNodeIndex)>;
@@ -52,7 +52,7 @@ impl<K, V> Default for DefaultCache<K, V> {
 impl<K, V> QueryCache for DefaultCache<K, V>
 where
     K: Eq + Hash + Copy + Debug,
-    V: Copy + Debug,
+    V: Copy,
 {
     type Key = K;
     type Value = V;
@@ -120,7 +120,7 @@ impl<V> Default for SingleCache<V> {
 
 impl<V> QueryCache for SingleCache<V>
 where
-    V: Copy + Debug,
+    V: Copy,
 {
     type Key = ();
     type Value = V;
@@ -164,7 +164,7 @@ impl<K: Idx, V> Default for VecCache<K, V> {
 impl<K, V> QueryCache for VecCache<K, V>
 where
     K: Eq + Idx + Copy + Debug,
-    V: Copy + Debug,
+    V: Copy,
 {
     type Key = K;
     type Value = V;

compiler/rustc_query_system/src/query/config.rs

@@ -20,10 +20,12 @@ pub trait QueryConfig<Qcx: QueryContext>: Copy {
     // `Key` and `Value` are `Copy` instead of `Clone` to ensure copying them stays cheap,
     // but it isn't necessary.
     type Key: DepNodeParams<Qcx::DepContext> + Eq + Hash + Copy + Debug;
-    type Value: Debug + Copy;
+    type Value: Copy;
 
     type Cache: QueryCache<Key = Self::Key, Value = Self::Value>;
 
+    fn format_value(self) -> fn(&Self::Value) -> String;
+
     // Don't use this method to access query results, instead use the methods on TyCtxt
     fn query_state<'a>(self, tcx: Qcx) -> &'a QueryState<Self::Key, Qcx::DepKind>
     where

compiler/rustc_query_system/src/query/plumbing.rs

@@ -411,7 +411,8 @@ where
         // get evaluated first, and re-feed the query.
         if let Some((cached_result, _)) = cache.lookup(&key) {
             panic!(
-                "fed query later has its value computed. The already cached value: {cached_result:?}"
+                "fed query later has its value computed. The already cached value: {}",
+                (query.format_value())(&cached_result)
             );
         }
     }
@@ -582,6 +583,7 @@ where
                     &result,
                     prev_dep_node_index,
                     query.hash_result(),
+                    query.format_value(),
                 );
             }
 
@@ -627,19 +629,21 @@ where
         &result,
         prev_dep_node_index,
         query.hash_result(),
+        query.format_value(),
     );
 
     Some((result, dep_node_index))
 }
 
 #[inline]
-#[instrument(skip(tcx, dep_graph_data, result, hash_result), level = "debug")]
+#[instrument(skip(tcx, dep_graph_data, result, hash_result, format_value), level = "debug")]
-pub(crate) fn incremental_verify_ich<Tcx, V: Debug>(
+pub(crate) fn incremental_verify_ich<Tcx, V>(
     tcx: Tcx,
     dep_graph_data: &DepGraphData<Tcx::DepKind>,
     result: &V,
     prev_index: SerializedDepNodeIndex,
     hash_result: Option<fn(&mut StableHashingContext<'_>, &V) -> Fingerprint>,
+    format_value: fn(&V) -> String,
 ) where
     Tcx: DepContext,
 {
@@ -654,7 +658,7 @@ pub(crate) fn incremental_verify_ich<Tcx, V: Debug>(
     let old_hash = dep_graph_data.prev_fingerprint_of(prev_index);
 
     if new_hash != old_hash {
-        incremental_verify_ich_failed(tcx, prev_index, result);
+        incremental_verify_ich_failed(tcx, prev_index, &|| format_value(&result));
     }
 }
 
@@ -678,7 +682,7 @@ where
 fn incremental_verify_ich_failed<Tcx>(
     tcx: Tcx,
     prev_index: SerializedDepNodeIndex,
-    result: &dyn Debug,
+    result: &dyn Fn() -> String,
 ) where
     Tcx: DepContext,
 {
@@ -708,7 +712,7 @@ fn incremental_verify_ich_failed<Tcx>(
             run_cmd,
             dep_node: format!("{dep_node:?}"),
         });
-        panic!("Found unstable fingerprints for {dep_node:?}: {result:?}");
+        panic!("Found unstable fingerprints for {dep_node:?}: {}", result());
     }
 
     INSIDE_VERIFY_PANIC.with(|in_panic| in_panic.set(old_in_panic));