Ensure that `Fingerprint` caching respects hashing configuration

Fixes #92266

In some `HashStable` impls, we use a cache to avoid re-computing
the same `Fingerprint` from the same structure (e.g. an `AdtDef`).
However, the `StableHashingContext` used can be configured to
perform hashing in different ways (e.g. skipping `Span`s). This
configuration information is not included in the cache key,
which will cause an incorrect `Fingerprint` to be used if
we hash the same structure with different `StableHashingContext`
settings.

To fix this, the configuration settings of `StableHashingContext`
are split out into a separate `HashingControls` struct. This
struct is used as part of the cache key, ensuring that our caches
always produce the correct result for the given settings.

With this in place, we now turn off `Span` hashing during the
entire process of computing the hash included in legacy symbols.
This current has no effect, but will matter when a future PR
starts hashing more `Span`s that we currently skip.

3 files changed, 28 insertions, 23 deletions

diff --git a/compiler/rustc_query_system/src/ich/hcx.rs b/compiler/rustc_query_system/src/ich/hcx.rs
index 5f31fa04b8a..9f9de707e7a 100644
--- a/compiler/rustc_query_system/src/ich/hcx.rs
+++ b/compiler/rustc_query_system/src/ich/hcx.rs
@@ -3,6 +3,7 @@ use rustc_ast as ast;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_data_structures::stable_hasher::{HashingControls, NodeIdHashingMode};
 use rustc_data_structures::sync::Lrc;
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -27,19 +28,11 @@ pub struct StableHashingContext<'a> {
     definitions: &'a Definitions,
     cstore: &'a dyn CrateStore,
     pub(super) body_resolver: BodyResolver<'a>,
-    hash_spans: bool,
-    pub(super) node_id_hashing_mode: NodeIdHashingMode,
-
     // Very often, we are hashing something that does not need the
     // `CachingSourceMapView`, so we initialize it lazily.
     raw_source_map: &'a SourceMap,
     caching_source_map: Option<CachingSourceMapView<'a>>,
-}
-
-#[derive(PartialEq, Eq, Clone, Copy)]
-pub enum NodeIdHashingMode {
-    Ignore,
-    HashDefPath,
+    pub(super) hashing_controls: HashingControls,
 }
 
 /// The `BodyResolver` allows mapping a `BodyId` to the corresponding `hir::Body`.
@@ -72,8 +65,10 @@ impl<'a> StableHashingContext<'a> {
             cstore,
             caching_source_map: None,
             raw_source_map: sess.source_map(),
-            hash_spans: hash_spans_initial,
-            node_id_hashing_mode: NodeIdHashingMode::HashDefPath,
+            hashing_controls: HashingControls {
+                hash_spans: hash_spans_initial,
+                node_id_hashing_mode: NodeIdHashingMode::HashDefPath,
+            },
         }
     }
 
@@ -133,10 +128,10 @@ impl<'a> StableHashingContext<'a> {
 
     #[inline]
     pub fn while_hashing_spans<F: FnOnce(&mut Self)>(&mut self, hash_spans: bool, f: F) {
-        let prev_hash_spans = self.hash_spans;
-        self.hash_spans = hash_spans;
+        let prev_hash_spans = self.hashing_controls.hash_spans;
+        self.hashing_controls.hash_spans = hash_spans;
         f(self);
-        self.hash_spans = prev_hash_spans;
+        self.hashing_controls.hash_spans = prev_hash_spans;
     }
 
     #[inline]
@@ -145,10 +140,10 @@ impl<'a> StableHashingContext<'a> {
         mode: NodeIdHashingMode,
         f: F,
     ) {
-        let prev = self.node_id_hashing_mode;
-        self.node_id_hashing_mode = mode;
+        let prev = self.hashing_controls.node_id_hashing_mode;
+        self.hashing_controls.node_id_hashing_mode = mode;
         f(self);
-        self.node_id_hashing_mode = prev;
+        self.hashing_controls.node_id_hashing_mode = prev;
     }
 
     #[inline]
@@ -183,6 +178,10 @@ impl<'a> StableHashingContext<'a> {
         }
         IGNORED_ATTRIBUTES.with(|attrs| attrs.contains(&name))
     }
+
+    pub fn hashing_controls(&self) -> HashingControls {
+        self.hashing_controls.clone()
+    }
 }
 
 impl<'a> HashStable<StableHashingContext<'a>> for ast::NodeId {
@@ -195,7 +194,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for ast::NodeId {
 impl<'a> rustc_span::HashStableContext for StableHashingContext<'a> {
     #[inline]
     fn hash_spans(&self) -> bool {
-        self.hash_spans
+        self.hashing_controls.hash_spans
     }
 
     #[inline]
@@ -215,6 +214,11 @@ impl<'a> rustc_span::HashStableContext for StableHashingContext<'a> {
     ) -> Option<(Lrc<SourceFile>, usize, BytePos, usize, BytePos)> {
         self.source_map().span_data_to_lines_and_cols(span)
     }
+
+    #[inline]
+    fn hashing_controls(&self) -> HashingControls {
+        self.hashing_controls.clone()
+    }
 }
 
 impl<'a> rustc_session::HashStableContext for StableHashingContext<'a> {}
diff --git a/compiler/rustc_query_system/src/ich/impls_hir.rs b/compiler/rustc_query_system/src/ich/impls_hir.rs
index 3117140a5b6..bf3cf6a48fd 100644
--- a/compiler/rustc_query_system/src/ich/impls_hir.rs
+++ b/compiler/rustc_query_system/src/ich/impls_hir.rs
@@ -11,7 +11,7 @@ impl<'ctx> rustc_hir::HashStableContext for StableHashingContext<'ctx> {
     #[inline]
     fn hash_hir_id(&mut self, hir_id: hir::HirId, hasher: &mut StableHasher) {
         let hcx = self;
-        match hcx.node_id_hashing_mode {
+        match hcx.hashing_controls.node_id_hashing_mode {
             NodeIdHashingMode::Ignore => {
                 // Don't do anything.
             }
@@ -89,12 +89,12 @@ impl<'ctx> rustc_hir::HashStableContext for StableHashingContext<'ctx> {
 
     #[inline]
     fn hash_hir_item_like<F: FnOnce(&mut Self)>(&mut self, f: F) {
-        let prev_hash_node_ids = self.node_id_hashing_mode;
-        self.node_id_hashing_mode = NodeIdHashingMode::Ignore;
+        let prev_hash_node_ids = self.hashing_controls.node_id_hashing_mode;
+        self.hashing_controls.node_id_hashing_mode = NodeIdHashingMode::Ignore;
 
         f(self);
 
-        self.node_id_hashing_mode = prev_hash_node_ids;
+        self.hashing_controls.node_id_hashing_mode = prev_hash_node_ids;
     }
 
     #[inline]
diff --git a/compiler/rustc_query_system/src/ich/mod.rs b/compiler/rustc_query_system/src/ich/mod.rs
index 54416902e5f..c42fcc9c82e 100644
--- a/compiler/rustc_query_system/src/ich/mod.rs
+++ b/compiler/rustc_query_system/src/ich/mod.rs
@@ -1,6 +1,7 @@
 //! ICH - Incremental Compilation Hash
 
-pub use self::hcx::{NodeIdHashingMode, StableHashingContext};
+pub use self::hcx::StableHashingContext;
+pub use rustc_data_structures::stable_hasher::NodeIdHashingMode;
 use rustc_span::symbol::{sym, Symbol};
 
 mod hcx;