impl !PartialOrd for HirId

4 files changed, 16 insertions, 22 deletions

diff --git a/compiler/rustc_hir/src/hir_id.rs b/compiler/rustc_hir/src/hir_id.rs
index 3fa06620ea8..b48a081d371 100644
--- a/compiler/rustc_hir/src/hir_id.rs
+++ b/compiler/rustc_hir/src/hir_id.rs
@@ -83,6 +83,12 @@ pub struct HirId {
     pub local_id: ItemLocalId,
 }
 
+// To ensure correctness of incremental compilation,
+// `HirId` must not implement `Ord` or `PartialOrd`.
+// See https://github.com/rust-lang/rust/issues/90317.
+impl !Ord for HirId {}
+impl !PartialOrd for HirId {}
+
 impl Debug for HirId {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // Example: HirId(DefId(0:1 ~ aa[7697]::{use#0}).10)
@@ -116,10 +122,6 @@ impl HirId {
     pub fn make_owner(owner: LocalDefId) -> Self {
         Self { owner: OwnerId { def_id: owner }, local_id: ItemLocalId::ZERO }
     }
-
-    pub fn index(self) -> (usize, usize) {
-        (rustc_index::Idx::index(self.owner.def_id), rustc_index::Idx::index(self.local_id))
-    }
 }
 
 impl fmt::Display for HirId {
@@ -128,18 +130,6 @@ impl fmt::Display for HirId {
     }
 }
 
-impl Ord for HirId {
-    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
-        (self.index()).cmp(&(other.index()))
-    }
-}
-
-impl PartialOrd for HirId {
-    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
-        Some(self.cmp(other))
-    }
-}
-
 rustc_data_structures::define_stable_id_collections!(HirIdMap, HirIdSet, HirIdMapEntry, HirId);
 rustc_data_structures::define_id_collections!(
     ItemLocalMap,
diff --git a/compiler/rustc_hir/src/lib.rs b/compiler/rustc_hir/src/lib.rs
index 4a839d40571..6bc0f797cca 100644
--- a/compiler/rustc_hir/src/lib.rs
+++ b/compiler/rustc_hir/src/lib.rs
@@ -11,6 +11,7 @@
 #![feature(debug_closure_helpers)]
 #![feature(exhaustive_patterns)]
 #![feature(let_chains)]
+#![feature(negative_impls)]
 #![feature(never_type)]
 #![feature(rustc_attrs)]
 #![feature(variant_count)]
diff --git a/compiler/rustc_lint_defs/src/lib.rs b/compiler/rustc_lint_defs/src/lib.rs
index 9ea9f9cdb92..7fdbae3a59d 100644
--- a/compiler/rustc_lint_defs/src/lib.rs
+++ b/compiler/rustc_lint_defs/src/lib.rs
@@ -8,7 +8,8 @@ use rustc_data_structures::stable_hasher::{
 };
 use rustc_error_messages::{DiagMessage, MultiSpan};
 use rustc_hir::def::Namespace;
-use rustc_hir::{HashStableContext, HirId, MissingLifetimeKind};
+use rustc_hir::def_id::DefPathHash;
+use rustc_hir::{HashStableContext, HirId, ItemLocalId, MissingLifetimeKind};
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
 pub use rustc_span::edition::Edition;
 use rustc_span::{Ident, MacroRulesNormalizedIdent, Span, Symbol, sym};
@@ -102,7 +103,7 @@ pub enum Applicability {
 /// The index values have a type of `u16` to reduce the size of the `LintExpectationId`.
 /// It's reasonable to assume that no user will define 2^16 attributes on one node or
 /// have that amount of lints listed. `u16` values should therefore suffice.
-#[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash, Encodable, Decodable)]
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash, Encodable, Decodable)]
 pub enum LintExpectationId {
     /// Used for lints emitted during the `EarlyLintPass`. This id is not
     /// hash stable and should not be cached.
@@ -156,13 +157,14 @@ impl<HCX: rustc_hir::HashStableContext> HashStable<HCX> for LintExpectationId {
 }
 
 impl<HCX: rustc_hir::HashStableContext> ToStableHashKey<HCX> for LintExpectationId {
-    type KeyType = (HirId, u16, u16);
+    type KeyType = (DefPathHash, ItemLocalId, u16, u16);
 
     #[inline]
-    fn to_stable_hash_key(&self, _: &HCX) -> Self::KeyType {
+    fn to_stable_hash_key(&self, hcx: &HCX) -> Self::KeyType {
         match self {
             LintExpectationId::Stable { hir_id, attr_index, lint_index: Some(lint_index) } => {
-                (*hir_id, *attr_index, *lint_index)
+                let (def_path_hash, lint_idx) = hir_id.to_stable_hash_key(hcx);
+                (def_path_hash, lint_idx, *attr_index, *lint_index)
             }
             _ => {
                 unreachable!("HashStable should only be called for a filled `LintExpectationId`")
diff --git a/compiler/rustc_passes/src/dead.rs b/compiler/rustc_passes/src/dead.rs
index 54168758d0b..0060e726a8e 100644
--- a/compiler/rustc_passes/src/dead.rs
+++ b/compiler/rustc_passes/src/dead.rs
@@ -1130,7 +1130,8 @@ impl<'tcx> DeadVisitor<'tcx> {
         if dead_codes.is_empty() {
             return;
         }
-        dead_codes.sort_by_key(|v| v.level);
+        // FIXME: `dead_codes` should probably be morally equivalent to `IndexMap<(Level, LintExpectationId), (DefId, Symbol)>`
+        dead_codes.sort_by_key(|v| v.level.0);
         for group in dead_codes.chunk_by(|a, b| a.level == b.level) {
             self.lint_at_single_level(&group, participle, Some(def_id), report_on);
         }