5 files changed, 33 insertions, 18 deletions
diff --git a/compiler/rustc_middle/src/query/erase.rs b/compiler/rustc_middle/src/query/erase.rs
index 7039749b1b7..5666a59e38e 100644
--- a/compiler/rustc_middle/src/query/erase.rs
+++ b/compiler/rustc_middle/src/query/erase.rs
@@ -177,8 +177,8 @@ impl EraseType for Option<mir::DestructuredConstant<'_>> {
     type Result = [u8; size_of::<Option<mir::DestructuredConstant<'static>>>()];
 }
 
-impl EraseType for Option<ty::EarlyBinder<ty::TraitRef<'_>>> {
-    type Result = [u8; size_of::<Option<ty::EarlyBinder<ty::TraitRef<'static>>>>()];
+impl EraseType for Option<ty::EarlyBinder<ty::ImplTraitHeader<'_>>> {
+    type Result = [u8; size_of::<Option<ty::EarlyBinder<ty::ImplTraitHeader<'static>>>>()];
 }
 
 impl EraseType for Option<ty::EarlyBinder<Ty<'_>>> {
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 5a158edab72..60d195e4d3e 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -846,17 +846,13 @@ rustc_queries! {
         cache_on_disk_if { true }
     }
 
-    /// Given an `impl_id`, return the trait it implements.
+    /// Given an `impl_id`, return the trait it implements along with some header information.
     /// Return `None` if this is an inherent impl.
-    query impl_trait_ref(impl_id: DefId) -> Option<ty::EarlyBinder<ty::TraitRef<'tcx>>> {
+    query impl_trait_header(impl_id: DefId) -> Option<ty::EarlyBinder<ty::ImplTraitHeader<'tcx>>> {
         desc { |tcx| "computing trait implemented by `{}`", tcx.def_path_str(impl_id) }
         cache_on_disk_if { impl_id.is_local() }
         separate_provide_extern
     }
-    query impl_polarity(impl_id: DefId) -> ty::ImplPolarity {
-        desc { |tcx| "computing implementation polarity of `{}`", tcx.def_path_str(impl_id) }
-        separate_provide_extern
-    }
 
     query issue33140_self_ty(key: DefId) -> Option<ty::EarlyBinder<ty::Ty<'tcx>>> {
         desc { |tcx| "computing Self type wrt issue #33140 `{}`", tcx.def_path_str(key) }
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 9a0eea6592f..bd86c1c284e 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -2316,6 +2316,20 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn module_children_local(self, def_id: LocalDefId) -> &'tcx [ModChild] {
         self.resolutions(()).module_children.get(&def_id).map_or(&[], |v| &v[..])
     }
+
+    /// Given an `impl_id`, return the trait it implements.
+    /// Return `None` if this is an inherent impl.
+    pub fn impl_trait_ref(
+        self,
+        def_id: impl IntoQueryParam<DefId>,
+    ) -> Option<ty::EarlyBinder<ty::TraitRef<'tcx>>> {
+        Some(self.impl_trait_header(def_id)?.map_bound(|h| h.trait_ref))
+    }
+
+    pub fn impl_polarity(self, def_id: impl IntoQueryParam<DefId>) -> ty::ImplPolarity {
+        self.impl_trait_header(def_id)
+            .map_or(ty::ImplPolarity::Positive, |h| h.skip_binder().polarity)
+    }
 }
 
 /// Parameter attributes that can only be determined by examining the body of a function instead
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index af77ba02ad2..6ee74ef2fb6 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -248,6 +248,12 @@ pub struct ImplHeader<'tcx> {
     pub predicates: Vec<Predicate<'tcx>>,
 }
 
+#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, TyEncodable, TyDecodable, HashStable)]
+pub struct ImplTraitHeader<'tcx> {
+    pub trait_ref: ty::TraitRef<'tcx>,
+    pub polarity: ImplPolarity,
+}
+
 #[derive(Copy, Clone, PartialEq, Eq, Debug, TypeFoldable, TypeVisitable)]
 pub enum ImplSubject<'tcx> {
     Trait(TraitRef<'tcx>),
@@ -1602,17 +1608,16 @@ impl<'tcx> TyCtxt<'tcx> {
         def_id1: DefId,
         def_id2: DefId,
     ) -> Option<ImplOverlapKind> {
-        let impl_trait_ref1 = self.impl_trait_ref(def_id1);
-        let impl_trait_ref2 = self.impl_trait_ref(def_id2);
+        let impl1 = self.impl_trait_header(def_id1).unwrap().instantiate_identity();
+        let impl2 = self.impl_trait_header(def_id2).unwrap().instantiate_identity();
+
         // If either trait impl references an error, they're allowed to overlap,
         // as one of them essentially doesn't exist.
-        if impl_trait_ref1.is_some_and(|tr| tr.instantiate_identity().references_error())
-            || impl_trait_ref2.is_some_and(|tr| tr.instantiate_identity().references_error())
-        {
+        if impl1.references_error() || impl2.references_error() {
             return Some(ImplOverlapKind::Permitted { marker: false });
         }
 
-        match (self.impl_polarity(def_id1), self.impl_polarity(def_id2)) {
+        match (impl1.polarity, impl2.polarity) {
             (ImplPolarity::Reservation, _) | (_, ImplPolarity::Reservation) => {
                 // `#[rustc_reservation_impl]` impls don't overlap with anything
                 return Some(ImplOverlapKind::Permitted { marker: false });
@@ -1627,10 +1632,9 @@ impl<'tcx> TyCtxt<'tcx> {
         };
 
         let is_marker_overlap = {
-            let is_marker_impl = |trait_ref: Option<EarlyBinder<TraitRef<'_>>>| -> bool {
-                trait_ref.is_some_and(|tr| self.trait_def(tr.skip_binder().def_id).is_marker)
-            };
-            is_marker_impl(impl_trait_ref1) && is_marker_impl(impl_trait_ref2)
+            let is_marker_impl =
+                |trait_ref: TraitRef<'_>| -> bool { self.trait_def(trait_ref.def_id).is_marker };
+            is_marker_impl(impl1.trait_ref) && is_marker_impl(impl2.trait_ref)
         };
 
         if is_marker_overlap {
diff --git a/compiler/rustc_middle/src/ty/parameterized.rs b/compiler/rustc_middle/src/ty/parameterized.rs
index 47f9d9e61ad..045856dd9cd 100644
--- a/compiler/rustc_middle/src/ty/parameterized.rs
+++ b/compiler/rustc_middle/src/ty/parameterized.rs
@@ -134,4 +134,5 @@ parameterized_over_tcx! {
     ty::Predicate,
     ty::Clause,
     ty::ClauseKind,
+    ty::ImplTraitHeader
 }