Use a struct instead of a tuple

compiler/rustc_middle/src/query/erase.rs

@@ -177,9 +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<'_>>, ty::ImplPolarity)> {
-    type Result =
-        [u8; size_of::<Option<(ty::EarlyBinder<ty::TraitRef<'static>>, ty::ImplPolarity)>>()];
+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<'_>>> {

compiler/rustc_middle/src/query/mod.rs

@@ -848,7 +848,7 @@ rustc_queries! {
 
     /// 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_header(impl_id: DefId) -> Option<(ty::EarlyBinder<ty::TraitRef<'tcx>>, ty::ImplPolarity)> {
+    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

compiler/rustc_middle/src/ty/context.rs

@@ -2315,7 +2315,7 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         def_id: impl IntoQueryParam<DefId>,
     ) -> Option<ty::EarlyBinder<ty::TraitRef<'tcx>>> {
-        Some(self.impl_trait_header(def_id)?.0)
+        Some(self.impl_trait_header(def_id)?.map_bound(|h| h.trait_ref))
     }
 }
 

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>),

compiler/rustc_middle/src/ty/parameterized.rs

@@ -134,4 +134,5 @@ parameterized_over_tcx! {
     ty::Predicate,
     ty::Clause,
     ty::ClauseKind,
+    ty::ImplTraitHeader
 }