Use a struct instead of a tuple

compiler/rustc_hir_analysis/src/collect.rs

@@ -1326,7 +1326,7 @@ fn suggest_impl_trait<'tcx>(
 fn impl_trait_header(
     tcx: TyCtxt<'_>,
     def_id: LocalDefId,
-) -> Option<(ty::EarlyBinder<ty::TraitRef<'_>>, ty::ImplPolarity)> {
+) -> Option<ty::EarlyBinder<ty::ImplTraitHeader<'_>>> {
     let icx = ItemCtxt::new(tcx, def_id);
     let item = tcx.hir().expect_item(def_id);
     let impl_ = item.expect_impl();
@@ -1336,7 +1336,7 @@ fn impl_trait_header(
         .map(|ast_trait_ref| {
             let selfty = tcx.type_of(def_id).instantiate_identity();
 
-            let impl_trait_ref = if let Some(ErrorGuaranteed { .. }) = check_impl_constness(
+            let trait_ref = if let Some(ErrorGuaranteed { .. }) = check_impl_constness(
                 tcx,
                 tcx.is_const_trait_impl_raw(def_id.to_def_id()),
                 ast_trait_ref,
@@ -1362,7 +1362,10 @@ fn impl_trait_header(
             } else {
                 icx.astconv().instantiate_mono_trait_ref(ast_trait_ref, selfty)
             };
-            (ty::EarlyBinder::bind(impl_trait_ref), polarity_of_impl(tcx, def_id,  impl_, item.span))
+            ty::EarlyBinder::bind(ty::ImplTraitHeader {
+                trait_ref,
+                polarity: polarity_of_impl(tcx, def_id,  impl_, item.span)
+            })
         })
 }
 

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1973,7 +1973,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
 
             if of_trait && let Some(header) = tcx.impl_trait_header(def_id) {
                 record!(self.tables.impl_trait_header[def_id] <- header);
-                let (trait_ref, _polarity) = header;
+                let trait_ref = header.map_bound(|h| h.trait_ref);
 
                 let trait_ref = trait_ref.instantiate_identity();
                 let simplified_self_ty = fast_reject::simplify_type(

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -423,7 +423,7 @@ define_tables! {
     variances_of: Table<DefIndex, LazyArray<ty::Variance>>,
     fn_sig: Table<DefIndex, LazyValue<ty::EarlyBinder<ty::PolyFnSig<'static>>>>,
     codegen_fn_attrs: Table<DefIndex, LazyValue<CodegenFnAttrs>>,
-    impl_trait_header: Table<DefIndex, LazyValue<(ty::EarlyBinder<ty::TraitRef<'static>>, ty::ImplPolarity)>>,
+    impl_trait_header: Table<DefIndex, LazyValue<ty::EarlyBinder<ty::ImplTraitHeader<'static>>>>,
     const_param_default: Table<DefIndex, LazyValue<ty::EarlyBinder<rustc_middle::ty::Const<'static>>>>,
     object_lifetime_default: Table<DefIndex, LazyValue<ObjectLifetimeDefault>>,
     optimized_mir: Table<DefIndex, LazyValue<mir::Body<'static>>>,

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
 }