hir: Remove the generic type parameter from MaybeOwned

It's only ever used with a reference to `OwnerInfo` as an argument.

compiler/rustc_ast_lowering/src/item.rs

@@ -25,7 +25,7 @@ pub(super) struct ItemLowerer<'a, 'hir> {
     pub(super) tcx: TyCtxt<'hir>,
     pub(super) resolver: &'a mut ResolverAstLowering,
     pub(super) ast_index: &'a IndexSlice<LocalDefId, AstOwner<'a>>,
-    pub(super) owners: &'a mut IndexVec<LocalDefId, hir::MaybeOwner<&'hir hir::OwnerInfo<'hir>>>,
+    pub(super) owners: &'a mut IndexVec<LocalDefId, hir::MaybeOwner<'hir>>,
 }
 
 /// When we have a ty alias we *may* have two where clauses. To give the best diagnostics, we set the span
@@ -64,10 +64,7 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
         }
     }
 
-    pub(super) fn lower_node(
-        &mut self,
-        def_id: LocalDefId,
-    ) -> hir::MaybeOwner<&'hir hir::OwnerInfo<'hir>> {
+    pub(super) fn lower_node(&mut self, def_id: LocalDefId) -> hir::MaybeOwner<'hir> {
         let owner = self.owners.ensure_contains_elem(def_id, || hir::MaybeOwner::Phantom);
         if let hir::MaybeOwner::Phantom = owner {
             let node = self.ast_index[def_id];

compiler/rustc_ast_lowering/src/lib.rs

@@ -99,7 +99,7 @@ struct LoweringContext<'a, 'hir> {
     /// Attributes inside the owner being lowered.
     attrs: SortedMap<hir::ItemLocalId, &'hir [Attribute]>,
     /// Collect items that were created by lowering the current owner.
-    children: Vec<(LocalDefId, hir::MaybeOwner<&'hir hir::OwnerInfo<'hir>>)>,
+    children: Vec<(LocalDefId, hir::MaybeOwner<'hir>)>,
 
     coroutine_kind: Option<hir::CoroutineKind>,
 
@@ -415,7 +415,7 @@ fn index_crate<'a>(
 /// This hash will then be part of the crate_hash which is stored in the metadata.
 fn compute_hir_hash(
     tcx: TyCtxt<'_>,
-    owners: &IndexSlice<LocalDefId, hir::MaybeOwner<&hir::OwnerInfo<'_>>>,
+    owners: &IndexSlice<LocalDefId, hir::MaybeOwner<'_>>,
 ) -> Fingerprint {
     let mut hir_body_nodes: Vec<_> = owners
         .iter_enumerated()

compiler/rustc_hir/src/hir.rs

@@ -894,34 +894,23 @@ impl<'tcx> OwnerInfo<'tcx> {
 }
 
 #[derive(Copy, Clone, Debug, HashStable_Generic)]
-pub enum MaybeOwner<T> {
-    Owner(T),
+pub enum MaybeOwner<'tcx> {
+    Owner(&'tcx OwnerInfo<'tcx>),
     NonOwner(HirId),
     /// Used as a placeholder for unused LocalDefId.
     Phantom,
 }
 
-impl<T> MaybeOwner<T> {
-    pub fn as_owner(self) -> Option<T> {
+impl<'tcx> MaybeOwner<'tcx> {
+    pub fn as_owner(self) -> Option<&'tcx OwnerInfo<'tcx>> {
         match self {
             MaybeOwner::Owner(i) => Some(i),
             MaybeOwner::NonOwner(_) | MaybeOwner::Phantom => None,
         }
     }
 
-    pub fn map<U>(self, f: impl FnOnce(T) -> U) -> MaybeOwner<U> {
-        match self {
-            MaybeOwner::Owner(i) => MaybeOwner::Owner(f(i)),
-            MaybeOwner::NonOwner(hir_id) => MaybeOwner::NonOwner(hir_id),
-            MaybeOwner::Phantom => MaybeOwner::Phantom,
-        }
-    }
-
-    pub fn unwrap(self) -> T {
-        match self {
-            MaybeOwner::Owner(i) => i,
-            MaybeOwner::NonOwner(_) | MaybeOwner::Phantom => panic!("Not a HIR owner"),
-        }
+    pub fn unwrap(self) -> &'tcx OwnerInfo<'tcx> {
+        self.as_owner().unwrap_or_else(|| panic!("Not a HIR owner"))
     }
 }
 
@@ -933,7 +922,7 @@ impl<T> MaybeOwner<T> {
 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/hir.html
 #[derive(Debug)]
 pub struct Crate<'hir> {
-    pub owners: IndexVec<LocalDefId, MaybeOwner<&'hir OwnerInfo<'hir>>>,
+    pub owners: IndexVec<LocalDefId, MaybeOwner<'hir>>,
     // Only present when incr. comp. is enabled.
     pub opt_hir_hash: Option<Fingerprint>,
 }

compiler/rustc_middle/src/hir/mod.rs

@@ -127,12 +127,11 @@ pub fn provide(providers: &mut Providers) {
     providers.hir_crate_items = map::hir_crate_items;
     providers.crate_hash = map::crate_hash;
     providers.hir_module_items = map::hir_module_items;
-    providers.opt_local_def_id_to_hir_id = |tcx, id| {
-        let owner = tcx.hir_crate(()).owners[id].map(|_| ());
-        Some(match owner {
-            MaybeOwner::Owner(_) => HirId::make_owner(id),
-            MaybeOwner::Phantom => bug!("No HirId for {:?}", id),
+    providers.opt_local_def_id_to_hir_id = |tcx, def_id| {
+        Some(match tcx.hir_crate(()).owners[def_id] {
+            MaybeOwner::Owner(_) => HirId::make_owner(def_id),
             MaybeOwner::NonOwner(hir_id) => hir_id,
+            MaybeOwner::Phantom => bug!("No HirId for {:?}", def_id),
         })
     };
     providers.opt_hir_owner_nodes =

compiler/rustc_middle/src/query/erase.rs

@@ -185,8 +185,8 @@ impl EraseType for Option<ty::EarlyBinder<Ty<'_>>> {
     type Result = [u8; size_of::<Option<ty::EarlyBinder<Ty<'static>>>>()];
 }
 
-impl<T> EraseType for rustc_hir::MaybeOwner<&'_ T> {
-    type Result = [u8; size_of::<rustc_hir::MaybeOwner<&'static ()>>()];
+impl EraseType for rustc_hir::MaybeOwner<'_> {
+    type Result = [u8; size_of::<rustc_hir::MaybeOwner<'static>>()];
 }
 
 impl<T: EraseType> EraseType for ty::EarlyBinder<T> {