Auto merge of #96431 - petrochenkov:parent, r=cjgillot

rustc: Panic by default in `DefIdTree::parent`

Only crate root def-ids don't have a parent, and in majority of cases the argument of `DefIdTree::parent` cannot be a crate root.
So we now panic by default in `parent` and introduce a new non-panicing function `opt_parent` for cases where the argument can be a crate root.

Same applies to `local_parent`/`opt_local_parent`.

Author: bors

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -90,7 +90,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         {
             if let ty::FnDef(id, _) = *literal.ty().kind() {
                 debug!("add_moved_or_invoked_closure_note: id={:?}", id);
-                if self.infcx.tcx.parent(id) == self.infcx.tcx.lang_items().fn_once_trait() {
+                if Some(self.infcx.tcx.parent(id)) == self.infcx.tcx.lang_items().fn_once_trait() {
                     let closure = match args.first() {
                         Some(Operand::Copy(ref place)) | Some(Operand::Move(ref place))
                             if target == place.local_or_deref_local() =>

compiler/rustc_codegen_llvm/src/debuginfo/utils.rs

@@ -46,7 +46,7 @@ pub fn DIB<'a, 'll>(cx: &'a CodegenCx<'ll, '_>) -> &'a DIBuilder<'ll> {
 }
 
 pub fn get_namespace_for_item<'ll>(cx: &CodegenCx<'ll, '_>, def_id: DefId) -> &'ll DIScope {
-    item_namespace(cx, cx.tcx.parent(def_id).expect("get_namespace_for_item: missing parent?"))
+    item_namespace(cx, cx.tcx.parent(def_id))
 }
 
 #[derive(Debug, PartialEq, Eq)]

compiler/rustc_const_eval/src/const_eval/fn_queries.rs

@@ -17,7 +17,7 @@ pub fn is_unstable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Symbol> {
 }
 
 pub fn is_parent_const_impl_raw(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
-    let parent_id = tcx.local_parent(def_id).unwrap();
+    let parent_id = tcx.local_parent(def_id);
     tcx.def_kind(parent_id) == DefKind::Impl
         && tcx.impl_constness(parent_id) == hir::Constness::Const
 }

compiler/rustc_const_eval/src/util/call_kind.rs

@@ -128,9 +128,9 @@ pub fn call_kind<'tcx>(
         } else {
             None
         };
-        let parent_self_ty = tcx
-            .parent(method_did)
-            .filter(|did| tcx.def_kind(*did) == rustc_hir::def::DefKind::Impl)
+        let parent_did = tcx.parent(method_did);
+        let parent_self_ty = (tcx.def_kind(parent_did) == rustc_hir::def::DefKind::Impl)
+            .then_some(parent_did)
             .and_then(|did| match tcx.type_of(did).kind() {
                 ty::Adt(def, ..) => Some(def.did()),
                 _ => None,

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -341,7 +341,7 @@ impl InferenceDiagnosticsData {
 
 impl InferenceDiagnosticsParentData {
     fn for_def_id(tcx: TyCtxt<'_>, def_id: DefId) -> Option<InferenceDiagnosticsParentData> {
-        let parent_def_id = tcx.parent(def_id)?;
+        let parent_def_id = tcx.parent(def_id);
 
         let parent_name =
             tcx.def_key(parent_def_id).disambiguated_data.data.get_opt_name()?.to_string();
@@ -854,10 +854,8 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         if let Some((DefKind::AssocFn, def_id)) =
             self.in_progress_typeck_results?.borrow().type_dependent_def(hir_id)
         {
-            return self
-                .tcx
-                .parent(def_id)
-                .filter(|&parent_def_id| self.tcx.is_trait(parent_def_id));
+            let parent_def_id = self.tcx.parent(def_id);
+            return self.tcx.is_trait(parent_def_id).then_some(parent_def_id);
         }
 
         None

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/util.rs

@@ -42,7 +42,7 @@ pub fn find_param_with_region<'tcx>(
     let (id, bound_region) = match *anon_region {
         ty::ReFree(ref free_region) => (free_region.scope, free_region.bound_region),
         ty::ReEarlyBound(ebr) => {
-            (tcx.parent(ebr.def_id).unwrap(), ty::BoundRegionKind::BrNamed(ebr.def_id, ebr.name))
+            (tcx.parent(ebr.def_id), ty::BoundRegionKind::BrNamed(ebr.def_id, ebr.name))
         }
         _ => return None, // not a free region
     };

compiler/rustc_lint/src/types.rs

@@ -1471,7 +1471,7 @@ impl InvalidAtomicOrdering {
             && let Some(adt) = cx.tcx.type_of(impl_did).ty_adt_def()
             // skip extension traits, only lint functions from the standard library
             && cx.tcx.trait_id_of_impl(impl_did).is_none()
-            && let Some(parent) = cx.tcx.parent(adt.did())
+            && let parent = cx.tcx.parent(adt.did())
             && cx.tcx.is_diagnostic_item(sym::atomic_mod, parent)
             && ATOMIC_TYPES.contains(&cx.tcx.item_name(adt.did()))
         {
@@ -1486,9 +1486,9 @@ impl InvalidAtomicOrdering {
         orderings.iter().any(|ordering| {
             tcx.item_name(did) == *ordering && {
                 let parent = tcx.parent(did);
-                parent == atomic_ordering
+                Some(parent) == atomic_ordering
                     // needed in case this is a ctor, not a variant
-                    || parent.map_or(false, |parent| tcx.parent(parent) == atomic_ordering)
+                    || tcx.opt_parent(parent) == atomic_ordering
             }
         })
     }

compiler/rustc_middle/src/hir/map/mod.rs

@@ -546,7 +546,7 @@ impl<'hir> Map<'hir> {
         let def_kind = self.tcx.def_kind(def_id);
         match def_kind {
             DefKind::Trait | DefKind::TraitAlias => def_id,
-            DefKind::TyParam | DefKind::ConstParam => self.tcx.local_parent(def_id).unwrap(),
+            DefKind::TyParam | DefKind::ConstParam => self.tcx.local_parent(def_id),
             _ => bug!("ty_param_owner: {:?} is a {:?} not a type parameter", def_id, def_kind),
         }
     }

compiler/rustc_middle/src/middle/stability.rs

@@ -289,7 +289,7 @@ fn suggestion_for_allocator_api(
     feature: Symbol,
 ) -> Option<(Span, String, String, Applicability)> {
     if feature == sym::allocator_api {
-        if let Some(trait_) = tcx.parent(def_id) {
+        if let Some(trait_) = tcx.opt_parent(def_id) {
             if tcx.is_diagnostic_item(sym::Vec, trait_) {
                 let sm = tcx.sess.parse_sess.source_map();
                 let inner_types = sm.span_extend_to_prev_char(span, '<', true);

compiler/rustc_middle/src/ty/context.rs

@@ -1491,7 +1491,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 (free_region.scope.expect_local(), free_region.bound_region)
             }
             ty::ReEarlyBound(ref ebr) => (
-                self.parent(ebr.def_id).unwrap().expect_local(),
+                self.local_parent(ebr.def_id.expect_local()),
                 ty::BoundRegionKind::BrNamed(ebr.def_id, ebr.name),
             ),
             _ => return None, // not a free region