delegation: fix cycles during delayed lowering

compiler/rustc_ast_lowering/src/delegation.rs

@@ -437,6 +437,7 @@ impl<'hir, R: ResolverAstLoweringExt<'hir>> LoweringContext<'_, 'hir, R> {
             // also nested delegations may need to access information about this code (#154332),
             // so it is better to leave this code as opposed to bodies of extern functions,
             // which are completely erased from existence.
+            // FIXME(fn_delegation): fix `help` in error message (see `inner-attr.stderr`)
             if param_count == 0
                 && let Some(block) = block
             {

compiler/rustc_ast_lowering/src/item.rs

@@ -38,7 +38,7 @@ pub(super) enum Owners<'a, 'hir> {
 }
 
 impl<'hir> Owners<'_, 'hir> {
-    fn get_or_insert_mut(&mut self, def_id: LocalDefId) -> &mut hir::MaybeOwner<'hir> {
+    pub(super) fn get_or_insert_mut(&mut self, def_id: LocalDefId) -> &mut hir::MaybeOwner<'hir> {
         match self {
             Owners::IndexVec(index_vec) => {
                 index_vec.ensure_contains_elem(def_id, || hir::MaybeOwner::Phantom)

compiler/rustc_ast_lowering/src/lib.rs

@@ -39,6 +39,7 @@ use std::mem;
 use std::sync::Arc;
 
 use rustc_ast::node_id::NodeMap;
+use rustc_ast::visit::AssocCtxt;
 use rustc_ast::{self as ast, *};
 use rustc_attr_parsing::{AttributeParser, Late, OmitDoc};
 use rustc_data_structures::fingerprint::Fingerprint;
@@ -53,8 +54,8 @@ use rustc_hir::def_id::{CRATE_DEF_ID, LOCAL_CRATE, LocalDefId};
 use rustc_hir::definitions::{DefPathData, DisambiguatorState};
 use rustc_hir::lints::{AttributeLint, DelayedLint};
 use rustc_hir::{
-    self as hir, AngleBrackets, ConstArg, GenericArg, HirId, ItemLocalMap, LifetimeSource,
-    LifetimeSyntax, ParamName, Target, TraitCandidate, find_attr,
+    self as hir, AngleBrackets, ConstArg, DelayedOwner, GenericArg, HirId, ItemLocalMap,
+    LifetimeSource, LifetimeSyntax, ParamName, Target, TraitCandidate, find_attr,
 };
 use rustc_index::{Idx, IndexSlice, IndexVec};
 use rustc_macros::extension;
@@ -633,13 +634,35 @@ pub fn lower_to_hir(tcx: TyCtxt<'_>, (): ()) -> mid_hir::Crate<'_> {
     let mut delayed_ids: FxIndexSet<LocalDefId> = Default::default();
 
     for def_id in ast_index.indices() {
-        match &ast_index[def_id] {
-            AstOwner::Item(Item { kind: ItemKind::Delegation { .. }, .. })
-            | AstOwner::AssocItem(Item { kind: AssocItemKind::Delegation { .. }, .. }, _) => {
-                delayed_ids.insert(def_id);
+        let delayed_owner = match &ast_index[def_id] {
+            AstOwner::Item(Item {
+                kind: ItemKind::Delegation(box Delegation { ident, .. }),
+                ..
+            }) => Some(DelayedOwner { kind: hir::DelayedOwnerKind::Item, ident: *ident }),
+            AstOwner::AssocItem(
+                Item { kind: AssocItemKind::Delegation(box Delegation { ident, .. }), .. },
+                ctx,
+            ) => {
+                let kind = match ctx {
+                    AssocCtxt::Trait => hir::DelayedOwnerKind::TraitItem,
+                    AssocCtxt::Impl { .. } => hir::DelayedOwnerKind::ImplItem,
+                };
+
+                Some(DelayedOwner { kind, ident: *ident })
             }
-            _ => lowerer.lower_node(def_id),
+            _ => None,
         };
+
+        if let Some(delayed_owner) = delayed_owner {
+            delayed_ids.insert(def_id);
+
+            let owner = lowerer.owners.get_or_insert_mut(def_id);
+            if let hir::MaybeOwner::Phantom = owner {
+                *owner = hir::MaybeOwner::Delayed(delayed_owner)
+            }
+        } else {
+            lowerer.lower_node(def_id);
+        }
     }
 
     // Don't hash unless necessary, because it's expensive.

compiler/rustc_hir/src/hir.rs

@@ -1641,10 +1641,24 @@ impl<'tcx> OwnerInfo<'tcx> {
     }
 }
 
+#[derive(Copy, Clone, Debug, HashStable_Generic)]
+pub enum DelayedOwnerKind {
+    Item,
+    ImplItem,
+    TraitItem,
+}
+
+#[derive(Copy, Clone, Debug, HashStable_Generic)]
+pub struct DelayedOwner {
+    pub ident: Ident,
+    pub kind: DelayedOwnerKind,
+}
+
 #[derive(Copy, Clone, Debug, HashStable_Generic)]
 pub enum MaybeOwner<'tcx> {
     Owner(&'tcx OwnerInfo<'tcx>),
     NonOwner(HirId),
+    Delayed(DelayedOwner),
     /// Used as a placeholder for unused LocalDefId.
     Phantom,
 }
@@ -1653,12 +1667,16 @@ 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,
+            _ => None,
         }
     }
 
     pub fn unwrap(self) -> &'tcx OwnerInfo<'tcx> {
-        self.as_owner().unwrap_or_else(|| panic!("Not a HIR owner"))
+        self.as_owner().unwrap_or_else(|| panic!("not a HIR owner"))
+    }
+
+    pub fn expect_delayed(self) -> DelayedOwner {
+        if let MaybeOwner::Delayed(owner) = self { owner } else { panic!("not a delayed owner") }
     }
 }
 

compiler/rustc_hir/src/intravisit.rs

@@ -117,6 +117,7 @@ pub trait HirTyCtxt<'hir> {
     fn hir_trait_item(&self, id: TraitItemId) -> &'hir TraitItem<'hir>;
     fn hir_impl_item(&self, id: ImplItemId) -> &'hir ImplItem<'hir>;
     fn hir_foreign_item(&self, id: ForeignItemId) -> &'hir ForeignItem<'hir>;
+    fn is_delayed(&self, id: LocalDefId) -> bool;
 }
 
 // Used when no tcx is actually available, forcing manual implementation of nested visitors.
@@ -139,6 +140,9 @@ impl<'hir> HirTyCtxt<'hir> for ! {
     fn hir_foreign_item(&self, _: ForeignItemId) -> &'hir ForeignItem<'hir> {
         unreachable!();
     }
+    fn is_delayed(&self, _: LocalDefId) -> bool {
+        unreachable!()
+    }
 }
 
 pub mod nested_filter {
@@ -226,6 +230,8 @@ pub trait Visitor<'v>: Sized {
     /// or `ControlFlow<T>`.
     type Result: VisitorResult = ();
 
+    const VISIT_DELAYED: bool = true;
+
     /// If `type NestedFilter` is set to visit nested items, this method
     /// must also be overridden to provide a map to retrieve nested items.
     fn maybe_tcx(&mut self) -> Self::MaybeTyCtxt {
@@ -244,18 +250,23 @@ pub trait Visitor<'v>: Sized {
     /// this method is if you want a nested pattern but cannot supply a
     /// `TyCtxt`; see `maybe_tcx` for advice.
     fn visit_nested_item(&mut self, id: ItemId) -> Self::Result {
-        if Self::NestedFilter::INTER {
+        if self.should_visit_maybe_delayed_inter(id.owner_id.def_id) {
             let item = self.maybe_tcx().hir_item(id);
             try_visit!(self.visit_item(item));
         }
         Self::Result::output()
     }
 
+    // Now delayed owners are only delegations, which are either item, trait item or impl item.
+    fn should_visit_maybe_delayed_inter(&mut self, id: LocalDefId) -> bool {
+        Self::NestedFilter::INTER && (Self::VISIT_DELAYED || !self.maybe_tcx().is_delayed(id))
+    }
+
     /// Like `visit_nested_item()`, but for trait items. See
     /// `visit_nested_item()` for advice on when to override this
     /// method.
     fn visit_nested_trait_item(&mut self, id: TraitItemId) -> Self::Result {
-        if Self::NestedFilter::INTER {
+        if self.should_visit_maybe_delayed_inter(id.owner_id.def_id) {
             let item = self.maybe_tcx().hir_trait_item(id);
             try_visit!(self.visit_trait_item(item));
         }
@@ -266,7 +277,7 @@ pub trait Visitor<'v>: Sized {
     /// `visit_nested_item()` for advice on when to override this
     /// method.
     fn visit_nested_impl_item(&mut self, id: ImplItemId) -> Self::Result {
-        if Self::NestedFilter::INTER {
+        if self.should_visit_maybe_delayed_inter(id.owner_id.def_id) {
             let item = self.maybe_tcx().hir_impl_item(id);
             try_visit!(self.visit_impl_item(item));
         }

compiler/rustc_interface/src/passes.rs

@@ -1054,6 +1054,10 @@ pub fn emit_delayed_lints(tcx: TyCtxt<'_>) {
 /// Runs all analyses that we guarantee to run, even if errors were reported in earlier analyses.
 /// This function never fails.
 fn run_required_analyses(tcx: TyCtxt<'_>) {
+    // Forces all delayed owners to be lowered and drops AST crate after it.
+    // Also refetches hir_crate_items to prevent multiple threads from blocking on it later.
+    tcx.force_delayed_owners_lowering();
+
     if tcx.sess.opts.unstable_opts.input_stats {
         rustc_passes::input_stats::print_hir_stats(tcx);
     }
@@ -1062,11 +1066,6 @@ fn run_required_analyses(tcx: TyCtxt<'_>) {
     #[cfg(all(not(doc), debug_assertions))]
     rustc_passes::hir_id_validator::check_crate(tcx);
 
-    // Prefetch this to prevent multiple threads from blocking on it later.
-    // This is needed since the `hir_id_validator::check_crate` call above is not guaranteed
-    // to use `hir_crate_items`.
-    tcx.ensure_done().hir_crate_items(());
-
     let sess = tcx.sess;
     sess.time("misc_checking_1", || {
         par_fns(&mut [

compiler/rustc_middle/src/hir/map.rs

@@ -7,7 +7,7 @@ use rustc_ast::visit::{VisitorResult, walk_list};
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::svh::Svh;
-use rustc_data_structures::sync::{DynSend, DynSync, par_for_each_in, spawn, try_par_for_each_in};
+use rustc_data_structures::sync::{DynSend, DynSync, par_for_each_in, try_par_for_each_in};
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId, LocalModDefId};
 use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
@@ -835,18 +835,8 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     #[inline]
-    fn hir_opt_ident(self, id: HirId) -> Option<Ident> {
-        match self.hir_node(id) {
-            Node::Pat(&Pat { kind: PatKind::Binding(_, _, ident, _), .. }) => Some(ident),
-            // A `Ctor` doesn't have an identifier itself, but its parent
-            // struct/variant does. Compare with `hir::Map::span`.
-            Node::Ctor(..) => match self.parent_hir_node(id) {
-                Node::Item(item) => Some(item.kind.ident().unwrap()),
-                Node::Variant(variant) => Some(variant.ident),
-                _ => unreachable!(),
-            },
-            node => node.ident(),
-        }
+    pub fn hir_opt_ident(self, id: HirId) -> Option<Ident> {
+        self.hir_crate(()).opt_ident(self, id)
     }
 
     #[inline]
@@ -1115,6 +1105,10 @@ impl<'tcx> intravisit::HirTyCtxt<'tcx> for TyCtxt<'tcx> {
     fn hir_foreign_item(&self, id: ForeignItemId) -> &'tcx ForeignItem<'tcx> {
         (*self).hir_foreign_item(id)
     }
+
+    fn is_delayed(&self, id: LocalDefId) -> bool {
+        (*self).hir_crate(()).delayed_ids.contains(&id)
+    }
 }
 
 impl<'tcx> pprust_hir::PpAnn for TyCtxt<'tcx> {
@@ -1212,8 +1206,14 @@ fn upstream_crates(tcx: TyCtxt<'_>) -> Vec<(StableCrateId, Svh)> {
     upstream_crates
 }
 
+#[derive(Clone, Copy)]
+enum ItemCollectionKind {
+    Crate,
+    Mod(LocalModDefId),
+}
+
 pub(super) fn hir_module_items(tcx: TyCtxt<'_>, module_id: LocalModDefId) -> ModuleItems {
-    let mut collector = ItemCollector::new(tcx, false);
+    let mut collector = ItemCollector::new(tcx, ItemCollectionKind::Mod(module_id));
 
     let (hir_mod, span, hir_id) = tcx.hir_get_module(module_id);
     collector.visit_mod(hir_mod, span, hir_id);
@@ -1245,26 +1245,8 @@ pub(super) fn hir_module_items(tcx: TyCtxt<'_>, module_id: LocalModDefId) -> Mod
     }
 }
 
-fn force_delayed_owners_lowering(tcx: TyCtxt<'_>) {
-    let krate = tcx.hir_crate(());
-    for &id in &krate.delayed_ids {
-        tcx.ensure_done().lower_delayed_owner(id);
-    }
-
-    let (_, krate) = krate.delayed_resolver.steal();
-    let prof = tcx.sess.prof.clone();
-
-    // Drop AST to free memory. It can be expensive so try to drop it on a separate thread.
-    spawn(move || {
-        let _timer = prof.verbose_generic_activity("drop_ast");
-        drop(krate);
-    });
-}
-
 pub(crate) fn hir_crate_items(tcx: TyCtxt<'_>, _: ()) -> ModuleItems {
-    force_delayed_owners_lowering(tcx);
-
-    let mut collector = ItemCollector::new(tcx, true);
+    let mut collector = ItemCollector::new(tcx, ItemCollectionKind::Crate);
 
     // A "crate collector" and "module collector" start at a
     // module item (the former starts at the crate root) but only
@@ -1327,9 +1309,9 @@ struct ItemCollector<'tcx> {
 }
 
 impl<'tcx> ItemCollector<'tcx> {
-    fn new(tcx: TyCtxt<'tcx>, crate_collector: bool) -> ItemCollector<'tcx> {
-        ItemCollector {
-            crate_collector,
+    fn new(tcx: TyCtxt<'tcx>, collection_kind: ItemCollectionKind) -> ItemCollector<'tcx> {
+        let mut collector = ItemCollector {
+            crate_collector: matches!(collection_kind, ItemCollectionKind::Crate),
             tcx,
             submodules: Vec::default(),
             items: Vec::default(),
@@ -1341,12 +1323,39 @@ impl<'tcx> ItemCollector<'tcx> {
             nested_bodies: Vec::default(),
             delayed_lint_items: Vec::default(),
             eiis: Vec::default(),
+        };
+
+        let krate = tcx.hir_crate(());
+        let delayed_kinds = krate
+            .delayed_ids
+            .iter()
+            .copied()
+            .map(|id| (id, krate.owners[id].expect_delayed().kind))
+            .filter(|(id, _)| match collection_kind {
+                ItemCollectionKind::Crate => true,
+                ItemCollectionKind::Mod(mod_id) => tcx.parent_module_from_def_id(*id) == mod_id,
+            });
+
+        // FIXME(fn_delegation): need to add delayed lints, eiis
+        for (def_id, kind) in delayed_kinds {
+            let owner_id = OwnerId { def_id };
+
+            match kind {
+                DelayedOwnerKind::Item => collector.items.push(ItemId { owner_id }),
+                DelayedOwnerKind::ImplItem => collector.impl_items.push(ImplItemId { owner_id }),
+                DelayedOwnerKind::TraitItem => collector.trait_items.push(TraitItemId { owner_id }),
+            };
+
+            collector.body_owners.push(def_id);
         }
+
+        collector
     }
 }
 
 impl<'hir> Visitor<'hir> for ItemCollector<'hir> {
     type NestedFilter = nested_filter::All;
+    const VISIT_DELAYED: bool = false;
 
     fn maybe_tcx(&mut self) -> Self::MaybeTyCtxt {
         self.tcx