Auto merge of #89124 - cjgillot:owner-info, r=michaelwoerister

Index and hash HIR as part of lowering

Part of https://github.com/rust-lang/rust/pull/88186
~Based on https://github.com/rust-lang/rust/pull/88880 (see merge commit).~

Once HIR is lowered, it is later indexed by the `index_hir` query and hashed for `crate_hash`. This PR moves those post-processing steps to lowering itself. As a side objective, the HIR crate data structure is refactored as an `IndexVec<LocalDefId, Option<OwnerInfo<'hir>>>` where `OwnerInfo` stores all the relevant information for an HIR owner.

r? `@michaelwoerister`
cc `@petrochenkov`

compiler/rustc_hir/src/hir.rs

@@ -1,5 +1,5 @@
 use crate::def::{CtorKind, DefKind, Res};
-use crate::def_id::{DefId, CRATE_DEF_ID};
+use crate::def_id::DefId;
 crate use crate::hir_id::{HirId, ItemLocalId};
 use crate::LangItem;
 
@@ -9,6 +9,7 @@ use rustc_ast::{Attribute, FloatTy, IntTy, Label, LitKind, StrStyle, TraitObject
 pub use rustc_ast::{BorrowKind, ImplPolarity, IsAuto};
 pub use rustc_ast::{CaptureBy, Movability, Mutability};
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
+use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_index::vec::IndexVec;
 use rustc_macros::HashStable_Generic;
@@ -662,6 +663,74 @@ pub struct WhereEqPredicate<'hir> {
     pub rhs_ty: &'hir Ty<'hir>,
 }
 
+/// HIR node coupled with its parent's id in the same HIR owner.
+///
+/// The parent is trash when the node is a HIR owner.
+#[derive(Clone, Debug)]
+pub struct ParentedNode<'tcx> {
+    pub parent: ItemLocalId,
+    pub node: Node<'tcx>,
+}
+
+/// Attributes owned by a HIR owner.
+#[derive(Debug)]
+pub struct AttributeMap<'tcx> {
+    pub map: BTreeMap<ItemLocalId, &'tcx [Attribute]>,
+    pub hash: Fingerprint,
+}
+
+impl<'tcx> AttributeMap<'tcx> {
+    pub const EMPTY: &'static AttributeMap<'static> =
+        &AttributeMap { map: BTreeMap::new(), hash: Fingerprint::ZERO };
+
+    #[inline]
+    pub fn get(&self, id: ItemLocalId) -> &'tcx [Attribute] {
+        self.map.get(&id).copied().unwrap_or(&[])
+    }
+}
+
+/// Map of all HIR nodes inside the current owner.
+/// These nodes are mapped by `ItemLocalId` alongside the index of their parent node.
+/// The HIR tree, including bodies, is pre-hashed.
+#[derive(Debug)]
+pub struct OwnerNodes<'tcx> {
+    /// Pre-computed hash of the full HIR.
+    pub hash_including_bodies: Fingerprint,
+    /// Pre-computed hash of the item signature, sithout recursing into the body.
+    pub hash_without_bodies: Fingerprint,
+    /// Full HIR for the current owner.
+    // The zeroth node's parent should never be accessed: the owner's parent is computed by the
+    // hir_owner_parent query.  It is set to `ItemLocalId::INVALID` to force an ICE if accidentally
+    // used.
+    pub nodes: IndexVec<ItemLocalId, Option<ParentedNode<'tcx>>>,
+    /// Content of local bodies.
+    pub bodies: IndexVec<ItemLocalId, Option<&'tcx Body<'tcx>>>,
+}
+
+/// Full information resulting from lowering an AST node.
+#[derive(Debug, HashStable_Generic)]
+pub struct OwnerInfo<'hir> {
+    /// Contents of the HIR.
+    pub nodes: OwnerNodes<'hir>,
+    /// Map from each nested owner to its parent's local id.
+    pub parenting: FxHashMap<LocalDefId, ItemLocalId>,
+    /// Collected attributes of the HIR nodes.
+    pub attrs: AttributeMap<'hir>,
+    /// Map indicating what traits are in scope for places where this
+    /// is relevant; generated by resolve.
+    pub trait_map: FxHashMap<ItemLocalId, Box<[TraitCandidate]>>,
+}
+
+impl<'tcx> OwnerInfo<'tcx> {
+    #[inline]
+    pub fn node(&self) -> OwnerNode<'tcx> {
+        use rustc_index::vec::Idx;
+        let node = self.nodes.nodes[ItemLocalId::new(0)].as_ref().unwrap().node;
+        let node = node.as_owner().unwrap(); // Indexing must ensure it is an OwnerNode.
+        node
+    }
+}
+
 /// The top-level data structure that stores the entire contents of
 /// the crate currently being compiled.
 ///
@@ -670,41 +739,8 @@ pub struct WhereEqPredicate<'hir> {
 /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/hir.html
 #[derive(Debug)]
 pub struct Crate<'hir> {
-    pub owners: IndexVec<LocalDefId, Option<OwnerNode<'hir>>>,
-    pub bodies: BTreeMap<BodyId, Body<'hir>>,
-
-    /// Map indicating what traits are in scope for places where this
-    /// is relevant; generated by resolve.
-    pub trait_map: FxHashMap<LocalDefId, FxHashMap<ItemLocalId, Box<[TraitCandidate]>>>,
-
-    /// Collected attributes from HIR nodes.
-    pub attrs: BTreeMap<HirId, &'hir [Attribute]>,
-}
-
-impl Crate<'hir> {
-    pub fn module(&self) -> &'hir Mod<'hir> {
-        if let Some(OwnerNode::Crate(m)) = self.owners[CRATE_DEF_ID] { m } else { panic!() }
-    }
-
-    pub fn item(&self, id: ItemId) -> &'hir Item<'hir> {
-        self.owners[id.def_id].as_ref().unwrap().expect_item()
-    }
-
-    pub fn trait_item(&self, id: TraitItemId) -> &'hir TraitItem<'hir> {
-        self.owners[id.def_id].as_ref().unwrap().expect_trait_item()
-    }
-
-    pub fn impl_item(&self, id: ImplItemId) -> &'hir ImplItem<'hir> {
-        self.owners[id.def_id].as_ref().unwrap().expect_impl_item()
-    }
-
-    pub fn foreign_item(&self, id: ForeignItemId) -> &'hir ForeignItem<'hir> {
-        self.owners[id.def_id].as_ref().unwrap().expect_foreign_item()
-    }
-
-    pub fn body(&self, id: BodyId) -> &Body<'hir> {
-        &self.bodies[&id]
-    }
+    pub owners: IndexVec<LocalDefId, Option<OwnerInfo<'hir>>>,
+    pub hir_hash: Fingerprint,
 }
 
 /// A block of statements `{ .. }`, which may have a label (in this case the