Move the hir().krate() method to a query and remove the Krate dep node

src/librustc/arena.rs

@@ -127,7 +127,7 @@ macro_rules! arena_types {
             [] tys: rustc::ty::TyS<$tcx>,
 
             // HIR types
-            [few] hir_forest: rustc::hir::map::Forest<$tcx>,
+            [few] hir_krate: rustc_hir::Crate<$tcx>,
             [] arm: rustc_hir::Arm<$tcx>,
             [] attribute: syntax::ast::Attribute,
             [] block: rustc_hir::Block<$tcx>,

src/librustc/dep_graph/dep_node.rs

@@ -35,7 +35,7 @@
 //! "infer" some properties for each kind of `DepNode`:
 //!
 //! * Whether a `DepNode` of a given kind has any parameters at all. Some
-//!   `DepNode`s, like `Krate`, represent global concepts with only one value.
+//!   `DepNode`s, like `AllLocalTraitImpls`, represent global concepts with only one value.
 //! * Whether it is possible, in principle, to reconstruct a query key from a
 //!   given `DepNode`. Many `DepKind`s only require a single `DefId` parameter,
 //!   in which case it is possible to map the node's fingerprint back to the
@@ -400,19 +400,6 @@ rustc_dep_node_append!([define_dep_nodes!][ <'tcx>
     // We use this for most things when incr. comp. is turned off.
     [] Null,
 
-    // Represents the `Krate` as a whole (the `hir::Krate` value) (as
-    // distinct from the krate module). This is basically a hash of
-    // the entire krate, so if you read from `Krate` (e.g., by calling
-    // `tcx.hir().krate()`), we will have to assume that any change
-    // means that you need to be recompiled. This is because the
-    // `Krate` value gives you access to all other items. To avoid
-    // this fate, do not call `tcx.hir().krate()`; instead, prefer
-    // wrappers like `tcx.visit_all_items_in_krate()`.  If there is no
-    // suitable wrapper, you can use `tcx.dep_graph.ignore()` to gain
-    // access to the krate, but you must remember to add suitable
-    // edges yourself for the individual items that you read.
-    [eval_always] Krate,
-
     // Represents the body of a function or method. The def-id is that of the
     // function/method.
     [eval_always] HirBody(DefId),

src/librustc/hir/map/collector.rs

@@ -223,12 +223,9 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
             (commandline_args_hash, crate_disambiguator.to_fingerprint()),
         );
 
-        let (_, crate_hash) = input_dep_node_and_hash(
-            self.dep_graph,
-            &mut self.hcx,
-            DepNode::new_no_params(DepKind::Krate),
-            crate_hash_input,
-        );
+        let mut stable_hasher = StableHasher::new();
+        crate_hash_input.hash_stable(&mut self.hcx, &mut stable_hasher);
+        let crate_hash: Fingerprint = stable_hasher.finish();
 
         let svh = Svh::new(crate_hash.to_smaller_hash());
         (self.map, svh)

src/librustc/hir/map/hir_id_validator.rs

@@ -12,7 +12,7 @@ pub fn check_crate(hir_map: &Map<'_>) {
 
     let errors = Lock::new(Vec::new());
 
-    par_iter(&hir_map.krate().modules).for_each(|(module_id, _)| {
+    par_iter(&hir_map.krate.modules).for_each(|(module_id, _)| {
         let local_def_id = hir_map.local_def_id(*module_id);
         hir_map.visit_item_likes_in_module(
             local_def_id,

src/librustc/hir/map/mod.rs

@@ -129,30 +129,6 @@ impl<'hir> Entry<'hir> {
     }
 }
 
-/// Stores a crate and any number of inlined items from other crates.
-pub struct Forest<'hir> {
-    krate: Crate<'hir>,
-    pub dep_graph: DepGraph,
-}
-
-impl Forest<'hir> {
-    pub fn new(krate: Crate<'hir>, dep_graph: &DepGraph) -> Forest<'hir> {
-        Forest { krate, dep_graph: dep_graph.clone() }
-    }
-
-    pub fn krate(&self) -> &Crate<'hir> {
-        self.dep_graph.read(DepNode::new_no_params(DepKind::Krate));
-        &self.krate
-    }
-
-    /// This is used internally in the dependency tracking system.
-    /// Use the `krate` method to ensure your dependency on the
-    /// crate is tracked.
-    pub fn untracked_krate(&self) -> &Crate<'hir> {
-        &self.krate
-    }
-}
-
 /// This type is effectively a `HashMap<HirId, Entry<'hir>>`,
 /// but it is implemented as 2 layers of arrays.
 /// - first we have `A = IndexVec<DefIndex, B>` mapping `DefIndex`s to an inner value
@@ -162,11 +138,8 @@ pub(super) type HirEntryMap<'hir> = IndexVec<DefIndex, IndexVec<ItemLocalId, Opt
 /// Represents a mapping from `NodeId`s to AST elements and their parent `NodeId`s.
 #[derive(Clone)]
 pub struct Map<'hir> {
-    /// The backing storage for all the AST nodes.
-    pub forest: &'hir Forest<'hir>,
+    krate: &'hir Crate<'hir>,
 
-    /// Same as the dep_graph in forest, just available with one fewer
-    /// deref. This is a gratuitous micro-optimization.
     pub dep_graph: DepGraph,
 
     /// The SVH of the local crate.
@@ -217,6 +190,13 @@ impl<'hir> Iterator for ParentHirIterator<'_, 'hir> {
 }
 
 impl<'hir> Map<'hir> {
+    /// This is used internally in the dependency tracking system.
+    /// Use the `krate` method to ensure your dependency on the
+    /// crate is tracked.
+    pub fn untracked_krate(&self) -> &Crate<'hir> {
+        &self.krate
+    }
+
     #[inline]
     fn lookup(&self, id: HirId) -> Option<&Entry<'hir>> {
         let local_map = self.map.get(id.owner)?;
@@ -401,40 +381,36 @@ impl<'hir> Map<'hir> {
         self.lookup(id).cloned()
     }
 
-    pub fn krate(&self) -> &'hir Crate<'hir> {
-        self.forest.krate()
-    }
-
     pub fn item(&self, id: HirId) -> &'hir Item<'hir> {
         self.read(id);
 
-        // N.B., intentionally bypass `self.forest.krate()` so that we
+        // N.B., intentionally bypass `self.krate()` so that we
         // do not trigger a read of the whole krate here
-        self.forest.krate.item(id)
+        self.krate.item(id)
     }
 
     pub fn trait_item(&self, id: TraitItemId) -> &'hir TraitItem<'hir> {
         self.read(id.hir_id);
 
-        // N.B., intentionally bypass `self.forest.krate()` so that we
+        // N.B., intentionally bypass `self.krate()` so that we
         // do not trigger a read of the whole krate here
-        self.forest.krate.trait_item(id)
+        self.krate.trait_item(id)
     }
 
     pub fn impl_item(&self, id: ImplItemId) -> &'hir ImplItem<'hir> {
         self.read(id.hir_id);
 
-        // N.B., intentionally bypass `self.forest.krate()` so that we
+        // N.B., intentionally bypass `self.krate()` so that we
         // do not trigger a read of the whole krate here
-        self.forest.krate.impl_item(id)
+        self.krate.impl_item(id)
     }
 
     pub fn body(&self, id: BodyId) -> &'hir Body<'hir> {
         self.read(id.hir_id);
 
-        // N.B., intentionally bypass `self.forest.krate()` so that we
+        // N.B., intentionally bypass `self.krate()` so that we
         // do not trigger a read of the whole krate here
-        self.forest.krate.body(id)
+        self.krate.body(id)
     }
 
     pub fn fn_decl_by_hir_id(&self, hir_id: HirId) -> Option<&'hir FnDecl<'hir>> {
@@ -530,9 +506,9 @@ impl<'hir> Map<'hir> {
     pub fn trait_impls(&self, trait_did: DefId) -> &'hir [HirId] {
         self.dep_graph.read(DepNode::new_no_params(DepKind::AllLocalTraitImpls));
 
-        // N.B., intentionally bypass `self.forest.krate()` so that we
+        // N.B., intentionally bypass `self.krate()` so that we
         // do not trigger a read of the whole krate here
-        self.forest.krate.trait_impls.get(&trait_did).map_or(&[], |xs| &xs[..])
+        self.krate.trait_impls.get(&trait_did).map_or(&[], |xs| &xs[..])
     }
 
     /// Gets the attributes on the crate. This is preferable to
@@ -542,15 +518,15 @@ impl<'hir> Map<'hir> {
         let def_path_hash = self.definitions.def_path_hash(CRATE_DEF_INDEX);
 
         self.dep_graph.read(def_path_hash.to_dep_node(DepKind::Hir));
-        &self.forest.krate.attrs
+        &self.krate.attrs
     }
 
     pub fn get_module(&self, module: DefId) -> (&'hir Mod<'hir>, Span, HirId) {
         let hir_id = self.as_local_hir_id(module).unwrap();
         self.read(hir_id);
         match self.find_entry(hir_id).unwrap().node {
             Node::Item(&Item { span, kind: ItemKind::Mod(ref m), .. }) => (m, span, hir_id),
-            Node::Crate => (&self.forest.krate.module, self.forest.krate.span, hir_id),
+            Node::Crate => (&self.krate.module, self.krate.span, hir_id),
             node => panic!("not a module: {:?}", node),
         }
     }
@@ -567,7 +543,7 @@ impl<'hir> Map<'hir> {
         // in the expect_* calls the loops below
         self.read(hir_id);
 
-        let module = &self.forest.krate.modules[&hir_id];
+        let module = &self.krate.modules[&hir_id];
 
         for id in &module.items {
             visitor.visit_item(self.expect_item(*id));
@@ -984,7 +960,7 @@ impl<'hir> Map<'hir> {
             // Unit/tuple structs/variants take the attributes straight from
             // the struct/variant definition.
             Some(Node::Ctor(..)) => return self.attrs(self.get_parent_item(id)),
-            Some(Node::Crate) => Some(&self.forest.krate.attrs[..]),
+            Some(Node::Crate) => Some(&self.krate.attrs[..]),
             _ => None,
         };
         attrs.unwrap_or(&[])
@@ -1063,7 +1039,7 @@ impl<'hir> Map<'hir> {
             Some(Node::Visibility(v)) => bug!("unexpected Visibility {:?}", v),
             Some(Node::Local(local)) => local.span,
             Some(Node::MacroDef(macro_def)) => macro_def.span,
-            Some(Node::Crate) => self.forest.krate.span,
+            Some(Node::Crate) => self.krate.span,
             None => bug!("hir::map::Map::span: id not in map: {:?}", hir_id),
         }
     }
@@ -1231,7 +1207,8 @@ impl Named for ImplItem<'_> {
 pub fn map_crate<'hir>(
     sess: &rustc_session::Session,
     cstore: &CrateStoreDyn,
-    forest: &'hir Forest<'hir>,
+    krate: &'hir Crate<'hir>,
+    dep_graph: DepGraph,
     definitions: Definitions,
 ) -> Map<'hir> {
     let _prof_timer = sess.prof.generic_activity("build_hir_map");
@@ -1244,31 +1221,18 @@ pub fn map_crate<'hir>(
         .collect();
 
     let (map, crate_hash) = {
-        let hcx = crate::ich::StableHashingContext::new(sess, &forest.krate, &definitions, cstore);
-
-        let mut collector = NodeCollector::root(
-            sess,
-            &forest.krate,
-            &forest.dep_graph,
-            &definitions,
-            &hir_to_node_id,
-            hcx,
-        );
-        intravisit::walk_crate(&mut collector, &forest.krate);
+        let hcx = crate::ich::StableHashingContext::new(sess, krate, &definitions, cstore);
+
+        let mut collector =
+            NodeCollector::root(sess, krate, &dep_graph, &definitions, &hir_to_node_id, hcx);
+        intravisit::walk_crate(&mut collector, krate);
 
         let crate_disambiguator = sess.local_crate_disambiguator();
         let cmdline_args = sess.opts.dep_tracking_hash();
         collector.finalize_and_compute_crate_hash(crate_disambiguator, cstore, cmdline_args)
     };
 
-    let map = Map {
-        forest,
-        dep_graph: forest.dep_graph.clone(),
-        crate_hash,
-        map,
-        hir_to_node_id,
-        definitions,
-    };
+    let map = Map { krate, dep_graph, crate_hash, map, hir_to_node_id, definitions };
 
     sess.time("validate_HIR_map", || {
         hir_id_validator::check_crate(&map);

src/librustc/hir/mod.rs

@@ -7,7 +7,48 @@ pub mod exports;
 pub mod map;
 
 use crate::ty::query::Providers;
+use crate::ty::TyCtxt;
+use rustc_hir::def_id::LOCAL_CRATE;
+use rustc_hir::print;
+use rustc_hir::Crate;
+use std::ops::Deref;
+
+/// A wrapper type which allows you to access HIR.
+#[derive(Clone)]
+pub struct Hir<'tcx> {
+    tcx: TyCtxt<'tcx>,
+    map: &'tcx map::Map<'tcx>,
+}
+
+impl<'tcx> Hir<'tcx> {
+    pub fn krate(&self) -> &'tcx Crate<'tcx> {
+        self.tcx.hir_crate(LOCAL_CRATE)
+    }
+}
+
+impl<'tcx> Deref for Hir<'tcx> {
+    type Target = &'tcx map::Map<'tcx>;
+
+    #[inline(always)]
+    fn deref(&self) -> &Self::Target {
+        &self.map
+    }
+}
+
+impl<'hir> print::PpAnn for Hir<'hir> {
+    fn nested(&self, state: &mut print::State<'_>, nested: print::Nested) {
+        self.map.nested(state, nested)
+    }
+}
+
+impl<'tcx> TyCtxt<'tcx> {
+    #[inline(always)]
+    pub fn hir(self) -> Hir<'tcx> {
+        Hir { tcx: self, map: &self.hir_map }
+    }
+}
 
 pub fn provide(providers: &mut Providers<'_>) {
+    providers.hir_crate = |tcx, _| tcx.hir_map.untracked_krate();
     map::provide(providers);
 }

src/librustc/query/mod.rs

@@ -43,6 +43,18 @@ rustc_queries! {
     }
 
     Other {
+        // Represents crate as a whole (as distinct from the top-level crate module).
+        // If you call `hir_crate` (e.g., indirectly by calling `tcx.hir().krate()`),
+        // we will have to assume that any change means that you need to be recompiled.
+        // This is because the `hir_crate` query gives you access to all other items.
+        // To avoid this fate, do not call `tcx.hir().krate()`; instead,
+        // prefer wrappers like `tcx.visit_all_items_in_krate()`.
+        query hir_crate(key: CrateNum) -> &'tcx Crate<'tcx> {
+            eval_always
+            no_hash
+            desc { "get the crate HIR" }
+        }
+
         /// Records the type of every item.
         query type_of(key: DefId) -> Ty<'tcx> {
             cache_on_disk_if { key.is_local() }

src/librustc/ty/context.rs

@@ -966,7 +966,8 @@ pub struct GlobalCtxt<'tcx> {
     /// Export map produced by name resolution.
     export_map: FxHashMap<DefId, Vec<Export<hir::HirId>>>,
 
-    hir_map: hir_map::Map<'tcx>,
+    /// This should usually be accessed with the `tcx.hir()` method.
+    pub(crate) hir_map: hir_map::Map<'tcx>,
 
     /// A map from `DefPathHash` -> `DefId`. Includes `DefId`s from the local crate
     /// as well as all upstream crates. Only populated in incremental mode.
@@ -1019,11 +1020,6 @@ pub struct GlobalCtxt<'tcx> {
 }
 
 impl<'tcx> TyCtxt<'tcx> {
-    #[inline(always)]
-    pub fn hir(self) -> &'tcx hir_map::Map<'tcx> {
-        &self.hir_map
-    }
-
     pub fn alloc_steal_mir(self, mir: BodyAndCache<'tcx>) -> &'tcx Steal<BodyAndCache<'tcx>> {
         self.arena.alloc(Steal::new(mir))
     }
@@ -1328,7 +1324,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
     #[inline(always)]
     pub fn create_stable_hashing_context(self) -> StableHashingContext<'tcx> {
-        let krate = self.gcx.hir_map.forest.untracked_krate();
+        let krate = self.gcx.hir_map.untracked_krate();
 
         StableHashingContext::new(self.sess, krate, self.hir().definitions(), &*self.cstore)
     }

src/librustc/ty/query/mod.rs

@@ -45,7 +45,7 @@ use rustc_data_structures::sync::Lrc;
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, DefIdSet, DefIndex};
-use rustc_hir::{HirIdSet, ItemLocalId, TraitCandidate};
+use rustc_hir::{Crate, HirIdSet, ItemLocalId, TraitCandidate};
 use rustc_index::vec::IndexVec;
 use rustc_target::spec::PanicStrategy;
 

src/librustc/ty/query/plumbing.rs

@@ -1177,7 +1177,6 @@ pub fn force_from_dep_node(tcx: TyCtxt<'_>, dep_node: &DepNode) -> bool {
         // These are inputs that are expected to be pre-allocated and that
         // should therefore always be red or green already.
         DepKind::AllLocalTraitImpls |
-        DepKind::Krate |
         DepKind::CrateMetadata |
         DepKind::HirBody |
         DepKind::Hir |