Auto merge of #59042 - ljedrz:HirIdification_rework_map, r=<try>

HirIdification: rework Map

The next iteration of HirIdification (#57578).

- remove `NodeId` from `Entry`
- change `Map::map` to an `FxHashMap<HirId, Entry>`
- base the `NodeId` `Map` methods on `HirId` ones (reverses the current state)
- HirIdify `librustdoc` a little bit (some `NodeId` `Map` methods were converted to work on `HirId`s)

The second change might have performance implications, so I'd do a perf run to be sure it's fine; it simplifies the codebase and shouldn't have an impact as long as the `Map` searches are cached (which is now possible thanks to using `HirId`s).

r? @Zoxc

src/librustc/hir/map/collector.rs

@@ -8,8 +8,8 @@ use crate::ich::Fingerprint;
 use crate::middle::cstore::CrateStore;
 use crate::session::CrateDisambiguator;
 use crate::session::Session;
-use std::iter::repeat;
-use syntax::ast::{NodeId, CRATE_NODE_ID};
+use crate::util::nodemap::FxHashMap;
+use syntax::ast::NodeId;
 use syntax::source_map::SourceMap;
 use syntax_pos::Span;
 
@@ -25,7 +25,7 @@ pub(super) struct NodeCollector<'a, 'hir> {
     source_map: &'a SourceMap,
 
     /// The node map
-    map: Vec<Option<Entry<'hir>>>,
+    map: FxHashMap<HirId, Entry<'hir>>,
     /// The parent of this node
     parent_node: hir::HirId,
 
@@ -146,7 +146,7 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
         let mut collector = NodeCollector {
             krate,
             source_map: sess.source_map(),
-            map: repeat(None).take(sess.current_node_id_count()).collect(),
+            map: Default::default(),
             parent_node: hir::CRATE_HIR_ID,
             current_signature_dep_index: root_mod_sig_dep_index,
             current_full_dep_index: root_mod_full_dep_index,
@@ -158,9 +158,8 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
             hcx,
             hir_body_nodes,
         };
-        collector.insert_entry(CRATE_NODE_ID, Entry {
-            parent: CRATE_NODE_ID,
-            parent_hir: hir::CRATE_HIR_ID,
+        collector.insert_entry(hir::CRATE_HIR_ID, Entry {
+            parent: hir::CRATE_HIR_ID,
             dep_node: root_mod_sig_dep_index,
             node: Node::Crate,
         });
@@ -172,7 +171,7 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
                                                   crate_disambiguator: CrateDisambiguator,
                                                   cstore: &dyn CrateStore,
                                                   commandline_args_hash: u64)
-                                                  -> (Vec<Option<Entry<'hir>>>, Svh)
+                                                  -> (FxHashMap<HirId, Entry<'hir>>, Svh)
     {
         self.hir_body_nodes.sort_unstable_by_key(|bn| bn.0);
 
@@ -223,15 +222,14 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
         (self.map, svh)
     }
 
-    fn insert_entry(&mut self, id: NodeId, entry: Entry<'hir>) {
+    fn insert_entry(&mut self, id: HirId, entry: Entry<'hir>) {
         debug!("hir_map: {:?} => {:?}", id, entry);
-        self.map[id.as_usize()] = Some(entry);
+        self.map.insert(id, entry);
     }
 
     fn insert(&mut self, span: Span, hir_id: HirId, node: Node<'hir>) {
         let entry = Entry {
-            parent: self.hir_to_node_id[&self.parent_node],
-            parent_hir: self.parent_node,
+            parent: self.parent_node,
             dep_node: if self.currently_in_body {
                 self.current_full_dep_index
             } else {
@@ -240,12 +238,11 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
             node,
         };
 
-        let node_id = self.hir_to_node_id[&hir_id];
-
         // Make sure that the DepNode of some node coincides with the HirId
         // owner of that node.
         if cfg!(debug_assertions) {
-           assert_eq!(self.definitions.node_to_hir_id(node_id), hir_id);
+            let node_id = self.hir_to_node_id[&hir_id];
+            assert_eq!(self.definitions.node_to_hir_id(node_id), hir_id);
 
             if hir_id.owner != self.current_dep_node_owner {
                 let node_str = match self.definitions.opt_def_index(node_id) {
@@ -278,7 +275,7 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
             }
         }
 
-        self.insert_entry(node_id, entry);
+        self.insert_entry(hir_id, entry);
     }
 
     fn with_parent<F: FnOnce(&mut Self)>(