From fdb5fe2ed8c0ccd351e56d3afaa8b2a986e878b7 Mon Sep 17 00:00:00 2001
From: CastilloDel <delcastillodelarosadaniel@gmail.com>
Date: Sat, 12 Nov 2022 19:07:33 +0100
Subject: [PATCH] Change LoweringContext.children to Vec

---
 compiler/rustc_ast_lowering/src/item.rs | 17 +++++++++++------
 compiler/rustc_ast_lowering/src/lib.rs  |  9 ++++-----
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 76316a574ac..e43bec300bd 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -6,7 +6,6 @@
 use rustc_ast::ptr::P;
 use rustc_ast::visit::AssocCtxt;
 use rustc_ast::*;
-use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
@@ -67,7 +66,7 @@ fn with_lctx(
             // HirId handling.
             bodies: Vec::new(),
             attrs: SortedMap::default(),
-            children: FxHashMap::default(),
+            children: Vec::default(),
             current_hir_id_owner: hir::CRATE_OWNER_ID,
             item_local_id_counter: hir::ItemLocalId::new(0),
             node_id_to_local_id: Default::default(),
@@ -95,7 +94,13 @@ fn with_lctx(
         for (def_id, info) in lctx.children {
             self.owners.ensure_contains_elem(def_id, || hir::MaybeOwner::Phantom);
             debug_assert!(matches!(self.owners[def_id], hir::MaybeOwner::Phantom));
-            self.owners[def_id] = info;
+            match (self.owners[def_id], info) {
+                (hir::MaybeOwner::Phantom, _)
+                | (hir::MaybeOwner::NonOwner(_), hir::MaybeOwner::Owner(_)) => {
+                    self.owners[def_id] = info;
+                }
+                _ => unreachable!(),
+            }
         }
     }
 
@@ -534,12 +539,12 @@ fn lower_use_tree(
                 for new_node_id in [id1, id2] {
                     let new_id = self.local_def_id(new_node_id);
                     let Some(res) = resolutions.next() else {
+                        debug_assert!(self.children.iter().find(|(id, _)| id == &new_id).is_none());
                         // Associate an HirId to both ids even if there is no resolution.
-                        let _old = self.children.insert(
+                        self.children.push((
                             new_id,
-                            hir::MaybeOwner::NonOwner(hir::HirId::make_owner(new_id)),
+                            hir::MaybeOwner::NonOwner(hir::HirId::make_owner(new_id))),
                         );
-                        debug_assert!(_old.is_none());
                         continue;
                     };
                     let ident = *ident;
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 0af9b40afe3..cac9096780b 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -106,7 +106,7 @@ struct LoweringContext<'a, 'hir> {
     /// Attributes inside the owner being lowered.
     attrs: SortedMap<hir::ItemLocalId, &'hir [Attribute]>,
     /// Collect items that were created by lowering the current owner.
-    children: FxHashMap<LocalDefId, hir::MaybeOwner<&'hir hir::OwnerInfo<'hir>>>,
+    children: Vec<(LocalDefId, hir::MaybeOwner<&'hir hir::OwnerInfo<'hir>>)>,
 
     generator_kind: Option<hir::GeneratorKind>,
 
@@ -610,8 +610,8 @@ fn with_hir_id_owner(
         self.impl_trait_defs = current_impl_trait_defs;
         self.impl_trait_bounds = current_impl_trait_bounds;
 
-        let _old = self.children.insert(def_id, hir::MaybeOwner::Owner(info));
-        debug_assert!(_old.is_none())
+        debug_assert!(self.children.iter().find(|(id, _)| id == &def_id).is_none());
+        self.children.push((def_id, hir::MaybeOwner::Owner(info)));
     }
 
     /// Installs the remapping `remap` in scope while `f` is being executed.
@@ -718,8 +718,7 @@ fn lower_node_id(&mut self, ast_node_id: NodeId) -> hir::HirId {
 
                 assert_ne!(local_id, hir::ItemLocalId::new(0));
                 if let Some(def_id) = self.opt_local_def_id(ast_node_id) {
-                    // Do not override a `MaybeOwner::Owner` that may already here.
-                    self.children.entry(def_id).or_insert(hir::MaybeOwner::NonOwner(hir_id));
+                    self.children.push((def_id, hir::MaybeOwner::NonOwner(hir_id)));
                     self.local_id_to_def_id.insert(local_id, def_id);
                 }