From c520cf225310e0d1d3ebf513034255cee3f76e30 Mon Sep 17 00:00:00 2001
From: Camille GILLOT <gillot.camille@gmail.com>
Date: Fri, 11 Jun 2021 18:55:14 +0200
Subject: [PATCH] Arena-allocate Crate during lowering.

---
 compiler/rustc_ast_lowering/src/lib.rs | 9 +++++----
 compiler/rustc_interface/src/passes.rs | 3 +--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 9592c1d2fab..7a4e39376a8 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -296,7 +296,7 @@ pub fn lower_crate<'a, 'hir>(
     resolver: &'a mut dyn ResolverAstLowering,
     nt_to_tokenstream: NtToTokenstream,
     arena: &'hir Arena<'hir>,
-) -> hir::Crate<'hir> {
+) -> &'hir hir::Crate<'hir> {
     let _prof_timer = sess.prof.verbose_generic_activity("hir_lowering");
 
     LoweringContext {
@@ -403,7 +403,7 @@ enum AnonymousLifetimeMode {
 }
 
 impl<'a, 'hir> LoweringContext<'a, 'hir> {
-    fn lower_crate(mut self, c: &Crate) -> hir::Crate<'hir> {
+    fn lower_crate(mut self, c: &Crate) -> &'hir hir::Crate<'hir> {
         /// Full-crate AST visitor that inserts into a fresh
         /// `LoweringContext` any information that may be
         /// needed from arbitrary locations in the crate,
@@ -530,7 +530,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             }
         }
 
-        hir::Crate {
+        let krate = hir::Crate {
             item: module,
             exported_macros: self.arena.alloc_from_iter(self.exported_macros),
             non_exported_macro_attrs: self.arena.alloc_from_iter(self.non_exported_macro_attrs),
@@ -545,7 +545,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             proc_macros,
             trait_map,
             attrs: self.attrs,
-        }
+        };
+        self.arena.alloc(krate)
     }
 
     fn insert_item(&mut self, item: hir::Item<'hir>) -> hir::ItemId {
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index e08c8faaa52..f5a085250a6 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -460,7 +460,7 @@ pub fn lower_to_hir<'res, 'tcx>(
     resolver: &'res mut Resolver<'_>,
     krate: &'res ast::Crate,
     arena: &'tcx rustc_ast_lowering::Arena<'tcx>,
-) -> Crate<'tcx> {
+) -> &'tcx Crate<'tcx> {
     // Lower AST to HIR.
     let hir_crate = rustc_ast_lowering::lower_crate(
         sess,
@@ -796,7 +796,6 @@ pub fn create_global_ctxt<'tcx>(
     let krate = resolver
         .borrow_mut()
         .access(|resolver| lower_to_hir(sess, &lint_store, resolver, krate, hir_arena));
-    let krate = &*hir_arena.alloc(krate);
     let resolver_outputs = BoxedResolver::to_resolver_outputs(resolver);
 
     let query_result_on_disk_cache = rustc_incremental::load_query_result_cache(sess);