2 files changed, 13 insertions, 2 deletions
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 1e14b4d6723..8b1c63cd21d 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -49,6 +49,7 @@ use rustc_attr_parsing::{AttributeParser, OmitDoc};
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_data_structures::sync::spawn;
 use rustc_data_structures::tagged_ptr::TaggedRef;
 use rustc_errors::{DiagArgFromDisplay, DiagCtxtHandle, StashKey};
 use rustc_hir::def::{DefKind, LifetimeRes, Namespace, PartialRes, PerNS, Res};
@@ -454,9 +455,14 @@ pub fn lower_to_hir(tcx: TyCtxt<'_>, (): ()) -> hir::Crate<'_> {
         .lower_node(def_id);
     }
 
-    // Drop AST to free memory
     drop(ast_index);
-    sess.time("drop_ast", || drop(krate));
+
+    // Drop AST to free memory. It can be expensive so try to drop it on a separate thread.
+    let prof = sess.prof.clone();
+    spawn(move || {
+        let _timer = prof.verbose_generic_activity("drop_ast");
+        drop(krate);
+    });
 
     // Don't hash unless necessary, because it's expensive.
     let opt_hir_hash =
diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
index f94d788a9b0..4a6929ef011 100644
--- a/compiler/rustc_ast_lowering/src/pat.rs
+++ b/compiler/rustc_ast_lowering/src/pat.rs
@@ -464,6 +464,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         )
                     }),
             ),
+            TyPatKind::Or(variants) => {
+                hir::TyPatKind::Or(self.arena.alloc_from_iter(
+                    variants.iter().map(|pat| self.lower_ty_pat_mut(pat, base_type)),
+                ))
+            }
             TyPatKind::Err(guar) => hir::TyPatKind::Err(*guar),
         };