Rollup merge of #115081 - Zoxc:expn-id-decode, r=cjgillot

Allow overwriting ExpnId for concurrent decoding

These assertions only hold for the single threaded compiler. They were triggered in https://github.com/rust-lang/rust/pull/115003.

1 files changed, 3 insertions, 3 deletions

diff --git a/compiler/rustc_span/src/hygiene.rs b/compiler/rustc_span/src/hygiene.rs
index ab57d5c6803..88081700c3b 100644
--- a/compiler/rustc_span/src/hygiene.rs
+++ b/compiler/rustc_span/src/hygiene.rs
@@ -1291,11 +1291,11 @@ pub fn register_expn_id(
     let expn_id = ExpnId { krate, local_id };
     HygieneData::with(|hygiene_data| {
         let _old_data = hygiene_data.foreign_expn_data.insert(expn_id, data);
-        debug_assert!(_old_data.is_none());
+        debug_assert!(_old_data.is_none() || cfg!(parallel_compiler));
         let _old_hash = hygiene_data.foreign_expn_hashes.insert(expn_id, hash);
-        debug_assert!(_old_hash.is_none());
+        debug_assert!(_old_hash.is_none() || _old_hash == Some(hash));
         let _old_id = hygiene_data.expn_hash_to_expn_id.insert(hash, expn_id);
-        debug_assert!(_old_id.is_none());
+        debug_assert!(_old_id.is_none() || _old_id == Some(expn_id));
     });
     expn_id
 }