Auto merge of #78415 - tgnottingham:expn_id_tag_hash, r=Aaron1011

rustc_span: avoid hashing ExpnId tag when using cached hash
rust-lang · Oct 28, 2020 · 31ee872 · 31ee872
2 parents 3dddf6a + a3623e0
commit 31ee872
Showing 1 changed file with 1 addition and 2 deletions.
diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
@@ -1925,9 +1925,7 @@ impl<CTX: HashStableContext> HashStable<CTX> for ExpnId {
             return;
         }
 
-        TAG_NOT_ROOT.hash_stable(ctx, hasher);
         let index = self.as_u32() as usize;
-
         let res = CACHE.with(|cache| cache.borrow().get(index).copied().flatten());
 
         if let Some(res) = res {
@@ -1936,6 +1934,7 @@ impl<CTX: HashStableContext> HashStable<CTX> for ExpnId {
             let new_len = index + 1;
 
             let mut sub_hasher = StableHasher::new();
+            TAG_NOT_ROOT.hash_stable(ctx, &mut sub_hasher);
             self.expn_data().hash_stable(ctx, &mut sub_hasher);
             let sub_hash: Fingerprint = sub_hasher.finish();