Choose encoding format in caller code.

2 files changed, 16 insertions, 3 deletions

diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 4b72ac86957..8b8ca987b38 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -377,7 +377,11 @@ impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for ExpnId {
         let local_cdata = decoder.cdata();
         let sess = decoder.sess.unwrap();
 
-        rustc_span::hygiene::decode_expn_id(decoder, |cnum, index| {
+        let cnum = CrateNum::decode(decoder)?;
+        let index = u32::decode(decoder)?;
+
+        let expn_id = rustc_span::hygiene::decode_expn_id(cnum, index, |expn_id| {
+            let ExpnId { krate: cnum, local_id: index } = expn_id;
             // Lookup local `ExpnData`s in our own crate data. Foreign `ExpnData`s
             // are stored in the owning crate, to avoid duplication.
             debug_assert_ne!(cnum, LOCAL_CRATE);
@@ -399,7 +403,8 @@ impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for ExpnId {
                 .unwrap()
                 .decode((&crate_data, sess));
             (expn_data, expn_hash)
-        })
+        });
+        Ok(expn_id)
     }
 }
 
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 4684daef4a1..6877d6ef542 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -182,7 +182,15 @@ impl<'a, 'tcx> Encodable<EncodeContext<'a, 'tcx>> for SyntaxContext {
 
 impl<'a, 'tcx> Encodable<EncodeContext<'a, 'tcx>> for ExpnId {
     fn encode(&self, s: &mut EncodeContext<'a, 'tcx>) -> opaque::EncodeResult {
-        rustc_span::hygiene::raw_encode_expn_id(*self, &s.hygiene_ctxt, s)
+        if self.krate == LOCAL_CRATE {
+            // We will only write details for local expansions.  Non-local expansions will fetch
+            // data from the corresponding crate's metadata.
+            // FIXME(#43047) FIXME(#74731) We may eventually want to avoid relying on external
+            // metadata from proc-macro crates.
+            s.hygiene_ctxt.schedule_expn_data_for_encoding(*self);
+        }
+        self.krate.encode(s)?;
+        self.local_id.encode(s)
     }
 }