X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=src%2Flibrustc_metadata%2Frmeta%2Fencoder.rs;h=f75f0b74a0e1e19eed3290bd55e477826e1e6f50;hb=39e593ab14c53fda63c3f2756716c5ad3cbb6465;hp=3f92226e5480d879c46b4b0396023f514bea8e07;hpb=543f03d24118d3af784aa98c507c00e30c796a0e;p=rust.git

diff --git a/src/librustc_metadata/rmeta/encoder.rs b/src/librustc_metadata/rmeta/encoder.rs
index 3f92226e548..f75f0b74a0e 100644
--- a/src/librustc_metadata/rmeta/encoder.rs
+++ b/src/librustc_metadata/rmeta/encoder.rs
@@ -279,6 +279,10 @@ fn specialized_encode(&mut self, span: &Span) -> Result<(), Self::Error> {
         // cross-crate inconsistencies (getting one behavior in the same
         // crate, and a different behavior in another crate) due to the
         // limited surface that proc-macros can expose.
+        //
+        // IMPORTANT: If this is ever changed, be sure to update
+        // `rustc_span::hygiene::raw_encode_expn_id` to handle
+        // encoding `ExpnData` for proc-macro crates.
         if self.is_proc_macro {
             SyntaxContext::root().encode(self)?;
         } else {