Avoid returning original macro if expansion fails.

Closes #11692. Instead of returning the original expression, a dummy expression
(with identical span) is returned. This prevents infinite loops of failed
expansions as well as odd double error messages in certain situations.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libsyntax/ext/bytes.rs b/src/libsyntax/ext/bytes.rs
index 39bb870b969..68aa757c524 100644
--- a/src/libsyntax/ext/bytes.rs
+++ b/src/libsyntax/ext/bytes.rs
@@ -21,7 +21,7 @@ use std::char;
 pub fn expand_syntax_ext(cx: &mut ExtCtxt, sp: Span, tts: &[ast::TokenTree]) -> base::MacResult {
     // Gather all argument expressions
     let exprs = match get_exprs_from_tts(cx, sp, tts) {
-        None => return MacResult::dummy_expr(),
+        None => return MacResult::dummy_expr(sp),
         Some(e) => e,
     };
     let mut bytes = ~[];