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, 6 insertions, 6 deletions

diff --git a/src/libsyntax/ext/source_util.rs b/src/libsyntax/ext/source_util.rs
index 150f054b2af..c81ee55c237 100644
--- a/src/libsyntax/ext/source_util.rs
+++ b/src/libsyntax/ext/source_util.rs
@@ -83,7 +83,7 @@ pub fn expand_include(cx: &mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
     -> base::MacResult {
     let file = match get_single_str_from_tts(cx, sp, tts, "include!") {
         Some(f) => f,
-        None => return MacResult::dummy_expr(),
+        None => return MacResult::dummy_expr(sp),
     };
     // The file will be added to the code map by the parser
     let mut p =
@@ -101,13 +101,13 @@ pub fn expand_include_str(cx: &mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
     -> base::MacResult {
     let file = match get_single_str_from_tts(cx, sp, tts, "include_str!") {
         Some(f) => f,
-        None => return MacResult::dummy_expr()
+        None => return MacResult::dummy_expr(sp)
     };
     let file = res_rel_file(cx, sp, &Path::new(file));
     let bytes = match File::open(&file).read_to_end() {
         Err(e) => {
             cx.span_err(sp, format!("couldn't read {}: {}", file.display(), e));
-            return MacResult::dummy_expr();
+            return MacResult::dummy_expr(sp);
         }
         Ok(bytes) => bytes,
     };
@@ -123,7 +123,7 @@ pub fn expand_include_str(cx: &mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
         }
         None => {
             cx.span_err(sp, format!("{} wasn't a utf-8 file", file.display()));
-            return MacResult::dummy_expr();
+            return MacResult::dummy_expr(sp);
         }
     }
 }
@@ -133,13 +133,13 @@ pub fn expand_include_bin(cx: &mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
 {
     let file = match get_single_str_from_tts(cx, sp, tts, "include_bin!") {
         Some(f) => f,
-        None => return MacResult::dummy_expr()
+        None => return MacResult::dummy_expr(sp)
     };
     let file = res_rel_file(cx, sp, &Path::new(file));
     match File::open(&file).read_to_end() {
         Err(e) => {
             cx.span_err(sp, format!("couldn't read {}: {}", file.display(), e));
-            return MacResult::dummy_expr();
+            return MacResult::dummy_expr(sp);
         }
         Ok(bytes) => {
             base::MRExpr(cx.expr_lit(sp, ast::LitBinary(Rc::new(bytes))))