From cd54b3e4483a331326a7508de6c24c90664ae392 Mon Sep 17 00:00:00 2001
From: Michael Lamparski <diagonaldevice@gmail.com>
Date: Wed, 2 May 2018 20:51:39 -0400
Subject: forbid empty identifiers from concat_idents

---
 src/libsyntax_ext/concat_idents.rs | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'src/libsyntax_ext')

diff --git a/src/libsyntax_ext/concat_idents.rs b/src/libsyntax_ext/concat_idents.rs
index 544b1410d3d..b8345e7cf40 100644
--- a/src/libsyntax_ext/concat_idents.rs
+++ b/src/libsyntax_ext/concat_idents.rs
@@ -31,6 +31,11 @@ pub fn expand_syntax_ext<'cx>(cx: &'cx mut ExtCtxt,
         return base::DummyResult::expr(sp);
     }
 
+    if tts.is_empty() {
+        cx.span_err(sp, "concat_idents! takes 1 or more arguments.");
+        return DummyResult::expr(sp);
+    }
+
     let mut res_str = String::new();
     for (i, e) in tts.iter().enumerate() {
         if i & 1 == 1 {
-- 
cgit 1.4.1-3-g733a5