From 3dc3d9d18fba0396afa73644865c687b2e64815e Mon Sep 17 00:00:00 2001
From: Edwin Cheng <edwin0cheng@gmail.com>
Date: Wed, 4 Mar 2020 01:03:44 +0800
Subject: Fix a bug for single dollar sign macro

---
 crates/ra_mbe/src/parser.rs | 6 +++++-
 crates/ra_mbe/src/tests.rs  | 1 +
 2 files changed, 6 insertions(+), 1 deletion(-)

(limited to 'crates/ra_mbe/src')

diff --git a/crates/ra_mbe/src/parser.rs b/crates/ra_mbe/src/parser.rs
index 10a6f300a..034150432 100644
--- a/crates/ra_mbe/src/parser.rs
+++ b/crates/ra_mbe/src/parser.rs
@@ -90,7 +90,11 @@ fn next_op<'a>(
 ) -> Result<Op<'a>, ExpandError> {
     let res = match first {
         tt::TokenTree::Leaf(tt::Leaf::Punct(tt::Punct { char: '$', .. })) => {
-            let second = src.next().ok_or_else(|| err!("bad var 1"))?;
+            // Note that the '$' itself is a valid token inside macro_rules.
+            let second = match src.next() {
+                None => return Ok(Op::TokenTree(first)),
+                Some(it) => it,
+            };
             match second {
                 tt::TokenTree::Subtree(subtree) => {
                     let (separator, kind) = parse_repeat(src)?;
diff --git a/crates/ra_mbe/src/tests.rs b/crates/ra_mbe/src/tests.rs
index cb228702f..1dba82915 100644
--- a/crates/ra_mbe/src/tests.rs
+++ b/crates/ra_mbe/src/tests.rs
@@ -23,6 +23,7 @@ mod rule_parsing {
         check("($($i:ident)*) => ($_)");
         check("($($true:ident)*) => ($true)");
         check("($($false:ident)*) => ($false)");
+        check("($) => ($)");
     }
 
     #[test]
-- 
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