Allow , to delimit macro 2.0 rules

crates/mbe/src/lib.rs

@@ -220,9 +220,11 @@ impl MacroDef {
             while src.len() > 0 {
                 let rule = Rule::parse(&mut src, true)?;
                 rules.push(rule);
-                if let Err(()) = src.expect_char(';') {
+                if let Err(()) = src.expect_any_char(&[';', ',']) {
                     if src.len() > 0 {
-                        return Err(ParseError::Expected("expected `;`".to_string()));
+                        return Err(ParseError::Expected(
+                            "expected `;` or `,` to delimit rules".to_string(),
+                        ));
                     }
                     break;
                 }

crates/mbe/src/tests/expand.rs

@@ -662,6 +662,21 @@ macro foo {
     .assert_expand_items("foo!(bar);", "fn bar () {}");
 }
 
+#[test]
+fn test_macro_2_0_panic_2015() {
+    parse_macro2(
+        r#"
+macro panic_2015 {
+    () => (
+    ),
+    (bar) => (
+    ),
+}
+"#,
+    )
+    .assert_expand_items("panic_2015!(bar);", "");
+}
+
 #[test]
 fn test_path() {
     parse_macro(

crates/mbe/src/tt_iter.rs

@@ -34,6 +34,17 @@ impl<'a> TtIter<'a> {
         }
     }
 
+    pub(crate) fn expect_any_char(&mut self, chars: &[char]) -> Result<(), ()> {
+        match self.next() {
+            Some(tt::TokenTree::Leaf(tt::Leaf::Punct(tt::Punct { char: c, .. })))
+                if chars.contains(c) =>
+            {
+                Ok(())
+            }
+            _ => Err(()),
+        }
+    }
+
     pub(crate) fn expect_subtree(&mut self) -> Result<&'a tt::Subtree, ()> {
         match self.next() {
             Some(tt::TokenTree::Subtree(it)) => Ok(it),