treat unexpected EOF as incomplete reduction in bracketed_comment

src/parser/char_reader.rs

@@ -117,7 +117,7 @@ impl<R: Read> CharReader<R> {
         // Branch using `>=` instead of the more correct `==`
         // to tell the compiler that the pos..cap slice is always valid.
         if self.pos >= self.buf.len() {
-            debug_assert!(self.pos == self.buf.len());
+            debug_assert!(self.pos >= self.buf.len());
 
             self.buf.clear();