Provide more complete AST accessors to support usage in rustc

crates/ra_syntax/src/ast/expr_extensions.rs

@@ -52,6 +52,10 @@ impl ast::RefExpr {
     pub fn is_mut(&self) -> bool {
         self.syntax().children_with_tokens().any(|n| n.kind() == T![mut])
     }
+
+    pub fn raw_token(&self) -> Option<SyntaxToken> {
+        None // FIXME: implement &raw
+    }
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]