Fix issue with indirect return for C++ member function w/no args

diff --git a/gen/src/write.rs b/gen/src/write.rs
index c06fce9..2cf9faf 100644
--- a/gen/src/write.rs
+++ b/gen/src/write.rs
@@ -424,7 +424,7 @@
     }
     let indirect_return = indirect_return(efn, types);
     if indirect_return {
-        if !efn.args.is_empty() {
+        if !efn.args.is_empty() || efn.receiver.is_some() {
             write!(out, ", ");
         }
         write_indirect_return_type_space(out, efn.ret.as_ref().unwrap());