sol

In my case, it work when adding `if statement` that make sure the function being executed is the main function. If not, the above error has occurred. How about edit...

Try `DeclareEnumIdent`:) It works for me when using filter string like `state = READY`. ``` DeclareIdent(fieldName, filtering.TypeString) ``` I referenced [this test code](https://github.com/einride/aip-go/blob/1972602194602564e3a34e378d815724901c188f/filtering/checker_test.go#L345).