{"ast_node_type":"other","tokens":[{"end":75,"kind":"keyword","start":0,"text":"FnArg::Copy(op)"}]}
            FnArg::Copy(op) => FnArg::Copy(self.project_field(op, field)?),
        interp_ok(match arg {
            FnArg::InPlace(mplace) => FnArg::InPlace(self.project_field(mplace, field)?),