lightscript@0.5.9:
https://wcjohnson.github.io/lscdiag/?v=1&s=eMOafcKOQQrCgzAQRcKvIsKzwqogEsKpFsOqwqbCnsKgF1ApMcKJNjbCmsKQTMKgIMK5e8KTHsOAw5nDjHzDuMK8eQfDjMOywovDngoHw60Bwq_CjcKawrTCu24TSDlFwpoSW2vCvsKuw457EsOnw7rCucOVwobCr8KNIsKaQMKLw5bCi1DCnDUOcMOaWybDksKlHMKDFsOowqXCn8OGfMOYacO2w4jCpkvDj8OGPGszPsOsEEFewqYew5Ipw6rDtMKkwqjDhgLCnFDCgsKhw6BPw40jwqTCqsOSO8K9w49yw7nCq8Opw41IJWzDhCrCucK8w5ExKw12wqRsw4o7woQQwrtKOsKMwqwTw4UxwoQfwpw7VHQ

The highlighted AST node is being parsed as an ArrayPattern when it should be an ArrayExpression. Note that this does not happen above in the CallExpression but only within the ConditionalExpression.

Possibly a Babylon bug. No resolution as yet, am investigating.