### Version 2.6.7 ### Reproduction link [https://jsfiddle.net/3qbky0z7/4/](https://jsfiddle.net/3qbky0z7/4/) ### Steps to reproduce Create custom directive with a dynamic argument: ```v-test:[deep.arg]="value"``` ### What is expected? It should get the value from path `deep.arg`. ### What is actually happening? Inside the binding object of a custom directive, `arg` key have value `[deep`. <!-- generated by vue-issues. DO NOT REMOVE -->