"$delete" with warning "avoid using JavaScript unary operator as property name"

[taichunmin]

Version

2.2.6

Reproduction link

https://codepen.io/taichunmin/pen/KmdgPQ

Steps to reproduce

use $delete in @click

What is expected?

this.$delete is a Vue function, not unary operator

What is actually happening?

a warning "avoid using JavaScript unary operator as property name"

[taichunmin]

Thanks.