Mixin provide with Symbols don't get merged properly

[privatenumber]

Version

2.5.16

Reproduction link

https://jsfiddle.net/hirokiosame/38nzxq6c/26/

Steps to reproduce

Run the code. The injected result will show [undefined, "bar"] in the console.

What is expected?

For the merging to work properly. The expected result is ['foo', 'bar'], which is what you'll see when you convert keyA and keyB into strings.

What is actually happening?

Merging fails: [undefined, "bar"]

[privatenumber]

@posva Would you mind taking a look at this?

[yyx990803]

Closed via #7926