When using [Boolean, String] props, Boolean does not work properly

[alexgrozav]

Version

2.5.13

Reproduction link

https://jsfiddle.net/50wL7mdz/165238/

Steps to reproduce

Create a component property that has [Boolean, String] types. The HTML5-like attribute doesn't behave like a normal Boolean value anymore, instead it gets discarded as empty string.

What is expected?

I would expect both the HTML5 attribute and the v-bind attribute to have the same output.

What is actually happening?

When adding String as a prop type as well, the HTML5 attribute version is not working.

[alexgrozav]

Seems related to #3879

[posva]

Duplicate of #7485