False unused pattern warning when using patterns

[Ahajha]

Problem description

I have an example project that I described in this discussion: #955

I falsely believed that the patterns weren't applying, since they were giving a warning that they weren't be applied, but it turns out the warning is false and it actually worked.

The warning I believe happens since stubgen checks against the .matches field of pattern, but that field isn't updated anywhere. So probably we just need to update that field when we get matches.