reflect: rawFieldByNameFunc: copy index slice to avoid later overwrites

[dgryski]

No description provided.

[lpereira]

In #4287, there's a commit implementing FieldByNameFunc() in terms of VisibleFields() (and implementing FieldByName() interms of FieldByNameFunc()). It removes over 120 lines of code, simplifying the code quite a bit. Is there any downside is using that version of the code instead?

[dgryski]

Because FieldByName is able to short-circuit walking the struct while VisibileFields necessarily needs to process every single field.

[lpereira]

Ah, makes sense. Yeah, we can clean that up later. I'm rebasing #4287 on this patch then.

[dgryski]

Commit merged as part of #4287