11531: fix: Make fill_match_arms assist handle doc(hidden) and non_exhaustive r=Veykril a=OleStrohm
Fixes#11499Fixes#11500
This keeps track of the relevant attributes and adds in a wildcard pat at the end of the match when necessary.
I decided to do them in the same PR since they both needed the ability to add a wildcard arm, and so their changes would overlap if done separately, but I'll split them up if that seems better.
This is my first PR to rust-analyzer, so all feedback is greatly appreciated!
Co-authored-by: Ole Strohm <strohm99@gmail.com>
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