TrackStateType is easy to get wrong

[andiwand]

I feel like TrackStateType is easy to get wrong in recent work here #3413 and here #3438.

The flags sound exclusive and are use that way in various places looking at the diff here https://github.com/acts-project/acts/pull/3438/files.

I would propose to replace at least parts of the combinations with an enum to enumerate a few common easy and exclusive cases

• Measurement
• Hole
• Outlier

Potentially Material could also be an enum value or handled with a flag. Similar with SharedHit and Parameters. While I am not sure if we really rely on Parameters anywhere.

Orthogonally to this I would prefer to have this as a copied value type that can be get from or set to the track state because the type name does not indicate that it is a proxy.

[paulgessinger]

It needed to become a proxy, because the underlying storage needed to cast it back and forth between a trivial memory representation in the backend. With an enum, assignment would have to change to a setter so it can be converted to the underlying representation, if you want to get rid of the proxy type.

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[github-actions]

This issue/PR has been automatically marked as stale because it has not had recent activity. The stale label will be removed if any interaction occurs.