= case lookup thing (biThingHashMap buildInfo) of
Just v -> Right v
Nothing -> Left ["Can't happen: thing has no hash in mapping"]
- f Ways = Right $ intercalate "-" $ biWays buildInfo
+ f Ways = case biMaybeWays buildInfo of
+ Just ways -> Right $ intercalate "-" ways
+ Nothing -> Left ["Can't happen: No ways, but Ways is used"]