type DefUse = (Maybe Defs, Uses)
-- | A number of 'DefUse's in dependency order: earlier 'Defs' scope over later 'Uses'
+-- In a single (def, use) pair, the defs also scope over the uses
type DefUses = [DefUse]
emptyDUs :: DefUses
get (Nothing, _u1) d2 = d2
get (Just d1, _u1) d2 = d1 `unionNameSets` d2
-duUses :: DefUses -> Uses
+allUses :: DefUses -> Uses
-- ^ Just like 'allUses', but 'Defs' are not eliminated from the 'Uses' returned
-duUses dus = foldr get emptyNameSet dus
+allUses dus = foldr get emptyNameSet dus
where
get (_d1, u1) u2 = u1 `unionNameSets` u2
-allUses :: DefUses -> Uses
+duUses :: DefUses -> Uses
-- ^ Collect all 'Uses', regardless of whether the group is itself used,
-- but remove 'Defs' on the way
-allUses dus
+duUses dus
= foldr get emptyNameSet dus
where
get (Nothing, rhs_uses) uses = rhs_uses `unionNameSets` uses