ruleLhsFVIds :: CoreRule -> FV
-- ^ This finds all locally-defined free Ids on the left hand side of a rule
-- and returns an FV computation
ruleLhsFVIds (BuiltinRule {}) = emptyFV
ruleLhsFVIds :: CoreRule -> FV
ruleLhsFVIds (BuiltinRule {}) = emptyFV
ruleLhsFVIds (BuiltinRule {}) = emptyFV