bndrRuleAndUnfoldingFVs :: Id -> FV
bndrRuleAndUnfoldingFVs id
  | isId id   = idRuleFVs id `unionFV` idUnfoldingFVs id
  | otherwise = emptyFV
bndrRuleAndUnfoldingFVs :: Id -> FV
bndrRuleAndUnfoldingFVs id
  | isId id   = idRuleFVs id `unionFV` idUnfoldingFVs id
  | otherwise = emptyFV
bndrRuleAndUnfoldingFVs id
  | isId id   = idRuleFVs id `unionFV` idUnfoldingFVs id
  | otherwise = emptyFV